in reply to XML::Twig parsing poorly structured content

In the h3 handler, set a global header, and use it in the div handler. 
#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use XML::Twig;

my $header;
my $twig = 'XML::Twig'->new(
    twig_handlers => {
        h3 => sub { $header = $_->text; $_->purge; },
        'div[@class="event"]' => sub {
            say $header, "\t", $_->text;
            $_->purge;
        },
    },
);
$twig->parsefile('file.xml');

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In bigger projects, you don't want to have a global header. Instead, you can create a new class that has two attributes, header and twig, which delegates all the XML related work to the latter and stores the headers in the former.

#!/usr/bin/perl
{   package XML::Twig::WithHeader;

    use feature qw{ say };

    use Moo;
    use XML::Twig;

    has _header => ( is => 'rw',   init_arg => undef );
    has _twig   => ( is => 'lazy', init_arg => undef );

    sub _build__twig {
        my ($self) = @_;
        my $twig = 'XML::Twig'->new(
            twig_handlers => {
                h3 => sub { $self->_header($_->text); $_->purge; },
                'div[@class="event"]' => sub {
                    say $self->_header, "\t", $_->text;
                    $_->purge;
                },
            },
        );
    }

    sub parse {
        my ($self, $file) = @_;
        $self->_twig->parsefile($file);
    }
}

my $twig = 'XML::Twig::WithHeader'->new;
$twig->parse('file.xml');

[download]

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

[download]

Replies are listed 'Best First'.
Re^2: XML::Twig parsing poorly structured content
by slugger415 (Monk) on Jan 25, 2017 at 00:36 UTC

    Looks very nice, thank you! and it works, at least for my sample XML.

    I'm not familiar with this handler construction:

    'div[@class="event"]'

    It looks rather XSL-ish. Is there some explanation of how that works? The reason I ask (sheepishly) is that my pseudo XML is simpler than the real stuff, meaning it has sub-levels that I want to parse, e.g.:

    <h3 class="current-day">Thursday, February 2</h3>
 <div class="event">
  <div class="title">Event 1</div>
  <span class="time">7:30pm</span>
  <span class="location">Main Street</span>
 </div>
 <div class="event">
  <div class="title">Event 2</div>
  <span class="time">9pm</span>
  <span class="location">Green Street</span>
 </div>

    [download]

    Sorry not to be more detailed in my original post. Much appreciated.

[reply]
[d/l]
[select]
      > rather XSL-ish

      It's called XPath. It's used and supported in a wider range of tools/languages/libraries than just XSL. This particular expression means "a div element whose class attribute has the value "event".

      > want to parse

      Then you can't use handlers, as you need access to more than just a subtree. The following shows how to do it. Using XML::LibXML would simplify the code in such a case, in my opinion.

      #!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use XML::Twig;

my $twig = 'XML::Twig'->new;
$twig->parsefile(shift);

my $root = $twig->root;
for my $header($root->descendants('h3')) {
    my $date = $header->text;
    my @events = $header->next_siblings(sub {
        my ($elt) = @_;
        'div' eq $elt->name && $elt->prev_sibling('h3') == $header
    });
    say join "\t", $date, map $_->text, $_->children for @events;
}

      [download]

      ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

      [download]
[reply]
[d/l]
[select]
      "I'm not familiar with this handler construction: 'div[@class="event"]'"

      Here's the current W3C Recommendation: "XML Path Language (XPath) 2.0 (Second Edition)".

      In almost all cases, I find the "3.2.4 Abbreviated Syntax" section adequate for my needs. This has a description of 'div[@class="event"]' (as para[@type="warning"]); and lots more besides.

      — Ken

[reply]
[d/l]
[select]

        Thank you Ken! very useful (and more to learn, as always).

        Scott

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