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;
13 use Scalar::Util 'blessed', 'reftype', 'weaken';
14 use Sub::Name 'subname';
15 use Devel::GlobalDestruction 'in_global_destruction';
17 use List::MoreUtils 'all';
19 our $VERSION = '1.04';
20 $VERSION = eval $VERSION;
21 our $AUTHORITY = 'cpan:STEVAN';
23 use base 'Class::MOP::Module',
24 'Class::MOP::Mixin::HasAttributes',
25 'Class::MOP::Mixin::HasMethods';
35 $package_name = shift;
38 $package_name = $options{package};
41 ($package_name && !ref($package_name))
42 || confess "You must pass a package name and it cannot be blessed";
44 return Class::MOP::get_metaclass_by_name($package_name)
45 || $class->_construct_class_instance(package => $package_name, @_);
48 # NOTE: (meta-circularity)
49 # this is a special form of _construct_instance
50 # (see below), which is used to construct class
51 # meta-object instances for any Class::MOP::*
52 # class. All other classes will use the more
53 # normal &construct_instance.
54 sub _construct_class_instance {
56 my $options = @_ == 1 ? $_[0] : {@_};
57 my $package_name = $options->{package};
58 (defined $package_name && $package_name)
59 || confess "You must pass a package name";
61 # return the metaclass if we have it cached,
62 # and it is still defined (it has not been
63 # reaped by DESTROY yet, which can happen
64 # annoyingly enough during global destruction)
66 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
72 ? $class->_real_ref_name
75 # now create the metaclass
77 if ($class eq 'Class::MOP::Class') {
78 $meta = $class->_new($options);
82 # it is safe to use meta here because
83 # class will always be a subclass of
84 # Class::MOP::Class, which defines meta
85 $meta = $class->meta->_construct_instance($options)
88 # and check the metaclass compatibility
89 $meta->_check_metaclass_compatibility();
91 Class::MOP::store_metaclass_by_name($package_name, $meta);
94 # we need to weaken any anon classes
95 # so that they can call DESTROY properly
96 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
104 # NOTE: we need to deal with the possibility of class immutability here,
105 # and then get the name of the class appropriately
106 return $self->is_immutable
107 ? $self->_get_mutable_metaclass_name()
114 return Class::MOP::Class->initialize($class)->new_object(@_)
115 if $class ne __PACKAGE__;
117 my $options = @_ == 1 ? $_[0] : {@_};
120 # inherited from Class::MOP::Package
121 'package' => $options->{package},
124 # since the following attributes will
125 # actually be loaded from the symbol
126 # table, and actually bypass the instance
127 # entirely, we can just leave these things
128 # listed here for reference, because they
129 # should not actually have a value associated
131 'namespace' => \undef,
134 # inherited from Class::MOP::Module
136 'authority' => \undef,
138 # defined in Class::MOP::Class
139 'superclasses' => \undef,
142 'attribute_metaclass' =>
143 ( $options->{'attribute_metaclass'} || 'Class::MOP::Attribute' ),
144 'method_metaclass' =>
145 ( $options->{'method_metaclass'} || 'Class::MOP::Method' ),
146 'wrapped_method_metaclass' => (
147 $options->{'wrapped_method_metaclass'}
148 || 'Class::MOP::Method::Wrapped'
150 'instance_metaclass' =>
151 ( $options->{'instance_metaclass'} || 'Class::MOP::Instance' ),
152 'immutable_trait' => (
153 $options->{'immutable_trait'}
154 || 'Class::MOP::Class::Immutable::Trait'
156 'constructor_name' => ( $options->{constructor_name} || 'new' ),
157 'constructor_class' => (
158 $options->{constructor_class} || 'Class::MOP::Method::Constructor'
160 'destructor_class' => $options->{destructor_class},
164 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
165 sub update_package_cache_flag {
168 # we can manually update the cache number
169 # since we are actually adding the method
170 # to our cache as well. This avoids us
171 # having to regenerate the method_map.
173 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
176 ## Metaclass compatibility
178 my %base_metaclass = (
179 attribute_metaclass => 'Class::MOP::Attribute',
180 method_metaclass => 'Class::MOP::Method',
181 wrapped_method_metaclass => 'Class::MOP::Method::Wrapped',
182 instance_metaclass => 'Class::MOP::Instance',
183 constructor_class => 'Class::MOP::Method::Constructor',
184 destructor_class => 'Class::MOP::Method::Destructor',
187 sub _base_metaclasses { %base_metaclass }
190 sub _check_metaclass_compatibility {
193 my @superclasses = $self->superclasses
196 $self->_fix_metaclass_incompatibility(@superclasses);
198 my %base_metaclass = $self->_base_metaclasses;
200 # this is always okay ...
202 if ref($self) eq 'Class::MOP::Class'
204 my $meta = $self->$_;
205 !defined($meta) || $meta eq $base_metaclass{$_};
207 keys %base_metaclass;
209 for my $superclass (@superclasses) {
210 $self->_check_class_metaclass_compatibility($superclass);
213 for my $metaclass_type ( keys %base_metaclass ) {
214 next unless defined $self->$metaclass_type;
215 for my $superclass (@superclasses) {
216 $self->_check_single_metaclass_compatibility( $metaclass_type,
222 sub _class_metaclass_is_compatible {
224 my ( $superclass_name ) = @_;
226 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
229 my $super_meta_type = $super_meta->_real_ref_name;
231 return $self->isa($super_meta_type);
234 sub _check_class_metaclass_compatibility {
236 my ( $superclass_name ) = @_;
238 if (!$self->_class_metaclass_is_compatible($superclass_name)) {
239 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
241 my $super_meta_type = $super_meta->_real_ref_name;
243 confess "The metaclass of " . $self->name . " ("
244 . (ref($self)) . ")" . " is not compatible with "
245 . "the metaclass of its superclass, "
246 . $superclass_name . " (" . ($super_meta_type) . ")";
250 sub _single_metaclass_is_compatible {
252 my ( $metaclass_type, $superclass_name ) = @_;
254 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
257 # for instance, Moose::Meta::Class has a error_class attribute, but
258 # Class::MOP::Class doesn't - this shouldn't be an error
259 return 1 unless $super_meta->can($metaclass_type);
260 # for instance, Moose::Meta::Class has a destructor_class, but
261 # Class::MOP::Class doesn't - this shouldn't be an error
262 return 1 unless defined $super_meta->$metaclass_type;
263 # if metaclass is defined in superclass but not here, it's not compatible
264 # this is a really odd case
265 return 0 unless defined $self->$metaclass_type;
267 return $self->$metaclass_type->isa($super_meta->$metaclass_type);
270 sub _check_single_metaclass_compatibility {
272 my ( $metaclass_type, $superclass_name ) = @_;
274 if (!$self->_single_metaclass_is_compatible($metaclass_type, $superclass_name)) {
275 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
276 my $metaclass_type_name = $metaclass_type;
277 $metaclass_type_name =~ s/_(?:meta)?class$//;
278 $metaclass_type_name =~ s/_/ /g;
279 confess "The $metaclass_type_name metaclass for "
280 . $self->name . " (" . ($self->$metaclass_type)
281 . ")" . " is not compatible with the "
282 . "$metaclass_type_name metaclass of its "
283 . "superclass, " . $superclass_name . " ("
284 . ($super_meta->$metaclass_type) . ")";
288 sub _can_fix_class_metaclass_incompatibility_by_subclassing {
290 my ($super_meta) = @_;
292 my $super_meta_type = $super_meta->_real_ref_name;
294 return $super_meta_type ne blessed($self)
295 && $super_meta->isa(blessed($self));
298 sub _can_fix_single_metaclass_incompatibility_by_subclassing {
300 my ($metaclass_type, $super_meta) = @_;
302 my $specific_meta = $self->$metaclass_type;
303 return unless $super_meta->can($metaclass_type);
304 my $super_specific_meta = $super_meta->$metaclass_type;
306 # for instance, Moose::Meta::Class has a destructor_class, but
307 # Class::MOP::Class doesn't - this shouldn't be an error
308 return unless defined $super_specific_meta;
310 # if metaclass is defined in superclass but not here, it's fixable
311 # this is a really odd case
312 return 1 unless defined $specific_meta;
314 return $specific_meta ne $super_specific_meta
315 && $super_specific_meta->isa($specific_meta);
318 sub _can_fix_metaclass_incompatibility_by_subclassing {
320 my ($super_meta) = @_;
322 return 1 if $self->_can_fix_class_metaclass_incompatibility_by_subclassing($super_meta);
324 my %base_metaclass = $self->_base_metaclasses;
325 for my $metaclass_type (keys %base_metaclass) {
326 return 1 if $self->_can_fix_single_metaclass_incompatibility_by_subclassing($metaclass_type, $super_meta);
332 sub _can_fix_metaclass_incompatibility {
334 return $self->_can_fix_metaclass_incompatibility_by_subclassing(@_);
337 sub _fix_metaclass_incompatibility {
339 my @supers = map { Class::MOP::Class->initialize($_) } @_;
342 for my $super (@supers) {
344 if $self->_can_fix_metaclass_incompatibility($super);
346 return unless $necessary;
348 for my $super (@supers) {
349 if (!$self->_class_metaclass_is_compatible($super->name)) {
350 $self->_fix_class_metaclass_incompatibility($super);
354 my %base_metaclass = $self->_base_metaclasses;
355 for my $metaclass_type (keys %base_metaclass) {
356 for my $super (@supers) {
357 if (!$self->_single_metaclass_is_compatible($metaclass_type, $super->name)) {
358 $self->_fix_single_metaclass_incompatibility(
359 $metaclass_type, $super
366 sub _fix_class_metaclass_incompatibility {
368 my ( $super_meta ) = @_;
370 if ($self->_can_fix_class_metaclass_incompatibility_by_subclassing($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 $super_meta_name->meta->rebless_instance($self);
382 sub _fix_single_metaclass_incompatibility {
384 my ( $metaclass_type, $super_meta ) = @_;
386 if ($self->_can_fix_single_metaclass_incompatibility_by_subclassing($metaclass_type, $super_meta)) {
388 || confess "Can't fix metaclass incompatibility for "
390 . " because it is not pristine.";
392 $self->{$metaclass_type} = $super_meta->$metaclass_type;
400 # this should be sufficient, if you have a
401 # use case where it is not, write a test and
403 my $ANON_CLASS_SERIAL = 0;
406 # we need a sufficiently annoying prefix
407 # this should suffice for now, this is
408 # used in a couple of places below, so
409 # need to put it up here for now.
410 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
414 no warnings 'uninitialized';
415 $self->name =~ /^$ANON_CLASS_PREFIX/o;
418 sub create_anon_class {
419 my ($class, %options) = @_;
420 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
421 return $class->create($package_name, %options);
425 # this will only get called for
426 # anon-classes, all other calls
427 # are assumed to occur during
428 # global destruction and so don't
429 # really need to be handled explicitly
433 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
435 no warnings 'uninitialized';
436 my $name = $self->name;
437 return unless $name =~ /^$ANON_CLASS_PREFIX/o;
439 # Moose does a weird thing where it replaces the metaclass for
440 # class when fixing metaclass incompatibility. In that case,
441 # we don't want to clean out the namespace now. We can detect
442 # that because Moose will explicitly update the singleton
443 # cache in Class::MOP.
