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 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.
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