在MongoEngine中使用reverse_delete_rule时,如何使用循环或前向ReferenceField?
问题描述:
该代码炸弹:在MongoEngine中使用reverse_delete_rule时,如何使用循环或前向ReferenceField?
from mongoengine import *
class Employee(Document):
name = StringField()
boss = ReferenceField("Employee", reverse_delete_rule = NULLIFY)
继承人的例外:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "[…]/mongoengine/base.py", line 791, in __new__
new_class = super_new(cls, name, bases, attrs)
File "[…]/mongoengine/base.py", line 630, in __new__
f.document_type.register_delete_rule(new_class,
File "[…]/mongoengine/fields.py", line 757, in document_type
self.document_type_obj = get_document(self.document_type_obj)
File "[…]/mongoengine/base.py", line 136, in get_document
""".strip() % name)
mongoengine.base.NotRegistered: `Employee` has not been registered
in the document registry.
Importing the document class automatically registers it, has it
been imported?
卸下reverse_delete_rule
解决了这个问题,但我想有此规则。
我想这一点,和它的作品,但它确实看起来像废话,我担心可能会有不好的副作用(到目前为止,我还没有看到任何,虽然):
from mongoengine import *
class Employee(Document):
pass # required for the reverse_delete_rule to work on the boss field,
# because the Employee class needs to exist.
class Employee(Document):
name = StringField()
boss = ReferenceField("Employee", reverse_delete_rule = NULLIFY)
有任何想法吗?这不应该被视为MongoEngine中的错误吗?
答
尝试使用'self'
代替'Employee'
:
from mongoengine import *
class Employee(Document):
name = StringField()
boss = ReferenceField("self", reverse_delete_rule = NULLIFY)
查看详情:https://mongoengine-odm.readthedocs.org/en/latest/guide/defining-documents.html#reference-fields。
谢谢,它的作品!这解决了“自我”问题,而不是“前进”问题(如果我需要引用稍后定义的类)? – MiniQuark 2013-04-04 14:36:50
对于这种情况,可能更好地使用'GenericReferenceField'(https://mongoengine-odm.readthedocs.org/en/latest/guide/defining-documents.html#generic-reference-fields)。 – tbicr 2013-04-04 15:36:24