444 my $current_meta = Class::MOP::get_metaclass_by_name($name);
445 return if $current_meta ne $self;
447 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/o);
449 @{$name . '::ISA'} = ();
450 %{$name . '::'} = ();
451 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
453 Class::MOP::remove_metaclass_by_name($name);
458 # creating classes with MOP ...
461 my ( $class, @args ) = @_;
463 unshift @args, 'package' if @args % 2 == 1;
465 my (%options) = @args;
466 my $package_name = $options{package};
468 (ref $options{superclasses} eq 'ARRAY')
469 || confess "You must pass an ARRAY ref of superclasses"
470 if exists $options{superclasses};
472 (ref $options{attributes} eq 'ARRAY')
473 || confess "You must pass an ARRAY ref of attributes"
474 if exists $options{attributes};
476 (ref $options{methods} eq 'HASH')
477 || confess "You must pass a HASH ref of methods"
478 if exists $options{methods};
480 my (%initialize_options) = @args;
481 delete @initialize_options{qw(
489 my $meta = $class->initialize( $package_name => %initialize_options );
491 $meta->_instantiate_module( $options{version}, $options{authority} );
494 $meta->add_method('meta' => sub {
495 $class->initialize(ref($_[0]) || $_[0]);
498 $meta->superclasses(@{$options{superclasses}})
499 if exists $options{superclasses};
501 # process attributes first, so that they can
502 # install accessors, but locally defined methods
503 # can then overwrite them. It is maybe a little odd, but
504 # I think this should be the order of things.
505 if (exists $options{attributes}) {
506 foreach my $attr (@{$options{attributes}}) {
507 $meta->add_attribute($attr);
510 if (exists $options{methods}) {
511 foreach my $method_name (keys %{$options{methods}}) {
512 $meta->add_method($method_name, $options{methods}->{$method_name});
521 # all these attribute readers will be bootstrapped
522 # away in the Class::MOP bootstrap section
524 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
525 sub immutable_trait { $_[0]->{'immutable_trait'} }
526 sub constructor_class { $_[0]->{'constructor_class'} }
527 sub constructor_name { $_[0]->{'constructor_name'} }
528 sub destructor_class { $_[0]->{'destructor_class'} }
530 # Instance Construction & Cloning
536 # we need to protect the integrity of the
537 # Class::MOP::Class singletons here, so we
538 # delegate this to &construct_class_instance
539 # which will deal with the singletons
540 return $class->_construct_class_instance(@_)
541 if $class->name->isa('Class::MOP::Class');
542 return $class->_construct_instance(@_);
545 sub _construct_instance {
547 my $params = @_ == 1 ? $_[0] : {@_};
548 my $meta_instance = $class->get_meta_instance();
550 # the code below is almost certainly incorrect
551 # but this is foreign inheritance, so we might
552 # have to kludge it in the end.
554 if (my $instance_class = blessed($params->{__INSTANCE__})) {
555 ($instance_class eq $class->name)
556 || confess "Objects passed as the __INSTANCE__ parameter must "
557 . "already be blessed into the correct class, but "
558 . "$params->{__INSTANCE__} is not a " . $class->name;
559 $instance = $params->{__INSTANCE__};
561 elsif (exists $params->{__INSTANCE__}) {
562 confess "The __INSTANCE__ parameter must be a blessed reference, not "
563 . $params->{__INSTANCE__};
566 $instance = $meta_instance->create_instance();
568 foreach my $attr ($class->get_all_attributes()) {
569 $attr->initialize_instance_slot($meta_instance, $instance, $params);
572 # this will only work for a HASH instance type
573 if ($class->is_anon_class) {
574 (reftype($instance) eq 'HASH')
575 || confess "Currently only HASH based instances are supported with instance of anon-classes";
577 # At some point we should make this official
578 # as a reserved slot name, but right now I am
579 # going to keep it here.
580 # my $RESERVED_MOP_SLOT = '__MOP__';
581 $instance->{'__MOP__'} = $class;
587 sub get_meta_instance {
589 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
592 sub _create_meta_instance {
595 my $instance = $self->instance_metaclass->new(
596 associated_metaclass => $self,
597 attributes => [ $self->get_all_attributes() ],
600 $self->add_meta_instance_dependencies()
601 if $instance->is_dependent_on_superclasses();
608 my $instance = shift;
609 (blessed($instance) && $instance->isa($class->name))
610 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
613 # we need to protect the integrity of the
614 # Class::MOP::Class singletons here, they
615 # should not be cloned.
