Know-How für Ihr Projekt

Perl Documentation


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:

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.


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