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:

  match 'hello', :to => HelloController.action(:index)

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

Rendering Helpers

ActionController::Metal by default provides no utilities for rendering views, partials, or other responses aside from explicitly calling of 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 ActionController::Rendering
    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.