Django请求框架 'ManyRelatedField'对象在修改get_fields中的查询集时没有属性 'queryset'

Question

我在 StorySerializer 中的 GET/api/stories/169/ 上收到以下错误，如下评论中所述:

AttributeError at /api/stories/169/
'ManyRelatedField' object has no attribute 'queryset'

在检查该对象后，我发现如果我更改该行...

fields['feature'].queryset = fields['feature'].queryset.filter(user=user)

至

fields['photos'].child_relation.queryset = fields['photos'].child_relation.queryset.filter(user=user)

...似乎有效。但这种方法没有记录，我确信这不是正确的方法。

我有这些模型:

class Story(CommonInfo):
    user = models.ForeignKey(User)
    text = models.TextField(max_length=5000,blank=True)
    feature = models.ForeignKey("Feature", blank=True, null=True)
    tags = models.ManyToManyField("Tag")

class Feature(CommonInfo):
    user = models.ForeignKey(User)
    name = models.CharField(max_length=50)

class Photo(CommonInfo):
    user = models.ForeignKey(User)
    image = ImageField(upload_to='photos')
    story = models.ForeignKey("Story", blank=True, null=True, related_name='photos', on_delete=models.SET_NULL)

还有一个StorySerializer:

class StorySerializer(serializers.HyperlinkedModelSerializer):
    user = serializers.CharField(read_only=True) 
    comments = serializers.HyperlinkedRelatedField(read_only=True, view_name='comment-detail', many=True)

    def get_fields(self, *args, **kwargs):
        user = self.context['request'].user
        fields = super(StorySerializer, self).get_fields(*args, **kwargs)

        ## Restrict the options that the user can pick to the Features
        ## and Photos that they own
        # This line works:
        fields['feature'].queryset = fields['feature'].queryset.filter(user=user)

        # This line throws the error:           
        fields['photos'].queryset = fields['photos'].queryset.filter(user=user)

        return fields

    class Meta:
        model = Story
        fields = ('url', 'user', 'text', 'comments', 'photos', 'feature', 'tags')

我做错了什么？我觉得这与 ForeignKey 关系的方向有关。

Answer 1

两个要点。

1. 当从用户的 View 中过滤查询集时，所有外键对象检索将仅生成特定用户的对象。因此无需在 get_fields 内过滤用户。

   class StoryList(generics.ListAPIView):
       serializer_class = StorySerializer
   
        def get_queryset(self):
            # consider there is login check before code is reaching here
            # since this filtered by the user and any susbquent 
            # foreign key objects will belong only to this user
            return Story.objects.filter(user=self.request.user)
   

2. 一旦对用户进行过滤，您就可以使用另一个序列化程序或 SerializerMethodField 来相应地构造数据。下面的代码应该适用于您的情况。

    class UserSerializer(serializers.HyperlinkedModelSerializer):
        class Meta:
            # Allow only url and id
            fields = ['id', 'url']
            extra_kwargs = {'url': {'view_name': 'user-detail'}}
   
    class FeatureSerializer(serializers.HyperlinkedModelSerializer):
        class Meta:
            fields = ['id', 'url']
            extra_kwargs = {'url': {'view_name': 'feature-detail'}}
   
    class PhotoSerializer(serializers.HyperlinkedModelSerializer):
        class Meta:
            fields = ['id', 'url']
            extra_kwargs = {'url': {'view_name': 'photo-detail'}}
   
   class StorySerializer(serializers.HyperlinkedModelSerializer):
       user = UserSerializer(read_only=True) 
       comments = serializers.HyperlinkedRelatedField(read_only=True, 
                              view_name='comment-detail', many=True)
       # this work because of related names
       features = FeatureSerializers(many=True)
       photos = PhotoSerializers(many=True)
       # add tags serializer as well
       text = serializers.CharField()
   
       class Meta:
            fields = ['id', 'users', 'photos', 'features', ...]