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 no warnings 'uninitialized';
452 my $name = $self->name;
453 return unless $name =~ /^$ANON_CLASS_PREFIX/o;
455 # Moose does a weird thing where it replaces the metaclass for
456 # class when fixing metaclass incompatibility. In that case,
457 # we don't want to clean out the namespace now. We can detect
458 # that because Moose will explicitly update the singleton
459 # cache in Class::MOP.
460 my $current_meta = Class::MOP::get_metaclass_by_name($name);
461 return if $current_meta ne $self;
463 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/o);
465 @{$name . '::ISA'} = ();
466 %{$name . '::'} = ();
467 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
469 Class::MOP::remove_metaclass_by_name($name);
474 # creating classes with MOP ...
477 my ( $class, @args ) = @_;
479 unshift @args, 'package' if @args % 2 == 1;
481 my (%options) = @args;
482 my $package_name = $options{package};
484 (ref $options{superclasses} eq 'ARRAY')
485 || confess "You must pass an ARRAY ref of superclasses"
486 if exists $options{superclasses};
488 (ref $options{attributes} eq 'ARRAY')
489 || confess "You must pass an ARRAY ref of attributes"
490 if exists $options{attributes};
492 (ref $options{methods} eq 'HASH')
493 || confess "You must pass a HASH ref of methods"
494 if exists $options{methods};
496 $options{meta_name} = 'meta'
497 unless exists $options{meta_name};
499 my (%initialize_options) = @args;
500 delete @initialize_options{qw(
509 my $meta = $class->initialize( $package_name => %initialize_options );
511 $meta->_instantiate_module( $options{version}, $options{authority} );
513 $meta->_add_meta_method($options{meta_name})
514 if defined $options{meta_name};
516 $meta->superclasses(@{$options{superclasses}})
517 if exists $options{superclasses};
519 # process attributes first, so that they can
520 # install accessors, but locally defined methods
521 # can then overwrite them. It is maybe a little odd, but
522 # I think this should be the order of things.
523 if (exists $options{attributes}) {
524 foreach my $attr (@{$options{attributes}}) {
525 $meta->add_attribute($attr);
528 if (exists $options{methods}) {
529 foreach my $method_name (keys %{$options{methods}}) {
530 $meta->add_method($method_name, $options{methods}->{$method_name});
536 # Instance Construction & Cloning
542 # we need to protect the integrity of the
543 # Class::MOP::Class singletons here, so we
544 # delegate this to &construct_class_instance
545 # which will deal with the singletons
546 return $class->_construct_class_instance(@_)
547 if $class->name->isa('Class::MOP::Class');
548 return $class->_construct_instance(@_);
551 sub _construct_instance {
553 my $params = @_ == 1 ? $_[0] : {@_};
554 my $meta_instance = $class->get_meta_instance();
556 # the code below is almost certainly incorrect
557 # but this is foreign inheritance, so we might
558 # have to kludge it in the end.
560 if (my $instance_class = blessed($params->{__INSTANCE__})) {
561 ($instance_class eq $class->name)
562 || confess "Objects passed as the __INSTANCE__ parameter must "
563 . "already be blessed into the correct class, but "
564 . "$params->{__INSTANCE__} is not a " . $class->name;
565 $instance = $params->{__INSTANCE__};
567 elsif (exists $params->{__INSTANCE__}) {
568 confess "The __INSTANCE__ parameter must be a blessed reference, not "
569 . $params->{__INSTANCE__};
572 $instance = $meta_instance->create_instance();
574 foreach my $attr ($class->get_all_attributes()) {
575 $attr->initialize_instance_slot($meta_instance, $instance, $params);
577 if (Class::MOP::metaclass_is_weak($class->name)) {
578 $meta_instance->_set_mop_slot($instance, $class);
583 sub _inline_new_object {
587 'my $class = shift;',
588 '$class = Scalar::Util::blessed($class) || $class;',
589 $self->_inline_fallback_constructor('$class'),
590 $self->_inline_params('$params', '$class'),
591 $self->_inline_generate_instance('$instance', '$class'),
592 $self->_inline_slot_initializers,
593 $self->_inline_preserve_weak_metaclasses,
594 $self->_inline_extra_init,
599 sub _inline_fallback_constructor {
603 'return ' . $self->_generate_fallback_constructor($class),
604 'if ' . $class . ' ne \'' . $self->name . '\';',
608 sub _generate_fallback_constructor {
611 return 'Class::MOP::Class->initialize(' . $class . ')->new_object(@_)',
616 my ($params, $class) = @_;
618 'my ' . $params . ' = @_ == 1 ? $_[0] : {@_};',
622 sub _inline_generate_instance {
624 my ($inst, $class) = @_;
626 'my ' . $inst . ' = ' . $self->_inline_create_instance($class) . ';',
630 sub _inline_create_instance {
633 return $self->get_meta_instance->inline_create_instance(@_);
636 sub _inline_slot_initializers {
641 return map { $self->_inline_slot_initializer($_, $idx++) }
642 sort { $a->name cmp $b->name } $self->get_all_attributes;
645 sub _inline_slot_initializer {
647 my ($attr, $idx) = @_;
649 if (defined(my $init_arg = $attr->init_arg)) {
651 'if (exists $params->{\'' . $init_arg . '\'}) {',
652 $self->_inline_init_attr_from_constructor($attr, $idx),
655 if (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
664 elsif (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
676 sub _inline_init_attr_from_constructor {
678 my ($attr, $idx) = @_;
680 my @initial_value = $attr->_inline_set_value(
681 '$instance', '$params->{\'' . $attr->init_arg . '\'}',
684 push @initial_value, (
685 '$attrs->[' . $idx . ']->set_initial_value(',
687 $attr->_inline_instance_get('$instance'),
689 ) if $attr->has_initializer;
691 return @initial_value;
694 sub _inline_init_attr_from_default {
696 my ($attr, $idx) = @_;
698 my $default = $self->_inline_default_value($attr, $idx);
699 return unless $default;
701 my @initial_value = $attr->_inline_set_value('$instance', $default);
703 push @initial_value, (
704 '$attrs->[' . $idx . ']->set_initial_value(',
706 $attr->_inline_instance_get('$instance'),
708 ) if $attr->has_initializer;
710 return @initial_value;
713 sub _inline_default_value {
715 my ($attr, $index) = @_;
717 if ($attr->has_default) {
719 # default values can either be CODE refs
720 # in which case we need to call them. Or
721 # they can be scalars (strings/numbers)
722 # in which case we can just deal with them
723 # in the code we eval.
724 if ($attr->is_default_a_coderef) {
725 return '$defaults->[' . $index . ']->($instance)';
728 return '$defaults->[' . $index . ']';
731 elsif ($attr->has_builder) {
732 return '$instance->' . $attr->builder;
739 sub _inline_preserve_weak_metaclasses {
741 if (Class::MOP::metaclass_is_weak($self->name)) {
743 $self->_inline_set_mop_slot(
744 '$instance', 'Class::MOP::class_of($class)'
753 sub _inline_extra_init { }
756 sub get_meta_instance {
758 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
761 sub _create_meta_instance {
764 my $instance = $self->instance_metaclass->new(
765 associated_metaclass => $self,
766 attributes => [ $self->get_all_attributes() ],
769 $self->add_meta_instance_dependencies()
770 if $instance->is_dependent_on_superclasses();
775 sub _inline_rebless_instance {
778 return $self->get_meta_instance->inline_rebless_instance_structure(@_);
781 sub _inline_get_mop_slot {
784 return $self->get_meta_instance->_inline_get_mop_slot(@_);
787 sub _inline_set_mop_slot {
790 return $self->get_meta_instance->_inline_set_mop_slot(@_);
793 sub _inline_clear_mop_slot {
796 return $self->get_meta_instance->_inline_clear_mop_slot(@_);
801 my $instance = shift;
802 (blessed($instance) && $instance->isa($class->name))
803 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
806 # we need to protect the integrity of the
807 # Class::MOP::Class singletons here, they
808 # should not be cloned.
809 return $instance if $instance->isa('Class::MOP::Class');
810 $class->_clone_instance($instance, @_);
813 sub _clone_instance {
814 my ($class, $instance, %params) = @_;
816 || confess "You can only clone instances, ($instance) is not a blessed instance";
817 my $meta_instance = $class->get_meta_instance();
818 my $clone = $meta_instance->clone_instance($instance);
819 foreach my $attr ($class->get_all_attributes()) {
820 if ( defined( my $init_arg = $attr->init_arg ) ) {
821 if (exists $params{$init_arg}) {
822 $attr->set_value($clone, $params{$init_arg});
829 sub _force_rebless_instance {
830 my ($self, $instance, %params) = @_;
831 my $old_metaclass = Class::MOP::class_of($instance);
833 $old_metaclass->rebless_instance_away($instance, $self, %params)
836 my $meta_instance = $self->get_meta_instance;
838 if (Class::MOP::metaclass_is_weak($old_metaclass->name)) {
839 $meta_instance->_clear_mop_slot($instance);
843 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
844 $meta_instance->rebless_instance_structure($_[1], $self);
846 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
848 if (Class::MOP::metaclass_is_weak($self->name)) {
849 $meta_instance->_set_mop_slot($instance, $self);
853 sub rebless_instance {
854 my ($self, $instance, %params) = @_;
855 my $old_metaclass = Class::MOP::class_of($instance);
857 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
858 $self->name->isa($old_class)
859 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
861 $self->_force_rebless_instance($_[1], %params);
866 sub rebless_instance_back {
867 my ( $self, $instance ) = @_;
868 my $old_metaclass = Class::MOP::class_of($instance);
871 = $old_metaclass ? $old_metaclass->name : blessed($instance);
872 $old_class->isa( $self->name )
874 "You may rebless only into a superclass of ($old_class), of which ("
878 $self->_force_rebless_instance($_[1]);
883 sub rebless_instance_away {
884 # this intentionally does nothing, it is just a hook
887 sub _fixup_attributes_after_rebless {
889 my ($instance, $rebless_from, %params) = @_;
890 my $meta_instance = $self->get_meta_instance;
892 for my $attr ( $rebless_from->get_all_attributes ) {
893 next if $self->find_attribute_by_name( $attr->name );
894 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
897 foreach my $attr ( $self->get_all_attributes ) {
898 if ( $attr->has_value($instance) ) {
899 if ( defined( my $init_arg = $attr->init_arg ) ) {
900 $params{$init_arg} = $attr->get_value($instance)
901 unless exists $params{$init_arg};
904 $attr->set_value($instance, $attr->get_value($instance));
909 foreach my $attr ($self->get_all_attributes) {
910 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
914 sub _attach_attribute {
915 my ($self, $attribute) = @_;
916 $attribute->attach_to_class($self);
919 sub _post_add_attribute {
920 my ( $self, $attribute ) = @_;
922 $self->invalidate_meta_instances;
924 # invalidate package flag here
927 $attribute->install_accessors;
930 $self->remove_attribute( $attribute->name );
935 sub remove_attribute {
938 my $removed_attribute = $self->SUPER::remove_attribute(@_)
941 $self->invalidate_meta_instances;
943 $removed_attribute->remove_accessors;
944 $removed_attribute->detach_from_class;
946 return$removed_attribute;
949 sub find_attribute_by_name {
950 my ( $self, $attr_name ) = @_;
952 foreach my $class ( $self->linearized_isa ) {
953 # fetch the meta-class ...
954 my $meta = Class::MOP::Class->initialize($class);
955 return $meta->get_attribute($attr_name)
956 if $meta->has_attribute($attr_name);
962 sub get_all_attributes {
964 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
965 reverse $self->linearized_isa;
966 return values %attrs;
974 my $isa = $self->get_or_add_package_symbol('@ISA');
981 # on 5.8 and below, we need to call
982 # a method to get Perl to detect
983 # a cycle in the class hierarchy
984 my $class = $self->name;
988 # we need to check the metaclass
989 # compatibility here so that we can
990 # be sure that the superclass is
991 # not potentially creating an issues
992 # we don't know about
994 $self->_check_metaclass_compatibility();
995 $self->_superclasses_updated();
1001 sub _superclasses_updated {
1003 $self->update_meta_instance_dependencies();
1004 # keep strong references to all our parents, so they don't disappear if
1005 # they are anon classes and don't have any direct instances
1006 $self->_superclass_metas(
1007 map { Class::MOP::class_of($_) } $self->superclasses
1011 sub _superclass_metas {
1013 $self->{_superclass_metas} = [@_];
1018 my $super_class = $self->name;
1020 return @{ $super_class->mro::get_isarev() };
1023 sub direct_subclasses {
1025 my $super_class = $self->name;
1030 } Class::MOP::Class->initialize($_)->superclasses
1031 } $self->subclasses;
1034 sub linearized_isa {
1035 return @{ mro::get_linear_isa( (shift)->name ) };
1038 sub class_precedence_list {
1040 my $name = $self->name;
1042 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
1044 # We need to check for circular inheritance here
1045 # if we are are not on 5.10, cause 5.8 detects it
1046 # late. This will do nothing if all is well, and
1047 # blow up otherwise. Yes, it's an ugly hack, better
1048 # suggestions are welcome.
1050 ($name || return)->isa('This is a test for circular inheritance')
1053 # if our mro is c3, we can
1054 # just grab the linear_isa
1055 if (mro::get_mro($name) eq 'c3') {
1056 return @{ mro::get_linear_isa($name) }
1060 # we can't grab the linear_isa for dfs
1061 # since it has all the duplicates
1066 Class::MOP::Class->initialize($_)->class_precedence_list()
1067 } $self->superclasses()
1075 my $fetch_and_prepare_method = sub {
1076 my ($self, $method_name) = @_;
1077 my $wrapped_metaclass = $self->wrapped_method_metaclass;
1079 my $method = $self->get_method($method_name);
1080 # if we dont have local ...
1082 # try to find the next method
1083 $method = $self->find_next_method_by_name($method_name);
1084 # die if it does not exist
1086 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
1087 # and now make sure to wrap it
1088 # even if it is already wrapped
1089 # because we need a new sub ref
1090 $method = $wrapped_metaclass->wrap($method,
1091 package_name => $self->name,
1092 name => $method_name,
1096 # now make sure we wrap it properly
1097 $method = $wrapped_metaclass->wrap($method,
1098 package_name => $self->name,
1099 name => $method_name,
1100 ) unless $method->isa($wrapped_metaclass);
1102 $self->add_method($method_name => $method);
1106 sub add_before_method_modifier {
1107 my ($self, $method_name, $method_modifier) = @_;
1108 (defined $method_name && length $method_name)
1109 || confess "You must pass in a method name";
1110 my $method = $fetch_and_prepare_method->($self, $method_name);
1111 $method->add_before_modifier(
1112 subname(':before' => $method_modifier)
1116 sub add_after_method_modifier {
1117 my ($self, $method_name, $method_modifier) = @_;
1118 (defined $method_name && length $method_name)
1119 || confess "You must pass in a method name";
1120 my $method = $fetch_and_prepare_method->($self, $method_name);
1121 $method->add_after_modifier(
1122 subname(':after' => $method_modifier)
1126 sub add_around_method_modifier {
1127 my ($self, $method_name, $method_modifier) = @_;
1128 (defined $method_name && length $method_name)
1129 || confess "You must pass in a method name";
1130 my $method = $fetch_and_prepare_method->($self, $method_name);
1131 $method->add_around_modifier(
1132 subname(':around' => $method_modifier)
1137 # the methods above used to be named like this:
1138 # ${pkg}::${method}:(before|after|around)
1139 # but this proved problematic when using one modifier
1140 # to wrap multiple methods (something which is likely
1141 # to happen pretty regularly IMO). So instead of naming
1142 # it like this, I have chosen to just name them purely
1143 # with their modifier names, like so:
1144 # :(before|after|around)
1145 # The fact is that in a stack trace, it will be fairly
1146 # evident from the context what method they are attached
1147 # to, and so don't need the fully qualified name.
1150 sub find_method_by_name {
1151 my ($self, $method_name) = @_;
1152 (defined $method_name && length $method_name)
1153 || confess "You must define a method name to find";
1154 foreach my $class ($self->linearized_isa) {
1155 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1156 return $method if defined $method;
1161 sub get_all_methods {
1165 for my $class ( reverse $self->linearized_isa ) {
1166 my $meta = Class::MOP::Class->initialize($class);
1168 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1171 return values %methods;
1174 sub get_all_method_names {
1177 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
1180 sub find_all_methods_by_name {
1181 my ($self, $method_name) = @_;
1182 (defined $method_name && length $method_name)
1183 || confess "You must define a method name to find";
1185 foreach my $class ($self->linearized_isa) {
1186 # fetch the meta-class ...
1187 my $meta = Class::MOP::Class->initialize($class);
1189 name => $method_name,
1191 code => $meta->get_method($method_name)
1192 } if $meta->has_method($method_name);
1197 sub find_next_method_by_name {
1198 my ($self, $method_name) = @_;
1199 (defined $method_name && length $method_name)
1200 || confess "You must define a method name to find";
1201 my @cpl = $self->linearized_isa;
1202 shift @cpl; # discard ourselves
1203 foreach my $class (@cpl) {
1204 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1205 return $method if defined $method;
1210 sub update_meta_instance_dependencies {
1213 if ( $self->{meta_instance_dependencies} ) {
1214 return $self->add_meta_instance_dependencies;
1218 sub add_meta_instance_dependencies {
1221 $self->remove_meta_instance_dependencies;
1223 my @attrs = $self->get_all_attributes();
1226 my @classes = grep { not $seen{ $_->name }++ }
1227 map { $_->associated_class } @attrs;
1229 foreach my $class (@classes) {
1230 $class->add_dependent_meta_instance($self);
1233 $self->{meta_instance_dependencies} = \@classes;
1236 sub remove_meta_instance_dependencies {
1239 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1240 foreach my $class (@$classes) {
1241 $class->remove_dependent_meta_instance($self);
1251 sub add_dependent_meta_instance {
1252 my ( $self, $metaclass ) = @_;
1253 push @{ $self->{dependent_meta_instances} }, $metaclass;
1256 sub remove_dependent_meta_instance {
1257 my ( $self, $metaclass ) = @_;
1258 my $name = $metaclass->name;
1259 @$_ = grep { $_->name ne $name } @$_
1260 for $self->{dependent_meta_instances};
1263 sub invalidate_meta_instances {
1265 $_->invalidate_meta_instance()
1266 for $self, @{ $self->{dependent_meta_instances} };
1269 sub invalidate_meta_instance {
1271 undef $self->{_meta_instance};
1274 # check if we can reinitialize
1278 # if any local attr is defined
1279 return if $self->get_attribute_list;
1281 # or any non-declared methods
1282 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1283 return if $method->isa("Class::MOP::Method::Generated");
1284 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1292 sub is_mutable { 1 }
1293 sub is_immutable { 0 }
1295 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1297 sub _immutable_options {
1298 my ( $self, @args ) = @_;
1301 inline_accessors => 1,
1302 inline_constructor => 1,
1303 inline_destructor => 0,
1305 immutable_trait => $self->immutable_trait,
1306 constructor_name => $self->constructor_name,
1307 constructor_class => $self->constructor_class,
1308 destructor_class => $self->destructor_class,
1313 sub make_immutable {
1314 my ( $self, @args ) = @_;
1316 if ( $self->is_mutable ) {
1317 $self->_initialize_immutable( $self->_immutable_options(@args) );
1318 $self->_rebless_as_immutable(@args);
1329 if ( $self->is_immutable ) {
1330 my @args = $self->immutable_options;
1331 $self->_rebless_as_mutable();
1332 $self->_remove_inlined_code(@args);
1333 delete $self->{__immutable};
1341 sub _rebless_as_immutable {
1342 my ( $self, @args ) = @_;
1344 $self->{__immutable}{original_class} = ref $self;
1346 bless $self => $self->_immutable_metaclass(@args);
1349 sub _immutable_metaclass {
1350 my ( $self, %args ) = @_;
1352 if ( my $class = $args{immutable_metaclass} ) {
1356 my $trait = $args{immutable_trait} = $self->immutable_trait
1357 || confess "no immutable trait specified for $self";
1359 my $meta = $self->meta;
1360 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1364 if ( $meta_attr and $trait eq $meta_attr->default ) {
1365 # if the trait is the same as the default we try and pick a
1366 # predictable name for the immutable metaclass
1367 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1370 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1371 $trait, 'ForMetaClass', ref($self);
1375 if Class::MOP::is_class_loaded($class_name);
1377 # If the metaclass is a subclass of CMOP::Class which has had
1378 # metaclass roles applied (via Moose), then we want to make sure
1379 # that we preserve that anonymous class (see Fey::ORM for an
1380 # example of where this matters).
