1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
|
.\" -*- mode: troff; coding: utf-8 -*-
.\" Automatically generated by Pod::Man 5.01 (Pod::Simple 3.43)
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>.
.ie n \{\
. ds C` ""
. ds C' ""
'br\}
.el\{\
. ds C`
. ds C'
'br\}
.\"
.\" Escape single quotes in literal strings from groff's Unicode transform.
.ie \n(.g .ds Aq \(aq
.el .ds Aq '
.\"
.\" If the F register is >0, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
.\" entries marked with X<> in POD. Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.\"
.\" Avoid warning from groff about undefined register 'F'.
.de IX
..
.nr rF 0
.if \n(.g .if rF .nr rF 1
.if (\n(rF:(\n(.g==0)) \{\
. if \nF \{\
. de IX
. tm Index:\\$1\t\\n%\t"\\$2"
..
. if !\nF==2 \{\
. nr % 0
. nr F 2
. \}
. \}
.\}
.rr rF
.\" ========================================================================
.\"
.IX Title "Tie::Scalar 3perl"
.TH Tie::Scalar 3perl 2024-05-30 "perl v5.38.2" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
Tie::Scalar, Tie::StdScalar \- base class definitions for tied scalars
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 2
\& package NewScalar;
\& require Tie::Scalar;
\&
\& @ISA = qw(Tie::Scalar);
\&
\& sub FETCH { ... } # Provide a needed method
\& sub TIESCALAR { ... } # Overrides inherited method
\&
\&
\& package NewStdScalar;
\& require Tie::Scalar;
\&
\& @ISA = qw(Tie::StdScalar);
\&
\& # All methods provided by default, so define
\& # only what needs be overridden
\& sub FETCH { ... }
\&
\&
\& package main;
\&
\& tie $new_scalar, \*(AqNewScalar\*(Aq;
\& tie $new_std_scalar, \*(AqNewStdScalar\*(Aq;
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This module provides some skeletal methods for scalar-tying classes. See
perltie for a list of the functions required in tying a scalar to a
package. The basic \fBTie::Scalar\fR package provides a \f(CW\*(C`new\*(C'\fR method, as well
as methods \f(CW\*(C`TIESCALAR\*(C'\fR, \f(CW\*(C`FETCH\*(C'\fR and \f(CW\*(C`STORE\*(C'\fR. The \fBTie::StdScalar\fR
package provides all the methods specified in perltie. It inherits from
\&\fBTie::Scalar\fR and causes scalars tied to it to behave exactly like the
built-in scalars, allowing for selective overloading of methods. The \f(CW\*(C`new\*(C'\fR
method is provided as a means of legacy support for classes that forget to
provide their own \f(CW\*(C`TIESCALAR\*(C'\fR method.
.PP
For developers wishing to write their own tied-scalar classes, the methods
are summarized below. The perltie section not only documents these, but
has sample code as well:
.IP "TIESCALAR classname, LIST" 4
.IX Item "TIESCALAR classname, LIST"
The method invoked by the command \f(CW\*(C`tie $scalar, classname\*(C'\fR. Associates a new
scalar instance with the specified class. \f(CW\*(C`LIST\*(C'\fR would represent additional
arguments (along the lines of AnyDBM_File and compatriots) needed to
complete the association.
.IP "FETCH this" 4
.IX Item "FETCH this"
Retrieve the value of the tied scalar referenced by \fIthis\fR.
.IP "STORE this, value" 4
.IX Item "STORE this, value"
Store data \fIvalue\fR in the tied scalar referenced by \fIthis\fR.
.IP "DESTROY this" 4
.IX Item "DESTROY this"
Free the storage associated with the tied scalar referenced by \fIthis\fR.
This is rarely needed, as Perl manages its memory quite well. But the
option exists, should a class wish to perform specific actions upon the
destruction of an instance.
.SS "Tie::Scalar vs Tie::StdScalar"
.IX Subsection "Tie::Scalar vs Tie::StdScalar"
\&\f(CW\*(C`Tie::Scalar\*(C'\fR provides all the necessary methods, but one should realize
they do not do anything useful. Calling \f(CW\*(C`Tie::Scalar::FETCH\*(C'\fR or
\&\f(CW\*(C`Tie::Scalar::STORE\*(C'\fR results in a (trappable) croak. And if you inherit
from \f(CW\*(C`Tie::Scalar\*(C'\fR, you \fImust\fR provide either a \f(CW\*(C`new\*(C'\fR or a
\&\f(CW\*(C`TIESCALAR\*(C'\fR method.
.PP
If you are looking for a class that does everything for you that you don't
define yourself, use the \f(CW\*(C`Tie::StdScalar\*(C'\fR class, not the
\&\f(CW\*(C`Tie::Scalar\*(C'\fR one.
.SH "MORE INFORMATION"
.IX Header "MORE INFORMATION"
The perltie section uses a good example of tying scalars by associating
process IDs with priority.
|
