How to detect whether XML elements have child elements

Question

I am using the CPAN XML::LibXML module to process the XML data below. I need to to determine whether each element has a child element or not. Searching around I can't find any example for that purpose.

<A>
    <ts>2012</ts>
    <T>M1</T>
    <T>M2</T>
    <B>
        <id>PC</id>
        <r>10</r>
        <r>30</r>
    </B>
</A>

This is the Perl code I havae written

#!/usr/bin/perl

use strict;
use warnings;

use XML::LibXML;

my ($x,$elname,$haschild)= ();
my $parser = XML::LibXML->new();
my $npo    = $parser->parse_file("test.xml");
my $rootel = $npo -> getDocumentElement();
$elname = $rootel -> nodeName();
print "Root name=$elname\n";

foreach $x ($rootel->childNodes) {
    $elname = $x -> nodeName();
    $haschild = $x->hasChildNodes;
    print "Child name = $elname and has child = $haschild.\n" unless ($elname =~ /#text/i);
}

While I used childNodes to go through each node, I just can't find an easy way to determine whether the node has a child or not.

I am expecting to get result after looping through all the nodes that:

A: Has children
ts: Has none
T: has none
T: has none
B: Has children
id: Has none
r: Has none
r: Has none

The result I am getting is like this:

Root name=A
Child name = ts and has child = 1.
Child name = T and has child = 1.
Child name = T and has child = 1.
Child name = B and has child = 1.

It seems all nodes return true after the hasChildNodes condition check.

Answer 1

What you are asking for is the number of child elements of a node. The child nodes would include text and insignificant whitespace.

The easiest way to count the number of child elements a node has is to use findnodes('*')->size as the XPath expression * counts only child elements.

Here is some code that does what you describe

use v5.14;
use warnings;

use XML::LibXML;

my $xml = XML::LibXML->load_xml(string => <<XML);
<A>
    <ts>2012</ts>
    <T>M1</T>
    <T>M2</T>
    <B>
        <id>PC</id>
        <r>10</r>
        <r>30</r>
    </B>
</A>
XML

my $nodes = $xml->findnodes('//*');
foreach my $node ($nodes->get_nodelist) {
  my $children;
  for ($node->findnodes('*')->size) {
    $children = 'none' when 0;
    $children = '1 child' when 1;
    default { $children = "$_ children" }
  }
  printf "%s: has %s\n", $node->localname, $children;
}

output

A: has 4 children
ts: has none
T: has none
T: has none
B: has 3 children
id: has none
r: has none
r: has none

Answer 2

What about the hasChildNodes method?

use XML::LibXML;
my $xml = XML::LibXML->createDocument;
$xml->setDocumentElement($xml->createElement('root'));
$xml->documentElement->addChild($xml->createElement('son'));
for my $node ($xml->documentElement,
              $xml->documentElement->firstChild) {
    print $node->hasChildNodes, "\n";
}

Prints

1
0

Keep in mind that a text node is a child node, too (i.e. node and element are different notions).