From: Sean O'Dell <sean@...>
Date: 2004-06-29T08:50:13+09:00
Subject: Re: Is it considered Harmful?

On Monday 28 June 2004 16:01, Gavin Sinclair wrote:
> On Tuesday, June 29, 2004, 4:04:21 AM, Sean wrote:
> >> You're missing his point.
> >>
> >> If I call Array.new, I certainly get an array whose #initialize
> >> has been called.
> >>
> >> But if I then do arr.class = Net::HTTP, then Net:HTTP#initialize
> >> does NOT get called (e.g., to set the host name or whatever).
> >
> > Ah...I see why I haven't connected with that issue now.  I think of this
> > as a "buyer beware" issue.  If you change an existing object's class, be
> > sure you change it to something that understands the object it is
> > receiving.  I think even #become would have these problems.
>
> No it wouldn't.  Objects are supposed to represent data and behaviour.
> #become keeps both intact.  #class= changes only the behaviour.  If
> something does't work after #become, it's not because the use of
> #become introduced an inconsistency.  The same cannot be said of
> #class=.  That's not necessarily a point against it...

I realized my error regarding #become after reading another post.

> > Even using include could introduce methods to a class which didn't
> > initialize instance data the way it expects.
>
> ...as this demonstrates.  Ruby contains lots of features that make it
> easy to write broken programs.  #class= should be considered in that
> light.  I don't see it as being very useful (stateless behaviour can
> be elegantly captured by modules), but I'm sure it could be.

I think both #class= and #become have a lot of the same potential pitfalls, 
but I agree that #become encourages better data encapsulation.  Assigning the 
data of an object to another class arbitrarily (such as is possible with 
#class=), in OOP terms, is a bit out there.

I should try and remember how well Ruby implements OOP and how such 
suggestions would really rub people the wrong way who want to preserve that.  
I was only concerned with keeping Ruby from crashing, and adding C code to 
protect it more, and I really didn't consider how it would affect Ruby's 
OO-ness (I didn't say paradigm).

	Sean O'Dell