Commit | Line | Data |
94b19069 |
1 | |
2 | package Class::MOP; |
3 | |
4 | use strict; |
5 | use warnings; |
6 | |
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7 | use Scalar::Util 'blessed'; |
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8 | use Carp 'confess'; |
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9 | |
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10 | use Class::MOP::Class; |
11 | use Class::MOP::Attribute; |
12 | use Class::MOP::Method; |
13 | |
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14 | our $VERSION = '0.01'; |
15 | |
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16 | sub import { |
17 | shift; |
18 | return unless @_; |
19 | if ($_[0] eq ':universal') { |
20 | *UNIVERSAL::meta = sub { |
21 | Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) |
22 | }; |
23 | } |
1a7ebbb3 |
24 | else { |
25 | my $pkg = caller(); |
26 | no strict 'refs'; |
27 | *{$pkg . '::' . $_[0]} = sub { |
28 | Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) |
29 | }; |
30 | } |
2eb717d5 |
31 | } |
8b978dd5 |
32 | |
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33 | ## ---------------------------------------------------------------------------- |
34 | ## Bootstrapping |
35 | ## ---------------------------------------------------------------------------- |
36 | ## The code below here is to bootstrap our MOP with itself. This is also |
37 | ## sometimes called "tying the knot". By doing this, we make it much easier |
38 | ## to extend the MOP through subclassing and such since now you can use the |
39 | ## MOP itself to extend itself. |
40 | ## |
41 | ## Yes, I know, thats weird and insane, but it's a good thing, trust me :) |
42 | ## ---------------------------------------------------------------------------- |
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43 | |
44 | # We need to add in the meta-attributes here so that |
45 | # any subclass of Class::MOP::* will be able to |
46 | # inherit them using &construct_instance |
47 | |
48 | ## Class::MOP::Class |
49 | |
50 | Class::MOP::Class->meta->add_attribute( |
51 | Class::MOP::Attribute->new('$:pkg' => ( |
52 | init_arg => ':pkg' |
53 | )) |
54 | ); |
55 | |
56 | Class::MOP::Class->meta->add_attribute( |
57 | Class::MOP::Attribute->new('%:attrs' => ( |
58 | init_arg => ':attrs', |
59 | default => sub { {} } |
60 | )) |
61 | ); |
62 | |
63 | ## Class::MOP::Attribute |
64 | |
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')); |
72 | |
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 { |
79 | my $class = shift; |
80 | my $name = shift; |
81 | my %options = @_; |
82 | |
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}; |
88 | |
89 | bless $class->meta->construct_instance(name => $name, %options) => $class; |
90 | }); |
91 | |
94b19069 |
92 | 1; |
93 | |
94 | __END__ |
95 | |
96 | =pod |
97 | |
98 | =head1 NAME |
99 | |
100 | Class::MOP - A Meta Object Protocol for Perl 5 |
101 | |
102 | =head1 SYNOPSIS |
103 | |
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104 | # ... |
94b19069 |
105 | |
106 | =head1 DESCRIPTON |
107 | |
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 |
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111 | protocol for its manipulation and introspection. |
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112 | |
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. |
117 | |
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118 | =head2 What is a Meta Object Protocol? |
119 | |
120 | A meta object protocol is an API to an object system. |
121 | |
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. |
126 | |
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). |
136 | |
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137 | =head2 Yet Another Class Builder!! Why? |
138 | |
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. |
143 | |
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144 | =head2 Who is this module for? |
145 | |
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 |
151 | of method dispatch. |
152 | |
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153 | =head2 What changes do I have to make to use this module? |
154 | |
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155 | This module was designed to be as unintrusive as possible. Many of |
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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 |
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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. |
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161 | |
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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. |
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167 | |
168 | =head2 A Note about Performance? |
169 | |
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. |
179 | |
180 | This library in particular does it's absolute best to avoid putting |
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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. |
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184 | |
94b19069 |
185 | =head1 PROTOCOLS |
186 | |
187 | The protocol is divided into 3 main sub-protocols: |
188 | |
189 | =over 4 |
190 | |
191 | =item The Class protocol |
192 | |
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. |
196 | |
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197 | See L<Class::MOP::Class> for more details. |
198 | |
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199 | =item The Attribute protocol |
200 | |
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. |
206 | |
552e3d24 |
207 | See L<Class::MOP::Attribute> for more details. |
208 | |
94b19069 |
209 | =item The Method protocol |
210 | |
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. |
215 | |
552e3d24 |
216 | See L<Class::MOP::Method> for more details. |
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217 | |
218 | =back |
219 | |
7184ca14 |
220 | head1 BUGS |
221 | |
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 |
224 | to cpan-RT. |
225 | |
552e3d24 |
226 | =head1 SEE ALSO |
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227 | |
552e3d24 |
228 | =head2 Books |
8b978dd5 |
229 | |
230 | =over 4 |
231 | |
552e3d24 |
232 | =item "The Art of the Meta Object Protocol" |
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233 | |
552e3d24 |
234 | =item "Advances in Object-Oriented Metalevel Architecture and Reflection" |
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235 | |
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236 | =item "Putting MetaClasses to Work" |
237 | |
94b19069 |
238 | =back |
239 | |
552e3d24 |
240 | =head2 Prior Art |
8b978dd5 |
241 | |
242 | =over 4 |
243 | |
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244 | =item The Perl 6 MetaModel work in the Pugs project |
8b978dd5 |
245 | |
246 | =over 4 |
247 | |
552e3d24 |
248 | =item L<http://svn.openfoundry.org/pugs/perl5/Perl6-MetaModel> |
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249 | |
552e3d24 |
250 | =item L<http://svn.openfoundry.org/pugs/perl5/Perl6-ObjectSpace> |
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251 | |
252 | =back |
253 | |
94b19069 |
254 | =back |
255 | |
256 | =head1 AUTHOR |
257 | |
258 | Stevan Little E<gt>stevan@iinteractive.comE<lt> |
259 | |
552e3d24 |
260 | Rob Kinyon E<gt>rob@iinteractive.comE<lt> |
261 | |
94b19069 |
262 | =head1 COPYRIGHT AND LICENSE |
263 | |
264 | Copyright 2006 by Infinity Interactive, Inc. |
265 | |
266 | L<http://www.iinteractive.com> |
267 | |
268 | This library is free software; you can redistribute it and/or modify |
269 | it under the same terms as Perl itself. |
270 | |
271 | =cut |