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

Hi to all, I'm wondering if it's possible to use dynamic paths to element in xml document. Now I'm using XML::Simple and I want to do something like this:

use XML::Simple;
my $fh = IO::File->new('/root/regions.xml');
my $data = XML::Simple::XMLin($fh);
$data->{root}->{configs}->$VAR->{region_prefix}

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Or is there some other way, or workaround that will not require to rewrite whole script for for this?

Thanks in advance.

Replies are listed 'Best First'.
Re: Perl XML "dynamic paths "?
by daxim (Curate) on Aug 16, 2012 at 14:03 UTC
    What you wrote already works, you just need to correct the syntax: 
    $data->{root}->{configs}->{$VAR}->{region_prefix}

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    Better style: 
    $data->{root}{configs}{$VAR}{region_prefix}

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    PS: Future-proof your program by enabling strict mode. This ensures you get the same data structure even when the number of elements change.
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      Thanks to you too, it helped.
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Re: Perl XML "dynamic paths "?
by Corion (Patriarch) on Aug 16, 2012 at 13:54 UTC
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      Sorry for the late answer. This is example of my config, a node number is the $VAR, in my case. I may need to use config options from <node3> or <nodeN>, that's why I need some sort of variable I guess. 
      <?xml version='1.0'?>
<regions>
  <node3>
    <instance_num>0</instance_num>
    <common_db_template>165.sql</common_db_template>
    <lib_db_template>165b.sql</lib_db_template>
    <region>node3</region>
    <region_db_host>192.168.38.1</region_db_host>
    <region_db_port>3306</region_db_port>
    <region_name>node3.test.com</region_name>
    <region_prefix>Nd3_</region_prefix>
  </node3>
  <node4>
    <instance_num>0</instance_num>
    <common_db_template>165.sql</common_db_template>
    <lib_db_template>165b.sql</lib_db_template>
    <region>node4</region>
    <region_db_host>192.168.22.1</region_db_host>
    <region_db_port>3308</region_db_port>
    <region_name>node4.test.com</region_name>
    <region_prefix>Nd4_</region_prefix>
  </node4>
  <node5>
    <instance_num>0</instance_num>
    <common_db_template>165.sql</common_db_template>
    <lib_db_template>165b.sql</lib_db_template>
    <region>node5</region>
    <region_db_host>192.168.1.1</region_db_host>
    <region_db_port>3306</region_db_port>
    <region_name>node5.test.com</region_name>
    <region_prefix>Nd5_</region_prefix>
  </node5>
</regions>

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        If all you need is one specific element of your path to change, then using ->{$VAR}-> already is enough. See Data::Dumper for getting output of a Perl data structure, and References Quick Reference for how to use references. References are what XML::Simple returns.

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