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 $options->{weaken};
120 # NOTE: we need to deal with the possibility of class immutability here,
121 # and then get the name of the class appropriately
122 return $self->is_immutable
123 ? $self->_get_mutable_metaclass_name()
130 return Class::MOP::Class->initialize($class)->new_object(@_)
131 if $class ne __PACKAGE__;
133 my $options = @_ == 1 ? $_[0] : {@_};
136 # inherited from Class::MOP::Package
137 'package' => $options->{package},
140 # since the following attributes will
141 # actually be loaded from the symbol
142 # table, and actually bypass the instance
143 # entirely, we can just leave these things
144 # listed here for reference, because they
145 # should not actually have a value associated
147 'namespace' => \undef,
150 # inherited from Class::MOP::Module
152 'authority' => \undef,
154 # defined in Class::MOP::Class
155 'superclasses' => \undef,
158 'attribute_metaclass' =>
159 ( $options->{'attribute_metaclass'} || 'Class::MOP::Attribute' ),
160 'method_metaclass' =>
161 ( $options->{'method_metaclass'} || 'Class::MOP::Method' ),
162 'wrapped_method_metaclass' => (
163 $options->{'wrapped_method_metaclass'}
164 || 'Class::MOP::Method::Wrapped'
166 'instance_metaclass' =>
167 ( $options->{'instance_metaclass'} || 'Class::MOP::Instance' ),
168 'immutable_trait' => (
169 $options->{'immutable_trait'}
170 || 'Class::MOP::Class::Immutable::Trait'
172 'constructor_name' => ( $options->{constructor_name} || 'new' ),
173 'constructor_class' => (
174 $options->{constructor_class} || 'Class::MOP::Method::Constructor'
176 'destructor_class' => $options->{destructor_class},
180 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 $options{weaken} = 1 unless exists $options{weaken};
448 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
449 return $class->create($package_name, %options);
453 # this will only get called for
454 # anon-classes, all other calls
455 # are assumed to occur during
456 # global destruction and so don't
457 # really need to be handled explicitly
461 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
463 no warnings 'uninitialized';
464 my $name = $self->name;
465 return unless $name =~ /^$ANON_CLASS_PREFIX/o;
467 # Moose does a weird thing where it replaces the metaclass for
468 # class when fixing metaclass incompatibility. In that case,
469 # we don't want to clean out the namespace now. We can detect
470 # that because Moose will explicitly update the singleton
471 # cache in Class::MOP.
472 my $current_meta = Class::MOP::get_metaclass_by_name($name);
473 return if $current_meta ne $self;
475 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/o);
477 @{$name . '::ISA'} = ();
478 %{$name . '::'} = ();
479 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
481 Class::MOP::remove_metaclass_by_name($name);
486 # creating classes with MOP ...
489 my ( $class, @args ) = @_;
491 unshift @args, 'package' if @args % 2 == 1;
493 my (%options) = @args;
494 my $package_name = $options{package};
496 (ref $options{superclasses} eq 'ARRAY')
497 || confess "You must pass an ARRAY ref of superclasses"
498 if exists $options{superclasses};
500 (ref $options{attributes} eq 'ARRAY')
501 || confess "You must pass an ARRAY ref of attributes"
502 if exists $options{attributes};
504 (ref $options{methods} eq 'HASH')
505 || confess "You must pass a HASH ref of methods"
506 if exists $options{methods};
508 $options{meta_name} = 'meta'
509 unless exists $options{meta_name};
511 my (%initialize_options) = @args;
512 delete @initialize_options{qw(
521 my $meta = $class->initialize( $package_name => %initialize_options );
523 $meta->_instantiate_module( $options{version}, $options{authority} );
525 $meta->_add_meta_method($options{meta_name})
526 if defined $options{meta_name};
528 $meta->superclasses(@{$options{superclasses}})
529 if exists $options{superclasses};
531 # process attributes first, so that they can
532 # install accessors, but locally defined methods
533 # can then overwrite them. It is maybe a little odd, but
534 # I think this should be the order of things.
535 if (exists $options{attributes}) {
536 foreach my $attr (@{$options{attributes}}) {
537 $meta->add_attribute($attr);
540 if (exists $options{methods}) {
541 foreach my $method_name (keys %{$options{methods}}) {
542 $meta->add_method($method_name, $options{methods}->{$method_name});
551 # all these attribute readers will be bootstrapped
552 # away in the Class::MOP bootstrap section
554 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
555 sub immutable_trait { $_[0]->{'immutable_trait'} }
556 sub constructor_class { $_[0]->{'constructor_class'} }
557 sub constructor_name { $_[0]->{'constructor_name'} }
558 sub destructor_class { $_[0]->{'destructor_class'} }
560 # Instance Construction & Cloning
566 # we need to protect the integrity of the
567 # Class::MOP::Class singletons here, so we
568 # delegate this to &construct_class_instance
569 # which will deal with the singletons
570 return $class->_construct_class_instance(@_)
571 if $class->name->isa('Class::MOP::Class');
572 return $class->_construct_instance(@_);
575 sub _construct_instance {
577 my $params = @_ == 1 ? $_[0] : {@_};
578 my $meta_instance = $class->get_meta_instance();
580 # the code below is almost certainly incorrect
581 # but this is foreign inheritance, so we might
582 # have to kludge it in the end.
584 if (my $instance_class = blessed($params->{__INSTANCE__})) {
585 ($instance_class eq $class->name)
586 || confess "Objects passed as the __INSTANCE__ parameter must "
587 . "already be blessed into the correct class, but "
588 . "$params->{__INSTANCE__} is not a " . $class->name;
589 $instance = $params->{__INSTANCE__};
591 elsif (exists $params->{__INSTANCE__}) {
592 confess "The __INSTANCE__ parameter must be a blessed reference, not "
593 . $params->{__INSTANCE__};
596 $instance = $meta_instance->create_instance();
598 foreach my $attr ($class->get_all_attributes()) {
599 $attr->initialize_instance_slot($meta_instance, $instance, $params);
602 # this will only work for a HASH instance type
603 if ($class->is_anon_class) {
604 (reftype($instance) eq 'HASH')
605 || confess "Currently only HASH based instances are supported with instance of anon-classes";
607 # At some point we should make this official
608 # as a reserved slot name, but right now I am
609 # going to keep it here.
610 # my $RESERVED_MOP_SLOT = '__MOP__';
611 $instance->{'__MOP__'} = $class;
617 sub get_meta_instance {
619 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
622 sub _create_meta_instance {
625 my $instance = $self->instance_metaclass->new(
626 associated_metaclass => $self,
627 attributes => [ $self->get_all_attributes() ],
630 $self->add_meta_instance_dependencies()
631 if $instance->is_dependent_on_superclasses();
636 sub inline_create_instance {
639 return $self->get_meta_instance->inline_create_instance(@_);
642 sub inline_rebless_instance {
645 return $self->get_meta_instance->inline_rebless_instance_structure(@_);
650 my $instance = shift;
651 (blessed($instance) && $instance->isa($class->name))
652 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
655 # we need to protect the integrity of the
656 # Class::MOP::Class singletons here, they
657 # should not be cloned.
658 return $instance if $instance->isa('Class::MOP::Class');
659 $class->_clone_instance($instance, @_);
662 sub _clone_instance {
663 my ($class, $instance, %params) = @_;
665 || confess "You can only clone instances, ($instance) is not a blessed instance";
666 my $meta_instance = $class->get_meta_instance();
667 my $clone = $meta_instance->clone_instance($instance);
668 foreach my $attr ($class->get_all_attributes()) {
669 if ( defined( my $init_arg = $attr->init_arg ) ) {
670 if (exists $params{$init_arg}) {
671 $attr->set_value($clone, $params{$init_arg});
678 sub _force_rebless_instance {
679 my ($self, $instance, %params) = @_;
680 my $old_metaclass = Class::MOP::class_of($instance);
682 $old_metaclass->rebless_instance_away($instance, $self, %params)
685 if ($old_metaclass->is_anon_class) {
686 delete $instance->{__MOP__};
689 my $meta_instance = $self->get_meta_instance;
692 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
693 $meta_instance->rebless_instance_structure($_[1], $self);
695 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
698 # this will only work for a HASH instance type
699 if ($self->is_anon_class) {
700 (reftype($instance) eq 'HASH')
701 || confess "Currently only HASH based instances are supported with instance of anon-classes";
703 # At some point we should make this official
704 # as a reserved slot name, but right now I am
705 # going to keep it here.
706 # my $RESERVED_MOP_SLOT = '__MOP__';
707 $instance->{'__MOP__'} = $self;
711 sub rebless_instance {
712 my ($self, $instance, %params) = @_;
713 my $old_metaclass = Class::MOP::class_of($instance);
715 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
716 $self->name->isa($old_class)
717 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
719 $self->_force_rebless_instance($_[1], %params);
724 sub rebless_instance_back {
725 my ( $self, $instance ) = @_;
726 my $old_metaclass = Class::MOP::class_of($instance);
729 = $old_metaclass ? $old_metaclass->name : blessed($instance);
730 $old_class->isa( $self->name )
732 "You may rebless only into a superclass of ($old_class), of which ("
736 $self->_force_rebless_instance($_[1]);
741 sub rebless_instance_away {
742 # this intentionally does nothing, it is just a hook
745 sub _fixup_attributes_after_rebless {
747 my ($instance, $rebless_from, %params) = @_;
748 my $meta_instance = $self->get_meta_instance;
750 for my $attr ( $rebless_from->get_all_attributes ) {
751 next if $self->find_attribute_by_name( $attr->name );
752 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
755 foreach my $attr ( $self->get_all_attributes ) {
756 if ( $attr->has_value($instance) ) {
757 if ( defined( my $init_arg = $attr->init_arg ) ) {
758 $params{$init_arg} = $attr->get_value($instance)
759 unless exists $params{$init_arg};
762 $attr->set_value($instance, $attr->get_value($instance));
767 foreach my $attr ($self->get_all_attributes) {
768 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
772 sub _attach_attribute {
773 my ($self, $attribute) = @_;
774 $attribute->attach_to_class($self);
777 sub _post_add_attribute {
778 my ( $self, $attribute ) = @_;
780 $self->invalidate_meta_instances;
782 # invalidate package flag here
785 $attribute->install_accessors;
788 $self->remove_attribute( $attribute->name );
793 sub remove_attribute {
796 my $removed_attribute = $self->SUPER::remove_attribute(@_)
799 $self->invalidate_meta_instances;
801 $removed_attribute->remove_accessors;
802 $removed_attribute->detach_from_class;
804 return$removed_attribute;
807 sub find_attribute_by_name {
808 my ( $self, $attr_name ) = @_;
810 foreach my $class ( $self->linearized_isa ) {
811 # fetch the meta-class ...
812 my $meta = Class::MOP::Class->initialize($class);
813 return $meta->get_attribute($attr_name)
814 if $meta->has_attribute($attr_name);
820 sub get_all_attributes {
822 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
823 reverse $self->linearized_isa;
824 return values %attrs;
832 my $isa = $self->get_or_add_package_symbol(
833 { sigil => '@', type => 'ARRAY', name => 'ISA' } );
840 # on 5.8 and below, we need to call
841 # a method to get Perl to detect
842 # a cycle in the class hierarchy
843 my $class = $self->name;
847 # we need to check the metaclass
848 # compatibility here so that we can
849 # be sure that the superclass is
850 # not potentially creating an issues
851 # we don't know about
853 $self->_check_metaclass_compatibility();
854 $self->_superclasses_updated();
860 sub _superclasses_updated {
862 $self->update_meta_instance_dependencies();
867 my $super_class = $self->name;
869 return @{ $super_class->mro::get_isarev() };
872 sub direct_subclasses {
874 my $super_class = $self->name;
879 } Class::MOP::Class->initialize($_)->superclasses
884 return @{ mro::get_linear_isa( (shift)->name ) };
887 sub class_precedence_list {
889 my $name = $self->name;
891 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
893 # We need to check for circular inheritance here
894 # if we are are not on 5.10, cause 5.8 detects it
895 # late. This will do nothing if all is well, and
896 # blow up otherwise. Yes, it's an ugly hack, better
897 # suggestions are welcome.
899 ($name || return)->isa('This is a test for circular inheritance')
902 # if our mro is c3, we can
903 # just grab the linear_isa
904 if (mro::get_mro($name) eq 'c3') {
905 return @{ mro::get_linear_isa($name) }
909 # we can't grab the linear_isa for dfs
910 # since it has all the duplicates
915 Class::MOP::Class->initialize($_)->class_precedence_list()
916 } $self->superclasses()
924 my $fetch_and_prepare_method = sub {
925 my ($self, $method_name) = @_;
926 my $wrapped_metaclass = $self->wrapped_method_metaclass;
928 my $method = $self->get_method($method_name);
929 # if we dont have local ...
931 # try to find the next method
932 $method = $self->find_next_method_by_name($method_name);
933 # die if it does not exist
935 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
936 # and now make sure to wrap it
937 # even if it is already wrapped
938 # because we need a new sub ref
939 $method = $wrapped_metaclass->wrap($method,
940 package_name => $self->name,
941 name => $method_name,
945 # now make sure we wrap it properly
946 $method = $wrapped_metaclass->wrap($method,
947 package_name => $self->name,
948 name => $method_name,
949 ) unless $method->isa($wrapped_metaclass);
951 $self->add_method($method_name => $method);
955 sub add_before_method_modifier {
956 my ($self, $method_name, $method_modifier) = @_;
957 (defined $method_name && length $method_name)
958 || confess "You must pass in a method name";
959 my $method = $fetch_and_prepare_method->($self, $method_name);
960 $method->add_before_modifier(
961 subname(':before' => $method_modifier)
965 sub add_after_method_modifier {
966 my ($self, $method_name, $method_modifier) = @_;
967 (defined $method_name && length $method_name)
968 || confess "You must pass in a method name";
969 my $method = $fetch_and_prepare_method->($self, $method_name);
970 $method->add_after_modifier(
971 subname(':after' => $method_modifier)
975 sub add_around_method_modifier {
976 my ($self, $method_name, $method_modifier) = @_;
977 (defined $method_name && length $method_name)
978 || confess "You must pass in a method name";
979 my $method = $fetch_and_prepare_method->($self, $method_name);
980 $method->add_around_modifier(
981 subname(':around' => $method_modifier)
986 # the methods above used to be named like this:
987 # ${pkg}::${method}:(before|after|around)
988 # but this proved problematic when using one modifier
989 # to wrap multiple methods (something which is likely
990 # to happen pretty regularly IMO). So instead of naming
991 # it like this, I have chosen to just name them purely
992 # with their modifier names, like so:
993 # :(before|after|around)
994 # The fact is that in a stack trace, it will be fairly
995 # evident from the context what method they are attached
996 # to, and so don't need the fully qualified name.
999 sub find_method_by_name {
1000 my ($self, $method_name) = @_;
1001 (defined $method_name && length $method_name)
1002 || confess "You must define a method name to find";
1003 foreach my $class ($self->linearized_isa) {
1004 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1005 return $method if defined $method;
1010 sub get_all_methods {
1014 for my $class ( reverse $self->linearized_isa ) {
1015 my $meta = Class::MOP::Class->initialize($class);
1017 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1020 return values %methods;
1023 sub get_all_method_names {
1026 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
1029 sub find_all_methods_by_name {
1030 my ($self, $method_name) = @_;
1031 (defined $method_name && length $method_name)
1032 || confess "You must define a method name to find";
1034 foreach my $class ($self->linearized_isa) {
1035 # fetch the meta-class ...
1036 my $meta = Class::MOP::Class->initialize($class);
1038 name => $method_name,
1040 code => $meta->get_method($method_name)
1041 } if $meta->has_method($method_name);
1046 sub find_next_method_by_name {
1047 my ($self, $method_name) = @_;
1048 (defined $method_name && length $method_name)
1049 || confess "You must define a method name to find";
1050 my @cpl = $self->linearized_isa;
1051 shift @cpl; # discard ourselves
1052 foreach my $class (@cpl) {
1053 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1054 return $method if defined $method;
1059 sub update_meta_instance_dependencies {
1062 if ( $self->{meta_instance_dependencies} ) {
1063 return $self->add_meta_instance_dependencies;
1067 sub add_meta_instance_dependencies {
1070 $self->remove_meta_instance_dependencies;
1072 my @attrs = $self->get_all_attributes();
1075 my @classes = grep { not $seen{ $_->name }++ }
1076 map { $_->associated_class } @attrs;
1078 foreach my $class (@classes) {
1079 $class->add_dependent_meta_instance($self);
1082 $self->{meta_instance_dependencies} = \@classes;
1085 sub remove_meta_instance_dependencies {
1088 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1089 foreach my $class (@$classes) {
1090 $class->remove_dependent_meta_instance($self);
1100 sub add_dependent_meta_instance {
1101 my ( $self, $metaclass ) = @_;
1102 push @{ $self->{dependent_meta_instances} }, $metaclass;
1105 sub remove_dependent_meta_instance {
1106 my ( $self, $metaclass ) = @_;
1107 my $name = $metaclass->name;
1108 @$_ = grep { $_->name ne $name } @$_
1109 for $self->{dependent_meta_instances};
1112 sub invalidate_meta_instances {
1114 $_->invalidate_meta_instance()
1115 for $self, @{ $self->{dependent_meta_instances} };
1118 sub invalidate_meta_instance {
1120 undef $self->{_meta_instance};
1123 # check if we can reinitialize
1127 # if any local attr is defined
1128 return if $self->get_attribute_list;
1130 # or any non-declared methods
1131 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1132 return if $method->isa("Class::MOP::Method::Generated");
1133 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1141 sub is_mutable { 1 }
1142 sub is_immutable { 0 }
1144 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1146 sub _immutable_options {
1147 my ( $self, @args ) = @_;
1150 inline_accessors => 1,
1151 inline_constructor => 1,
1152 inline_destructor => 0,
1154 immutable_trait => $self->immutable_trait,
1155 constructor_name => $self->constructor_name,
1156 constructor_class => $self->constructor_class,
1157 destructor_class => $self->destructor_class,
1162 sub make_immutable {
1163 my ( $self, @args ) = @_;
1165 if ( $self->is_mutable ) {
1166 $self->_initialize_immutable( $self->_immutable_options(@args) );
1167 $self->_rebless_as_immutable(@args);
1178 if ( $self->is_immutable ) {
1179 my @args = $self->immutable_options;
1180 $self->_rebless_as_mutable();
1181 $self->_remove_inlined_code(@args);
1182 delete $self->{__immutable};
1190 sub _rebless_as_immutable {
1191 my ( $self, @args ) = @_;
1193 $self->{__immutable}{original_class} = ref $self;
1195 bless $self => $self->_immutable_metaclass(@args);
1198 sub _immutable_metaclass {
1199 my ( $self, %args ) = @_;
1201 if ( my $class = $args{immutable_metaclass} ) {
1205 my $trait = $args{immutable_trait} = $self->immutable_trait
1206 || confess "no immutable trait specified for $self";
1208 my $meta = $self->meta;
1209 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1213 if ( $meta_attr and $trait eq $meta_attr->default ) {
1214 # if the trait is the same as the default we try and pick a
1215 # predictable name for the immutable metaclass
1216 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1219 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1220 $trait, 'ForMetaClass', ref($self);
1224 if Class::MOP::is_class_loaded($class_name);
1226 # If the metaclass is a subclass of CMOP::Class which has had
1227 # metaclass roles applied (via Moose), then we want to make sure
1228 # that we preserve that anonymous class (see Fey::ORM for an
1229 # example of where this matters).
1230 my $meta_name = $meta->_real_ref_name;
1232 my $immutable_meta = $meta_name->create(
1234 superclasses => [ ref $self ],
1237 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1239 $immutable_meta->make_immutable(
1240 inline_constructor => 0,
1241 inline_accessors => 0,
1247 sub _remove_inlined_code {
1250 $self->remove_method( $_->name ) for $self->_inlined_methods;
1252 delete $self->{__immutable}{inlined_methods};
1255 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1257 sub _add_inlined_method {
1258 my ( $self, $method ) = @_;
1260 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1263 sub _initialize_immutable {
1264 my ( $self, %args ) = @_;
1266 $self->{__immutable}{options} = \%args;
1267 $self->_install_inlined_code(%args);
1270 sub _install_inlined_code {
1271 my ( $self, %args ) = @_;
1274 $self->_inline_accessors(%args) if $args{inline_accessors};
1275 $self->_inline_constructor(%args) if $args{inline_constructor};
1276 $self->_inline_destructor(%args) if $args{inline_destructor};
1279 sub _rebless_as_mutable {
1282 bless $self, $self->_get_mutable_metaclass_name;
1287 sub _inline_accessors {
1290 foreach my $attr_name ( $self->get_attribute_list ) {
1291 $self->get_attribute($attr_name)->install_accessors(1);
1295 sub _inline_constructor {
1296 my ( $self, %args ) = @_;
1298 my $name = $args{constructor_name};
1299 # A class may not even have a constructor, and that's okay.
1300 return unless defined $name;
1302 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1303 my $class = $self->name;
1304 warn "Not inlining a constructor for $class since it defines"
1305 . " its own constructor.\n"
1306 . "If you are certain you don't need to inline your"
1307 . " constructor, specify inline_constructor => 0 in your"
1308 . " call to $class->meta->make_immutable\n";
1312 my $constructor_class = $args{constructor_class};
1314 Class::MOP::load_class($constructor_class);
1316 my $constructor = $constructor_class->new(
1320 package_name => $self->name,
1324 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1325 $self->add_method( $name => $constructor );
1326 $self->_add_inlined_method($constructor);
1330 sub _inline_destructor {
1331 my ( $self, %args ) = @_;
1333 ( exists $args{destructor_class} && defined $args{destructor_class} )
1334 || confess "The 'inline_destructor' option is present, but "
1335 . "no destructor class was specified";
1337 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1338 my $class = $self->name;
1339 warn "Not inlining a destructor for $class since it defines"
1340 . " its own destructor.\n";
1344 my $destructor_class = $args{destructor_class};
1346 Class::MOP::load_class($destructor_class);
1348 return unless $destructor_class->is_needed($self);
1350 my $destructor = $destructor_class->new(
1353 package_name => $self->name,
1357 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1358 $self->add_method( 'DESTROY' => $destructor );
1359 $self->_add_inlined_method($destructor);
1371 Class::MOP::Class - Class Meta Object
1375 # assuming that class Foo
1376 # has been defined, you can
1378 # use this for introspection ...
1380 # add a method to Foo ...
1381 Foo->meta->add_method( 'bar' => sub {...} )
1383 # get a list of all the classes searched
1384 # the method dispatcher in the correct order
1385 Foo->meta->class_precedence_list()
1387 # remove a method from Foo
1388 Foo->meta->remove_method('bar');
1390 # or use this to actually create classes ...
1392 Class::MOP::Class->create(
1395 superclasses => ['Foo'],
1397 Class::MOP::Attribute->new('$bar'),
1398 Class::MOP::Attribute->new('$baz'),
1401 calculate_bar => sub {...},
1402 construct_baz => sub {...}
1409 The Class Protocol is the largest and most complex part of the
1410 Class::MOP meta-object protocol. It controls the introspection and
1411 manipulation of Perl 5 classes, and it can create them as well. The
1412 best way to understand what this module can do is to read the
1413 documentation for each of its methods.
1417 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1421 =head2 Class construction
1423 These methods all create new C<Class::MOP::Class> objects. These
1424 objects can represent existing classes or they can be used to create
1425 new classes from scratch.
1427 The metaclass object for a given class is a singleton. If you attempt
1428 to create a metaclass for the same class twice, you will just get the
1433 =item B<< Class::MOP::Class->create($package_name, %options) >>
1435 This method creates a new C<Class::MOP::Class> object with the given
1436 package name. It accepts a number of options:
1442 An optional version number for the newly created package.
1446 An optional authority for the newly created package.
1448 =item * superclasses
1450 An optional array reference of superclass names.
1454 An optional hash reference of methods for the class. The keys of the
1455 hash reference are method names and values are subroutine references.
1459 An optional array reference of L<Class::MOP::Attribute> objects.
1463 Specifies the name to install the C<meta> method for this class under.
1464 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1465 given, no meta method will be installed.
1469 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1471 This method works just like C<< Class::MOP::Class->create >> but it
1472 creates an "anonymous" class. In fact, the class does have a name, but
1473 that name is a unique name generated internally by this module.
1475 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1476 parameters that C<create> accepts.
1478 Anonymous classes are destroyed once the metaclass they are attached
1479 to goes out of scope, and will be removed from Perl's internal symbol
1482 All instances of an anonymous class keep a special reference to the
1483 metaclass object, which prevents the metaclass from going out of scope
1484 while any instances exist.
1486 This only works if the instance is based on a hash reference, however.
1488 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1490 This method will initialize a C<Class::MOP::Class> object for the
1491 named package. Unlike C<create>, this method I<will not> create a new
1494 The purpose of this method is to retrieve a C<Class::MOP::Class>
1495 object for introspecting an existing class.
1497 If an existing C<Class::MOP::Class> object exists for the named
1498 package, it will be returned, and any options provided will be
1501 If the object does not yet exist, it will be created.
1503 The valid options that can be passed to this method are
1504 C<attribute_metaclass>, C<method_metaclass>,
1505 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1506 optional, and default to the appropriate class in the C<Class::MOP>
1511 =head2 Object instance construction and cloning
1513 These methods are all related to creating and/or cloning object
1518 =item B<< $metaclass->clone_object($instance, %params) >>
1520 This method clones an existing object instance. Any parameters you
1521 provide are will override existing attribute values in the object.
1523 This is a convenience method for cloning an object instance, then
1524 blessing it into the appropriate package.
1526 You could implement a clone method in your class, using this method:
1529 my ($self, %params) = @_;
1530 $self->meta->clone_object($self, %params);
1533 =item B<< $metaclass->rebless_instance($instance, %params) >>
1535 This method changes the class of C<$instance> to the metaclass's class.
1537 You can only rebless an instance into a subclass of its current
1538 class. If you pass any additional parameters, these will be treated
1539 like constructor parameters and used to initialize the object's
1540 attributes. Any existing attributes that are already set will be
1543 Before reblessing the instance, this method will call
1544 C<rebless_instance_away> on the instance's current metaclass. This method
1545 will be passed the instance, the new metaclass, and any parameters
1546 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1547 does nothing; it is merely a hook.
1549 =item B<< $metaclass->rebless_instance_back($instance) >>
1551 Does the same thing as C<rebless_instance>, except that you can only
1552 rebless an instance into one of its superclasses. Any attributes that
1553 do not exist in the superclass will be deinitialized.
1555 This is a much more dangerous operation than C<rebless_instance>,
1556 especially when multiple inheritance is involved, so use this carefully!
1558 =item B<< $metaclass->new_object(%params) >>
1560 This method is used to create a new object of the metaclass's
1561 class. Any parameters you provide are used to initialize the
1562 instance's attributes. A special C<__INSTANCE__> key can be passed to
1563 provide an already generated instance, rather than having Class::MOP
1564 generate it for you. This is mostly useful for using Class::MOP with
1565 foreign classes which generate instances using their own constructors.
1567 =item B<< $metaclass->instance_metaclass >>
1569 Returns the class name of the instance metaclass. See
1570 L<Class::MOP::Instance> for more information on the instance
1573 =item B<< $metaclass->get_meta_instance >>
1575 Returns an instance of the C<instance_metaclass> to be used in the
1576 construction of a new instance of the class.
1578 =item B<< $metaclass->inline_create_instance($class_var) >>
1580 =item B<< $metaclass->inline_rebless_instance($instance_var, $class_var) >>
1582 These methods takes variable names, and use them to create an inline snippet
1583 of code that will create a new instance of the class.
1587 =head2 Informational predicates
1589 These are a few predicate methods for asking information about the
1594 =item B<< $metaclass->is_anon_class >>
1596 This returns true if the class was created by calling C<<
1597 Class::MOP::Class->create_anon_class >>.
1599 =item B<< $metaclass->is_mutable >>
1601 This returns true if the class is still mutable.
1603 =item B<< $metaclass->is_immutable >>
1605 This returns true if the class has been made immutable.
1607 =item B<< $metaclass->is_pristine >>
1609 A class is I<not> pristine if it has non-inherited attributes or if it
1610 has any generated methods.
1614 =head2 Inheritance Relationships
1618 =item B<< $metaclass->superclasses(@superclasses) >>
1620 This is a read-write accessor which represents the superclass
1621 relationships of the metaclass's class.
1623 This is basically sugar around getting and setting C<@ISA>.
1625 =item B<< $metaclass->class_precedence_list >>
1627 This returns a list of all of the class's ancestor classes. The
1628 classes are returned in method dispatch order.
1630 =item B<< $metaclass->linearized_isa >>
1632 This returns a list based on C<class_precedence_list> but with all
1635 =item B<< $metaclass->subclasses >>
1637 This returns a list of all subclasses for this class, even indirect
1640 =item B<< $metaclass->direct_subclasses >>
1642 This returns a list of immediate subclasses for this class, which does not
1643 include indirect subclasses.
1647 =head2 Method introspection and creation
1649 These methods allow you to introspect a class's methods, as well as
1650 add, remove, or change methods.
1652 Determining what is truly a method in a Perl 5 class requires some
1653 heuristics (aka guessing).
1655 Methods defined outside the package with a fully qualified name (C<sub
1656 Package::name { ... }>) will be included. Similarly, methods named
1657 with a fully qualified name using L<Sub::Name> are also included.
1659 However, we attempt to ignore imported functions.
1661 Ultimately, we are using heuristics to determine what truly is a
1662 method in a class, and these heuristics may get the wrong answer in
1663 some edge cases. However, for most "normal" cases the heuristics work
1668 =item B<< $metaclass->get_method($method_name) >>
1670 This will return a L<Class::MOP::Method> for the specified
1671 C<$method_name>. If the class does not have the specified method, it
1674 =item B<< $metaclass->has_method($method_name) >>
1676 Returns a boolean indicating whether or not the class defines the
1677 named method. It does not include methods inherited from parent
1680 =item B<< $metaclass->get_method_list >>
1682 This will return a list of method I<names> for all methods defined in
1685 =item B<< $metaclass->add_method($method_name, $method) >>
1687 This method takes a method name and a subroutine reference, and adds
1688 the method to the class.
1690 The subroutine reference can be a L<Class::MOP::Method>, and you are
1691 strongly encouraged to pass a meta method object instead of a code
1692 reference. If you do so, that object gets stored as part of the
1693 class's method map directly. If not, the meta information will have to
1694 be recreated later, and may be incorrect.
1696 If you provide a method object, this method will clone that object if
1697 the object's package name does not match the class name. This lets us
1698 track the original source of any methods added from other classes
1699 (notably Moose roles).
1701 =item B<< $metaclass->remove_method($method_name) >>
1703 Remove the named method from the class. This method returns the
1704 L<Class::MOP::Method> object for the method.
1706 =item B<< $metaclass->method_metaclass >>
1708 Returns the class name of the method metaclass, see
1709 L<Class::MOP::Method> for more information on the method metaclass.
1711 =item B<< $metaclass->wrapped_method_metaclass >>
1713 Returns the class name of the wrapped method metaclass, see
1714 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1717 =item B<< $metaclass->get_all_methods >>
1719 This will traverse the inheritance hierarchy and return a list of all
1720 the L<Class::MOP::Method> objects for this class and its parents.
1722 =item B<< $metaclass->find_method_by_name($method_name) >>
1724 This will return a L<Class::MOP::Method> for the specified
1725 C<$method_name>. If the class does not have the specified method, it
1728 Unlike C<get_method>, this method I<will> look for the named method in
1731 =item B<< $metaclass->get_all_method_names >>
1733 This will return a list of method I<names> for all of this class's
1734 methods, including inherited methods.
1736 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1738 This method looks for the named method in the class and all of its
1739 parents. It returns every matching method it finds in the inheritance
1740 tree, so it returns a list of methods.
1742 Each method is returned as a hash reference with three keys. The keys
1743 are C<name>, C<class>, and C<code>. The C<code> key has a
1744 L<Class::MOP::Method> object as its value.
1746 The list of methods is distinct.
1748 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1750 This method returns the first method in any superclass matching the
1751 given name. It is effectively the method that C<SUPER::$method_name>
1756 =head2 Attribute introspection and creation
1758 Because Perl 5 does not have a core concept of attributes in classes,
1759 we can only return information about attributes which have been added
1760 via this class's methods. We cannot discover information about
1761 attributes which are defined in terms of "regular" Perl 5 methods.
1765 =item B<< $metaclass->get_attribute($attribute_name) >>
1767 This will return a L<Class::MOP::Attribute> for the specified
1768 C<$attribute_name>. If the class does not have the specified
1769 attribute, it returns C<undef>.
1771 NOTE that get_attribute does not search superclasses, for that you
1772 need to use C<find_attribute_by_name>.
1774 =item B<< $metaclass->has_attribute($attribute_name) >>
1776 Returns a boolean indicating whether or not the class defines the
1777 named attribute. It does not include attributes inherited from parent
1780 =item B<< $metaclass->get_attribute_list >>
1782 This will return a list of attributes I<names> for all attributes
1783 defined in this class. Note that this operates on the current class
1784 only, it does not traverse the inheritance hierarchy.
1786 =item B<< $metaclass->get_all_attributes >>
1788 This will traverse the inheritance hierarchy and return a list of all
1789 the L<Class::MOP::Attribute> objects for this class and its parents.
1791 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1793 This will return a L<Class::MOP::Attribute> for the specified
1794 C<$attribute_name>. If the class does not have the specified
1795 attribute, it returns C<undef>.
1797 Unlike C<get_attribute>, this attribute I<will> look for the named
1798 attribute in superclasses.
1800 =item B<< $metaclass->add_attribute(...) >>
1802 This method accepts either an existing L<Class::MOP::Attribute>
1803 object or parameters suitable for passing to that class's C<new>
1806 The attribute provided will be added to the class.
1808 Any accessor methods defined by the attribute will be added to the
1809 class when the attribute is added.
1811 If an attribute of the same name already exists, the old attribute
1812 will be removed first.
1814 =item B<< $metaclass->remove_attribute($attribute_name) >>
1816 This will remove the named attribute from the class, and
1817 L<Class::MOP::Attribute> object.
1819 Removing an attribute also removes any accessor methods defined by the
1822 However, note that removing an attribute will only affect I<future>
1823 object instances created for this class, not existing instances.
1825 =item B<< $metaclass->attribute_metaclass >>
1827 Returns the class name of the attribute metaclass for this class. By
1828 default, this is L<Class::MOP::Attribute>.
1832 =head2 Class Immutability
1834 Making a class immutable "freezes" the class definition. You can no
1835 longer call methods which alter the class, such as adding or removing
1836 methods or attributes.
1838 Making a class immutable lets us optimize the class by inlining some
1839 methods, and also allows us to optimize some methods on the metaclass
1842 After immutabilization, the metaclass object will cache most informational
1843 methods that returns information about methods or attributes. Methods which
1844 would alter the class, such as C<add_attribute> and C<add_method>, will
1845 throw an error on an immutable metaclass object.
1847 The immutabilization system in L<Moose> takes much greater advantage
1848 of the inlining features than Class::MOP itself does.
1852 =item B<< $metaclass->make_immutable(%options) >>
1854 This method will create an immutable transformer and use it to make
1855 the class and its metaclass object immutable.
1857 This method accepts the following options:
1861 =item * inline_accessors
1863 =item * inline_constructor
1865 =item * inline_destructor
1867 These are all booleans indicating whether the specified method(s)
1870 By default, accessors and the constructor are inlined, but not the
1873 =item * immutable_trait
1875 The name of a class which will be used as a parent class for the
1876 metaclass object being made immutable. This "trait" implements the
1877 post-immutability functionality of the metaclass (but not the
1878 transformation itself).
1880 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1882 =item * constructor_name
1884 This is the constructor method name. This defaults to "new".
1886 =item * constructor_class
1888 The name of the method metaclass for constructors. It will be used to
1889 generate the inlined constructor. This defaults to
1890 "Class::MOP::Method::Constructor".
1892 =item * replace_constructor
1894 This is a boolean indicating whether an existing constructor should be
1895 replaced when inlining a constructor. This defaults to false.
1897 =item * destructor_class
1899 The name of the method metaclass for destructors. It will be used to
1900 generate the inlined destructor. This defaults to
1901 "Class::MOP::Method::Denstructor".
1903 =item * replace_destructor
1905 This is a boolean indicating whether an existing destructor should be
1906 replaced when inlining a destructor. This defaults to false.
1910 =item B<< $metaclass->immutable_options >>
1912 Returns a hash of the options used when making the class immutable, including
1913 both defaults and anything supplied by the user in the call to C<<
1914 $metaclass->make_immutable >>. This is useful if you need to temporarily make
1915 a class mutable and then restore immutability as it was before.
1917 =item B<< $metaclass->make_mutable >>
1919 Calling this method reverse the immutabilization transformation.
1923 =head2 Method Modifiers
1925 Method modifiers are hooks which allow a method to be wrapped with
1926 I<before>, I<after> and I<around> method modifiers. Every time a
1927 method is called, its modifiers are also called.
1929 A class can modify its own methods, as well as methods defined in
1932 =head3 How method modifiers work?
1934 Method modifiers work by wrapping the original method and then
1935 replacing it in the class's symbol table. The wrappers will handle
1936 calling all the modifiers in the appropriate order and preserving the
1937 calling context for the original method.
1939 The return values of C<before> and C<after> modifiers are
1940 ignored. This is because their purpose is B<not> to filter the input
1941 and output of the primary method (this is done with an I<around>
1944 This may seem like an odd restriction to some, but doing this allows
1945 for simple code to be added at the beginning or end of a method call
1946 without altering the function of the wrapped method or placing any
1947 extra responsibility on the code of the modifier.
1949 Of course if you have more complex needs, you can use the C<around>
1950 modifier which allows you to change both the parameters passed to the
1951 wrapped method, as well as its return value.
1953 Before and around modifiers are called in last-defined-first-called
1954 order, while after modifiers are called in first-defined-first-called
1955 order. So the call tree might looks something like this:
1967 =head3 What is the performance impact?
1969 Of course there is a performance cost associated with method
1970 modifiers, but we have made every effort to make that cost directly
1971 proportional to the number of modifier features you use.
1973 The wrapping method does its best to B<only> do as much work as it
1974 absolutely needs to. In order to do this we have moved some of the
1975 performance costs to set-up time, where they are easier to amortize.
1977 All this said, our benchmarks have indicated the following:
1979 simple wrapper with no modifiers 100% slower
1980 simple wrapper with simple before modifier 400% slower
1981 simple wrapper with simple after modifier 450% slower
1982 simple wrapper with simple around modifier 500-550% slower
1983 simple wrapper with all 3 modifiers 1100% slower
1985 These numbers may seem daunting, but you must remember, every feature
1986 comes with some cost. To put things in perspective, just doing a
1987 simple C<AUTOLOAD> which does nothing but extract the name of the
1988 method called and return it costs about 400% over a normal method
1993 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1995 This wraps the specified method with the supplied subroutine
1996 reference. The modifier will be called as a method itself, and will
1997 receive the same arguments as are passed to the method.
1999 When the modifier exits, the wrapped method will be called.
2001 The return value of the modifier will be ignored.
2003 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2005 This wraps the specified method with the supplied subroutine
2006 reference. The modifier will be called as a method itself, and will
2007 receive the same arguments as are passed to the method.
2009 When the wrapped methods exits, the modifier will be called.
2011 The return value of the modifier will be ignored.
2013 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2015 This wraps the specified method with the supplied subroutine
2018 The first argument passed to the modifier will be a subroutine
2019 reference to the wrapped method. The second argument is the object,
2020 and after that come any arguments passed when the method is called.
2022 The around modifier can choose to call the original method, as well as
2023 what arguments to pass if it does so.
2025 The return value of the modifier is what will be seen by the caller.
2029 =head2 Introspection
2033 =item B<< Class::MOP::Class->meta >>
2035 This will return a L<Class::MOP::Class> instance for this class.
2037 It should also be noted that L<Class::MOP> will actually bootstrap
2038 this module by installing a number of attribute meta-objects into its
2045 Stevan Little E<lt>stevan@iinteractive.comE<gt>
2047 =head1 COPYRIGHT AND LICENSE
2049 Copyright 2006-2010 by Infinity Interactive, Inc.
2051 L<http://www.iinteractive.com>
2053 This library is free software; you can redistribute it and/or modify
2054 it under the same terms as Perl itself.