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/cmop/rebless_overload.t regressions
788 $meta_instance->rebless_instance_structure($_[1], $self);
790 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
792 if (Class::MOP::metaclass_is_weak($self->name)) {
793 $meta_instance->_set_mop_slot($instance, $self);
797 sub rebless_instance {
798 my ($self, $instance, %params) = @_;
799 my $old_metaclass = Class::MOP::class_of($instance);
801 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
802 $self->name->isa($old_class)
803 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
805 $self->_force_rebless_instance($_[1], %params);
810 sub rebless_instance_back {
811 my ( $self, $instance ) = @_;
812 my $old_metaclass = Class::MOP::class_of($instance);
815 = $old_metaclass ? $old_metaclass->name : blessed($instance);
816 $old_class->isa( $self->name )
818 "You may rebless only into a superclass of ($old_class), of which ("
822 $self->_force_rebless_instance($_[1]);
827 sub rebless_instance_away {
828 # this intentionally does nothing, it is just a hook
831 sub _fixup_attributes_after_rebless {
833 my ($instance, $rebless_from, %params) = @_;
834 my $meta_instance = $self->get_meta_instance;
836 for my $attr ( $rebless_from->get_all_attributes ) {
837 next if $self->find_attribute_by_name( $attr->name );
838 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
841 foreach my $attr ( $self->get_all_attributes ) {
842 if ( $attr->has_value($instance) ) {
843 if ( defined( my $init_arg = $attr->init_arg ) ) {
844 $params{$init_arg} = $attr->get_value($instance)
845 unless exists $params{$init_arg};
848 $attr->set_value($instance, $attr->get_value($instance));
853 foreach my $attr ($self->get_all_attributes) {
854 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
858 sub _attach_attribute {
859 my ($self, $attribute) = @_;
860 $attribute->attach_to_class($self);
863 sub _post_add_attribute {
864 my ( $self, $attribute ) = @_;
866 $self->invalidate_meta_instances;
868 # invalidate package flag here
871 $attribute->install_accessors;
874 $self->remove_attribute( $attribute->name );
879 sub remove_attribute {
882 my $removed_attribute = $self->SUPER::remove_attribute(@_)
885 $self->invalidate_meta_instances;
887 $removed_attribute->remove_accessors;
888 $removed_attribute->detach_from_class;
890 return$removed_attribute;
893 sub find_attribute_by_name {
894 my ( $self, $attr_name ) = @_;
896 foreach my $class ( $self->linearized_isa ) {
897 # fetch the meta-class ...
898 my $meta = Class::MOP::Class->initialize($class);
899 return $meta->get_attribute($attr_name)
900 if $meta->has_attribute($attr_name);
906 sub get_all_attributes {
908 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
909 reverse $self->linearized_isa;
910 return values %attrs;
918 my $isa = $self->get_or_add_package_symbol('@ISA');
925 # on 5.8 and below, we need to call
926 # a method to get Perl to detect
927 # a cycle in the class hierarchy
928 my $class = $self->name;
932 # we need to check the metaclass
933 # compatibility here so that we can
934 # be sure that the superclass is
935 # not potentially creating an issues
936 # we don't know about
938 $self->_check_metaclass_compatibility();
939 $self->_superclasses_updated();
945 sub _superclasses_updated {
947 $self->update_meta_instance_dependencies();
948 # keep strong references to all our parents, so they don't disappear if
949 # they are anon classes and don't have any direct instances
950 $self->_superclass_metas(
951 map { Class::MOP::class_of($_) } $self->superclasses
955 sub _superclass_metas {
957 $self->{_superclass_metas} = [@_];
962 my $super_class = $self->name;
964 return @{ $super_class->mro::get_isarev() };
967 sub direct_subclasses {
969 my $super_class = $self->name;
974 } Class::MOP::Class->initialize($_)->superclasses
979 return @{ mro::get_linear_isa( (shift)->name ) };
982 sub class_precedence_list {
984 my $name = $self->name;
986 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
988 # We need to check for circular inheritance here
989 # if we are are not on 5.10, cause 5.8 detects it
990 # late. This will do nothing if all is well, and
991 # blow up otherwise. Yes, it's an ugly hack, better
992 # suggestions are welcome.
