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 | |
32 | our $AUTHORITY = 'cpan:STEVAN'; |
33 | |
34 | XSLoader::load( |
35 | 'Moose', |
017eb15a |
36 | $Moose::{VERSION} ? $Moose::{VERSION} : () |
38bf2a25 |
37 | ); |
38 | |
39 | { |
40 | # Metaclasses are singletons, so we cache them here. |
41 | # there is no need to worry about destruction though |
42 | # because they should die only when the program dies. |
43 | # After all, do package definitions even get reaped? |
44 | # Anonymous classes manage their own destruction. |
45 | my %METAS; |
46 | |
47 | sub get_all_metaclasses { %METAS } |
48 | sub get_all_metaclass_instances { values %METAS } |
49 | sub get_all_metaclass_names { keys %METAS } |
50 | sub get_metaclass_by_name { $METAS{$_[0]} } |
51 | sub store_metaclass_by_name { $METAS{$_[0]} = $_[1] } |
52 | sub weaken_metaclass { weaken($METAS{$_[0]}) } |
53 | sub metaclass_is_weak { isweak($METAS{$_[0]}) } |
54 | sub does_metaclass_exist { exists $METAS{$_[0]} && defined $METAS{$_[0]} } |
55 | sub remove_metaclass_by_name { delete $METAS{$_[0]}; return } |
56 | |
57 | # This handles instances as well as class names |
58 | sub class_of { |
59 | return unless defined $_[0]; |
60 | my $class = blessed($_[0]) || $_[0]; |
61 | return $METAS{$class}; |
62 | } |
63 | |
64 | # NOTE: |
65 | # We only cache metaclasses, meaning instances of |
66 | # Class::MOP::Class. We do not cache instance of |
67 | # Class::MOP::Package or Class::MOP::Module. Mostly |
68 | # because I don't yet see a good reason to do so. |
69 | } |
70 | |
71 | sub _class_to_pmfile { |
72 | my $class = shift; |
73 | |
74 | my $file = $class . '.pm'; |
75 | $file =~ s{::}{/}g; |
76 | |
77 | return $file; |
78 | } |
79 | |
80 | sub load_first_existing_class { |
81 | my $classes = Data::OptList::mkopt(\@_) |
82 | or return; |
83 | |
84 | foreach my $class (@{ $classes }) { |
85 | my $name = $class->[0]; |
86 | unless ( _is_valid_class_name($name) ) { |
87 | my $display = defined($name) ? $name : 'undef'; |
88 | confess "Invalid class name ($display)"; |
89 | } |
90 | } |
91 | |
92 | my $found; |
93 | my %exceptions; |
94 | |
95 | for my $class (@{ $classes }) { |
96 | my ($name, $options) = @{ $class }; |
97 | |
98 | if ($options) { |
99 | return $name if is_class_loaded($name, $options); |
100 | if (is_class_loaded($name)) { |
101 | # we already know it's loaded and too old, but we call |
102 | # ->VERSION anyway to generate the exception for us |
103 | $name->VERSION($options->{-version}); |
104 | } |
105 | } |
106 | else { |
107 | return $name if is_class_loaded($name); |
108 | } |
109 | |
110 | my $file = _class_to_pmfile($name); |
111 | return $name if try { |
112 | local $SIG{__DIE__}; |
113 | require $file; |
114 | $name->VERSION($options->{-version}) |
115 | if defined $options->{-version}; |
116 | return 1; |
117 | } |
118 | catch { |
119 | unless (/^Can't locate \Q$file\E in \@INC/) { |
120 | confess "Couldn't load class ($name) because: $_"; |
121 | } |
122 | |
123 | return; |
124 | }; |
125 | } |
126 | |
127 | if ( @{ $classes } > 1 ) { |
128 | my @list = map { $_->[0] } @{ $classes }; |
129 | confess "Can't locate any of @list in \@INC (\@INC contains: @INC)."; |
130 | } else { |
131 | confess "Can't locate " . _class_to_pmfile($classes->[0]->[0]) . " in \@INC (\@INC contains: @INC)."; |
132 | } |
133 | } |
134 | |
135 | sub load_class { |
136 | load_first_existing_class($_[0], ref $_[1] ? $_[1] : ()); |
137 | |
138 | # This is done to avoid breaking code which checked the return value. Said |
139 | # code is dumb. The return value was _always_ true, since it dies on |
140 | # failure! |
141 | return 1; |
142 | } |
143 | |
144 | sub _is_valid_class_name { |
145 | my $class = shift; |
146 | |
147 | return 0 if ref($class); |
148 | return 0 unless defined($class); |
149 | return 0 unless length($class); |
150 | |
151 | return 1 if $class =~ /^\w+(?:::\w+)*$/; |
152 | |
153 | return 0; |
154 | } |
155 | |
156 | ## ---------------------------------------------------------------------------- |
157 | ## Setting up our environment ... |
158 | ## ---------------------------------------------------------------------------- |
159 | ## Class::MOP needs to have a few things in the global perl environment so |
160 | ## that it can operate effectively. Those things are done here. |
161 | ## ---------------------------------------------------------------------------- |
162 | |
163 | # ... nothing yet actually ;) |
164 | |
165 | ## ---------------------------------------------------------------------------- |
166 | ## Bootstrapping |
167 | ## ---------------------------------------------------------------------------- |
168 | ## The code below here is to bootstrap our MOP with itself. This is also |
169 | ## sometimes called "tying the knot". By doing this, we make it much easier |
170 | ## to extend the MOP through subclassing and such since now you can use the |
171 | ## MOP itself to extend itself. |
172 | ## |
173 | ## Yes, I know, thats weird and insane, but it's a good thing, trust me :) |
174 | ## ---------------------------------------------------------------------------- |
175 | |
176 | # We need to add in the meta-attributes here so that |
177 | # any subclass of Class::MOP::* will be able to |
178 | # inherit them using _construct_instance |
179 | |
180 | ## -------------------------------------------------------- |
181 | ## Class::MOP::Mixin::HasMethods |
182 | |
183 | Class::MOP::Mixin::HasMethods->meta->add_attribute( |
184 | Class::MOP::Attribute->new('_methods' => ( |
185 | reader => { |
186 | # NOTE: |
187 | # we just alias the original method |
188 | # rather than re-produce it here |
189 | '_method_map' => \&Class::MOP::Mixin::HasMethods::_method_map |
190 | }, |
191 | default => sub { {} } |
192 | )) |
193 | ); |
194 | |
195 | Class::MOP::Mixin::HasMethods->meta->add_attribute( |
196 | Class::MOP::Attribute->new('method_metaclass' => ( |
197 | reader => { |
198 | # NOTE: |
199 | # we just alias the original method |
200 | # rather than re-produce it here |
201 | 'method_metaclass' => \&Class::MOP::Mixin::HasMethods::method_metaclass |
202 | }, |
203 | default => 'Class::MOP::Method', |
204 | )) |
205 | ); |
206 | |
207 | Class::MOP::Mixin::HasMethods->meta->add_attribute( |
208 | Class::MOP::Attribute->new('wrapped_method_metaclass' => ( |
209 | reader => { |
210 | # NOTE: |
211 | # we just alias the original method |
212 | # rather than re-produce it here |
213 | 'wrapped_method_metaclass' => \&Class::MOP::Mixin::HasMethods::wrapped_method_metaclass |
214 | }, |
215 | default => 'Class::MOP::Method::Wrapped', |
216 | )) |
217 | ); |
218 | |
219 | ## -------------------------------------------------------- |
220 | ## Class::MOP::Mixin::HasMethods |
221 | |
222 | Class::MOP::Mixin::HasAttributes->meta->add_attribute( |
223 | Class::MOP::Attribute->new('attributes' => ( |
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 | # |
229 | # we just alias the original method |
230 | # rather than re-produce it here |
231 | '_attribute_map' => \&Class::MOP::Mixin::HasAttributes::_attribute_map |
232 | }, |
233 | default => sub { {} } |
234 | )) |
235 | ); |
236 | |
237 | Class::MOP::Mixin::HasAttributes->meta->add_attribute( |
238 | Class::MOP::Attribute->new('attribute_metaclass' => ( |
239 | reader => { |
240 | # NOTE: |
241 | # we just alias the original method |
242 | # rather than re-produce it here |
243 | 'attribute_metaclass' => \&Class::MOP::Mixin::HasAttributes::attribute_metaclass |
244 | }, |
245 | default => 'Class::MOP::Attribute', |
246 | )) |
247 | ); |
248 | |
249 | ## -------------------------------------------------------- |
250 | ## Class::MOP::Package |
251 | |
252 | Class::MOP::Package->meta->add_attribute( |
253 | Class::MOP::Attribute->new('package' => ( |
254 | reader => { |
255 | # NOTE: we need to do this in order |
256 | # for the instance meta-object to |
257 | # not fall into meta-circular death |
258 | # |
259 | # we just alias the original method |
260 | # rather than re-produce it here |
261 | 'name' => \&Class::MOP::Package::name |
262 | }, |
263 | )) |
264 | ); |
265 | |
266 | Class::MOP::Package->meta->add_attribute( |
267 | Class::MOP::Attribute->new('namespace' => ( |
268 | reader => { |
269 | # NOTE: |
270 | # we just alias the original method |
271 | # rather than re-produce it here |
272 | 'namespace' => \&Class::MOP::Package::namespace |
273 | }, |
274 | init_arg => undef, |
275 | default => sub { \undef } |
276 | )) |
277 | ); |
278 | |
279 | ## -------------------------------------------------------- |
280 | ## Class::MOP::Module |
281 | |
282 | # NOTE: |
283 | # yeah this is kind of stretching things a bit, |
284 | # but truthfully the version should be an attribute |
285 | # of the Module, the weirdness comes from having to |
286 | # stick to Perl 5 convention and store it in the |
287 | # $VERSION package variable. Basically if you just |
288 | # squint at it, it will look how you want it to look. |
289 | # Either as a package variable, or as a attribute of |
290 | # the metaclass, isn't abstraction great :) |
291 | |
292 | Class::MOP::Module->meta->add_attribute( |
293 | Class::MOP::Attribute->new('version' => ( |
294 | reader => { |
295 | # NOTE: |
296 | # we just alias the original method |
297 | # rather than re-produce it here |
298 | 'version' => \&Class::MOP::Module::version |
299 | }, |
300 | init_arg => undef, |
301 | default => sub { \undef } |
302 | )) |
303 | ); |
304 | |
305 | # NOTE: |
306 | # By following the same conventions as version here, |
307 | # we are opening up the possibility that people can |
308 | # use the $AUTHORITY in non-Class::MOP modules as |
309 | # well. |
310 | |
311 | Class::MOP::Module->meta->add_attribute( |
312 | Class::MOP::Attribute->new('authority' => ( |
313 | reader => { |
314 | # NOTE: |
315 | # we just alias the original method |
316 | # rather than re-produce it here |
317 | 'authority' => \&Class::MOP::Module::authority |
318 | }, |
319 | init_arg => undef, |
320 | default => sub { \undef } |
321 | )) |
322 | ); |
323 | |
324 | ## -------------------------------------------------------- |
325 | ## Class::MOP::Class |
326 | |
327 | Class::MOP::Class->meta->add_attribute( |
328 | Class::MOP::Attribute->new('superclasses' => ( |
329 | accessor => { |
330 | # NOTE: |
331 | # we just alias the original method |
332 | # rather than re-produce it here |
333 | 'superclasses' => \&Class::MOP::Class::superclasses |
334 | }, |
335 | init_arg => undef, |
336 | default => sub { \undef } |
337 | )) |
338 | ); |
339 | |
340 | Class::MOP::Class->meta->add_attribute( |
341 | Class::MOP::Attribute->new('instance_metaclass' => ( |
342 | reader => { |
343 | # NOTE: we need to do this in order |
344 | # for the instance meta-object to |
345 | # not fall into meta-circular death |
346 | # |
347 | # we just alias the original method |
348 | # rather than re-produce it here |
349 | 'instance_metaclass' => \&Class::MOP::Class::instance_metaclass |
350 | }, |
351 | default => 'Class::MOP::Instance', |
352 | )) |
353 | ); |
354 | |
355 | Class::MOP::Class->meta->add_attribute( |
356 | Class::MOP::Attribute->new('immutable_trait' => ( |
357 | reader => { |
358 | 'immutable_trait' => \&Class::MOP::Class::immutable_trait |
359 | }, |
360 | default => "Class::MOP::Class::Immutable::Trait", |
361 | )) |
362 | ); |
363 | |
364 | Class::MOP::Class->meta->add_attribute( |
365 | Class::MOP::Attribute->new('constructor_name' => ( |
366 | reader => { |
367 | 'constructor_name' => \&Class::MOP::Class::constructor_name, |
368 | }, |
369 | default => "new", |
370 | )) |
371 | ); |
372 | |
373 | Class::MOP::Class->meta->add_attribute( |
374 | Class::MOP::Attribute->new('constructor_class' => ( |
375 | reader => { |
376 | 'constructor_class' => \&Class::MOP::Class::constructor_class, |
377 | }, |
378 | default => "Class::MOP::Method::Constructor", |
379 | )) |
380 | ); |
381 | |
382 | |
383 | Class::MOP::Class->meta->add_attribute( |
384 | Class::MOP::Attribute->new('destructor_class' => ( |
385 | reader => { |
386 | 'destructor_class' => \&Class::MOP::Class::destructor_class, |
387 | }, |
388 | )) |
389 | ); |
390 | |
391 | # NOTE: |
392 | # we don't actually need to tie the knot with |
393 | # Class::MOP::Class here, it is actually handled |
394 | # within Class::MOP::Class itself in the |
395 | # _construct_class_instance method. |
396 | |
397 | ## -------------------------------------------------------- |
398 | ## Class::MOP::Mixin::AttributeCore |
399 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
400 | Class::MOP::Attribute->new('name' => ( |
401 | reader => { |
402 | # NOTE: we need to do this in order |
403 | # for the instance meta-object to |
404 | # not fall into meta-circular death |
405 | # |
406 | # we just alias the original method |
407 | # rather than re-produce it here |
408 | 'name' => \&Class::MOP::Mixin::AttributeCore::name |
409 | } |
410 | )) |
411 | ); |
412 | |
413 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
414 | Class::MOP::Attribute->new('accessor' => ( |
415 | reader => { 'accessor' => \&Class::MOP::Mixin::AttributeCore::accessor }, |
416 | predicate => { 'has_accessor' => \&Class::MOP::Mixin::AttributeCore::has_accessor }, |
417 | )) |
418 | ); |
419 | |
420 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
421 | Class::MOP::Attribute->new('reader' => ( |
422 | reader => { 'reader' => \&Class::MOP::Mixin::AttributeCore::reader }, |
423 | predicate => { 'has_reader' => \&Class::MOP::Mixin::AttributeCore::has_reader }, |
424 | )) |
425 | ); |
426 | |
427 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
428 | Class::MOP::Attribute->new('initializer' => ( |
429 | reader => { 'initializer' => \&Class::MOP::Mixin::AttributeCore::initializer }, |
430 | predicate => { 'has_initializer' => \&Class::MOP::Mixin::AttributeCore::has_initializer }, |
431 | )) |
432 | ); |
433 | |
434 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
435 | Class::MOP::Attribute->new('definition_context' => ( |
436 | reader => { 'definition_context' => \&Class::MOP::Mixin::AttributeCore::definition_context }, |
437 | )) |
438 | ); |
439 | |
440 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
441 | Class::MOP::Attribute->new('writer' => ( |
442 | reader => { 'writer' => \&Class::MOP::Mixin::AttributeCore::writer }, |
443 | predicate => { 'has_writer' => \&Class::MOP::Mixin::AttributeCore::has_writer }, |
444 | )) |
445 | ); |
446 | |
447 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
448 | Class::MOP::Attribute->new('predicate' => ( |
449 | reader => { 'predicate' => \&Class::MOP::Mixin::AttributeCore::predicate }, |
450 | predicate => { 'has_predicate' => \&Class::MOP::Mixin::AttributeCore::has_predicate }, |
451 | )) |
452 | ); |
453 | |
454 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
455 | Class::MOP::Attribute->new('clearer' => ( |
456 | reader => { 'clearer' => \&Class::MOP::Mixin::AttributeCore::clearer }, |
457 | predicate => { 'has_clearer' => \&Class::MOP::Mixin::AttributeCore::has_clearer }, |
458 | )) |
459 | ); |
460 | |
461 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
462 | Class::MOP::Attribute->new('builder' => ( |
463 | reader => { 'builder' => \&Class::MOP::Mixin::AttributeCore::builder }, |
464 | predicate => { 'has_builder' => \&Class::MOP::Mixin::AttributeCore::has_builder }, |
465 | )) |
466 | ); |
467 | |
468 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
469 | Class::MOP::Attribute->new('init_arg' => ( |
470 | reader => { 'init_arg' => \&Class::MOP::Mixin::AttributeCore::init_arg }, |
471 | predicate => { 'has_init_arg' => \&Class::MOP::Mixin::AttributeCore::has_init_arg }, |
472 | )) |
473 | ); |
474 | |
475 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
476 | Class::MOP::Attribute->new('default' => ( |
477 | # default has a custom 'reader' method ... |
478 | predicate => { 'has_default' => \&Class::MOP::Mixin::AttributeCore::has_default }, |
479 | )) |
480 | ); |
481 | |
482 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
483 | Class::MOP::Attribute->new('insertion_order' => ( |
484 | reader => { 'insertion_order' => \&Class::MOP::Mixin::AttributeCore::insertion_order }, |
485 | writer => { '_set_insertion_order' => \&Class::MOP::Mixin::AttributeCore::_set_insertion_order }, |
486 | predicate => { 'has_insertion_order' => \&Class::MOP::Mixin::AttributeCore::has_insertion_order }, |
487 | )) |
488 | ); |
489 | |
490 | ## -------------------------------------------------------- |
491 | ## Class::MOP::Attribute |
492 | Class::MOP::Attribute->meta->add_attribute( |
493 | Class::MOP::Attribute->new('associated_class' => ( |
494 | reader => { |
495 | # NOTE: we need to do this in order |
496 | # for the instance meta-object to |
497 | # not fall into meta-circular death |
498 | # |
499 | # we just alias the original method |
500 | # rather than re-produce it here |
501 | 'associated_class' => \&Class::MOP::Attribute::associated_class |
502 | } |
503 | )) |
504 | ); |
505 | |
506 | Class::MOP::Attribute->meta->add_attribute( |
507 | Class::MOP::Attribute->new('associated_methods' => ( |
508 | reader => { 'associated_methods' => \&Class::MOP::Attribute::associated_methods }, |
509 | default => sub { [] } |
510 | )) |
511 | ); |
512 | |
513 | Class::MOP::Attribute->meta->add_method('clone' => sub { |
514 | my $self = shift; |
515 | $self->meta->clone_object($self, @_); |
516 | }); |
517 | |
518 | ## -------------------------------------------------------- |
519 | ## Class::MOP::Method |
520 | Class::MOP::Method->meta->add_attribute( |
521 | Class::MOP::Attribute->new('body' => ( |
522 | reader => { 'body' => \&Class::MOP::Method::body }, |
523 | )) |
524 | ); |
525 | |
526 | Class::MOP::Method->meta->add_attribute( |
527 | Class::MOP::Attribute->new('associated_metaclass' => ( |
528 | reader => { 'associated_metaclass' => \&Class::MOP::Method::associated_metaclass }, |
529 | )) |
530 | ); |
531 | |
532 | Class::MOP::Method->meta->add_attribute( |
533 | Class::MOP::Attribute->new('package_name' => ( |
534 | reader => { 'package_name' => \&Class::MOP::Method::package_name }, |
535 | )) |
536 | ); |
537 | |
538 | Class::MOP::Method->meta->add_attribute( |
539 | Class::MOP::Attribute->new('name' => ( |
540 | reader => { 'name' => \&Class::MOP::Method::name }, |
541 | )) |
542 | ); |
543 | |
544 | Class::MOP::Method->meta->add_attribute( |
545 | Class::MOP::Attribute->new('original_method' => ( |
546 | reader => { 'original_method' => \&Class::MOP::Method::original_method }, |
547 | writer => { '_set_original_method' => \&Class::MOP::Method::_set_original_method }, |
548 | )) |
549 | ); |
550 | |
551 | ## -------------------------------------------------------- |
552 | ## Class::MOP::Method::Wrapped |
553 | |
554 | # NOTE: |
555 | # the way this item is initialized, this |
556 | # really does not follow the standard |
557 | # practices of attributes, but we put |
558 | # it here for completeness |
559 | Class::MOP::Method::Wrapped->meta->add_attribute( |
560 | Class::MOP::Attribute->new('modifier_table') |
561 | ); |
562 | |
563 | ## -------------------------------------------------------- |
564 | ## Class::MOP::Method::Generated |
565 | |
566 | Class::MOP::Method::Generated->meta->add_attribute( |
567 | Class::MOP::Attribute->new('is_inline' => ( |
568 | reader => { 'is_inline' => \&Class::MOP::Method::Generated::is_inline }, |
569 | default => 0, |
570 | )) |
571 | ); |
572 | |
573 | Class::MOP::Method::Generated->meta->add_attribute( |
574 | Class::MOP::Attribute->new('definition_context' => ( |
575 | reader => { 'definition_context' => \&Class::MOP::Method::Generated::definition_context }, |
576 | )) |
577 | ); |
578 | |
579 | |
580 | ## -------------------------------------------------------- |
581 | ## Class::MOP::Method::Inlined |
582 | |
583 | Class::MOP::Method::Inlined->meta->add_attribute( |
584 | Class::MOP::Attribute->new('_expected_method_class' => ( |
585 | reader => { '_expected_method_class' => \&Class::MOP::Method::Inlined::_expected_method_class }, |
586 | )) |
587 | ); |
588 | |
589 | ## -------------------------------------------------------- |
590 | ## Class::MOP::Method::Accessor |
591 | |
592 | Class::MOP::Method::Accessor->meta->add_attribute( |
593 | Class::MOP::Attribute->new('attribute' => ( |
594 | reader => { |
595 | 'associated_attribute' => \&Class::MOP::Method::Accessor::associated_attribute |
596 | }, |
597 | )) |
598 | ); |
599 | |
600 | Class::MOP::Method::Accessor->meta->add_attribute( |
601 | Class::MOP::Attribute->new('accessor_type' => ( |
602 | reader => { 'accessor_type' => \&Class::MOP::Method::Accessor::accessor_type }, |
603 | )) |
604 | ); |
605 | |
606 | ## -------------------------------------------------------- |
607 | ## Class::MOP::Method::Constructor |
608 | |
609 | Class::MOP::Method::Constructor->meta->add_attribute( |
610 | Class::MOP::Attribute->new('options' => ( |
611 | reader => { |
612 | 'options' => \&Class::MOP::Method::Constructor::options |
613 | }, |
614 | default => sub { +{} } |
615 | )) |
616 | ); |
617 | |
618 | Class::MOP::Method::Constructor->meta->add_attribute( |
619 | Class::MOP::Attribute->new('associated_metaclass' => ( |
620 | init_arg => "metaclass", # FIXME alias and rename |
621 | reader => { |
622 | 'associated_metaclass' => \&Class::MOP::Method::Constructor::associated_metaclass |
623 | }, |
624 | )) |
625 | ); |
626 | |
627 | ## -------------------------------------------------------- |
628 | ## Class::MOP::Instance |
629 | |
630 | # NOTE: |
631 | # these don't yet do much of anything, but are just |
632 | # included for completeness |
633 | |
634 | Class::MOP::Instance->meta->add_attribute( |
635 | Class::MOP::Attribute->new('associated_metaclass', |
636 | reader => { associated_metaclass => \&Class::MOP::Instance::associated_metaclass }, |
637 | ), |
638 | ); |
639 | |
640 | Class::MOP::Instance->meta->add_attribute( |
641 | Class::MOP::Attribute->new('_class_name', |
642 | init_arg => undef, |
643 | reader => { _class_name => \&Class::MOP::Instance::_class_name }, |
644 | #lazy => 1, # not yet supported by Class::MOP but out our version does it anyway |
645 | #default => sub { $_[0]->associated_metaclass->name }, |
646 | ), |
647 | ); |
648 | |
649 | Class::MOP::Instance->meta->add_attribute( |
650 | Class::MOP::Attribute->new('attributes', |
651 | reader => { attributes => \&Class::MOP::Instance::get_all_attributes }, |
652 | ), |
653 | ); |
654 | |
655 | Class::MOP::Instance->meta->add_attribute( |
656 | Class::MOP::Attribute->new('slots', |
657 | reader => { slots => \&Class::MOP::Instance::slots }, |
658 | ), |
659 | ); |
660 | |
661 | Class::MOP::Instance->meta->add_attribute( |
662 | Class::MOP::Attribute->new('slot_hash', |
663 | reader => { slot_hash => \&Class::MOP::Instance::slot_hash }, |
664 | ), |
665 | ); |
666 | |
667 | ## -------------------------------------------------------- |
668 | ## Class::MOP::Object |
669 | |
670 | # need to replace the meta method there with a real meta method object |
671 | Class::MOP::Object->meta->_add_meta_method('meta'); |
672 | |
673 | ## -------------------------------------------------------- |
674 | ## Class::MOP::Mixin |
675 | |
676 | # need to replace the meta method there with a real meta method object |
677 | Class::MOP::Mixin->meta->_add_meta_method('meta'); |
678 | |
679 | require Class::MOP::Deprecated unless our $no_deprecated; |
680 | |
681 | # we need the meta instance of the meta instance to be created now, in order |
682 | # for the constructor to be able to use it |
683 | Class::MOP::Instance->meta->get_meta_instance; |
684 | |
685 | # pretend the add_method never happenned. it hasn't yet affected anything |
686 | undef Class::MOP::Instance->meta->{_package_cache_flag}; |
687 | |
688 | ## -------------------------------------------------------- |
689 | ## Now close all the Class::MOP::* classes |
690 | |
691 | # NOTE: we don't need to inline the the accessors this only lengthens |
692 | # the compile time of the MOP, and gives us no actual benefits. |
693 | |
694 | $_->meta->make_immutable( |
695 | inline_constructor => 0, |
696 | constructor_name => "_new", |
697 | inline_accessors => 0, |
698 | ) for qw/ |
699 | Class::MOP::Package |
700 | Class::MOP::Module |
701 | Class::MOP::Class |
702 | |
703 | Class::MOP::Attribute |
704 | Class::MOP::Method |
705 | Class::MOP::Instance |
706 | |
707 | Class::MOP::Object |
708 | |
709 | Class::MOP::Method::Generated |
710 | Class::MOP::Method::Inlined |
711 | |
712 | Class::MOP::Method::Accessor |
713 | Class::MOP::Method::Constructor |
714 | Class::MOP::Method::Wrapped |
715 | |
716 | Class::MOP::Method::Meta |
717 | /; |
718 | |
719 | $_->meta->make_immutable( |
720 | inline_constructor => 0, |
721 | constructor_name => undef, |
722 | inline_accessors => 0, |
723 | ) for qw/ |
724 | Class::MOP::Mixin |
725 | Class::MOP::Mixin::AttributeCore |
726 | Class::MOP::Mixin::HasAttributes |
727 | Class::MOP::Mixin::HasMethods |
728 | /; |
729 | |
730 | 1; |
731 | |
732 | # ABSTRACT: A Meta Object Protocol for Perl 5 |
733 | |
734 | __END__ |
735 | |
736 | =pod |
737 | |
738 | =head1 DESCRIPTION |
739 | |
740 | This module is a fully functioning meta object protocol for the |
741 | Perl 5 object system. It makes no attempt to change the behavior or |
742 | characteristics of the Perl 5 object system, only to create a |
743 | protocol for its manipulation and introspection. |
744 | |
745 | That said, it does attempt to create the tools for building a rich set |
746 | of extensions to the Perl 5 object system. Every attempt has been made |
747 | to abide by the spirit of the Perl 5 object system that we all know |
748 | and love. |
749 | |
750 | This documentation is sparse on conceptual details. We suggest looking |
751 | at the items listed in the L<SEE ALSO> section for more |
752 | information. In particular the book "The Art of the Meta Object |
753 | Protocol" was very influential in the development of this system. |
754 | |
755 | =head2 What is a Meta Object Protocol? |
756 | |
757 | A meta object protocol is an API to an object system. |
758 | |
759 | To be more specific, it abstracts the components of an object system |
760 | (classes, object, methods, object attributes, etc.). These |
761 | abstractions can then be used to inspect and manipulate the object |
762 | system which they describe. |
763 | |
764 | It can be said that there are two MOPs for any object system; the |
765 | implicit MOP and the explicit MOP. The implicit MOP handles things |
766 | like method dispatch or inheritance, which happen automatically as |
767 | part of how the object system works. The explicit MOP typically |
768 | handles the introspection/reflection features of the object system. |
769 | |
770 | All object systems have implicit MOPs. Without one, they would not |
771 | work. Explicit MOPs are much less common, and depending on the |
772 | language can vary from restrictive (Reflection in Java or C#) to wide |
773 | open (CLOS is a perfect example). |
774 | |
775 | =head2 Yet Another Class Builder! Why? |
776 | |
777 | This is B<not> a class builder so much as a I<class builder |
778 | B<builder>>. The intent is that an end user will not use this module |
779 | directly, but instead this module is used by module authors to build |
780 | extensions and features onto the Perl 5 object system. |
781 | |
782 | This system is used by L<Moose>, which supplies a powerful class |
783 | builder system built entirely on top of C<Class::MOP>. |
784 | |
785 | =head2 Who is this module for? |
786 | |
787 | This module is for anyone who has ever created or wanted to create a |
788 | module for the Class:: namespace. The tools which this module provides |
789 | make doing complex Perl 5 wizardry simpler, by removing such barriers |
790 | as the need to hack symbol tables, or understand the fine details of |
791 | method dispatch. |
792 | |
793 | =head2 What changes do I have to make to use this module? |
794 | |
795 | This module was designed to be as unintrusive as possible. Many of its |
796 | features are accessible without B<any> change to your existing |
797 | code. It is meant to be a compliment to your existing code and not an |
798 | intrusion on your code base. Unlike many other B<Class::> modules, |
799 | this module B<does not> require you subclass it, or even that you |
800 | C<use> it in within your module's package. |
801 | |
802 | The only features which requires additions to your code are the |
803 | attribute handling and instance construction features, and these are |
804 | both completely optional features. The only reason for this is because |
805 | Perl 5's object system does not actually have these features built |
806 | in. More information about this feature can be found below. |
807 | |
808 | =head2 About Performance |
809 | |
810 | It is a common misconception that explicit MOPs are a performance hit. |
811 | This is not a universal truth, it is a side-effect of some specific |
812 | implementations. For instance, using Java reflection is slow because |
813 | the JVM cannot take advantage of any compiler optimizations, and the |
814 | JVM has to deal with much more runtime type information as well. |
815 | |
816 | Reflection in C# is marginally better as it was designed into the |
817 | language and runtime (the CLR). In contrast, CLOS (the Common Lisp |
818 | Object System) was built to support an explicit MOP, and so |
819 | performance is tuned for it. |
820 | |
821 | This library in particular does its absolute best to avoid putting |
822 | B<any> drain at all upon your code's performance. In fact, by itself |
823 | it does nothing to affect your existing code. So you only pay for what |
824 | you actually use. |
825 | |
826 | =head2 About Metaclass compatibility |
827 | |
828 | This module makes sure that all metaclasses created are both upwards |
829 | and downwards compatible. The topic of metaclass compatibility is |
830 | highly esoteric and is something only encountered when doing deep and |
831 | involved metaclass hacking. There are two basic kinds of metaclass |
832 | incompatibility; upwards and downwards. |
833 | |
834 | Upwards metaclass compatibility means that the metaclass of a |
835 | given class is either the same as (or a subclass of) all of the |
836 | class's ancestors. |
837 | |
838 | Downward metaclass compatibility means that the metaclasses of a |
839 | given class's ancestors are all either the same as (or a subclass |
840 | of) that metaclass. |
841 | |
842 | Here is a diagram showing a set of two classes (C<A> and C<B>) and |
843 | two metaclasses (C<Meta::A> and C<Meta::B>) which have correct |
844 | metaclass compatibility both upwards and downwards. |
845 | |
846 | +---------+ +---------+ |
847 | | Meta::A |<----| Meta::B | <....... (instance of ) |
848 | +---------+ +---------+ <------- (inherits from) |
849 | ^ ^ |
850 | : : |
851 | +---------+ +---------+ |
852 | | A |<----| B | |
853 | +---------+ +---------+ |
854 | |
855 | In actuality, I<all> of a class's metaclasses must be compatible, |
856 | not just the class metaclass. That includes the instance, attribute, |
857 | and method metaclasses, as well as the constructor and destructor |
858 | classes. |
859 | |
860 | C<Class::MOP> will attempt to fix some simple types of |
861 | incompatibilities. If all the metaclasses for the parent class are |
862 | I<subclasses> of the child's metaclasses then we can simply replace |
863 | the child's metaclasses with the parent's. In addition, if the child |
864 | is missing a metaclass that the parent has, we can also just make the |
865 | child use the parent's metaclass. |
866 | |
867 | As I said this is a highly esoteric topic and one you will only run |
868 | into if you do a lot of subclassing of L<Class::MOP::Class>. If you |
869 | are interested in why this is an issue see the paper I<Uniform and |
870 | safe metaclass composition> linked to in the L<SEE ALSO> section of |
871 | this document. |
872 | |
873 | =head2 Using custom metaclasses |
874 | |
875 | Always use the L<metaclass> pragma when using a custom metaclass, this |
876 | will ensure the proper initialization order and not accidentally |
877 | create an incorrect type of metaclass for you. This is a very rare |
878 | problem, and one which can only occur if you are doing deep metaclass |
879 | programming. So in other words, don't worry about it. |
880 | |
881 | Note that if you're using L<Moose> we encourage you to I<not> use |
882 | L<metaclass> pragma, and instead use L<Moose::Util::MetaRole> to apply |
883 | roles to a class's metaclasses. This topic is covered at length in |
884 | various L<Moose::Cookbook> recipes. |
885 | |
886 | =head1 PROTOCOLS |
887 | |
888 | The meta-object protocol is divided into 4 main sub-protocols: |
889 | |
890 | =head2 The Class protocol |
891 | |
892 | This provides a means of manipulating and introspecting a Perl 5 |
893 | class. It handles symbol table hacking for you, and provides a rich |
894 | set of methods that go beyond simple package introspection. |
895 | |
896 | See L<Class::MOP::Class> for more details. |
897 | |
898 | =head2 The Attribute protocol |
899 | |
900 | This provides a consistent representation for an attribute of a Perl 5 |
901 | class. Since there are so many ways to create and handle attributes in |
902 | Perl 5 OO, the Attribute protocol provide as much of a unified |
