Question

我正在尝试使用ListSerializer，以便可以在POST上的列表中创建/反序列化多个对象。我按照https://www.django-rest-framework.org/api-guide/serializers/#listserializer的指南进行操作，但是在访问端点时似乎遇到了此错误。

assert self.child is not None, '``child`` is a required argument.'

python3.7/site-packages/rest_framework/serializers.py in __init__, line 592

我的序列化器如下：

class PredictionListSerializer(serializers.ListSerializer):

    def update(self, instance, validated_data):
        pass

    def create(self, validated_data):
        predictions = [Prediction(**item) for item in validated_data]
        return Prediction.objects.bulk_create(predictions)

class NestedPredictionSerializer(serializers.ModelSerializer):
    id = serializers.IntegerField(read_only=True)
    # Nested Serializer
    data = DataSerializer()

    class Meta:
        model = Prediction
        list_serializer_class = PredictionListSerializer
        fields = ('id', 'specimen_id', 'data' 'date_added',)
        extra_kwargs = {
            'slug': {'validators': []},
        }
        datatables_always_serialize = ('id',)

在初始化ListSerializer时会引发断言错误，但是，像这样在ViewSet中初始化序列化器。

class BulkPredictionViewSet(viewsets.ModelViewSet):
    queryset = Prediction.objects.all()
    serializer_class = PredictionListSerializer

有人熟悉这个问题吗？我想知道我对序列化程序初始化的缺乏控制（因为我使用的是ViewSet）是否会影响这一点。如果我尝试将NestedPredictionSerializer传递到ViewSet中，则会得到"Invalid data. Expected a dictionary, but got list."

编辑：

我能够覆盖ViewSet中的get_serializer方法来设置many = True，并将序列化器作为NestedPredictionSerializer传递给NestedPredictionSerializer，以识别POST上的列表。豪伯，现在我收到错误When a serializer is passed a ``data`` keyword argument you must call ``.is_valid()`` before attempting to access the serialized ``.data`` representation. You should either call ``.is_valid()`` first, or access ``.initial_data`` instead.

Answer 1

仅将many=True用于create action：

class BulkPredictionViewSet(viewsets.ModelViewSet):
    queryset = Prediction.objects.all()
    serializer_class = NestedPredictionSerializer

    def get_serializer(self, *args, **kwargs):
        serializer_class = self.get_serializer_class()
        kwargs['context'] = self.get_serializer_context()
        if if self.action == 'create': 
            kwargs['many'] = True
        return serializer_class(*args, **kwargs)

您不需要使用PredictionListSerializer，因为many=True会自动创建ListSerializer。

Answer 2

当以下阅读建议结合此答案时，我能够同时执行POST和GET：https://stackoverflow.com/a/45651309/3439441

我覆盖的ViewSet.get_serializer现在看起来像这样：

    def get_serializer(self, *args, **kwargs):
        if self.request.method.lower() == 'post':
            data = kwargs.get('data')
            kwargs['many'] = isinstance(data, list)
        return super(BulkPredictionViewSet, self).get_serializer(*args, **kwargs)

LIstSerializer AssertionError

2 个答案: