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 our $VERSION = '1.11';
21 $VERSION = eval $VERSION;
22 our $AUTHORITY = 'cpan:STEVAN';
24 use base 'Class::MOP::Module',
25 'Class::MOP::Mixin::HasAttributes',
26 'Class::MOP::Mixin::HasMethods';
36 $package_name = shift;
39 $package_name = $options{package};
42 ($package_name && !ref($package_name))
43 || confess "You must pass a package name and it cannot be blessed";
45 return Class::MOP::get_metaclass_by_name($package_name)
46 || $class->_construct_class_instance(package => $package_name, @_);
50 my ( $class, @args ) = @_;
51 unshift @args, "package" if @args % 2;
53 my $old_metaclass = blessed($options{package})
55 : Class::MOP::get_metaclass_by_name($options{package});
56 $options{weaken} = Class::MOP::metaclass_is_weak($old_metaclass->name)
57 if !exists $options{weaken}
58 && blessed($old_metaclass)
59 && $old_metaclass->isa('Class::MOP::Class');
60 $old_metaclass->_remove_generated_metaobjects
61 if $old_metaclass && $old_metaclass->isa('Class::MOP::Class');
62 my $new_metaclass = $class->SUPER::reinitialize(%options);
63 $new_metaclass->_restore_metaobjects_from($old_metaclass)
64 if $old_metaclass && $old_metaclass->isa('Class::MOP::Class');
65 return $new_metaclass;
68 # NOTE: (meta-circularity)
69 # this is a special form of _construct_instance
70 # (see below), which is used to construct class
71 # meta-object instances for any Class::MOP::*
72 # class. All other classes will use the more
73 # normal &construct_instance.
74 sub _construct_class_instance {
76 my $options = @_ == 1 ? $_[0] : {@_};
77 my $package_name = $options->{package};
78 (defined $package_name && $package_name)
79 || confess "You must pass a package name";
81 # return the metaclass if we have it cached,
82 # and it is still defined (it has not been
83 # reaped by DESTROY yet, which can happen
84 # annoyingly enough during global destruction)
86 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
92 ? $class->_real_ref_name
95 # now create the metaclass
97 if ($class eq 'Class::MOP::Class') {
98 $meta = $class->_new($options);
102 # it is safe to use meta here because
103 # class will always be a subclass of
104 # Class::MOP::Class, which defines meta
105 $meta = $class->meta->_construct_instance($options)
108 # and check the metaclass compatibility
109 $meta->_check_metaclass_compatibility();
111 Class::MOP::store_metaclass_by_name($package_name, $meta);
114 # we need to weaken any anon classes
115 # so that they can call DESTROY properly
116 Class::MOP::weaken_metaclass($package_name) if $options->{weaken};
124 # NOTE: we need to deal with the possibility of class immutability here,
125 # and then get the name of the class appropriately
126 return $self->is_immutable
127 ? $self->_get_mutable_metaclass_name()
134 return Class::MOP::Class->initialize($class)->new_object(@_)
135 if $class ne __PACKAGE__;
137 my $options = @_ == 1 ? $_[0] : {@_};
140 # inherited from Class::MOP::Package
141 'package' => $options->{package},
144 # since the following attributes will
145 # actually be loaded from the symbol
146 # table, and actually bypass the instance
147 # entirely, we can just leave these things
148 # listed here for reference, because they
149 # should not actually have a value associated
151 'namespace' => \undef,
154 # inherited from Class::MOP::Module
156 'authority' => \undef,
158 # defined in Class::MOP::Class
159 'superclasses' => \undef,
162 'attribute_metaclass' =>
163 ( $options->{'attribute_metaclass'} || 'Class::MOP::Attribute' ),
164 'method_metaclass' =>
165 ( $options->{'method_metaclass'} || 'Class::MOP::Method' ),
166 'wrapped_method_metaclass' => (
167 $options->{'wrapped_method_metaclass'}
168 || 'Class::MOP::Method::Wrapped'
170 'instance_metaclass' =>
171 ( $options->{'instance_metaclass'} || 'Class::MOP::Instance' ),
172 'immutable_trait' => (
173 $options->{'immutable_trait'}
174 || 'Class::MOP::Class::Immutable::Trait'
176 'constructor_name' => ( $options->{constructor_name} || 'new' ),
177 'constructor_class' => (
178 $options->{constructor_class} || 'Class::MOP::Method::Constructor'
180 'destructor_class' => $options->{destructor_class},
184 ## Metaclass compatibility
186 my %base_metaclass = (
187 attribute_metaclass => 'Class::MOP::Attribute',
188 method_metaclass => 'Class::MOP::Method',
189 wrapped_method_metaclass => 'Class::MOP::Method::Wrapped',
190 instance_metaclass => 'Class::MOP::Instance',
191 constructor_class => 'Class::MOP::Method::Constructor',
192 destructor_class => 'Class::MOP::Method::Destructor',
195 sub _base_metaclasses { %base_metaclass }
198 sub _check_metaclass_compatibility {
201 my @superclasses = $self->superclasses
204 $self->_fix_metaclass_incompatibility(@superclasses);
206 my %base_metaclass = $self->_base_metaclasses;
208 # this is always okay ...
