Ruby - Programming Language
This course covers the basics of programming in Ruby. Work your way through the videos and we'll teach you everything you need to know to start your programming journey!

In One Video

Lesson 36
Author : Mike Dane
Last Updated : November, 2017


Ruby Overview

Ruby is a general purpose, dynamically typed and reflective, object oriented programming language that was created in the 1990s by Yukihiro Matsumoto.

The original intent when creating ruby was to create a true Object Oriented scripting language. Which at the time, in Matsumoto’s optinion, didn’t exist. Ruby was designed to be simple at it’s core, but with an object system that was fully integreated into the language, and not tacked on as a glorified addon.

At the core of ruby is the desire for programmer productivity and fun. Ruby’s core focus is on the programmer not the machine. Therefore ruby attempts to remove as much confusion as possible from the programming process by utilizing a simple, readable syntax and deeply integrated object orientation.

How Ruby Runs

Generally all ruby code is run using an interpreter, although with some implementations of ruby it is possible to compile the code and run it on a virtual machine.

The most popular ruby interpreter is called MRI which stands for Matz’s Ruby Interpreter. Unfortunatly there is no official Ruby Language Reference, so generally the Matz interpreter is seen as the language standard.

Ruby utilizes a garbage collector and it’s syntax is very minimal and simple.

One reason Ruby has become so popular is due to the Ruby on Rails web application framework. Rails is extremely easy to use which is why it’s the framework of choice for tons of large companies like Github, Twitch and Hulu.

Choosing an IDE

Many developers choose to write Ruby using a basic text editor, but there are also more specilized integrated development enviornments, some of the most popular include RubyMine, Aptana RadRails and Vim.

Code

Printing

Copyputs "Hello"
print "World"
puts "!"

Variables and Data Types

Copy=begin
 Names are case-sensitive and may begin with:
     letters, _
 After, may include
     letters, numbers, _
 Convention says
     Start with a lowercase word, then additional words are lowercase separated
     by an underscore
     ex. my_first_variable
=end
name = "Mike"     # Strings
age = 30          # Integer
gpa = 3.5         # Decimal
is_tall = true    # Boolean -> True/False

name = "John"

puts "Your name is #{name}"
puts "Your name is " + name

Casting and Converting

Copyputs  3.14.to_i
puts  3.to_f
puts "3.0".to_s

puts 100 + "50".to_i
puts  100 + "50.99".to_f

Strings

Copygreeting = "Hello"
#indexes:   01234

puts greeting.length
puts greeting[0]
puts greeting.include? "llo"
puts greeting.include? "z"
puts greeting[1,3]

Numbers

Copyputs  2 * 3         # Basic Arithmetic: +, -, /, *
puts  2**3          # Exponent
puts  10 % 3        # Modulus Op. : returns remainder of 10/3
puts  1 + 2 * 3     # order of operations
puts 10 / 3.0       # int's and doubles


num = 10
num += 100          # +=, -=, /=, *=
puts num

num = -36.8
puts  num.abs()
puts  num.round()

# Math class has useful math methods
puts Math.sqrt(144)
puts Math.log(0)

User Input

Copyputs "Enter your name: "
name = gets                             #.chomp
puts "Hello #{name}, how are you"

puts "Enter first num: "
num1 = gets.chomp
puts "enter second num: "
num2 = gets.chomp
puts num1.to_f + num2.to_f

Arrays

Copylucky_numbers = [4, 8, "fifteen", 16, 23, 42.0]
#       indexes  0  1       2      3   4   5

lucky_numbers[0] = 90
puts lucky_numbers[0]
puts lucky_numbers[1]
puts lucky_numbers[-1]

puts "\n\n"
puts lucky_numbers[2,3]
puts "\n\n"
puts lucky_numbers[2..4]
puts "\n\n"

puts lucky_numbers.length

2 Dimensional Arrays

Copynumber_grid = [[],[]]
# numberGrid = [ [1, 2], [3, 4] ]
number_grid[0][0] = 99

puts number_grid[0][0]
puts number_grid[0][1]

Array Methods

Copyfriends = []
friends.push("Oscar")
friends.push("Angela")
friends.push("Kevin")

# friends.pop
puts  friends
puts "\n"

puts friends.reverse
puts "\n"

puts friends.sort
puts "\n"

puts  friends.include? "Oscar"

Methods

Copydef add_numbers(num1, num2=99)
     return num1 + num2
end

sum = add_numbers(4, 3)
puts sum

If Statements

Copyis_student = false
is_smart = false

if is_student and is_smart
	puts "You are a student"
elsif is_student and !is_smart
	puts "You are not a smart student"
else
	puts "You are not a student and not smart"
end

# >, <, >=, <=, !=, ==, String.equals()
if 1 > 3
	puts "number comparison was true"
end

if "a" > "b"
     puts "string comparison was true"
end

Switch Statements

Copymy_grade = "A"
case my_grade
     when "A"
		puts "You Pass"
     when "F"
     	puts "You fail"
     else
     	puts "Invalid grade"
end

Dictionaries

Copytest_grades = {
    "Andy" => "B+",
    :Stanley => "C",
    "Ryan" => "A",
    3 => 95.2
}

test_grades["Andy"] = "B-"
puts test_grades["Andy"]
puts test_grades[:Stanley]
puts test_grades[3]

While Loops

Copyindex = 1
while index <= 5
	puts index
	index += 1
end

For Loops

Copyfor index in 0..5
    puts index
end

5.times do |index|
    puts index
end

lucky_nums = [4, 8, 15, 16, 23, 42]
for lucky_num in lucky_nums
    puts lucky_num
end

lucky_nums.each do |lucky_num|
     puts lucky_num
end

Exception Catching

Copybegin
     # puts bad_variable
     num = 10/0
rescue ZeroDivisionError
     puts "Error"
rescue
     puts "All other errors"
end

raise "Made Up Exception"

Classes and Objects

Copyclass Book
     attr_accessor :title, :author

     def readBook()
          puts "Reading #{self.title} by #{self.author}"
     end
end

book1 = Book.new()
book1.title = "Harry Potter"
book1.author = "JK Rowling"

book1.readBook()
puts book1.title

Constructors

Copyclass Book
     attr_accessor :title, :author
     def initialize(title, author)
          @title = title
          @author = author
     end

     def readBook()
          puts "Reading #{self.title} by #{@author}"
     end
end

book1 = Book.new("Harry Potter", "JK Rowling")
# book1.title = "Half-Blood Prince"

puts book1.title

Getters and Setters

Copyclass Book
     attr_accessor :title, :author
     def initialize(title, author)
          self.title = title
          @author = author
     end

     def title=(title)
          puts "Set"
          @title = title
     end
     def title
          puts "Get"
          return @title
     end
end

book1 = Book.new("Harry Potter", "JK Rowling")

puts book1.title

Inheritance

Copyclass Chef

     attr_accessor :name, :age
     def initialize(name, age)
          @name = name
          @age = age
     end

     def make_chicken()
          puts "The chef makes chicken"
     end

     def make_salad()
          puts "The chef makes salad"
     end

     def make_special_dish()
          puts "The chef makes a special dish"
     end
end

class ItalianChef < Chef

     attr_accessor :country_of_origin
     def initialize(name, age, country_of_origin)
          @country_of_origin = country_of_origin
          super(name, age)
     end

     def make_pasta()
          puts "The chef makes pasta"
     end

     def make_special_dish()
          puts "The chef makes chicken parm"
     end
end

my_chef = Chef.new()
my_chef.make_chicken()

my_italian_chef = ItalianChef.new()
my_italian_chef.make_chicken()