in reply to perl & XML: getting last child?

Thanks for the help on the last child... Related question for situations where there is no value in the node but i need to return a "0" to maintain the appropriate output file structure. Modifying the original files slightly below: 
 
xml

<library>
    <cd>
        <artist></artist>
    </cd>
    <book>
      <title>Perl Best Practices</title>
      <author>Damian Conway</author>
      <isbn>0596001738</isbn>
      <pages>542</pages>
      <image src="http://www.oreilly.com/catalog/covers/perlbp.s.gif"
             width="145" height="190" />
    </book>
    <book>
      <title>Perl Cookbook, Second Edition</title>
      <author>Tom Christiansen</author>
      <author>Nathan Torkington</author>
      <isbn>0596003137</isbn>
      <pages>964</pages>
      <image src="http://www.oreilly.com/catalog/covers/perlckbk2.s.gi
+f"
             width="145" height="190" />
    </book>
    <book>
      <title>Guitar</title>
      <author>Mark Phillips</author>
      <author>John Chappell</author>
      <isbn>076455106X</isbn>
      <pages>392</pages>
      <image src="http://media.wiley.com/product_data/coverImage/6X/07
+645510/076455106X.jpg"
             width="100" height="125" />
    </book>
  </library>

[download]
Incorporating some of the previous suggestions, new code looks like this. Problem arises when <artist> is null (or there is no entry). 
 
#!/usr/bin/perl -w

  use strict;
  use warnings;

  my $filename = 'library1.xml';
  
  use XML::LibXML;

  my $parser = XML::LibXML->new();
  my $doc    = $parser->parse_file($filename);




    print $_->data . " | " foreach ($doc->findnodes('/library/cd/artis
+t/text()'));

    my @nodes = $doc->findnodes('/library/book[last()]'); 
    foreach my $node (@nodes) {
    print $node->findvalue( 'title')." | \n";
    
    
}

[download]

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Re^2: perl & XML: getting last child?
by Lotus1 (Vicar) on Apr 19, 2013 at 01:27 UTC

    You can test what is returned from the text node. There is an xpath expression to do this also but I usually just test it like this. (untested code)

    foreach ($doc->findnodes('/library/cd/artist/text()'){
   my $artist = $_->data;
   if ($artist){
      print "$artist | ";
   }
   else {
      print "0 | ";
   }
}

    [download]

    If the artist was formerly called Prince I'm not sure whether Perl will evaluate that symbol to true or false, (or male or female)... it's a little confusing.

    Update: The above won't work since findnodes() will only return the nodes that have text. I often have the situation where I need to add text to empty text nodes. Here is something closer.

    foreach ($doc->findnodes('/library/cd/artist')){   #update: added ')'
   my $artist = $_->to_literal;
   if ($artist){
      print "$artist | ";
      #to change the text use my $textnode=$_->findnodes('./text()')
      # then use $textnode->setData('new text');
   }
   else {
      print "0 | ";
      # you can use $_->appendTextNode('text to add') here
   }
}

    [download]

    Another option is to loop through seperately the nodes with no text using the not() funtion of xpath.

    foreach ($doc->findnodes('/library/cd/artist[not(text())]'){
[reply]
[d/l]
[select]
      I cannot get your code to work. Any ideas? thanks
[reply]

        Typically I look at the warnings and errors and fix any problems until the code will run. Then I look at the output to see if I'm getting the expected results and make changes and read the documentation for any modules or functions that aren't working like I expect. I also put in extra print statements to test my assumptions of how the code should work.

        The code I posted has a missing parenthesis but otherwise does what you requested. The second warning message points you to the exact line where this occurs.

        syntax error at C:\b\perlmonks\xml\1029217.pl line __, near "){"
[reply]
[d/l]

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