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 unless $name =~ /^$ANON_CLASS_PREFIX/o;
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 $self;
467 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/o);
469 @{$name . '::ISA'} = ();
470 %{$name . '::'} = ();
471 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
473 Class::MOP::remove_metaclass_by_name($name);
478 # creating classes with MOP ...
481 my ( $class, @args ) = @_;
483 unshift @args, 'package' if @args % 2 == 1;
485 my (%options) = @args;
486 my $package_name = $options{package};
488 (ref $options{superclasses} eq 'ARRAY')
489 || confess "You must pass an ARRAY ref of superclasses"
490 if exists $options{superclasses};
492 (ref $options{attributes} eq 'ARRAY')
493 || confess "You must pass an ARRAY ref of attributes"
494 if exists $options{attributes};
496 (ref $options{methods} eq 'HASH')
497 || confess "You must pass a HASH ref of methods"
498 if exists $options{methods};
500 $options{meta_name} = 'meta'
501 unless exists $options{meta_name};
503 my (%initialize_options) = @args;
504 delete @initialize_options{qw(
513 my $meta = $class->initialize( $package_name => %initialize_options );
515 $meta->_instantiate_module( $options{version}, $options{authority} );
517 $meta->_add_meta_method($options{meta_name})
518 if defined $options{meta_name};
520 $meta->superclasses(@{$options{superclasses}})
521 if exists $options{superclasses};
523 # process attributes first, so that they can
524 # install accessors, but locally defined methods
525 # can then overwrite them. It is maybe a little odd, but
526 # I think this should be the order of things.
527 if (exists $options{attributes}) {
528 foreach my $attr (@{$options{attributes}}) {
529 $meta->add_attribute($attr);
532 if (exists $options{methods}) {
533 foreach my $method_name (keys %{$options{methods}}) {
534 $meta->add_method($method_name, $options{methods}->{$method_name});
540 # Instance Construction & Cloning
546 # we need to protect the integrity of the
547 # Class::MOP::Class singletons here, so we
548 # delegate this to &construct_class_instance
549 # which will deal with the singletons
550 return $class->_construct_class_instance(@_)
551 if $class->name->isa('Class::MOP::Class');
552 return $class->_construct_instance(@_);
555 sub _construct_instance {
557 my $params = @_ == 1 ? $_[0] : {@_};
558 my $meta_instance = $class->get_meta_instance();
560 # the code below is almost certainly incorrect
561 # but this is foreign inheritance, so we might
562 # have to kludge it in the end.
564 if (my $instance_class = blessed($params->{__INSTANCE__})) {
565 ($instance_class eq $class->name)
566 || confess "Objects passed as the __INSTANCE__ parameter must "
567 . "already be blessed into the correct class, but "
568 . "$params->{__INSTANCE__} is not a " . $class->name;
569 $instance = $params->{__INSTANCE__};
571 elsif (exists $params->{__INSTANCE__}) {
572 confess "The __INSTANCE__ parameter must be a blessed reference, not "
573 . $params->{__INSTANCE__};
576 $instance = $meta_instance->create_instance();
578 foreach my $attr ($class->get_all_attributes()) {
579 $attr->initialize_instance_slot($meta_instance, $instance, $params);
581 if (Class::MOP::metaclass_is_weak($class->name)) {
582 $meta_instance->_set_mop_slot($instance, $class);
587 sub _inline_new_object {
591 'my $class = shift;',
592 '$class = Scalar::Util::blessed($class) || $class;',
593 $self->_inline_fallback_constructor('$class'),
594 $self->_inline_params('$params', '$class'),
595 $self->_inline_generate_instance('$instance', '$class'),
596 $self->_inline_slot_initializers,
597 $self->_inline_preserve_weak_metaclasses,
598 $self->_inline_extra_init,
603 sub _inline_fallback_constructor {
607 'return ' . $self->_generate_fallback_constructor($class),
608 'if ' . $class . ' ne \'' . $self->name . '\';',
612 sub _generate_fallback_constructor {
615 return 'Class::MOP::Class->initialize(' . $class . ')->new_object(@_)',
620 my ($params, $class) = @_;
622 'my ' . $params . ' = @_ == 1 ? $_[0] : {@_};',
626 sub _inline_generate_instance {
628 my ($inst, $class) = @_;
630 'my ' . $inst . ' = ' . $self->_inline_create_instance($class) . ';',
634 sub _inline_create_instance {
637 return $self->get_meta_instance->inline_create_instance(@_);
640 sub _inline_slot_initializers {
645 return map { $self->_inline_slot_initializer($_, $idx++) }
646 sort { $a->name cmp $b->name } $self->get_all_attributes;
649 sub _inline_slot_initializer {
651 my ($attr, $idx) = @_;
653 if (defined(my $init_arg = $attr->init_arg)) {
655 'if (exists $params->{\'' . $init_arg . '\'}) {',
656 $self->_inline_init_attr_from_constructor($attr, $idx),
659 if (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
668 elsif (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
680 sub _inline_init_attr_from_constructor {
682 my ($attr, $idx) = @_;
684 my @initial_value = $attr->_inline_set_value(
685 '$instance', '$params->{\'' . $attr->init_arg . '\'}',
688 push @initial_value, (
689 '$attrs->[' . $idx . ']->set_initial_value(',
691 $attr->_inline_instance_get('$instance'),
693 ) if $attr->has_initializer;
695 return @initial_value;
698 sub _inline_init_attr_from_default {
700 my ($attr, $idx) = @_;
702 my $default = $self->_inline_default_value($attr, $idx);
703 return unless $default;
705 my @initial_value = $attr->_inline_set_value('$instance', $default);
707 push @initial_value, (
708 '$attrs->[' . $idx . ']->set_initial_value(',
710 $attr->_inline_instance_get('$instance'),
712 ) if $attr->has_initializer;
714 return @initial_value;
717 sub _inline_default_value {
719 my ($attr, $index) = @_;
721 if ($attr->has_default) {
723 # default values can either be CODE refs
724 # in which case we need to call them. Or
725 # they can be scalars (strings/numbers)
726 # in which case we can just deal with them
727 # in the code we eval.
