phpman > man > 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 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 that 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.