2 package Class::MOP::Class;
7 use Class::MOP::Instance;
8 use Class::MOP::Method::Wrapped;
9 use Class::MOP::Method::Accessor;
10 use Class::MOP::Method::Constructor;
11 use Class::MOP::MiniTrait;
14 use Scalar::Util 'blessed', 'reftype', 'weaken';
15 use Sub::Name 'subname';
17 use List::MoreUtils 'all';
19 use base 'Class::MOP::Module',
20 'Class::MOP::Mixin::HasAttributes',
21 'Class::MOP::Mixin::HasMethods';
31 $package_name = shift;
34 $package_name = $options{package};
37 ($package_name && !ref($package_name))
38 || confess "You must pass a package name and it cannot be blessed";
40 return Class::MOP::get_metaclass_by_name($package_name)
41 || $class->_construct_class_instance(package => $package_name, @_);
45 my ( $class, @args ) = @_;
46 unshift @args, "package" if @args % 2;
48 my $old_metaclass = blessed($options{package})
50 : Class::MOP::get_metaclass_by_name($options{package});
51 $options{weaken} = Class::MOP::metaclass_is_weak($old_metaclass->name)
52 if !exists $options{weaken}
53 && blessed($old_metaclass)
54 && $old_metaclass->isa('Class::MOP::Class');
55 $old_metaclass->_remove_generated_metaobjects
56 if $old_metaclass && $old_metaclass->isa('Class::MOP::Class');
57 my $new_metaclass = $class->SUPER::reinitialize(%options);
58 $new_metaclass->_restore_metaobjects_from($old_metaclass)
59 if $old_metaclass && $old_metaclass->isa('Class::MOP::Class');
60 return $new_metaclass;
63 # NOTE: (meta-circularity)
64 # this is a special form of _construct_instance
65 # (see below), which is used to construct class
66 # meta-object instances for any Class::MOP::*
67 # class. All other classes will use the more
68 # normal &construct_instance.
69 sub _construct_class_instance {
71 my $options = @_ == 1 ? $_[0] : {@_};
72 my $package_name = $options->{package};
73 (defined $package_name && $package_name)
74 || confess "You must pass a package name";
76 # return the metaclass if we have it cached,
77 # and it is still defined (it has not been
78 # reaped by DESTROY yet, which can happen
79 # annoyingly enough during global destruction)
81 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
87 ? $class->_real_ref_name
90 # now create the metaclass
92 if ($class eq 'Class::MOP::Class') {
93 $meta = $class->_new($options);
97 # it is safe to use meta here because
98 # class will always be a subclass of
99 # Class::MOP::Class, which defines meta
100 $meta = $class->meta->_construct_instance($options)
103 # and check the metaclass compatibility
104 $meta->_check_metaclass_compatibility();
106 Class::MOP::store_metaclass_by_name($package_name, $meta);
109 # we need to weaken any anon classes
110 # so that they can call DESTROY properly
111 Class::MOP::weaken_metaclass($package_name) if $options->{weaken};
119 # NOTE: we need to deal with the possibility of class immutability here,
120 # and then get the name of the class appropriately
121 return $self->is_immutable
122 ? $self->_get_mutable_metaclass_name()
129 return Class::MOP::Class->initialize($class)->new_object(@_)
130 if $class ne __PACKAGE__;
132 my $options = @_ == 1 ? $_[0] : {@_};
135 # inherited from Class::MOP::Package
136 'package' => $options->{package},
139 # since the following attributes will
140 # actually be loaded from the symbol
141 # table, and actually bypass the instance
142 # entirely, we can just leave these things
143 # listed here for reference, because they
144 # should not actually have a value associated
146 'namespace' => \undef,
149 # inherited from Class::MOP::Module
151 'authority' => \undef,
153 # defined in Class::MOP::Class
154 'superclasses' => \undef,
157 'attribute_metaclass' =>
158 ( $options->{'attribute_metaclass'} || 'Class::MOP::Attribute' ),
159 'method_metaclass' =>
160 ( $options->{'method_metaclass'} || 'Class::MOP::Method' ),
161 'wrapped_method_metaclass' => (
162 $options->{'wrapped_method_metaclass'}
163 || 'Class::MOP::Method::Wrapped'
165 'instance_metaclass' =>
166 ( $options->{'instance_metaclass'} || 'Class::MOP::Instance' ),
167 'immutable_trait' => (
168 $options->{'immutable_trait'}
169 || 'Class::MOP::Class::Immutable::Trait'
171 'constructor_name' => ( $options->{constructor_name} || 'new' ),
172 'constructor_class' => (
173 $options->{constructor_class} || 'Class::MOP::Method::Constructor'
175 'destructor_class' => $options->{destructor_class},
179 ## Metaclass compatibility
181 my %base_metaclass = (
182 attribute_metaclass => 'Class::MOP::Attribute',
183 method_metaclass => 'Class::MOP::Method',
184 wrapped_method_metaclass => 'Class::MOP::Method::Wrapped',
185 instance_metaclass => 'Class::MOP::Instance',
186 constructor_class => 'Class::MOP::Method::Constructor',
187 destructor_class => 'Class::MOP::Method::Destructor',
190 sub _base_metaclasses { %base_metaclass }
193 sub _check_metaclass_compatibility {
196 my @superclasses = $self->superclasses
199 $self->_fix_metaclass_incompatibility(@superclasses);
201 my %base_metaclass = $self->_base_metaclasses;
203 # this is always okay ...
205 if ref($self) eq 'Class::MOP::Class'
207 my $meta = $self->$_;
208 !defined($meta) || $meta eq $base_metaclass{$_};
210 keys %base_metaclass;
212 for my $superclass (@superclasses) {
213 $self->_check_class_metaclass_compatibility($superclass);
216 for my $metaclass_type ( keys %base_metaclass ) {
217 next unless defined $self->$metaclass_type;
218 for my $superclass (@superclasses) {
219 $self->_check_single_metaclass_compatibility( $metaclass_type,
225 sub _check_class_metaclass_compatibility {
227 my ( $superclass_name ) = @_;
229 if (!$self->_class_metaclass_is_compatible($superclass_name)) {
230 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
232 my $super_meta_type = $super_meta->_real_ref_name;
234 confess "The metaclass of " . $self->name . " ("
235 . (ref($self)) . ")" . " is not compatible with "
236 . "the metaclass of its superclass, "
237 . $superclass_name . " (" . ($super_meta_type) . ")";
241 sub _class_metaclass_is_compatible {
243 my ( $superclass_name ) = @_;
245 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
248 my $super_meta_name = $super_meta->_real_ref_name;
250 return $self->_is_compatible_with($super_meta_name);
253 sub _check_single_metaclass_compatibility {
255 my ( $metaclass_type, $superclass_name ) = @_;
257 if (!$self->_single_metaclass_is_compatible($metaclass_type, $superclass_name)) {
258 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
259 my $metaclass_type_name = $metaclass_type;
260 $metaclass_type_name =~ s/_(?:meta)?class$//;
261 $metaclass_type_name =~ s/_/ /g;
262 confess "The $metaclass_type_name metaclass for "
263 . $self->name . " (" . ($self->$metaclass_type)
264 . ")" . " is not compatible with the "
265 . "$metaclass_type_name metaclass of its "
266 . "superclass, $superclass_name ("
267 . ($super_meta->$metaclass_type) . ")";
271 sub _single_metaclass_is_compatible {
273 my ( $metaclass_type, $superclass_name ) = @_;
275 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
278 # for instance, Moose::Meta::Class has a error_class attribute, but
279 # Class::MOP::Class doesn't - this shouldn't be an error
280 return 1 unless $super_meta->can($metaclass_type);
281 # for instance, Moose::Meta::Class has a destructor_class, but
282 # Class::MOP::Class doesn't - this shouldn't be an error
283 return 1 unless defined $super_meta->$metaclass_type;
284 # if metaclass is defined in superclass but not here, it's not compatible
285 # this is a really odd case
286 return 0 unless defined $self->$metaclass_type;
288 return $self->$metaclass_type->_is_compatible_with($super_meta->$metaclass_type);
291 sub _fix_metaclass_incompatibility {
293 my @supers = map { Class::MOP::Class->initialize($_) } @_;
296 for my $super (@supers) {
298 if $self->_can_fix_metaclass_incompatibility($super);
300 return unless $necessary;
302 for my $super (@supers) {
303 if (!$self->_class_metaclass_is_compatible($super->name)) {
304 $self->_fix_class_metaclass_incompatibility($super);
308 my %base_metaclass = $self->_base_metaclasses;
309 for my $metaclass_type (keys %base_metaclass) {
310 for my $super (@supers) {
311 if (!$self->_single_metaclass_is_compatible($metaclass_type, $super->name)) {
312 $self->_fix_single_metaclass_incompatibility(
313 $metaclass_type, $super
320 sub _can_fix_metaclass_incompatibility {
322 my ($super_meta) = @_;
324 return 1 if $self->_class_metaclass_can_be_made_compatible($super_meta);
326 my %base_metaclass = $self->_base_metaclasses;
327 for my $metaclass_type (keys %base_metaclass) {
328 return 1 if $self->_single_metaclass_can_be_made_compatible($super_meta, $metaclass_type);
334 sub _class_metaclass_can_be_made_compatible {
336 my ($super_meta) = @_;
338 return $self->_can_be_made_compatible_with($super_meta->_real_ref_name);
341 sub _single_metaclass_can_be_made_compatible {
343 my ($super_meta, $metaclass_type) = @_;
345 my $specific_meta = $self->$metaclass_type;
347 return unless $super_meta->can($metaclass_type);
348 my $super_specific_meta = $super_meta->$metaclass_type;
350 # for instance, Moose::Meta::Class has a destructor_class, but
351 # Class::MOP::Class doesn't - this shouldn't be an error
352 return unless defined $super_specific_meta;
354 # if metaclass is defined in superclass but not here, it's fixable
355 # this is a really odd case
356 return 1 unless defined $specific_meta;
358 return 1 if $specific_meta->_can_be_made_compatible_with($super_specific_meta);
361 sub _fix_class_metaclass_incompatibility {
363 my ( $super_meta ) = @_;
365 if ($self->_class_metaclass_can_be_made_compatible($super_meta)) {
367 || confess "Can't fix metaclass incompatibility for "
369 . " because it is not pristine.";
371 my $super_meta_name = $super_meta->_real_ref_name;
373 $self->_make_compatible_with($super_meta_name);
377 sub _fix_single_metaclass_incompatibility {
379 my ( $metaclass_type, $super_meta ) = @_;
381 if ($self->_single_metaclass_can_be_made_compatible($super_meta, $metaclass_type)) {
383 || confess "Can't fix metaclass incompatibility for "
385 . " because it is not pristine.";
387 my $new_metaclass = $self->$metaclass_type
388 ? $self->$metaclass_type->_get_compatible_metaclass($super_meta->$metaclass_type)
389 : $super_meta->$metaclass_type;
390 $self->{$metaclass_type} = $new_metaclass;
394 sub _restore_metaobjects_from {
398 $self->_restore_metamethods_from($old_meta);
399 $self->_restore_metaattributes_from($old_meta);
402 sub _remove_generated_metaobjects {
405 for my $attr (map { $self->get_attribute($_) } $self->get_attribute_list) {
406 $attr->remove_accessors;
410 # creating classes with MOP ...
416 unshift @args, 'package' if @args % 2 == 1;
419 (ref $options{superclasses} eq 'ARRAY')
420 || confess "You must pass an ARRAY ref of superclasses"
421 if exists $options{superclasses};
423 (ref $options{attributes} eq 'ARRAY')
424 || confess "You must pass an ARRAY ref of attributes"
425 if exists $options{attributes};
427 (ref $options{methods} eq 'HASH')
428 || confess "You must pass a HASH ref of methods"
429 if exists $options{methods};
431 my $package = delete $options{package};
432 my $superclasses = delete $options{superclasses};
433 my $attributes = delete $options{attributes};
434 my $methods = delete $options{methods};
435 my $meta_name = exists $options{meta_name}
436 ? delete $options{meta_name}
439 my $meta = $class->SUPER::create($package => %options);
441 $meta->_add_meta_method($meta_name)
442 if defined $meta_name;
444 $meta->superclasses(@{$superclasses})
445 if defined $superclasses;
447 # process attributes first, so that they can
448 # install accessors, but locally defined methods
449 # can then overwrite them. It is maybe a little odd, but
450 # I think this should be the order of things.
451 if (defined $attributes) {
452 foreach my $attr (@{$attributes}) {
453 $meta->add_attribute($attr);
456 if (defined $methods) {
457 foreach my $method_name (keys %{$methods}) {
458 $meta->add_method($method_name, $methods->{$method_name});
464 # XXX: something more intelligent here?
