From: Matthias Georgi <matti_g@...>
Date: 2004-05-14T19:18:58+09:00
Subject: Re: [RCR] subclasses of string as hash keys

On Fri, 14 May 2004 18:08:57 +0900, Robert Klemme <bob.news@gmx.net> wrote:

> This is debatable - and there *have* been lengthy debates about that.  
> For
> example, Java's class String is declared 'final', i.e. it can't be
> inherited from.  I have only a slight tendency to not do it but I agree
> that there might be situations where subclassing is the more appropriate
> option.  Though it seems to me that they are rather rare than common.

e.g. a class which represents the an object id, the object id have to be
a string , because it's stored in database. So to get a part of the id,
you define an accessor, which scans the string.
But from a practical view, I'd rather go with some module_functions,
because the conversions all over the code like String#to_oid are too messy.

>
> Note also, that with Delegator you can quite easily wrap a String and add
> functionality as you see fit.

Yes, but when it comes to binary representation, I have to call everywhere
to_s, also not beatyful.

>
>> but the easiest way is to extend class String.
>> namespaces would be really good solution for that.
>
> How exactly would namespaces solve this problem?

The term namespace is possibly wrong, but my idea is:

namespace MyNames

   class String  # makes a copy of String class
   end

   s = "xxx"     # constructor of MyNames::String is called

end

Same thing for every string creation.
But that would require a lot of change in the interpreter,
every rb_str_new() must know the current namespace.

Recently I attended a lecture of the creator(Erik Ernst) of the
language gbeta, which solves this problem nicely, but
 from a very different approach.


-- 
Matthias Georgi
matti_g@gmx.de