python - MongoEngine 模式 - 名称错误

Question

我在名为 model.py 的文件中有以下模式

from mongoengine import *

class Subject(Document):
    uri = StringField(required=True)
    resources = ListField(ReferenceField(ResourceSubject))

class ResourceSubject(Document):
    subject = ReferenceField(Subject,reverse_delete_rule=CASCADE)
    resource = ReferenceField(Resource)

class Resource(EmbeddedDocument):
    uri = StringField()
    title = StringField()
    snippet = StringField()
    image = StringField()
    source = StringField()
    adapter = StringField()

出于某种原因，当我尝试初始化一个主题时，subj = Subject(uri="hello").save() 我收到一个名称错误:NameError: name 'ResourceSubject ' 未定义。

我不明白原因，我猜这与框架有关？我尝试将类分离到单个文件中，然后导入，但我仍然遇到相同的错误。我错过了什么？

此行引发错误:resources = ListField(ReferenceField(ResourceSubject))

Answer 1

将 ResourceSubject 放入引号:

resources = ListField(ReferenceField('ResourceSubject'))