While

Now that we've understood booleans, we can put them to real use with loops.

First up, the while loop, which repeats a code snippet over and over until a condition that it's given isn't met anymore.

count = 0
while count < 4
 print "Ruby! "
 count = count + 1
end

//Output Below

Ruby! Ruby! Ruby! Ruby!

Indeed! The while loop will display "Ruby " and add 1 to count variable while it's less than 4.

While 2.0

Did you notice I said that loops repeat themselves until a condition isn't met anymore?

This condition goes after the while keyword and can use any comparison or logical operator.

count = 4
while count != 0
 print "Loopy! "
 count = count - 1
end

//Output Below

Loopy! Loopy! Loopy! Loopy!

Sweet! We've told the loop to run while count isn't equal to 0 and are subtracting 1 from count in every iteration, until the condition is false.

Until

Let's look at the until loop, shall we? Unlike the while loop, it runs until a condition is met.

count = 5
until count == 0
 print 'Dizzy? '
 count = count - 1
end

Nice! I didn't even have to explain that this code snippet will run until count is exactly equal to 0, did I?

Until 2.0

We can use boolean operators with loops, too. Look!

n_1 = 1
n_2 = 2
until n_1 == 4 && n_2 == 5
 print 'Whirly! '
 n_1 = n_1 + 1
 n_2 = n_2 + 1
end

//Output Below

Whirly! Whirly! Whirly!

That's right! What's different here is that we're adding 1 to both of the counters, until both conditions are true.

Ranges

Ranges are handy things in Ruby. We create so-called inclusive ranges with .. and exclusive ranges with .... But what does that mean?

Let's take a look at what the first one does.

print *1 .. 5

//Output Below

12345

Nice! The inclusive range will display 12345 because it includes the last number

Ranges 2.0

When we want to have a range that does not include the last number, we use ....

Can you guess what other sign is needed to make this range work?

print * 1 ... 5

//Output Below

1234

Great work! We create an exclusive range by using .... The range will display 1234 and exclude the 5.

Psst: the * sign is also known as the splat operator. We'll come back to it in a bit, okay?

For for for!

So now that we've mastered ranges, we can go into for loops, which are great when we know exactly how many times we want the loop to run.

for number in 1 .. 5
 print "Again! "
end

//Output Below

Again! Again! Again! Again! Again!

Huzzah! The for loop uses a temporary control variable and says: for every number in the range, repeat what's between the loop and the end keyword.

Psst: we can use any name we like for the control variable. Many folks use i, for example.

Infinity and beyond!

So we've looked closely at the while and until loops but, at times, they can be risky.

If we don't cut them off at some point, they will go into an infinite loop, which causes programs to ... crash.

count = 0
while count != 3
 print 'Infinity'
end

//Output Below

InfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinityInfinity

Eeeek, we forgot to increment or decrement count! That way, the loops keeps running because count will never be anything other than 0.

Code blocks

We've been working with code blocks, but what exactly are they? Well, they're snippets of code that exist in between keywords.

count = 0
while count < 2
 print "I'm a block! "
 count = count + 1
end

//Output Below

I'm a block! I'm a block!

Fantastic! while, until and for at the beginning and end at the end are keywords that make code blocks.

Assignment operators

We've been doing a lot of increasing or decreasing variables by 1 and reassigning them to the original variable. Might there be a shortcut?

count = 1
print count += 1

//Output Below

2

Isn't that handy? These assignment operators perform the operations they're supposed to but automatically reassign the results to the variables before them.

Psst: we can also use -=, *=, /= to shorten our code.

Reservations

Do you remember when we talked about reserved words? Well, we can add these recent keywords to the list because they're reserved as well.

for loop in 1 ... 5
 print "All work and no play makes Johnny a dull boy. "
end

//Output Below

All work and no play makes Johnny a dull boy. All work and no play makes Johnny a dull boy. All work and no play makes Johnny a dull boy. All work and no play makes Johnny a dull boy. 

Of course, while, until, for and end are off-limits. You remember that and, or, not, true and false are also on the list, right?

All together now!

We've just wrapped our incredible minds around while, until and for loops as well as ranges, code blocks, and assignment operators.

Not bad. Not bad at all. Now, what's the output for this loop going to be?

for i in 1 .. 5
 j = 1
 while j <= i
  print j
  j += 1
 end
end

//Output Below

1 12 123 1234 12345

See that? We can put loops within other loops to create nested loops.

Looped Adventure!

Let's help "Bob Jones" keep his momentum going and put him in the loop about his treasure-hunting progress.

Create a loop that'll display some encouraging words until "Bob" has found four treasures. Also, be sure to mention how many he's got left.

treasures = 0
until treasures == 4
 treasures += 1
 print "Sweet, #{4 - treasures} to go! "
end

//Output Below

Sweet, 3 to go! Sweet, 2 to go! Sweet, 1 to go! Sweet, 0 to go! 

