This chapter demonstrates about the Ruby Object Oriented Ruby is an pure Object Oriented Programming Language in which every thing is appear to ruby as an object and following are the concepts covered in this chapter.

• Ruby Class and Objects
• Ruby Instance Methods
• Ruby Class Methods and Variables
• Access Control
• Class Inheritance
• Class Constants

Class define blue print of a data type actually which is not used to define any data but which defines class name means i.e what the class name consist and what operations it will performs on object. In class definition which is starts with class key word and precede by its class name and its is delimited with end the snippet below demonstrates the class as shown below. [ruby] class Box code end [/ruby] Class provides blue print for Objects basically class contain several objects so objects are created from classes user can define the objects with new keyword the snippet below demonstrates the ruby objects as shown below. [ruby] box1 = Box.new box2 = Box.new [/ruby]

Ruby instance methods are defined same as the normal methods by using the def keyword which is used as class instance and the functionality is not limited only for instance variables which can do a lots as per the user requirement. the code below demonstrates the ruby instance methods as shown below. [ruby] # define a class class Box # constructor method def initialize(w,h) @width, @height = w, h end # instance method def getArea @width * @height end end # create an object box = Box.new(10, 20) # call instance methods a = box.getArea() puts "Area of the box is : #{a}" [/ruby] Result By running the above code in command prompt, the output can be obtained as shown in the image below.

class variables are similar to the variables which share between all instances of class. Class variable prefixed with two @ characters and class is defined with class definition. def self.methodname() is used to define method of the class which ends with a delimiter and it should be called with class name i.e, classname.methodname  as shown in below code. [ruby] class Box # Initialize our class variables @@count = 0 def initialize(w,h) # assign instance avriables @width, @height = w, h @@count += 1 end def self.printCount() puts "Box count is : #@@count" end end [/ruby]

Ruby have three methods of protection to the instance methods those are the public, private and protected. Ruby doesn't have any access controls on class variables, instances. The code below demonstrates the three access modifiers as shown. [ruby] # define a class class Box # constructor method def initialize(w,h) @width, @height = w, h end # instance method by default it is public def getArea getWidth() * getHeight end # define private accessor methods def getWidth @width end def getHeight @height end # make them private private :getWidth, :getHeight # instance method to print area def printArea @area = getWidth() * getHeight puts "Big box area is : #@area" end # make it protected protected :printArea end # create an object box = Box.new(10, 20) # call instance methods a = box.getArea() puts "Area of the box is : #{a}" # try to call protected or methods box.printArea() [/ruby] Result By running the above code in command prompt, the output can be obtained as shown in the image below.

Inheritance provides rescue the code functionality and improves fast and best implementation of code but ruby doesn't support the multiple inheritance but which support mixins which means sepecialized implementation of multiple inheritance. The code below demonstrates the class Inheritance as shown below. [ruby] # define a class class Box # constructor method def initialize(w,h) @width, @height = w, h end # instance method def getArea @width * @height end end # define a subclass class BigBox < Box # add a new instance method def printArea @area = @width * @height puts "Big box area is : #@area" end end # create an object box = BigBox.new(10, 20) # print the area box.printArea() [/ruby] Result By running the above code in command prompt, the output can be obtained as shown in the image below.

• Ruby supports mixins inheritance.
• Ruby instance methods same as normal methods.
• Class is blue print of data type.