How can I access attributes and elements from XML::LibXML in Perl? - perl

Question

I am having trouble understanding / using name spaces with XML::LibXML package in Perl. I can access an element successfully but not an attribute. I have the following code which accesses an XML file (http://pastebin.com/f3fb9d1d0).
my $tree = $parser->parse_file($file); # parses the file contents into the new libXML object.
my $xpc = XML::LibXML::XPathContext->new($tree);
$xpc->registerNs(microplateML => 'http://moleculardevices.com/microplateML');
I then try and access an element called common-name and an attribute called name.
foreach my $camelid ($xpc->findnodes('//microplateML:species')) {
my $latin_name = $camelid->findvalue('#name');
my $common_name = $camelid->findvalue('common-name');
print "$latin_name, $common_name" ;
}
But only the latin-name (#name) is printing out, the common-name is not. What am I doing wrong and how can I get the common-name to print out as well?
What does the #name do in this case? I presume it is an array, and that attributes should be put into an array as there can be more than one, but elements (like common-name) should not be because there should just be one?
I've been following the examples here: http://www.xml.com/pub/a/2001/11/14/xml-libxml.html
and here: http://perl-xml.sourceforge.net/faq/#namespaces_xpath, and trying to get their example camel script working with my namespace, hence the weird namespace.

Answer 1

Make sure you XML file is valid then use $node->getAttribute("someAttribute") to access attributes.
#name is a attribute name. You'd use it in findnodes() to specify elements with a given attribute set. Eg. a path like:
//camelids/species[#name="Camelus bactrianus"]/
Here is a simple/contrived example:
#!/usr/bin/perl -w
use XML::LibXML;
my $parser = XML::LibXML->new();
my $doc = $parser->parse_file('/Users/castle/Desktop/animal.xml');
my $xc = XML::LibXML::XPathContext->new( $doc->documentElement() );
$xc->registerNs('ns', 'http://moleculardevices.com/microplateML');
my #n = $xc->findnodes('//ns:species');
foreach $nod (#n) {
print "A: ".$nod->getAttribute("name")."\n";
my #c = $xc->findnodes("./ns:common-name", $nod);
foreach $cod (#c) {
print "B: ".$cod->nodeName;
print " = ";
print $cod->getFirstChild()->getData()."\n";
}
}
Output is:
perl ./xmltest.pl
A: Camelus bactrianus
B: common-name = Bactrian Camel