From: Michael Neumann <neumann@...>
Date: 2001-05-08T21:57:06+09:00
Subject: [ruby-talk:14864] Re: Polymorphic methods

Benjamin J. Tilly wrote:
> Yes.  Two solutions.
> 
> 1. Create a hash whose keys are the types of object you want, and
>    whose values are the subroutines you want.  (You can create
>    anonymous subroutines with the "proc" method in the kernel.)
>    Then you can do this:
> 
>      def doIt (object)
>        $action[object.type][object]
>      end
> 
>    Feel free to add existence checks and a default case.  Also
>    you may want to add logic to follow the inheritance hierarchy
>    in case someone tries to subclass a type you know about.  This
>    is called "dispatching on a hash lookup".

My solution is similar to yours, only that it uses method_missing:

class StaticPoly

  def test_Fixnum(number)
    p "its a number"
  end

  def test_String(str)
    p "its a string"
  end

  def method_missing(id, *args)
    send(id.to_s + "_" + args[0].type.to_s, *args)
  end
end

obj = StaticPoly.new
obj.test(3)     # => its a number 
obj.test("ha")  # => its a string 


If you introduce a naming scheme for the parameter-types, perhaps
like JNI or the linker of C++ does you could use overloading where 
looking at more than one argument.

Regards,

Michael

-- 
Michael Neumann
merlin.zwo InfoDesign GmbH
http://www.merlin-zwo.de