"forcearray" - Forcing Element Contents as Arrays

Perl Tutorials - Herong's Tutorial Examples

Dr. Herong Yang, Version 5.10

Perl Tutorials - Herong's Tutorial Examples

∟XML::Simple Module - XML Parser and Generator

∟"forcearray" - Forcing Element Contents as Arrays

This section provides a tutorial example on how to use the 'forcearray' option to parse XML element contents as arrays instead of hashes.

The "forcearray" applies to the XMLin() method to force the contents of all elements to be parsed as arrays instead of hashes.

The following program shows you how to use the "forcearray" option and other options like, "keeproot" and "searchpath:

#- XmlSimpleArray.pl
#- Copyright (c) 1999 by Dr. Herong Yang, http://www.herongyang.com/
#
   use XML::Simple;
   use Data::Dumper;
   my $xs = new XML::Simple(keeproot => 1,searchpath => ".");
   my $ref = $xs->XMLin("user.xml");
   my $xml = $xs->XMLout($ref);
   print "\nHash dump without 'forcearray => 1':\n";
   print Dumper($ref);
   print "\nXML output without 'forcearray => 1':\n";
   print $xml;
   my $xs = new XML::Simple(keeproot => 1,searchpath => ".",
      forcearray => 1,);
   my $ref = $xs->XMLin("user.xml");
   my $xml = $xs->XMLout($ref);
   print "\nHash dump with 'forcearray => 1':\n";
   print Dumper($ref);
   print "\nXML output with 'forcearray => 1':\n";
   print $xml;
   exit;

The input file, user.xml, has the following XML:

<?xml version="1.0"?>
<user status="active">
 <!-- This is not a real user. -->
 <first_name>Mike</first_name>
 <last_name>Lee</last_name>
</user>

Here is the output of the program:

Hash dump without 'forcearray => 1':
$VAR1 = {
          'user' => {
                      'first_name' => 'Mike',
                      'status' => 'active',
                      'last_name' => 'Lee'
                    }
        };

XML output without 'forcearray => 1':
<user first_name="Mike" status="active" last_name="Lee" />

Hash dump with 'forcearray => 1':
$VAR1 = {
          'user' => [
                      {
                        'first_name' => [
                                          'Mike'
                                        ],
                        'status' => 'active',
                        'last_name' => [
                                         'Lee'
                                       ]
                      }
                    ]
        };

XML output with 'forcearray => 1':
<user status="active">
  <first_name>Mike</first_name>
  <last_name>Lee</last_name>
</user>

A couple of the interesting things to note here:

Remember to specify the directory with "searchpath" where the XML input file is, even if it is the current directory.
The ?xml statement in the XML input was ignored.
"keeproot" keeped the root tag "user" correctly for us.
Without "forcearray => 1", child elements with only text contents were parsed as hash entries of keys and values, where the values are the text contents. But the attribute of the parent element was also parsed as a hash entry. So those child elements and the attribute can not be distinguished once parsed into the hash structure.
If you want to maintain the difference between attributes and child elements with only text contents, you should use the "forcearray => 1" option.
The order of hash entries did not match the order of elements in the XML input.

Table of Contents

About This Book

Perl on Linux Systems

ActivePerl on Windows Systems

Data Types: Values and Variables

Expressions, Operations and Simple Statements

User Defined Subroutines

Perl Built-in Debugger

Name Spaces and Perl Module Files

Symbolic (or Soft) References

Hard References - Addresses of Memory Objects

Objects (or References) and Classes (or Packages)