903 | approach as possible. Of course, you are always free to extend this |
904 | protocol by subclassing the appropriate classes. |
905 | |
906 | See L<Class::MOP::Attribute> for more details. |
907 | |
908 | =head2 The Method protocol |
909 | |
910 | This provides a means of manipulating and introspecting methods in the |
911 | Perl 5 object system. As with attributes, there are many ways to |
912 | approach this topic, so we try to keep it pretty basic, while still |
913 | making it possible to extend the system in many ways. |
914 | |
915 | See L<Class::MOP::Method> for more details. |
916 | |
917 | =head2 The Instance protocol |
918 | |
919 | This provides a layer of abstraction for creating object instances. |
920 | Since the other layers use this protocol, it is relatively easy to |
921 | change the type of your instances from the default hash reference to |
922 | some other type of reference. Several examples are provided in the |
923 | F<examples/> directory included in this distribution. |
924 | |
925 | See L<Class::MOP::Instance> for more details. |
926 | |
927 | =head1 FUNCTIONS |
928 | |
929 | Note that this module does not export any constants or functions. |
930 | |
931 | =head2 Constants |
932 | |
933 | =over 4 |
934 | |
935 | =item I<Class::MOP::IS_RUNNING_ON_5_10> |
936 | |
937 | We set this constant depending on what version perl we are on, this |
938 | allows us to take advantage of new 5.10 features and stay backwards |
939 | compatible. |
940 | |
941 | =back |
942 | |
943 | =head2 Utility functions |
944 | |
945 | Note that these are all called as B<functions, not methods>. |
946 | |
947 | =over 4 |
948 | |
949 | =item B<Class::MOP::load_class($class_name, \%options?)> |
950 | |
951 | This will load the specified C<$class_name>, if it is not already |
952 | loaded (as reported by C<is_class_loaded>). This function can be used |
953 | in place of tricks like C<eval "use $module"> or using C<require> |
954 | unconditionally. |
955 | |
956 | If the module cannot be loaded, an exception is thrown. |
957 | |
958 | You can pass a hash reference with options as second argument. The |
959 | only option currently recognised is C<-version>, which will ensure |
960 | that the loaded class has at least the required version. |
961 | |
962 | See also L</Class Loading Options>. |
963 | |
964 | For historical reasons, this function explicitly returns a true value. |
965 | |
966 | =item B<Class::MOP::is_class_loaded($class_name, \%options?)> |
967 | |
968 | Returns a boolean indicating whether or not C<$class_name> has been |
969 | loaded. |
970 | |
971 | This does a basic check of the symbol table to try and determine as |
972 | best it can if the C<$class_name> is loaded, it is probably correct |
973 | about 99% of the time, but it can be fooled into reporting false |
974 | positives. In particular, loading any of the core L<IO> modules will |
975 | cause most of the rest of the core L<IO> modules to falsely report |
976 | having been loaded, due to the way the base L<IO> module works. |
977 | |
978 | You can pass a hash reference with options as second argument. The |
979 | only option currently recognised is C<-version>, which will ensure |
980 | that the loaded class has at least the required version. |
981 | |
982 | See also L</Class Loading Options>. |
983 | |
984 | =item B<Class::MOP::get_code_info($code)> |
985 | |
986 | This function returns two values, the name of the package the C<$code> |
987 | is from and the name of the C<$code> itself. This is used by several |
988 | elements of the MOP to determine where a given C<$code> reference is |
989 | from. |
990 | |
991 | =item B<Class::MOP::class_of($instance_or_class_name)> |
992 | |
993 | This will return the metaclass of the given instance or class name. If the |
994 | class lacks a metaclass, no metaclass will be initialized, and C<undef> will be |
995 | returned. |
996 | |
997 | =item B<Class::MOP::check_package_cache_flag($pkg)> |
998 | |
999 | B<NOTE: DO NOT USE THIS FUNCTION, IT IS FOR INTERNAL USE ONLY!> |
1000 | |
1001 | This will return an integer that is managed by L<Class::MOP::Class> to |
1002 | determine if a module's symbol table has been altered. |
1003 | |
1004 | In Perl 5.10 or greater, this flag is package specific. However in |
1005 | versions prior to 5.10, this will use the C<PL_sub_generation> |
1006 | variable which is not package specific. |
1007 | |
1008 | =item B<Class::MOP::load_first_existing_class(@class_names)> |
1009 | |
1010 | =item B<Class::MOP::load_first_existing_class($classA, \%optionsA?, $classB, ...)> |
1011 | |
1012 | B<NOTE: DO NOT USE THIS FUNCTION, IT IS FOR INTERNAL USE ONLY!> |
1013 | |
1014 | Given a list of class names, this function will attempt to load each |
1015 | one in turn. |
1016 | |
1017 | If it finds a class it can load, it will return that class' name. If |
1018 | none of the classes can be loaded, it will throw an exception. |
1019 | |
1020 | Additionally, you can pass a hash reference with options after each |
1021 | class name. Currently, only C<-version> is recognised and will ensure |
1022 | that the loaded class has at least the required version. If the class |
1023 | version is not sufficient, an exception will be raised. |
1024 | |
1025 | See also L</Class Loading Options>. |
1026 | |
1027 | =back |
1028 | |
1029 | =head2 Metaclass cache functions |
1030 | |
1031 | Class::MOP holds a cache of metaclasses. The following are functions |
1032 | (B<not methods>) which can be used to access that cache. It is not |
1033 | recommended that you mess with these. Bad things could happen, but if |
