7 use Scalar::Util 'blessed';
10 use Class::MOP::Class;
11 use Class::MOP::Attribute;
12 use Class::MOP::Method;
14 our $VERSION = '0.01';
19 if ($_[0] eq ':universal') {
20 *UNIVERSAL::meta = sub {
21 Class::MOP::Class->initialize(blessed($_[0]) || $_[0])
27 *{$pkg . '::' . $_[0]} = sub {
28 Class::MOP::Class->initialize(blessed($_[0]) || $_[0])
33 ## ----------------------------------------------------------------------------
35 ## ----------------------------------------------------------------------------
36 ## The code below here is to bootstrap our MOP with itself. This is also
37 ## sometimes called "tying the knot". By doing this, we make it much easier
38 ## to extend the MOP through subclassing and such since now you can use the
39 ## MOP itself to extend itself.
41 ## Yes, I know, thats weird and insane, but it's a good thing, trust me :)
42 ## ----------------------------------------------------------------------------
44 # We need to add in the meta-attributes here so that
45 # any subclass of Class::MOP::* will be able to
46 # inherit them using &construct_instance
50 Class::MOP::Class->meta->add_attribute(
51 Class::MOP::Attribute->new('$:pkg' => (
56 Class::MOP::Class->meta->add_attribute(
57 Class::MOP::Attribute->new('%:attrs' => (
63 ## Class::MOP::Attribute
65 Class::MOP::Attribute->meta->add_attribute(Class::MOP::Attribute->new('name'));
66 Class::MOP::Attribute->meta->add_attribute(Class::MOP::Attribute->new('accessor'));
67 Class::MOP::Attribute->meta->add_attribute(Class::MOP::Attribute->new('reader'));
68 Class::MOP::Attribute->meta->add_attribute(Class::MOP::Attribute->new('writer'));
69 Class::MOP::Attribute->meta->add_attribute(Class::MOP::Attribute->new('predicate'));
70 Class::MOP::Attribute->meta->add_attribute(Class::MOP::Attribute->new('init_arg'));
71 Class::MOP::Attribute->meta->add_attribute(Class::MOP::Attribute->new('default'));
73 # NOTE: (meta-circularity)
74 # This should be one of the last things done
75 # it will "tie the knot" with Class::MOP::Attribute
76 # so that it uses the attributes meta-objects
77 # to construct itself.
78 Class::MOP::Attribute->meta->add_method('new' => sub {
83 (defined $name && $name)
84 || confess "You must provide a name for the attribute";
85 (!exists $options{reader} && !exists $options{writer})
86 || confess "You cannot declare an accessor and reader and/or writer functions"
87 if exists $options{accessor};
89 bless $class->meta->construct_instance(name => $name, %options) => $class;
100 Class::MOP - A Meta Object Protocol for Perl 5
108 This module is an attempt to create a meta object protocol for the
109 Perl 5 object system. It makes no attempt to change the behavior or
110 characteristics of the Perl 5 object system, only to create a
111 protocol for its manipulation and introspection.
113 That said, it does attempt to create the tools for building a rich
114 set of extensions to the Perl 5 object system. Every attempt has been
115 made for these tools to keep to the spirit of the Perl 5 object
116 system that we all know and love.
118 =head2 What is a Meta Object Protocol?
120 A meta object protocol is an API to an object system.
122 To be more specific, it is a set of abstractions of the components of
123 an object system (typically things like; classes, object, methods,
124 object attributes, etc.). These abstractions can then be used to both
125 inspect and manipulate the object system which they describe.
127 It can be said that there are two MOPs for any object system; the
128 implicit MOP, and the explicit MOP. The implicit MOP handles things
129 like method dispatch or inheritance, which happen automatically as
130 part of how the object system works. The explicit MOP typically
131 handles the introspection/reflection features of the object system.
132 All object systems have implicit MOPs, without one, they would not
133 work. Explict MOPs however as less common, and depending on the
134 language can vary from restrictive (Reflection in Java or C#) to
135 wide open (CLOS is a perfect example).
