ruby-on-rails - 关联记录满足特定条件的记录的范围？

Question

我有一个Customer模型，每个客户都有很多工作：

class Customer < ActiveRecord::Base
  has_many :jobs
end

class Job < ActiveRecord::Base
  belongs_to :customer

  def self.unbilled
    finished.uninvoiced # these are other scopes on Job
  end
end

如何定义一个范围，Customer该范围将返回所有未开票工作的客户列表？

Answer 1

您也许可以合并范围：

class Customer < ActiveRecord::Base
  has_many :jobs

  scope :freeloaders, joins(:jobs).merge(Job.unbilled)
end