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

Hi,

I am trying to extract xml data with the xml::parser module and to store them into an array of hashes for further processing - tag extraction works fine, but storing the tag values into the array of hashes is the issue.

May be you can assist me here and what I am doing wrong:

xml data file:

<Catalog>
<Category>
<Name>Arts &amp; Entertainment</Name>
<Site>
<Id>...</Id>
<Title>...</Title>
</Site>
<Site>
<Id>...</Id>
<Title>...</Title>
</Site>
</Category>
<Catalog>

[download]

perl prg:

$parser = XML::Parser->new(Handlers => {Start => \&start,
                                        Char  => \&char,
                                        End   => \&end}
                          );
sub start{
    my ($p, $elt, %atts) = @_;

    if ($elt eq 'Site') {
        %site = (); #this is the hash per one site
        }

    if ($elt eq 'Id')                         { $tag_id = 1; }
    if ($elt eq 'Title')                      { $tag_title = 1; }
 }

sub char {
    my ($p, $str) = @_;
    if ($tag_id eq 1) {
        $id     = trim($str);
       }
    if ($tag_title eq 1) {
        $title = trim($str);
       }
}

sub end{
    my ($p, $elt) = @_;

    if ($tag_id eq 1 and $elt eq 'Id') {
        $site{ $id } = $id;
        $tag_id = 0;
        }

    if ($tag_title eq 1 and $elt eq 'Title') {
        $site{ $title } = $title;
        $tag_title = 0;
        }

     if ($elt eq 'Site') {
    push(@cb, %site);
    print %site . "\n";
    }
}

# if I want to process now the @cb then no data are inside.

[download]
Thanks for assistance, Peter

Replies are listed 'Best First'.
Re: parse xml and store data in array of hashesh
by Anonymous Monk on Jul 22, 2011 at 07:04 UTC
    To build an array of hashes , you need to store, hashrefs in the array, like this 
    #!/usr/bin/perl --
use strict;
use warnings;
my %foo = 1..2;
my @bar = %foo;
push @bar, \%foo;
use Data::Dumper;
print Dumper( \@bar );
__END__
$VAR1 = [
          '1',
          2,
          {
            '1' => 2
          }
        ];

    [download]

    See the \ operator takes a reference, to an array (\@array), to a hash (\%hash), to a scalar (\$scalar)

    See Tutorials: References quick reference

[reply]
[d/l]
      Hi, thanks very much for quick repl; but even with stored hash references in sub _end; the array @cb does not have data when trying to print them Greetings, Peter
[reply]
        Hi, you're welcome :)

        You made it very easy as your question was very effective (How do I post a question effectively? , How do I compose an effective node title?).

        Here is a similar approach using XML::Twig 

        #!/usr/bin/perl --
#~ 2011-07-23-08:42:20+0000 by Anonymous Monk
#~ perltidy -csc -otr -opr -ce -nibc -i=4
use strict;
use warnings;
use autodie;    # dies if open/close... fail
use Data::Dumper;
use XML::Twig;

Main( @ARGV );
exit( 0 );

sub Main {
    Demo();
}

sub NotDemoMeaningfulName {
    my ($xml) = @_;
    my @data;
    my %site;
    my $t = XML::Twig->new(
        twig_handlers => {
            '//Site' => sub {
                warn $_->path;
                push @data, {%site} if %site;
                %site = ();
                $_->purge;    # free memory
            },
            '//Site/Id' => sub {
                warn $_->path;
                $site{Id} = $_->trimmed_text;
            },
            '//Site/Title' => sub {
                warn $_->path;
                $site{Title} = $_->trimmed_text;
            },
        },
    );
    $t->xparse($xml);
    $t->purge;
    return \@data;
} ## end sub NotDemoMeaningfulName

sub Demo {
    my $ref = NotDemoMeaningfulName( DemoData() );
    print Dumper($ref);
}

sub DemoData {

#~ http://perlmonks.com/?abspart=1;displaytype=displaycode;node_id=916
+054;part=1
    my $xml = <<'__XML__';
<Catalog>
  <Category>
    <Name>Arts &amp; Entertainment</Name>
    <Site>
      <Id>01-id...</Id>
      <Title>01-title...</Title>
    </Site>
    <Site>
      <Id>02-id...</Id>
      <Title>02-title...</Title>
    </Site>
  </Category>
</Catalog>
__XML__
    return $xml;
} ## end sub DemoData
__END__
$ perl xml.twig.916054.pl
/Catalog/Category/Site/Id at xml.twig.916054.pl line 30.
/Catalog/Category/Site/Title at xml.twig.916054.pl line 34.
/Catalog/Category/Site at xml.twig.916054.pl line 24.
/Catalog/Category/Site/Id at xml.twig.916054.pl line 30.
/Catalog/Category/Site/Title at xml.twig.916054.pl line 34.
/Catalog/Category/Site at xml.twig.916054.pl line 24.
$VAR1 = [
          {
            'Id' => '01-id...',
            'Title' => '01-title...'
          },
          {
            'Id' => '02-id...',
            'Title' => '02-title...'
          }
        ];

        [download]
[reply]
[d/l]
Re: parse xml and store data in array of hashesh
by metaperl (Curate) on Jul 22, 2011 at 16:41 UTC
[reply]
Re: parse xml and store data in array of hashesh
by Jenda (Abbot) on Jul 25, 2011 at 21:39 UTC

    XML::Parser is too low-level. Have a look at XML::Rules.

    Also evaluating a hash in string context doesn't give you the contents of the hash. It returns two numbers separated by slash whose meaning is most probably the least of your worries. Pushing a hash into an array also doesn't do what you seem to think.

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

[reply]

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