From: Mathieu Bouchard <matju@...>
Date: 2005-03-03T03:24:56+09:00
Subject: Re: Continuation example


On Wed, 2 Mar 2005, ES wrote:
> 
> It'd be great fun if exception handling could *literally* be described
> parallel to the method :)

You need "around-methods", an AOP concept taken from CommonLISP. You
define the error handler as an around-method called foo, put a
begin/rescue/ensure block that normally just runs "super", which calls the
supermethod, which is not necessarily in a superclass. In this case, what
gets run is the regular-method foo of the same class.

You can achieve a similar effect without AOP by putting error handling in
foo() and the code in foo_real().

An alternative is to have two classes instead, and put the error-handling
in the subclass. This is what MetaRuby (matju's) did to achieve
contract-checking. However it doesn't lend itself to subclassing, as the
first foo is executed inside the error handling (the 2nd foo) but the 3rd
foo is executed outside of it.

_____________________________________________________________________
Mathieu Bouchard -=- Montr�al QC Canada -=- http://artengine.ca/matju