From: Andrew Timberlake <andrew@...>
Date: 2009-05-22T00:29:06+09:00
Subject: Re: Extending Float

On Thu, May 21, 2009 at 5:11 PM, Jp Hastings-spital
<jphastings@gmail.com> wrote:
> Maybe I haven't wrapped my head around OOP in the way I should have, can
> anyone explain to me why I can't do this?:
> --
> class Percentage < Float
>  def to_s(decimalplaces = 0)
>    (((self * 10**(decimalplaces+2)).round)/10**decimalplaces).to_s+"%"
>  end
> end
>
> puts Percentage.new(0.5)
> --
> I just get the following error:
>  NoMethodError: undefined method ‘new’ for Percentage:Class
>
> I hope its obvious what I'm trying to do, let me know if there's a way
> to achieve this that I'm missing!
> Thanks in advance

Use a delegate class

require 'delegate'
class Percentage < DelegateClass(Float)
  def to_s(decimalplaces = 0)
    (((self * 10**(decimalplaces+2)).round)/10**decimalplaces).to_s+"%"
  end
end

percentage = Percentage.new(0.5)
percentage.to_s #=> "50%"

Andrew Timberlake
http://ramblingsonrails.com
http://www.linkedin.com/in/andrewtimberlake

"I have never let my schooling interfere with my education" - Mark Twain