616 return $instance if $instance->isa('Class::MOP::Class');
617 $class->_clone_instance($instance, @_);
620 sub _clone_instance {
621 my ($class, $instance, %params) = @_;
623 || confess "You can only clone instances, ($instance) is not a blessed instance";
624 my $meta_instance = $class->get_meta_instance();
625 my $clone = $meta_instance->clone_instance($instance);
626 foreach my $attr ($class->get_all_attributes()) {
627 if ( defined( my $init_arg = $attr->init_arg ) ) {
628 if (exists $params{$init_arg}) {
629 $attr->set_value($clone, $params{$init_arg});
636 sub rebless_instance {
637 my ($self, $instance, %params) = @_;
639 my $old_metaclass = Class::MOP::class_of($instance);
641 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
642 $self->name->isa($old_class)
643 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
645 $old_metaclass->rebless_instance_away($instance, $self, %params)
648 my $meta_instance = $self->get_meta_instance();
651 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
652 $meta_instance->rebless_instance_structure($_[1], $self);
654 foreach my $attr ( $self->get_all_attributes ) {
655 if ( $attr->has_value($instance) ) {
656 if ( defined( my $init_arg = $attr->init_arg ) ) {
657 $params{$init_arg} = $attr->get_value($instance)
658 unless exists $params{$init_arg};
661 $attr->set_value($instance, $attr->get_value($instance));
666 foreach my $attr ($self->get_all_attributes) {
667 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
673 sub rebless_instance_back {
674 my ( $self, $instance ) = @_;
676 my $old_metaclass = Class::MOP::class_of($instance);
679 = $old_metaclass ? $old_metaclass->name : blessed($instance);
680 $old_class->isa( $self->name )
682 "You may rebless only into a superclass of ($old_class), of which ("
686 $old_metaclass->rebless_instance_away( $instance, $self )
689 my $meta_instance = $self->get_meta_instance;
691 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
692 $meta_instance->rebless_instance_structure( $_[1], $self );
694 for my $attr ( $old_metaclass->get_all_attributes ) {
695 next if $self->has_attribute( $attr->name );
696 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
702 sub rebless_instance_away {
703 # this intentionally does nothing, it is just a hook
706 sub _attach_attribute {
707 my ($self, $attribute) = @_;
708 $attribute->attach_to_class($self);
711 sub _post_add_attribute {
712 my ( $self, $attribute ) = @_;
714 $self->invalidate_meta_instances;
716 # invalidate package flag here
719 $attribute->install_accessors;
722 $self->remove_attribute( $attribute->name );
727 sub remove_attribute {
730 my $removed_attribute = $self->SUPER::remove_attribute(@_)
733 $self->invalidate_meta_instances;
735 $removed_attribute->remove_accessors;
736 $removed_attribute->detach_from_class;
738 return$removed_attribute;
741 sub find_attribute_by_name {
742 my ( $self, $attr_name ) = @_;
744 foreach my $class ( $self->linearized_isa ) {
745 # fetch the meta-class ...
746 my $meta = Class::MOP::Class->initialize($class);
747 return $meta->get_attribute($attr_name)
748 if $meta->has_attribute($attr_name);
754 sub get_all_attributes {
756 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
757 reverse $self->linearized_isa;
758 return values %attrs;
765 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
768 @{$self->get_package_symbol($var_spec)} = @supers;
771 # on 5.8 and below, we need to call
772 # a method to get Perl to detect
773 # a cycle in the class hierarchy
774 my $class = $self->name;
778 # we need to check the metaclass
779 # compatibility here so that we can
780 # be sure that the superclass is
781 # not potentially creating an issues
782 # we don't know about
784 $self->_check_metaclass_compatibility();
785 $self->_superclasses_updated();
787 @{$self->get_package_symbol($var_spec)};
790 sub _superclasses_updated {
792 $self->update_meta_instance_dependencies();
797 my $super_class = $self->name;
799 return @{ $super_class->mro::get_isarev() };
802 sub direct_subclasses {
804 my $super_class = $self->name;
809 } Class::MOP::Class->initialize($_)->superclasses
814 return @{ mro::get_linear_isa( (shift)->name ) };
817 sub class_precedence_list {
819 my $name = $self->name;
821 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
823 # We need to check for circular inheritance here
824 # if we are are not on 5.10, cause 5.8 detects it
825 # late. This will do nothing if all is well, and
826 # blow up otherwise. Yes, it's an ugly hack, better
827 # suggestions are welcome.
829 ($name || return)->isa('This is a test for circular inheritance')
832 # if our mro is c3, we can
833 # just grab the linear_isa
834 if (mro::get_mro($name) eq 'c3') {
835 return @{ mro::get_linear_isa($name) }
839 # we can't grab the linear_isa for dfs
840 # since it has all the duplicates
845 Class::MOP::Class->initialize($_)->class_precedence_list()
846 } $self->superclasses()
854 my $fetch_and_prepare_method = sub {
855 my ($self, $method_name) = @_;
856 my $wrapped_metaclass = $self->wrapped_method_metaclass;
858 my $method = $self->get_method($method_name);
859 # if we dont have local ...
861 # try to find the next method
862 $method = $self->find_next_method_by_name($method_name);
863 # die if it does not exist
865 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
866 # and now make sure to wrap it
867 # even if it is already wrapped
868 # because we need a new sub ref
869 $method = $wrapped_metaclass->wrap($method,
870 package_name => $self->name,
871 name => $method_name,
875 # now make sure we wrap it properly
876 $method = $wrapped_metaclass->wrap($method,
877 package_name => $self->name,
878 name => $method_name,
879 ) unless $method->isa($wrapped_metaclass);
881 $self->add_method($method_name => $method);
885 sub add_before_method_modifier {
886 my ($self, $method_name, $method_modifier) = @_;
887 (defined $method_name && length $method_name)
888 || confess "You must pass in a method name";
889 my $method = $fetch_and_prepare_method->($self, $method_name);
890 $method->add_before_modifier(
891 subname(':before' => $method_modifier)
895 sub add_after_method_modifier {
896 my ($self, $method_name, $method_modifier) = @_;
897 (defined $method_name && length $method_name)
898 || confess "You must pass in a method name";
899 my $method = $fetch_and_prepare_method->($self, $method_name);
900 $method->add_after_modifier(
901 subname(':after' => $method_modifier)
905 sub add_around_method_modifier {
906 my ($self, $method_name, $method_modifier) = @_;
907 (defined $method_name && length $method_name)
908 || confess "You must pass in a method name";
909 my $method = $fetch_and_prepare_method->($self, $method_name);
910 $method->add_around_modifier(
911 subname(':around' => $method_modifier)
916 # the methods above used to be named like this:
917 # ${pkg}::${method}:(before|after|around)
918 # but this proved problematic when using one modifier
919 # to wrap multiple methods (something which is likely
920 # to happen pretty regularly IMO). So instead of naming
921 # it like this, I have chosen to just name them purely
922 # with their modifier names, like so:
923 # :(before|after|around)
924 # The fact is that in a stack trace, it will be fairly
925 # evident from the context what method they are attached
926 # to, and so don't need the fully qualified name.
