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

action
content_type
content_type=
controller_name
controller_name
dispatch
headers
location
location=
make_response!
media_type
middleware
new
params
params=
performed?
reset_session
response=
response_body=
session
status
status=
url_for
use

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 code

# 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

🔎 See on GitHub

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 code

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

🔎 See on GitHub

dispatch(name, req, res)

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

📝 Source code

# 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

🔎 See on GitHub

make_response!(request)

📝 Source code

# 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

🔎 See on GitHub

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 code

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

🔎 See on GitHub

new()

📝 Source code

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

🔎 See on GitHub

use(...)

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

📝 Source code

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

🔎 See on GitHub

Instance Public methods

content_type

Delegates to ActionDispatch::Response#content_type

📝 Source code

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

🔎 See on GitHub

content_type=

Delegates to ActionDispatch::Response#content_type=

📝 Source code

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

🔎 See on GitHub

controller_name()

Delegates to the class’s ::controller_name.

📝 Source code

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

🔎 See on GitHub

headers

Delegates to ActionDispatch::Response#headers.

📝 Source code

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

🔎 See on GitHub

location

Delegates to ActionDispatch::Response#location

📝 Source code

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

🔎 See on GitHub

location=

Delegates to ActionDispatch::Response#location=

📝 Source code

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

🔎 See on GitHub

media_type

Delegates to ActionDispatch::Response#media_type

📝 Source code

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

🔎 See on GitHub

params()

📝 Source code

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

🔎 See on GitHub

params=(val)

📝 Source code

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

🔎 See on GitHub

performed?()

Tests if render or redirect has already happened.

📝 Source code

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

🔎 See on GitHub

reset_session()

📝 Source code

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

🔎 See on GitHub

response=(response)

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

📝 Source code

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

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

🔎 See on GitHub

response_body=(body)

📝 Source code

# 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

🔎 See on GitHub

session

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

📝 Source code

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

🔎 See on GitHub

status

Delegates to ActionDispatch::Response#status

📝 Source code

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

🔎 See on GitHub

status=

Delegates to ActionDispatch::Response#status=

📝 Source code

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

🔎 See on GitHub

url_for(string)

Basic url_for that can be overridden for more robust functionality.

📝 Source code

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

🔎 See on GitHub

ActionController::Metal < AbstractController::Base

Action Controller Metal

Rendering Helpers

Redirection Helpers

Other Helpers

Methods

Attributes

Class Public methods

action(name)

controller_name()

Returns

dispatch(name, req, res)

make_response!(request)

middleware()

new()

use(...)

Instance Public methods

content_type

content_type=

controller_name()

headers

location

location=

media_type

params()

params=(val)

performed?()

reset_session()

response=(response)

response_body=(body)

session

status

status=

url_for(string)

Action Controller `Metal`

`Rendering` `Helpers`

Redirection `Helpers`

Other `Helpers`