994 ($name || return)->isa('This is a test for circular inheritance')
997 # if our mro is c3, we can
998 # just grab the linear_isa
999 if (mro::get_mro($name) eq 'c3') {
1000 return @{ mro::get_linear_isa($name) }
1004 # we can't grab the linear_isa for dfs
1005 # since it has all the duplicates
1010 Class::MOP::Class->initialize($_)->class_precedence_list()
1011 } $self->superclasses()
1019 my $fetch_and_prepare_method = sub {
1020 my ($self, $method_name) = @_;
1021 my $wrapped_metaclass = $self->wrapped_method_metaclass;
1023 my $method = $self->get_method($method_name);
1024 # if we dont have local ...
1026 # try to find the next method
1027 $method = $self->find_next_method_by_name($method_name);
1028 # die if it does not exist
1030 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
1031 # and now make sure to wrap it
1032 # even if it is already wrapped
1033 # because we need a new sub ref
1034 $method = $wrapped_metaclass->wrap($method,
1035 package_name => $self->name,
1036 name => $method_name,
1040 # now make sure we wrap it properly
1041 $method = $wrapped_metaclass->wrap($method,
1042 package_name => $self->name,
1043 name => $method_name,
1044 ) unless $method->isa($wrapped_metaclass);
1046 $self->add_method($method_name => $method);
1050 sub add_before_method_modifier {
1051 my ($self, $method_name, $method_modifier) = @_;
1052 (defined $method_name && length $method_name)
1053 || confess "You must pass in a method name";
1054 my $method = $fetch_and_prepare_method->($self, $method_name);
1055 $method->add_before_modifier(
1056 subname(':before' => $method_modifier)
1060 sub add_after_method_modifier {
1061 my ($self, $method_name, $method_modifier) = @_;
1062 (defined $method_name && length $method_name)
1063 || confess "You must pass in a method name";
1064 my $method = $fetch_and_prepare_method->($self, $method_name);
1065 $method->add_after_modifier(
1066 subname(':after' => $method_modifier)
1070 sub add_around_method_modifier {
1071 my ($self, $method_name, $method_modifier) = @_;
1072 (defined $method_name && length $method_name)
1073 || confess "You must pass in a method name";
1074 my $method = $fetch_and_prepare_method->($self, $method_name);
1075 $method->add_around_modifier(
1076 subname(':around' => $method_modifier)
1081 # the methods above used to be named like this:
1082 # ${pkg}::${method}:(before|after|around)
1083 # but this proved problematic when using one modifier
1084 # to wrap multiple methods (something which is likely
1085 # to happen pretty regularly IMO). So instead of naming
1086 # it like this, I have chosen to just name them purely
1087 # with their modifier names, like so:
1088 # :(before|after|around)
1089 # The fact is that in a stack trace, it will be fairly
1090 # evident from the context what method they are attached
1091 # to, and so don't need the fully qualified name.
1094 sub find_method_by_name {
1095 my ($self, $method_name) = @_;
1096 (defined $method_name && length $method_name)
1097 || confess "You must define a method name to find";
1098 foreach my $class ($self->linearized_isa) {
1099 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1100 return $method if defined $method;
1105 sub get_all_methods {
1109 for my $class ( reverse $self->linearized_isa ) {
1110 my $meta = Class::MOP::Class->initialize($class);
1112 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1115 return values %methods;
1118 sub get_all_method_names {
1121 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
1124 sub find_all_methods_by_name {
1125 my ($self, $method_name) = @_;
1126 (defined $method_name && length $method_name)
1127 || confess "You must define a method name to find";
1129 foreach my $class ($self->linearized_isa) {
1130 # fetch the meta-class ...
