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 = '1.09';
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 $old_metaclass->_remove_generated_metaobjects
57 if $old_metaclass && $old_metaclass->isa('Class::MOP::Class');
58 my $new_metaclass = $class->SUPER::reinitialize(@args);
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 $meta->is_anon_class;
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 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
181 sub update_package_cache_flag {
184 # we can manually update the cache number
185 # since we are actually adding the method
186 # to our cache as well. This avoids us
187 # having to regenerate the method_map.
189 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
192 ## Metaclass compatibility
194 my %base_metaclass = (
195 attribute_metaclass => 'Class::MOP::Attribute',
196 method_metaclass => 'Class::MOP::Method',
197 wrapped_method_metaclass => 'Class::MOP::Method::Wrapped',
198 instance_metaclass => 'Class::MOP::Instance',
199 constructor_class => 'Class::MOP::Method::Constructor',
200 destructor_class => 'Class::MOP::Method::Destructor',
203 sub _base_metaclasses { %base_metaclass }
206 sub _check_metaclass_compatibility {
209 my @superclasses = $self->superclasses
212 $self->_fix_metaclass_incompatibility(@superclasses);
214 my %base_metaclass = $self->_base_metaclasses;
216 # this is always okay ...
218 if ref($self) eq 'Class::MOP::Class'
220 my $meta = $self->$_;
221 !defined($meta) || $meta eq $base_metaclass{$_};
223 keys %base_metaclass;
225 for my $superclass (@superclasses) {
226 $self->_check_class_metaclass_compatibility($superclass);
229 for my $metaclass_type ( keys %base_metaclass ) {
230 next unless defined $self->$metaclass_type;
231 for my $superclass (@superclasses) {
232 $self->_check_single_metaclass_compatibility( $metaclass_type,
238 sub _check_class_metaclass_compatibility {
240 my ( $superclass_name ) = @_;
242 if (!$self->_class_metaclass_is_compatible($superclass_name)) {
243 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
245 my $super_meta_type = $super_meta->_real_ref_name;
247 confess "The metaclass of " . $self->name . " ("
248 . (ref($self)) . ")" . " is not compatible with "
249 . "the metaclass of its superclass, "
250 . $superclass_name . " (" . ($super_meta_type) . ")";
254 sub _class_metaclass_is_compatible {
256 my ( $superclass_name ) = @_;
258 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
261 my $super_meta_name = $super_meta->_real_ref_name;
263 return $self->_is_compatible_with($super_meta_name);
266 sub _check_single_metaclass_compatibility {
268 my ( $metaclass_type, $superclass_name ) = @_;
270 if (!$self->_single_metaclass_is_compatible($metaclass_type, $superclass_name)) {
271 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
272 my $metaclass_type_name = $metaclass_type;
273 $metaclass_type_name =~ s/_(?:meta)?class$//;
274 $metaclass_type_name =~ s/_/ /g;
275 confess "The $metaclass_type_name metaclass for "
276 . $self->name . " (" . ($self->$metaclass_type)
277 . ")" . " is not compatible with the "
278 . "$metaclass_type_name metaclass of its "
279 . "superclass, $superclass_name ("
280 . ($super_meta->$metaclass_type) . ")";
284 sub _single_metaclass_is_compatible {
286 my ( $metaclass_type, $superclass_name ) = @_;
288 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
291 # for instance, Moose::Meta::Class has a error_class attribute, but
292 # Class::MOP::Class doesn't - this shouldn't be an error
293 return 1 unless $super_meta->can($metaclass_type);
294 # for instance, Moose::Meta::Class has a destructor_class, but
295 # Class::MOP::Class doesn't - this shouldn't be an error
296 return 1 unless defined $super_meta->$metaclass_type;
297 # if metaclass is defined in superclass but not here, it's not compatible
298 # this is a really odd case
299 return 0 unless defined $self->$metaclass_type;
301 return $self->$metaclass_type->_is_compatible_with($super_meta->$metaclass_type);
304 sub _fix_metaclass_incompatibility {
306 my @supers = map { Class::MOP::Class->initialize($_) } @_;
309 for my $super (@supers) {
311 if $self->_can_fix_metaclass_incompatibility($super);
313 return unless $necessary;
315 for my $super (@supers) {
316 if (!$self->_class_metaclass_is_compatible($super->name)) {
317 $self->_fix_class_metaclass_incompatibility($super);
321 my %base_metaclass = $self->_base_metaclasses;
322 for my $metaclass_type (keys %base_metaclass) {
323 for my $super (@supers) {
324 if (!$self->_single_metaclass_is_compatible($metaclass_type, $super->name)) {
325 $self->_fix_single_metaclass_incompatibility(
326 $metaclass_type, $super
333 sub _can_fix_metaclass_incompatibility {
335 my ($super_meta) = @_;
337 return 1 if $self->_class_metaclass_can_be_made_compatible($super_meta);
339 my %base_metaclass = $self->_base_metaclasses;
340 for my $metaclass_type (keys %base_metaclass) {
341 return 1 if $self->_single_metaclass_can_be_made_compatible($super_meta, $metaclass_type);
347 sub _class_metaclass_can_be_made_compatible {
349 my ($super_meta) = @_;
351 return $self->_can_be_made_compatible_with($super_meta->_real_ref_name);
354 sub _single_metaclass_can_be_made_compatible {
356 my ($super_meta, $metaclass_type) = @_;
358 my $specific_meta = $self->$metaclass_type;
360 return unless $super_meta->can($metaclass_type);
361 my $super_specific_meta = $super_meta->$metaclass_type;
363 # for instance, Moose::Meta::Class has a destructor_class, but
364 # Class::MOP::Class doesn't - this shouldn't be an error
365 return unless defined $super_specific_meta;
367 # if metaclass is defined in superclass but not here, it's fixable
368 # this is a really odd case
369 return 1 unless defined $specific_meta;
371 return 1 if $specific_meta->_can_be_made_compatible_with($super_specific_meta);
374 sub _fix_class_metaclass_incompatibility {
376 my ( $super_meta ) = @_;
378 if ($self->_class_metaclass_can_be_made_compatible($super_meta)) {
380 || confess "Can't fix metaclass incompatibility for "
382 . " because it is not pristine.";
384 my $super_meta_name = $super_meta->_real_ref_name;
386 $self->_make_compatible_with($super_meta_name);
390 sub _fix_single_metaclass_incompatibility {
392 my ( $metaclass_type, $super_meta ) = @_;
394 if ($self->_single_metaclass_can_be_made_compatible($super_meta, $metaclass_type)) {
396 || confess "Can't fix metaclass incompatibility for "
398 . " because it is not pristine.";
400 my $new_metaclass = $self->$metaclass_type
401 ? $self->$metaclass_type->_get_compatible_metaclass($super_meta->$metaclass_type)
402 : $super_meta->$metaclass_type;
403 $self->{$metaclass_type} = $new_metaclass;
407 sub _restore_metaobjects_from {
411 $self->_restore_metamethods_from($old_meta);
412 $self->_restore_metaattributes_from($old_meta);
415 sub _remove_generated_metaobjects {
418 for my $attr (map { $self->get_attribute($_) } $self->get_attribute_list) {
419 $attr->remove_accessors;
427 # this should be sufficient, if you have a
428 # use case where it is not, write a test and
430 my $ANON_CLASS_SERIAL = 0;
433 # we need a sufficiently annoying prefix
434 # this should suffice for now, this is
435 # used in a couple of places below, so
436 # need to put it up here for now.
437 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
441 no warnings 'uninitialized';
442 $self->name =~ /^$ANON_CLASS_PREFIX/o;
445 sub create_anon_class {
446 my ($class, %options) = @_;
447 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
448 return $class->create($package_name, %options);
452 # this will only get called for
453 # anon-classes, all other calls
454 # are assumed to occur during
455 # global destruction and so don't
456 # really need to be handled explicitly
460 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
462 no warnings 'uninitialized';
463 my $name = $self->name;
464 return unless $name =~ /^$ANON_CLASS_PREFIX/o;
466 # Moose does a weird thing where it replaces the metaclass for
467 # class when fixing metaclass incompatibility. In that case,
468 # we don't want to clean out the namespace now. We can detect
469 # that because Moose will explicitly update the singleton
470 # cache in Class::MOP.
471 my $current_meta = Class::MOP::get_metaclass_by_name($name);
472 return if $current_meta ne $self;
474 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/o);
476 @{$name . '::ISA'} = ();
477 %{$name . '::'} = ();
478 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
480 Class::MOP::remove_metaclass_by_name($name);
485 # creating classes with MOP ...
488 my ( $class, @args ) = @_;
490 unshift @args, 'package' if @args % 2 == 1;
492 my (%options) = @args;
493 my $package_name = $options{package};
495 (ref $options{superclasses} eq 'ARRAY')
496 || confess "You must pass an ARRAY ref of superclasses"
497 if exists $options{superclasses};
499 (ref $options{attributes} eq 'ARRAY')
500 || confess "You must pass an ARRAY ref of attributes"
501 if exists $options{attributes};
503 (ref $options{methods} eq 'HASH')
504 || confess "You must pass a HASH ref of methods"
505 if exists $options{methods};
507 $options{meta_name} = 'meta'
508 unless exists $options{meta_name};
510 my (%initialize_options) = @args;
511 delete @initialize_options{qw(
520 my $meta = $class->initialize( $package_name => %initialize_options );
522 $meta->_instantiate_module( $options{version}, $options{authority} );
524 $meta->_add_meta_method($options{meta_name})
525 if defined $options{meta_name};
527 $meta->superclasses(@{$options{superclasses}})
528 if exists $options{superclasses};
530 # process attributes first, so that they can
531 # install accessors, but locally defined methods
532 # can then overwrite them. It is maybe a little odd, but
533 # I think this should be the order of things.
534 if (exists $options{attributes}) {
535 foreach my $attr (@{$options{attributes}}) {
536 $meta->add_attribute($attr);
539 if (exists $options{methods}) {
540 foreach my $method_name (keys %{$options{methods}}) {
541 $meta->add_method($method_name, $options{methods}->{$method_name});
550 # all these attribute readers will be bootstrapped
551 # away in the Class::MOP bootstrap section
553 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
554 sub immutable_trait { $_[0]->{'immutable_trait'} }
555 sub constructor_class { $_[0]->{'constructor_class'} }
556 sub constructor_name { $_[0]->{'constructor_name'} }
557 sub destructor_class { $_[0]->{'destructor_class'} }
559 # Instance Construction & Cloning
565 # we need to protect the integrity of the
566 # Class::MOP::Class singletons here, so we
567 # delegate this to &construct_class_instance
568 # which will deal with the singletons
569 return $class->_construct_class_instance(@_)
570 if $class->name->isa('Class::MOP::Class');
571 return $class->_construct_instance(@_);
574 sub _construct_instance {
576 my $params = @_ == 1 ? $_[0] : {@_};
577 my $meta_instance = $class->get_meta_instance();
579 # the code below is almost certainly incorrect
580 # but this is foreign inheritance, so we might
581 # have to kludge it in the end.
583 if (my $instance_class = blessed($params->{__INSTANCE__})) {
584 ($instance_class eq $class->name)
585 || confess "Objects passed as the __INSTANCE__ parameter must "
586 . "already be blessed into the correct class, but "
587 . "$params->{__INSTANCE__} is not a " . $class->name;
588 $instance = $params->{__INSTANCE__};
590 elsif (exists $params->{__INSTANCE__}) {
591 confess "The __INSTANCE__ parameter must be a blessed reference, not "
592 . $params->{__INSTANCE__};
595 $instance = $meta_instance->create_instance();
597 foreach my $attr ($class->get_all_attributes()) {
598 $attr->initialize_instance_slot($meta_instance, $instance, $params);
601 # this will only work for a HASH instance type
602 if ($class->is_anon_class) {
603 (reftype($instance) eq 'HASH')
604 || confess "Currently only HASH based instances are supported with instance of anon-classes";
606 # At some point we should make this official
607 # as a reserved slot name, but right now I am
608 # going to keep it here.
609 # my $RESERVED_MOP_SLOT = '__MOP__';
610 $instance->{'__MOP__'} = $class;
616 sub get_meta_instance {
618 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
621 sub _create_meta_instance {
624 my $instance = $self->instance_metaclass->new(
625 associated_metaclass => $self,
626 attributes => [ $self->get_all_attributes() ],
629 $self->add_meta_instance_dependencies()
630 if $instance->is_dependent_on_superclasses();
635 sub inline_create_instance {
638 return $self->get_meta_instance->inline_create_instance(@_);
641 sub inline_rebless_instance {
644 return $self->get_meta_instance->inline_rebless_instance_structure(@_);
649 my $instance = shift;
650 (blessed($instance) && $instance->isa($class->name))
651 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
654 # we need to protect the integrity of the
655 # Class::MOP::Class singletons here, they
656 # should not be cloned.
657 return $instance if $instance->isa('Class::MOP::Class');
658 $class->_clone_instance($instance, @_);
661 sub _clone_instance {
662 my ($class, $instance, %params) = @_;
664 || confess "You can only clone instances, ($instance) is not a blessed instance";
665 my $meta_instance = $class->get_meta_instance();
666 my $clone = $meta_instance->clone_instance($instance);
667 foreach my $attr ($class->get_all_attributes()) {
668 if ( defined( my $init_arg = $attr->init_arg ) ) {
669 if (exists $params{$init_arg}) {
670 $attr->set_value($clone, $params{$init_arg});
677 sub _force_rebless_instance {
678 my ($self, $instance, %params) = @_;
679 my $old_metaclass = Class::MOP::class_of($instance);
681 $old_metaclass->rebless_instance_away($instance, $self, %params)
684 if ($old_metaclass->is_anon_class) {
685 delete $instance->{__MOP__};
688 my $meta_instance = $self->get_meta_instance;
691 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
692 $meta_instance->rebless_instance_structure($_[1], $self);
694 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
697 # this will only work for a HASH instance type
698 if ($self->is_anon_class) {
699 (reftype($instance) eq 'HASH')
700 || confess "Currently only HASH based instances are supported with instance of anon-classes";
702 # At some point we should make this official
703 # as a reserved slot name, but right now I am
704 # going to keep it here.
705 # my $RESERVED_MOP_SLOT = '__MOP__';
706 $instance->{'__MOP__'} = $self;
710 sub rebless_instance {
711 my ($self, $instance, %params) = @_;
712 my $old_metaclass = Class::MOP::class_of($instance);
714 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
715 $self->name->isa($old_class)
716 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
718 $self->_force_rebless_instance($_[1], %params);
723 sub rebless_instance_back {
724 my ( $self, $instance ) = @_;
725 my $old_metaclass = Class::MOP::class_of($instance);
728 = $old_metaclass ? $old_metaclass->name : blessed($instance);
729 $old_class->isa( $self->name )
731 "You may rebless only into a superclass of ($old_class), of which ("
735 $self->_force_rebless_instance($_[1]);
740 sub rebless_instance_away {
741 # this intentionally does nothing, it is just a hook
744 sub _fixup_attributes_after_rebless {
746 my ($instance, $rebless_from, %params) = @_;
747 my $meta_instance = $self->get_meta_instance;
749 for my $attr ( $rebless_from->get_all_attributes ) {
750 next if $self->find_attribute_by_name( $attr->name );
751 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
754 foreach my $attr ( $self->get_all_attributes ) {
755 if ( $attr->has_value($instance) ) {
756 if ( defined( my $init_arg = $attr->init_arg ) ) {
757 $params{$init_arg} = $attr->get_value($instance)
758 unless exists $params{$init_arg};
761 $attr->set_value($instance, $attr->get_value($instance));
766 foreach my $attr ($self->get_all_attributes) {
767 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
771 sub _attach_attribute {
772 my ($self, $attribute) = @_;
773 $attribute->attach_to_class($self);
776 sub _post_add_attribute {
777 my ( $self, $attribute ) = @_;
779 $self->invalidate_meta_instances;
781 # invalidate package flag here
784 $attribute->install_accessors;
787 $self->remove_attribute( $attribute->name );
792 sub remove_attribute {
795 my $removed_attribute = $self->SUPER::remove_attribute(@_)
798 $self->invalidate_meta_instances;
800 $removed_attribute->remove_accessors;
801 $removed_attribute->detach_from_class;
803 return$removed_attribute;
806 sub find_attribute_by_name {
807 my ( $self, $attr_name ) = @_;
809 foreach my $class ( $self->linearized_isa ) {
810 # fetch the meta-class ...
811 my $meta = Class::MOP::Class->initialize($class);
812 return $meta->get_attribute($attr_name)
813 if $meta->has_attribute($attr_name);
819 sub get_all_attributes {
821 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
822 reverse $self->linearized_isa;
823 return values %attrs;
831 my $isa = $self->get_or_add_package_symbol(
832 { sigil => '@', type => 'ARRAY', name => 'ISA' } );
839 # on 5.8 and below, we need to call
840 # a method to get Perl to detect
841 # a cycle in the class hierarchy
842 my $class = $self->name;
846 # we need to check the metaclass
847 # compatibility here so that we can
848 # be sure that the superclass is
849 # not potentially creating an issues
850 # we don't know about
852 $self->_check_metaclass_compatibility();
853 $self->_superclasses_updated();
859 sub _superclasses_updated {
861 $self->update_meta_instance_dependencies();
866 my $super_class = $self->name;
868 return @{ $super_class->mro::get_isarev() };
871 sub direct_subclasses {
873 my $super_class = $self->name;
878 } Class::MOP::Class->initialize($_)->superclasses
883 return @{ mro::get_linear_isa( (shift)->name ) };
886 sub class_precedence_list {
888 my $name = $self->name;
890 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
892 # We need to check for circular inheritance here
893 # if we are are not on 5.10, cause 5.8 detects it
894 # late. This will do nothing if all is well, and
895 # blow up otherwise. Yes, it's an ugly hack, better
896 # suggestions are welcome.
898 ($name || return)->isa('This is a test for circular inheritance')
901 # if our mro is c3, we can
902 # just grab the linear_isa
903 if (mro::get_mro($name) eq 'c3') {
904 return @{ mro::get_linear_isa($name) }
908 # we can't grab the linear_isa for dfs
909 # since it has all the duplicates
914 Class::MOP::Class->initialize($_)->class_precedence_list()
915 } $self->superclasses()
923 my $fetch_and_prepare_method = sub {
924 my ($self, $method_name) = @_;
925 my $wrapped_metaclass = $self->wrapped_method_metaclass;
927 my $method = $self->get_method($method_name);
928 # if we dont have local ...
930 # try to find the next method
931 $method = $self->find_next_method_by_name($method_name);
932 # die if it does not exist
934 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
935 # and now make sure to wrap it
936 # even if it is already wrapped
937 # because we need a new sub ref
938 $method = $wrapped_metaclass->wrap($method,
939 package_name => $self->name,
940 name => $method_name,
944 # now make sure we wrap it properly
945 $method = $wrapped_metaclass->wrap($method,
946 package_name => $self->name,
947 name => $method_name,
948 ) unless $method->isa($wrapped_metaclass);
950 $self->add_method($method_name => $method);
954 sub add_before_method_modifier {
955 my ($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_before_modifier(
960 subname(':before' => $method_modifier)
964 sub add_after_method_modifier {
965 my ($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_after_modifier(
970 subname(':after' => $method_modifier)
974 sub add_around_method_modifier {
975 my ($self, $method_name, $method_modifier) = @_;
976 (defined $method_name && length $method_name)
977 || confess "You must pass in a method name";
978 my $method = $fetch_and_prepare_method->($self, $method_name);
979 $method->add_around_modifier(
980 subname(':around' => $method_modifier)
985 # the methods above used to be named like this:
986 # ${pkg}::${method}:(before|after|around)
987 # but this proved problematic when using one modifier
988 # to wrap multiple methods (something which is likely
989 # to happen pretty regularly IMO). So instead of naming
990 # it like this, I have chosen to just name them purely
991 # with their modifier names, like so:
992 # :(before|after|around)
993 # The fact is that in a stack trace, it will be fairly
994 # evident from the context what method they are attached
995 # to, and so don't need the fully qualified name.
998 sub find_method_by_name {
999 my ($self, $method_name) = @_;
1000 (defined $method_name && length $method_name)
1001 || confess "You must define a method name to find";
1002 foreach my $class ($self->linearized_isa) {
1003 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1004 return $method if defined $method;
1009 sub get_all_methods {
1013 for my $class ( reverse $self->linearized_isa ) {
1014 my $meta = Class::MOP::Class->initialize($class);
1016 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1019 return values %methods;
1022 sub get_all_method_names {
1025 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
1028 sub find_all_methods_by_name {
1029 my ($self, $method_name) = @_;
1030 (defined $method_name && length $method_name)
1031 || confess "You must define a method name to find";
1033 foreach my $class ($self->linearized_isa) {
1034 # fetch the meta-class ...
1035 my $meta = Class::MOP::Class->initialize($class);
1037 name => $method_name,
1039 code => $meta->get_method($method_name)
1040 } if $meta->has_method($method_name);
1045 sub find_next_method_by_name {
1046 my ($self, $method_name) = @_;
1047 (defined $method_name && length $method_name)
1048 || confess "You must define a method name to find";
1049 my @cpl = $self->linearized_isa;
1050 shift @cpl; # discard ourselves
1051 foreach my $class (@cpl) {
1052 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1053 return $method if defined $method;
1058 sub update_meta_instance_dependencies {
1061 if ( $self->{meta_instance_dependencies} ) {
1062 return $self->add_meta_instance_dependencies;
1066 sub add_meta_instance_dependencies {
1069 $self->remove_meta_instance_dependencies;
1071 my @attrs = $self->get_all_attributes();
1074 my @classes = grep { not $seen{ $_->name }++ }
1075 map { $_->associated_class } @attrs;
1077 foreach my $class (@classes) {
1078 $class->add_dependent_meta_instance($self);
1081 $self->{meta_instance_dependencies} = \@classes;
1084 sub remove_meta_instance_dependencies {
1087 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1088 foreach my $class (@$classes) {
1089 $class->remove_dependent_meta_instance($self);
1099 sub add_dependent_meta_instance {
1100 my ( $self, $metaclass ) = @_;
1101 push @{ $self->{dependent_meta_instances} }, $metaclass;
1104 sub remove_dependent_meta_instance {
1105 my ( $self, $metaclass ) = @_;
1106 my $name = $metaclass->name;
1107 @$_ = grep { $_->name ne $name } @$_
1108 for $self->{dependent_meta_instances};
1111 sub invalidate_meta_instances {
1113 $_->invalidate_meta_instance()
1114 for $self, @{ $self->{dependent_meta_instances} };
1117 sub invalidate_meta_instance {
1119 undef $self->{_meta_instance};
1122 # check if we can reinitialize
1126 # if any local attr is defined
1127 return if $self->get_attribute_list;
1129 # or any non-declared methods
1130 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1131 return if $method->isa("Class::MOP::Method::Generated");
1132 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1140 sub is_mutable { 1 }
1141 sub is_immutable { 0 }
1143 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1145 sub _immutable_options {
1146 my ( $self, @args ) = @_;
1149 inline_accessors => 1,
1150 inline_constructor => 1,
1151 inline_destructor => 0,
1153 immutable_trait => $self->immutable_trait,
1154 constructor_name => $self->constructor_name,
1155 constructor_class => $self->constructor_class,
1156 destructor_class => $self->destructor_class,
1161 sub make_immutable {
1162 my ( $self, @args ) = @_;
1164 if ( $self->is_mutable ) {
1165 $self->_initialize_immutable( $self->_immutable_options(@args) );
1166 $self->_rebless_as_immutable(@args);
1177 if ( $self->is_immutable ) {
1178 my @args = $self->immutable_options;
1179 $self->_rebless_as_mutable();
1180 $self->_remove_inlined_code(@args);
1181 delete $self->{__immutable};
1189 sub _rebless_as_immutable {
1190 my ( $self, @args ) = @_;
1192 $self->{__immutable}{original_class} = ref $self;
1194 bless $self => $self->_immutable_metaclass(@args);
1197 sub _immutable_metaclass {
1198 my ( $self, %args ) = @_;
1200 if ( my $class = $args{immutable_metaclass} ) {
1204 my $trait = $args{immutable_trait} = $self->immutable_trait
1205 || confess "no immutable trait specified for $self";
1207 my $meta = $self->meta;
1208 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1212 if ( $meta_attr and $trait eq $meta_attr->default ) {
1213 # if the trait is the same as the default we try and pick a
1214 # predictable name for the immutable metaclass
1215 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1218 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1219 $trait, 'ForMetaClass', ref($self);
1223 if Class::MOP::is_class_loaded($class_name);
1225 # If the metaclass is a subclass of CMOP::Class which has had
1226 # metaclass roles applied (via Moose), then we want to make sure
1227 # that we preserve that anonymous class (see Fey::ORM for an
1228 # example of where this matters).
1229 my $meta_name = $meta->_real_ref_name;
1231 my $immutable_meta = $meta_name->create(
1233 superclasses => [ ref $self ],
1236 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1238 $immutable_meta->make_immutable(
1239 inline_constructor => 0,
1240 inline_accessors => 0,
1246 sub _remove_inlined_code {
1249 $self->remove_method( $_->name ) for $self->_inlined_methods;
1251 delete $self->{__immutable}{inlined_methods};
1254 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1256 sub _add_inlined_method {
1257 my ( $self, $method ) = @_;
1259 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1262 sub _initialize_immutable {
1263 my ( $self, %args ) = @_;
1265 $self->{__immutable}{options} = \%args;
1266 $self->_install_inlined_code(%args);
1269 sub _install_inlined_code {
1270 my ( $self, %args ) = @_;
1273 $self->_inline_accessors(%args) if $args{inline_accessors};
1274 $self->_inline_constructor(%args) if $args{inline_constructor};
1275 $self->_inline_destructor(%args) if $args{inline_destructor};
1278 sub _rebless_as_mutable {
1281 bless $self, $self->_get_mutable_metaclass_name;
1286 sub _inline_accessors {
1289 foreach my $attr_name ( $self->get_attribute_list ) {
1290 $self->get_attribute($attr_name)->install_accessors(1);
1294 sub _inline_constructor {
1295 my ( $self, %args ) = @_;
1297 my $name = $args{constructor_name};
1298 # A class may not even have a constructor, and that's okay.
1299 return unless defined $name;
1301 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1302 my $class = $self->name;
1303 warn "Not inlining a constructor for $class since it defines"
1304 . " its own constructor.\n"
1305 . "If you are certain you don't need to inline your"
1306 . " constructor, specify inline_constructor => 0 in your"
1307 . " call to $class->meta->make_immutable\n";
1311 my $constructor_class = $args{constructor_class};
1313 Class::MOP::load_class($constructor_class);
1315 my $constructor = $constructor_class->new(
1319 package_name => $self->name,
1323 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1324 $self->add_method( $name => $constructor );
1325 $self->_add_inlined_method($constructor);
1329 sub _inline_destructor {
1330 my ( $self, %args ) = @_;
1332 ( exists $args{destructor_class} && defined $args{destructor_class} )
1333 || confess "The 'inline_destructor' option is present, but "
1334 . "no destructor class was specified";
1336 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1337 my $class = $self->name;
1338 warn "Not inlining a destructor for $class since it defines"
1339 . " its own destructor.\n";
1343 my $destructor_class = $args{destructor_class};
1345 Class::MOP::load_class($destructor_class);
1347 return unless $destructor_class->is_needed($self);
1349 my $destructor = $destructor_class->new(
1352 package_name => $self->name,
1356 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1357 $self->add_method( 'DESTROY' => $destructor );
1358 $self->_add_inlined_method($destructor);
1370 Class::MOP::Class - Class Meta Object
1374 # assuming that class Foo
1375 # has been defined, you can
1377 # use this for introspection ...
1379 # add a method to Foo ...
1380 Foo->meta->add_method( 'bar' => sub {...} )
1382 # get a list of all the classes searched
1383 # the method dispatcher in the correct order
1384 Foo->meta->class_precedence_list()
1386 # remove a method from Foo
1387 Foo->meta->remove_method('bar');
1389 # or use this to actually create classes ...
1391 Class::MOP::Class->create(
1394 superclasses => ['Foo'],
1396 Class::MOP::Attribute->new('$bar'),
1397 Class::MOP::Attribute->new('$baz'),
1400 calculate_bar => sub {...},
1401 construct_baz => sub {...}
1408 The Class Protocol is the largest and most complex part of the
1409 Class::MOP meta-object protocol. It controls the introspection and
1410 manipulation of Perl 5 classes, and it can create them as well. The
1411 best way to understand what this module can do is to read the
1412 documentation for each of its methods.
1416 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1420 =head2 Class construction
1422 These methods all create new C<Class::MOP::Class> objects. These
1423 objects can represent existing classes or they can be used to create
1424 new classes from scratch.
1426 The metaclass object for a given class is a singleton. If you attempt
1427 to create a metaclass for the same class twice, you will just get the
1432 =item B<< Class::MOP::Class->create($package_name, %options) >>
1434 This method creates a new C<Class::MOP::Class> object with the given
1435 package name. It accepts a number of options:
1441 An optional version number for the newly created package.
1445 An optional authority for the newly created package.
1447 =item * superclasses
1449 An optional array reference of superclass names.
1453 An optional hash reference of methods for the class. The keys of the
1454 hash reference are method names and values are subroutine references.
1458 An optional array reference of L<Class::MOP::Attribute> objects.
1462 Specifies the name to install the C<meta> method for this class under.
1463 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1464 given, no meta method will be installed.
1468 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1470 This method works just like C<< Class::MOP::Class->create >> but it
1471 creates an "anonymous" class. In fact, the class does have a name, but
1472 that name is a unique name generated internally by this module.
1474 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1475 parameters that C<create> accepts.
1477 Anonymous classes are destroyed once the metaclass they are attached
1478 to goes out of scope, and will be removed from Perl's internal symbol
1481 All instances of an anonymous class keep a special reference to the
1482 metaclass object, which prevents the metaclass from going out of scope
1483 while any instances exist.
1485 This only works if the instance is based on a hash reference, however.
1487 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1489 This method will initialize a C<Class::MOP::Class> object for the
1490 named package. Unlike C<create>, this method I<will not> create a new
1493 The purpose of this method is to retrieve a C<Class::MOP::Class>
1494 object for introspecting an existing class.
1496 If an existing C<Class::MOP::Class> object exists for the named
1497 package, it will be returned, and any options provided will be
1500 If the object does not yet exist, it will be created.
1502 The valid options that can be passed to this method are
1503 C<attribute_metaclass>, C<method_metaclass>,
1504 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1505 optional, and default to the appropriate class in the C<Class::MOP>
1510 =head2 Object instance construction and cloning
1512 These methods are all related to creating and/or cloning object
1517 =item B<< $metaclass->clone_object($instance, %params) >>
1519 This method clones an existing object instance. Any parameters you
1520 provide are will override existing attribute values in the object.
1522 This is a convenience method for cloning an object instance, then
1523 blessing it into the appropriate package.
1525 You could implement a clone method in your class, using this method:
1528 my ($self, %params) = @_;
1529 $self->meta->clone_object($self, %params);
1532 =item B<< $metaclass->rebless_instance($instance, %params) >>
1534 This method changes the class of C<$instance> to the metaclass's class.
1536 You can only rebless an instance into a subclass of its current
1537 class. If you pass any additional parameters, these will be treated
1538 like constructor parameters and used to initialize the object's
1539 attributes. Any existing attributes that are already set will be
1542 Before reblessing the instance, this method will call
1543 C<rebless_instance_away> on the instance's current metaclass. This method
1544 will be passed the instance, the new metaclass, and any parameters
1545 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1546 does nothing; it is merely a hook.
1548 =item B<< $metaclass->rebless_instance_back($instance) >>
1550 Does the same thing as C<rebless_instance>, except that you can only
1551 rebless an instance into one of its superclasses. Any attributes that
1552 do not exist in the superclass will be deinitialized.
1554 This is a much more dangerous operation than C<rebless_instance>,
1555 especially when multiple inheritance is involved, so use this carefully!
1557 =item B<< $metaclass->new_object(%params) >>
1559 This method is used to create a new object of the metaclass's
1560 class. Any parameters you provide are used to initialize the
1561 instance's attributes. A special C<__INSTANCE__> key can be passed to
1562 provide an already generated instance, rather than having Class::MOP
1563 generate it for you. This is mostly useful for using Class::MOP with
1564 foreign classes which generate instances using their own constructors.
1566 =item B<< $metaclass->instance_metaclass >>
1568 Returns the class name of the instance metaclass. See
1569 L<Class::MOP::Instance> for more information on the instance
1572 =item B<< $metaclass->get_meta_instance >>
1574 Returns an instance of the C<instance_metaclass> to be used in the
1575 construction of a new instance of the class.
1577 =item B<< $metaclass->inline_create_instance($class_var) >>
1579 =item B<< $metaclass->inline_rebless_instance($instance_var, $class_var) >>
1581 These methods takes variable names, and use them to create an inline snippet
1582 of code that will create a new instance of the class.
1586 =head2 Informational predicates
1588 These are a few predicate methods for asking information about the
1593 =item B<< $metaclass->is_anon_class >>
1595 This returns true if the class was created by calling C<<
1596 Class::MOP::Class->create_anon_class >>.
1598 =item B<< $metaclass->is_mutable >>
1600 This returns true if the class is still mutable.
1602 =item B<< $metaclass->is_immutable >>
1604 This returns true if the class has been made immutable.
1606 =item B<< $metaclass->is_pristine >>
1608 A class is I<not> pristine if it has non-inherited attributes or if it
1609 has any generated methods.
1613 =head2 Inheritance Relationships
1617 =item B<< $metaclass->superclasses(@superclasses) >>
1619 This is a read-write accessor which represents the superclass
1620 relationships of the metaclass's class.
1622 This is basically sugar around getting and setting C<@ISA>.
1624 =item B<< $metaclass->class_precedence_list >>
1626 This returns a list of all of the class's ancestor classes. The
1627 classes are returned in method dispatch order.
1629 =item B<< $metaclass->linearized_isa >>
1631 This returns a list based on C<class_precedence_list> but with all
1634 =item B<< $metaclass->subclasses >>
1636 This returns a list of all subclasses for this class, even indirect
1639 =item B<< $metaclass->direct_subclasses >>
1641 This returns a list of immediate subclasses for this class, which does not
1642 include indirect subclasses.
1646 =head2 Method introspection and creation
1648 These methods allow you to introspect a class's methods, as well as
1649 add, remove, or change methods.
1651 Determining what is truly a method in a Perl 5 class requires some
1652 heuristics (aka guessing).
1654 Methods defined outside the package with a fully qualified name (C<sub
1655 Package::name { ... }>) will be included. Similarly, methods named
1656 with a fully qualified name using L<Sub::Name> are also included.
1658 However, we attempt to ignore imported functions.
1660 Ultimately, we are using heuristics to determine what truly is a
1661 method in a class, and these heuristics may get the wrong answer in
1662 some edge cases. However, for most "normal" cases the heuristics work
1667 =item B<< $metaclass->get_method($method_name) >>
1669 This will return a L<Class::MOP::Method> for the specified
1670 C<$method_name>. If the class does not have the specified method, it
1673 =item B<< $metaclass->has_method($method_name) >>
1675 Returns a boolean indicating whether or not the class defines the
1676 named method. It does not include methods inherited from parent
1679 =item B<< $metaclass->get_method_list >>
1681 This will return a list of method I<names> for all methods defined in
1684 =item B<< $metaclass->add_method($method_name, $method) >>
1686 This method takes a method name and a subroutine reference, and adds
1687 the method to the class.
1689 The subroutine reference can be a L<Class::MOP::Method>, and you are
1690 strongly encouraged to pass a meta method object instead of a code
1691 reference. If you do so, that object gets stored as part of the
1692 class's method map directly. If not, the meta information will have to
1693 be recreated later, and may be incorrect.
1695 If you provide a method object, this method will clone that object if
1696 the object's package name does not match the class name. This lets us
1697 track the original source of any methods added from other classes
1698 (notably Moose roles).
1700 =item B<< $metaclass->remove_method($method_name) >>
1702 Remove the named method from the class. This method returns the
1703 L<Class::MOP::Method> object for the method.
1705 =item B<< $metaclass->method_metaclass >>
1707 Returns the class name of the method metaclass, see
1708 L<Class::MOP::Method> for more information on the method metaclass.
1710 =item B<< $metaclass->wrapped_method_metaclass >>
1712 Returns the class name of the wrapped method metaclass, see
1713 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1716 =item B<< $metaclass->get_all_methods >>
1718 This will traverse the inheritance hierarchy and return a list of all
1719 the L<Class::MOP::Method> objects for this class and its parents.
1721 =item B<< $metaclass->find_method_by_name($method_name) >>
1723 This will return a L<Class::MOP::Method> for the specified
1724 C<$method_name>. If the class does not have the specified method, it
1727 Unlike C<get_method>, this method I<will> look for the named method in
1730 =item B<< $metaclass->get_all_method_names >>
1732 This will return a list of method I<names> for all of this class's
1733 methods, including inherited methods.
1735 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1737 This method looks for the named method in the class and all of its
1738 parents. It returns every matching method it finds in the inheritance
1739 tree, so it returns a list of methods.
1741 Each method is returned as a hash reference with three keys. The keys
1742 are C<name>, C<class>, and C<code>. The C<code> key has a
1743 L<Class::MOP::Method> object as its value.
1745 The list of methods is distinct.
1747 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1749 This method returns the first method in any superclass matching the
1750 given name. It is effectively the method that C<SUPER::$method_name>
1755 =head2 Attribute introspection and creation
1757 Because Perl 5 does not have a core concept of attributes in classes,
1758 we can only return information about attributes which have been added
1759 via this class's methods. We cannot discover information about
1760 attributes which are defined in terms of "regular" Perl 5 methods.
1764 =item B<< $metaclass->get_attribute($attribute_name) >>
1766 This will return a L<Class::MOP::Attribute> for the specified
1767 C<$attribute_name>. If the class does not have the specified
1768 attribute, it returns C<undef>.
1770 NOTE that get_attribute does not search superclasses, for that you
1771 need to use C<find_attribute_by_name>.
1773 =item B<< $metaclass->has_attribute($attribute_name) >>
1775 Returns a boolean indicating whether or not the class defines the
1776 named attribute. It does not include attributes inherited from parent
1779 =item B<< $metaclass->get_attribute_list >>
1781 This will return a list of attributes I<names> for all attributes
1782 defined in this class. Note that this operates on the current class
1783 only, it does not traverse the inheritance hierarchy.
1785 =item B<< $metaclass->get_all_attributes >>
1787 This will traverse the inheritance hierarchy and return a list of all
1788 the L<Class::MOP::Attribute> objects for this class and its parents.
1790 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1792 This will return a L<Class::MOP::Attribute> for the specified
1793 C<$attribute_name>. If the class does not have the specified
1794 attribute, it returns C<undef>.
1796 Unlike C<get_attribute>, this attribute I<will> look for the named
1797 attribute in superclasses.
1799 =item B<< $metaclass->add_attribute(...) >>
1801 This method accepts either an existing L<Class::MOP::Attribute>
1802 object or parameters suitable for passing to that class's C<new>
1805 The attribute provided will be added to the class.
1807 Any accessor methods defined by the attribute will be added to the
1808 class when the attribute is added.
1810 If an attribute of the same name already exists, the old attribute
1811 will be removed first.
1813 =item B<< $metaclass->remove_attribute($attribute_name) >>
1815 This will remove the named attribute from the class, and
1816 L<Class::MOP::Attribute> object.
1818 Removing an attribute also removes any accessor methods defined by the
1821 However, note that removing an attribute will only affect I<future>
1822 object instances created for this class, not existing instances.
1824 =item B<< $metaclass->attribute_metaclass >>
1826 Returns the class name of the attribute metaclass for this class. By
1827 default, this is L<Class::MOP::Attribute>.
1831 =head2 Class Immutability
1833 Making a class immutable "freezes" the class definition. You can no
1834 longer call methods which alter the class, such as adding or removing
1835 methods or attributes.
1837 Making a class immutable lets us optimize the class by inlining some
1838 methods, and also allows us to optimize some methods on the metaclass
1841 After immutabilization, the metaclass object will cache most informational
1842 methods that returns information about methods or attributes. Methods which
1843 would alter the class, such as C<add_attribute> and C<add_method>, will
1844 throw an error on an immutable metaclass object.
1846 The immutabilization system in L<Moose> takes much greater advantage
1847 of the inlining features than Class::MOP itself does.
1851 =item B<< $metaclass->make_immutable(%options) >>
1853 This method will create an immutable transformer and use it to make
1854 the class and its metaclass object immutable.
1856 This method accepts the following options:
1860 =item * inline_accessors
1862 =item * inline_constructor
1864 =item * inline_destructor
1866 These are all booleans indicating whether the specified method(s)
1869 By default, accessors and the constructor are inlined, but not the
1872 =item * immutable_trait
1874 The name of a class which will be used as a parent class for the
1875 metaclass object being made immutable. This "trait" implements the
1876 post-immutability functionality of the metaclass (but not the
1877 transformation itself).
1879 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1881 =item * constructor_name
1883 This is the constructor method name. This defaults to "new".
1885 =item * constructor_class
1887 The name of the method metaclass for constructors. It will be used to
1888 generate the inlined constructor. This defaults to
1889 "Class::MOP::Method::Constructor".
1891 =item * replace_constructor
1893 This is a boolean indicating whether an existing constructor should be
1894 replaced when inlining a constructor. This defaults to false.
1896 =item * destructor_class
1898 The name of the method metaclass for destructors. It will be used to
1899 generate the inlined destructor. This defaults to
1900 "Class::MOP::Method::Denstructor".
1902 =item * replace_destructor
1904 This is a boolean indicating whether an existing destructor should be
1905 replaced when inlining a destructor. This defaults to false.
1909 =item B<< $metaclass->immutable_options >>
1911 Returns a hash of the options used when making the class immutable, including
1912 both defaults and anything supplied by the user in the call to C<<
1913 $metaclass->make_immutable >>. This is useful if you need to temporarily make
1914 a class mutable and then restore immutability as it was before.
1916 =item B<< $metaclass->make_mutable >>
1918 Calling this method reverse the immutabilization transformation.
1922 =head2 Method Modifiers
1924 Method modifiers are hooks which allow a method to be wrapped with
1925 I<before>, I<after> and I<around> method modifiers. Every time a
1926 method is called, its modifiers are also called.
1928 A class can modify its own methods, as well as methods defined in
1931 =head3 How method modifiers work?
1933 Method modifiers work by wrapping the original method and then
1934 replacing it in the class's symbol table. The wrappers will handle
1935 calling all the modifiers in the appropriate order and preserving the
1936 calling context for the original method.
1938 The return values of C<before> and C<after> modifiers are
1939 ignored. This is because their purpose is B<not> to filter the input
1940 and output of the primary method (this is done with an I<around>
1943 This may seem like an odd restriction to some, but doing this allows
1944 for simple code to be added at the beginning or end of a method call
1945 without altering the function of the wrapped method or placing any
1946 extra responsibility on the code of the modifier.
1948 Of course if you have more complex needs, you can use the C<around>
1949 modifier which allows you to change both the parameters passed to the
1950 wrapped method, as well as its return value.
1952 Before and around modifiers are called in last-defined-first-called
1953 order, while after modifiers are called in first-defined-first-called
1954 order. So the call tree might looks something like this:
1966 =head3 What is the performance impact?
1968 Of course there is a performance cost associated with method
1969 modifiers, but we have made every effort to make that cost directly
1970 proportional to the number of modifier features you use.
1972 The wrapping method does its best to B<only> do as much work as it
1973 absolutely needs to. In order to do this we have moved some of the
1974 performance costs to set-up time, where they are easier to amortize.
1976 All this said, our benchmarks have indicated the following:
1978 simple wrapper with no modifiers 100% slower
1979 simple wrapper with simple before modifier 400% slower
1980 simple wrapper with simple after modifier 450% slower
1981 simple wrapper with simple around modifier 500-550% slower
1982 simple wrapper with all 3 modifiers 1100% slower
1984 These numbers may seem daunting, but you must remember, every feature
1985 comes with some cost. To put things in perspective, just doing a
1986 simple C<AUTOLOAD> which does nothing but extract the name of the
1987 method called and return it costs about 400% over a normal method
1992 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1994 This wraps the specified method with the supplied subroutine
1995 reference. The modifier will be called as a method itself, and will
1996 receive the same arguments as are passed to the method.
1998 When the modifier exits, the wrapped method will be called.
2000 The return value of the modifier will be ignored.
2002 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2004 This wraps the specified method with the supplied subroutine
2005 reference. The modifier will be called as a method itself, and will
2006 receive the same arguments as are passed to the method.
2008 When the wrapped methods exits, the modifier will be called.
2010 The return value of the modifier will be ignored.
2012 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2014 This wraps the specified method with the supplied subroutine
2017 The first argument passed to the modifier will be a subroutine
2018 reference to the wrapped method. The second argument is the object,
2019 and after that come any arguments passed when the method is called.
2021 The around modifier can choose to call the original method, as well as
2022 what arguments to pass if it does so.
2024 The return value of the modifier is what will be seen by the caller.
2028 =head2 Introspection
2032 =item B<< Class::MOP::Class->meta >>
2034 This will return a L<Class::MOP::Class> instance for this class.
2036 It should also be noted that L<Class::MOP> will actually bootstrap
2037 this module by installing a number of attribute meta-objects into its
2044 Stevan Little E<lt>stevan@iinteractive.comE<gt>
2046 =head1 COPYRIGHT AND LICENSE
2048 Copyright 2006-2010 by Infinity Interactive, Inc.
2050 L<http://www.iinteractive.com>
2052 This library is free software; you can redistribute it and/or modify
2053 it under the same terms as Perl itself.