From: Joel VanderWerf <vjoel@...>
Date: 2005-06-23T05:54:16+09:00
Subject: Re: [ANN] traits-0.3.0

Ralph "PJPizza" Siegler wrote:
> On Wed, Jun 22, 2005 at 09:18:13PM +0900, Ara.T.Howard wrote:
> 
>>URLS
>>
>>  http://raa.ruby-lang.org/search.rhtml?search=traits
>>  http://codeforpeople.com/lib/ruby/traits
>>
>>ABOUT
>>
>>  traits.rb aims to be a better set of attr_* methods and encourages better
>>  living through meta-programming and uniform access priciples.  traits.rb
>>  supercedes attributes.rb.  why?  the name is shorter ;-)
> 
> 
> Hello Ara,
> 
> would it be possible to have a kind  of observer on traits, kind of like Apple/obc/cocoa's   KVO?
> 
> 
> 
> Ralph "PJPizza" Siegler

I'm not sure what those observers do, but the observable module on RAA 
can be used orthogonally with any pair of methods #attr and #attr=, as 
in the following example:

[~] cat foo.rb
require 'observable'
class A
   def foo; 3; end
   def foo=(x); p x; end
   extend Observable
   observable :foo
end

a = A.new

a.when_foo(Object) {|val| p "changing foo to #{val.inspect}"}

a.foo = "zap"

[~] ruby foo.rb
"changing foo to 3"
"zap"
"changing foo to \"zap\""


So presumably this could be used with traits without modifying either 
library.