728 if ($attr->is_default_a_coderef) {
729 return '$defaults->[' . $index . ']->($instance)';
732 return '$defaults->[' . $index . ']';
735 elsif ($attr->has_builder) {
736 return '$instance->' . $attr->builder;
743 sub _inline_preserve_weak_metaclasses {
745 if (Class::MOP::metaclass_is_weak($self->name)) {
747 $self->_inline_set_mop_slot(
748 '$instance', 'Class::MOP::class_of($class)'
757 sub _inline_extra_init { }
760 sub get_meta_instance {
762 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
765 sub _create_meta_instance {
768 my $instance = $self->instance_metaclass->new(
769 associated_metaclass => $self,
770 attributes => [ $self->get_all_attributes() ],
773 $self->add_meta_instance_dependencies()
774 if $instance->is_dependent_on_superclasses();
779 sub _inline_rebless_instance {
782 return $self->get_meta_instance->inline_rebless_instance_structure(@_);
785 sub _inline_get_mop_slot {
788 return $self->get_meta_instance->_inline_get_mop_slot(@_);
791 sub _inline_set_mop_slot {
794 return $self->get_meta_instance->_inline_set_mop_slot(@_);
797 sub _inline_clear_mop_slot {
800 return $self->get_meta_instance->_inline_clear_mop_slot(@_);
805 my $instance = shift;
806 (blessed($instance) && $instance->isa($class->name))
807 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
810 # we need to protect the integrity of the
811 # Class::MOP::Class singletons here, they
812 # should not be cloned.
813 return $instance if $instance->isa('Class::MOP::Class');
814 $class->_clone_instance($instance, @_);
817 sub _clone_instance {
818 my ($class, $instance, %params) = @_;
820 || confess "You can only clone instances, ($instance) is not a blessed instance";
821 my $meta_instance = $class->get_meta_instance();
822 my $clone = $meta_instance->clone_instance($instance);
823 foreach my $attr ($class->get_all_attributes()) {
824 if ( defined( my $init_arg = $attr->init_arg ) ) {
825 if (exists $params{$init_arg}) {
826 $attr->set_value($clone, $params{$init_arg});
833 sub _force_rebless_instance {
834 my ($self, $instance, %params) = @_;
835 my $old_metaclass = Class::MOP::class_of($instance);
837 $old_metaclass->rebless_instance_away($instance, $self, %params)
840 my $meta_instance = $self->get_meta_instance;
842 if (Class::MOP::metaclass_is_weak($old_metaclass->name)) {
843 $meta_instance->_clear_mop_slot($instance);
847 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
848 $meta_instance->rebless_instance_structure($_[1], $self);
850 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
852 if (Class::MOP::metaclass_is_weak($self->name)) {
853 $meta_instance->_set_mop_slot($instance, $self);
857 sub rebless_instance {
858 my ($self, $instance, %params) = @_;
859 my $old_metaclass = Class::MOP::class_of($instance);
861 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
862 $self->name->isa($old_class)
863 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
865 $self->_force_rebless_instance($_[1], %params);
870 sub rebless_instance_back {
871 my ( $self, $instance ) = @_;
872 my $old_metaclass = Class::MOP::class_of($instance);
875 = $old_metaclass ? $old_metaclass->name : blessed($instance);
876 $old_class->isa( $self->name )
878 "You may rebless only into a superclass of ($old_class), of which ("
882 $self->_force_rebless_instance($_[1]);
887 sub rebless_instance_away {
888 # this intentionally does nothing, it is just a hook
891 sub _fixup_attributes_after_rebless {
893 my ($instance, $rebless_from, %params) = @_;
894 my $meta_instance = $self->get_meta_instance;
896 for my $attr ( $rebless_from->get_all_attributes ) {
897 next if $self->find_attribute_by_name( $attr->name );
898 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
901 foreach my $attr ( $self->get_all_attributes ) {
902 if ( $attr->has_value($instance) ) {
903 if ( defined( my $init_arg = $attr->init_arg ) ) {
904 $params{$init_arg} = $attr->get_value($instance)
905 unless exists $params{$init_arg};
908 $attr->set_value($instance, $attr->get_value($instance));
913 foreach my $attr ($self->get_all_attributes) {
914 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
918 sub _attach_attribute {
919 my ($self, $attribute) = @_;
920 $attribute->attach_to_class($self);
923 sub _post_add_attribute {
924 my ( $self, $attribute ) = @_;
926 $self->invalidate_meta_instances;
928 # invalidate package flag here
931 $attribute->install_accessors;
934 $self->remove_attribute( $attribute->name );
939 sub remove_attribute {
942 my $removed_attribute = $self->SUPER::remove_attribute(@_)
945 $self->invalidate_meta_instances;
947 $removed_attribute->remove_accessors;
948 $removed_attribute->detach_from_class;
950 return$removed_attribute;
953 sub find_attribute_by_name {
954 my ( $self, $attr_name ) = @_;
956 foreach my $class ( $self->linearized_isa ) {
957 # fetch the meta-class ...
958 my $meta = Class::MOP::Class->initialize($class);
959 return $meta->get_attribute($attr_name)
960 if $meta->has_attribute($attr_name);
966 sub get_all_attributes {
968 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
969 reverse $self->linearized_isa;
970 return values %attrs;
978 my $isa = $self->get_or_add_package_symbol('@ISA');
985 # on 5.8 and below, we need to call
986 # a method to get Perl to detect
987 # a cycle in the class hierarchy
988 my $class = $self->name;
992 # we need to check the metaclass
993 # compatibility here so that we can
994 # be sure that the superclass is
995 # not potentially creating an issues
996 # we don't know about
998 $self->_check_metaclass_compatibility();
999 $self->_superclasses_updated();
1005 sub _superclasses_updated {
1007 $self->update_meta_instance_dependencies();
1008 # keep strong references to all our parents, so they don't disappear if
1009 # they are anon classes and don't have any direct instances
1010 $self->_superclass_metas(
1011 map { Class::MOP::class_of($_) } $self->superclasses
1015 sub _superclass_metas {
1017 $self->{_superclass_metas} = [@_];
1022 my $super_class = $self->name;
1024 return @{ $super_class->mro::get_isarev() };
1027 sub direct_subclasses {
1029 my $super_class = $self->name;
1034 } Class::MOP::Class->initialize($_)->superclasses
1035 } $self->subclasses;
1038 sub linearized_isa {
1039 return @{ mro::get_linear_isa( (shift)->name ) };
1042 sub class_precedence_list {
1044 my $name = $self->name;
1046 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
1048 # We need to check for circular inheritance here
1049 # if we are are not on 5.10, cause 5.8 detects it
1050 # late. This will do nothing if all is well, and
1051 # blow up otherwise. Yes, it's an ugly hack, better
1052 # suggestions are welcome.
1054 ($name || return)->isa('This is a test for circular inheritance')
1057 # if our mro is c3, we can
1058 # just grab the linear_isa
1059 if (mro::get_mro($name) eq 'c3') {
1060 return @{ mro::get_linear_isa($name) }
1064 # we can't grab the linear_isa for dfs
1065 # since it has all the duplicates
1070 Class::MOP::Class->initialize($_)->class_precedence_list()
1071 } $self->superclasses()
1079 my $fetch_and_prepare_method = sub {
1080 my ($self, $method_name) = @_;
1081 my $wrapped_metaclass = $self->wrapped_method_metaclass;
1083 my $method = $self->get_method($method_name);
1084 # if we dont have local ...
1086 # try to find the next method
1087 $method = $self->find_next_method_by_name($method_name);
1088 # die if it does not exist
1090 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
1091 # and now make sure to wrap it
1092 # even if it is already wrapped
1093 # because we need a new sub ref
1094 $method = $wrapped_metaclass->wrap($method,
1095 package_name => $self->name,
1096 name => $method_name,
1100 # now make sure we wrap it properly
1101 $method = $wrapped_metaclass->wrap($method,
1102 package_name => $self->name,
1103 name => $method_name,
1104 ) unless $method->isa($wrapped_metaclass);
1106 $self->add_method($method_name => $method);
1110 sub add_before_method_modifier {
1111 my ($self, $method_name, $method_modifier) = @_;
1112 (defined $method_name && length $method_name)
1113 || confess "You must pass in a method name";
1114 my $method = $fetch_and_prepare_method->($self, $method_name);
1115 $method->add_before_modifier(
1116 subname(':before' => $method_modifier)
1120 sub add_after_method_modifier {
1121 my ($self, $method_name, $method_modifier) = @_;
1122 (defined $method_name && length $method_name)
1123 || confess "You must pass in a method name";
1124 my $method = $fetch_and_prepare_method->($self, $method_name);
1125 $method->add_after_modifier(
1126 subname(':after' => $method_modifier)
1130 sub add_around_method_modifier {
1131 my ($self, $method_name, $method_modifier) = @_;
1132 (defined $method_name && length $method_name)
1133 || confess "You must pass in a method name";
1134 my $method = $fetch_and_prepare_method->($self, $method_name);
1135 $method->add_around_modifier(
1136 subname(':around' => $method_modifier)
1141 # the methods above used to be named like this:
1142 # ${pkg}::${method}:(before|after|around)
1143 # but this proved problematic when using one modifier
1144 # to wrap multiple methods (something which is likely
1145 # to happen pretty regularly IMO). So instead of naming
1146 # it like this, I have chosen to just name them purely
1147 # with their modifier names, like so:
1148 # :(before|after|around)
1149 # The fact is that in a stack trace, it will be fairly
1150 # evident from the context what method they are attached
1151 # to, and so don't need the fully qualified name.
1154 sub find_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 foreach my $class ($self->linearized_isa) {
1159 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1160 return $method if defined $method;
1165 sub get_all_methods {
1169 for my $class ( reverse $self->linearized_isa ) {
1170 my $meta = Class::MOP::Class->initialize($class);
1172 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1175 return values %methods;
1178 sub get_all_method_names {
1181 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
1184 sub find_all_methods_by_name {
1185 my ($self, $method_name) = @_;
1186 (defined $method_name && length $method_name)
1187 || confess "You must define a method name to find";
1189 foreach my $class ($self->linearized_isa) {
1190 # fetch the meta-class ...
1191 my $meta = Class::MOP::Class->initialize($class);
1193 name => $method_name,
1195 code => $meta->get_method($method_name)
1196 } if $meta->has_method($method_name);
1201 sub find_next_method_by_name {
1202 my ($self, $method_name) = @_;
1203 (defined $method_name && length $method_name)
1204 || confess "You must define a method name to find";
1205 my @cpl = $self->linearized_isa;
1206 shift @cpl; # discard ourselves
1207 foreach my $class (@cpl) {
1208 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1209 return $method if defined $method;
1214 sub update_meta_instance_dependencies {
1217 if ( $self->{meta_instance_dependencies} ) {
1218 return $self->add_meta_instance_dependencies;
1222 sub add_meta_instance_dependencies {
1225 $self->remove_meta_instance_dependencies;
1227 my @attrs = $self->get_all_attributes();
1230 my @classes = grep { not $seen{ $_->name }++ }
1231 map { $_->associated_class } @attrs;
1233 foreach my $class (@classes) {
1234 $class->add_dependent_meta_instance($self);
1237 $self->{meta_instance_dependencies} = \@classes;
1240 sub remove_meta_instance_dependencies {
1243 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1244 foreach my $class (@$classes) {
1245 $class->remove_dependent_meta_instance($self);
1255 sub add_dependent_meta_instance {
1256 my ( $self, $metaclass ) = @_;
1257 push @{ $self->{dependent_meta_instances} }, $metaclass;
1260 sub remove_dependent_meta_instance {
1261 my ( $self, $metaclass ) = @_;
1262 my $name = $metaclass->name;
1263 @$_ = grep { $_->name ne $name } @$_
1264 for $self->{dependent_meta_instances};
1267 sub invalidate_meta_instances {
1269 $_->invalidate_meta_instance()
1270 for $self, @{ $self->{dependent_meta_instances} };
1273 sub invalidate_meta_instance {
1275 undef $self->{_meta_instance};
1278 # check if we can reinitialize
1282 # if any local attr is defined
1283 return if $self->get_attribute_list;
1285 # or any non-declared methods
1286 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1287 return if $method->isa("Class::MOP::Method::Generated");
1288 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1296 sub is_mutable { 1 }
1297 sub is_immutable { 0 }
1299 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1301 sub _immutable_options {
1302 my ( $self, @args ) = @_;
1305 inline_accessors => 1,
1306 inline_constructor => 1,
1307 inline_destructor => 0,
1309 immutable_trait => $self->immutable_trait,
1310 constructor_name => $self->constructor_name,
1311 constructor_class => $self->constructor_class,
1312 destructor_class => $self->destructor_class,
1317 sub make_immutable {
1318 my ( $self, @args ) = @_;
1320 if ( $self->is_mutable ) {
1321 $self->_initialize_immutable( $self->_immutable_options(@args) );
1322 $self->_rebless_as_immutable(@args);
1333 if ( $self->is_immutable ) {
1334 my @args = $self->immutable_options;
1335 $self->_rebless_as_mutable();
1336 $self->_remove_inlined_code(@args);
1337 delete $self->{__immutable};
1345 sub _rebless_as_immutable {
1346 my ( $self, @args ) = @_;
1348 $self->{__immutable}{original_class} = ref $self;
1350 bless $self => $self->_immutable_metaclass(@args);
1353 sub _immutable_metaclass {
1354 my ( $self, %args ) = @_;
1356 if ( my $class = $args{immutable_metaclass} ) {
1360 my $trait = $args{immutable_trait} = $self->immutable_trait
1361 || confess "no immutable trait specified for $self";
1363 my $meta = $self->meta;
1364 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1368 if ( $meta_attr and $trait eq $meta_attr->default ) {
1369 # if the trait is the same as the default we try and pick a
1370 # predictable name for the immutable metaclass
1371 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1374 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1375 $trait, 'ForMetaClass', ref($self);
1379 if Class::MOP::is_class_loaded($class_name);
1381 # If the metaclass is a subclass of CMOP::Class which has had
1382 # metaclass roles applied (via Moose), then we want to make sure
1383 # that we preserve that anonymous class (see Fey::ORM for an
1384 # example of where this matters).
1385 my $meta_name = $meta->_real_ref_name;
1387 my $immutable_meta = $meta_name->create(
1389 superclasses => [ ref $self ],
1392 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1394 $immutable_meta->make_immutable(
1395 inline_constructor => 0,
1396 inline_accessors => 0,
1402 sub _remove_inlined_code {
1405 $self->remove_method( $_->name ) for $self->_inlined_methods;
1407 delete $self->{__immutable}{inlined_methods};
1410 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1412 sub _add_inlined_method {
1413 my ( $self, $method ) = @_;
1415 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1418 sub _initialize_immutable {
1419 my ( $self, %args ) = @_;
1421 $self->{__immutable}{options} = \%args;
1422 $self->_install_inlined_code(%args);
1425 sub _install_inlined_code {
1426 my ( $self, %args ) = @_;
1429 $self->_inline_accessors(%args) if $args{inline_accessors};
1430 $self->_inline_constructor(%args) if $args{inline_constructor};
1431 $self->_inline_destructor(%args) if $args{inline_destructor};
1434 sub _rebless_as_mutable {
1437 bless $self, $self->_get_mutable_metaclass_name;
1442 sub _inline_accessors {
1445 foreach my $attr_name ( $self->get_attribute_list ) {
1446 $self->get_attribute($attr_name)->install_accessors(1);
1450 sub _inline_constructor {
1451 my ( $self, %args ) = @_;
1453 my $name = $args{constructor_name};
1454 # A class may not even have a constructor, and that's okay.
1455 return unless defined $name;
1457 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1458 my $class = $self->name;
1459 warn "Not inlining a constructor for $class since it defines"
1460 . " its own constructor.\n"
1461 . "If you are certain you don't need to inline your"
1462 . " constructor, specify inline_constructor => 0 in your"
1463 . " call to $class->meta->make_immutable\n";
1467 my $constructor_class = $args{constructor_class};
1469 Class::MOP::load_class($constructor_class);
1471 my $constructor = $constructor_class->new(
1475 package_name => $self->name,
1479 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1480 $self->add_method( $name => $constructor );
1481 $self->_add_inlined_method($constructor);
1485 sub _inline_destructor {
1486 my ( $self, %args ) = @_;
1488 ( exists $args{destructor_class} && defined $args{destructor_class} )
1489 || confess "The 'inline_destructor' option is present, but "
1490 . "no destructor class was specified";
1492 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1493 my $class = $self->name;
1494 warn "Not inlining a destructor for $class since it defines"
1495 . " its own destructor.\n";
1499 my $destructor_class = $args{destructor_class};
1501 Class::MOP::load_class($destructor_class);
1503 return unless $destructor_class->is_needed($self);
1505 my $destructor = $destructor_class->new(
1508 package_name => $self->name,
1512 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1513 $self->add_method( 'DESTROY' => $destructor );
1514 $self->_add_inlined_method($destructor);
1520 # ABSTRACT: Class Meta Object
1528 # assuming that class Foo
1529 # has been defined, you can
1531 # use this for introspection ...
1533 # add a method to Foo ...
1534 Foo->meta->add_method( 'bar' => sub {...} )
1536 # get a list of all the classes searched
1537 # the method dispatcher in the correct order
1538 Foo->meta->class_precedence_list()
1540 # remove a method from Foo
1541 Foo->meta->remove_method('bar');
1543 # or use this to actually create classes ...
1545 Class::MOP::Class->create(
1548 superclasses => ['Foo'],
1550 Class::MOP::Attribute->new('$bar'),
1551 Class::MOP::Attribute->new('$baz'),
1554 calculate_bar => sub {...},
1555 construct_baz => sub {...}
1562 The Class Protocol is the largest and most complex part of the
1563 Class::MOP meta-object protocol. It controls the introspection and
1564 manipulation of Perl 5 classes, and it can create them as well. The
1565 best way to understand what this module can do is to read the
1566 documentation for each of its methods.
1570 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1574 =head2 Class construction
1576 These methods all create new C<Class::MOP::Class> objects. These
1577 objects can represent existing classes or they can be used to create
1578 new classes from scratch.
1580 The metaclass object for a given class is a singleton. If you attempt
1581 to create a metaclass for the same class twice, you will just get the
1586 =item B<< Class::MOP::Class->create($package_name, %options) >>
1588 This method creates a new C<Class::MOP::Class> object with the given
1589 package name. It accepts a number of options:
1595 An optional version number for the newly created package.
1599 An optional authority for the newly created package.
1601 =item * superclasses
1603 An optional array reference of superclass names.
1607 An optional hash reference of methods for the class. The keys of the
1608 hash reference are method names and values are subroutine references.
1612 An optional array reference of L<Class::MOP::Attribute> objects.
1616 Specifies the name to install the C<meta> method for this class under.
1617 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1618 given, no meta method will be installed.
1622 If true, the metaclass that is stored in the global cache will be a
1625 Classes created in this way are destroyed once the metaclass they are
1626 attached to goes out of scope, and will be removed from Perl's internal
1629 All instances of a class with a weakened metaclass keep a special
1630 reference to the metaclass object, which prevents the metaclass from
1631 going out of scope while any instances exist.
1633 This only works if the instance is based on a hash reference, however.
1637 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1639 This method works just like C<< Class::MOP::Class->create >> but it
1640 creates an "anonymous" class. In fact, the class does have a name, but
1641 that name is a unique name generated internally by this module.
1643 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1644 parameters that C<create> accepts.
