Ruby - a pure object oriented language

Codecamp Suceava - 24 June 2017
What is an object-oriented language? Why is Ruby considered an OOP language and which are its main features?
An overview of meta programming.

1. Petru CIOATĂ
Ruby - a pure
object oriented
language

2. Petru CIOATĂ
Summary
●Ruby Intro
●What is an OOP language?
●Everything is an object ...
●Class vs Instance
●Inheritance. Modules and Mixins
●Metaprogramming overview
●Metaprogramming DEMO
●Q&A

3. Petru CIOATĂ
Ruby is ...
“A dynamic, open source programming language with a focus on simplicity and
productivity. It has an elegant syntax that is natural to read and easy to write.”

4. Petru CIOATĂ
Ruby is ...

●Dynamic
●Reflective
●Object-Oriented
●General-Purpose
●Dynamically typing

5. Petru CIOATĂ

6. Petru CIOATĂ
What is an OOP language?
A brief OOP History
The main OOP Concepts:
●Abstraction
●Encapsulation
●Inheritance
●Polymorphism

7. Petru CIOATĂ
Everything is an object ...
●-24.abs
●112 .send(:+, 8)
●true.class
●nil.equal?(false)
●“hello”.reverse
●(1..10).to_a
●[1, 2, 3].reverse!
●Class.class

8. Petru CIOATĂ
Everything is an object ...


If it walks like a duck and quaks like a duck, I would call it a duck

9. Petru CIOATĂ
Class vs Instance


●Instance
●Instance variables
●Instance methods


class Presentation
# class variables
@@total_no = 0
# constructor
def initialize(
title, author, track_no, duration)
@@total_no += 1
# instance variables
@title = title
@author = author
@track_no = track_no
@duration = duration
end
# instance methods
def to_s
"Welcome to #{@title} presented by
#{@author}"
end
end


ruby_oop = Presentation.new("Ruby OOP", "Petru", 1, 30)
puts ruby_oop.to_s # Welcome to Ruby-OOP presented by Petru

ruby_oop.instance_variables # [:@title, :@author, :@track_no, :@duration]

Presentation.instance_methods(false) # [:to_s]

10. Petru CIOATĂ
Class vs Instance


●Class
●Class Variables
●Class Methods

class Presentation
# class methods
def self.no_of_presentations
@@total_no
end

def Presentation.no_of_presentations
@@total_no
end

class << self
def no_of_presentations
@@total_no
end

def total_duration(*presentations)
presentations.collect(&:duration)
.inject(0, &:+)
end
end
end

ruby_oop = Presentation.new( "Ruby a pure OOP language", "Petru", 1, 30)
vue_js = Presentation.new( "Vue JS Intro", "Dan Ichim", 1, 40)

puts Presentation.no_of_presentations
puts Presentation.total_duration( ruby_oop, vue_js)

Presentation.methods(false) # [:no_of_presentations, :total_duration]
Presentation.class_variables(false) # [:total_no]

11. Petru CIOATĂ
Class as Instance

#### class as Object
Presentation = Class.new do
@@total_no = 0

def initialize(title, author, track_no,
duration)
@title = title
@author = author
@track_no = track_no
@duration = duration
@@total_no += 1
end

def to_s
"Welcome to #{@title} presented by
#{@author}"
end
end

ruby_oop = Presentation.new("Ruby a pure OOP language", "Petru", 1, 30)
puts ruby_oop.to_s

ruby_oop.instance_variables # [:@title, :@author, :@track_no, :@duration]

Presentation.instance_methods(false) # [:to_s]


Presentation.superclass
Class.superclass

12. Petru CIOATĂ
Inheritance. Modules and mixins
class Shape
attr_accessor :name
def initialize(name)
@name = name
end

def area
puts "TBI"
end

def perimeter
puts "TBI"
end
end

class Square < Shape
attr_accessor :side_length

def initialize(name,
side_length)
@side_length = side_length
super(name)
end

def area
4 * self.side_length
end

def perimeter
self.side_length ** 2
end
end
s = Square.new("patratel", 1.5)
puts s.to_s
puts s.area
puts s.perimeter

●Single inheritance
●Accessor and attributes
○attr_reader
○attr_writer
○attr_accessor

13. Petru CIOATĂ
Inheritance. Modules and mixins
module HelperMethods
def characteristic(*attributes)
attributes.inject(desc = "Shape :"){|attribute| desc << " #{attribute}"}
end

def hello_there
p "Hello from module”
end
end

class Square < Shape
include HelperMethods
end

s = Square.new("patratel", 1.5)
puts s.characteristics(s.name, s.side_length)
s.hello_there

class Square < Shape
extend HelperMethods
end

Square.characteristics
Square.hello_there

14. Petru CIOATĂ
Inheritance. Modules and mixins

15. Petru CIOATĂ
Metaprogramming overview
●Writing code that manipulates language constructs at runtime

16. Petru CIOATĂ
Metaprogramming DEMO
●Open class
●Monkey Patching
●method_missing
●define_method
●class_eval
●instance_eval

17. Petru CIOATĂ
Books
https://www.amazon.com/dp/0596516177
https://www.amazon.com/dp/0321721330/
https://www.amazon.com/dp/B00N9I0RMQ/

18. Petru CIOATĂ

19. Petru CIOATĂ