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.
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
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
You can refer to the modules included in ActionController::Base to see other features you can bring into your metal controller.
Returns a Rack endpoint for the given action name.
# File lib/action_controller/metal.rb, line 229 def self.action(name, klass = ActionDispatch::Request) middleware_stack.build(name.to_s) do |env| new.dispatch(name, klass.new(env)) end end
Makes the controller a Rack endpoint that runs the action in the given env‘s action_dispatch.request.path_parameters key.
# File lib/action_controller/metal.rb, line 224 def self.call(env) action(env['action_dispatch.request.path_parameters'][:action]).call(env) end
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.
string
# File lib/action_controller/metal.rb, line 114 def self.controller_name @controller_name ||= name.demodulize.sub(/Controller$/, '').underscore end
Alias for middleware_stack.
# File lib/action_controller/metal.rb, line 218 def self.middleware middleware_stack end
# File lib/action_controller/metal.rb, line 157 def content_type headers["Content-Type"] end
Basic implementations for content_type=, location=, and headers are provided to reduce the dependency on the RackDelegation module in Renderer and Redirector.
# File lib/action_controller/metal.rb, line 153 def content_type=(type) headers["Content-Type"] = type.to_s end
Delegates to the class’ controller_name
# File lib/action_controller/metal.rb, line 119 def controller_name self.class.controller_name end
# File lib/action_controller/metal.rb, line 104 def env @_env ||= {} end
# File lib/action_controller/metal.rb, line 161 def location headers["Location"] end
# File lib/action_controller/metal.rb, line 165 def location=(url) headers["Location"] = url end
# File lib/action_controller/metal.rb, line 141 def params @_params ||= request.parameters end
# File lib/action_controller/metal.rb, line 145 def params=(val) @_params = val end
# File lib/action_controller/metal.rb, line 187 def performed? response_body || (response && response.committed?) end
# File lib/action_controller/metal.rb, line 182 def response_body=(body) body = [body] unless body.nil? || body.respond_to?(:each) super end
# File lib/action_controller/metal.rb, line 174 def status @_status end
# File lib/action_controller/metal.rb, line 178 def status=(status) @_status = Rack::Utils.status_code(status) end
basic url_for that can be overridden for more robust functionality
# File lib/action_controller/metal.rb, line 170 def url_for(string) string end
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