You may have read the following excellent blogpost by Brian Helmkamp of CodeClimate. It nicely describes 7 types of objects that can be extracted from models and controllers in a Rails-app.
7 Patterns to Refactor Fat ActiveRecord Models https://codeclimate.com/blog/7-ways-to-decompose-fat-activerecord-models/ Brian Helmkamp on Oct 17, 2012.
Here are my thoughts on it, reading it as an experienced rails developer, 7 years later 😅 👴