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';
16 use Devel::GlobalDestruction 'in_global_destruction';
18 use List::MoreUtils 'all';
20 use base 'Class::MOP::Module',
21 'Class::MOP::Mixin::HasAttributes',
22 'Class::MOP::Mixin::HasMethods';
32 $package_name = shift;
35 $package_name = $options{package};
38 ($package_name && !ref($package_name))
39 || confess "You must pass a package name and it cannot be blessed";
41 return Class::MOP::get_metaclass_by_name($package_name)
42 || $class->_construct_class_instance(package => $package_name, @_);
46 my ( $class, @args ) = @_;
47 unshift @args, "package" if @args % 2;
49 my $old_metaclass = blessed($options{package})
51 : Class::MOP::get_metaclass_by_name($options{package});
52 $options{weaken} = Class::MOP::metaclass_is_weak($old_metaclass->name)
53 if !exists $options{weaken}
54 && blessed($old_metaclass)
55 && $old_metaclass->isa('Class::MOP::Class');
56 $old_metaclass->_remove_generated_metaobjects
57 if $old_metaclass && $old_metaclass->isa('Class::MOP::Class');
58 my $new_metaclass = $class->SUPER::reinitialize(%options);
59 $new_metaclass->_restore_metaobjects_from($old_metaclass)
60 if $old_metaclass && $old_metaclass->isa('Class::MOP::Class');
61 return $new_metaclass;
64 # NOTE: (meta-circularity)
65 # this is a special form of _construct_instance
66 # (see below), which is used to construct class
67 # meta-object instances for any Class::MOP::*
68 # class. All other classes will use the more
69 # normal &construct_instance.
70 sub _construct_class_instance {
72 my $options = @_ == 1 ? $_[0] : {@_};
73 my $package_name = $options->{package};
74 (defined $package_name && $package_name)
75 || confess "You must pass a package name";
77 # return the metaclass if we have it cached,
78 # and it is still defined (it has not been
79 # reaped by DESTROY yet, which can happen
80 # annoyingly enough during global destruction)
82 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
88 ? $class->_real_ref_name
91 # now create the metaclass
93 if ($class eq 'Class::MOP::Class') {
94 $meta = $class->_new($options);
98 # it is safe to use meta here because
99 # class will always be a subclass of
100 # Class::MOP::Class, which defines meta
101 $meta = $class->meta->_construct_instance($options)
104 # and check the metaclass compatibility
105 $meta->_check_metaclass_compatibility();
107 Class::MOP::store_metaclass_by_name($package_name, $meta);
110 # we need to weaken any anon classes
111 # so that they can call DESTROY properly
112 Class::MOP::weaken_metaclass($package_name) if $options->{weaken};
120 # NOTE: we need to deal with the possibility of class immutability here,
121 # and then get the name of the class appropriately
122 return $self->is_immutable
123 ? $self->_get_mutable_metaclass_name()
130 return Class::MOP::Class->initialize($class)->new_object(@_)
131 if $class ne __PACKAGE__;
133 my $options = @_ == 1 ? $_[0] : {@_};
136 # inherited from Class::MOP::Package
137 'package' => $options->{package},
140 # since the following attributes will
141 # actually be loaded from the symbol
142 # table, and actually bypass the instance
143 # entirely, we can just leave these things
144 # listed here for reference, because they
145 # should not actually have a value associated
147 'namespace' => \undef,
150 # inherited from Class::MOP::Module
152 'authority' => \undef,
154 # defined in Class::MOP::Class
155 'superclasses' => \undef,
158 'attribute_metaclass' =>
159 ( $options->{'attribute_metaclass'} || 'Class::MOP::Attribute' ),
160 'method_metaclass' =>
161 ( $options->{'method_metaclass'} || 'Class::MOP::Method' ),
162 'wrapped_method_metaclass' => (
163 $options->{'wrapped_method_metaclass'}
164 || 'Class::MOP::Method::Wrapped'
166 'instance_metaclass' =>
167 ( $options->{'instance_metaclass'} || 'Class::MOP::Instance' ),
168 'immutable_trait' => (
169 $options->{'immutable_trait'}
170 || 'Class::MOP::Class::Immutable::Trait'
172 'constructor_name' => ( $options->{constructor_name} || 'new' ),
173 'constructor_class' => (
174 $options->{constructor_class} || 'Class::MOP::Method::Constructor'
176 'destructor_class' => $options->{destructor_class},
180 ## Metaclass compatibility
182 my %base_metaclass = (
183 attribute_metaclass => 'Class::MOP::Attribute',
184 method_metaclass => 'Class::MOP::Method',
185 wrapped_method_metaclass => 'Class::MOP::Method::Wrapped',
186 instance_metaclass => 'Class::MOP::Instance',
187 constructor_class => 'Class::MOP::Method::Constructor',
188 destructor_class => 'Class::MOP::Method::Destructor',
191 sub _base_metaclasses { %base_metaclass }
194 sub _check_metaclass_compatibility {
197 my @superclasses = $self->superclasses
200 $self->_fix_metaclass_incompatibility(@superclasses);
202 my %base_metaclass = $self->_base_metaclasses;
204 # this is always okay ...