210 if ref($self) eq 'Class::MOP::Class'
212 my $meta = $self->$_;
213 !defined($meta) || $meta eq $base_metaclass{$_};
215 keys %base_metaclass;
217 for my $superclass (@superclasses) {
218 $self->_check_class_metaclass_compatibility($superclass);
221 for my $metaclass_type ( keys %base_metaclass ) {
222 next unless defined $self->$metaclass_type;
223 for my $superclass (@superclasses) {
224 $self->_check_single_metaclass_compatibility( $metaclass_type,
230 sub _check_class_metaclass_compatibility {
232 my ( $superclass_name ) = @_;
234 if (!$self->_class_metaclass_is_compatible($superclass_name)) {
235 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
237 my $super_meta_type = $super_meta->_real_ref_name;
239 confess "The metaclass of " . $self->name . " ("
240 . (ref($self)) . ")" . " is not compatible with "
241 . "the metaclass of its superclass, "
242 . $superclass_name . " (" . ($super_meta_type) . ")";
246 sub _class_metaclass_is_compatible {
248 my ( $superclass_name ) = @_;
250 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
253 my $super_meta_name = $super_meta->_real_ref_name;
255 return $self->_is_compatible_with($super_meta_name);
258 sub _check_single_metaclass_compatibility {
260 my ( $metaclass_type, $superclass_name ) = @_;
262 if (!$self->_single_metaclass_is_compatible($metaclass_type, $superclass_name)) {
263 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
264 my $metaclass_type_name = $metaclass_type;
265 $metaclass_type_name =~ s/_(?:meta)?class$//;
266 $metaclass_type_name =~ s/_/ /g;
267 confess "The $metaclass_type_name metaclass for "
268 . $self->name . " (" . ($self->$metaclass_type)
269 . ")" . " is not compatible with the "
270 . "$metaclass_type_name metaclass of its "
271 . "superclass, $superclass_name ("
272 . ($super_meta->$metaclass_type) . ")";
276 sub _single_metaclass_is_compatible {
278 my ( $metaclass_type, $superclass_name ) = @_;
280 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
283 # for instance, Moose::Meta::Class has a error_class attribute, but
284 # Class::MOP::Class doesn't - this shouldn't be an error
285 return 1 unless $super_meta->can($metaclass_type);
286 # for instance, Moose::Meta::Class has a destructor_class, but
287 # Class::MOP::Class doesn't - this shouldn't be an error
288 return 1 unless defined $super_meta->$metaclass_type;
289 # if metaclass is defined in superclass but not here, it's not compatible
290 # this is a really odd case
291 return 0 unless defined $self->$metaclass_type;
293 return $self->$metaclass_type->_is_compatible_with($super_meta->$metaclass_type);
296 sub _fix_metaclass_incompatibility {
298 my @supers = map { Class::MOP::Class->initialize($_) } @_;
301 for my $super (@supers) {
303 if $self->_can_fix_metaclass_incompatibility($super);
305 return unless $necessary;
307 for my $super (@supers) {
308 if (!$self->_class_metaclass_is_compatible($super->name)) {
309 $self->_fix_class_metaclass_incompatibility($super);
313 my %base_metaclass = $self->_base_metaclasses;
314 for my $metaclass_type (keys %base_metaclass) {
315 for my $super (@supers) {
316 if (!$self->_single_metaclass_is_compatible($metaclass_type, $super->name)) {
317 $self->_fix_single_metaclass_incompatibility(
318 $metaclass_type, $super
325 sub _can_fix_metaclass_incompatibility {
327 my ($super_meta) = @_;
329 return 1 if $self->_class_metaclass_can_be_made_compatible($super_meta);
331 my %base_metaclass = $self->_base_metaclasses;
332 for my $metaclass_type (keys %base_metaclass) {
333 return 1 if $self->_single_metaclass_can_be_made_compatible($super_meta, $metaclass_type);
339 sub _class_metaclass_can_be_made_compatible {
341 my ($super_meta) = @_;
343 return $self->_can_be_made_compatible_with($super_meta->_real_ref_name);
346 sub _single_metaclass_can_be_made_compatible {
348 my ($super_meta, $metaclass_type) = @_;
350 my $specific_meta = $self->$metaclass_type;
352 return unless $super_meta->can($metaclass_type);
353 my $super_specific_meta = $super_meta->$metaclass_type;
355 # for instance, Moose::Meta::Class has a destructor_class, but
356 # Class::MOP::Class doesn't - this shouldn't be an error
357 return unless defined $super_specific_meta;
359 # if metaclass is defined in superclass but not here, it's fixable
360 # this is a really odd case
361 return 1 unless defined $specific_meta;
363 return 1 if $specific_meta->_can_be_made_compatible_with($super_specific_meta);
366 sub _fix_class_metaclass_incompatibility {
368 my ( $super_meta ) = @_;
370 if ($self->_class_metaclass_can_be_made_compatible($super_meta)) {
372 || confess "Can't fix metaclass incompatibility for "
374 . " because it is not pristine.";
376 my $super_meta_name = $super_meta->_real_ref_name;
378 $self->_make_compatible_with($super_meta_name);
382 sub _fix_single_metaclass_incompatibility {
384 my ( $metaclass_type, $super_meta ) = @_;
386 if ($self->_single_metaclass_can_be_made_compatible($super_meta, $metaclass_type)) {
388 || confess "Can't fix metaclass incompatibility for "
390 . " because it is not pristine.";
392 my $new_metaclass = $self->$metaclass_type
393 ? $self->$metaclass_type->_get_compatible_metaclass($super_meta->$metaclass_type)
394 : $super_meta->$metaclass_type;
395 $self->{$metaclass_type} = $new_metaclass;
399 sub _restore_metaobjects_from {
403 $self->_restore_metamethods_from($old_meta);
404 $self->_restore_metaattributes_from($old_meta);
407 sub _remove_generated_metaobjects {
410 for my $attr (map { $self->get_attribute($_) } $self->get_attribute_list) {
411 $attr->remove_accessors;
419 # this should be sufficient, if you have a
420 # use case where it is not, write a test and
422 my $ANON_CLASS_SERIAL = 0;
425 # we need a sufficiently annoying prefix
426 # this should suffice for now, this is
427 # used in a couple of places below, so
428 # need to put it up here for now.
429 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
433 no warnings 'uninitialized';
434 $self->name =~ /^$ANON_CLASS_PREFIX/o;
437 sub create_anon_class {
438 my ($class, %options) = @_;
439 $options{weaken} = 1 unless exists $options{weaken};
440 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
441 return $class->create($package_name, %options);
445 # this will only get called for
446 # anon-classes, all other calls
447 # are assumed to occur during
448 # global destruction and so don't
449 # really need to be handled explicitly
453 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
455 no warnings 'uninitialized';
456 my $name = $self->name;
457 return unless $name =~ /^$ANON_CLASS_PREFIX/o;
459 # Moose does a weird thing where it replaces the metaclass for
460 # class when fixing metaclass incompatibility. In that case,
461 # we don't want to clean out the namespace now. We can detect
462 # that because Moose will explicitly update the singleton
463 # cache in Class::MOP.
464 my $current_meta = Class::MOP::get_metaclass_by_name($name);
465 return if $current_meta ne $self;
467 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/o);
469 @{$name . '::ISA'} = ();
470 %{$name . '::'} = ();
471 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
473 Class::MOP::remove_metaclass_by_name($name);
478 # creating classes with MOP ...
