Question

我有一个例外尝试在序列化程序weight上获取字段WeightHistorySerializer的值时，出现 Got AttributeError。序列化程序字段的名称可能不正确，并且与QuerySet实例上的任何属性或键都不匹配。原始异常文本为：'QuerySet'对象没有属性'weight'。 当我尝试检索数据时。

models.py

class WeightHistory(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    weight = models.FloatField(null=False, blank=False)
    created_at = models.DateTimeField(auto_now_add=True)

serializers.py

class WeightHistorySerializer(serializers. HyperlinkedModelSerializer):
    class Meta:        
        model = WeightHistory        
        fields = (
            'id', 
            'weight',
            'user_id',
            'created_at'
        )   
        read_only_fields = ('id',)

views.py

def weight_history_detail(request, user_id):
    # Retrieve, update or delete a weight_history/detail.
    try:
        weight_history = WeightHistory.objects.filter(user_id=user_id)
    except WeightHistory.DoesNotExist:
        return Response(status=status.HTTP_404_NOT_FOUND)

    if request.method == 'GET':
        serializer = WeightHistorySerializer(weight_history)
        return Response(serializer.data)

如果更改为

weight_history = WeightHistory.objects.get(user_id=user_id)

它仅返回一行，但是我希望所有行都具有给定的user_id。因此，我该怎么做才能获得具有给定user_id的所有列表。

Answer 1

'QuerySet' object has no attribute 'weight'.

是的。 QuerySet是Set，是对象列表。

<QuerySet [<Object1>, <Object2>,..]>

并且该列表没有属性weight。相反，QuerySet内部的对象具有属性weight。

weight_history = WeightHistory.objects.filter(user_id=user_id)

filter返回QuerySet，是WeightHistory对象的列表，其中包含user_id=user_id。

您正在尝试将列表序列化为单个对象。

代替此：

serializer = WeightHistorySerializer(weight_history)

执行以下操作：

serializer = WeightHistorySerializer(weight_history, many=True)

many=True告诉序列化程序要传递序列化对象的列表。

此外，

try:
   weight_history = WeightHistory.objects.filter(user_id=user_id)
except WeightHistory.DoesNotExist:
   return Response(status=status.HTTP_404_NOT_FOUND)

这根本不会引发异常。如果没有对象，则filter返回一个空的QuerySet。 <QuerySet []>。

所以最终的代码是：

def weight_history_detail(request, user_id):
    # Retrieve, update or delete a weight_history/detail.
    weight_history = WeightHistory.objects.filter(user_id=user_id)
    if weight_history.count()<1:
        return Response(status=status.HTTP_404_NOT_FOUND)

    if request.method == 'GET':
        serializer = WeightHistorySerializer(weight_history, many=True)
        return Response(serializer.data)

Answer 2

<块引用>

views.py

def weight_history_detail(request, user_id):
    # Retrieve, update or delete a weight_history/detail.
    try:
        weight_history = WeightHistory.objects.get(user_id=user_id) #get
        except WeightHistory.DoesNotExist:
        return Response(status=status.HTTP_404_NOT_FOUND)

    if request.method == 'GET':
        serializer = WeightHistorySerializer(weight_history)
        return Response(serializer.data)

使用 get 而不是 filter 它会解决你的错误

原始异常文本为：'QuerySet'对象没有属性'weight'

2 个答案: