如何在Json（Django Rest框架）中返回带有额外字段的对象列表

我使用ModelViewSet通过get_queryset生成项目列表。我想返回一个包含对象列表和一个额外字段（DurationField的总时间）的json。 例如：

我该怎么做？下面是我的代码

模型视图集：

class ModelViewSet(viewsets.ModelViewSet):
    queryset = Model.objects.all()
        serializer_class = ModelSerializer
        permission_classes = (IsAuthenticated,)

        def get_queryset(self):
            user = self.request.user
            list = Model.objects.filter(user=user)
            total_time = .. ## sum the duration of list of objects

            ## I want to return the list and total_time
            return list

class ModelViewSet(viewsets.ModelViewSet):
    queryset = Model.objects.all()
        serializer_class = ModelSerializer
        permission_classes = (IsAuthenticated,)
    renderer_classes = (ModelJSONRenderer, )

    def get_queryset(self):
        user = self.request.user
        list = Model.objects.filter(user=user)

        self.total_time = .. ## sum the duration of list of objects

        return list

    def get_renderer_context(self):
        """
        Returns a dict that is passed through to Renderer.render(),
        as the `renderer_context` keyword argument.
        """
        return {
            'view': self,
            'args': getattr(self, 'args', ()),
            'kwargs': getattr(self, 'kwargs', {}),
            'request': getattr(self, 'request', None),
            'total_time': self.total_time
        }

serializers.py：

class ModelSerializer(serializers.ModelSerializer):
            pk = serializers.IntegerField(read_only=True)
            user = serializers.PrimaryKeyRelatedField(queryset=User.objects.all(), required=False, allow_null=True)
            project = serializers.PrimaryKeyRelatedField(queryset=Project.objects.all(), required=False, allow_null=True)
            class Meta:
                model = Model

                fields = ('pk', 'title', 'user', 'project', 'duration')

网址：

---

一种方法是对分页器进行子类化（默认分页类是

PageNumberPagination

），并调整

get\u paginated\u响应。这完全没有经过测试，但可能是这样的：

from rest_framework.pagination import PageNumberPagination

class CustomPageNumberPagination(PageNumberPagination):

    def get_paginated_response(self, data, total_time):
        return Response(OrderedDict([
            ('count', self.page.paginator.count),
            ('next', self.get_next_link()),
            ('previous', self.get_previous_link()),
            ('total_time', total_time),
            ('results', data)
        ]))


class ModelViewSet(viewsets.ModelViewSet):
    queryset = Model.objects.all()
    serializer_class = ModelSerializer
    permission_classes = (IsAuthenticated,)
    pagination_class = CustomPageNumberPagination

    def get_queryset(self):
        user = self.request.user
        list = Model.objects.filter(user=user)

        self.total_time = .. ## sum the duration of list of objects

        return list

    def get_paginated_response(self, data):
        return self.paginator.get_paginated_response(data, self.total_time)

不管怎样，希望这有点帮助

祝你好运
 我终于做到了！但我不确定这是否是最好的做法。如果有人有更好的想法，请分享

class ModelJSONRenderer(JSONRenderer):
    """
    Add "objects" and "total_time" in Json
    """
    def render(self, data, accepted_media_type=None, renderer_context=None):
        data = {'objects': data, 'total_time': renderer_context['total_time']}
        return super(ModelJSONRenderer, self).render(data, accepted_media_type, renderer_context)

模型视图集：

class ModelViewSet(viewsets.ModelViewSet):
    queryset = Model.objects.all()
        serializer_class = ModelSerializer
        permission_classes = (IsAuthenticated,)

        def get_queryset(self):
            user = self.request.user
            list = Model.objects.filter(user=user)
            total_time = .. ## sum the duration of list of objects

            ## I want to return the list and total_time
            return list

class ModelViewSet(viewsets.ModelViewSet):
    queryset = Model.objects.all()
        serializer_class = ModelSerializer
        permission_classes = (IsAuthenticated,)
    renderer_classes = (ModelJSONRenderer, )

    def get_queryset(self):
        user = self.request.user
        list = Model.objects.filter(user=user)

        self.total_time = .. ## sum the duration of list of objects

        return list

    def get_renderer_context(self):
        """
        Returns a dict that is passed through to Renderer.render(),
        as the `renderer_context` keyword argument.
        """
        return {
            'view': self,
            'args': getattr(self, 'args', ()),
            'kwargs': getattr(self, 'kwargs', {}),
            'request': getattr(self, 'request', None),
            'total_time': self.total_time
        }

谢谢@caffeineed！但我不知道这是否是最好的做法！如果您能告诉我您对代码的意见，我将不胜感激！我不确定在这个场景中是否存在“最佳实践”。如果你发现一些对你有用的东西，并且它不是非常复杂和/或不可能维护，那么我说用它来运行。遗憾的是，我现在不能考虑你的解决方案，但我认为这个概念看起来很合理。干杯再次感谢@CaffeineFueled；）