465 sub _anon_package_prefix { 'Class::MOP::Class::__ANON__::SERIAL::' }
467 sub create_anon_class { shift->create_anon(@_) }
468 sub is_anon_class { shift->is_anon(@_) }
470 sub _anon_cache_key {
473 # Makes something like Super::Class|Super::Class::2
475 join( '|', sort @{ $options{superclasses} || [] } ),
479 # Instance Construction & Cloning
485 # we need to protect the integrity of the
486 # Class::MOP::Class singletons here, so we
487 # delegate this to &construct_class_instance
488 # which will deal with the singletons
489 return $class->_construct_class_instance(@_)
490 if $class->name->isa('Class::MOP::Class');
491 return $class->_construct_instance(@_);
494 sub _construct_instance {
496 my $params = @_ == 1 ? $_[0] : {@_};
497 my $meta_instance = $class->get_meta_instance();
499 # the code below is almost certainly incorrect
500 # but this is foreign inheritance, so we might
501 # have to kludge it in the end.
503 if (my $instance_class = blessed($params->{__INSTANCE__})) {
504 ($instance_class eq $class->name)
505 || confess "Objects passed as the __INSTANCE__ parameter must "
506 . "already be blessed into the correct class, but "
507 . "$params->{__INSTANCE__} is not a " . $class->name;
508 $instance = $params->{__INSTANCE__};
510 elsif (exists $params->{__INSTANCE__}) {
511 confess "The __INSTANCE__ parameter must be a blessed reference, not "
512 . $params->{__INSTANCE__};
515 $instance = $meta_instance->create_instance();
517 foreach my $attr ($class->get_all_attributes()) {
518 $attr->initialize_instance_slot($meta_instance, $instance, $params);
520 if (Class::MOP::metaclass_is_weak($class->name)) {
521 $meta_instance->_set_mop_slot($instance, $class);
526 sub _inline_new_object {
530 'my $class = shift;',
531 '$class = Scalar::Util::blessed($class) || $class;',
532 $self->_inline_fallback_constructor('$class'),
533 $self->_inline_params('$params', '$class'),
534 $self->_inline_generate_instance('$instance', '$class'),
535 $self->_inline_slot_initializers,
536 $self->_inline_preserve_weak_metaclasses,
537 $self->_inline_extra_init,
542 sub _inline_fallback_constructor {
546 'return ' . $self->_generate_fallback_constructor($class),
547 'if ' . $class . ' ne \'' . $self->name . '\';',
551 sub _generate_fallback_constructor {
554 return 'Class::MOP::Class->initialize(' . $class . ')->new_object(@_)',
559 my ($params, $class) = @_;
561 'my ' . $params . ' = @_ == 1 ? $_[0] : {@_};',
565 sub _inline_generate_instance {
567 my ($inst, $class) = @_;
569 'my ' . $inst . ' = ' . $self->_inline_create_instance($class) . ';',
573 sub _inline_create_instance {
576 return $self->get_meta_instance->inline_create_instance(@_);
579 sub _inline_slot_initializers {
584 return map { $self->_inline_slot_initializer($_, $idx++) }
585 sort { $a->name cmp $b->name } $self->get_all_attributes;
588 sub _inline_slot_initializer {
590 my ($attr, $idx) = @_;
592 if (defined(my $init_arg = $attr->init_arg)) {
594 'if (exists $params->{\'' . $init_arg . '\'}) {',
595 $self->_inline_init_attr_from_constructor($attr, $idx),
598 if (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
607 elsif (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
619 sub _inline_init_attr_from_constructor {
621 my ($attr, $idx) = @_;
623 my @initial_value = $attr->_inline_set_value(
624 '$instance', '$params->{\'' . $attr->init_arg . '\'}',
627 push @initial_value, (
628 '$attrs->[' . $idx . ']->set_initial_value(',
630 $attr->_inline_instance_get('$instance'),
632 ) if $attr->has_initializer;
634 return @initial_value;
637 sub _inline_init_attr_from_default {
639 my ($attr, $idx) = @_;
641 my $default = $self->_inline_default_value($attr, $idx);
642 return unless $default;
644 my @initial_value = $attr->_inline_set_value('$instance', $default);
646 push @initial_value, (
647 '$attrs->[' . $idx . ']->set_initial_value(',
649 $attr->_inline_instance_get('$instance'),
651 ) if $attr->has_initializer;
653 return @initial_value;
656 sub _inline_default_value {
658 my ($attr, $index) = @_;
660 if ($attr->has_default) {
662 # default values can either be CODE refs
663 # in which case we need to call them. Or
664 # they can be scalars (strings/numbers)
665 # in which case we can just deal with them
666 # in the code we eval.
667 if ($attr->is_default_a_coderef) {
668 return '$defaults->[' . $index . ']->($instance)';
671 return '$defaults->[' . $index . ']';
674 elsif ($attr->has_builder) {
675 return '$instance->' . $attr->builder;
682 sub _inline_preserve_weak_metaclasses {
684 if (Class::MOP::metaclass_is_weak($self->name)) {
686 $self->_inline_set_mop_slot(
687 '$instance', 'Class::MOP::class_of($class)'
696 sub _inline_extra_init { }
699 sub get_meta_instance {
701 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
704 sub _create_meta_instance {
707 my $instance = $self->instance_metaclass->new(
708 associated_metaclass => $self,
709 attributes => [ $self->get_all_attributes() ],
712 $self->add_meta_instance_dependencies()
713 if $instance->is_dependent_on_superclasses();
718 sub _inline_rebless_instance {
721 return $self->get_meta_instance->inline_rebless_instance_structure(@_);
724 sub _inline_get_mop_slot {
727 return $self->get_meta_instance->_inline_get_mop_slot(@_);
730 sub _inline_set_mop_slot {
733 return $self->get_meta_instance->_inline_set_mop_slot(@_);
736 sub _inline_clear_mop_slot {
739 return $self->get_meta_instance->_inline_clear_mop_slot(@_);
744 my $instance = shift;
745 (blessed($instance) && $instance->isa($class->name))
746 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
749 # we need to protect the integrity of the
750 # Class::MOP::Class singletons here, they
751 # should not be cloned.
