按关系属性排序的查询(M:N)

Question

我有一个简单的多对多ER描述如下:

型号order.rb:

class Order < ActiveRecord::Base
  has_many :cronologies
  has_many :statuses, :through => :cronologies
end

型号cronology.rb:

class Cronology < ActiveRecord::Base
  belongs_to :order
  belongs_to :status
  validates_uniqueness_of :order_id, :scope => :status_id
end

型号status.rb:

class Status < ActiveRecord::Base
  has_many :cronologies
  has_many :orders, :through => :cronologies
end

下面的代码让我获得分配给订单的所有状态.

@order.statuses

...但是如何通过cronology表的"created_at"属性获取状态？

Answer 1

@order.statuses.all(:order => "cronologies.created_at")

如果您总是希望以这种方式订购,请将其关联起来.

class Order < ActiveRecord::Base
  has_many :cronologies
  has_many :statuses, :through => :cronologies, :order => "cronologies.created_at"
end