Django REST 框架 |从 ManyToMany 字段按计数排序

Question

我正在学习 Django REST Framework 的课程，但我在尝试从 django_filters[=38= 设置 ordering 配置时遇到了困难] 变成 ViewSet.

ordering = ('-members__count')

在课程的原始代码中，-members__count 被用作 return 成员总数的查询，但是当我尝试使用相同的语法时，我得到了这个错误：

错误：

Cannot resolve keyword 'count' into field. Choices are: auth_token, circle, created, date_joined, email, first_name, groups, id, invitation, invited_by, is_active, is_client, is_staff, is_superuser, is_verified, issued_by, last_login, last_name, logentry, membership, modified, password, phone_number, profile, user_permissions, username

也许我误解了这个错误，但所有这些建议的选项都对应于我模型中的字段。此外，在课程中它指出这是一种查询表示格式，用于获取该字段的总数，所以我对此有点困惑。

无论如何，这是我的代码的简历，但您也可以在此 repo 中查看我的完整详细代码以备不时之需：https://github.com/cadasmeq/comparte_ride/tree/master/cride/circles.

查看：

# Filters from rest_framework.filters import SearchFilter, OrderingFilter from django_filters.rest_framework import DjangoFilterBackend class CircleViewSet(mixins.CreateModelMixin, mixins.RetrieveModelMixin, mixins.UpdateModelMixin, mixins.ListModelMixin, viewsets.GenericViewSet): """Circle view set.""" serializer_class = CircleModelSerializer lookup_field = 'slug_name' # Filters filter_backends = (SearchFilter, OrderingFilter, DjangoFilterBackend) search_fields = ('slug_name', 'name') ordering_fields = ('rides_offered', 'rides_taken', 'name', 'created', 'member_limit') ordering = ('-members__count', '-rides_offered', '-rides_taken') filter_fields = ('verified', 'is_limited')

型号：

class Circle(CRideModel): """Circle model. A circle is a private group where rides are offered and taken by its members. To join a circle a user must receive an unique invitation code from an existing circle member. """ members = models.ManyToManyField( "users.User", through='circles.Membership', through_fields=('circle', 'user') )

先谢谢你们了，我对生疏的英语感到抱歉哈哈

Answer 1

您出现此错误是因为您正在尝试访问 User 模型的属性。它在 User 模型上找不到 count。据我了解，您要做的是按 ManyToManyField members.

上每个圈子的成员数量排序

为此我会使用 annotate，将 members__count 重命名为 members_count 并执行类似（未测试）的操作：

from django.db.models import Count

class CircleViewSet(mixins.CreateModelMixin,
                    mixins.RetrieveModelMixin,
                    mixins.UpdateModelMixin,
                    mixins.ListModelMixin,
                    viewsets.GenericViewSet):
    """Circle view set."""

    serializer_class = CircleModelSerializer
    lookup_field = 'slug_name'

    # Filters
    filter_backends = (SearchFilter, OrderingFilter, DjangoFilterBackend)
    search_fields = ('slug_name', 'name')
    ordering_fields = ('rides_offered', 'rides_taken', 'name', 'created', 'member_limit')
    ordering = ('-members_count', '-rides_offered', '-rides_taken')
    filter_fields = ('verified', 'is_limited')

    def get_queryset(self):
        """Restrict list to public-only."""
        queryset = Circle.objects.annotate(members_count=Count('members')).all()
        if self.action == 'list':
            return queryset.filter(is_public=True)
        return queryset

Django REST 框架 |从 ManyToMany 字段按计数排序

Django REST Framework | Ordering by Count from a ManyToMany Field

django

manytomanyfield

django-rest-framework