From: Eric Hodel <drbrain@...7.net>
Date: 2007-06-22T17:12:45+09:00
Subject: Re: Why doesn't rescue catch Exception by default?

On Jun 21, 2007, at 21:04, Seth wrote:

> From:
> http://www.rubycentral.com/book/tut_exceptions.html
>
> --- BEGIN
> When you need to raise an exception, you can use one of the built-in
> Exception classes, or you can create one of your own. If you create  
> your
> own, you might want to make it a subclass of StandardError or one  
> of its
> children. If you don't, your exception won't be caught by default.
> --- END
>
> My question is *why* doesn't it handle the most generalized class,
> Exception, by default?  What's the logic behind this?

 From http://www.zenspider.com/Languages/Ruby/QuickRef.html#34:

Exception
     NoMemoryError
     ScriptError
         LoadError
         NotImplementedError
         SyntaxError
     SignalException
         Interrupt
     StandardError (default for rescue)
         [...]
     SystemExit
     fatal

You don't want to rescue any of these other exceptions (besides  
StandardError and friends) unless you really know what you're doing.

Don't create your own exception classes by subclassing Exception  
directly, subclass the closest matching exception class, or subclass  
RuntimeError or StandardError.

--
Poor workers blame their tools. Good workers build better tools. The  
best
workers get their tools to do the work for them. -- Syndicate Wars