Question

关注此官方tutorial我已对此进行了编码：

#! /usr/bin/env python

from mongoengine import *

connect('tumbleblog')


class User(Document):
  email = StringField(required=True)
  first_name = StringField(max_length=50)
  last_name = StringField(max_length=50)

class Comment(EmbeddedDocument):
  content = StringField()
  name = StringField(max_length=120)

class Post(Document):
  title = StringField(max_length=120, required=True)
  author = ReferenceField(User, reverse_delete_rule=CASCADE)
  tags = ListField(StringField(max_length=30))
  comments = ListField(EmbeddedDocumentField(Comment))

class TextPost(Post):
  content = StringField()

class ImagePost(Post):
  image_path = StringField()

class LinkPost(Post):
  link_url = StringField()


john = User(email="example@gmail.com",first_name='john', last_name='doe')
john.save()

但我不知道为什么在尝试运行它时会说：

/Library/Python/2.7/site-packages/mongoengine/fields.py:736: FutureWarning: ReferenceFields will default to using ObjectId  strings in 0.8, set DBRef=True if this isn't desired
  warnings.warn(msg, FutureWarning)
/Library/Python/2.7/site-packages/mongoengine/base.py:589: FutureWarning: TextPost uses inheritance, the default for allow_inheritance is changing to off by default. Please add it to the document meta.
  FutureWarning
/Library/Python/2.7/site-packages/mongoengine/base.py:589: FutureWarning: ImagePost uses inheritance, the default for allow_inheritance is changing to off by default. Please add it to the document meta.
  FutureWarning
/Library/Python/2.7/site-packages/mongoengine/base.py:589: FutureWarning: LinkPost uses inheritance, the default for allow_inheritance is changing to off by default. Please add it to the document meta.
  FutureWarning
[Finished in 0.2s]

我哪里出错了？我遵循了官方教程。我错过了什么？

PS Mongodb启动并运行

Answer 1

未来警告会提醒您在升级之前需要解决的MongoEngine未来版本中的更改。

警告是：

ReferenceFields默认使用0.8中的ObjectId字符串，如果不需要则设置DBRef = True

这意味着 - 如果您不想更改和迁移数据，则应将定义更改为：

ReferenceField(User, dbref=False)  # Uses the original way of storing dbrefs
ReferenceField(User, dbref=True)   # Uses a simpler way of storing dbrefs

Answer 2

您的代码在定义之前使用Comment。订单在Python中很重要。

请参阅示例https://stackoverflow.com/a/2985085/1256394。

Answer 3

好吧，如果您不喜欢这些警告，可以使Post看起来像：

class Post(Document):
    meta = {'allow_inheritance': True}
    ...
    author = ReferenceField(User, reverse_delete_rule=CASCADE, dbref=False)
    ...

有关详细信息，请参阅http://mongoengine-odm.readthedocs.org/en/latest/upgrade.html和https://github.com/hmarr/mongoengine/issues/437。

mongoengine中的问题：ReferenceFields将默认使用ObjectId

3 个答案: