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 Class::Load 'is_class_loaded', 'load_class';
15 use Scalar::Util 'blessed', 'reftype', 'weaken';
16 use Sub::Name 'subname';
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;
411 # creating classes with MOP ...
417 unshift @args, 'package' if @args % 2 == 1;
420 (ref $options{superclasses} eq 'ARRAY')
421 || confess "You must pass an ARRAY ref of superclasses"
422 if exists $options{superclasses};
424 (ref $options{attributes} eq 'ARRAY')
425 || confess "You must pass an ARRAY ref of attributes"
426 if exists $options{attributes};
428 (ref $options{methods} eq 'HASH')
429 || confess "You must pass a HASH ref of methods"
430 if exists $options{methods};
432 my $package = delete $options{package};
433 my $superclasses = delete $options{superclasses};
434 my $attributes = delete $options{attributes};
435 my $methods = delete $options{methods};
436 my $meta_name = exists $options{meta_name}
437 ? delete $options{meta_name}
440 my $meta = $class->SUPER::create($package => %options);
442 $meta->_add_meta_method($meta_name)
443 if defined $meta_name;
445 $meta->superclasses(@{$superclasses})
446 if defined $superclasses;
448 # process attributes first, so that they can
449 # install accessors, but locally defined methods
450 # can then overwrite them. It is maybe a little odd, but
451 # I think this should be the order of things.
452 if (defined $attributes) {
453 foreach my $attr (@{$attributes}) {
454 $meta->add_attribute($attr);
457 if (defined $methods) {
458 foreach my $method_name (keys %{$methods}) {
459 $meta->add_method($method_name, $methods->{$method_name});
465 # XXX: something more intelligent here?
466 sub _anon_package_prefix { 'Class::MOP::Class::__ANON__::SERIAL::' }
468 sub create_anon_class { shift->create_anon(@_) }
469 sub is_anon_class { shift->is_anon(@_) }
471 sub _anon_cache_key {
474 # Makes something like Super::Class|Super::Class::2
476 join( '|', sort @{ $options{superclasses} || [] } ),
480 # Instance Construction & Cloning
486 # we need to protect the integrity of the
487 # Class::MOP::Class singletons here, so we
488 # delegate this to &construct_class_instance
489 # which will deal with the singletons
490 return $class->_construct_class_instance(@_)
491 if $class->name->isa('Class::MOP::Class');
492 return $class->_construct_instance(@_);
495 sub _construct_instance {
497 my $params = @_ == 1 ? $_[0] : {@_};
498 my $meta_instance = $class->get_meta_instance();
500 # the code below is almost certainly incorrect
501 # but this is foreign inheritance, so we might
502 # have to kludge it in the end.
504 if (my $instance_class = blessed($params->{__INSTANCE__})) {
505 ($instance_class eq $class->name)
506 || confess "Objects passed as the __INSTANCE__ parameter must "
507 . "already be blessed into the correct class, but "
508 . "$params->{__INSTANCE__} is not a " . $class->name;
509 $instance = $params->{__INSTANCE__};
511 elsif (exists $params->{__INSTANCE__}) {
512 confess "The __INSTANCE__ parameter must be a blessed reference, not "
513 . $params->{__INSTANCE__};
516 $instance = $meta_instance->create_instance();
518 foreach my $attr ($class->get_all_attributes()) {
519 $attr->initialize_instance_slot($meta_instance, $instance, $params);
521 if (Class::MOP::metaclass_is_weak($class->name)) {
522 $meta_instance->_set_mop_slot($instance, $class);
527 sub _inline_new_object {
531 'my $class = shift;',
532 '$class = Scalar::Util::blessed($class) || $class;',
533 $self->_inline_fallback_constructor('$class'),
534 $self->_inline_params('$params', '$class'),
535 $self->_inline_generate_instance('$instance', '$class'),
536 $self->_inline_slot_initializers,
537 $self->_inline_preserve_weak_metaclasses,
538 $self->_inline_extra_init,
543 sub _inline_fallback_constructor {
547 'return ' . $self->_generate_fallback_constructor($class),
548 'if ' . $class . ' ne \'' . $self->name . '\';',
552 sub _generate_fallback_constructor {
555 return 'Class::MOP::Class->initialize(' . $class . ')->new_object(@_)',
560 my ($params, $class) = @_;
562 'my ' . $params . ' = @_ == 1 ? $_[0] : {@_};',
566 sub _inline_generate_instance {
568 my ($inst, $class) = @_;
570 'my ' . $inst . ' = ' . $self->_inline_create_instance($class) . ';',
574 sub _inline_create_instance {
577 return $self->get_meta_instance->inline_create_instance(@_);
580 sub _inline_slot_initializers {
585 return map { $self->_inline_slot_initializer($_, $idx++) }
586 sort { $a->name cmp $b->name } $self->get_all_attributes;
589 sub _inline_slot_initializer {
591 my ($attr, $idx) = @_;
593 if (defined(my $init_arg = $attr->init_arg)) {
595 'if (exists $params->{\'' . $init_arg . '\'}) {',
596 $self->_inline_init_attr_from_constructor($attr, $idx),
599 if (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
608 elsif (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
620 sub _inline_init_attr_from_constructor {
622 my ($attr, $idx) = @_;
624 my @initial_value = $attr->_inline_set_value(
625 '$instance', '$params->{\'' . $attr->init_arg . '\'}',
628 push @initial_value, (
629 '$attrs->[' . $idx . ']->set_initial_value(',
631 $attr->_inline_instance_get('$instance'),
633 ) if $attr->has_initializer;
635 return @initial_value;
638 sub _inline_init_attr_from_default {
640 my ($attr, $idx) = @_;
642 my $default = $self->_inline_default_value($attr, $idx);
643 return unless $default;
645 my @initial_value = $attr->_inline_set_value('$instance', $default);
647 push @initial_value, (
648 '$attrs->[' . $idx . ']->set_initial_value(',
650 $attr->_inline_instance_get('$instance'),
652 ) if $attr->has_initializer;
654 return @initial_value;
657 sub _inline_default_value {
659 my ($attr, $index) = @_;
661 if ($attr->has_default) {
663 # default values can either be CODE refs
664 # in which case we need to call them. Or
665 # they can be scalars (strings/numbers)
666 # in which case we can just deal with them
667 # in the code we eval.
