Python Django-预取过滤器不适用于多对多模型

我想要一个组的端点，该端点可以按周和年过滤对象。组与“通过”arg to成员具有多对多关系。会员资格外键给用户。将外键贷记给用户

我有以下型号：

class Group(models.Model):
    name = models.CharField(max_length=128, unique=True)
    members = models.ManyToManyField(settings.AUTH_USER_MODEL, related_name="memberships", 
    through='Membership')
    
class Membership(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, related_name="membership", 
    on_delete=models.CASCADE)
    group = models.ForeignKey(Group, on_delete=models.CASCADE)
    
class Credits(models.Model):
    credits = models.IntegerField()
    year = models.IntegerField(default=date.today().isocalendar()[0])
    week = models.IntegerField(default=date.today().isocalendar()[1])
    user = models.ForeignKey(settings.AUTH_USER_MODEL, related_name="credits", 
    on_delete=models.CASCADE)

class User(AbstractBaseUser, PermissionsMixin):
    email = models.EmailField(max_length=255, unique=True)
    username = NameField(max_length=25, unique=True,                              
    is_active = models.BooleanField(default=True)
    is_staff = models.BooleanField(default=False)

序列化程序：

class MembershipSerializer(serializers.ModelSerializer):
    username = serializers.ReadOnlyField(source='user.username')
    credits = CreditsSerializer(source='user.credits', many=True, required=False, allow_null=True)

    class Meta:
        model = Membership
        fields = ('id', 'is_admin', 'user_id', 'username', 'credits')
        read_only_fields = ('id',)

        depth = 1


class GroupSerializer(serializers.ModelSerializer):
    memberships = MembershipSerializer(source='membership_set', many=True)

    class Meta:
        model = Group
        fields = ('id', 'name', 'memberships')

我的团体观点是：

class GroupSet(generics.ListAPIView):
    lookup_field = 'name'
    serializer_class = GroupSerializer

    def get_queryset(self):

        year = self.request.query_params.get('year', None)
        week = self.request.query_params.get('week', None)
        name = self.request.query_params.get('name', None)

        if name and week and year is not None:

            prefetchCredits = Prefetch('members__credits', 
            queryset=Credits.objects.filter(year=year, week=week), to_attr='credit_objs')

            group = Group.objects.filter(name__iexact=name).prefetch_related(prefetchCredits)

            return group

信用卡上的过滤器不工作。我以前使用过这种视图结构，其中预取过滤器确实起作用，但模型没有多对多关系

我试图迭代预回迁积分以筛选出正确的对象，但我得到一个错误：“预回迁”对象不可编辑

我一直在了解下面的结构。只有一个credits对象应与year and week筛选器一起显示

[
    {
        "id": 3,
        "name": "Group2",
        "memberships": [
            {
                "id": 3,
                "user_id": 2,
                "username": "test1",
                "credits": [
                    {
                        "credits": 800,
                        "year": 2020,
                        "week": 41
                    },
                    {
                        "credits": 1000,
                        "year": 2020,
                        "week": 40
                    },
                    {
                        "credits": 996,
                        "year": 2020,
                        "week": 39
                    }
                ],

---

模型“组”和类“信用”之间没有直接联系，因此无法直接预取信用

首先，您需要预取相关成员（成员资格），并使用多级预取来包括该成员资格的信用

可以在预取内部的queryset上使用预取，以形成多级预取结构

prefetchCredits = Prefetch('user__credits', queryset=Credits.objects.filter(year=year, week=week))
prefetchMembership = Prefetch(
    'membership_set', 
    queryset=Membership.objects.prefetch_related(prefetchCredits)
)
group = Group.objects.filter(name__iexact=name).prefetch_related(prefetchMembership)

---

此外，积分预取的名称更改为“users\uu Credits”，以匹配序列化程序“source”的名称。

您不能在

预取

对象上迭代。

预回迁

对象不存储任何数据，它只是预回迁任务的表示。您可以使用

to_attr

来存储过滤后的值。您能分享

组序列化程序吗？@WillemVanOnsem感谢您的快速回复。我添加了Serializers@WillemVanOnsem在本例中，您将如何使用to_attr？我已将添加到了to_attr并将其中的对象存储在列表中。然后添加了一个新过滤器，对列表中的对象进行过滤，但仍然不起作用。谢谢！这正是我想要的