Django EmbeddedModelField 在执行 PUT 请求时说 "This field may not be blank"，尽管字段具有 "blank=True"

Question

我正在使用 django-rest-framework 创建 Django 应用程序并使用 djongo 连接到 MongoDB。我有这样的嵌套模型:

class Group(models.Model):
    users = models.ArrayModelField(
        model_container=User
    )

class User(models.Model):
    number = models.IntegerField(
        default=None,
        null=True
    )

    song = models.EmbeddedModelField(
        model_container=Song,
        null=True,
        blank=True
    )

    class Meta:
        abstract = True

class Song(models.Model):
    mp3_file = models.URLField(
        default=None,
        blank=True,
        null=True
    )

    comments = models.CharField(
        max_length=250,
        default='',
        blank=True
    )

    class Meta:
        abstract = True

创建组时，用户和歌曲的创建没有任何问题。例如，创建时，组可能如下所示:

{
    "name": "Sample",
    "users: [
        {
            "number": null,
            "song": {
                "mp3_file": null,
                "comments": ""
            }
        }
    ]
}

一切正常。但是，如果我尝试执行 PUT 请求并且不更改“number”、“mp3_file”或“comments”的值，我将收到以下错误消息:

"user": [
    {
        "number": [
            "This field may not be null."
        ],
        "song": {
            "mp3_file": [
                "This field may not be null."
            ],
            "comments": [
                "This field may not be blank."
            ]
        }
    }
]

关于如何修复此错误的任何想法？我只是使用通用的 RetrieveUpdateDestroyAPIView 作为此端点的 View 。

编辑:我也尝试过重新创建所有迁移以及删除表并重新创建它，但这些方法都没有帮助。

编辑: 这是 View :

class GroupDetail(generics.RetrieveUpdateDestroyAPIView):
    serializer_class = GroupSerializer
    queryset = Group.objects.all()
    lookup_field = 'group_name'
    lookup_url_kwarg = 'group_name'

还有序列化器:

class GroupSerializer(serializers.HyperlinkedModelSerializer):
    users = UserSerializer(many=True)

    def update(self, instance, validated_data):
        if validated_data.get('group_name', None) is not None:
            instance.__setattr__('group_name', validated_data.get('group_name'))

        instance.save()

        return instance

    class Meta:
        model = Group
        fields = (
            'group_name',
            'users'
        )


class UserSerializer(serializers.Serializer):
    number = serializers.IntegerField()
    song = SongSerializer()


class SongSerializer(serializers.Serializer):
    mp3_file = serializers.URLField()
    comments = serializers.CharField(
        max_length=250
    )

但部分问题在于，由于数据验证不正确，甚至从未访问过序列化器。

Answer 1

尝试改变:

class UserSerializer(serializers.Serializer):
    number = serializers.IntegerField(allow_null=True)
    song = SongSerializer()

class SongSerializer(serializers.Serializer):
    mp3_file = serializers.URLField(allow_blank=True)
    comments = serializers.CharField(
        max_length=250, allow_blank=True
    )