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Class: ActionController::Base

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Subclasses:
Rails::ApplicationController, Rails::InfoController, Rails::MailersController, Rails::WelcomeController, ActionView::TestCase::TestController
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
Instance Chain:
Inherits: ActionController::Metal
Defined in: actionpack/lib/action_controller/base.rb

Overview

Action Controllers are the core of a web request in Rails. They are made up of one or more actions that are executed on request and then either it renders a template or redirects to another action. An action is defined as a public method on the controller, which will automatically be made accessible to the web-server through Rails Routes.

By default, only the ApplicationController in a Rails application inherits from Base. All other controllers in turn inherit from ApplicationController. This gives you one class to configure things such as request forgery protection and filtering of sensitive request parameters.

A sample controller could look like this:

class PostsController < ApplicationController
  def index
    @posts = Post.all
  end

  def create
    @post = Post.create params[:post]
    redirect_to posts_path
  end
end

Actions, by default, render a template in the app/views directory corresponding to the name of the controller and action after executing code in the action. For example, the index action of the PostsController would render the template app/views/posts/index.html.erb by default after populating the @posts instance variable.

Unlike index, the create action will not render a template. After performing its main purpose (creating a new post), it initiates a redirect instead. This redirect works by returning an external “302 Moved” HTTP response that takes the user to the index action.

These two methods represent the two basic action archetypes used in Action Controllers. Get-and-show and do-and-redirect. Most actions are variations on these themes.

Requests

For every request, the router determines the value of the controller and action keys. These determine which controller and action are called. The remaining request parameters, the session (if one is available), and the full request with all the HTTP headers are made available to the action through accessor methods. Then the action is performed.

The full request object is available via the request accessor and is primarily used to query for HTTP headers:

def server_ip
  location = request.env["REMOTE_ADDR"]
  render plain: "This server hosted at #{location}"
end

Parameters

All request parameters, whether they come from a GET or POST request, or from the URL, are available through the params method which returns a hash. For example, an action that was performed through /posts?category=All&limit=5 will include { "category" => "All", "limit" => "5" } in params.

It's also possible to construct multi-dimensional parameter hashes by specifying keys using brackets, such as:

<input type="text" name="post[name]" value="david">
<input type="text" name="post[address]" value="hyacintvej">

A request stemming from a form holding these inputs will include { "post" => { "name" => "david", "address" => "hyacintvej" } }. If the address input had been named post[address][street], the params would have included { "post" => { "address" => { "street" => "hyacintvej" } } }. There's no limit to the depth of the nesting.

Sessions

Sessions allow you to store objects in between requests. This is useful for objects that are not yet ready to be persisted, such as a Signup object constructed in a multi-paged process, or objects that don't change much and are needed all the time, such as a User object for a system that requires login. The session should not be used, however, as a cache for objects where it's likely they could be changed unknowingly. It's usually too much work to keep it all synchronized – something databases already excel at.

You can place objects in the session by using the session method, which accesses a hash:

session[:person] = Person.authenticate(user_name, password)

And retrieved again through the same hash:

Hello #{session[:person]}

For removing objects from the session, you can either assign a single key to nil:

# removes :person from session
session[:person] = nil

or you can remove the entire session with reset_session.

Sessions are stored by default in a browser cookie that's cryptographically signed, but unencrypted. This prevents the user from tampering with the session but also allows them to see its contents.

Do not put secret information in cookie-based sessions!

Responses

Each action results in a response, which holds the headers and document to be sent to the user's browser. The actual response object is generated automatically through the use of renders and redirects and requires no user intervention.

Renders

Action Controller sends content to the user by using one of five rendering methods. The most versatile and common is the rendering of a template. Included in the Action Pack is the Action View, which enables rendering of ::ERB templates. It's automatically configured. The controller passes objects to the view by assigning instance variables:

def show
  @post = Post.find(params[:id])
end

Which are then automatically available to the view:

Title: <%= @post.title %>

You don't have to rely on the automated rendering. For example, actions that could result in the rendering of different templates will use the manual rendering methods:

def search
  @results = Search.find(params[:query])
  case @results.count
    when 0 then render action: "no_results"
    when 1 then render action: "show"
    when 2..10 then render action: "show_many"
  end
end

Read more about writing ::ERB and Builder templates in ::ActionView::Base.

Redirects

Redirects are used to move from one action to another. For example, after a create action, which stores a blog entry to the database, we might like to show the user the new entry. Because we're following good DRY principles (Don't Repeat Yourself), we're going to reuse (and redirect to) a show action that we'll assume has already been created. The code might look like this:

def create
  @entry = Entry.new(params[:entry])
  if @entry.save
    # The entry was saved correctly, redirect to show
    redirect_to action: 'show', id: @entry.id
  else
    # things didn't go so well, do something else
  end
end

In this case, after saving our new entry to the database, the user is redirected to the show method, which is then executed. Note that this is an external HTTP-level redirection which will cause the browser to make a second request (a GET to the show action), and not some internal re-routing which calls both “create” and then “show” within one request.

