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', |
36 | $Moose::{VERSION} ? $Moose::{VERSION} |
37 | : $ENV{_XS_VERSION} ? $ENV{_XS_VERSION} |
38 | : () |
39 | ); |
40 | |
41 | { |
42 | # Metaclasses are singletons, so we cache them here. |
43 | # there is no need to worry about destruction though |
44 | # because they should die only when the program dies. |
45 | # After all, do package definitions even get reaped? |
46 | # Anonymous classes manage their own destruction. |
47 | my %METAS; |
48 | |
49 | sub get_all_metaclasses { %METAS } |
50 | sub get_all_metaclass_instances { values %METAS } |
51 | sub get_all_metaclass_names { keys %METAS } |
52 | sub get_metaclass_by_name { $METAS{$_[0]} } |
53 | sub store_metaclass_by_name { $METAS{$_[0]} = $_[1] } |
54 | sub weaken_metaclass { weaken($METAS{$_[0]}) } |
55 | sub metaclass_is_weak { isweak($METAS{$_[0]}) } |
56 | sub does_metaclass_exist { exists $METAS{$_[0]} && defined $METAS{$_[0]} } |
57 | sub remove_metaclass_by_name { delete $METAS{$_[0]}; return } |
58 | |
59 | # This handles instances as well as class names |
60 | sub class_of { |
61 | return unless defined $_[0]; |
62 | my $class = blessed($_[0]) || $_[0]; |
63 | return $METAS{$class}; |
64 | } |
65 | |
66 | # NOTE: |
67 | # We only cache metaclasses, meaning instances of |
68 | # Class::MOP::Class. We do not cache instance of |
69 | # Class::MOP::Package or Class::MOP::Module. Mostly |
70 | # because I don't yet see a good reason to do so. |
71 | } |
72 | |
73 | sub _class_to_pmfile { |
74 | my $class = shift; |
75 | |
76 | my $file = $class . '.pm'; |
77 | $file =~ s{::}{/}g; |
78 | |
79 | return $file; |
80 | } |
81 | |
82 | sub load_first_existing_class { |
83 | my $classes = Data::OptList::mkopt(\@_) |
84 | or return; |
85 | |
86 | foreach my $class (@{ $classes }) { |
87 | my $name = $class->[0]; |
88 | unless ( _is_valid_class_name($name) ) { |
89 | my $display = defined($name) ? $name : 'undef'; |
90 | confess "Invalid class name ($display)"; |
91 | } |
92 | } |
93 | |
94 | my $found; |
95 | my %exceptions; |
96 | |
97 | for my $class (@{ $classes }) { |
98 | my ($name, $options) = @{ $class }; |
99 | |
100 | if ($options) { |
101 | return $name if is_class_loaded($name, $options); |
102 | if (is_class_loaded($name)) { |
103 | # we already know it's loaded and too old, but we call |
104 | # ->VERSION anyway to generate the exception for us |
105 | $name->VERSION($options->{-version}); |
106 | } |
107 | } |
108 | else { |
109 | return $name if is_class_loaded($name); |
110 | } |
111 | |
112 | my $file = _class_to_pmfile($name); |
113 | return $name if try { |
114 | local $SIG{__DIE__}; |
115 | require $file; |
116 | $name->VERSION($options->{-version}) |
117 | if defined $options->{-version}; |
118 | return 1; |
119 | } |
120 | catch { |
121 | unless (/^Can't locate \Q$file\E in \@INC/) { |
122 | confess "Couldn't load class ($name) because: $_"; |
123 | } |
124 | |
125 | return; |
126 | }; |
127 | } |
128 | |
129 | if ( @{ $classes } > 1 ) { |
130 | my @list = map { $_->[0] } @{ $classes }; |
131 | confess "Can't locate any of @list in \@INC (\@INC contains: @INC)."; |
132 | } else { |
133 | confess "Can't locate " . _class_to_pmfile($classes->[0]->[0]) . " in \@INC (\@INC contains: @INC)."; |
134 | } |
135 | } |
136 | |
137 | sub load_class { |
138 | load_first_existing_class($_[0], ref $_[1] ? $_[1] : ()); |
139 | |
140 | # This is done to avoid breaking code which checked the return value. Said |
141 | # code is dumb. The return value was _always_ true, since it dies on |
142 | # failure! |
143 | return 1; |
144 | } |
145 | |
146 | sub _is_valid_class_name { |
147 | my $class = shift; |
148 | |
149 | return 0 if ref($class); |
150 | return 0 unless defined($class); |
151 | return 0 unless length($class); |
152 | |
153 | return 1 if $class =~ /^\w+(?:::\w+)*$/; |
154 | |
155 | return 0; |
156 | } |
157 | |
158 | ## ---------------------------------------------------------------------------- |
159 | ## Setting up our environment ... |
160 | ## ---------------------------------------------------------------------------- |
161 | ## Class::MOP needs to have a few things in the global perl environment so |
162 | ## that it can operate effectively. Those things are done here. |
163 | ## ---------------------------------------------------------------------------- |
164 | |
165 | # ... nothing yet actually ;) |
166 | |
167 | ## ---------------------------------------------------------------------------- |
168 | ## Bootstrapping |
169 | ## ---------------------------------------------------------------------------- |
170 | ## The code below here is to bootstrap our MOP with itself. This is also |
171 | ## sometimes called "tying the knot". By doing this, we make it much easier |
172 | ## to extend the MOP through subclassing and such since now you can use the |
173 | ## MOP itself to extend itself. |
174 | ## |
175 | ## Yes, I know, thats weird and insane, but it's a good thing, trust me :) |
176 | ## ---------------------------------------------------------------------------- |
177 | |
178 | # We need to add in the meta-attributes here so that |
179 | # any subclass of Class::MOP::* will be able to |
180 | # inherit them using _construct_instance |
181 | |
182 | ## -------------------------------------------------------- |
183 | ## Class::MOP::Mixin::HasMethods |
184 | |
185 | Class::MOP::Mixin::HasMethods->meta->add_attribute( |
186 | Class::MOP::Attribute->new('_methods' => ( |
187 | reader => { |
188 | # NOTE: |
189 | # we just alias the original method |