1034 | you are brave and willing to risk it: go for it! |
1035 | |
1036 | =over 4 |
1037 | |
1038 | =item B<Class::MOP::get_all_metaclasses> |
1039 | |
1040 | This will return a hash of all the metaclass instances that have |
1041 | been cached by L<Class::MOP::Class>, keyed by the package name. |
1042 | |
1043 | =item B<Class::MOP::get_all_metaclass_instances> |
1044 | |
1045 | This will return a list of all the metaclass instances that have |
1046 | been cached by L<Class::MOP::Class>. |
1047 | |
1048 | =item B<Class::MOP::get_all_metaclass_names> |
1049 | |
1050 | This will return a list of all the metaclass names that have |
1051 | been cached by L<Class::MOP::Class>. |
1052 | |
1053 | =item B<Class::MOP::get_metaclass_by_name($name)> |
1054 | |
1055 | This will return a cached L<Class::MOP::Class> instance, or nothing |
1056 | if no metaclass exists with that C<$name>. |
1057 | |
1058 | =item B<Class::MOP::store_metaclass_by_name($name, $meta)> |
1059 | |
1060 | This will store a metaclass in the cache at the supplied C<$key>. |
1061 | |
1062 | =item B<Class::MOP::weaken_metaclass($name)> |
1063 | |
1064 | In rare cases (e.g. anonymous metaclasses) it is desirable to |
1065 | store a weakened reference in the metaclass cache. This |
1066 | function will weaken the reference to the metaclass stored |
1067 | in C<$name>. |
1068 | |
1069 | =item B<Class::MOP::metaclass_is_weak($name)> |
1070 | |
1071 | Returns true if the metaclass for C<$name> has been weakened |
1072 | (via C<weaken_metaclass>). |
1073 | |
1074 | =item B<Class::MOP::does_metaclass_exist($name)> |
1075 | |
1076 | This will return true of there exists a metaclass stored in the |
1077 | C<$name> key, and return false otherwise. |
1078 | |
1079 | =item B<Class::MOP::remove_metaclass_by_name($name)> |
1080 | |
1081 | This will remove the metaclass stored in the C<$name> key. |
1082 | |
1083 | =back |
1084 | |
1085 | =head2 Class Loading Options |
1086 | |
1087 | =over 4 |
1088 | |
1089 | =item -version |
1090 | |
1091 | Can be used to pass a minimum required version that will be checked |
1092 | against the class version after it was loaded. |
1093 | |
1094 | =back |
1095 | |
1096 | =head1 SEE ALSO |
1097 | |
1098 | =head2 Books |
1099 | |
1100 | There are very few books out on Meta Object Protocols and Metaclasses |
1101 | because it is such an esoteric topic. The following books are really |
1102 | the only ones I have found. If you know of any more, B<I<please>> |
1103 | email me and let me know, I would love to hear about them. |
1104 | |
1105 | =over 4 |
1106 | |
1107 | =item I<The Art of the Meta Object Protocol> |
1108 | |
1109 | =item I<Advances in Object-Oriented Metalevel Architecture and Reflection> |
1110 | |
1111 | =item I<Putting MetaClasses to Work> |
1112 | |
1113 | =item I<Smalltalk: The Language> |
1114 | |
1115 | =back |
1116 | |
1117 | =head2 Papers |
1118 | |
1119 | =over 4 |
1120 | |
1121 | =item "Uniform and safe metaclass composition" |
1122 | |
1123 | An excellent paper by the people who brought us the original Traits paper. |
1124 | This paper is on how Traits can be used to do safe metaclass composition, |
1125 | and offers an excellent introduction section which delves into the topic of |
1126 | metaclass compatibility. |
1127 | |
1128 | L<http://www.iam.unibe.ch/~scg/Archive/Papers/Duca05ySafeMetaclassTrait.pdf> |
1129 | |
1130 | =item "Safe Metaclass Programming" |
1131 | |
1132 | This paper seems to precede the above paper, and propose a mix-in based |
1133 | approach as opposed to the Traits based approach. Both papers have similar |
1134 | information on the metaclass compatibility problem space. |
1135 | |
1136 | L<http://citeseer.ist.psu.edu/37617.html> |
1137 | |
1138 | =back |
1139 | |
1140 | =head2 Prior Art |
1141 | |
1142 | =over 4 |
1143 | |
1144 | =item The Perl 6 MetaModel work in the Pugs project |
1145 | |
1146 | =over 4 |
1147 | |
1148 | =item L<http://svn.openfoundry.org/pugs/misc/Perl-MetaModel/> |
1149 | |
1150 | =item L<http://github.com/perl6/p5-modules/tree/master/Perl6-ObjectSpace/> |
1151 | |
1152 | =back |
1153 | |
1154 | =back |
1155 | |
1156 | =head2 Articles |
1157 | |
1158 | =over 4 |
1159 | |
1160 | =item CPAN Module Review of Class::MOP |
1161 | |
1162 | L<http://www.oreillynet.com/onlamp/blog/2006/06/cpan_module_review_classmop.html> |
1163 | |
1164 | =back |
1165 | |
1166 | =head1 SIMILAR MODULES |
1167 | |
1168 | As I have said above, this module is a class-builder-builder, so it is |
1169 | not the same thing as modules like L<Class::Accessor> and |
1170 | L<Class::MethodMaker>. That being said there are very few modules on CPAN |
1171 | with similar goals to this module. The one I have found which is most |
1172 | like this module is L<Class::Meta>, although it's philosophy and the MOP it |
1173 | creates are very different from this modules. |
1174 | |
1175 | =head1 BUGS |
1176 | |
1177 | All complex software has bugs lurking in it, and this module is no |
1178 | exception. |
1179 | |
1180 | Please report any bugs to C<bug-class-mop@rt.cpan.org>, or through the |
1181 | web interface at L<http://rt.cpan.org>. |
1182 | |
1183 | You can also discuss feature requests or possible bugs on the Moose |
1184 | mailing list (moose@perl.org) or on IRC at |
1185 | L<irc://irc.perl.org/#moose>. |
1186 | |
1187 | =head1 ACKNOWLEDGEMENTS |
1188 | |
1189 | =over 4 |
1190 | |
1191 | =item Rob Kinyon |
1192 | |
1193 | Thanks to Rob for actually getting the development of this module kick-started. |
1194 | |
1195 | =back |
1196 | |
1197 | =cut |