型別錯誤：ManyRelatedManager型別的物件在djangorest框架中不是JSON可序列化的

我正在嘗試使用他們的 ID 作為主鍵將一些學生添加到教師班級，但我遇到了上述錯誤。

我有這樣的老師和學生的模型。

class Student(TimeStampAbstractModel):
    user = models.OneToOneField(User, related_name="student", on_delete=models.CASCADE)
    college_name = models.CharField(max_length=255, default="", blank=True)
    address = models.CharField(max_length=255, default="", blank=True)

    def __str__(self):
        return self.user.name

class Teacher(TimeStampAbstractModel):
    user = models.OneToOneField(User, related_name="teacher", on_delete=models.CASCADE)
    address = models.CharField(max_length=255, default="", blank=True)
    students_in_class = models.ManyToManyField(Student,related_name="teacher")

    def __str__(self):
        return self.user.name

在這里，教師模型可以在一個班級中擁有許多具有他們的 id 的學生。我使用 put api 呼叫將學生一鍵添加到老師。

我的看法：

from rest_framework import status
class AddtoClassView(APIView):
    

    def put(self,request,pk,*args,**kwargs):
        id =pk
        teacher = Teacher.objects.get(id=id)
        serializer = TeacherSerializer(teacher,data=request.data)
        if serializer.is_valid():
            serializer.save()
            print("iam if")
            return Response({
                "message":"Student has been added to class.",
                "data": serializer.data
            },status=status.HTTP_200_OK)

        # else:
        print("iam else")
        return Response(serializer.data)

我的序列化器：

class TeacherSerializer(serializers.ModelSerializer):
    students_in_class = serializers.PrimaryKeyRelatedField(
        read_only= True
    )
    address = serializers.CharField(required=False)
    # user = serializers.PrimaryKeyRelatedField(read_only=True)

    class Meta:
        model = Teacher
        fields = ["address","students_in_class"]
        # fields = '__all__'

    def update(self, instance, validated_data):
        instance.address = validated_data.get("address")
        instance.save()
        stu = validated_data.get("students_in_class")
        print(stu)
        if stu is not None:
            print("iam stu")
            instance.students_in_class.add(stu)
        instance.save()
        super(TeacherSerializer,self).update(instance, validated_data)
        return instance

這里我使用了 student_in_class 作為 pk 欄位（我仍然不明白何時使用 integarfield 以及何時使用 pk 欄位）。我知道因為我將 id 添加到 student_in_class 欄位中，所以我不應該將它用作read_only = true，但是我必須使用否則它會產生錯誤。如何解決這個問題？另外，我真的不知道在序列化程式類中將哪些欄位定義為哪些欄位。

更新代碼：

class TeacherSerializer(serializers.ModelSerializer):
    # students_in_class = serializers.PrimaryKeyRelatedField(
    #     many = True, read_only= True
    # )
    students_in_class = serializers.ListField(
        source="students_in_class.all",
        child=serializers.PrimaryKeyRelatedField(queryset=Student.objects.all()),
    )
    address = serializers.CharField(required=False)
    # user = serializers.PrimaryKeyRelatedField(read_only=True)

    class Meta:
        model = Teacher
        fields = ["address","students_in_class"]
        # fields = '__all__'

    def update(self, instance, validated_data):
        instance.address = validated_data['students_in_class']['all']
        instance.save()
        stu = validated_data.get("students_in_class")
        print(stu)
        if stu is not None:
            print("iam stu")
            instance.students_in_class.add(stu)
        instance.save()
        super(TeacherSerializer,self).update(instance, validated_data)
        return instance

uj5u.com熱心網友回復：

由于您使用的是 m2m 欄位，因此您需要students_in_class. 所以解決方案將是這樣的。（免責宣告：代碼未經測驗）。

class TeacherSerializer(serializers.ModelSerializer):
    students_in_class = serializers.ListField(
        source="students_in_class.all", 
        child=serializers.PrimaryKeyRelatedField(queryset=Student.objects.all()),
    )

序列化錯誤將得到解決，因為現在您已students_in_class.all作為源包含在內。您需要使用以下內容訪問資料：validated_data['students_in_class']['all']

如果您想以不同的方式序列化您的輸出，您可以根據需要設定students_in_class為write_only并覆寫序列化程式表示。：

class TeacherSerializer(serializers.ModelSerializer):
    students_in_class = serializers.ListField(
        child=serializers.PrimaryKeyRelatedField(queryset=Student.objects.all()),
        write_only=True
    )
    # your code

    def to_representation(self, instance):
        ret = super().to_representation(instance)
        ret['students_in_class'] = StudentSerializer(instance.students_in_class.all(), many=True).data
        return ret

uj5u.com熱心網友回復：

以下代碼有效：

class TeacherSerializer(serializers.ModelSerializer):
    students_in_class = serializers.PrimaryKeyRelatedField(
        many = True,queryset=Student.objects.all()
    )
    address = serializers.CharField(required=False)

    class Meta:
        model = Teacher
        fields = ["address","students_in_class"]


    def update(self, instance, validated_data):
        instance.address = validated_data.get("address")
        instance.save()
        stu = validated_data.pop("students_in_class")

        for stus in stu:
            instance.students_in_class.add(stus)

        instance.save()
        super(TeacherSerializer,self).update(instance, validated_data)
        return instance

標籤：姜戈 接口 Django 休息框架 首要的关键 django 序列化器

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