Learn Ruby: 2. Basics

Let's explore fundamental Ruby concepts through interactive console examples using irb.

Classes and Initialization

class Terminal
  attr_accessor :title

  def initialize(title = 'Awesome Term')
    @title = title
  end

  def run(command = nil)
    puts "Welcome to {title}!"
    puts "Running your '{command}' command..." if command
  end
end

Key concepts: instance variables (prefixed with @), the initialize method, and require_relative for loading external files.

Getters, Setters, and Attribute Accessors

attr_reader, attr_writer, and attr_accessor are shortcuts to avoid writing boilerplate getter/setter methods.

String Operations

Double quotes support interpolation and escape characters; single quotes are literal.

lang = 'ruby'
puts lang.upcase        # => RUBY
puts lang.capitalize    # => Ruby
lang.upcase!            # Modifies original
puts "Hello! " * 3      # => Hello! Hello! Hello!

Numeric Types

counter = 300
counter += 100          # => 400
pi = 3.14
ten = 10
ten.to_f                # => 10.0

Use .to_i and .to_s to convert between types.

Symbols

Symbols share a single memory location, unlike strings:

:hello.object_id        # => always the same
"hello".object_id       # changes each time

Boolean and Nil

false and nil are always falsy. true, 0, and any object are truthy.

Arrays

arr = ['Ruby', 'on', 'Rails', 7]
arr.join(' ')           # => Ruby on Rails 7
arr[0]                  # => Ruby
arr[-1]                 # => 7

arr << 1                # Add to end
arr.push(9)
arr.unshift(5)          # Add to beginning
arr.pop                 # Remove last
arr.shift               # Remove first
arr[0..3]               # Slice

Hashes

h = {
  name: 'Alex',
  age: 28,
  langs: %w(Ruby Elixir Dart)
}

puts h[:name]           # => Alex

Note: symbol and string keys are distinct.

Constants

RUBY_VERSION = "3.0.1"
SomeString = "hello"
SomeString = "changes"  # Warning issued

Ranges

(1..10).to_a            # => [1, 2, 3, ..., 10]
(1..10) === 5           # => true

Control Structures

if version > 2.6
  puts "Ok"
elsif version >= 2.3 || version <= 2.5
  puts "Legacy"
else
  puts "Very old"
end

unless is_eq
  puts "enter unless block"
end

case age
when 1..18
  puts "<=18"
when 19...31
  puts ">18"
else
  puts age
end