xml - empty node

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

I am trying to retrieve data from various nodes in an xml file. Unfortunately, there are times when the nodes have no values so i am trying to format the data to return a "0" or some character so that the output is consistent with files that do have values or text. thanks


#!/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()'));

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

XML file below - alternatives would be if artist "adele" were blank for example.


<library>
    <cd>
        <artist>adele</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]

Comment on xml - empty node Select or Download Code

Replies are listed 'Best First'.
Re: xml - empty node by Lotus1 (Vicar) on Apr 24, 2013 at 14:48 UTC
I already answered this question at your other thread. This node is basically a repost with a broken version of the code I provided. But you didn't give me a chance to respond to the original post. Why did you remove the parentheses in the if block? The anonymous poster already pointed out the error. Some basic perl tutorials will help you with syntax. When you post questions like these you need to tell us what warnings and errors you get and where you are stuck. Telling us that something doesn't work just means you expect us to do everything to debug "your" code. You don't need both the `-w` after perl and `use warnings;` Why not test your code with several cd/artists in the xml file, some empty and some with values?	[reply] [d/l] [select]
Re: xml - empty node by Anonymous Monk on Apr 24, 2013 at 14:09 UTC
read perlintro and length if( length $foo ){ print 1 } else { print 2 }	[reply]
Re^2: xml - empty node by Lotus1 (Vicar) on Apr 24, 2013 at 14:50 UTC
length() isn't needed here since $foo is the result of `$_->to_literal` which returns either a string an empty string.	[reply] [d/l]
Re^3: xml - empty node by Anonymous Monk on Apr 24, 2013 at 14:59 UTC
length() isn't needed here sure it is, it clarifies intent	[reply]
Re^4: xml - empty node by Lotus1 (Vicar) on Apr 24, 2013 at 15:36 UTC