668 if ($attr->is_default_a_coderef) {
669 return '$defaults->[' . $index . ']->($instance)';
672 return '$defaults->[' . $index . ']';
675 elsif ($attr->has_builder) {
676 return '$instance->' . $attr->builder;
683 sub _inline_preserve_weak_metaclasses {
685 if (Class::MOP::metaclass_is_weak($self->name)) {
687 $self->_inline_set_mop_slot(
688 '$instance', 'Class::MOP::class_of($class)'
697 sub _inline_extra_init { }
699 sub _eval_environment {
702 my @attrs = sort { $a->name cmp $b->name } $self->get_all_attributes;
704 my $defaults = [map { $_->default } @attrs];
707 '$defaults' => \$defaults,
712 sub get_meta_instance {
714 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
717 sub _create_meta_instance {
720 my $instance = $self->instance_metaclass->new(
721 associated_metaclass => $self,
722 attributes => [ $self->get_all_attributes() ],
725 $self->add_meta_instance_dependencies()
726 if $instance->is_dependent_on_superclasses();
731 # TODO: this is actually not being used!
732 sub _inline_rebless_instance {
735 return $self->get_meta_instance->inline_rebless_instance_structure(@_);
738 sub _inline_get_mop_slot {
741 return $self->get_meta_instance->_inline_get_mop_slot(@_);
744 sub _inline_set_mop_slot {
747 return $self->get_meta_instance->_inline_set_mop_slot(@_);
750 sub _inline_clear_mop_slot {
753 return $self->get_meta_instance->_inline_clear_mop_slot(@_);
758 my $instance = shift;
759 (blessed($instance) && $instance->isa($class->name))
760 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
763 # we need to protect the integrity of the
764 # Class::MOP::Class singletons here, they
765 # should not be cloned.
766 return $instance if $instance->isa('Class::MOP::Class');
767 $class->_clone_instance($instance, @_);
770 sub _clone_instance {
771 my ($class, $instance, %params) = @_;
773 || confess "You can only clone instances, ($instance) is not a blessed instance";
774 my $meta_instance = $class->get_meta_instance();
775 my $clone = $meta_instance->clone_instance($instance);
776 foreach my $attr ($class->get_all_attributes()) {
777 if ( defined( my $init_arg = $attr->init_arg ) ) {
778 if (exists $params{$init_arg}) {
779 $attr->set_value($clone, $params{$init_arg});
786 sub _force_rebless_instance {
787 my ($self, $instance, %params) = @_;
788 my $old_metaclass = Class::MOP::class_of($instance);
790 $old_metaclass->rebless_instance_away($instance, $self, %params)
793 my $meta_instance = $self->get_meta_instance;
795 if (Class::MOP::metaclass_is_weak($old_metaclass->name)) {
796 $meta_instance->_clear_mop_slot($instance);
800 # we use $_[1] here because of t/cmop/rebless_overload.t regressions
802 $meta_instance->rebless_instance_structure($_[1], $self);
804 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
806 if (Class::MOP::metaclass_is_weak($self->name)) {
807 $meta_instance->_set_mop_slot($instance, $self);
811 sub rebless_instance {
812 my ($self, $instance, %params) = @_;
813 my $old_metaclass = Class::MOP::class_of($instance);
815 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
816 $self->name->isa($old_class)
817 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
819 $self->_force_rebless_instance($_[1], %params);
824 sub rebless_instance_back {
825 my ( $self, $instance ) = @_;
826 my $old_metaclass = Class::MOP::class_of($instance);
829 = $old_metaclass ? $old_metaclass->name : blessed($instance);
830 $old_class->isa( $self->name )
832 "You may rebless only into a superclass of ($old_class), of which ("
836 $self->_force_rebless_instance($_[1]);
841 sub rebless_instance_away {
842 # this intentionally does nothing, it is just a hook
845 sub _fixup_attributes_after_rebless {
847 my ($instance, $rebless_from, %params) = @_;
848 my $meta_instance = $self->get_meta_instance;
850 for my $attr ( $rebless_from->get_all_attributes ) {
851 next if $self->find_attribute_by_name( $attr->name );
852 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
855 foreach my $attr ( $self->get_all_attributes ) {
856 if ( $attr->has_value($instance) ) {
857 if ( defined( my $init_arg = $attr->init_arg ) ) {
858 $params{$init_arg} = $attr->get_value($instance)
859 unless exists $params{$init_arg};
862 $attr->set_value($instance, $attr->get_value($instance));
867 foreach my $attr ($self->get_all_attributes) {
868 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
872 sub _attach_attribute {
873 my ($self, $attribute) = @_;
874 $attribute->attach_to_class($self);
877 sub _post_add_attribute {
878 my ( $self, $attribute ) = @_;
880 $self->invalidate_meta_instances;
882 # invalidate package flag here
885 $attribute->install_accessors;
888 $self->remove_attribute( $attribute->name );
893 sub remove_attribute {
896 my $removed_attribute = $self->SUPER::remove_attribute(@_)
899 $self->invalidate_meta_instances;
901 $removed_attribute->remove_accessors;
902 $removed_attribute->detach_from_class;
904 return$removed_attribute;
907 sub find_attribute_by_name {
908 my ( $self, $attr_name ) = @_;
910 foreach my $class ( $self->linearized_isa ) {
911 # fetch the meta-class ...
