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 { }
698 sub _eval_environment {
701 my @attrs = sort { $a->name cmp $b->name } $self->get_all_attributes;
703 my $defaults = [map { $_->default } @attrs];
706 '$defaults' => \$defaults,
711 sub get_meta_instance {
713 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
716 sub _create_meta_instance {
719 my $instance = $self->instance_metaclass->new(
720 associated_metaclass => $self,
721 attributes => [ $self->get_all_attributes() ],
724 $self->add_meta_instance_dependencies()
725 if $instance->is_dependent_on_superclasses();
730 # TODO: this is actually not being used!
731 sub _inline_rebless_instance {
734 return $self->get_meta_instance->inline_rebless_instance_structure(@_);
737 sub _inline_get_mop_slot {
740 return $self->get_meta_instance->_inline_get_mop_slot(@_);
743 sub _inline_set_mop_slot {
746 return $self->get_meta_instance->_inline_set_mop_slot(@_);
749 sub _inline_clear_mop_slot {
752 return $self->get_meta_instance->_inline_clear_mop_slot(@_);
757 my $instance = shift;
758 (blessed($instance) && $instance->isa($class->name))
759 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
762 # we need to protect the integrity of the
763 # Class::MOP::Class singletons here, they
764 # should not be cloned.
765 return $instance if $instance->isa('Class::MOP::Class');
766 $class->_clone_instance($instance, @_);
769 sub _clone_instance {
770 my ($class, $instance, %params) = @_;
772 || confess "You can only clone instances, ($instance) is not a blessed instance";
773 my $meta_instance = $class->get_meta_instance();
774 my $clone = $meta_instance->clone_instance($instance);
775 foreach my $attr ($class->get_all_attributes()) {
776 if ( defined( my $init_arg = $attr->init_arg ) ) {
777 if (exists $params{$init_arg}) {
778 $attr->set_value($clone, $params{$init_arg});
785 sub _force_rebless_instance {
786 my ($self, $instance, %params) = @_;
787 my $old_metaclass = Class::MOP::class_of($instance);
789 $old_metaclass->rebless_instance_away($instance, $self, %params)
792 my $meta_instance = $self->get_meta_instance;
794 if (Class::MOP::metaclass_is_weak($old_metaclass->name)) {
795 $meta_instance->_clear_mop_slot($instance);
799 # we use $_[1] here because of t/cmop/rebless_overload.t regressions
801 $meta_instance->rebless_instance_structure($_[1], $self);
803 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
805 if (Class::MOP::metaclass_is_weak($self->name)) {
806 $meta_instance->_set_mop_slot($instance, $self);
810 sub rebless_instance {
811 my ($self, $instance, %params) = @_;
812 my $old_metaclass = Class::MOP::class_of($instance);
814 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
815 $self->name->isa($old_class)
816 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
818 $self->_force_rebless_instance($_[1], %params);
823 sub rebless_instance_back {
824 my ( $self, $instance ) = @_;
825 my $old_metaclass = Class::MOP::class_of($instance);
828 = $old_metaclass ? $old_metaclass->name : blessed($instance);
829 $old_class->isa( $self->name )
831 "You may rebless only into a superclass of ($old_class), of which ("
835 $self->_force_rebless_instance($_[1]);
840 sub rebless_instance_away {
841 # this intentionally does nothing, it is just a hook
844 sub _fixup_attributes_after_rebless {
846 my ($instance, $rebless_from, %params) = @_;
847 my $meta_instance = $self->get_meta_instance;
849 for my $attr ( $rebless_from->get_all_attributes ) {
850 next if $self->find_attribute_by_name( $attr->name );
851 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
854 foreach my $attr ( $self->get_all_attributes ) {
855 if ( $attr->has_value($instance) ) {
856 if ( defined( my $init_arg = $attr->init_arg ) ) {
857 $params{$init_arg} = $attr->get_value($instance)
858 unless exists $params{$init_arg};
861 $attr->set_value($instance, $attr->get_value($instance));
866 foreach my $attr ($self->get_all_attributes) {
867 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
871 sub _attach_attribute {
872 my ($self, $attribute) = @_;
873 $attribute->attach_to_class($self);
876 sub _post_add_attribute {
877 my ( $self, $attribute ) = @_;
879 $self->invalidate_meta_instances;
881 # invalidate package flag here
884 $attribute->install_accessors;
887 $self->remove_attribute( $attribute->name );
892 sub remove_attribute {
895 my $removed_attribute = $self->SUPER::remove_attribute(@_)
898 $self->invalidate_meta_instances;
900 $removed_attribute->remove_accessors;
901 $removed_attribute->detach_from_class;
903 return$removed_attribute;
906 sub find_attribute_by_name {
907 my ( $self, $attr_name ) = @_;
909 foreach my $class ( $self->linearized_isa ) {
910 # fetch the meta-class ...
911 my $meta = Class::MOP::Class->initialize($class);
912 return $meta->get_attribute($attr_name)
913 if $meta->has_attribute($attr_name);
919 sub get_all_attributes {
921 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
922 reverse $self->linearized_isa;
923 return values %attrs;
931 my $isa = $self->get_or_add_package_symbol('@ISA');
938 # on 5.8 and below, we need to call
939 # a method to get Perl to detect
940 # a cycle in the class hierarchy
941 my $class = $self->name;
945 # we need to check the metaclass
946 # compatibility here so that we can
947 # be sure that the superclass is
948 # not potentially creating an issues
949 # we don't know about
951 $self->_check_metaclass_compatibility();
952 $self->_superclasses_updated();
958 sub _superclasses_updated {
960 $self->update_meta_instance_dependencies();
961 # keep strong references to all our parents, so they don't disappear if
962 # they are anon classes and don't have any direct instances
963 $self->_superclass_metas(
964 map { Class::MOP::class_of($_) } $self->superclasses
968 sub _superclass_metas {
970 $self->{_superclass_metas} = [@_];
975 my $super_class = $self->name;
977 return @{ $super_class->mro::get_isarev() };
980 sub direct_subclasses {
982 my $super_class = $self->name;
987 } Class::MOP::Class->initialize($_)->superclasses
992 return @{ mro::get_linear_isa( (shift)->name ) };
995 sub class_precedence_list {
997 my $name = $self->name;
999 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
1001 # We need to check for circular inheritance here
1002 # if we are are not on 5.10, cause 5.8 detects it
1003 # late. This will do nothing if all is well, and
1004 # blow up otherwise. Yes, it's an ugly hack, better
1005 # suggestions are welcome.
1007 ($name || return)->isa('This is a test for circular inheritance')
1010 # if our mro is c3, we can
1011 # just grab the linear_isa
1012 if (mro::get_mro($name) eq 'c3') {
1013 return @{ mro::get_linear_isa($name) }
1017 # we can't grab the linear_isa for dfs
1018 # since it has all the duplicates
1023 Class::MOP::Class->initialize($_)->class_precedence_list()
1024 } $self->superclasses()
1032 my $fetch_and_prepare_method = sub {
1033 my ($self, $method_name) = @_;
1034 my $wrapped_metaclass = $self->wrapped_method_metaclass;
1036 my $method = $self->get_method($method_name);
1037 # if we dont have local ...
1039 # try to find the next method
1040 $method = $self->find_next_method_by_name($method_name);
1041 # die if it does not exist
1043 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
1044 # and now make sure to wrap it
1045 # even if it is already wrapped
1046 # because we need a new sub ref
1047 $method = $wrapped_metaclass->wrap($method,
1048 package_name => $self->name,
1049 name => $method_name,
1053 # now make sure we wrap it properly
1054 $method = $wrapped_metaclass->wrap($method,
1055 package_name => $self->name,
1056 name => $method_name,
1057 ) unless $method->isa($wrapped_metaclass);
1059 $self->add_method($method_name => $method);
1063 sub add_before_method_modifier {
1064 my ($self, $method_name, $method_modifier) = @_;
1065 (defined $method_name && length $method_name)
1066 || confess "You must pass in a method name";
1067 my $method = $fetch_and_prepare_method->($self, $method_name);
1068 $method->add_before_modifier(
1069 subname(':before' => $method_modifier)
1073 sub add_after_method_modifier {
1074 my ($self, $method_name, $method_modifier) = @_;
1075 (defined $method_name && length $method_name)
1076 || confess "You must pass in a method name";
1077 my $method = $fetch_and_prepare_method->($self, $method_name);
1078 $method->add_after_modifier(
1079 subname(':after' => $method_modifier)
1083 sub add_around_method_modifier {
1084 my ($self, $method_name, $method_modifier) = @_;
1085 (defined $method_name && length $method_name)
1086 || confess "You must pass in a method name";
1087 my $method = $fetch_and_prepare_method->($self, $method_name);
1088 $method->add_around_modifier(
1089 subname(':around' => $method_modifier)
1094 # the methods above used to be named like this:
1095 # ${pkg}::${method}:(before|after|around)
1096 # but this proved problematic when using one modifier
1097 # to wrap multiple methods (something which is likely
1098 # to happen pretty regularly IMO). So instead of naming
1099 # it like this, I have chosen to just name them purely
1100 # with their modifier names, like so:
1101 # :(before|after|around)
1102 # The fact is that in a stack trace, it will be fairly
1103 # evident from the context what method they are attached
1104 # to, and so don't need the fully qualified name.
