使用'alias'关键字实现Rails回调

Question

我正在玩着使用别名方法实现Rails模型回调（after_save，before_save）等。它所做的只是将save方法别名为save_with_callbacks。它的工作原理除before_save必须在save被定义或alias关键字引发错误后调用。我仍然在理解Rails回调是如何工作的，但是想知道是否有方法在模型中的任何地方使用before_filter。

module ClassMethods 
    def before_save 
    class_eval do 
     # old_save points to save 
     # save points to save_with_callbacks 
     alias :old_save :save 
     alias :save :save_with_callbacks 
    end 
    end 
end 

module InstanceMethods 
    def save_with_callbacks 
    @save_with_callbacks_text = 'Saving with callbacks' 
    old_save 
    end 
end 

class Task 
    extend ClassMethods 
    include InstanceMethods 

    attr_reader :save_text, :save_with_callbacks_text 

    def save 
    @save_text = 'Saving' 
    end 

    # Needs to be called after save, save_with_callbacks are defined 
    before_save 
end 

Answer 1

我忘了用户通常不定义'save'方法，但让ORM为你做。将save方法移至InstanceMethods并解决了该问题。