190 | # rather than re-produce it here |
191 | '_method_map' => \&Class::MOP::Mixin::HasMethods::_method_map |
192 | }, |
193 | default => sub { {} } |
194 | )) |
195 | ); |
196 | |
197 | Class::MOP::Mixin::HasMethods->meta->add_attribute( |
198 | Class::MOP::Attribute->new('method_metaclass' => ( |
199 | reader => { |
200 | # NOTE: |
201 | # we just alias the original method |
202 | # rather than re-produce it here |
203 | 'method_metaclass' => \&Class::MOP::Mixin::HasMethods::method_metaclass |
204 | }, |
205 | default => 'Class::MOP::Method', |
206 | )) |
207 | ); |
208 | |
209 | Class::MOP::Mixin::HasMethods->meta->add_attribute( |
210 | Class::MOP::Attribute->new('wrapped_method_metaclass' => ( |
211 | reader => { |
212 | # NOTE: |
213 | # we just alias the original method |
214 | # rather than re-produce it here |
215 | 'wrapped_method_metaclass' => \&Class::MOP::Mixin::HasMethods::wrapped_method_metaclass |
216 | }, |
217 | default => 'Class::MOP::Method::Wrapped', |
218 | )) |
219 | ); |
220 | |
221 | ## -------------------------------------------------------- |
222 | ## Class::MOP::Mixin::HasMethods |
223 | |
224 | Class::MOP::Mixin::HasAttributes->meta->add_attribute( |
225 | Class::MOP::Attribute->new('attributes' => ( |
226 | reader => { |
227 | # NOTE: we need to do this in order |
228 | # for the instance meta-object to |
229 | # not fall into meta-circular death |
230 | # |
231 | # we just alias the original method |
232 | # rather than re-produce it here |
233 | '_attribute_map' => \&Class::MOP::Mixin::HasAttributes::_attribute_map |
234 | }, |
235 | default => sub { {} } |
236 | )) |
237 | ); |
238 | |
239 | Class::MOP::Mixin::HasAttributes->meta->add_attribute( |
240 | Class::MOP::Attribute->new('attribute_metaclass' => ( |
241 | reader => { |
242 | # NOTE: |
243 | # we just alias the original method |
244 | # rather than re-produce it here |
245 | 'attribute_metaclass' => \&Class::MOP::Mixin::HasAttributes::attribute_metaclass |
246 | }, |
247 | default => 'Class::MOP::Attribute', |
248 | )) |
249 | ); |
250 | |
251 | ## -------------------------------------------------------- |
252 | ## Class::MOP::Package |
253 | |
254 | Class::MOP::Package->meta->add_attribute( |
255 | Class::MOP::Attribute->new('package' => ( |
256 | reader => { |
257 | # NOTE: we need to do this in order |
258 | # for the instance meta-object to |
259 | # not fall into meta-circular death |
260 | # |
261 | # we just alias the original method |
262 | # rather than re-produce it here |
263 | 'name' => \&Class::MOP::Package::name |
264 | }, |
265 | )) |
266 | ); |
267 | |
268 | Class::MOP::Package->meta->add_attribute( |
269 | Class::MOP::Attribute->new('namespace' => ( |
270 | reader => { |
271 | # NOTE: |
272 | # we just alias the original method |
273 | # rather than re-produce it here |
274 | 'namespace' => \&Class::MOP::Package::namespace |
275 | }, |
276 | init_arg => undef, |
277 | default => sub { \undef } |
278 | )) |
279 | ); |
280 | |
281 | ## -------------------------------------------------------- |
282 | ## Class::MOP::Module |
283 | |
284 | # NOTE: |
285 | # yeah this is kind of stretching things a bit, |
286 | # but truthfully the version should be an attribute |
287 | # of the Module, the weirdness comes from having to |
288 | # stick to Perl 5 convention and store it in the |
289 | # $VERSION package variable. Basically if you just |
290 | # squint at it, it will look how you want it to look. |
291 | # Either as a package variable, or as a attribute of |
292 | # the metaclass, isn't abstraction great :) |
293 | |
294 | Class::MOP::Module->meta->add_attribute( |
295 | Class::MOP::Attribute->new('version' => ( |
296 | reader => { |
297 | # NOTE: |
298 | # we just alias the original method |
299 | # rather than re-produce it here |
300 | 'version' => \&Class::MOP::Module::version |
301 | }, |
302 | init_arg => undef, |
303 | default => sub { \undef } |
304 | )) |
305 | ); |
306 | |
307 | # NOTE: |
308 | # By following the same conventions as version here, |
309 | # we are opening up the possibility that people can |
310 | # use the $AUTHORITY in non-Class::MOP modules as |
311 | # well. |
312 | |
313 | Class::MOP::Module->meta->add_attribute( |
314 | Class::MOP::Attribute->new('authority' => ( |
315 | reader => { |
316 | # NOTE: |
317 | # we just alias the original method |
318 | # rather than re-produce it here |
319 | 'authority' => \&Class::MOP::Module::authority |
320 | }, |
321 | init_arg => undef, |
322 | default => sub { \undef } |
323 | )) |
324 | ); |
325 | |
326 | ## -------------------------------------------------------- |
327 | ## Class::MOP::Class |
328 | |
329 | Class::MOP::Class->meta->add_attribute( |
330 | Class::MOP::Attribute->new('superclasses' => ( |
331 | accessor => { |
332 | # NOTE: |
333 | # we just alias the original method |
334 | # rather than re-produce it here |
335 | 'superclasses' => \&Class::MOP::Class::superclasses |
336 | }, |
337 | init_arg => undef, |
338 | default => sub { \undef } |
339 | )) |
340 | ); |
341 | |
342 | Class::MOP::Class->meta->add_attribute( |
343 | Class::MOP::Attribute->new('instance_metaclass' => ( |
344 | reader => { |
345 | # NOTE: we need to do this in order |
346 | # for the instance meta-object to |
347 | # not fall into meta-circular death |
348 | # |
349 | # we just alias the original method |
350 | # rather than re-produce it here |
351 | 'instance_metaclass' => \&Class::MOP::Class::instance_metaclass |
352 | }, |
353 | default => 'Class::MOP::Instance', |
354 | )) |
355 | ); |
356 | |
357 | Class::MOP::Class->meta->add_attribute( |
358 | Class::MOP::Attribute->new('immutable_trait' => ( |
359 | reader => { |
360 | 'immutable_trait' => \&Class::MOP::Class::immutable_trait |
361 | }, |
362 | default => "Class::MOP::Class::Immutable::Trait", |
363 | )) |
364 | ); |
365 | |
366 | Class::MOP::Class->meta->add_attribute( |
367 | Class::MOP::Attribute->new('constructor_name' => ( |
368 | reader => { |
369 | 'constructor_name' => \&Class::MOP::Class::constructor_name, |
370 | }, |
371 | default => "new", |
372 | )) |
373 | ); |
374 | |
375 | Class::MOP::Class->meta->add_attribute( |
376 | Class::MOP::Attribute->new('constructor_class' => ( |
377 | reader => { |
378 | 'constructor_class' => \&Class::MOP::Class::constructor_class, |
379 | }, |
380 | default => "Class::MOP::Method::Constructor", |
381 | )) |
382 | ); |
383 | |
384 | |
385 | Class::MOP::Class->meta->add_attribute( |
386 | Class::MOP::Attribute->new('destructor_class' => ( |
387 | reader => { |
388 | 'destructor_class' => \&Class::MOP::Class::destructor_class, |
389 | }, |
390 | )) |
391 | ); |
392 | |
393 | # NOTE: |
394 | # we don't actually need to tie the knot with |
395 | # Class::MOP::Class here, it is actually handled |
396 | # within Class::MOP::Class itself in the |
397 | # _construct_class_instance method. |
398 | |
399 | ## -------------------------------------------------------- |
400 | ## Class::MOP::Mixin::AttributeCore |
401 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
402 | Class::MOP::Attribute->new('name' => ( |
403 | reader => { |
404 | # NOTE: we need to do this in order |
405 | # for the instance meta-object to |
406 | # not fall into meta-circular death |
407 | # |
408 | # we just alias the original method |
409 | # rather than re-produce it here |
410 | 'name' => \&Class::MOP::Mixin::AttributeCore::name |
411 | } |
412 | )) |
413 | ); |
414 | |
415 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
416 | Class::MOP::Attribute->new('accessor' => ( |
417 | reader => { 'accessor' => \&Class::MOP::Mixin::AttributeCore::accessor }, |
418 | predicate => { 'has_accessor' => \&Class::MOP::Mixin::AttributeCore::has_accessor }, |
419 | )) |
420 | ); |
421 | |
422 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
423 | Class::MOP::Attribute->new('reader' => ( |
424 | reader => { 'reader' => \&Class::MOP::Mixin::AttributeCore::reader }, |
425 | predicate => { 'has_reader' => \&Class::MOP::Mixin::AttributeCore::has_reader }, |
426 | )) |
427 | ); |
428 | |
429 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
430 | Class::MOP::Attribute->new('initializer' => ( |
431 | reader => { 'initializer' => \&Class::MOP::Mixin::AttributeCore::initializer }, |
432 | predicate => { 'has_initializer' => \&Class::MOP::Mixin::AttributeCore::has_initializer }, |
433 | )) |
434 | ); |
435 | |
436 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
437 | Class::MOP::Attribute->new('definition_context' => ( |
438 | reader => { 'definition_context' => \&Class::MOP::Mixin::AttributeCore::definition_context }, |
439 | )) |
440 | ); |
441 | |
442 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
443 | Class::MOP::Attribute->new('writer' => ( |
444 | reader => { 'writer' => \&Class::MOP::Mixin::AttributeCore::writer }, |
445 | predicate => { 'has_writer' => \&Class::MOP::Mixin::AttributeCore::has_writer }, |
446 | )) |
447 | ); |
448 | |
449 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
450 | Class::MOP::Attribute->new('predicate' => ( |
451 | reader => { 'predicate' => \&Class::MOP::Mixin::AttributeCore::predicate }, |
452 | predicate => { 'has_predicate' => \&Class::MOP::Mixin::AttributeCore::has_predicate }, |
453 | )) |
454 | ); |
455 | |
456 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
457 | Class::MOP::Attribute->new('clearer' => ( |
458 | reader => { 'clearer' => \&Class::MOP::Mixin::AttributeCore::clearer }, |
459 | predicate => { 'has_clearer' => \&Class::MOP::Mixin::AttributeCore::has_clearer }, |
460 | )) |
461 | ); |
462 | |
463 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
464 | Class::MOP::Attribute->new('builder' => ( |
465 | reader => { 'builder' => \&Class::MOP::Mixin::AttributeCore::builder }, |
466 | predicate => { 'has_builder' => \&Class::MOP::Mixin::AttributeCore::has_builder }, |
467 | )) |
468 | ); |
469 | |
470 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
471 | Class::MOP::Attribute->new('init_arg' => ( |
472 | reader => { 'init_arg' => \&Class::MOP::Mixin::AttributeCore::init_arg }, |
473 | predicate => { 'has_init_arg' => \&Class::MOP::Mixin::AttributeCore::has_init_arg }, |
474 | )) |
475 | ); |
476 | |
477 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
478 | Class::MOP::Attribute->new('default' => ( |
479 | # default has a custom 'reader' method ... |
480 | predicate => { 'has_default' => \&Class::MOP::Mixin::AttributeCore::has_default }, |
481 | )) |
482 | ); |
483 | |
484 | Class::MOP::Mixin::AttributeCore->meta->add_attribute( |
485 | Class::MOP::Attribute->new('insertion_order' => ( |
486 | reader => { 'insertion_order' => \&Class::MOP::Mixin::AttributeCore::insertion_order }, |
487 | writer => { '_set_insertion_order' => \&Class::MOP::Mixin::AttributeCore::_set_insertion_order }, |
488 | predicate => { 'has_insertion_order' => \&Class::MOP::Mixin::AttributeCore::has_insertion_order }, |
489 | )) |
490 | ); |
491 | |
492 | ## -------------------------------------------------------- |
493 | ## Class::MOP::Attribute |
494 | Class::MOP::Attribute->meta->add_attribute( |
495 | Class::MOP::Attribute->new('associated_class' => ( |
496 | reader => { |
497 | # NOTE: we need to do this in order |
498 | # for the instance meta-object to |
499 | # not fall into meta-circular death |
500 | # |
501 | # we just alias the original method |
502 | # rather than re-produce it here |
503 | 'associated_class' => \&Class::MOP::Attribute::associated_class |
504 | } |
505 | )) |
506 | ); |
507 | |
508 | Class::MOP::Attribute->meta->add_attribute( |
509 | Class::MOP::Attribute->new('associated_methods' => ( |
510 | reader => { 'associated_methods' => \&Class::MOP::Attribute::associated_methods }, |
511 | default => sub { [] } |
512 | )) |
513 | ); |
514 | |
515 | Class::MOP::Attribute->meta->add_method('clone' => sub { |
516 | my $self = shift; |
517 | $self->meta->clone_object($self, @_); |
518 | }); |
519 | |
520 | ## -------------------------------------------------------- |
521 | ## Class::MOP::Method |
522 | Class::MOP::Method->meta->add_attribute( |
523 | Class::MOP::Attribute->new('body' => ( |
524 | reader => { 'body' => \&Class::MOP::Method::body }, |
525 | )) |
526 | ); |
527 | |
528 | Class::MOP::Method->meta->add_attribute( |
529 | Class::MOP::Attribute->new('associated_metaclass' => ( |
530 | reader => { 'associated_metaclass' => \&Class::MOP::Method::associated_metaclass }, |
531 | )) |
532 | ); |
533 | |
534 | Class::MOP::Method->meta->add_attribute( |
535 | Class::MOP::Attribute->new('package_name' => ( |
536 | reader => { 'package_name' => \&Class::MOP::Method::package_name }, |
537 | )) |
538 | ); |
539 | |
540 | Class::MOP::Method->meta->add_attribute( |
541 | Class::MOP::Attribute->new('name' => ( |
542 | reader => { 'name' => \&Class::MOP::Method::name }, |
543 | )) |
544 | ); |
545 | |
546 | Class::MOP::Method->meta->add_attribute( |
547 | Class::MOP::Attribute->new('original_method' => ( |
548 | reader => { 'original_method' => \&Class::MOP::Method::original_method }, |
549 | writer => { '_set_original_method' => \&Class::MOP::Method::_set_original_method }, |
550 | )) |
551 | ); |
552 | |
553 | ## -------------------------------------------------------- |
554 | ## Class::MOP::Method::Wrapped |
555 | |
556 | # NOTE: |
557 | # the way this item is initialized, this |
558 | # really does not follow the standard |
559 | # practices of attributes, but we put |
560 | # it here for completeness |
561 | Class::MOP::Method::Wrapped->meta->add_attribute( |
562 | Class::MOP::Attribute->new('modifier_table') |
563 | ); |
564 | |
565 | ## -------------------------------------------------------- |
566 | ## Class::MOP::Method::Generated |
567 | |
568 | Class::MOP::Method::Generated->meta->add_attribute( |
569 | Class::MOP::Attribute->new('is_inline' => ( |
570 | reader => { 'is_inline' => \&Class::MOP::Method::Generated::is_inline }, |
571 | default => 0, |
572 | )) |
573 | ); |
574 | |
575 | Class::MOP::Method::Generated->meta->add_attribute( |
576 | Class::MOP::Attribute->new('definition_context' => ( |
577 | reader => { 'definition_context' => \&Class::MOP::Method::Generated::definition_context }, |
578 | )) |
579 | ); |
580 | |
581 | |
582 | ## -------------------------------------------------------- |
583 | ## Class::MOP::Method::Inlined |
584 | |
585 | Class::MOP::Method::Inlined->meta->add_attribute( |
586 | Class::MOP::Attribute->new('_expected_method_class' => ( |
587 | reader => { '_expected_method_class' => \&Class::MOP::Method::Inlined::_expected_method_class }, |
588 | )) |
589 | ); |
590 | |
591 | ## -------------------------------------------------------- |
592 | ## Class::MOP::Method::Accessor |
593 | |
594 | Class::MOP::Method::Accessor->meta->add_attribute( |
595 | Class::MOP::Attribute->new('attribute' => ( |
596 | reader => { |
597 | 'associated_attribute' => \&Class::MOP::Method::Accessor::associated_attribute |
598 | }, |
599 | )) |
600 | ); |
601 | |
602 | Class::MOP::Method::Accessor->meta->add_attribute( |
603 | Class::MOP::Attribute->new('accessor_type' => ( |
604 | reader => { 'accessor_type' => \&Class::MOP::Method::Accessor::accessor_type }, |
605 | )) |
606 | ); |
607 | |
608 | ## -------------------------------------------------------- |
609 | ## Class::MOP::Method::Constructor |
610 | |
611 | Class::MOP::Method::Constructor->meta->add_attribute( |
612 | Class::MOP::Attribute->new('options' => ( |
613 | reader => { |
614 | 'options' => \&Class::MOP::Method::Constructor::options |
615 | }, |
616 | default => sub { +{} } |
617 | )) |
618 | ); |
619 | |
620 | Class::MOP::Method::Constructor->meta->add_attribute( |
621 | Class::MOP::Attribute->new('associated_metaclass' => ( |
622 | init_arg => "metaclass", # FIXME alias and rename |
623 | reader => { |
624 | 'associated_metaclass' => \&Class::MOP::Method::Constructor::associated_metaclass |
625 | }, |
626 | )) |
627 | ); |
628 | |
629 | ## -------------------------------------------------------- |
630 | ## Class::MOP::Instance |
631 | |
632 | # NOTE: |
633 | # these don't yet do much of anything, but are just |
634 | # included for completeness |
635 | |
636 | Class::MOP::Instance->meta->add_attribute( |
637 | Class::MOP::Attribute->new('associated_metaclass', |
638 | reader => { associated_metaclass => \&Class::MOP::Instance::associated_metaclass }, |
639 | ), |
640 | ); |
641 | |
642 | Class::MOP::Instance->meta->add_attribute( |
643 | Class::MOP::Attribute->new('_class_name', |
644 | init_arg => undef, |
645 | reader => { _class_name => \&Class::MOP::Instance::_class_name }, |
646 | #lazy => 1, # not yet supported by Class::MOP but out our version does it anyway |
647 | #default => sub { $_[0]->associated_metaclass->name }, |
648 | ), |
649 | ); |
650 | |
651 | Class::MOP::Instance->meta->add_attribute( |
