扶手：覆盖的ActiveRecord联想法 [英] Rails: Overriding ActiveRecord association method

问题描述

有没有办法覆盖由一个ActiveRecord协会提供的方法之一？

Is there a way to override one of the methods provided by an ActiveRecord association?

比方说我有以下典型的多态的has_many：通过关联：

Say for example I have the following typical polymorphic has_many :through association:

class Story < ActiveRecord::Base
    has_many :taggings, :as => :taggable
    has_many :tags, :through => :taggings, :order => :name
end


class Tag < ActiveRecord::Base
    has_many :taggings, :dependent => :destroy
    has_many :stories, :through => :taggings, :source => :taggable, :source_type => "Story"
end

正如你可能知道这​​增加了相关方法像标签，标签和其中的故事模型整体转换;＆LT;，标签=，tags.empty？等等。

As you probably know this adds a whole slew of associated methods to the Story model like tags, tags<<, tags=, tags.empty?, etc.

我如何去重写这些方法之一？具体的标签＆LT;＆LT;方法。这是pretty的容易覆盖一个普通的类方法，但我似乎无法找到如何覆盖关联方法的任何信息。做这样的事情

How do I go about overriding one of these methods? Specifically the tags<< method. It's pretty easy to override a normal class methods but I can't seem to find any information on how to override association methods. Doing something like

def tags<< *new_tags
    #do stuff
end

产生一个语法错误，当它被称为所以它显然不是那么简单。

produces a syntax error when it's called so it's obviously not that simple.

推荐答案

您可以使用的has_many 块与方法扩展您的关联。见注释使用块来扩展你的联想<一href="http://apidock.com/rails/ActiveRecord/Associations/ClassMethods/has_many#461-User-a-block-to-extend-your-associations">here.
覆盖现有的方法也适用，不知道它是否是一个好主意，但是。

You can use block with has_many to extend your association with methods. See comment "Use a block to extend your associations" here.
Overriding existing methods also works, don't know whether it is a good idea however.

  has_many :tags, :through => :taggings, :order => :name do
    def << (value)
      "overriden" #your code here
      super value
    end     
  end

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