XML::Twig Question (sorta)

zericm has asked for the wisdom of the Perl Monks concerning the following question:

All,

I've got this pretty simple chunk of code here:

    @projectEvents = ($dcrTwigCopy->descendants('tab[@tabType="events"
+]'));
    
    if (@projectEvents) {
        print "\n\nWe have an array!\n";
        populateEventManifest(@projectEvents, $eventManFh);
    }

sub populateEventManifest {
    my( @events, $eventManFh ) = @_;
    foreach my $event (@events) { 
        $event->print($eventManFh);
    }
}
[download]

When I do that final print statement to a file handle, I get:

Use of uninitialized value in print at /System/Library/Perl/5.8.8/darwin-thread-multi-2level/IO/Handle.pm line 401.

But when I drop the filehandle, it prints fine to STDOUT. Not looking for a specific answer here (I'd rather learn to fish), but some suggestions as to where I should cast my net.

Thanks,
Eric

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Re: XML::Twig Question (sorta) by Anno (Deacon) on Mar 28, 2009 at 18:23 UTC
The line `my( @events, $eventManFh ) = @_;` will never assign anything to `$eventManFh`. `my $eventManFh = pop; my @events = @_; # ...` [download] Anno	[reply] [d/l] [select]
Re: XML::Twig Question (sorta) by ikegami (Patriarch) on Mar 28, 2009 at 19:12 UTC
Anno is quite right. Here's a quick explanation. When you call a subroutine, the arguments are flattened into a list. `sub foo { print("There are ", 0+@_, " args\n"); print("They are @_\n"); } my @a = qw( a b c ); my $n = 123; foo(@a, $n);` [download] `There are 4 args They are a b c 123` [download] For this reason, an array reference is usually passed instead of the contents of the array. `foo(\@a, $n);` [download] `There are 2 args They are ARRAY(0x1829aec) 123` [download] In your case, it would be `populateEventManifest(\@projectEvents, $eventManFh); # <-- extra \ sub populateEventManifest { my( $events, $eventManFh ) = @_; # <-- scalar foreach my $event (@$events) { # <-- extra $ $event->print($eventManFh); } }` [download] Anno provided an alternative solution.	[reply] [d/l] [select]