752 return $instance if $instance->isa('Class::MOP::Class');
753 $class->_clone_instance($instance, @_);
756 sub _clone_instance {
757 my ($class, $instance, %params) = @_;
759 || confess "You can only clone instances, ($instance) is not a blessed instance";
760 my $meta_instance = $class->get_meta_instance();
761 my $clone = $meta_instance->clone_instance($instance);
762 foreach my $attr ($class->get_all_attributes()) {
763 if ( defined( my $init_arg = $attr->init_arg ) ) {
764 if (exists $params{$init_arg}) {
765 $attr->set_value($clone, $params{$init_arg});
772 sub _force_rebless_instance {
773 my ($self, $instance, %params) = @_;
774 my $old_metaclass = Class::MOP::class_of($instance);
776 $old_metaclass->rebless_instance_away($instance, $self, %params)
779 my $meta_instance = $self->get_meta_instance;
781 if (Class::MOP::metaclass_is_weak($old_metaclass->name)) {
782 $meta_instance->_clear_mop_slot($instance);
786 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
787 $meta_instance->rebless_instance_structure($_[1], $self);
789 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
791 if (Class::MOP::metaclass_is_weak($self->name)) {
792 $meta_instance->_set_mop_slot($instance, $self);
796 sub rebless_instance {
797 my ($self, $instance, %params) = @_;
798 my $old_metaclass = Class::MOP::class_of($instance);
800 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
801 $self->name->isa($old_class)
802 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
804 $self->_force_rebless_instance($_[1], %params);
809 sub rebless_instance_back {
810 my ( $self, $instance ) = @_;
811 my $old_metaclass = Class::MOP::class_of($instance);
814 = $old_metaclass ? $old_metaclass->name : blessed($instance);
815 $old_class->isa( $self->name )
817 "You may rebless only into a superclass of ($old_class), of which ("
821 $self->_force_rebless_instance($_[1]);
826 sub rebless_instance_away {
827 # this intentionally does nothing, it is just a hook
830 sub _fixup_attributes_after_rebless {
832 my ($instance, $rebless_from, %params) = @_;
833 my $meta_instance = $self->get_meta_instance;
835 for my $attr ( $rebless_from->get_all_attributes ) {
836 next if $self->find_attribute_by_name( $attr->name );
837 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
840 foreach my $attr ( $self->get_all_attributes ) {
841 if ( $attr->has_value($instance) ) {
842 if ( defined( my $init_arg = $attr->init_arg ) ) {
843 $params{$init_arg} = $attr->get_value($instance)
844 unless exists $params{$init_arg};
847 $attr->set_value($instance, $attr->get_value($instance));
852 foreach my $attr ($self->get_all_attributes) {
853 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
857 sub _attach_attribute {
858 my ($self, $attribute) = @_;
859 $attribute->attach_to_class($self);
862 sub _post_add_attribute {
863 my ( $self, $attribute ) = @_;
865 $self->invalidate_meta_instances;
867 # invalidate package flag here
870 $attribute->install_accessors;
873 $self->remove_attribute( $attribute->name );
878 sub remove_attribute {
881 my $removed_attribute = $self->SUPER::remove_attribute(@_)
884 $self->invalidate_meta_instances;
886 $removed_attribute->remove_accessors;
887 $removed_attribute->detach_from_class;
889 return$removed_attribute;
892 sub find_attribute_by_name {
893 my ( $self, $attr_name ) = @_;
895 foreach my $class ( $self->linearized_isa ) {
896 # fetch the meta-class ...
897 my $meta = Class::MOP::Class->initialize($class);
898 return $meta->get_attribute($attr_name)
899 if $meta->has_attribute($attr_name);
905 sub get_all_attributes {
907 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
908 reverse $self->linearized_isa;
909 return values %attrs;
917 my $isa = $self->get_or_add_package_symbol('@ISA');
924 # on 5.8 and below, we need to call
925 # a method to get Perl to detect
926 # a cycle in the class hierarchy
927 my $class = $self->name;
931 # we need to check the metaclass
932 # compatibility here so that we can
933 # be sure that the superclass is
934 # not potentially creating an issues
935 # we don't know about
937 $self->_check_metaclass_compatibility();
938 $self->_superclasses_updated();
944 sub _superclasses_updated {
946 $self->update_meta_instance_dependencies();
947 # keep strong references to all our parents, so they don't disappear if
948 # they are anon classes and don't have any direct instances
949 $self->_superclass_metas(
950 map { Class::MOP::class_of($_) } $self->superclasses
954 sub _superclass_metas {
956 $self->{_superclass_metas} = [@_];
961 my $super_class = $self->name;
963 return @{ $super_class->mro::get_isarev() };
966 sub direct_subclasses {
968 my $super_class = $self->name;
973 } Class::MOP::Class->initialize($_)->superclasses
978 return @{ mro::get_linear_isa( (shift)->name ) };
981 sub class_precedence_list {
983 my $name = $self->name;
985 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
987 # We need to check for circular inheritance here
988 # if we are are not on 5.10, cause 5.8 detects it
989 # late. This will do nothing if all is well, and
990 # blow up otherwise. Yes, it's an ugly hack, better
991 # suggestions are welcome.
993 ($name || return)->isa('This is a test for circular inheritance')
996 # if our mro is c3, we can
997 # just grab the linear_isa
998 if (mro::get_mro($name) eq 'c3') {
999 return @{ mro::get_linear_isa($name) }
1003 # we can't grab the linear_isa for dfs
1004 # since it has all the duplicates
1009 Class::MOP::Class->initialize($_)->class_precedence_list()
1010 } $self->superclasses()
1018 my $fetch_and_prepare_method = sub {
1019 my ($self, $method_name) = @_;
1020 my $wrapped_metaclass = $self->wrapped_method_metaclass;
1022 my $method = $self->get_method($method_name);
1023 # if we dont have local ...
1025 # try to find the next method
1026 $method = $self->find_next_method_by_name($method_name);
1027 # die if it does not exist
1029 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
1030 # and now make sure to wrap it
1031 # even if it is already wrapped
1032 # because we need a new sub ref
1033 $method = $wrapped_metaclass->wrap($method,
1034 package_name => $self->name,
1035 name => $method_name,
1039 # now make sure we wrap it properly
1040 $method = $wrapped_metaclass->wrap($method,
1041 package_name => $self->name,
1042 name => $method_name,
1043 ) unless $method->isa($wrapped_metaclass);
1045 $self->add_method($method_name => $method);
1049 sub add_before_method_modifier {
1050 my ($self, $method_name, $method_modifier) = @_;
1051 (defined $method_name && length $method_name)
1052 || confess "You must pass in a method name";
1053 my $method = $fetch_and_prepare_method->($self, $method_name);
1054 $method->add_before_modifier(
1055 subname(':before' => $method_modifier)
1059 sub add_after_method_modifier {
1060 my ($self, $method_name, $method_modifier) = @_;
1061 (defined $method_name && length $method_name)
1062 || confess "You must pass in a method name";
1063 my $method = $fetch_and_prepare_method->($self, $method_name);
1064 $method->add_after_modifier(
1065 subname(':after' => $method_modifier)
1069 sub add_around_method_modifier {
1070 my ($self, $method_name, $method_modifier) = @_;
1071 (defined $method_name && length $method_name)
1072 || confess "You must pass in a method name";
1073 my $method = $fetch_and_prepare_method->($self, $method_name);
1074 $method->add_around_modifier(
1075 subname(':around' => $method_modifier)
1080 # the methods above used to be named like this:
1081 # ${pkg}::${method}:(before|after|around)
1082 # but this proved problematic when using one modifier
1083 # to wrap multiple methods (something which is likely
1084 # to happen pretty regularly IMO). So instead of naming
1085 # it like this, I have chosen to just name them purely
1086 # with their modifier names, like so:
1087 # :(before|after|around)
1088 # The fact is that in a stack trace, it will be fairly
1089 # evident from the context what method they are attached
1090 # to, and so don't need the fully qualified name.