1381 my $meta_name = $meta->_real_ref_name;
1383 my $immutable_meta = $meta_name->create(
1385 superclasses => [ ref $self ],
1388 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1390 $immutable_meta->make_immutable(
1391 inline_constructor => 0,
1392 inline_accessors => 0,
1398 sub _remove_inlined_code {
1401 $self->remove_method( $_->name ) for $self->_inlined_methods;
1403 delete $self->{__immutable}{inlined_methods};
1406 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1408 sub _add_inlined_method {
1409 my ( $self, $method ) = @_;
1411 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1414 sub _initialize_immutable {
1415 my ( $self, %args ) = @_;
1417 $self->{__immutable}{options} = \%args;
1418 $self->_install_inlined_code(%args);
1421 sub _install_inlined_code {
1422 my ( $self, %args ) = @_;
1425 $self->_inline_accessors(%args) if $args{inline_accessors};
1426 $self->_inline_constructor(%args) if $args{inline_constructor};
1427 $self->_inline_destructor(%args) if $args{inline_destructor};
1430 sub _rebless_as_mutable {
1433 bless $self, $self->_get_mutable_metaclass_name;
1438 sub _inline_accessors {
1441 foreach my $attr_name ( $self->get_attribute_list ) {
1442 $self->get_attribute($attr_name)->install_accessors(1);
1446 sub _inline_constructor {
1447 my ( $self, %args ) = @_;
1449 my $name = $args{constructor_name};
1450 # A class may not even have a constructor, and that's okay.
1451 return unless defined $name;
1453 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1454 my $class = $self->name;
1455 warn "Not inlining a constructor for $class since it defines"
1456 . " its own constructor.\n"
1457 . "If you are certain you don't need to inline your"
1458 . " constructor, specify inline_constructor => 0 in your"
1459 . " call to $class->meta->make_immutable\n";
1463 my $constructor_class = $args{constructor_class};
1465 Class::MOP::load_class($constructor_class);
1467 my $constructor = $constructor_class->new(
1471 package_name => $self->name,
1475 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1476 $self->add_method( $name => $constructor );
1477 $self->_add_inlined_method($constructor);
1481 sub _inline_destructor {
1482 my ( $self, %args ) = @_;
1484 ( exists $args{destructor_class} && defined $args{destructor_class} )
1485 || confess "The 'inline_destructor' option is present, but "
1486 . "no destructor class was specified";
1488 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1489 my $class = $self->name;
1490 warn "Not inlining a destructor for $class since it defines"
1491 . " its own destructor.\n";
1495 my $destructor_class = $args{destructor_class};
1497 Class::MOP::load_class($destructor_class);
1499 return unless $destructor_class->is_needed($self);
1501 my $destructor = $destructor_class->new(
1504 package_name => $self->name,
1508 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1509 $self->add_method( 'DESTROY' => $destructor );
1510 $self->_add_inlined_method($destructor);
1516 # ABSTRACT: Class Meta Object
1524 # assuming that class Foo
1525 # has been defined, you can
1527 # use this for introspection ...
1529 # add a method to Foo ...
1530 Foo->meta->add_method( 'bar' => sub {...} )
1532 # get a list of all the classes searched
1533 # the method dispatcher in the correct order
1534 Foo->meta->class_precedence_list()
1536 # remove a method from Foo
1537 Foo->meta->remove_method('bar');
1539 # or use this to actually create classes ...
1541 Class::MOP::Class->create(
1544 superclasses => ['Foo'],
1546 Class::MOP::Attribute->new('$bar'),
1547 Class::MOP::Attribute->new('$baz'),
1550 calculate_bar => sub {...},
1551 construct_baz => sub {...}
1558 The Class Protocol is the largest and most complex part of the
1559 Class::MOP meta-object protocol. It controls the introspection and
1560 manipulation of Perl 5 classes, and it can create them as well. The
1561 best way to understand what this module can do is to read the
1562 documentation for each of its methods.
1566 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1570 =head2 Class construction
1572 These methods all create new C<Class::MOP::Class> objects. These
1573 objects can represent existing classes or they can be used to create
1574 new classes from scratch.
1576 The metaclass object for a given class is a singleton. If you attempt
1577 to create a metaclass for the same class twice, you will just get the
1582 =item B<< Class::MOP::Class->create($package_name, %options) >>
1584 This method creates a new C<Class::MOP::Class> object with the given
1585 package name. It accepts a number of options:
1591 An optional version number for the newly created package.
1595 An optional authority for the newly created package.
1597 =item * superclasses
1599 An optional array reference of superclass names.
1603 An optional hash reference of methods for the class. The keys of the
1604 hash reference are method names and values are subroutine references.
1608 An optional array reference of L<Class::MOP::Attribute> objects.
1612 Specifies the name to install the C<meta> method for this class under.
1613 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1614 given, no meta method will be installed.
1618 If true, the metaclass that is stored in the global cache will be a
1621 Classes created in this way are destroyed once the metaclass they are
1622 attached to goes out of scope, and will be removed from Perl's internal
1625 All instances of a class with a weakened metaclass keep a special
1626 reference to the metaclass object, which prevents the metaclass from
1627 going out of scope while any instances exist.
1629 This only works if the instance is based on a hash reference, however.
1633 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1635 This method works just like C<< Class::MOP::Class->create >> but it
1636 creates an "anonymous" class. In fact, the class does have a name, but
1637 that name is a unique name generated internally by this module.
