use_renderers

Adds, by name, a renderer or renderers to the `_renderers` available to call within controller actions.

It is useful when rendering from an ActionController::Metal controller or otherwise to add an available renderer proc to a specific controller.

Both ActionController::Base and ActionController::API include ActionController::Renderers::All, making all renderers available in the controller. See Renderers::RENDERERS and Renderers.add.

Since ActionController::Metal controllers cannot render, the controller must include AbstractController::Rendering, ActionController::Rendering, and ActionController::Renderers, and have at least one renderer.

Rather than including ActionController::Renderers::All and including all renderers, you may specify which renderers to include by passing the renderer name or names to `use_renderers`. For example, a controller that includes only the `:json` renderer (`_render_with_renderer_json`) might look like:

class MetalRenderingController < ActionController::Metal
  include AbstractController::Rendering
  include ActionController::Rendering
  include ActionController::Renderers

  use_renderers :json

  def show
    render json: record
  end
end

You must specify a `use_renderer`, else the `controller.renderer` and `controller._renderers` will be `nil`, and the action will fail.