Commit | Line | Data |
38bf2a25 |
1 | |
2 | package Class::MOP; |
3 | |
4 | use strict; |
5 | use warnings; |
6 | |
7 | use 5.008; |
8 | |
9 | use MRO::Compat; |
10 | |
11 | use Carp 'confess'; |
12 | use Scalar::Util 'weaken', 'isweak', 'reftype', 'blessed'; |
13 | use Data::OptList; |
14 | use Try::Tiny; |
15 | |
16 | use Class::MOP::Mixin::AttributeCore; |
17 | use Class::MOP::Mixin::HasAttributes; |
18 | use Class::MOP::Mixin::HasMethods; |
19 | use Class::MOP::Class; |
20 | use Class::MOP::Attribute; |
21 | use Class::MOP::Method; |
22 | |
23 | BEGIN { |
24 | *IS_RUNNING_ON_5_10 = ($] < 5.009_005) |
25 | ? sub () { 0 } |
26 | : sub () { 1 }; |
27 | |
28 | # this is either part of core or set up appropriately by MRO::Compat |
29 | *check_package_cache_flag = \&mro::get_pkg_gen; |
30 | } |
31 | |
38bf2a25 |
32 | XSLoader::load( |
33 | 'Moose', |
202b6e57 |
34 | $Class::MOP::{VERSION} ? ${ $Class::MOP::{VERSION} } : () |
38bf2a25 |
35 | ); |
36 | |
37 | { |
38 | # Metaclasses are singletons, so we cache them here. |
39 | # there is no need to worry about destruction though |
40 | # because they should die only when the program dies. |
41 | # After all, do package definitions even get reaped? |
42 | # Anonymous classes manage their own destruction. |
43 | my %METAS; |
44 | |
45 | sub get_all_metaclasses { %METAS } |
46 | sub get_all_metaclass_instances { values %METAS } |
47 | sub get_all_metaclass_names { keys %METAS } |
48 | sub get_metaclass_by_name { $METAS{$_[0]} } |
49 | sub store_metaclass_by_name { $METAS{$_[0]} = $_[1] } |
50 | sub weaken_metaclass { weaken($METAS{$_[0]}) } |
51 | sub metaclass_is_weak { isweak($METAS{$_[0]}) } |
52 | sub does_metaclass_exist { exists $METAS{$_[0]} && defined $METAS{$_[0]} } |
53 | sub remove_metaclass_by_name { delete $METAS{$_[0]}; return } |
54 | |
55 | # This handles instances as well as class names |
56 | sub class_of { |
57 | return unless defined $_[0]; |
58 | my $class = blessed($_[0]) || $_[0]; |
59 | return $METAS{$class}; |
60 | } |
61 | |
62 | # NOTE: |
63 | # We only cache metaclasses, meaning instances of |
64 | # Class::MOP::Class. We do not cache instance of |
65 | # Class::MOP::Package or Class::MOP::Module. Mostly |
66 | # because I don't yet see a good reason to do so. |
67 | } |
68 | |
69 | sub _class_to_pmfile { |
70 | my $class = shift; |
71 | |
72 | my $file = $class . '.pm'; |
73 | $file =~ s{::}{/}g; |
74 | |
75 | return $file; |
76 | } |
77 | |
78 | sub load_first_existing_class { |
79 | my $classes = Data::OptList::mkopt(\@_) |
80 | or return; |
81 | |
82 | foreach my $class (@{ $classes }) { |
83 | my $name = $class->[0]; |
84 | unless ( _is_valid_class_name($name) ) { |
85 | my $display = defined($name) ? $name : 'undef'; |
86 | confess "Invalid class name ($display)"; |
87 | } |
88 | } |
89 | |
90 | my $found; |
91 | my %exceptions; |
92 | |
93 | for my $class (@{ $classes }) { |
94 | my ($name, $options) = @{ $class }; |
95 | |
96 | if ($options) { |
97 | return $name if is_class_loaded($name, $options); |
98 | if (is_class_loaded($name)) { |
99 | # we already know it's loaded and too old, but we call |
100 | # ->VERSION anyway to generate the exception for us |
101 | $name->VERSION($options->{-version}); |
102 | } |
103 | } |
104 | else { |
105 | return $name if is_class_loaded($name); |
106 | } |
107 | |
108 | my $file = _class_to_pmfile($name); |
109 | return $name if try { |
110 | local $SIG{__DIE__}; |
111 | require $file; |
112 | $name->VERSION($options->{-version}) |
113 | if defined $options->{-version}; |
114 | return 1; |
115 | } |
116 | catch { |
117 | unless (/^Can't locate \Q$file\E in \@INC/) { |
118 | confess "Couldn't load class ($name) because: $_"; |
119 | } |
120 | |
121 | return; |
122 | }; |
123 | } |
124 | |
125 | if ( @{ $classes } > 1 ) { |
126 | my @list = map { $_->[0] } @{ $classes }; |
127 | confess "Can't locate any of @list in \@INC (\@INC contains: @INC)."; |
128 | } else { |
129 | confess "Can't locate " . _class_to_pmfile($classes->[0]->[0]) . " in \@INC (\@INC contains: @INC)."; |
130 | } |
131 | } |
132 | |
133 | sub load_class { |
134 | load_first_existing_class($_[0], ref $_[1] ? $_[1] : ()); |
135 | |
136 | # This is done to avoid breaking code which checked the return value. Said |
137 | # code is dumb. The return value was _always_ true, since it dies on |
138 | # failure! |
139 | return 1; |
140 | } |
141 | |
142 | sub _is_valid_class_name { |
143 | my $class = shift; |
144 | |
145 | return 0 if ref($class); |
146 | return 0 unless defined($class); |
147 | return 0 unless length($class); |
148 | |
149 | return 1 if $class =~ /^\w+(?:::\w+)*$/; |
150 | |
151 | return 0; |
152 | } |
153 | |
154 | ## ---------------------------------------------------------------------------- |
155 | ## Setting up our environment ... |
156 | ## ---------------------------------------------------------------------------- |
157 | ## Class::MOP needs to have a few things in the global perl environment so |
158 | ## that it can operate effectively. Those things are done here. |
159 | ## ---------------------------------------------------------------------------- |
160 | |
161 | # ... nothing yet actually ;) |
162 | |
163 | ## ---------------------------------------------------------------------------- |
164 | ## Bootstrapping |
165 | ## ---------------------------------------------------------------------------- |
166 | ## The code below here is to bootstrap our MOP with itself. This is also |
167 | ## sometimes called "tying the knot". By doing this, we make it much easier |
168 | ## to extend the MOP through subclassing and such since now you can use the |
169 | ## MOP itself to extend itself. |
170 | ## |
171 | ## Yes, I know, thats weird and insane, but it's a good thing, trust me :) |
172 | ## ---------------------------------------------------------------------------- |
173 | |
174 | # We need to add in the meta-attributes here so that |
175 | # any subclass of Class::MOP::* will be able to |
176 | # inherit them using _construct_instance |
177 | |
178 | ## -------------------------------------------------------- |
179 | ## Class::MOP::Mixin::HasMethods |
180 | |
181 | Class::MOP::Mixin::HasMethods->meta->add_attribute( |
182 | Class::MOP::Attribute->new('_methods' => ( |
183 | reader => { |
184 | # NOTE: |
185 | # we just alias the original method |
186 | # rather than re-produce it here |
187 | '_method_map' => \&Class::MOP::Mixin::HasMethods::_method_map |
188 | }, |
189 | default => sub { {} } |
190 | )) |
191 | ); |
192 | |
193 | Class::MOP::Mixin::HasMethods->meta->add_attribute( |
194 | Class::MOP::Attribute->new('method_metaclass' => ( |
195 | reader => { |
196 | # NOTE: |
197 | # we just alias the original method |
198 | # rather than re-produce it here |
199 | 'method_metaclass' => \&Class::MOP::Mixin::HasMethods::method_metaclass |
200 | }, |
201 | default => 'Class::MOP::Method', |
202 | )) |
203 | ); |
204 | |
205 | Class::MOP::Mixin::HasMethods->meta->add_attribute( |
206 | Class::MOP::Attribute->new('wrapped_method_metaclass' => ( |
207 | reader => { |
208 | # NOTE: |
209 | # we just alias the original method |
210 | # rather than re-produce it here |
211 | 'wrapped_method_metaclass' => \&Class::MOP::Mixin::HasMethods::wrapped_method_metaclass |
212 | }, |
213 | default => 'Class::MOP::Method::Wrapped', |
214 | )) |
215 | ); |
216 | |
217 | ## -------------------------------------------------------- |
218 | ## Class::MOP::Mixin::HasMethods |
219 | |
220 | Class::MOP::Mixin::HasAttributes->meta->add_attribute( |
221 | Class::MOP::Attribute->new('attributes' => ( |
222 | reader => { |
223 | # NOTE: we need to do this in order |
224 | # for the instance meta-object to |
225 | # not fall into meta-circular death |
226 | # |
227 | # we just alias the original method |
228 | # rather than re-produce it here |
229 | '_attribute_map' => \&Class::MOP::Mixin::HasAttributes::_attribute_map |
230 | }, |
231 | default => sub { {} } |
232 | )) |
233 | ); |
234 | |
235 | Class::MOP::Mixin::HasAttributes->meta->add_attribute( |
236 | Class::MOP::Attribute->new('attribute_metaclass' => ( |
237 | reader => { |
238 | # NOTE: |
239 | # we just alias the original method |
240 | # rather than re-produce it here |
241 | 'attribute_metaclass' => \&Class::MOP::Mixin::HasAttributes::attribute_metaclass |
242 | }, |
243 | default => 'Class::MOP::Attribute', |
244 | )) |
245 | ); |
246 | |
247 | ## -------------------------------------------------------- |
248 | ## Class::MOP::Package |
249 | |
250 | Class::MOP::Package->meta->add_attribute( |
251 | Class::MOP::Attribute->new('package' => ( |
252 | reader => { |
253 | # NOTE: we need to do this in order |
254 | # for the instance meta-object to |
255 | # not fall into meta-circular death |
256 | # |
257 | # we just alias the original method |
258 | # rather than re-produce it here |
259 | 'name' => \&Class::MOP::Package::name |
260 | }, |
261 | )) |
262 | ); |
263 | |
264 | Class::MOP::Package->meta->add_attribute( |
265 | Class::MOP::Attribute->new('namespace' => ( |
266 | reader => { |
267 | # NOTE: |
268 | # we just alias the original method |
269 | # rather than re-produce it here |
270 | 'namespace' => \&Class::MOP::Package::namespace |
271 | }, |
272 | init_arg => undef, |
273 | default => sub { \undef } |
274 | )) |
275 | ); |
276 | |
277 | ## -------------------------------------------------------- |
278 | ## Class::MOP::Module |
279 | |
280 | # NOTE: |
281 | # yeah this is kind of stretching things a bit, |
282 | # but truthfully the version should be an attribute |
283 | # of the Module, the weirdness comes from having to |
284 | # stick to Perl 5 convention and store it in the |
285 | # $VERSION package variable. Basically if you just |
286 | # squint at it, it will look how you want it to look. |
287 | # Either as a package variable, or as a attribute of |
288 | # the metaclass, isn't abstraction great :) |
289 | |
290 | Class::MOP::Module->meta->add_attribute( |
291 | Class::MOP::Attribute->new('version' => ( |
292 | reader => { |
293 | # NOTE: |
294 | # we just alias the original method |
295 | # rather than re-produce it here |
296 | 'version' => \&Class::MOP::Module::version |
297 | }, |
298 | init_arg => undef, |
299 | default => sub { \undef } |
300 | )) |
301 | ); |
302 | |
303 | # NOTE: |
304 | # By following the same conventions as version here, |
305 | # we are opening up the possibility that people can |
306 | # use the $AUTHORITY in non-Class::MOP modules as |
307 | # well. |
308 | |
309 | Class::MOP::Module->meta->add_attribute( |
310 | Class::MOP::Attribute->new('authority' => ( |
311 | reader => { |
312 | # NOTE: |
313 | # we just alias the original method |
314 | # rather than re-produce it here |
315 | 'authority' => \&Class::MOP::Module::authority |
316 | }, |
317 | init_arg => undef, |
318 | default => sub { \undef } |
319 | )) |
320 | ); |
321 | |
322 | ## -------------------------------------------------------- |
323 | ## Class::MOP::Class |
324 | |
325 | Class::MOP::Class->meta->add_attribute( |
326 | Class::MOP::Attribute->new('superclasses' => ( |
327 | accessor => { |
328 | # NOTE: |
329 | # we just alias the original method |
330 | # rather than re-produce it here |
331 | 'superclasses' => \&Class::MOP::Class::superclasses |
332 | }, |
333 | init_arg => undef, |
334 | default => sub { \undef } |
335 | )) |
336 | ); |
337 | |
338 | Class::MOP::Class->meta->add_attribute( |
339 | Class::MOP::Attribute->new('instance_metaclass' => ( |
340 | reader => { |
341 | # NOTE: we need to do this in order |
342 | # for the instance meta-object to |
343 | # not fall into meta-circular death |
344 | # |
345 | # we just alias the original method |
346 | # rather than re-produce it here |
347 | 'instance_metaclass' => \&Class::MOP::Class::instance_metaclass |
348 | }, |
349 | default => 'Class::MOP::Instance', |
350 | )) |
351 | ); |
352 | |
353 | Class::MOP::Class->meta->add_attribute( |
354 | Class::MOP::Attribute->new('immutable_trait' => ( |
355 | reader => { |
356 | 'immutable_trait' => \&Class::MOP::Class::immutable_trait |
357 | }, |
358 | default => "Class::MOP::Class::Immutable::Trait", |
359 | )) |
360 | ); |
361 | |
362 | Class::MOP::Class->meta->add_attribute( |
363 | Class::MOP::Attribute->new('constructor_name' => ( |
364 | reader => { |
365 | 'constructor_name' => \&Class::MOP::Class::constructor_name, |
366 | }, |
367 | default => "new", |
368 | )) |
369 | ); |
370 | |
371 | Class::MOP::Class->meta->add_attribute( |
372 | Class::MOP::Attribute->new('constructor_class' => ( |
373 | reader => { |
374 | 'constructor_class' => \&Class::MOP::Class::constructor_class, |
375 | }, |
376 | default => "Class::MOP::Method::Constructor", |
377 | )) |
378 | ); |
379 | |
380 | |
381 | Class::MOP::Class->meta->add_attribute( |
382 | Class::MOP::Attribute->new('destructor_class' => ( |
383 | reader => { |
384 | 'destructor_class' => \&Class::MOP::Class::destructor_class, |
385 | }, |
386 | )) |
387 | ); |
388 | |
389 | # NOTE: |
390 | # we don't actually need to tie the knot with |
391 | # Class::MOP::Class here, it is actually handled |
392 | # within Class::MOP::Class itself in the |
393 | # _construct_class_instance method. |
394 | |
395 | ## -------------------------------------------------------- |
396 | ## Class::MOP::Mixin::AttributeCore |
397 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
398 | Class::MOP::Attribute->new('name' => ( |
399 | reader => { |
400 | # NOTE: we need to do this in order |
401 | # for the instance meta-object to |
402 | # not fall into meta-circular death |
403 | # |
404 | # we just alias the original method |
405 | # rather than re-produce it here |
406 | 'name' => \&Class::MOP::Mixin::AttributeCore::name |
407 | } |
408 | )) |
409 | ); |
410 | |
411 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
412 | Class::MOP::Attribute->new('accessor' => ( |
413 | reader => { 'accessor' => \&Class::MOP::Mixin::AttributeCore::accessor }, |
414 | predicate => { 'has_accessor' => \&Class::MOP::Mixin::AttributeCore::has_accessor }, |
415 | )) |
416 | ); |
417 | |
418 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
419 | Class::MOP::Attribute->new('reader' => ( |
420 | reader => { 'reader' => \&Class::MOP::Mixin::AttributeCore::reader }, |
421 | predicate => { 'has_reader' => \&Class::MOP::Mixin::AttributeCore::has_reader }, |
422 | )) |
423 | ); |
424 | |
425 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
426 | Class::MOP::Attribute->new('initializer' => ( |
427 | reader => { 'initializer' => \&Class::MOP::Mixin::AttributeCore::initializer }, |
428 | predicate => { 'has_initializer' => \&Class::MOP::Mixin::AttributeCore::has_initializer }, |
429 | )) |
430 | ); |
431 | |
432 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
433 | Class::MOP::Attribute->new('definition_context' => ( |
434 | reader => { 'definition_context' => \&Class::MOP::Mixin::AttributeCore::definition_context }, |
435 | )) |
436 | ); |
437 | |
438 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
439 | Class::MOP::Attribute->new('writer' => ( |
440 | reader => { 'writer' => \&Class::MOP::Mixin::AttributeCore::writer }, |
441 | predicate => { 'has_writer' => \&Class::MOP::Mixin::AttributeCore::has_writer }, |
442 | )) |
443 | ); |
444 | |
445 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
446 | Class::MOP::Attribute->new('predicate' => ( |
447 | reader => { 'predicate' => \&Class::MOP::Mixin::AttributeCore::predicate }, |
448 | predicate => { 'has_predicate' => \&Class::MOP::Mixin::AttributeCore::has_predicate }, |
449 | )) |
450 | ); |
451 | |
452 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
453 | Class::MOP::Attribute->new('clearer' => ( |
454 | reader => { 'clearer' => \&Class::MOP::Mixin::AttributeCore::clearer }, |
455 | predicate => { 'has_clearer' => \&Class::MOP::Mixin::AttributeCore::has_clearer }, |
456 | )) |
457 | ); |
458 | |
459 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
460 | Class::MOP::Attribute->new('builder' => ( |
461 | reader => { 'builder' => \&Class::MOP::Mixin::AttributeCore::builder }, |
462 | predicate => { 'has_builder' => \&Class::MOP::Mixin::AttributeCore::has_builder }, |
463 | )) |
464 | ); |
465 | |
466 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
467 | Class::MOP::Attribute->new('init_arg' => ( |
468 | reader => { 'init_arg' => \&Class::MOP::Mixin::AttributeCore::init_arg }, |
469 | predicate => { 'has_init_arg' => \&Class::MOP::Mixin::AttributeCore::has_init_arg }, |
470 | )) |
471 | ); |
472 | |
473 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
474 | Class::MOP::Attribute->new('default' => ( |
475 | # default has a custom 'reader' method ... |
476 | predicate => { 'has_default' => \&Class::MOP::Mixin::AttributeCore::has_default }, |
477 | )) |
478 | ); |
479 | |
480 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
481 | Class::MOP::Attribute->new('insertion_order' => ( |
482 | reader => { 'insertion_order' => \&Class::MOP::Mixin::AttributeCore::insertion_order }, |
483 | writer => { '_set_insertion_order' => \&Class::MOP::Mixin::AttributeCore::_set_insertion_order }, |
484 | predicate => { 'has_insertion_order' => \&Class::MOP::Mixin::AttributeCore::has_insertion_order }, |
485 | )) |
486 | ); |
487 | |
488 | ## -------------------------------------------------------- |
489 | ## Class::MOP::Attribute |
490 | Class::MOP::Attribute->meta->add_attribute( |
491 | Class::MOP::Attribute->new('associated_class' => ( |
492 | reader => { |
493 | # NOTE: we need to do this in order |
494 | # for the instance meta-object to |
495 | # not fall into meta-circular death |
496 | # |
497 | # we just alias the original method |
498 | # rather than re-produce it here |
499 | 'associated_class' => \&Class::MOP::Attribute::associated_class |
500 | } |
501 | )) |
502 | ); |
503 | |
504 | Class::MOP::Attribute->meta->add_attribute( |
505 | Class::MOP::Attribute->new('associated_methods' => ( |
506 | reader => { 'associated_methods' => \&Class::MOP::Attribute::associated_methods }, |
507 | default => sub { [] } |
508 | )) |
509 | ); |
510 | |
511 | Class::MOP::Attribute->meta->add_method('clone' => sub { |
512 | my $self = shift; |
513 | $self->meta->clone_object($self, @_); |
514 | }); |
515 | |
516 | ## -------------------------------------------------------- |
517 | ## Class::MOP::Method |
518 | Class::MOP::Method->meta->add_attribute( |
519 | Class::MOP::Attribute->new('body' => ( |
520 | reader => { 'body' => \&Class::MOP::Method::body }, |
521 | )) |
522 | ); |
523 | |
524 | Class::MOP::Method->meta->add_attribute( |
525 | Class::MOP::Attribute->new('associated_metaclass' => ( |
526 | reader => { 'associated_metaclass' => \&Class::MOP::Method::associated_metaclass }, |
527 | )) |
528 | ); |
529 | |
530 | Class::MOP::Method->meta->add_attribute( |
531 | Class::MOP::Attribute->new('package_name' => ( |
532 | reader => { 'package_name' => \&Class::MOP::Method::package_name }, |
533 | )) |
534 | ); |
535 | |
536 | Class::MOP::Method->meta->add_attribute( |
537 | Class::MOP::Attribute->new('name' => ( |
538 | reader => { 'name' => \&Class::MOP::Method::name }, |
539 | )) |
540 | ); |
541 | |
542 | Class::MOP::Method->meta->add_attribute( |
543 | Class::MOP::Attribute->new('original_method' => ( |
544 | reader => { 'original_method' => \&Class::MOP::Method::original_method }, |
545 | writer => { '_set_original_method' => \&Class::MOP::Method::_set_original_method }, |
546 | )) |
547 | ); |
548 | |
549 | ## -------------------------------------------------------- |
550 | ## Class::MOP::Method::Wrapped |
551 | |
552 | # NOTE: |
553 | # the way this item is initialized, this |
554 | # really does not follow the standard |
555 | # practices of attributes, but we put |
556 | # it here for completeness |
557 | Class::MOP::Method::Wrapped->meta->add_attribute( |
558 | Class::MOP::Attribute->new('modifier_table') |
559 | ); |
560 | |
561 | ## -------------------------------------------------------- |
562 | ## Class::MOP::Method::Generated |
563 | |
564 | Class::MOP::Method::Generated->meta->add_attribute( |
565 | Class::MOP::Attribute->new('is_inline' => ( |
566 | reader => { 'is_inline' => \&Class::MOP::Method::Generated::is_inline }, |
567 | default => 0, |
568 | )) |
569 | ); |
570 | |
571 | Class::MOP::Method::Generated->meta->add_attribute( |
572 | Class::MOP::Attribute->new('definition_context' => ( |
573 | reader => { 'definition_context' => \&Class::MOP::Method::Generated::definition_context }, |
574 | )) |
575 | ); |
576 | |
577 | |
578 | ## -------------------------------------------------------- |
579 | ## Class::MOP::Method::Inlined |
580 | |
581 | Class::MOP::Method::Inlined->meta->add_attribute( |
582 | Class::MOP::Attribute->new('_expected_method_class' => ( |
583 | reader => { '_expected_method_class' => \&Class::MOP::Method::Inlined::_expected_method_class }, |
584 | )) |
585 | ); |
586 | |
587 | ## -------------------------------------------------------- |
588 | ## Class::MOP::Method::Accessor |
589 | |
590 | Class::MOP::Method::Accessor->meta->add_attribute( |
591 | Class::MOP::Attribute->new('attribute' => ( |
592 | reader => { |
593 | 'associated_attribute' => \&Class::MOP::Method::Accessor::associated_attribute |
594 | }, |
595 | )) |
596 | ); |
597 | |
598 | Class::MOP::Method::Accessor->meta->add_attribute( |
599 | Class::MOP::Attribute->new('accessor_type' => ( |
600 | reader => { 'accessor_type' => \&Class::MOP::Method::Accessor::accessor_type }, |
601 | )) |
602 | ); |
603 | |
604 | ## -------------------------------------------------------- |
605 | ## Class::MOP::Method::Constructor |
606 | |
607 | Class::MOP::Method::Constructor->meta->add_attribute( |
608 | Class::MOP::Attribute->new('options' => ( |
609 | reader => { |
610 | 'options' => \&Class::MOP::Method::Constructor::options |
611 | }, |
612 | default => sub { +{} } |
613 | )) |
614 | ); |
615 | |
616 | Class::MOP::Method::Constructor->meta->add_attribute( |
617 | Class::MOP::Attribute->new('associated_metaclass' => ( |
618 | init_arg => "metaclass", # FIXME alias and rename |
619 | reader => { |
620 | 'associated_metaclass' => \&Class::MOP::Method::Constructor::associated_metaclass |
621 | }, |
622 | )) |
623 | ); |
624 | |
625 | ## -------------------------------------------------------- |
626 | ## Class::MOP::Instance |
627 | |
628 | # NOTE: |
629 | # these don't yet do much of anything, but are just |
630 | # included for completeness |
631 | |
632 | Class::MOP::Instance->meta->add_attribute( |
633 | Class::MOP::Attribute->new('associated_metaclass', |
634 | reader => { associated_metaclass => \&Class::MOP::Instance::associated_metaclass }, |
635 | ), |
636 | ); |
637 | |
638 | Class::MOP::Instance->meta->add_attribute( |
639 | Class::MOP::Attribute->new('_class_name', |
640 | init_arg => undef, |
641 | reader => { _class_name => \&Class::MOP::Instance::_class_name }, |
642 | #lazy => 1, # not yet supported by Class::MOP but out our version does it anyway |
643 | #default => sub { $_[0]->associated_metaclass->name }, |
644 | ), |
645 | ); |
646 | |
647 | Class::MOP::Instance->meta->add_attribute( |
648 | Class::MOP::Attribute->new('attributes', |
649 | reader => { attributes => \&Class::MOP::Instance::get_all_attributes }, |
650 | ), |
651 | ); |
652 | |
653 | Class::MOP::Instance->meta->add_attribute( |
654 | Class::MOP::Attribute->new('slots', |
655 | reader => { slots => \&Class::MOP::Instance::slots }, |
656 | ), |
657 | ); |
658 | |
659 | Class::MOP::Instance->meta->add_attribute( |
660 | Class::MOP::Attribute->new('slot_hash', |
661 | reader => { slot_hash => \&Class::MOP::Instance::slot_hash }, |
662 | ), |
663 | ); |
664 | |
665 | ## -------------------------------------------------------- |
666 | ## Class::MOP::Object |
667 | |
668 | # need to replace the meta method there with a real meta method object |
669 | Class::MOP::Object->meta->_add_meta_method('meta'); |
670 | |
671 | ## -------------------------------------------------------- |
672 | ## Class::MOP::Mixin |
673 | |
674 | # need to replace the meta method there with a real meta method object |
675 | Class::MOP::Mixin->meta->_add_meta_method('meta'); |
676 | |
677 | require Class::MOP::Deprecated unless our $no_deprecated; |
678 | |
679 | # we need the meta instance of the meta instance to be created now, in order |
680 | # for the constructor to be able to use it |
681 | Class::MOP::Instance->meta->get_meta_instance; |
682 | |
683 | # pretend the add_method never happenned. it hasn't yet affected anything |
684 | undef Class::MOP::Instance->meta->{_package_cache_flag}; |
685 | |
686 | ## -------------------------------------------------------- |
687 | ## Now close all the Class::MOP::* classes |
688 | |
689 | # NOTE: we don't need to inline the the accessors this only lengthens |
690 | # the compile time of the MOP, and gives us no actual benefits. |
691 | |
692 | $_->meta->make_immutable( |
693 | inline_constructor => 0, |
694 | constructor_name => "_new", |
695 | inline_accessors => 0, |
696 | ) for qw/ |
697 | Class::MOP::Package |
698 | Class::MOP::Module |
699 | Class::MOP::Class |
700 | |
701 | Class::MOP::Attribute |
702 | Class::MOP::Method |
703 | Class::MOP::Instance |
704 | |
705 | Class::MOP::Object |
706 | |
707 | Class::MOP::Method::Generated |
708 | Class::MOP::Method::Inlined |
709 | |
710 | Class::MOP::Method::Accessor |
711 | Class::MOP::Method::Constructor |
712 | Class::MOP::Method::Wrapped |
713 | |
714 | Class::MOP::Method::Meta |
715 | /; |
716 | |
717 | $_->meta->make_immutable( |
718 | inline_constructor => 0, |
719 | constructor_name => undef, |
720 | inline_accessors => 0, |
721 | ) for qw/ |
722 | Class::MOP::Mixin |
723 | Class::MOP::Mixin::AttributeCore |
724 | Class::MOP::Mixin::HasAttributes |
725 | Class::MOP::Mixin::HasMethods |
726 | /; |
727 | |
728 | 1; |
729 | |
730 | # ABSTRACT: A Meta Object Protocol for Perl 5 |
731 | |
732 | __END__ |
733 | |
734 | =pod |
735 | |
736 | =head1 DESCRIPTION |
737 | |
738 | This module is a fully functioning meta object protocol for the |
739 | Perl 5 object system. It makes no attempt to change the behavior or |
740 | characteristics of the Perl 5 object system, only to create a |
741 | protocol for its manipulation and introspection. |
742 | |
743 | That said, it does attempt to create the tools for building a rich set |
744 | of extensions to the Perl 5 object system. Every attempt has been made |
745 | to abide by the spirit of the Perl 5 object system that we all know |
746 | and love. |
747 | |
748 | This documentation is sparse on conceptual details. We suggest looking |
749 | at the items listed in the L<SEE ALSO> section for more |
750 | information. In particular the book "The Art of the Meta Object |
751 | Protocol" was very influential in the development of this system. |
752 | |
753 | =head2 What is a Meta Object Protocol? |
754 | |
755 | A meta object protocol is an API to an object system. |
756 | |
757 | To be more specific, it abstracts the components of an object system |
758 | (classes, object, methods, object attributes, etc.). These |
759 | abstractions can then be used to inspect and manipulate the object |
760 | system which they describe. |
761 | |
762 | It can be said that there are two MOPs for any object system; the |
763 | implicit MOP and the explicit MOP. The implicit MOP handles things |
764 | like method dispatch or inheritance, which happen automatically as |
765 | part of how the object system works. The explicit MOP typically |
766 | handles the introspection/reflection features of the object system. |
767 | |
768 | All object systems have implicit MOPs. Without one, they would not |
769 | work. Explicit MOPs are much less common, and depending on the |
770 | language can vary from restrictive (Reflection in Java or C#) to wide |
771 | open (CLOS is a perfect example). |
772 | |
773 | =head2 Yet Another Class Builder! Why? |
774 | |
775 | This is B<not> a class builder so much as a I<class builder |
776 | B<builder>>. The intent is that an end user will not use this module |
777 | directly, but instead this module is used by module authors to build |
778 | extensions and features onto the Perl 5 object system. |
779 | |
780 | This system is used by L<Moose>, which supplies a powerful class |
781 | builder system built entirely on top of C<Class::MOP>. |
782 | |
783 | =head2 Who is this module for? |
784 | |
785 | This module is for anyone who has ever created or wanted to create a |
786 | module for the Class:: namespace. The tools which this module provides |
787 | make doing complex Perl 5 wizardry simpler, by removing such barriers |
788 | as the need to hack symbol tables, or understand the fine details of |
789 | method dispatch. |
790 | |
791 | =head2 What changes do I have to make to use this module? |
792 | |
793 | This module was designed to be as unintrusive as possible. Many of its |
794 | features are accessible without B<any> change to your existing |
795 | code. It is meant to be a compliment to your existing code and not an |
796 | intrusion on your code base. Unlike many other B<Class::> modules, |
797 | this module B<does not> require you subclass it, or even that you |
798 | C<use> it in within your module's package. |
799 | |
800 | The only features which requires additions to your code are the |
801 | attribute handling and instance construction features, and these are |
802 | both completely optional features. The only reason for this is because |
803 | Perl 5's object system does not actually have these features built |
804 | in. More information about this feature can be found below. |
805 | |
806 | =head2 About Performance |
807 | |
808 | It is a common misconception that explicit MOPs are a performance hit. |
809 | This is not a universal truth, it is a side-effect of some specific |
810 | implementations. For instance, using Java reflection is slow because |
811 | the JVM cannot take advantage of any compiler optimizations, and the |
812 | JVM has to deal with much more runtime type information as well. |
813 | |
814 | Reflection in C# is marginally better as it was designed into the |
815 | language and runtime (the CLR). In contrast, CLOS (the Common Lisp |
816 | Object System) was built to support an explicit MOP, and so |
817 | performance is tuned for it. |
818 | |
819 | This library in particular does its absolute best to avoid putting |
820 | B<any> drain at all upon your code's performance. In fact, by itself |
821 | it does nothing to affect your existing code. So you only pay for what |
822 | you actually use. |
823 | |
824 | =head2 About Metaclass compatibility |
825 | |
826 | This module makes sure that all metaclasses created are both upwards |
827 | and downwards compatible. The topic of metaclass compatibility is |
828 | highly esoteric and is something only encountered when doing deep and |
829 | involved metaclass hacking. There are two basic kinds of metaclass |
830 | incompatibility; upwards and downwards. |
831 | |
832 | Upwards metaclass compatibility means that the metaclass of a |
833 | given class is either the same as (or a subclass of) all of the |
834 | class's ancestors. |
835 | |
836 | Downward metaclass compatibility means that the metaclasses of a |
837 | given class's ancestors are all either the same as (or a subclass |
838 | of) that metaclass. |
839 | |
840 | Here is a diagram showing a set of two classes (C<A> and C<B>) and |
841 | two metaclasses (C<Meta::A> and C<Meta::B>) which have correct |
842 | metaclass compatibility both upwards and downwards. |
843 | |
844 | +---------+ +---------+ |
845 | | Meta::A |<----| Meta::B | <....... (instance of ) |
846 | +---------+ +---------+ <------- (inherits from) |
847 | ^ ^ |
848 | : : |
849 | +---------+ +---------+ |
850 | | A |<----| B | |
851 | +---------+ +---------+ |
852 | |
853 | In actuality, I<all> of a class's metaclasses must be compatible, |
854 | not just the class metaclass. That includes the instance, attribute, |
855 | and method metaclasses, as well as the constructor and destructor |
856 | classes. |
857 | |
858 | C<Class::MOP> will attempt to fix some simple types of |
859 | incompatibilities. If all the metaclasses for the parent class are |
860 | I<subclasses> of the child's metaclasses then we can simply replace |
861 | the child's metaclasses with the parent's. In addition, if the child |
862 | is missing a metaclass that the parent has, we can also just make the |
863 | child use the parent's metaclass. |
864 | |
865 | As I said this is a highly esoteric topic and one you will only run |