1639 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1640 parameters that C<create> accepts.
1642 Anonymous classes default to C<< weaken => 1 >>, although this can be
1645 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1647 This method will initialize a C<Class::MOP::Class> object for the
1648 named package. Unlike C<create>, this method I<will not> create a new
1651 The purpose of this method is to retrieve a C<Class::MOP::Class>
1652 object for introspecting an existing class.
1654 If an existing C<Class::MOP::Class> object exists for the named
1655 package, it will be returned, and any options provided will be
1658 If the object does not yet exist, it will be created.
1660 The valid options that can be passed to this method are
1661 C<attribute_metaclass>, C<method_metaclass>,
1662 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1663 optional, and default to the appropriate class in the C<Class::MOP>
1668 =head2 Object instance construction and cloning
1670 These methods are all related to creating and/or cloning object
1675 =item B<< $metaclass->clone_object($instance, %params) >>
1677 This method clones an existing object instance. Any parameters you
1678 provide are will override existing attribute values in the object.
1680 This is a convenience method for cloning an object instance, then
1681 blessing it into the appropriate package.
1683 You could implement a clone method in your class, using this method:
1686 my ($self, %params) = @_;
1687 $self->meta->clone_object($self, %params);
1690 =item B<< $metaclass->rebless_instance($instance, %params) >>
1692 This method changes the class of C<$instance> to the metaclass's class.
1694 You can only rebless an instance into a subclass of its current
1695 class. If you pass any additional parameters, these will be treated
1696 like constructor parameters and used to initialize the object's
1697 attributes. Any existing attributes that are already set will be
1700 Before reblessing the instance, this method will call
1701 C<rebless_instance_away> on the instance's current metaclass. This method
1702 will be passed the instance, the new metaclass, and any parameters
1703 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1704 does nothing; it is merely a hook.
1706 =item B<< $metaclass->rebless_instance_back($instance) >>
1708 Does the same thing as C<rebless_instance>, except that you can only
1709 rebless an instance into one of its superclasses. Any attributes that
1710 do not exist in the superclass will be deinitialized.
1712 This is a much more dangerous operation than C<rebless_instance>,
1713 especially when multiple inheritance is involved, so use this carefully!
1715 =item B<< $metaclass->new_object(%params) >>
1717 This method is used to create a new object of the metaclass's
1718 class. Any parameters you provide are used to initialize the
1719 instance's attributes. A special C<__INSTANCE__> key can be passed to
1720 provide an already generated instance, rather than having Class::MOP
1721 generate it for you. This is mostly useful for using Class::MOP with
1722 foreign classes which generate instances using their own constructors.
1724 =item B<< $metaclass->instance_metaclass >>
1726 Returns the class name of the instance metaclass. See
1727 L<Class::MOP::Instance> for more information on the instance
1730 =item B<< $metaclass->get_meta_instance >>
1732 Returns an instance of the C<instance_metaclass> to be used in the
1733 construction of a new instance of the class.
1737 =head2 Informational predicates
1739 These are a few predicate methods for asking information about the
1744 =item B<< $metaclass->is_anon_class >>
1746 This returns true if the class was created by calling C<<
1747 Class::MOP::Class->create_anon_class >>.
1749 =item B<< $metaclass->is_mutable >>
1751 This returns true if the class is still mutable.
1753 =item B<< $metaclass->is_immutable >>
1755 This returns true if the class has been made immutable.
1757 =item B<< $metaclass->is_pristine >>
1759 A class is I<not> pristine if it has non-inherited attributes or if it
1760 has any generated methods.
1764 =head2 Inheritance Relationships
1768 =item B<< $metaclass->superclasses(@superclasses) >>
1770 This is a read-write accessor which represents the superclass
1771 relationships of the metaclass's class.
1773 This is basically sugar around getting and setting C<@ISA>.
1775 =item B<< $metaclass->class_precedence_list >>
1777 This returns a list of all of the class's ancestor classes. The
1778 classes are returned in method dispatch order.
1780 =item B<< $metaclass->linearized_isa >>
1782 This returns a list based on C<class_precedence_list> but with all
1785 =item B<< $metaclass->subclasses >>
1787 This returns a list of all subclasses for this class, even indirect
1790 =item B<< $metaclass->direct_subclasses >>
1792 This returns a list of immediate subclasses for this class, which does not
1793 include indirect subclasses.
1797 =head2 Method introspection and creation
1799 These methods allow you to introspect a class's methods, as well as
1800 add, remove, or change methods.
1802 Determining what is truly a method in a Perl 5 class requires some
1803 heuristics (aka guessing).
1805 Methods defined outside the package with a fully qualified name (C<sub
1806 Package::name { ... }>) will be included. Similarly, methods named
1807 with a fully qualified name using L<Sub::Name> are also included.
1809 However, we attempt to ignore imported functions.
1811 Ultimately, we are using heuristics to determine what truly is a
1812 method in a class, and these heuristics may get the wrong answer in
1813 some edge cases. However, for most "normal" cases the heuristics work
1818 =item B<< $metaclass->get_method($method_name) >>
1820 This will return a L<Class::MOP::Method> for the specified
1821 C<$method_name>. If the class does not have the specified method, it
1824 =item B<< $metaclass->has_method($method_name) >>
1826 Returns a boolean indicating whether or not the class defines the
1827 named method. It does not include methods inherited from parent
1830 =item B<< $metaclass->get_method_list >>
1832 This will return a list of method I<names> for all methods defined in
1835 =item B<< $metaclass->add_method($method_name, $method) >>
1837 This method takes a method name and a subroutine reference, and adds
1838 the method to the class.
1840 The subroutine reference can be a L<Class::MOP::Method>, and you are
1841 strongly encouraged to pass a meta method object instead of a code
1842 reference. If you do so, that object gets stored as part of the
1843 class's method map directly. If not, the meta information will have to
1844 be recreated later, and may be incorrect.
1846 If you provide a method object, this method will clone that object if
1847 the object's package name does not match the class name. This lets us
1848 track the original source of any methods added from other classes
1849 (notably Moose roles).
1851 =item B<< $metaclass->remove_method($method_name) >>
1853 Remove the named method from the class. This method returns the
1854 L<Class::MOP::Method> object for the method.
1856 =item B<< $metaclass->method_metaclass >>
1858 Returns the class name of the method metaclass, see
1859 L<Class::MOP::Method> for more information on the method metaclass.
1861 =item B<< $metaclass->wrapped_method_metaclass >>
1863 Returns the class name of the wrapped method metaclass, see
1864 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1867 =item B<< $metaclass->get_all_methods >>
1869 This will traverse the inheritance hierarchy and return a list of all
1870 the L<Class::MOP::Method> objects for this class and its parents.
1872 =item B<< $metaclass->find_method_by_name($method_name) >>
1874 This will return a L<Class::MOP::Method> for the specified
1875 C<$method_name>. If the class does not have the specified method, it
1878 Unlike C<get_method>, this method I<will> look for the named method in
1881 =item B<< $metaclass->get_all_method_names >>
1883 This will return a list of method I<names> for all of this class's
1884 methods, including inherited methods.
1886 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1888 This method looks for the named method in the class and all of its
1889 parents. It returns every matching method it finds in the inheritance
1890 tree, so it returns a list of methods.
1892 Each method is returned as a hash reference with three keys. The keys
1893 are C<name>, C<class>, and C<code>. The C<code> key has a
1894 L<Class::MOP::Method> object as its value.
1896 The list of methods is distinct.
1898 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1900 This method returns the first method in any superclass matching the
1901 given name. It is effectively the method that C<SUPER::$method_name>
1906 =head2 Attribute introspection and creation
1908 Because Perl 5 does not have a core concept of attributes in classes,
1909 we can only return information about attributes which have been added
1910 via this class's methods. We cannot discover information about
1911 attributes which are defined in terms of "regular" Perl 5 methods.
1915 =item B<< $metaclass->get_attribute($attribute_name) >>
1917 This will return a L<Class::MOP::Attribute> for the specified
1918 C<$attribute_name>. If the class does not have the specified
1919 attribute, it returns C<undef>.
1921 NOTE that get_attribute does not search superclasses, for that you
1922 need to use C<find_attribute_by_name>.
1924 =item B<< $metaclass->has_attribute($attribute_name) >>
1926 Returns a boolean indicating whether or not the class defines the
1927 named attribute. It does not include attributes inherited from parent
1930 =item B<< $metaclass->get_attribute_list >>
1932 This will return a list of attributes I<names> for all attributes
1933 defined in this class. Note that this operates on the current class
1934 only, it does not traverse the inheritance hierarchy.
1936 =item B<< $metaclass->get_all_attributes >>
1938 This will traverse the inheritance hierarchy and return a list of all
1939 the L<Class::MOP::Attribute> objects for this class and its parents.
1941 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1943 This will return a L<Class::MOP::Attribute> for the specified
1944 C<$attribute_name>. If the class does not have the specified
1945 attribute, it returns C<undef>.
1947 Unlike C<get_attribute>, this attribute I<will> look for the named
1948 attribute in superclasses.
1950 =item B<< $metaclass->add_attribute(...) >>
1952 This method accepts either an existing L<Class::MOP::Attribute>
1953 object or parameters suitable for passing to that class's C<new>
1956 The attribute provided will be added to the class.
1958 Any accessor methods defined by the attribute will be added to the
1959 class when the attribute is added.
1961 If an attribute of the same name already exists, the old attribute
1962 will be removed first.
1964 =item B<< $metaclass->remove_attribute($attribute_name) >>
1966 This will remove the named attribute from the class, and
1967 L<Class::MOP::Attribute> object.
1969 Removing an attribute also removes any accessor methods defined by the
1972 However, note that removing an attribute will only affect I<future>
1973 object instances created for this class, not existing instances.
1975 =item B<< $metaclass->attribute_metaclass >>
1977 Returns the class name of the attribute metaclass for this class. By
1978 default, this is L<Class::MOP::Attribute>.
1982 =head2 Class Immutability
1984 Making a class immutable "freezes" the class definition. You can no
1985 longer call methods which alter the class, such as adding or removing
1986 methods or attributes.
1988 Making a class immutable lets us optimize the class by inlining some
1989 methods, and also allows us to optimize some methods on the metaclass
1992 After immutabilization, the metaclass object will cache most informational
1993 methods that returns information about methods or attributes. Methods which
1994 would alter the class, such as C<add_attribute> and C<add_method>, will
1995 throw an error on an immutable metaclass object.
1997 The immutabilization system in L<Moose> takes much greater advantage
1998 of the inlining features than Class::MOP itself does.
2002 =item B<< $metaclass->make_immutable(%options) >>
2004 This method will create an immutable transformer and use it to make
2005 the class and its metaclass object immutable.
2007 This method accepts the following options:
2011 =item * inline_accessors
2013 =item * inline_constructor
2015 =item * inline_destructor
2017 These are all booleans indicating whether the specified method(s)
2020 By default, accessors and the constructor are inlined, but not the
2023 =item * immutable_trait
2025 The name of a class which will be used as a parent class for the
2026 metaclass object being made immutable. This "trait" implements the
2027 post-immutability functionality of the metaclass (but not the
2028 transformation itself).
2030 This defaults to L<Class::MOP::Class::Immutable::Trait>.
2032 =item * constructor_name
2034 This is the constructor method name. This defaults to "new".
2036 =item * constructor_class
2038 The name of the method metaclass for constructors. It will be used to
2039 generate the inlined constructor. This defaults to
2040 "Class::MOP::Method::Constructor".
2042 =item * replace_constructor
2044 This is a boolean indicating whether an existing constructor should be
2045 replaced when inlining a constructor. This defaults to false.
2047 =item * destructor_class
2049 The name of the method metaclass for destructors. It will be used to
2050 generate the inlined destructor. This defaults to
2051 "Class::MOP::Method::Denstructor".
2053 =item * replace_destructor
2055 This is a boolean indicating whether an existing destructor should be
2056 replaced when inlining a destructor. This defaults to false.
2060 =item B<< $metaclass->immutable_options >>
2062 Returns a hash of the options used when making the class immutable, including
2063 both defaults and anything supplied by the user in the call to C<<
2064 $metaclass->make_immutable >>. This is useful if you need to temporarily make
2065 a class mutable and then restore immutability as it was before.
2067 =item B<< $metaclass->make_mutable >>
2069 Calling this method reverse the immutabilization transformation.
2073 =head2 Method Modifiers
2075 Method modifiers are hooks which allow a method to be wrapped with
2076 I<before>, I<after> and I<around> method modifiers. Every time a
2077 method is called, its modifiers are also called.
2079 A class can modify its own methods, as well as methods defined in
2082 =head3 How method modifiers work?
2084 Method modifiers work by wrapping the original method and then
2085 replacing it in the class's symbol table. The wrappers will handle
2086 calling all the modifiers in the appropriate order and preserving the
2087 calling context for the original method.
2089 The return values of C<before> and C<after> modifiers are
2090 ignored. This is because their purpose is B<not> to filter the input
2091 and output of the primary method (this is done with an I<around>
2094 This may seem like an odd restriction to some, but doing this allows
2095 for simple code to be added at the beginning or end of a method call
2096 without altering the function of the wrapped method or placing any
2097 extra responsibility on the code of the modifier.
2099 Of course if you have more complex needs, you can use the C<around>
2100 modifier which allows you to change both the parameters passed to the
2101 wrapped method, as well as its return value.
2103 Before and around modifiers are called in last-defined-first-called
2104 order, while after modifiers are called in first-defined-first-called
2105 order. So the call tree might looks something like this:
2117 =head3 What is the performance impact?
2119 Of course there is a performance cost associated with method
2120 modifiers, but we have made every effort to make that cost directly
2121 proportional to the number of modifier features you use.
2123 The wrapping method does its best to B<only> do as much work as it
2124 absolutely needs to. In order to do this we have moved some of the
2125 performance costs to set-up time, where they are easier to amortize.
2127 All this said, our benchmarks have indicated the following:
2129 simple wrapper with no modifiers 100% slower
2130 simple wrapper with simple before modifier 400% slower
2131 simple wrapper with simple after modifier 450% slower
2132 simple wrapper with simple around modifier 500-550% slower
2133 simple wrapper with all 3 modifiers 1100% slower
2135 These numbers may seem daunting, but you must remember, every feature
2136 comes with some cost. To put things in perspective, just doing a
2137 simple C<AUTOLOAD> which does nothing but extract the name of the
2138 method called and return it costs about 400% over a normal method
2143 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
2145 This wraps the specified method with the supplied subroutine
2146 reference. The modifier will be called as a method itself, and will
2147 receive the same arguments as are passed to the method.
2149 When the modifier exits, the wrapped method will be called.
2151 The return value of the modifier will be ignored.
2153 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2155 This wraps the specified method with the supplied subroutine
2156 reference. The modifier will be called as a method itself, and will
2157 receive the same arguments as are passed to the method.
2159 When the wrapped methods exits, the modifier will be called.
2161 The return value of the modifier will be ignored.
2163 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2165 This wraps the specified method with the supplied subroutine
2168 The first argument passed to the modifier will be a subroutine
2169 reference to the wrapped method. The second argument is the object,
2170 and after that come any arguments passed when the method is called.
2172 The around modifier can choose to call the original method, as well as
2173 what arguments to pass if it does so.
2175 The return value of the modifier is what will be seen by the caller.
2179 =head2 Introspection
2183 =item B<< Class::MOP::Class->meta >>
2185 This will return a L<Class::MOP::Class> instance for this class.
2187 It should also be noted that L<Class::MOP> will actually bootstrap
2188 this module by installing a number of attribute meta-objects into its