Rails：保存子项时更新父对象

In my app, a Conversation has many Messages. How to I update the updated_at attribute of a Conversation when a new Message in that Conversation is created/saved?

在我的应用程序中，Conversation有很多消息。如何在创建/保存该对话中的新消息时更新对话的updated_at属性？

I'm aware of :touch => true, which does this, but it also updates Conversation when a Message is destroyed, which is not what I want.

我知道：touch => true，这样做，但它也会在Message被销毁时更新Conversation，这不是我想要的。

Thanks.

谢谢。

Models

楷模

class Conversation < ActiveRecord::Base
  has_many :messages 
end

class Message < ActiveRecord::Base
  belongs_to :conversation
end

3 个解决方案

#1

use callback inside Message class

在Message类中使用回调

after_save do
  conversation.update_attribute(:updated_at, Time.now)
end

#2

You can just define it on the relationship as well.

您也可以在关系上定义它。

class Message < ActiveRecord::Base
  belongs_to :conversation, touch: true
end

(Source same as William G's answer: http://apidock.com/rails/ActiveRecord/Persistence/touch)

（来源与William G的答案相同：http：//apidock.com/rails/ActiveRecord/Persistence/touch）

#3

I prefer this solution for Rails 3:

我更喜欢Rails 3的这个解决方案：

class Message < ActiveRecord::Base
  belongs_to :conversation

  after_save :update_conversation

  def update_conversation
    self.conversation.touch
  end
end

Source: http://apidock.com/rails/ActiveRecord/Persistence/touch

资料来源：http：//apidock.com/rails/ActiveRecord/Persistence/touch

#1