Tie::Scalar(3perl)               Perl Programmers Reference Guide              Tie::Scalar(3perl)



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
       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.

   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 you don't define yourself, use
       the "Tie::StdScalar" class, not the "Tie::Scalar" one.

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



perl v5.20.2                                2014-12-27                         Tie::Scalar(3perl)