2 package Class::MOP::Class;
7 use Class::MOP::Instance;
8 use Class::MOP::Method::Wrapped;
9 use Class::MOP::Method::Accessor;
10 use Class::MOP::Method::Constructor;
11 use Class::MOP::MiniTrait;
14 use Scalar::Util 'blessed', 'reftype', 'weaken';
15 use Sub::Name 'subname';
16 use Devel::GlobalDestruction 'in_global_destruction';
18 use List::MoreUtils 'all';
20 our $VERSION = '1.11';
21 $VERSION = eval $VERSION;
22 our $AUTHORITY = 'cpan:STEVAN';
24 use base 'Class::MOP::Module',
25 'Class::MOP::Mixin::HasAttributes',
26 'Class::MOP::Mixin::HasMethods';
36 $package_name = shift;
39 $package_name = $options{package};
42 ($package_name && !ref($package_name))
43 || confess "You must pass a package name and it cannot be blessed";
45 return Class::MOP::get_metaclass_by_name($package_name)
46 || $class->_construct_class_instance(package => $package_name, @_);
50 my ( $class, @args ) = @_;
51 unshift @args, "package" if @args % 2;
53 my $old_metaclass = blessed($options{package})
55 : Class::MOP::get_metaclass_by_name($options{package});
56 $options{weaken} = Class::MOP::metaclass_is_weak($old_metaclass->name)
57 if !exists $options{weaken}
58 && blessed($old_metaclass)
59 && $old_metaclass->isa('Class::MOP::Class');
60 $old_metaclass->_remove_generated_metaobjects
61 if $old_metaclass && $old_metaclass->isa('Class::MOP::Class');
62 my $new_metaclass = $class->SUPER::reinitialize(%options);
63 $new_metaclass->_restore_metaobjects_from($old_metaclass)
64 if $old_metaclass && $old_metaclass->isa('Class::MOP::Class');
65 return $new_metaclass;
68 # NOTE: (meta-circularity)
69 # this is a special form of _construct_instance
70 # (see below), which is used to construct class
71 # meta-object instances for any Class::MOP::*
72 # class. All other classes will use the more
73 # normal &construct_instance.
74 sub _construct_class_instance {
76 my $options = @_ == 1 ? $_[0] : {@_};
77 my $package_name = $options->{package};
78 (defined $package_name && $package_name)
79 || confess "You must pass a package name";
81 # return the metaclass if we have it cached,
82 # and it is still defined (it has not been
83 # reaped by DESTROY yet, which can happen
84 # annoyingly enough during global destruction)
86 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
92 ? $class->_real_ref_name
95 # now create the metaclass
97 if ($class eq 'Class::MOP::Class') {
98 $meta = $class->_new($options);
102 # it is safe to use meta here because
103 # class will always be a subclass of
104 # Class::MOP::Class, which defines meta
105 $meta = $class->meta->_construct_instance($options)
108 # and check the metaclass compatibility
109 $meta->_check_metaclass_compatibility();
111 Class::MOP::store_metaclass_by_name($package_name, $meta);
114 # we need to weaken any anon classes
115 # so that they can call DESTROY properly
116 Class::MOP::weaken_metaclass($package_name) if $options->{weaken};
124 # NOTE: we need to deal with the possibility of class immutability here,
125 # and then get the name of the class appropriately
126 return $self->is_immutable
127 ? $self->_get_mutable_metaclass_name()
134 return Class::MOP::Class->initialize($class)->new_object(@_)
135 if $class ne __PACKAGE__;
137 my $options = @_ == 1 ? $_[0] : {@_};
140 # inherited from Class::MOP::Package
141 'package' => $options->{package},
144 # since the following attributes will
145 # actually be loaded from the symbol
146 # table, and actually bypass the instance
147 # entirely, we can just leave these things
148 # listed here for reference, because they
149 # should not actually have a value associated
151 'namespace' => \undef,
154 # inherited from Class::MOP::Module
156 'authority' => \undef,
158 # defined in Class::MOP::Class
159 'superclasses' => \undef,
162 'attribute_metaclass' =>
163 ( $options->{'attribute_metaclass'} || 'Class::MOP::Attribute' ),
164 'method_metaclass' =>
165 ( $options->{'method_metaclass'} || 'Class::MOP::Method' ),
166 'wrapped_method_metaclass' => (
167 $options->{'wrapped_method_metaclass'}
168 || 'Class::MOP::Method::Wrapped'
170 'instance_metaclass' =>
171 ( $options->{'instance_metaclass'} || 'Class::MOP::Instance' ),
172 'immutable_trait' => (
173 $options->{'immutable_trait'}
174 || 'Class::MOP::Class::Immutable::Trait'
176 'constructor_name' => ( $options->{constructor_name} || 'new' ),
177 'constructor_class' => (
178 $options->{constructor_class} || 'Class::MOP::Method::Constructor'
180 'destructor_class' => $options->{destructor_class},
184 ## Metaclass compatibility
186 my %base_metaclass = (
187 attribute_metaclass => 'Class::MOP::Attribute',
188 method_metaclass => 'Class::MOP::Method',
189 wrapped_method_metaclass => 'Class::MOP::Method::Wrapped',
190 instance_metaclass => 'Class::MOP::Instance',
191 constructor_class => 'Class::MOP::Method::Constructor',
192 destructor_class => 'Class::MOP::Method::Destructor',
195 sub _base_metaclasses { %base_metaclass }
198 sub _check_metaclass_compatibility {
201 my @superclasses = $self->superclasses
204 $self->_fix_metaclass_incompatibility(@superclasses);
206 my %base_metaclass = $self->_base_metaclasses;
208 # this is always okay ...
