Django外键on_delete：使用models.SET时如何将参数传递给callable

This is my models.py:

这是我的models.py:

def set_image(instance):
    return Image.objects.filter(user=instance.user)[0]

class User(models.Model):
    user = models.CharField(max_length=50)

class Image(models.Model):
    user = models.ForeignKey(User)
    image = models.ImageField(upload_to='media')

class Item(models.Model):
    user = models.ForeignKey(User)
    image = models.ForeignKey(
        Image,
        blank=True,
        null=True,
        on_delete=models.SET(set_image)
    )

When I delete an 'Image', it's related 'Item' calls set_image, which returns an error, because models.SET doesn't pass the instance to the callable. How can I change this behavior? Should I override models.SET or is there any other way around it?

当我删除'Image'时,它与'Item'相关,调用set_image,它返回一个错误,因为models.SET没有将实例传递给callable。我该如何改变这种行为?我应该覆盖models.SET还是有其他方法吗?

1 个解决方案

#1

Override the Image delete method to remove the Item ForeignKey

覆盖Image delete方法以删除Item ForeignKey

The following can be used as an intermediary model base class to add this functionality to all of your models:

以下内容可用作中间模型基类,以将此功能添加到所有模型中:

from django.db import models

class Model(models.Model):
    """
    Intermediate model base class.
    """
    class Meta:
        abstract = True

    def delete(self, *args, **kwargs):
        self.clear_nullable_related()
        super(Model, self).delete(*args, **kwargs)

    def clear_nullable_related(self):
        """
        Recursively clears any nullable foreign key fields on related objects.
        Django is hard-wired for cascading deletes, which is very dangerous for
        us. This simulates ON DELETE SET NULL behavior manually.
        """
        for related in self._meta.get_all_related_objects():
            accessor = related.get_accessor_name()
            related_set = getattr(self, accessor)

            if related.field.null:
                related_set.clear()
            else:
                for related_object in related_set.all():
                    related_object.clear_nullable_related()

source

#1