parsing complex xml structure with xml::simple

bfdi533 has asked for the wisdom of the Perl Monks concerning the following question:

I have an xml input file that I need to parse and the structure is pretty complex. I have been working my way through the structure fairly well but have run into a situation that I do not know how to handle. I am using code to dereference parts of the xml structure to more easily deal with them.

One part is throwing me though. I have a set that is a Row(s) of Detail info that can either contain a hash or an array of hashes. I had been dealing with this as an array of hashes but when it gets to a single hash rather than an array the code crashes with an "Not an ARRAY reference at ..." error.

Here is the code:

if ($checks->{Detail}) {
    foreach my $detail (@{$checks->{Detail}->{Row}}) {
        foreach my $col (@{$detail->{Col}}) {
            print "$col \n";
        }
    }
}
[download]

And here is a piece of the data:

        <Check>
                <Detail>
                        <Head>
                                <Col>User</Col>
                                <Col>Weak Password</Col>
                                <Col>Locked Out</Col>
                                <Col>Disabled</Col>
                        </Head>
                        <Row Grade="0">
                                <Col>Guest</Col>
                                <Col>Weak</Col>
                                <Col>-</Col>
                                <Col>Disabled</Col>
                        </Row>
                        <Row Grade="0">
                                <Col>SUPPORT_388945a0</Col>
                                <Col>-</Col>
                                <Col>-</Col>
                                <Col>Disabled</Col>
                        </Row>
                        <Row Grade="5">
                                <Col>Administrator</Col>
                                <Col>-</Col>
                                <Col>-</Col>
                                <Col>-</Col>
                        </Row>
                </Detail>
        </Check>
        <Check>
                <Detail>
                        <Head>
                                <Col>Drive Letter</Col>
                                <Col>File System</Col>
                        </Head>
                        <Row Grade="5">
                                <Col>C:</Col>
                                <Col>NTFS</Col>
                        </Row>
                </Detail>
        </Check>
[download]

How can I go about handling the multiple rows versus the single row situation with efficient code?

Is there a way to check to see if a variable is an array a has and execute an if/then/else code segment?

Comment on parsing complex xml structure with xml::simple Select or Download Code

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Re: parsing complex xml structure with xml::simple by davorg (Chancellor) on Aug 01, 2006 at 14:25 UTC
You can use ref to find out what kind of reference a scalar holds. But I strongly suspect that what you really need here is XML::Simple's ForceArray option. -- <http://dave.org.uk> "The first rule of Perl club is you do not talk about Perl club." -- Chip Salzenberg	[reply]
Re: parsing complex xml structure with xml::simple by ptum (Priest) on Aug 01, 2006 at 14:26 UTC
Happily, there is: ref will help you to identify an array reference. You could do something like this: `if (ref($detail->{Col}) eq 'ARRAY') { # do something } else { # do something else }` [download] Update: Hmmph. I get up at 4:40 am and davorg still beat me to this answer, darn those timezone-advantaged monks! Plus, his answer is better. That ForceArray solution looks cool. No good deed goes unpunished. -- (attributed to) Oscar Wilde	[reply] [d/l]
Re^2: parsing complex xml structure with xml::simple by bfdi533 (Friar) on Aug 01, 2006 at 15:06 UTC
This is a good solution. I know that for the most part that most of the items will NOT be contained in arrays so for the ones that I know about, this seems like just the ticket! Thanks!	[reply]
Re: parsing complex xml structure with xml::simple by GrandFather (Saint) on Aug 01, 2006 at 18:50 UTC
You may find XML::TreeBuilder easier to deal with than XML::Simple for non-trivial XML: `use strict; use warnings; use XML::TreeBuilder; my $xmlStr = <<'STR';` [download] Read more... OP's data (2 kB) `STR my $tree = XML::TreeBuilder->new; $tree->parse ($xmlStr); for ($tree->find ('Detail')) { for ($_->find ('Row')) { print "Col: " . $_->as_text () . "\n" for ($_->find ('Col')); } }` [download] Prints: `Col: Guest Col: Weak Col: - Col: Disabled Col: SUPPORT_388945a0 Col: - Col: - Col: Disabled Col: Administrator Col: - Col: - Col: - Col: C: Col: NTFS` [download] DWIM is Perl's answer to Gödel	[reply] [d/l] [select]
Re: parsing complex xml structure with xml::simple by planetscape (Chancellor) on Aug 02, 2006 at 18:04 UTC
I totally agree with davorg's assessment that what you probably want is ForceArray => 1. I've noted several other potentially useful options here. However, I would also like to point out that XML::Twig has much to recommend it, including a mode that behaves almost exactly as XML::Simple, but also extensive documents and tutorials. XML::Twig also handles stuff that XML::Simple simply can't. HTH, planetscape	[reply]