通过SerializerMethodField筛选django REST结果

Question

class ImageSerializer(serializers.ModelSerializer):
    is_annotated = serializers.SerializerMethodField('has_annotation')

    class Meta:
        model = Image
        fields = '__all__'

    @staticmethod
    def has_annotation(image):
        return image.annotation_set.count() > 0

class ImageViewSet(viewsets.ModelViewSet):
    serializer_class = ImageSerializer
    lookup_field = 'id'
    permission_classes = [
        Or(IsAdmin),
        IsAuthenticated
    ]

    def get_queryset(self):
        queryset = Image.objects

        is_annotated_filter = self.request.query_params.get('is_annotated', None)
        if is_annotated_filter is not None:
            queryset = queryset.filter.annotate(
                cnt=Count('annotation')).filter(cnt__gte=1)

        queryset_order = get_queryset_order(self.request)
        return queryset.order_by(queryset_order).all()

• http://www.django-rest-framework.org/api-guide/filtering/#filtering-abs-query-parameters
• http://www.django-rest-framework.org/api-guide/fields/#serializermethodfield

Answer 1

我想您误解了：1）序列化器MethodField，它的主要用途是只读的，并且序列化器不会用于筛选QuerySet。

我会更像这些来过滤：

from django.db.models import Count

queryset.filter.annotate(
    cnt=Count('annotation_set')
).filter(cnt__gte=1)

但是...你可以走得更好：

from django.db.models import Count
queryset = Image.objects.annotate(
    cnt_annotations=Count('annotation_set')
)

@staticmethod
def has_annotation(image):
    if hasattr(obj, 'has_annotation'):
        return bool(obj.cnt_annotations)
    else:
        return None