652 | Class::MOP::Attribute->new('attributes', |
653 | reader => { attributes => \&Class::MOP::Instance::get_all_attributes }, |
654 | ), |
655 | ); |
656 | |
657 | Class::MOP::Instance->meta->add_attribute( |
658 | Class::MOP::Attribute->new('slots', |
659 | reader => { slots => \&Class::MOP::Instance::slots }, |
660 | ), |
661 | ); |
662 | |
663 | Class::MOP::Instance->meta->add_attribute( |
664 | Class::MOP::Attribute->new('slot_hash', |
665 | reader => { slot_hash => \&Class::MOP::Instance::slot_hash }, |
666 | ), |
667 | ); |
668 | |
669 | ## -------------------------------------------------------- |
670 | ## Class::MOP::Object |
671 | |
672 | # need to replace the meta method there with a real meta method object |
673 | Class::MOP::Object->meta->_add_meta_method('meta'); |
674 | |
675 | ## -------------------------------------------------------- |
676 | ## Class::MOP::Mixin |
677 | |
678 | # need to replace the meta method there with a real meta method object |
679 | Class::MOP::Mixin->meta->_add_meta_method('meta'); |
680 | |
681 | require Class::MOP::Deprecated unless our $no_deprecated; |
682 | |
683 | # we need the meta instance of the meta instance to be created now, in order |
684 | # for the constructor to be able to use it |
685 | Class::MOP::Instance->meta->get_meta_instance; |
686 | |
687 | # pretend the add_method never happenned. it hasn't yet affected anything |
688 | undef Class::MOP::Instance->meta->{_package_cache_flag}; |
689 | |
690 | ## -------------------------------------------------------- |
691 | ## Now close all the Class::MOP::* classes |
692 | |
693 | # NOTE: we don't need to inline the the accessors this only lengthens |
694 | # the compile time of the MOP, and gives us no actual benefits. |
695 | |
696 | $_->meta->make_immutable( |
697 | inline_constructor => 0, |
698 | constructor_name => "_new", |
699 | inline_accessors => 0, |
700 | ) for qw/ |
701 | Class::MOP::Package |
702 | Class::MOP::Module |
703 | Class::MOP::Class |
704 | |
705 | Class::MOP::Attribute |
706 | Class::MOP::Method |
707 | Class::MOP::Instance |
708 | |
709 | Class::MOP::Object |
710 | |
711 | Class::MOP::Method::Generated |
712 | Class::MOP::Method::Inlined |
713 | |
714 | Class::MOP::Method::Accessor |
715 | Class::MOP::Method::Constructor |
716 | Class::MOP::Method::Wrapped |
717 | |
718 | Class::MOP::Method::Meta |
719 | /; |
720 | |
721 | $_->meta->make_immutable( |
722 | inline_constructor => 0, |
723 | constructor_name => undef, |
724 | inline_accessors => 0, |
725 | ) for qw/ |
726 | Class::MOP::Mixin |
727 | Class::MOP::Mixin::AttributeCore |
728 | Class::MOP::Mixin::HasAttributes |
729 | Class::MOP::Mixin::HasMethods |
730 | /; |
731 | |
732 | 1; |
733 | |
734 | # ABSTRACT: A Meta Object Protocol for Perl 5 |
735 | |
736 | __END__ |
737 | |
738 | =pod |
739 | |
740 | =head1 DESCRIPTION |
741 | |
742 | This module is a fully functioning meta object protocol for the |
743 | Perl 5 object system. It makes no attempt to change the behavior or |
744 | characteristics of the Perl 5 object system, only to create a |
745 | protocol for its manipulation and introspection. |
746 | |
747 | That said, it does attempt to create the tools for building a rich set |
748 | of extensions to the Perl 5 object system. Every attempt has been made |
749 | to abide by the spirit of the Perl 5 object system that we all know |
750 | and love. |
751 | |
752 | This documentation is sparse on conceptual details. We suggest looking |
753 | at the items listed in the L<SEE ALSO> section for more |
754 | information. In particular the book "The Art of the Meta Object |
755 | Protocol" was very influential in the development of this system. |
756 | |
757 | =head2 What is a Meta Object Protocol? |
758 | |
759 | A meta object protocol is an API to an object system. |
760 | |
761 | To be more specific, it abstracts the components of an object system |
762 | (classes, object, methods, object attributes, etc.). These |
763 | abstractions can then be used to inspect and manipulate the object |
764 | system which they describe. |
765 | |
766 | It can be said that there are two MOPs for any object system; the |
767 | implicit MOP and the explicit MOP. The implicit MOP handles things |
768 | like method dispatch or inheritance, which happen automatically as |
769 | part of how the object system works. The explicit MOP typically |
770 | handles the introspection/reflection features of the object system. |
771 | |
772 | All object systems have implicit MOPs. Without one, they would not |
773 | work. Explicit MOPs are much less common, and depending on the |
774 | language can vary from restrictive (Reflection in Java or C#) to wide |
775 | open (CLOS is a perfect example). |
776 | |
777 | =head2 Yet Another Class Builder! Why? |
778 | |
779 | This is B<not> a class builder so much as a I<class builder |
780 | B<builder>>. The intent is that an end user will not use this module |
781 | directly, but instead this module is used by module authors to build |
782 | extensions and features onto the Perl 5 object system. |
783 | |
784 | This system is used by L<Moose>, which supplies a powerful class |
785 | builder system built entirely on top of C<Class::MOP>. |
786 | |
787 | =head2 Who is this module for? |
788 | |
789 | This module is for anyone who has ever created or wanted to create a |
790 | module for the Class:: namespace. The tools which this module provides |
791 | make doing complex Perl 5 wizardry simpler, by removing such barriers |
792 | as the need to hack symbol tables, or understand the fine details of |
