From: Joel VanderWerf <vjoel@...>
Date: 2005-06-23T13:45:05+09:00
Subject: Re: [ANN] traits-0.3.0

Devin Mullins wrote:
> I'm not sure I'd ever use it, but if you're looking for ideas, I think a 
> protocol by which to register observers would be pretty neat.
> 
> *reads email about 'observable' library*
> 
> I mean, uh, an improvement over the observable library. Something like 
> this, perchance:
> 
> class C
>  has :a, :observers => true
>  has :b, :validators => true
> end
> 
> c = C.new
> c.observe(:a) { |old,new|
>  blah
> }
> c.observe(:a) { |old,new|
>  additional_blah
> }
> c.validate(:b) { |old,new|
>  blah?
> }
> 
> If not blah?, then b is not changed.

Currently, observers just get notified after the action has happened. A 
pre-action hook might be useful. I'll look into it next time I update 
'observable'.