From: Robert Klemme <bob.news@...>
Date: 2004-03-05T20:09:43+09:00
Subject: Re: rescue inside block -> syntax error


"Joe Mason" <joe@notcharles.ca> schrieb im Newsbeitrag
news:slrnc4gj4e.9vj.joe@gate.notcharles.ca...
> In article <c29fhn$1ptopm$1@ID-52924.news.uni-berlin.de>, Robert Klemme
wrote:
> > There's an issue that limits the usability of do..ensure..end:
Typically
> > you do resource allocation *outside* the begin..end because you don't
want
> > the ensure clause to be executed if something during init fails:
> >
> > container.each do |obj|
> >   processor = create_processor_in_a_way_that_might_throw()
> >
> >   begin
> >     processor.do_work()
> >     processor.do_more_work()
> >   ensure
> >     processor.cleanup()
> >   end
> > end
>
> But wouldn't the ruby way be to write this?

No, because that would duplicate cleanup code.

>  container.each do |obj|
>    processor.create_in_a_way_that_might_throw do |proc|

I gues you rather mean

ProcessorClass.create_in_a_way_that_might_throw do |proc|

>      proc.do_work()
>      proc.do_more_work()
>    ensure
>      proc.cleanup()

The cleanup wrong here because it is done in method
create_in_a_way_that_might_throw() in this scheme after the yield (see
File.open() and below).

>    end
>  end
>
> Joe

And how then will you implement create_in_a_way_that_might_throw()?
That's the second example I gave - slightly changed to fit the naming:

def create_in_a_way_that_might_throw()
  # initialization, might throw
  processor = ...

  begin
    yield processor
  ensure
    processor.cleanup()
  end
end

Regards

    robert