1646 Anonymous classes default to C<< weaken => 1 >>, although this can be
1649 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1651 This method will initialize a C<Class::MOP::Class> object for the
1652 named package. Unlike C<create>, this method I<will not> create a new
1655 The purpose of this method is to retrieve a C<Class::MOP::Class>
1656 object for introspecting an existing class.
1658 If an existing C<Class::MOP::Class> object exists for the named
1659 package, it will be returned, and any options provided will be
1662 If the object does not yet exist, it will be created.
1664 The valid options that can be passed to this method are
1665 C<attribute_metaclass>, C<method_metaclass>,
1666 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1667 optional, and default to the appropriate class in the C<Class::MOP>
1672 =head2 Object instance construction and cloning
1674 These methods are all related to creating and/or cloning object
1679 =item B<< $metaclass->clone_object($instance, %params) >>
1681 This method clones an existing object instance. Any parameters you
1682 provide are will override existing attribute values in the object.
1684 This is a convenience method for cloning an object instance, then
1685 blessing it into the appropriate package.
1687 You could implement a clone method in your class, using this method:
1690 my ($self, %params) = @_;
1691 $self->meta->clone_object($self, %params);
1694 =item B<< $metaclass->rebless_instance($instance, %params) >>
1696 This method changes the class of C<$instance> to the metaclass's class.
1698 You can only rebless an instance into a subclass of its current
1699 class. If you pass any additional parameters, these will be treated
1700 like constructor parameters and used to initialize the object's
1701 attributes. Any existing attributes that are already set will be
1704 Before reblessing the instance, this method will call
1705 C<rebless_instance_away> on the instance's current metaclass. This method
1706 will be passed the instance, the new metaclass, and any parameters
1707 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1708 does nothing; it is merely a hook.
1710 =item B<< $metaclass->rebless_instance_back($instance) >>
1712 Does the same thing as C<rebless_instance>, except that you can only
1713 rebless an instance into one of its superclasses. Any attributes that
1714 do not exist in the superclass will be deinitialized.
1716 This is a much more dangerous operation than C<rebless_instance>,
1717 especially when multiple inheritance is involved, so use this carefully!
1719 =item B<< $metaclass->new_object(%params) >>
1721 This method is used to create a new object of the metaclass's
1722 class. Any parameters you provide are used to initialize the
1723 instance's attributes. A special C<__INSTANCE__> key can be passed to
1724 provide an already generated instance, rather than having Class::MOP
1725 generate it for you. This is mostly useful for using Class::MOP with
1726 foreign classes which generate instances using their own constructors.
1728 =item B<< $metaclass->instance_metaclass >>
1730 Returns the class name of the instance metaclass. See
1731 L<Class::MOP::Instance> for more information on the instance
1734 =item B<< $metaclass->get_meta_instance >>
1736 Returns an instance of the C<instance_metaclass> to be used in the
1737 construction of a new instance of the class.
1741 =head2 Informational predicates
1743 These are a few predicate methods for asking information about the
1748 =item B<< $metaclass->is_anon_class >>
1750 This returns true if the class was created by calling C<<
1751 Class::MOP::Class->create_anon_class >>.
1753 =item B<< $metaclass->is_mutable >>
1755 This returns true if the class is still mutable.
1757 =item B<< $metaclass->is_immutable >>
1759 This returns true if the class has been made immutable.
1761 =item B<< $metaclass->is_pristine >>
1763 A class is I<not> pristine if it has non-inherited attributes or if it
1764 has any generated methods.
1768 =head2 Inheritance Relationships
1772 =item B<< $metaclass->superclasses(@superclasses) >>
1774 This is a read-write accessor which represents the superclass
1775 relationships of the metaclass's class.
1777 This is basically sugar around getting and setting C<@ISA>.
1779 =item B<< $metaclass->class_precedence_list >>
1781 This returns a list of all of the class's ancestor classes. The
1782 classes are returned in method dispatch order.
1784 =item B<< $metaclass->linearized_isa >>
1786 This returns a list based on C<class_precedence_list> but with all
1789 =item B<< $metaclass->subclasses >>
1791 This returns a list of all subclasses for this class, even indirect
1794 =item B<< $metaclass->direct_subclasses >>
1796 This returns a list of immediate subclasses for this class, which does not
1797 include indirect subclasses.
1801 =head2 Method introspection and creation
1803 These methods allow you to introspect a class's methods, as well as
1804 add, remove, or change methods.
1806 Determining what is truly a method in a Perl 5 class requires some
1807 heuristics (aka guessing).
1809 Methods defined outside the package with a fully qualified name (C<sub
1810 Package::name { ... }>) will be included. Similarly, methods named
1811 with a fully qualified name using L<Sub::Name> are also included.
1813 However, we attempt to ignore imported functions.
1815 Ultimately, we are using heuristics to determine what truly is a
1816 method in a class, and these heuristics may get the wrong answer in
1817 some edge cases. However, for most "normal" cases the heuristics work
1822 =item B<< $metaclass->get_method($method_name) >>
1824 This will return a L<Class::MOP::Method> for the specified
1825 C<$method_name>. If the class does not have the specified method, it
1828 =item B<< $metaclass->has_method($method_name) >>
1830 Returns a boolean indicating whether or not the class defines the
1831 named method. It does not include methods inherited from parent
1834 =item B<< $metaclass->get_method_list >>
1836 This will return a list of method I<names> for all methods defined in
1839 =item B<< $metaclass->add_method($method_name, $method) >>
1841 This method takes a method name and a subroutine reference, and adds
1842 the method to the class.
