Re: [Boston.pm] quick XML::Twig / variable scope problem
On Fri, 24 Aug 2007 19:32:05 -0400 Alex Brelsfoard [EMAIL PROTECTED] wrote:
AB I would like to call a function that declares a few variables and then runs
AB some XML::Twig processes which in turn access update said original
AB variables.
AB But I'm getting an error from my twig functions when they try to access the
AB before-defined variables.
...
AB sub main {
AB my $catalog_timestamp;
AB my $objinfo_timestamp;
AB my %fields;
... calls get_catalog_timestamp ...
AB }
AB An example of the twig functions:
AB sub get_catalog_timestamp {
AB my ($twig, $elt) = @_;
AB # get the PublishTimeStamp attribute
AB $catalog_timestamp = $elt-att('PublishTimestamp');
AB $twig-purge();
AB }
Either set up a global settings hash outside main(), which every
function accesses, or have a global function that returns a hash inside
a closure, e.g.
{
my %settings;
sub settings { return \%settings; }
}
settings()-{yes} = 'no';
For settings, always try to consolidate them into a single holder (hash,
object, whatever) because then you can easily track usage and refactor
it as needed. I usually do something a little more elaborate:
use constant CATALOG_TIMESTAMP = 'catalog_timestamp';
settings()-{CATALOG_TIMESTAMP()} = 'timestamp data';
to avoid typos in the hash key, which make very annoying bugs. I
usually use the same hash with Getopt::Long to have a single place for
all program options.
HTH
Ted
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Re: [Boston.pm] quick XML::Twig / variable scope problem
No, don't use globals. I'm pretty sure (read: too lazy to test) that
you can send an anonymous subroutine like this:
my $localobject = new MyTwigClass($catalog_timestamp);
twig_handlers = {
'Catalog' = sub { return $localobjext-get_catalog_timestamp(); },
}
$localobject will not get garbage collected when it is out of scope
because it's still referenced by the anonymous subroutine.
Jeremy Muhlich wrote:
On Fri, 2007-08-24 at 19:32 -0400, Alex Brelsfoard wrote:
sub main {
my $catalog_timestamp;
...
sub get_catalog_timestamp {
...
$catalog_timestamp = $elt-att('PublishTimestamp');
Global symbol $catalog_timestamp requires explicit package name
Yep. You can get away with accessing those lexicals in a function when
your main code is at the top level in the script. But when you have
the variable declarations inside one function, the other function can't
see them.
I would do away with main, moving the code out into the top level. If
you *really* have your heart set on your main function (why???), you
could move just the declarations of the global variables outside of
it.
-- Jeremy
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--
Sincerely *Duane Bronson*
[EMAIL PROTECTED] mailto:[EMAIL PROTECTED]
http://www.nerdlogic.com/
453 Washington St. #4A, Boston, MA 02111
617.515.2909
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