Question

我是订单模型和其他与之相关的模型。用户可以删除任何这些项目，如果删除后订单为空，我必须执行检查，如果为真，则设置为活动False。一些基本代码来说明它

class Order(models.Model):
    paid = models.BooleanField(default=False)
    active = models.BooleanField(default=True)
    user = models.ForeignKey(settings.AUTH_USER_MODEL)

    def empty_order():
         """
         I must implement it
         """

class HomeOrder(models.Model):
    ...
    order = models.OneToOneField(Order, related_name='primary_home')

class TourOrder(models.Model):
    ...
    order = models.ForeignKey(Order, related_name='tours')

我有一个post_delete信号与每个与Order相关的模型相关联：

post_delete.connect(delete_order_if_empty, sender=HomeOrder)
post_delete.connect(delete_order_if_empty, sender=TourOrder)

def delete_order_if_empty(sender, instance, **kwargs):
    if instance.order.empty_order():
        instance.order.active = False
        instance.order.save()

订单可以有一个Home，所以如果Home存在，我可以执行 order.primary_home ，如果Home不存在，它将引发AttributeError，因为它是OneToOne关系。

订单可以有多个Tours，所以在 empty_order 方法中，我想做一些检查，如下所示。

def empty_order():
    home = hasattr(self, 'primary_home')  # Avoid AttributeError exception
    tours = self.tours.exists()
    this_order_has_something = primary_home or tours
    return not this_order_has_something

现在，当我删除HomeOrder时，信号被引发但是empty_method从未意识到此HomeOrder不再存在。例如：

>>>o=Order.objects.create(...)
>>>o.primary_home # raise AttributeError
>>>h=HomeOrder.objetcs.create(order=o, ...)
>>>o.primary_home  # <HomeOrder: home-xx>
>>>h.delete()
>>>o.primary_home # still <HomeOrder: home-xx> Why?
>>>o.refresh_from_db()   
>>>o.primary_home # again <HomeOrder: home-xx>

删除后存在django相关字段

0 个答案: