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 return if not $self->is_mutable;
1262 my ($file, $line) = (caller)[1..2];
1264 $self->_initialize_immutable(
1267 $self->_immutable_options(@args),
1269 $self->_rebless_as_immutable(@args);
1276 if ( $self->is_immutable ) {
1277 my @args = $self->immutable_options;
1278 $self->_rebless_as_mutable();
1279 $self->_remove_inlined_code(@args);
1280 delete $self->{__immutable};
1288 sub _rebless_as_immutable {
1289 my ( $self, @args ) = @_;
1291 $self->{__immutable}{original_class} = ref $self;
1293 bless $self => $self->_immutable_metaclass(@args);
1296 sub _immutable_metaclass {
1297 my ( $self, %args ) = @_;
1299 if ( my $class = $args{immutable_metaclass} ) {
1303 my $trait = $args{immutable_trait} = $self->immutable_trait
1304 || confess "no immutable trait specified for $self";
1306 my $meta = $self->meta;
1307 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1311 if ( $meta_attr and $trait eq $meta_attr->default ) {
1312 # if the trait is the same as the default we try and pick a
1313 # predictable name for the immutable metaclass
1314 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1317 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1318 $trait, 'ForMetaClass', ref($self);
1322 if Class::MOP::is_class_loaded($class_name);
1324 # If the metaclass is a subclass of CMOP::Class which has had
1325 # metaclass roles applied (via Moose), then we want to make sure
1326 # that we preserve that anonymous class (see Fey::ORM for an
1327 # example of where this matters).
1328 my $meta_name = $meta->_real_ref_name;
1330 my $immutable_meta = $meta_name->create(
1332 superclasses => [ ref $self ],
1335 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1337 $immutable_meta->make_immutable(
1338 inline_constructor => 0,
1339 inline_accessors => 0,
1345 sub _remove_inlined_code {
1348 $self->remove_method( $_->name ) for $self->_inlined_methods;
1350 delete $self->{__immutable}{inlined_methods};
1353 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1355 sub _add_inlined_method {
1356 my ( $self, $method ) = @_;
1358 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1361 sub _initialize_immutable {
1362 my ( $self, %args ) = @_;
1364 $self->{__immutable}{options} = \%args;
1365 $self->_install_inlined_code(%args);
1368 sub _install_inlined_code {
1369 my ( $self, %args ) = @_;
1372 $self->_inline_accessors(%args) if $args{inline_accessors};
1373 $self->_inline_constructor(%args) if $args{inline_constructor};
1374 $self->_inline_destructor(%args) if $args{inline_destructor};
1377 sub _rebless_as_mutable {
1380 bless $self, $self->_get_mutable_metaclass_name;
1385 sub _inline_accessors {
1388 foreach my $attr_name ( $self->get_attribute_list ) {
1389 $self->get_attribute($attr_name)->install_accessors(1);
1393 sub _inline_constructor {
1394 my ( $self, %args ) = @_;
1396 my $name = $args{constructor_name};
1397 # A class may not even have a constructor, and that's okay.
