From: Dave Burt <dave@...>
Date: 2005-05-07T21:59:23+09:00
Subject: Re: object reference handle (like perl's reference to scalar)

>> My Ref module at http://www.dave.burt.id.au/ruby/ref.rb now tries to 
>> behave as much like the referred-to object as possible. You above Module 
>> case statement will work with Refs now, as will uses of respond_to? is_a? 
>> kind_of? and class. A Ref will additionally respond_to a few unique 
>> methods (ie deref, deref=).
>
> Hm, and what do you do if you have to test for Ref objects?

variable.ref?

> I didn't follow this thread thoroughly, all I can say is that I personally 
> haven't missed refs in Ruby until now.  There are certainly things that 
> speak in favour of your concept.
>
> But there are also problems.  Ironically some of them seem to be caused by 
> the fact that you make a Ref behave like the original instance as much as 
> possible.  That way Ref usage is more implicit than explicit and this can 
> lead to confusion or subtle errors due to aliasing (i.e. you think you got 
> a copy of something and modify it and some other piece of code breaks 
> because it was just a ref).

You're right about that. I prefer the new implementation:
  Ref = Struct.new(:deref)

> <soapbox>
> It still might be worthwile, I just get the feeling that people try to 
> stuff things from other programming languages into Ruby because they found 
> them cute / useful / the only way to solve certain things in that 
> language.  IMHO programming languages are different for a reason and often 
> it's much better to adhere to the old saying "when in Rome do as the 
> Romans do"... :-)
> </soapbox>

I don't think what I've done here is anything like that. The concept of a 
reference here is just a wrapper or pointer, and it has to have a use. Sure, 
it causes problems in C and Perl, and Ruby definitely offers more elegant 
tools fo most of the problems that are solved in those languages with 
pointers, but I'm coming from a Rubyist's perspective here, and all I'm 
proposing is a new container, for a single object.

And I think Austin's PDF::Writer example is one case where it's useful (that 
is, passing an object by reference into a method so the method can replace 
the object).

Cheers,
Dave