From: Robert Klemme <bob.news@...>
Date: 2004-11-03T22:03:51+09:00
Subject: Re: Programmatically and dynamically catching exceptions


"Tim Sutherland" <timsuth@ihug.co.nz> schrieb im Newsbeitrag
news:slrncohddq.pa3.timsuth@europa.zone...
> In article <2urqndF2cbspnU1@uni-berlin.de>, Robert Klemme wrote:
> >
> >"Logan Capaldo" <logancapaldo@gmail.com> schrieb im Newsbeitrag
> >news:4521f6680411022134451a94d1@mail.gmail.com...
> >> Thanks thats quite neat.
> >>
> >> On Wed, 3 Nov 2004 13:20:28 +0900, Yohanes Santoso
> >> <ysantoso-rubytalk@dessyku.is-a-geek.org> wrote:
> >> > Logan Capaldo <logancapaldo@gmail.com> writes:
> >> >
> >> >
> >> >
> >> > > Allright here was my idea which seems to have been shattered by
the
> >> > > realities of Ruby.
> >> > >
> >> > > I was thinking of a class called Try. You would do something like
> >> > >
> >> > > class Try
> >> > > ...
> >> > > end
> >> > >
> >> > > tryblock = Try.new { #This block would normally be wrapped in a
> >begin...rescue
> >> > >                            }
> >> > >
> >> > > tryblock.add_exhandler(:SomeException) { |ex| some_code }
> >> > >
> >> > > tryblock.execute #or possibly tryblock.call ?
> >> > >
> >> > > Basically the idea was going to be you could subclass Try and
> >provide
> >> > > default sensible handling of your Exceptions (if you were writing
a
> >> > > library for instance) . Users could then then wrap it in a
> >> > > begin...rescue block to catch other exceptions or use
add_exhandler
> >to
> >> > > overide the default handler. (Possibly provide a way to get the
old
> >> > > handler and and use it in the new).
> >> > >
> >> > > my idea was going to be that I could do something like
> >> > >
> >> >
> >> > class Try
> >> >   def execute
> >> >     begin
> >> >       user_proc.call(*user_proc_args)
> >> >     rescue Error => e
> >> >       elt = (exhandlers.select{|obj| e.class ==
> >obj.exception_class})[0]
> >> >       if elt
> >> >         elt.exception_handler.call(e)
> >> >       else
> >> >         raise e
> >> >       end
> >> >     end
> >> >   end
> >> > end
> >
> >We can save three more lines :-)
> >
> >class Try
> >  def execute
> >    begin
> >      user_proc.call(*user_proc_args)
> >    rescue Error => e
> >      elt = (exhandlers.select{|obj| e.class ==
obj.exception_class})[0]
> >      raise unless elt
> >      elt.exception_handler.call(e)
> >    end
> >  end
> >end
>
> As long as we're saving lines...
>
> class Try
>   def execute
>     user_proc.call(*user_proc_args)
>   rescue Error => e
>     elt = (exhandlers.select{|obj| e.class == obj.exception_class})[0]
or raise
>     elt.exception_handler.call(e)
>   end
> end

Ha!  Very nice indeed!  Didn't think of that one. :-)

    robert