1131 my $meta = Class::MOP::Class->initialize($class);
1133 name => $method_name,
1135 code => $meta->get_method($method_name)
1136 } if $meta->has_method($method_name);
1141 sub find_next_method_by_name {
1142 my ($self, $method_name) = @_;
1143 (defined $method_name && length $method_name)
1144 || confess "You must define a method name to find";
1145 my @cpl = $self->linearized_isa;
1146 shift @cpl; # discard ourselves
1147 foreach my $class (@cpl) {
1148 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1149 return $method if defined $method;
1154 sub update_meta_instance_dependencies {
1157 if ( $self->{meta_instance_dependencies} ) {
1158 return $self->add_meta_instance_dependencies;
1162 sub add_meta_instance_dependencies {
1165 $self->remove_meta_instance_dependencies;
1167 my @attrs = $self->get_all_attributes();
1170 my @classes = grep { not $seen{ $_->name }++ }
1171 map { $_->associated_class } @attrs;
1173 foreach my $class (@classes) {
1174 $class->add_dependent_meta_instance($self);
1177 $self->{meta_instance_dependencies} = \@classes;
1180 sub remove_meta_instance_dependencies {
1183 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1184 foreach my $class (@$classes) {
1185 $class->remove_dependent_meta_instance($self);
1195 sub add_dependent_meta_instance {
1196 my ( $self, $metaclass ) = @_;
1197 push @{ $self->{dependent_meta_instances} }, $metaclass;
1200 sub remove_dependent_meta_instance {
1201 my ( $self, $metaclass ) = @_;
1202 my $name = $metaclass->name;
1203 @$_ = grep { $_->name ne $name } @$_
1204 for $self->{dependent_meta_instances};
1207 sub invalidate_meta_instances {
1209 $_->invalidate_meta_instance()
1210 for $self, @{ $self->{dependent_meta_instances} };
1213 sub invalidate_meta_instance {
1215 undef $self->{_meta_instance};
1218 # check if we can reinitialize
1222 # if any local attr is defined
1223 return if $self->get_attribute_list;
1225 # or any non-declared methods
1226 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1227 return if $method->isa("Class::MOP::Method::Generated");
1228 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1236 sub is_mutable { 1 }
1237 sub is_immutable { 0 }
1239 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1241 sub _immutable_options {
1242 my ( $self, @args ) = @_;
1245 inline_accessors => 1,
1246 inline_constructor => 1,
1247 inline_destructor => 0,
1249 immutable_trait => $self->immutable_trait,
1250 constructor_name => $self->constructor_name,
1251 constructor_class => $self->constructor_class,
1252 destructor_class => $self->destructor_class,
1257 sub make_immutable {
1258 my ( $self, @args ) = @_;
1260 my ($file, $line) = (caller)[1..2];
1261 if ( $self->is_mutable ) {
1262 $self->_initialize_immutable(
1265 $self->_immutable_options(@args),
1267 $self->_rebless_as_immutable(@args);
1278 if ( $self->is_immutable ) {
1279 my @args = $self->immutable_options;
1280 $self->_rebless_as_mutable();
1281 $self->_remove_inlined_code(@args);
1282 delete $self->{__immutable};
1290 sub _rebless_as_immutable {
1291 my ( $self, @args ) = @_;
1293 $self->{__immutable}{original_class} = ref $self;
1295 bless $self => $self->_immutable_metaclass(@args);
1298 sub _immutable_metaclass {
1299 my ( $self, %args ) = @_;
1301 if ( my $class = $args{immutable_metaclass} ) {
1305 my $trait = $args{immutable_trait} = $self->immutable_trait
1306 || confess "no immutable trait specified for $self";
1308 my $meta = $self->meta;
1309 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1313 if ( $meta_attr and $trait eq $meta_attr->default ) {
1314 # if the trait is the same as the default we try and pick a
1315 # predictable name for the immutable metaclass
1316 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1319 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1320 $trait, 'ForMetaClass', ref($self);
1324 if Class::MOP::is_class_loaded($class_name);
1326 # If the metaclass is a subclass of CMOP::Class which has had
1327 # metaclass roles applied (via Moose), then we want to make sure
1328 # that we preserve that anonymous class (see Fey::ORM for an
1329 # example of where this matters).
