django model - on_delete = models.PROTECT（）

I'm trying to use on_delete with my models but my IDE is asking me for: collector, fields, sub_objs, using (i.e. ..., on_delete=models.PROTECT(collector, fields, sub_objs, using)).

我正在尝试使用on_delete和我的模型，但我的IDE要求我：collector，fields，sub_objs，using（即...，on_delete = models.PROTECT（collector，fields，sub_objs，using））。

Can someone please tell me what these are and give me a quick example because I can find them documented anywhere :(

有人可以请告诉我这些是什么，并给我一个快速的例子，因为我可以在任何地方找到它们:(

3 个解决方案

#1

Ignore your IDE. It is trying to get you to call the models.PROTECT function, which does indeed take those arguments. But you actually want to pass the function itself:

忽略你的IDE。它试图让你调用models.PROTECT函数，它确实采用了这些参数。但是你实际上想要传递函数本身：

my_field = models.ForeignKey(..., on_delete=models.PROTECT)

ie without the parentheses that would call the function.

即没有可以调用函数的括号。

(Insert rant about using an IDE with a dynamic language here...)

（在这里插入关于使用带有动态语言的IDE的咆哮......）

#2

Import like:(Python 2.7)

导入如：（Python 2.7）

from django.db.models.deletion import PROTECT

Then you can use it directly.

然后你可以直接使用它。

category = ForeignKey(TCategory, PROTECT, null=False, blank=False)

#3

-1

models.PROTECT prevents deletions but does not raise an error by default.

models.PROTECT可以防止删除，但默认情况下不会引发错误。

you can create a custom exception for it, which is already protected.

您可以为它创建一个已经受保护的自定义例外。

from django.db import IntegrityError

class ModelIsProtectedError(IntegrityError):
    pass

def prevent_deletions(sender, instance, *args, **kwargs):
    raise ModelIsProtectedError("This model can not be deleted")


#in your models.py:
pre_delete.connect(prevent_deletions, sender=<your model>)

#1