From: William Morgan <wmorgan-ruby-talk@...>
Date: 2005-07-08T02:27:27+09:00
Subject: Re: Inheriting Array and slice() behaviour

Excerpts from Robert Klemme's mail of  6 Jul 2005 (EDT):
> I wouldn't be so certain of this.  It's normal for operations like
> #dup and #clone to behave that way.  Also, part of the smartness of
> ruby is that you can simply do self.class.new to get a new instance of
> the same class.  And often you need to create an instance of the same
> class.  That's not too abnormal.

Dup and clone work on objects that have already been initialized.
Self.class.new is done explicitly, so that's fine too---if the
constructor has required arguments, you supply them at that point.

My problem with Array#slice is that the objects created will never have
#initialize called. Indeed, they never *can* have it called, because who
knows what arguments need to be supplied.

> IMHO if there is a problem then with proper initialization of the new
> instance.  OTOH, inheriting classes like Array is seldom really good.
> There are too many methods that return plain arrays and you end up
> with Arrays anyway.  Delegation, ad hoc modification or extension with
> a Module is often better.

I agree that it's seldom a good idea (and it certainly wasn't in this
case). But sometimes it could be the right thing to do.

-- 
William <wmorgan-ruby-talk@masanjin.net>