我想保留用户何时更改地址的记录.
这样,订单放置时,始终可以引用订单放置时使用的用户地址.
可能的模式
users ( id username email ... ) user_addresses ( id label line_1 line_2 city state zip ... ) user_addresses_map ( user_id user_address_id start_time end_time ) orders ( id user_id user_address_id order_status_id ... created_at updated_at )
select ua.* from orders o join users u on u.id = o.user_id join user_addressses_map uam on uam.user_id = u.id and uam.user_address_id = o.user_address_id join user_addresses ua on ua.id = uam.user_address_id and uam.start_time < o.created_at and (uam.end_time >= o.created_at or uam.end_time is null) ;
编辑：解决方案
@KandadaBoggu发布了一个很棒的解决方案. Vestal Versions plugin是一个很好的解决方案.
摘自http://github.com/laserlemon/vestal_versions的摘录
最后,DRY ActiveRecord版本控制！
07002 by 07003 was a great start,but it Failed to keep up with ActiveRecord’s introduction of dirty objects in version 2.1. Additionally,each versioned model needs its own versions table that duplicates most of the original table’s columns. The versions table is then populated with records that often duplicate most of the original record’s attributes. All in all,not very DRY.
07004 requires only one versions table (polymorphically associated with its parent models) and no changes whatsoever to existing tables. But it goes one step DRYer by storing a serialized hash of only the models’ changes. Think modern version control systems. By traversing the record of changes,the models can be reverted to any point in time.
And that’s just what vestal_versions does. Not only can a model be reverted to a prevIoUs version number but also to a date or time!
解决方法
有关详细信息,请参阅this屏幕截图.
class Address < ActiveRecord::Base
belongs_to :user
versioned
end
class Order < ActiveRecord::Base
belongs_to :user
def address
@address ||= (user.address.revert_to(updated_at) and user.address)
end
end