From: Robert Klemme <bob.news@...>
Date: 2003-09-11T20:32:21+09:00
Subject: Re: What *are* variables? Which are nil now?


"Hugh Sasse Staff Elec Eng" <hgs@dmu.ac.uk> schrieb im Newsbeitrag
news:Pine.GSO.4.53.0309111033140.26256@neelix...
> On Thu, 11 Sep 2003, Robert Klemme wrote:
>
> >
> > "Hugh Sasse Staff Elec Eng" <hgs@dmu.ac.uk> schrieb im Newsbeitrag
> > news:Pine.GSO.4.53.0309110023200.26201@neelix...
> > > I found out what caused it:
> > >    @dirs += entries.collect{|f| stuff_here(f)}.compact!
> > >
> > > The bang method caused the blow up, but even defining
> > >
>         [Nil#to_a]
> > >
> > > did not trap it.
> > > Where does the "#<"..."failed to convert nil to Array"...>
> > > message come from? Somewhere untrappable?
> >
> > Since
> >
> > @dirs += entries.collect{|f| stuff_here(f)}.compact!
> >
> > <=>
> >
> > @dirs = ( @dirs + entries.collect{|f| stuff_here(f)}.compact! )
> >
> > Assuming that @dirs is an Array, Array.+ tries to convert the argument
> > (which is the result of the expr right to the "+") to an Array and
throws
> > the exception
>
> Agreed, but is the point where the message is generated accessible,
> such that I can interpose something?  This Array#+ isn't calling
> arg.to_a as far as the above shows...

You can

- redefine Array#+
- look into the sources for Array#+

But isn't the stack trace good enough for catching the error you got?

    robert