ActionController::Metal with doorkeeper

If you're using ActionController::Metal for your API and you want to protect it with doorkeeper OAuth, you just need to include a few modules:

class MetalController < ActionController::Metal
  include AbstractController::Callbacks
  include ActionController::Head
  include Doorkeeper::Helpers::Filter

  doorkeeper_for :all

  def index
    self.response_body = { :ok => true }.to_json
  end
end

This is the bare minimum to get either an :unauthorized response (that's why the Head module was included) or a authorized response with the response body.

Since doorkeeper uses a before filter, you need to include the AbstractController::Callbacks module.