1844 The subroutine reference can be a L<Class::MOP::Method>, and you are
1845 strongly encouraged to pass a meta method object instead of a code
1846 reference. If you do so, that object gets stored as part of the
1847 class's method map directly. If not, the meta information will have to
1848 be recreated later, and may be incorrect.
1850 If you provide a method object, this method will clone that object if
1851 the object's package name does not match the class name. This lets us
1852 track the original source of any methods added from other classes
1853 (notably Moose roles).
1855 =item B<< $metaclass->remove_method($method_name) >>
1857 Remove the named method from the class. This method returns the
1858 L<Class::MOP::Method> object for the method.
1860 =item B<< $metaclass->method_metaclass >>
1862 Returns the class name of the method metaclass, see
1863 L<Class::MOP::Method> for more information on the method metaclass.
1865 =item B<< $metaclass->wrapped_method_metaclass >>
1867 Returns the class name of the wrapped method metaclass, see
1868 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1871 =item B<< $metaclass->get_all_methods >>
1873 This will traverse the inheritance hierarchy and return a list of all
1874 the L<Class::MOP::Method> objects for this class and its parents.
1876 =item B<< $metaclass->find_method_by_name($method_name) >>
1878 This will return a L<Class::MOP::Method> for the specified
1879 C<$method_name>. If the class does not have the specified method, it
1882 Unlike C<get_method>, this method I<will> look for the named method in
1885 =item B<< $metaclass->get_all_method_names >>
1887 This will return a list of method I<names> for all of this class's
1888 methods, including inherited methods.
1890 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1892 This method looks for the named method in the class and all of its
1893 parents. It returns every matching method it finds in the inheritance
1894 tree, so it returns a list of methods.
1896 Each method is returned as a hash reference with three keys. The keys
1897 are C<name>, C<class>, and C<code>. The C<code> key has a
1898 L<Class::MOP::Method> object as its value.
1900 The list of methods is distinct.
1902 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1904 This method returns the first method in any superclass matching the
1905 given name. It is effectively the method that C<SUPER::$method_name>
1910 =head2 Attribute introspection and creation
1912 Because Perl 5 does not have a core concept of attributes in classes,
1913 we can only return information about attributes which have been added
1914 via this class's methods. We cannot discover information about
1915 attributes which are defined in terms of "regular" Perl 5 methods.
1919 =item B<< $metaclass->get_attribute($attribute_name) >>
1921 This will return a L<Class::MOP::Attribute> for the specified
1922 C<$attribute_name>. If the class does not have the specified
1923 attribute, it returns C<undef>.
1925 NOTE that get_attribute does not search superclasses, for that you
1926 need to use C<find_attribute_by_name>.
1928 =item B<< $metaclass->has_attribute($attribute_name) >>
1930 Returns a boolean indicating whether or not the class defines the
1931 named attribute. It does not include attributes inherited from parent
1934 =item B<< $metaclass->get_attribute_list >>
1936 This will return a list of attributes I<names> for all attributes
1937 defined in this class. Note that this operates on the current class
1938 only, it does not traverse the inheritance hierarchy.
1940 =item B<< $metaclass->get_all_attributes >>
1942 This will traverse the inheritance hierarchy and return a list of all
1943 the L<Class::MOP::Attribute> objects for this class and its parents.
1945 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1947 This will return a L<Class::MOP::Attribute> for the specified
1948 C<$attribute_name>. If the class does not have the specified
1949 attribute, it returns C<undef>.
1951 Unlike C<get_attribute>, this attribute I<will> look for the named
1952 attribute in superclasses.
1954 =item B<< $metaclass->add_attribute(...) >>
1956 This method accepts either an existing L<Class::MOP::Attribute>
1957 object or parameters suitable for passing to that class's C<new>
1960 The attribute provided will be added to the class.
1962 Any accessor methods defined by the attribute will be added to the
1963 class when the attribute is added.
1965 If an attribute of the same name already exists, the old attribute
1966 will be removed first.
1968 =item B<< $metaclass->remove_attribute($attribute_name) >>
1970 This will remove the named attribute from the class, and
1971 L<Class::MOP::Attribute> object.
1973 Removing an attribute also removes any accessor methods defined by the
1976 However, note that removing an attribute will only affect I<future>
1977 object instances created for this class, not existing instances.
1979 =item B<< $metaclass->attribute_metaclass >>
1981 Returns the class name of the attribute metaclass for this class. By
1982 default, this is L<Class::MOP::Attribute>.
1986 =head2 Class Immutability
1988 Making a class immutable "freezes" the class definition. You can no
1989 longer call methods which alter the class, such as adding or removing
1990 methods or attributes.
1992 Making a class immutable lets us optimize the class by inlining some
1993 methods, and also allows us to optimize some methods on the metaclass
1996 After immutabilization, the metaclass object will cache most informational
1997 methods that returns information about methods or attributes. Methods which
1998 would alter the class, such as C<add_attribute> and C<add_method>, will
1999 throw an error on an immutable metaclass object.
2001 The immutabilization system in L<Moose> takes much greater advantage
2002 of the inlining features than Class::MOP itself does.
