Django嵌套一对多序列化器问题：无法获取三级分类嵌套数据

我正在构建数据库间的关联关系，当前接口仅返回二级分类数据，无法展示三级分类的嵌套结构。

当前返回结果 #

[
{
"id":1,
"title":"mobile",
"category_two":[
{
"id":3,
"title":"brand"
},
{
"id":4,
"title":"memory"
}
]
}
]

期望返回结果 #

[
{
"id":1,
"title":"mobile",
"category_two":[
{
"id":3,
"title":"brand",
"category_three":[
{
"id":1,
"title":"samsung"
},
{
"id":2,
"title":"apple"
}
]
},
{
"id":4,
"title":"memory",
"category_three":[
{
"id":1,
"title":"32gb"
},
{
"id":2,
"title":"64gb"
}
]
}
]
}
]

现有代码实现 #

views #

class get_Category(APIView):
    def get(self, request):
        category = CategoryOne.objects.all()
        serializer = CategoryTwoSerializer(category, many=True)
        return Response(serializer.data)  

serializers #

class CategoryOneSerializer(serializers.ModelSerializer):
    
    class Meta:
        model = CategoryOne
        fields = '__all__'

class CategoryTwoSerializer(serializers.ModelSerializer):
    category_two= CategoryOneSerializer(many=True,read_only=True)
    class Meta:
        model = CategoryTwo
        fields = '__all__'
        depth=5
        

class CategoryThreeSerializer(serializers.ModelSerializer):
    category_three = CategoryTwoSerializer(many=True,read_only=True)
    class Meta:
        model = CategoryThree
        fields = '__all__'
        depth=5

models #

class CategoryOne(models.Model):
    title = models.CharField(max_length=225)
    
    def __str__(self):
        return self.title


class CategoryTwo(models.Model):
    title = models.CharField(max_length=255)
    categoryone = models.ForeignKey(CategoryOne,related_name='category_two',on_delete=models.SET_NULL,null=True)


    def __str__(self):
        return self.title
    
class CategoryThree(models.Model):
    title = models.CharField(max_length=255)
    categorytwo = models.ForeignKey(CategoryTwo,related_name='category_three',on_delete=models.SET_NULL,null=True)

    def __str__(self):
        return self.title

解决方案 #

你的代码存在几个关键问题，导致无法返回三级分类嵌套结构：

1. 序列化器关联逻辑错误：

   • CategoryTwoSerializer错误关联了CategoryOneSerializer，但CategoryOne通过related_name='category_two'关联的是CategoryTwo实例，应该在CategoryOneSerializer中嵌套CategoryTwoSerializer。
   • CategoryThreeSerializer错误关联了CategoryTwoSerializer，正确逻辑是在CategoryTwoSerializer中嵌套CategoryThreeSerializer，对应CategoryTwo的related_name='category_three'。

2. 视图使用了错误的序列化器：

   • 视图查询CategoryOne数据，却用了CategoryTwoSerializer，应该使用CategoryOneSerializer来序列化一级分类及其关联的二级、三级分类。

3. 不必要的depth参数：

   • 手动嵌套序列化器时无需设置depth，否则会导致序列化逻辑冲突。

修改后的代码如下：

修改后的serializers #

class CategoryThreeSerializer(serializers.ModelSerializer):
    class Meta:
        model = CategoryThree
        fields = '__all__'

class CategoryTwoSerializer(serializers.ModelSerializer):
    # 关联三级分类
    category_three = CategoryThreeSerializer(many=True, read_only=True)
    class Meta:
        model = CategoryTwo
        fields = '__all__'

class CategoryOneSerializer(serializers.ModelSerializer):
    # 关联二级分类
    category_two = CategoryTwoSerializer(many=True, read_only=True)
    class Meta:
        model = CategoryOne
        fields = '__all__'

修改后的views #

class get_Category(APIView):
    def get(self, request):
        category = CategoryOne.objects.all()
        # 使用正确的序列化器
        serializer = CategoryOneSerializer(category, many=True)
        return Response(serializer.data)  

修改后接口即可返回包含三级分类的嵌套结构，与期望结果一致。

内容的提问来源于stack exchange，提问作者zor