Hash::Flatten(3pm)					User Contributed Perl Documentation					Hash::Flatten(3pm)

NAME

       Hash::Flatten - flatten/unflatten complex data hashes

SYNOPSIS

	       # Exported functions
	       use Hash::Flatten qw(:all);
	       $flat_hash = flatten($nested_hash);
	       $nested_hash = unflatten($flat_hash);

	       # OO interface
	       my $o = new Hash::Flatten({
		       HashDelimiter => '->',
		       ArrayDelimiter => '=>',
		       OnRefScalar => 'warn',
	       });
	       $flat_hash = $o->flatten($nested_hash);
	       $nested_hash = $o->unflatten($flat_hash);

DESCRIPTION

       Converts back and forth between a nested hash structure and a flat hash of delimited key-value pairs.  Useful for protocols that only
       support key-value pairs (such as CGI and DBMs).

   Functional interface
       $flat_hash = flatten($nested_hash, \%options)
	   Reduces a nested data-structure to key-value form.  The top-level container must be hashref.  For example:

		   $nested = {
			   'x' => 1,
			   'y' => {
				   'a' => 2,
				   'b' => 3
			   },
			   'z' => [
				   'a', 'b', 'c'
			   ]
		   }

		   $flat = flatten($nested);
		   use Data::Dumper;
		   print Dumper($flat);

		   $VAR1 = {
			   'y.a' => 2,
			   'x' => 1,
			   'y.b' => 3,
			   'z:0' => 'a',
			   'z:1' => 'b',
			   'z:2' => 'c'
		   };

	   The "\%options" hashref can be used to override the default behaviour (see "OPTIONS").

       $nested_hash = unflatten($flat_hash, \%options)
	   The unflatten() routine takes the flattened hash and returns the original nested hash (see "CAVEATS" though).

   OO interface
       $o = new Hash::Flatten(\%options)
	   Options can be squirreled away in an object (see "OPTIONS")

       $flat = $o->flatten($nested)
	   Flatten the structure using the options stored in the object.

       $nested = $o->unflatten($flat)
	   Unflatten the structure using the options stored in the object.

OPTIONS

       HashDelimiter and ArrayDelimiter
	   By default, hash dereferences are denoted by a dot, and array dereferences are denoted by a colon. However you may change these
	   characters to any string you want, because you don't want there to be any confusion as to which part of a string is the 'key' and which
	   is the 'delimiter'. You may use multicharacter strings if you prefer.

       OnRefScalar and OnRefRef and OnRefGlob
	   Behaviour if a reference of this type is encountered during flattening.  Possible values are 'die', 'warn' (default behaviour but
	   warns) or a coderef which is passed the reference and should return the flattened value.

	   By default references to references, and references to scalars, are followed silently.

       EscapeSequence
	   This is the character or sequence of characters that will be used to escape the hash and array delimiters.  The default escape sequence
	   is '\'. The escaping strategy is to place the escape sequence in front of delimiter sequences; the escape sequence itself is escaped
	   by replacing it with two instances.

       DisableEscapes
	   Stop the escaping from happening.  No escape sequences will be added to flattened output, nor interpreted on the way back.

	   WARNING: If your structure has keys that contain the delimiter characters, it will not be possible to unflatten the structure
	   correctly.

CAVEATS

       Any blessings will be discarded during flattening, so that if you flatten an object you must re-bless() it on unflattening.

       Note that there is no delimiter for scalar references, or references to references.  If your structure to be flattened contains scalar, or
       reference, references these will be followed by default, i.e.  "'foo' => \\\$foo" will be collapsed to "'foo' => $foo".  You can
       override this behaviour using the OnRefScalar and OnRefRef constructor option.

       Recursive structures are detected and cause a fatal error.

SEE ALSO

       The perlmonks site has a helpful introduction to when and why you might want to flatten a hash:
       http://www.perlmonks.org/index.pl?node_id=234186

       CGI::Expand
	   Unflattens hashes using "." as a delimiter, similar to Template::Toolkit's behaviour.

       Tie::MultiDim
	   This provides a tie interface to unflattening a data structure if you specify a "template" for the structure of the data.

       MLDBM
	   This also provides a tie interface but reduces a nested structure to key-value form by serialising the values below the top level.

VERSION

       $Id: Flatten.pm,v 1.19 2009/05/09 12:42:02 jamiel Exp $

AUTHOR

       John Alden & P Kent <cpan _at_ bbc _dot_ co _dot_ uk>

COPYRIGHT

       (c) BBC 2005. This program is free software; you can redistribute it and/or modify it under the GNU GPL.

       See the file COPYING in this distribution, or http://www.gnu.org/licenses/gpl.txt

perl v5.10.1							    2010-09-24							Hash::Flatten(3pm)