210 if ref($self) eq 'Class::MOP::Class'
212 my $meta = $self->$_;
213 !defined($meta) || $meta eq $base_metaclass{$_};
215 keys %base_metaclass;
217 for my $superclass (@superclasses) {
218 $self->_check_class_metaclass_compatibility($superclass);
221 for my $metaclass_type ( keys %base_metaclass ) {
222 next unless defined $self->$metaclass_type;
223 for my $superclass (@superclasses) {
224 $self->_check_single_metaclass_compatibility( $metaclass_type,
230 sub _check_class_metaclass_compatibility {
232 my ( $superclass_name ) = @_;
234 if (!$self->_class_metaclass_is_compatible($superclass_name)) {
235 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
237 my $super_meta_type = $super_meta->_real_ref_name;
239 confess "The metaclass of " . $self->name . " ("
240 . (ref($self)) . ")" . " is not compatible with "
241 . "the metaclass of its superclass, "
242 . $superclass_name . " (" . ($super_meta_type) . ")";
246 sub _class_metaclass_is_compatible {
248 my ( $superclass_name ) = @_;
250 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
253 my $super_meta_name = $super_meta->_real_ref_name;
255 return $self->_is_compatible_with($super_meta_name);
258 sub _check_single_metaclass_compatibility {
260 my ( $metaclass_type, $superclass_name ) = @_;
262 if (!$self->_single_metaclass_is_compatible($metaclass_type, $superclass_name)) {
263 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
264 my $metaclass_type_name = $metaclass_type;
265 $metaclass_type_name =~ s/_(?:meta)?class$//;
266 $metaclass_type_name =~ s/_/ /g;
267 confess "The $metaclass_type_name metaclass for "
268 . $self->name . " (" . ($self->$metaclass_type)
269 . ")" . " is not compatible with the "
270 . "$metaclass_type_name metaclass of its "
271 . "superclass, $superclass_name ("
272 . ($super_meta->$metaclass_type) . ")";
276 sub _single_metaclass_is_compatible {
278 my ( $metaclass_type, $superclass_name ) = @_;
280 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
283 # for instance, Moose::Meta::Class has a error_class attribute, but
284 # Class::MOP::Class doesn't - this shouldn't be an error
285 return 1 unless $super_meta->can($metaclass_type);
286 # for instance, Moose::Meta::Class has a destructor_class, but
287 # Class::MOP::Class doesn't - this shouldn't be an error
288 return 1 unless defined $super_meta->$metaclass_type;
289 # if metaclass is defined in superclass but not here, it's not compatible
290 # this is a really odd case
291 return 0 unless defined $self->$metaclass_type;
293 return $self->$metaclass_type->_is_compatible_with($super_meta->$metaclass_type);
296 sub _fix_metaclass_incompatibility {
298 my @supers = map { Class::MOP::Class->initialize($_) } @_;
301 for my $super (@supers) {
303 if $self->_can_fix_metaclass_incompatibility($super);
305 return unless $necessary;
307 for my $super (@supers) {
308 if (!$self->_class_metaclass_is_compatible($super->name)) {
309 $self->_fix_class_metaclass_incompatibility($super);
313 my %base_metaclass = $self->_base_metaclasses;
314 for my $metaclass_type (keys %base_metaclass) {
315 for my $super (@supers) {
316 if (!$self->_single_metaclass_is_compatible($metaclass_type, $super->name)) {
317 $self->_fix_single_metaclass_incompatibility(
318 $metaclass_type, $super
325 sub _can_fix_metaclass_incompatibility {
327 my ($super_meta) = @_;
329 return 1 if $self->_class_metaclass_can_be_made_compatible($super_meta);
331 my %base_metaclass = $self->_base_metaclasses;
332 for my $metaclass_type (keys %base_metaclass) {
333 return 1 if $self->_single_metaclass_can_be_made_compatible($super_meta, $metaclass_type);
339 sub _class_metaclass_can_be_made_compatible {
341 my ($super_meta) = @_;
343 return $self->_can_be_made_compatible_with($super_meta->_real_ref_name);
346 sub _single_metaclass_can_be_made_compatible {
348 my ($super_meta, $metaclass_type) = @_;
350 my $specific_meta = $self->$metaclass_type;
352 return unless $super_meta->can($metaclass_type);
353 my $super_specific_meta = $super_meta->$metaclass_type;
355 # for instance, Moose::Meta::Class has a destructor_class, but
356 # Class::MOP::Class doesn't - this shouldn't be an error
357 return unless defined $super_specific_meta;
359 # if metaclass is defined in superclass but not here, it's fixable
360 # this is a really odd case
361 return 1 unless defined $specific_meta;
363 return 1 if $specific_meta->_can_be_made_compatible_with($super_specific_meta);
366 sub _fix_class_metaclass_incompatibility {
368 my ( $super_meta ) = @_;
370 if ($self->_class_metaclass_can_be_made_compatible($super_meta)) {
372 || confess "Can't fix metaclass incompatibility for "
374 . " because it is not pristine.";
376 my $super_meta_name = $super_meta->_real_ref_name;
378 $self->_make_compatible_with($super_meta_name);
382 sub _fix_single_metaclass_incompatibility {
384 my ( $metaclass_type, $super_meta ) = @_;
386 if ($self->_single_metaclass_can_be_made_compatible($super_meta, $metaclass_type)) {
388 || confess "Can't fix metaclass incompatibility for "
390 . " because it is not pristine.";
392 my $new_metaclass = $self->$metaclass_type
393 ? $self->$metaclass_type->_get_compatible_metaclass($super_meta->$metaclass_type)
394 : $super_meta->$metaclass_type;
395 $self->{$metaclass_type} = $new_metaclass;
399 sub _restore_metaobjects_from {
403 $self->_restore_metamethods_from($old_meta);
404 $self->_restore_metaattributes_from($old_meta);
407 sub _remove_generated_metaobjects {
410 for my $attr (map { $self->get_attribute($_) } $self->get_attribute_list) {
411 $attr->remove_accessors;
419 # this should be sufficient, if you have a
420 # use case where it is not, write a test and
422 my $ANON_CLASS_SERIAL = 0;
425 # we need a sufficiently annoying prefix
426 # this should suffice for now, this is
427 # used in a couple of places below, so
428 # need to put it up here for now.
429 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
433 no warnings 'uninitialized';
434 $self->name =~ /^$ANON_CLASS_PREFIX/o;
437 sub create_anon_class {
438 my ($class, %options) = @_;
439 $options{weaken} = 1 unless exists $options{weaken};
440 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
441 return $class->create($package_name, %options);
445 # this will only get called for
446 # anon-classes, all other calls
447 # are assumed to occur during
448 # global destruction and so don't
449 # really need to be handled explicitly
453 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
455 no warnings 'uninitialized';
456 my $name = $self->name;
457 return unless $name =~ /^$ANON_CLASS_PREFIX/o;
459 # Moose does a weird thing where it replaces the metaclass for
460 # class when fixing metaclass incompatibility. In that case,
461 # we don't want to clean out the namespace now. We can detect
462 # that because Moose will explicitly update the singleton
463 # cache in Class::MOP.
464 my $current_meta = Class::MOP::get_metaclass_by_name($name);
465 return if $current_meta ne $self;
467 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/o);
469 @{$name . '::ISA'} = ();
470 %{$name . '::'} = ();
471 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
473 Class::MOP::remove_metaclass_by_name($name);
478 # creating classes with MOP ...
481 my ( $class, @args ) = @_;
483 unshift @args, 'package' if @args % 2 == 1;
485 my (%options) = @args;
486 my $package_name = $options{package};
488 (ref $options{superclasses} eq 'ARRAY')
489 || confess "You must pass an ARRAY ref of superclasses"
490 if exists $options{superclasses};
492 (ref $options{attributes} eq 'ARRAY')
493 || confess "You must pass an ARRAY ref of attributes"
494 if exists $options{attributes};
496 (ref $options{methods} eq 'HASH')
497 || confess "You must pass a HASH ref of methods"
498 if exists $options{methods};
500 $options{meta_name} = 'meta'
501 unless exists $options{meta_name};
503 my (%initialize_options) = @args;
504 delete @initialize_options{qw(
513 my $meta = $class->initialize( $package_name => %initialize_options );
515 $meta->_instantiate_module( $options{version}, $options{authority} );
517 $meta->_add_meta_method($options{meta_name})
518 if defined $options{meta_name};
520 $meta->superclasses(@{$options{superclasses}})
521 if exists $options{superclasses};
523 # process attributes first, so that they can
524 # install accessors, but locally defined methods
525 # can then overwrite them. It is maybe a little odd, but
526 # I think this should be the order of things.