Learn more about redirect_to and what options you have in Redirecting.

Calling multiple redirects or renders

An action may contain only a single render or a single redirect. Attempting to try to do either again will result in a DoubleRenderError:

def do_something
  redirect_to action: "elsewhere"
  render action: "overthere" # raises DoubleRenderError
end

If you need to redirect on the condition of something, then be sure to add “and return” to halt execution.

def do_something
  redirect_to(action: "elsewhere") and return if monkeys.nil?
  render action: "overthere" # won't be called if monkeys is nil
end

Constant Summary

::AbstractController::Rendering - Included

DEFAULT_PROTECTED_INSTANCE_VARIABLES

Rendering - Included

RENDER_FORMATS_IN_PRIORITY

Renderers - Included

RENDERERS

::ActiveSupport::Callbacks - Included

CALLBACK_FILTER_TYPES

RequestForgeryProtection - Included

AUTHENTICITY_TOKEN_LENGTH

ForceSSL - Included

ACTION_OPTIONS, REDIRECT_OPTIONS, URL_OPTIONS

ParamsWrapper - Included

EXCLUDE_PARAMETERS

Class Attribute Summary

Metal - Inherited

::AbstractController::Base - Inherited

.abstract?
.supports_path?

Returns true if the given controller is capable of rendering a path.

Class Method Summary

Metal - Inherited

.action

Returns a ::Rack endpoint for the given action name.

.call

Makes the controller a ::Rack endpoint that runs the action in the given env's action_dispatch.request.path_parameters key.

.controller_name

Returns the last part of the controller's name, underscored, without the ending Controller.

.middleware

Alias for middleware_stack.

.new,
.use

Pushes the given ::Rack middleware and its arguments to the bottom of the middleware stack.

::AbstractController::Base - Inherited

.abstract,
.abstract!

Define a controller as abstract.

.action_methods

A list of method names that should be considered actions.

.clear_action_methods!

action_methods are cached and there is sometimes need to refresh them.

.controller_path

Returns the full controller name, underscored, without the ending Controller.

.hidden_actions

The list of hidden actions.

.internal_methods

A list of all internal methods for a controller.

.method_added

Refresh the cached action_methods when a new action_method is added.

::ActiveSupport::DescendantsTracker - Extended

Instance Attribute Summary

Instrumentation - Included

Rescue - Included

#rescue_handlers, #rescue_handlers?,
#show_detailed_exceptions?

Override this method if you want to customize when detailed exceptions must be shown.

RequestForgeryProtection - Included

StrongParameters - Included

#params

Returns a new Parameters object that has been instantiated with the request.parameters.

#params=

Assigns the given value to the params hash.

#rescue_handlers, #rescue_handlers?

Caching::ConfigMethods - Included

EtagWithTemplateDigest - Included

Renderers::All - Included

::ActionView::Layouts - Included

#_layout_conditions, #action_has_layout=,
#action_has_layout?

Controls whether an action should be rendered using a layout.

::ActionView::Rendering - Included

Redirecting - Included

RackDelegation - Included

::AbstractController::UrlFor - Included

Helpers - Included

::AbstractController::Rendering - Included

::ActionView::ViewPaths - Included

Metal - Inherited

#content_type,
#content_type=

Basic implementations for content_type=, location=, and headers are provided to reduce the dependency on the RackDelegation module in Renderer and Redirector.

#env, #env=,
#headers

The details below can be overridden to support a specific Request and Response object.

#location, #location=, #middleware_stack, #middleware_stack?, #params, #params=,
#performed?

Tests if render or redirect has already happened.

#request

The details below can be overridden to support a specific Request and Response object.

#response

The details below can be overridden to support a specific Request and Response object.

#response_body=, #session, #status, #status=

::AbstractController::Base - Inherited

Instance Method Summary

ParamsWrapper - Included

#process_action

Performs parameters wrapping upon the request.

Instrumentation - Included

Rescue - Included

HttpAuthentication::Token::ControllerMethods - Included

HttpAuthentication::Digest::ControllerMethods - Included

#authenticate_or_request_with_http_digest,
#authenticate_with_http_digest

Authenticate with HTTP Digest, returns true or false.

#request_http_digest_authentication

Render output including the HTTP Digest authentication header.

HttpAuthentication::Basic::ControllerMethods - Included

DataStreaming - Included

#send_data

Sends the given binary data to the browser.

#send_file

Sends the file.

ForceSSL - Included

#force_ssl_redirect

Redirect the existing request to use the HTTPS protocol.

Flash - Included

::ActiveSupport::Rescuable - Included

#handler_for_rescue,
#rescue_with_handler

Tries to rescue the exception by looking up and calling a registered handler.

ImplicitRender - Included

MimeResponds - Included

#respond_to

Without web-service support, an action which collects the data for displaying a list of people might look something like this:

#respond_with

Caching - Included

Caching::Fragments - Included

#expire_fragment

Removes fragments from the cache.

#fragment_cache_key

Given a key (as described in expire_fragment), returns a key suitable for use in reading, writing, or expiring a cached fragment.