1330 my $meta_name = $meta->_real_ref_name;
1332 my $immutable_meta = $meta_name->create(
1334 superclasses => [ ref $self ],
1337 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1339 $immutable_meta->make_immutable(
1340 inline_constructor => 0,
1341 inline_accessors => 0,
1347 sub _remove_inlined_code {
1350 $self->remove_method( $_->name ) for $self->_inlined_methods;
1352 delete $self->{__immutable}{inlined_methods};
1355 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1357 sub _add_inlined_method {
1358 my ( $self, $method ) = @_;
1360 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1363 sub _initialize_immutable {
1364 my ( $self, %args ) = @_;
1366 $self->{__immutable}{options} = \%args;
1367 $self->_install_inlined_code(%args);
1370 sub _install_inlined_code {
1371 my ( $self, %args ) = @_;
1374 $self->_inline_accessors(%args) if $args{inline_accessors};
1375 $self->_inline_constructor(%args) if $args{inline_constructor};
1376 $self->_inline_destructor(%args) if $args{inline_destructor};
1379 sub _rebless_as_mutable {
1382 bless $self, $self->_get_mutable_metaclass_name;
1387 sub _inline_accessors {
1390 foreach my $attr_name ( $self->get_attribute_list ) {
1391 $self->get_attribute($attr_name)->install_accessors(1);
1395 sub _inline_constructor {
1396 my ( $self, %args ) = @_;
1398 my $name = $args{constructor_name};
1399 # A class may not even have a constructor, and that's okay.
1400 return unless defined $name;
1402 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1403 my $class = $self->name;
1404 warn "Not inlining a constructor for $class since it defines"
1405 . " its own constructor.\n"
1406 . "If you are certain you don't need to inline your"
1407 . " constructor, specify inline_constructor => 0 in your"
1408 . " call to $class->meta->make_immutable\n";
1412 my $constructor_class = $args{constructor_class};
1414 Class::MOP::load_class($constructor_class);
1416 my $constructor = $constructor_class->new(
1420 package_name => $self->name,
1422 definition_context => {
1423 description => "constructor " . $self->name . "::" . $name,
1424 file => $args{file},
1425 line => $args{line},
1429 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1430 $self->add_method( $name => $constructor );
1431 $self->_add_inlined_method($constructor);
1435 sub _inline_destructor {
1436 my ( $self, %args ) = @_;
1438 ( exists $args{destructor_class} && defined $args{destructor_class} )
1439 || confess "The 'inline_destructor' option is present, but "
1440 . "no destructor class was specified";
1442 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1443 my $class = $self->name;
1444 warn "Not inlining a destructor for $class since it defines"
1445 . " its own destructor.\n";
1449 my $destructor_class = $args{destructor_class};
1451 Class::MOP::load_class($destructor_class);
1453 return unless $destructor_class->is_needed($self);
1455 my $destructor = $destructor_class->new(
1458 package_name => $self->name,
1460 definition_context => {
1461 description => "destructor " . $self->name . "::DESTROY",
1462 file => $args{file},
1463 line => $args{line},
1467 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1468 $self->add_method( 'DESTROY' => $destructor );
1469 $self->_add_inlined_method($destructor);
1475 # ABSTRACT: Class Meta Object
1483 # assuming that class Foo
1484 # has been defined, you can
1486 # use this for introspection ...
1488 # add a method to Foo ...
1489 Foo->meta->add_method( 'bar' => sub {...} )
1491 # get a list of all the classes searched
1492 # the method dispatcher in the correct order
1493 Foo->meta->class_precedence_list()
1495 # remove a method from Foo
1496 Foo->meta->remove_method('bar');
1498 # or use this to actually create classes ...
1500 Class::MOP::Class->create(
1503 superclasses => ['Foo'],
1505 Class::MOP::Attribute->new('$bar'),
1506 Class::MOP::Attribute->new('$baz'),
1509 calculate_bar => sub {...},
1510 construct_baz => sub {...}
1517 The Class Protocol is the largest and most complex part of the
1518 Class::MOP meta-object protocol. It controls the introspection and
1519 manipulation of Perl 5 classes, and it can create them as well. The
1520 best way to understand what this module can do is to read the
1521 documentation for each of its methods.
1525 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1529 =head2 Class construction
1531 These methods all create new C<Class::MOP::Class> objects. These
1532 objects can represent existing classes or they can be used to create
1533 new classes from scratch.
1535 The metaclass object for a given class is a singleton. If you attempt
1536 to create a metaclass for the same class twice, you will just get the
1541 =item B<< Class::MOP::Class->create($package_name, %options) >>
1543 This method creates a new C<Class::MOP::Class> object with the given
1544 package name. It accepts a number of options:
1550 An optional version number for the newly created package.
1554 An optional authority for the newly created package.
1556 =item * superclasses
1558 An optional array reference of superclass names.
1562 An optional hash reference of methods for the class. The keys of the
1563 hash reference are method names and values are subroutine references.
