Question

我正在使用Ruby on Rails v3.2.2。我通过以下方式与用于alias_method关联的has_many :through建立关联：

class Resource < ActiveRecord::Base
  has_many :article_associations
  alias_method :post_associations, :article_associations

  has_many :users, :through => :post_associations
end

当我执行@article.users时，我收到以下错误：

ActiveRecord::HasManyThroughAssociationNotFoundError
Could not find the association :post_associations in model Article

为什么会这样？有没有办法让它按预期工作？也就是说，如何通过＆＃34;别名＆＃34;正确地返回@article.users。 :post_associations？

注意：我想＆＃34;陈述＆＃34; /＆＃34;使用＆＃34; :post_associations语句中的has_many :users, :through => :post_associations因为我正在尝试动态构建＆＃34; （即元编程）has_many :through关联。

Ruby on Rails 框架跟踪是：

activerecord (3.2.2) lib/active_record/reflection.rb:501:in `check_validity!'
activerecord (3.2.2) lib/active_record/associations/association.rb:26:in `initialize'
activerecord (3.2.2) lib/active_record/associations/collection_association.rb:24:in `initialize'
activerecord (3.2.2) lib/active_record/associations/has_many_through_association.rb:10:in `initialize'
activerecord (3.2.2) lib/active_record/associations.rb:157:in `new'
activerecord (3.2.2) lib/active_record/associations.rb:157:in `association'
activerecord (3.2.2) lib/active_record/associations/builder/association.rb:44:in `block in define_readers'
...

Answer 1

我没有看到你需要alias_method命名你的关联的原因。

相反，你可以直接做这样的事情，

class Resource < ActiveRecord::Base
  has_many :post_associations, :foreign_key => :resource_id, :class_name => "ArticleAssociation"
  has_many :users, :through => :post_associations
end

另一种解决方案

class Resource < ActiveRecord::Base
  has_many :article_associations
  has_many :users, :through => :article_associations
end

def post_associations
  self.article_associations
end

您需要执行以下任一操作

resource.post_associations

或

resource.article_associations

Answer 2

看起来你正试图实现polymorphic associations。

如何正确使用has_many：through with alias_method？

2 个答案: