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mhartl/sample_app_3rd_edition
The sample app for the 3rd edition of the Ruby on Rails Tutorial
The reference implementation for Michael Hartl's Rails Tutorial (3rd edition), covering a Twitter-like app with users, microposts, follows, and image uploads. This is a teaching artifact, not a production starter — its purpose is to let tutorial readers compare their code against a known-good state.
Chapter-specific git branches are genuinely useful for debugging where you went wrong mid-tutorial. The app covers a realistic slice of Rails features: auth from scratch with has_secure_password, account activation via email tokens, CarrierWave file uploads, and a follow graph with a self-join. Integration tests cover the full user flows, not just unit-level model tests. Seeds file and schema are included so you can get a working database in one command.
Last pushed January 2022, targeting Rails 4.x — the asset pipeline uses CoffeeScript and Sprockets, both of which you'd rip out immediately in any real project today. No API layer, Turbo/Hotwire, or anything post-2015 frontend. Uploaded files land in public/uploads committed to git, which is a bad habit to learn. Config uses secrets.yml (deprecated since Rails 5.2) instead of credentials.yml.enc, so anyone following along picks up a pattern that Rails itself has moved away from.