如何在django rest framework generics中使用limit.RetrieveAPIView

Question

作为generics.RetrieveAPIView在django rest框架中应该只返回一条记录,我想在get查询方法中使用限制,如下所示

class PortUserView(generics.RetrieveAPIView):
    lookup_field = 'user'

    def get_queryset(self):

        return PortUser.objects.all()[:1]

得到这样的错误" 切片一旦切片就无法过滤查询 ".

我的代码有什么问题？

Answer 1

您无需担心在查询时从查询集返回单个对象retrieve.DRF将使用GenericAPIView中.get_object()定义的方法自动为您处理.

您可以使用以下代码,DRF将为您处理该retrieve操作.

class PortUserView(generics.RetrieveAPIView):
    lookup_field = 'user'
    queryset = PortUser.objects.all()

的get_object(个体经营)

返回应该用于详细视图的对象实例.默认使用lookup_field参数来过滤基本查询集.

retrieve行动源代码:

def retrieve(self, request, *args, **kwargs):
    instance = self.get_object() # here the object is retrieved
    serializer = self.get_serializer(instance)
    return Response(serializer.data)

我们可以看到DRF使用该.get_object()函数从查询集中获取对象.要执行过滤,它使用lookup_field视图中定义的.

这是get_object()使事情更清晰的实际代码.

def get_object(self):
        """
        Returns the object the view is displaying.

        You may want to override this if you need to provide non-standard
        queryset lookups.  Eg if objects are referenced using multiple
        keyword arguments in the url conf.
        """
        queryset = self.filter_queryset(self.get_queryset())

        # Perform the lookup filtering.
        lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field

        assert lookup_url_kwarg in self.kwargs, (
            'Expected view %s to be called with a URL keyword argument '
            'named "%s". Fix your URL conf, or set the `.lookup_field` '
            'attribute on the view correctly.' %
            (self.__class__.__name__, lookup_url_kwarg)
        )

        filter_kwargs = {self.lookup_field: self.kwargs[lookup_url_kwarg]}
        obj = get_object_or_404(queryset, **filter_kwargs) # <-- can see that filtering is performed on the base of 'lookup_field'

        # May raise a permission denied
        self.check_object_permissions(self.request, obj)

        return obj # will return the single retrieved object