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diff --git a/railties/guides/source/getting_started.textile b/railties/guides/source/getting_started.textile index a6ac7f0f5b..a231713991 100644 --- a/railties/guides/source/getting_started.textile +++ b/railties/guides/source/getting_started.textile @@ -9,17 +9,17 @@ This guide covers getting up and running with Ruby on Rails. After reading it, y endprologue. -WARNING. This Guide is based on Rails 2.3.3. Some of the code shown here will not work in other versions of Rails. +WARNING. This Guide is based on Rails 3.0. Some of the code shown here will not work in earlier versions of Rails. -h3. This Guide Assumes +h3. 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. However, to get the most out of it, you need to have some prerequisites installed: -* The "Ruby":http://www.ruby-lang.org/en/downloads language +* The "Ruby":http://www.ruby-lang.org/en/downloads language version 1.8.7 or higher * The "RubyGems":http://rubyforge.org/frs/?group_id=126 packaging system -* A working installation of "SQLite":http://www.sqlite.org (preferred), "MySQL":http://www.mysql.com, or "PostgreSQL":http://www.postgresql.org +* A working installation of the "SQLite3 Database":http://www.sqlite.org -It is highly recommended that you *familiarize yourself with Ruby before diving into Rails*. You will find it much easier to follow what's going on with a Rails application if you understand basic Ruby syntax. Rails isn't going to magically revolutionize the way you write web applications if you have no experience with the language it uses. There are some good free resources on the internet for learning Ruby, including: +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 some good free resources on the internet for learning Ruby, including: * "Mr. Neighborly's Humble Little Ruby Book":http://www.humblelittlerubybook.com * "Programming Ruby":http://www.ruby-doc.org/docs/ProgrammingRuby/ @@ -27,19 +27,19 @@ It is highly recommended that you *familiarize yourself with Ruby before diving h3. What is Rails? -Rails is a web development framework written in the Ruby 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. Longtime Rails developers also report that it makes web application development more fun. +Rails is a web application development framework written in the Ruby 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. That is, it assumes that there is a best way to do things, and it's designed to encourage that best 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. +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 several guiding principles: * DRY - "Don't Repeat Yourself" - suggests that writing the same code over and over again is a bad thing. -* Convention Over Configuration - means that Rails makes assumptions about what you want to do and how you're going to do it, rather than letting you tweak every little thing through endless configuration files. +* Convention Over Configuration - means that Rails makes assumptions about what you want to do and how you're going to do it, rather than requiring you to specify every little thing through endless configuration files. * REST is the best pattern for web applications - organizing your application around resources and standard HTTP verbs is the fastest way to go. h4. The MVC Architecture -Rails is organized around the Model, View, Controller architecture, usually just called MVC. MVC benefits include: +At the core of Rails is the Model, View, Controller architecture, usually just called MVC. MVC benefits include: * Isolation of business logic from the user interface * Ease of keeping code DRY @@ -59,15 +59,23 @@ Controllers provide the "glue" between models and views. In Rails, controllers a h4. The Components of Rails -Rails provides a full stack of components for creating web applications, including: +Rails ships as many individual components. -* Action Controller -* Action View -* Active Record +* Action Pack + ** Action Controller + ** Action Dispatch + ** Action View * Action Mailer +* Active Model +* Active Record * Active Resource -* Railties * Active Support +* Railties + + +h5. Action Pack + +Action Pack is a single gem that contains Action Controller, Action View and Action Dispatch. The "VC" part of "MVC". h5. Action Controller @@ -77,38 +85,46 @@ h5. Action View Action View manages the views of your Rails application. It can create both HTML and XML output by default. Action View manages rendering templates, including nested and partial templates, and includes built-in AJAX support. -h5. Active Record +h5. Action Dispatch -Active Record is the base for the models in a Rails application. It provides database independence, basic CRUD functionality, advanced finding capabilities, and the ability to relate models to one another, among other services. +Action Dispatch handles routing of web requests and dispatches them as you want, either to your application, any other Rack application. h5. Action Mailer Action Mailer is a framework for building e-mail services. You can use Action Mailer to send emails based on flexible templates, or to receive and process incoming email. -h5. Active Resource +h5. Active Model -Active Resource provides a framework for managing the connection between business objects and RESTful web services. It implements a way to map web-based resources to local objects with CRUD semantics. +Active Model provides a defined interface between the Action Pack gem services and Object Relationship Mapping gems such as Active Record. Active Model allows Rails to utilize other ORM frameworks in place of Active Record if your application needs this. -h5. Railties +h5. Active Record + +Active Record is the base for the models in a Rails application. It provides database independence, basic CRUD functionality, advanced finding capabilities, and the ability to relate models to one another, among other services. -Railties is the core Rails code that builds new Rails applications and glues the various frameworks together in any Rails application. +h5. Active Resource + +Active Resource provides a framework for managing the connection between business objects and RESTful web services. It implements a way to map web-based resources to local objects with CRUD semantics. h5. Active Support Active Support is an extensive collection of utility classes and standard Ruby library extensions that are used in the Rails, both by the core code and by your applications. +h5. Railties + +Railties is the core Rails code that builds new Rails applications and glues the various frameworks and plugins together in any Rails application. + h4. REST -The foundation of the RESTful architecture is generally considered to be Roy Fielding's doctoral thesis, "Architectural Styles and the Design of Network-based Software Architectures":http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm. Fortunately, you need not read this entire document to understand how REST works in Rails. REST, an acronym for Representational State Transfer, boils down to two main principles for our purposes: +Rest stands for Representational State Transfer and is the foundation of the RESTful architecture. This is generally considered to be Roy Fielding's doctoral thesis, "Architectural Styles and the Design of Network-based Software Architectures":http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm. While you can read through the thesis, REST in terms of Rails boils down to two main principles: -* Using resource identifiers (which, for the purposes of discussion, you can think of as URLs) to represent resources +* Using resource identifiers such as URLs to represent resources. * Transferring representations of the state of that resource between system components. For example, to a Rails application a request such as this: <tt>DELETE /photos/17</tt> -would be understood to refer to a photo resource with the ID of 17, and to indicate a desired action - deleting that resource. REST is a natural style for the architecture of web applications, and Rails makes it even more natural by using conventions to shield you from some of the RESTful complexities and browser quirks. +would be understood to refer to a photo resource with the ID of 17, and to indicate a desired action - deleting that resource. REST is a natural style for the architecture of web applications, and Rails hooks into this shielding you from many of the RESTful complexities and browser quirks. If you'd like more details on REST as an architectural style, these resources are more approachable than Fielding's thesis: @@ -126,35 +142,25 @@ h4. Installing Rails In most cases, the easiest way to install Rails is to take advantage of RubyGems: <shell> -$ gem install rails +Usually run this as the root user: +# gem install rails </shell> -NOTE. There are some special circumstances in which you might want to use an alternate installation strategy: - -* If you're working on Windows, you may find it easier to install Instant Rails. Be aware, though, that "Instant Rails":http://instantrails.rubyforge.org/wiki/wiki.pl releases tend to lag seriously behind the actual Rails version. Also, you will find that Rails development on Windows is overall less pleasant than on other operating systems. If at all possible, we suggest that you install a Linux virtual machine and use that for Rails development, instead of using Windows. -* If you want to keep up with cutting-edge changes to Rails, you'll want to clone the "Rails source code":http://github.com/rails/rails/tree/master from github. This is not recommended as an option for beginners, though. +NOTE. In the Rails 3.0.0-beta, you will need to manually install the dependencies for Rails itself as a bug in rubygems will cause these to not be installed, see the "3.0 Release Notes":http://guides.rails.info/3_0_release_notes.html for the commands to run. -WARNING. As of mid-2009, cloning the master branch will get you preliminary Rails 3.0 code. To follow along with this guide, you should clone the 2-3-stable branch instead. +TIP. If you're working on Windows, you may find it easier to install "Instant Rails":http://instantrails.rubyforge.org/wiki/wiki.pl. Be aware, though, that Instant Rails releases tend to lag seriously behind the actual Rails version. Also, you will find that Rails development on Windows is overall less pleasant than on other operating systems. If at all possible, we suggest that you install a Linux virtual machine and use that for Rails development, instead of using Windows. h4. Creating the Blog Application -Open a terminal, navigate to a folder where you have rights to create files, and type: +The best way to use this guide is to follow each step as it happens, no code or step needed to make this example application has been left out, so you can literally follow along step by step. If you need to see the completed code, you can download it from "Getting Started Code":http://github.com/mikel/getting-started-code. -<shell> -$ rails blog -</shell> - -This will create a Rails application that uses a SQLite database for data storage. If you prefer to use MySQL, run this command instead: +To begin, open a terminal, navigate to a folder where you have rights to create files, and type: <shell> -$ rails blog -d mysql +$ rails blog </shell> -And if you're using PostgreSQL for data storage, run this command: - -<shell> -$ rails blog -d postgresql -</shell> +This will create a Rails application called Blog in a directory called blog. TIP: You can see all of the switches that the Rails application builder accepts by running <tt>rails -h</tt>. @@ -167,52 +173,62 @@ $ cd blog In any case, Rails will create a folder in your working directory called <tt>blog</tt>. Open up that folder and explore its contents. Most of the work in this tutorial will happen in the <tt>app/</tt> folder, but here's a basic rundown on the function of each folder that Rails creates in a new application by default: |_.File/Folder|_.Purpose| -|README|This is a brief instruction manual for your application. Use it to tell others what your application does, how to set it up, and so on.| +|Gemfile|This file allows you to specify what gem dependencies are needed for your Rails application.| +|README.rdoc|This is a brief instruction manual for your application. Use it to tell others what your application does, how to set it up, and so on.| |Rakefile|This file contains batch jobs that can be run from the terminal.| |app/|Contains the controllers, models, and views for your application. You'll focus on this folder for the remainder of this guide.| |config/|Configure your application's runtime rules, routes, database, and more.| +|config.ru|Rack configuration for Rack based servers used to start the application.| |db/|Shows your current database schema, as well as the database migrations. You'll learn about migrations shortly.| |doc/|In-depth documentation for your application.| |lib/|Extended modules for your application (not covered in this guide).| |log/|Application log files.| |public/|The only folder seen to the world as-is. This is where your images, javascript, stylesheets (CSS), and other static files go.| -|script/|Scripts provided by Rails to do recurring tasks, such as benchmarking, plugin installation, and starting the console or the web server.| +|script/|Contains the rails script that starts your app and can contain other scripts you use to deploy or run your application.| |test/|Unit tests, fixtures, and other test apparatus. These are covered in "Testing Rails Applications":testing.html| |tmp/|Temporary files| -|vendor/|A place for third-party code. In a typical Rails application, this includes Ruby Gems, the Rails source code (if you install it into your project) and plugins containing additional prepackaged functionality.| +|vendor/|A place for all third-party code. In a typical Rails application, this includes Ruby Gems, the Rails source code (if you install it into your project) and plugins containing additional prepackaged functionality.| + +h4. Installing the Required Gems + +Rails uses the "Bundler":http://www.github.com/carlhuda/bundler gem to populate the +vendor+ directory with all the gems your application depends on. As we don't need any special gems beyond the default, we just need to do the following: + +<shell> +As the root user: +# gem install bundler +# bundle install +</shell> + +This will copy down the versions of all the gems you need to start a rails application. h4. Configuring a Database Just about every Rails application will interact with a database. The database to use is specified in a configuration file, +config/database.yml+. -If you open this file in a new Rails application, you'll see a default database configuration using SQLite. The file contains sections for three different environments in which Rails can run by default: +If you open this file in a new Rails application, you'll see a default database configuration using SQLite3. The file contains sections for three different environments in which Rails can run by default: * The +development+ environment is used on your development computer as you interact manually with the application * The +test+ environment is used to run automated tests * The +production+ environment is used when you deploy your application for the world to use. -h5. Configuring a SQLite Database +h5. Configuring a SQLite3 Database -Rails comes with built-in support for "SQLite":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 a SQLite database when creating a new project, but you can always change it later. +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 a SQLite database when creating a new project, but you can always change it later. -Here's the section of the default configuration file with connection information for the development environment: +Here's the section of the default configuration file (<tt>config/database.yml</tt>) with connection information for the development environment: <yaml> development: -adapter: sqlite3 -database: db/development.sqlite3 -pool: 5 -timeout: 5000 + adapter: sqlite3 + database: db/development.sqlite3 + pool: 5 + timeout: 5000 </yaml> -If you don't have any database set up, SQLite is the easiest to get installed. If you're on OS X 10.5 or greater on a Mac, you already have it. Otherwise, you can install it using RubyGems: - -<shell> -$ gem install sqlite3-ruby -</shell> +NOTE: In this guide we are using an SQLite3 database for data storage, this is because it is a zero configuration database that just works. Rails also supports MySQL 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. h5. Configuring a MySQL Database -If you choose to use MySQL, your +config/database.yml+ will look a little different. Here's the development section: +If you choose to use MySQL instead of the shipped Sqlite3 database, your +config/database.yml+ will look a little different. Here's the development section: <yaml> development: @@ -229,7 +245,7 @@ If your development computer's MySQL installation includes a root user with an e h5. Configuring a PostgreSQL Database -If you choose to use PostgreSQL, your +config/database.yml+ will be customized to use PostgreSQL databases: +Finally if you choose to use PostgreSQL, your +config/database.yml+ will be customized to use PostgreSQL databases: <yaml> development: @@ -251,66 +267,73 @@ Now that you have your database configured, it's time to have Rails create an em $ rake db:create </shell> -NOTE. Rake is a general-purpose command-runner that Rails uses for many things. You can see the list of available rake commands in your application by running +rake -T+. +This will create your development and test SQLite3 databases inside the <tt>db/</tt> folder. + +TIP: Rake is a general-purpose command-runner that Rails uses for many things. You can see the list of available rake commands in your application by running +rake -T+. h3. Hello, Rails! -One of the traditional places to start with a new language is by getting some text up on screen quickly. To do that in Rails, you need to create at minimum a controller and a view. Fortunately, you can do that in a single command. Enter this command in your terminal: +One of the traditional places to start with a new language is by getting some text up on screen quickly, to do this, you need to get your Rails application server running. + +h4. 