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.\" ========================================================================
.\"
.IX Title "Tie::Scalar 3"
.TH Tie::Scalar 3 "2002-11-24" "perl v5.8.0" "Perl Programmers Reference Guide"
.SH "NAME"
Tie::Scalar, Tie::StdScalar \- base class definitions for tied scalars
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&    package NewScalar;
\&    require Tie::Scalar;
.Ve
.PP
.Vb 1
\&    @ISA = (Tie::Scalar);
.Ve
.PP
.Vb 2
\&    sub FETCH { ... }           # Provide a needed method
\&    sub TIESCALAR { ... }       # Overrides inherited method
.Ve
.PP
.Vb 2
\&    package NewStdScalar;
\&    require Tie::Scalar;
.Ve
.PP
.Vb 1
\&    @ISA = (Tie::StdScalar);
.Ve
.PP
.Vb 2
\&    # All methods provided by default, so define only what needs be overridden
\&    sub FETCH { ... }
.Ve
.PP
.Vb 1
\&    package main;
.Ve
.PP
.Vb 2
\&    tie $new_scalar, 'NewScalar';
\&    tie $new_std_scalar, 'NewStdScalar';
.Ve
.SH "DESCRIPTION"
.IX Header "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 \fBTie::Scalar\fR package provides a \f(CW\*(C`new\*(C'\fR method, as well
as methods \f(CW\*(C`TIESCALAR\*(C'\fR, \f(CW\*(C`FETCH\*(C'\fR and \f(CW\*(C`STORE\*(C'\fR. The \fBTie::StdScalar\fR
package provides all the methods specified in  perltie. It inherits from
\&\fBTie::Scalar\fR and causes scalars tied to it to behave exactly like the
built-in scalars, allowing for selective overloading of methods. The \f(CW\*(C`new\*(C'\fR
method is provided as a means of grandfathering, for classes that forget to
provide their own \f(CW\*(C`TIESCALAR\*(C'\fR method.
.PP
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:
.IP "\s-1TIESCALAR\s0 classname, \s-1LIST\s0" 4
.IX Item "TIESCALAR classname, LIST"
The method invoked by the command \f(CW\*(C`tie $scalar, classname\*(C'\fR. Associates a new
scalar instance with the specified class. \f(CW\*(C`LIST\*(C'\fR would represent additional
arguments (along the lines of AnyDBM_File and compatriots) needed to
complete the association.
.IP "\s-1FETCH\s0 this" 4
.IX Item "FETCH this"
Retrieve the value of the tied scalar referenced by \fIthis\fR.
.IP "\s-1STORE\s0 this, value" 4
.IX Item "STORE this, value"
Store data \fIvalue\fR in the tied scalar referenced by \fIthis\fR.
.IP "\s-1DESTROY\s0 this" 4
.IX Item "DESTROY this"
Free the storage associated with the tied scalar referenced by \fIthis\fR.
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.
.SH "MORE INFORMATION"
.IX Header "MORE INFORMATION"
The perltie section uses a good example of tying scalars by associating
process IDs with priority.