793 | method dispatch. |
794 | |
795 | =head2 What changes do I have to make to use this module? |
796 | |
797 | This module was designed to be as unintrusive as possible. Many of its |
798 | features are accessible without B<any> change to your existing |
799 | code. It is meant to be a compliment to your existing code and not an |
800 | intrusion on your code base. Unlike many other B<Class::> modules, |
801 | this module B<does not> require you subclass it, or even that you |
802 | C<use> it in within your module's package. |
803 | |
804 | The only features which requires additions to your code are the |
805 | attribute handling and instance construction features, and these are |
806 | both completely optional features. The only reason for this is because |
807 | Perl 5's object system does not actually have these features built |
808 | in. More information about this feature can be found below. |
809 | |
810 | =head2 About Performance |
811 | |
812 | It is a common misconception that explicit MOPs are a performance hit. |
813 | This is not a universal truth, it is a side-effect of some specific |
814 | implementations. For instance, using Java reflection is slow because |
815 | the JVM cannot take advantage of any compiler optimizations, and the |
816 | JVM has to deal with much more runtime type information as well. |
817 | |
818 | Reflection in C# is marginally better as it was designed into the |
819 | language and runtime (the CLR). In contrast, CLOS (the Common Lisp |
820 | Object System) was built to support an explicit MOP, and so |
821 | performance is tuned for it. |
822 | |
823 | This library in particular does its absolute best to avoid putting |
824 | B<any> drain at all upon your code's performance. In fact, by itself |
825 | it does nothing to affect your existing code. So you only pay for what |
826 | you actually use. |
827 | |
828 | =head2 About Metaclass compatibility |
829 | |
830 | This module makes sure that all metaclasses created are both upwards |
831 | and downwards compatible. The topic of metaclass compatibility is |
832 | highly esoteric and is something only encountered when doing deep and |
833 | involved metaclass hacking. There are two basic kinds of metaclass |
834 | incompatibility; upwards and downwards. |
835 | |
836 | Upwards metaclass compatibility means that the metaclass of a |
837 | given class is either the same as (or a subclass of) all of the |
838 | class's ancestors. |
839 | |
840 | Downward metaclass compatibility means that the metaclasses of a |
841 | given class's ancestors are all either the same as (or a subclass |
842 | of) that metaclass. |
843 | |
844 | Here is a diagram showing a set of two classes (C<A> and C<B>) and |
845 | two metaclasses (C<Meta::A> and C<Meta::B>) which have correct |
846 | metaclass compatibility both upwards and downwards. |
847 | |
848 | +---------+ +---------+ |
849 | | Meta::A |<----| Meta::B | <....... (instance of ) |
850 | +---------+ +---------+ <------- (inherits from) |
851 | ^ ^ |
852 | : : |
853 | +---------+ +---------+ |
854 | | A |<----| B | |
855 | +---------+ +---------+ |
856 | |
857 | In actuality, I<all> of a class's metaclasses must be compatible, |
858 | not just the class metaclass. That includes the instance, attribute, |
859 | and method metaclasses, as well as the constructor and destructor |
860 | classes. |
861 | |
862 | C<Class::MOP> will attempt to fix some simple types of |
863 | incompatibilities. If all the metaclasses for the parent class are |
864 | I<subclasses> of the child's metaclasses then we can simply replace |
865 | the child's metaclasses with the parent's. In addition, if the child |
866 | is missing a metaclass that the parent has, we can also just make the |
867 | child use the parent's metaclass. |
868 | |
869 | As I said this is a highly esoteric topic and one you will only run |
870 | into if you do a lot of subclassing of L<Class::MOP::Class>. If you |
871 | are interested in why this is an issue see the paper I<Uniform and |
872 | safe metaclass composition> linked to in the L<SEE ALSO> section of |
873 | this document. |
874 | |
875 | =head2 Using custom metaclasses |
876 | |
877 | Always use the L<metaclass> pragma when using a custom metaclass, this |
878 | will ensure the proper initialization order and not accidentally |
879 | create an incorrect type of metaclass for you. This is a very rare |
880 | problem, and one which can only occur if you are doing deep metaclass |
881 | programming. So in other words, don't worry about it. |
882 | |
883 | Note that if you're using L<Moose> we encourage you to I<not> use |
884 | L<metaclass> pragma, and instead use L<Moose::Util::MetaRole> to apply |
885 | roles to a class's metaclasses. This topic is covered at length in |
886 | various L<Moose::Cookbook> recipes. |
887 | |
888 | =head1 PROTOCOLS |
889 | |
890 | The meta-object protocol is divided into 4 main sub-protocols: |
891 | |
892 | =head2 The Class protocol |
893 | |
894 | This provides a means of manipulating and introspecting a Perl 5 |
895 | class. It handles symbol table hacking for you, and provides a rich |
896 | set of methods that go beyond simple package introspection. |
897 | |
898 | See L<Class::MOP::Class> for more details. |
899 | |
900 | =head2 The Attribute protocol |
901 | |
902 | This provides a consistent representation for an attribute of a Perl 5 |
903 | class. Since there are so many ways to create and handle attributes in |
904 | Perl 5 OO, the Attribute protocol provide as much of a unified |