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: <shell> -$ rails generate controller home index +$ rails server </shell> -TIP: If you're on Windows, or your Ruby is set up in some non-standard fashion, you may need to explicitly pass Rails +script+ commands to Ruby: +rails generate controller home index+. +This will fire up an instance of the Mongrel web server by default (Rails can also use several other web servers). To see your application in action, open a browser window and navigate to "http://localhost:3000":http://localhost:3000. You should see Rails' default information page: -Rails will create several files for you, including +app/views/home/index.html.erb+. This is the template that will be used to display the results of the +index+ action (method) in the +home+ controller. Open this file in your text editor and edit it to contain a single line of code: +!images/rails_welcome.png(Welcome Aboard screenshot)! -<code class="html"> -<h1>Hello, Rails!</h1> -</code> +TIP: To stop the web server, hit Ctrl+C in the terminal window where it's running. In development mode, Rails does not generally require you to stop the server; changes you make in files will be automatically picked up by the server. -h4. Starting up the Web 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. You can also click on the _About your application’s environment_ link to see a summary of your Application's environment. -You actually have a functional Rails application already - after running only two commands! To see it, you need to start a web server on your development machine. You can do this by running another command: +h4. Say "Hello", Rails + +To get Rails saying "Hello", you need to create at minimum a controller and a view. Fortunately, you can do that in a single command. Enter this command in your terminal: <shell> -$ rails server +$ rails generate controller home index </shell> -This will fire up an instance of the Mongrel web server by default (Rails can also use several other web servers). To see your application in action, open a browser window and navigate to +http://localhost:3000+. You should see Rails' default information page: - -!images/rails_welcome.png(Welcome Aboard screenshot)! +TIP: If you're on Windows, or your Ruby is set up in some non-standard fashion, you may need to explicitly pass Rails +rails+ commands to Ruby: +ruby \path\to\rails controller home index+. -TIP: To stop the web server, hit Ctrl+C in the terminal window where it's running. In development mode, Rails does not generally require you to stop the server; changes you make in files will be automatically picked up by the server. +Rails will create several files for you, including +app/views/home/index.html.erb+. This is the template that will be used to display the results of the +index+ action (method) in the +home+ controller. Open this file in your text editor and edit it to contain a single line of code: -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. To view the page you just created, navigate to +http://localhost:3000/home/index+. +<code class="html"> +<h1>Hello, Rails!</h1> +</code> h4. Setting the Application Home Page -You'd probably like to replace the "Welcome Aboard" page with your own application's home page. The first step to doing this is to delete the default page from your application: +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":http://localhost:3000, instead of the "Welcome Aboard" smoke test. + +The first step to doing this is to delete the default page from your application: <shell> $ rm public/index.html </shell> -Now, you have to tell Rails where your actual home page is located. Open the file +config/routes.rb+ in your editor. This is your application's, _routing file_, which holds entries in a special DSL (domain-specific language) that tells Rails how to connect incoming requests to controllers and actions. At the bottom of the file you'll see the _default routes_: +We need to do this as Rails will deliver any static file in the +public+ directory in preference to any dynamic contact we generate from the controllers. -<ruby> -map.connect ':controller/:action/:id' -map.connect ':controller/:action/:id.:format' -</ruby> +Now, you have to tell Rails where your actual home page is located. Open the file +config/routes.rb+ in your editor. This is your application's _routing file_ which holds entries in a special DSL (domain-specific language) that tells Rails how to connect incoming requests to controllers and actions. There are only comments in this file, so we need to add at the top the following: -The default routes handle simple requests such as +/home/index+: Rails translates that into a call to the +index+ action in the +home+ controller. As another example, +/posts/edit/1+ would run the +edit+ action in the +posts+ controller with an +id+ of 1. +<ruby> +Blog::Application.routes.draw do |map| -To hook up your home page, you need to add another line to the routing file, above the default routes: + root :to => "home#index" -<ruby> -map.root :controller => "home" + # The priority is based upon order of creation: + # first created -> highest priority. + #... </ruby> -This line illustrates one tiny bit of the "convention over configuration" approach: if you don't specify an action, Rails assumes the +index+ action. +The +root :to => "home#index"+ tells Rails to map the root action to the home controller's index action. -Now if you navigate to +http://localhost:3000+ in your browser, you'll see the +home/index+ view. +Now if you navigate to "http://localhost:3000":http://localhost:3000 in your browser, you'll see +Hello, Rails!+. NOTE. For more information about routing, refer to "Rails Routing from the Outside In":routing.html. @@ -328,30 +351,31 @@ $ rails generate scaffold Post name:string title:string content:text NOTE. While scaffolding will get you up and running quickly, the "one size fits all" code that it generates is unlikely to be a perfect fit for your application. In most cases, you'll need to customize the generated code. Many experienced Rails developers avoid scaffolding entirely, preferring to write all or most of their source code from scratch. -The scaffold generator will build 14 files in your application, along with some folders, and edit one more. Here's a quick overview of what it creates: - -|_.File |_.Purpose| -|app/models/post.rb |The Post model| -|db/migrate/20090113124235_create_posts.rb |Migration to create the posts table in your database (your name will include a different timestamp)| -|app/views/posts/index.html.erb |A view to display an index of all posts | -|app/views/posts/show.html.erb |A view to display a single post| -|app/views/posts/new.html.erb |A view to create a new post| -|app/views/posts/edit.html.erb |A view to edit an existing post| -|app/views/layouts/posts.html.erb |A view to control the overall look and feel of the other posts views| -|public/stylesheets/scaffold.css |Cascading style sheet to make the scaffolded views look better| -|app/controllers/posts_controller.rb |The Posts controller| -|test/functional/posts_controller_test.rb |Functional testing harness for the posts controller| -|app/helpers/posts_helper.rb |Helper functions to be used from the posts views| -|config/routes.rb |Edited to include routing information for posts| -|test/fixtures/posts.yml |Dummy posts for use in testing| -|test/unit/post_test.rb |Unit testing harness for the posts model| -|test/unit/helpers/posts_helper_test.rb |Unit testing harness for the posts helper| +The scaffold generator will build 15 files in your application, along with some folders, and edit one more. Here's a quick overview of what it creates: + +|_.File |_.Purpose| +|db/migrate/20100207214725_create_posts.rb.rb |Migration to create the posts table in your database (your name will include a different timestamp)| +|app/models/post.rb |The Post model| +|test/unit/post_test.rb |Unit testing harness for the posts model| +|test/fixtures/posts.yml |Dummy posts for use in testing| +|app/controllers/posts_controller.rb |The Posts controller| +|app/views/posts/index.html.erb |A view to display an index of all posts | +|app/views/posts/edit.html.erb |A view to edit an existing post| +|app/views/posts/show.html.erb |A view to display a single post| +|app/views/posts/new.html.erb |A view to create a new post| +|app/views/posts/_form.html.erb |A view to control the overall look and feel of the other posts views| +|app/views/layouts/posts.html.erb |A view to control the overall look and feel of the other posts views| +|test/functional/posts_controller_test.rb |Functional testing harness for the posts controller| +|app/helpers/posts_helper.rb |Helper functions to be used from the posts views| +|config/routes.rb |Edited to include routing information for posts| +|test/unit/helpers/posts_helper_test.rb |Unit testing harness for the posts helper| +|public/stylesheets/scaffold.css |Cascading style sheet to make the scaffolded views look better| h4. Running a Migration One of the products of the +rails generate scaffold+ command is a _database migration_. 