1107 sub find_method_by_name {
1108 my ($self, $method_name) = @_;
1109 (defined $method_name && length $method_name)
1110 || confess "You must define a method name to find";
1111 foreach my $class ($self->linearized_isa) {
1112 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1113 return $method if defined $method;
1118 sub get_all_methods {
1122 for my $class ( reverse $self->linearized_isa ) {
1123 my $meta = Class::MOP::Class->initialize($class);
1125 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1128 return values %methods;
1131 sub get_all_method_names {
1134 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
1137 sub find_all_methods_by_name {
1138 my ($self, $method_name) = @_;
1139 (defined $method_name && length $method_name)
1140 || confess "You must define a method name to find";
1142 foreach my $class ($self->linearized_isa) {
1143 # fetch the meta-class ...
1144 my $meta = Class::MOP::Class->initialize($class);
1146 name => $method_name,
1148 code => $meta->get_method($method_name)
1149 } if $meta->has_method($method_name);
1154 sub find_next_method_by_name {
1155 my ($self, $method_name) = @_;
1156 (defined $method_name && length $method_name)
1157 || confess "You must define a method name to find";
1158 my @cpl = $self->linearized_isa;
1159 shift @cpl; # discard ourselves
1160 foreach my $class (@cpl) {
1161 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1162 return $method if defined $method;
1167 sub update_meta_instance_dependencies {
1170 if ( $self->{meta_instance_dependencies} ) {
1171 return $self->add_meta_instance_dependencies;
1175 sub add_meta_instance_dependencies {
1178 $self->remove_meta_instance_dependencies;
1180 my @attrs = $self->get_all_attributes();
1183 my @classes = grep { not $seen{ $_->name }++ }
1184 map { $_->associated_class } @attrs;
1186 foreach my $class (@classes) {
1187 $class->add_dependent_meta_instance($self);
1190 $self->{meta_instance_dependencies} = \@classes;
1193 sub remove_meta_instance_dependencies {
1196 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1197 foreach my $class (@$classes) {
1198 $class->remove_dependent_meta_instance($self);
1208 sub add_dependent_meta_instance {
1209 my ( $self, $metaclass ) = @_;
1210 push @{ $self->{dependent_meta_instances} }, $metaclass;
1213 sub remove_dependent_meta_instance {
1214 my ( $self, $metaclass ) = @_;
1215 my $name = $metaclass->name;
1216 @$_ = grep { $_->name ne $name } @$_
1217 for $self->{dependent_meta_instances};
1220 sub invalidate_meta_instances {
1222 $_->invalidate_meta_instance()
1223 for $self, @{ $self->{dependent_meta_instances} };
1226 sub invalidate_meta_instance {
1228 undef $self->{_meta_instance};
1231 # check if we can reinitialize
1235 # if any local attr is defined
1236 return if $self->get_attribute_list;
1238 # or any non-declared methods
1239 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1240 return if $method->isa("Class::MOP::Method::Generated");
1241 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1249 sub is_mutable { 1 }
1250 sub is_immutable { 0 }
1252 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1254 sub _immutable_options {
1255 my ( $self, @args ) = @_;
1258 inline_accessors => 1,
1259 inline_constructor => 1,
1260 inline_destructor => 0,
1262 immutable_trait => $self->immutable_trait,
1263 constructor_name => $self->constructor_name,
1264 constructor_class => $self->constructor_class,
1265 destructor_class => $self->destructor_class,
1270 sub make_immutable {
1271 my ( $self, @args ) = @_;
1273 return unless $self->is_mutable;
1275 my ($file, $line) = (caller)[1..2];
1277 $self->_initialize_immutable(
1280 $self->_immutable_options(@args),
1282 $self->_rebless_as_immutable(@args);
1290 if ( $self->is_immutable ) {
1291 my @args = $self->immutable_options;
1292 $self->_rebless_as_mutable();
1293 $self->_remove_inlined_code(@args);
1294 delete $self->{__immutable};
1302 sub _rebless_as_immutable {
1303 my ( $self, @args ) = @_;
1305 $self->{__immutable}{original_class} = ref $self;
1307 bless $self => $self->_immutable_metaclass(@args);
1310 sub _immutable_metaclass {
1311 my ( $self, %args ) = @_;
1313 if ( my $class = $args{immutable_metaclass} ) {
1317 my $trait = $args{immutable_trait} = $self->immutable_trait
1318 || confess "no immutable trait specified for $self";
1320 my $meta = $self->meta;
1321 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1325 if ( $meta_attr and $trait eq $meta_attr->default ) {
1326 # if the trait is the same as the default we try and pick a
1327 # predictable name for the immutable metaclass
1328 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1331 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1332 $trait, 'ForMetaClass', ref($self);
1336 if Class::MOP::is_class_loaded($class_name);
1338 # If the metaclass is a subclass of CMOP::Class which has had
1339 # metaclass roles applied (via Moose), then we want to make sure
1340 # that we preserve that anonymous class (see Fey::ORM for an
1341 # example of where this matters).
1342 my $meta_name = $meta->_real_ref_name;
1344 my $immutable_meta = $meta_name->create(
1346 superclasses => [ ref $self ],
1349 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1351 $immutable_meta->make_immutable(
1352 inline_constructor => 0,
1353 inline_accessors => 0,
1359 sub _remove_inlined_code {
1362 $self->remove_method( $_->name ) for $self->_inlined_methods;
1364 delete $self->{__immutable}{inlined_methods};
1367 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1369 sub _add_inlined_method {
1370 my ( $self, $method ) = @_;
1372 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1375 sub _initialize_immutable {
1376 my ( $self, %args ) = @_;
1378 $self->{__immutable}{options} = \%args;
1379 $self->_install_inlined_code(%args);
1382 sub _install_inlined_code {
1383 my ( $self, %args ) = @_;
1386 $self->_inline_accessors(%args) if $args{inline_accessors};
1387 $self->_inline_constructor(%args) if $args{inline_constructor};
1388 $self->_inline_destructor(%args) if $args{inline_destructor};
1391 sub _rebless_as_mutable {
1394 bless $self, $self->_get_mutable_metaclass_name;
1399 sub _inline_accessors {
1402 foreach my $attr_name ( $self->get_attribute_list ) {
1403 $self->get_attribute($attr_name)->install_accessors(1);
1407 sub _inline_constructor {
1408 my ( $self, %args ) = @_;
1410 my $name = $args{constructor_name};
1411 # A class may not even have a constructor, and that's okay.
1412 return unless defined $name;
1414 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1415 my $class = $self->name;
1416 warn "Not inlining a constructor for $class since it defines"
1417 . " its own constructor.\n"
1418 . "If you are certain you don't need to inline your"
1419 . " constructor, specify inline_constructor => 0 in your"
1420 . " call to $class->meta->make_immutable\n";
1424 my $constructor_class = $args{constructor_class};
1426 Class::MOP::load_class($constructor_class);
1428 my $constructor = $constructor_class->new(
1432 package_name => $self->name,
1434 definition_context => {
1435 description => "constructor " . $self->name . "::" . $name,
1436 file => $args{file},
1437 line => $args{line},
1441 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1442 $self->add_method( $name => $constructor );
1443 $self->_add_inlined_method($constructor);
1447 sub _inline_destructor {
1448 my ( $self, %args ) = @_;
1450 ( exists $args{destructor_class} && defined $args{destructor_class} )
1451 || confess "The 'inline_destructor' option is present, but "
1452 . "no destructor class was specified";
1454 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1455 my $class = $self->name;
1456 warn "Not inlining a destructor for $class since it defines"
1457 . " its own destructor.\n";
1461 my $destructor_class = $args{destructor_class};
1463 Class::MOP::load_class($destructor_class);
1465 return unless $destructor_class->is_needed($self);
1467 my $destructor = $destructor_class->new(
1470 package_name => $self->name,
1472 definition_context => {
1473 description => "destructor " . $self->name . "::DESTROY",
1474 file => $args{file},
1475 line => $args{line},
1479 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1480 $self->add_method( 'DESTROY' => $destructor );
1481 $self->_add_inlined_method($destructor);
1487 # ABSTRACT: Class Meta Object
1495 # assuming that class Foo
1496 # has been defined, you can
1498 # use this for introspection ...
1500 # add a method to Foo ...
1501 Foo->meta->add_method( 'bar' => sub {...} )
1503 # get a list of all the classes searched
1504 # the method dispatcher in the correct order
1505 Foo->meta->class_precedence_list()
1507 # remove a method from Foo
1508 Foo->meta->remove_method('bar');
1510 # or use this to actually create classes ...
