💎 Ruby Handbook

Overview

Ruby is a dynamic, interpreted, object-oriented language designed for developer happiness. Everything in Ruby is an object. It is famous for the Ruby on Rails web framework.

Version Ruby 3.x  Paradigm OOP, Functional, Scripting  Typing Dynamic, Duck

Core Concepts

Variables

• local_var — local variable
• @instance_var — instance variable
• @@class_var — class variable
• $global_var — global variable
• CONSTANT — constant (uppercase)

Data Types

• Integer, Float, String, Symbol
• Array — [1, 2, 3]
• Hash — { key: value }
• Range — (1..10)
• nil — absence of value

Blocks, Procs & Lambdas

• Block: array.each { |x| puts x }
• Proc.new { |x| x * 2 }
• Lambda: ->(x) { x * 2 }
• Yield to pass control to a block

Object-Oriented Ruby

• Everything is an object — including integers
• attr_accessor, attr_reader, attr_writer
• Modules as mixins: include, extend
• Open classes — can reopen any class
• Method missing for dynamic dispatch

Key Frameworks & Tools

Category	Framework / Tool
Web	Ruby on Rails, Sinatra, Hanami
Testing	RSpec, Minitest, Capybara
Package Mgmt	RubyGems, Bundler
DevOps	Chef, Vagrant (written in Ruby)
ORM	ActiveRecord

Common Interview Topics

• Symbols vs Strings
• Proc vs Lambda differences
• Mixins vs inheritance
• Metaprogramming with define_method, method_missing
• Frozen objects and immutability
• Garbage collection in MRI Ruby