python - Python 中的自引用类变量

Question

我正在尝试在 Graphene-Django 中实现类似文件夹的类型。文件夹可以包含文件或文件夹。这样做:

Django 模型:

from django.db import models
class Folder(models.Model):
    name = models.CharField(...)
    parent = models.ForeignKey('self')

class File(models.Model):
    name = models.CharField(...)
    content = models.TextField(...)

Graphite 烯API:

from files.models import Folder, File

class FolderNode(DjangoObjectType):
    folders = graphene.List(FolderNode)

    def resolve_folders(self, args, context, info):
        return Folder.objects.filter(parent=self)

    class Meta:
        model = Folder

失败，因为我无法在其自己的类定义中引用FolderNode。将答案应用于 another question :

class FolderNode(DjangoObjectType):
    def __new__(cls, *args, **kwargs):
        cls.folders = graphene.List(cls)
        return object.__new__(cls, *args, **kwargs)

    def resolve_folders(self, args, context, info):
        return Folder.objects.filter(parent=self)

    class Meta:
        model = Folder

也不起作用，因为 Graphene 在决定向 API 添加什么内容时只看到属于声明一部分的类变量。有什么想法吗？

Answer 1

基于https://github.com/graphql-python/graphene/issues/110 ，正确的方法是使用字符串:

class FolderNode(DjangoObjectType):
    folders = graphene.List('FolderNode')