Tie::Scalar(3pm) Perl Programmers Reference Guide Tie::Scalar(3pm)
NAME
Tie::Scalar, Tie::StdScalar - base class definitions for tied scalars
SYNOPSIS
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, 'NewScalar';
tie $new_std_scalar, 'NewStdScalar';
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 Tie::Scalar package provides a "new" method, as well
as methods "TIESCALAR", "FETCH" and "STORE". The Tie::StdScalar package
provides all the methods specified in perltie. It inherits from
Tie::Scalar and causes scalars tied to it to behave exactly like the
built-in scalars, allowing for selective overloading of methods. The
"new" method is provided as a means of legacy support for classes that
forget to provide their own "TIESCALAR" method.
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:
TIESCALAR classname, LIST
The method invoked by the command "tie $scalar, classname".
Associates a new scalar instance with the specified class. "LIST"
would represent additional arguments (along the lines of
AnyDBM_File and compatriots) needed to complete the association.
FETCH this
Retrieve the value of the tied scalar referenced by this.
STORE this, value
Store data value in the tied scalar referenced by this.
DESTROY this
Free the storage associated with the tied scalar referenced by
this. 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.
Tie::Scalar vs Tie::StdScalar
"Tie::Scalar" provides all the necessary methods, but one should
realize they do not do anything useful. Calling "Tie::Scalar::FETCH" or
"Tie::Scalar::STORE" results in a (trappable) croak. And if you inherit
from "Tie::Scalar", you must provide either a "new" or a "TIESCALAR"
method.
If you are looking for a class that does everything for you that you
don't define yourself, use the "Tie::StdScalar" class, not the
"Tie::Scalar" one.
MORE INFORMATION
The perltie(1) section uses a good example of tying scalars by
associating process IDs with priority.
perl v5.38.2 2023-11-28 Tie::Scalar(3pm)
perl 5.38.2 - Generated Sat Dec 14 13:27:05 CST 2024