1093 sub find_method_by_name {
1094 my ($self, $method_name) = @_;
1095 (defined $method_name && length $method_name)
1096 || confess "You must define a method name to find";
1097 foreach my $class ($self->linearized_isa) {
1098 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1099 return $method if defined $method;
1104 sub get_all_methods {
1108 for my $class ( reverse $self->linearized_isa ) {
1109 my $meta = Class::MOP::Class->initialize($class);
1111 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1114 return values %methods;
1117 sub get_all_method_names {
1120 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
1123 sub find_all_methods_by_name {
1124 my ($self, $method_name) = @_;
1125 (defined $method_name && length $method_name)
1126 || confess "You must define a method name to find";
1128 foreach my $class ($self->linearized_isa) {
1129 # fetch the meta-class ...
1130 my $meta = Class::MOP::Class->initialize($class);
1132 name => $method_name,
1134 code => $meta->get_method($method_name)
1135 } if $meta->has_method($method_name);
1140 sub find_next_method_by_name {
1141 my ($self, $method_name) = @_;
1142 (defined $method_name && length $method_name)
1143 || confess "You must define a method name to find";
1144 my @cpl = $self->linearized_isa;
1145 shift @cpl; # discard ourselves
1146 foreach my $class (@cpl) {
1147 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1148 return $method if defined $method;
1153 sub update_meta_instance_dependencies {
1156 if ( $self->{meta_instance_dependencies} ) {
1157 return $self->add_meta_instance_dependencies;
1161 sub add_meta_instance_dependencies {
1164 $self->remove_meta_instance_dependencies;
1166 my @attrs = $self->get_all_attributes();
1169 my @classes = grep { not $seen{ $_->name }++ }
1170 map { $_->associated_class } @attrs;
1172 foreach my $class (@classes) {
1173 $class->add_dependent_meta_instance($self);
1176 $self->{meta_instance_dependencies} = \@classes;
1179 sub remove_meta_instance_dependencies {
1182 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1183 foreach my $class (@$classes) {
1184 $class->remove_dependent_meta_instance($self);
1194 sub add_dependent_meta_instance {
1195 my ( $self, $metaclass ) = @_;
1196 push @{ $self->{dependent_meta_instances} }, $metaclass;
1199 sub remove_dependent_meta_instance {
1200 my ( $self, $metaclass ) = @_;
1201 my $name = $metaclass->name;
1202 @$_ = grep { $_->name ne $name } @$_
1203 for $self->{dependent_meta_instances};
1206 sub invalidate_meta_instances {
1208 $_->invalidate_meta_instance()
1209 for $self, @{ $self->{dependent_meta_instances} };
1212 sub invalidate_meta_instance {
1214 undef $self->{_meta_instance};
1217 # check if we can reinitialize
1221 # if any local attr is defined
1222 return if $self->get_attribute_list;
1224 # or any non-declared methods
1225 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1226 return if $method->isa("Class::MOP::Method::Generated");
1227 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1235 sub is_mutable { 1 }
1236 sub is_immutable { 0 }
1238 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1240 sub _immutable_options {
1241 my ( $self, @args ) = @_;
1244 inline_accessors => 1,
1245 inline_constructor => 1,
1246 inline_destructor => 0,
1248 immutable_trait => $self->immutable_trait,
1249 constructor_name => $self->constructor_name,
1250 constructor_class => $self->constructor_class,
1251 destructor_class => $self->destructor_class,
1256 sub make_immutable {
1257 my ( $self, @args ) = @_;
1259 my ($file, $line) = (caller)[1..2];
1260 if ( $self->is_mutable ) {
1261 $self->_initialize_immutable(
1262 $self->_immutable_options(@args),
1266 $self->_rebless_as_immutable(@args);
1277 if ( $self->is_immutable ) {
1278 my @args = $self->immutable_options;
1279 $self->_rebless_as_mutable();
1280 $self->_remove_inlined_code(@args);
1281 delete $self->{__immutable};
1289 sub _rebless_as_immutable {
1290 my ( $self, @args ) = @_;
1292 $self->{__immutable}{original_class} = ref $self;
1294 bless $self => $self->_immutable_metaclass(@args);
1297 sub _immutable_metaclass {
1298 my ( $self, %args ) = @_;
1300 if ( my $class = $args{immutable_metaclass} ) {
1304 my $trait = $args{immutable_trait} = $self->immutable_trait
1305 || confess "no immutable trait specified for $self";
1307 my $meta = $self->meta;
1308 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1312 if ( $meta_attr and $trait eq $meta_attr->default ) {
1313 # if the trait is the same as the default we try and pick a
1314 # predictable name for the immutable metaclass
1315 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1318 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1319 $trait, 'ForMetaClass', ref($self);
1323 if Class::MOP::is_class_loaded($class_name);
1325 # If the metaclass is a subclass of CMOP::Class which has had
1326 # metaclass roles applied (via Moose), then we want to make sure
1327 # that we preserve that anonymous class (see Fey::ORM for an
1328 # example of where this matters).
1329 my $meta_name = $meta->_real_ref_name;
1331 my $immutable_meta = $meta_name->create(
1333 superclasses => [ ref $self ],
1336 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1338 $immutable_meta->make_immutable(
1339 inline_constructor => 0,
1340 inline_accessors => 0,
1346 sub _remove_inlined_code {
1349 $self->remove_method( $_->name ) for $self->_inlined_methods;
1351 delete $self->{__immutable}{inlined_methods};
1354 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1356 sub _add_inlined_method {
1357 my ( $self, $method ) = @_;
1359 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1362 sub _initialize_immutable {
1363 my ( $self, %args ) = @_;
1365 $self->{__immutable}{options} = \%args;
1366 $self->_install_inlined_code(%args);
1369 sub _install_inlined_code {
1370 my ( $self, %args ) = @_;
1373 $self->_inline_accessors(%args) if $args{inline_accessors};
1374 $self->_inline_constructor(%args) if $args{inline_constructor};
1375 $self->_inline_destructor(%args) if $args{inline_destructor};
1378 sub _rebless_as_mutable {
1381 bless $self, $self->_get_mutable_metaclass_name;
1386 sub _inline_accessors {
1389 foreach my $attr_name ( $self->get_attribute_list ) {
1390 $self->get_attribute($attr_name)->install_accessors(1);
1394 sub _inline_constructor {
1395 my ( $self, %args ) = @_;
1397 my $name = $args{constructor_name};
1398 # A class may not even have a constructor, and that's okay.