1398 return unless defined $name;
1400 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1401 my $class = $self->name;
1402 warn "Not inlining a constructor for $class since it defines"
1403 . " its own constructor.\n"
1404 . "If you are certain you don't need to inline your"
1405 . " constructor, specify inline_constructor => 0 in your"
1406 . " call to $class->meta->make_immutable\n";
1410 my $constructor_class = $args{constructor_class};
1412 Class::MOP::load_class($constructor_class);
1414 my $constructor = $constructor_class->new(
1418 package_name => $self->name,
1420 definition_context => {
1421 description => "constructor " . $self->name . "::" . $name,
1422 file => $args{file},
1423 line => $args{line},
1427 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1428 $self->add_method( $name => $constructor );
1429 $self->_add_inlined_method($constructor);
1433 sub _inline_destructor {
1434 my ( $self, %args ) = @_;
1436 ( exists $args{destructor_class} && defined $args{destructor_class} )
1437 || confess "The 'inline_destructor' option is present, but "
1438 . "no destructor class was specified";
1440 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1441 my $class = $self->name;
1442 warn "Not inlining a destructor for $class since it defines"
1443 . " its own destructor.\n";
1447 my $destructor_class = $args{destructor_class};
1449 Class::MOP::load_class($destructor_class);
1451 return unless $destructor_class->is_needed($self);
1453 my $destructor = $destructor_class->new(
1456 package_name => $self->name,
1458 definition_context => {
1459 description => "destructor " . $self->name . "::DESTROY",
1460 file => $args{file},
1461 line => $args{line},
1465 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1466 $self->add_method( 'DESTROY' => $destructor );
1467 $self->_add_inlined_method($destructor);
1473 # ABSTRACT: Class Meta Object
1481 # assuming that class Foo
1482 # has been defined, you can
1484 # use this for introspection ...
1486 # add a method to Foo ...
1487 Foo->meta->add_method( 'bar' => sub {...} )
1489 # get a list of all the classes searched
1490 # the method dispatcher in the correct order
1491 Foo->meta->class_precedence_list()
1493 # remove a method from Foo
1494 Foo->meta->remove_method('bar');
1496 # or use this to actually create classes ...
1498 Class::MOP::Class->create(
1501 superclasses => ['Foo'],
1503 Class::MOP::Attribute->new('$bar'),
1504 Class::MOP::Attribute->new('$baz'),
1507 calculate_bar => sub {...},
1508 construct_baz => sub {...}
1515 The Class Protocol is the largest and most complex part of the
1516 Class::MOP meta-object protocol. It controls the introspection and
1517 manipulation of Perl 5 classes, and it can create them as well. The
1518 best way to understand what this module can do is to read the
1519 documentation for each of its methods.
1523 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1527 =head2 Class construction
1529 These methods all create new C<Class::MOP::Class> objects. These
1530 objects can represent existing classes or they can be used to create
1531 new classes from scratch.
1533 The metaclass object for a given class is a singleton. If you attempt
1534 to create a metaclass for the same class twice, you will just get the
1539 =item B<< Class::MOP::Class->create($package_name, %options) >>
1541 This method creates a new C<Class::MOP::Class> object with the given
1542 package name. It accepts a number of options:
1548 An optional version number for the newly created package.
1552 An optional authority for the newly created package.
1554 =item * superclasses
1556 An optional array reference of superclass names.
1560 An optional hash reference of methods for the class. The keys of the
1561 hash reference are method names and values are subroutine references.
1565 An optional array reference of L<Class::MOP::Attribute> objects.
1569 Specifies the name to install the C<meta> method for this class under.
1570 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1571 given, no meta method will be installed.
1575 If true, the metaclass that is stored in the global cache will be a
1578 Classes created in this way are destroyed once the metaclass they are
1579 attached to goes out of scope, and will be removed from Perl's internal
1582 All instances of a class with a weakened metaclass keep a special
1583 reference to the metaclass object, which prevents the metaclass from
1584 going out of scope while any instances exist.
1586 This only works if the instance is based on a hash reference, however.
1590 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1592 This method works just like C<< Class::MOP::Class->create >> but it
1593 creates an "anonymous" class. In fact, the class does have a name, but
1594 that name is a unique name generated internally by this module.
1596 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1597 parameters that C<create> accepts.
1599 Anonymous classes default to C<< weaken => 1 >>, although this can be
1602 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1604 This method will initialize a C<Class::MOP::Class> object for the
1605 named package. Unlike C<create>, this method I<will not> create a new
1608 The purpose of this method is to retrieve a C<Class::MOP::Class>
1609 object for introspecting an existing class.
1611 If an existing C<Class::MOP::Class> object exists for the named
1612 package, it will be returned, and any options provided will be
1615 If the object does not yet exist, it will be created.
1617 The valid options that can be passed to this method are
1618 C<attribute_metaclass>, C<method_metaclass>,
1619 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1620 optional, and default to the appropriate class in the C<Class::MOP>
1625 =head2 Object instance construction and cloning
1627 These methods are all related to creating and/or cloning object
1632 =item B<< $metaclass->clone_object($instance, %params) >>
1634 This method clones an existing object instance. Any parameters you
1635 provide are will override existing attribute values in the object.
1637 This is a convenience method for cloning an object instance, then
1638 blessing it into the appropriate package.
1640 You could implement a clone method in your class, using this method:
1643 my ($self, %params) = @_;
1644 $self->meta->clone_object($self, %params);
1647 =item B<< $metaclass->rebless_instance($instance, %params) >>
1649 This method changes the class of C<$instance> to the metaclass's class.
1651 You can only rebless an instance into a subclass of its current
1652 class. If you pass any additional parameters, these will be treated
1653 like constructor parameters and used to initialize the object's
1654 attributes. Any existing attributes that are already set will be
1657 Before reblessing the instance, this method will call
1658 C<rebless_instance_away> on the instance's current metaclass. This method
1659 will be passed the instance, the new metaclass, and any parameters
1660 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1661 does nothing; it is merely a hook.
1663 =item B<< $metaclass->rebless_instance_back($instance) >>
1665 Does the same thing as C<rebless_instance>, except that you can only
1666 rebless an instance into one of its superclasses. Any attributes that
1667 do not exist in the superclass will be deinitialized.
1669 This is a much more dangerous operation than C<rebless_instance>,
1670 especially when multiple inheritance is involved, so use this carefully!
1672 =item B<< $metaclass->new_object(%params) >>
1674 This method is used to create a new object of the metaclass's
1675 class. Any parameters you provide are used to initialize the
1676 instance's attributes. A special C<__INSTANCE__> key can be passed to
1677 provide an already generated instance, rather than having Class::MOP
1678 generate it for you. This is mostly useful for using Class::MOP with
1679 foreign classes which generate instances using their own constructors.
1681 =item B<< $metaclass->instance_metaclass >>
1683 Returns the class name of the instance metaclass. See
1684 L<Class::MOP::Instance> for more information on the instance
1687 =item B<< $metaclass->get_meta_instance >>
1689 Returns an instance of the C<instance_metaclass> to be used in the
1690 construction of a new instance of the class.
1694 =head2 Informational predicates
1696 These are a few predicate methods for asking information about the
1701 =item B<< $metaclass->is_anon_class >>
1703 This returns true if the class was created by calling C<<
1704 Class::MOP::Class->create_anon_class >>.
1706 =item B<< $metaclass->is_mutable >>
1708 This returns true if the class is still mutable.
1710 =item B<< $metaclass->is_immutable >>
1712 This returns true if the class has been made immutable.
1714 =item B<< $metaclass->is_pristine >>
1716 A class is I<not> pristine if it has non-inherited attributes or if it
1717 has any generated methods.
1721 =head2 Inheritance Relationships
1725 =item B<< $metaclass->superclasses(@superclasses) >>
1727 This is a read-write accessor which represents the superclass
1728 relationships of the metaclass's class.
1730 This is basically sugar around getting and setting C<@ISA>.
1732 =item B<< $metaclass->class_precedence_list >>
1734 This returns a list of all of the class's ancestor classes. The
1735 classes are returned in method dispatch order.
1737 =item B<< $metaclass->linearized_isa >>
1739 This returns a list based on C<class_precedence_list> but with all
1742 =item B<< $metaclass->subclasses >>
1744 This returns a list of all subclasses for this class, even indirect
1747 =item B<< $metaclass->direct_subclasses >>
1749 This returns a list of immediate subclasses for this class, which does not
1750 include indirect subclasses.
