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 for my $method ($old_meta->_get_local_methods) {
412 $self->_make_metaobject_compatible($method);
413 $self->add_method($method->name => $method);
416 for my $attr (sort { $a->insertion_order <=> $b->insertion_order }
417 map { $old_meta->get_attribute($_) }
418 $old_meta->get_attribute_list) {
419 $self->_make_metaobject_compatible($attr);
420 $self->add_attribute($attr);
424 sub _remove_generated_metaobjects {
427 for my $attr (map { $self->get_attribute($_) } $self->get_attribute_list) {
428 $attr->remove_accessors;
432 sub _make_metaobject_compatible {
435 my $current_single_meta_name = $self->_get_associated_single_metaclass($object);
436 $object->_make_compatible_with($current_single_meta_name);
439 sub _get_associated_single_metaclass {
441 my ($single_meta_name) = @_;
443 my $current_single_meta_name;
444 if ($single_meta_name->isa('Class::MOP::Method')) {
445 $current_single_meta_name = $self->method_metaclass;
447 elsif ($single_meta_name->isa('Class::MOP::Attribute')) {
448 $current_single_meta_name = $self->attribute_metaclass;
451 confess "Can't make $single_meta_name compatible, it isn't an "
452 . "attribute or method metaclass.";
455 return $current_single_meta_name;
462 # this should be sufficient, if you have a
463 # use case where it is not, write a test and
465 my $ANON_CLASS_SERIAL = 0;
468 # we need a sufficiently annoying prefix
469 # this should suffice for now, this is
470 # used in a couple of places below, so
471 # need to put it up here for now.
472 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
476 no warnings 'uninitialized';
477 $self->name =~ /^$ANON_CLASS_PREFIX/o;
480 sub create_anon_class {
481 my ($class, %options) = @_;
482 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
483 return $class->create($package_name, %options);
487 # this will only get called for
488 # anon-classes, all other calls
489 # are assumed to occur during
490 # global destruction and so don't
491 # really need to be handled explicitly
495 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
497 no warnings 'uninitialized';
498 my $name = $self->name;
499 return unless $name =~ /^$ANON_CLASS_PREFIX/o;
501 # Moose does a weird thing where it replaces the metaclass for
502 # class when fixing metaclass incompatibility. In that case,
503 # we don't want to clean out the namespace now. We can detect
504 # that because Moose will explicitly update the singleton
505 # cache in Class::MOP.
506 my $current_meta = Class::MOP::get_metaclass_by_name($name);
507 return if $current_meta ne $self;
509 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/o);
511 @{$name . '::ISA'} = ();
512 %{$name . '::'} = ();
513 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
515 Class::MOP::remove_metaclass_by_name($name);
520 # creating classes with MOP ...
523 my ( $class, @args ) = @_;
525 unshift @args, 'package' if @args % 2 == 1;
527 my (%options) = @args;
528 my $package_name = $options{package};
530 (ref $options{superclasses} eq 'ARRAY')
531 || confess "You must pass an ARRAY ref of superclasses"
532 if exists $options{superclasses};
534 (ref $options{attributes} eq 'ARRAY')
535 || confess "You must pass an ARRAY ref of attributes"
536 if exists $options{attributes};
538 (ref $options{methods} eq 'HASH')
539 || confess "You must pass a HASH ref of methods"
540 if exists $options{methods};
542 my (%initialize_options) = @args;
543 delete @initialize_options{qw(
552 my $meta = $class->initialize( $package_name => %initialize_options );
554 $meta->_instantiate_module( $options{version}, $options{authority} );
557 $meta->add_method('meta' => sub {
558 if (Class::MOP::DEBUG_NO_META()) {
560 if (my $meta = try { $self->SUPER::meta }) {
561 return $meta if $meta->isa('Class::MOP::Class');
563 confess "'meta' method called by MOP internals"
564 if caller =~ /Class::MOP|metaclass/;
566 $class->initialize(ref($_[0]) || $_[0]);
567 }) unless $options{no_meta};
569 $meta->superclasses(@{$options{superclasses}})
570 if exists $options{superclasses};
572 # process attributes first, so that they can
573 # install accessors, but locally defined methods
574 # can then overwrite them. It is maybe a little odd, but
575 # I think this should be the order of things.
576 if (exists $options{attributes}) {
577 foreach my $attr (@{$options{attributes}}) {
578 $meta->add_attribute($attr);
581 if (exists $options{methods}) {
582 foreach my $method_name (keys %{$options{methods}}) {
583 $meta->add_method($method_name, $options{methods}->{$method_name});
592 # all these attribute readers will be bootstrapped
593 # away in the Class::MOP bootstrap section
595 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
596 sub immutable_trait { $_[0]->{'immutable_trait'} }
597 sub constructor_class { $_[0]->{'constructor_class'} }
598 sub constructor_name { $_[0]->{'constructor_name'} }
599 sub destructor_class { $_[0]->{'destructor_class'} }
601 # Instance Construction & Cloning
607 # we need to protect the integrity of the
608 # Class::MOP::Class singletons here, so we
609 # delegate this to &construct_class_instance
610 # which will deal with the singletons
611 return $class->_construct_class_instance(@_)
612 if $class->name->isa('Class::MOP::Class');
613 return $class->_construct_instance(@_);
616 sub _construct_instance {
618 my $params = @_ == 1 ? $_[0] : {@_};
619 my $meta_instance = $class->get_meta_instance();
621 # the code below is almost certainly incorrect
622 # but this is foreign inheritance, so we might
623 # have to kludge it in the end.
625 if (my $instance_class = blessed($params->{__INSTANCE__})) {
626 ($instance_class eq $class->name)
627 || confess "Objects passed as the __INSTANCE__ parameter must "
628 . "already be blessed into the correct class, but "
629 . "$params->{__INSTANCE__} is not a " . $class->name;
630 $instance = $params->{__INSTANCE__};
632 elsif (exists $params->{__INSTANCE__}) {
633 confess "The __INSTANCE__ parameter must be a blessed reference, not "
634 . $params->{__INSTANCE__};
637 $instance = $meta_instance->create_instance();
639 foreach my $attr ($class->get_all_attributes()) {
640 $attr->initialize_instance_slot($meta_instance, $instance, $params);
643 # this will only work for a HASH instance type
644 if ($class->is_anon_class) {
645 (reftype($instance) eq 'HASH')
646 || confess "Currently only HASH based instances are supported with instance of anon-classes";
648 # At some point we should make this official
649 # as a reserved slot name, but right now I am
650 # going to keep it here.
651 # my $RESERVED_MOP_SLOT = '__MOP__';
652 $instance->{'__MOP__'} = $class;
658 sub get_meta_instance {
660 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
663 sub _create_meta_instance {
666 my $instance = $self->instance_metaclass->new(
667 associated_metaclass => $self,
668 attributes => [ $self->get_all_attributes() ],
671 $self->add_meta_instance_dependencies()
672 if $instance->is_dependent_on_superclasses();
677 sub inline_create_instance {
680 return $self->get_meta_instance->inline_create_instance(@_);
683 sub inline_rebless_instance {
686 return $self->get_meta_instance->inline_rebless_instance_structure(@_);
691 my $instance = shift;
692 (blessed($instance) && $instance->isa($class->name))
693 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
696 # we need to protect the integrity of the
697 # Class::MOP::Class singletons here, they
698 # should not be cloned.
699 return $instance if $instance->isa('Class::MOP::Class');
700 $class->_clone_instance($instance, @_);
703 sub _clone_instance {
704 my ($class, $instance, %params) = @_;
706 || confess "You can only clone instances, ($instance) is not a blessed instance";
707 my $meta_instance = $class->get_meta_instance();
708 my $clone = $meta_instance->clone_instance($instance);
709 foreach my $attr ($class->get_all_attributes()) {
710 if ( defined( my $init_arg = $attr->init_arg ) ) {
711 if (exists $params{$init_arg}) {
712 $attr->set_value($clone, $params{$init_arg});
719 sub _force_rebless_instance {
720 my ($self, $instance, %params) = @_;
721 my $old_metaclass = Class::MOP::class_of($instance);
723 $old_metaclass->rebless_instance_away($instance, $self, %params)
726 my $meta_instance = $self->get_meta_instance;
729 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
730 $meta_instance->rebless_instance_structure($_[1], $self);
732 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
735 sub rebless_instance {
736 my ($self, $instance, %params) = @_;
737 my $old_metaclass = Class::MOP::class_of($instance);
739 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
740 $self->name->isa($old_class)
741 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
743 $self->_force_rebless_instance($_[1], %params);
748 sub rebless_instance_back {
749 my ( $self, $instance ) = @_;
750 my $old_metaclass = Class::MOP::class_of($instance);
753 = $old_metaclass ? $old_metaclass->name : blessed($instance);
754 $old_class->isa( $self->name )
756 "You may rebless only into a superclass of ($old_class), of which ("
760 $self->_force_rebless_instance($_[1]);
765 sub rebless_instance_away {
766 # this intentionally does nothing, it is just a hook
769 sub _fixup_attributes_after_rebless {
771 my ($instance, $rebless_from, %params) = @_;
772 my $meta_instance = $self->get_meta_instance;
774 for my $attr ( $rebless_from->get_all_attributes ) {
775 next if $self->find_attribute_by_name( $attr->name );
776 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
779 foreach my $attr ( $self->get_all_attributes ) {
780 if ( $attr->has_value($instance) ) {
781 if ( defined( my $init_arg = $attr->init_arg ) ) {
782 $params{$init_arg} = $attr->get_value($instance)
783 unless exists $params{$init_arg};
786 $attr->set_value($instance, $attr->get_value($instance));
791 foreach my $attr ($self->get_all_attributes) {
792 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
796 sub _attach_attribute {
797 my ($self, $attribute) = @_;
798 $attribute->attach_to_class($self);
801 sub _post_add_attribute {
802 my ( $self, $attribute ) = @_;
804 $self->invalidate_meta_instances;
806 # invalidate package flag here
809 $attribute->install_accessors;
812 $self->remove_attribute( $attribute->name );
817 sub remove_attribute {
820 my $removed_attribute = $self->SUPER::remove_attribute(@_)
823 $self->invalidate_meta_instances;
825 $removed_attribute->remove_accessors;
826 $removed_attribute->detach_from_class;
828 return$removed_attribute;
831 sub find_attribute_by_name {
832 my ( $self, $attr_name ) = @_;
834 foreach my $class ( $self->linearized_isa ) {
835 # fetch the meta-class ...
836 my $meta = Class::MOP::Class->initialize($class);
837 return $meta->get_attribute($attr_name)
838 if $meta->has_attribute($attr_name);
844 sub get_all_attributes {
846 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
847 reverse $self->linearized_isa;
848 return values %attrs;
856 my $isa = $self->get_or_add_package_symbol(
857 { sigil => '@', type => 'ARRAY', name => 'ISA' } );
864 # on 5.8 and below, we need to call
865 # a method to get Perl to detect
866 # a cycle in the class hierarchy
867 my $class = $self->name;
871 # we need to check the metaclass
872 # compatibility here so that we can
873 # be sure that the superclass is
874 # not potentially creating an issues
875 # we don't know about
877 $self->_check_metaclass_compatibility();
878 $self->_superclasses_updated();
884 sub _superclasses_updated {
886 $self->update_meta_instance_dependencies();
891 my $super_class = $self->name;
893 return @{ $super_class->mro::get_isarev() };
896 sub direct_subclasses {
898 my $super_class = $self->name;
903 } Class::MOP::Class->initialize($_)->superclasses
908 return @{ mro::get_linear_isa( (shift)->name ) };
911 sub class_precedence_list {
913 my $name = $self->name;
915 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
917 # We need to check for circular inheritance here
918 # if we are are not on 5.10, cause 5.8 detects it
919 # late. This will do nothing if all is well, and
920 # blow up otherwise. Yes, it's an ugly hack, better
921 # suggestions are welcome.
923 ($name || return)->isa('This is a test for circular inheritance')
926 # if our mro is c3, we can
927 # just grab the linear_isa
928 if (mro::get_mro($name) eq 'c3') {
929 return @{ mro::get_linear_isa($name) }
933 # we can't grab the linear_isa for dfs
934 # since it has all the duplicates
939 Class::MOP::Class->initialize($_)->class_precedence_list()
940 } $self->superclasses()
948 my $fetch_and_prepare_method = sub {
949 my ($self, $method_name) = @_;
950 my $wrapped_metaclass = $self->wrapped_method_metaclass;
952 my $method = $self->get_method($method_name);
953 # if we dont have local ...
955 # try to find the next method
956 $method = $self->find_next_method_by_name($method_name);
957 # die if it does not exist
959 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
960 # and now make sure to wrap it
961 # even if it is already wrapped
962 # because we need a new sub ref
963 $method = $wrapped_metaclass->wrap($method,
964 package_name => $self->name,
965 name => $method_name,
969 # now make sure we wrap it properly
970 $method = $wrapped_metaclass->wrap($method,
971 package_name => $self->name,
972 name => $method_name,
973 ) unless $method->isa($wrapped_metaclass);
975 $self->add_method($method_name => $method);
979 sub add_before_method_modifier {
980 my ($self, $method_name, $method_modifier) = @_;
981 (defined $method_name && length $method_name)
982 || confess "You must pass in a method name";
983 my $method = $fetch_and_prepare_method->($self, $method_name);
984 $method->add_before_modifier(
985 subname(':before' => $method_modifier)
989 sub add_after_method_modifier {
990 my ($self, $method_name, $method_modifier) = @_;
991 (defined $method_name && length $method_name)
992 || confess "You must pass in a method name";
993 my $method = $fetch_and_prepare_method->($self, $method_name);
994 $method->add_after_modifier(
995 subname(':after' => $method_modifier)
999 sub add_around_method_modifier {
1000 my ($self, $method_name, $method_modifier) = @_;
1001 (defined $method_name && length $method_name)
1002 || confess "You must pass in a method name";
1003 my $method = $fetch_and_prepare_method->($self, $method_name);
1004 $method->add_around_modifier(
1005 subname(':around' => $method_modifier)
1010 # the methods above used to be named like this:
1011 # ${pkg}::${method}:(before|after|around)
1012 # but this proved problematic when using one modifier
1013 # to wrap multiple methods (something which is likely
1014 # to happen pretty regularly IMO). So instead of naming
1015 # it like this, I have chosen to just name them purely
1016 # with their modifier names, like so:
1017 # :(before|after|around)
1018 # The fact is that in a stack trace, it will be fairly
1019 # evident from the context what method they are attached
1020 # to, and so don't need the fully qualified name.
1023 sub find_method_by_name {
1024 my ($self, $method_name) = @_;
1025 (defined $method_name && length $method_name)
1026 || confess "You must define a method name to find";
1027 foreach my $class ($self->linearized_isa) {
1028 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1029 return $method if defined $method;
1034 sub get_all_methods {
1038 for my $class ( reverse $self->linearized_isa ) {
1039 my $meta = Class::MOP::Class->initialize($class);
1041 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1044 return values %methods;
1047 sub get_all_method_names {
1050 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
1053 sub find_all_methods_by_name {
1054 my ($self, $method_name) = @_;
1055 (defined $method_name && length $method_name)
1056 || confess "You must define a method name to find";
1058 foreach my $class ($self->linearized_isa) {
1059 # fetch the meta-class ...
1060 my $meta = Class::MOP::Class->initialize($class);
1062 name => $method_name,
1064 code => $meta->get_method($method_name)
1065 } if $meta->has_method($method_name);
1070 sub find_next_method_by_name {
1071 my ($self, $method_name) = @_;
1072 (defined $method_name && length $method_name)
1073 || confess "You must define a method name to find";
1074 my @cpl = $self->linearized_isa;
1075 shift @cpl; # discard ourselves
1076 foreach my $class (@cpl) {
1077 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1078 return $method if defined $method;
1083 sub update_meta_instance_dependencies {
1086 if ( $self->{meta_instance_dependencies} ) {
1087 return $self->add_meta_instance_dependencies;
1091 sub add_meta_instance_dependencies {
1094 $self->remove_meta_instance_dependencies;
1096 my @attrs = $self->get_all_attributes();
1099 my @classes = grep { not $seen{ $_->name }++ }
1100 map { $_->associated_class } @attrs;
1102 foreach my $class (@classes) {
1103 $class->add_dependent_meta_instance($self);
1106 $self->{meta_instance_dependencies} = \@classes;
1109 sub remove_meta_instance_dependencies {
1112 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1113 foreach my $class (@$classes) {
1114 $class->remove_dependent_meta_instance($self);
1124 sub add_dependent_meta_instance {
1125 my ( $self, $metaclass ) = @_;
1126 push @{ $self->{dependent_meta_instances} }, $metaclass;
1129 sub remove_dependent_meta_instance {
1130 my ( $self, $metaclass ) = @_;
1131 my $name = $metaclass->name;
1132 @$_ = grep { $_->name ne $name } @$_
1133 for $self->{dependent_meta_instances};
1136 sub invalidate_meta_instances {
1138 $_->invalidate_meta_instance()
1139 for $self, @{ $self->{dependent_meta_instances} };
1142 sub invalidate_meta_instance {
1144 undef $self->{_meta_instance};
1147 # check if we can reinitialize
1151 # if any local attr is defined
1152 return if $self->get_attribute_list;
1154 # or any non-declared methods
1155 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1156 return if $method->isa("Class::MOP::Method::Generated");
1157 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1165 sub is_mutable { 1 }
1166 sub is_immutable { 0 }
1168 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1170 sub _immutable_options {
1171 my ( $self, @args ) = @_;
1174 inline_accessors => 1,
1175 inline_constructor => 1,
1176 inline_destructor => 0,
1178 immutable_trait => $self->immutable_trait,
1179 constructor_name => $self->constructor_name,
1180 constructor_class => $self->constructor_class,
1181 destructor_class => $self->destructor_class,
1186 sub make_immutable {
1187 my ( $self, @args ) = @_;
1189 if ( $self->is_mutable ) {
1190 $self->_initialize_immutable( $self->_immutable_options(@args) );
1191 $self->_rebless_as_immutable(@args);
1202 if ( $self->is_immutable ) {
1203 my @args = $self->immutable_options;
1204 $self->_rebless_as_mutable();
1205 $self->_remove_inlined_code(@args);
1206 delete $self->{__immutable};
1214 sub _rebless_as_immutable {
1215 my ( $self, @args ) = @_;
1217 $self->{__immutable}{original_class} = ref $self;
1219 bless $self => $self->_immutable_metaclass(@args);
1222 sub _immutable_metaclass {
1223 my ( $self, %args ) = @_;
1225 if ( my $class = $args{immutable_metaclass} ) {
1229 my $trait = $args{immutable_trait} = $self->immutable_trait
1230 || confess "no immutable trait specified for $self";
1232 my $meta = $self->meta;
1233 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1237 if ( $meta_attr and $trait eq $meta_attr->default ) {
1238 # if the trait is the same as the default we try and pick a
1239 # predictable name for the immutable metaclass
1240 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1243 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1244 $trait, 'ForMetaClass', ref($self);
1248 if Class::MOP::is_class_loaded($class_name);
1250 # If the metaclass is a subclass of CMOP::Class which has had
1251 # metaclass roles applied (via Moose), then we want to make sure
1252 # that we preserve that anonymous class (see Fey::ORM for an
1253 # example of where this matters).
1254 my $meta_name = $meta->_real_ref_name;
1256 my $immutable_meta = $meta_name->create(
1258 superclasses => [ ref $self ],
1261 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1263 $immutable_meta->make_immutable(
1264 inline_constructor => 0,
1265 inline_accessors => 0,
1271 sub _remove_inlined_code {
1274 $self->remove_method( $_->name ) for $self->_inlined_methods;
1276 delete $self->{__immutable}{inlined_methods};
1279 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1281 sub _add_inlined_method {
1282 my ( $self, $method ) = @_;
1284 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1287 sub _initialize_immutable {
1288 my ( $self, %args ) = @_;
1290 $self->{__immutable}{options} = \%args;
1291 $self->_install_inlined_code(%args);
1294 sub _install_inlined_code {
1295 my ( $self, %args ) = @_;
1298 $self->_inline_accessors(%args) if $args{inline_accessors};
1299 $self->_inline_constructor(%args) if $args{inline_constructor};
1300 $self->_inline_destructor(%args) if $args{inline_destructor};
1303 sub _rebless_as_mutable {
1306 bless $self, $self->_get_mutable_metaclass_name;
1311 sub _inline_accessors {
1314 foreach my $attr_name ( $self->get_attribute_list ) {
1315 $self->get_attribute($attr_name)->install_accessors(1);
1319 sub _inline_constructor {
1320 my ( $self, %args ) = @_;
1322 my $name = $args{constructor_name};
1323 # A class may not even have a constructor, and that's okay.
1324 return unless defined $name;
1326 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1327 my $class = $self->name;
1328 warn "Not inlining a constructor for $class since it defines"
1329 . " its own constructor.\n"
1330 . "If you are certain you don't need to inline your"
1331 . " constructor, specify inline_constructor => 0 in your"
1332 . " call to $class->meta->make_immutable\n";
1336 my $constructor_class = $args{constructor_class};
1338 Class::MOP::load_class($constructor_class);
1340 my $constructor = $constructor_class->new(
1344 package_name => $self->name,
1348 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1349 $self->add_method( $name => $constructor );
1350 $self->_add_inlined_method($constructor);
1354 sub _inline_destructor {
1355 my ( $self, %args ) = @_;
1357 ( exists $args{destructor_class} && defined $args{destructor_class} )
1358 || confess "The 'inline_destructor' option is present, but "
1359 . "no destructor class was specified";
1361 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1362 my $class = $self->name;
1363 warn "Not inlining a destructor for $class since it defines"
1364 . " its own destructor.\n";
1368 my $destructor_class = $args{destructor_class};
1370 Class::MOP::load_class($destructor_class);
1372 return unless $destructor_class->is_needed($self);
1374 my $destructor = $destructor_class->new(
1377 package_name => $self->name,
1381 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1382 $self->add_method( 'DESTROY' => $destructor );
1383 $self->_add_inlined_method($destructor);
1395 Class::MOP::Class - Class Meta Object
1399 # assuming that class Foo
1400 # has been defined, you can
1402 # use this for introspection ...
1404 # add a method to Foo ...
1405 Foo->meta->add_method( 'bar' => sub {...} )
1407 # get a list of all the classes searched
1408 # the method dispatcher in the correct order
1409 Foo->meta->class_precedence_list()
1411 # remove a method from Foo
1412 Foo->meta->remove_method('bar');
1414 # or use this to actually create classes ...
1416 Class::MOP::Class->create(
1419 superclasses => ['Foo'],
1421 Class::MOP::Attribute->new('$bar'),
1422 Class::MOP::Attribute->new('$baz'),
1425 calculate_bar => sub {...},
1426 construct_baz => sub {...}
1433 The Class Protocol is the largest and most complex part of the
1434 Class::MOP meta-object protocol. It controls the introspection and
1435 manipulation of Perl 5 classes, and it can create them as well. The
1436 best way to understand what this module can do is to read the
1437 documentation for each of its methods.
1441 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1445 =head2 Class construction
1447 These methods all create new C<Class::MOP::Class> objects. These
1448 objects can represent existing classes or they can be used to create
1449 new classes from scratch.
1451 The metaclass object for a given class is a singleton. If you attempt
1452 to create a metaclass for the same class twice, you will just get the
1457 =item B<< Class::MOP::Class->create($package_name, %options) >>
1459 This method creates a new C<Class::MOP::Class> object with the given
1460 package name. It accepts a number of options:
1466 An optional version number for the newly created package.
1470 An optional authority for the newly created package.
1472 =item * superclasses
1474 An optional array reference of superclass names.
1478 An optional hash reference of methods for the class. The keys of the
1479 hash reference are method names and values are subroutine references.
1483 An optional array reference of L<Class::MOP::Attribute> objects.
1487 If true, a C<meta> method will not be installed into the class.
1491 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1493 This method works just like C<< Class::MOP::Class->create >> but it
1494 creates an "anonymous" class. In fact, the class does have a name, but
1495 that name is a unique name generated internally by this module.
1497 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1498 parameters that C<create> accepts.
1500 Anonymous classes are destroyed once the metaclass they are attached
1501 to goes out of scope, and will be removed from Perl's internal symbol
1504 All instances of an anonymous class keep a special reference to the
1505 metaclass object, which prevents the metaclass from going out of scope
1506 while any instances exist.
1508 This only works if the instance is based on a hash reference, however.
1510 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1512 This method will initialize a C<Class::MOP::Class> object for the
1513 named package. Unlike C<create>, this method I<will not> create a new
1516 The purpose of this method is to retrieve a C<Class::MOP::Class>
1517 object for introspecting an existing class.
1519 If an existing C<Class::MOP::Class> object exists for the named
1520 package, it will be returned, and any options provided will be
1523 If the object does not yet exist, it will be created.
1525 The valid options that can be passed to this method are
1526 C<attribute_metaclass>, C<method_metaclass>,
1527 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1528 optional, and default to the appropriate class in the C<Class::MOP>
1533 =head2 Object instance construction and cloning
1535 These methods are all related to creating and/or cloning object
1540 =item B<< $metaclass->clone_object($instance, %params) >>
1542 This method clones an existing object instance. Any parameters you
1543 provide are will override existing attribute values in the object.
1545 This is a convenience method for cloning an object instance, then
1546 blessing it into the appropriate package.
1548 You could implement a clone method in your class, using this method:
1551 my ($self, %params) = @_;
1552 $self->meta->clone_object($self, %params);
1555 =item B<< $metaclass->rebless_instance($instance, %params) >>
1557 This method changes the class of C<$instance> to the metaclass's class.
1559 You can only rebless an instance into a subclass of its current
1560 class. If you pass any additional parameters, these will be treated
1561 like constructor parameters and used to initialize the object's
1562 attributes. Any existing attributes that are already set will be
1565 Before reblessing the instance, this method will call
1566 C<rebless_instance_away> on the instance's current metaclass. This method
1567 will be passed the instance, the new metaclass, and any parameters
1568 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1569 does nothing; it is merely a hook.
1571 =item B<< $metaclass->rebless_instance_back($instance) >>
1573 Does the same thing as C<rebless_instance>, except that you can only
1574 rebless an instance into one of its superclasses. Any attributes that
1575 do not exist in the superclass will be deinitialized.
1577 This is a much more dangerous operation than C<rebless_instance>,
1578 especially when multiple inheritance is involved, so use this carefully!
1580 =item B<< $metaclass->new_object(%params) >>
1582 This method is used to create a new object of the metaclass's
1583 class. Any parameters you provide are used to initialize the
1584 instance's attributes. A special C<__INSTANCE__> key can be passed to
1585 provide an already generated instance, rather than having Class::MOP
1586 generate it for you. This is mostly useful for using Class::MOP with
1587 foreign classes which generate instances using their own constructors.
1589 =item B<< $metaclass->instance_metaclass >>
1591 Returns the class name of the instance metaclass. See
1592 L<Class::MOP::Instance> for more information on the instance
1595 =item B<< $metaclass->get_meta_instance >>
1597 Returns an instance of the C<instance_metaclass> to be used in the
1598 construction of a new instance of the class.
1600 =item B<< $metaclass->inline_create_instance($class_var) >>
1602 =item B<< $metaclass->inline_rebless_instance($instance_var, $class_var) >>
1604 These methods takes variable names, and use them to create an inline snippet
1605 of code that will create a new instance of the class.
1609 =head2 Informational predicates
1611 These are a few predicate methods for asking information about the
1616 =item B<< $metaclass->is_anon_class >>
1618 This returns true if the class was created by calling C<<
1619 Class::MOP::Class->create_anon_class >>.
1621 =item B<< $metaclass->is_mutable >>
1623 This returns true if the class is still mutable.
1625 =item B<< $metaclass->is_immutable >>
1627 This returns true if the class has been made immutable.
1629 =item B<< $metaclass->is_pristine >>
1631 A class is I<not> pristine if it has non-inherited attributes or if it
1632 has any generated methods.
1636 =head2 Inheritance Relationships
1640 =item B<< $metaclass->superclasses(@superclasses) >>
1642 This is a read-write accessor which represents the superclass
1643 relationships of the metaclass's class.
1645 This is basically sugar around getting and setting C<@ISA>.
1647 =item B<< $metaclass->class_precedence_list >>
1649 This returns a list of all of the class's ancestor classes. The
1650 classes are returned in method dispatch order.
1652 =item B<< $metaclass->linearized_isa >>
1654 This returns a list based on C<class_precedence_list> but with all
1657 =item B<< $metaclass->subclasses >>
1659 This returns a list of all subclasses for this class, even indirect
1662 =item B<< $metaclass->direct_subclasses >>
1664 This returns a list of immediate subclasses for this class, which does not
1665 include indirect subclasses.
1669 =head2 Method introspection and creation
1671 These methods allow you to introspect a class's methods, as well as
1672 add, remove, or change methods.
1674 Determining what is truly a method in a Perl 5 class requires some
1675 heuristics (aka guessing).
1677 Methods defined outside the package with a fully qualified name (C<sub
1678 Package::name { ... }>) will be included. Similarly, methods named
1679 with a fully qualified name using L<Sub::Name> are also included.
1681 However, we attempt to ignore imported functions.
1683 Ultimately, we are using heuristics to determine what truly is a
1684 method in a class, and these heuristics may get the wrong answer in
1685 some edge cases. However, for most "normal" cases the heuristics work
1690 =item B<< $metaclass->get_method($method_name) >>
1692 This will return a L<Class::MOP::Method> for the specified
1693 C<$method_name>. If the class does not have the specified method, it
1696 =item B<< $metaclass->has_method($method_name) >>
1698 Returns a boolean indicating whether or not the class defines the
1699 named method. It does not include methods inherited from parent
1702 =item B<< $metaclass->get_method_list >>
1704 This will return a list of method I<names> for all methods defined in
1707 =item B<< $metaclass->add_method($method_name, $method) >>
1709 This method takes a method name and a subroutine reference, and adds
1710 the method to the class.
1712 The subroutine reference can be a L<Class::MOP::Method>, and you are
1713 strongly encouraged to pass a meta method object instead of a code
1714 reference. If you do so, that object gets stored as part of the
1715 class's method map directly. If not, the meta information will have to
1716 be recreated later, and may be incorrect.
1718 If you provide a method object, this method will clone that object if
1719 the object's package name does not match the class name. This lets us
1720 track the original source of any methods added from other classes
1721 (notably Moose roles).
1723 =item B<< $metaclass->remove_method($method_name) >>
1725 Remove the named method from the class. This method returns the
1726 L<Class::MOP::Method> object for the method.
1728 =item B<< $metaclass->method_metaclass >>
1730 Returns the class name of the method metaclass, see
1731 L<Class::MOP::Method> for more information on the method metaclass.
1733 =item B<< $metaclass->wrapped_method_metaclass >>
1735 Returns the class name of the wrapped method metaclass, see
1736 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1739 =item B<< $metaclass->get_all_methods >>
1741 This will traverse the inheritance hierarchy and return a list of all
1742 the L<Class::MOP::Method> objects for this class and its parents.
1744 =item B<< $metaclass->find_method_by_name($method_name) >>
1746 This will return a L<Class::MOP::Method> for the specified
1747 C<$method_name>. If the class does not have the specified method, it
1750 Unlike C<get_method>, this method I<will> look for the named method in
1753 =item B<< $metaclass->get_all_method_names >>
1755 This will return a list of method I<names> for all of this class's
1756 methods, including inherited methods.
1758 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1760 This method looks for the named method in the class and all of its
1761 parents. It returns every matching method it finds in the inheritance
1762 tree, so it returns a list of methods.
1764 Each method is returned as a hash reference with three keys. The keys
1765 are C<name>, C<class>, and C<code>. The C<code> key has a
1766 L<Class::MOP::Method> object as its value.
1768 The list of methods is distinct.
1770 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1772 This method returns the first method in any superclass matching the
1773 given name. It is effectively the method that C<SUPER::$method_name>
1778 =head2 Attribute introspection and creation
1780 Because Perl 5 does not have a core concept of attributes in classes,
1781 we can only return information about attributes which have been added
1782 via this class's methods. We cannot discover information about
1783 attributes which are defined in terms of "regular" Perl 5 methods.
1787 =item B<< $metaclass->get_attribute($attribute_name) >>
1789 This will return a L<Class::MOP::Attribute> for the specified
1790 C<$attribute_name>. If the class does not have the specified
1791 attribute, it returns C<undef>.
1793 NOTE that get_attribute does not search superclasses, for that you
1794 need to use C<find_attribute_by_name>.
1796 =item B<< $metaclass->has_attribute($attribute_name) >>
1798 Returns a boolean indicating whether or not the class defines the
1799 named attribute. It does not include attributes inherited from parent
1802 =item B<< $metaclass->get_attribute_list >>
1804 This will return a list of attributes I<names> for all attributes
1805 defined in this class. Note that this operates on the current class
1806 only, it does not traverse the inheritance hierarchy.
1808 =item B<< $metaclass->get_all_attributes >>
1810 This will traverse the inheritance hierarchy and return a list of all
1811 the L<Class::MOP::Attribute> objects for this class and its parents.
1813 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1815 This will return a L<Class::MOP::Attribute> for the specified
1816 C<$attribute_name>. If the class does not have the specified
1817 attribute, it returns C<undef>.
1819 Unlike C<get_attribute>, this attribute I<will> look for the named
1820 attribute in superclasses.
1822 =item B<< $metaclass->add_attribute(...) >>
1824 This method accepts either an existing L<Class::MOP::Attribute>
1825 object or parameters suitable for passing to that class's C<new>
1828 The attribute provided will be added to the class.
1830 Any accessor methods defined by the attribute will be added to the
1831 class when the attribute is added.
1833 If an attribute of the same name already exists, the old attribute
1834 will be removed first.
1836 =item B<< $metaclass->remove_attribute($attribute_name) >>
1838 This will remove the named attribute from the class, and
1839 L<Class::MOP::Attribute> object.
1841 Removing an attribute also removes any accessor methods defined by the
1844 However, note that removing an attribute will only affect I<future>
1845 object instances created for this class, not existing instances.
1847 =item B<< $metaclass->attribute_metaclass >>
1849 Returns the class name of the attribute metaclass for this class. By
1850 default, this is L<Class::MOP::Attribute>.
1854 =head2 Class Immutability
1856 Making a class immutable "freezes" the class definition. You can no
1857 longer call methods which alter the class, such as adding or removing
1858 methods or attributes.
1860 Making a class immutable lets us optimize the class by inlining some
1861 methods, and also allows us to optimize some methods on the metaclass
1864 After immutabilization, the metaclass object will cache most informational
1865 methods that returns information about methods or attributes. Methods which
1866 would alter the class, such as C<add_attribute> and C<add_method>, will
1867 throw an error on an immutable metaclass object.
1869 The immutabilization system in L<Moose> takes much greater advantage
1870 of the inlining features than Class::MOP itself does.
1874 =item B<< $metaclass->make_immutable(%options) >>
1876 This method will create an immutable transformer and use it to make
1877 the class and its metaclass object immutable.
1879 This method accepts the following options:
1883 =item * inline_accessors
1885 =item * inline_constructor
1887 =item * inline_destructor
1889 These are all booleans indicating whether the specified method(s)
1892 By default, accessors and the constructor are inlined, but not the
1895 =item * immutable_trait
1897 The name of a class which will be used as a parent class for the
1898 metaclass object being made immutable. This "trait" implements the
1899 post-immutability functionality of the metaclass (but not the
1900 transformation itself).
1902 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1904 =item * constructor_name
1906 This is the constructor method name. This defaults to "new".
1908 =item * constructor_class
1910 The name of the method metaclass for constructors. It will be used to
1911 generate the inlined constructor. This defaults to
1912 "Class::MOP::Method::Constructor".
1914 =item * replace_constructor
1916 This is a boolean indicating whether an existing constructor should be
1917 replaced when inlining a constructor. This defaults to false.
1919 =item * destructor_class
1921 The name of the method metaclass for destructors. It will be used to
1922 generate the inlined destructor. This defaults to
1923 "Class::MOP::Method::Denstructor".
1925 =item * replace_destructor
1927 This is a boolean indicating whether an existing destructor should be
1928 replaced when inlining a destructor. This defaults to false.
1932 =item B<< $metaclass->immutable_options >>
1934 Returns a hash of the options used when making the class immutable, including
1935 both defaults and anything supplied by the user in the call to C<<
1936 $metaclass->make_immutable >>. This is useful if you need to temporarily make
1937 a class mutable and then restore immutability as it was before.
1939 =item B<< $metaclass->make_mutable >>
1941 Calling this method reverse the immutabilization transformation.
1945 =head2 Method Modifiers
1947 Method modifiers are hooks which allow a method to be wrapped with
1948 I<before>, I<after> and I<around> method modifiers. Every time a
1949 method is called, its modifiers are also called.
1951 A class can modify its own methods, as well as methods defined in
1954 =head3 How method modifiers work?
1956 Method modifiers work by wrapping the original method and then
1957 replacing it in the class's symbol table. The wrappers will handle
1958 calling all the modifiers in the appropriate order and preserving the
1959 calling context for the original method.
1961 The return values of C<before> and C<after> modifiers are
1962 ignored. This is because their purpose is B<not> to filter the input
1963 and output of the primary method (this is done with an I<around>
1966 This may seem like an odd restriction to some, but doing this allows
1967 for simple code to be added at the beginning or end of a method call
1968 without altering the function of the wrapped method or placing any
1969 extra responsibility on the code of the modifier.
1971 Of course if you have more complex needs, you can use the C<around>
1972 modifier which allows you to change both the parameters passed to the
1973 wrapped method, as well as its return value.
1975 Before and around modifiers are called in last-defined-first-called
1976 order, while after modifiers are called in first-defined-first-called
1977 order. So the call tree might looks something like this:
1989 =head3 What is the performance impact?
1991 Of course there is a performance cost associated with method
1992 modifiers, but we have made every effort to make that cost directly
1993 proportional to the number of modifier features you use.
1995 The wrapping method does its best to B<only> do as much work as it
1996 absolutely needs to. In order to do this we have moved some of the
1997 performance costs to set-up time, where they are easier to amortize.
1999 All this said, our benchmarks have indicated the following:
2001 simple wrapper with no modifiers 100% slower
2002 simple wrapper with simple before modifier 400% slower
2003 simple wrapper with simple after modifier 450% slower
2004 simple wrapper with simple around modifier 500-550% slower
2005 simple wrapper with all 3 modifiers 1100% slower
2007 These numbers may seem daunting, but you must remember, every feature
2008 comes with some cost. To put things in perspective, just doing a
2009 simple C<AUTOLOAD> which does nothing but extract the name of the
2010 method called and return it costs about 400% over a normal method
2015 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
2017 This wraps the specified method with the supplied subroutine
2018 reference. The modifier will be called as a method itself, and will
2019 receive the same arguments as are passed to the method.
2021 When the modifier exits, the wrapped method will be called.
2023 The return value of the modifier will be ignored.
2025 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2027 This wraps the specified method with the supplied subroutine
2028 reference. The modifier will be called as a method itself, and will
2029 receive the same arguments as are passed to the method.
2031 When the wrapped methods exits, the modifier will be called.
2033 The return value of the modifier will be ignored.
2035 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2037 This wraps the specified method with the supplied subroutine
2040 The first argument passed to the modifier will be a subroutine
2041 reference to the wrapped method. The second argument is the object,
2042 and after that come any arguments passed when the method is called.
2044 The around modifier can choose to call the original method, as well as
2045 what arguments to pass if it does so.
2047 The return value of the modifier is what will be seen by the caller.
2051 =head2 Introspection
2055 =item B<< Class::MOP::Class->meta >>
2057 This will return a L<Class::MOP::Class> instance for this class.
2059 It should also be noted that L<Class::MOP> will actually bootstrap
2060 this module by installing a number of attribute meta-objects into its
2067 Stevan Little E<lt>stevan@iinteractive.comE<gt>
2069 =head1 COPYRIGHT AND LICENSE
2071 Copyright 2006-2010 by Infinity Interactive, Inc.
2073 L<http://www.iinteractive.com>
2075 This library is free software; you can redistribute it and/or modify
2076 it under the same terms as Perl itself.