Django

Question

我正在努力编写一个 Django GET，returns 如下所示的响应：

{
"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"
    }
  ]
}

给定一个list_id，响应returns列表的基本信息（"id"，"updated_date"），以及列表中项目的顺序.在列表顺序中的每个项目中，它还会获取相关的项目详细信息（嵌套在 "item" 中）。我能够在没有 "item" 详细信息（"id"、"name"、"location" 字段）且没有错误的情况下获得此响应：

{
"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"
    }
  ]
}

再次没有错误，我可以毫无问题地检索第一个嵌套级别。问题是让 "item" 信息显示在每个 "list_order" 中。下面是我的模型、序列化器和视图。

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 })

我是 Django 的新手，喜欢它目前提供的功能，尽管我可能正在考虑以 "SQL" 的方式来做这件事。我读过 select_related() 和 prefetch_related()，但不确定我将如何将其应用于这种情况。非常感谢任何帮助，如果我可以提供任何其他信息，请告诉我。

Answer 1

在您的 ListOrderSerializer 中，您正在尝试序列化 item。而在 ListOrder 模型中，您使用了字段名称 item_id

解决方案:

在ListOrderSerializer中：

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

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