From: zuzu <sean.zuzu@...>
Date: 2004-08-24T11:20:44+09:00
Subject: Re: *with* block?

On Tue, 24 Aug 2004 11:03:23 +0900, David A. Black <dblack@wobblini.net> wrote:
> Hi --
> 
> 
> 
> On Tue, 24 Aug 2004, Zach Dennis wrote:
> 
> > I am looking for a structure like:
> >
> > my_obj = boxWidget.new
> > with my_obj do
> >     x = 0
> >     y = 10
> >     width = 100
> >     height = 100
> > end
> >
> > instead of having to say
> >
> > my_obj = boxWidget.new
> > my_obj.x = 0
> > my_obj.y = 10
> > my_obj.width = 100
> > my_obj.height = 100
> >
> >
> >
> > Can you do this already? If not....anyone support an RCR for it besides me?
> 
> Every assignment to a bare identifier (x = 0) is parsed as an
> assignment to a local variable.  If you want to call a "="-style
> method, you have to give the receiver explicitly.  So I don't think a
> "with" keyword would add much to what you can already do with
> instance_eval:
> 
>   my_obj = BoxWidget.new
>   my_obj.instance_eval do
>     self.x = 0
>     self.y = 0
>     ...
>   end
> 
> which then isn't a whole lot better than my_obj.x = 0 and so on.
> 
> Another thing people sometimes do is:
> 
>   my_obj = BoxWidget.new do |bw|
>     bw.x = 0
>     bw.y = 10
>     ...
>   end
> 
> which can be nice because it packages the initialization with the
> creation of the object, but of course it only works if
> BoxWidget#initialize yields the new object.
> 
> David
> 
> --
> David A. Black
> dblack@wobblini.net
> 
> 

my very first thought was of .class_eval, but "obviously"
.instance_eval is correct.

i find this interesting because this seems to me to be the way to do
prototype-based objects rather than class-based objects in ruby;
similar to the Self language w/r/t smalltalk.  (though offhand i'm not
sure how an object would get cloned before doing this modifying.)

peace,
-z