Ruby examples

Ruby examples.md

Integers

1 + 1
2 * 2
5 / 3
5 % 3
5 ** 2

String

"Hi"
'Hi'
"My age is #{1+2}"
puts "Hi"
printf("%d", 2+2)

Boolean

true
false
nil

false and nil are falsy, everything else is truthy

if, unless, until, while, case

if x == 1
  puts "X é 1"
else
  puts "X não é 1"
end

unless x == 0
  puts "X não é 0"
else
  puts "X é 0"
end

message = case grade
when "A"
  puts "Congratulations!"
when "B"
  puts "Well done"
when "C"
  puts "You can do better than that"
when "D"
  puts "Study harder"
when "E"
  puts "Did you do the tests?"
else
  puts "WTF of grade is that"
end

puts "0" if x == 0

x = 0

while x < 10
  puts "Valor de x é: #{x}"
  x += 1
end

x = 0

until x == 10
  puts "Valor de x é: #{x}"
  x += 1
end

for i in [1, 2, 3]
  puts i
end

```ruby
[1,2,3].each do |i|
  puts i
end

RegExp

'abcd' =~ /abcd/
'abcd' =~ /ab[cg][db]/

'abcd' =~ /[a-z]*/
'abcd' =~ /[a-z]*1/

'abcd1' =~ /[a-z]*[0-9]+/
'abcd1' =~ /[a-z]*[0-9]+/
'abcd1' =~ /[a-z]*\d?/
'abcd' =~ /^\w{4}$/
'abcd' =~ /a(.*)d/
'Sorocaba' =~ %r#[Ss]orocaba#

Symbol

:abcd
:aaa_daa
:aaaa_1
"aaa".__id__ == "aaa".__id__
:aaa.__id__ == :aaa.__id__

Range

(1..10)
(1...10)
('a'..'z')
('aa'..'zz')

('a'..'z') === 'q'
('a'..'z').to_a

Methods

def my_method(my_argument)
  puts my_argument
end

my_method("OK")
my_method(1)
my_method "OK"

def my_method(my_first_argument, my_last_optional_argument = false)
  puts "Eu tenho um último argumento" if my_last_optional_argument
  puts my_first_argument
end

Object

"Hi".size
"Sorocaba".reverse
"Sorocaba".downcase
"Sorocaba".upcase

1.zero?
1.even?
32.to_s
-1.abs

/a/.match("aaa")

String.new("aaaa")

String.class

Classes

class Dog
  def bark
    puts "Au"
  end
end

dog = Dog.new
dog.bark

class Dog
  def initialize(age)
    @age = age
  end

  def puppy?
    @age <= 1
  end
end

dog = Dog.new(2)
dog.puppy?

dog2 = Dog.new(1)
dog.puppy?

class Dog
  def self.initialize_puppy
    self.new(0)
  end
end

dog = Dog.initialize_puppy
dog.class
dog.puppy?

class Dog
  def age
    @age
  end

  def age=(age)
    @age = age
  end
end

dog = Dog.initialize_puppy
dog.age
dog.age = 10
dog.age

class Dog
  attr_writer :name
end

dog = Dog.new
dog.name = "Rex"
dog.name

class Dog
  attr_accessor :race
end

dog = Dog.new
dog.race = "Chihuahua"
dog.race

class Dog
  attr_reader :mad?
end

dog = Dog.new
dog.mad?

== and ===

/a/ == 'a'
(1..10) == 1
String == "A"
'a' === 'a'

/a/ === 'a'
(1..10) === 1
String === "A"

case price
when 0..10
  puts "Cheap"
when 11..100
  puts "Not so cheap"
when 101..1000
  puts "Expensive"
when 1001..10000
  puts "Fucking expensive"
else
  puts "I wonder who would buy it"
end

case object
when String
  puts object
when Fixnum
  puts object.to_s
when Symbol
  puts object.to_s
when MyAwesomeClass
  puts object.inspect
end

Array

list_of_chars = ["a", "b", "c"]

list_of_chars[0]
list_of_chars[2]
list_of_chars[-1]

list_of_chars = Array.new(10)

list_of_chars.pop
list_of_chars.push

list_of_chars.unshift
list_of_chars.shift

list_of_chars.size
list_of_chars.join(",")

Hash

hash = { :a => 10, :b => 5 }
hash[:a]
hash[:b]

hash.keys
hash.values

hash2 = { :c => 15, :d => 20}
hash.merge(hash2)

Functional programming

Block

[1,2,3].each do |item|
  puts item
end

Proc and Lambda

my_lambda_method = lambda { |x| puts x }
my_proc_method = Proc.new { |x| puts x }

[1,2,3].each(&my_lambda_method)
[1,3,4].each(&my_proc_method)

def each_squared_element(array, method)
  array.each do |elem|
    method.call(elem)
  end
end

def each_squared_element_2(array, &method)
  array.each do |elem|
    yield(elem)
  end
end

def call_method(method)
  method.call
end

Proc vs Lambda

arg_error_lambda = lambda { |x| puts x }
arg_error_proc = Proc.new { |x| puts x }

call_method(arg_error_lambda)
call_method(arg_error_proc)

returned_lambda = lambda { return "OK" }
returned_proc = Proc.new { return "Not ok" }

call_method(returned_lambda)
call_method(returned_proc)

Modules

module SayHi
  def say_hi
    puts "Hi"
  end
end

class Dog
  include SayHi
end

dog = Dog.new
dog = dog.say_hi

class Dog
  extend SayHi
end

Dog.say_hi

OOP

Array.ancestors

class Dog
  def bark
    puts "Au"
  end
end

class Doberman < Dog
end

dog = Doberman.new
dog.bark

Monkey patches

an_array = ['a', 'b', 'c']

an_array.first
an_array.last

an_array.second

class Array
  def second
    self[1]
  end
end