From: Robert Klemme <bob.news@...>
Date: 2003-06-02T17:23:42+09:00
Subject: Re: Return from ensure


"Gennady" <gfb@tonesoft.com> schrieb im Newsbeitrag
news:001101c32624$5aef3490$c20ca8c0@gfb...
> Hi, Rubyists
>
> Actually, I saw a remark on ruby-talk once that "return" is dagerous,
> however I could not imagine it is that dangerous. Today I spent 2 hours
> debugging the code that looked perfectly normal otherwise. I was able
reduce
> the code to the following fragment:
>
> def test
>   begin
>     raise "ERROR"
>   ensure
>     return "some value"
>   end
> end
>
> test
> puts "Nothing happened"
>
>
> Yes, it prints out "Nothing happened", and if you comment out "return"
you
> will see the exception. I just wanted to provide a return value for the
> function here, so I naturally used "return" statement. I know that in
Ruby
> you can return something without explicit "return" and I usually do this
> every time. However, at that unfortunate moment my instinct injected
> "return" -- and, here we go, 2 hours of fun.
>
> Any comments?

"ensure" is inappropriate for catching exceptions and returning something
else. You must use "rescue" for this.  The purpose of "ensure" is to have
a piece of code that is invoked regardless of how the block is exited.
This code however should only do cleanup and not modification of the exit
procedure - as you have experienced.

You'll find this very nicely documented in the pickaxe chapter
"Exceptions, Catch, and Throw".

Regards

    robert