The Shape Example in Ruby

Contributed by Guy N. Hurst

Notes

After putting together this comparison, Guy Hurst sent me the following note.

I found your page at http://onestepback.org/oostuff/ to be very interesting.

I have been working with ruby lately, and looked at that version. I realized that I could suggest a shorter version (much shorter) to the provided ruby script.

Basically, by using 'attr_accessor :var' instead of 'attr :var', one can get or set the var using 'instance.var' or 'instance.var=xxx' and dispense with defining/using getVar() or setVar() methods.

Code for Ruby

File: Shape.rb

class Shape
  attr_accessor :x, :y
  
  # constructor
  def initialize(initx, inity)
    @x=initx
    @y=inity
  end
  
  # move the x & y position of the object
  def moveTo(newx, newy)
    @x=newx
    @y=newy
  end
  def rMoveTo(newx, newy)
    moveTo(newx + @x, newy + @y)
  end
end

File: Rectangle.rb

require "Shape.rb"

class Rectangle < Shape
  attr_accessor :width, :height
  
  # constructor
  def initialize(initx, inity, initwidth, initheight)
    super(initx, inity)
    @width=initwidth
    @height=initheight
  end
  
  # draw the rectangle
  def draw
    print("Drawing a Rectangle at:(", @x, ",", @y,
      "), width ", @width, ", height ", @height, "\n")
  end
end

File: Circle.rb

require "Shape.rb"

class Circle < Shape
  attr_accessor :radius
  
  # constructor
  def initialize(initx, inity, initradius)
    super(initx, inity)
    @radius=initradius
  end
  
  # draw the circle
  def draw
    print("Draw a Circle at:(", @x, ",", @y,
      "), radius ", @radius, "\n")
  end
end

File: Polymorph.rb

require "Rectangle.rb"
require "Circle.rb"

# create a collection containing various shape instances
scribble = [Rectangle.new(10, 20, 5, 6), Circle.new(15, 25, 8)]

# iterate through the collection and handle shapes polymorphically
scribble.each do |ashape|
  ashape.draw
  ashape.rMoveTo(100, 100)
  ashape.draw
end

# access a rectangle specific function
arectangle = Rectangle.new(0, 0, 15, 15)
arectangle.width=30
arectangle.draw