MongoEngine : Extending DynamicDocument and using meta collection

[Sicabol]

Hi !

These are my first steps using mongoengine. For now I don't use any framework.

My MongoDB database is already existing and works in a PHP solution. I am trying to translate my PHP development to Python. In my Python code, I want to have one file per collection, all in a "models" directory. My controllers will be outside of the "models" directory and will use theses models to perform the different tasks. As I have several collections and as I would need to create common methods for all of the objects, I have decided to create a generic MongoDocument class extending DynamicDocument, the objects classes will then extend MongoDocument. The problem is that I can't access the collections when using meta collection.

For now, here is the files tree :

test.py
models/

__init__.py
mongodocument.py
variables.py

Here are the codes :

models/__init__.py :

from mongoengine import connect
connect('mydb', host='mongodb://myserver.com', replicaSet='myrs')

models/mongodocument.py :

from mongoengine import *

class MongoDocument(DynamicDocument):
    meta = {
        'allow_inheritance': True,
        'abstract': True
    }

models/variables.py :

from mongoengine import *
from mongodocument import *

class Variables(MongoDocument):
    meta = {
        'collection': 'variables'
    }
   
    name = StringField(required=True)
    value = StringField()
    values = DictField()
    modified = LongField()
   
    def update_modified(self):
        from time import time
        self.modified = int(time())

test.py :

from models.variable import Variables

print Variables._collection
print Variables._get_collection_name()
variable = Variables.objects.get(name="nb_articles_fr")

Here are the results when I call test.py :

None
variables
Traceback (most recent call last):
  File "testpdt.py", line 5, in <module>
    variable = Variables.objects.get(name="nb_articles_fr")
  File "/usr/local/lib/python2.7/dist-packages/mongoengine/queryset/base.py", line 242, in get
    raise queryset._document.DoesNotExist(msg)
models.variable.DoesNotExist: Variables matching query does not exist.

The problem is that apparently Variables doesn't use the "variables" collection from my database - even if Variables._get_collection_name() returns "variables". If Variables extends directly DynamicDocument and if I remove the meta part of models/variables.py, I can acces to the nb_articles_fr" document.

I must be missing something :)
Don't forget my idea is to have some generic methods for all my objects. For example, the "update_modified" method could appear in the MongoDocument class (don't comment about the timestamp, I'm working on old data which was using timestamps ;) ).

Thanks for any advice !

[Sicabol]

OK, apparently I shouldn't have used "allow_inheritance" in MongoDocument class, it was a misunderstanding. "abstract:True" is enough.