"Bob" and us, we're most definitely on the hunt and making great progress!

filling = "bacon"
if filling == "bacon" 
  print "Bacon sandwich!"
end

 sandwich!

filling = "cheese"
if filling == "bacon"
 print "Bacon sandwich!"
else 
 print "Cheese sandwich!"
end

Cheese sandwich!

filling = "egg salad"
if filling == "bacon"
  print "Bacon sandwich!"
elsif  filling == "cheese"
  print "Cheese sandwich!"
else
  print "Egg salad! Yum!"
end

Egg salad! Yum!

hunger = false
if hunger
 print "Give me sandwiches!"
else 
 print "I don't want sandwiches."
end

I don't want sandwiches.

hunger = true
if !hunger
 print "I don't want sandwiches"
else
 print "Give me sandwiches!"
end

Give me sandwiches!

booly = true
if booly
 print "Hurrah!"
elsif booly && 1 + 1 == 2
 print "Hurrah again!"
else
 print "No hurrahs."
end

Hurrah!

my_string = "Wubba dub dub"
if 8 < 10
  my_string
end

Wubba dub dub

thirsty = true 
thirsty ? "Water!" : "No, thanks."

Water!

sleepy = false
unless sleepy
 "I've had too much coffee!"
else
 "Naps are the best!"
end

I've had too much coffee!

x = -10
if x > -5
 unless x > 5
  print "In between -5 and 5"
 else
  print "Greater than 5"
 end
else
 print "Less than -5"
end

Less than -5

weather = "sunny"
if weather == "cloudy"
 print "Nothing to worry about!"
elsif weather == "rainy"
 print "Bring an umbrella!"
else
 print "Sunglasses out!"
end

Sunglasses out!

array = [] 

treasure = ["jewels", "gold"]

treasure = ["jewels", "gold"]
print treasure[0]

"jewels"

nums = [2, 3]
print nums[0] + nums[1] + nums[-1]

8

treasure = ["jewels", "gold"]
treasure.push("silver")
print treasure

["jewels", "gold", "silver"]

tools = ["shovel", "map", "compass", "rucksack"]
print tools.length 

4

numbers = [5, 2, 4, 3, 1]
print numbers.sort 

[1, 2, 3, 4, 5]

treasure = ["jewels", "gold"]
treasure.each do |piece|
 puts piece.capitalize
end

Jewels
Gold

tools = ["Shovel", "Map"]
tools.each do |tool|
 puts tool.upcase
end

SHOVEL
MAP

3.times { print "Go! " }

Go! Go! Go!

say = ["I","love", "arrays"]
say.each { |word| print word + " "}

I love arrays 

paths = ["North", "South", "East"]
puts "There are #{paths.count}" class="subst paths that we can take"
paths.each { |path| puts "We can go " + path }
puts "Let's go " + paths[-1]

There are 3 paths we can take
We can go North
We can go SouthWe can go East
Let's go East

hash = {} 

hash = { "name" => "Dipper" }
print hash["name"]

Dipper

ruby = { "gem" => true }
ruby["color"] = "red"
print ruby

{"gem"=>true, "color"=>"red"}

ruby = { "color" => "pink" }
ruby["color"] = "black"
print ruby

{"color"=>"ruby"}

adventure = { "tool" => "map", 
          "another_tool" => "map" }
print adventure["tool"]

{"tool"=>"map", "another_tool"=>"map"}

tool = { "name" => "map", 
       "amount" => 1, 
    "available" => true }
puts tool["name"]
puts tool["amount"]

map
1

origins = { "Columbus" => "Italian", "Cousteau" => "French" }
origins.each do |key, value|
 puts "#{key} was #{value}"
end

"Columbus was Italian"
"Cousteau was French"

tool = { "name" => "compass", 
       "amount" => 1, 
    "available" => true }
print tool.length

3

gem = { "name" => "ruby", 
       "color" => "red" }
gem.has_key?("shape")

false

gem = { "name" => "ruby",
       "color" => "red" }
print gem.has_value?("red")

true

tools = { "shovel" => "digs",
             "map" => "directs" }
tools["flashlight"] = "illuminates"
tools.each { |tool, action| puts "The #{tool} #{action}" }

The shovel digs
The map directs
The flashlight illuminates

explorer = {"name" => "Bob Jones", 
           "levels" => 7, 
          "retired" => false }
print "#{explorer['name']} has leveled up #{explorer['levels']} times!"

Bob Jones has leveled up 7 times!

gems = ["ruby", "opal", "diamond"]
length = 0
gems.each do |gem|
 length += 1
end
print length

3

def puts_numbers
 1..5.each { |num| print num }
end

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

def greet(explorer)
 puts "Hello #{explorer}!"
end
greet("Dipper") 

Hello Dipper!

def greet(greeting, explorer)
 puts "#{greeting} #{explorer}!"
end
greet("Hi there", "Bob")

Hi there Bob!

def greet(greeting, * explorers)
 explorers.each do |explorer| 
  puts "#{greeting} #{explorer}!"
 end
end
greet("Yo", "Bob", "Maria")

Yo, Bob!
Yo, Maria! 

def triple(number)
 return number * 3
end

my_number = triple(3)
print my_number

9

def triple(number)
 return number * 3
end
def triple_pie_count(number)
 puts "#{number} pies! Yay!"
end

pies = triple(3)
triple_pie_count(pies)