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/20090113124235_create_posts.rb+ file (remember, yours will have a slightly different name), here's what you'll find: +If you look in the +db/migrate/20100207214725_create_posts.rb+ file (remember, yours will have a slightly different name), here's what you'll find: <ruby> class CreatePosts < ActiveRecord::Migration @@ -371,7 +395,7 @@ class CreatePosts < ActiveRecord::Migration end </ruby> -If you were to translate that into words, it says something like: when this migration is run, create a table named +posts+ with two string columns (+name+ and +title+) and a text column (+content+), and generate timestamp fields to track record creation and updating. You can learn the detailed syntax for migrations in the "Rails Database Migrations":migrations.html guide. +The above migration creates two methods, +up+, called when you run this migration into the database, and +down+ in case you need to reverse the changes made by this migration at a later date. The +up+ command in this case creates a +posts+ table with two string columns and a text column. It also is creating two timestamp fields to track record creation and updating. More information about Rails migrations can be found in the "Rails Database Migrations":migrations.html guide. At this point, you can use a rake command to run the migration: @@ -379,7 +403,14 @@ At this point, you can use a rake command to run the migration: $ rake db:migrate </shell> -Remember, you can't run migrations before running +rake db:create+ to create your database, as we covered earlier. +Rails will execute this migration command and tell you it created the Posts table. + +<shell> +== CreatePosts: migrating ==================================================== +-- create_table(:posts) + -> 0.0019s +== CreatePosts: migrated (0.0020s) =========================================== +</shell> 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. @@ -396,7 +427,7 @@ The +link_to+ method is one of Rails' built-in view helpers. It creates a hyperl h4. Working with Posts in the Browser -Now you're ready to start working with posts. To do that, navigate to +http://localhost:3000+ and then click the "My Blog" link: +Now you're ready to start working with posts. To do that, navigate to "http://localhost:3000":http://localhost:3000/ and then click the "My Blog" link: !images/posts_index.png(Posts Index screenshot)! @@ -423,8 +454,9 @@ Rails includes methods to help you validate the data that you send to models. Op <ruby> class Post < ActiveRecord::Base - validates_presence_of :name, :title - validates_length_of :title, :minimum => 5 + validates :name, :presence => true + validates :title, :presence => true, + :length => { :minimum => 5 } end </ruby> @@ -442,15 +474,15 @@ After the console loads, you can use it to work with your application's models: <shell> >> p = Post.create(:content => "A new post") -=> #<Post id: nil, name: nil, title: nil, content: "A new post", -created_at: nil, updated_at: nil> +=> #<Post id: nil, name: nil, title: nil, + content: "A new post", created_at: nil, + updated_at: nil> >> p.save => false >> p.errors -=> #<ActiveRecord::Errors:0x23bcf0c @base=#<Post id: nil, name: nil, -title: nil, content: "A new post", created_at: nil, updated_at: nil>, -@errors={"name"=>["can't be blank"], "title"=>["can't be blank", -"is too short (minimum is 5 characters)"]}> +=> #<OrderedHash { :title=>["can't be blank", + "is too short (minimum is 5 characters)"], + :name=>["can't be blank"] }> </shell> This code shows creating a new +Post+ instance, attempting to save it and getting +false+ for a return value (indicating that the save failed), and inspecting the +errors+ of the post. @@ -472,11 +504,11 @@ def index end </ruby> -This code sets the +@posts+ instance variable to an array of all posts in the database. +Post.find(:all)+ or +Post.all+ calls the +Post+ model to return all of the posts that are currently in the database, with no limiting conditions. +This code sets the +@posts+ instance variable to an array of all posts in the database. +Post.all+ calls the +Post+ model to return all of the posts that are currently in the database, with no limiting conditions. TIP: For more information on finding records with Active Record, see "Active Record Query Interface":active_record_querying.html. -The +respond_to+ block handles both HTML and XML calls to this action. If you browse to +http://localhost:3000/posts.xml+, you'll see all of the posts in XML format. The HTML format looks for a view in +app/views/posts/+ with a name that corresponds to the action name. Rails makes all of the instance variables from the action available to the view. Here's +app/views/posts/index.html.erb+: +The +respond_to+ block handles both HTML and XML calls to this action. If you browse to "http://localhost:3000/posts.xml":http://localhost:3000/posts.xml, you'll see all of the posts in XML format. The HTML format looks for a view in +app/views/posts/+ with a name that corresponds to the action name. Rails makes all of the instance variables from the action available to the view. Here's +app/views/posts/index.html.erb+: <erb> <h1>Listing posts</h1> @@ -486,17 +518,19 @@ The +respond_to+ block handles both HTML and XML calls to this action. If you br <th>Name</th> <th>Title</th> <th>Content</th> + <th></th> + <th></th> + <th></th> </tr> <% @posts.each do |post| %> <tr> - <td><%=h post.name %></td> - <td><%=h post.title %></td> - <td><%=h post.content %></td> + <td><%= post.name %></td> + <td><%= post.title %></td> + <td><%= post.content %></td> <td><%= link_to 'Show', post %></td> <td><%= link_to 'Edit', edit_post_path(post) %></td> - <td><%= link_to 'Destroy', post, :confirm => 'Are you sure?', - :method => :delete %></td> + <td><%= link_to 'Destroy', post, :confirm => 'Are you sure?', :method => :delete %></td> </tr> <% end %> </table> @@ -508,10 +542,11 @@ The +respond_to+ block handles both HTML and XML calls to this action. If you br This view iterates over the contents of the +@posts+ array to display content and links. A few things to note in the view: -* +h+ is a Rails helper method to sanitize displayed data, preventing cross-site scripting attacks * +link_to+ builds a hyperlink to a particular destination * +edit_post_path+ is a helper that Rails provides as part of RESTful routing. You'll see a variety of these helpers for the different actions that the controller includes. +NOTE. In previous versions of Rails, you had to use +<%=h post.name %>+ so that any HTML would be escaped before being inserted into the page. In Rails 3.0, this is now the default. To get unescaped HTML, you now use +<%= raw post.name %>+. + TIP: For more details on the rendering process, see "Layouts and Rendering in Rails":layouts_and_rendering.html. h4. Customizing the Layout @@ -519,21 +554,17 @@ h4. Customizing the Layout The view is only part of the story of how HTML is displayed in your web browser. Rails also has the concept of +layouts+, which are containers for views. When Rails renders a view to the browser, it does so by putting the view's HTML into a layout's HTML. The +rails generate scaffold+ command automatically created a default layout, +app/views/layouts/posts.html.erb+, for the posts. Open this layout in your editor and modify the +body+ tag: <erb> -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" - "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> - -<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> +<!DOCTYPE html> +<html> <head> - <meta http-equiv="content-type" - content="text/html;charset=UTF-8" /> <title>Posts: <%= controller.action_name %></title> <%= stylesheet_link_tag 'scaffold' %> </head> <body style="background: #EEEEEE;"> -<p style="color: green"><%= flash[:notice] %></p> +<p class="notice"><%= notice %></p> -<%= yield %> +<%= yield %> </body> </html> @@ -561,34 +592,48 @@ The +new.html.erb+ view displays this empty Post to the user: <erb> <h1>New post</h1> +<%= render 'form' %> + +<%= link_to 'Back', posts_path %> +</erb> + +The +<%= render 'form' %>+ line is our first introduction to _partials_ in Rails. A partial is a snippet of HTML and Ruby code that can be reused in multiple locations. In this case, the form used to make a new post, is basically identical to a form used to edit a post, both have text fields for the name and title and a text area for the content with a button to make a new post or update the existing post. + +If you take a look at +views/posts/_form.html.erb+ file, you will see the following: + +<erb> <% form_for(@post) do |f| %> <%= f.error_messages %> - <p> + <div class="field"> <%= f.label :name %><br /> <%= f.text_field :name %> - </p> - <p> + </div> + <div class="field"> <%= f.label :title %><br /> <%= f.text_field :title %> - </p> - <p> + </div> + <div class="field"> <%= f.label :content %><br /> <%= f.text_area :content %> - </p> - <p> - <%= f.submit "Create" %> - </p> + </div> + <div class="actions"> + <%= f.submit %> + </div> <% end %> - -<%= link_to 'Back', posts_path %> </erb> +This partial receives all the instance variables defined in the calling view file, so in this case, the controller assigned the new Post object to +@post+ and so, this is available in both the view and partial as +@post+. + +For more information on partials, refer to the "Layouts and Rendering in Rails":layouts_and_rendering.html#using-partials guide. + The +form_for+ block is used to create an HTML form. Within this block, you have access to methods to build various controls on the form. For example, +f.text_field :name+ tells Rails to create a text input on the form, and to hook it up