1399 return unless defined $name;
1401 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1402 my $class = $self->name;
1403 warn "Not inlining a constructor for $class since it defines"
1404 . " its own constructor.\n"
1405 . "If you are certain you don't need to inline your"
1406 . " constructor, specify inline_constructor => 0 in your"
1407 . " call to $class->meta->make_immutable\n";
1411 my $constructor_class = $args{constructor_class};
1413 Class::MOP::load_class($constructor_class);
1415 my $constructor = $constructor_class->new(
1419 package_name => $self->name,
1421 definition_context => {
1422 description => "constructor " . $self->name . "::" . $name,
1423 file => $args{file},
1424 line => $args{line},
1428 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1429 $self->add_method( $name => $constructor );
1430 $self->_add_inlined_method($constructor);
1434 sub _inline_destructor {
1435 my ( $self, %args ) = @_;
1437 ( exists $args{destructor_class} && defined $args{destructor_class} )
1438 || confess "The 'inline_destructor' option is present, but "
1439 . "no destructor class was specified";
1441 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1442 my $class = $self->name;
1443 warn "Not inlining a destructor for $class since it defines"
1444 . " its own destructor.\n";
1448 my $destructor_class = $args{destructor_class};
1450 Class::MOP::load_class($destructor_class);
1452 return unless $destructor_class->is_needed($self);
1454 my $destructor = $destructor_class->new(
1457 package_name => $self->name,
1459 definition_context => {
1460 description => "destructor " . $self->name . "::DESTROY",
1461 file => $args{file},
1462 line => $args{line},
1466 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1467 $self->add_method( 'DESTROY' => $destructor );
1468 $self->_add_inlined_method($destructor);
1474 # ABSTRACT: Class Meta Object
1482 # assuming that class Foo
1483 # has been defined, you can
1485 # use this for introspection ...
1487 # add a method to Foo ...
1488 Foo->meta->add_method( 'bar' => sub {...} )
1490 # get a list of all the classes searched
1491 # the method dispatcher in the correct order
1492 Foo->meta->class_precedence_list()
1494 # remove a method from Foo
1495 Foo->meta->remove_method('bar');
1497 # or use this to actually create classes ...
1499 Class::MOP::Class->create(
1502 superclasses => ['Foo'],
1504 Class::MOP::Attribute->new('$bar'),
1505 Class::MOP::Attribute->new('$baz'),
1508 calculate_bar => sub {...},
1509 construct_baz => sub {...}
1516 The Class Protocol is the largest and most complex part of the
1517 Class::MOP meta-object protocol. It controls the introspection and
1518 manipulation of Perl 5 classes, and it can create them as well. The
1519 best way to understand what this module can do is to read the
1520 documentation for each of its methods.
1524 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1528 =head2 Class construction
1530 These methods all create new C<Class::MOP::Class> objects. These
1531 objects can represent existing classes or they can be used to create
1532 new classes from scratch.
1534 The metaclass object for a given class is a singleton. If you attempt
1535 to create a metaclass for the same class twice, you will just get the
1540 =item B<< Class::MOP::Class->create($package_name, %options) >>
1542 This method creates a new C<Class::MOP::Class> object with the given
1543 package name. It accepts a number of options:
1549 An optional version number for the newly created package.
1553 An optional authority for the newly created package.
1555 =item * superclasses
1557 An optional array reference of superclass names.
1561 An optional hash reference of methods for the class. The keys of the
1562 hash reference are method names and values are subroutine references.
1566 An optional array reference of L<Class::MOP::Attribute> objects.
1570 Specifies the name to install the C<meta> method for this class under.
1571 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1572 given, no meta method will be installed.
1576 If true, the metaclass that is stored in the global cache will be a
1579 Classes created in this way are destroyed once the metaclass they are
1580 attached to goes out of scope, and will be removed from Perl's internal
1583 All instances of a class with a weakened metaclass keep a special
1584 reference to the metaclass object, which prevents the metaclass from
1585 going out of scope while any instances exist.
1587 This only works if the instance is based on a hash reference, however.
1591 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1593 This method works just like C<< Class::MOP::Class->create >> but it
1594 creates an "anonymous" class. In fact, the class does have a name, but
1595 that name is a unique name generated internally by this module.
1597 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1598 parameters that C<create> accepts.
1600 Anonymous classes default to C<< weaken => 1 >>, although this can be
1603 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1605 This method will initialize a C<Class::MOP::Class> object for the
1606 named package. Unlike C<create>, this method I<will not> create a new
1609 The purpose of this method is to retrieve a C<Class::MOP::Class>
1610 object for introspecting an existing class.
1612 If an existing C<Class::MOP::Class> object exists for the named
1613 package, it will be returned, and any options provided will be
1616 If the object does not yet exist, it will be created.
1618 The valid options that can be passed to this method are
1619 C<attribute_metaclass>, C<method_metaclass>,
1620 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1621 optional, and default to the appropriate class in the C<Class::MOP>
1626 =head2 Object instance construction and cloning
1628 These methods are all related to creating and/or cloning object
1633 =item B<< $metaclass->clone_object($instance, %params) >>
1635 This method clones an existing object instance. Any parameters you
1636 provide are will override existing attribute values in the object.
1638 This is a convenience method for cloning an object instance, then
1639 blessing it into the appropriate package.
1641 You could implement a clone method in your class, using this method:
1644 my ($self, %params) = @_;
1645 $self->meta->clone_object($self, %params);
1648 =item B<< $metaclass->rebless_instance($instance, %params) >>
1650 This method changes the class of C<$instance> to the metaclass's class.
1652 You can only rebless an instance into a subclass of its current
1653 class. If you pass any additional parameters, these will be treated
1654 like constructor parameters and used to initialize the object's
1655 attributes. Any existing attributes that are already set will be
1658 Before reblessing the instance, this method will call
1659 C<rebless_instance_away> on the instance's current metaclass. This method
1660 will be passed the instance, the new metaclass, and any parameters
1661 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1662 does nothing; it is merely a hook.
1664 =item B<< $metaclass->rebless_instance_back($instance) >>
1666 Does the same thing as C<rebless_instance>, except that you can only
1667 rebless an instance into one of its superclasses. Any attributes that
1668 do not exist in the superclass will be deinitialized.
1670 This is a much more dangerous operation than C<rebless_instance>,
1671 especially when multiple inheritance is involved, so use this carefully!
1673 =item B<< $metaclass->new_object(%params) >>
1675 This method is used to create a new object of the metaclass's
1676 class. Any parameters you provide are used to initialize the
1677 instance's attributes. A special C<__INSTANCE__> key can be passed to
1678 provide an already generated instance, rather than having Class::MOP
1679 generate it for you. This is mostly useful for using Class::MOP with
1680 foreign classes which generate instances using their own constructors.