206 if ref($self) eq 'Class::MOP::Class'
208 my $meta = $self->$_;
209 !defined($meta) || $meta eq $base_metaclass{$_};
211 keys %base_metaclass;
213 for my $superclass (@superclasses) {
214 $self->_check_class_metaclass_compatibility($superclass);
217 for my $metaclass_type ( keys %base_metaclass ) {
218 next unless defined $self->$metaclass_type;
219 for my $superclass (@superclasses) {
220 $self->_check_single_metaclass_compatibility( $metaclass_type,
226 sub _check_class_metaclass_compatibility {
228 my ( $superclass_name ) = @_;
230 if (!$self->_class_metaclass_is_compatible($superclass_name)) {
231 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
233 my $super_meta_type = $super_meta->_real_ref_name;
235 confess "The metaclass of " . $self->name . " ("
236 . (ref($self)) . ")" . " is not compatible with "
237 . "the metaclass of its superclass, "
238 . $superclass_name . " (" . ($super_meta_type) . ")";
242 sub _class_metaclass_is_compatible {
244 my ( $superclass_name ) = @_;
246 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
249 my $super_meta_name = $super_meta->_real_ref_name;
251 return $self->_is_compatible_with($super_meta_name);
254 sub _check_single_metaclass_compatibility {
256 my ( $metaclass_type, $superclass_name ) = @_;
258 if (!$self->_single_metaclass_is_compatible($metaclass_type, $superclass_name)) {
259 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
260 my $metaclass_type_name = $metaclass_type;
261 $metaclass_type_name =~ s/_(?:meta)?class$//;
262 $metaclass_type_name =~ s/_/ /g;
263 confess "The $metaclass_type_name metaclass for "
264 . $self->name . " (" . ($self->$metaclass_type)
265 . ")" . " is not compatible with the "
266 . "$metaclass_type_name metaclass of its "
267 . "superclass, $superclass_name ("
268 . ($super_meta->$metaclass_type) . ")";
272 sub _single_metaclass_is_compatible {
274 my ( $metaclass_type, $superclass_name ) = @_;
276 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
279 # for instance, Moose::Meta::Class has a error_class attribute, but
280 # Class::MOP::Class doesn't - this shouldn't be an error
281 return 1 unless $super_meta->can($metaclass_type);
282 # for instance, Moose::Meta::Class has a destructor_class, but
283 # Class::MOP::Class doesn't - this shouldn't be an error
284 return 1 unless defined $super_meta->$metaclass_type;
285 # if metaclass is defined in superclass but not here, it's not compatible
286 # this is a really odd case
287 return 0 unless defined $self->$metaclass_type;
289 return $self->$metaclass_type->_is_compatible_with($super_meta->$metaclass_type);
292 sub _fix_metaclass_incompatibility {
294 my @supers = map { Class::MOP::Class->initialize($_) } @_;
297 for my $super (@supers) {
299 if $self->_can_fix_metaclass_incompatibility($super);
301 return unless $necessary;
303 for my $super (@supers) {
304 if (!$self->_class_metaclass_is_compatible($super->name)) {
305 $self->_fix_class_metaclass_incompatibility($super);
309 my %base_metaclass = $self->_base_metaclasses;
310 for my $metaclass_type (keys %base_metaclass) {
311 for my $super (@supers) {
312 if (!$self->_single_metaclass_is_compatible($metaclass_type, $super->name)) {
313 $self->_fix_single_metaclass_incompatibility(
314 $metaclass_type, $super
321 sub _can_fix_metaclass_incompatibility {
323 my ($super_meta) = @_;
325 return 1 if $self->_class_metaclass_can_be_made_compatible($super_meta);
327 my %base_metaclass = $self->_base_metaclasses;
328 for my $metaclass_type (keys %base_metaclass) {
329 return 1 if $self->_single_metaclass_can_be_made_compatible($super_meta, $metaclass_type);
335 sub _class_metaclass_can_be_made_compatible {
337 my ($super_meta) = @_;
339 return $self->_can_be_made_compatible_with($super_meta->_real_ref_name);
342 sub _single_metaclass_can_be_made_compatible {
344 my ($super_meta, $metaclass_type) = @_;
346 my $specific_meta = $self->$metaclass_type;
348 return unless $super_meta->can($metaclass_type);
349 my $super_specific_meta = $super_meta->$metaclass_type;
351 # for instance, Moose::Meta::Class has a destructor_class, but
352 # Class::MOP::Class doesn't - this shouldn't be an error
353 return unless defined $super_specific_meta;
355 # if metaclass is defined in superclass but not here, it's fixable
356 # this is a really odd case
357 return 1 unless defined $specific_meta;
359 return 1 if $specific_meta->_can_be_made_compatible_with($super_specific_meta);
362 sub _fix_class_metaclass_incompatibility {
364 my ( $super_meta ) = @_;
366 if ($self->_class_metaclass_can_be_made_compatible($super_meta)) {
368 || confess "Can't fix metaclass incompatibility for "
370 . " because it is not pristine.";
372 my $super_meta_name = $super_meta->_real_ref_name;
374 $self->_make_compatible_with($super_meta_name);
378 sub _fix_single_metaclass_incompatibility {
380 my ( $metaclass_type, $super_meta ) = @_;
382 if ($self->_single_metaclass_can_be_made_compatible($super_meta, $metaclass_type)) {
384 || confess "Can't fix metaclass incompatibility for "
386 . " because it is not pristine.";
388 my $new_metaclass = $self->$metaclass_type
389 ? $self->$metaclass_type->_get_compatible_metaclass($super_meta->$metaclass_type)
390 : $super_meta->$metaclass_type;
391 $self->{$metaclass_type} = $new_metaclass;
395 sub _restore_metaobjects_from {
399 $self->_restore_metamethods_from($old_meta);
400 $self->_restore_metaattributes_from($old_meta);
403 sub _remove_generated_metaobjects {
406 for my $attr (map { $self->get_attribute($_) } $self->get_attribute_list) {
407 $attr->remove_accessors;
415 # this should be sufficient, if you have a
416 # use case where it is not, write a test and
418 my $ANON_CLASS_SERIAL = 0;
421 # we need a sufficiently annoying prefix
422 # this should suffice for now, this is
423 # used in a couple of places below, so
424 # need to put it up here for now.
425 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
429 no warnings 'uninitialized';
430 $self->name =~ /^$ANON_CLASS_PREFIX/o;
433 sub create_anon_class {
434 my ($class, %options) = @_;
435 $options{weaken} = 1 unless exists $options{weaken};
436 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
437 return $class->create($package_name, %options);
441 # this will only get called for
442 # anon-classes, all other calls
443 # are assumed to occur during
444 # global destruction and so don't
445 # really need to be handled explicitly
449 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
451 $self->free_anon_class
452 if $self->is_anon_class;
455 sub free_anon_class {
457 my $name = $self->name;
459 # Moose does a weird thing where it replaces the metaclass for
460 # class when fixing metaclass incompatibility. In that case,
461 # we don't want to clean out the namespace now. We can detect
462 # that because Moose will explicitly update the singleton
463 # cache in Class::MOP.
464 my $current_meta = Class::MOP::get_metaclass_by_name($name);
465 return if $current_meta ne $self;
467 my ($first_fragments, $last_fragment) = ($name =~ /^(.*)::(.*)$/);
470 @{$name . '::ISA'} = ();
471 %{$name . '::'} = ();
472 delete ${$first_fragments . '::'}{$last_fragment . '::'};
474 Class::MOP::remove_metaclass_by_name($name);
479 # creating classes with MOP ...
482 my ( $class, @args ) = @_;
484 unshift @args, 'package' if @args % 2 == 1;
486 my (%options) = @args;
487 my $package_name = $options{package};
489 (ref $options{superclasses} eq 'ARRAY')
490 || confess "You must pass an ARRAY ref of superclasses"
491 if exists $options{superclasses};
493 (ref $options{attributes} eq 'ARRAY')
494 || confess "You must pass an ARRAY ref of attributes"
495 if exists $options{attributes};
497 (ref $options{methods} eq 'HASH')
498 || confess "You must pass a HASH ref of methods"
499 if exists $options{methods};
501 $options{meta_name} = 'meta'
502 unless exists $options{meta_name};
504 my (%initialize_options) = @args;
505 delete @initialize_options{qw(
514 my $meta = $class->initialize( $package_name => %initialize_options );
516 $meta->_instantiate_module( $options{version}, $options{authority} );
518 $meta->_add_meta_method($options{meta_name})
519 if defined $options{meta_name};
521 $meta->superclasses(@{$options{superclasses}})
522 if exists $options{superclasses};
524 # process attributes first, so that they can
525 # install accessors, but locally defined methods
526 # can then overwrite them. It is maybe a little odd, but
527 # I think this should be the order of things.
528 if (exists $options{attributes}) {
529 foreach my $attr (@{$options{attributes}}) {
530 $meta->add_attribute($attr);
533 if (exists $options{methods}) {
534 foreach my $method_name (keys %{$options{methods}}) {
535 $meta->add_method($method_name, $options{methods}->{$method_name});
541 # Instance Construction & Cloning
547 # we need to protect the integrity of the
548 # Class::MOP::Class singletons here, so we
549 # delegate this to &construct_class_instance
550 # which will deal with the singletons
551 return $class->_construct_class_instance(@_)
552 if $class->name->isa('Class::MOP::Class');
553 return $class->_construct_instance(@_);
556 sub _construct_instance {
558 my $params = @_ == 1 ? $_[0] : {@_};
559 my $meta_instance = $class->get_meta_instance();
561 # the code below is almost certainly incorrect
562 # but this is foreign inheritance, so we might
563 # have to kludge it in the end.
565 if (my $instance_class = blessed($params->{__INSTANCE__})) {
566 ($instance_class eq $class->name)
567 || confess "Objects passed as the __INSTANCE__ parameter must "
568 . "already be blessed into the correct class, but "
569 . "$params->{__INSTANCE__} is not a " . $class->name;
570 $instance = $params->{__INSTANCE__};
572 elsif (exists $params->{__INSTANCE__}) {
573 confess "The __INSTANCE__ parameter must be a blessed reference, not "
574 . $params->{__INSTANCE__};
577 $instance = $meta_instance->create_instance();
579 foreach my $attr ($class->get_all_attributes()) {
580 $attr->initialize_instance_slot($meta_instance, $instance, $params);
582 if (Class::MOP::metaclass_is_weak($class->name)) {
583 $meta_instance->_set_mop_slot($instance, $class);
588 sub _inline_new_object {
592 'my $class = shift;',
593 '$class = Scalar::Util::blessed($class) || $class;',
594 $self->_inline_fallback_constructor('$class'),
595 $self->_inline_params('$params', '$class'),
596 $self->_inline_generate_instance('$instance', '$class'),
597 $self->_inline_slot_initializers,
598 $self->_inline_preserve_weak_metaclasses,
599 $self->_inline_extra_init,
604 sub _inline_fallback_constructor {
608 'return ' . $self->_generate_fallback_constructor($class),
609 'if ' . $class . ' ne \'' . $self->name . '\';',
613 sub _generate_fallback_constructor {
616 return 'Class::MOP::Class->initialize(' . $class . ')->new_object(@_)',
621 my ($params, $class) = @_;
623 'my ' . $params . ' = @_ == 1 ? $_[0] : {@_};',
627 sub _inline_generate_instance {
629 my ($inst, $class) = @_;
631 'my ' . $inst . ' = ' . $self->_inline_create_instance($class) . ';',
635 sub _inline_create_instance {
638 return $self->get_meta_instance->inline_create_instance(@_);
641 sub _inline_slot_initializers {
646 return map { $self->_inline_slot_initializer($_, $idx++) }
647 sort { $a->name cmp $b->name } $self->get_all_attributes;
650 sub _inline_slot_initializer {
652 my ($attr, $idx) = @_;
654 if (defined(my $init_arg = $attr->init_arg)) {
656 'if (exists $params->{\'' . $init_arg . '\'}) {',
657 $self->_inline_init_attr_from_constructor($attr, $idx),
660 if (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
669 elsif (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
681 sub _inline_init_attr_from_constructor {
683 my ($attr, $idx) = @_;
685 my @initial_value = $attr->_inline_set_value(
686 '$instance', '$params->{\'' . $attr->init_arg . '\'}',
689 push @initial_value, (
690 '$attrs->[' . $idx . ']->set_initial_value(',
692 $attr->_inline_instance_get('$instance'),
694 ) if $attr->has_initializer;
696 return @initial_value;
699 sub _inline_init_attr_from_default {
701 my ($attr, $idx) = @_;
703 my $default = $self->_inline_default_value($attr, $idx);
704 return unless $default;
706 my @initial_value = $attr->_inline_set_value('$instance', $default);
708 push @initial_value, (
709 '$attrs->[' . $idx . ']->set_initial_value(',
711 $attr->_inline_instance_get('$instance'),
713 ) if $attr->has_initializer;
715 return @initial_value;
718 sub _inline_default_value {
720 my ($attr, $index) = @_;
722 if ($attr->has_default) {
724 # default values can either be CODE refs
725 # in which case we need to call them. Or
726 # they can be scalars (strings/numbers)
727 # in which case we can just deal with them
728 # in the code we eval.
729 if ($attr->is_default_a_coderef) {
730 return '$defaults->[' . $index . ']->($instance)';
733 return '$defaults->[' . $index . ']';
736 elsif ($attr->has_builder) {
737 return '$instance->' . $attr->builder;
744 sub _inline_preserve_weak_metaclasses {
746 if (Class::MOP::metaclass_is_weak($self->name)) {
748 $self->_inline_set_mop_slot(
749 '$instance', 'Class::MOP::class_of($class)'
758 sub _inline_extra_init { }
761 sub get_meta_instance {
763 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
766 sub _create_meta_instance {
769 my $instance = $self->instance_metaclass->new(
770 associated_metaclass => $self,
771 attributes => [ $self->get_all_attributes() ],
774 $self->add_meta_instance_dependencies()
775 if $instance->is_dependent_on_superclasses();
780 sub _inline_rebless_instance {
783 return $self->get_meta_instance->inline_rebless_instance_structure(@_);
786 sub _inline_get_mop_slot {
789 return $self->get_meta_instance->_inline_get_mop_slot(@_);
792 sub _inline_set_mop_slot {
795 return $self->get_meta_instance->_inline_set_mop_slot(@_);
798 sub _inline_clear_mop_slot {
801 return $self->get_meta_instance->_inline_clear_mop_slot(@_);
806 my $instance = shift;
807 (blessed($instance) && $instance->isa($class->name))
808 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
811 # we need to protect the integrity of the
812 # Class::MOP::Class singletons here, they
813 # should not be cloned.
814 return $instance if $instance->isa('Class::MOP::Class');
815 $class->_clone_instance($instance, @_);
818 sub _clone_instance {
819 my ($class, $instance, %params) = @_;
821 || confess "You can only clone instances, ($instance) is not a blessed instance";
822 my $meta_instance = $class->get_meta_instance();
823 my $clone = $meta_instance->clone_instance($instance);
824 foreach my $attr ($class->get_all_attributes()) {
825 if ( defined( my $init_arg = $attr->init_arg ) ) {
826 if (exists $params{$init_arg}) {
827 $attr->set_value($clone, $params{$init_arg});
834 sub _force_rebless_instance {
835 my ($self, $instance, %params) = @_;
836 my $old_metaclass = Class::MOP::class_of($instance);
838 $old_metaclass->rebless_instance_away($instance, $self, %params)
841 my $meta_instance = $self->get_meta_instance;
843 if (Class::MOP::metaclass_is_weak($old_metaclass->name)) {
844 $meta_instance->_clear_mop_slot($instance);
848 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
849 $meta_instance->rebless_instance_structure($_[1], $self);
851 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
853 if (Class::MOP::metaclass_is_weak($self->name)) {
854 $meta_instance->_set_mop_slot($instance, $self);
858 sub rebless_instance {
859 my ($self, $instance, %params) = @_;
860 my $old_metaclass = Class::MOP::class_of($instance);
862 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
863 $self->name->isa($old_class)
864 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
866 $self->_force_rebless_instance($_[1], %params);
871 sub rebless_instance_back {
872 my ( $self, $instance ) = @_;
873 my $old_metaclass = Class::MOP::class_of($instance);
876 = $old_metaclass ? $old_metaclass->name : blessed($instance);
877 $old_class->isa( $self->name )
879 "You may rebless only into a superclass of ($old_class), of which ("
883 $self->_force_rebless_instance($_[1]);
888 sub rebless_instance_away {
889 # this intentionally does nothing, it is just a hook
892 sub _fixup_attributes_after_rebless {
894 my ($instance, $rebless_from, %params) = @_;
895 my $meta_instance = $self->get_meta_instance;
897 for my $attr ( $rebless_from->get_all_attributes ) {
898 next if $self->find_attribute_by_name( $attr->name );
899 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
902 foreach my $attr ( $self->get_all_attributes ) {
903 if ( $attr->has_value($instance) ) {
904 if ( defined( my $init_arg = $attr->init_arg ) ) {
905 $params{$init_arg} = $attr->get_value($instance)
906 unless exists $params{$init_arg};
909 $attr->set_value($instance, $attr->get_value($instance));
914 foreach my $attr ($self->get_all_attributes) {
915 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
919 sub _attach_attribute {
920 my ($self, $attribute) = @_;
921 $attribute->attach_to_class($self);
924 sub _post_add_attribute {
925 my ( $self, $attribute ) = @_;
927 $self->invalidate_meta_instances;
929 # invalidate package flag here
932 $attribute->install_accessors;
935 $self->remove_attribute( $attribute->name );
940 sub remove_attribute {
943 my $removed_attribute = $self->SUPER::remove_attribute(@_)
946 $self->invalidate_meta_instances;
948 $removed_attribute->remove_accessors;
949 $removed_attribute->detach_from_class;
951 return$removed_attribute;
954 sub find_attribute_by_name {
955 my ( $self, $attr_name ) = @_;
957 foreach my $class ( $self->linearized_isa ) {
958 # fetch the meta-class ...
959 my $meta = Class::MOP::Class->initialize($class);
960 return $meta->get_attribute($attr_name)
961 if $meta->has_attribute($attr_name);
967 sub get_all_attributes {
969 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
970 reverse $self->linearized_isa;
971 return values %attrs;
979 my $isa = $self->get_or_add_package_symbol('@ISA');
986 # on 5.8 and below, we need to call
987 # a method to get Perl to detect
988 # a cycle in the class hierarchy
989 my $class = $self->name;
993 # we need to check the metaclass
994 # compatibility here so that we can
995 # be sure that the superclass is
996 # not potentially creating an issues
997 # we don't know about
999 $self->_check_metaclass_compatibility();
1000 $self->_superclasses_updated();
1006 sub _superclasses_updated {
1008 $self->update_meta_instance_dependencies();
1009 # keep strong references to all our parents, so they don't disappear if
1010 # they are anon classes and don't have any direct instances
1011 $self->_superclass_metas(
1012 map { Class::MOP::class_of($_) } $self->superclasses
1016 sub _superclass_metas {
1018 $self->{_superclass_metas} = [@_];
1023 my $super_class = $self->name;
1025 return @{ $super_class->mro::get_isarev() };
1028 sub direct_subclasses {
1030 my $super_class = $self->name;
1035 } Class::MOP::Class->initialize($_)->superclasses
1036 } $self->subclasses;
1039 sub linearized_isa {
1040 return @{ mro::get_linear_isa( (shift)->name ) };
1043 sub class_precedence_list {
1045 my $name = $self->name;
1047 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
1049 # We need to check for circular inheritance here
1050 # if we are are not on 5.10, cause 5.8 detects it
1051 # late. This will do nothing if all is well, and
1052 # blow up otherwise. Yes, it's an ugly hack, better
1053 # suggestions are welcome.
1055 ($name || return)->isa('This is a test for circular inheritance')
1058 # if our mro is c3, we can
1059 # just grab the linear_isa
1060 if (mro::get_mro($name) eq 'c3') {
1061 return @{ mro::get_linear_isa($name) }
1065 # we can't grab the linear_isa for dfs
1066 # since it has all the duplicates
1071 Class::MOP::Class->initialize($_)->class_precedence_list()
1072 } $self->superclasses()
1080 my $fetch_and_prepare_method = sub {
1081 my ($self, $method_name) = @_;
1082 my $wrapped_metaclass = $self->wrapped_method_metaclass;
1084 my $method = $self->get_method($method_name);
1085 # if we dont have local ...
1087 # try to find the next method
1088 $method = $self->find_next_method_by_name($method_name);
1089 # die if it does not exist
1091 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
1092 # and now make sure to wrap it
1093 # even if it is already wrapped
1094 # because we need a new sub ref
1095 $method = $wrapped_metaclass->wrap($method,
1096 package_name => $self->name,
1097 name => $method_name,
1101 # now make sure we wrap it properly
1102 $method = $wrapped_metaclass->wrap($method,
1103 package_name => $self->name,
1104 name => $method_name,
1105 ) unless $method->isa($wrapped_metaclass);
1107 $self->add_method($method_name => $method);
1111 sub add_before_method_modifier {
1112 my ($self, $method_name, $method_modifier) = @_;
1113 (defined $method_name && length $method_name)
1114 || confess "You must pass in a method name";
1115 my $method = $fetch_and_prepare_method->($self, $method_name);
1116 $method->add_before_modifier(
1117 subname(':before' => $method_modifier)
1121 sub add_after_method_modifier {
1122 my ($self, $method_name, $method_modifier) = @_;
1123 (defined $method_name && length $method_name)
1124 || confess "You must pass in a method name";
1125 my $method = $fetch_and_prepare_method->($self, $method_name);
1126 $method->add_after_modifier(
1127 subname(':after' => $method_modifier)
1131 sub add_around_method_modifier {
1132 my ($self, $method_name, $method_modifier) = @_;
1133 (defined $method_name && length $method_name)
1134 || confess "You must pass in a method name";
1135 my $method = $fetch_and_prepare_method->($self, $method_name);
1136 $method->add_around_modifier(
1137 subname(':around' => $method_modifier)
1142 # the methods above used to be named like this:
1143 # ${pkg}::${method}:(before|after|around)
1144 # but this proved problematic when using one modifier
1145 # to wrap multiple methods (something which is likely
1146 # to happen pretty regularly IMO). So instead of naming
1147 # it like this, I have chosen to just name them purely
1148 # with their modifier names, like so:
1149 # :(before|after|around)
1150 # The fact is that in a stack trace, it will be fairly
1151 # evident from the context what method they are attached
1152 # to, and so don't need the fully qualified name.
1155 sub find_method_by_name {
1156 my ($self, $method_name) = @_;
1157 (defined $method_name && length $method_name)
1158 || confess "You must define a method name to find";
1159 foreach my $class ($self->linearized_isa) {
1160 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1161 return $method if defined $method;
1166 sub get_all_methods {
1170 for my $class ( reverse $self->linearized_isa ) {
1171 my $meta = Class::MOP::Class->initialize($class);
1173 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1176 return values %methods;
1179 sub get_all_method_names {
1182 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
1185 sub find_all_methods_by_name {
1186 my ($self, $method_name) = @_;
1187 (defined $method_name && length $method_name)
1188 || confess "You must define a method name to find";
1190 foreach my $class ($self->linearized_isa) {
1191 # fetch the meta-class ...
1192 my $meta = Class::MOP::Class->initialize($class);
1194 name => $method_name,
1196 code => $meta->get_method($method_name)
1197 } if $meta->has_method($method_name);
1202 sub find_next_method_by_name {
1203 my ($self, $method_name) = @_;
1204 (defined $method_name && length $method_name)
1205 || confess "You must define a method name to find";
1206 my @cpl = $self->linearized_isa;
1207 shift @cpl; # discard ourselves
1208 foreach my $class (@cpl) {
1209 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1210 return $method if defined $method;
1215 sub update_meta_instance_dependencies {
1218 if ( $self->{meta_instance_dependencies} ) {
1219 return $self->add_meta_instance_dependencies;
1223 sub add_meta_instance_dependencies {
1226 $self->remove_meta_instance_dependencies;
1228 my @attrs = $self->get_all_attributes();
1231 my @classes = grep { not $seen{ $_->name }++ }
1232 map { $_->associated_class } @attrs;
1234 foreach my $class (@classes) {
1235 $class->add_dependent_meta_instance($self);
1238 $self->{meta_instance_dependencies} = \@classes;
1241 sub remove_meta_instance_dependencies {
1244 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1245 foreach my $class (@$classes) {
1246 $class->remove_dependent_meta_instance($self);
1256 sub add_dependent_meta_instance {
1257 my ( $self, $metaclass ) = @_;
1258 push @{ $self->{dependent_meta_instances} }, $metaclass;
1261 sub remove_dependent_meta_instance {
1262 my ( $self, $metaclass ) = @_;
1263 my $name = $metaclass->name;
1264 @$_ = grep { $_->name ne $name } @$_
1265 for $self->{dependent_meta_instances};
1268 sub invalidate_meta_instances {
1270 $_->invalidate_meta_instance()
1271 for $self, @{ $self->{dependent_meta_instances} };
1274 sub invalidate_meta_instance {
1276 undef $self->{_meta_instance};
1279 # check if we can reinitialize
1283 # if any local attr is defined
1284 return if $self->get_attribute_list;
1286 # or any non-declared methods
1287 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1288 return if $method->isa("Class::MOP::Method::Generated");
1289 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1297 sub is_mutable { 1 }
1298 sub is_immutable { 0 }
1300 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1302 sub _immutable_options {
1303 my ( $self, @args ) = @_;
1306 inline_accessors => 1,
1307 inline_constructor => 1,
1308 inline_destructor => 0,
1310 immutable_trait => $self->immutable_trait,
1311 constructor_name => $self->constructor_name,
1312 constructor_class => $self->constructor_class,
1313 destructor_class => $self->destructor_class,
1318 sub make_immutable {
1319 my ( $self, @args ) = @_;
1321 if ( $self->is_mutable ) {
1322 $self->_initialize_immutable( $self->_immutable_options(@args) );
1323 $self->_rebless_as_immutable(@args);
1334 if ( $self->is_immutable ) {
1335 my @args = $self->immutable_options;
1336 $self->_rebless_as_mutable();
1337 $self->_remove_inlined_code(@args);
1338 delete $self->{__immutable};
1346 sub _rebless_as_immutable {
1347 my ( $self, @args ) = @_;
1349 $self->{__immutable}{original_class} = ref $self;
1351 bless $self => $self->_immutable_metaclass(@args);
1354 sub _immutable_metaclass {
1355 my ( $self, %args ) = @_;
1357 if ( my $class = $args{immutable_metaclass} ) {
1361 my $trait = $args{immutable_trait} = $self->immutable_trait
1362 || confess "no immutable trait specified for $self";
1364 my $meta = $self->meta;
1365 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1369 if ( $meta_attr and $trait eq $meta_attr->default ) {
1370 # if the trait is the same as the default we try and pick a
1371 # predictable name for the immutable metaclass
1372 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1375 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1376 $trait, 'ForMetaClass', ref($self);
1380 if Class::MOP::is_class_loaded($class_name);
1382 # If the metaclass is a subclass of CMOP::Class which has had
1383 # metaclass roles applied (via Moose), then we want to make sure
1384 # that we preserve that anonymous class (see Fey::ORM for an
1385 # example of where this matters).
1386 my $meta_name = $meta->_real_ref_name;
1388 my $immutable_meta = $meta_name->create(
1390 superclasses => [ ref $self ],
1393 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1395 $immutable_meta->make_immutable(
1396 inline_constructor => 0,
1397 inline_accessors => 0,
1403 sub _remove_inlined_code {
1406 $self->remove_method( $_->name ) for $self->_inlined_methods;
1408 delete $self->{__immutable}{inlined_methods};
1411 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1413 sub _add_inlined_method {
1414 my ( $self, $method ) = @_;
1416 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1419 sub _initialize_immutable {
1420 my ( $self, %args ) = @_;
1422 $self->{__immutable}{options} = \%args;
1423 $self->_install_inlined_code(%args);
1426 sub _install_inlined_code {
1427 my ( $self, %args ) = @_;
1430 $self->_inline_accessors(%args) if $args{inline_accessors};
1431 $self->_inline_constructor(%args) if $args{inline_constructor};
1432 $self->_inline_destructor(%args) if $args{inline_destructor};
1435 sub _rebless_as_mutable {
1438 bless $self, $self->_get_mutable_metaclass_name;
1443 sub _inline_accessors {
1446 foreach my $attr_name ( $self->get_attribute_list ) {
1447 $self->get_attribute($attr_name)->install_accessors(1);
1451 sub _inline_constructor {
1452 my ( $self, %args ) = @_;
1454 my $name = $args{constructor_name};
1455 # A class may not even have a constructor, and that's okay.
