Class::InsideOut::Manual::About 1.03

Class::InsideOut::Manual::About is a guide to this and other implementations of the inside-out technique.
This manual provides an overview of the inside-out technique and its application within Class::InsideOut and other modules. It also provides a list of references for further study.
Inside-out object basics
Inside-out objects use the blessed reference as an index into lexical data structures holding object properties, rather than using the blessed reference itself as a data structure.
$self->{ name } = "Larry"; # classic, hash-based object
$name{ refaddr $self } = "Larry"; # inside-out
The inside-out approach offers three major benefits:
- Enforced encapsulation: object properties cannot be accessed directly from ouside the lexical scope that declared them
- Making the property name part of a lexical variable rather than a hash-key means that typos in the name will be caught as compile-time errors (if using strict)
- If the memory address of the blessed reference is used as the index, the reference can be of any type
In exchange for these benefits, robust implementation of inside-out objects can be quite complex. Class::InsideOut manages that complexity.
Philosophy of Class::InsideOut
Class::InsideOut provides a set of tools for building safe inside-out classes with maximum flexibility.
It aims to offer minimal restrictions beyond those necessary for robustness of the inside-out technique. All capabilities necessary for robustness should be automatic. Anything that can be optional should be. The design should not introduce new restrictions unrelated to inside-out objects, such as attributes and CHECK blocks that cause problems for mod_perl or the use of source filters for syntatic sugar.
As a result, only a few things are mandatory:
- Properties must be based on hashes and declared via property
- Property hashes must be keyed on the Scalar::Util::refaddr
- register must be called on all new objects
All other implementation details, including constructors, initializers and class inheritance management are left to the user (though a very simple constructor is available as a convenience). This does requires some additional work, but maximizes freedom. Class::InsideOut is intended to be a base class providing only fundamental features. Subclasses of Class::InsideOut could be written that build upon it to provide particular styles of constructor, destructor and inheritance support.