527 if (exists $options{attributes}) {
528 foreach my $attr (@{$options{attributes}}) {
529 $meta->add_attribute($attr);
532 if (exists $options{methods}) {
533 foreach my $method_name (keys %{$options{methods}}) {
534 $meta->add_method($method_name, $options{methods}->{$method_name});
540 # Instance Construction & Cloning
546 # we need to protect the integrity of the
547 # Class::MOP::Class singletons here, so we
548 # delegate this to &construct_class_instance
549 # which will deal with the singletons
550 return $class->_construct_class_instance(@_)
551 if $class->name->isa('Class::MOP::Class');
552 return $class->_construct_instance(@_);
555 sub _construct_instance {
557 my $params = @_ == 1 ? $_[0] : {@_};
558 my $meta_instance = $class->get_meta_instance();
560 # the code below is almost certainly incorrect
561 # but this is foreign inheritance, so we might
562 # have to kludge it in the end.
564 if (my $instance_class = blessed($params->{__INSTANCE__})) {
565 ($instance_class eq $class->name)
566 || confess "Objects passed as the __INSTANCE__ parameter must "
567 . "already be blessed into the correct class, but "
568 . "$params->{__INSTANCE__} is not a " . $class->name;
569 $instance = $params->{__INSTANCE__};
571 elsif (exists $params->{__INSTANCE__}) {
572 confess "The __INSTANCE__ parameter must be a blessed reference, not "
573 . $params->{__INSTANCE__};
576 $instance = $meta_instance->create_instance();
578 foreach my $attr ($class->get_all_attributes()) {
579 $attr->initialize_instance_slot($meta_instance, $instance, $params);
581 if (Class::MOP::metaclass_is_weak($class->name)) {
582 $meta_instance->_set_mop_slot($instance, $class);
587 sub _inline_new_object {
591 'my $class = shift;',
592 '$class = Scalar::Util::blessed($class) || $class;',
593 $self->_inline_fallback_constructor('$class'),
594 $self->_inline_params('$params', '$class'),
595 $self->_inline_generate_instance('$instance', '$class'),
596 $self->_inline_slot_initializers,
597 $self->_inline_preserve_weak_metaclasses,
598 $self->_inline_extra_init,
603 sub _inline_fallback_constructor {
607 'return ' . $self->_generate_fallback_constructor($class),
608 'if ' . $class . ' ne \'' . $self->name . '\';',
612 sub _generate_fallback_constructor {
615 return 'Class::MOP::Class->initialize(' . $class . ')->new_object(@_)',
620 my ($params, $class) = @_;
622 'my ' . $params . ' = @_ == 1 ? $_[0] : {@_};',
626 sub _inline_generate_instance {
628 my ($inst, $class) = @_;
630 'my ' . $inst . ' = ' . $self->_inline_create_instance($class) . ';',
634 sub _inline_create_instance {
637 return $self->get_meta_instance->inline_create_instance(@_);
640 sub _inline_slot_initializers {
645 return map { $self->_inline_slot_initializer($_, $idx++) }
646 sort { $a->name cmp $b->name } $self->get_all_attributes;
649 sub _inline_slot_initializer {
651 my ($attr, $idx) = @_;
653 if (defined(my $init_arg = $attr->init_arg)) {
655 'if (exists $params->{\'' . $init_arg . '\'}) {',
656 $self->_inline_init_attr_from_constructor($attr, $idx),
659 if (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
668 elsif (my @default = $self->_inline_init_attr_from_default($attr, $idx)) {
680 sub _inline_init_attr_from_constructor {
682 my ($attr, $idx) = @_;
684 return $attr->_inline_set_value(
685 '$instance', '$params->{\'' . $attr->init_arg . '\'}'
689 sub _inline_init_attr_from_default {
691 my ($attr, $idx) = @_;
693 my $default = $self->_inline_default_value($attr, $idx);
694 return unless $default;
696 return $attr->_inline_set_value('$instance', $default);
699 sub _inline_default_value {
701 my ($attr, $index) = @_;
703 if ($attr->has_default) {
705 # default values can either be CODE refs
706 # in which case we need to call them. Or
707 # they can be scalars (strings/numbers)
708 # in which case we can just deal with them
709 # in the code we eval.
710 if ($attr->is_default_a_coderef) {
711 return '$defaults->[' . $index . ']->($instance)';
714 return '$defaults->[' . $index . ']';
717 elsif ($attr->has_builder) {
718 return '$instance->' . $attr->builder;
725 sub _inline_preserve_weak_metaclasses {
727 if (Class::MOP::metaclass_is_weak($self->name)) {
729 $self->_inline_set_mop_slot(
730 '$instance', 'Class::MOP::class_of($class)'
739 sub _inline_extra_init { }
742 sub get_meta_instance {
744 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
747 sub _create_meta_instance {
750 my $instance = $self->instance_metaclass->new(
751 associated_metaclass => $self,
752 attributes => [ $self->get_all_attributes() ],
755 $self->add_meta_instance_dependencies()
756 if $instance->is_dependent_on_superclasses();
761 sub _inline_rebless_instance {
764 return $self->get_meta_instance->inline_rebless_instance_structure(@_);
767 sub _inline_get_mop_slot {
770 return $self->get_meta_instance->_inline_get_mop_slot(@_);
773 sub _inline_set_mop_slot {
776 return $self->get_meta_instance->_inline_set_mop_slot(@_);
779 sub _inline_clear_mop_slot {
782 return $self->get_meta_instance->_inline_clear_mop_slot(@_);
787 my $instance = shift;
788 (blessed($instance) && $instance->isa($class->name))
789 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
792 # we need to protect the integrity of the
793 # Class::MOP::Class singletons here, they
794 # should not be cloned.
