On 11/15/05, John Doe <[EMAIL PROTECTED]> wrote:
> David Baird am Dienstag, 15. November 2005 11.07:
> > On 11/15/05, John Doe <[EMAIL PROTECTED]> wrote:
> > > Jeremy Nixon am Dienstag, 15. November 2005 08.06:
> > > > Peter1 Alvin <[EMAIL PROTECTED]> wrote:
> [...]
> > > > { # start a lexical scope
> > > > my %d_cache;
> > > > sub handler {
> > > > # stuff
> > > > if (not defined($d_cache{$foo})) {
> > > > # pull in directory listing and store it in $d_cache{$foo}
> > > > }
> > > > # proceed to use $d_cache{$foo} information
> > > > }
> > > > } end lexical scope
> > > >
> > > > This way, a directory is only actually read once (at most) per server
> > > > child process.
> > >
> > > Hi Jeremy
> > >
> > > Hope it's not a stupid question, but are you sure %d_cache survives a
> > > request? Maybe I'm totally misunderstanding something but I thought after
> > > the point
> > >
> > > } end lexical scope
> > >
> > > %d_cache gets destroyed (if not still referenced from somewhere else).
> > >
> > > I would have left out the scope-{} to keep %d_cache at file level.
> > > Would that be wrong? And why?
> >
> > The handler() sub stays in scope - it's basically a global variable,
> > and it holds a reference to %d_cache. So %d_cache goes out of scope,
> > but doesn't get destroyed. It hangs around until the next time
> > handler() is called, at which point you're back in the same scope and
> > can access %d_cache again.
>
> Hi David
>
> thanks a lot for your answer! I have still a last question to get it 100%:
>
> The (lexical scoped) code as shown above does _not_ show the required
> referencing of %d_cache, right? Something like
>
> if (not defined($d_cache{$foo}))
>
> is not sufficient, right?
>
> Whereas something like
>
> $keep_ref=\%d_cache;
>
> in the handler() would, right?
>
> (If I'm not right, I didn't get something basic right, although I read a lot
> of documentation about this issue... I would have to review/change a lot of
> code I've written)
>
> Thanks a lot in advance
>
No, the 'reference' to the lexical variable doesn't need to be a 'Perl
reference', just some mention of the variable in the code. That will
make it stick around, but only within the lexical scope specified.
d.