866 | into if you do a lot of subclassing of L<Class::MOP::Class>. If you |
867 | are interested in why this is an issue see the paper I<Uniform and |
868 | safe metaclass composition> linked to in the L<SEE ALSO> section of |
869 | this document. |
870 | |
871 | =head2 Using custom metaclasses |
872 | |
873 | Always use the L<metaclass> pragma when using a custom metaclass, this |
874 | will ensure the proper initialization order and not accidentally |
875 | create an incorrect type of metaclass for you. This is a very rare |
876 | problem, and one which can only occur if you are doing deep metaclass |
877 | programming. So in other words, don't worry about it. |
878 | |
879 | Note that if you're using L<Moose> we encourage you to I<not> use |
880 | L<metaclass> pragma, and instead use L<Moose::Util::MetaRole> to apply |
881 | roles to a class's metaclasses. This topic is covered at length in |
882 | various L<Moose::Cookbook> recipes. |
883 | |
884 | =head1 PROTOCOLS |
885 | |
886 | The meta-object protocol is divided into 4 main sub-protocols: |
887 | |
888 | =head2 The Class protocol |
889 | |
890 | This provides a means of manipulating and introspecting a Perl 5 |
891 | class. It handles symbol table hacking for you, and provides a rich |
892 | set of methods that go beyond simple package introspection. |
893 | |
894 | See L<Class::MOP::Class> for more details. |
895 | |
896 | =head2 The Attribute protocol |
897 | |
898 | This provides a consistent representation for an attribute of a Perl 5 |
899 | class. Since there are so many ways to create and handle attributes in |
900 | Perl 5 OO, the Attribute protocol provide as much of a unified |
901 | approach as possible. Of course, you are always free to extend this |
902 | protocol by subclassing the appropriate classes. |
903 | |
904 | See L<Class::MOP::Attribute> for more details. |
905 | |
906 | =head2 The Method protocol |
907 | |
908 | This provides a means of manipulating and introspecting methods in the |
909 | Perl 5 object system. As with attributes, there are many ways to |
910 | approach this topic, so we try to keep it pretty basic, while still |
911 | making it possible to extend the system in many ways. |
912 | |
913 | See L<Class::MOP::Method> for more details. |
914 | |
915 | =head2 The Instance protocol |
916 | |
917 | This provides a layer of abstraction for creating object instances. |
918 | Since the other layers use this protocol, it is relatively easy to |
919 | change the type of your instances from the default hash reference to |
920 | some other type of reference. Several examples are provided in the |
921 | F<examples/> directory included in this distribution. |
922 | |
923 | See L<Class::MOP::Instance> for more details. |
924 | |
925 | =head1 FUNCTIONS |
926 | |
927 | Note that this module does not export any constants or functions. |
928 | |
38bf2a25 |
929 | =head2 Utility functions |
930 | |
931 | Note that these are all called as B<functions, not methods>. |
932 | |
933 | =over 4 |
934 | |
935 | =item B<Class::MOP::load_class($class_name, \%options?)> |
936 | |
937 | This will load the specified C<$class_name>, if it is not already |
938 | loaded (as reported by C<is_class_loaded>). This function can be used |
939 | in place of tricks like C<eval "use $module"> or using C<require> |
940 | unconditionally. |
941 | |
942 | If the module cannot be loaded, an exception is thrown. |
943 | |
944 | You can pass a hash reference with options as second argument. The |
7bb4be82 |
945 | only option currently recognized is C<-version>, which will ensure |
38bf2a25 |
946 | that the loaded class has at least the required version. |
947 | |
38bf2a25 |
948 | For historical reasons, this function explicitly returns a true value. |
949 | |
950 | =item B<Class::MOP::is_class_loaded($class_name, \%options?)> |
951 | |
952 | Returns a boolean indicating whether or not C<$class_name> has been |
953 | loaded. |
954 | |
955 | This does a basic check of the symbol table to try and determine as |
956 | best it can if the C<$class_name> is loaded, it is probably correct |
957 | about 99% of the time, but it can be fooled into reporting false |
958 | positives. In particular, loading any of the core L<IO> modules will |
959 | cause most of the rest of the core L<IO> modules to falsely report |
960 | having been loaded, due to the way the base L<IO> module works. |
961 | |
962 | You can pass a hash reference with options as second argument. The |
7bb4be82 |
963 | only option currently recognized is C<-version>, which will ensure |
38bf2a25 |
964 | that the loaded class has at least the required version. |
965 | |
38bf2a25 |
966 | =item B<Class::MOP::get_code_info($code)> |
967 | |
968 | This function returns two values, the name of the package the C<$code> |
969 | is from and the name of the C<$code> itself. This is used by several |
970 | elements of the MOP to determine where a given C<$code> reference is |
971 | from. |
972 | |
973 | =item B<Class::MOP::class_of($instance_or_class_name)> |
974 | |
975 | This will return the metaclass of the given instance or class name. If the |
976 | class lacks a metaclass, no metaclass will be initialized, and C<undef> will be |
977 | returned. |
978 | |
38bf2a25 |
979 | =back |
980 | |
981 | =head2 Metaclass cache functions |
982 | |
983 | Class::MOP holds a cache of metaclasses. The following are functions |
