Django的OneToOne领域自我 [英] Django OneToOne field to self
问题描述
如何为相同的 Model
定义 OneToOne
关系?
我有一个名为 Order
的模型,该模型可以与另一个 Order
配对code>。现在,我试图弄清楚如何处理这种关系的模型。
我的想法:
class Order(models.Model):
paired_order = models.OneToOneField(self)
OR:
class Pairing(models.Model):
order1 =模型.ForeignKey(Order,related_name ='pairing')
order2 =模型.ForeignKey(Order,related_name ='pairing')
您怎么看?哪个更有效?
我想简单地调用配对的电话。所以我会做类似的事情:
order.paired_order
或:
order.pairing.paired
我希望这种关系是对称的,因此对于每对订单,我称相同的东西并获得配对订单。
配对模型将是一个很好的解决方案,因为我可以向此关系添加其他信息,但是存在一个问题,我必须检测到它是哪个顺序,所以无法调用 order.pairing.order1
,因为我不知道我是否在调用同一订单。
编辑:
>>来自_app导入模型
>> order1 = models.Order(flight_number = xxx)
>>> order2 = models.Order(flight_number = yyy,paired_order = order1)
>> order1.paired_order.flight_number
返回没有对象没有....
问题是,当我将order1设置为order2的配对订单时,我想要相反方向的同一件事。因此, order1.paired_order = order2
也会执行 order2.paired_order = order1
。
配对模型将是一个很好的解决方案,因为我可以为该关系添加其他
信息。
在这种情况下,您可以对那组订单(您称其为配对)进行建模,并添加快捷方式来检索配对的订单。 / p>
class OrderPair(models.Model):
通过
#附加信息在这里
类Order(models.Model):
对= models.ForeignKey(to = OrderPair,related_name = orders)
#您必须添加自定义验证
#以确保只有2个订单可以属于同一个 OrderPair。
@property
def paired_order(self):
返回self.pair.orders .exclude(id = self.id).first()
一旦你有为此,您可能还希望缓存配对的订单,以避免查询过多。在那种情况下,您不需要相关的名称,因此可以使用 +
(在Django中是不太明显的东西)。
class Order(models.Model):
...
cached_paired_order = models.ForeignKey(to ='self',related_name ='+' )
@属性
def paired_order(self):
如果self.cached_paired_order:
...
else:
...
How to define OneToOne
relationship to the same Model
?
I have a model called Order
which can be paired with another one Order
. Now I'm trying to figure out how to handle models for this relationship.
My ideas:
class Order(models.Model):
paired_order = models.OneToOneField(self)
OR:
class Pairing(models.Model):
order1 = models.ForeignKey(Order, related_name='pairing')
order2 = models.ForeignKey(Order, related_name='pairing')
What do you think? Which is more efficient?
I want to have simple calling of paired ones. So I would do something like:
order.paired_order
OR:
order.pairing.paired
I want this relation symmetrical so for each pair of orders I call the same thing and get paired order.
Pairing model would be a good solution because I can add additional information to this relationship, but there is a problem that I would have to detect which order is it, so I couldn't call order.pairing.order1
because I don't know whether I'm not calling the same order.
EDIT:
>>> from _app import models
>>> order1 = models.Order(flight_number="xxx")
>>> order2 = models.Order(flight_number="yyy", paired_order=order1)
>>> order1.paired_order.flight_number
RETURNS None object has not ....
The problem is that when I set order1 is a paired order for order2, I want the same thing in opposite direction. So order1.paired_order = order2
do this as well order2.paired_order = order1
.
Pairing model would be a good solution because I can add additional information to this relationship.
In that case, you could model that group of "orders" (you've called it Pairing) and add a shortcut to retrieve the paired order.
class OrderPair(models.Model):
pass
# additional information goes here
class Order(models.Model):
pair = models.ForeignKey(to="OrderPair", related_name="orders")
# you'll have to add custom validation
# to make sure that only 2 orders can belong to the same "OrderPair"
@property
def paired_order(self):
return self.pair.orders.exclude(id=self.id).first()
Once you've got this working, you might also want to cache the paired order to avoid too many queries. In that case, you don't want a related name so you can use +
(the less explicit thing in Django ever).
class Order(models.Model):
...
cached_paired_order = models.ForeignKey(to='self', related_name='+')
@property
def paired_order(self):
if self.cached_paired_order:
...
else:
...
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