Rails 3：可选的has_one关联的范围

Question

我有两种模式：销售和付款

class Sale < ActiveRecord::Base
  has_one :payment
end

class SaleCancelation < ActiveRecord::Base
  belongs_to :payment
end

我想创建两个范围，“付款”和“不付款”。

“with_payment”可以轻松实现：

class Sale < ActiveRecord::Base
  scope :with_payment, joins( :payment )
end

但是，我如何创建一个范围，找出不的每笔销售都有相关的付款？

Answer 1

怎么样：

scope :without_payment, where( 'id not in (select sales_id from payments)' )

Answer 2

另一种方法：

scope :without_profile, lambda { includes(:user_profile).where('user_profiles.id is null') }

Answer 3

class Sale < ActiveRecord::Base
    scope :with_payment, joins( :payment )
    scope :without_payment, Sale.all - Sale.with_payment
end