1. OOP n Ruby 101
By: Dr. Mathias Fonkam 1

2. Topics Why OOP? Key ideas & Principles: Example Ruby class code & use
Classes
Objects
Identity
State
Behavior
object relationships
object interactions
class relationships
Encapsulation
Inheritance
Example Ruby class code & use
Example with Inheritance
Ruby Object Model
Objects in Ruby…. (Posted whole Chapter on this!)

3. Why Objects & OOP?
To help manage growing complexity of software development & maintenance
modularization
Abstraction
code reuse

4. Key OOP Ideas & Principles: example view
Classes
Objects
Identity
State
Behavior
object relationships

5. Classes & Objects: UML diagram – Encapsulation!

6. Class/Object: code & use
# good_dog.rb
class GoodDog
def initialize(name)
@name = name
end
def get_name
@name
def set_name(name) # can be written as: name=(n)
def speak
says arf!"
sparky = GoodDog.new("Sparky")
puts sparky.speak
puts sparky.get_name
sparky.set_name = "Spartacus"

7. Class/Object Relationships: Inheritance
# p033mammal.rb 
class Mammal  
  def breathe  
    puts "inhale and exhale"  
  end  
end     
class Cat < Mammal  
  def speak  
    puts "Meow"  
rani = Cat.new  
rani.breathe  
rani.speak  

8. Class/Object Relationships: Inheritance – UML?
# p035inherit.rb .. continued
# class F sub-class of GF  
class F < GF  
 def initialize  
   puts 'In F class'  
 end  
end     
# class S sub-class of F  
class S < F  
  puts 'In S class'  
son = S.new  
son.gfmethod  
# p035inherit.rb
class GF  
  def initialize  
   puts 'In GF class'  
 end  
  def gfmethod  
   puts 'GF method call' 
  end  
end  
  # tbc

9. Ruby Object Model

10. Ruby Object Model in Details

11. Objects in Ruby Where is puts from? # simple_ints.rb puts 6.object_id
# simple.rb
puts "Ruby language"
Where is puts from?
# simple_ints.rb
puts 6.object_id
puts 6.even?
puts 6.zero?
puts 6.class
# simple2.rb
Kernel.puts "Ruby language"
Kernel.puts "Ruby language".size

12. Objects in Ruby: object creation
May be implicit (with object literals) or explicit
# Example literals.rb
4.times { puts "Ruby" }
puts "Ruby".size
puts "Ruby".downcase
puts [1, 2, 3].include? 3
puts [1, 2, 3].empty?
puts :name.class
puts :name.frozen?
puts (1..6).class
puts (1..6).include? 4
# Example formal.rb
s1 = String.new "Ruby"
puts s1.size
puts s1.downcase
a1 = Array.new
a1.push 1, 2, 3
puts a1.include? 3
puts a1.empty?
r1 = Range.new 1, 6
puts r1.class
puts r1.include? 4

13. Objects in Ruby: the toplevel – main
May be implicit (with object literals) or explicit
# Example toplevel.rb – lies outside everything
n1 = 3
n2 = 5
puts local_variables
Kernel.puts self
puts self.class

14. Objects in Ruby: the toplevel – main
# Example toplevel2.rb – run & try to explain
# =========== Another example=========
@name = "Jane"
@age = 17
def info
is years old"
end
puts self.instance_variables
puts self.private_methods.include? :info
puts info