481 my ( $class, @args ) = @_;
483 unshift @args, 'package' if @args % 2 == 1;
485 my (%options) = @args;
486 my $package_name = $options{package};
488 (ref $options{superclasses} eq 'ARRAY')
489 || confess "You must pass an ARRAY ref of superclasses"
490 if exists $options{superclasses};
492 (ref $options{attributes} eq 'ARRAY')
493 || confess "You must pass an ARRAY ref of attributes"
494 if exists $options{attributes};
496 (ref $options{methods} eq 'HASH')
497 || confess "You must pass a HASH ref of methods"
498 if exists $options{methods};
500 $options{meta_name} = 'meta'
501 unless exists $options{meta_name};
503 my (%initialize_options) = @args;
504 delete @initialize_options{qw(
513 my $meta = $class->initialize( $package_name => %initialize_options );
515 $meta->_instantiate_module( $options{version}, $options{authority} );
517 $meta->_add_meta_method($options{meta_name})
518 if defined $options{meta_name};
520 $meta->superclasses(@{$options{superclasses}})
521 if exists $options{superclasses};
523 # process attributes first, so that they can
524 # install accessors, but locally defined methods
525 # can then overwrite them. It is maybe a little odd, but
526 # I think this should be the order of things.
527 if (exists $options{attributes}) {
528 foreach my $attr (@{$options{attributes}}) {
529 $meta->add_attribute($attr);
532 if (exists $options{methods}) {
533 foreach my $method_name (keys %{$options{methods}}) {
534 $meta->add_method($method_name, $options{methods}->{$method_name});
540 # Instance Construction & Cloning
546 # we need to protect the integrity of the
547 # Class::MOP::Class singletons here, so we
548 # delegate this to &construct_class_instance
549 # which will deal with the singletons
550 return $class->_construct_class_instance(@_)
551 if $class->name->isa('Class::MOP::Class');
552 return $class->_construct_instance(@_);
555 sub _construct_instance {
557 my $params = @_ == 1 ? $_[0] : {@_};
558 my $meta_instance = $class->get_meta_instance();
560 # the code below is almost certainly incorrect
561 # but this is foreign inheritance, so we might
562 # have to kludge it in the end.
564 if (my $instance_class = blessed($params->{__INSTANCE__})) {
565 ($instance_class eq $class->name)
566 || confess "Objects passed as the __INSTANCE__ parameter must "
567 . "already be blessed into the correct class, but "
568 . "$params->{__INSTANCE__} is not a " . $class->name;
569 $instance = $params->{__INSTANCE__};
571 elsif (exists $params->{__INSTANCE__}) {
572 confess "The __INSTANCE__ parameter must be a blessed reference, not "
573 . $params->{__INSTANCE__};
576 $instance = $meta_instance->create_instance();
578 foreach my $attr ($class->get_all_attributes()) {
579 $attr->initialize_instance_slot($meta_instance, $instance, $params);
581 if (Class::MOP::metaclass_is_weak($class->name)) {
582 $meta_instance->_set_mop_slot($instance, $class);
588 sub get_meta_instance {
590 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
593 sub _create_meta_instance {
596 my $instance = $self->instance_metaclass->new(
597 associated_metaclass => $self,
598 attributes => [ $self->get_all_attributes() ],
601 $self->add_meta_instance_dependencies()
602 if $instance->is_dependent_on_superclasses();
607 sub inline_create_instance {
610 return $self->get_meta_instance->inline_create_instance(@_);
613 sub inline_rebless_instance {
616 return $self->get_meta_instance->inline_rebless_instance_structure(@_);
619 sub _inline_get_mop_slot {
622 return $self->get_meta_instance->_inline_get_mop_slot(@_);
625 sub _inline_set_mop_slot {
628 return $self->get_meta_instance->_inline_set_mop_slot(@_);
631 sub _inline_clear_mop_slot {
634 return $self->get_meta_instance->_inline_clear_mop_slot(@_);
639 my $instance = shift;
640 (blessed($instance) && $instance->isa($class->name))
641 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
644 # we need to protect the integrity of the
645 # Class::MOP::Class singletons here, they
646 # should not be cloned.
647 return $instance if $instance->isa('Class::MOP::Class');
648 $class->_clone_instance($instance, @_);
651 sub _clone_instance {
652 my ($class, $instance, %params) = @_;
654 || confess "You can only clone instances, ($instance) is not a blessed instance";
655 my $meta_instance = $class->get_meta_instance();
656 my $clone = $meta_instance->clone_instance($instance);
657 foreach my $attr ($class->get_all_attributes()) {
658 if ( defined( my $init_arg = $attr->init_arg ) ) {
659 if (exists $params{$init_arg}) {
660 $attr->set_value($clone, $params{$init_arg});
667 sub _force_rebless_instance {
668 my ($self, $instance, %params) = @_;
669 my $old_metaclass = Class::MOP::class_of($instance);
671 $old_metaclass->rebless_instance_away($instance, $self, %params)
674 my $meta_instance = $self->get_meta_instance;
676 if (Class::MOP::metaclass_is_weak($old_metaclass->name)) {
677 $meta_instance->_clear_mop_slot($instance);
681 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
682 $meta_instance->rebless_instance_structure($_[1], $self);
684 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
686 if (Class::MOP::metaclass_is_weak($self->name)) {
687 $meta_instance->_set_mop_slot($instance, $self);
691 sub rebless_instance {
692 my ($self, $instance, %params) = @_;
693 my $old_metaclass = Class::MOP::class_of($instance);
695 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
696 $self->name->isa($old_class)
697 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
699 $self->_force_rebless_instance($_[1], %params);
704 sub rebless_instance_back {
705 my ( $self, $instance ) = @_;
706 my $old_metaclass = Class::MOP::class_of($instance);
709 = $old_metaclass ? $old_metaclass->name : blessed($instance);
710 $old_class->isa( $self->name )
712 "You may rebless only into a superclass of ($old_class), of which ("
716 $self->_force_rebless_instance($_[1]);
721 sub rebless_instance_away {
722 # this intentionally does nothing, it is just a hook
725 sub _fixup_attributes_after_rebless {
727 my ($instance, $rebless_from, %params) = @_;
728 my $meta_instance = $self->get_meta_instance;
730 for my $attr ( $rebless_from->get_all_attributes ) {
731 next if $self->find_attribute_by_name( $attr->name );
732 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
735 foreach my $attr ( $self->get_all_attributes ) {
736 if ( $attr->has_value($instance) ) {
737 if ( defined( my $init_arg = $attr->init_arg ) ) {
738 $params{$init_arg} = $attr->get_value($instance)
739 unless exists $params{$init_arg};
742 $attr->set_value($instance, $attr->get_value($instance));
747 foreach my $attr ($self->get_all_attributes) {
748 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
752 sub _attach_attribute {
753 my ($self, $attribute) = @_;
754 $attribute->attach_to_class($self);
757 sub _post_add_attribute {
758 my ( $self, $attribute ) = @_;
760 $self->invalidate_meta_instances;
762 # invalidate package flag here
765 $attribute->install_accessors;
768 $self->remove_attribute( $attribute->name );
773 sub remove_attribute {
776 my $removed_attribute = $self->SUPER::remove_attribute(@_)
779 $self->invalidate_meta_instances;
781 $removed_attribute->remove_accessors;
782 $removed_attribute->detach_from_class;
784 return$removed_attribute;
787 sub find_attribute_by_name {
788 my ( $self, $attr_name ) = @_;
790 foreach my $class ( $self->linearized_isa ) {
791 # fetch the meta-class ...
792 my $meta = Class::MOP::Class->initialize($class);
793 return $meta->get_attribute($attr_name)
794 if $meta->has_attribute($attr_name);
800 sub get_all_attributes {
802 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
803 reverse $self->linearized_isa;
804 return values %attrs;
812 my $isa = $self->get_or_add_package_symbol('@ISA');
819 # on 5.8 and below, we need to call
820 # a method to get Perl to detect
821 # a cycle in the class hierarchy
822 my $class = $self->name;
826 # we need to check the metaclass
827 # compatibility here so that we can
828 # be sure that the superclass is
829 # not potentially creating an issues
830 # we don't know about
832 $self->_check_metaclass_compatibility();
833 $self->_superclasses_updated();
839 sub _superclasses_updated {
841 $self->update_meta_instance_dependencies();
842 # keep strong references to all our parents, so they don't disappear if
843 # they are anon classes and don't have any direct instances
844 $self->_superclass_metas(
845 map { Class::MOP::class_of($_) } $self->superclasses
849 sub _superclass_metas {
851 $self->{_superclass_metas} = [@_];
856 my $super_class = $self->name;
858 return @{ $super_class->mro::get_isarev() };
861 sub direct_subclasses {
863 my $super_class = $self->name;
868 } Class::MOP::Class->initialize($_)->superclasses
873 return @{ mro::get_linear_isa( (shift)->name ) };
876 sub class_precedence_list {
878 my $name = $self->name;
880 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
882 # We need to check for circular inheritance here
883 # if we are are not on 5.10, cause 5.8 detects it
884 # late. This will do nothing if all is well, and
885 # blow up otherwise. Yes, it's an ugly hack, better
886 # suggestions are welcome.
888 ($name || return)->isa('This is a test for circular inheritance')
891 # if our mro is c3, we can
892 # just grab the linear_isa
893 if (mro::get_mro($name) eq 'c3') {
894 return @{ mro::get_linear_isa($name) }
898 # we can't grab the linear_isa for dfs
899 # since it has all the duplicates
904 Class::MOP::Class->initialize($_)->class_precedence_list()
905 } $self->superclasses()
913 my $fetch_and_prepare_method = sub {
914 my ($self, $method_name) = @_;
915 my $wrapped_metaclass = $self->wrapped_method_metaclass;
917 my $method = $self->get_method($method_name);
918 # if we dont have local ...
920 # try to find the next method
921 $method = $self->find_next_method_by_name($method_name);
922 # die if it does not exist
924 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
925 # and now make sure to wrap it
926 # even if it is already wrapped
927 # because we need a new sub ref
928 $method = $wrapped_metaclass->wrap($method,
929 package_name => $self->name,
930 name => $method_name,
934 # now make sure we wrap it properly
935 $method = $wrapped_metaclass->wrap($method,
936 package_name => $self->name,
937 name => $method_name,
938 ) unless $method->isa($wrapped_metaclass);
940 $self->add_method($method_name => $method);
944 sub add_before_method_modifier {
945 my ($self, $method_name, $method_modifier) = @_;
946 (defined $method_name && length $method_name)
947 || confess "You must pass in a method name";
948 my $method = $fetch_and_prepare_method->($self, $method_name);
949 $method->add_before_modifier(
950 subname(':before' => $method_modifier)
954 sub add_after_method_modifier {
955 my ($self, $method_name, $method_modifier) = @_;
956 (defined $method_name && length $method_name)
957 || confess "You must pass in a method name";
958 my $method = $fetch_and_prepare_method->($self, $method_name);
959 $method->add_after_modifier(
960 subname(':after' => $method_modifier)
964 sub add_around_method_modifier {
965 my ($self, $method_name, $method_modifier) = @_;
966 (defined $method_name && length $method_name)
967 || confess "You must pass in a method name";
968 my $method = $fetch_and_prepare_method->($self, $method_name);
969 $method->add_around_modifier(
970 subname(':around' => $method_modifier)
975 # the methods above used to be named like this:
976 # ${pkg}::${method}:(before|after|around)
977 # but this proved problematic when using one modifier
978 # to wrap multiple methods (something which is likely
979 # to happen pretty regularly IMO). So instead of naming
980 # it like this, I have chosen to just name them purely
981 # with their modifier names, like so:
982 # :(before|after|around)
983 # The fact is that in a stack trace, it will be fairly
984 # evident from the context what method they are attached
985 # to, and so don't need the fully qualified name.
988 sub find_method_by_name {
989 my ($self, $method_name) = @_;
990 (defined $method_name && length $method_name)
991 || confess "You must define a method name to find";
992 foreach my $class ($self->linearized_isa) {
993 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
994 return $method if defined $method;
999 sub get_all_methods {
1003 for my $class ( reverse $self->linearized_isa ) {
1004 my $meta = Class::MOP::Class->initialize($class);
1006 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1009 return values %methods;
1012 sub get_all_method_names {
1015 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
1018 sub find_all_methods_by_name {
1019 my ($self, $method_name) = @_;
1020 (defined $method_name && length $method_name)
1021 || confess "You must define a method name to find";
1023 foreach my $class ($self->linearized_isa) {
1024 # fetch the meta-class ...
1025 my $meta = Class::MOP::Class->initialize($class);
1027 name => $method_name,
1029 code => $meta->get_method($method_name)
1030 } if $meta->has_method($method_name);
1035 sub find_next_method_by_name {
1036 my ($self, $method_name) = @_;
1037 (defined $method_name && length $method_name)
1038 || confess "You must define a method name to find";
1039 my @cpl = $self->linearized_isa;
1040 shift @cpl; # discard ourselves
1041 foreach my $class (@cpl) {
1042 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1043 return $method if defined $method;
1048 sub update_meta_instance_dependencies {
1051 if ( $self->{meta_instance_dependencies} ) {
1052 return $self->add_meta_instance_dependencies;
1056 sub add_meta_instance_dependencies {
1059 $self->remove_meta_instance_dependencies;
1061 my @attrs = $self->get_all_attributes();
1064 my @classes = grep { not $seen{ $_->name }++ }
1065 map { $_->associated_class } @attrs;
1067 foreach my $class (@classes) {
1068 $class->add_dependent_meta_instance($self);
1071 $self->{meta_instance_dependencies} = \@classes;
1074 sub remove_meta_instance_dependencies {
1077 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1078 foreach my $class (@$classes) {
1079 $class->remove_dependent_meta_instance($self);
1089 sub add_dependent_meta_instance {
1090 my ( $self, $metaclass ) = @_;
1091 push @{ $self->{dependent_meta_instances} }, $metaclass;
1094 sub remove_dependent_meta_instance {
1095 my ( $self, $metaclass ) = @_;
1096 my $name = $metaclass->name;
1097 @$_ = grep { $_->name ne $name } @$_
1098 for $self->{dependent_meta_instances};
1101 sub invalidate_meta_instances {
1103 $_->invalidate_meta_instance()
1104 for $self, @{ $self->{dependent_meta_instances} };
1107 sub invalidate_meta_instance {
1109 undef $self->{_meta_instance};
1112 # check if we can reinitialize
1116 # if any local attr is defined
1117 return if $self->get_attribute_list;
1119 # or any non-declared methods
1120 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1121 return if $method->isa("Class::MOP::Method::Generated");
1122 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1130 sub is_mutable { 1 }
1131 sub is_immutable { 0 }
1133 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1135 sub _immutable_options {
1136 my ( $self, @args ) = @_;
1139 inline_accessors => 1,
1140 inline_constructor => 1,
1141 inline_destructor => 0,
1143 immutable_trait => $self->immutable_trait,
1144 constructor_name => $self->constructor_name,
1145 constructor_class => $self->constructor_class,
1146 destructor_class => $self->destructor_class,
1151 sub make_immutable {
1152 my ( $self, @args ) = @_;
1154 if ( $self->is_mutable ) {
1155 $self->_initialize_immutable( $self->_immutable_options(@args) );
1156 $self->_rebless_as_immutable(@args);
1167 if ( $self->is_immutable ) {
1168 my @args = $self->immutable_options;
1169 $self->_rebless_as_mutable();
1170 $self->_remove_inlined_code(@args);
1171 delete $self->{__immutable};
1179 sub _rebless_as_immutable {
1180 my ( $self, @args ) = @_;
1182 $self->{__immutable}{original_class} = ref $self;
1184 bless $self => $self->_immutable_metaclass(@args);
1187 sub _immutable_metaclass {
1188 my ( $self, %args ) = @_;
1190 if ( my $class = $args{immutable_metaclass} ) {
1194 my $trait = $args{immutable_trait} = $self->immutable_trait
1195 || confess "no immutable trait specified for $self";
1197 my $meta = $self->meta;
1198 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1202 if ( $meta_attr and $trait eq $meta_attr->default ) {
1203 # if the trait is the same as the default we try and pick a
1204 # predictable name for the immutable metaclass
1205 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1208 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1209 $trait, 'ForMetaClass', ref($self);
1213 if Class::MOP::is_class_loaded($class_name);
1215 # If the metaclass is a subclass of CMOP::Class which has had
1216 # metaclass roles applied (via Moose), then we want to make sure
1217 # that we preserve that anonymous class (see Fey::ORM for an
1218 # example of where this matters).
1219 my $meta_name = $meta->_real_ref_name;
1221 my $immutable_meta = $meta_name->create(
1223 superclasses => [ ref $self ],
1226 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1228 $immutable_meta->make_immutable(
1229 inline_constructor => 0,
1230 inline_accessors => 0,
1236 sub _remove_inlined_code {
1239 $self->remove_method( $_->name ) for $self->_inlined_methods;
1241 delete $self->{__immutable}{inlined_methods};
1244 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1246 sub _add_inlined_method {
1247 my ( $self, $method ) = @_;
1249 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1252 sub _initialize_immutable {
1253 my ( $self, %args ) = @_;
1255 $self->{__immutable}{options} = \%args;
1256 $self->_install_inlined_code(%args);
1259 sub _install_inlined_code {
1260 my ( $self, %args ) = @_;
1263 $self->_inline_accessors(%args) if $args{inline_accessors};
1264 $self->_inline_constructor(%args) if $args{inline_constructor};
1265 $self->_inline_destructor(%args) if $args{inline_destructor};
1268 sub _rebless_as_mutable {
1271 bless $self, $self->_get_mutable_metaclass_name;
1276 sub _inline_accessors {
1279 foreach my $attr_name ( $self->get_attribute_list ) {
1280 $self->get_attribute($attr_name)->install_accessors(1);
1284 sub _inline_constructor {
1285 my ( $self, %args ) = @_;
1287 my $name = $args{constructor_name};
1288 # A class may not even have a constructor, and that's okay.
1289 return unless defined $name;
1291 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1292 my $class = $self->name;
1293 warn "Not inlining a constructor for $class since it defines"
1294 . " its own constructor.\n"
1295 . "If you are certain you don't need to inline your"
1296 . " constructor, specify inline_constructor => 0 in your"
1297 . " call to $class->meta->make_immutable\n";
1301 my $constructor_class = $args{constructor_class};
1303 Class::MOP::load_class($constructor_class);
1305 my $constructor = $constructor_class->new(
1309 package_name => $self->name,
1313 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1314 $self->add_method( $name => $constructor );
1315 $self->_add_inlined_method($constructor);
1319 sub _inline_destructor {
1320 my ( $self, %args ) = @_;
1322 ( exists $args{destructor_class} && defined $args{destructor_class} )
1323 || confess "The 'inline_destructor' option is present, but "
1324 . "no destructor class was specified";
1326 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1327 my $class = $self->name;
1328 warn "Not inlining a destructor for $class since it defines"
1329 . " its own destructor.\n";
1333 my $destructor_class = $args{destructor_class};
1335 Class::MOP::load_class($destructor_class);
1337 return unless $destructor_class->is_needed($self);
1339 my $destructor = $destructor_class->new(
1342 package_name => $self->name,
1346 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1347 $self->add_method( 'DESTROY' => $destructor );
1348 $self->_add_inlined_method($destructor);
1360 Class::MOP::Class - Class Meta Object
1364 # assuming that class Foo
1365 # has been defined, you can
1367 # use this for introspection ...
1369 # add a method to Foo ...
1370 Foo->meta->add_method( 'bar' => sub {...} )
1372 # get a list of all the classes searched
1373 # the method dispatcher in the correct order
1374 Foo->meta->class_precedence_list()
1376 # remove a method from Foo
1377 Foo->meta->remove_method('bar');
1379 # or use this to actually create classes ...
1381 Class::MOP::Class->create(
1384 superclasses => ['Foo'],
1386 Class::MOP::Attribute->new('$bar'),
1387 Class::MOP::Attribute->new('$baz'),
1390 calculate_bar => sub {...},
1391 construct_baz => sub {...}
1398 The Class Protocol is the largest and most complex part of the
1399 Class::MOP meta-object protocol. It controls the introspection and
1400 manipulation of Perl 5 classes, and it can create them as well. The
1401 best way to understand what this module can do is to read the
1402 documentation for each of its methods.
1406 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1410 =head2 Class construction
1412 These methods all create new C<Class::MOP::Class> objects. These
1413 objects can represent existing classes or they can be used to create
1414 new classes from scratch.
1416 The metaclass object for a given class is a singleton. If you attempt
1417 to create a metaclass for the same class twice, you will just get the
1422 =item B<< Class::MOP::Class->create($package_name, %options) >>
1424 This method creates a new C<Class::MOP::Class> object with the given
1425 package name. It accepts a number of options:
1431 An optional version number for the newly created package.
1435 An optional authority for the newly created package.
1437 =item * superclasses
1439 An optional array reference of superclass names.
1443 An optional hash reference of methods for the class. The keys of the
1444 hash reference are method names and values are subroutine references.
1448 An optional array reference of L<Class::MOP::Attribute> objects.
1452 Specifies the name to install the C<meta> method for this class under.
1453 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1454 given, no meta method will be installed.
1458 If true, the metaclass that is stored in the global cache will be a
1461 Classes created in this way are destroyed once the metaclass they are
1462 attached to goes out of scope, and will be removed from Perl's internal
1465 All instances of a class with a weakened metaclass keep a special
1466 reference to the metaclass object, which prevents the metaclass from
1467 going out of scope while any instances exist.
1469 This only works if the instance is based on a hash reference, however.
1473 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1475 This method works just like C<< Class::MOP::Class->create >> but it
1476 creates an "anonymous" class. In fact, the class does have a name, but
1477 that name is a unique name generated internally by this module.
1479 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1480 parameters that C<create> accepts.
1482 Anonymous classes default to C<< weaken => 1 >>, although this can be
1485 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1487 This method will initialize a C<Class::MOP::Class> object for the
1488 named package. Unlike C<create>, this method I<will not> create a new
1491 The purpose of this method is to retrieve a C<Class::MOP::Class>
1492 object for introspecting an existing class.
1494 If an existing C<Class::MOP::Class> object exists for the named
1495 package, it will be returned, and any options provided will be
1498 If the object does not yet exist, it will be created.
1500 The valid options that can be passed to this method are
1501 C<attribute_metaclass>, C<method_metaclass>,
1502 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1503 optional, and default to the appropriate class in the C<Class::MOP>
1508 =head2 Object instance construction and cloning
1510 These methods are all related to creating and/or cloning object
1515 =item B<< $metaclass->clone_object($instance, %params) >>
1517 This method clones an existing object instance. Any parameters you
1518 provide are will override existing attribute values in the object.
1520 This is a convenience method for cloning an object instance, then
1521 blessing it into the appropriate package.
1523 You could implement a clone method in your class, using this method:
1526 my ($self, %params) = @_;
1527 $self->meta->clone_object($self, %params);
1530 =item B<< $metaclass->rebless_instance($instance, %params) >>
1532 This method changes the class of C<$instance> to the metaclass's class.
1534 You can only rebless an instance into a subclass of its current
1535 class. If you pass any additional parameters, these will be treated
1536 like constructor parameters and used to initialize the object's
1537 attributes. Any existing attributes that are already set will be
1540 Before reblessing the instance, this method will call
1541 C<rebless_instance_away> on the instance's current metaclass. This method
1542 will be passed the instance, the new metaclass, and any parameters
1543 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1544 does nothing; it is merely a hook.
1546 =item B<< $metaclass->rebless_instance_back($instance) >>
1548 Does the same thing as C<rebless_instance>, except that you can only
1549 rebless an instance into one of its superclasses. Any attributes that
1550 do not exist in the superclass will be deinitialized.
1552 This is a much more dangerous operation than C<rebless_instance>,
1553 especially when multiple inheritance is involved, so use this carefully!
1555 =item B<< $metaclass->new_object(%params) >>
1557 This method is used to create a new object of the metaclass's
1558 class. Any parameters you provide are used to initialize the
1559 instance's attributes. A special C<__INSTANCE__> key can be passed to
1560 provide an already generated instance, rather than having Class::MOP
1561 generate it for you. This is mostly useful for using Class::MOP with
1562 foreign classes which generate instances using their own constructors.
1564 =item B<< $metaclass->instance_metaclass >>
1566 Returns the class name of the instance metaclass. See
1567 L<Class::MOP::Instance> for more information on the instance
1570 =item B<< $metaclass->get_meta_instance >>
1572 Returns an instance of the C<instance_metaclass> to be used in the
1573 construction of a new instance of the class.
1575 =item B<< $metaclass->inline_create_instance($class_var) >>
1577 =item B<< $metaclass->inline_rebless_instance($instance_var, $class_var) >>
1579 These methods takes variable names, and use them to create an inline snippet
1580 of code that will create a new instance of the class.
1584 =head2 Informational predicates
1586 These are a few predicate methods for asking information about the
1591 =item B<< $metaclass->is_anon_class >>
1593 This returns true if the class was created by calling C<<
1594 Class::MOP::Class->create_anon_class >>.
1596 =item B<< $metaclass->is_mutable >>
1598 This returns true if the class is still mutable.
1600 =item B<< $metaclass->is_immutable >>
1602 This returns true if the class has been made immutable.
1604 =item B<< $metaclass->is_pristine >>
1606 A class is I<not> pristine if it has non-inherited attributes or if it
1607 has any generated methods.
1611 =head2 Inheritance Relationships
1615 =item B<< $metaclass->superclasses(@superclasses) >>
1617 This is a read-write accessor which represents the superclass
1618 relationships of the metaclass's class.
1620 This is basically sugar around getting and setting C<@ISA>.
1622 =item B<< $metaclass->class_precedence_list >>
1624 This returns a list of all of the class's ancestor classes. The
1625 classes are returned in method dispatch order.
1627 =item B<< $metaclass->linearized_isa >>
1629 This returns a list based on C<class_precedence_list> but with all
1632 =item B<< $metaclass->subclasses >>
1634 This returns a list of all subclasses for this class, even indirect
1637 =item B<< $metaclass->direct_subclasses >>
1639 This returns a list of immediate subclasses for this class, which does not
1640 include indirect subclasses.
1644 =head2 Method introspection and creation
1646 These methods allow you to introspect a class's methods, as well as
1647 add, remove, or change methods.
1649 Determining what is truly a method in a Perl 5 class requires some
1650 heuristics (aka guessing).
1652 Methods defined outside the package with a fully qualified name (C<sub
1653 Package::name { ... }>) will be included. Similarly, methods named
1654 with a fully qualified name using L<Sub::Name> are also included.
1656 However, we attempt to ignore imported functions.
1658 Ultimately, we are using heuristics to determine what truly is a
1659 method in a class, and these heuristics may get the wrong answer in
1660 some edge cases. However, for most "normal" cases the heuristics work
1665 =item B<< $metaclass->get_method($method_name) >>
1667 This will return a L<Class::MOP::Method> for the specified
1668 C<$method_name>. If the class does not have the specified method, it
1671 =item B<< $metaclass->has_method($method_name) >>
1673 Returns a boolean indicating whether or not the class defines the
1674 named method. It does not include methods inherited from parent
1677 =item B<< $metaclass->get_method_list >>
1679 This will return a list of method I<names> for all methods defined in
1682 =item B<< $metaclass->add_method($method_name, $method) >>
1684 This method takes a method name and a subroutine reference, and adds
1685 the method to the class.
1687 The subroutine reference can be a L<Class::MOP::Method>, and you are
1688 strongly encouraged to pass a meta method object instead of a code
1689 reference. If you do so, that object gets stored as part of the
1690 class's method map directly. If not, the meta information will have to
1691 be recreated later, and may be incorrect.
1693 If you provide a method object, this method will clone that object if
1694 the object's package name does not match the class name. This lets us
1695 track the original source of any methods added from other classes
1696 (notably Moose roles).
1698 =item B<< $metaclass->remove_method($method_name) >>
1700 Remove the named method from the class. This method returns the
1701 L<Class::MOP::Method> object for the method.
1703 =item B<< $metaclass->method_metaclass >>
1705 Returns the class name of the method metaclass, see
1706 L<Class::MOP::Method> for more information on the method metaclass.
1708 =item B<< $metaclass->wrapped_method_metaclass >>
1710 Returns the class name of the wrapped method metaclass, see
1711 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1714 =item B<< $metaclass->get_all_methods >>
1716 This will traverse the inheritance hierarchy and return a list of all
1717 the L<Class::MOP::Method> objects for this class and its parents.
1719 =item B<< $metaclass->find_method_by_name($method_name) >>
1721 This will return a L<Class::MOP::Method> for the specified
1722 C<$method_name>. If the class does not have the specified method, it
1725 Unlike C<get_method>, this method I<will> look for the named method in
1728 =item B<< $metaclass->get_all_method_names >>
1730 This will return a list of method I<names> for all of this class's
1731 methods, including inherited methods.
1733 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1735 This method looks for the named method in the class and all of its
1736 parents. It returns every matching method it finds in the inheritance
1737 tree, so it returns a list of methods.
1739 Each method is returned as a hash reference with three keys. The keys
1740 are C<name>, C<class>, and C<code>. The C<code> key has a
1741 L<Class::MOP::Method> object as its value.
1743 The list of methods is distinct.
1745 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1747 This method returns the first method in any superclass matching the
1748 given name. It is effectively the method that C<SUPER::$method_name>
1753 =head2 Attribute introspection and creation
1755 Because Perl 5 does not have a core concept of attributes in classes,
1756 we can only return information about attributes which have been added
1757 via this class's methods. We cannot discover information about
1758 attributes which are defined in terms of "regular" Perl 5 methods.
1762 =item B<< $metaclass->get_attribute($attribute_name) >>
1764 This will return a L<Class::MOP::Attribute> for the specified
1765 C<$attribute_name>. If the class does not have the specified
1766 attribute, it returns C<undef>.
1768 NOTE that get_attribute does not search superclasses, for that you
1769 need to use C<find_attribute_by_name>.
1771 =item B<< $metaclass->has_attribute($attribute_name) >>
1773 Returns a boolean indicating whether or not the class defines the
1774 named attribute. It does not include attributes inherited from parent
1777 =item B<< $metaclass->get_attribute_list >>
1779 This will return a list of attributes I<names> for all attributes
1780 defined in this class. Note that this operates on the current class
1781 only, it does not traverse the inheritance hierarchy.
1783 =item B<< $metaclass->get_all_attributes >>
1785 This will traverse the inheritance hierarchy and return a list of all
1786 the L<Class::MOP::Attribute> objects for this class and its parents.
1788 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1790 This will return a L<Class::MOP::Attribute> for the specified
1791 C<$attribute_name>. If the class does not have the specified
1792 attribute, it returns C<undef>.
1794 Unlike C<get_attribute>, this attribute I<will> look for the named
1795 attribute in superclasses.
1797 =item B<< $metaclass->add_attribute(...) >>
1799 This method accepts either an existing L<Class::MOP::Attribute>
1800 object or parameters suitable for passing to that class's C<new>
1803 The attribute provided will be added to the class.
1805 Any accessor methods defined by the attribute will be added to the
1806 class when the attribute is added.
1808 If an attribute of the same name already exists, the old attribute
1809 will be removed first.
1811 =item B<< $metaclass->remove_attribute($attribute_name) >>
1813 This will remove the named attribute from the class, and
1814 L<Class::MOP::Attribute> object.
1816 Removing an attribute also removes any accessor methods defined by the
1819 However, note that removing an attribute will only affect I<future>
1820 object instances created for this class, not existing instances.