984 | (B<not methods>) which can be used to access that cache. It is not |
985 | recommended that you mess with these. Bad things could happen, but if |
986 | you are brave and willing to risk it: go for it! |
987 | |
988 | =over 4 |
989 | |
990 | =item B<Class::MOP::get_all_metaclasses> |
991 | |
992 | This will return a hash of all the metaclass instances that have |
993 | been cached by L<Class::MOP::Class>, keyed by the package name. |
994 | |
995 | =item B<Class::MOP::get_all_metaclass_instances> |
996 | |
997 | This will return a list of all the metaclass instances that have |
998 | been cached by L<Class::MOP::Class>. |
999 | |
1000 | =item B<Class::MOP::get_all_metaclass_names> |
1001 | |
1002 | This will return a list of all the metaclass names that have |
1003 | been cached by L<Class::MOP::Class>. |
1004 | |
1005 | =item B<Class::MOP::get_metaclass_by_name($name)> |
1006 | |
1007 | This will return a cached L<Class::MOP::Class> instance, or nothing |
1008 | if no metaclass exists with that C<$name>. |
1009 | |
1010 | =item B<Class::MOP::store_metaclass_by_name($name, $meta)> |
1011 | |
1012 | This will store a metaclass in the cache at the supplied C<$key>. |
1013 | |
1014 | =item B<Class::MOP::weaken_metaclass($name)> |
1015 | |
1016 | In rare cases (e.g. anonymous metaclasses) it is desirable to |
1017 | store a weakened reference in the metaclass cache. This |
1018 | function will weaken the reference to the metaclass stored |
1019 | in C<$name>. |
1020 | |
1021 | =item B<Class::MOP::metaclass_is_weak($name)> |
1022 | |
1023 | Returns true if the metaclass for C<$name> has been weakened |
1024 | (via C<weaken_metaclass>). |
1025 | |
1026 | =item B<Class::MOP::does_metaclass_exist($name)> |
1027 | |
1028 | This will return true of there exists a metaclass stored in the |
1029 | C<$name> key, and return false otherwise. |
1030 | |
1031 | =item B<Class::MOP::remove_metaclass_by_name($name)> |
1032 | |
1033 | This will remove the metaclass stored in the C<$name> key. |
1034 | |
1035 | =back |
1036 | |
38bf2a25 |
1037 | =head1 SEE ALSO |
1038 | |
1039 | =head2 Books |
1040 | |
1041 | There are very few books out on Meta Object Protocols and Metaclasses |
1042 | because it is such an esoteric topic. The following books are really |
1043 | the only ones I have found. If you know of any more, B<I<please>> |
1044 | email me and let me know, I would love to hear about them. |
1045 | |
1046 | =over 4 |
1047 | |
1048 | =item I<The Art of the Meta Object Protocol> |
1049 | |
1050 | =item I<Advances in Object-Oriented Metalevel Architecture and Reflection> |
1051 | |
1052 | =item I<Putting MetaClasses to Work> |
1053 | |
1054 | =item I<Smalltalk: The Language> |
1055 | |
1056 | =back |
1057 | |
1058 | =head2 Papers |
1059 | |
1060 | =over 4 |
1061 | |
1062 | =item "Uniform and safe metaclass composition" |
1063 | |
1064 | An excellent paper by the people who brought us the original Traits paper. |
1065 | This paper is on how Traits can be used to do safe metaclass composition, |
1066 | and offers an excellent introduction section which delves into the topic of |
1067 | metaclass compatibility. |
1068 | |
1069 | L<http://www.iam.unibe.ch/~scg/Archive/Papers/Duca05ySafeMetaclassTrait.pdf> |
1070 | |
1071 | =item "Safe Metaclass Programming" |
1072 | |
1073 | This paper seems to precede the above paper, and propose a mix-in based |
1074 | approach as opposed to the Traits based approach. Both papers have similar |
1075 | information on the metaclass compatibility problem space. |
1076 | |
1077 | L<http://citeseer.ist.psu.edu/37617.html> |
1078 | |
1079 | =back |
1080 | |
1081 | =head2 Prior Art |
1082 | |
1083 | =over 4 |
1084 | |
1085 | =item The Perl 6 MetaModel work in the Pugs project |
1086 | |
1087 | =over 4 |
1088 | |
1089 | =item L<http://svn.openfoundry.org/pugs/misc/Perl-MetaModel/> |
1090 | |
1091 | =item L<http://github.com/perl6/p5-modules/tree/master/Perl6-ObjectSpace/> |
1092 | |
1093 | =back |
1094 | |
1095 | =back |
1096 | |
1097 | =head2 Articles |
1098 | |
1099 | =over 4 |
1100 | |
1101 | =item CPAN Module Review of Class::MOP |
1102 | |
1103 | L<http://www.oreillynet.com/onlamp/blog/2006/06/cpan_module_review_classmop.html> |
1104 | |
1105 | =back |
1106 | |
1107 | =head1 SIMILAR MODULES |
1108 | |
1109 | As I have said above, this module is a class-builder-builder, so it is |
1110 | not the same thing as modules like L<Class::Accessor> and |
1111 | L<Class::MethodMaker>. That being said there are very few modules on CPAN |
1112 | with similar goals to this module. The one I have found which is most |
69229b40 |
1113 | like this module is L<Class::Meta>, although its philosophy and the MOP it |
38bf2a25 |
1114 | creates are very different from this modules. |
1115 | |
1116 | =head1 BUGS |
1117 | |
1118 | All complex software has bugs lurking in it, and this module is no |
1119 | exception. |
1120 | |
1121 | Please report any bugs to C<bug-class-mop@rt.cpan.org>, or through the |
1122 | web interface at L<http://rt.cpan.org>. |
1123 | |
1124 | You can also discuss feature requests or possible bugs on the Moose |
1125 | mailing list (moose@perl.org) or on IRC at |
1126 | L<irc://irc.perl.org/#moose>. |
1127 | |
1128 | =head1 ACKNOWLEDGEMENTS |
1129 | |
1130 | =over 4 |
1131 | |
1132 | =item Rob Kinyon |
1133 | |
1134 | Thanks to Rob for actually getting the development of this module kick-started. |
1135 | |
1136 | =back |
1137 | |
1138 | =cut |