ActionController::Resources

• actionpack/lib/action_controller/resources.rb

Overview

ActionController::Resources are a way of defining RESTful \resources. A RESTful \resource, in basic terms, is something that can be pointed at and it will respond with a representation of the data requested. In real terms this could mean a user with a browser requests an HTML page, or that a desktop application requests XML data.

RESTful design is based on the assumption that there are four generic verbs that a user of an application can request from a \resource (the noun).

\Resources can be requested using four basic HTTP verbs (GET, POST, PUT, DELETE), the method used denotes the type of action that should take place.

The Different Methods and their Usage

• GET - Requests for a \resource, no saving or editing of a \resource should occur in a GET request.
• POST - Creation of \resources.
• PUT - Editing of attributes on a \resource.
• DELETE - Deletion of a \resource.

Examples

  # A GET request on the Posts resource is asking for all Posts
  GET /posts

  # A GET request on a single Post resource is asking for that particular Post
  GET /posts/1

  # A POST request on the Posts resource is asking for a Post to be created with the supplied details
  POST /posts # with => { :post => { :title => "My Whizzy New Post", :body => "I've got a brand new combine harvester" } }

  # A PUT request on a single Post resource is asking for a Post to be updated
  PUT /posts # with => { :id => 1, :post => { :title => "Changed Whizzy Title" } }

  # A DELETE request on a single Post resource is asking for it to be deleted
  DELETE /posts # with => { :id => 1 }

By using the REST convention, users of our application can assume certain things about how the data is requested and how it is returned. Rails simplifies the routing part of RESTful design by supplying you with methods to create them in your routes.rb file.

Read more about REST at en.wikipedia.org/wiki/Representational_State_Transfer

• resource
• resources

Creates named routes for implementing verb-oriented controllers for a singleton \resource. A singleton \resource is global to its current context. For unnested singleton \resources, the \resource is global to the current user visiting the application, such as a user‘s /account profile. For nested singleton \resources, the \resource is global to its parent \resource, such as a projects \resource that has_one :project_manager. The project_manager should be mapped as a singleton \resource under projects:

  map.resources :projects do |project|
    project.resource :project_manager
  end

See resources for general conventions. These are the main differences:

• A singular name is given to map.resource. The default controller name is still taken from the plural name.
• To specify a custom plural name, use the :plural option. There is no :singular option.
• No default index route is created for the singleton \resource controller.
• When nesting singleton \resources, only the singular name is used as the path prefix (example: ‘account/messages/1’)

For example:

  map.resource :account

maps these actions in the Accounts controller:

  class AccountsController < ActionController::Base
    # GET new_account_url
    def new
      # return an HTML form for describing the new account
    end

    # POST account_url
    def create
      # create an account
    end

    # GET account_url
    def show
      # find and return the account
    end

    # GET edit_account_url
    def edit
      # return an HTML form for editing the account
    end

    # PUT account_url
    def update
      # find and update the account
    end

    # DELETE account_url
    def destroy
      # delete the account
    end
  end

Along with the routes themselves, resource generates named routes for use in controllers and views. map.resource :account produces these named routes and helpers:

  Named Route   Helpers
  ============  =============================================
  account       account_url, hash_for_account_url,
                account_path, hash_for_account_path

  new_account   new_account_url, hash_for_new_account_url,
                new_account_path, hash_for_new_account_path

  edit_account  edit_account_url, hash_for_edit_account_url,
                edit_account_path, hash_for_edit_account_path

Creates named routes for implementing verb-oriented controllers for a collection \resource.

