1Tie::Scalar(3pm)       Perl Programmers Reference Guide       Tie::Scalar(3pm)
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NAME

6       Tie::Scalar, Tie::StdScalar - base class definitions for tied scalars
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SYNOPSIS

9           package NewScalar;
10           require Tie::Scalar;
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12           @ISA = qw(Tie::Scalar);
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14           sub FETCH { ... }           # Provide a needed method
15           sub TIESCALAR { ... }       # Overrides inherited method
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18           package NewStdScalar;
19           require Tie::Scalar;
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21           @ISA = qw(Tie::StdScalar);
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23           # All methods provided by default, so define
24           # only what needs be overridden
25           sub FETCH { ... }
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28           package main;
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30           tie $new_scalar, 'NewScalar';
31           tie $new_std_scalar, 'NewStdScalar';
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DESCRIPTION

34       This module provides some skeletal methods for scalar-tying classes.
35       See perltie for a list of the functions required in tying a scalar to a
36       package. The basic Tie::Scalar package provides a "new" method, as well
37       as methods "TIESCALAR", "FETCH" and "STORE". The Tie::StdScalar package
38       provides all the methods specified in  perltie. It inherits from
39       Tie::Scalar and causes scalars tied to it to behave exactly like the
40       built-in scalars, allowing for selective overloading of methods. The
41       "new" method is provided as a means of grandfathering, for classes that
42       forget to provide their own "TIESCALAR" method.
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44       For developers wishing to write their own tied-scalar classes, the
45       methods are summarized below. The perltie section not only documents
46       these, but has sample code as well:
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48       TIESCALAR classname, LIST
49           The method invoked by the command "tie $scalar, classname".
50           Associates a new scalar instance with the specified class. "LIST"
51           would represent additional arguments (along the lines of
52           AnyDBM_File and compatriots) needed to complete the association.
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54       FETCH this
55           Retrieve the value of the tied scalar referenced by this.
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57       STORE this, value
58           Store data value in the tied scalar referenced by this.
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60       DESTROY this
61           Free the storage associated with the tied scalar referenced by
62           this.  This is rarely needed, as Perl manages its memory quite
63           well. But the option exists, should a class wish to perform
64           specific actions upon the destruction of an instance.
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66   Tie::Scalar vs Tie::StdScalar
67       "Tie::Scalar" provides all the necessary methods, but one should
68       realize they do not do anything useful. Calling "Tie::Scalar::FETCH" or
69       "Tie::Scalar::STORE" results in a (trappable) croak. And if you inherit
70       from "Tie::Scalar", you must provide either a "new" or a "TIESCALAR"
71       method.
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73       If you are looking for a class that does everything for you that you
74       don't define yourself, use the "Tie::StdScalar" class, not the
75       "Tie::Scalar" one.
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MORE INFORMATION

78       The perltie section uses a good example of tying scalars by associating
79       process IDs with priority.
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83perl v5.34.0                      2021-10-18                  Tie::Scalar(3pm)
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