HABTM 多态关系 [英] HABTM Polymorphic Relationship

问题描述

我对 Rails 还很陌生，我正在尝试建立一个多态的 HABTM 关系.问题是我想要关联三个模型.

I'm pretty new to Rails, and i'm trying to do a polymorphic HABTM relationship. The problem is that I have three models that I want to relate.

第一个是事件模型，然后是两种参与者:用户和联系人.

The first one is the Event model and then are two kind of attendees: Users and Contacts.

我想做的是能够将用户和联系人作为参与者联系起来.所以，我现在的代码是:

What I want to do is to be able to relate as an attendee both users and contacts. So, what i have right now in my code is:

事件模型

has_and_belongs_to_many :attendees, :polymorphic => true

用户模型

has_and_belongs_to_many :events, :as => :attendees

联系方式

has_and_belongs_to_may :events, :as => :attendees

1. HABTM 表迁移需要如何进行?我有点困惑，我没有找到任何帮助.
2. 它会起作用吗?

推荐答案

不，你不能那样做，没有多态 has_and_belongs_to_many 关联这样的东西.

No, you can't do that, there's no such thing as a polymorphic has_and_belongs_to_many association.

您可以做的是创建一个中间模型.大概是这样的:

What you can do is create a middle model. It would probably be something like this:

class Subscription < ActiveRecord::Base
  belongs_to :attendee, :polymorphic => true
  belongs_to :event
end

class Event < ActiveRecord::Base
  has_many :subscriptions
end

class User < ActiveRecord::Base
  has_many :subscriptions, :as => :attendee
  has_many :events, :through => :subscriptions
end

class Contact < ActiveRecord::Base
  has_many :subscriptions, :as => :attendee
  has_many :events, :through => :subscriptions
end

通过这种方式，订阅模型的行为类似于 N:N 关系中的链接表，但允许您对事件具有多态行为.

This way the Subscription model behaves like the link table in a N:N relationship but allows you to have the polymorphic behavior to the Event.

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