1567 An optional array reference of L<Class::MOP::Attribute> objects.
1571 Specifies the name to install the C<meta> method for this class under.
1572 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1573 given, no meta method will be installed.
1577 If true, the metaclass that is stored in the global cache will be a
1580 Classes created in this way are destroyed once the metaclass they are
1581 attached to goes out of scope, and will be removed from Perl's internal
1584 All instances of a class with a weakened metaclass keep a special
1585 reference to the metaclass object, which prevents the metaclass from
1586 going out of scope while any instances exist.
1588 This only works if the instance is based on a hash reference, however.
1592 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1594 This method works just like C<< Class::MOP::Class->create >> but it
1595 creates an "anonymous" class. In fact, the class does have a name, but
1596 that name is a unique name generated internally by this module.
1598 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1599 parameters that C<create> accepts.
1601 Anonymous classes default to C<< weaken => 1 >>, although this can be
1604 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1606 This method will initialize a C<Class::MOP::Class> object for the
1607 named package. Unlike C<create>, this method I<will not> create a new
1610 The purpose of this method is to retrieve a C<Class::MOP::Class>
1611 object for introspecting an existing class.
1613 If an existing C<Class::MOP::Class> object exists for the named
1614 package, it will be returned, and any options provided will be
1617 If the object does not yet exist, it will be created.
1619 The valid options that can be passed to this method are
1620 C<attribute_metaclass>, C<method_metaclass>,
1621 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1622 optional, and default to the appropriate class in the C<Class::MOP>
1627 =head2 Object instance construction and cloning
1629 These methods are all related to creating and/or cloning object
1634 =item B<< $metaclass->clone_object($instance, %params) >>
1636 This method clones an existing object instance. Any parameters you
1637 provide are will override existing attribute values in the object.
1639 This is a convenience method for cloning an object instance, then
1640 blessing it into the appropriate package.
1642 You could implement a clone method in your class, using this method:
1645 my ($self, %params) = @_;
1646 $self->meta->clone_object($self, %params);
1649 =item B<< $metaclass->rebless_instance($instance, %params) >>
1651 This method changes the class of C<$instance> to the metaclass's class.
1653 You can only rebless an instance into a subclass of its current
1654 class. If you pass any additional parameters, these will be treated
1655 like constructor parameters and used to initialize the object's
1656 attributes. Any existing attributes that are already set will be
1659 Before reblessing the instance, this method will call
1660 C<rebless_instance_away> on the instance's current metaclass. This method
1661 will be passed the instance, the new metaclass, and any parameters
1662 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1663 does nothing; it is merely a hook.
1665 =item B<< $metaclass->rebless_instance_back($instance) >>
1667 Does the same thing as C<rebless_instance>, except that you can only
1668 rebless an instance into one of its superclasses. Any attributes that
1669 do not exist in the superclass will be deinitialized.
1671 This is a much more dangerous operation than C<rebless_instance>,
1672 especially when multiple inheritance is involved, so use this carefully!
1674 =item B<< $metaclass->new_object(%params) >>
1676 This method is used to create a new object of the metaclass's
1677 class. Any parameters you provide are used to initialize the
1678 instance's attributes. A special C<__INSTANCE__> key can be passed to
1679 provide an already generated instance, rather than having Class::MOP
1680 generate it for you. This is mostly useful for using Class::MOP with
1681 foreign classes which generate instances using their own constructors.
1683 =item B<< $metaclass->instance_metaclass >>
1685 Returns the class name of the instance metaclass. See
1686 L<Class::MOP::Instance> for more information on the instance
1689 =item B<< $metaclass->get_meta_instance >>
1691 Returns an instance of the C<instance_metaclass> to be used in the
1692 construction of a new instance of the class.
1696 =head2 Informational predicates
1698 These are a few predicate methods for asking information about the
1703 =item B<< $metaclass->is_anon_class >>
1705 This returns true if the class was created by calling C<<
1706 Class::MOP::Class->create_anon_class >>.
1708 =item B<< $metaclass->is_mutable >>
1710 This returns true if the class is still mutable.
1712 =item B<< $metaclass->is_immutable >>
1714 This returns true if the class has been made immutable.
1716 =item B<< $metaclass->is_pristine >>
1718 A class is I<not> pristine if it has non-inherited attributes or if it
1719 has any generated methods.
