How to fetch/detect an xml node is empty

Hi All,

Using perl, v5.8.2,

I have a XML file(mytest.xml) with content like this
Some title 2 [HTML]

Some title 1
somename.pdf

Some title 2

[/HTML]
and I am pulling the data of the

nodes, so I wrote this to get the value of the pdf nodes.
use XML: Smiley Very Happy

OM;

use XML: Smiley Tongue

arser;
my $file = "/myhome/local/mytest.xml";
my $parser = new XML: Smiley Very Happy

OM:

arser;
my $doc = $parser->parsefile($file);
my $appCount = $doc->getElementsByTagName("pdf");
my $appCounter = $appCount->getLength;
for(my $i=0;$i<$appCounter;$i++){
my $pdfValue = $doc->getElementsByTagName("pdf")->item($i)->getFirstChild->getData;
print"$pdfValue\n";
}

when the value of $i is '0' , i am getting the value "somename.pdf" but when the value of $i is 1 then i get this error " Can't call method "getData" on an undefined value at test.ipl" , since the pdf node is empty. How to handle this , how to know if the node is empty . Please suggest

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Comments

Adam Stoller

[...]
my $appCount = $doc->getElementsByTagName("pdf");
my $appCounter = $appCount->getLength;
for(my $i=0;$i<$appCounter;$i++){
my $pdfValue = $doc->getElementsByTagName("pdf")->item($i)->getFirstChild->getData;
print"$pdfValue\n";
}

when the value of $i is '0' , i am getting the value "somename.pdf" but when the value of $i is 1 then i get this error " Can't call method "getData" on an undefined value at test.ipl" , since the pdf node is empty. How to handle this , how to know if the node is empty . Please suggest

The fact that you're getting an error when trying to dereference an object (twice) that you are not sure has any sub-values to be referenced should clue you in as to where you might start testing.

E.g. something like this perhaps:

... 
if ($doc->getElementsByTagName("pdf")->item($i) != null)  {
    if ($doc->getElementsByTagName("pdf")->item($i)->getFirstChild() != null) {
        my $pdfValue = $doc->getElementsByTagName("pdf")->item($i)->getFirstChild->getData;
        print"$pdfValue\n";
    }
}

Note: I'm not saying the above is the "best" way to code it - just that it would seem the obvious method to deal with your existing issue with your existing coding.

Nawin

Thanks ghoti,

yes ofcourse I did make a mistake to debug it.

Actually was testing the empty node like this

if ($doc->getElementsByTagName("pdf")->item($i)) { } Hence was struck with the error.

Thanks appreciate you inputs

Rick Poulin

if ($doc->getElementsByTagName("pdf")->item($i)) { } Hence was struck with the error.

This basically checks the length of the array of <pdf> elements, it doesn't check whether the pdf element contains a text node.

Nawin

This basically checks the length of the array of elements, it doesn't check whether the pdf element contains a text node.

I think this ,

my $appCount = $doc->getElementsByTagName("pdf");
my $appCounter = $appCount->getLength;

$appCount->getLength , get you the length of the array of elements , pls correct me if I am wrong

Rick Poulin

You know there's often more than one way to accomplish the same thing in programming, right? If you want to be pedantic about it, the ->item($i) call checks whether the i-th item is null. Given where the nodelist came from, that will only be the case if $i is outside the length of the nodelist. You're still not actually checking whether that item contains a child text node.