slugger415 has asked for the wisdom of the Perl Monks concerning the following question:

Hi Perlers, I am still learning XML::Twig and have a question. I have a couple of event handlers set up thusly, parsing a list of filenames stored in @files:

foreach my $file (@files){
# set up the XML parser:
 my $twig= XML::Twig->new( 
  twig_handlers => { topicref => \&topicref_processing,
               xref => \&topicref_processing },
 );
 $twig->parsefile($file);
 $twig->purge;
}

[download]

And I have the handler set up something like this:

sub topicref_processing {
  my($twig, $topicref) = @_;
  my($atts) = $topicref->atts();
  if($$atts{'keyref'}){
   ### associate this keyref with $file
  }
}

[download]

What I want to do is, if the handler finds a keyref attribute in the xref or topicref element, store that in a hash with the $file name as the key, something like $keyrefs{$file}{$$atts{'keyref'}} = 'keyref'.

What I can't figure out is, how to pass the name in $file to the event handler, or conversely, how to associate the found attribute back to the $file. I'm probably missing something obvious, but can't puzzle it out.

Any suggestions would be greatly appreciated.

Scott

Replies are listed 'Best First'.
Re: XML::Twig newbie question
by Anonymous Monk on Sep 18, 2012 at 02:19 UTC

    What I can't figure out is, how to pass the name in $file to the event handler, or conversely, how to associate the found attribute back to the $file. I'm probably missing something obvious, but can't puzzle it out. Any suggestions would be greatly appreciated.

    You're missing closures, examples in XML::Twig traversing tree and storing in an array, XML::Twig n00b, Tutorials: Closure on Closures 

    for my $file ( ... ){
    my $filename = $file;
    my %filnameKeyref;
    my $topicref = sub {
       ...
       $filenameKeyref{ $filename };
       return;
    };

    my $twig= XML::Twig->new(  ... => $topicref );
    $twig->...;
}

    [download]

    Although you ought to write that as 

    for my $file ( ... ){
    my $complexAssociations = FooAssoc( $file );
    WalkAndTalk( $complexAssociations );
}

    [download]
[reply]
[d/l]
[select]

      Another way would be to make the subroutine curried (that is expecting to get the parameters separately, not all at once): 

      foreach my $file (@files){
# set up the XML parser:
 my $twig= XML::Twig->new( 
  twig_handlers => { topicref => topicref_processing($file),
               xref => topicref_processing($file) },
 );
 $twig->parsefile($file);
 $twig->purge;
}

sub topicref_processing {
  my ($file) = @_;
  return sub {
    my($twig, $topicref) = @_;
    my($atts) = $topicref->atts();
    if($$atts{'keyref'}){
     ### associate this keyref with $file
    }
  }
}

      [download]

      Jenda
      Enoch was right!
      Enjoy the last years of Rome.

[reply]
[d/l]

        Another way would be to make the subroutine curried (that is expecting to get the parameters separately, not all at once):

        Sure, you could write your closure that way ( the schönfinkeling way), but it gains you nothing in this example, it just takes a little more memory

[reply]

        "Curried?" sounds delicious! :-) Never heard that phrase before.

        Thank you, this is a simple solution that works perfectly for me.

        Scott

[reply]

      Thank you for the suggestions; I will study the examples and try to understand them. A bit over my head at first sight.

      Scott

[reply]
Re: XML::Twig newbie question
by remiah (Hermit) on Sep 18, 2012 at 15:03 UTC

    There is another way ,which you find it in tutorial of twig. Please see "sub make{" and its handler registration.

    my $twig= XML::Twig->new( 
  twig_handlers => { topicref => sub{ topicref_processing(@_, $filenam
+e);},
);
sub topicref_processing{
my($twig,$elt, $filename)=@_; 
    ####you can get twig and elt here.
}

    [download]
    I wonder why links to XML::Twig documents have so much troubles...?

[reply]
[d/l]
[reply]

        Thanks.
        Updated my bookmark.

[reply]

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