has_one 有两个外键? [英] has_one with two foreign keys?

问题描述

我有两个类 Message 和 User.消息具有 user 的 sender_id 和 recipient_id 两个外键.如何建立关系，我将能够为发件人和收件人获取用户，例如 @message.sender.name 和 @message.recipient.name

I have two classes Message and User. Message has sender_id and recipient_id both foreign keys for User. How to build relationship where I'll be able to get user for both sender and recipient, like @message.sender.name and @message.recipient.name

我尝试过这样做:

class Message < ActiveRecord::Base  

  belongs_to :sender, :class_name => 'User', :foreign_key => 'sender'
  belongs_to :recipient, :class_name => 'User', :foreign_key => 'recipient'

end   

class User < ActiveRecord::Base

  has_many :recivied_messages, :class_name => 'Message', :foreign_key => 'recipient'
  has_many :send_messages, :class_name => 'Message', :foreign_key => 'sender'
end

但它没有帮助，例如，当我尝试访问 @message.recipient.name 时，它​​说未定义的方法‘名称’"

But it didn't help, when I'm trying to access to, for instance, @message.recipient.name it says that "undefined method `name'"

推荐答案

您可以使用 :class_name 属性来设置哪个类用于外键:

You can use the :class_name property to set which class gets used for a foreign key:

class Message < ActiveRecord::Base
  has_one :sender, :class_name => User
  has_one :recipient, :class_name => User
end

class User < ActiveRecord::Base
  belongs_to :sent_messages, :class_name => Message
  belongs_to :received_messages, :class_name => Message
end

另外，你说你使用 sender_id 和 recipient_id 作为外键，但在你的代码中你有 :foreign_key =>'sender' 和 :foreign_key =>'收件人'.您是否尝试将它们更改为 :foreign_key =>'sender_id' 和 :foreign_key =>'recipient_id'?所以:

Also, you say you are using sender_id and recipient_id for the foreign keys, but in your code you have :foreign_key => 'sender' and :foreign_key => 'recipient'. Have you tried changing them to :foreign_key => 'sender_id' and :foreign_key => 'recipient_id'? So:

class Message < ActiveRecord::Base
  has_one :sender, :class_name => User, :foreign_key => 'sender_id'
  has_one :recipient, :class_name => User, :foreign_key => 'recipient_id'
end

class User < ActiveRecord::Base
  belongs_to :sent_messages, :class_name => Message, # ...etc
  belongs_to :received_messages, :class_name => Message, # ...etc
end

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