gistfile1.rb

def self.routes
  Raptor.routes(self) do
    index :responder => JSONResponder
  end
end

class JSONResponder
  def initialize(resource, action, params)
    @resource = resource
    @action = action
    @presenter_name = params[:present]
  end

  def respond(record, injector)
    injector.add_record(record)
    presenter_class = @resource.send("#{@presenter_name}_presenter")
    presenter = injector.call(presenter_class.method(:new))

    Rack::Response.new(presenter.to_json, 200, {"Content-Type" => "application/json"})
  end
end