Question

在model.py，我有两个模特

class student(models.Model):
    name = models.CharField(max_length=255)
    registration_number = models.CharField(max_length=255)
    session = models.CharField(max_length=255)
    college = models.ForeignKey(to='college', on_delete=models.CASCADE)

    class Meta:
        db_table = 'student'


class semester(models.Model):
    semester = models.IntegerField()
    student = models.ForeignKey(to='student', on_delete=models.CASCADE)
    sgpa = models.FloatField()
    grade = models.CharField(max_length=255)
    is_fail = models.BooleanField(default=True)

    class Meta:
        db_table = 'semester'

Serializer类看起来像

class SemesterSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.semester
        fields = ('id', 'semester', 'sgpa', 'grade', 'is_fail',)

class StudentSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.student
        fields = ('id', 'name', 'registration_number', 'college', 'session',)

和views.py包含

class SemesterViewSet(viewsets.ModelViewSet):    
    def get_queryset(self):
        if 'semester' in self.kwargs:
            return models.semester.objects.filter(semester=self.kwargs['semester'])
        else:
            return models.semester.objects.all()

    lookup_field = 'semester'
    serializer_class = serializer.SemesterSerializer

网址格式

router = DefaultRouter()
router.register('semester', views.SemesterViewSet, base_name='semester')
urlpatterns = [
    url(r'', include(router.urls)),
]

当我尝试访问url/semester/8时，引发了MultipleObjectsReturned异常并显示get() returned more than one semester -- it returned 2!错误消息。在这里，我没有使用任何get()方法。为什么会这样，解决方案是什么？我需要显示学期的所有结果。

Answer 1

从视图中删除lookup_field或将其更改为lookup_field = 'id'
该错误是因为当您调用retrieve()方法时，在其内部调用get_object()，该查询与查询相似，类似于 <击>

<击>

semester.objects.get(semester=semester.objects.get(id=8).semester)

<击>

semester.objects.get(lookup_field=parameter)

示例：

semester.objects.get(semester=8)

因此，如果有超过1个学期的实例具有相同的semester值，则会引发错误

的 UPDATE-1
尝试覆盖视图中的retrieve()方法，

from rest_framework.response import Response class SemesterViewSet(ModelViewSet): def get_queryset(self): if 'semester' in self.kwargs: return semester.objects.filter(semester=self.kwargs['semester']) else: return semester.objects.all() lookup_field = 'semester' serializer_class = SemesterSerializer def retrieve(self, request, *args, **kwargs): # Change is here << serializer = self.get_serializer(self.get_queryset(), many=True) return Response(data=serializer.data)

尽管使用了filter（）方法，但是django rest框架get（）返回了多个对象

1 个答案: