AttributeError: 'QuerySet' object has no attribute 'category'

Question

我正在使用 DRF 从 API 获取和创建数据。我正在为模型 Question 和属性 category 而苦苦挣扎，这也是一个模型。所以为了创建和读取数据，我必须实现方法。因此，每当我创建一个问题时，它的类别是一个整数，但当我读取它时，它是一个对象。

每当我使用默认 API 路由时，我都可以创建和读取数据，但每当我编写不同的路由时，我都会收到以下错误：

AttributeError: Got AttributeError when attempting to get a value for field category on serializer QuestionSerializer. The serializer field might be named incorrectly and not match any attribute or key on the QuerySet instance. Original exception text was: 'QuerySet' object has no attribute 'category'.

这是我的自定义代码，哪里有问题...:[=21=]

class UserQuestions(APIView):
    permission_classes = [permissions.IsAuthenticated]

    def get(self, request, *args, **kwargs):
        questions = Question.objects.filter(created_by=request.user.id).all()
        data = QuestionSerializer(questions).data

        return Response({
            'questions': data
        })

以防万一，这是我的答案的实现：


class RelatedFieldAlternative(serializers.PrimaryKeyRelatedField):
    def __init__(self, **kwargs):
        self.serializer = kwargs.pop('serializer', None)
        if self.serializer is not None and not issubclass(self.serializer, serializers.Serializer):
            raise TypeError('"serializer" no es una clase serializer válida')

        super().__init__(**kwargs)

    def use_pk_only_optimization(self):
        return False if self.serializer else True

    def to_representation(self, instance):
        if self.serializer:
            return self.serializer(instance, context=self.context).data
        return super().to_representation(instance)


class CategorySerializer(serializers.ModelSerializer):
    class Meta:
        model = Category
        fields = '__all__'


class QuestionSerializer(serializers.ModelSerializer):
    <b>category = RelatedFieldAlternative(queryset=Category.objects.all(), serializer=CategorySerializer)</b>
    answers = AnswerSerializer(many=True, source='answer_set', allow_null=True, required=False)
    created_by = UserSerializer(required=False)

    <b>def to_representation(self, instance):
        response = super().to_representation(instance)
        response['category'] = CategorySerializer(instance.category).data
        return response</b>

    class Meta:
        model = Question
        fields = '__all__'

这是 Question 模型：

class Question(models.Model):
    id = models.AutoField(primary_key=True)
    category = models.ForeignKey(Category, on_delete=models.CASCADE, null=True)
    question = models.CharField(max_length=1000)
    ...

那么，我做错了什么？

Answer 1

首先，您要将多个项目传递给序列化程序，因此您应该使用 many=True。所以在你的情况下，它将是

data = QuestionSerializer(questions, many=True).data

其次，您不需要 relatedFieldAlternative。您可以只使用嵌套的串行器。

class CategorySerializer(serializers.ModelSerializer):
    class Meta:
        model = Category
        fields = '__all__'


class QuestionSerializer(serializers.ModelSerializer):
     category = CategorySerializer()

      class Meta:
         model = Question
         fields = '__all__'

AttributeError: 'QuerySet' object has no attribute 'category'

AttributeError: 'QuerySet' object has no attribute 'category'

python

django

django-models

django-serializer

django-rest-framework