929 sub find_method_by_name {
930 my ($self, $method_name) = @_;
931 (defined $method_name && length $method_name)
932 || confess "You must define a method name to find";
933 foreach my $class ($self->linearized_isa) {
934 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
935 return $method if defined $method;
940 sub get_all_methods {
944 for my $class ( reverse $self->linearized_isa ) {
945 my $meta = Class::MOP::Class->initialize($class);
947 $methods{ $_->name } = $_ for $meta->_get_local_methods;
950 return values %methods;
953 sub get_all_method_names {
956 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
959 sub find_all_methods_by_name {
960 my ($self, $method_name) = @_;
961 (defined $method_name && length $method_name)
962 || confess "You must define a method name to find";
964 foreach my $class ($self->linearized_isa) {
965 # fetch the meta-class ...
966 my $meta = Class::MOP::Class->initialize($class);
968 name => $method_name,
970 code => $meta->get_method($method_name)
971 } if $meta->has_method($method_name);
976 sub find_next_method_by_name {
977 my ($self, $method_name) = @_;
978 (defined $method_name && length $method_name)
979 || confess "You must define a method name to find";
980 my @cpl = $self->linearized_isa;
981 shift @cpl; # discard ourselves
982 foreach my $class (@cpl) {
983 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
984 return $method if defined $method;
989 sub update_meta_instance_dependencies {
992 if ( $self->{meta_instance_dependencies} ) {
993 return $self->add_meta_instance_dependencies;
997 sub add_meta_instance_dependencies {
1000 $self->remove_meta_instance_dependencies;
1002 my @attrs = $self->get_all_attributes();
1005 my @classes = grep { not $seen{ $_->name }++ }
1006 map { $_->associated_class } @attrs;
1008 foreach my $class (@classes) {
1009 $class->add_dependent_meta_instance($self);
1012 $self->{meta_instance_dependencies} = \@classes;
1015 sub remove_meta_instance_dependencies {
1018 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1019 foreach my $class (@$classes) {
1020 $class->remove_dependent_meta_instance($self);
1030 sub add_dependent_meta_instance {
1031 my ( $self, $metaclass ) = @_;
1032 push @{ $self->{dependent_meta_instances} }, $metaclass;
1035 sub remove_dependent_meta_instance {
1036 my ( $self, $metaclass ) = @_;
1037 my $name = $metaclass->name;
1038 @$_ = grep { $_->name ne $name } @$_
1039 for $self->{dependent_meta_instances};
1042 sub invalidate_meta_instances {
1044 $_->invalidate_meta_instance()
1045 for $self, @{ $self->{dependent_meta_instances} };
1048 sub invalidate_meta_instance {
1050 undef $self->{_meta_instance};
1053 # check if we can reinitialize
1057 # if any local attr is defined
1058 return if $self->get_attribute_list;
1060 # or any non-declared methods
1061 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1062 return if $method->isa("Class::MOP::Method::Generated");
1063 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1071 sub is_mutable { 1 }
1072 sub is_immutable { 0 }
1074 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1076 sub _immutable_options {
1077 my ( $self, @args ) = @_;
1080 inline_accessors => 1,
1081 inline_constructor => 1,
1082 inline_destructor => 0,
1084 immutable_trait => $self->immutable_trait,
1085 constructor_name => $self->constructor_name,
1086 constructor_class => $self->constructor_class,
1087 destructor_class => $self->destructor_class,
1092 sub make_immutable {
1093 my ( $self, @args ) = @_;
1095 if ( $self->is_mutable ) {
1096 $self->_initialize_immutable( $self->_immutable_options(@args) );
1097 $self->_rebless_as_immutable(@args);
1108 if ( $self->is_immutable ) {
1109 my @args = $self->immutable_options;
1110 $self->_rebless_as_mutable();
1111 $self->_remove_inlined_code(@args);
1112 delete $self->{__immutable};
1120 sub _rebless_as_immutable {
1121 my ( $self, @args ) = @_;
1123 $self->{__immutable}{original_class} = ref $self;
1125 bless $self => $self->_immutable_metaclass(@args);
1128 sub _immutable_metaclass {
1129 my ( $self, %args ) = @_;
1131 if ( my $class = $args{immutable_metaclass} ) {
1135 my $trait = $args{immutable_trait} = $self->immutable_trait
1136 || confess "no immutable trait specified for $self";
1138 my $meta = $self->meta;
1139 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1143 if ( $meta_attr and $trait eq $meta_attr->default ) {
1144 # if the trait is the same as the default we try and pick a
1145 # predictable name for the immutable metaclass
1146 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1149 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1150 $trait, 'ForMetaClass', ref($self);
1154 if Class::MOP::is_class_loaded($class_name);
1156 # If the metaclass is a subclass of CMOP::Class which has had
1157 # metaclass roles applied (via Moose), then we want to make sure
1158 # that we preserve that anonymous class (see Fey::ORM for an
1159 # example of where this matters).