#fragment_exist?

Check if a cached fragment from the location signified by key exists (see expire_fragment for acceptable formats).

#read_fragment

Reads a cached fragment from the location signified by key (see expire_fragment for acceptable formats).

#write_fragment

Writes content to the location signified by key (see expire_fragment for acceptable formats).

::AbstractController::Callbacks - Included

#process_action

Override AbstractController::Base's process_action to run the process_action callbacks around the normal behavior.

::ActiveSupport::Callbacks - Included

#run_callbacks

Runs the callbacks for the given event.

ConditionalGet - Included

#expires_in

Sets a HTTP 1.1 Cache-Control header.

#expires_now

Sets a HTTP 1.1 Cache-Control header of no-cache so no caching should occur by the browser or intermediate caches (like caching proxy servers).

#fresh_when

Sets the etag, last_modified, or both on the response and renders a 304 Not Modified response if the request is already fresh.

#stale?

Sets the etag and/or last_modified on the response and checks it against the client request.

Head - Included

#head

Returns a response that has no content (merely headers).

Renderers - Included

Rendering - Included

#render_to_body,
#render_to_string

Overwrite render_to_string because body can now be set to a rack body.

::ActionView::Rendering - Included

#render_to_body, #rendered_format,
#view_context

An instance of a view class.

#view_renderer

Returns an object that is able to render templates.

Redirecting - Included

#redirect_to

Redirects the browser to the target specified in options.

RackDelegation - Included

::ActiveSupport::Benchmarkable - Included

#benchmark

Allows you to measure the execution time of a block in a template and records the result to the log.

UrlFor - Included

::AbstractController::UrlFor - Included

::ActionDispatch::Routing::UrlFor - Included

#initialize,
#url_for

Generate a url based on the options provided, default_url_options and the routes defined in routes.rb.

#url_options

Hook overridden in controller to add request information with default_url_options.

::ActionDispatch::Routing::PolymorphicRoutes - Included

#polymorphic_path

Returns the path component of a URL for the given record.

#polymorphic_url

Constructs a call to a named RESTful route for the given record and returns the resulting URL string.

ModelNaming - Included

#convert_to_model

Converts the given object to an ::ActiveModel compliant one.

#model_name_from_record_or_class

::AbstractController::Translation - Included

#l
#localize

Delegates to I18n.localize.

#t
#translate

Delegates to I18n.translate.

::AbstractController::Rendering - Included

#_normalize_args

Normalize args by converting render “foo” to render :action => “foo” and render “foo/bar” to render :file => “foo/bar”.

#_normalize_options

Normalize options.

#_normalize_render

Normalize args and options.

#_process_format

Process the rendered format.

#_process_options

Process extra options.

#render

Normalize arguments, options and then delegates render_to_body and sticks the result in self.response_body.

#render_to_body

Performs the actual template rendering.

#render_to_string

Raw rendering of a template to a string.

#rendered_format

Returns Content-Type of rendered content :api: public.

#view_assigns

This method should return a hash with assigns.

::ActionView::ViewPaths - Included

#append_view_path, #details_for_lookup,
#lookup_context

LookupContext is the object responsible to hold all information required to lookup templates, i.e. view paths and details.

#prepend_view_path, #template_exists?

Metal - Inherited

#controller_name

Delegates to the class' controller_name.

#url_for

Basic url_for that can be overridden for more robust functionality.

::AbstractController::Base - Inherited

#action_methods

Delegates to the class' #action_methods

#available_action?

Returns true if a method for the action is available and can be dispatched, false otherwise.

#controller_path

Delegates to the class' #controller_path

#process

Calls the action going through the entire action dispatch stack.

::ActiveSupport::Configurable - Included

#config

Reads and writes attributes from a configuration OrderedHash.

Constructor Details

This class inherits a constructor from ActionController::Metal

Class Method Details

.protected_instance_variables

[ GitHub ]

  
# File 'actionpack/lib/action_controller/base.rb', line 262

def self.protected_instance_variables
  PROTECTED_IVARS
end

.without_modules(*modules)

Shortcut helper that returns all the modules included in Base except the ones passed as arguments:

class MyBaseController < ActionController::Metal
  ActionController::Base.without_modules(:ParamsWrapper, :Streaming).each do |left|
    include left
  end
end

This gives better control over what you want to exclude and makes it easier to create a bare controller class, instead of listing the modules required manually.

[ GitHub ]

  
# File 'actionpack/lib/action_controller/base.rb', line 195

def self.without_modules(*modules)
  modules = modules.map do |m|
    m.is_a?(Symbol) ? ActionController.const_get(m) : m
  end

  MODULES - modules
end

Instance Method Details

#request

Returns an ::ActionDispatch::Request instance that represents the current request.

[ GitHub ]

  
# File 'actionpack/lib/action_controller/base.rb', line 172

rdoc_method :method: request

#response

Returns an ::ActionDispatch::Response that represents the current response.

[ GitHub ]

  
# File 'actionpack/lib/action_controller/base.rb', line 178

rdoc_method :method: response