Django rest framework 有效相关字段未被序列化程序找到但存在于请求中

Question

我有 2 个相关模型，我正在尝试执行 ajax 'multipart/form' post 请求。但似乎由于某种原因，有关相关模型的数据未被序列化程序识别。我尝试编辑视图集的 'create' 方法，以了解为什么数据未通过，但无济于事。我认为这个问题与 json 序列化有关，但我不知道如何解决它

以下是我尝试过的一些方法：

models.py

class Dream(models.Model):
    # Some fields
    ...

class Milestone(models.Model):
    title = models.CharField(max_length=100)
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    date = models.DateTimeField(auto_now_add=True)
    description = models.TextField(max_length=500)
    dream = models.ForeignKey(
        Dream, on_delete=models.CASCADE, related_name='milestones')

serializers.py

class DreamSerializer(TaggitSerializer, serializers.ModelSerializer):
    milestones = MilestoneSerializer(many=True, read_only=False)
    class Meta:
        model = Dream
        fields = (..., 'milestones')


class MilestoneSerializer(serializers.ModelSerializer):
    class Meta:
        model = Milestone
        fields = ('id', 'title', 'user', 'date', 'description', 'dream')
        read_only_fields = ('user', 'dream', 'date')

views.py

class DreamViewSet(viewsets.ModelViewSet):
    queryset = Dream.objects.prefetch_related('user').all()
    serializer_class = DreamSerializer
    permission_classes = [permissions.IsAuthenticated]

    # Tried to manually override the create function to fix the error
    def create(self, request, *args, **kwargs):
        print(request.data) # <QueryDict: {'title': ['test'], 'image':[<InMemoryUploadedFile: somePhoto.jpg (image/jpeg)>], ... , 'milestones': ['[{"title":"test1","description":"test1"}]']}>
        
        # seems like it is evaluating to string literal '[{"title":"test1","description":"test1"}]'
        print(request.data['milestones']) # [{"title":"test1","description":"test1"}]
        print(type(request.data['milestones'])) # <class 'str'>
        cleaned_data = request.data.copy()
        milestones = cleaned_data.pop('milestones', [])
        print(milestones) # ['[{"title":"test1","description":"test1"}]'] (type list)
        if len(milestones):
            # tried to manually deserialize data 
            cleaned_data['milestones'] = json.loads(milestones[0])

        milestone_serializer = MilestoneSerializer(
            data=cleaned_data['milestones'], many=True)
        print(cleaned_data) # <QueryDict: {'title': ['test'], 'image': [<InMemoryUploadedFile: somePhoto.jpg (image/jpeg)>], 'milestones': [[{'title': 'test1', 'description': 'test1'}]]}>
        print(milestone_serializer.is_valid()) # True
        print(milestone_serializer.data) # [OrderedDict([('title', 'test1'), ('description', 'test1')])]
        serializer = self.get_serializer(data=cleaned_data)

        if serializer.is_valid(): # False
            # not executedd
            print(serializer.validated_data)
            self.perform_create(serializer)
            headers = self.get_success_headers(serializer.data)
            return Response(serializer.data, status=201, headers=headers)
        else:
            print(serializer.errors) # {'milestones': [ErrorDetail(string='This field is required.', code='required')]}

在前端：

async add({title, image, ..., milestones}) {
    const imageFile = new File([image], `somePhoto.jpg`, {
      type: image.type,
    });
    
    const formData = new FormData();
    formData.append("title", title);
    formData.append("image", imageFile);
    ....
    formData.append("milestones", JSON.stringify(milestones));

    await axios.post(endpoint, formData); // status: 400, statusText: 'Bad Request',  milestones: ['This field is required.']
}

Answer 1

它不起作用，因为在 DreamSerializer 中，您将里程碑字段设置为里程碑对象列表。但是在前端你将它设置为字符串。你需要先改变它。而且我觉得创建逻辑应该写在serializer的create方法中。首先定义其他字段用于写入里程碑数据。

import json

class DreamSerializer(TaggitSerializer, serializers.ModelSerializer):
    milestones = MilestoneSerializer(many=True, read_only=True)
    milestone_str = serializers.CharField(write_only = True)

    class Meta:
        model = Dream
        fields = (..., 'milestones', 'milestone_str')

    def create(self, validated_data):
        milestone_str = validated_data.pop('milestone_str')
        milestone_data = json.loads(milestone_str)

        milestone_serializer = MilestoneSerializer(
            data=milestone_data, many=True)

        if milestone_serializer.is_valid():

            # create Dream object first
            dream = Dream.objects.create(**validated_data)

            for milestone_item in milestone_data:
                Milestone.objects.create(dream = dream, **milestone_item)
            return dream
        else:
            raise serializers.ValidationError("invalid milestone data")

那么在views.py中就不需要定义create方法了

class DreamViewSet(viewsets.ModelViewSet):
    queryset = Dream.objects.prefetch_related('user').all()
    serializer_class = DreamSerializer
    permission_classes = [permissions.IsAuthenticated]

在前端，

async add({title, image, ..., milestones}) {
    ...

    formData.append("milestone_str", JSON.stringify(milestones));

    ...
}

Django rest framework 有效相关字段未被序列化程序找到但存在于请求中

Django rest framework valid related field not found by serializer but present in request

python

django

django-rest-framework