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 legacy support 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.