Ruby on Rails

I've took this post like basis but receive empty response every time. What's wrong?

Basic controller:

class Api::V1::BaseController < ActionController::Metal    include AbstractController::Rendering    include AbstractController::Callbacks    include AbstractController::Helpers      include ActionController::HttpAuthentication::Token::ControllerMethods    include ActionController::Rendering    include ActionController::Renderers::All    include ActionController::MimeResponds    include ActionController::Instrumentation      append_view_path "#{Rails.root}/app/views"      respond_to :json    end

Controller:

class Api::V1::UsersController < Api::V1::BaseController      def index      @user = User.find(params[:id])    end    end

RABL template:

object @user    attributes :first_name