Tie::Scalar, Tie::StdScalar - base class definitions for tied scalars
sub FETCH { ... } # Provide a needed method
sub TIESCALAR { ... } # Overrides inherited method
# All methods provided by default, so define only what needs be overridden
tie $new_scalar, 'NewScalar';
tie $new_std_scalar, 'NewStdScalar';
This module provides some skeletal methods for scalar-tying classes. See
L<perltie> for a list of the functions required in tying a scalar to a
package. The basic B<Tie::Scalar> package provides a C<new> method, as well
as methods C<TIESCALAR>, C<FETCH> and C<STORE>. The B<Tie::StdScalar>
package provides all the methods specified in L<perltie>. It inherits from
B<Tie::Scalar> and causes scalars tied to it to behave exactly like the
built-in scalars, allowing for selective overloading of methods. The C<new>
method is provided as a means of grandfathering, for classes that forget to
provide their own C<TIESCALAR> method.
For developers wishing to write their own tied-scalar classes, the methods
are summarized below. The L<perltie> section not only documents these, but
=item TIESCALAR classname, LIST
The method invoked by the command C<tie $scalar, classname>. Associates a new
scalar instance with the specified class. C<LIST> would represent additional
arguments (along the lines of L<AnyDBM_File> and compatriots) needed to
complete the association.
Retrieve the value of the tied scalar referenced by I<this>.
Store data I<value> in the tied scalar referenced by I<this>.
Free the storage associated with the tied scalar referenced by I<this>.
This is rarely needed, as Perl manages its memory quite well. But the
option exists, should a class wish to perform specific actions upon the
destruction of an instance.
The L<perltie> section uses a good example of tying scalars by associating
process IDs with priority.
# "Grandfather" the new, a la Tie::Hash
if ($pkg->can('new') and $pkg ne __PACKAGE__
) {
warnings
::warnif
("WARNING: calling ${pkg}->new since ${pkg}->TIESCALAR is missing");
croak
"$pkg doesn't define a TIESCALAR method";
croak
"$pkg doesn't define a FETCH method";
croak
"$pkg doesn't define a STORE method";
# The Tie::StdScalar package provides scalars that behave exactly like
# Perl's built-in scalars. Good base to inherit from, if you're only going to
my $instance = shift || undef;
return bless \
$instance => $class;