MirOS Manual: Tie::Scalar(3p)

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


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


         package NewScalar;
         require Tie::Scalar;

         @ISA = (Tie::Scalar);

         sub FETCH { ... }           # Provide a needed method
         sub TIESCALAR { ... }       # Overrides inherited method

         package NewStdScalar;
         require Tie::Scalar;

         @ISA = (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 overload-
     ing 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 sec-
     tion 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 argu-
         ments (along the lines of AnyDBM_File and compatriots)
         needed to complete the association.

     FETCH this
         Retrieve the value of the tied scalar referenced by

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


     STORE this, value
         Store data value in the tied scalar referenced by this.

     DESTROY this
         Free the storage associated with the tied scalar refer-
         enced 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 destruc-
         tion of an instance.


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

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