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1 | |
2 | package Class::MOP; |
3 | |
4 | use strict; |
5 | use warnings; |
6 | |
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7 | use Scalar::Util 'blessed'; |
8 | |
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9 | use Class::MOP::Class; |
10 | use Class::MOP::Attribute; |
11 | use Class::MOP::Method; |
12 | |
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13 | our $VERSION = '0.01'; |
14 | |
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15 | sub import { |
16 | shift; |
17 | return unless @_; |
18 | if ($_[0] eq ':universal') { |
19 | *UNIVERSAL::meta = sub { |
20 | Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) |
21 | }; |
22 | } |
23 | } |
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24 | |
94b19069 |
25 | 1; |
26 | |
27 | __END__ |
28 | |
29 | =pod |
30 | |
31 | =head1 NAME |
32 | |
33 | Class::MOP - A Meta Object Protocol for Perl 5 |
34 | |
35 | =head1 SYNOPSIS |
36 | |
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37 | use Class::MOP ':universal'; |
38 | |
39 | package Foo; |
40 | |
41 | Foo->meta->add_method('foo' => sub { ... }); |
94b19069 |
42 | |
43 | =head1 DESCRIPTON |
44 | |
45 | This module is an attempt to create a meta object protocol for the |
46 | Perl 5 object system. It makes no attempt to change the behavior or |
47 | characteristics of the Perl 5 object system, only to create a |
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48 | protocol for its manipulation and introspection. |
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49 | |
50 | That said, it does attempt to create the tools for building a rich |
51 | set of extensions to the Perl 5 object system. Every attempt has been |
52 | made for these tools to keep to the spirit of the Perl 5 object |
53 | system that we all know and love. |
54 | |
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55 | =head2 What is a Meta Object Protocol? |
56 | |
57 | A meta object protocol is an API to an object system. |
58 | |
59 | To be more specific, it is a set of abstractions of the components of |
60 | an object system (typically things like; classes, object, methods, |
61 | object attributes, etc.). These abstractions can then be used to both |
62 | inspect and manipulate the object system which they describe. |
63 | |
64 | It can be said that there are two MOPs for any object system; the |
65 | implicit MOP, and the explicit MOP. The implicit MOP handles things |
66 | like method dispatch or inheritance, which happen automatically as |
67 | part of how the object system works. The explicit MOP typically |
68 | handles the introspection/reflection features of the object system. |
69 | All object systems have implicit MOPs, without one, they would not |
70 | work. Explict MOPs however as less common, and depending on the |
71 | language can vary from restrictive (Reflection in Java or C#) to |
72 | wide open (CLOS is a perfect example). |
73 | |
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74 | =head2 Yet Another Class Builder!! Why? |
75 | |
76 | This is B<not> a class builder so much as it is a I<class builder |
77 | B<builder>>. My intent is that an end user does not use this module |
78 | directly, but instead this module is used by module authors to |
79 | build extensions and features onto the Perl 5 object system. |
80 | |
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81 | =head2 Who is this module for? |
82 | |
83 | This module is specifically for anyone who has ever created or |
84 | wanted to create a module for the Class:: namespace. The tools which |
85 | this module will provide will hopefully make it easier to do more |
86 | complex things with Perl 5 classes by removing such barriers as |
87 | the need to hack the symbol tables, or understand the fine details |
88 | of method dispatch. |
89 | |
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90 | =head2 What changes do I have to make to use this module? |
91 | |
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92 | This module was designed to be as unintrusive as possible. Many of |
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93 | it's features are accessible without B<any> change to your existsing |
94 | code at all. It is meant to be a compliment to your existing code and |
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95 | not an intrusion on your code base. Unlike many other B<Class::> |
96 | modules, this module does require you subclass it, or even that you |
97 | C<use> it in within your module's package. |
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98 | |
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99 | The only features which requires additions to your code are the |
100 | attribute handling and instance construction features, and these are |
101 | both optional features as well. The only reason for this is because |
102 | Perl 5's object system does not actually have these features built |
103 | in. More information about this feature can be found below. |
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104 | |
105 | =head2 A Note about Performance? |
106 | |
107 | It is a common misconception that explict MOPs are performance drains. |
108 | But this is not a universal truth at all, it is an side-effect of |
109 | specific implementations. For instance, using Java reflection is much |
110 | slower because the JVM cannot take advantage of any compiler |
111 | optimizations, and the JVM has to deal with much more runtime type |
112 | information as well. Reflection in C# is marginally better as it was |
113 | designed into the language and runtime (the CLR). In contrast, CLOS |
114 | (the Common Lisp Object System) was built to support an explicit MOP, |
115 | and so performance is tuned for it. |
116 | |
117 | This library in particular does it's absolute best to avoid putting |
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118 | B<any> drain at all upon your code's performance. In fact, by itself |
119 | it does nothing to affect your existing code. So you only pay for |
120 | what you actually use. |
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121 | |
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122 | =head1 PROTOCOLS |
123 | |
124 | The protocol is divided into 3 main sub-protocols: |
125 | |
126 | =over 4 |
127 | |
128 | =item The Class protocol |
129 | |
130 | This provides a means of manipulating and introspecting a Perl 5 |
131 | class. It handles all of symbol table hacking for you, and provides |
132 | a rich set of methods that go beyond simple package introspection. |
133 | |
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134 | See L<Class::MOP::Class> for more details. |
135 | |
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136 | =item The Attribute protocol |
137 | |
138 | This provides a consistent represenation for an attribute of a |
139 | Perl 5 class. Since there are so many ways to create and handle |
140 | atttributes in Perl 5 OO, this attempts to provide as much of a |
141 | unified approach as possible, while giving the freedom and |
142 | flexibility to subclass for specialization. |
143 | |
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144 | See L<Class::MOP::Attribute> for more details. |
145 | |
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146 | =item The Method protocol |
147 | |
148 | This provides a means of manipulating and introspecting methods in |
149 | the Perl 5 object system. As with attributes, there are many ways to |
150 | approach this topic, so we try to keep it pretty basic, while still |
151 | making it possible to extend the system in many ways. |
152 | |
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153 | See L<Class::MOP::Method> for more details. |
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154 | |
155 | =back |
156 | |
552e3d24 |
157 | =head1 SEE ALSO |
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158 | |
552e3d24 |
159 | =head2 Books |
8b978dd5 |
160 | |
161 | =over 4 |
162 | |
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163 | =item "The Art of the Meta Object Protocol" |
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164 | |
552e3d24 |
165 | =item "Advances in Object-Oriented Metalevel Architecture and Reflection" |
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166 | |
94b19069 |
167 | =back |
168 | |
552e3d24 |
169 | =head2 Prior Art |
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170 | |
171 | =over 4 |
172 | |
552e3d24 |
173 | =item The Perl 6 MetaModel work |
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174 | |
175 | =over 4 |
176 | |
552e3d24 |
177 | =item L<http://svn.openfoundry.org/pugs/perl5/Perl6-MetaModel> |
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178 | |
552e3d24 |
179 | =item L<http://svn.openfoundry.org/pugs/perl5/Perl6-ObjectSpace> |
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180 | |
181 | =back |
182 | |
94b19069 |
183 | =back |
184 | |
185 | =head1 AUTHOR |
186 | |
187 | Stevan Little E<gt>stevan@iinteractive.comE<lt> |
188 | |
552e3d24 |
189 | Rob Kinyon E<gt>rob@iinteractive.comE<lt> |
190 | |
94b19069 |
191 | =head1 COPYRIGHT AND LICENSE |
192 | |
193 | Copyright 2006 by Infinity Interactive, Inc. |
194 | |
195 | L<http://www.iinteractive.com> |
196 | |
197 | This library is free software; you can redistribute it and/or modify |
198 | it under the same terms as Perl itself. |
199 | |
200 | =cut |