From: ara.t.howard@...
Date: 2007-03-20T23:42:06+09:00
Subject: Re: does Ruby not support multiple "initialize" methods for a class???

On Tue, 20 Mar 2007, Greg Hauptmann wrote:

> I have a class that can be created from a couple of scenarios, and for each
> the initial data to populate the class is different.  I was going to create
> two "initialize" methods with their own specific method signature to cover
> off these two scenarios however I guess I will need to perhaps just create
> two separate/normal methods for this.  Perhaps then it would be like:
>
> a = Klass.new
> a.create_for_scenario_one (...)

you can use class methods to return objects, as others have mentioned, but it
also extremely easy to do your own function signature matching in ruby

     harp:~ > cat a.rb
     class C
       def initialize *argv, &block
         case argv
         when match(Fixnum)
           initialize_from_int argv[0]
         when match(Fixnum, Float)
           initialize_from_int_float argv[0], argv[1]
         else
           raise ArgumentError, argv.inspect
         end
       end

       def initialize_from_int int
         @int = int
         @float = 0.0
       end

       def initialize_from_int_float int, float
         @int = int
         @float = float
       end

       class Pattern
         def initialize template
           @template = template
         end
         def === objects
           return false unless @template.size == objects.size
           @template.each_with_index do |pat, idx|
             return false unless pat === objects[idx]
           end
           return true
         end
       end
       def match *template
         Pattern.new template
       end
     end

     p C.new(42)
     p C.new(42,42.0)



     harp:~ > ruby a.rb
     #<C:0xb75cff08 @float=0.0, @int=42>
     #<C:0xb75cfcd8 @float=42.0, @int=42>


however, function signature overloading is very confusing when mixed with
default parameters.  most people simply ignore this and live with the bugs in
c++.

regards.

-a
-- 
be kind whenever possible... it is always possible.
- the dalai lama