to the +name+ attribute of the instance being displayed. You can only use these methods with attributes of the model that the form is based on (in this case +name+, +title+, and +content+). Rails uses +form_for+ in preference to having you write raw HTML because the code is more succinct, and because it explicitly ties the form to a particular model instance. +The +form_for+ block is also smart enough to work out if you are doing a _New Post_ or an _Edit Post_ action, and will set the form +action+ tags and submit button names appropriately in the HTML output. + TIP: If you need to create an HTML form that displays arbitrary fields, not tied to a model, you should use the +form_tag+ method, which provides shortcuts for building forms that are not necessarily tied to a model instance. -When the user clicks the +Create+ button on this form, the browser will send information back to the +create+ method of the controller (Rails knows to call the +create+ method because the form is sent with an HTTP POST request; that's one of the conventions that I mentioned earlier): +When the user clicks the +Create Post+ button on this form, the browser will send information back to the +create+ method of the controller (Rails knows to call the +create+ method because the form is sent with an HTTP POST request; that's one of the conventions that I mentioned earlier): <ruby> def create @@ -596,22 +641,24 @@ def create respond_to do |format| if @post.save - flash[:notice] = 'Post was successfully created.' - format.html { redirect_to(@post) } - format.xml { render :xml => @post, :status => :created, - :location => @post } + format.html { redirect_to(@post, + :notice => 'Post was successfully created.') } + format.xml { render :xml => @post, + :status => :created, :location => @post } else format.html { render :action => "new" } format.xml { render :xml => @post.errors, - :status => :unprocessable_entity } + :status => :unprocessable_entity } end end end </ruby> -The +create+ action instantiates a new Post object from the data supplied by the user on the form, which Rails makes available in the +params+ hash. After saving the new post, it uses +flash[:notice]+ to create an informational message for the user, and redirects to the show action for the post. If there's any problem, the +create+ action just shows the +new+ view a second time, with any error messages. +The +create+ action instantiates a new Post object from the data supplied by the user on the form, which Rails makes available in the +params+ hash. After successfully saving the new post, returns the appropriate format that the user has requested (HTML in our case). It then redirects the user to the resulting post +show+ action and sets a notice to the user that the Post was successfully created. + +If the post was not successfully saved, due to a validation error, then the controller returns the user back to the +new+ action with any error messages so that the user has the chance to fix the error and try again. -Rails provides the +flash+ hash (usually just called the Flash) so that messages can be carried over to another action, providing the user with useful information on the status of their request. In the case of +create+, the user never actually sees any page rendered during the Post creation process, because it immediately redirects to the new Post as soon Rails saves the record. The Flash carries over a message to the next action, so that when the user is redirected back to the +show+ action, they are presented with a message saying "Post was successfully created." +The "Post was successfully created" message is stored inside of the Rails +flash+ hash, (usually just called the Flash) so that messages can be carried over to another action, providing the user with useful information on the status of their request. In the case of +create+, the user never actually sees any page rendered during the Post creation process, because it immediately redirects to the new Post as soon Rails saves the record. The Flash carries over a message to the next action, so that when the user is redirected back to the +show+ action, they are presented with a message saying "Post was successfully created." h4. Showing an Individual Post @@ -633,17 +680,17 @@ The +show+ action uses +Post.find+ to search for a single record in the database <erb> <p> <b>Name:</b> - <%=h @post.name %> + <%= @post.name %> </p> <p> <b>Title:</b> - <%=h @post.title %> + <%= @post.title %> </p> <p> <b>Content:</b> - <%=h @post.content %> + <%= @post.content %> </p> @@ -666,30 +713,15 @@ After finding the requested post, Rails uses the +edit.html.erb+ view to display <erb> <h1>Editing post</h1> -<% form_for(@post) do |f| %> - <%= f.error_messages %> - - <p> - <%= f.label :name %><br /> - <%= f.text_field :name %> - </p> - <p> - <%= f.label :title %><br /> - <%= f.text_field :title %> - </p> - <p> - <%= f.label :content %><br /> - <%= f.text_area :content %> - </p> - <p> - <%= f.submit "Update" %> - </p> -<% end %> +<%= render 'form' %> <%= link_to 'Show', @post %> | <%= link_to 'Back', posts_path %> +<% end %> </erb> +Again, as with the +new+ action, the +edit+ action is using the +form+ partial, this time however, the form will do a PUT action to the PostsController and the submit button will display "Update Post" + Submitting the form created by this view will invoke the +update+ action within the controller: <ruby> @@ -698,13 +730,13 @@ def update respond_to do |format| if @post.update_attributes(params[:post]) - flash[:notice] = 'Post was successfully updated.' - format.html { redirect_to(@post) } + format.html { redirect_to(@post, + :notice => 'Post was successfully updated.') } format.xml { head :ok } else format.html { render :action => "edit" } format.xml { render :xml => @post.errors, - :status => :unprocessable_entity } + :status => :unprocessable_entity } end end end @@ -712,8 +744,6 @@ end In the +update+ action, Rails first uses the +:id+ parameter passed back from the edit view to locate the database record that's being edited. The +update_attributes+ call then takes the rest of the parameters from the request and applies them to this record. If all goes well, the user is redirected to the post's +show+ view. If there are any problems, it's back to +edit+ to correct them. -NOTE. Sharp-eyed readers will have noticed that the +form_for+ declaration is identical for the +new+ and +edit+ views. Rails generates different code for the two forms because it's smart enough to notice that in the one case it's being passed a new record that has never been saved, and in the other case an existing record that has already been saved to the database. In a production Rails application, you would ordinarily eliminate this duplication by moving identical code to a _partial template_, which you could then include in both parent templates. But the scaffold generator tries not to make too many assumptions, and generates code that's easy to modify if you want different forms for +create+ and +edit+. - h4. Destroying a Post Finally, clicking one of the +destroy+ links sends the associated id to the +destroy+ action: @@ -732,124 +762,6 @@ end The +destroy+ method of an Active Record model instance removes the corresponding record from the database. After that's done, there isn't any record to display, so Rails redirects the user's browser to the index view for the model. -h3. DRYing up the Code - -At this point, it's worth looking at some of the tools that Rails provides to eliminate duplication in your code. In particular, you can use _partials_ to clean up duplication in views and _filters_ to help with duplication in controllers. - -h4. Using Partials to Eliminate View Duplication - -As you saw earlier, the scaffold-generated views for the +new+ and +edit+ actions are largely identical. You can pull the shared code out into a partial template. This requires editing the new and edit views, and adding a new template. The new +_form.html.erb+ template should be saved in the same +app/views/posts+ folder as the files from which it is being extracted. Note that the name of this file begins with an underscore; that's the Rails naming convention for partial templates. - -<tt>new.html.erb</tt>: - -<erb> -<h1>New post</h1> - -<%= render :partial => "form" %> - -<%= link_to 'Back', posts_path %> -</erb> - -<tt>edit.html.erb</tt>: - -<erb> -<h1>Editing post</h1> - -<%= render :partial => "form" %> - -<%= link_to 'Show', @post %> | -<%= link_to 'Back', posts_path %> -</erb> - -<tt>_form.html.erb</tt>: - -<erb> -<% form_for(@post) do |f| %> - <%= f.error_messages %> - - <p> - <%= f.label :name %><br /> - <%= f.text_field :name %> - </p> - <p> - <%= f.label :title, "title" %><br /> - <%= f.text_field :title %> - </p> - <p> - <%= f.label :content %><br /> - <%= f.text_area :content %> - </p> - <p> - <%= f.submit "Save" %> - </p> -<% end %> -</erb> - -Now, when Rails renders the +new+ or +edit+ view, it will insert the +_form+ partial at the indicated point. Note the naming convention for partials: if you refer to a partial named +form+ inside of a view, the corresponding file is +_form.html.erb+, with a leading underscore. - -For more information on partials, refer to the "Layouts and Rendering in Rails":layouts_and_rendering.html#using-partials