1512 Class::MOP::Class->create(
1515 superclasses => ['Foo'],
1517 Class::MOP::Attribute->new('$bar'),
1518 Class::MOP::Attribute->new('$baz'),
1521 calculate_bar => sub {...},
1522 construct_baz => sub {...}
1529 The Class Protocol is the largest and most complex part of the
1530 Class::MOP meta-object protocol. It controls the introspection and
1531 manipulation of Perl 5 classes, and it can create them as well. The
1532 best way to understand what this module can do is to read the
1533 documentation for each of its methods.
1537 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1541 =head2 Class construction
1543 These methods all create new C<Class::MOP::Class> objects. These
1544 objects can represent existing classes or they can be used to create
1545 new classes from scratch.
1547 The metaclass object for a given class is a singleton. If you attempt
1548 to create a metaclass for the same class twice, you will just get the
1553 =item B<< Class::MOP::Class->create($package_name, %options) >>
1555 This method creates a new C<Class::MOP::Class> object with the given
1556 package name. It accepts a number of options:
1562 An optional version number for the newly created package.
1566 An optional authority for the newly created package.
1568 =item * superclasses
1570 An optional array reference of superclass names.
1574 An optional hash reference of methods for the class. The keys of the
1575 hash reference are method names and values are subroutine references.
1579 An optional array reference of L<Class::MOP::Attribute> objects.
1583 Specifies the name to install the C<meta> method for this class under.
1584 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1585 given, no meta method will be installed.
1589 If true, the metaclass that is stored in the global cache will be a
1592 Classes created in this way are destroyed once the metaclass they are
1593 attached to goes out of scope, and will be removed from Perl's internal
1596 All instances of a class with a weakened metaclass keep a special
1597 reference to the metaclass object, which prevents the metaclass from
1598 going out of scope while any instances exist.
1600 This only works if the instance is based on a hash reference, however.
1604 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1606 This method works just like C<< Class::MOP::Class->create >> but it
1607 creates an "anonymous" class. In fact, the class does have a name, but
1608 that name is a unique name generated internally by this module.
1610 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1611 parameters that C<create> accepts.
1613 Anonymous classes default to C<< weaken => 1 >>, although this can be
1616 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1618 This method will initialize a C<Class::MOP::Class> object for the
1619 named package. Unlike C<create>, this method I<will not> create a new
1622 The purpose of this method is to retrieve a C<Class::MOP::Class>
1623 object for introspecting an existing class.
1625 If an existing C<Class::MOP::Class> object exists for the named
1626 package, it will be returned, and any options provided will be
1629 If the object does not yet exist, it will be created.
1631 The valid options that can be passed to this method are
1632 C<attribute_metaclass>, C<method_metaclass>,
1633 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1634 optional, and default to the appropriate class in the C<Class::MOP>
1639 =head2 Object instance construction and cloning
1641 These methods are all related to creating and/or cloning object
1646 =item B<< $metaclass->clone_object($instance, %params) >>
1648 This method clones an existing object instance. Any parameters you
1649 provide are will override existing attribute values in the object.
1651 This is a convenience method for cloning an object instance, then
1652 blessing it into the appropriate package.
1654 You could implement a clone method in your class, using this method:
1657 my ($self, %params) = @_;
1658 $self->meta->clone_object($self, %params);
1661 =item B<< $metaclass->rebless_instance($instance, %params) >>
1663 This method changes the class of C<$instance> to the metaclass's class.
1665 You can only rebless an instance into a subclass of its current
1666 class. If you pass any additional parameters, these will be treated
1667 like constructor parameters and used to initialize the object's
1668 attributes. Any existing attributes that are already set will be
1671 Before reblessing the instance, this method will call
1672 C<rebless_instance_away> on the instance's current metaclass. This method
1673 will be passed the instance, the new metaclass, and any parameters
1674 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1675 does nothing; it is merely a hook.
1677 =item B<< $metaclass->rebless_instance_back($instance) >>
1679 Does the same thing as C<rebless_instance>, except that you can only
1680 rebless an instance into one of its superclasses. Any attributes that
1681 do not exist in the superclass will be deinitialized.
1683 This is a much more dangerous operation than C<rebless_instance>,
1684 especially when multiple inheritance is involved, so use this carefully!
1686 =item B<< $metaclass->new_object(%params) >>
1688 This method is used to create a new object of the metaclass's
1689 class. Any parameters you provide are used to initialize the
1690 instance's attributes. A special C<__INSTANCE__> key can be passed to
1691 provide an already generated instance, rather than having Class::MOP
1692 generate it for you. This is mostly useful for using Class::MOP with
1693 foreign classes which generate instances using their own constructors.
