Tie::Hash::Vivify - Create hashes that autovivify in interesting ways.
This module implements a hash where if you read a key that doesn't exist, it will call a code reference to fill that slot with a value.
use Tie::Hash::Vivify; my $default = 0; tie my %hash => 'Tie::Hash::Vivify', sub { "default" . $default++ }; print $hash{foo}; # default0 print $hash{bar}; # default1 print $hash{foo}; # default0 $hash{baz} = "hello"; print $hash{baz}; # hello my $hashref = Tie::Hash::Vivify->new(sub { "default" }); $hashref->{foo}; # default # ...
You can also create your magic hash in an objecty way:
my $hashref = Tie::Hash::Vivify->new(sub { "my default" });
By default, hashes contained within your hash do *not* inherit magical vivification behaviour. If you want them to, then pass some extra params thus:
tie my %hash => 'Tie::Hash::Vivify', sub { "default" . $default++ }, infect_children => 1; my $hashref = Tie::Hash::Vivify->new(sub { "my default" }, infect_children => 1);
This will not, however, work if the child you insert is already tied - that would require re-tieing it, which would lose whatever magic behaviour the original had.
scalar(%tied_hash) appears to not work properly on perl 5.8.2 and earlier. I don't really care, and frankly nor should you. In the unlikely event that you do care, please submit a patch.
scalar(%tied_hash)
Luke Palmer, lrpalmer gmail com (original author)
David Cantrell <david@cantrell.org.uk> (current maintainer)
Copyright (C) 2005 by Luke Palmer
Some parts Copyright 2010 David Cantrell <david@cantrell.org.uk>.
This software is free-as-in-speech software, and may be used, distributed, and modified under the terms of either the GNU General Public Licence version 2 or the Artistic Licence. It's up to you which one you use. The full text of the licences can be found in the files GPL2.txt and ARTISTIC.txt, respectively.
To install Tie::Hash::Vivify, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Tie::Hash::Vivify
CPAN shell
perl -MCPAN -e shell install Tie::Hash::Vivify
For more information on module installation, please visit the detailed CPAN module installation guide.