Commit | Line | Data |
94b19069 |
1 | |
2 | package Class::MOP; |
3 | |
4 | use strict; |
5 | use warnings; |
6 | |
727919c5 |
7 | use Carp 'confess'; |
be7677c7 |
8 | use Scalar::Util 'weaken'; |
8b978dd5 |
9 | |
2eb717d5 |
10 | use Class::MOP::Class; |
11 | use Class::MOP::Attribute; |
12 | use Class::MOP::Method; |
13 | |
857f87a7 |
14 | use Class::MOP::Class::Immutable; |
15 | |
c4260b45 |
16 | our $VERSION = '0.34'; |
f0480c45 |
17 | our $AUTHORITY = 'cpan:STEVAN'; |
94b19069 |
18 | |
be7677c7 |
19 | { |
20 | # Metaclasses are singletons, so we cache them here. |
21 | # there is no need to worry about destruction though |
22 | # because they should die only when the program dies. |
23 | # After all, do package definitions even get reaped? |
24 | my %METAS; |
25 | |
26 | # means of accessing all the metaclasses that have |
27 | # been initialized thus far (for mugwumps obj browser) |
28 | sub get_all_metaclasses { %METAS } |
29 | sub get_all_metaclass_instances { values %METAS } |
30 | sub get_all_metaclass_names { keys %METAS } |
31 | sub get_metaclass_by_name { $METAS{$_[0]} } |
32 | sub store_metaclass_by_name { $METAS{$_[0]} = $_[1] } |
33 | sub weaken_metaclass { weaken($METAS{$_[0]}) } |
34 | sub does_metaclass_exist { exists $METAS{$_[0]} && defined $METAS{$_[0]} } |
35 | sub remove_metaclass_by_name { $METAS{$_[0]} = undef } |
36 | |
37 | # NOTE: |
38 | # We only cache metaclasses, meaning instances of |
39 | # Class::MOP::Class. We do not cache instance of |
40 | # Class::MOP::Package or Class::MOP::Module. Mostly |
41 | # because I don't yet see a good reason to do so. |
42 | } |
43 | |
aa448b16 |
44 | ## ---------------------------------------------------------------------------- |
45 | ## Setting up our environment ... |
46 | ## ---------------------------------------------------------------------------- |
47 | ## Class::MOP needs to have a few things in the global perl environment so |
48 | ## that it can operate effectively. Those things are done here. |
49 | ## ---------------------------------------------------------------------------- |
50 | |
3bf7644b |
51 | # ... nothing yet actually ;) |
8b978dd5 |
52 | |
b51af7f9 |
53 | ## ---------------------------------------------------------------------------- |
54 | ## Bootstrapping |
55 | ## ---------------------------------------------------------------------------- |
56 | ## The code below here is to bootstrap our MOP with itself. This is also |
57 | ## sometimes called "tying the knot". By doing this, we make it much easier |
58 | ## to extend the MOP through subclassing and such since now you can use the |
59 | ## MOP itself to extend itself. |
60 | ## |
61 | ## Yes, I know, thats weird and insane, but it's a good thing, trust me :) |
62 | ## ---------------------------------------------------------------------------- |
727919c5 |
63 | |
64 | # We need to add in the meta-attributes here so that |
65 | # any subclass of Class::MOP::* will be able to |
66 | # inherit them using &construct_instance |
67 | |
f0480c45 |
68 | ## -------------------------------------------------------- |
6d5355c3 |
69 | ## Class::MOP::Package |
727919c5 |
70 | |
6d5355c3 |
71 | Class::MOP::Package->meta->add_attribute( |
351bd7d4 |
72 | Class::MOP::Attribute->new('$:package' => ( |
b880e0de |
73 | reader => { |
74 | # NOTE: we need to do this in order |
75 | # for the instance meta-object to |
76 | # not fall into meta-circular death |
77 | 'name' => sub { (shift)->{'$:package'} } |
78 | }, |
7b31baf4 |
79 | init_arg => ':package', |
727919c5 |
80 | )) |
81 | ); |
82 | |
a5e51f0b |
83 | Class::MOP::Package->meta->add_attribute( |
84 | Class::MOP::Attribute->new('%:namespace' => ( |
85 | reader => { |
56dcfc1a |
86 | # NOTE: |
87 | # because of issues with the Perl API |
88 | # to the typeglob in some versions, we |
89 | # need to just always grab a new |
90 | # reference to the hash here. Ideally |
91 | # we could just store a ref and it would |
92 | # Just Work, but oh well :\ |
93 | 'namespace' => sub { |
94 | no strict 'refs'; |
95 | \%{$_[0]->name . '::'} |
96 | } |
a5e51f0b |
97 | }, |
98 | # NOTE: |
99 | # protect this from silliness |
a2ee6c61 |
100 | init_arg => '!............( DO NOT DO THIS )............!', |
c4260b45 |
101 | default => sub { \undef } |
a5e51f0b |
102 | )) |
103 | ); |
104 | |
9d6dce77 |
105 | # NOTE: |
106 | # use the metaclass to construct the meta-package |
107 | # which is a superclass of the metaclass itself :P |
108 | Class::MOP::Package->meta->add_method('initialize' => sub { |
109 | my $class = shift; |
110 | my $package_name = shift; |
111 | $class->meta->new_object(':package' => $package_name, @_); |
112 | }); |
113 | |
f0480c45 |
114 | ## -------------------------------------------------------- |
115 | ## Class::MOP::Module |
116 | |
117 | # NOTE: |
118 | # yeah this is kind of stretching things a bit, |
119 | # but truthfully the version should be an attribute |
120 | # of the Module, the weirdness comes from having to |
121 | # stick to Perl 5 convention and store it in the |
122 | # $VERSION package variable. Basically if you just |
123 | # squint at it, it will look how you want it to look. |
124 | # Either as a package variable, or as a attribute of |
125 | # the metaclass, isn't abstraction great :) |
126 | |
127 | Class::MOP::Module->meta->add_attribute( |
128 | Class::MOP::Attribute->new('$:version' => ( |
129 | reader => { |
130 | 'version' => sub { |
131 | my $self = shift; |
132 | ${$self->get_package_symbol('$VERSION')}; |
133 | } |
134 | }, |
135 | # NOTE: |
136 | # protect this from silliness |
137 | init_arg => '!............( DO NOT DO THIS )............!', |
c4260b45 |
138 | default => sub { \undef } |
f0480c45 |
139 | )) |
140 | ); |
141 | |
142 | # NOTE: |
143 | # By following the same conventions as version here, |
144 | # we are opening up the possibility that people can |
145 | # use the $AUTHORITY in non-Class::MOP modules as |
146 | # well. |
147 | |
148 | Class::MOP::Module->meta->add_attribute( |
149 | Class::MOP::Attribute->new('$:authority' => ( |
150 | reader => { |
151 | 'authority' => sub { |
152 | my $self = shift; |
153 | ${$self->get_package_symbol('$AUTHORITY')}; |
154 | } |
155 | }, |
156 | # NOTE: |
157 | # protect this from silliness |
158 | init_arg => '!............( DO NOT DO THIS )............!', |
c4260b45 |
159 | default => sub { \undef } |
f0480c45 |
160 | )) |
161 | ); |
162 | |
163 | ## -------------------------------------------------------- |
6d5355c3 |
164 | ## Class::MOP::Class |
165 | |
727919c5 |
166 | Class::MOP::Class->meta->add_attribute( |
351bd7d4 |
167 | Class::MOP::Attribute->new('%:attributes' => ( |
f7259199 |
168 | reader => { |
169 | # NOTE: we need to do this in order |
170 | # for the instance meta-object to |
171 | # not fall into meta-circular death |
172 | 'get_attribute_map' => sub { (shift)->{'%:attributes'} } |
173 | }, |
351bd7d4 |
174 | init_arg => ':attributes', |
727919c5 |
175 | default => sub { {} } |
176 | )) |
177 | ); |
178 | |
351bd7d4 |
179 | Class::MOP::Class->meta->add_attribute( |
c4260b45 |
180 | Class::MOP::Attribute->new('%:methods' => ( |
181 | reader => { |
182 | # NOTE: |
183 | # as with the $VERSION and $AUTHORITY above |
184 | # sometimes we don't/can't store directly |
185 | # inside the instance, so we need the accessor |
186 | # to just DWIM |
187 | 'get_method_map' => sub { |
188 | my $self = shift; |
189 | # FIXME: |
190 | # there is a faster/better way |
191 | # to do this, I am sure :) |
192 | return +{ |
193 | map { |
194 | $_ => $self->get_method($_) |
195 | } grep { |
196 | $self->has_method($_) |
197 | } $self->list_all_package_symbols |
198 | }; |
199 | } |
200 | }, |
201 | init_arg => '!............( DO NOT DO THIS )............!', |
202 | default => sub { \undef } |
203 | )) |
204 | ); |
205 | |
206 | Class::MOP::Class->meta->add_attribute( |
351bd7d4 |
207 | Class::MOP::Attribute->new('$:attribute_metaclass' => ( |
7b31baf4 |
208 | reader => 'attribute_metaclass', |
351bd7d4 |
209 | init_arg => ':attribute_metaclass', |
210 | default => 'Class::MOP::Attribute', |
211 | )) |
212 | ); |
213 | |
214 | Class::MOP::Class->meta->add_attribute( |
215 | Class::MOP::Attribute->new('$:method_metaclass' => ( |
7b31baf4 |
216 | reader => 'method_metaclass', |
351bd7d4 |
217 | init_arg => ':method_metaclass', |
218 | default => 'Class::MOP::Method', |
219 | )) |
220 | ); |
221 | |
2bab2be6 |
222 | Class::MOP::Class->meta->add_attribute( |
223 | Class::MOP::Attribute->new('$:instance_metaclass' => ( |
b880e0de |
224 | reader => { |
225 | # NOTE: we need to do this in order |
226 | # for the instance meta-object to |
227 | # not fall into meta-circular death |
228 | 'instance_metaclass' => sub { (shift)->{'$:instance_metaclass'} } |
229 | }, |
2bab2be6 |
230 | init_arg => ':instance_metaclass', |
231 | default => 'Class::MOP::Instance', |
232 | )) |
233 | ); |
234 | |
9d6dce77 |
235 | # NOTE: |
236 | # we don't actually need to tie the knot with |
237 | # Class::MOP::Class here, it is actually handled |
238 | # within Class::MOP::Class itself in the |
239 | # construct_class_instance method. |
240 | |
f0480c45 |
241 | ## -------------------------------------------------------- |
727919c5 |
242 | ## Class::MOP::Attribute |
243 | |
7b31baf4 |
244 | Class::MOP::Attribute->meta->add_attribute( |
245 | Class::MOP::Attribute->new('name' => ( |
b880e0de |
246 | reader => { |
247 | # NOTE: we need to do this in order |
248 | # for the instance meta-object to |
249 | # not fall into meta-circular death |
250 | 'name' => sub { (shift)->{name} } |
251 | } |
7b31baf4 |
252 | )) |
253 | ); |
254 | |
255 | Class::MOP::Attribute->meta->add_attribute( |
256 | Class::MOP::Attribute->new('associated_class' => ( |
b880e0de |
257 | reader => { |
258 | # NOTE: we need to do this in order |
259 | # for the instance meta-object to |
260 | # not fall into meta-circular death |
261 | 'associated_class' => sub { (shift)->{associated_class} } |
262 | } |
7b31baf4 |
263 | )) |
264 | ); |
265 | |
266 | Class::MOP::Attribute->meta->add_attribute( |
267 | Class::MOP::Attribute->new('accessor' => ( |
268 | reader => 'accessor', |
269 | predicate => 'has_accessor', |
270 | )) |
271 | ); |
272 | |
273 | Class::MOP::Attribute->meta->add_attribute( |
274 | Class::MOP::Attribute->new('reader' => ( |
275 | reader => 'reader', |
276 | predicate => 'has_reader', |
277 | )) |
278 | ); |
279 | |
280 | Class::MOP::Attribute->meta->add_attribute( |
281 | Class::MOP::Attribute->new('writer' => ( |
282 | reader => 'writer', |
283 | predicate => 'has_writer', |
284 | )) |
285 | ); |
286 | |
287 | Class::MOP::Attribute->meta->add_attribute( |
288 | Class::MOP::Attribute->new('predicate' => ( |
289 | reader => 'predicate', |
290 | predicate => 'has_predicate', |
291 | )) |
292 | ); |
293 | |
294 | Class::MOP::Attribute->meta->add_attribute( |
7d28758b |
295 | Class::MOP::Attribute->new('clearer' => ( |
296 | reader => 'clearer', |
297 | predicate => 'has_clearer', |
298 | )) |
299 | ); |
300 | |
301 | Class::MOP::Attribute->meta->add_attribute( |
7b31baf4 |
302 | Class::MOP::Attribute->new('init_arg' => ( |
303 | reader => 'init_arg', |
304 | predicate => 'has_init_arg', |
305 | )) |
306 | ); |
307 | |
308 | Class::MOP::Attribute->meta->add_attribute( |
309 | Class::MOP::Attribute->new('default' => ( |
310 | # default has a custom 'reader' method ... |
311 | predicate => 'has_default', |
312 | )) |
313 | ); |
314 | |
727919c5 |
315 | |
316 | # NOTE: (meta-circularity) |
317 | # This should be one of the last things done |
318 | # it will "tie the knot" with Class::MOP::Attribute |
319 | # so that it uses the attributes meta-objects |
320 | # to construct itself. |
321 | Class::MOP::Attribute->meta->add_method('new' => sub { |
322 | my $class = shift; |
323 | my $name = shift; |
324 | my %options = @_; |
325 | |
326 | (defined $name && $name) |
327 | || confess "You must provide a name for the attribute"; |
5659d76e |
328 | $options{init_arg} = $name |
329 | if not exists $options{init_arg}; |
148b4697 |
330 | |
331 | (Class::MOP::Attribute::is_default_a_coderef(\%options)) |
332 | || confess("References are not allowed as default values, you must ". |
333 | "wrap then in a CODE reference (ex: sub { [] } and not [])") |
334 | if exists $options{default} && ref $options{default}; |
651955fb |
335 | |
5659d76e |
336 | # return the new object |
337 | $class->meta->new_object(name => $name, %options); |
338 | }); |
339 | |
340 | Class::MOP::Attribute->meta->add_method('clone' => sub { |
a740253a |
341 | my $self = shift; |
a27ae83f |
342 | $self->meta->clone_object($self, @_); |
727919c5 |
343 | }); |
344 | |
f0480c45 |
345 | ## -------------------------------------------------------- |
346 | ## Now close all the Class::MOP::* classes |
4d47b77f |
347 | |
348 | Class::MOP::Package ->meta->make_immutable(inline_constructor => 0); |
349 | Class::MOP::Module ->meta->make_immutable(inline_constructor => 0); |
350 | Class::MOP::Class ->meta->make_immutable(inline_constructor => 0); |
351 | Class::MOP::Attribute->meta->make_immutable(inline_constructor => 0); |
352 | Class::MOP::Method ->meta->make_immutable(inline_constructor => 0); |
353 | Class::MOP::Instance ->meta->make_immutable(inline_constructor => 0); |
6e57504d |
354 | Class::MOP::Object ->meta->make_immutable(inline_constructor => 0); |
4d47b77f |
355 | |
94b19069 |
356 | 1; |
357 | |
358 | __END__ |
359 | |
360 | =pod |
361 | |
362 | =head1 NAME |
363 | |
364 | Class::MOP - A Meta Object Protocol for Perl 5 |
365 | |
366 | =head1 SYNOPSIS |
367 | |
a2e85e6c |
368 | # ... This will come later, for now see |
369 | # the other SYNOPSIS for more information |
94b19069 |
370 | |
371 | =head1 DESCRIPTON |
372 | |
373 | This module is an attempt to create a meta object protocol for the |
374 | Perl 5 object system. It makes no attempt to change the behavior or |
375 | characteristics of the Perl 5 object system, only to create a |
27e31eaf |
376 | protocol for its manipulation and introspection. |
94b19069 |
377 | |
378 | That said, it does attempt to create the tools for building a rich |