1160 my $meta_name = $meta->_real_ref_name;
1162 my $immutable_meta = $meta_name->create(
1164 superclasses => [ ref $self ],
1167 Class::MOP::load_class($trait);
1168 for my $meth ( Class::MOP::Class->initialize($trait)->get_all_methods ) {
1169 my $meth_name = $meth->name;
1171 if ( $immutable_meta->find_method_by_name( $meth_name ) ) {
1172 $immutable_meta->add_around_method_modifier( $meth_name, $meth->body );
1175 $immutable_meta->add_method( $meth_name, $meth->clone );
1179 $immutable_meta->make_immutable(
1180 inline_constructor => 0,
1181 inline_accessors => 0,
1187 sub _remove_inlined_code {
1190 $self->remove_method( $_->name ) for $self->_inlined_methods;
1192 delete $self->{__immutable}{inlined_methods};
1195 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1197 sub _add_inlined_method {
1198 my ( $self, $method ) = @_;
1200 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1203 sub _initialize_immutable {
1204 my ( $self, %args ) = @_;
1206 $self->{__immutable}{options} = \%args;
1207 $self->_install_inlined_code(%args);
1210 sub _install_inlined_code {
1211 my ( $self, %args ) = @_;
1214 $self->_inline_accessors(%args) if $args{inline_accessors};
1215 $self->_inline_constructor(%args) if $args{inline_constructor};
1216 $self->_inline_destructor(%args) if $args{inline_destructor};
1219 sub _rebless_as_mutable {
1222 bless $self, $self->_get_mutable_metaclass_name;
1227 sub _inline_accessors {
1230 foreach my $attr_name ( $self->get_attribute_list ) {
1231 $self->get_attribute($attr_name)->install_accessors(1);
1235 sub _inline_constructor {
1236 my ( $self, %args ) = @_;
1238 my $name = $args{constructor_name};
1239 # A class may not even have a constructor, and that's okay.
1240 return unless defined $name;
1242 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1243 my $class = $self->name;
1244 warn "Not inlining a constructor for $class since it defines"
1245 . " its own constructor.\n"
1246 . "If you are certain you don't need to inline your"
1247 . " constructor, specify inline_constructor => 0 in your"
1248 . " call to $class->meta->make_immutable\n";
1252 my $constructor_class = $args{constructor_class};
1254 Class::MOP::load_class($constructor_class);
1256 my $constructor = $constructor_class->new(
1260 package_name => $self->name,
1264 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1265 $self->add_method( $name => $constructor );
1266 $self->_add_inlined_method($constructor);
1270 sub _inline_destructor {
1271 my ( $self, %args ) = @_;
1273 ( exists $args{destructor_class} && defined $args{destructor_class} )
1274 || confess "The 'inline_destructor' option is present, but "
1275 . "no destructor class was specified";
1277 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1278 my $class = $self->name;
1279 warn "Not inlining a destructor for $class since it defines"
1280 . " its own destructor.\n";
1284 my $destructor_class = $args{destructor_class};
1286 Class::MOP::load_class($destructor_class);
1288 return unless $destructor_class->is_needed($self);
1290 my $destructor = $destructor_class->new(
1293 package_name => $self->name,
1297 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1298 $self->add_method( 'DESTROY' => $destructor );
1299 $self->_add_inlined_method($destructor);
1311 Class::MOP::Class - Class Meta Object
1315 # assuming that class Foo
1316 # has been defined, you can
1318 # use this for introspection ...
1320 # add a method to Foo ...
1321 Foo->meta->add_method( 'bar' => sub {...} )
1323 # get a list of all the classes searched
1324 # the method dispatcher in the correct order
1325 Foo->meta->class_precedence_list()
1327 # remove a method from Foo
1328 Foo->meta->remove_method('bar');
1330 # or use this to actually create classes ...
1332 Class::MOP::Class->create(
1335 superclasses => ['Foo'],
1337 Class::MOP::Attribute->new('$bar'),
1338 Class::MOP::Attribute->new('$baz'),
1341 calculate_bar => sub {...},
1342 construct_baz => sub {...}
1349 The Class Protocol is the largest and most complex part of the
1350 Class::MOP meta-object protocol. It controls the introspection and
1351 manipulation of Perl 5 classes, and it can create them as well. The
1352 best way to understand what this module can do is to read the
1353 documentation for each of its methods.
1357 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1361 =head2 Class construction
1363 These methods all create new C<Class::MOP::Class> objects. These
1364 objects can represent existing classes or they can be used to create
1365 new classes from scratch.
1367 The metaclass object for a given class is a singleton. If you attempt
1368 to create a metaclass for the same class twice, you will just get the
1373 =item B<< Class::MOP::Class->create($package_name, %options) >>
1375 This method creates a new C<Class::MOP::Class> object with the given
1376 package name. It accepts a number of options:
1382 An optional version number for the newly created package.
1386 An optional authority for the newly created package.
1388 =item * superclasses
1390 An optional array reference of superclass names.
1394 An optional hash reference of methods for the class. The keys of the
1395 hash reference are method names and values are subroutine references.
1399 An optional array reference of L<Class::MOP::Attribute> objects.
1403 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1405 This method works just like C<< Class::MOP::Class->create >> but it
1406 creates an "anonymous" class. In fact, the class does have a name, but
1407 that name is a unique name generated internally by this module.
1409 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1410 parameters that C<create> accepts.
1412 Anonymous classes are destroyed once the metaclass they are attached
1413 to goes out of scope, and will be removed from Perl's internal symbol
1416 All instances of an anonymous class keep a special reference to the
1417 metaclass object, which prevents the metaclass from going out of scope
1418 while any instances exist.
1420 This only works if the instance is based on a hash reference, however.
1422 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1424 This method will initialize a C<Class::MOP::Class> object for the
1425 named package. Unlike C<create>, this method I<will not> create a new
1428 The purpose of this method is to retrieve a C<Class::MOP::Class>
1429 object for introspecting an existing class.
1431 If an existing C<Class::MOP::Class> object exists for the named
1432 package, it will be returned, and any options provided will be
1435 If the object does not yet exist, it will be created.
1437 The valid options that can be passed to this method are
1438 C<attribute_metaclass>, C<method_metaclass>,
1439 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1440 optional, and default to the appropriate class in the C<Class::MOP>
1445 =head2 Object instance construction and cloning
1447 These methods are all related to creating and/or cloning object
1452 =item B<< $metaclass->clone_object($instance, %params) >>
1454 This method clones an existing object instance. Any parameters you
1455 provide are will override existing attribute values in the object.
1457 This is a convenience method for cloning an object instance, then
1458 blessing it into the appropriate package.
1460 You could implement a clone method in your class, using this method:
1463 my ($self, %params) = @_;
1464 $self->meta->clone_object($self, %params);
1467 =item B<< $metaclass->rebless_instance($instance, %params) >>
1469 This method changes the class of C<$instance> to the metaclass's class.
1471 You can only rebless an instance into a subclass of its current
1472 class. If you pass any additional parameters, these will be treated
1473 like constructor parameters and used to initialize the object's
1474 attributes. Any existing attributes that are already set will be
1477 Before reblessing the instance, this method will call
1478 C<rebless_instance_away> on the instance's current metaclass. This method
1479 will be passed the instance, the new metaclass, and any parameters
1480 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1481 does nothing; it is merely a hook.
1483 =item B<< $metaclass->rebless_instance_back($instance) >>
1485 Does the same thing as C<rebless_instance>, except that you can only
1486 rebless an instance into one of its superclasses. Any attributes that
1487 do not exist in the superclass will be deinitialized.
1489 This is a much more dangerous operation than C<rebless_instance>,
1490 especially when multiple inheritance is involved, so use this carefully!
1492 =item B<< $metaclass->new_object(%params) >>
1494 This method is used to create a new object of the metaclass's
1495 class. Any parameters you provide are used to initialize the
1496 instance's attributes. A special C<__INSTANCE__> key can be passed to
1497 provide an already generated instance, rather than having Class::MOP
1498 generate it for you. This is mostly useful for using Class::MOP with
1499 foreign classes which generate instances using their own constructors.
1501 =item B<< $metaclass->instance_metaclass >>
1503 Returns the class name of the instance metaclass. See
1504 L<Class::MOP::Instance> for more information on the instance
1507 =item B<< $metaclass->get_meta_instance >>
1509 Returns an instance of the C<instance_metaclass> to be used in the
1510 construction of a new instance of the class.
1514 =head2 Informational predicates
1516 These are a few predicate methods for asking information about the
1521 =item B<< $metaclass->is_anon_class >>
1523 This returns true if the class was created by calling C<<
1524 Class::MOP::Class->create_anon_class >>.
1526 =item B<< $metaclass->is_mutable >>
1528 This returns true if the class is still mutable.
1530 =item B<< $metaclass->is_immutable >>
1532 This returns true if the class has been made immutable.
1534 =item B<< $metaclass->is_pristine >>
1536 A class is I<not> pristine if it has non-inherited attributes or if it
1537 has any generated methods.
1541 =head2 Inheritance Relationships
1545 =item B<< $metaclass->superclasses(@superclasses) >>
1547 This is a read-write accessor which represents the superclass
1548 relationships of the metaclass's class.
1550 This is basically sugar around getting and setting C<@ISA>.
1552 =item B<< $metaclass->class_precedence_list >>
1554 This returns a list of all of the class's ancestor classes. The
1555 classes are returned in method dispatch order.
1557 =item B<< $metaclass->linearized_isa >>
1559 This returns a list based on C<class_precedence_list> but with all
1562 =item B<< $metaclass->subclasses >>
1564 This returns a list of all subclasses for this class, even indirect
1567 =item B<< $metaclass->direct_subclasses >>
1569 This returns a list of immediate subclasses for this class, which does not
1570 include indirect subclasses.
1574 =head2 Method introspection and creation
1576 These methods allow you to introspect a class's methods, as well as
1577 add, remove, or change methods.
1579 Determining what is truly a method in a Perl 5 class requires some
1580 heuristics (aka guessing).
1582 Methods defined outside the package with a fully qualified name (C<sub
1583 Package::name { ... }>) will be included. Similarly, methods named
1584 with a fully qualified name using L<Sub::Name> are also included.
1586 However, we attempt to ignore imported functions.
1588 Ultimately, we are using heuristics to determine what truly is a
1589 method in a class, and these heuristics may get the wrong answer in
1590 some edge cases. However, for most "normal" cases the heuristics work
1595 =item B<< $metaclass->get_method($method_name) >>
1597 This will return a L<Class::MOP::Method> for the specified
1598 C<$method_name>. If the class does not have the specified method, it
1601 =item B<< $metaclass->has_method($method_name) >>
1603 Returns a boolean indicating whether or not the class defines the
1604 named method. It does not include methods inherited from parent
1607 =item B<< $metaclass->get_method_list >>
1609 This will return a list of method I<names> for all methods defined in
1612 =item B<< $metaclass->add_method($method_name, $method) >>
1614 This method takes a method name and a subroutine reference, and adds
1615 the method to the class.
1617 The subroutine reference can be a L<Class::MOP::Method>, and you are
1618 strongly encouraged to pass a meta method object instead of a code
1619 reference. If you do so, that object gets stored as part of the
1620 class's method map directly. If not, the meta information will have to
1621 be recreated later, and may be incorrect.
1623 If you provide a method object, this method will clone that object if
1624 the object's package name does not match the class name. This lets us
1625 track the original source of any methods added from other classes
1626 (notably Moose roles).