1695 =item B<< $metaclass->instance_metaclass >>
1697 Returns the class name of the instance metaclass. See
1698 L<Class::MOP::Instance> for more information on the instance
1701 =item B<< $metaclass->get_meta_instance >>
1703 Returns an instance of the C<instance_metaclass> to be used in the
1704 construction of a new instance of the class.
1708 =head2 Informational predicates
1710 These are a few predicate methods for asking information about the
1715 =item B<< $metaclass->is_anon_class >>
1717 This returns true if the class was created by calling C<<
1718 Class::MOP::Class->create_anon_class >>.
1720 =item B<< $metaclass->is_mutable >>
1722 This returns true if the class is still mutable.
1724 =item B<< $metaclass->is_immutable >>
1726 This returns true if the class has been made immutable.
1728 =item B<< $metaclass->is_pristine >>
1730 A class is I<not> pristine if it has non-inherited attributes or if it
1731 has any generated methods.
1735 =head2 Inheritance Relationships
1739 =item B<< $metaclass->superclasses(@superclasses) >>
1741 This is a read-write accessor which represents the superclass
1742 relationships of the metaclass's class.
1744 This is basically sugar around getting and setting C<@ISA>.
1746 =item B<< $metaclass->class_precedence_list >>
1748 This returns a list of all of the class's ancestor classes. The
1749 classes are returned in method dispatch order.
1751 =item B<< $metaclass->linearized_isa >>
1753 This returns a list based on C<class_precedence_list> but with all
1756 =item B<< $metaclass->subclasses >>
1758 This returns a list of all subclasses for this class, even indirect
1761 =item B<< $metaclass->direct_subclasses >>
1763 This returns a list of immediate subclasses for this class, which does not
1764 include indirect subclasses.
1768 =head2 Method introspection and creation
1770 These methods allow you to introspect a class's methods, as well as
1771 add, remove, or change methods.
1773 Determining what is truly a method in a Perl 5 class requires some
1774 heuristics (aka guessing).
1776 Methods defined outside the package with a fully qualified name (C<sub
1777 Package::name { ... }>) will be included. Similarly, methods named
1778 with a fully qualified name using L<Sub::Name> are also included.
1780 However, we attempt to ignore imported functions.
1782 Ultimately, we are using heuristics to determine what truly is a
1783 method in a class, and these heuristics may get the wrong answer in
1784 some edge cases. However, for most "normal" cases the heuristics work
1789 =item B<< $metaclass->get_method($method_name) >>
1791 This will return a L<Class::MOP::Method> for the specified
1792 C<$method_name>. If the class does not have the specified method, it
1795 =item B<< $metaclass->has_method($method_name) >>
1797 Returns a boolean indicating whether or not the class defines the
1798 named method. It does not include methods inherited from parent
1801 =item B<< $metaclass->get_method_list >>
1803 This will return a list of method I<names> for all methods defined in
1806 =item B<< $metaclass->add_method($method_name, $method) >>
1808 This method takes a method name and a subroutine reference, and adds
1809 the method to the class.
1811 The subroutine reference can be a L<Class::MOP::Method>, and you are
1812 strongly encouraged to pass a meta method object instead of a code
1813 reference. If you do so, that object gets stored as part of the
1814 class's method map directly. If not, the meta information will have to
1815 be recreated later, and may be incorrect.
1817 If you provide a method object, this method will clone that object if
1818 the object's package name does not match the class name. This lets us
1819 track the original source of any methods added from other classes
1820 (notably Moose roles).
1822 =item B<< $metaclass->remove_method($method_name) >>
1824 Remove the named method from the class. This method returns the
1825 L<Class::MOP::Method> object for the method.
1827 =item B<< $metaclass->method_metaclass >>
1829 Returns the class name of the method metaclass, see
1830 L<Class::MOP::Method> for more information on the method metaclass.
1832 =item B<< $metaclass->wrapped_method_metaclass >>
1834 Returns the class name of the wrapped method metaclass, see
1835 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1838 =item B<< $metaclass->get_all_methods >>
1840 This will traverse the inheritance hierarchy and return a list of all
1841 the L<Class::MOP::Method> objects for this class and its parents.
