Framework cheatsheet

Ruby on Rails 8 Cheatsheet

Create apps, generate code, manage the database and run tests with the Rails 8 command line.

Getting started

Install Rails — Install the Rails gem. Needs Ruby installed.
Check the Rails version — Print the installed Rails version.
Create an app — Generate a new Rails application in a folder named myapp.
Create an app that uses PostgreSQL — Choose a database other than the default SQLite.
Create an API-only app — Skip the view layer and middleware that browser apps need.
Install the gems — Install the gems listed in the Gemfile.
Start the development server — Run the app at http://localhost:3000.
Start the server on another port — Use a different port when 3000 is taken.
Open the Rails console — Start an IRB session with the app loaded. Handy for trying out models.
List the routes — Show every route, with the controller action it maps to.
Show app and environment details — Print the Ruby, Rails and database versions and the environment.

Generate a model — Create a model, its migration and a test.
Generate a controller — Create a controller with index and show actions and their views.
Generate a full CRUD scaffold — Create model, controller, views, routes and tests in one go.
Generate a migration — Create a migration that adds a column. Rails reads the intent from the name.
Generate authentication — Add the built-in authentication system introduced in Rails 8: sessions, users and password reset.
Generate a background job — Create an Active Job class.
Undo a generator — Remove the files a generator created.

Create the databases — Create the development and test databases.
Run migrations — Apply pending migrations and update db/schema.rb.
Check migration status — Show which migrations have been run.
Roll back the last migration — Undo the most recent migration.
Load seed data — Load the data in db/seeds.rb into the database.
Prepare the database — Create the database if it is missing, then migrate. Safe to run repeatedly.
Drop and recreate the database — Drop, recreate, load the schema and seed.
Open the database shell — Open psql, mysql or sqlite3, depending on your configuration.

Edit encrypted credentials — Open config/credentials.yml.enc in your editor. Set EDITOR first, for example EDITOR="code --wait".
Run code in the app — Run a Ruby snippet with the app loaded.
List TODO comments — Find TODO, FIXME and OPTIMIZE annotations in the code.
List the middleware stack — Show the middleware requests pass through.
Check autoloading — Verify that file names match the constants they define.
Clear temporary files — Clear cache, sockets and sessions in tmp.
Precompile assets — Build the asset files for production.
Update config for a new Rails version — After upgrading the gem, update configuration files, reviewing each change.

Set up servers and deploy — Install Docker on the servers if needed, set up accessories and deploy for the first time.
Deploy a new version — Build and push the image, then roll it out with no downtime.
Follow the app logs — Stream logs from the app containers.
Open a Rails console on the server — Run a console in the production container. This is an alias that the Rails 8 config/deploy.yml defines.
Roll back a release — Switch back to an earlier version, using a version shown by kamal app containers.

Angular 22 cheatsheet — Angular CLI commands and standalone component, signals, template, routing, HTTP and forms snippets.
Astro cheatsheet — Build fast content sites with Astro: components, layouts, routing, content collections, islands, endpoints and deployment.
Django 6 cheatsheet — Create projects, run migrations, test and deploy Django apps, plus the ORM queries you use every day.
.NET and ASP.NET Core 10 cheatsheet — The dotnet CLI for creating, building, testing and publishing projects, plus common ASP.NET Core and EF Core code.
Express 5 cheatsheet — Build HTTP servers and APIs with Express 5 on Node.js.
FastAPI 0.115 cheatsheet — Install, run, test and deploy FastAPI apps from the command line.