1723 =head2 Inheritance Relationships
1727 =item B<< $metaclass->superclasses(@superclasses) >>
1729 This is a read-write accessor which represents the superclass
1730 relationships of the metaclass's class.
1732 This is basically sugar around getting and setting C<@ISA>.
1734 =item B<< $metaclass->class_precedence_list >>
1736 This returns a list of all of the class's ancestor classes. The
1737 classes are returned in method dispatch order.
1739 =item B<< $metaclass->linearized_isa >>
1741 This returns a list based on C<class_precedence_list> but with all
1744 =item B<< $metaclass->subclasses >>
1746 This returns a list of all subclasses for this class, even indirect
1749 =item B<< $metaclass->direct_subclasses >>
1751 This returns a list of immediate subclasses for this class, which does not
1752 include indirect subclasses.
1756 =head2 Method introspection and creation
1758 These methods allow you to introspect a class's methods, as well as
1759 add, remove, or change methods.
1761 Determining what is truly a method in a Perl 5 class requires some
1762 heuristics (aka guessing).
1764 Methods defined outside the package with a fully qualified name (C<sub
1765 Package::name { ... }>) will be included. Similarly, methods named
1766 with a fully qualified name using L<Sub::Name> are also included.
1768 However, we attempt to ignore imported functions.
1770 Ultimately, we are using heuristics to determine what truly is a
1771 method in a class, and these heuristics may get the wrong answer in
1772 some edge cases. However, for most "normal" cases the heuristics work
1777 =item B<< $metaclass->get_method($method_name) >>
1779 This will return a L<Class::MOP::Method> for the specified
1780 C<$method_name>. If the class does not have the specified method, it
1783 =item B<< $metaclass->has_method($method_name) >>
1785 Returns a boolean indicating whether or not the class defines the
1786 named method. It does not include methods inherited from parent
1789 =item B<< $metaclass->get_method_list >>
1791 This will return a list of method I<names> for all methods defined in
1794 =item B<< $metaclass->add_method($method_name, $method) >>
1796 This method takes a method name and a subroutine reference, and adds
1797 the method to the class.
1799 The subroutine reference can be a L<Class::MOP::Method>, and you are
1800 strongly encouraged to pass a meta method object instead of a code
1801 reference. If you do so, that object gets stored as part of the
1802 class's method map directly. If not, the meta information will have to
1803 be recreated later, and may be incorrect.
1805 If you provide a method object, this method will clone that object if
1806 the object's package name does not match the class name. This lets us
1807 track the original source of any methods added from other classes
1808 (notably Moose roles).
1810 =item B<< $metaclass->remove_method($method_name) >>
1812 Remove the named method from the class. This method returns the
1813 L<Class::MOP::Method> object for the method.
1815 =item B<< $metaclass->method_metaclass >>
1817 Returns the class name of the method metaclass, see
1818 L<Class::MOP::Method> for more information on the method metaclass.
1820 =item B<< $metaclass->wrapped_method_metaclass >>
1822 Returns the class name of the wrapped method metaclass, see
1823 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1826 =item B<< $metaclass->get_all_methods >>
1828 This will traverse the inheritance hierarchy and return a list of all
1829 the L<Class::MOP::Method> objects for this class and its parents.
1831 =item B<< $metaclass->find_method_by_name($method_name) >>
1833 This will return a L<Class::MOP::Method> for the specified
1834 C<$method_name>. If the class does not have the specified method, it
1837 Unlike C<get_method>, this method I<will> look for the named method in
1840 =item B<< $metaclass->get_all_method_names >>
1842 This will return a list of method I<names> for all of this class's
1843 methods, including inherited methods.
1845 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1847 This method looks for the named method in the class and all of its
1848 parents. It returns every matching method it finds in the inheritance
1849 tree, so it returns a list of methods.
1851 Each method is returned as a hash reference with three keys. The keys
1852 are C<name>, C<class>, and C<code>. The C<code> key has a
1853 L<Class::MOP::Method> object as its value.
1855 The list of methods is distinct.
1857 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1859 This method returns the first method in any superclass matching the
1860 given name. It is effectively the method that C<SUPER::$method_name>
1865 =head2 Attribute introspection and creation
1867 Because Perl 5 does not have a core concept of attributes in classes,
1868 we can only return information about attributes which have been added
1869 via this class's methods. We cannot discover information about
1870 attributes which are defined in terms of "regular" Perl 5 methods.
1874 =item B<< $metaclass->get_attribute($attribute_name) >>
1876 This will return a L<Class::MOP::Attribute> for the specified
1877 C<$attribute_name>. If the class does not have the specified
1878 attribute, it returns C<undef>.
1880 NOTE that get_attribute does not search superclasses, for that you
1881 need to use C<find_attribute_by_name>.
1883 =item B<< $metaclass->has_attribute($attribute_name) >>
1885 Returns a boolean indicating whether or not the class defines the
1886 named attribute. It does not include attributes inherited from parent
1889 =item B<< $metaclass->get_attribute_list >>
1891 This will return a list of attributes I<names> for all attributes
1892 defined in this class. Note that this operates on the current class
1893 only, it does not traverse the inheritance hierarchy.
1895 =item B<< $metaclass->get_all_attributes >>
1897 This will traverse the inheritance hierarchy and return a list of all
1898 the L<Class::MOP::Attribute> objects for this class and its parents.
1900 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1902 This will return a L<Class::MOP::Attribute> for the specified
1903 C<$attribute_name>. If the class does not have the specified
1904 attribute, it returns C<undef>.
1906 Unlike C<get_attribute>, this attribute I<will> look for the named
1907 attribute in superclasses.
1909 =item B<< $metaclass->add_attribute(...) >>
1911 This method accepts either an existing L<Class::MOP::Attribute>
1912 object or parameters suitable for passing to that class's C<new>
1915 The attribute provided will be added to the class.
1917 Any accessor methods defined by the attribute will be added to the
1918 class when the attribute is added.
1920 If an attribute of the same name already exists, the old attribute
1921 will be removed first.
1923 =item B<< $metaclass->remove_attribute($attribute_name) >>
1925 This will remove the named attribute from the class, and
1926 L<Class::MOP::Attribute> object.
1928 Removing an attribute also removes any accessor methods defined by the
1931 However, note that removing an attribute will only affect I<future>
1932 object instances created for this class, not existing instances.
1934 =item B<< $metaclass->attribute_metaclass >>
1936 Returns the class name of the attribute metaclass for this class. By
1937 default, this is L<Class::MOP::Attribute>.
1941 =head2 Class Immutability
1943 Making a class immutable "freezes" the class definition. You can no
1944 longer call methods which alter the class, such as adding or removing
1945 methods or attributes.
1947 Making a class immutable lets us optimize the class by inlining some
1948 methods, and also allows us to optimize some methods on the metaclass
1951 After immutabilization, the metaclass object will cache most informational
1952 methods that returns information about methods or attributes. Methods which
1953 would alter the class, such as C<add_attribute> and C<add_method>, will
1954 throw an error on an immutable metaclass object.
1956 The immutabilization system in L<Moose> takes much greater advantage
1957 of the inlining features than Class::MOP itself does.
1961 =item B<< $metaclass->make_immutable(%options) >>
1963 This method will create an immutable transformer and use it to make
1964 the class and its metaclass object immutable.
1966 This method accepts the following options:
1970 =item * inline_accessors
1972 =item * inline_constructor
1974 =item * inline_destructor
1976 These are all booleans indicating whether the specified method(s)
1979 By default, accessors and the constructor are inlined, but not the
1982 =item * immutable_trait
1984 The name of a class which will be used as a parent class for the
1985 metaclass object being made immutable. This "trait" implements the
1986 post-immutability functionality of the metaclass (but not the
1987 transformation itself).
1989 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1991 =item * constructor_name
1993 This is the constructor method name. This defaults to "new".
1995 =item * constructor_class
1997 The name of the method metaclass for constructors. It will be used to
1998 generate the inlined constructor. This defaults to
1999 "Class::MOP::Method::Constructor".
