From: Harry Ohlsen <harryo@...>
Date: 2001-11-29T07:53:34+09:00
Subject: [ruby-talk:26846] Re: overload possible?

Here's a different approach.  I think it makes the usage a bit more
"obvious", but that's only IMHO.  The only issue I have with it is
that this version doesn't catch the case where the particular set
of argument types does not have a block of code associated with
it.

I think that's a significant problem, so if someone can see an
elegant way to make it fall over if a method is called with an
unexpected set of argument types, I'd love to hear it.

Note that I wrote this just to see if it was possible and have never
actually found a need to use it :-).

This is in overload.rb ...

   module Overload
 
       def signature(args, *types, &block)
           argsSignature  = (args.collect  { |a| a.type.to_s }).join("-")
           typesSignature = types.join("-")
 
           if argsSignature == typesSignature
               block.call(*args)
           end
       end
 
   end

So, to define a class Fred that has an overloaded method hello(), we
could then do ...

   require "overload"

   class Fred
 
       include Overload
 
       def hello(*args)
           signature(args, :Fixnum, :String, :Float) do
               |i, s, f|
 
               puts "(Fixnum, String, Float) -> [ #{i}, \"#{s}\", #{f} ]"
           end
 
           signature(args, :String, :Fixnum) do
               |s, i|
 
               puts "(String, Fixnum) -> [ \"#{s}\", #{i} ]"
           end
       end
 
   end
 
   f = Fred.new
 
   f.hello(123, "hello", 123.456)
   f.hello("hello", 123)