The document explains the use of collections and iterators in Ruby, including how to loop using 'while' and 'times'. It covers creating and accessing arrays and hashes, as well as performing operations on them, such as merging hashes and manipulating array values using methods like 'each' and 'map'. Additionally, it showcases examples of conditional loops and various array and hash operations.

1. Collections & IteratorsWith Hashes & Arrays

2. Iterators: Conditional Looping“while” allows us to loop through code while a set condition is truex = 1while x < 10 puts x.to_s + “ iteration”x += 1end

3. Times5.times { puts “hello” }5.times { |num| puts “hi”+num.to_s}99.times do |beer_num| puts "#{beer_num} bottles of beer”end99.times do puts "some bottles of beer”end

4. Creating a new arrayx = [1, 2, 3, 4]=> [1, 2, 3, 4]x = %w(1 2 3 4) => [“1”, “2”, “3”, “4”]chef = Array.new(3, “bork”)=> [“bork”, “bork”, bork”]

5. Accessing Array Valuesa = [ "a", "b", "c", "d", "e" ] a[0] #=> "a”a[2] #=> "c”a[6] #=> nila[1, 2] #=> ["b", "c”]a[1..3] #=> ["b", "c", "d”]a[1…3] #=> ["b", "c"]

6. Operations on Arrays[ 1, 2, 3 ] * 3 => [1, 2, 3, 1, 2, 3, 1, 2, 3][ 1, 2, 3 ].join(“,”)"1,2,3”[ 1, 2, 3 ] + [ 4, 5 ] => [1, 2, 3, 4, 5][ 1, 1, 2, 2, 3, 3, 4, 5 ] - [ 1, 2, 4 ]=> [3, 3, 5][ 1, 2 ] << "c" << "d" << [ 3, 4 ] => [1, 2, "c", "d", [3, 4]]

7. Creating a Hashh = { "a" => 100, "b" => 200 }h[“a”]h = { 1 => “a”, “b” => “hello” }h[1]

8. Operations on Hashes: Mergeh1 = { "a" => 100, "b" => 200 } => {"a"=>100, "b"=>200}h2 = { "b" => 254, "c" => 300 }=>{"b"=>254, "c"=>300}h3 = h1.merge(h2)=> {"a"=>100, "b"=>254, "c"=>300}h1=> {"a"=>100, "b"=>200}h1.merge!(h2)=> {"a"=>100, "b"=>254, "c"=>300}

9. Operations on Hashesh = { "a" => 100, "b" => 200 } h.delete("a”)h = { "a" => 100, "b" => 200, "c" => 300, "d" => 400 }letters = h.keys h = { "a" => 100, "b" => 200, "c" => 300 } numbers = h.values

10. Each>> superheroes = ["catwoman", "batman", "wonderwoman"]>> superheroes.each { | s | puts "#{ s } save me!" }catwoman save me!batman save me!wonderwomansave me!>> dogs = ["fido", "fifi", "rex", "fluffy"]>> dogs_i_want = []>> dogs.each do |dog| >? dogs_i_want.push(dog) if dog != "fluffy" >? end>> dogs=> ["fido", "fifi", "rex", "fluffy"]>> dogs_i_want=> ["fido", "fifi", "rex"]

11. Mapsuperheroes = ["catwoman", "batman", "wonderwoman"]>> superheroes.map { |s| s.upcase } => ["CATWOMAN", "BATMAN", "WONDERWOMAN"]Shorter (available in Rails or Ruby 1.8.7+): >> superheroes.map(&:upcase) => ["CATWOMAN", "BATMAN", ”WONDERWOMAN”]