SYNOPSIS
use Hash::WithDefaults;
%main = ( ... );
tie %h1, 'Hash::WithDefaults', {...};
tied(%h1)->AddDefault(\%main);
tie %h2, 'Hash::WithDefaults', [...];
tied(%h2)->AddDefault(\%main);
# now if you use $h1{$key}, the value is looked up first
# in %h1, then in %main.
DESCRIPTION
This module implements hashes that support ``defaults''. That is you may specify several more hashes in which the data will be looked up in case it is not found in the current hash.Object creation
tie %hash, 'Hash::WithDefault', [$case_option], [\%values];
tie %hash, 'Hash::WithDefault', [$case_option], [\@values];
tie %hash, 'Hash::WithDefault', [$case_option], [%values];
The optional $case_option may be one of these values:
Sensitive - the hash will be case sensitive Tolower - the hash will be case sensitive, all keys are made lowercase Toupper - the hash will be case sensitive, all keys are made uppercase Preserve - the hash will be case insensitive, the case is preserved Lower - the hash will be case insensitive, all keys are made lowercase Upper - the hash will be case insensitive, all keys are made uppercase
If you pass a hash or array reference or an even list of keys and values to the tie() function, those keys and values will be COPIED to the resulting magical hash!
After you tie() the hash, you use it just like any other hash.
Functions
AddDefault
tied(%hash)->AddDefault(\%defaults);
This instructs the object to include the %defaults in the search for values. After this the value will be looked up first in %hash itself and then in %defaults.
You may keep modifying the %defaults and your changes WILL be visible through %hash!
You may add as many defaults to one Hash::WithDefaults object as you like, they will be searched in the order you add them.
If you delete a key from the tied hash, it's only deleted from the list of specific keys, the defaults are never modified through the tied hash. This means that you may get a default value for a key after you deletethe key from the tied hash!
GetDefaults
$defaults = tied(%hash)->GetDefaults();
push @$defaults, \%another_default;
Returns a reference to the array that stores the defaults. You may delete or insert hash references into the array, but make sure you NEVER EVER insert anything else than a hash reference into the array!
Config::IniHash example
use Config::IniHash;
$config = ReadIni $inifile, withdefaults => 1, case => 'preserve';
if (exists $config->{':default'}) {
my $default = $config->{':default'};
foreach my $section (keys %$config) {
next if $section =~ /^:/;
tied(%{$config->{$section}})->AddDefault($default)
}
}
And now all normal sections will get the default values from [:default] section ;-)
COPYRIGHT
Copyright (c) 2002-2009 Jan Krynicky <[email protected]>. All rights reserved.This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.