379 | set of extensions to the Perl 5 object system. Every attempt has been |
380 | made for these tools to keep to the spirit of the Perl 5 object |
381 | system that we all know and love. |
382 | |
40483095 |
383 | This documentation is admittedly sparse on details, as time permits |
384 | I will try to improve them. For now, I suggest looking at the items |
385 | listed in the L<SEE ALSO> section for more information. In particular |
386 | the book "The Art of the Meta Object Protocol" was very influential |
387 | in the development of this system. |
388 | |
bfe4d0fc |
389 | =head2 What is a Meta Object Protocol? |
390 | |
391 | A meta object protocol is an API to an object system. |
392 | |
393 | To be more specific, it is a set of abstractions of the components of |
394 | an object system (typically things like; classes, object, methods, |
395 | object attributes, etc.). These abstractions can then be used to both |
396 | inspect and manipulate the object system which they describe. |
397 | |
398 | It can be said that there are two MOPs for any object system; the |
399 | implicit MOP, and the explicit MOP. The implicit MOP handles things |
400 | like method dispatch or inheritance, which happen automatically as |
401 | part of how the object system works. The explicit MOP typically |
402 | handles the introspection/reflection features of the object system. |
403 | All object systems have implicit MOPs, without one, they would not |
404 | work. Explict MOPs however as less common, and depending on the |
405 | language can vary from restrictive (Reflection in Java or C#) to |
406 | wide open (CLOS is a perfect example). |
407 | |
e16da3e6 |
408 | =head2 Yet Another Class Builder!! Why? |
409 | |
410 | This is B<not> a class builder so much as it is a I<class builder |
411 | B<builder>>. My intent is that an end user does not use this module |
412 | directly, but instead this module is used by module authors to |
413 | build extensions and features onto the Perl 5 object system. |
414 | |
94b19069 |
415 | =head2 Who is this module for? |
416 | |
417 | This module is specifically for anyone who has ever created or |
418 | wanted to create a module for the Class:: namespace. The tools which |
419 | this module will provide will hopefully make it easier to do more |
420 | complex things with Perl 5 classes by removing such barriers as |
421 | the need to hack the symbol tables, or understand the fine details |
422 | of method dispatch. |
423 | |
bfe4d0fc |
424 | =head2 What changes do I have to make to use this module? |
425 | |
2eb717d5 |
426 | This module was designed to be as unintrusive as possible. Many of |
343203ee |
427 | its features are accessible without B<any> change to your existsing |
bfe4d0fc |
428 | code at all. It is meant to be a compliment to your existing code and |
2eb717d5 |
429 | not an intrusion on your code base. Unlike many other B<Class::> |
a2e85e6c |
430 | modules, this module B<does not> require you subclass it, or even that |
431 | you C<use> it in within your module's package. |
bfe4d0fc |
432 | |
2eb717d5 |
433 | The only features which requires additions to your code are the |
434 | attribute handling and instance construction features, and these are |
a2e85e6c |
435 | both completely optional features. The only reason for this is because |
2eb717d5 |
436 | Perl 5's object system does not actually have these features built |
437 | in. More information about this feature can be found below. |
bfe4d0fc |
438 | |
439 | =head2 A Note about Performance? |
440 | |