guide. - -h4. Using Filters to Eliminate Controller Duplication - -At this point, if you look at the controller for posts, you'll see some duplication: - -<ruby> -class PostsController < ApplicationController - # ... - def show - @post = Post.find(params[:id]) - # ... - end - - def edit - @post = Post.find(params[:id]) - end - - def update - @post = Post.find(params[:id]) - # ... - end - - def destroy - @post = Post.find(params[:id]) - # ... - end -end -</ruby> - -Four instances of the exact same line of code doesn't seem very DRY. Rails provides _filters_ as a way to address this sort of repeated code. In this case, you can DRY things up by using a +before_filter+: - -<ruby> -class PostsController < ApplicationController - before_filter :find_post, - :only => [:show, :edit, :update, :destroy] - # ... - def show - # ... - end - - def edit - end - - def update - # ... - end - - def destroy - # ... - end - -private - def find_post - @post = Post.find(params[:id]) - end -end -</ruby> - -Rails runs _before filters_ before any action in the controller. You can use the +:only+ clause to limit a before filter to only certain actions, or an +:except+ clause to specifically skip a before filter for certain actions. Rails also allows you to define _after filters_ that run after processing an action, as well as _around filters_ that surround the processing of actions. Filters can also be defined in external classes to make it easy to share them between controllers. - -For more information on filters, see the "Action Controller Overview":action_controller_overview.html guide. - h3. Adding a Second Model Now that you've seen what's in a model built with scaffolding, it's time to add a second model to the application. The second model will handle comments on blog posts. @@ -859,14 +771,13 @@ h4. Generating a Model Models in Rails use a singular name, and their corresponding database tables use a plural name. For the model to hold comments, the convention is to use the name Comment. Even if you don't want to use the entire apparatus set up by scaffolding, most Rails developers still use generators to make things like models and controllers. To create the new model, run this command in your terminal: <shell> -$ rails generate model Comment commenter:string body:text - post:references +$ rails generate model Comment commenter:string body:text post:references </shell> This command will generate four files: * +app/models/comment.rb+ - The model -* +db/migrate/20091013214407_create_comments.rb+ - The migration +* +db/migrate/20100207235629_create_comments.rb+ - The migration * +test/unit/comment_test.rb+ and +test/fixtures/comments.yml+ - The test harness. First, take a look at +comment.rb+: @@ -905,7 +816,14 @@ The +t.references+ line sets up a foreign key column for the association between $ rake db:migrate </shell> -Rails is smart enough to only execute the migrations that have not already been run against the current database. +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: + +<shell> +== CreateComments: migrating ================================================= +-- create_table(:comments) + -> 0.0017s +== CreateComments: migrated (0.0018s) ======================================== +</shell> h4. Associating Models @@ -926,8 +844,10 @@ You'll need to edit the +post.rb+ file to add the other side of the association: <ruby> class Post < ActiveRecord::Base - validates_presence_of :name, :title - validates_length_of :title, :minimum => 5 + validates :name, :presence => true + validates :title, :presence => true, + :length => { :minimum => 5 } + has_many :comments end </ruby> @@ -936,12 +856,14 @@ These two declarations enable a good bit of automatic behavior. For example, if TIP: For more information on Active Record associations, see the "Active Record Associations":association_basics.html guide. -h4. Adding a Route +h4. Adding a Route for Comments -_Routes_ are entries in the +config/routes.rb+ file that tell Rails how to match incoming HTTP requests to controller actions. Open up that file and find the existing line referring to +posts+ (it will be right at the top of the file). Then edit it as follows: +As with the +home+ 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, you will see an entry that was added automatically for +posts+ near the top by the scaffold generator, +resources :posts+, edit it as follows: <ruby> -map.resources :posts, :has_many => :comments +resources :posts do + resources :comments +end </ruby> This creates +comments+ as a _nested resource_ within +posts+. This is another part of capturing the hierarchical relationship that exists between posts and comments. @@ -953,249 +875,300 @@ h4. Generating a Controller With the model in hand, you can turn your attention to creating a matching controller. Again, there's a generator for this: <shell> -$ rails generate controller Comments index show new edit +$ rails generate controller Comments </shell> -This creates eight files: +This creates four files: * +app/controllers/comments_controller.rb+ - The controller * +app/helpers/comments_helper.rb+ - A view helper file -* +app/views/comments/index.html.erb+ - The view for the index action -* +app/views/comments/show.html.erb+ - The view for the show action -* +app/views/comments/new.html.erb+ - The view for the new action -* +app/views/comments/edit.html.erb+ - The view for the edit action * +test/functional/comments_controller_test.rb+ - The functional tests for the controller * +test/unit/helpers/comments_helper_test.rb+ - The unit tests for the helper -The controller will be generated with empty methods and views for each action that you specified in the call to +rails generate controller+: +Like with any blog, our readers will create their comments directly after reading the post, and once they have added their comment, will be sent back to the post 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. -<ruby> -class CommentsController < ApplicationController - def index - end - - def show - end - - def new - end +So first, we'll wire up the Post show template (+/app/views/posts/show.html.erb+) to let us make a new comment: - def edit - end +<erb> +<p> + <b>Name:</b> + <%= @post.name %> +</p> -end -</ruby> +<p> + <b>Title:</b> + <%= @post.title %> +</p> -You'll need to flesh this out with code to actually process requests appropriately in each method. Here's a version that (for simplicity's sake) only responds to requests that require HTML: +<p> + <b>Content:</b> + <%= @post.content %> +</p> -<ruby> -class CommentsController < ApplicationController - before_filter :find_post +<h2>Add a comment:</h2> +<% form_for([@post, @post.comments.build]) do |f| %> + <%= f.error_messages %> - def index - @comments = @post.comments - end + <div class="field"> + <%= f.label :commenter %><br /> + <%= f.text_field :commenter %> + </div> + <div class="field"> + <%= f.label :body %><br /> + <%= f.text_area :body %> + </div> + <div class="actions"> + <%= f.submit %> + </div> +<% end %> - def show - @comment = @post.comments.find(params[:id]) - end +<%= link_to 'Edit Post', edit_post_path(@post) %> | +<%= link_to 'Back to Posts', posts_path %> | +</erb> - def new - @comment = @post.comments.build - end +This adds a form on the Post show page that creates a new comment, which will call the +CommentsController+ +create+ action, so let's wire that up: +<ruby> +class CommentsController < ApplicationController def create - @comment = @post.comments.build(params[:comment]) - if @comment.save - redirect_to post_comment_url(@post, @comment) - else - render :action => "new" - end - end - - def edit - @comment = @post.comments.find(params[:id]) - end - - def update - @comment = Comment.find(params[:id]) - if @comment.update_attributes(params[:comment]) - redirect_to post_comment_url(@post, @comment) - else - render :action => "edit" - end - end - - def destroy - @comment = Comment.find(params[:id]) - @comment.destroy - redirect_to post_comments_path(@post) - end - -private - def find_post @post = Post.find(params[:post_id]) + @comment = @post.comments.create(params[:comment]) + redirect_to post_path(@post) end - end </ruby> -You'll see a bit more complexity here than you did in the controller for posts. That's a side-effect of the nesting that you've set up; each request for a comment has to keep track of the post to which the comment is attached. +You'll see a bit more complexity here than you did in the controller for posts. That's a side-effect of the nesting that you've set up; each request for a comment has to keep track of the post to which the comment is attached, thus the initial find action to the Post model to get the post in question. In addition, the code takes advantage of some of the methods available for an association. For example, in the +new+ method, it calls -<ruby> -@comment = @post.comments.build -</ruby> - -This creates a new +Comment+ object _and_ sets up the +post_id+ field to have the +id+ from the specified +Post+ object in a single operation. - -h4. Building Views - -Because you skipped scaffolding, you'll need to build views for comments "by hand". Invoking +rails generate controller+ will give you skeleton views, but they'll be devoid of actual content. Here's a first pass at fleshing out the comment