ruby-on-rails – 如何在模型中调用ApplicationController中定义

class ApplicationController < ActionController::Base
   helper_method :get_active_gateway
   def get_active_gateway(cart)
     cart.account.gateways
   end
end

当我在模型中调用此方法时

class Order < ActiveRecord::Base
   def transfer
     active= get_active_gateway(self.cart)
   end
end

它抛出错误undefined局部变量get_active_gateway.

所以我写了

class Order < ActiveRecord::Base
   def transfer
    active= ApplicationContoller.helpers.get_active_gateway(self.cart)
   end
end

那么Nilclass就是抛出错误未定义的方法.

我在Rails 3.2.0中工作.

请给出解决方案.