795 return $instance if $instance->isa('Class::MOP::Class');
796 $class->_clone_instance($instance, @_);
799 sub _clone_instance {
800 my ($class, $instance, %params) = @_;
802 || confess "You can only clone instances, ($instance) is not a blessed instance";
803 my $meta_instance = $class->get_meta_instance();
804 my $clone = $meta_instance->clone_instance($instance);
805 foreach my $attr ($class->get_all_attributes()) {
806 if ( defined( my $init_arg = $attr->init_arg ) ) {
807 if (exists $params{$init_arg}) {
808 $attr->set_value($clone, $params{$init_arg});
815 sub _force_rebless_instance {
816 my ($self, $instance, %params) = @_;
817 my $old_metaclass = Class::MOP::class_of($instance);
819 $old_metaclass->rebless_instance_away($instance, $self, %params)
822 my $meta_instance = $self->get_meta_instance;
824 if (Class::MOP::metaclass_is_weak($old_metaclass->name)) {
825 $meta_instance->_clear_mop_slot($instance);
829 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
830 $meta_instance->rebless_instance_structure($_[1], $self);
832 $self->_fixup_attributes_after_rebless($instance, $old_metaclass, %params);
834 if (Class::MOP::metaclass_is_weak($self->name)) {
835 $meta_instance->_set_mop_slot($instance, $self);
839 sub rebless_instance {
840 my ($self, $instance, %params) = @_;
841 my $old_metaclass = Class::MOP::class_of($instance);
843 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
844 $self->name->isa($old_class)
845 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
847 $self->_force_rebless_instance($_[1], %params);
852 sub rebless_instance_back {
853 my ( $self, $instance ) = @_;
854 my $old_metaclass = Class::MOP::class_of($instance);
857 = $old_metaclass ? $old_metaclass->name : blessed($instance);
858 $old_class->isa( $self->name )
860 "You may rebless only into a superclass of ($old_class), of which ("
864 $self->_force_rebless_instance($_[1]);
869 sub rebless_instance_away {
870 # this intentionally does nothing, it is just a hook
873 sub _fixup_attributes_after_rebless {
875 my ($instance, $rebless_from, %params) = @_;
876 my $meta_instance = $self->get_meta_instance;
878 for my $attr ( $rebless_from->get_all_attributes ) {
879 next if $self->find_attribute_by_name( $attr->name );
880 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
883 foreach my $attr ( $self->get_all_attributes ) {
884 if ( $attr->has_value($instance) ) {
885 if ( defined( my $init_arg = $attr->init_arg ) ) {
886 $params{$init_arg} = $attr->get_value($instance)
887 unless exists $params{$init_arg};
890 $attr->set_value($instance, $attr->get_value($instance));
895 foreach my $attr ($self->get_all_attributes) {
896 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
900 sub _attach_attribute {
901 my ($self, $attribute) = @_;
902 $attribute->attach_to_class($self);
905 sub _post_add_attribute {
906 my ( $self, $attribute ) = @_;
908 $self->invalidate_meta_instances;
910 # invalidate package flag here
913 $attribute->install_accessors;
916 $self->remove_attribute( $attribute->name );
921 sub remove_attribute {
924 my $removed_attribute = $self->SUPER::remove_attribute(@_)
927 $self->invalidate_meta_instances;
929 $removed_attribute->remove_accessors;
930 $removed_attribute->detach_from_class;
932 return$removed_attribute;
935 sub find_attribute_by_name {
936 my ( $self, $attr_name ) = @_;
938 foreach my $class ( $self->linearized_isa ) {
939 # fetch the meta-class ...
940 my $meta = Class::MOP::Class->initialize($class);
941 return $meta->get_attribute($attr_name)
942 if $meta->has_attribute($attr_name);
948 sub get_all_attributes {
950 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
951 reverse $self->linearized_isa;
952 return values %attrs;
960 my $isa = $self->get_or_add_package_symbol('@ISA');
967 # on 5.8 and below, we need to call
968 # a method to get Perl to detect
969 # a cycle in the class hierarchy
970 my $class = $self->name;
974 # we need to check the metaclass
975 # compatibility here so that we can
976 # be sure that the superclass is
977 # not potentially creating an issues
978 # we don't know about
980 $self->_check_metaclass_compatibility();
981 $self->_superclasses_updated();
987 sub _superclasses_updated {
989 $self->update_meta_instance_dependencies();
990 # keep strong references to all our parents, so they don't disappear if
991 # they are anon classes and don't have any direct instances
992 $self->_superclass_metas(
993 map { Class::MOP::class_of($_) } $self->superclasses
997 sub _superclass_metas {
999 $self->{_superclass_metas} = [@_];
1004 my $super_class = $self->name;
1006 return @{ $super_class->mro::get_isarev() };
1009 sub direct_subclasses {
1011 my $super_class = $self->name;
1016 } Class::MOP::Class->initialize($_)->superclasses
1017 } $self->subclasses;
1020 sub linearized_isa {
1021 return @{ mro::get_linear_isa( (shift)->name ) };
1024 sub class_precedence_list {
1026 my $name = $self->name;
1028 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
1030 # We need to check for circular inheritance here
1031 # if we are are not on 5.10, cause 5.8 detects it
1032 # late. This will do nothing if all is well, and
1033 # blow up otherwise. Yes, it's an ugly hack, better
1034 # suggestions are welcome.
1036 ($name || return)->isa('This is a test for circular inheritance')
1039 # if our mro is c3, we can
1040 # just grab the linear_isa
1041 if (mro::get_mro($name) eq 'c3') {
1042 return @{ mro::get_linear_isa($name) }
1046 # we can't grab the linear_isa for dfs
1047 # since it has all the duplicates
1052 Class::MOP::Class->initialize($_)->class_precedence_list()
1053 } $self->superclasses()
1061 my $fetch_and_prepare_method = sub {
1062 my ($self, $method_name) = @_;
1063 my $wrapped_metaclass = $self->wrapped_method_metaclass;
1065 my $method = $self->get_method($method_name);
1066 # if we dont have local ...
1068 # try to find the next method
1069 $method = $self->find_next_method_by_name($method_name);
1070 # die if it does not exist
1072 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
1073 # and now make sure to wrap it
1074 # even if it is already wrapped
1075 # because we need a new sub ref
1076 $method = $wrapped_metaclass->wrap($method,
1077 package_name => $self->name,
1078 name => $method_name,
1082 # now make sure we wrap it properly
1083 $method = $wrapped_metaclass->wrap($method,
1084 package_name => $self->name,
1085 name => $method_name,
1086 ) unless $method->isa($wrapped_metaclass);
1088 $self->add_method($method_name => $method);
1092 sub add_before_method_modifier {
1093 my ($self, $method_name, $method_modifier) = @_;
1094 (defined $method_name && length $method_name)
1095 || confess "You must pass in a method name";
1096 my $method = $fetch_and_prepare_method->($self, $method_name);
1097 $method->add_before_modifier(
1098 subname(':before' => $method_modifier)
1102 sub add_after_method_modifier {
1103 my ($self, $method_name, $method_modifier) = @_;
1104 (defined $method_name && length $method_name)
1105 || confess "You must pass in a method name";
1106 my $method = $fetch_and_prepare_method->($self, $method_name);
1107 $method->add_after_modifier(
1108 subname(':after' => $method_modifier)
1112 sub add_around_method_modifier {
1113 my ($self, $method_name, $method_modifier) = @_;
1114 (defined $method_name && length $method_name)
1115 || confess "You must pass in a method name";
1116 my $method = $fetch_and_prepare_method->($self, $method_name);
1117 $method->add_around_modifier(
1118 subname(':around' => $method_modifier)
1123 # the methods above used to be named like this:
1124 # ${pkg}::${method}:(before|after|around)
1125 # but this proved problematic when using one modifier
1126 # to wrap multiple methods (something which is likely
1127 # to happen pretty regularly IMO). So instead of naming
1128 # it like this, I have chosen to just name them purely
1129 # with their modifier names, like so:
1130 # :(before|after|around)
1131 # The fact is that in a stack trace, it will be fairly
1132 # evident from the context what method they are attached
1133 # to, and so don't need the fully qualified name.
