# Prefer readable over clever
users.select(&:active?).map(&:email)

# Guard clauses over nested conditionals
def process(user)
  return unless user.active?
  return if user.banned?

  # Happy path at normal indentation
  send_notification(user)
end

# Implicit returns
def full_name
  "#{first_name} #{last_name}"
end

# Trailing conditionals for simple cases
send_email if user.subscribed?
raise ArgumentError, "Invalid" unless valid?

# Check behavior, not class
def export(target)
  target.write(data) if target.respond_to?(:write)
end

# Accept anything that quacks like a duck
class Report
  def initialize(formatter)
    @formatter = formatter  # Any object with #format method
  end
end

# Blocks for configuration
Rails.application.configure do |config|
  config.cache_store = :memory_store
end

# Blocks for resource management
File.open("data.txt") do |file|
  process(file.read)
end  # File automatically closed

# Custom iterators
def each_with_status
  items.each_with_index do |item, i|
    yield item, "#{i + 1}/#{items.size}"
  end
end

# Rails 8 app
rails new myapp --database=postgresql

# Sinatra microservice
bundle gem my_service --no-test

# CLI tool
bundle gem my_cli --no-test
# Add thor to gemspec

# Generators (Rails)
bin/rails g model User name:string email:string
bin/rails g controller Posts index show
bin/rails g authentication

# Development
bin/dev                    # Start with Procfile.dev
bin/rails test             # Run tests
bin/rails db:migrate       # Run migrations

# Deployment (Kamal)
kamal setup && kamal deploy

app/
├── controllers/     # HTTP request handling
├── models/          # Business logic and data
├── views/           # Templates and partials
├── services/        # Complex operations
├── jobs/            # Background processing
├── javascript/      # Stimulus controllers
│   └── controllers/
└── assets/
    └── stylesheets/ # Tailwind CSS

my_gem/
├── lib/
│   ├── my_gem.rb         # Entry point
│   └── my_gem/
│       ├── version.rb
│       └── ...
├── test/                  # Minitest
├── my_gem.gemspec
└── Gemfile