137 =head2 Yet Another Class Builder!! Why?
139 This is B<not> a class builder so much as it is a I<class builder
140 B<builder>>. My intent is that an end user does not use this module
141 directly, but instead this module is used by module authors to
142 build extensions and features onto the Perl 5 object system.
144 =head2 Who is this module for?
146 This module is specifically for anyone who has ever created or
147 wanted to create a module for the Class:: namespace. The tools which
148 this module will provide will hopefully make it easier to do more
149 complex things with Perl 5 classes by removing such barriers as
150 the need to hack the symbol tables, or understand the fine details
153 =head2 What changes do I have to make to use this module?
155 This module was designed to be as unintrusive as possible. Many of
156 it's features are accessible without B<any> change to your existsing
157 code at all. It is meant to be a compliment to your existing code and
158 not an intrusion on your code base. Unlike many other B<Class::>
159 modules, this module does require you subclass it, or even that you
160 C<use> it in within your module's package.
162 The only features which requires additions to your code are the
163 attribute handling and instance construction features, and these are
164 both optional features as well. The only reason for this is because
165 Perl 5's object system does not actually have these features built
166 in. More information about this feature can be found below.
168 =head2 A Note about Performance?
170 It is a common misconception that explict MOPs are performance drains.
171 But this is not a universal truth at all, it is an side-effect of
172 specific implementations. For instance, using Java reflection is much
173 slower because the JVM cannot take advantage of any compiler
174 optimizations, and the JVM has to deal with much more runtime type
175 information as well. Reflection in C# is marginally better as it was
176 designed into the language and runtime (the CLR). In contrast, CLOS
177 (the Common Lisp Object System) was built to support an explicit MOP,
178 and so performance is tuned for it.
180 This library in particular does it's absolute best to avoid putting
181 B<any> drain at all upon your code's performance. In fact, by itself
182 it does nothing to affect your existing code. So you only pay for
183 what you actually use.
187 The protocol is divided into 3 main sub-protocols:
191 =item The Class protocol
193 This provides a means of manipulating and introspecting a Perl 5
194 class. It handles all of symbol table hacking for you, and provides
195 a rich set of methods that go beyond simple package introspection.
197 See L<Class::MOP::Class> for more details.
199 =item The Attribute protocol
201 This provides a consistent represenation for an attribute of a
202 Perl 5 class. Since there are so many ways to create and handle
203 atttributes in Perl 5 OO, this attempts to provide as much of a
204 unified approach as possible, while giving the freedom and
205 flexibility to subclass for specialization.
207 See L<Class::MOP::Attribute> for more details.
209 =item The Method protocol
211 This provides a means of manipulating and introspecting methods in
212 the Perl 5 object system. As with attributes, there are many ways to
213 approach this topic, so we try to keep it pretty basic, while still
214 making it possible to extend the system in many ways.
216 See L<Class::MOP::Method> for more details.
222 All complex software has bugs lurking in it, and this module is no
223 exception. If you find a bug please either email me, or add the bug
232 =item "The Art of the Meta Object Protocol"
234 =item "Advances in Object-Oriented Metalevel Architecture and Reflection"
236 =item "Putting MetaClasses to Work"
244 =item The Perl 6 MetaModel work in the Pugs project
248 =item L<http://svn.openfoundry.org/pugs/perl5/Perl6-MetaModel>
250 =item L<http://svn.openfoundry.org/pugs/perl5/Perl6-ObjectSpace>
258 Stevan Little E<gt>stevan@iinteractive.comE<lt>
260 Rob Kinyon E<gt>rob@iinteractive.comE<lt>
262 =head1 COPYRIGHT AND LICENSE
264 Copyright 2006 by Infinity Interactive, Inc.
266 L<http://www.iinteractive.com>
268 This library is free software; you can redistribute it and/or modify
269 it under the same terms as Perl itself.