perldoc > Tie::Scalar

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📖 NAME

Tie::Scalar, Tie::StdScalar - base class definitions for tied scalars

🚀 Quick Reference

Use Case	Command	Description
📦 Create a tied scalar class	package NewScalar; @ISA = qw(Tie::Scalar);	🛠️ Inherit from Tie::Scalar and provide mandatory methods (FETCH, TIESCALAR, etc.)
📦 Create a tied scalar with default behaviors	package NewStdScalar; @ISA = qw(Tie::StdScalar);	📋 Inherit from Tie::StdScalar; only override needed methods.
🔗 Tie a scalar variable	tie $scalar, 'ClassName';	🔗 Associate a scalar variable with a tying class.

🔖 SYNOPSIS

    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';

📝 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 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 vs Tie::StdScalar

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 that you don't define yourself, use the Tie::StdScalar class, not the Tie::Scalar one.

📚 MORE INFORMATION

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

📖 NAME 🚀 Quick Reference 🔖 SYNOPSIS 📝 DESCRIPTION 📚 MORE INFORMATION