From: Eric Hodel <drbrain@...7.net>
Date: 2005-08-31T03:14:35+09:00
Subject: Re: custom exceptions

On 30 Aug 2005, at 10:52, Joe Van Dyk wrote:

> When should you define your own exceptions?  Any rules of thumb?

I define custom exceptions when I need to differentiate them from the  
built-in exceptions.

> I'm writing an application that runs on a computer and listens for
> requests to start, kill, and view log files for other applications on
> that computer.  Say I get a request to start an application on that
> computer and the requested executable doesn't exist.  Should I throw a
> custom exception then?  Or, say an application dies unexpectedly.
> What should I use for an exception then?

Sometimes an exception with a message is enough.  Other times I need  
to know the difference between two RuntimeErrors with different  
messages.

I create my own exceptions for the second case because rescue  
FooError is easier than reading exception messages.

-- 
Eric Hodel - drbrain@segment7.net - http://segment7.net
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