views. - -The +views/comments/index.html.erb+ view: +Once we have made the new comment, we send the user back to the +post_path(@post)+ URL. This runs the +show+ action of the +PostsController+ which then renders the +show.html.erb+ template where we want the comment to show, so then, we'll add that to the +app/view/posts/show.html.erb+. <erb> -<h1>Comments for <%= @post.title %></h1> - -<table> - <tr> - <th>Commenter</th> - <th>Body</th> - </tr> - -<% for comment in @comments %> - <tr> - <td><%=h comment.commenter %></td> - <td><%=h comment.body %></td> - <td><%= link_to 'Show', post_comment_path(@post, comment) %></td> - <td> - <%= link_to 'Edit', edit_post_comment_path(@post, comment) %> - </td> - <td> - <%= link_to 'Destroy', post_comment_path(@post, comment), - :confirm => 'Are you sure?', :method => :delete %> - </td> - </tr> -<% end %> -</table> +<p> + <b>Name:</b> + <%= @post.name %> +</p> -<br /> +<p> + <b>Title:</b> + <%= @post.title %> +</p> -<%= link_to 'New comment', new_post_comment_path(@post) %> -<%= link_to 'Back to Post', @post %> -</erb> +<p> + <b>Content:</b> + <%= @post.content %> +</p> -The +views/comments/new.html.erb+ view: +<h2>Comments</h2> +<% @post.comments.each do |comment| %> + <p> + <b>Commenter:</b> + <%= comment.commenter %> + </p> -<erb> -<h1>New comment</h1> + <p> + <b>Comment:</b> + <%= comment.body %> + </p> +<% end %> -<% form_for([@post, @comment]) do |f| %> +<h2>Add a comment:</h2> +<% form_for([@post, @post.comments.build]) do |f| %> <%= f.error_messages %> - <p> + <div class="field"> <%= f.label :commenter %><br /> <%= f.text_field :commenter %> - </p> - <p> + </div> + <div class="field"> <%= f.label :body %><br /> <%= f.text_area :body %> - </p> - <p> - <%= f.submit "Create" %> - </p> + </div> + <div class="actions"> + <%= f.submit %> + </div> <% end %> -<%= link_to 'Back', post_comments_path(@post) %> +<br /> + +<%= link_to 'Edit Post', edit_post_path(@post) %> | +<%= link_to 'Back to Posts', posts_path %> | </erb> -The +views/comments/show.html.erb+ view: +Now you can add posts and comments to your blog and have them show up in the right places. -<erb> -<h1>Comment on <%= @post.title %></h1> +h3. Refactorization + +Now that we have Posts and Comments working, we can take a look at the +app/views/posts/show.html.erb+ template, it is getting long and awkward, we can use partials to clean this up. + +h4. Rendering Partial Collections + +First will make a comment partial to extract showing all the comments for the post, so make a file +app/views/comments/_comment.html.erb+ and put into it: +<erb> <p> <b>Commenter:</b> - <%=h @comment.commenter %> + <%= comment.commenter %> </p> <p> <b>Comment:</b> - <%=h @comment.body %> + <%= comment.body %> </p> - -<%= link_to 'Edit', edit_post_comment_path(@post, @comment) %> | -<%= link_to 'Back', post_comments_path(@post) %> </erb> -The +views/comments/edit.html.erb+ view: +Then in the +app/views/posts/show.html.erb+ you can change it to look like the following: <erb> -<h1>Editing comment</h1> +<p> + <b>Name:</b> + <%= @post.name %> +</p> + +<p> + <b>Title:</b> + <%= @post.title %> +</p> + +<p> + <b>Content:</b> + <%= @post.content %> +</p> + +<h2>Comments</h2> +<%= render :partial => "comments/comment", + :collection => @post.comments %> -<% form_for([@post, @comment]) do |f| %> +<h2>Add a comment:</h2> +<% form_for([@post, @post.comments.build]) do |f| %> <%= f.error_messages %> - <p> + <div class="field"> <%= f.label :commenter %><br /> <%= f.text_field :commenter %> - </p> - <p> + </div> + <div class="field"> <%= f.label :body %><br /> <%= f.text_area :body %> - </p> - <p> - <%= f.submit "Update" %> - </p> + </div> + <div class="actions"> + <%= f.submit %> + </div> <% end %> -<%= link_to 'Show', post_comment_path(@post, @comment) %> | -<%= link_to 'Back', post_comments_path(@post) %> +<br /> + +<%= link_to 'Edit Post', edit_post_path(@post) %> | +<%= link_to 'Back to Posts', posts_path %> | </erb> -Again, the added complexity here (compared to the views you saw for managing posts) comes from the necessity of juggling a post and its comments at the same time. +This will now render the partial in +app/views/comments/_comment.html.erb+ once for each comment that is in the +@post.comments+ collection. As the +render+ method iterates over the <tt>@post.comments</tt> 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. -h4. Hooking Comments to Posts +h4. Rendering a Partial Form -As a next step, I'll modify the +views/posts/show.html.erb+ view to show the comments on that post, and to allow managing those comments: +Lets also move that new comment section out to it's own partial, again, you create a file +app/views/comments/_form.html.erb+ and in it you put: + +<erb> +<% form_for([@post, @post.comments.build]) do |f| %> + <%= f.error_messages %> + + <div class="field"> + <%= f.label :commenter %><br /> + <%= f.text_field :commenter %> + </div> + <div class="field"> + <%= f.label :body %><br /> + <%= f.text_area :body %> + </div> + <div class="actions"> + <%= f.submit %> + </div> +<% end %> +</erb> + +Then you make the +app/views/posts/show.html.erb+ look like the following: <erb> <p> <b>Name:</b> - <%=h @post.name %> + <%= @post.name %> </p> <p> <b>Title:</b> - <%=h @post.title %> + <%= @post.title %> </p> <p> <b>Content:</b> - <%=h @post.content %> + <%= @post.content %> </p> <h2>Comments</h2> -<% @post.comments.each do |c| %> - <p> - <b>Commenter:</b> - <%=h c.commenter %> - </p> +<%= render :partial => "comments/comment", + :collection => @post.comments %> - <p> - <b>Comment:</b> - <%=h c.body %> - </p> -<% end %> +<h2>Add a comment:</h2> +<%= render "comments/form" %> + +<br /> <%= link_to 'Edit Post', edit_post_path(@post) %> | <%= link_to 'Back to Posts', posts_path %> | -<%= link_to 'Manage Comments', post_comments_path(@post) %> </erb> -Note that each post has its own individual comments collection, accessible as +@post.comments+. That's a consequence of the declarative associations in the models. Path helpers such as +post_comments_path+ come from the nested route declaration in +config/routes.rb+. +The second render just defines the partial template we want to render, <tt>comments/form</tt>, Rails is smart enough to spot the forward slash in that string and realise that you want to render the <tt>_form.html.erb</tt> file in the <tt>app/views/comments</tt> directory. + +The +@post+ object is available any partials rendered in the view because we defined it as an instance variable. + +h3. Deleting Comments + +Another important feature on 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 +DELETE+ action in the +CommentsController+. + +So first, let's add the delete link in the +app/views/comments/_comment.html.erb+ partial: + +<erb> +<p> + <b>Commenter:</b> + <%= comment.commenter %> +</p> + +<p> + <b>Comment:</b> + <%= comment.body %> +</p> + +<p> + <%= link_to 'Destroy Comment', [comment.post, comment], + :confirm => 'Are you sure?', + :method => :delete %> +</p> +</erb> + +Clicking this new "Destroy Comment" link will fire off a <tt>DELETE /posts/:id/comments/:id</tt> 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: + +<ruby> +class CommentsController < ApplicationController + + def create + @post = Post.find(params[:post_id]) + @comment = @post.comments.create(params[:comment]) + redirect_to post_path(@post) + end + + def destroy + @post = Post.find(params[:post_id]) + @comment = @post.comments.find(params[:id]) + @comment.destroy + redirect_to post_path(@post) + end + +end +</ruby> + +The +destroy+ action will find the post we are looking at, locate the comment within the <tt>@post.comments</tt> collection, and then remove it from the database and send us back to the show action for the post. + h4. Deleting Associated Objects @@ -1203,21 +1176,81 @@ If you decide at some point to delete a post, you likely want to delete the comm <ruby> class Post < ActiveRecord::Base - validates_presence_of :name, :title - validates_length_of :title, :minimum => 5 + validates :name, :presence => true + validates :title, :presence => true, + :length => { :minimum => 5 } has_many :comments, :dependent => :destroy end -</ruby> +</ruby> + +h3. Security + +Before you publish your blog online, you will most likely want to prevent just anyone from being able to add, edit and delete posts or delete comments. + +Rails provides a very simple http authentication system that will work nicely in this situation. First, we enable simple HTTP based authentication in our <tt>app/controllers/application_controller.rb</tt>: + +<ruby> +class ApplicationController < ActionController::Base + protect_from_forgery + + private + + def authenticate + authenticate_or_request_with_http_basic do |user_name, password| + user_name == 'admin' && password == 'password' + end + end + +end +</ruby> + +You can obviously change the username and password to whatever you want. We put this method inside of +ApplicationController+ so that it is available to all of our controllers. + +Then in the +PostsController+ 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 <tt>before_filter</tt> method, which allows us to specify that Rails must run a method and only then allow access to the requested action if that method allows it. + +To use the before filter, we specify it at the top