1754 =head2 Method introspection and creation
1756 These methods allow you to introspect a class's methods, as well as
1757 add, remove, or change methods.
1759 Determining what is truly a method in a Perl 5 class requires some
1760 heuristics (aka guessing).
1762 Methods defined outside the package with a fully qualified name (C<sub
1763 Package::name { ... }>) will be included. Similarly, methods named
1764 with a fully qualified name using L<Sub::Name> are also included.
1766 However, we attempt to ignore imported functions.
1768 Ultimately, we are using heuristics to determine what truly is a
1769 method in a class, and these heuristics may get the wrong answer in
1770 some edge cases. However, for most "normal" cases the heuristics work
1775 =item B<< $metaclass->get_method($method_name) >>
1777 This will return a L<Class::MOP::Method> for the specified
1778 C<$method_name>. If the class does not have the specified method, it
1781 =item B<< $metaclass->has_method($method_name) >>
1783 Returns a boolean indicating whether or not the class defines the
1784 named method. It does not include methods inherited from parent
1787 =item B<< $metaclass->get_method_list >>
1789 This will return a list of method I<names> for all methods defined in
1792 =item B<< $metaclass->add_method($method_name, $method) >>
1794 This method takes a method name and a subroutine reference, and adds
1795 the method to the class.
1797 The subroutine reference can be a L<Class::MOP::Method>, and you are
1798 strongly encouraged to pass a meta method object instead of a code
1799 reference. If you do so, that object gets stored as part of the
1800 class's method map directly. If not, the meta information will have to
1801 be recreated later, and may be incorrect.
1803 If you provide a method object, this method will clone that object if
1804 the object's package name does not match the class name. This lets us
1805 track the original source of any methods added from other classes
1806 (notably Moose roles).
1808 =item B<< $metaclass->remove_method($method_name) >>
1810 Remove the named method from the class. This method returns the
1811 L<Class::MOP::Method> object for the method.
1813 =item B<< $metaclass->method_metaclass >>
1815 Returns the class name of the method metaclass, see
1816 L<Class::MOP::Method> for more information on the method metaclass.
1818 =item B<< $metaclass->wrapped_method_metaclass >>
1820 Returns the class name of the wrapped method metaclass, see
1821 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1824 =item B<< $metaclass->get_all_methods >>
1826 This will traverse the inheritance hierarchy and return a list of all
1827 the L<Class::MOP::Method> objects for this class and its parents.
1829 =item B<< $metaclass->find_method_by_name($method_name) >>
1831 This will return a L<Class::MOP::Method> for the specified
1832 C<$method_name>. If the class does not have the specified method, it
1835 Unlike C<get_method>, this method I<will> look for the named method in
1838 =item B<< $metaclass->get_all_method_names >>
1840 This will return a list of method I<names> for all of this class's
1841 methods, including inherited methods.
1843 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1845 This method looks for the named method in the class and all of its
1846 parents. It returns every matching method it finds in the inheritance
1847 tree, so it returns a list of methods.
1849 Each method is returned as a hash reference with three keys. The keys
1850 are C<name>, C<class>, and C<code>. The C<code> key has a
1851 L<Class::MOP::Method> object as its value.
1853 The list of methods is distinct.
1855 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1857 This method returns the first method in any superclass matching the
1858 given name. It is effectively the method that C<SUPER::$method_name>
1863 =head2 Attribute introspection and creation
1865 Because Perl 5 does not have a core concept of attributes in classes,
1866 we can only return information about attributes which have been added
1867 via this class's methods. We cannot discover information about
1868 attributes which are defined in terms of "regular" Perl 5 methods.
1872 =item B<< $metaclass->get_attribute($attribute_name) >>
1874 This will return a L<Class::MOP::Attribute> for the specified
1875 C<$attribute_name>. If the class does not have the specified
1876 attribute, it returns C<undef>.
1878 NOTE that get_attribute does not search superclasses, for that you
1879 need to use C<find_attribute_by_name>.
1881 =item B<< $metaclass->has_attribute($attribute_name) >>
1883 Returns a boolean indicating whether or not the class defines the
1884 named attribute. It does not include attributes inherited from parent
1887 =item B<< $metaclass->get_attribute_list >>
1889 This will return a list of attributes I<names> for all attributes
1890 defined in this class. Note that this operates on the current class
1891 only, it does not traverse the inheritance hierarchy.
1893 =item B<< $metaclass->get_all_attributes >>
1895 This will traverse the inheritance hierarchy and return a list of all
1896 the L<Class::MOP::Attribute> objects for this class and its parents.
1898 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1900 This will return a L<Class::MOP::Attribute> for the specified
1901 C<$attribute_name>. If the class does not have the specified
1902 attribute, it returns C<undef>.
1904 Unlike C<get_attribute>, this attribute I<will> look for the named
1905 attribute in superclasses.
1907 =item B<< $metaclass->add_attribute(...) >>
1909 This method accepts either an existing L<Class::MOP::Attribute>
1910 object or parameters suitable for passing to that class's C<new>
1913 The attribute provided will be added to the class.
1915 Any accessor methods defined by the attribute will be added to the
1916 class when the attribute is added.
1918 If an attribute of the same name already exists, the old attribute
1919 will be removed first.
1921 =item B<< $metaclass->remove_attribute($attribute_name) >>
1923 This will remove the named attribute from the class, and
1924 L<Class::MOP::Attribute> object.
1926 Removing an attribute also removes any accessor methods defined by the
1929 However, note that removing an attribute will only affect I<future>
1930 object instances created for this class, not existing instances.
1932 =item B<< $metaclass->attribute_metaclass >>
1934 Returns the class name of the attribute metaclass for this class. By
1935 default, this is L<Class::MOP::Attribute>.
1939 =head2 Class Immutability
1941 Making a class immutable "freezes" the class definition. You can no
1942 longer call methods which alter the class, such as adding or removing
1943 methods or attributes.
1945 Making a class immutable lets us optimize the class by inlining some
1946 methods, and also allows us to optimize some methods on the metaclass
1949 After immutabilization, the metaclass object will cache most informational
1950 methods that returns information about methods or attributes. Methods which
1951 would alter the class, such as C<add_attribute> and C<add_method>, will
1952 throw an error on an immutable metaclass object.
1954 The immutabilization system in L<Moose> takes much greater advantage
1955 of the inlining features than Class::MOP itself does.
1959 =item B<< $metaclass->make_immutable(%options) >>
1961 This method will create an immutable transformer and use it to make
1962 the class and its metaclass object immutable.
1964 This method accepts the following options:
1968 =item * inline_accessors
1970 =item * inline_constructor
1972 =item * inline_destructor
1974 These are all booleans indicating whether the specified method(s)
1977 By default, accessors and the constructor are inlined, but not the
1980 =item * immutable_trait
1982 The name of a class which will be used as a parent class for the
1983 metaclass object being made immutable. This "trait" implements the
1984 post-immutability functionality of the metaclass (but not the
1985 transformation itself).
1987 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1989 =item * constructor_name
1991 This is the constructor method name. This defaults to "new".
1993 =item * constructor_class
1995 The name of the method metaclass for constructors. It will be used to
1996 generate the inlined constructor. This defaults to
1997 "Class::MOP::Method::Constructor".
1999 =item * replace_constructor
2001 This is a boolean indicating whether an existing constructor should be
2002 replaced when inlining a constructor. This defaults to false.
2004 =item * destructor_class
2006 The name of the method metaclass for destructors. It will be used to
2007 generate the inlined destructor. This defaults to
2008 "Class::MOP::Method::Denstructor".