441 | It is a common misconception that explict MOPs are performance drains. |
442 | But this is not a universal truth at all, it is an side-effect of |
443 | specific implementations. For instance, using Java reflection is much |
444 | slower because the JVM cannot take advantage of any compiler |
445 | optimizations, and the JVM has to deal with much more runtime type |
446 | information as well. Reflection in C# is marginally better as it was |
447 | designed into the language and runtime (the CLR). In contrast, CLOS |
448 | (the Common Lisp Object System) was built to support an explicit MOP, |
449 | and so performance is tuned for it. |
450 | |
451 | This library in particular does it's absolute best to avoid putting |
2eb717d5 |
452 | B<any> drain at all upon your code's performance. In fact, by itself |
453 | it does nothing to affect your existing code. So you only pay for |
454 | what you actually use. |
bfe4d0fc |
455 | |
550d56db |
456 | =head2 About Metaclass compatibility |
457 | |
458 | This module makes sure that all metaclasses created are both upwards |
459 | and downwards compatible. The topic of metaclass compatibility is |
460 | highly esoteric and is something only encountered when doing deep and |
461 | involved metaclass hacking. There are two basic kinds of metaclass |
462 | incompatibility; upwards and downwards. |
463 | |
464 | Upwards metaclass compatibility means that the metaclass of a |
465 | given class is either the same as (or a subclass of) all of the |
466 | class's ancestors. |
467 | |
468 | Downward metaclass compatibility means that the metaclasses of a |
469 | given class's anscestors are all either the same as (or a subclass |
470 | of) that metaclass. |
471 | |
472 | Here is a diagram showing a set of two classes (C<A> and C<B>) and |
473 | two metaclasses (C<Meta::A> and C<Meta::B>) which have correct |
474 | metaclass compatibility both upwards and downwards. |
475 | |
476 | +---------+ +---------+ |
477 | | Meta::A |<----| Meta::B | <....... (instance of ) |
478 | +---------+ +---------+ <------- (inherits from) |
479 | ^ ^ |
480 | : : |
481 | +---------+ +---------+ |
482 | | A |<----| B | |
483 | +---------+ +---------+ |
484 | |
485 | As I said this is a highly esoteric topic and one you will only run |
486 | into if you do a lot of subclassing of B<Class::MOP::Class>. If you |
487 | are interested in why this is an issue see the paper |
488 | I<Uniform and safe metaclass composition> linked to in the |
489 | L<SEE ALSO> section of this document. |
490 | |
aa448b16 |
491 | =head2 Using custom metaclasses |
492 | |
493 | Always use the metaclass pragma when using a custom metaclass, this |
494 | will ensure the proper initialization order and not accidentely |
495 | create an incorrect type of metaclass for you. This is a very rare |
496 | problem, and one which can only occur if you are doing deep metaclass |
497 | programming. So in other words, don't worry about it. |
498 | |
94b19069 |
499 | =head1 PROTOCOLS |
500 | |
501 | The protocol is divided into 3 main sub-protocols: |
502 | |
503 | =over 4 |
504 | |
505 | =item The Class protocol |
506 | |
507 | This provides a means of manipulating and introspecting a Perl 5 |
508 | class. It handles all of symbol table hacking for you, and provides |
509 | a rich set of methods that go beyond simple package introspection. |
510 | |
552e3d24 |
511 | See L<Class::MOP::Class> for more details. |
512 | |
94b19069 |
513 | =item The Attribute protocol |
514 | |
515 | This provides a consistent represenation for an attribute of a |
