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Diffstat (limited to 'guides/source/active_support_core_extensions.md')
-rw-r--r-- | guides/source/active_support_core_extensions.md | 195 |
1 files changed, 118 insertions, 77 deletions
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md index 101a4f5b42..1a43bd206e 100644 --- a/guides/source/active_support_core_extensions.md +++ b/guides/source/active_support_core_extensions.md @@ -10,7 +10,7 @@ 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 ActiveSupport provides. +* What extensions Active Support provides. -------------------------------------------------------------------------------- @@ -37,9 +37,10 @@ For every single method defined as a core extension this guide has a note that s NOTE: Defined in `active_support/core_ext/object/blank.rb`. -That means that this single call is enough: +That means that you can require it like this: ```ruby +require 'active_support' require 'active_support/core_ext/object/blank' ``` @@ -52,6 +53,7 @@ The next level is to simply load all extensions to `Object`. As a rule of thumb, Thus, to load all extensions to `Object` (including `blank?`): ```ruby +require 'active_support' require 'active_support/core_ext/object' ``` @@ -60,6 +62,7 @@ require 'active_support/core_ext/object' You may prefer just to load all core extensions, there is a file for that: ```ruby +require 'active_support' require 'active_support/core_ext' ``` @@ -96,12 +99,13 @@ INFO: The predicate for strings uses the Unicode-aware character class `[:space: WARNING: Note that numbers are not mentioned. In particular, 0 and 0.0 are **not** blank. -For example, this method from `ActionDispatch::Session::AbstractStore` uses `blank?` for checking whether a session key is present: +For example, this method from `ActionController::HttpAuthentication::Token::ControllerMethods` uses `blank?` for checking whether a token is present: ```ruby -def ensure_session_key! - if @key.blank? - raise ArgumentError, 'A key is required...' +def authenticate(controller, &login_procedure) + token, options = token_and_options(controller.request) + unless token.blank? + login_procedure.call(token, options) end end ``` @@ -166,7 +170,7 @@ NOTE: Defined in `active_support/core_ext/object/duplicable.rb`. ### `deep_dup` -The `deep_dup` method returns 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: +The `deep_dup` method returns 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'] @@ -175,14 +179,14 @@ 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'] +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'] +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. @@ -195,8 +199,8 @@ duplicate = array.deep_dup duplicate.first.gsub!('string', 'foo') -array #=> ['string'] -duplicate #=> ['foo'] +array # => ['string'] +duplicate # => ['foo'] ``` If the object is not duplicable, `deep_dup` will just return it: @@ -418,6 +422,12 @@ TIP: Since `with_options` forwards calls to its receiver they can be nested. Eac 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. @@ -439,6 +449,22 @@ 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, Streams, 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: @@ -476,12 +502,11 @@ NOTE: Defined in `active_support/core_ext/kernel/reporting.rb`. ### `in?` -The predicate `in?` tests if an object is included in another object or a list of objects. An `ArgumentError` exception will be raised if a single argument is passed and it does not respond to `include?`. +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 1.in?([1,2]) # => true "lo".in?("hello") # => true 25.in?