From: dblack@...
Date: 2003-02-12T02:05:43+09:00
Subject: Re: inheriting from base classes

Hi --

On Wed, 12 Feb 2003, Gavin Sinclair wrote:

> That's what you should be aiming for in OO code: users don't have to
> do any low-level stuff on your objects.  You implement just the
> methods they need.  They shouldn't have to know that Array is used to
> implement it.

They don't; If they're just require'ing a library, and using the
published/documented interface, that's all they need to know.

> Of course, you need a way of building up a roster.  That might be by
> parsing a text file, or you may need to resort to:
>
>   class ClassRoster
>     def <<(o)
>       @roster = []
>     end
>   end
>
> Rather than say "gosh, what a pain doing such a boring method", look
> for ways to eliminate the need for it.

class ClassRoster < Array   # :-)

> Or, if a few such methods are
> indeed perfectly justifiable, then use one of Ruby's forwarding
> mechanisms, or try to do more than just delegate (error checking, for
> instance).
>
> At the end of the day, the fewer methods per class, the better.
> Superfluous methods cloud the intention of the class.  (String et al
> are excluded from this rule for obvious reasons.)

This comes back to the original question -- why?  Especially in a
language where runtime objects may or may not correspond to the
capabilities of their (historical) class.


David

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