1136 sub find_method_by_name {
1137 my ($self, $method_name) = @_;
1138 (defined $method_name && length $method_name)
1139 || confess "You must define a method name to find";
1140 foreach my $class ($self->linearized_isa) {
1141 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1142 return $method if defined $method;
1147 sub get_all_methods {
1151 for my $class ( reverse $self->linearized_isa ) {
1152 my $meta = Class::MOP::Class->initialize($class);
1154 $methods{ $_->name } = $_ for $meta->_get_local_methods;
1157 return values %methods;
1160 sub get_all_method_names {
1163 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
1166 sub find_all_methods_by_name {
1167 my ($self, $method_name) = @_;
1168 (defined $method_name && length $method_name)
1169 || confess "You must define a method name to find";
1171 foreach my $class ($self->linearized_isa) {
1172 # fetch the meta-class ...
1173 my $meta = Class::MOP::Class->initialize($class);
1175 name => $method_name,
1177 code => $meta->get_method($method_name)
1178 } if $meta->has_method($method_name);
1183 sub find_next_method_by_name {
1184 my ($self, $method_name) = @_;
1185 (defined $method_name && length $method_name)
1186 || confess "You must define a method name to find";
1187 my @cpl = $self->linearized_isa;
1188 shift @cpl; # discard ourselves
1189 foreach my $class (@cpl) {
1190 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
1191 return $method if defined $method;
1196 sub update_meta_instance_dependencies {
1199 if ( $self->{meta_instance_dependencies} ) {
1200 return $self->add_meta_instance_dependencies;
1204 sub add_meta_instance_dependencies {
1207 $self->remove_meta_instance_dependencies;
1209 my @attrs = $self->get_all_attributes();
1212 my @classes = grep { not $seen{ $_->name }++ }
1213 map { $_->associated_class } @attrs;
1215 foreach my $class (@classes) {
1216 $class->add_dependent_meta_instance($self);
1219 $self->{meta_instance_dependencies} = \@classes;
1222 sub remove_meta_instance_dependencies {
1225 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1226 foreach my $class (@$classes) {
1227 $class->remove_dependent_meta_instance($self);
1237 sub add_dependent_meta_instance {
1238 my ( $self, $metaclass ) = @_;
1239 push @{ $self->{dependent_meta_instances} }, $metaclass;
1242 sub remove_dependent_meta_instance {
1243 my ( $self, $metaclass ) = @_;
1244 my $name = $metaclass->name;
1245 @$_ = grep { $_->name ne $name } @$_
1246 for $self->{dependent_meta_instances};
1249 sub invalidate_meta_instances {
1251 $_->invalidate_meta_instance()
1252 for $self, @{ $self->{dependent_meta_instances} };
1255 sub invalidate_meta_instance {
1257 undef $self->{_meta_instance};
1260 # check if we can reinitialize
1264 # if any local attr is defined
1265 return if $self->get_attribute_list;
1267 # or any non-declared methods
1268 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1269 return if $method->isa("Class::MOP::Method::Generated");
1270 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1278 sub is_mutable { 1 }
1279 sub is_immutable { 0 }
1281 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1283 sub _immutable_options {
1284 my ( $self, @args ) = @_;
1287 inline_accessors => 1,
1288 inline_constructor => 1,
1289 inline_destructor => 0,
1291 immutable_trait => $self->immutable_trait,
1292 constructor_name => $self->constructor_name,
1293 constructor_class => $self->constructor_class,
1294 destructor_class => $self->destructor_class,
1299 sub make_immutable {
1300 my ( $self, @args ) = @_;
1302 if ( $self->is_mutable ) {
1303 $self->_initialize_immutable( $self->_immutable_options(@args) );
1304 $self->_rebless_as_immutable(@args);
1315 if ( $self->is_immutable ) {
1316 my @args = $self->immutable_options;
1317 $self->_rebless_as_mutable();
1318 $self->_remove_inlined_code(@args);
1319 delete $self->{__immutable};
1327 sub _rebless_as_immutable {
1328 my ( $self, @args ) = @_;
1330 $self->{__immutable}{original_class} = ref $self;
1332 bless $self => $self->_immutable_metaclass(@args);
1335 sub _immutable_metaclass {
1336 my ( $self, %args ) = @_;
1338 if ( my $class = $args{immutable_metaclass} ) {
1342 my $trait = $args{immutable_trait} = $self->immutable_trait
1343 || confess "no immutable trait specified for $self";
1345 my $meta = $self->meta;
1346 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1350 if ( $meta_attr and $trait eq $meta_attr->default ) {
1351 # if the trait is the same as the default we try and pick a
1352 # predictable name for the immutable metaclass
1353 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1356 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1357 $trait, 'ForMetaClass', ref($self);
1361 if Class::MOP::is_class_loaded($class_name);
1363 # If the metaclass is a subclass of CMOP::Class which has had
1364 # metaclass roles applied (via Moose), then we want to make sure
1365 # that we preserve that anonymous class (see Fey::ORM for an
1366 # example of where this matters).
1367 my $meta_name = $meta->_real_ref_name;
1369 my $immutable_meta = $meta_name->create(
1371 superclasses => [ ref $self ],
1374 Class::MOP::MiniTrait::apply( $immutable_meta, $trait );
1376 $immutable_meta->make_immutable(
1377 inline_constructor => 0,
1378 inline_accessors => 0,
1384 sub _remove_inlined_code {
1387 $self->remove_method( $_->name ) for $self->_inlined_methods;
1389 delete $self->{__immutable}{inlined_methods};
1392 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1394 sub _add_inlined_method {
1395 my ( $self, $method ) = @_;
1397 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1400 sub _initialize_immutable {
1401 my ( $self, %args ) = @_;
1403 $self->{__immutable}{options} = \%args;
1404 $self->_install_inlined_code(%args);
1407 sub _install_inlined_code {
1408 my ( $self, %args ) = @_;
1411 $self->_inline_accessors(%args) if $args{inline_accessors};
1412 $self->_inline_constructor(%args) if $args{inline_constructor};
1413 $self->_inline_destructor(%args) if $args{inline_destructor};
1416 sub _rebless_as_mutable {
1419 bless $self, $self->_get_mutable_metaclass_name;
1424 sub _inline_accessors {
1427 foreach my $attr_name ( $self->get_attribute_list ) {
1428 $self->get_attribute($attr_name)->install_accessors(1);
1432 sub _inline_constructor {
1433 my ( $self, %args ) = @_;
1435 my $name = $args{constructor_name};
1436 # A class may not even have a constructor, and that's okay.
1437 return unless defined $name;
1439 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1440 my $class = $self->name;
1441 warn "Not inlining a constructor for $class since it defines"
1442 . " its own constructor.\n"
1443 . "If you are certain you don't need to inline your"
1444 . " constructor, specify inline_constructor => 0 in your"
1445 . " call to $class->meta->make_immutable\n";
1449 my $constructor_class = $args{constructor_class};
1451 Class::MOP::load_class($constructor_class);
1453 my $constructor = $constructor_class->new(
1457 package_name => $self->name,
1461 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1462 $self->add_method( $name => $constructor );
1463 $self->_add_inlined_method($constructor);
1467 sub _inline_destructor {
1468 my ( $self, %args ) = @_;
1470 ( exists $args{destructor_class} && defined $args{destructor_class} )
1471 || confess "The 'inline_destructor' option is present, but "
1472 . "no destructor class was specified";
1474 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1475 my $class = $self->name;
1476 warn "Not inlining a destructor for $class since it defines"
1477 . " its own destructor.\n";
1481 my $destructor_class = $args{destructor_class};
1483 Class::MOP::load_class($destructor_class);
1485 return unless $destructor_class->is_needed($self);
1487 my $destructor = $destructor_class->new(
1490 package_name => $self->name,
1494 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1495 $self->add_method( 'DESTROY' => $destructor );
1496 $self->_add_inlined_method($destructor);
1508 Class::MOP::Class - Class Meta Object
1512 # assuming that class Foo
1513 # has been defined, you can
1515 # use this for introspection ...
1517 # add a method to Foo ...
1518 Foo->meta->add_method( 'bar' => sub {...} )
1520 # get a list of all the classes searched
1521 # the method dispatcher in the correct order
1522 Foo->meta->class_precedence_list()
1524 # remove a method from Foo
1525 Foo->meta->remove_method('bar');
1527 # or use this to actually create classes ...
1529 Class::MOP::Class->create(
1532 superclasses => ['Foo'],
1534 Class::MOP::Attribute->new('$bar'),
1535 Class::MOP::Attribute->new('$baz'),
1538 calculate_bar => sub {...},
1539 construct_baz => sub {...}
1546 The Class Protocol is the largest and most complex part of the
1547 Class::MOP meta-object protocol. It controls the introspection and
1548 manipulation of Perl 5 classes, and it can create them as well. The
1549 best way to understand what this module can do is to read the
1550 documentation for each of its methods.
1554 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1558 =head2 Class construction
1560 These methods all create new C<Class::MOP::Class> objects. These
1561 objects can represent existing classes or they can be used to create
1562 new classes from scratch.
1564 The metaclass object for a given class is a singleton. If you attempt
1565 to create a metaclass for the same class twice, you will just get the
1570 =item B<< Class::MOP::Class->create($package_name, %options) >>
1572 This method creates a new C<Class::MOP::Class> object with the given
1573 package name. It accepts a number of options:
1579 An optional version number for the newly created package.
1583 An optional authority for the newly created package.
1585 =item * superclasses
1587 An optional array reference of superclass names.
1591 An optional hash reference of methods for the class. The keys of the
1592 hash reference are method names and values are subroutine references.
1596 An optional array reference of L<Class::MOP::Attribute> objects.
1600 Specifies the name to install the C<meta> method for this class under.
1601 If it is not passed, C<meta> is assumed, and if C<undef> is explicitly
1602 given, no meta method will be installed.
1606 If true, the metaclass that is stored in the global cache will be a
1609 Classes created in this way are destroyed once the metaclass they are
1610 attached to goes out of scope, and will be removed from Perl's internal
1613 All instances of a class with a weakened metaclass keep a special
1614 reference to the metaclass object, which prevents the metaclass from
1615 going out of scope while any instances exist.
1617 This only works if the instance is based on a hash reference, however.
1621 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1623 This method works just like C<< Class::MOP::Class->create >> but it
1624 creates an "anonymous" class. In fact, the class does have a name, but
1625 that name is a unique name generated internally by this module.
1627 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1628 parameters that C<create> accepts.
1630 Anonymous classes default to C<< weaken => 1 >>, although this can be
1633 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1635 This method will initialize a C<Class::MOP::Class> object for the
1636 named package. Unlike C<create>, this method I<will not> create a new
1639 The purpose of this method is to retrieve a C<Class::MOP::Class>
1640 object for introspecting an existing class.
1642 If an existing C<Class::MOP::Class> object exists for the named
1643 package, it will be returned, and any options provided will be
1646 If the object does not yet exist, it will be created.
1648 The valid options that can be passed to this method are
1649 C<attribute_metaclass>, C<method_metaclass>,
1650 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1651 optional, and default to the appropriate class in the C<Class::MOP>
1656 =head2 Object instance construction and cloning
1658 These methods are all related to creating and/or cloning object
1663 =item B<< $metaclass->clone_object($instance, %params) >>
1665 This method clones an existing object instance. Any parameters you
1666 provide are will override existing attribute values in the object.
1668 This is a convenience method for cloning an object instance, then
1669 blessing it into the appropriate package.
1671 You could implement a clone method in your class, using this method:
1674 my ($self, %params) = @_;
1675 $self->meta->clone_object($self, %params);
1678 =item B<< $metaclass->rebless_instance($instance, %params) >>
1680 This method changes the class of C<$instance> to the metaclass's class.
1682 You can only rebless an instance into a subclass of its current
1683 class. If you pass any additional parameters, these will be treated
1684 like constructor parameters and used to initialize the object's
1685 attributes. Any existing attributes that are already set will be
1688 Before reblessing the instance, this method will call
1689 C<rebless_instance_away> on the instance's current metaclass. This method
1690 will be passed the instance, the new metaclass, and any parameters
1691 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1692 does nothing; it is merely a hook.
1694 =item B<< $metaclass->rebless_instance_back($instance) >>
1696 Does the same thing as C<rebless_instance>, except that you can only
1697 rebless an instance into one of its superclasses. Any attributes that
1698 do not exist in the superclass will be deinitialized.
1700 This is a much more dangerous operation than C<rebless_instance>,
1701 especially when multiple inheritance is involved, so use this carefully!
1703 =item B<< $metaclass->new_object(%params) >>
1705 This method is used to create a new object of the metaclass's
1706 class. Any parameters you provide are used to initialize the
1707 instance's attributes. A special C<__INSTANCE__> key can be passed to
1708 provide an already generated instance, rather than having Class::MOP
1709 generate it for you. This is mostly useful for using Class::MOP with
1710 foreign classes which generate instances using their own constructors.
1712 =item B<< $metaclass->instance_metaclass >>
1714 Returns the class name of the instance metaclass. See
1715 L<Class::MOP::Instance> for more information on the instance
1718 =item B<< $metaclass->get_meta_instance >>
1720 Returns an instance of the C<instance_metaclass> to be used in the
1721 construction of a new instance of the class.
1725 =head2 Informational predicates
1727 These are a few predicate methods for asking information about the
1732 =item B<< $metaclass->is_anon_class >>
1734 This returns true if the class was created by calling C<<
1735 Class::MOP::Class->create_anon_class >>.
1737 =item B<< $metaclass->is_mutable >>
1739 This returns true if the class is still mutable.
1741 =item B<< $metaclass->is_immutable >>
1743 This returns true if the class has been made immutable.
1745 =item B<< $metaclass->is_pristine >>
1747 A class is I<not> pristine if it has non-inherited attributes or if it
1748 has any generated methods.
1752 =head2 Inheritance Relationships
1756 =item B<< $metaclass->superclasses(@superclasses) >>
1758 This is a read-write accessor which represents the superclass
1759 relationships of the metaclass's class.
1761 This is basically sugar around getting and setting C<@ISA>.
1763 =item B<< $metaclass->class_precedence_list >>
1765 This returns a list of all of the class's ancestor classes. The
1766 classes are returned in method dispatch order.
1768 =item B<< $metaclass->linearized_isa >>
1770 This returns a list based on C<class_precedence_list> but with all
1773 =item B<< $metaclass->subclasses >>
1775 This returns a list of all subclasses for this class, even indirect
1778 =item B<< $metaclass->direct_subclasses >>
1780 This returns a list of immediate subclasses for this class, which does not
1781 include indirect subclasses.
1785 =head2 Method introspection and creation
1787 These methods allow you to introspect a class's methods, as well as
1788 add, remove, or change methods.
1790 Determining what is truly a method in a Perl 5 class requires some
1791 heuristics (aka guessing).
1793 Methods defined outside the package with a fully qualified name (C<sub
1794 Package::name { ... }>) will be included. Similarly, methods named
1795 with a fully qualified name using L<Sub::Name> are also included.
1797 However, we attempt to ignore imported functions.
1799 Ultimately, we are using heuristics to determine what truly is a
1800 method in a class, and these heuristics may get the wrong answer in
1801 some edge cases. However, for most "normal" cases the heuristics work
1806 =item B<< $metaclass->get_method($method_name) >>
1808 This will return a L<Class::MOP::Method> for the specified
1809 C<$method_name>. If the class does not have the specified method, it
1812 =item B<< $metaclass->has_method($method_name) >>
1814 Returns a boolean indicating whether or not the class defines the
1815 named method. It does not include methods inherited from parent
1818 =item B<< $metaclass->get_method_list >>
1820 This will return a list of method I<names> for all methods defined in
1823 =item B<< $metaclass->add_method($method_name, $method) >>
1825 This method takes a method name and a subroutine reference, and adds
1826 the method to the class.
1828 The subroutine reference can be a L<Class::MOP::Method>, and you are
1829 strongly encouraged to pass a meta method object instead of a code
1830 reference. If you do so, that object gets stored as part of the
1831 class's method map directly. If not, the meta information will have to
1832 be recreated later, and may be incorrect.
1834 If you provide a method object, this method will clone that object if
1835 the object's package name does not match the class name. This lets us
1836 track the original source of any methods added from other classes
1837 (notably Moose roles).
1839 =item B<< $metaclass->remove_method($method_name) >>
1841 Remove the named method from the class. This method returns the
1842 L<Class::MOP::Method> object for the method.
1844 =item B<< $metaclass->method_metaclass >>
1846 Returns the class name of the method metaclass, see
1847 L<Class::MOP::Method> for more information on the method metaclass.
1849 =item B<< $metaclass->wrapped_method_metaclass >>
1851 Returns the class name of the wrapped method metaclass, see
1852 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1855 =item B<< $metaclass->get_all_methods >>
1857 This will traverse the inheritance hierarchy and return a list of all
1858 the L<Class::MOP::Method> objects for this class and its parents.
1860 =item B<< $metaclass->find_method_by_name($method_name) >>
1862 This will return a L<Class::MOP::Method> for the specified
1863 C<$method_name>. If the class does not have the specified method, it
1866 Unlike C<get_method>, this method I<will> look for the named method in
1869 =item B<< $metaclass->get_all_method_names >>
1871 This will return a list of method I<names> for all of this class's
1872 methods, including inherited methods.
1874 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1876 This method looks for the named method in the class and all of its
1877 parents. It returns every matching method it finds in the inheritance
1878 tree, so it returns a list of methods.
1880 Each method is returned as a hash reference with three keys. The keys
1881 are C<name>, C<class>, and C<code>. The C<code> key has a
1882 L<Class::MOP::Method> object as its value.
1884 The list of methods is distinct.
1886 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1888 This method returns the first method in any superclass matching the
1889 given name. It is effectively the method that C<SUPER::$method_name>
1894 =head2 Attribute introspection and creation
1896 Because Perl 5 does not have a core concept of attributes in classes,
1897 we can only return information about attributes which have been added
1898 via this class's methods. We cannot discover information about
1899 attributes which are defined in terms of "regular" Perl 5 methods.
1903 =item B<< $metaclass->get_attribute($attribute_name) >>
1905 This will return a L<Class::MOP::Attribute> for the specified
1906 C<$attribute_name>. If the class does not have the specified
1907 attribute, it returns C<undef>.
1909 NOTE that get_attribute does not search superclasses, for that you
1910 need to use C<find_attribute_by_name>.
1912 =item B<< $metaclass->has_attribute($attribute_name) >>
1914 Returns a boolean indicating whether or not the class defines the
1915 named attribute. It does not include attributes inherited from parent
1918 =item B<< $metaclass->get_attribute_list >>
1920 This will return a list of attributes I<names> for all attributes
1921 defined in this class. Note that this operates on the current class
1922 only, it does not traverse the inheritance hierarchy.
1924 =item B<< $metaclass->get_all_attributes >>
1926 This will traverse the inheritance hierarchy and return a list of all
1927 the L<Class::MOP::Attribute> objects for this class and its parents.
1929 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1931 This will return a L<Class::MOP::Attribute> for the specified
1932 C<$attribute_name>. If the class does not have the specified
1933 attribute, it returns C<undef>.
1935 Unlike C<get_attribute>, this attribute I<will> look for the named
1936 attribute in superclasses.
1938 =item B<< $metaclass->add_attribute(...) >>
1940 This method accepts either an existing L<Class::MOP::Attribute>
1941 object or parameters suitable for passing to that class's C<new>
1944 The attribute provided will be added to the class.
1946 Any accessor methods defined by the attribute will be added to the
1947 class when the attribute is added.
1949 If an attribute of the same name already exists, the old attribute
1950 will be removed first.
1952 =item B<< $metaclass->remove_attribute($attribute_name) >>
1954 This will remove the named attribute from the class, and
1955 L<Class::MOP::Attribute> object.
1957 Removing an attribute also removes any accessor methods defined by the
1960 However, note that removing an attribute will only affect I<future>
1961 object instances created for this class, not existing instances.
1963 =item B<< $metaclass->attribute_metaclass >>
1965 Returns the class name of the attribute metaclass for this class. By
1966 default, this is L<Class::MOP::Attribute>.
1970 =head2 Class Immutability
1972 Making a class immutable "freezes" the class definition. You can no
1973 longer call methods which alter the class, such as adding or removing
1974 methods or attributes.
1976 Making a class immutable lets us optimize the class by inlining some
1977 methods, and also allows us to optimize some methods on the metaclass
1980 After immutabilization, the metaclass object will cache most informational
1981 methods that returns information about methods or attributes. Methods which
1982 would alter the class, such as C<add_attribute> and C<add_method>, will
1983 throw an error on an immutable metaclass object.
1985 The immutabilization system in L<Moose> takes much greater advantage
1986 of the inlining features than Class::MOP itself does.
1990 =item B<< $metaclass->make_immutable(%options) >>
1992 This method will create an immutable transformer and use it to make
1993 the class and its metaclass object immutable.
1995 This method accepts the following options:
1999 =item * inline_accessors
2001 =item * inline_constructor
2003 =item * inline_destructor
2005 These are all booleans indicating whether the specified method(s)
2008 By default, accessors and the constructor are inlined, but not the
2011 =item * immutable_trait
2013 The name of a class which will be used as a parent class for the
2014 metaclass object being made immutable. This "trait" implements the
2015 post-immutability functionality of the metaclass (but not the
2016 transformation itself).
2018 This defaults to L<Class::MOP::Class::Immutable::Trait>.
2020 =item * constructor_name
2022 This is the constructor method name. This defaults to "new".
2024 =item * constructor_class
2026 The name of the method metaclass for constructors. It will be used to
2027 generate the inlined constructor. This defaults to
2028 "Class::MOP::Method::Constructor".
2030 =item * replace_constructor
2032 This is a boolean indicating whether an existing constructor should be
2033 replaced when inlining a constructor. This defaults to false.
2035 =item * destructor_class
2037 The name of the method metaclass for destructors. It will be used to
2038 generate the inlined destructor. This defaults to
2039 "Class::MOP::Method::Denstructor".
2041 =item * replace_destructor
2043 This is a boolean indicating whether an existing destructor should be
2044 replaced when inlining a destructor. This defaults to false.
2048 =item B<< $metaclass->immutable_options >>
2050 Returns a hash of the options used when making the class immutable, including
2051 both defaults and anything supplied by the user in the call to C<<
2052 $metaclass->make_immutable >>. This is useful if you need to temporarily make
2053 a class mutable and then restore immutability as it was before.
2055 =item B<< $metaclass->make_mutable >>
2057 Calling this method reverse the immutabilization transformation.
2061 =head2 Method Modifiers
2063 Method modifiers are hooks which allow a method to be wrapped with
2064 I<before>, I<after> and I<around> method modifiers. Every time a
2065 method is called, its modifiers are also called.
2067 A class can modify its own methods, as well as methods defined in
2070 =head3 How method modifiers work?
2072 Method modifiers work by wrapping the original method and then
2073 replacing it in the class's symbol table. The wrappers will handle
2074 calling all the modifiers in the appropriate order and preserving the
2075 calling context for the original method.
2077 The return values of C<before> and C<after> modifiers are
2078 ignored. This is because their purpose is B<not> to filter the input
2079 and output of the primary method (this is done with an I<around>
2082 This may seem like an odd restriction to some, but doing this allows
2083 for simple code to be added at the beginning or end of a method call
2084 without altering the function of the wrapped method or placing any
2085 extra responsibility on the code of the modifier.
2087 Of course if you have more complex needs, you can use the C<around>
2088 modifier which allows you to change both the parameters passed to the
2089 wrapped method, as well as its return value.
2091 Before and around modifiers are called in last-defined-first-called
2092 order, while after modifiers are called in first-defined-first-called
2093 order. So the call tree might looks something like this:
2105 =head3 What is the performance impact?
2107 Of course there is a performance cost associated with method
2108 modifiers, but we have made every effort to make that cost directly
2109 proportional to the number of modifier features you use.
2111 The wrapping method does its best to B<only> do as much work as it
2112 absolutely needs to. In order to do this we have moved some of the
2113 performance costs to set-up time, where they are easier to amortize.
2115 All this said, our benchmarks have indicated the following:
2117 simple wrapper with no modifiers 100% slower
2118 simple wrapper with simple before modifier 400% slower
2119 simple wrapper with simple after modifier 450% slower
2120 simple wrapper with simple around modifier 500-550% slower
2121 simple wrapper with all 3 modifiers 1100% slower
2123 These numbers may seem daunting, but you must remember, every feature
2124 comes with some cost. To put things in perspective, just doing a
2125 simple C<AUTOLOAD> which does nothing but extract the name of the
2126 method called and return it costs about 400% over a normal method
2131 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
2133 This wraps the specified method with the supplied subroutine
2134 reference. The modifier will be called as a method itself, and will
2135 receive the same arguments as are passed to the method.
2137 When the modifier exits, the wrapped method will be called.
2139 The return value of the modifier will be ignored.
2141 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
2143 This wraps the specified method with the supplied subroutine
2144 reference. The modifier will be called as a method itself, and will
2145 receive the same arguments as are passed to the method.
2147 When the wrapped methods exits, the modifier will be called.
2149 The return value of the modifier will be ignored.
2151 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
2153 This wraps the specified method with the supplied subroutine
2156 The first argument passed to the modifier will be a subroutine
2157 reference to the wrapped method. The second argument is the object,
2158 and after that come any arguments passed when the method is called.
2160 The around modifier can choose to call the original method, as well as
2161 what arguments to pass if it does so.
2163 The return value of the modifier is what will be seen by the caller.
2167 =head2 Introspection
2171 =item B<< Class::MOP::Class->meta >>
2173 This will return a L<Class::MOP::Class> instance for this class.
2175 It should also be noted that L<Class::MOP> will actually bootstrap
2176 this module by installing a number of attribute meta-objects into its
2183 Stevan Little E<lt>stevan@iinteractive.comE<gt>
2185 =head1 COPYRIGHT AND LICENSE
2187 Copyright 2006-2010 by Infinity Interactive, Inc.
2189 L<http://www.iinteractive.com>
2191 This library is free software; you can redistribute it and/or modify
2192 it under the same terms as Perl itself.