(30..50) # => false @@ -599,7 +624,7 @@ NOTE: Defined in `active_support/core_ext/module/attr_internal.rb`. #### Module Attributes -The macros `mattr_reader`, `mattr_writer`, and `mattr_accessor` are analogous to the `cattr_*` macros defined for class. Check [Class Attributes](#class-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: @@ -710,7 +735,7 @@ X.local_constants # => [:X1, :X2, :Y] X::Y.local_constants # => [:Y1, :X1] ``` -The names are returned as symbols. (The deprecated method `local_constant_names` returns strings.) +The names are returned as symbols. NOTE: Defined in `active_support/core_ext/module/introspection.rb`. @@ -863,7 +888,7 @@ class User < ActiveRecord::Base end ``` -With that configuration you get a user's name via his profile, `user.profile.name`, but it could be handy to still be able to access such attribute directly: +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 < ActiveRecord::Base @@ -1039,7 +1064,7 @@ For convenience `class_attribute` also defines an instance predicate which is th 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. +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` @@ -1068,6 +1093,15 @@ end we can access `field_error_proc` in views. +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) { true } +end +``` + 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 @@ -1085,7 +1119,7 @@ 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/class/attribute_accessors.rb`. +NOTE: Defined in `active_support/core_ext/module/attribute_accessors.rb`. `active_support/core_ext/class/attribute_accessors.rb` is deprecated and will be removed in Ruby on Rails 4.2. ### Subclasses & Descendants @@ -1225,6 +1259,18 @@ Calling `to_s` on a safe string returns a safe string, but coercion with `to_str 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: @@ -1424,7 +1470,7 @@ The method `pluralize` returns the plural of its receiver: 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: +`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" @@ -1508,7 +1554,7 @@ ActiveSupport::Inflector.inflections do |inflect| inflect.acronym 'SSL' end -"SSLError".underscore.camelize #=> "SSLError" +"SSLError".underscore.camelize # => "SSLError" ``` `camelize` is aliased to `camelcase`. @@ -1738,6 +1784,12 @@ The method `humanize` gives you a sensible name for display out of an attribute "comments_count".humanize # => "Comments count" ``` +The capitalization of the first word can be turned off by setting the optional parameter `capitalize` to false: + +```ruby +"author_id".humanize(capitalize: false) # => "author" +``` + The helper method `full_messages` uses `humanize` as a fallback to include attribute names: ```ruby @@ -1964,7 +2016,7 @@ Produce a string representation of a number in human-readable words: 1234567890123456.to_s(:human) # => "1.23 Quadrillion" ``` -NOTE: Defined in `active_support/core_ext/numeric/formatting.rb`. +NOTE: Defined in `active_support/core_ext/numeric/conversions.rb`. Extensions to `Integer` ----------------------- @@ -2012,8 +2064,33 @@ NOTE: Defined in `active_support/core_ext/integer/inflections.rb`. Extensions to `BigDecimal` -------------------------- +### `to_s` -... +The method `to_s` is aliased to `to_formatted_s`. This provides a convenient way to display a BigDecimal value in floating-point notation: + +```ruby +BigDecimal.new(5.00, 6).to_s # => "5.0" +``` + +### `to_formatted_s` + +Te method `to_formatted_s` provides a default specifier of "F". This means that a simple call to `to_formatted_s` or `to_s` will result in floating point representation instead of engineering notation: + +```ruby +BigDecimal.new(5.00, 6).to_formatted_s # => "5.0" +``` + +and that symbol specifiers are also supported: + +```ruby +BigDecimal.new(5.00, 6).to_formatted_s(:db) # => "5.0" +``` + +Engineering notation is still supported: + +```ruby +BigDecimal.new(5.00, 6).to_formatted_s("e") # => "0.5E1" +``` Extensions to `Enumerable` -------------------------- @@ -2208,15 +2285,15 @@ The defaults for these options can be localized, their keys are: | `:words_connector` | `support.array.words_connector` | | `:last_word_connector` | `support.array.last_word_connector` | -Options `:connector` and `:skip_last_comma` are deprecated. - 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, it may be passed the symbol `:db` as argument. That's typically used with collections of ARs. Returned strings are: +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" @@ -2372,7 +2449,8 @@ NOTE: Defined in `active_support/core_ext/array/wrap.rb`. ### Duplicating -The method `Array.deep_dup` duplicates itself and all objects inside recursively with ActiveSupport method `Object#deep_dup`. It works like `Array#map` with sending `deep_dup` method to each object inside. +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]] @@ -2381,7 +2459,7 @@ dup[1][2] = 4 array[1][2] == nil # => true ``` -NOTE: Defined in `active_support/core_ext/array/deep_dup.rb`. +NOTE: Defined in `active_support/core_ext/object/deep_dup.rb`. ### Grouping @@ -2593,7 +2671,8 @@ 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 ActiveSupport method `Object#deep_dup`. It works like `Enumerator#each_with_object` with sending `deep_dup` method to each pair inside. +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] } } @@ -2606,45 +2685,7 @@ hash[:b][:e] == nil # => true hash[:b][:d] == [3, 4] # => true ``` -NOTE: Defined in `active_support/core_ext/hash/deep_dup.rb`. - -### Diffing - -The method `diff` returns a hash that represents a diff of the receiver and the argument with the following logic: - -* Pairs `key`, `value` that exist in both hashes do not belong to the diff hash. - -* If both hashes have `key`, but with different values, the pair in the receiver wins. - -* The rest is just merged. - -```ruby -{a: 1}.diff(a: 1) -# => {}, first rule - -{a: 1}.diff(a: 2) -# => {:a=>1}, second rule - -{a: 1}.diff(b: 2) -# => {:a=>1, :b=>2}, third rule - -{a: 1, b: 2, c: 3}.diff(b: 1, c: 3, d: 4) -# => {:a=>1, :b=>2, :d=>4}, all rules - -{}.diff({}) # => {} -{a: 1}.diff({}) # => {:a=>1} -{}.diff(a: 1) # => {:a=>1} -``` - -An important property of this diff hash is that you can retrieve the original hash by applying `diff` twice: - -```ruby -hash.diff(hash2).diff(hash2) == hash -``` - -Diffing hashes may be useful for error messages related to expected option hashes for example. - -NOTE: Defined in `active_support/core_ext/hash/diff.rb`. +NOTE: Defined in `active_support/core_ext/object/deep_dup.rb`. ### Working with Keys @@ -2672,14 +2713,14 @@ NOTE: Defined in `active_support/core_ext/hash/except.rb`. The method `transform_keys` accepts a block and returns a hash that has applied the block operations to each of the keys in the receiver: ```ruby -{nil => nil, 1 => 1, a: :a}.transform_keys{ |key| key.to_s.upcase } +{nil => nil, 1 => 1, a: :a}.transform_keys { |key| key.to_s.upcase } # => {"" => nil, "A" => :a, "1" => 1} ``` The result in case of collision is undefined: ```ruby -{"a" => 1, a: 2}.transform_keys{ |key| key.to_s.upcase } +{"a" => 1, a: 2}.transform_keys { |key| key.to_s.upcase } # => {"A" => 2}, in my test, can't rely on this result though ``` @@ -2687,11 +2728,11 @@ This method may be useful for example to build specialized conversions. For inst ```ruby def stringify_keys - transform_keys{ |key| key.to_s } + transform_keys { |key| key.to_s } end ... def symbolize_keys - transform_keys{ |key| key.to_sym rescue key } + transform_keys { |key| key.to_sym rescue key } end ``` @@ -2700,7 +2741,7 @@ There's also the bang variant `transform_keys!` that applies the block operation Besides that, one can use `deep_transform_keys` and `deep_transform_keys!` to perform the block operation on 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_transform_keys{ |key| key.to_s.upcase } +{nil => nil, 1 => 1, nested: {a: 3, 5 => 5}}.deep_transform_keys { |key| key.to_s.upcase } # => {""=>nil, "1"=>1, "NESTED"=>{"A"=>3, "5"=>5}} ``` @@ -3779,13 +3820,13 @@ def default_helper_module! module_path = module_name.underscore helper module_path rescue MissingSourceFile => e - raise e unless e.is_missing? "#{module_path}_helper" + 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`. +NOTE: Defined in `actionpack/lib/abstract_controller/helpers.rb`. Extensions to `LoadError` ------------------------- @@ -3808,4 +3849,4 @@ rescue NameError => e end ``` -NOTE: Defined in `active_support/core_ext/load_error.rb`. +NOTE: Defined in `actionpack/lib/abstract_controller/helpers.rb`. |