Django 删除用作外键的对象
我有以下型号:Django 删除用作外键的对象,django,rest,django-rest-framework,Django,Rest,Django Rest Framework,我有以下型号: class Target(models.Model): name = models.CharField(max_length=100, blank=False) class SubTarget(models.Model): target = models.ForeignKey(Target, related_name='sub_targets') name = models.CharField(max_length=100, blank=True, n
class Target(models.Model):
name = models.CharField(max_length=100, blank=False)
class SubTarget(models.Model):
target = models.ForeignKey(Target, related_name='sub_targets')
name = models.CharField(max_length=100, blank=True, null=True, default='')
例如,我运行下一个代码:
target = Target(name='test-target')
target.save()
sub_target = SubTarget(name='test-sub-target, target=target)
sub_target.save()
现在我有了带外键的sub_目标对象
我的目标序列化程序如下所示:
class TargetSerializer(serializers.ModelSerializer):
class Meta:
model = Target
fields = ('id', 'name', 'sub_targets')
depth = 1
read_only_fields = ('sub_targets',)
以及适当的看法:
class TargetDetail(generics.RetrieveUpdateDestroyAPIView):
model = Target
serializer_class = TargetSerializer
所以,没有什么可以阻止我删除带有外键的对象。此外,此操作还删除了相关的子_目标对象。我怎样才能避免这种行为 我不确定,但我想您是在问如何在删除目标对象时防止子目标对象被删除。默认情况下,Django在删除级联上进行模拟。您可以使用on_delete关键字控制此行为 因此:
您可以覆盖模型的删除操作,如:
class Target(models.Model):
name = models.CharField(max_length=100, blank=False)
def delete(self, *args, **kwargs):
for robject in self._meta.get_all_related_objects():
if robject is not None:
q = Q(**{"%s__id" % robject.field.name: self.id})
if robject.model.objects.filter(q).exists():
raise Exception("Item has active reference.")
try:
with transaction.atomic():
super(Target, self).delete(*args, **kwargs)
except Exception, exp:
raise exp
请注意,如果相关对象与另一个对象没有反向关系,则它不起作用。在寻找一种方法来检查模型实例是否可以在django中删除后,我遇到了许多示例,但没有按预期工作。希望这个解决方案能有所帮助 让我们首先创建一个抽象模型类,它可以被其他模型继承
class ModelIsDeletable(models.Model):
name = models.CharField(max_length=200, blank=True, null=True, unique=True)
description = models.CharField(max_length=200, blank=True, null=True)
date_modified = models.DateTimeField(auto_now_add=True)
def is_deletable(self):
# get all the related object
for rel in self._meta.get_fields():
try:
# check if there is a relationship with at least one related object
related = rel.related_model.objects.filter(**{rel.field.name: self})
if related.exists():
# if there is return a Tuple of flag = False the related_model object
return False, related
except AttributeError: # an attribute error for field occurs when checking for AutoField
pass # just pass as we dont need to check for AutoField
return True, None
class Meta:
abstract = True
例子
假设我们有三种组织模式,部门和员工类型
一个组织中可以有这么多部门
一个组织有一种特殊的员工类型
class StaffType(ModelIsDeletable):
pensionable = models.BooleanField(default=False)
class Organization(ModelIsDeletable):
staff_type = models.ForeignKey(to=StaffType)
class Department(ModelIsDeletable):
organization = models.ForeignKey(to=Organization, to_field="id")
比如说,在添加了一些信息之后,您希望删除一个组织模型实例
这已经和一个部门联系在一起了
例如我们有
组织机构表=>(名称=工程,主键=1)
部门表=>(名称=开发人员,组织机构=1,主键=1)
现在当你试图删除一个组织后,得到它的pk
a_org = Organization.objects.get(pk=1)
有了这个,你可以检查它是否可以删除
deletable, related_obj = a_org.is_deletable()
if not deletable:
# do some stuff with the related_obj list
else:
# call the delete function
a_org.delete()
也许你可以尝试另一种方法,我刚刚用Django 1.8为我的项目得到了它
instance = get_object_or_404(MyModel, pk=pk)
eliminate = True
for robject in instance._meta.get_all_related_objects():
if robject is not None:
if robject.related_model.objects.filter(**{robject.field.name: instance}).exists() and eliminate:
eliminate = False
if eliminate:
instance.delete()
# additional code
else:
# additional code
pass
延迟回复,但这也可以通过使用外键上的
model.PROTECT来避免
target=models.ForeignKey(
目标,相关的\u name='sub\u targets',在\u delete=models.PROTECT上
)
instance = get_object_or_404(MyModel, pk=pk)
eliminate = True
for robject in instance._meta.get_all_related_objects():
if robject is not None:
if robject.related_model.objects.filter(**{robject.field.name: instance}).exists() and eliminate:
eliminate = False
if eliminate:
instance.delete()
# additional code
else:
# additional code
pass
class BaseModel(models.Model):
def can_delete(self):
# get all the related object to be deleted
for related in get_candidate_relations_to_delete(self._meta):
field = related.field
if field.remote_field.on_delete == models.PROTECT:
# check for relationship with at least one related object
related = related.related_model.objects.filter(**{related.field.name: self})
if related.exists():
return False, related
return True, None
class Meta:
abstract = True