From: David Alan Black <dblack@...>
Date: 2002-02-17T21:49:10+09:00
Subject: Re: dump/load a class that has C and Ruby data

Hello --

On Sun, 17 Feb 2002, Joel VanderWerf wrote:

>
> I have some classes whose instances have C data as well as Ruby attrs.
> If I Marshal::dump them, I lose the C part. So I have to define _dump in
> my classes. Well, it's not so hard to pack my C data up into a string. I
> can even put this string in a Ruby attribute. But then how do I dump the
> Ruby part? I don't really want to reimplement all the work in
> Marshal::dump just for my classes. I wish there was a way to call
> Marshal::dump with an argument that said "ignore the _dump". Then my
> _dump could first pack the C data into an attr, and then call dump in
> this way, and I'd be all set. Shouldn't Marshal::dump be more easy to
> reuse?
>
> Anybody know a way to do this?

You could put a hook into Marshal::dump, and flag the objects you
wanted to receive special treatment.  Adapting an idea from Dave
Thomas, in the recent respond_to? thread:

   module Marshal
     class << self
       alias :olddump :dump
       def dump(obj,*args)
	 if obj.kind_of? SpecialDumpee
	   puts "Special treatment!"
	 end
	 olddump(obj,*args)
       end
     end
   end

   module SpecialDumpee
   end

   class Thing
     include SpecialDumpee
     # ...
   end

   Marshal.dump(Thing.new) # =>  "Special treatment!"


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav