tie::refhash(3pm) [osx man page]

Tie::RefHash(3pm)					 Perl Programmers Reference Guide					 Tie::RefHash(3pm)

NAME

       Tie::RefHash - use references as hash keys

SYNOPSIS

	   require 5.004;
	   use Tie::RefHash;
	   tie HASHVARIABLE, 'Tie::RefHash', LIST;
	   tie HASHVARIABLE, 'Tie::RefHash::Nestable', LIST;

	   untie HASHVARIABLE;

DESCRIPTION

       This module provides the ability to use references as hash keys if you first "tie" the hash variable to this module.  Normally, only the
       keys of the tied hash itself are preserved as references; to use references as keys in hashes-of-hashes, use Tie::RefHash::Nestable,
       included as part of Tie::RefHash.

       It is implemented using the standard perl TIEHASH interface.  Please see the "tie" entry in perlfunc(1) and perltie(1) for more
       information.

       The Nestable version works by looking for hash references being stored and converting them to tied hashes so that they too can have
       references as keys.  This will happen without warning whenever you store a reference to one of your own hashes in the tied hash.

EXAMPLE

	   use Tie::RefHash;
	   tie %h, 'Tie::RefHash';
	   $a = [];
	   $b = {};
	   $c = *main;
	   $d = "gunk";
	   $e = sub { 'foo' };
	   %h = ($a => 1, $b => 2, $c => 3, $d => 4, $e => 5);
	   $a->[0] = 'foo';
	   $b->{foo} = 'bar';
	   for (keys %h) {
	      print ref($_), "
";
	   }

	   tie %h, 'Tie::RefHash::Nestable';
	   $h{$a}->{$b} = 1;
	   for (keys %h, keys %{$h{$a}}) {
	      print ref($_), "
";
	   }

THREAD SUPPORT

       Tie::RefHash fully supports threading using the "CLONE" method.

STORABLE SUPPORT

       Storable hooks are provided for semantically correct serialization and cloning of tied refhashes.

RELIC SUPPORT

       This version of Tie::RefHash seems to no longer work with 5.004. This has not been throughly investigated. Patches welcome ;-)

LICENSE

       This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself

MAINTAINER

       Yuval Kogman <nothingmuch@woobling.org>

AUTHOR

       Gurusamy Sarathy        gsar@activestate.com

       'Nestable' by Ed Avis   ed@membled.com

SEE ALSO

       perl(1), perlfunc(1), perltie(1)

perl v5.16.2							    2012-10-11							 Tie::RefHash(3pm)

Tie::RefHash::Weak(3pm) 				User Contributed Perl Documentation				   Tie::RefHash::Weak(3pm)

NAME

       Tie::RefHash::Weak - A Tie::RefHash subclass with weakened references in the keys.

SYNOPSIS

	       use Tie::RefHash::Weak;
	       tie my %h, 'Tie::RefHash::Weak';

	       # OR:

	       use Tie::RefHash::Weak 'fieldhash';
	       fieldhash my %h;

	       { # new scope
		       my $val = "foo";

		       $h{$val} = "bar"; # key is weak ref

		       print join(", ", keys %h); # contains $val, returns regular reference
	       }
	       # $val goes out of scope, refcount goes to zero
	       # weak references to $val are now undefined

	       keys %h; # no longer contains $val

	       # see also Tie::RefHash

DESCRIPTION

       The Tie::RefHash module can be used to access hashes by reference. This is useful when you index by object, for example.

       The problem with Tie::RefHash, and cross indexing, is that sometimes the index should not contain strong references to the objecs.
       Tie::RefHash's internal structures contain strong references to the key, and provide no convenient means to make those references weak.

       This subclass of Tie::RefHash has weak keys, instead of strong ones. The values are left unaltered, and you'll have to make sure there are
       no strong references there yourself.

FUNCTIONS

       For compatibility with Hash::Util::FieldHash, this module will, upon request, export the following two functions. You may also write "use
       Tie::RefHash::Weak ':all'".

       fieldhash %hash
	   This ties the hash and returns a reference to it.

       fieldhashes \%hash1, \%hash2 ...
	   This ties each hash that is passed to it as a reference. It returns the list of references in list context, or the number of hashes in
	   scalar context.

THREAD SAFETY

       Tie::RefHash version 1.32 and above have correct handling of threads (with respect to changing reference addresses). If your module
       requires Tie::RefHash::Weak to be thread aware you need to depend on both Tie::RefHash::Weak and Tie::RefHash version 1.32 (or later).

       Version 0.02 and later of Tie::RefHash::Weak depend on a thread-safe version of Tie::RefHash anyway, so if you are using the latest version
       this should already be taken care of for you.

5.10.0 COMPATIBILITY
       Due to a minor change in Perl 5.10.0 a bug in the handling of magic freeing was uncovered causing segmentation faults.

       This has been patched but not released yet, as of 0.08.

CAVEAT

       You can use an LVALUE reference (such as "substr ...") as a hash key, but due to a bug in perl (see
       <http://rt.perl.org/rt3/Public/Bug/Display.html?id=46943>) it might not be possible to weaken a reference to it, in which case the hash
       element will never be deleted automatically.

AUTHORS

       Yuval Kogman <nothingmuch@woobling.org>

       some maintenance by Hans Dieter Pearcey <hdp@pobox.com>

COPYRIGHT &; LICENSE
	       Copyright (c) 2004 Yuval Kogman. All rights reserved
	       This program is free software; you can redistribute
	       it and/or modify it under the same terms as Perl itself.

SEE ALSO

       Tie::RefHash, Class::DBI (the live object cache), "Perl_magic_killbackrefs" in mg.c

perl v5.10.1							    2008-10-18						   Tie::RefHash::Weak(3pm)