has_one 有两个外键？

Question

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

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’”

Answer 1

您可以使用:class_name 属性来设置哪个类用于外键：

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，您说您使用sender_id 和recipient_id 作为外键，但在您的代码中您有:foreign_key => 'sender' 和:foreign_key => 'recipient'。您是否尝试将它们更改为:foreign_key => 'sender_id' 和:foreign_key => 'recipient_id'？所以：

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