2010 =item * replace_destructor
2012 This is a boolean indicating whether an existing destructor should be
2013 replaced when inlining a destructor. This defaults to false.
2017 =item B<< $metaclass->immutable_options >>
2019 Returns a hash of the options used when making the class immutable, including
2020 both defaults and anything supplied by the user in the call to C<<
2021 $metaclass->make_immutable >>. This is useful if you need to temporarily make
2022 a class mutable and then restore immutability as it was before.
2024 =item B<< $metaclass->make_mutable >>
2026 Calling this method reverse the immutabilization transformation.
2030 =head2 Method Modifiers
2032 Method modifiers are hooks which allow a method to be wrapped with
2033 I<before>, I<after> and I<around> method modifiers. Every time a
2034 method is called, its modifiers are also called.
2036 A class can modify its own methods, as well as methods defined in
2039 =head3 How method modifiers work?
2041 Method modifiers work by wrapping the original method and then
2042 replacing it in the class's symbol table. The wrappers will handle
2043 calling all the modifiers in the appropriate order and preserving the
2044 calling context for the original method.
2046 The return values of C<before> and C<after> modifiers are
2047 ignored. This is because their purpose is B<not> to filter the input
2048 and output of the primary method (this is done with an I<around>
2051 This may seem like an odd restriction to some, but doing this allows
2052 for simple code to be added at the beginning or end of a method call
2053 without altering the function of the wrapped method or placing any
2054 extra responsibility on the code of the modifier.
2056 Of course if you have more complex needs, you can use the C<around>
2057 modifier which allows you to change both the parameters passed to the
2058 wrapped method, as well as its return value.
2060 Before and around modifiers are called in last-defined-first-called
2061 order, while after modifiers are called in first-defined-first-called
2062 order. So the call tree might looks something like this:
2074 =head3 What is the performance impact?
2076 Of course there is a performance cost associated with method
2077 modifiers, but we have made every effort to make that cost directly
2078 proportional to the number of modifier features you use.
2080 The wrapping method does its best to B<only> do as much work as it
2081 absolutely needs to. In order to do this we have moved some of the
2082 performance costs to set-up time, where they are easier to amortize.
2084 All this said, our benchmarks have indicated the following:
2086 simple wrapper with no modifiers 100% slower
2087 simple wrapper with simple before modifier 400% slower
2088 simple wrapper with simple after modifier 450% slower
2089 simple wrapper with simple around modifier 500-550% slower
2090 simple wrapper with all 3 modifiers 1100% slower
2092 These numbers may seem daunting, but you must remember, every feature
2093 comes with some cost. To put things in perspective, just doing a
2094 simple C<AUTOLOAD> which does nothing but extract the name of the
2095 method called and return it costs about 400% over a normal method
2100 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
2102 This wraps the specified method with the supplied subroutine
2103 reference. The modifier will be called as a method itself, and will
2104 receive the same arguments as are passed to the method.
2106 When the modifier exits, the wrapped method will be called.
2108 The return value of the modifier will be ignored.
2110 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2112 This wraps the specified method with the supplied subroutine
2113 reference. The modifier will be called as a method itself, and will
2114 receive the same arguments as are passed to the method.
2116 When the wrapped methods exits, the modifier will be called.
2118 The return value of the modifier will be ignored.
2120 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2122 This wraps the specified method with the supplied subroutine
2125 The first argument passed to the modifier will be a subroutine
2126 reference to the wrapped method. The second argument is the object,
2127 and after that come any arguments passed when the method is called.
2129 The around modifier can choose to call the original method, as well as
2130 what arguments to pass if it does so.
2132 The return value of the modifier is what will be seen by the caller.
2136 =head2 Introspection
2140 =item B<< Class::MOP::Class->meta >>
2142 This will return a L<Class::MOP::Class> instance for this class.
2144 It should also be noted that L<Class::MOP> will actually bootstrap
2145 this module by installing a number of attribute meta-objects into its