jbuilder X rails-api

[SunnyTam]

can anyone help? I have set a helper method on ApplicationHelper and try to make it work on rails-api X jbuilder. However, it shows
undefined local variable or method current_user_detail'`

this is my ApplicationHelper

module ApplicationHelper
  def current_user_detail
    User.find(current_user.id).user_detail if user_signed_in?
  end
end

this is my Application controller

class ApplicationController <ActionController::API
  include ActionController::ImplicitRender
  include ActionController::Helpers

can someone help?