ruby-on-rails - 不能有 has_one :through association ' where the :through association is a collection

Question

我有以下关联。 PropertyOwner 是一个连接模型，它属于一个属性(property)，多态地属于一个所有者，在下面的例子中是一个 ForeclosureDefense。一切正常，直到我拥有 has_one :main_property。这个想法是 ForeclosureDefense 模型可以有很多属性，但最后一个属性是主要属性:

class ForeclosureDefense < ActiveRecord::Base
  has_many :property_owners, as: :owner
  has_many :properties, through: :property_owners
  has_one :main_property, through: :property_owners, source: :property, order: 'created_at desc'
end

class PropertyOwner < ActiveRecord::Base
  belongs_to :property
  belongs_to :owner, polymorphic: :true
end

class Property < ActiveRecord::Base
  has_many :property_owners
  has_many :owners, through: :property_owners
  has_many :foreclosure_owners, through: :property_owners, source: :owner, source_type: "ForeclosureDefense"
  has_many :folder_owners, through: :property_owners, source: :owner, source_type: "Folder"
end

不幸的是，当我尝试使用 has_one :main_property 关联时，出现以下错误:

ActiveRecord::HasOneThroughCantAssociateThroughCollection:不能有 has_one :through 关联“ForeclosureDefense#main_property”，其中 :through 关联“ForeclosureDefense#property_owners”是一个集合。

我究竟做错了什么？

Answer 1

我的解决方案只是将其添加为类级宏:

def main_property
  properties.order('created_at desc').first
end