ActionController::Renderer allows you to render arbitrary templates without requirement of being in controller actions.

You get a concrete renderer class by invoking ActionController::Base#renderer. For example:


It allows you to call method render directly.

ApplicationController.renderer.render template: '...'

You can use this shortcut in a controller, instead of the previous example:

ApplicationController.render template: '...'

render allows you to use the same options that you can use when rendering in a controller. For example:

FooController.render :action, locals: { ... }, assigns: { ... }

The template will be rendered in a Rack environment which is accessible through ActionController::Renderer#env. You can set it up in two ways:

  • by changing renderer defaults, like

    ApplicationController.renderer.defaults # => hash with default Rack environment
  • by initializing an instance of renderer by passing it a custom environment. 'post', https: true)
DEFAULTS = { http_host: "", https: false, method: "get", script_name: "", input: "" }.freeze
RACK_KEY_TRANSLATION = { http_host: "HTTP_HOST", https: "HTTPS", method: "REQUEST_METHOD", script_name: "SCRIPT_NAME", input: "rack.input" }
[R] controller
[R] defaults
Class Public methods
for(controller, env = {}, defaults = DEFAULTS.dup)

Create a new renderer instance for a specific controller class.

# File actionpack/lib/action_controller/renderer.rb, line 48
def self.for(controller, env = {}, defaults = DEFAULTS.dup)
  new(controller, env, defaults)
new(controller, env, defaults)

Accepts a custom Rack environment to render templates in. It will be merged with the default Rack environment defined by ActionController::Renderer::DEFAULTS.

# File actionpack/lib/action_controller/renderer.rb, line 65
def initialize(controller, env, defaults)
  @controller = controller
  @defaults = defaults
  @env = normalize_keys defaults, env
Instance Public methods
new(env = {})

Create a new renderer for the same controller but with a new env.

# File actionpack/lib/action_controller/renderer.rb, line 53
def new(env = {}) controller, env, defaults

Render templates with any options from ActionController::Base#render_to_string.

The primary options are:

  • :partial - See ActionView::PartialRenderer for details.

  • :file - Renders an explicit template file. Add :locals to pass in, if so desired. It shouldn’t be used directly with unsanitized user input due to lack of validation.

  • :inline - Renders an ERB template string.

  • :plain - Renders provided text and sets the content type as text/plain.

  • :html - Renders the provided HTML safe string, otherwise performs HTML escape on the string first. Sets the content type as text/html.

  • :json - Renders the provided hash or object in JSON. You don't need to call .to_json on the object you want to render.

  • :body - Renders provided text and sets content type of text/plain.

If no options hash is passed or if :update is specified, then:

If an object responding to render_in is passed, render_in is called on the object, passing in the current view context.

Otherwise, a partial is rendered using the second parameter as the locals hash.

Also aliased as: render_to_string
# File actionpack/lib/action_controller/renderer.rb, line 91
def render(*args)
  raise "missing controller" unless controller

  request = @env
  request.routes = controller._routes

  instance =
  instance.set_request! request
  instance.set_response! controller.make_response!(request)
Alias for: render

Create a new renderer for the same controller but with new defaults.

# File actionpack/lib/action_controller/renderer.rb, line 58
def with_defaults(defaults) controller, @env, self.defaults.merge(defaults)