From: timsuth@... (Tim Sutherland)
Date: 2004-11-03T19:43:50+09:00
Subject: Re: Programmatically and dynamically catching exceptions

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