如何在 Json 中返回带有额外字段的对象列表（Django Rest Framework）

Question

我正在使用 ModelViewSet 通过 get_queryset 生成项目列表。我想返回一个带有对象列表和一个额外字段（DurationField 的总时间）的 json。 示例：

{  
   "total_time":"00:10:00",
   "objects":[  
      {  
         "pk":1,
         "title":"Title",
         "duration": "00:05:00"
      },
      {  
         "pk":1,
         "title":"Title",
         "duration": "00:05:00"
      }
   ]
}

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

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：

router = DefaultRouter()
router.register(r'^', views.ModelViewSet)
urlpatterns = [
    url(r'^api', include(router.urls)),
]

Answer 1

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_paginated_response。这完全未经测试，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)

无论如何，希望这会有所帮助。

祝你好运！

Answer 2

我终于做到了！但我不确定这是否是最佳做法。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,)
    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
        }