根据django中的相关对象过滤queryset

Question

我使用django-guardian库，我想创建Manager来根据用户权限过滤对象。

例如：

 from guardian.shortcuts import get_objects_for_user
 class WithUser(models.Manager):
     user_obj = None
     def assign_user(self,user_obj):
         self.user_obj = user_obj
         qs = super().get_queryset()
         #########################
         # how I know if the current qs have related field and how to get related field managers.
         #???????????????
     def get_queryset(self):
         qs = super().get_queryset()
         if self.user_obj:
              qs = get_objects_for_user(self.user_obj,"view_%s"%self.model.__name__.lower(),qs,accept_global_perms=False)
         return qs

class A(models.Model):
    # the model fields
    objects = WithUser()

class B(models.Model):
    # the model fields
    a = models.ForeignKey(A,on_delete=Model.CASCADE)
    objects = WithUser()

class C(models.Model):
    # the model fields
    b = models.ForeignKey(B,on_delete=Model.CASCADE)
    objects = WithUser()

如何根据C对象的权限和A、B的权限过滤C对象。

我希望通用规则根据其权限和相关对象的权限过滤任何模型对象。

Answer 1

我会创建一个特殊的 ForeinKey 字段来标记这些字段。

class PermissionForeignKey(models.ForeignKey):
    # we only use this class to mark the field
    pass

# you can add lru_cache here to speed up
# you could also move this to the model as @classproperty
def perm_fk_fields(model):
    fk_fields = []
    for field in model._meta.get_fields():
        if isinstance(field, PermissionForeignKey):
            fk_fields.append(field)
            fk_model_fields = perm_fk_fields(field.remote_field.model)
            if fk_model_fields:
                fk_fields.append([field, fk_model_fields])

    return fk_fields

# in your model
class B(models.Model):
    # the model fields
    a = PermissionForeignKey(A,on_delete=Model.CASCADE)