Question

这些是我的模特。py

class Grade(models.Model):
    grade = models.CharField(max_length=255, primary_key=True)
class Student(models.Model):
    name = models.CharField(max_length=255) 
    grade = models.ForeignKey(grade, on_delete=models.CASCADE)
    rollno = models.BigIntegerField()

我想做的是制作一个序列化程序，该序列化程序使用url：“ check / {str：pk} /”为我提供所有学生到特定年级的列表（实现获取和删除方法）。在我的序列化器中，我试图将两个模型结合起来，如下所示：

class MySerializer(serializers.ModelSerializer):
    allStudents = serializers.SerializerMethodField()
    class Meta:
        model = Grade
        fields = ("grade", "allStudents")

    def get_allStudents(self, obj):
        s_list = []
        fields = ['name', 'grade', 'rollno']
        for stds in obj:
            s_list.append(model_to_dict(stds, fields=fields))
        return s_list

我的views.py如下所示：

class IndividualGrade(generics.RetrieveUpdateDestroyAPIView):
    '''
    PUT check/{grade}/
    GET check/{grade}/
    DELETE check/{grade}/
    '''
    queryset = Grade.objects.all()
    serializer_class = MySerializer

    def get(self, request, *args, **kwargs):  
        try:
            s1 = Grade.objects.get(grade=kwargs["pk"])
            all_stds = Student.objects.filter(grade=s1) 
            a_grade = Grade.objects.get(grade=s1)
            return Response(MySerializer(a_grade, all_stds ).data)
        except Grade.DoesNotExist:
            return Response(
                data={
                    "message": "Grade with id: {} does not exist".format(kwargs["pk"])
                },
                status=status.HTTP_404_NOT_FOUND
            )

    def delete(self, request, *args, **kwargs):        
        try:
            Grade.objects.get(grade=kwargs["pk"]).delete()
            return Response(status=status.HTTP_204_NO_CONTENT)            
        except Grade.DoesNotExist:
            return Response(
                data={
                    "message": "Grade with id: {} does not exist".format(kwargs["pk"])
                },
                status=status.HTTP_404_NOT_FOUND
            )

这给了我以下错误：

"message": "Grade with id: grade9 does not exist"

虽然条目肯定存在。因为我可以删除它，所以它不会显示添加的字段。

对于不是马上就可以使用的序列化器，我真的很天真。

仍然不确定我在做什么错。另外，我想知道是否可以在SerializerMethodFiled中使用另一个序列化器

编辑 1.更新输入请求：http://127.0.0.1:8000/check/grade5/

JSON输入：

{
    "grade": "grade5",
    "allstudents": [
        {
            "name": "Shub",
            "grade": "grade5",
            "rollno": 4
        }
    ]
}

Answer 1

在您理解SerializerMethodField是什么的同时，我认为您不是在这里编码。您不需要传递任何额外的内容即可使用SerializerMethodField获取值。意味着，您不需要将all_stds作为MySerializer的参数来传递。因此，您应该像这样更新序列化器：

class StudentSerializer(serializers.ModelSerializer):
    class Meta:
        model = Student
        fields = ('name', 'grade', 'rollno')


class MySerializer(serializers.ModelSerializer):
    def get_allStudents(self, obj):
        # here obj is a Grade Object
        # we can get all the students by `obj.student_set.all()` via reverse relationship
        return StudentSerializer(obj.student_set.all(), many=True).data

此外，当您使用RetriveUpdateDestroyApiView时，它将处理所有get，patch，put，delete方法。您无需在视图中覆盖它们。因此，遵循以下代码即可满足您的需求。

class IndividualGrade(generics.RetrieveUpdateDestroyAPIView):
    '''
    PUT check/{grade}/
    GET check/{grade}/
    DELETE check/{grade}/
    '''
    queryset = Grade.objects.all()
    serializer_class = MySerializer

    # No more code is needed

不使用SerializerMethodField显示添加的字段

1 个答案: