1Hash::WithDefaults(3) User Contributed Perl DocumentationHash::WithDefaults(3)
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NAME

6       Hash::WithDefaults
7
8        - class for hashes with key-casing requirements supporting defaults
9
10       version 0.05
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SYNOPSIS

13         use Hash::WithDefaults;
14
15         %main = ( ... );
16         tie %h1, 'Hash::WithDefaults', {...};
17         tied(%h1)->AddDefault(\%main);
18         tie %h2, 'Hash::WithDefaults', [...];
19         tied(%h2)->AddDefault(\%main);
20
21         # now if you use $h1{$key}, the value is looked up first
22         # in %h1, then in %main.
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DESCRIPTION

25       This module implements hashes that support "defaults". That is you may
26       specify several more hashes in which the data will be looked up in case
27       it is not found in the current hash.
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29   Object creation
30               tie %hash, 'Hash::WithDefault', [$case_option], [\%values];
31               tie %hash, 'Hash::WithDefault', [$case_option], [\@values];
32               tie %hash, 'Hash::WithDefault', [$case_option], [%values];
33
34       The optional $case_option may be one of these values:
35
36         Sensitive     - the hash will be case sensitive
37         Tolower       - the hash will be case sensitive, all keys are made lowercase
38         Toupper       - the hash will be case sensitive, all keys are made uppercase
39         Preserve      - the hash will be case insensitive, the case is preserved
40         Lower - the hash will be case insensitive, all keys are made lowercase
41         Upper - the hash will be case insensitive, all keys are made uppercase
42
43       If you pass a hash or array reference or an even list of keys and
44       values to the tie() function, those keys and values will be COPIED to
45       the resulting magical hash!
46
47       After you tie() the hash, you use it just like any other hash.
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49   Functions
50       AddDefault
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52               tied(%hash)->AddDefault(\%defaults);
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54       This instructs the object to include the %defaults in the search for
55       values.  After this the value will be looked up first in %hash itself
56       and then in %defaults.
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58       You may keep modifying the %defaults and your changes WILL be visible
59       through %hash!
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61       You may add as many defaults to one Hash::WithDefaults object as you
62       like, they will be searched in the order you add them.
63
64       If you delete a key from the tied hash, it's only deleted from the list
65       of specific keys, the defaults are never modified through the tied
66       hash. This means that you may get a default value for a key after you
67       deletethe key from the tied hash!
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69       GetDefaults
70
71               $defaults = tied(%hash)->GetDefaults();
72               push @$defaults, \%another_default;
73
74       Returns a reference to the array that stores the defaults.  You may
75       delete or insert hash references into the array, but make sure you
76       NEVER EVER insert anything else than a hash reference into the array!
77
78   Config::IniHash example
79         use Config::IniHash;
80         $config = ReadIni $inifile, withdefaults => 1, case => 'preserve';
81
82         if (exists $config->{':default'}) {
83           my $default = $config->{':default'};
84           foreach my $section (keys %$config) {
85             next if $section =~ /^:/;
86                 tied(%{$config->{$section}})->AddDefault($default)
87           }
88         }
89
90       And now all normal sections will get the default values from [:default]
91       section ;-)
92

AUTHOR

94       Jan Krynicky <Jenda@Krynicky.cz> http://Jenda.Krynicky.cz
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97       Copyright (c) 2002-2009 Jan Krynicky <Jenda@Krynicky.cz>. All rights
98       reserved.
99
100       This program is free software; you can redistribute it and/or modify it
101       under the same terms as Perl itself.
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105perl v5.38.0                      2023-07-20             Hash::WithDefaults(3)
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