python - 带有 Flask 'mongoengine.errors.NotRegistered' 问题的 mongoengine

Question

我想使用mongoengine和flask定义两个文档，用户包含以下主题，主题包含发布用户。

我在user.py中定义User文档，在topic.py中定义Topic文档。仅在 topic.py 中我导入 User clakk，在 user.py 中我不导入 Topic 类为了避免导入循环。

user.py:
class User(Document):
    username = StringField(unique=True, required=True)
    following_topics = ListField(ReferenceField('Topic', reverse_delete_rule=PULL, unique=True))


topic.py:
from user import User
class Topic(Document, ModelMixin):
    title = StringField(default='')
    user = ReferenceField(User, required=True)

但是当我启动flask时，出现错误，我该如何修复？

mongoengine.errors.NotRegistered: `Topic` has not been registered in the document registry. Importing the document class automatically registers it, has it been imported?

Answer 1

El Problema se solucionaba importando en orden.

user.py: 
from topic import Topic 
class User(Document):
    username = StringField(unique=True, required=True)
    following_topics = ListField(ReferenceField('Topic', reverse_delete_rule=PULL, unique=True))

topic.py: 
class Topic(Document, ModelMixin):
    title = StringField(default='')
    user = ReferenceField('User', required=True)