From: Edward Faulkner <ef@...>
Date: 2005-10-19T07:16:38+09:00
Subject: Re: Catch/throw vs rescue/raise/retry

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On Wed, Oct 19, 2005 at 07:07:05AM +0900, Warren Seltzer wrote:
> There appear to be 2 separate exception mechanisms in Ruby, catch/throw a=
nd
> rescue/raise/retry.  Is this right?

Yes, but they're not used for the same thing. =20

rescue/raise is used to signal error conditions.  This is analogous to
Exceptions in Java or C++.

Throw/catch is used to unwind the stack to a desired point.  It's like
a labeled break.  For example:

catch(:done){
  loop {
    do_work
    if time_to_stop? throw :done
  }
}

It's nice because you can break out of arbitrarily nested loops/blocks/etc.

regards,
Ed

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