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