905 | approach as possible. Of course, you are always free to extend this |
906 | protocol by subclassing the appropriate classes. |
907 | |
908 | See L<Class::MOP::Attribute> for more details. |
909 | |
910 | =head2 The Method protocol |
911 | |
912 | This provides a means of manipulating and introspecting methods in the |
913 | Perl 5 object system. As with attributes, there are many ways to |
914 | approach this topic, so we try to keep it pretty basic, while still |
915 | making it possible to extend the system in many ways. |
916 | |
917 | See L<Class::MOP::Method> for more details. |
918 | |
919 | =head2 The Instance protocol |
920 | |
921 | This provides a layer of abstraction for creating object instances. |
922 | Since the other layers use this protocol, it is relatively easy to |
923 | change the type of your instances from the default hash reference to |
924 | some other type of reference. Several examples are provided in the |
925 | F<examples/> directory included in this distribution. |
926 | |
927 | See L<Class::MOP::Instance> for more details. |
928 | |
929 | =head1 FUNCTIONS |
930 | |
931 | Note that this module does not export any constants or functions. |
932 | |
933 | =head2 Constants |
934 | |
935 | =over 4 |
936 | |
937 | =item I<Class::MOP::IS_RUNNING_ON_5_10> |
938 | |
939 | We set this constant depending on what version perl we are on, this |
940 | allows us to take advantage of new 5.10 features and stay backwards |
941 | compatible. |
942 | |
943 | =back |
944 | |
945 | =head2 Utility functions |
946 | |
947 | Note that these are all called as B<functions, not methods>. |
948 | |
949 | =over 4 |
950 | |
951 | =item B<Class::MOP::load_class($class_name, \%options?)> |
952 | |
953 | This will load the specified C<$class_name>, if it is not already |
954 | loaded (as reported by C<is_class_loaded>). This function can be used |
955 | in place of tricks like C<eval "use $module"> or using C<require> |
956 | unconditionally. |
957 | |
958 | If the module cannot be loaded, an exception is thrown. |
959 | |
960 | You can pass a hash reference with options as second argument. The |
961 | only option currently recognised is C<-version>, which will ensure |
962 | that the loaded class has at least the required version. |
963 | |
964 | See also L</Class Loading Options>. |
965 | |
966 | For historical reasons, this function explicitly returns a true value. |
967 | |
968 | =item B<Class::MOP::is_class_loaded($class_name, \%options?)> |
969 | |
970 | Returns a boolean indicating whether or not C<$class_name> has been |
971 | loaded. |
972 | |
973 | This does a basic check of the symbol table to try and determine as |
974 | best it can if the C<$class_name> is loaded, it is probably correct |
975 | about 99% of the time, but it can be fooled into reporting false |
976 | positives. In particular, loading any of the core L<IO> modules will |
977 | cause most of the rest of the core L<IO> modules to falsely report |
978 | having been loaded, due to the way the base L<IO> module works. |
979 | |
980 | You can pass a hash reference with options as second argument. The |
981 | only option currently recognised is C<-version>, which will ensure |
982 | that the loaded class has at least the required version. |
983 | |
984 | See also L</Class Loading Options>. |
985 | |
986 | =item B<Class::MOP::get_code_info($code)> |
987 | |
988 | This function returns two values, the name of the package the C<$code> |
989 | is from and the name of the C<$code> itself. This is used by several |
990 | elements of the MOP to determine where a given C<$code> reference is |
991 | from. |
992 | |
993 | =item B<Class::MOP::class_of($instance_or_class_name)> |
994 | |
995 | This will return the metaclass of the given instance or class name. If the |
996 | class lacks a metaclass, no metaclass will be initialized, and C<undef> will be |
997 | returned. |
998 | |
999 | =item B<Class::MOP::check_package_cache_flag($pkg)> |
1000 | |
1001 | B<NOTE: DO NOT USE THIS FUNCTION, IT IS FOR INTERNAL USE ONLY!> |
1002 | |
1003 | This will return an integer that is managed by L<Class::MOP::Class> to |
1004 | determine if a module's symbol table has been altered. |
1005 | |
1006 | In Perl 5.10 or greater, this flag is package specific. However in |
1007 | versions prior to 5.10, this will use the C<PL_sub_generation> |
1008 | variable which is not package specific. |
1009 | |
1010 | =item B<Class::MOP::load_first_existing_class(@class_names)> |
1011 | |
1012 | =item B<Class::MOP::load_first_existing_class($classA, \%optionsA?, $classB, ...)> |
1013 | |
1014 | B<NOTE: DO NOT USE THIS FUNCTION, IT IS FOR INTERNAL USE ONLY!> |
1015 | |
1016 | Given a list of class names, this function will attempt to load each |
1017 | one in turn. |
1018 | |
1019 | If it finds a class it can load, it will return that class' name. If |
1020 | none of the classes can be loaded, it will throw an exception. |
1021 | |
1022 | Additionally, you can pass a hash reference with options after each |
1023 | class name. Currently, only C<-version> is recognised and will ensure |
1024 | that the loaded class has at least the required version. If the class |
1025 | version is not sufficient, an exception will be raised. |
1026 | |
1027 | See also L</Class Loading Options>. |
1028 | |
1029 | =back |
1030 | |
1031 | =head2 Metaclass cache functions |
1032 | |
1033 | Class::MOP holds a cache of metaclasses. The following are functions |
1034 | (B<not methods>) which can be used to access that cache. It is not |
1035 | recommended that you mess with these. Bad things could happen, but if |
