与has_many建立联系：通过多个模型

Question

请帮助了解如何@project.payments拥有此树：

Project
   |__Stages
         |__Costs
              |__Payments

project.rb

 has_many :stages
 has_many :costs, :through => stages

stage.rb

belongs_to :project
has_many :costs
has_many :payments :through => costs

cost.rb

belongs_to :stage
has_many :payments

payment.rb

belongs_to :cost

Answer 1

注意：由于这是一个嵌套的has_many：through关系，它只适用于Rails 3.1+（3.1的RC4已经出局）

project.rb

has_many :payments, :through => costs