2006 =item B<< $metaclass->make_immutable(%options) >>
2008 This method will create an immutable transformer and use it to make
2009 the class and its metaclass object immutable.
2011 This method accepts the following options:
2015 =item * inline_accessors
2017 =item * inline_constructor
2019 =item * inline_destructor
2021 These are all booleans indicating whether the specified method(s)
2024 By default, accessors and the constructor are inlined, but not the
2027 =item * immutable_trait
2029 The name of a class which will be used as a parent class for the
2030 metaclass object being made immutable. This "trait" implements the
2031 post-immutability functionality of the metaclass (but not the
2032 transformation itself).
2034 This defaults to L<Class::MOP::Class::Immutable::Trait>.
2036 =item * constructor_name
2038 This is the constructor method name. This defaults to "new".
2040 =item * constructor_class
2042 The name of the method metaclass for constructors. It will be used to
2043 generate the inlined constructor. This defaults to
2044 "Class::MOP::Method::Constructor".
2046 =item * replace_constructor
2048 This is a boolean indicating whether an existing constructor should be
2049 replaced when inlining a constructor. This defaults to false.
2051 =item * destructor_class
2053 The name of the method metaclass for destructors. It will be used to
2054 generate the inlined destructor. This defaults to
2055 "Class::MOP::Method::Denstructor".
2057 =item * replace_destructor
2059 This is a boolean indicating whether an existing destructor should be
2060 replaced when inlining a destructor. This defaults to false.
2064 =item B<< $metaclass->immutable_options >>
2066 Returns a hash of the options used when making the class immutable, including
2067 both defaults and anything supplied by the user in the call to C<<
2068 $metaclass->make_immutable >>. This is useful if you need to temporarily make
2069 a class mutable and then restore immutability as it was before.
2071 =item B<< $metaclass->make_mutable >>
2073 Calling this method reverse the immutabilization transformation.
2077 =head2 Method Modifiers
2079 Method modifiers are hooks which allow a method to be wrapped with
2080 I<before>, I<after> and I<around> method modifiers. Every time a
2081 method is called, its modifiers are also called.
2083 A class can modify its own methods, as well as methods defined in
2086 =head3 How method modifiers work?
2088 Method modifiers work by wrapping the original method and then
2089 replacing it in the class's symbol table. The wrappers will handle
2090 calling all the modifiers in the appropriate order and preserving the
2091 calling context for the original method.
2093 The return values of C<before> and C<after> modifiers are
2094 ignored. This is because their purpose is B<not> to filter the input
2095 and output of the primary method (this is done with an I<around>
2098 This may seem like an odd restriction to some, but doing this allows
2099 for simple code to be added at the beginning or end of a method call
2100 without altering the function of the wrapped method or placing any
2101 extra responsibility on the code of the modifier.
2103 Of course if you have more complex needs, you can use the C<around>
2104 modifier which allows you to change both the parameters passed to the
2105 wrapped method, as well as its return value.
2107 Before and around modifiers are called in last-defined-first-called
2108 order, while after modifiers are called in first-defined-first-called
2109 order. So the call tree might looks something like this:
2121 =head3 What is the performance impact?
2123 Of course there is a performance cost associated with method
2124 modifiers, but we have made every effort to make that cost directly
2125 proportional to the number of modifier features you use.
2127 The wrapping method does its best to B<only> do as much work as it
2128 absolutely needs to. In order to do this we have moved some of the
2129 performance costs to set-up time, where they are easier to amortize.
2131 All this said, our benchmarks have indicated the following:
2133 simple wrapper with no modifiers 100% slower
2134 simple wrapper with simple before modifier 400% slower
2135 simple wrapper with simple after modifier 450% slower
2136 simple wrapper with simple around modifier 500-550% slower
2137 simple wrapper with all 3 modifiers 1100% slower
2139 These numbers may seem daunting, but you must remember, every feature
2140 comes with some cost. To put things in perspective, just doing a
2141 simple C<AUTOLOAD> which does nothing but extract the name of the
2142 method called and return it costs about 400% over a normal method
2147 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
2149 This wraps the specified method with the supplied subroutine
2150 reference. The modifier will be called as a method itself, and will
2151 receive the same arguments as are passed to the method.
2153 When the modifier exits, the wrapped method will be called.
2155 The return value of the modifier will be ignored.
2157 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2159 This wraps the specified method with the supplied subroutine
2160 reference. The modifier will be called as a method itself, and will
2161 receive the same arguments as are passed to the method.
2163 When the wrapped methods exits, the modifier will be called.
2165 The return value of the modifier will be ignored.
2167 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2169 This wraps the specified method with the supplied subroutine
2172 The first argument passed to the modifier will be a subroutine
2173 reference to the wrapped method. The second argument is the object,
2174 and after that come any arguments passed when the method is called.
2176 The around modifier can choose to call the original method, as well as
2177 what arguments to pass if it does so.
2179 The return value of the modifier is what will be seen by the caller.
2183 =head2 Introspection
2187 =item B<< Class::MOP::Class->meta >>
2189 This will return a L<Class::MOP::Class> instance for this class.
2191 It should also be noted that L<Class::MOP> will actually bootstrap
2192 this module by installing a number of attribute meta-objects into its