1Tie::Hash::Method(3)  User Contributed Perl Documentation Tie::Hash::Method(3)
2
3
4

NAME

6       Tie::Hash::Method - Tied hash with specific methods overriden by
7       callbacks
8

VERSION

10       Version 0.02
11

SYNOPSIS

13           tie my %hash, 'Tie::Hash::Method',
14               FETCH => sub {
15                   exists $_[0]->base_hash->{$_[1]} ? $_[0]->base_hash->{$_[1]} : $_[1]
16               };
17

DESCRIPTION

19       Tie::Hash::Method provides a way to create a tied hash with specific
20       overriden behaviour without having to create a new class to do it. A
21       tied hash with no methods overriden is functionally equivalent to a
22       normal hash.
23
24       Each method in a standard tie can be overriden by providing a callback
25       to the tie call. So for instance if you wanted a tied hash that changed
26       'foo' into 'bar' on store you could say:
27
28           tie my %hash, 'Tie::Hash::Method',
29               STORE => sub {
30                   (my $v=pop)=~s/foo/bar/g if defined $_[2];
31                   return $_[0]->base_hash->{$_[1]}=$v;
32               };
33
34       The callback is called with exactly the same arguments as the tie
35       itself, in particular the tied object is always passed as the first
36       argument.
37
38       The tied object is itself an array, which contains a second hash in the
39       HASH slot (index 0) which is used to perform the default operations.
40
41       The callbacks available are in a hash keyed by name in the METHOD slot
42       of the array (index 1).
43
44       If your code needs to store extra data in the object it should be
45       stored in the PRIVATE slot of the object (index 2). No future release
46       of this module will ever use or alter anything in that slot.
47
48       The arguments passed to the tie constructor will be seperated by the
49       case of their keys. The ones with all capitals will be stored in the
50       METHOD hash, and the rest will be stored in the PRIVATE hash.
51
52   CALLBACKS
53       STORE this, key, value
54           Store datum value into key for the tied hash this.
55
56       FETCH this, key
57           Retrieve the datum in key for the tied hash this.
58
59       FIRSTKEY this
60           Return the first key in the hash.
61
62       NEXTKEY this, lastkey
63           Return the next key in the hash.
64
65       EXISTS this, key
66           Verify that key exists with the tied hash this.
67
68       DELETE this, key
69           Delete the key key from the tied hash this.
70
71       CLEAR this
72           Clear all values from the tied hash this.
73
74       SCALAR this
75           Returns what evaluating the hash in scalar context yields.
76
77   Methods
78       base_hash
79           return or sets the underlying hash for this tie.
80
81               $_[0]->base_hash->{$key}= $value;
82
83       h   alias for base_hash.
84
85               $_[0]->h->{$key}= $value;
86
87       private_hash
88           Return or sets the hash of private data associated with this tie.
89           This value will never be touched by any code in this class or its
90           subclasses.  It is purely object specific.
91
92               $_[0]->p->{'something'}= 'cake!';
93
94       p   alias for private_hash
95
96       method_hash
97           return or sets the hash of methods that are overriden for this tie.
98           Exactly why you would want to use this is a little beyond my
99           imagination, but for those who can think of a reason here is a nice
100           way to do it. :-)
101
102       methods
103           Returns a list of methods that are overriden for this tie. Why this
104           would be useful escapes me, but here it is anyway for Completeness
105           sake, whoever she is, but people are always coding for her so I
106           might as well too.
107
108   Exportable Subs
109       The following subs are exportable on request:
110
111       hash_overload(PAIRS)
112           Returns a reference to a hash tied with the specified callbacks
113           overriden. Just a short cut.
114
115       HASH
116           Constant subroutine equivalent to 0
117
118       METHOD
119           Constant subroutine equivalent to 1
120
121       PRIVATE
122           Constant subroutine equivalent to 2
123

AUTHOR

125       Yves Orton, "<yves at cpan.org>"
126

BUGS

128       Please report any bugs or feature requests to "bug-tie-hash-method at
129       rt.cpan.org", or through the web interface at
130       <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Tie-Hash-Method>.  I
131       will be notified, and then you'll automatically be notified of progress
132       on your bug as I make changes.
133

SUPPORT

135       You can find documentation for this module with the perldoc command.
136
137           perldoc Tie::Hash::Method
138
139       You can also look for information at:
140
141       •   RT: CPAN's request tracker
142
143           <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Tie-Hash-Method>
144
145       •   AnnoCPAN: Annotated CPAN documentation
146
147           <http://annocpan.org/dist/Tie-Hash-Method>
148
149       •   CPAN Ratings
150
151           <http://cpanratings.perl.org/d/Tie-Hash-Method>
152
153       •   Search CPAN
154
155           <http://search.cpan.org/dist/Tie-Hash-Method>
156

ACKNOWLEDGEMENTS

159       Copyright 2008 Yves Orton, all rights reserved.
160
161       This program is free software; you can redistribute it and/or modify it
162       under the same terms as Perl itself.
163
164
165
166perl v5.36.0                      2023-01-20              Tie::Hash::Method(3)



        

    


            
        

        

            Impressum