Mixin 和类常量

Question

我有 1 个班级和 1 个模块：

约会.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

调用 #say_alert 给我：

uninitialized constant Module::ALERT

Answer 1

答案很简单，

问题是我在常量定义之前将模块包含在我的类中。我还稍微重构了我的代码，因此它正确使用了 @rbates 在 http://railscasts.com/episodes/398-service-objects 建议的关注点

现在我的代码可以工作了：

app/models/appointment.rb

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

  include Events
end

app/models/concerns/appointment/events.rb

class Appointment
  module Events
    extend ActiveSupport::Concern

    def say_alert
     puts ALERT
    end
  end
end

$ rails 控制台

Appointment.last.say_alert
=> "hello!"

Answer 2

对不起，没有答案，但代码太长，无法评论：

您按什么顺序加载文件？以及如何调用#say_alert？

这段代码运行良好：

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

---

在您发表评论后： 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

我使用 ruby​​ 2.1.5