1822 =item B<< $metaclass->attribute_metaclass >>
1824 Returns the class name of the attribute metaclass for this class. By
1825 default, this is L<Class::MOP::Attribute>.
1829 =head2 Class Immutability
1831 Making a class immutable "freezes" the class definition. You can no
1832 longer call methods which alter the class, such as adding or removing
1833 methods or attributes.
1835 Making a class immutable lets us optimize the class by inlining some
1836 methods, and also allows us to optimize some methods on the metaclass
1839 After immutabilization, the metaclass object will cache most informational
1840 methods that returns information about methods or attributes. Methods which
1841 would alter the class, such as C<add_attribute> and C<add_method>, will
1842 throw an error on an immutable metaclass object.
1844 The immutabilization system in L<Moose> takes much greater advantage
1845 of the inlining features than Class::MOP itself does.
1849 =item B<< $metaclass->make_immutable(%options) >>
1851 This method will create an immutable transformer and use it to make
1852 the class and its metaclass object immutable.
1854 This method accepts the following options:
1858 =item * inline_accessors
1860 =item * inline_constructor
1862 =item * inline_destructor
1864 These are all booleans indicating whether the specified method(s)
1867 By default, accessors and the constructor are inlined, but not the
1870 =item * immutable_trait
1872 The name of a class which will be used as a parent class for the
1873 metaclass object being made immutable. This "trait" implements the
1874 post-immutability functionality of the metaclass (but not the
1875 transformation itself).
1877 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1879 =item * constructor_name
1881 This is the constructor method name. This defaults to "new".
1883 =item * constructor_class
1885 The name of the method metaclass for constructors. It will be used to
1886 generate the inlined constructor. This defaults to
1887 "Class::MOP::Method::Constructor".
1889 =item * replace_constructor
1891 This is a boolean indicating whether an existing constructor should be
1892 replaced when inlining a constructor. This defaults to false.
1894 =item * destructor_class
1896 The name of the method metaclass for destructors. It will be used to
1897 generate the inlined destructor. This defaults to
1898 "Class::MOP::Method::Denstructor".
1900 =item * replace_destructor
1902 This is a boolean indicating whether an existing destructor should be
1903 replaced when inlining a destructor. This defaults to false.
1907 =item B<< $metaclass->immutable_options >>
1909 Returns a hash of the options used when making the class immutable, including
1910 both defaults and anything supplied by the user in the call to C<<
1911 $metaclass->make_immutable >>. This is useful if you need to temporarily make
1912 a class mutable and then restore immutability as it was before.
1914 =item B<< $metaclass->make_mutable >>
1916 Calling this method reverse the immutabilization transformation.
1920 =head2 Method Modifiers
1922 Method modifiers are hooks which allow a method to be wrapped with
1923 I<before>, I<after> and I<around> method modifiers. Every time a
1924 method is called, its modifiers are also called.
1926 A class can modify its own methods, as well as methods defined in
1929 =head3 How method modifiers work?
1931 Method modifiers work by wrapping the original method and then
1932 replacing it in the class's symbol table. The wrappers will handle
1933 calling all the modifiers in the appropriate order and preserving the
1934 calling context for the original method.
1936 The return values of C<before> and C<after> modifiers are
1937 ignored. This is because their purpose is B<not> to filter the input
1938 and output of the primary method (this is done with an I<around>
1941 This may seem like an odd restriction to some, but doing this allows
1942 for simple code to be added at the beginning or end of a method call
1943 without altering the function of the wrapped method or placing any
1944 extra responsibility on the code of the modifier.
1946 Of course if you have more complex needs, you can use the C<around>
1947 modifier which allows you to change both the parameters passed to the
1948 wrapped method, as well as its return value.
1950 Before and around modifiers are called in last-defined-first-called
1951 order, while after modifiers are called in first-defined-first-called
1952 order. So the call tree might looks something like this:
1964 =head3 What is the performance impact?
1966 Of course there is a performance cost associated with method
1967 modifiers, but we have made every effort to make that cost directly
1968 proportional to the number of modifier features you use.
1970 The wrapping method does its best to B<only> do as much work as it
1971 absolutely needs to. In order to do this we have moved some of the
1972 performance costs to set-up time, where they are easier to amortize.
1974 All this said, our benchmarks have indicated the following:
1976 simple wrapper with no modifiers 100% slower
1977 simple wrapper with simple before modifier 400% slower
1978 simple wrapper with simple after modifier 450% slower
1979 simple wrapper with simple around modifier 500-550% slower
1980 simple wrapper with all 3 modifiers 1100% slower
1982 These numbers may seem daunting, but you must remember, every feature
1983 comes with some cost. To put things in perspective, just doing a
1984 simple C<AUTOLOAD> which does nothing but extract the name of the
1985 method called and return it costs about 400% over a normal method
1990 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1992 This wraps the specified method with the supplied subroutine
1993 reference. The modifier will be called as a method itself, and will
1994 receive the same arguments as are passed to the method.
1996 When the modifier exits, the wrapped method will be called.
1998 The return value of the modifier will be ignored.
2000 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2002 This wraps the specified method with the supplied subroutine
2003 reference. The modifier will be called as a method itself, and will
2004 receive the same arguments as are passed to the method.
2006 When the wrapped methods exits, the modifier will be called.
2008 The return value of the modifier will be ignored.
2010 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2012 This wraps the specified method with the supplied subroutine
2015 The first argument passed to the modifier will be a subroutine
2016 reference to the wrapped method. The second argument is the object,
2017 and after that come any arguments passed when the method is called.
2019 The around modifier can choose to call the original method, as well as
2020 what arguments to pass if it does so.
2022 The return value of the modifier is what will be seen by the caller.
2026 =head2 Introspection
2030 =item B<< Class::MOP::Class->meta >>
2032 This will return a L<Class::MOP::Class> instance for this class.
2034 It should also be noted that L<Class::MOP> will actually bootstrap
2035 this module by installing a number of attribute meta-objects into its
2042 Stevan Little E<lt>stevan@iinteractive.comE<gt>
2044 =head1 COPYRIGHT AND LICENSE
2046 Copyright 2006-2010 by Infinity Interactive, Inc.
2048 L<http://www.iinteractive.com>
2050 This library is free software; you can redistribute it and/or modify
2051 it under the same terms as Perl itself.