Ruby Cheat Sheet

Here’s a Ruby cheat sheet with Ruby syntax and commonly used commands:

Variables

name = "John"
age = 25

Data Types

Strings:

greeting = "Hello, World!"

Numbers:

integer_number = 42
float_number = 3.14

Arrays:

numbers = [1, 2, 3, 4, 5]

Hashes:

person = { name: "Alice", age: 30 }

Control Flow

If-Else:

if condition
  # code to run if the condition is true
else
  # code to run if the condition is false
end

While Loop:

while condition
  # code to repeat as long as the condition is true
end

For Loop:

for i in 1..5
  # code to run for each iteration
end

Methods

def greet(name)
  puts "Hello, #{name}!"
end

greet("Bob")

Classes and Objects

class Dog
  attr_accessor :name, :age

  def initialize(name, age)
    @name = name
    @age = age
  end

  def bark
    puts "Woof!"
  end
end

my_dog = Dog.new("Buddy", 3)
my_dog.bark

File I/O

Read from a File:

File.open("example.txt", "r") do |file|
  contents = file.read
  puts contents
end

Write to a File:

File.open("example.txt", "w") do |file|
  file.puts "Hello, Ruby!"
end

Exception Handling

begin
  # code that might raise an exception
rescue SomeException => e
  puts "An error occurred: #{e.message}"
end

Symbols

# Symbols are lightweight strings often used as keys in hashes
status = :success

Enumerable Methods

Each:

numbers.each { |num| puts num }

Map:

doubled_numbers = numbers.map { |num| num * 2 }

Select:

even_numbers = numbers.select { |num| num.even? }

Regular Expressions

pattern = /\d+/
result = "123 Ruby".match(pattern)
puts result[0]  # Output: 123

Installing Gems

gem install gem_name

Using Gems

require 'gem_name'

This is a basic cheat sheet, and Ruby has many more features and nuances. For in-depth learning, refer to the official Ruby documentation.