我可以防止 Django 根据引用类型中的属性删除对象吗？

Question

想象一下 PetOwner 和一个 Pet 模型：

class PetOwner(models.Model):
  name = models.CharField()

class Pet(models.Model):
  owner = models.ForeignKey('PetOwner', on_delete=models.CASCADE)
  alive = models.BooleanField(default=True)

我希望可以删除 PetOwners，但前提是他们的所有相关宠物都不再活着。如果是这样，则可以删除 PetOwner，同时删除他所有关联的宠物（级联语义）。

这可能吗？

Answer 1

您正在谈论设置 'business rule'。您可以在多个地方写下您的 'business rules'，例如，在删除 PetOwners.

的每个视图或进程中

此外，您可以在模型上使用 override delete 方法。请记住：

Overridden model methods are not called on bulk operations

Note that the delete() method for an object is not necessarily called when deleting objects in bulk using a QuerySet or as a result of a cascading delete. To ensure customized delete logic gets executed, you can use pre_delete and/or post_delete signals.

这是覆盖删除的方法：

from django.core.exceptions import PermissionDenied

class PetOwner(models.Model):

  # ...

  def delete(self):
    has_pets_alive = self.pet_set.filter(alive=True).exists()
    if has_pets_alive:
        raise PermissionDenied("This owner has pets alive")        
    super(PetOwner, self).delete()

另一个解决方案是signals:

from django.db.models.signals import pre_delete 
from django.dispatch import receiver
    
@receiver(pre_delete, sender=PetOwner)
def check_pets_alive(sender, instance, **kwargs):
    has_pets_alive = instance.pet_set.filter(alive=True).exists()
    if has_pets_alive:
        raise PermissionDenied("This owner has pets alive")

我可以防止 Django 根据引用类型中的属性删除对象吗？

Can I prevent Django from deleting an object depending on an attribute in a referencing type?

django

django-models