可以从一个多态模型的单个记录属于两个（或更多）的模型，在同一时间？ [英] Can a single record from a polymorphic model belong to two (or more) models at the same time?

问题描述

一般新手的问题：如果我有一个名为消息多态模型，并呼吁其他两个型号过滤器和用户与的has_many：消息，因为在两个... 的关联。可以从信息单条记录属于用户和过滤器同时车型？例如，我可以做的：

General newbie question: If I have a polymorphic model called Message, and two other models called Filter and User with has_many: messages, as ... association on both. Can a single record from Message belong to User and Filter models at the same time? For example, can I do:

...
User.find(1).messages << Message.find(1)
Filter.find(1).messages << Message.find(1)
...

和具有消息＃1 在现有用户＃1 和过滤器＃1 ？该 RailsGuides给出了一个非常简短的解释的，所以这方面目前还不清楚我。

and have Message#1 available in in User#1 and Filter#1? The RailsGuides gives a very brief explanation, so this aspect is still unclear to me.

推荐答案

当然可以。比方说，一个消息具有所有者（可以是用户或某些其它类）和处理器（即可以是过滤器或某些其他类） 然后在邮件表，你需要列： owner_id，owner_type，processor_id，processor_type 。 而类应该是这个样子：

Yes you can. Let's say a message has owner (that can be User or some other class) and processor (that can be Filter or some other class) Then in the messages table you'll need columns: owner_id, owner_type, processor_id, processor_type. And the classes should look something like:

class Message
  belongs_to :owner, polymorphic: true
  belongs_to :processor, polymorphic: true
end

class User
  has_many :messages
end

class Filter
  has_many :messages
end

不过，为了使消息属于这两种模式，你需要做的是这样的：

However in order to make the message belong to both models you'll need to do something like this:

Message.create(owner: User.find(1), processor: Filter.find(1))
# or like this
User.find(1).messages << Message.create(processor: Filter.find(1))

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