Question

型号：

class Thread < ActiveRecord::Base
  has_many :threaded, :through => :threaded, :foreign_key => :thread_id

class ThreadFeed < ActiveRecord::Base
 belongs_to :threaded, :polymorphic => true

模型字段

Thread (id)
ThreadFeed (id, thread_id, threaded_id, threaded_type)

问题在于：

@thread.threaded

Rails使用（threaded_id，threaded_type）作为外键，我希望thread_id是外键。

Answer 1

看看这个Railscast，Polymorphism

它将使您更好地了解多态性的工作原理。

我注意到的第一个问题是它应该通过：threadfeed，而不是：threaded

class Thread < ActiveRecord::Base
  has_many :threadfeeds, :as => :threaded

在Railscast中，他有：

class Comment < ActiveRecord::Base
  belongs_to :commentable, :polymorphic => true
end

class Article < ActiveRecord::Base
  has_many :comments, :as => :commentable
end

class Photo < ActiveRecord::Base
  has_many :comments, :as => :commentable
  #...
end

class Event < ActiveRecord::Base
  has_many :comments, :as => :commentable
end

Answer 2

第一个问题是Thread不知道什么是feed：

class Thread < ActiveRecord::Base
    has_many :feeds, :through => :thread_feeds, :as => :feeded
    has_many :thread_feeds

class ThreadFeed < ActiveRecord::Base
     belongs_to :feeded, :polymorphic => true

第二个问题是多态的复杂性。这是一篇很棒的文章：http://blog.hasmanythrough.com/2006/4/3/polymorphic-through

帮助在模型中建立多态关系

2 个答案: