django - 如何在 Django 的自定义帐户模型中覆盖 user.groups 以实现 "virtual"组？

Question

我在使用 PermissionsMixin 的 Django 应用程序中有一个自定义帐户类:

class Account(AbstractBaseUser, PermissionsMixin):

我们的 CMS 在此类上调用各种 .groups 方法以确定权限。

我们本质上想要覆盖从这个自定义 Account 类中的 .groups 返回的查询集，并在特定条件下注入(inject)一个额外的组。 (即用户有一个有效的订阅，然后我们希望将“成员”作为该用户的组之一返回，尽管他们实际上并不在组中。)

我们应该如何处理这种覆盖？我们需要获取原始组，以免破坏基本组功能，然后将我们的“虚拟”组注入(inject)查询集中。

Answer 1

覆盖 get_queryset方法ManyRelatedManager . ManyRelatedManager 的对象类可以访问父实例。

代码示例:

def add_custom_queryset_to_many_related_manager(many_related_manage_cls):
    class ExtendedManyRelatedManager(many_related_manage_cls):
        def get_queryset(self):
            qs = super(ExtendedManyRelatedManager, self).get_queryset()
            # some condition based on the instance
            if self.instance.is_staff:
                return qs.union(Group.objects.filter(name='Gold Subscription'))
            return qs

    return ExtendedManyRelatedManager

ManyRelatedManager class is obtained from the ManyToManyDescriptor.

class ExtendedManyToManyDescriptor(ManyToManyDescriptor):

    @cached_property
    def related_manager_cls(self):
        model = self.rel.related_model if self.reverse else self.rel.model
        return add_custom_queryset_to_many_related_manager(create_forward_many_to_many_manager(
            model._default_manager.__class__,
            self.rel,
            reverse=self.reverse,
        ))

Associated the ExtendedManyToManyDescriptor with groups field when the Account class is initialized.

class ExtendedManyToManyField(ManyToManyField):

    def contribute_to_class(self, cls, name, **kwargs):
        super(ExtendedManyToManyField, self).contribute_to_class(cls, name, **kwargs)
        setattr(cls, self.name, ExtendedManyToManyDescriptor(self.remote_field, reverse=False))

Override PermissionsMixin to use ExtendedManyToManyField for groups field instead of ManyToManyField.

class ExtendedPermissionsMixin(PermissionsMixin):
    groups = ExtendedManyToManyField(
        Group,
        verbose_name=_('groups'),
        blank=True,
        help_text=_(
            'The groups this user belongs to. A user will get all permissions '
            'granted to each of their groups.'
        ),
        related_name="user_set",
        related_query_name="user",
    )

    class Meta:
        abstract = True

引用: django.db.models.fields.related_descriptors.create_forward_many_to_many_manager
测试:

account = Account.objects.get(id=1)
account.is_staff = True
account.save()

account.groups.all() 

# output
[<Group: Gold Subscription>]