1682 =item B<< $metaclass->instance_metaclass >>
1684 Returns the class name of the instance metaclass. See
1685 L<Class::MOP::Instance> for more information on the instance
1688 =item B<< $metaclass->get_meta_instance >>
1690 Returns an instance of the C<instance_metaclass> to be used in the
1691 construction of a new instance of the class.
1695 =head2 Informational predicates
1697 These are a few predicate methods for asking information about the
1702 =item B<< $metaclass->is_anon_class >>
1704 This returns true if the class was created by calling C<<
1705 Class::MOP::Class->create_anon_class >>.
1707 =item B<< $metaclass->is_mutable >>
1709 This returns true if the class is still mutable.
1711 =item B<< $metaclass->is_immutable >>
1713 This returns true if the class has been made immutable.
1715 =item B<< $metaclass->is_pristine >>
1717 A class is I<not> pristine if it has non-inherited attributes or if it
1718 has any generated methods.
1722 =head2 Inheritance Relationships
1726 =item B<< $metaclass->superclasses(@superclasses) >>
1728 This is a read-write accessor which represents the superclass
1729 relationships of the metaclass's class.
1731 This is basically sugar around getting and setting C<@ISA>.
1733 =item B<< $metaclass->class_precedence_list >>
1735 This returns a list of all of the class's ancestor classes. The
1736 classes are returned in method dispatch order.
1738 =item B<< $metaclass->linearized_isa >>
1740 This returns a list based on C<class_precedence_list> but with all
1743 =item B<< $metaclass->subclasses >>
1745 This returns a list of all subclasses for this class, even indirect
1748 =item B<< $metaclass->direct_subclasses >>
1750 This returns a list of immediate subclasses for this class, which does not
1751 include indirect subclasses.
1755 =head2 Method introspection and creation
1757 These methods allow you to introspect a class's methods, as well as
1758 add, remove, or change methods.
1760 Determining what is truly a method in a Perl 5 class requires some
1761 heuristics (aka guessing).
1763 Methods defined outside the package with a fully qualified name (C<sub
1764 Package::name { ... }>) will be included. Similarly, methods named
1765 with a fully qualified name using L<Sub::Name> are also included.
1767 However, we attempt to ignore imported functions.
1769 Ultimately, we are using heuristics to determine what truly is a
1770 method in a class, and these heuristics may get the wrong answer in
1771 some edge cases. However, for most "normal" cases the heuristics work
1776 =item B<< $metaclass->get_method($method_name) >>
1778 This will return a L<Class::MOP::Method> for the specified
1779 C<$method_name>. If the class does not have the specified method, it
1782 =item B<< $metaclass->has_method($method_name) >>
1784 Returns a boolean indicating whether or not the class defines the
1785 named method. It does not include methods inherited from parent
1788 =item B<< $metaclass->get_method_list >>
1790 This will return a list of method I<names> for all methods defined in
1793 =item B<< $metaclass->add_method($method_name, $method) >>
1795 This method takes a method name and a subroutine reference, and adds
1796 the method to the class.
1798 The subroutine reference can be a L<Class::MOP::Method>, and you are
1799 strongly encouraged to pass a meta method object instead of a code
1800 reference. If you do so, that object gets stored as part of the
1801 class's method map directly. If not, the meta information will have to
1802 be recreated later, and may be incorrect.
1804 If you provide a method object, this method will clone that object if
1805 the object's package name does not match the class name. This lets us
1806 track the original source of any methods added from other classes
1807 (notably Moose roles).
1809 =item B<< $metaclass->remove_method($method_name) >>
1811 Remove the named method from the class. This method returns the
1812 L<Class::MOP::Method> object for the method.
1814 =item B<< $metaclass->method_metaclass >>
1816 Returns the class name of the method metaclass, see
1817 L<Class::MOP::Method> for more information on the method metaclass.
1819 =item B<< $metaclass->wrapped_method_metaclass >>
1821 Returns the class name of the wrapped method metaclass, see
1822 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1825 =item B<< $metaclass->get_all_methods >>
1827 This will traverse the inheritance hierarchy and return a list of all
1828 the L<Class::MOP::Method> objects for this class and its parents.
1830 =item B<< $metaclass->find_method_by_name($method_name) >>
1832 This will return a L<Class::MOP::Method> for the specified
1833 C<$method_name>. If the class does not have the specified method, it
1836 Unlike C<get_method>, this method I<will> look for the named method in
1839 =item B<< $metaclass->get_all_method_names >>
1841 This will return a list of method I<names> for all of this class's
1842 methods, including inherited methods.
1844 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1846 This method looks for the named method in the class and all of its
1847 parents. It returns every matching method it finds in the inheritance
1848 tree, so it returns a list of methods.
1850 Each method is returned as a hash reference with three keys. The keys
1851 are C<name>, C<class>, and C<code>. The C<code> key has a
1852 L<Class::MOP::Method> object as its value.
1854 The list of methods is distinct.
1856 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1858 This method returns the first method in any superclass matching the
1859 given name. It is effectively the method that C<SUPER::$method_name>
1864 =head2 Attribute introspection and creation
1866 Because Perl 5 does not have a core concept of attributes in classes,
1867 we can only return information about attributes which have been added
1868 via this class's methods. We cannot discover information about
1869 attributes which are defined in terms of "regular" Perl 5 methods.
1873 =item B<< $metaclass->get_attribute($attribute_name) >>
1875 This will return a L<Class::MOP::Attribute> for the specified
1876 C<$attribute_name>. If the class does not have the specified
1877 attribute, it returns C<undef>.
1879 NOTE that get_attribute does not search superclasses, for that you
1880 need to use C<find_attribute_by_name>.
1882 =item B<< $metaclass->has_attribute($attribute_name) >>
1884 Returns a boolean indicating whether or not the class defines the
1885 named attribute. It does not include attributes inherited from parent
1888 =item B<< $metaclass->get_attribute_list >>
1890 This will return a list of attributes I<names> for all attributes
1891 defined in this class. Note that this operates on the current class
1892 only, it does not traverse the inheritance hierarchy.
1894 =item B<< $metaclass->get_all_attributes >>
1896 This will traverse the inheritance hierarchy and return a list of all
1897 the L<Class::MOP::Attribute> objects for this class and its parents.
1899 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1901 This will return a L<Class::MOP::Attribute> for the specified
1902 C<$attribute_name>. If the class does not have the specified
1903 attribute, it returns C<undef>.
1905 Unlike C<get_attribute>, this attribute I<will> look for the named
1906 attribute in superclasses.