9 pies! Yay!

def triple(number)
 return number * 3
end
def triple_pie_count(number)
 pies = triple(number)
 puts "#{pies} pies! Yay!"
end

triple_pie_count(1)

3 pies! Yay!

def is_gem?(stone)
 if stone == "ruby"
  true
 else
  false
 end
end

def cheer
 print 'Go explorer!'
end

cheer
cheer
cheer

Go explorer! Go explorer! Go explorer!

def add(*items)
 satchel = []
 items.each do |item|
  satchel.push(item)
 end
 print satchel
end

add('tin can', 'wrapper', 'bottle')

["tin can", "wrapper", "bottle"]

class Explorer
  attr_reader :name
  def initialize(name)
   @name = name
  end
end

explorer = Explorer.new("Bob")
print explorer.name

Bob

class Explorer 
end

attr_reader :name

class Explorer
 attr_reader :name
 def initialize(name)
  @name = name
 end
end

explorer = Explorer.new("Bob")
print explorer.name

Bob

class Explorer
 attr_reader :name
 def initialize(name)
  @name = name
 end
end

explorer = Explorer.new("Bob")
print explorer.name

Bob

class Explorer
 attr_reader :name
 def initialize(name)
  @name = name
 end
 def eat
  print "Munch!"
 end
end

explorer = Explorer.new("Bob")
explorer.eat 

Munch!

class Explorer
 attr_reader :name
 def initialize(name)
  @name = name
 end
 def eat
  print "Munch!"
 end
end

explorer = "Maria"
print explorer.eat

undefined method 'eat' for "Maria":String (NoMethodError)

class Explorer
 attr_reader :name, :age, :origin
 def initialize(name, age, origin)
  @name = name
  @age = age
  @origin = origin
 end
end

explorer = Explorer.new("Bob", 30, "Atlantis")
explorer.name 

Bob

class Explorer
  def eat
    print "Munch!"
  end
  def sleep
    print "Zzzz.."
  end
end

explorer = Explorer.new
explorer.eat

Munch!

class Explorer
 attr_reader :steps
 def initialize
  @steps = 0
 end
 def walk
  @steps += 1
 end
end

explorer = Explorer.new
explorer.walk
print explorer.steps

1

class Sandwich
 attr_reader :filling
 def initialize
  @filling = []
 end
 def add(filling)
  @filling.push(filling)
 end
end

sandwich = Sandwich.new
sandwich.add("cheese")
sandwich.add("bacon")
sandwich.filling

["cheese", "bacon"]

class Flashlight
 attr_reader :on
 def initialize
  @on = false
 end
 def switch_on
  @on = true
 end
 def switch_off
  @on = false
 end
end
   
light = Flashlight.new
light.switch_on 
print light.on

true

module Noise
 def make_noise(sound)
  print "#{sound}!"
 end
end

module Noise
 def make_noise(sound)
  print "#{sound}!"
 end
end

Noise.make_noise("Boo")

undefined method \\\\\\`make_noise' for Noise:Module (NoMethodError)

module Noise
 def make_noise(sound)
  print "#{sound}!"
 end
end
class Duck
 include Noise
end

duckling = Duck.new
duckling.make_noise('Quack')

Quack!

module Noise
 def make_noise(sound)
  print "#{sound}!"
 end
end
class Cow
 include Noise
end

calf = Cow.new
calf.make_noise("Moo")

Moo!

module Noise
 def make_noise(sound)
  print "#{sound}!"
 end
end
class Dog
 include Noise
 def distract
  print "SQUIRREL! "
 end
end

puppy = Dog.new
puppy.distract
puppy.make_noise("Woof")

SQUIRREL! Woof!

module Quadruped
 LEGS = 4 
end

class Dog
 include Quadruped 
 def stand
  "Has #{Quadruped::LEGS} legs!"
 end   
end

puppy = Dog.new
puppy.stand

Has 4 legs!

def Sheep
 include Noise
 include Quadruped
 def number_of_legs
  Quadruped::LEGS
 end
end

sheep = Sheep.new
sheep.make_noise('Baaah')
sheep.number_of_legs

Baaah!
4

module Adventure
 TOOLS = ["map", "compass"]
 class Person
  attr_reader :name
  def initialize(name)
   @name = name
  end
  def use(tool)
   "#{@name} used the #{tool}!"
  end
 end
end

p = Adventure::Person.new("Bob")
p.use(Adventure::TOOLS[0])

Bob used the map!

class Explorer
 include Noise
 attr_reader :name
 def initialize(name)
  @name = name
 end
end

bob = Explorer.new("Bob")
bob.make_noise("Wubba lubba dub dub")

Wubba lubba dub dub

module Discovery
 def jig
  puts "#{@name} does a jig!"
  puts "We mastered Ruby!"
 end
end
class Explorer
 include Discovery
 attr_reader :name
 
 def initialize(name)
  @name = name
 end
end

bob = Explorer.new("Bob")
bob.jig

Bob does a victory jig!We mastered Ruby!

irb(main):001:0>

irb(main):001:0> "Hello World"
=> "Hello World"

Ruby myRubyApp.rb