WDI Darth Vader

Ruby

Intro to Ruby

Scope

This document covers Strings, Hashes, Arrays, Loops, and Conditionals in Ruby.

String

'happy'.object_id

'happy'.gsub('ha', 'HAHAHA')
'happy'.split('')
'happy'.chars()

lichy = 'Lichard DeGray'
"My name is not #{lichy}" # String interpolation

number = 99
"#{ number } bottle#{ 's' unless number==1 } of beer on the wall... #{ number } bottle#{ 's' unless number==1 } of beer... take one down... pass it around... #{ number-1 } bottles of beer on the wall"

Array

nums = Array(1..2)    # auto-populate
letters = Array('a'..'z')   # auto-populate
my_things = ['apartment', 'laptop', 'cat', 'wii u']   # manual declaration
  • Grab a random sample from an array....
my_things.sample
  • Access a specific item at..
my_things.at(1)
  • First & last...
my_things.first
my_things.last
  • Adding items to an Array
arr = [1, 2, 3, 4]
arr.push(5) #=> [1, 2, 3, 4, 5]
arr << 6    #=> [1, 2, 3, 4, 5, 6]
  • Removing items from an array

arr =  [1, 2, 3, 4, 5, 6]
arr.pop #=> 6
arr #=> [1, 2, 3, 4, 5]

arr.shift #=> 1
arr #=> [2, 3, 4, 5]

arr.delete_at(2) #=> 4
arr #=> [2, 3, 5]

Hash

lich = {:name => 'Lichard', :age => 3}
kat = {:name => 'Kathew', :age => 3}
om = {:name => 'Omily', :age => 3}
  • Using the hash rocket syntax
    sample_hash   = {'one'=>1,'two'=>2}
sample_hash_2 = {:one=>1, :two=>2}
  • Using colons to create a hash will create the keys as symbols
sample_hash_3 = {one:1,two:2}
  • How to access a value (have to use bracket notation)

sample_hash_4 = {'one'=>1,'two'=>2,'three'=>3,'four'=>4,'five'=>5}
sample_hash_4["one"]  #=> Returns 1
sample_hash_4["five"] #=> Returns 5
  • How to change the value of an element
    sample_hash_4['one'] =  10

Loops

  • While loop

n = 1
while n < 11
  puts n
  n += 1
end
  • Until loop
n = 1
until n > 10
  puts n
  n += 1
end

sample_array = Array(1..5)
sample_array.each{|elem| puts elem}

sample_array.each do |elem|
  puts elem
  puts "The long way!!!"
end

each_example = [2,3,4].each{|elem| elem ** 2}
map_example  = [2,3,4].map{|elem| elem ** 2}

p each_example
p map_example

each_example_2 = {two:2,three:3,four:4}.each{|key,value| elem ** 2}
map_example_2 = {two:2,three:3,four:4}.map{|key,value| elem ** 2}

p each_example_2
p map_example_2

Conditionals

  • if/elsif/else/end
  • unless

  • one-liners

  • If/Elsif/Else

  • Unless you're using a one-liner then you need to end your if statement with and 'end' statement.


x = 2

if x < 3
  puts 'less than 3'
end

* Writing the same thing as a one-liner

if x < 3 then puts 'less than 3' end
puts 'less than 3' if x < 3

* Using elsif

if x < 2
  puts "less than 2"
elsif x == 2
  puts "It's two!"
else
  puts 'greater than two!'
end
  • Unless
  • My own personal preference is to avoid the 'not' operator and state conditions in the positive. Using the 'unless' keyword is great for this.


x = true

puts "it's true!" if x != false

unless x == false
  puts "it's true!"
end

* Unless can also be used as a one-liner

puts "it's true!" unless x == false

*** You cannot use elsif with unless, only else ***

unless x == false
  puts "it's true!"
else
  puts "it's false!"
end

unless x == false
  puts "it's true!"
elsif
  puts "it's false!"
end

#returns an error