From: "ara.t.howard" <ara.t.howard@...>
Date: 2007-11-09T11:00:33+09:00
Subject: Re: Best practises for exception handling


On Nov 8, 2007, at 3:04 PM, Alex Dunae wrote:

> I'm write a wrapper for a web service and am wondering about the best
> way to handle exceptions.
>
> The main method in the wrapper sends either a HEAD or GET request to a
> web server using Net::HTTP.
>
> Should I catch any exceptions thrown by Net::HTTP and then throw back
> my own exception, or should I leave the exceptions totally un-handled?


i generally do one of two things

a) let the exception pass through.  this is ok if, and only if, there  
is nothing reasonable your code could do to retry.  if you do retry  
you have you have a configurable numbmer of retries, of course.

b) wrap the errors.  my preferred approach is something like

   module Wrapper
     class Error < ::StandardError
       attr_accessor :exception

       def self.wrapping exception, *a, &b
         e = new *a, &b
         e.exception = exception
         e
       end
     end
     class Specific < Error; end
     class EvenMoreSpecific < Specific; end
   end

this allows client code respond appropriately to specific errors or  
simply to rescue the entire class of errors your wrapper might throw  
and, when you want to wrap another error you can

   rescue => e
     raise Error.wrapping(e)
   end

i would say that you have to have a good reason to pick b over a, but  
they do exist.

cheers.

a @ http://codeforpeople.com/
--
we can deny everything, except that we have the possibility of being  
better. simply reflect on that.
h.h. the 14th dalai lama