models.py 文件源码

def save(self, *args, **kwargs):
        is_add = not self.pk
        if is_add:
            self.self_type = ContentType.objects.get_for_model(type(self), for_concrete_model=False)
            self.created = now()

            self.sort_order = self.gallery.items.aggregate(
                max=Coalesce(models.Max('sort_order'), 0) + 1
            )['max']

        super().save(*args, **kwargs)