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在MongoEngine中使用reverse_delete_rule时,如何拥有循环或正向ReferenceField?

cyclic-reference mongoengine forward-declaration

1

MiniQuark · 技术社区 · 11 年前

这个代码轰炸:

from mongoengine import *

class Employee(Document):
    name = StringField()
    boss = ReferenceField("Employee", reverse_delete_rule = NULLIFY)

例外情况如下:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "[â¦]/mongoengine/base.py", line 791, in __new__
    new_class = super_new(cls, name, bases, attrs)
  File "[â¦]/mongoengine/base.py", line 630, in __new__
    f.document_type.register_delete_rule(new_class,
    File "[â¦]/mongoengine/fields.py", line 757, in document_type
    self.document_type_obj = get_document(self.document_type_obj)
  File "[â¦]/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?

正在删除 reverse_delete_rule 解决了这个问题,但我想要这个规则。

我试过这个,效果很好,但它看起来真的很糟糕,我担心可能会有不良副作用(不过到目前为止,我还没有看到任何副作用):

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)

有什么想法吗?这难道不应该被认为是MongoEngine中的一个bug吗?

1 回复 | 直到 11 年前

1

7

tbicr 11 年前

尝试使用 'self' 相反 'Employee' :

from mongoengine import *

class Employee(Document):
    name = StringField()
    boss = ReferenceField("self", reverse_delete_rule = NULLIFY)

查看详细信息: https://mongoengine-odm.readthedocs.org/en/latest/guide/defining-documents.html#reference-fields .