issue in mongoengine: ReferenceFields will default to using ObjectId

Question

Following this official tutorial I've coded this:

#! /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()

But I don't know why when trying to run it it says:

/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]

Where I went wrong? I've followed the official tutorial..Did I miss something?

PS Mongodb is up and running

There's nothing really 'wrong'. Future warnings are a common idiom in Python and other languages to alert you about things that will be deprecated. — Petri, Nov 06 '12 at 09:24

score 3 · Answer 1 · answered Nov 05 '12 at 08:26

3

The future warning is there to alert you to changes in future versions of MongoEngine that will need addressing before you upgrade.

The warning is:

ReferenceFields will default to using ObjectId strings in 0.8, set DBRef=True if this isn't desired

What that means is - if you dont want to change and migrate your data you should change the definition to:

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

answered Nov 05 '12 at 08:26

Ross

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What is rationale of moving away from DBRef? – Mitar May 18 '13 at 04:44
Space - ObjectId's are preferred over DBRefs – Ross May 20 '13 at 07:58

score 1 · Answer 2 · edited May 23 '17 at 12:27

1

Your code is using Comment before it is defined. Order matters in Python.

See for example https://stackoverflow.com/a/2985085/1256394.

edited May 23 '17 at 12:27

Community

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answered Nov 04 '12 at 14:48

Petri

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You're right, but this does not fixes everything See first post – gaggina Nov 04 '12 at 14:51

score 1 · Answer 3 · answered Nov 04 '12 at 15:24

Well, if you don't like that warnings, you can make Post to look like:

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

See http://mongoengine-odm.readthedocs.org/en/latest/upgrade.html and https://github.com/hmarr/mongoengine/issues/437 for more info.

issue in mongoengine: ReferenceFields will default to using ObjectId

3 Answers3