1456 return unless defined $name;
1458 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1459 my $class = $self->name;
1460 warn "Not inlining a constructor for $class since it defines"
1461 . " its own constructor.\n"
1462 . "If you are certain you don't need to inline your"
1463 . " constructor, specify inline_constructor => 0 in your"
1464 . " call to $class->meta->make_immutable\n";
1468 my $constructor_class = $args{constructor_class};
1470 Class::MOP::load_class($constructor_class);
1472 my $constructor = $constructor_class->new(
1476 package_name => $self->name,
1480 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1481 $self->add_method( $name => $constructor );
1482 $self->_add_inlined_method($constructor);
1486 sub _inline_destructor {
1487 my ( $self, %args ) = @_;
1489 ( exists $args{destructor_class} && defined $args{destructor_class} )
1490 || confess "The 'inline_destructor' option is present, but "
1491 . "no destructor class was specified";
1493 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1494 my $class = $self->name;
1495 warn "Not inlining a destructor for $class since it defines"
1496 . " its own destructor.\n";
1500 my $destructor_class = $args{destructor_class};
1502 Class::MOP::load_class($destructor_class);
1504 return unless $destructor_class->is_needed($self);
1506 my $destructor = $destructor_class->new(
1509 package_name => $self->name,
1513 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1514 $self->add_method( 'DESTROY' => $destructor );
1515 $self->_add_inlined_method($destructor);
1521 # ABSTRACT: Class Meta Object
1529 # assuming that class Foo
1530 # has been defined, you can
1532 # use this for introspection ...
1534 # add a method to Foo ...
1535 Foo->meta->add_method( 'bar' => sub {...} )
1537 # get a list of all the classes searched
1538 # the method dispatcher in the correct order
1539 Foo->meta->class_precedence_list()
1541 # remove a method from Foo
1542 Foo->meta->remove_method('bar');
1544 # or use this to actually create classes ...
1546 Class::MOP::Class->create(
1549 superclasses => ['Foo'],
1551 Class::MOP::Attribute->new('$bar'),
1552 Class::MOP::Attribute->new('$baz'),
1555 calculate_bar => sub {...},
1556 construct_baz => sub {...}
1563 The Class Protocol is the largest and most complex part of the
1564 Class::MOP meta-object protocol. It controls the introspection and
1565 manipulation of Perl 5 classes, and it can create them as well. The
1566 best way to understand what this module can do is to read the
1567 documentation for each of its methods.
1571 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1575 =head2 Class construction
1577 These methods all create new C<Class::MOP::Class> objects. These
1578 objects can represent existing classes or they can be used to create
1579 new classes from scratch.
1581 The metaclass object for a given class is a singleton. If you attempt
1582 to create a metaclass for the same class twice, you will just get the
1587 =item B<< Class::MOP::Class->create($package_name, %options) >>
1589 This method creates a new C<Class::MOP::Class> object with the given
1590 package name. It accepts a number of options:
1596 An optional version number for the newly created package.
1600 An optional authority for the newly created package.
1602 =item * superclasses
1604 An optional array reference of superclass names.
1608 An optional hash reference of methods for the class. The keys of the
1609 hash reference are method names and values are subroutine references.
1613 An optional array reference of L<Class::MOP::Attribute> objects.
1617 Specifies the name to install the C<meta> method for this class under.
1618 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1619 given, no meta method will be installed.
1623 If true, the metaclass that is stored in the global cache will be a
1626 Classes created in this way are destroyed once the metaclass they are
1627 attached to goes out of scope, and will be removed from Perl's internal
1630 All instances of a class with a weakened metaclass keep a special
1631 reference to the metaclass object, which prevents the metaclass from
1632 going out of scope while any instances exist.
1634 This only works if the instance is based on a hash reference, however.
1638 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1640 This method works just like C<< Class::MOP::Class->create >> but it
1641 creates an "anonymous" class. In fact, the class does have a name, but
1642 that name is a unique name generated internally by this module.
1644 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1645 parameters that C<create> accepts.
1647 Anonymous classes default to C<< weaken => 1 >>, although this can be
1650 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1652 This method will initialize a C<Class::MOP::Class> object for the
1653 named package. Unlike C<create>, this method I<will not> create a new
1656 The purpose of this method is to retrieve a C<Class::MOP::Class>
1657 object for introspecting an existing class.
1659 If an existing C<Class::MOP::Class> object exists for the named
1660 package, it will be returned, and any options provided will be
1663 If the object does not yet exist, it will be created.
1665 The valid options that can be passed to this method are
1666 C<attribute_metaclass>, C<method_metaclass>,
1667 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1668 optional, and default to the appropriate class in the C<Class::MOP>
1673 =head2 Object instance construction and cloning
1675 These methods are all related to creating and/or cloning object
1680 =item B<< $metaclass->clone_object($instance, %params) >>
1682 This method clones an existing object instance. Any parameters you
1683 provide are will override existing attribute values in the object.
1685 This is a convenience method for cloning an object instance, then
1686 blessing it into the appropriate package.
1688 You could implement a clone method in your class, using this method:
1691 my ($self, %params) = @_;
1692 $self->meta->clone_object($self, %params);
1695 =item B<< $metaclass->rebless_instance($instance, %params) >>
1697 This method changes the class of C<$instance> to the metaclass's class.
1699 You can only rebless an instance into a subclass of its current
1700 class. If you pass any additional parameters, these will be treated
1701 like constructor parameters and used to initialize the object's
1702 attributes. Any existing attributes that are already set will be
1705 Before reblessing the instance, this method will call
1706 C<rebless_instance_away> on the instance's current metaclass. This method
1707 will be passed the instance, the new metaclass, and any parameters
1708 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1709 does nothing; it is merely a hook.
1711 =item B<< $metaclass->rebless_instance_back($instance) >>
1713 Does the same thing as C<rebless_instance>, except that you can only
1714 rebless an instance into one of its superclasses. Any attributes that
1715 do not exist in the superclass will be deinitialized.
1717 This is a much more dangerous operation than C<rebless_instance>,
1718 especially when multiple inheritance is involved, so use this carefully!
1720 =item B<< $metaclass->new_object(%params) >>
1722 This method is used to create a new object of the metaclass's
1723 class. Any parameters you provide are used to initialize the
1724 instance's attributes. A special C<__INSTANCE__> key can be passed to
1725 provide an already generated instance, rather than having Class::MOP
1726 generate it for you. This is mostly useful for using Class::MOP with
1727 foreign classes which generate instances using their own constructors.
1729 =item B<< $metaclass->instance_metaclass >>
1731 Returns the class name of the instance metaclass. See
1732 L<Class::MOP::Instance> for more information on the instance
1735 =item B<< $metaclass->get_meta_instance >>
1737 Returns an instance of the C<instance_metaclass> to be used in the
1738 construction of a new instance of the class.
1742 =head2 Informational predicates
1744 These are a few predicate methods for asking information about the
1749 =item B<< $metaclass->is_anon_class >>
1751 This returns true if the class was created by calling C<<
1752 Class::MOP::Class->create_anon_class >>.
1754 =item B<< $metaclass->is_mutable >>
1756 This returns true if the class is still mutable.
1758 =item B<< $metaclass->is_immutable >>
1760 This returns true if the class has been made immutable.
1762 =item B<< $metaclass->is_pristine >>
1764 A class is I<not> pristine if it has non-inherited attributes or if it
1765 has any generated methods.
1769 =head2 Inheritance Relationships
1773 =item B<< $metaclass->superclasses(@superclasses) >>
1775 This is a read-write accessor which represents the superclass
1776 relationships of the metaclass's class.
1778 This is basically sugar around getting and setting C<@ISA>.
1780 =item B<< $metaclass->class_precedence_list >>
1782 This returns a list of all of the class's ancestor classes. The
1783 classes are returned in method dispatch order.
1785 =item B<< $metaclass->linearized_isa >>
1787 This returns a list based on C<class_precedence_list> but with all
1790 =item B<< $metaclass->subclasses >>
1792 This returns a list of all subclasses for this class, even indirect
1795 =item B<< $metaclass->direct_subclasses >>
1797 This returns a list of immediate subclasses for this class, which does not
1798 include indirect subclasses.
1802 =head2 Method introspection and creation
1804 These methods allow you to introspect a class's methods, as well as
1805 add, remove, or change methods.
1807 Determining what is truly a method in a Perl 5 class requires some
1808 heuristics (aka guessing).
1810 Methods defined outside the package with a fully qualified name (C<sub
1811 Package::name { ... }>) will be included. Similarly, methods named
1812 with a fully qualified name using L<Sub::Name> are also included.
1814 However, we attempt to ignore imported functions.
1816 Ultimately, we are using heuristics to determine what truly is a
1817 method in a class, and these heuristics may get the wrong answer in
1818 some edge cases. However, for most "normal" cases the heuristics work
1823 =item B<< $metaclass->get_method($method_name) >>
1825 This will return a L<Class::MOP::Method> for the specified
1826 C<$method_name>. If the class does not have the specified method, it
1829 =item B<< $metaclass->has_method($method_name) >>
1831 Returns a boolean indicating whether or not the class defines the
1832 named method. It does not include methods inherited from parent
1835 =item B<< $metaclass->get_method_list >>
1837 This will return a list of method I<names> for all methods defined in
1840 =item B<< $metaclass->add_method($method_name, $method) >>
1842 This method takes a method name and a subroutine reference, and adds
1843 the method to the class.
1845 The subroutine reference can be a L<Class::MOP::Method>, and you are
1846 strongly encouraged to pass a meta method object instead of a code
1847 reference. If you do so, that object gets stored as part of the
1848 class's method map directly. If not, the meta information will have to
1849 be recreated later, and may be incorrect.
1851 If you provide a method object, this method will clone that object if
1852 the object's package name does not match the class name. This lets us
1853 track the original source of any methods added from other classes
1854 (notably Moose roles).
1856 =item B<< $metaclass->remove_method($method_name) >>
1858 Remove the named method from the class. This method returns the
1859 L<Class::MOP::Method> object for the method.
1861 =item B<< $metaclass->method_metaclass >>
1863 Returns the class name of the method metaclass, see
1864 L<Class::MOP::Method> for more information on the method metaclass.
1866 =item B<< $metaclass->wrapped_method_metaclass >>
1868 Returns the class name of the wrapped method metaclass, see
1869 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1872 =item B<< $metaclass->get_all_methods >>
1874 This will traverse the inheritance hierarchy and return a list of all
1875 the L<Class::MOP::Method> objects for this class and its parents.
1877 =item B<< $metaclass->find_method_by_name($method_name) >>
1879 This will return a L<Class::MOP::Method> for the specified
1880 C<$method_name>. If the class does not have the specified method, it
1883 Unlike C<get_method>, this method I<will> look for the named method in
1886 =item B<< $metaclass->get_all_method_names >>
1888 This will return a list of method I<names> for all of this class's
1889 methods, including inherited methods.
1891 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1893 This method looks for the named method in the class and all of its
1894 parents. It returns every matching method it finds in the inheritance
1895 tree, so it returns a list of methods.
1897 Each method is returned as a hash reference with three keys. The keys
1898 are C<name>, C<class>, and C<code>. The C<code> key has a
1899 L<Class::MOP::Method> object as its value.
1901 The list of methods is distinct.
1903 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1905 This method returns the first method in any superclass matching the
1906 given name. It is effectively the method that C<SUPER::$method_name>
1911 =head2 Attribute introspection and creation
1913 Because Perl 5 does not have a core concept of attributes in classes,
1914 we can only return information about attributes which have been added
1915 via this class's methods. We cannot discover information about
1916 attributes which are defined in terms of "regular" Perl 5 methods.
1920 =item B<< $metaclass->get_attribute($attribute_name) >>
1922 This will return a L<Class::MOP::Attribute> for the specified
1923 C<$attribute_name>. If the class does not have the specified
1924 attribute, it returns C<undef>.
1926 NOTE that get_attribute does not search superclasses, for that you
1927 need to use C<find_attribute_by_name>.
1929 =item B<< $metaclass->has_attribute($attribute_name) >>
1931 Returns a boolean indicating whether or not the class defines the
1932 named attribute. It does not include attributes inherited from parent
1935 =item B<< $metaclass->get_attribute_list >>
1937 This will return a list of attributes I<names> for all attributes
1938 defined in this class. Note that this operates on the current class
1939 only, it does not traverse the inheritance hierarchy.
1941 =item B<< $metaclass->get_all_attributes >>
1943 This will traverse the inheritance hierarchy and return a list of all
1944 the L<Class::MOP::Attribute> objects for this class and its parents.
1946 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1948 This will return a L<Class::MOP::Attribute> for the specified
1949 C<$attribute_name>. If the class does not have the specified
1950 attribute, it returns C<undef>.