For example:

  map.resources :messages

will map the following actions in the corresponding controller:

  class MessagesController < ActionController::Base
    # GET messages_url
    def index
      # return all messages
    end

    # GET new_message_url
    def new
      # return an HTML form for describing a new message
    end

    # POST messages_url
    def create
      # create a new message
    end

    # GET message_url(:id => 1)
    def show
      # find and return a specific message
    end

    # GET edit_message_url(:id => 1)
    def edit
      # return an HTML form for editing a specific message
    end

    # PUT message_url(:id => 1)
    def update
      # find and update a specific message
    end

    # DELETE message_url(:id => 1)
    def destroy
      # delete a specific message
    end
  end

Along with the routes themselves, resources generates named routes for use in controllers and views. map.resources :messages produces the following named routes and helpers:

  Named Route   Helpers
  ============  =====================================================
  messages      messages_url, hash_for_messages_url,
                messages_path, hash_for_messages_path

  message       message_url(id), hash_for_message_url(id),
                message_path(id), hash_for_message_path(id)

  new_message   new_message_url, hash_for_new_message_url,
                new_message_path, hash_for_new_message_path

  edit_message  edit_message_url(id), hash_for_edit_message_url(id),
                edit_message_path(id), hash_for_edit_message_path(id)

You can use these helpers instead of url_for or methods that take url_for parameters. For example:

  redirect_to :controller => 'messages', :action => 'index'
  # and
  <%= link_to "edit this message", :controller => 'messages', :action => 'edit', :id => @message.id %>

now become:

  redirect_to messages_url
  # and
  <%= link_to "edit this message", edit_message_url(@message) # calls @message.id automatically

Since web browsers don‘t support the PUT and DELETE verbs, you will need to add a parameter ‘_method’ to your form tags. The form helpers make this a little easier. For an update form with a @message object:

  <%= form_tag message_path(@message), :method => :put %>

or

  <% form_for :message, @message, :url => message_path(@message), :html => {:method => :put} do |f| %>

or

  <% form_for @message do |f| %>

which takes into account whether @message is a new record or not and generates the path and method accordingly.

The resources method accepts the following options to customize the resulting routes:

• :collection - Add named routes for other actions that operate on the collection. Takes a hash of #{action} => #{method}, where method is :get/:post/:put/:delete, an array of any of the previous, or :any if the method does not matter. These routes map to a URL like /messages/rss, with a route of rss_messages_url.
• :member - Same as :collection, but for actions that operate on a specific member.
• :new - Same as :collection, but for actions that operate on the new \resource action.
• :controller - Specify the controller name for the routes.
• :singular - Specify the singular name used in the member routes.
• :requirements - Set custom routing parameter requirements.
• :conditions - Specify custom routing recognition conditions. \Resources sets the :method value for the method-specific routes.
• :as - Specify a different \resource name to use in the URL path. For example:

    # products_path == '/productos'
    map.resources :products, :as => 'productos' do |product|
      # product_reviews_path(product) == '/productos/1234/comentarios'
      product.resources :product_reviews, :as => 'comentarios'
    end
  

• :has_one - Specify nested \resources, this is a shorthand for mapping singleton \resources beneath the current.
• :has_many - Same has :has_one, but for plural \resources.

  You may directly specify the routing association with has_one and has_many like:

    map.resources :notes, :has_one => :author, :has_many => [:comments, :attachments]
  

  This is the same as:

    map.resources :notes do |notes|
      notes.resource  :author
      notes.resources :comments
      notes.resources :attachments
    end
  

• :path_names - Specify different names for the ‘new’ and ‘edit’ actions. For example:

    # new_products_path == '/productos/nuevo'
    map.resources :products, :as => 'productos', :path_names => { :new => 'nuevo', :edit => 'editar' }
  

  You can also set default action names from an environment, like this:

    config.action_controller.resources_path_names = { :new => 'nuevo', :edit => 'editar' }
  

• :path_prefix - Set a prefix to the routes with required route variables.

