From: ChrisH <chris.hulan@...>
Date: 2007-02-09T18:20:07+09:00
Subject: Re: Help begin/rescue/ensure

On Feb 9, 12:20 am, "S Kanakakorn" <configt...@gmail.com> wrote:
> I have this simple code.
>
 ...
> rescue
>   puts 'cannot connect '
> ensure
>   puts 'reach ensure point'
> end
> puts 'at last'
>
> --------------------------------------
>
> If I put in non existing host name (aaaa-lnx), then the statement
> "puts 'at last'" won't print out.
> The ensure blocks work fine.  Somehow, the "rescue" block can't catch
> the error.   This is my output.
>
> reach ensure point
> /Applications/Locomotive2/Bundles/standardRailsJan2007.locobundle/i386/lib/ruby/1.8/timeout.rb:54:in
> `open': execution expired (Timeout::Error)
>         from /Applications/Locomotive2/Bundles/standardRailsJan2007.locobundle/i386/lib/ruby/gems/1.8/gems/net-ssh-1.0.10/lib/net/ssh/transport/session.rb:88:in
> `initialize'
>
> If I put in a good hostname with wrong password, the "rescue" block
> will catch the error just fine.  Here is the output:
>
> cannot connect
> reach ensure point
> at last
>
> What did I do wrong ?


rescue without a specified exception defaults to StandardError.
Tiimeout::Error is a subclass of SignalException, which is a sibling
of StandardError, not a subclass.  Thus that exception doesn't match
your rescue, so the exception gets passed up the call stack, the
ensure
gets executed, but the code after it is bypassed.

For a picture of the exception class hierarchy see http://
www.insula.cz/dali/material/rubycl/RubyExceptionClasses.jpg

cheers
Chris