Mixins和类常量

Question

我有一个课程和一个模块：

appointment.rb

class Appointment < ActiveRecord::Base
  include Appointments::Events

  ALERT = "hello!"

end

events.rb

module Appointments
  module Events
    extend ActiveSupport::Concern

    def say_alert
      puts self.class::ALERT
    end
  end
end

给#say_alert打电话给我：

uninitialized constant Module::ALERT

Answer 1

对不起，没有回答，但是代码太长，不能发表评论：

按什么顺序加载文件？以及如何调用#say_alert？

此代码运行良好：

module Appointments
  module Events
    def say_alert
      puts self.class::ALERT
    end
  end
end

class Appointment 
  include Appointments::Events

  ALERT = "hello!"

end

Appointment.new.say_alert

在您的评论之后:它也适用于ActiveSupport::Concern

require 'active_support'
module Appointments
  module Events
    extend ActiveSupport::Concern
    def say_alert
      puts self.class::ALERT
    end
  end
end

class Appointment 
  include Appointments::Events

  ALERT = "hello!"

end

Appointment.new.say_alert

我用红宝石2.1.5

Answer 2

答案很简单，

问题是，在常量定义之前，我在类中包含了模块。我还对代码进行了一些重构，这样它就像@rbates在http://railscasts.com/episodes/398-service-objects上建议的那样正确地使用了关注点

现在我的代码起作用了：

应用程序/模型/任命。

class Appointment < ActiveRecord::Base  
  ALERTS = "hello!"

  include Events
end

应用程序/模型/关注事项/约会/事件app

class Appointment
  module Events
    extend ActiveSupport::Concern

    def say_alert
     puts ALERT
    end
  end
end

$ rails控制台

Appointment.last.say_alert
=> "hello!"