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Action Controller Metal ↑

ActionController::Metal is the simplest possible controller, providing a valid Rack interface without the additional niceties provided by ActionController::Base.

A sample metal controller might look like this:

class HelloController < ActionController::Metal
  def index
    self.response_body = "Hello World!"
  end
end

And then to route requests to your metal controller, you would add something like this to config/routes.rb:

get 'hello', to: HelloController.action(:index)

The ::action method returns a valid Rack application for the Rails router to dispatch to.

Rendering Helpers ↑

By default, ActionController::Metal provides no utilities for rendering views, partials, or other responses aside from some low-level setters such as response_body=, content_type=, and status=. To add the render helpers you’re used to having in a normal controller, you can do the following:

class HelloController < ActionController::Metal
  include AbstractController::Rendering
  include ActionView::Layouts
  append_view_path "#{Rails.root}/app/views"

  def index
    render "hello/index"
  end
end

Redirection Helpers ↑

To add redirection helpers to your metal controller, do the following:

class HelloController < ActionController::Metal
  include ActionController::Redirecting
  include Rails.application.routes.url_helpers

  def index
    redirect_to root_url
  end
end

Other Helpers ↑

You can refer to the modules included in ActionController::Base to see other features you can bring into your metal controller.

Methods
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Attributes

[R] request

The ActionDispatch::Request instance for the current request.
[R] response

The ActionDispatch::Response instance for the current response.

Class Public methods

action(name)

Returns a Rack endpoint for the given action name.

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 315
def self.action(name)
  app = lambda { |env|
    req = ActionDispatch::Request.new(env)
    res = make_response! req
    new.dispatch(name, req, res)
  }

  if middleware_stack.any?
    middleware_stack.build(name, app)
  else
    app
  end
end

controller_name()

Returns the last part of the controller’s name, underscored, without the ending Controller. For instance, PostsController returns posts. Namespaces are left out, so Admin::PostsController returns posts as well.

Returns ↑

  • string

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 130
def self.controller_name
  @controller_name ||= (name.demodulize.delete_suffix("Controller").underscore unless anonymous?)
end

dispatch(name, req, res)

Direct dispatch to the controller. Instantiates the controller, then executes the action named name.

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 331
def self.dispatch(name, req, res)
  if middleware_stack.any?
    middleware_stack.build(name) { |env| new.dispatch(name, req, res) }.call req.env
  else
    new.dispatch(name, req, res)
  end
end

make_response!(request)

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 134
def self.make_response!(request)
  ActionDispatch::Response.new.tap do |res|
    res.request = request
  end
end

middleware()

The middleware stack used by this controller.

By default uses a variation of ActionDispatch::MiddlewareStack which allows for the following syntax:

class PostsController < ApplicationController
  use AuthenticationMiddleware, except: [:index, :show]
end

Read more about [Rails middleware stack] (guides.rubyonrails.org/rails_on_rack.html#action-dispatcher-middleware-stack) in the guides.

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 310
def self.middleware
  middleware_stack
end

new()

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 210
def initialize
  @_request = nil
  @_response = nil
  @_response_body = nil
  @_routes = nil
  @_params = nil
  super
end

use(...)

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

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 293
def use(...)
  middleware_stack.use(...)
end

Instance Public methods

content_type

Delegates to ActionDispatch::Response#content_type

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 204
delegate :content_type, to: "@_response"

content_type=

Delegates to ActionDispatch::Response#content_type=

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 192
delegate :content_type=, to: "@_response"

controller_name()

Delegates to the class’s ::controller_name.

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 156
def controller_name
  self.class.controller_name
end

headers

Delegates to ActionDispatch::Response#headers.

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 180
delegate :headers, to: "@_response"

location

Delegates to ActionDispatch::Response#location

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 200
delegate :location, to: "@_response"

location=

Delegates to ActionDispatch::Response#location=

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 188
delegate :location=, to: "@_response"

media_type

Delegates to ActionDispatch::Response#media_type

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 208
delegate :media_type, to: "@_response"

params()

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 219
def params
  @_params ||= request.parameters
end

params=(val)

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 223
def params=(val)
  @_params = val
end

performed?()

Tests if render or redirect has already happened.

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 245
def performed?
  response_body || response.committed?
end

reset_session()

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 284
def reset_session
  @_request.reset_session
end

response=(response)

Assign the response and mark it as committed. No further processing will occur.

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 268
def response=(response)
  set_response!(response)

  # Force `performed?` to return true:
  @_response_body = true
end

response_body=(body)

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 234
def response_body=(body)
  if body
    body = [body] if body.is_a?(String)
    response.body = body
    super
  else
    response.reset_body!
  end
end

session

The ActionDispatch::Request::Session instance for the current request. See further details in the Active Controller Session guide.

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 176
delegate :session, to: "@_request"

status

Delegates to ActionDispatch::Response#status

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 196
delegate :status, to: "@_response"

status=

Delegates to ActionDispatch::Response#status=

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 184
delegate :status=, to: "@_response"

url_for(string)

Basic url_for that can be overridden for more robust functionality.

Source: show | on GitHub 

# File actionpack/lib/action_controller/metal.rb, line 230
def url_for(string)
  string
end