mysql - 通过另一个外键关联外键

Question

我有这 3 个模型

class User < ActiveRecord::Base
  has_many :answers, :as => :owner
end

class Answer < ActiveRecord::Base
  belongs_to :owner, :polymorphic => true
  has_one :test  
end

class Test < ActiveRecord::Base
  belongs_to :answer
end

所以我想通过模型将Test模型与模型关联起来，而不需要在它们之间创建新的关联，所以我将以下内容放入测试模型中：UserAnswer

has_one :owner, :through => :answer

但它不起作用，我收到了这个错误

ActiveRecord::HasManyThroughAssociationPolymorphicSourceError: Cannot have a has_many :through association 'Test#owner' on the polymorphic object 'Owner#owner'.

有什么帮助吗？

Answer 1

在Test：

delegate :owner, :to => :answer

Answer 2

您必须将source_type选项指定为owner多态关联

class Test < ActiveRecord::Base
  belongs_to :answer
  has_one :owner, :through => :answer, :source_type => "User"
end