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:
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.
Retrieve the value of the tied scalar referenced by this.
Store data value in the tied scalar referenced by 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.