Django Rest Model 中 User 字段的插入问题

fanzhh

发布于 2019-08-20 11:28:49

1.7K00

代码可运行

文章被收录于专栏：fanzhh的技术笔记fanzhh的技术笔记

运行总次数：0

代码可运行

使用Django Rest作为后端在做的项目中，Model是这样的：

class Sample(models.Model):
    ...
    creater = models.ForeignKey(User, on_delete=models.CASCADE)
    ...

Serializers是这样：

class SampleSerializer(serializers.ModelSerializer):
    class Meta:
        model = Sample
        fields = (...,'creater')

Views是这样：

class SampleList(generics.ListCreateAPIView):
    queryset = Sample.objects.all()
    serializer_class = SampleSerializer
    permission_classes = (IsOwnerOrReadOnly,)

    def perform_create(self, serializer):
        ...
        serializer.save(creater=self.request.user,...)

问题是，我在执行插入的时候，总是提示：

{"creater": ["This field is required."]}

百思不得其解，因为明明通过creater=self.request.user赋值了啊。后来在Model中，将creater字段修改为

creater = models.ForeignKey(User, on_delete=models.CASCADE, null=True, blank=True)

问题解决。

但这是为什么呢？谷歌后发现：

The perform_create method is called by your View's create method after serializer validation. At this stage, DRF will have found and flagged the missing user field.

原来视图中的perform_create操作晚于serializer的校验。上面的代码中，perform_create前DRF已经发现creater字段的缺失。

来看看rest_framework的源码：

class CreateModelMixin(object):
    """
    Create a model instance.
    """
    def create(self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        self.perform_create(serializer)
        headers = self.get_success_headers(serializer.data)
        return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)

    def perform_create(self, serializer):
        serializer.save()

    def get_success_headers(self, data):
        try:
            return {'Location': str(data[api_settings.URL_FIELD_NAME])}
        except (TypeError, KeyError):
            return {}

解决这个问题的方法有多种，除了上面的null=True, blank=True之外，还可以：