ruby

Ruby

A dynamic, interpreted language known for its elegant syntax.

When to Use

Rapid Web Application Development (Ruby on Rails): Building full-stack web applications, startups, and MVPs with unmatched developer velocity.
E-Commerce & Digital Storefronts: Powering platforms like Shopify, Spree Commerce, and custom checkout flows.
Developer Tooling & Automation: Authoring automated DevOps scripts, Homebrew formulas, and Fastlane mobile deployment pipelines.
Background Processing & Queues: Executing asynchronous jobs using Sidekiq backed by Redis.

Quick Start

puts "Hello, World!"

class Greeter def initialize(name) @name = name end

def say_hi puts "Hi #{@name}!" end end

g = Greeter.new("Alice") g.say_hi


## Core Concepts

### Object-Oriented Everything & Dynamic Metaprogramming

Every value in Ruby is a full-fledged object; classes can be modified dynamically at runtime:

```ruby
class Integer
  def to_usd
    "$#{format('%.2f', self)}"
  end
end

puts 100.to_usd # "$100.00"

Blocks, Procs & Enumerable Power

Passes executable code blocks to methods for clean data manipulation:

orders = [
  { id: 1, total: 45.0, status: :completed },
  { id: 2, total: 120.0, status: :pending },
  { id: 3, total: 85.0, status: :completed }
]

completed_revenue = orders
  .select { |o| o[:status] == :completed }
  .sum { |o| o[:total] }

puts "Completed Revenue: $#{completed_revenue}" # 130.0

Modern Concurrency (Fibers & Ractor)

Runs true parallel execution without Global VM Lock (GVL) contention using Ractors (Ruby 3+):

# Parallel computation across multiple CPU cores
r = Ractor.new do
  # Completely isolated memory space
  1_000_000.times.reduce(:+)
end

puts "Ractor Result: #{r.take}"

Common Patterns

Pattern Matching with Value Extraction (Ruby 3+)

Problem: Verbose nested if/elsif conditionals when handling structured JSON API responses.

Solution: Use Ruby 3 native pattern matching:

def handle_response(response)
  case response
  in { status: 200, data: { user: { name:, email: } } }
    puts "User found: #{name} <#{email}>"
  in { status: 404, error: msg }
    warn "Not found: #{msg}"
  in { status: (500..) }
    raise "Server error occurred"
  else
    puts "Unknown response format"
  end
end

Best Practices

Do:

Enable YJIT in Production: Launch Ruby with --yjit to enable the native Just-in-Time compiler, boosting performance 20-40%.
Use RuboCop with Modern Presets: Enforce style consistency and detect security pitfalls with automated RuboCop linting.
Freeze String Literals: Add # frozen_string_literal: true at the top of files to reduce heap string allocations.
Use Sorbet or RBS for Type Checking: Add static typing to mission-critical business modules.

Don't:

Use monkey-patching in application code: Overriding core methods globally creates fragile, untraceable bugs across gems.
Query the database inside loops (N+1): Use .includes() or .preload() in ActiveRecord to eager-load associations.
Rescue Exception: Always rescue StandardError (rescue => e); rescuing Exception catches system exit and termination signals.

Troubleshooting

Error	Cause	Solution
`NoMethodError: undefined method '...' for nil:NilClass`	Calling method on a nil object.	Use safe navigation operator `object&.method_name`.
`LoadError: cannot load such file -- ...`	Gem not installed or missing in Gemfile.	Run `bundle install` and execute script via `bundle exec ruby script.rb`.
`NameError: uninitialized constant`	Constant/Class not required or module nesting typo.	Check file require paths and ensure file naming matches Zeitwerk conventions.

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