1036 | you are brave and willing to risk it: go for it! |
1037 | |
1038 | =over 4 |
1039 | |
1040 | =item B<Class::MOP::get_all_metaclasses> |
1041 | |
1042 | This will return a hash of all the metaclass instances that have |
1043 | been cached by L<Class::MOP::Class>, keyed by the package name. |
1044 | |
1045 | =item B<Class::MOP::get_all_metaclass_instances> |
1046 | |
1047 | This will return a list of all the metaclass instances that have |
1048 | been cached by L<Class::MOP::Class>. |
1049 | |
1050 | =item B<Class::MOP::get_all_metaclass_names> |
1051 | |
1052 | This will return a list of all the metaclass names that have |
1053 | been cached by L<Class::MOP::Class>. |
1054 | |
1055 | =item B<Class::MOP::get_metaclass_by_name($name)> |
1056 | |
1057 | This will return a cached L<Class::MOP::Class> instance, or nothing |
1058 | if no metaclass exists with that C<$name>. |
1059 | |
1060 | =item B<Class::MOP::store_metaclass_by_name($name, $meta)> |
1061 | |
1062 | This will store a metaclass in the cache at the supplied C<$key>. |
1063 | |
1064 | =item B<Class::MOP::weaken_metaclass($name)> |
1065 | |
1066 | In rare cases (e.g. anonymous metaclasses) it is desirable to |
1067 | store a weakened reference in the metaclass cache. This |
1068 | function will weaken the reference to the metaclass stored |
1069 | in C<$name>. |
1070 | |
1071 | =item B<Class::MOP::metaclass_is_weak($name)> |
1072 | |
1073 | Returns true if the metaclass for C<$name> has been weakened |
1074 | (via C<weaken_metaclass>). |
1075 | |
1076 | =item B<Class::MOP::does_metaclass_exist($name)> |
1077 | |
1078 | This will return true of there exists a metaclass stored in the |
1079 | C<$name> key, and return false otherwise. |
1080 | |
1081 | =item B<Class::MOP::remove_metaclass_by_name($name)> |
1082 | |
1083 | This will remove the metaclass stored in the C<$name> key. |
1084 | |
1085 | =back |
1086 | |
1087 | =head2 Class Loading Options |
1088 | |
1089 | =over 4 |
1090 | |
1091 | =item -version |
1092 | |
1093 | Can be used to pass a minimum required version that will be checked |
1094 | against the class version after it was loaded. |
1095 | |
1096 | =back |
1097 | |
1098 | =head1 SEE ALSO |
1099 | |
1100 | =head2 Books |
1101 | |
1102 | There are very few books out on Meta Object Protocols and Metaclasses |
1103 | because it is such an esoteric topic. The following books are really |
1104 | the only ones I have found. If you know of any more, B<I<please>> |
1105 | email me and let me know, I would love to hear about them. |
1106 | |
1107 | =over 4 |
1108 | |
1109 | =item I<The Art of the Meta Object Protocol> |
1110 | |
1111 | =item I<Advances in Object-Oriented Metalevel Architecture and Reflection> |
1112 | |
1113 | =item I<Putting MetaClasses to Work> |
1114 | |
1115 | =item I<Smalltalk: The Language> |
1116 | |
1117 | =back |
1118 | |
1119 | =head2 Papers |
1120 | |
1121 | =over 4 |
1122 | |
1123 | =item "Uniform and safe metaclass composition" |
1124 | |
1125 | An excellent paper by the people who brought us the original Traits paper. |
1126 | This paper is on how Traits can be used to do safe metaclass composition, |
1127 | and offers an excellent introduction section which delves into the topic of |
1128 | metaclass compatibility. |
1129 | |
1130 | L<http://www.iam.unibe.ch/~scg/Archive/Papers/Duca05ySafeMetaclassTrait.pdf> |
1131 | |
1132 | =item "Safe Metaclass Programming" |
1133 | |
1134 | This paper seems to precede the above paper, and propose a mix-in based |
1135 | approach as opposed to the Traits based approach. Both papers have similar |
1136 | information on the metaclass compatibility problem space. |
1137 | |
1138 | L<http://citeseer.ist.psu.edu/37617.html> |
1139 | |
1140 | =back |
1141 | |
1142 | =head2 Prior Art |
1143 | |
1144 | =over 4 |
1145 | |
1146 | =item The Perl 6 MetaModel work in the Pugs project |
1147 | |
1148 | =over 4 |
1149 | |
1150 | =item L<http://svn.openfoundry.org/pugs/misc/Perl-MetaModel/> |
1151 | |
1152 | =item L<http://github.com/perl6/p5-modules/tree/master/Perl6-ObjectSpace/> |
1153 | |
1154 | =back |
1155 | |
1156 | =back |
1157 | |
1158 | =head2 Articles |
1159 | |
1160 | =over 4 |
1161 | |
1162 | =item CPAN Module Review of Class::MOP |
1163 | |
1164 | L<http://www.oreillynet.com/onlamp/blog/2006/06/cpan_module_review_classmop.html> |
1165 | |
1166 | =back |
1167 | |
1168 | =head1 SIMILAR MODULES |
1169 | |
1170 | As I have said above, this module is a class-builder-builder, so it is |
1171 | not the same thing as modules like L<Class::Accessor> and |
1172 | L<Class::MethodMaker>. That being said there are very few modules on CPAN |
1173 | with similar goals to this module. The one I have found which is most |
1174 | like this module is L<Class::Meta>, although it's philosophy and the MOP it |
1175 | creates are very different from this modules. |
1176 | |
1177 | =head1 BUGS |
1178 | |
1179 | All complex software has bugs lurking in it, and this module is no |
1180 | exception. |
1181 | |
1182 | Please report any bugs to C<bug-class-mop@rt.cpan.org>, or through the |
1183 | web interface at L<http://rt.cpan.org>. |
1184 | |
1185 | You can also discuss feature requests or possible bugs on the Moose |
1186 | mailing list (moose@perl.org) or on IRC at |
1187 | L<irc://irc.perl.org/#moose>. |
1188 | |
1189 | =head1 ACKNOWLEDGEMENTS |
1190 | |
1191 | =over 4 |
1192 | |
1193 | =item Rob Kinyon |
1194 | |
1195 | Thanks to Rob for actually getting the development of this module kick-started. |
1196 | |
1197 | =back |
1198 | |
1199 | =cut |