1843 =item B<< $metaclass->find_method_by_name($method_name) >>
1845 This will return a L<Class::MOP::Method> for the specified
1846 C<$method_name>. If the class does not have the specified method, it
1849 Unlike C<get_method>, this method I<will> look for the named method in
1852 =item B<< $metaclass->get_all_method_names >>
1854 This will return a list of method I<names> for all of this class's
1855 methods, including inherited methods.
1857 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1859 This method looks for the named method in the class and all of its
1860 parents. It returns every matching method it finds in the inheritance
1861 tree, so it returns a list of methods.
1863 Each method is returned as a hash reference with three keys. The keys
1864 are C<name>, C<class>, and C<code>. The C<code> key has a
1865 L<Class::MOP::Method> object as its value.
1867 The list of methods is distinct.
1869 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1871 This method returns the first method in any superclass matching the
1872 given name. It is effectively the method that C<SUPER::$method_name>
1877 =head2 Attribute introspection and creation
1879 Because Perl 5 does not have a core concept of attributes in classes,
1880 we can only return information about attributes which have been added
1881 via this class's methods. We cannot discover information about
1882 attributes which are defined in terms of "regular" Perl 5 methods.
1886 =item B<< $metaclass->get_attribute($attribute_name) >>
1888 This will return a L<Class::MOP::Attribute> for the specified
1889 C<$attribute_name>. If the class does not have the specified
1890 attribute, it returns C<undef>.
1892 NOTE that get_attribute does not search superclasses, for that you
1893 need to use C<find_attribute_by_name>.
1895 =item B<< $metaclass->has_attribute($attribute_name) >>
1897 Returns a boolean indicating whether or not the class defines the
1898 named attribute. It does not include attributes inherited from parent
1901 =item B<< $metaclass->get_attribute_list >>
1903 This will return a list of attributes I<names> for all attributes
1904 defined in this class. Note that this operates on the current class
1905 only, it does not traverse the inheritance hierarchy.
1907 =item B<< $metaclass->get_all_attributes >>
1909 This will traverse the inheritance hierarchy and return a list of all
1910 the L<Class::MOP::Attribute> objects for this class and its parents.
1912 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1914 This will return a L<Class::MOP::Attribute> for the specified
1915 C<$attribute_name>. If the class does not have the specified
1916 attribute, it returns C<undef>.
1918 Unlike C<get_attribute>, this attribute I<will> look for the named
1919 attribute in superclasses.
1921 =item B<< $metaclass->add_attribute(...) >>
1923 This method accepts either an existing L<Class::MOP::Attribute>
1924 object or parameters suitable for passing to that class's C<new>
1927 The attribute provided will be added to the class.
1929 Any accessor methods defined by the attribute will be added to the
1930 class when the attribute is added.
1932 If an attribute of the same name already exists, the old attribute
1933 will be removed first.
1935 =item B<< $metaclass->remove_attribute($attribute_name) >>
1937 This will remove the named attribute from the class, and
1938 L<Class::MOP::Attribute> object.
1940 Removing an attribute also removes any accessor methods defined by the
1943 However, note that removing an attribute will only affect I<future>
1944 object instances created for this class, not existing instances.
1946 =item B<< $metaclass->attribute_metaclass >>
1948 Returns the class name of the attribute metaclass for this class. By
1949 default, this is L<Class::MOP::Attribute>.
1953 =head2 Class Immutability
1955 Making a class immutable "freezes" the class definition. You can no
1956 longer call methods which alter the class, such as adding or removing
1957 methods or attributes.
1959 Making a class immutable lets us optimize the class by inlining some
1960 methods, and also allows us to optimize some methods on the metaclass
1963 After immutabilization, the metaclass object will cache most informational
1964 methods that returns information about methods or attributes. Methods which
1965 would alter the class, such as C<add_attribute> and C<add_method>, will
1966 throw an error on an immutable metaclass object.
1968 The immutabilization system in L<Moose> takes much greater advantage
1969 of the inlining features than Class::MOP itself does.
1973 =item B<< $metaclass->make_immutable(%options) >>
1975 This method will create an immutable transformer and use it to make
1976 the class and its metaclass object immutable.
1978 This method accepts the following options:
1982 =item * inline_accessors
1984 =item * inline_constructor
1986 =item * inline_destructor
1988 These are all booleans indicating whether the specified method(s)
1991 By default, accessors and the constructor are inlined, but not the
1994 =item * immutable_trait
1996 The name of a class which will be used as a parent class for the
1997 metaclass object being made immutable. This "trait" implements the
1998 post-immutability functionality of the metaclass (but not the
1999 transformation itself).