1908 =item B<< $metaclass->add_attribute(...) >>
1910 This method accepts either an existing L<Class::MOP::Attribute>
1911 object or parameters suitable for passing to that class's C<new>
1914 The attribute provided will be added to the class.
1916 Any accessor methods defined by the attribute will be added to the
1917 class when the attribute is added.
1919 If an attribute of the same name already exists, the old attribute
1920 will be removed first.
1922 =item B<< $metaclass->remove_attribute($attribute_name) >>
1924 This will remove the named attribute from the class, and
1925 L<Class::MOP::Attribute> object.
1927 Removing an attribute also removes any accessor methods defined by the
1930 However, note that removing an attribute will only affect I<future>
1931 object instances created for this class, not existing instances.
1933 =item B<< $metaclass->attribute_metaclass >>
1935 Returns the class name of the attribute metaclass for this class. By
1936 default, this is L<Class::MOP::Attribute>.
1940 =head2 Class Immutability
1942 Making a class immutable "freezes" the class definition. You can no
1943 longer call methods which alter the class, such as adding or removing
1944 methods or attributes.
1946 Making a class immutable lets us optimize the class by inlining some
1947 methods, and also allows us to optimize some methods on the metaclass
1950 After immutabilization, the metaclass object will cache most informational
1951 methods that returns information about methods or attributes. Methods which
1952 would alter the class, such as C<add_attribute> and C<add_method>, will
1953 throw an error on an immutable metaclass object.
1955 The immutabilization system in L<Moose> takes much greater advantage
1956 of the inlining features than Class::MOP itself does.
1960 =item B<< $metaclass->make_immutable(%options) >>
1962 This method will create an immutable transformer and use it to make
1963 the class and its metaclass object immutable.
1965 This method accepts the following options:
1969 =item * inline_accessors
1971 =item * inline_constructor
1973 =item * inline_destructor
1975 These are all booleans indicating whether the specified method(s)
1978 By default, accessors and the constructor are inlined, but not the
1981 =item * immutable_trait
1983 The name of a class which will be used as a parent class for the
1984 metaclass object being made immutable. This "trait" implements the
1985 post-immutability functionality of the metaclass (but not the
1986 transformation itself).
1988 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1990 =item * constructor_name
1992 This is the constructor method name. This defaults to "new".
1994 =item * constructor_class
1996 The name of the method metaclass for constructors. It will be used to
1997 generate the inlined constructor. This defaults to
1998 "Class::MOP::Method::Constructor".
2000 =item * replace_constructor
2002 This is a boolean indicating whether an existing constructor should be
2003 replaced when inlining a constructor. This defaults to false.
2005 =item * destructor_class
2007 The name of the method metaclass for destructors. It will be used to
2008 generate the inlined destructor. This defaults to
2009 "Class::MOP::Method::Denstructor".
2011 =item * replace_destructor
2013 This is a boolean indicating whether an existing destructor should be
2014 replaced when inlining a destructor. This defaults to false.
2018 =item B<< $metaclass->immutable_options >>
2020 Returns a hash of the options used when making the class immutable, including
2021 both defaults and anything supplied by the user in the call to C<<
2022 $metaclass->make_immutable >>. This is useful if you need to temporarily make
2023 a class mutable and then restore immutability as it was before.
2025 =item B<< $metaclass->make_mutable >>
2027 Calling this method reverse the immutabilization transformation.
2031 =head2 Method Modifiers
2033 Method modifiers are hooks which allow a method to be wrapped with
2034 I<before>, I<after> and I<around> method modifiers. Every time a
2035 method is called, its modifiers are also called.
2037 A class can modify its own methods, as well as methods defined in
2040 =head3 How method modifiers work?
2042 Method modifiers work by wrapping the original method and then
2043 replacing it in the class's symbol table. The wrappers will handle
2044 calling all the modifiers in the appropriate order and preserving the
2045 calling context for the original method.
2047 The return values of C<before> and C<after> modifiers are
2048 ignored. This is because their purpose is B<not> to filter the input
2049 and output of the primary method (this is done with an I<around>
2052 This may seem like an odd restriction to some, but doing this allows
2053 for simple code to be added at the beginning or end of a method call
2054 without altering the function of the wrapped method or placing any
2055 extra responsibility on the code of the modifier.
2057 Of course if you have more complex needs, you can use the C<around>
2058 modifier which allows you to change both the parameters passed to the
2059 wrapped method, as well as its return value.
2061 Before and around modifiers are called in last-defined-first-called
2062 order, while after modifiers are called in first-defined-first-called
2063 order. So the call tree might looks something like this:
2075 =head3 What is the performance impact?
2077 Of course there is a performance cost associated with method
2078 modifiers, but we have made every effort to make that cost directly
2079 proportional to the number of modifier features you use.
2081 The wrapping method does its best to B<only> do as much work as it
2082 absolutely needs to. In order to do this we have moved some of the
2083 performance costs to set-up time, where they are easier to amortize.
2085 All this said, our benchmarks have indicated the following:
2087 simple wrapper with no modifiers 100% slower
2088 simple wrapper with simple before modifier 400% slower
2089 simple wrapper with simple after modifier 450% slower
2090 simple wrapper with simple around modifier 500-550% slower
2091 simple wrapper with all 3 modifiers 1100% slower
2093 These numbers may seem daunting, but you must remember, every feature
2094 comes with some cost. To put things in perspective, just doing a
2095 simple C<AUTOLOAD> which does nothing but extract the name of the
2096 method called and return it costs about 400% over a normal method
2101 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
2103 This wraps the specified method with the supplied subroutine
2104 reference. The modifier will be called as a method itself, and will
2105 receive the same arguments as are passed to the method.
2107 When the modifier exits, the wrapped method will be called.
2109 The return value of the modifier will be ignored.
2111 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2113 This wraps the specified method with the supplied subroutine
2114 reference. The modifier will be called as a method itself, and will
2115 receive the same arguments as are passed to the method.
2117 When the wrapped methods exits, the modifier will be called.
2119 The return value of the modifier will be ignored.
2121 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2123 This wraps the specified method with the supplied subroutine
2126 The first argument passed to the modifier will be a subroutine
2127 reference to the wrapped method. The second argument is the object,
2128 and after that come any arguments passed when the method is called.
2130 The around modifier can choose to call the original method, as well as
2131 what arguments to pass if it does so.
2133 The return value of the modifier is what will be seen by the caller.
2137 =head2 Introspection
2141 =item B<< Class::MOP::Class->meta >>
2143 This will return a L<Class::MOP::Class> instance for this class.
2145 It should also be noted that L<Class::MOP> will actually bootstrap
2146 this module by installing a number of attribute meta-objects into its