1952 Unlike C<get_attribute>, this attribute I<will> look for the named
1953 attribute in superclasses.
1955 =item B<< $metaclass->add_attribute(...) >>
1957 This method accepts either an existing L<Class::MOP::Attribute>
1958 object or parameters suitable for passing to that class's C<new>
1961 The attribute provided will be added to the class.
1963 Any accessor methods defined by the attribute will be added to the
1964 class when the attribute is added.
1966 If an attribute of the same name already exists, the old attribute
1967 will be removed first.
1969 =item B<< $metaclass->remove_attribute($attribute_name) >>
1971 This will remove the named attribute from the class, and
1972 L<Class::MOP::Attribute> object.
1974 Removing an attribute also removes any accessor methods defined by the
1977 However, note that removing an attribute will only affect I<future>
1978 object instances created for this class, not existing instances.
1980 =item B<< $metaclass->attribute_metaclass >>
1982 Returns the class name of the attribute metaclass for this class. By
1983 default, this is L<Class::MOP::Attribute>.
1987 =head2 Class Immutability
1989 Making a class immutable "freezes" the class definition. You can no
1990 longer call methods which alter the class, such as adding or removing
1991 methods or attributes.
1993 Making a class immutable lets us optimize the class by inlining some
1994 methods, and also allows us to optimize some methods on the metaclass
1997 After immutabilization, the metaclass object will cache most informational
1998 methods that returns information about methods or attributes. Methods which
1999 would alter the class, such as C<add_attribute> and C<add_method>, will
2000 throw an error on an immutable metaclass object.
2002 The immutabilization system in L<Moose> takes much greater advantage
2003 of the inlining features than Class::MOP itself does.
2007 =item B<< $metaclass->make_immutable(%options) >>
2009 This method will create an immutable transformer and use it to make
2010 the class and its metaclass object immutable.
2012 This method accepts the following options:
2016 =item * inline_accessors
2018 =item * inline_constructor
2020 =item * inline_destructor
2022 These are all booleans indicating whether the specified method(s)
2025 By default, accessors and the constructor are inlined, but not the
2028 =item * immutable_trait
2030 The name of a class which will be used as a parent class for the
2031 metaclass object being made immutable. This "trait" implements the
2032 post-immutability functionality of the metaclass (but not the
2033 transformation itself).
2035 This defaults to L<Class::MOP::Class::Immutable::Trait>.
2037 =item * constructor_name
2039 This is the constructor method name. This defaults to "new".
2041 =item * constructor_class
2043 The name of the method metaclass for constructors. It will be used to
2044 generate the inlined constructor. This defaults to
2045 "Class::MOP::Method::Constructor".
2047 =item * replace_constructor
2049 This is a boolean indicating whether an existing constructor should be
2050 replaced when inlining a constructor. This defaults to false.
2052 =item * destructor_class
2054 The name of the method metaclass for destructors. It will be used to
2055 generate the inlined destructor. This defaults to
2056 "Class::MOP::Method::Denstructor".
2058 =item * replace_destructor
2060 This is a boolean indicating whether an existing destructor should be
2061 replaced when inlining a destructor. This defaults to false.
2065 =item B<< $metaclass->immutable_options >>
2067 Returns a hash of the options used when making the class immutable, including
2068 both defaults and anything supplied by the user in the call to C<<
2069 $metaclass->make_immutable >>. This is useful if you need to temporarily make
2070 a class mutable and then restore immutability as it was before.
2072 =item B<< $metaclass->make_mutable >>
2074 Calling this method reverse the immutabilization transformation.
2078 =head2 Method Modifiers
2080 Method modifiers are hooks which allow a method to be wrapped with
2081 I<before>, I<after> and I<around> method modifiers. Every time a
2082 method is called, its modifiers are also called.
2084 A class can modify its own methods, as well as methods defined in
2087 =head3 How method modifiers work?
2089 Method modifiers work by wrapping the original method and then
2090 replacing it in the class's symbol table. The wrappers will handle
2091 calling all the modifiers in the appropriate order and preserving the
2092 calling context for the original method.
2094 The return values of C<before> and C<after> modifiers are
2095 ignored. This is because their purpose is B<not> to filter the input
2096 and output of the primary method (this is done with an I<around>
2099 This may seem like an odd restriction to some, but doing this allows
2100 for simple code to be added at the beginning or end of a method call
2101 without altering the function of the wrapped method or placing any
2102 extra responsibility on the code of the modifier.
2104 Of course if you have more complex needs, you can use the C<around>
2105 modifier which allows you to change both the parameters passed to the
2106 wrapped method, as well as its return value.
2108 Before and around modifiers are called in last-defined-first-called
2109 order, while after modifiers are called in first-defined-first-called
2110 order. So the call tree might looks something like this:
2122 =head3 What is the performance impact?
2124 Of course there is a performance cost associated with method
2125 modifiers, but we have made every effort to make that cost directly
2126 proportional to the number of modifier features you use.
2128 The wrapping method does its best to B<only> do as much work as it
2129 absolutely needs to. In order to do this we have moved some of the
2130 performance costs to set-up time, where they are easier to amortize.
2132 All this said, our benchmarks have indicated the following:
2134 simple wrapper with no modifiers 100% slower
2135 simple wrapper with simple before modifier 400% slower
2136 simple wrapper with simple after modifier 450% slower
2137 simple wrapper with simple around modifier 500-550% slower
2138 simple wrapper with all 3 modifiers 1100% slower
2140 These numbers may seem daunting, but you must remember, every feature
2141 comes with some cost. To put things in perspective, just doing a
2142 simple C<AUTOLOAD> which does nothing but extract the name of the
2143 method called and return it costs about 400% over a normal method
2148 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
2150 This wraps the specified method with the supplied subroutine
2151 reference. The modifier will be called as a method itself, and will
2152 receive the same arguments as are passed to the method.
2154 When the modifier exits, the wrapped method will be called.
2156 The return value of the modifier will be ignored.
2158 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2160 This wraps the specified method with the supplied subroutine
2161 reference. The modifier will be called as a method itself, and will
2162 receive the same arguments as are passed to the method.
2164 When the wrapped methods exits, the modifier will be called.
2166 The return value of the modifier will be ignored.
2168 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2170 This wraps the specified method with the supplied subroutine
2173 The first argument passed to the modifier will be a subroutine
2174 reference to the wrapped method. The second argument is the object,
2175 and after that come any arguments passed when the method is called.
2177 The around modifier can choose to call the original method, as well as
2178 what arguments to pass if it does so.
2180 The return value of the modifier is what will be seen by the caller.
2184 =head2 Introspection
2188 =item B<< Class::MOP::Class->meta >>
2190 This will return a L<Class::MOP::Class> instance for this class.
2192 It should also be noted that L<Class::MOP> will actually bootstrap
2193 this module by installing a number of attribute meta-objects into its