2001 This defaults to L<Class::MOP::Class::Immutable::Trait>.
2003 =item * constructor_name
2005 This is the constructor method name. This defaults to "new".
2007 =item * constructor_class
2009 The name of the method metaclass for constructors. It will be used to
2010 generate the inlined constructor. This defaults to
2011 "Class::MOP::Method::Constructor".
2013 =item * replace_constructor
2015 This is a boolean indicating whether an existing constructor should be
2016 replaced when inlining a constructor. This defaults to false.
2018 =item * destructor_class
2020 The name of the method metaclass for destructors. It will be used to
2021 generate the inlined destructor. This defaults to
2022 "Class::MOP::Method::Denstructor".
2024 =item * replace_destructor
2026 This is a boolean indicating whether an existing destructor should be
2027 replaced when inlining a destructor. This defaults to false.
2031 =item B<< $metaclass->immutable_options >>
2033 Returns a hash of the options used when making the class immutable, including
2034 both defaults and anything supplied by the user in the call to C<<
2035 $metaclass->make_immutable >>. This is useful if you need to temporarily make
2036 a class mutable and then restore immutability as it was before.
2038 =item B<< $metaclass->make_mutable >>
2040 Calling this method reverse the immutabilization transformation.
2044 =head2 Method Modifiers
2046 Method modifiers are hooks which allow a method to be wrapped with
2047 I<before>, I<after> and I<around> method modifiers. Every time a
2048 method is called, its modifiers are also called.
2050 A class can modify its own methods, as well as methods defined in
2053 =head3 How method modifiers work?
2055 Method modifiers work by wrapping the original method and then
2056 replacing it in the class's symbol table. The wrappers will handle
2057 calling all the modifiers in the appropriate order and preserving the
2058 calling context for the original method.
2060 The return values of C<before> and C<after> modifiers are
2061 ignored. This is because their purpose is B<not> to filter the input
2062 and output of the primary method (this is done with an I<around>
2065 This may seem like an odd restriction to some, but doing this allows
2066 for simple code to be added at the beginning or end of a method call
2067 without altering the function of the wrapped method or placing any
2068 extra responsibility on the code of the modifier.
2070 Of course if you have more complex needs, you can use the C<around>
2071 modifier which allows you to change both the parameters passed to the
2072 wrapped method, as well as its return value.
2074 Before and around modifiers are called in last-defined-first-called
2075 order, while after modifiers are called in first-defined-first-called
2076 order. So the call tree might looks something like this:
2088 =head3 What is the performance impact?
2090 Of course there is a performance cost associated with method
2091 modifiers, but we have made every effort to make that cost directly
2092 proportional to the number of modifier features you use.
2094 The wrapping method does its best to B<only> do as much work as it
2095 absolutely needs to. In order to do this we have moved some of the
2096 performance costs to set-up time, where they are easier to amortize.
2098 All this said, our benchmarks have indicated the following:
2100 simple wrapper with no modifiers 100% slower
2101 simple wrapper with simple before modifier 400% slower
2102 simple wrapper with simple after modifier 450% slower
2103 simple wrapper with simple around modifier 500-550% slower
2104 simple wrapper with all 3 modifiers 1100% slower
2106 These numbers may seem daunting, but you must remember, every feature
2107 comes with some cost. To put things in perspective, just doing a
2108 simple C<AUTOLOAD> which does nothing but extract the name of the
2109 method called and return it costs about 400% over a normal method
2114 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
2116 This wraps the specified method with the supplied subroutine
2117 reference. The modifier will be called as a method itself, and will
2118 receive the same arguments as are passed to the method.
2120 When the modifier exits, the wrapped method will be called.
2122 The return value of the modifier will be ignored.
2124 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2126 This wraps the specified method with the supplied subroutine
2127 reference. The modifier will be called as a method itself, and will
2128 receive the same arguments as are passed to the method.
2130 When the wrapped methods exits, the modifier will be called.
2132 The return value of the modifier will be ignored.
2134 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2136 This wraps the specified method with the supplied subroutine
2139 The first argument passed to the modifier will be a subroutine
2140 reference to the wrapped method. The second argument is the object,
2141 and after that come any arguments passed when the method is called.
2143 The around modifier can choose to call the original method, as well as
2144 what arguments to pass if it does so.
2146 The return value of the modifier is what will be seen by the caller.
2150 =head2 Introspection
2154 =item B<< Class::MOP::Class->meta >>
2156 This will return a L<Class::MOP::Class> instance for this class.
2158 It should also be noted that L<Class::MOP> will actually bootstrap
2159 this module by installing a number of attribute meta-objects into its