# Codecademy: Ruby

1. Introduction to Ruby

my_num = 25
my_boolean = true
my_string = "Ruby"

3+3
3-3
3*3
3/3
3**3
3%3

puts "What's up" # newline
print "Montalvo"

"I love espresso".length
"Eric".reverse
puts "eric".upcase
puts "ERIC".downcase
puts "Eric".downcase.reverse.upcase

=begin
I'm a comment!
I don't need any # symbols.
=end

print "What's your first name?"
first_name = gets.chomp
first_name.capitalize!
puts "Your name is #{first_name}"

2. Control Flow in Ruby

x = 1
y = 2
if x < y
  puts "x is less than y!"
elsif x > y
  puts "x is greater than y!"
else
  puts "x equals y!"
end

hungry = false
unless hungry
  puts "I'm writing Ruby programs!"
else
  puts "Time to eat!"
end

is_true = 2 != 3
is_false = 2 == 3
test_1 = 17 > 16
test_2 = 21 < 30
test_3 = 9 >= 9
test_4 = -11 <= 4

true && true # => true
false || false # => false
!true # => false
(3 < 4 || false) && (false || true)

3. Looping with Ruby

counter = 1
while counter < 11
  puts counter
  counter += 1
end

counter = 1
until counter > 11
  puts counter
  counter += 1
end

for num in 1...10 # 1-9
  puts num
end

for num in 1..10 # 1-10
  puts num
end

i = 20
loop do
  i -= 1
  next if i % 2 != 0
  print "#{i}"
  break if i <= 0
end

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

array = [1,2,3,4,5]
array.each do |x|
  x += 10
  print "#{x}"
end

odds = [1,3,5,7,9]
odds.each do |n|
  print n*2
end

10.times { print "Chunky bacon!" }

4. Arrays and Hashes

demo_array = [100, 200, 300, 400, 500]
print demo_array[2]

multi_d_array = [[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0]]
multi_d_array.each { |x| puts "#{x}\n" }

my_hash = {
  "name" => "Eric",
  "age" => 26,
  "hungry?" => true
}
puts my_hash["name"]
puts my_hash["age"]
puts my_hash["hungry?"]

pets = Hash.new
pets["Stevie"] = "cat"
pets["John"] = "dog"
pets.each { |x, y| puts "#{x}: #{y}" }

5. Blocks and Sorting

def puts_1_to_10
  (1..10).each { |i| puts i }
end
puts_1_to_10

def cubertino(n)
  puts n ** 3
end
cubertino(8)

def what_up(greeting, *bros)
  bros.each { |bro| puts "#{greeting}, #{bro}!" }
end
what_up("What up", "Justin", "Ben", "Kevin Sorbo")

my_array = [3, 4, 8, 7, 1, 6, 5, 9, 2]
my_array.sort!

book_1 = "A Wrinkle in Time"
book_2 = "A Brief History of Time"
c = book_1 <=> book_2 # -1 (>), 0 (=), 1 (<)

6. Hashes and Symbols

symbol_hash = {
  :symbol1 => 1, # symbol1: 1,
  :symbol2 => 2, # symbol2: 2,
  :symbol3 => 3  # symbol3: 3
}

strings = ["HTML", "CSS", "JavaScript", "Python", "Ruby"]
symbols = Array.new
strings.each do |string|
    symbols.push(string.to_sym) # or string.intern
end

movie_ratings = {
  memento: 1,
  primer: 2,
  the_matrix: 3,
}
good_movies = movie_ratings.select { |m, r| r > 2 }
movie_ratings.each_key { |k| puts k }
movie_ratings.each_value { |v| puts v }

7. Refactoring

ruby_is_eloquent = true
ruby_is_ugly = false
puts "Ruby is eloquent!" if ruby_is_eloquent
puts "Ruby's not ugly!" unless ruby_is_ugly

puts 1>0 ? "True" : "False" # Ternary conditional expression

case greeting
  when "English" then puts "Hello!"
  when "French"  then puts "Bonjour!"
  when "German"  then puts "Guten Tag!"
  when "Finnish" then puts "Haloo!"
  else puts "I don't know that language!"
end

favorite_book = nil
favorite_book ||= "Guide to Ruby" # set
favorite_book ||= "Guide to Perl" # not set

def add(a,b)
  return a + b # a + b (without return)
end

"L".upto("P") { |l| puts l }

age = 26
age.respond_to?(:next) # true (27)

alphabet = ["a", "b", "c"]
alphabet << "d" # alphabet.push("d")
caption = "A giraffe surrounded by "
caption << "weezards!" # caption += "weezards!"

age = 26
I am " + age.to_s + " years old."
I am " << age.to_s << " years old."
I am #{age} years old."

8. Blocks, Procs, and Lambdas

fibs = [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
doubled_fibs = fibs.collect { |f| f*2 }

def double(p)
  yield p
end
double(1){ |x| x*2 }

floats = [1.2, 3.45, 0.91, 7.727, 11.42, 482.911]
round_down = Proc.new { |x| x.floor }
ints = floats.collect(&round_down)

hi = Proc.new { puts "Hello!" }
hi.call

numbers_array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
strings_array = numbers_array.collect(&:to_s)

strings = ["leonardo", "donatello", "raphael", "michaelangelo"]
symbolize = lambda { |s| s.to_sym }
symbols = strings.collect(&symbolize)

9. Object-Oriented Programming, Part I

class Person
  def initialize(name)
    @name = name
  end
end
me = Person.new("Eric")

class MyClass
  $my_variable = "Hello!" # global var
end
puts $my_variable

class Person
  @@people_count = 0 # class variable
  def initialize(name,age,profession)
    @name = name # instance var
    @age = age
    @profession = profession
  end
end

class ApplicationError
  def display_error
    puts "Error! Error!"
  end
end
class SuperBadError < ApplicationError # inheritance
  def display_error # override
    puts "SuperError! SuperError!"
    super # call parent method
  end
end
err = SuperBadError.new
err.display_error

10. Object-Oriented Programming, Part II

class Dog
  def initialize(name,breed)
    @name = name
    @breed = breed
  end
  public
  def bark
    puts "Woof!"
  end
  private
  def id
    @id_number = 12345
  end
end

module Circle
  PI = 3.141592653589793
  def Circle.area(radius)
    PI * radius**2
  end
  def Circle.circumference(radius)
    2 * PI * radius
  end
end

puts Math::PI
require 'date'
puts Date.today

module Action
  def jump
    @distance = rand(4) + 2
    puts "I jumped forward #{@distance} feet!"
  end
end
class Rabbit
  include Action
  attr_reader :name
  def initialize(name)
    @name = name
  end
end
peter = Rabbit.new("Peter")
peter.jump

module ThePresent
  def now
    puts "Time"
  end
end
class TheHereAnd
  extend ThePresent
end
TheHereAnd.now