如何通过多对多关联获取记录？

Question

我在Rails 4应用程序中有这些模型：

class Invoice < ActiveRecord::Base

  has_many  :allocations
  has_many  :payments, :through => :allocations

end

---

class Allocation < ActiveRecord::Base

  belongs_to :invoice
  belongs_to :payment

end

---

class Payment < ActiveRecord::Base

  has_many    :allocations
  has_many    :invoices, :through => :allocations

end

如何获取与某个特定invoices X相关的所有payment？

我一整天都试图绕过这一切，但无济于事。

感谢您的帮助。

Answer 1

简单如下：

payment.invoices

这将遵循您的关联，通过分配模型。

Answer 2

试试这个， 确定付款，然后确定这样的发票

payment_invoices = Payment.find(payment_id).invoices