Rails 3: Scope on an optional has_one association

Question

I have two models: Sale and Payment

class Sale < ActiveRecord::Base
  has_one :payment
end

class SaleCancelation < ActiveRecord::Base
  belongs_to :payment
end

I want to create two scopes, "with payment" and "without payment".

"with_payment" works easyly:

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

But how can I create a scope that finds every sale that does not have an associated Payment?

Answer 1

How about:

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

Answer 2

Another way to do it:

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