912 my $meta = Class::MOP::Class->initialize($class);
913 return $meta->get_attribute($attr_name)
914 if $meta->has_attribute($attr_name);
920 sub get_all_attributes {
922 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
923 reverse $self->linearized_isa;
924 return values %attrs;
932 my $isa = $self->get_or_add_package_symbol('@ISA');
939 # on 5.8 and below, we need to call
940 # a method to get Perl to detect
941 # a cycle in the class hierarchy
942 my $class = $self->name;
946 # we need to check the metaclass
947 # compatibility here so that we can
948 # be sure that the superclass is
949 # not potentially creating an issues
950 # we don't know about
952 $self->_check_metaclass_compatibility();
953 $self->_superclasses_updated();
959 sub _superclasses_updated {
961 $self->update_meta_instance_dependencies();
962 # keep strong references to all our parents, so they don't disappear if
963 # they are anon classes and don't have any direct instances
964 $self->_superclass_metas(
965 map { Class::MOP::class_of($_) } $self->superclasses
969 sub _superclass_metas {
971 $self->{_superclass_metas} = [@_];
976 my $super_class = $self->name;
978 return @{ $super_class->mro::get_isarev() };
981 sub direct_subclasses {
983 my $super_class = $self->name;
988 } Class::MOP::Class->initialize($_)->superclasses
993 return @{ mro::get_linear_isa( (shift)->name ) };
996 sub class_precedence_list {
998 my $name = $self->name;
1000 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
1002 # We need to check for circular inheritance here
1003 # if we are are not on 5.10, cause 5.8 detects it
1004 # late. This will do nothing if all is well, and
1005 # blow up otherwise. Yes, it's an ugly hack, better
1006 # suggestions are welcome.
1008 ($name || return)->isa('This is a test for circular inheritance')
1011 # if our mro is c3, we can
1012 # just grab the linear_isa
1013 if (mro::get_mro($name) eq 'c3') {
1014 return @{ mro::get_linear_isa($name) }
1018 # we can't grab the linear_isa for dfs
1019 # since it has all the duplicates
1024 Class::MOP::Class->initialize($_)->class_precedence_list()
1025 } $self->superclasses()
1033 my $fetch_and_prepare_method = sub {
1034 my ($self, $method_name) = @_;
1035 my $wrapped_metaclass = $self->wrapped_method_metaclass;
1037 my $method = $self->get_method($method_name);
1038 # if we dont have local ...
1040 # try to find the next method
1041 $method = $self->find_next_method_by_name($method_name);
1042 # die if it does not exist
1044 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
1045 # and now make sure to wrap it
1046 # even if it is already wrapped
1047 # because we need a new sub ref
1048 $method = $wrapped_metaclass->wrap($method,
1049 package_name => $self->name,
1050 name => $method_name,
1054 # now make sure we wrap it properly
1055 $method = $wrapped_metaclass->wrap($method,
1056 package_name => $self->name,
1057 name => $method_name,
1058 ) unless $method->isa($wrapped_metaclass);
1060 $self->add_method($method_name => $method);
1064 sub add_before_method_modifier {
1065 my ($self, $method_name, $method_modifier) = @_;
1066 (defined $method_name && length $method_name)
1067 || confess "You must pass in a method name";
1068 my $method = $fetch_and_prepare_method->($self, $method_name);
1069 $method->add_before_modifier(
1070 subname(':before' => $method_modifier)
1074 sub add_after_method_modifier {
1075 my ($self, $method_name, $method_modifier) = @_;
1076 (defined $method_name && length $method_name)
1077 || confess "You must pass in a method name";
1078 my $method = $fetch_and_prepare_method->($self, $method_name);
1079 $method->add_after_modifier(
1080 subname(':after' => $method_modifier)
1084 sub add_around_method_modifier {
1085 my ($self, $method_name, $method_modifier) = @_;
1086 (defined $method_name && length $method_name)
1087 || confess "You must pass in a method name";
1088 my $method = $fetch_and_prepare_method->($self, $method_name);
1089 $method->add_around_modifier(
1090 subname(':around' => $method_modifier)
1095 # the methods above used to be named like this:
1096 # ${pkg}::${method}:(before|after|around)
1097 # but this proved problematic when using one modifier
1098 # to wrap multiple methods (something which is likely
1099 # to happen pretty regularly IMO). So instead of naming
1100 # it like this, I have chosen to just name them purely
1101 # with their modifier names, like so:
1102 # :(before|after|around)
1103 # The fact is that in a stack trace, it will be fairly
1104 # evident from the context what method they are attached
1105 # to, and so don't need the fully qualified name.
1108 sub find_method_by_name {
1109 my ($self, $method_name) = @_;
1110 (defined $method_name && length $method_name)
1111 || confess "You must define a method name to find";
1112 foreach my $class ($self->linearized_isa, 'UNIVERSAL') {
1113 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1114 return $method if defined $method;
1119 sub get_all_methods {
1123 for my $class ( 'UNIVERSAL', reverse $self->linearized_isa ) {
1124 my $meta = Class::MOP::Class->initialize($class);
1126 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1129 return values %methods;
1132 sub get_all_method_names {
1134 map { $_->name } $self->get_all_methods;
1137 sub find_all_methods_by_name {
1138 my ($self, $method_name) = @_;
1139 (defined $method_name && length $method_name)
1140 || confess "You must define a method name to find";
1142 foreach my $class ($self->linearized_isa, 'UNIVERSAL') {
1143 # fetch the meta-class ...
1144 my $meta = Class::MOP::Class->initialize($class);
1146 name => $method_name,
1148 code => $meta->get_method($method_name)
1149 } if $meta->has_method($method_name);
1154 sub find_next_method_by_name {
1155 my ($self, $method_name) = @_;
1156 (defined $method_name && length $method_name)
1157 || confess "You must define a method name to find";
1158 my @cpl = ($self->linearized_isa, 'UNIVERSAL');
1159 shift @cpl; # discard ourselves
1160 foreach my $class (@cpl) {
1161 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1162 return $method if defined $method;
1167 sub update_meta_instance_dependencies {
1170 if ( $self->{meta_instance_dependencies} ) {
1171 return $self->add_meta_instance_dependencies;
1175 sub add_meta_instance_dependencies {
1178 $self->remove_meta_instance_dependencies;
1180 my @attrs = $self->get_all_attributes();
1183 my @classes = grep { not $seen{ $_->name }++ }
1184 map { $_->associated_class } @attrs;
1186 foreach my $class (@classes) {
1187 $class->add_dependent_meta_instance($self);
1190 $self->{meta_instance_dependencies} = \@classes;
1193 sub remove_meta_instance_dependencies {
1196 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1197 foreach my $class (@$classes) {
1198 $class->remove_dependent_meta_instance($self);
1208 sub add_dependent_meta_instance {
1209 my ( $self, $metaclass ) = @_;
1210 push @{ $self->{dependent_meta_instances} }, $metaclass;
1213 sub remove_dependent_meta_instance {
1214 my ( $self, $metaclass ) = @_;
1215 my $name = $metaclass->name;
1216 @$_ = grep { $_->name ne $name } @$_
1217 for $self->{dependent_meta_instances};
1220 sub invalidate_meta_instances {
1222 $_->invalidate_meta_instance()
1223 for $self, @{ $self->{dependent_meta_instances} };
1226 sub invalidate_meta_instance {
1228 undef $self->{_meta_instance};
1231 # check if we can reinitialize
1235 # if any local attr is defined
1236 return if $self->get_attribute_list;
1238 # or any non-declared methods
1239 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1240 return if $method->isa("Class::MOP::Method::Generated");
1241 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1249 sub is_mutable { 1 }
1250 sub is_immutable { 0 }
1252 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1254 sub _immutable_options {
1255 my ( $self, @args ) = @_;
1258 inline_accessors => 1,
1259 inline_constructor => 1,
1260 inline_destructor => 0,
1262 immutable_trait => $self->immutable_trait,
1263 constructor_name => $self->constructor_name,
1264 constructor_class => $self->constructor_class,
1265 destructor_class => $self->destructor_class,
1270 sub make_immutable {
1271 my ( $self, @args ) = @_;
1273 return unless $self->is_mutable;
1275 my ($file, $line) = (caller)[1..2];
1277 $self->_initialize_immutable(
1280 $self->_immutable_options(@args),
1282 $self->_rebless_as_immutable(@args);
1290 if ( $self->is_immutable ) {
1291 my @args = $self->immutable_options;
1292 $self->_rebless_as_mutable();
1293 $self->_remove_inlined_code(@args);
1294 delete $self->{__immutable};
1302 sub _rebless_as_immutable {
1303 my ( $self, @args ) = @_;
1305 $self->{__immutable}{original_class} = ref $self;
1307 bless $self => $self->_immutable_metaclass(@args);
1310 sub _immutable_metaclass {
1311 my ( $self, %args ) = @_;
1313 if ( my $class = $args{immutable_metaclass} ) {
1317 my $trait = $args{immutable_trait} = $self->immutable_trait
1318 || confess "no immutable trait specified for $self";
1320 my $meta = $self->meta;
1321 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1325 if ( $meta_attr and $trait eq $meta_attr->default ) {
1326 # if the trait is the same as the default we try and pick a
1327 # predictable name for the immutable metaclass
1328 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1331 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1332 $trait, 'ForMetaClass', ref($self);
1336 if is_class_loaded($class_name);
1338 # If the metaclass is a subclass of CMOP::Class which has had
1339 # metaclass roles applied (via Moose), then we want to make sure
1340 # that we preserve that anonymous class (see Fey::ORM for an
1341 # example of where this matters).
