Manpages - Tie_Scalar.3perl

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

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

$new_scalar, NewScalar; tie $new_std_scalar, NewStdScalar;

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 grandfathering, 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.

The perltie section uses a good example of tying scalars by associating process IDs with priority.