Ruby Development

The DHH/37signals way: convention over configuration, programmer happiness, and elegant simplicity.

Contents

• Critical Rules
• Verification
• Quick Reference
• Topics
• Stack Overview

Critical Rules

Always

• Follow Ruby/Rails naming conventions exactly
• Use generators (bin/rails g) for scaffolding
• Write tests first (TDD with Minitest)
• Keep controllers thin (under 10 lines per action)
• Return proper HTTP status codes
• Use strong parameters for all user input
• Index foreign keys in migrations

Never

• Fight conventions without excellent reason
• Put business logic in controllers or views
• Skip model validations
• Use render after successful mutations (use redirect_to)
• Store secrets in code (use credentials:edit)
• Write custom CSS when Tailwind utilities exist
• Reach for microservices before the monolith fails

Verification

After Editing Rails Files

Migration Safety:

• For migration files (db/migrate/*.rb), check for:
  • remove_column without safety checks (use strong_migrations gem)
  • rename_column or rename_table (consider add+copy+remove pattern)
  • NOT NULL constraints without default on existing tables
  • add_index without algorithm: :concurrently for large tables
  • change_column (may lock table and lose data)
• Deep validation (if time permits):
  • Test forward migration: rails db:migrate:up VERSION={version}
  • Test rollback: rails db:migrate:down VERSION={version}

Testing:

• If using Minitest: bin/rails test {test_file}
• If using RSpec: bundle exec rspec {spec_file}
• Run related tests by module: bin/rails test test/models/ or bundle exec rspec spec/models/

Linting:

• If standardrb is available: standardrb {files} or standardrb --fix {files}
• If rubocop is available: rubocop {files} or rubocop -a {files}

Security Scanning:

• If brakeman is available: bundle exec brakeman --quiet --format text
• Review high/medium confidence warnings

Before Committing

• Run StandardRB or RuboCop on changed files
• Run migration safety checks for new migrations
• Run tests for modified components
• Run Brakeman scan if reviewing or doing thorough validation
• Check CHANGELOG.md format if it exists

Quick Reference

Rails 8 (Default)

| Component | Default | Alternative | |-----------|---------|-------------| | Database | SQLite (dev/prod) | PostgreSQL | | Background Jobs | Solid Queue | Sidekiq | | Caching | Solid Cache | Redis | | WebSockets | Solid Cable | Redis | | Assets | Propshaft + Import Maps | esbuild | | CSS | Tailwind (standalone) | Bootstrap | | Deployment | Kamal | Capistrano |

Beyond Rails

| Use Case | Tool | |----------|------| | Microservices | Sinatra, Roda | | API-only | Grape | | Full-stack alternative | Hanami | | CLI tools | Thor, TTY | | Gem development | Bundler |

Topics

| Topic | Reference | Use When | |-------|-----------|----------| | Core | core.md | Writing idiomatic Ruby, organizing Rails files | | Models | models.md | Creating models, validations, associations, migrations | | Controllers | controllers.md | Building RESTful actions, strong params, filters | | Views | views.md | Creating templates, partials, layouts, helpers | | Hotwire | hotwire.md | Adding Turbo Drive/Frames/Streams, Stimulus | | API | api.md | Building JSON APIs, versioning, authentication | | Jobs | jobs.md | Setting up Solid Queue, Active Job, recurring jobs | | Security | security.md | Implementing authentication, authorization, CSRF | | Testing | testing.md | Writing Minitest, fixtures, system tests | | Performance | performance.md | Fixing N+1 queries, caching, indexing | | Deployment | deployment.md | Deploying with Kamal, Docker, zero-downtime | | Styling | styling.md | Setting up Tailwind CSS, responsive design | | Services | services.md | Creating service objects, result patterns | | Mobile | mobile.md | Building Hotwire Native, Bridge Components | | Debugging | debugging.md | Using binding.irb, byebug, Rails console |