some more docs for Class::MOP and the attribute functions for Class::MOP::Class

[gitmo/Class-MOP.git] / lib / Class / MOP.pm

package Class::MOP;

use strict;
use warnings;

use Scalar::Util 'blessed';

our $VERSION = '0.01';

# my %METAS;
# sub UNIVERSAL::meta { 
#     my $class = blessed($_[0]) || $_[0];
#     $METAS{$class} ||= Class::MOP::Class->initialize($class) 
# }

1;

__END__

=pod

=head1 NAME 

Class::MOP - A Meta Object Protocol for Perl 5

=head1 SYNOPSIS

  # ... coming soon

=head1 DESCRIPTON

This module is an attempt to create a meta object protocol for the 
Perl 5 object system. It makes no attempt to change the behavior or 
characteristics of the Perl 5 object system, only to create a 
protocol for its manipulation and introspection.

That said, it does attempt to create the tools for building a rich 
set of extensions to the Perl 5 object system. Every attempt has been 
made for these tools to keep to the spirit of the Perl 5 object 
system that we all know and love.

=head2 What is a Meta Object Protocol?

A meta object protocol is an API to an object system. 

To be more specific, it is a set of abstractions of the components of 
an object system (typically things like; classes, object, methods, 
object attributes, etc.). These abstractions can then be used to both 
inspect and manipulate the object system which they describe.

It can be said that there are two MOPs for any object system; the 
implicit MOP, and the explicit MOP. The implicit MOP handles things 
like method dispatch or inheritance, which happen automatically as 
part of how the object system works. The explicit MOP typically 
handles the introspection/reflection features of the object system. 
All object systems have implicit MOPs, without one, they would not 
work. Explict MOPs however as less common, and depending on the 
language can vary from restrictive (Reflection in Java or C#) to 
wide open (CLOS is a perfect example). 

=head2 Yet Another Class Builder!! Why?

This is B<not> a class builder so much as it is a I<class builder 
B<builder>>. My intent is that an end user does not use this module 
directly, but instead this module is used by module authors to 
build extensions and features onto the Perl 5 object system. 

=head2 Who is this module for?

This module is specifically for anyone who has ever created or 
wanted to create a module for the Class:: namespace. The tools which 
this module will provide will hopefully make it easier to do more 
complex things with Perl 5 classes by removing such barriers as 
the need to hack the symbol tables, or understand the fine details 
of method dispatch. 

=head2 What changes do I have to make to use this module?

This module was designed to be as unintrusive as possible. So many of 
it's features are accessible without B<any> change to your existsing 
code at all. It is meant to be a compliment to your existing code and 
not an intrusion on your code base.

The only feature which requires additions to your code are the 
attribute handling and instance construction features. The only reason 
for this is because Perl 5's object system does not actually have 
these features built in. More information about this feature can be 
found below.

=head2 A Note about Performance?

It is a common misconception that explict MOPs are performance drains. 
But this is not a universal truth at all, it is an side-effect of 
specific implementations. For instance, using Java reflection is much 
slower because the JVM cannot take advantage of any compiler 
optimizations, and the JVM has to deal with much more runtime type 
information as well. Reflection in C# is marginally better as it was 
designed into the language and runtime (the CLR). In contrast, CLOS 
(the Common Lisp Object System) was built to support an explicit MOP, 
and so performance is tuned for it. 

This library in particular does it's absolute best to avoid putting 
B<any> drain at all upon your code's performance, while still trying 
to make sure it is fast as well (although only as a secondary 
concern).

=head1 PROTOCOLS

The protocol is divided into 3 main sub-protocols:

=over 4

=item The Class protocol

This provides a means of manipulating and introspecting a Perl 5 
class. It handles all of symbol table hacking for you, and provides 
a rich set of methods that go beyond simple package introspection.

See L<Class::MOP::Class> for more details.

=item The Attribute protocol

This provides a consistent represenation for an attribute of a 
Perl 5 class. Since there are so many ways to create and handle 
atttributes in Perl 5 OO, this attempts to provide as much of a 
unified approach as possible, while giving the freedom and 
flexibility to subclass for specialization.

See L<Class::MOP::Attribute> for more details.

=item The Method protocol

This provides a means of manipulating and introspecting methods in 
the Perl 5 object system. As with attributes, there are many ways to 
approach this topic, so we try to keep it pretty basic, while still 
making it possible to extend the system in many ways.

See L<Class::MOP::Method> for more details.

=back

=head1 SEE ALSO

=head2 Books

=over 4

=item "The Art of the Meta Object Protocol"

=item "Advances in Object-Oriented Metalevel Architecture and Reflection"

=back

=head2 Prior Art

=over 4

=item The Perl 6 MetaModel work

=over 4

=item L<http://svn.openfoundry.org/pugs/perl5/Perl6-MetaModel>

=item L<http://svn.openfoundry.org/pugs/perl5/Perl6-ObjectSpace>

=back

=back

=head1 AUTHOR

Stevan Little E<gt>stevan@iinteractive.comE<lt>

Rob Kinyon E<gt>rob@iinteractive.comE<lt>

=head1 COPYRIGHT AND LICENSE

Copyright 2006 by Infinity Interactive, Inc.

L<http://www.iinteractive.com>

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself. 

=cut