Created
July 13, 2012 19:17
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| class Polygon | |
| @@sides = nil | |
| def self.sides | |
| @@sides | |
| end | |
| def self.count | |
| @@count | |
| end | |
| @@count = 0 | |
| def initialize | |
| @@count += 1 | |
| end | |
| end | |
| class Triangle < Polygon | |
| @@sides = 3 | |
| end | |
| class Square < Polygon | |
| @@sides = 4 | |
| end |
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| [1] pry(main)> require './classvars' | |
| => true | |
| # This makes sense | |
| [2] pry(main)> Polygon.count | |
| => 0 | |
| [3] pry(main)> p = Polygon.new | |
| => #<Polygon:0x007fb0a1ec3cc8> | |
| [4] pry(main)> t = Triangle.new | |
| => #<Triangle:0x007fb0a1ab01b8> | |
| [5] pry(main)> s = Square.new | |
| => #<Square:0x007fb0a3080290> | |
| [6] pry(main)> Polygon.count | |
| => 3 | |
| # This doesn't! | |
| [10] pry(main)> Square.sides | |
| => 4 | |
| [11] pry(main)> Triangle.sides | |
| => 4 |
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Yeah, ruby class variables are shared by all subclasses. I wrote this for demonstration purposes.