如何为子ModelSerializer设置实例以实现更新操作？

数据模型 #

class Parent:
    child = models.OneToOneField(Child)
    name = models.CharField()


class Child:
    name = models.CharField()

请求载荷示例 #

{
    "id": 1,
    "name": "Dad",
    "child": {
        "id": 2,
        "name": "Kiddo"
    }
}

序列化器代码 #

class ParentSerializers(serializers.ModelSerializer):
    class Meta:
        model = Parent
        fields = ("child", "name")

    child = ChildSerializer()

class ChildSerializer(serializers.ModelSerializer):
    class Meta:
        model = Child
        fields = ("name",)

视图代码 #

try:
    parent = Parent.objects.get(id=request.data["id"])
except Parent.DoesNotExist:
    parent = None

serializer = ParentSerializer(data=request.data, instance=parent)
serializer.is_valid(raise_exception=True)

问题描述 #

当Parent和Child实例已存在于数据库中时，传入上述请求会触发code=unique的ValidationError。原因是序列化器在“创建”模式下会校验主键唯一性，只有绑定到实例（“更新”模式）时才会跳过该校验。

目前已为ParentSerializer设置了instance=parent参数，但无法给嵌套的ChildSerializer设置对应实例。

临时解决方案 #

try:
    parent = Parent.objects.get(id=request.data["id"])
except Parent.DoesNotExist:
    parent = None

serializer = ParentSerializer(data=request.data, instance=parent)

if parent:
    try:
        serializer.fields.fields["child"].instance = parent.child
    except Child.DoesNotExist:
        pass

serializer.is_valid(raise_exception=True)

内容的提问来源于stack exchange，提问作者foucdeg