Question

我正在努力编写一个Django GET，它返回以下看起来的响应：

{
"lists": [
    {
        "id": "123",
        "list_order": [
            {
                "id": "123_1",
                "order": 1,
                "list_id": "123",
                "item_id": 9876,
                "item": {
                   "id": 9876,
                   "name": "item1",
                   "location": "California"
                }
            },
            {
                "id": "123_2",
                "order": 2,
                "list_id": "123",
                "item_id": 2484,
                "item": {
                   "id": 2484,
                   "name": "item2",
                   "location": "California"
                }
            }            
        ],
        "updated_date": "2018-03-15T00:00:00Z"
    }
  ]
}

给定list_id，响应返回列表中的基本信息（“id”，“updated_date”），以及列表中项目的顺序。在列表顺序中的每个项目内，它还会抓取相关项目详细信息（嵌套在“项目”中）。我能够在没有“item”详细信息（“id”，“name”，“location”字段）的情况下获得此响应并且没有错误：

{
"lists": [
    {
        "id": "123",
        "list_order": [
            {
                "id": "123_1",
                "order": 1,
                "list_id": "123",
                "item_id": 9876
            },
            {
                "id": "123_2",
                "order": 2,
                "list_id": "123",
                "item_id": 2484
            }            
        ],
        "updated_date": "2018-03-15T00:00:00Z"
    }
  ]
}

同样没有错误，我可以检索第一个嵌套级别而没有任何问题。问题是要在每个“list_order”中显示“item”信息。以下是我的模型，序列化程序和视图。

models.py

class Lists(models.Model):
    id = models.CharField(null=False, primary_key=True, max_length=900)
    updated_date = models.DateTimeField(blank=True, null=True)

    class Meta:
        managed = False
        db_table = 'tbl_lists'

class Items(models.Model):
    id = models.BigIntegerField(primary_key=True)
    name = models.TextField(blank=True, null=True)
    location = models.TextField(blank=True, null=True)

    class Meta:
        managed = False
        db_table = 'tbl_items'

class ListOrder(models.Model):
    id = models.CharField(null=False, primary_key=True, max_length=900)
    list_id = models.ForeignKey(Lists, db_column='list_id', related_name='list_order')
    item_id = models.ForeignKey(Items, db_column='item_id', related_name='items')
    order = models.BigIntegerField(blank=True, null=True)

    class Meta:
        managed = False
        db_table = 'tbl_list_order'

serializers.py

class ItemsSerializer(serializers.ModelSerializer):

    class Meta:
        model = Items
        fields = '__all__'

class ListOrderSerializer(serializers.ModelSerializer):

    item = ItemsSerializer(many=False, read_only=True)

    class Meta:
        model = ListOrder
        fields = '__all__'

class ListsSerializer(serializers.ModelSerializer):

    list_order = ListOrderSerializer(many=True, read_only=True)

    class Meta:
        model = Lists
        fields = '__all__'

views.py

class ListsViewSet(generics.ListCreateAPIView):
    """
      API endpoint that returns a list with its meta-information
    """

    queryset = Lists.objects.all()
    serializer_class = ListsSerializer  

    def get_queryset(self):
        list_id = self.kwargs['list_id']

        filters = [Q(id=list_id)]

        return Lists.objects.filter(*filters)


    def list(self, request, list_id):

        queryset = self.get_queryset()

        list_serializer = ListsSerializer(queryset, many=True)

        return Response({ 'lists': list_serializer.data })

我对Django很新，并且喜欢它到目前为止提供的内容，尽管我可能正在考虑以太多的“SQL”方式执行此操作。我读过有关select_related（）和prefetch_related（）的内容，但不确定如何将它应用于此案例。非常感谢任何帮助，如果我能提供任何其他信息，请告诉我。

Answer 1

在ListOrderSerializer您尝试序列化 item 。在ListOrder模型中，您使用了字段名称 item_id

<强>解决方案：

在ListOrderSerializer：

class ListOrderSerializer(serializers.ModelSerializer):
    item_id = ItemsSerializer(many=False, read_only=True)
    ...

Django - 使用外键深度检索多个级别的嵌套字段

1 个答案: