python -aggregate(Max(‘id’))返回异常’str’对象没有属性’email’

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我一直在尝试让用户获得最高ID,但没有成功.
这是我的用户模型：

class User(models.Model):
    email=models.EmailField(unique=True, null=False)
    name=models.TextField(null=True)

它的序列化器：

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ('id', 'email', 'name')

风景：

class GetHighestValue(generics.ListAPIView):
    serializer_class = UserSerializer

    def get_queryset(self):
        return User.objects.aggregate(Max('id'))

Got AttributeError when attempting to get a value for field email on
serializer UserSerializer. The serializer field might be named
incorrectly and not match any attribute or key on the str instance.
Original exception text was: ‘str’ object has no attribute ’email’.

追溯：

Traceback (most recent call last):
File
“/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py”,
line 149, in get_response
response = self.process_exception_by_middleware(e, request) File “/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py”,
line 147, in get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File “/usr/local/lib/python2.7/dist-packages/django/views/decorators/csrf.py”,
line 58, in wrapped_view
return view_func(*args, **kwargs)
File “/usr/local/lib/python2.7/dist-packages/django/views/generic/base.py”,
line 68, in view
return self.dispatch(request, *args, **kwargs)
File “/home/user/.local/lib/python2.7/site-packages/rest_framework/views.py”,
line 466, in dispatch
response = self.handle_exception(exc)
File “/home/user/.local/lib/python2.7/site-packages/rest_framework/views.py”,
line 463, in dispatch
response = handler(request, *args, **kwargs)
File “/home/user/.local/lib/python2.7/site-packages/rest_framework/generics.py”,
line 201, in get
return self.list(request, *args, **kwargs)
File “/home/user/.local/lib/python2.7/site-packages/rest_framework/mixins.py”,
line 48, in list
return Response(serializer.data)
File “/home/user/.local/lib/python2.7/site-packages/rest_framework/serializers.py”,
line 674, in data
ret = super(ListSerializer, self).data
File “/home/user/.local/lib/python2.7/site-packages/rest_framework/serializers.py”,
line 239, in data
self._data = self.to_representation(self.instance)
File “/home/user/.local/lib/python2.7/site-packages/rest_framework/serializers.py”,
line 614, in to_representation
self.child.to_representation(item) for item in iterable
File “/home/user/.local/lib/python2.7/site-packages/rest_framework/serializers.py”,
line 463, in to_representation
attribute = field.get_attribute(instance)
File “/home/user/.local/lib/python2.7/site-packages/rest_framework/fields.py”,
line 422, in get_attribute
raise type(exc)(msg) AttributeError: Got AttributeError when attempting to get a value for field email on serializer
UserSerializer. The serializer field might be named incorrectly and
not match any attribute or key on the str instance. Original
exception text was: ‘str’ object has no attribute ’email’.

解决方法:

问题在这里

def get_queryset(self):
    return User.objects.aggregate(Max('id'))

期望的返回值是一个查询集.但是聚合不返回查询集.使用User.objects.get()也不返回查询集.返回查询集的唯一方法是使用all()或filter()

def get_queryset(self):
    return User.objects.order_by(-'id')[0:1]

这里暗含all(),[0：1]确保您返回的是可迭代对象,而不是单个对象.

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