  Weblog comments usually belong to a post, so you might use resources like:

    map.resources :articles
    map.resources :comments, :path_prefix => '/articles/:article_id'
  

  You can nest resources calls to set this automatically:

    map.resources :articles do |article|
      article.resources :comments
    end
  

  The comment \resources work the same, but must now include a value for :article_id.

    article_comments_url(@article)
    article_comment_url(@article, @comment)
  
    article_comments_url(:article_id => @article)
    article_comment_url(:article_id => @article, :id => @comment)
  

  If you don‘t want to load all objects from the database you might want to use the article_id directly:

    articles_comments_url(@comment.article_id, @comment)
  

• :name_prefix - Define a prefix for all generated routes, usually ending in an underscore. Use this if you have named routes that may clash.

    map.resources :tags, :path_prefix => '/books/:book_id', :name_prefix => 'book_'
    map.resources :tags, :path_prefix => '/toys/:toy_id',   :name_prefix => 'toy_'
  

You may also use :name_prefix to override the generic named routes in a nested \resource:

  map.resources :articles do |article|
    article.resources :comments, :name_prefix => nil
  end

This will yield named \resources like so:

  comments_url(@article)
  comment_url(@article, @comment)

• :shallow - If true, paths for nested resources which reference a specific member (ie. those with an :id parameter) will not use the parent path prefix or name prefix.

The :shallow option is inherited by any nested resource(s).

For example, ‘users’, ‘posts’ and ‘comments’ all use shallow paths with the following nested resources:

  map.resources :users, :shallow => true do |user|
    user.resources :posts do |post|
      post.resources :comments
    end
  end
  # --> GET /users/1/posts (maps to the PostsController#index action as usual)
  #     also adds the usual named route called "user_posts"
  # --> GET /posts/2 (maps to the PostsController#show action as if it were not nested)
  #     also adds the named route called "post"
  # --> GET /posts/2/comments (maps to the CommentsController#index action)
  #     also adds the named route called "post_comments"
  # --> GET /comments/2 (maps to the CommentsController#show action as if it were not nested)
  #     also adds the named route called "comment"

You may also use :shallow in combination with the has_one and has_many shorthand notations like:

  map.resources :users, :has_many => { :posts => :comments }, :shallow => true

• :only and :except - Specify which of the seven default actions should be routed to.

:only and :except may be set to :all, :none, an action name or a list of action names. By default, routes are generated for all seven actions.

For example:

  map.resources :posts, :only => [:index, :show] do |post|
    post.resources :comments, :except => [:update, :destroy]
  end
  # --> GET /posts (maps to the PostsController#index action)
  # --> POST /posts (fails)
  # --> GET /posts/1 (maps to the PostsController#show action)
  # --> DELETE /posts/1 (fails)
  # --> POST /posts/1/comments (maps to the CommentsController#create action)
  # --> PUT /posts/1/comments/1 (fails)

The :only and :except options are inherited by any nested resource(s).

If map.resources is called with multiple resources, they all get the same options applied.

Examples:

  map.resources :messages, :path_prefix => "/thread/:thread_id"
  # --> GET /thread/7/messages/1

  map.resources :messages, :collection => { :rss => :get }
  # --> GET /messages/rss (maps to the #rss action)
  #     also adds a named route called "rss_messages"

  map.resources :messages, :member => { :mark => :post }
  # --> POST /messages/1/mark (maps to the #mark action)
  #     also adds a named route called "mark_message"

  map.resources :messages, :new => { :preview => :post }
  # --> POST /messages/new/preview (maps to the #preview action)
  #     also adds a named route called "preview_new_message"

  map.resources :messages, :new => { :new => :any, :preview => :post }
  # --> POST /messages/new/preview (maps to the #preview action)
  #     also adds a named route called "preview_new_message"
  # --> /messages/new can be invoked via any request method

  map.resources :messages, :controller => "categories",
        :path_prefix => "/category/:category_id",
        :name_prefix => "category_"
  # --> GET /categories/7/messages/1
  #     has named route "category_message"

The resources method sets HTTP method restrictions on the routes it generates. For example, making an HTTP POST on new_message_url will raise a RoutingError exception. The default route in config/routes.rb overrides this and allows invalid HTTP methods for \resource routes.