OO 



class Box
   def initialize(w,h)
      @width, @height = w, h
   end
end


# define a class
class Box
   # constructor method
   def initialize(w,h)
      @width, @height = w, h
   end

   # accessor methods
   def getWidth
      @width
   end
   def getHeight
      @height
   end

   # setter methods
   def setWidth=(value)
      @width = value
   end
   def setHeight=(value)
      @height = value
   end
end

# create an object
box = Box.new(10, 20)

# use setter methods
box.setWidth = 30
box.setHeight = 50

# use accessor methods
x = box.getWidth()
y = box.getHeight()

puts "Width of the box is : #{x}"
puts "Height of the box is : #{y}"



A class method is defined using def self.methodname() which ends with end delimiter and would be called using class name as classname.methodname

class variables @@



 def to_s     # To String
      "(w:#@width,h:#@height)"  # string formatting of the object.
   end


visibility

#!/usr/bin/ruby -w

# 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()


inheritance

Just add a < character and the name of the superclass to your class statement.
#!/usr/bin/ruby -w

# 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

   # change existing getArea method as follows
   def getArea
      @area = @width * @height
      puts "Big box area is : #@area"
   end
end

# create an object
box = BigBox.new(10, 20)

# print the area using overriden method.
box.getArea()

Operator Overloading:

We'd like the + operator to perform vector addition of two Box objects using +, the * operator to multiply a Box width and height by a scalar, and the unary - operator to do negate the width and height of the Box. Here is a version of the Box class with mathematical operators defined:

class Box
  def initialize(w,h) # Initialize the width and height
    @width,@height = w, h
  end

  def +(other)         # Define + to do vector addition
    Box.new(@width + other.width, @height + other.height)
  end

  def -@               # Define unary minus to negate width and height
    Box.new(-@width, -@height)
  end

  def *(scalar)        # To perform scalar multiplication
    Box.new(@width*scalar, @height*scalar)
  end
end

Freezing Objects:

Object.freeze.   Object.frozen?

























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