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


       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
           # only what needs be overridden
           sub FETCH { ... }

           package main;

           tie $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.

   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"

       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"


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

perl v5.24.0                      2016-03-01                  Tie::Scalar(3pm)

perl 5.24 - Generated Sat Nov 26 07:50:09 CST 2016
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