From: Alex Dunae <alex@...>
Date: 2007-11-09T13:28:14+09:00
Subject: Re: Best practises for exception handling

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Joel, A,

Thank you both for your responses - they made the gap in my knowledge 
quite plain, so I'm off to do some more homework on exceptions.


Alex

ara.t.howard wrote:
>
> On Nov 8, 2007, at 7:20 PM, Joel VanderWerf wrote:
>
>> Another possibility, somewhere between a and b: rescue the exception 
>> and re-raise, but add some more information to the message. That 
>> extra info might be, for example, IP address and port during network 
>> operations. This doesn't change the structure of exception handling, 
>> since the Exception subclass is the same and it will be handled at 
>> the same point, eventually, but it can be very useful for 
>> logging/debugging and for presenting an informative message to the 
>> user, if your program is interactive.
>
> good point joel, i recently added this to main:
>
> ...
>
>                 rescue Exception => e
>                   handle_exception e
>                 end
> ...
>
>     def handle_exception e
>       if e.respond_to?(:error_handler_before)
>         fcall(e, :error_handler_before, self)
>       end
>
>       if e.respond_to?(:error_handler_instead)
>         fcall(e, :error_handler_instead, self)
>       else
>         if e.respond_to? :status
>           exit_status(( e.status ))
>         end
>
>         if Softspoken === e or SystemExit === e
>           stderr.puts e.message unless(SystemExit === e and 
> e.message.to_s == 'exit') ### avoids double message for abort('message')
>         else
>           fatal{ e }
>         end
>       end
>
>       if e.respond_to?(:error_handler_after)
>         fcall(e, :error_handler_after, self)
>       end
>
>       exit_status(( exit_failure )) if exit_status == exit_success
>       exit_status(( Integer(exit_status) rescue(exit_status ? 0 : 1) ))
>       exit exit_status
>     end
>
> ...
>
> which basically allows exceptions to be extended with modules or have 
> methods defined on them which affect how they are handled.  it seems 
> like a useful pattern but i've only just started using it.
>
> cheers.
>
> a @ http://codeforpeople.com/
> -- 
> share your knowledge.  it's a way to achieve immortality.
> h.h. the 14th dalai lama
>
>
>
>

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