How to get ReferenceField data in mongoengine?

Question

I\'m have a problem that query set retrieving oid in json, and I would like to retrieve actual username of that User collection I have below:

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Answer 1

Currently this is not supported directly as MongoEngine only supports mongodb's extended json syntax.

All mongoengine does under the covers is use pymongo's json_utils to dump the data. Theres no reason why you can't use it explicitly eg:

    from bson import json_util

    class Inbox(db.Document):
        from_user    = db.ReferenceField(User, required=True)
        subject      = db.StringField(max_length=255, required=True)
        created_at   = db.DateTimeField(default=datetime.now)
        messages     = db.ListField(db.EmbeddedDocumentField(Message))


        def to_json(self):
            data = self.to_mongo() // get the pymongo representation of the document
            data["from_user"] = {"User": {"username": self.from_user.username}}
            return json_util.dumps(data)

            User.drop_collection()

    ...

    Inbox.drop_collection()

    ross = User(username="Ross").save()
    Inbox(from_user=ross, subject="Mongoengine should make json easier").save()

    doc = Inbox.objects.only('from_user', 'subject', 'created_at').get()
    print doc.to_json()

    {"_id": {"$oid": "538c3d71c3d384172fe35393"}, 
     "from_user": {"User": {"username": "Ross"}}, 
     "subject": "Mongoengine should make json easier", 
     "created_at": {"$date": 1401703297198}, "messages": []}

Updated

Example with custom queryset:

   from bson import json_util

    class CustomQuerySet(QuerySet):
         def to_json(self):
            return "[%s]" % (",".join([doc.to_json() for doc in self]))

    class Inbox(Document):
        from_user    = ReferenceField(User, required=True)
        subject      = StringField(max_length=255, required=True)
        created_at   = DateTimeField(default=datetime.now)
        messages     = ListField(EmbeddedDocumentField(Message))

        meta = {'queryset_class': CustomQuerySet}

        def to_json(self):
            data = self.to_mongo()
            data["from_user"] = {"User": {"username": self.from_user.username}}
            return json_util.dumps(data)

  ...
  ipdb> Inbox.objects.only('from_user', 'subject', 'created_at').to_json()
        '[{"_id": {"$oid": "538d84cbc3d3843eeeb5dbbe"}, 
           "from_user": {"User": {"username": "Ross"}}, 
           "subject": "Mongoengine should make json easier", 
           "created_at": {"$date": 1401787099246}, "messages": []}]'