of our +PostsController+, in this case, we want the user to be authenticated on every action, except for +index+ and +show+, so we write that: + +<ruby> +class PostsController < ApplicationController + + before_filter :authenticate, :except => [:index, :show] + + # GET /posts + # GET /posts.xml + def index + @posts = Post.all + respond_to do |format| +# snipped for brevity +</ruby> + +We also only want to allow authenticated users to delete comments, so in the +CommentsController+ we write: + +<ruby> +class CommentsController < ApplicationController + + before_filter :authenticate, :only => :destroy + + def create + @post = Post.find(params[:post_id]) +# snipped for brevity +</ruby> + +Now if you try to create a new post, you will be greeted with a basic HTTP Authentication challenge + +!images/challenge.png(Basic HTTP Authentication Challenge)! + h3. Building a Multi-Model Form -Comments and posts are edited on two separate forms - which makes sense, given the flow of this mini-application. But what if you want to edit more than one thing on a single form? Rails 2.3 offers new support for nested forms. Let's add support for giving each post multiple tags, right in the form where you create the post. First, create a new model to hold the tags: +Another piece of your average blog is the ability to tag posts. This requires that your application edits more than one thing on a single form. Rails offers support for nested forms. + +To demonstrate this, we will add support for giving each post multiple tags, right in the form where you create the post. First, create a new model to hold the tags: <shell> $ rails generate model tag name:string post:references </shell> -Run the migration to create the database table: +Again, run the migration to create the database table: <shell> $ rake db:migrate @@ -1227,9 +1260,11 @@ Next, edit the +post.rb+ file to create the other side of the association, and t <ruby> class Post < ActiveRecord::Base - validates_presence_of :name, :title - validates_length_of :title, :minimum => 5 - has_many :comments + validates :name, :presence => true + validates :title, :presence => true, + :length => { :minimum => 5 } + + has_many :comments, :dependent => :destroy has_many :tags accepts_nested_attributes_for :tags, :allow_destroy => :true, @@ -1239,54 +1274,150 @@ end The +:allow_destroy+ option on the nested attribute declaration tells Rails to display a "remove" checkbox on the view that you'll build shortly. The +:reject_if+ option prevents saving new tags that do not have any attributes filled in. -You'll also need to modify +views/posts/_form.html.erb+ to include the tags: +We will modify +views/posts/_form.html.erb+ to render a partial to make a tag: <erb> -<% @post.tags.build if @post.tags.empty? %> +<% @post.tags.build %> <% form_for(@post) do |post_form| %> <%= post_form.error_messages %> - <p> + <div class="field"> <%= post_form.label :name %><br /> <%= post_form.text_field :name %> - </p> - <p> - <%= post_form.label :title, "Title" %><br /> + </div> + <div class="field"> + <%= post_form.label :title %><br /> <%= post_form.text_field :title %> - </p> - <p> + </div> + <div class="field"> <%= post_form.label :content %><br /> <%= post_form.text_area :content %> - </p> + </div> <h2>Tags</h2> - <% post_form.fields_for :tags do |tag_form| %> - <p> - <%= tag_form.label :name, 'Tag:' %> - <%= tag_form.text_field :name %> - </p> - <% unless tag_form.object.nil? || tag_form.object.new_record? %> - <p> - <%= tag_form.label :_delete, 'Remove:' %> - <%= tag_form.check_box :_delete %> - </p> - <% end %> - <% end %> + <%= render :partial => 'tags/form', + :locals => {:form => post_form} %> + <div class="actions"> + <%= post_form.submit %> + </div> +<% end %> +</erb> - <p> - <%= post_form.submit "Save" %> - </p> +This example shows another option of the render helper, being able to pass in local variables, in this case, we want the local variable +form+ in the partial to refer to the +post_form+ object. + +You will also note that we also have changed the +f+ in <tt>form_for(@post) do |f|</tt> to <tt>post_form</tt> to clarify what is going on somewhat. + +We also add a <tt>@post.tags.build</tt> at the top of this form, this is to make sure there is a new tag ready to have it's name filled in by the user. If you do not build the new tag, then the form will not appear as there is no new Tag object ready to create. + +Now create the folder <tt>app/views/tags</tt> and make a file in there called <tt>_form.html.erb</tt> which contains the form for the tag: + +<erb> +<% form.fields_for :tags do |tag_form| %> + <div class="field"> + <%= tag_form.label :name, 'Tag:' %> + <%= tag_form.text_field :name %> + </div> + <% unless tag_form.object.nil? || tag_form.object.new_record? %> + <div class="field"> + <%= tag_form.label :_destroy, 'Remove:' %> + <%= tag_form.check_box :_destroy %> + </div> + <% end %> <% end %> </erb> +Finally, we will edit the <tt>app/views/posts/show.html.erb</tt> template to show our tags. + +<erb> +<p> + <b>Name:</b> + <%= @post.name %> +</p> + +<p> + <b>Title:</b> + <%= @post.title %> +</p> + +<p> + <b>Content:</b> + <%= @post.content %> +</p> + +<p> + <b>Tags:</b> + <%= @post.tags.map { |t| t.name }.join(", ") %> +</p> + +<h2>Comments</h2> +<%= render :partial => "comments/comment", + :collection => @post.comments %> + +<h2>Add a comment:</h2> +<%= render "comments/form" %> + + +<%= link_to 'Edit Post', edit_post_path(@post) %> | +<%= link_to 'Back to Posts', posts_path %> | +</erb> + With these changes in place, you'll find that you can edit a post and its tags directly on the same view. -NOTE. You may want to use JavaScript to dynamically add additional tags on a single form. For an example of this and other advanced techniques, see the "complex form examples application":http://github.com/alloy/complex-form-examples/tree/master. +However, that method call <tt>@post.tags.map { |t| t.name }.join(", ")</tt> is awkward, we could handle this by making a helper method. + +h3. View Helpers + +View Helpers live in <tt>app/helpers</tt> and provide small snippets of reusable code for views. In our case, we want a method that strings a bunch of objects together using their name attribute and joining them with a comma. As this is for the Post show template, we put it in the PostsHelper. + +Open up <tt>app/helpers/posts_helper.rb</tt> and add the following: + +<erb> +module PostsHelper + def join_tags(post) + post.tags.map { |t| t.name }.join(", ") + end +end +</erb> + +Now you can edit the view in <tt>app/views/posts/show.html.erb</tt> to look like this: + +<erb> +<p> + <b>Name:</b> + <%= @post.name %> +</p> + +<p> + <b>Title:</b> + <%= @post.title %> +</p> + +<p> + <b>Content:</b> + <%= @post.content %> +</p> + +<p> + <b>Tags:</b> + <%= join_tags(@post) %> +</p> + +<h2>Comments</h2> +<%= render :partial => "comments/comment", + :collection => @post.comments %> + +<h2>Add a comment:</h2> +<%= render "comments/form" %> + + +<%= link_to 'Edit Post', edit_post_path(@post) %> | +<%= link_to 'Back to Posts', posts_path %> | +</erb> h3. What's Next? Now that you've seen your first Rails application, you should feel free to update it and experiment on your own. But 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":http://guides.rubyonrails.org +* The "Ruby On Rails guides":http://guides.rails.info * The "Ruby on Rails mailing list":http://groups.google.com/group/rubyonrails-talk * The "#rubyonrails":irc://irc.freenode.net/#rubyonrails channel on irc.freenode.net * The "Rails Wiki":http://wiki.rubyonrails.org/ @@ -1296,10 +1427,13 @@ Rails also comes with built-in help that you can generate using the rake command * Running +rake doc:guides+ will put a full copy of the Rails Guides in the +doc/guides+ folder of your application. Open +doc/guides/index.html+ in your web browser to explore the Guides. * Running +rake doc:rails+ will put a full copy of the API documentation for Rails in the +doc/api+ folder of your application. Open +doc/api/index.html+ in your web browser to explore the API documentation. + h3. Changelog "Lighthouse ticket":http://rails.lighthouseapp.com/projects/16213-rails-guides/tickets/2 +* February 8, 2010: Full re-write for Rails 3.0-beta, added helpers and before_filters, refactored code by "Mikel Lindsaar":credits:html#raasdnil +* January 24, 2010: Re-write for Rails 3.0 by "Mikel Lindsaar":credits:html#raasdnil * July 18, 2009: Minor cleanup in anticipation of Rails 2.3.3 by "Mike Gunderloy":credits.html#mgunderloy * February 1, 2009: Updated for Rails 2.3 by "Mike Gunderloy":credits.html#mgunderloy * November 3, 2008: Formatting patch from Dave Rothlisberger @@ -1307,4 +1441,4 @@ h3. Changelog * October 16, 2008: Revised based on feedback from Pratik Naik by "Mike Gunderloy":credits.html#mgunderloy (not yet approved for publication) * October 13, 2008: First complete draft by "Mike Gunderloy":credits.html#mgunderloy (not yet approved for publication) * October 12, 2008: More detail, rearrangement, editing by "Mike Gunderloy":credits.html#mgunderloy (not yet approved for publication) -* September 8, 2008: initial version by James Miller (not yet approved for publication) +* September 8, 2008: initial version by "James Miller":credits.html#bensie (not yet approved for publication) |