Accessing outside variable using XML::Twig

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

Howdy howdy, I like XML Twig. However in the OO perl class I am programming I have a twig and am using to parse and XML file. So I assign the handler in the twig declaration, and when I start coding the handler in this class of mine I think "Oh, wait, the handler actually belongs to the twig, which is why the first argument is the twig itself. So, there is no way I can use this handler to take values from the XML item and pass it to an array in the class for use later on!" Am I wrong? Is there a way the class using the XML::Twig can swap info with the handlers?


package SampleClass;

sub new{
    my $class = shift;

    my $self = {};
    $self->{configFile} = shift;
    $self->{fileContents} = ();
    $self->{twig} = new XML::Twig(twig_handlers =>
                                    {
                                     tag => \&tagHandler,
                                     });
    bless $self, $class;
}

. . . 

sub tagHandler{
    my $twig = shift;
    my $tag = shift;
    my $client_name = $tag->first_child('client')->text;
    my $version = $tag->first_child('version')->text;
}
[download]

So I have this handler, and I want to take that text I am getting and use it in SampleClass. Not sure how.

Comment on Accessing outside variable using XML::Twig Download Code

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Re: Accessing outside variable using XML::Twig by Joost (Canon) on Jan 31, 2008 at 20:11 UTC
Whenever you've got this kind of problem (which is common in event-driven systems) the easiest solution is generally to use a closure: `$self->{twig} = new XML::Twig(twig_handlers => { tag => sub { my ($twig,$tag) = @_; + $self->tagHandler($tag) +; } });` [download] Note that the anonymous sub closes over the $self in the outer scope. Closures are extremely useful; you owe it to yourself to read up on them. here's an introductionary article on closures. updated formatting "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l]
Re^2: Accessing outside variable using XML::Twig by KarateCowboy (Initiate) on Jan 31, 2008 at 20:45 UTC
Wow. I read that. It is really cool. I can get this to work now! I did not expect to be able to do that!	[reply]
Re: Accessing outside variable using XML::Twig by GrandFather (Saint) on Jan 31, 2008 at 19:42 UTC
You may find the replies to Passing additional arguments to XML::Twig handlers of interest. Super Search is your friend - try the search ?node_id=3989;HIT=XML%3A%3ATwig;re=N;Wi Perl is environmentally friendly - it saves trees	[reply]
Re: Accessing outside variable using XML::Twig by mirod (Canon) on Jan 31, 2008 at 20:51 UTC
I guess this has become a FAQ, that's the second time this question is asked this week. So I added it to the XML::Twig FAQ.	[reply]