无法处理嵌套资源的DoesNotExist错误

Question

我在处理DoesNotExist错误时遇到了麻烦，我正在使用DRF和DRF嵌套路由器，当我创建一个新的Like对象时，我需要照片PK，这样我就可以将它添加到Like对象中。

我正在尝试捕捉当带有该PK的照片不存在时我得到的错误。这就是我在序列化程序中创建Like的方法：

class LikeModelSerializer(serializers.ModelSerializer):
    """ Like model serializer. """

    user = serializers.CharField(default=serializers.CurrentUserDefault())

    class Meta:
        """ Meta class. """

        model = Like
        fields = ('user', 'photo')
        read_only_fields = ('user', 'photo')

    def create(self, validated_data):
        # Get the photo pk from the view context (DRF-nested-routers) and
        # create the new like with the validated_data
        photo_pk = self.context['view'].kwargs["photo_pk"]
        try:
            photo = Photo.objects.get(id=photo_pk)
        except Photo.DoesNotExist:
            return Response(data={'detail': "The photo doesn't exist."}, status=status.HTTP_404_NOT_FOUND)
        validated_data["photo"] = photo
        like, created = Like.objects.get_or_create(**validated_data)
        if created:
            photo.total_likes += 1
            photo.save()
        return like

视图的perform_create：

def perform_create(self, serializer):
    """ Creates a new like.

    The substraction in the total_likes is made in the serializer.
    """
    serializer.is_valid(raise_exception=True)
    serializer.save()
    return Response(data=serializer.data, status=status.HTTP_200_OK)

我得到的响应是：{'user': 'my username here'}

我也尝试过使用except Photo.DoesNotExist，但它给出了相同的结果。

Answer 1

在序列化程序类的validate方法中执行检查将更加清晰。如果照片不在，请调高serializers.ValidationError。

我还没有测试代码，但我认为它可以工作。

class LikeModelSerializer(serializers.ModelSerializer):
   
    ...

    def validate(self, attrs):
        photo_pk = self.context['view'].kwargs["photo_pk"]
        try:
            photo = Photo.objects.get(id=photo_pk)
        except Photo.DoesNotExist:
            raise serializers.ValidationError({"detail": "The photo doesn't exist"})
        attrs["photo"] = photo
        return attrs

    def create(self, validated_data):
        # Get the photo pk from the view context (DRF-nested-routers) and
        # create the new like with the validated_data
        like, created = Like.objects.get_or_create(**validated_data)
        if created:
            photo.total_likes += 1
            photo.save()
        return like

def perform_create(self, serializer):
    """ Creates a new like.

    The substraction in the total_likes is made in the serializer.
    """
    if not serializer.is_valid():
        raise ValidationError(serializer.errors)
    serializer.save()
    return Response(data=serializer.data, status=status.HTTP_200_OK)