1342 my $meta_name = $meta->_real_ref_name;
1344 my $immutable_meta = $meta_name->create(
1346 superclasses => [ ref $self ],
1349 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1351 $immutable_meta->make_immutable(
1352 inline_constructor => 0,
1353 inline_accessors => 0,
1359 sub _remove_inlined_code {
1362 $self->remove_method( $_->name ) for $self->_inlined_methods;
1364 delete $self->{__immutable}{inlined_methods};
1367 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1369 sub _add_inlined_method {
1370 my ( $self, $method ) = @_;
1372 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1375 sub _initialize_immutable {
1376 my ( $self, %args ) = @_;
1378 $self->{__immutable}{options} = \%args;
1379 $self->_install_inlined_code(%args);
1382 sub _install_inlined_code {
1383 my ( $self, %args ) = @_;
1386 $self->_inline_accessors(%args) if $args{inline_accessors};
1387 $self->_inline_constructor(%args) if $args{inline_constructor};
1388 $self->_inline_destructor(%args) if $args{inline_destructor};
1391 sub _rebless_as_mutable {
1394 bless $self, $self->_get_mutable_metaclass_name;
1399 sub _inline_accessors {
1402 foreach my $attr_name ( $self->get_attribute_list ) {
1403 $self->get_attribute($attr_name)->install_accessors(1);
1407 sub _inline_constructor {
1408 my ( $self, %args ) = @_;
1410 my $name = $args{constructor_name};
1411 # A class may not even have a constructor, and that's okay.
1412 return unless defined $name;
1414 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1415 my $class = $self->name;
1416 warn "Not inlining a constructor for $class since it defines"
1417 . " its own constructor.\n"
1418 . "If you are certain you don't need to inline your"
1419 . " constructor, specify inline_constructor => 0 in your"
1420 . " call to $class->meta->make_immutable\n";
1424 my $constructor_class = $args{constructor_class};
1426 load_class($constructor_class);
1428 my $constructor = $constructor_class->new(
1432 package_name => $self->name,
1434 definition_context => {
1435 description => "constructor " . $self->name . "::" . $name,
1436 file => $args{file},
1437 line => $args{line},
1441 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1442 $self->add_method( $name => $constructor );
1443 $self->_add_inlined_method($constructor);
1447 sub _inline_destructor {
1448 my ( $self, %args ) = @_;
1450 ( exists $args{destructor_class} && defined $args{destructor_class} )
1451 || confess "The 'inline_destructor' option is present, but "
1452 . "no destructor class was specified";
1454 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1455 my $class = $self->name;
1456 warn "Not inlining a destructor for $class since it defines"
1457 . " its own destructor.\n";
1461 my $destructor_class = $args{destructor_class};
1463 load_class($destructor_class);
1465 return unless $destructor_class->is_needed($self);
1467 my $destructor = $destructor_class->new(
1470 package_name => $self->name,
1472 definition_context => {
1473 description => "destructor " . $self->name . "::DESTROY",
1474 file => $args{file},
1475 line => $args{line},
1479 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1480 $self->add_method( 'DESTROY' => $destructor );
1481 $self->_add_inlined_method($destructor);
1487 # ABSTRACT: Class Meta Object
1495 # assuming that class Foo
1496 # has been defined, you can
1498 # use this for introspection ...
1500 # add a method to Foo ...
1501 Foo->meta->add_method( 'bar' => sub {...} )
1503 # get a list of all the classes searched
1504 # the method dispatcher in the correct order
1505 Foo->meta->class_precedence_list()
1507 # remove a method from Foo
1508 Foo->meta->remove_method('bar');
1510 # or use this to actually create classes ...
1512 Class::MOP::Class->create(
1515 superclasses => ['Foo'],
1517 Class::MOP::Attribute->new('$bar'),
1518 Class::MOP::Attribute->new('$baz'),
1521 calculate_bar => sub {...},
1522 construct_baz => sub {...}
1529 The Class Protocol is the largest and most complex part of the
1530 Class::MOP meta-object protocol. It controls the introspection and
1531 manipulation of Perl 5 classes, and it can create them as well. The
1532 best way to understand what this module can do is to read the
1533 documentation for each of its methods.
1537 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1541 =head2 Class construction
1543 These methods all create new C<Class::MOP::Class> objects. These
1544 objects can represent existing classes or they can be used to create
1545 new classes from scratch.
1547 The metaclass object for a given class is a singleton. If you attempt
1548 to create a metaclass for the same class twice, you will just get the
1553 =item B<< Class::MOP::Class->create($package_name, %options) >>
1555 This method creates a new C<Class::MOP::Class> object with the given
1556 package name. It accepts a number of options:
1562 An optional version number for the newly created package.
1566 An optional authority for the newly created package.
1568 =item * superclasses
1570 An optional array reference of superclass names.
1574 An optional hash reference of methods for the class. The keys of the
1575 hash reference are method names and values are subroutine references.
1579 An optional array reference of L<Class::MOP::Attribute> objects.
1583 Specifies the name to install the C<meta> method for this class under.
1584 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1585 given, no meta method will be installed.
1589 If true, the metaclass that is stored in the global cache will be a
1592 Classes created in this way are destroyed once the metaclass they are
1593 attached to goes out of scope, and will be removed from Perl's internal
1596 All instances of a class with a weakened metaclass keep a special
1597 reference to the metaclass object, which prevents the metaclass from
1598 going out of scope while any instances exist.
1600 This only works if the instance is based on a hash reference, however.
1604 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1606 This method works just like C<< Class::MOP::Class->create >> but it
1607 creates an "anonymous" class. In fact, the class does have a name, but
1608 that name is a unique name generated internally by this module.
1610 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1611 parameters that C<create> accepts.
1613 Anonymous classes default to C<< weaken => 1 >>, although this can be
1616 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1618 This method will initialize a C<Class::MOP::Class> object for the
1619 named package. Unlike C<create>, this method I<will not> create a new
1622 The purpose of this method is to retrieve a C<Class::MOP::Class>
1623 object for introspecting an existing class.
1625 If an existing C<Class::MOP::Class> object exists for the named
1626 package, it will be returned, and any options provided will be
1629 If the object does not yet exist, it will be created.
1631 The valid options that can be passed to this method are
1632 C<attribute_metaclass>, C<method_metaclass>,
1633 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1634 optional, and default to the appropriate class in the C<Class::MOP>
1639 =head2 Object instance construction and cloning
1641 These methods are all related to creating and/or cloning object
1646 =item B<< $metaclass->clone_object($instance, %params) >>
1648 This method clones an existing object instance. Any parameters you
1649 provide are will override existing attribute values in the object.
1651 This is a convenience method for cloning an object instance, then
1652 blessing it into the appropriate package.
1654 You could implement a clone method in your class, using this method:
1657 my ($self, %params) = @_;
1658 $self->meta->clone_object($self, %params);
1661 =item B<< $metaclass->rebless_instance($instance, %params) >>
1663 This method changes the class of C<$instance> to the metaclass's class.
1665 You can only rebless an instance into a subclass of its current
1666 class. If you pass any additional parameters, these will be treated
1667 like constructor parameters and used to initialize the object's
1668 attributes. Any existing attributes that are already set will be
1671 Before reblessing the instance, this method will call
1672 C<rebless_instance_away> on the instance's current metaclass. This method
1673 will be passed the instance, the new metaclass, and any parameters
1674 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1675 does nothing; it is merely a hook.
1677 =item B<< $metaclass->rebless_instance_back($instance) >>
1679 Does the same thing as C<rebless_instance>, except that you can only
1680 rebless an instance into one of its superclasses. Any attributes that
1681 do not exist in the superclass will be deinitialized.
1683 This is a much more dangerous operation than C<rebless_instance>,
1684 especially when multiple inheritance is involved, so use this carefully!
1686 =item B<< $metaclass->new_object(%params) >>
1688 This method is used to create a new object of the metaclass's
1689 class. Any parameters you provide are used to initialize the
1690 instance's attributes. A special C<__INSTANCE__> key can be passed to
1691 provide an already generated instance, rather than having Class::MOP
1692 generate it for you. This is mostly useful for using Class::MOP with
1693 foreign classes which generate instances using their own constructors.
1695 =item B<< $metaclass->instance_metaclass >>
1697 Returns the class name of the instance metaclass. See
1698 L<Class::MOP::Instance> for more information on the instance
1701 =item B<< $metaclass->get_meta_instance >>
1703 Returns an instance of the C<instance_metaclass> to be used in the
1704 construction of a new instance of the class.
1708 =head2 Informational predicates
1710 These are a few predicate methods for asking information about the
1715 =item B<< $metaclass->is_anon_class >>
1717 This returns true if the class was created by calling C<<
1718 Class::MOP::Class->create_anon_class >>.
1720 =item B<< $metaclass->is_mutable >>
1722 This returns true if the class is still mutable.
1724 =item B<< $metaclass->is_immutable >>
1726 This returns true if the class has been made immutable.
1728 =item B<< $metaclass->is_pristine >>
1730 A class is I<not> pristine if it has non-inherited attributes or if it
1731 has any generated methods.
1735 =head2 Inheritance Relationships
1739 =item B<< $metaclass->superclasses(@superclasses) >>
1741 This is a read-write accessor which represents the superclass
1742 relationships of the metaclass's class.
1744 This is basically sugar around getting and setting C<@ISA>.
1746 =item B<< $metaclass->class_precedence_list >>
1748 This returns a list of all of the class's ancestor classes. The
1749 classes are returned in method dispatch order.
1751 =item B<< $metaclass->linearized_isa >>
1753 This returns a list based on C<class_precedence_list> but with all
1756 =item B<< $metaclass->subclasses >>
1758 This returns a list of all subclasses for this class, even indirect
1761 =item B<< $metaclass->direct_subclasses >>
1763 This returns a list of immediate subclasses for this class, which does not
1764 include indirect subclasses.
1768 =head2 Method introspection and creation
1770 These methods allow you to introspect a class's methods, as well as
1771 add, remove, or change methods.
1773 Determining what is truly a method in a Perl 5 class requires some
1774 heuristics (aka guessing).
1776 Methods defined outside the package with a fully qualified name (C<sub
1777 Package::name { ... }>) will be included. Similarly, methods named
1778 with a fully qualified name using L<Sub::Name> are also included.
1780 However, we attempt to ignore imported functions.
1782 Ultimately, we are using heuristics to determine what truly is a
1783 method in a class, and these heuristics may get the wrong answer in
1784 some edge cases. However, for most "normal" cases the heuristics work
1789 =item B<< $metaclass->get_method($method_name) >>
1791 This will return a L<Class::MOP::Method> for the specified
1792 C<$method_name>. If the class does not have the specified method, it
1795 =item B<< $metaclass->has_method($method_name) >>
1797 Returns a boolean indicating whether or not the class defines the
1798 named method. It does not include methods inherited from parent
1801 =item B<< $metaclass->get_method_list >>
1803 This will return a list of method I<names> for all methods defined in
1806 =item B<< $metaclass->add_method($method_name, $method) >>
1808 This method takes a method name and a subroutine reference, and adds
1809 the method to the class.
1811 The subroutine reference can be a L<Class::MOP::Method>, and you are
1812 strongly encouraged to pass a meta method object instead of a code
1813 reference. If you do so, that object gets stored as part of the
1814 class's method map directly. If not, the meta information will have to
1815 be recreated later, and may be incorrect.
1817 If you provide a method object, this method will clone that object if
1818 the object's package name does not match the class name. This lets us
1819 track the original source of any methods added from other classes
1820 (notably Moose roles).
1822 =item B<< $metaclass->remove_method($method_name) >>
1824 Remove the named method from the class. This method returns the
1825 L<Class::MOP::Method> object for the method.
1827 =item B<< $metaclass->method_metaclass >>
1829 Returns the class name of the method metaclass, see
1830 L<Class::MOP::Method> for more information on the method metaclass.
1832 =item B<< $metaclass->wrapped_method_metaclass >>
1834 Returns the class name of the wrapped method metaclass, see
1835 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1838 =item B<< $metaclass->get_all_methods >>
1840 This will traverse the inheritance hierarchy and return a list of all
1841 the L<Class::MOP::Method> objects for this class and its parents.
1843 =item B<< $metaclass->find_method_by_name($method_name) >>
1845 This will return a L<Class::MOP::Method> for the specified
1846 C<$method_name>. If the class does not have the specified method, it
1849 Unlike C<get_method>, this method I<will> look for the named method in
1852 =item B<< $metaclass->get_all_method_names >>
1854 This will return a list of method I<names> for all of this class's
1855 methods, including inherited methods.
1857 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1859 This method looks for the named method in the class and all of its
1860 parents. It returns every matching method it finds in the inheritance
1861 tree, so it returns a list of methods.
1863 Each method is returned as a hash reference with three keys. The keys
1864 are C<name>, C<class>, and C<code>. The C<code> key has a
1865 L<Class::MOP::Method> object as its value.
1867 The list of methods is distinct.
1869 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1871 This method returns the first method in any superclass matching the
1872 given name. It is effectively the method that C<SUPER::$method_name>
1877 =head2 Attribute introspection and creation
1879 Because Perl 5 does not have a core concept of attributes in classes,
1880 we can only return information about attributes which have been added
1881 via this class's methods. We cannot discover information about
1882 attributes which are defined in terms of "regular" Perl 5 methods.
1886 =item B<< $metaclass->get_attribute($attribute_name) >>
1888 This will return a L<Class::MOP::Attribute> for the specified
1889 C<$attribute_name>. If the class does not have the specified
1890 attribute, it returns C<undef>.
1892 NOTE that get_attribute does not search superclasses, for that you
1893 need to use C<find_attribute_by_name>.
1895 =item B<< $metaclass->has_attribute($attribute_name) >>
1897 Returns a boolean indicating whether or not the class defines the
1898 named attribute. It does not include attributes inherited from parent
1901 =item B<< $metaclass->get_attribute_list >>
1903 This will return a list of attributes I<names> for all attributes
1904 defined in this class. Note that this operates on the current class
1905 only, it does not traverse the inheritance hierarchy.
1907 =item B<< $metaclass->get_all_attributes >>
1909 This will traverse the inheritance hierarchy and return a list of all
1910 the L<Class::MOP::Attribute> objects for this class and its parents.
1912 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1914 This will return a L<Class::MOP::Attribute> for the specified
1915 C<$attribute_name>. If the class does not have the specified
1916 attribute, it returns C<undef>.
1918 Unlike C<get_attribute>, this attribute I<will> look for the named
1919 attribute in superclasses.
1921 =item B<< $metaclass->add_attribute(...) >>
1923 This method accepts either an existing L<Class::MOP::Attribute>
1924 object or parameters suitable for passing to that class's C<new>
1927 The attribute provided will be added to the class.
1929 Any accessor methods defined by the attribute will be added to the
1930 class when the attribute is added.
1932 If an attribute of the same name already exists, the old attribute
1933 will be removed first.
1935 =item B<< $metaclass->remove_attribute($attribute_name) >>
1937 This will remove the named attribute from the class, and
1938 L<Class::MOP::Attribute> object.
1940 Removing an attribute also removes any accessor methods defined by the
1943 However, note that removing an attribute will only affect I<future>
1944 object instances created for this class, not existing instances.
1946 =item B<< $metaclass->attribute_metaclass >>
1948 Returns the class name of the attribute metaclass for this class. By
1949 default, this is L<Class::MOP::Attribute>.
1953 =head2 Class Immutability
1955 Making a class immutable "freezes" the class definition. You can no
1956 longer call methods which alter the class, such as adding or removing
1957 methods or attributes.
1959 Making a class immutable lets us optimize the class by inlining some
1960 methods, and also allows us to optimize some methods on the metaclass
1963 After immutabilization, the metaclass object will cache most informational
1964 methods that returns information about methods or attributes. Methods which
1965 would alter the class, such as C<add_attribute> and C<add_method>, will
1966 throw an error on an immutable metaclass object.
1968 The immutabilization system in L<Moose> takes much greater advantage
1969 of the inlining features than Class::MOP itself does.
1973 =item B<< $metaclass->make_immutable(%options) >>
1975 This method will create an immutable transformer and use it to make
1976 the class and its metaclass object immutable.
1978 This method accepts the following options:
1982 =item * inline_accessors
1984 =item * inline_constructor
1986 =item * inline_destructor
1988 These are all booleans indicating whether the specified method(s)
1991 By default, accessors and the constructor are inlined, but not the
1994 =item * immutable_trait
1996 The name of a class which will be used as a parent class for the
1997 metaclass object being made immutable. This "trait" implements the
1998 post-immutability functionality of the metaclass (but not the
1999 transformation itself).
2001 This defaults to L<Class::MOP::Class::Immutable::Trait>.
2003 =item * constructor_name
2005 This is the constructor method name. This defaults to "new".
2007 =item * constructor_class
2009 The name of the method metaclass for constructors. It will be used to
2010 generate the inlined constructor. This defaults to
2011 "Class::MOP::Method::Constructor".
2013 =item * replace_constructor
2015 This is a boolean indicating whether an existing constructor should be
2016 replaced when inlining a constructor. This defaults to false.
2018 =item * destructor_class
2020 The name of the method metaclass for destructors. It will be used to
2021 generate the inlined destructor. This defaults to
2022 "Class::MOP::Method::Denstructor".
2024 =item * replace_destructor
2026 This is a boolean indicating whether an existing destructor should be
2027 replaced when inlining a destructor. This defaults to false.
2031 =item B<< $metaclass->immutable_options >>
2033 Returns a hash of the options used when making the class immutable, including
2034 both defaults and anything supplied by the user in the call to C<<
2035 $metaclass->make_immutable >>. This is useful if you need to temporarily make
2036 a class mutable and then restore immutability as it was before.
2038 =item B<< $metaclass->make_mutable >>
2040 Calling this method reverse the immutabilization transformation.
2044 =head2 Method Modifiers
2046 Method modifiers are hooks which allow a method to be wrapped with
2047 I<before>, I<after> and I<around> method modifiers. Every time a
2048 method is called, its modifiers are also called.
2050 A class can modify its own methods, as well as methods defined in
2053 =head3 How method modifiers work?
2055 Method modifiers work by wrapping the original method and then
2056 replacing it in the class's symbol table. The wrappers will handle
2057 calling all the modifiers in the appropriate order and preserving the
2058 calling context for the original method.
2060 The return values of C<before> and C<after> modifiers are
2061 ignored. This is because their purpose is B<not> to filter the input
2062 and output of the primary method (this is done with an I<around>
2065 This may seem like an odd restriction to some, but doing this allows
2066 for simple code to be added at the beginning or end of a method call
2067 without altering the function of the wrapped method or placing any
2068 extra responsibility on the code of the modifier.
2070 Of course if you have more complex needs, you can use the C<around>
2071 modifier which allows you to change both the parameters passed to the
2072 wrapped method, as well as its return value.
2074 Before and around modifiers are called in last-defined-first-called
2075 order, while after modifiers are called in first-defined-first-called
2076 order. So the call tree might looks something like this:
2088 =head3 What is the performance impact?
2090 Of course there is a performance cost associated with method
2091 modifiers, but we have made every effort to make that cost directly
2092 proportional to the number of modifier features you use.
2094 The wrapping method does its best to B<only> do as much work as it
2095 absolutely needs to. In order to do this we have moved some of the
2096 performance costs to set-up time, where they are easier to amortize.
2098 All this said, our benchmarks have indicated the following:
2100 simple wrapper with no modifiers 100% slower
2101 simple wrapper with simple before modifier 400% slower
2102 simple wrapper with simple after modifier 450% slower
2103 simple wrapper with simple around modifier 500-550% slower
2104 simple wrapper with all 3 modifiers 1100% slower
2106 These numbers may seem daunting, but you must remember, every feature
2107 comes with some cost. To put things in perspective, just doing a
2108 simple C<AUTOLOAD> which does nothing but extract the name of the
2109 method called and return it costs about 400% over a normal method
2114 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
2116 This wraps the specified method with the supplied subroutine
2117 reference. The modifier will be called as a method itself, and will
2118 receive the same arguments as are passed to the method.
2120 When the modifier exits, the wrapped method will be called.
2122 The return value of the modifier will be ignored.
2124 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2126 This wraps the specified method with the supplied subroutine
2127 reference. The modifier will be called as a method itself, and will
2128 receive the same arguments as are passed to the method.
2130 When the wrapped methods exits, the modifier will be called.
2132 The return value of the modifier will be ignored.
2134 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2136 This wraps the specified method with the supplied subroutine
2139 The first argument passed to the modifier will be a subroutine
2140 reference to the wrapped method. The second argument is the object,
2141 and after that come any arguments passed when the method is called.
2143 The around modifier can choose to call the original method, as well as
2144 what arguments to pass if it does so.
2146 The return value of the modifier is what will be seen by the caller.
2150 =head2 Introspection
2154 =item B<< Class::MOP::Class->meta >>
2156 This will return a L<Class::MOP::Class> instance for this class.
2158 It should also be noted that L<Class::MOP> will actually bootstrap
2159 this module by installing a number of attribute meta-objects into its