在 django 中序列化多个级别

Question

我正在运行一个 django 应用程序，我想为我的模型结构返回一个大的 JSON。问题是我总是收到以下错误：

在序列化程序 ThirdHighestSerializer 上尝试获取字段 Fourth_highest_objects 的值时出现 AttributeError。序列化程序字段可能命名不正确，并且与 ModelThirdHighest 实例上的任何属性或键都不匹配。原始异常文本为：“ModelThirdHighest”对象没有属性“fourth_highest_objects”。

我的模型结构有点复杂：

class ModelHighest(models.Model):
    name = models.CharField(
        max_length=120,
        primary_key=True,
        unique=True,
    )


class ModelSecondHighest(models.Model):
 
    model_highest = models.ManyToManyField(
        ModelHighest,
        default=None,
        blank=True,
    )
    model_third_highest = models.ManyToManyField(
        ModelThirdHighest,
        default=None,
        blank=True,
    )


class ModelThirdHighest(models.Model):
   name = models.CharField(max_length=120)
   

现在继承开始发挥作用：

class ModelSuper(models.Model):
    class Meta:
        abstract = False

    name = models.CharField(
        max_length=120,
    )

    

class ModelFourthHighest(ModelSuper):
       
    third_highest_relation = models.ForeignKey(
        ModelThirdHighest,
        on_delete=models.CASCADE,
        related_name="fourth_highest_objects",
    )

我想要的是一个包含所有内容的大型嵌套 JSON：

├── ModelHighest
    ├── ModelSecondHighest
        ├── ModelThirdHighest
           ├── ModelFourthdHighest
 

我可以得到直到ModelThirdHighest，但我不能序列化最后一个。我的序列化器如下所示：

class FourthHighestSerializer(serializers.ModelSerializer):
    """..."""

    class Meta:
        model = ModelFourthHighest
        fields = (
            "name"
        )


class ThirdHighestSerializer(serializers.ModelSerializer):
    """..."""

    fourth_highest_objects = FourthHighestSerializer(many=True)

    class Meta:
        model = ModelThirdHighest
        fields = (
            "name",
            "fourth_highest_objects",
        )



class SecondHighestSerializer(serializers.ModelSerializer):
    """..."""

    model_third_highest = ThirdHighestSerializer(
        many=True,
    )

    class Meta:
        model = ModelSecondHighest
        fields = (
            "name",
            "model_third_highest",
        )


class HighestSerializer(serializers.ModelSerializer):
    """Serializer with all information."""

    model_second_highest_set = ModelHighestSerializer(many=True)

    class Meta:
        model = ModelHighest
        fields = (
            "project_name",
            "model_second_highest_set"
        )

现在我知道错误是在ThirdHighestSerializer 中引发的，字段为fourth_highest_objects。再次，它给我带来了错误：

尝试在序列化程序 ThirdHighestSerializer 上获取字段 fourth_highest_objects 的值时出现 AttributeError。 序列化程序字段可能命名不正确，并且与 ModelThirdHighest 实例上的任何属性或键都不匹配。 原始异常文本为：“ModelThirdHighest”对象没有属性“fourth_highest_objects”。

但我很确定我必须为反向关系使用相关名称。我究竟做错了什么？我什至可以序列化到这些级别吗？

在此先感谢所有耐心阅读本文的人。我知道这有点棘手，我试图尽可能地解释。如果需要，我可以澄清。

感谢您的帮助！

编辑1：

即使我将代码更改为：

  fourth_highest_objects = serializers.SerializerMethodField()

    def get_fourth_highest_objects(self, obj):
        print(obj)
        return FourthHighestSerializer(obj.fourth_highest_objects.all(), many=True).data
   

我得到ModelThirdHighest没有属性fourth_highest_objects, yet in the shell I can do ModelThirdHighest.objecst.last().fourth_highest_objects.all()`没有问题的错误

EDIT2：甚至陌生人：

当我在序列化程序中执行print(dir(obj)) 时，我没有得到fourth_highest_objects 字段

但是当我进入我的 shell 时，我确实有这个字段....

所以我猜问题是序列化程序中缺少该字段。但是怎么会这样，我一点都不清楚……

Answer 1

# serializer.py
class FourthHighestSerializer(serializers.ModelSerializer):
    """..."""

    class Meta:
        model = ModelFourthHighest
        fields = (
            "name",
        )


class ThirdHighestSerializer(serializers.ModelSerializer):
    """..."""

    fourth_highest_objects = FourthHighestSerializer(many=True)

    class Meta:
        model = ModelThirdHighest
        fields = (
            "name",
            "fourth_highest_objects",
        )


class SecondHighestSerializer(serializers.ModelSerializer):
    """..."""

    model_third_highest = ThirdHighestSerializer(
        many=True,
    )

    class Meta:
        model = ModelSecondHighest
        fields = (
            "model_third_highest",
        )


class HighestSerializer(serializers.ModelSerializer):
    """Serializer with all information."""

    modelsecondhighest_set = SecondHighestSerializer(many=True)

    class Meta:
        model = ModelHighest
        fields = (
            "name",
            "modelsecondhighest_set"
        )

用法

import json

serializer = HighestSerializer(ModelHighest.objects.first())
result = json.dumps(serializer.data, indent=4)
print(result)

{
    "name": "Model highest - 1",
    "modelsecondhighest_set": [
        {
            "model_third_highest": [
                {
                    "name": "some name",
                    "fourth_highest_objects": [
                        {
                            "name": "some other name"
                        }
                    ]
                }
            ]
        }
    ]
}