From: Robert Klemme <bob.news@...>
Date: 2005-01-26T01:35:48+09:00
Subject: Re: Self and Ruby Comparisons


"Robert Klemme" <bob.news@gmx.net> schrieb im Newsbeitrag
news:35mlboF4m5ql5U1@individual.net...
>
> "Mathieu Bouchard" <matju@sympatico.ca> schrieb im Newsbeitrag
> news:Pine.LNX.4.21.0501250404130.16754-100000@mondrian.artengine.ca...
> >
> > On Mon, 24 Jan 2005, Csaba Henk wrote:
> >
> > > On 2005-01-23, Mystifier <mystifier@users.berlios.de> wrote:
> > > Btw, I hope you know that Ruby has almost full support for prototype
> > > based programming.
> >
> > Actually, Perl has it better, because you can change the class of an
> > object, and you can change the list of superclasses of any class.
> >
> > However, this is only a slight advantage, as some other people have
> > demonstrated you can do the same for Ruby using not that many lines of
C
> > code.
>
> And if a copy is sufficient you can do this even in pure Ruby:
>
> class Object
>   def cast(target_class)
>     copy = target_class.allocate
>
>     instance_variables.each do |var|
>       copy.instance_variable_set(var, instance_variable_get(var))
>     end
>
>     copy
>   end
> end

A slightly more sophisticated version:

class Object
  def cast(target_class)
    copy = case target_class
      when Class; target_class.allocate
      when Module; dup.extend(target_class)
      else target_class.class.allocate
    end

    instance_variables.each do |var|
      copy.instance_variable_set(var, instance_variable_get(var))
    end

    copy
  end
end

Cheers

    robert