Running code when mongoengine loads a document
We are trying to run code that modifies a document when it loads as part of schema maintenance. We have a document such as from mongoengine import Document from mongoengine.fields import IntField, StringField class User(Document): version = IntField(default=0) name = StringField() Instances of User are created with version=1 and saved. Later on, we modify this class as follows: class User(Document): version = IntField(default=0) name = StringField(max_length=20) Some of the version 1 documents now need to be truncated: def upgrade_1_to_2(self): self.name = self.name[:20] We want to automatically run that function whenever a User is retrieved from the database, and only if version == 1. (Future upgrades would be upgrade_2_to_3(), and so on.) Where in this API can I put code that runs when a document is retrieved?
Looks like it's a good candidate for the post_init signal and you can do a check there. See: http://docs.mongoengine.org/guide/signals.html
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