516 | Perl 5 class. Since there are so many ways to create and handle |
517 | atttributes in Perl 5 OO, this attempts to provide as much of a |
518 | unified approach as possible, while giving the freedom and |
519 | flexibility to subclass for specialization. |
520 | |
552e3d24 |
521 | See L<Class::MOP::Attribute> for more details. |
522 | |
94b19069 |
523 | =item The Method protocol |
524 | |
525 | This provides a means of manipulating and introspecting methods in |
526 | the Perl 5 object system. As with attributes, there are many ways to |
527 | approach this topic, so we try to keep it pretty basic, while still |
528 | making it possible to extend the system in many ways. |
529 | |
552e3d24 |
530 | See L<Class::MOP::Method> for more details. |
94b19069 |
531 | |
532 | =back |
533 | |
be7677c7 |
534 | =head1 FUNCTIONS |
535 | |
536 | Class::MOP holds a cache of metaclasses, the following are functions |
537 | (B<not methods>) which can be used to access that cache. It is not |
538 | recommended that you mess with this, bad things could happen. But if |
539 | you are brave and willing to risk it, go for it. |
540 | |
541 | =over 4 |
542 | |
543 | =item B<get_all_metaclasses> |
544 | |
b9d9fc0b |
545 | This will return an hash of all the metaclass instances that have |
546 | been cached by B<Class::MOP::Class> keyed by the package name. |
547 | |
be7677c7 |
548 | =item B<get_all_metaclass_instances> |
549 | |
b9d9fc0b |
550 | This will return an array of all the metaclass instances that have |
551 | been cached by B<Class::MOP::Class>. |
552 | |
be7677c7 |
553 | =item B<get_all_metaclass_names> |
554 | |
b9d9fc0b |
555 | This will return an array of all the metaclass names that have |
556 | been cached by B<Class::MOP::Class>. |
557 | |
be7677c7 |
558 | =item B<get_metaclass_by_name ($name)> |
559 | |
560 | =item B<store_metaclass_by_name ($name, $meta)> |
561 | |
562 | =item B<weaken_metaclass ($name)> |
563 | |
564 | =item B<does_metaclass_exist ($name)> |
565 | |
566 | =item B<remove_metaclass_by_name ($name)> |
567 | |
568 | =back |
569 | |
552e3d24 |
570 | =head1 SEE ALSO |
8b978dd5 |
571 | |
552e3d24 |
572 | =head2 Books |
8b978dd5 |
573 | |
a2e85e6c |
574 | There are very few books out on Meta Object Protocols and Metaclasses |
575 | because it is such an esoteric topic. The following books are really |
576 | the only ones I have found. If you know of any more, B<I<please>> |
577 | email me and let me know, I would love to hear about them. |
578 | |
8b978dd5 |
579 | =over 4 |
580 | |
552e3d24 |
581 | =item "The Art of the Meta Object Protocol" |
8b978dd5 |
582 | |
552e3d24 |
583 | =item "Advances in Object-Oriented Metalevel Architecture and Reflection" |
8b978dd5 |
584 | |
b51af7f9 |
585 | =item "Putting MetaClasses to Work" |
586 | |
a2e85e6c |
587 | =item "Smalltalk: The Language" |
588 | |
94b19069 |
589 | =back |
590 | |
550d56db |
591 | =head2 Papers |
592 | |
593 | =over 4 |
594 | |
595 | =item Uniform and safe metaclass composition |
596 | |
597 | An excellent paper by the people who brought us the original Traits paper. |
598 | This paper is on how Traits can be used to do safe metaclass composition, |
599 | and offers an excellent introduction section which delves into the topic of |
600 | metaclass compatibility. |
601 | |
602 | L<http://www.iam.unibe.ch/~scg/Archive/Papers/Duca05ySafeMetaclassTrait.pdf> |
603 | |
604 | =item Safe Metaclass Programming |
605 | |
606 | This paper seems to precede the above paper, and propose a mix-in based |
607 | approach as opposed to the Traits based approach. Both papers have similar |
608 | information on the metaclass compatibility problem space. |
609 | |
610 | L<http://citeseer.ist.psu.edu/37617.html> |
611 | |
612 | =back |
613 | |
552e3d24 |
614 | =head2 Prior Art |
8b978dd5 |
615 | |
616 | =over 4 |
617 | |
7184ca14 |
618 | =item The Perl 6 MetaModel work in the Pugs project |
8b978dd5 |
619 | |
620 | =over 4 |
621 | |
552e3d24 |
622 | =item L<http://svn.openfoundry.org/pugs/perl5/Perl6-MetaModel> |
8b978dd5 |
623 | |
552e3d24 |
624 | =item L<http://svn.openfoundry.org/pugs/perl5/Perl6-ObjectSpace> |
8b978dd5 |
625 | |
626 | =back |
627 | |
94b19069 |
628 | =back |
629 | |
a2e85e6c |
630 | =head1 SIMILAR MODULES |
631 | |
632 | As I have said above, this module is a class-builder-builder, so it is |
633 | not the same thing as modules like L<Class::Accessor> and |
634 | L<Class::MethodMaker>. That being said there are very few modules on CPAN |
635 | with similar goals to this module. The one I have found which is most |
550d56db |
636 | like this module is L<Class::Meta>, although it's philosophy and the MOP it |
637 | creates are very different from this modules. |
94b19069 |
638 | |
a2e85e6c |
639 | =head1 BUGS |
640 | |
641 | All complex software has bugs lurking in it, and this module is no |
642 | exception. If you find a bug please either email me, or add the bug |
643 | to cpan-RT. |
644 | |
22286063 |
645 | =head1 CODE COVERAGE |
646 | |
647 | I use L<Devel::Cover> to test the code coverage of my tests, below is the |
648 | L<Devel::Cover> report on this module's test suite. |
649 | |
650 | ---------------------------- ------ ------ ------ ------ ------ ------ ------ |
651 | File stmt bran cond sub pod time total |
652 | ---------------------------- ------ ------ ------ ------ ------ ------ ------ |
b9d9fc0b |
653 | Class/MOP.pm 78.0 87.5 55.6 71.4 100.0 12.4 76.8 |
654 | Class/MOP/Attribute.pm 83.4 75.6 86.7 94.4 100.0 8.9 85.2 |
655 | Class/MOP/Class.pm 96.9 75.8 43.2 98.0 100.0 55.3 83.6 |
656 | Class/MOP/Class/Immutable.pm 88.5 53.8 n/a 95.8 100.0 1.1 84.7 |
657 | Class/MOP/Instance.pm 87.9 75.0 33.3 89.7 100.0 10.1 89.1 |
658 | Class/MOP/Method.pm 97.6 60.0 57.9 76.9 100.0 1.5 82.8 |
659 | Class/MOP/Module.pm 87.5 n/a 11.1 83.3 100.0 0.3 66.7 |
660 | Class/MOP/Object.pm 100.0 n/a 33.3 100.0 100.0 0.1 89.5 |
661 | Class/MOP/Package.pm 95.1 69.0 33.3 100.0 100.0 9.9 85.5 |
662 | metaclass.pm 100.0 100.0 83.3 100.0 n/a 0.5 97.7 |
22286063 |
663 | ---------------------------- ------ ------ ------ ------ ------ ------ ------ |
b9d9fc0b |
664 | Total 91.5 72.1 48.8 90.7 100.0 100.0 84.2 |
22286063 |
665 | ---------------------------- ------ ------ ------ ------ ------ ------ ------ |
666 | |
a2e85e6c |
667 | =head1 ACKNOWLEDGEMENTS |
668 | |
669 | =over 4 |
670 | |
b9d9fc0b |
671 | =item Rob Kinyon |
a2e85e6c |
672 | |
673 | Thanks to Rob for actually getting the development of this module kick-started. |
674 | |
675 | =back |
676 | |
1a09d9cc |
677 | =head1 AUTHORS |
94b19069 |
678 | |
a2e85e6c |
679 | Stevan Little E<lt>stevan@iinteractive.comE<gt> |
552e3d24 |
680 | |
1a09d9cc |
681 | Yuval Kogman E<lt>nothingmuch@woobling.comE<gt> |
682 | |
94b19069 |
683 | =head1 COPYRIGHT AND LICENSE |
684 | |
685 | Copyright 2006 by Infinity Interactive, Inc. |
686 | |
687 | L<http://www.iinteractive.com> |
688 | |
689 | This library is free software; you can redistribute it and/or modify |
690 | it under the same terms as Perl itself. |
691 | |
692 | =cut |