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7.2.73 Tie::Scalar, Tie::StdScalar - Base Class Definitions for Tied Scalars

package NewScalar;
require Tie::Scalar;

@ISA = (Tie::Scalar);

sub FETCH { ... }           # Provides additional method
sub TIESCALAR { ... }       # Overrides inherited method

package NewStdScalar;
require Tie::Scalar;

@ISA = (Tie::StdScalar);

sub FETCH { ... }

package main;

tie $new_scalar, "NewScalar";
tie $new_std_scalar, "NewStdScalar";

This module provides some skeletal methods for scalar-tying classes. (See Chapter 5 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 methods specified in Chapter 5 . 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, methods are summarized below. ( Chapter 5 not only documents these, but also has sample code.)

TIESCALAR ClassName , LIST

The method invoked by the command:

tie $scalar, ClassName, 

LIST

Associates a new scalar instance with the specified class. LIST would represent additional arguments (along the lines of the AnyDBM_File library module and associated modules) needed to complete the association.

FETCH this

Retrieve the value of the tied scalar referenced by this .

STORE this, value

Store 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, since Perl manages its memory well. But the option exists, should a class wish to perform specific actions upon the destruction of an instance.

7.2.73.1 See also

Chapter 5 has a good example using tied scalars to associate process IDs with priority.


Previous: 7.2.72 Tie::Hash, Tie::StdHash - Base Class Definitions for Tied Hashes Programming Perl Next: 7.2.74 Tie::SubstrHash - Fixed-table-size, Fixed-key-length Hashing
7.2.72 Tie::Hash, Tie::StdHash - Base Class Definitions for Tied Hashes Book Index 7.2.74 Tie::SubstrHash - Fixed-table-size, Fixed-key-length Hashing











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