2001 =item * replace_constructor
2003 This is a boolean indicating whether an existing constructor should be
2004 replaced when inlining a constructor. This defaults to false.
2006 =item * destructor_class
2008 The name of the method metaclass for destructors. It will be used to
2009 generate the inlined destructor. This defaults to
2010 "Class::MOP::Method::Denstructor".
2012 =item * replace_destructor
2014 This is a boolean indicating whether an existing destructor should be
2015 replaced when inlining a destructor. This defaults to false.
2019 =item B<< $metaclass->immutable_options >>
2021 Returns a hash of the options used when making the class immutable, including
2022 both defaults and anything supplied by the user in the call to C<<
2023 $metaclass->make_immutable >>. This is useful if you need to temporarily make
2024 a class mutable and then restore immutability as it was before.
2026 =item B<< $metaclass->make_mutable >>
2028 Calling this method reverse the immutabilization transformation.
2032 =head2 Method Modifiers
2034 Method modifiers are hooks which allow a method to be wrapped with
2035 I<before>, I<after> and I<around> method modifiers. Every time a
2036 method is called, its modifiers are also called.
2038 A class can modify its own methods, as well as methods defined in
2041 =head3 How method modifiers work?
2043 Method modifiers work by wrapping the original method and then
2044 replacing it in the class's symbol table. The wrappers will handle
2045 calling all the modifiers in the appropriate order and preserving the
2046 calling context for the original method.
2048 The return values of C<before> and C<after> modifiers are
2049 ignored. This is because their purpose is B<not> to filter the input
2050 and output of the primary method (this is done with an I<around>
2053 This may seem like an odd restriction to some, but doing this allows
2054 for simple code to be added at the beginning or end of a method call
2055 without altering the function of the wrapped method or placing any
2056 extra responsibility on the code of the modifier.
2058 Of course if you have more complex needs, you can use the C<around>
2059 modifier which allows you to change both the parameters passed to the
2060 wrapped method, as well as its return value.
2062 Before and around modifiers are called in last-defined-first-called
2063 order, while after modifiers are called in first-defined-first-called
2064 order. So the call tree might looks something like this:
2076 =head3 What is the performance impact?
2078 Of course there is a performance cost associated with method
2079 modifiers, but we have made every effort to make that cost directly
2080 proportional to the number of modifier features you use.
2082 The wrapping method does its best to B<only> do as much work as it
2083 absolutely needs to. In order to do this we have moved some of the
2084 performance costs to set-up time, where they are easier to amortize.
2086 All this said, our benchmarks have indicated the following:
2088 simple wrapper with no modifiers 100% slower
2089 simple wrapper with simple before modifier 400% slower
2090 simple wrapper with simple after modifier 450% slower
2091 simple wrapper with simple around modifier 500-550% slower
2092 simple wrapper with all 3 modifiers 1100% slower
2094 These numbers may seem daunting, but you must remember, every feature
2095 comes with some cost. To put things in perspective, just doing a
2096 simple C<AUTOLOAD> which does nothing but extract the name of the
2097 method called and return it costs about 400% over a normal method
2102 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
2104 This wraps the specified method with the supplied subroutine
2105 reference. The modifier will be called as a method itself, and will
2106 receive the same arguments as are passed to the method.
2108 When the modifier exits, the wrapped method will be called.
2110 The return value of the modifier will be ignored.
2112 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2114 This wraps the specified method with the supplied subroutine
2115 reference. The modifier will be called as a method itself, and will
2116 receive the same arguments as are passed to the method.
2118 When the wrapped methods exits, the modifier will be called.
2120 The return value of the modifier will be ignored.
2122 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2124 This wraps the specified method with the supplied subroutine
2127 The first argument passed to the modifier will be a subroutine
2128 reference to the wrapped method. The second argument is the object,
2129 and after that come any arguments passed when the method is called.
2131 The around modifier can choose to call the original method, as well as
2132 what arguments to pass if it does so.
2134 The return value of the modifier is what will be seen by the caller.
2138 =head2 Introspection
2142 =item B<< Class::MOP::Class->meta >>
2144 This will return a L<Class::MOP::Class> instance for this class.
2146 It should also be noted that L<Class::MOP> will actually bootstrap
2147 this module by installing a number of attribute meta-objects into its