1628 =item B<< $metaclass->remove_method($method_name) >>
1630 Remove the named method from the class. This method returns the
1631 L<Class::MOP::Method> object for the method.
1633 =item B<< $metaclass->method_metaclass >>
1635 Returns the class name of the method metaclass, see
1636 L<Class::MOP::Method> for more information on the method metaclass.
1638 =item B<< $metaclass->wrapped_method_metaclass >>
1640 Returns the class name of the wrapped method metaclass, see
1641 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1644 =item B<< $metaclass->get_all_methods >>
1646 This will traverse the inheritance hierarchy and return a list of all
1647 the L<Class::MOP::Method> objects for this class and its parents.
1649 =item B<< $metaclass->find_method_by_name($method_name) >>
1651 This will return a L<Class::MOP::Method> for the specified
1652 C<$method_name>. If the class does not have the specified method, it
1655 Unlike C<get_method>, this method I<will> look for the named method in
1658 =item B<< $metaclass->get_all_method_names >>
1660 This will return a list of method I<names> for all of this class's
1661 methods, including inherited methods.
1663 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1665 This method looks for the named method in the class and all of its
1666 parents. It returns every matching method it finds in the inheritance
1667 tree, so it returns a list of methods.
1669 Each method is returned as a hash reference with three keys. The keys
1670 are C<name>, C<class>, and C<code>. The C<code> key has a
1671 L<Class::MOP::Method> object as its value.
1673 The list of methods is distinct.
1675 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1677 This method returns the first method in any superclass matching the
1678 given name. It is effectively the method that C<SUPER::$method_name>
1683 =head2 Attribute introspection and creation
1685 Because Perl 5 does not have a core concept of attributes in classes,
1686 we can only return information about attributes which have been added
1687 via this class's methods. We cannot discover information about
1688 attributes which are defined in terms of "regular" Perl 5 methods.
1692 =item B<< $metaclass->get_attribute($attribute_name) >>
1694 This will return a L<Class::MOP::Attribute> for the specified
1695 C<$attribute_name>. If the class does not have the specified
1696 attribute, it returns C<undef>.
1698 NOTE that get_attribute does not search superclasses, for that you
1699 need to use C<find_attribute_by_name>.
1701 =item B<< $metaclass->has_attribute($attribute_name) >>
1703 Returns a boolean indicating whether or not the class defines the
1704 named attribute. It does not include attributes inherited from parent
1707 =item B<< $metaclass->get_attribute_list >>
1709 This will return a list of attributes I<names> for all attributes
1710 defined in this class. Note that this operates on the current class
1711 only, it does not traverse the inheritance hierarchy.
1713 =item B<< $metaclass->get_all_attributes >>
1715 This will traverse the inheritance hierarchy and return a list of all
1716 the L<Class::MOP::Attribute> objects for this class and its parents.
1718 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1720 This will return a L<Class::MOP::Attribute> for the specified
1721 C<$attribute_name>. If the class does not have the specified
1722 attribute, it returns C<undef>.
1724 Unlike C<get_attribute>, this attribute I<will> look for the named
1725 attribute in superclasses.
1727 =item B<< $metaclass->add_attribute(...) >>
1729 This method accepts either an existing L<Class::MOP::Attribute>
1730 object or parameters suitable for passing to that class's C<new>
1733 The attribute provided will be added to the class.
1735 Any accessor methods defined by the attribute will be added to the
1736 class when the attribute is added.
1738 If an attribute of the same name already exists, the old attribute
1739 will be removed first.
1741 =item B<< $metaclass->remove_attribute($attribute_name) >>
1743 This will remove the named attribute from the class, and
1744 L<Class::MOP::Attribute> object.
1746 Removing an attribute also removes any accessor methods defined by the
1749 However, note that removing an attribute will only affect I<future>
1750 object instances created for this class, not existing instances.
1752 =item B<< $metaclass->attribute_metaclass >>
1754 Returns the class name of the attribute metaclass for this class. By
1755 default, this is L<Class::MOP::Attribute>.
1759 =head2 Class Immutability
1761 Making a class immutable "freezes" the class definition. You can no
1762 longer call methods which alter the class, such as adding or removing
1763 methods or attributes.
1765 Making a class immutable lets us optimize the class by inlining some
1766 methods, and also allows us to optimize some methods on the metaclass
1769 After immutabilization, the metaclass object will cache most informational
1770 methods that returns information about methods or attributes. Methods which
1771 would alter the class, such as C<add_attribute> and C<add_method>, will
1772 throw an error on an immutable metaclass object.
1774 The immutabilization system in L<Moose> takes much greater advantage
1775 of the inlining features than Class::MOP itself does.
1779 =item B<< $metaclass->make_immutable(%options) >>
1781 This method will create an immutable transformer and use it to make
1782 the class and its metaclass object immutable.
1784 This method accepts the following options:
1788 =item * inline_accessors
1790 =item * inline_constructor
1792 =item * inline_destructor
1794 These are all booleans indicating whether the specified method(s)
1797 By default, accessors and the constructor are inlined, but not the
1800 =item * immutable_trait
1802 The name of a class which will be used as a parent class for the
1803 metaclass object being made immutable. This "trait" implements the
1804 post-immutability functionality of the metaclass (but not the
1805 transformation itself).
1807 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1809 =item * constructor_name
1811 This is the constructor method name. This defaults to "new".
1813 =item * constructor_class
1815 The name of the method metaclass for constructors. It will be used to
1816 generate the inlined constructor. This defaults to
1817 "Class::MOP::Method::Constructor".
1819 =item * replace_constructor
1821 This is a boolean indicating whether an existing constructor should be
1822 replaced when inlining a constructor. This defaults to false.
1824 =item * destructor_class
1826 The name of the method metaclass for destructors. It will be used to
1827 generate the inlined destructor. This defaults to
1828 "Class::MOP::Method::Denstructor".
1830 =item * replace_destructor
1832 This is a boolean indicating whether an existing destructor should be
1833 replaced when inlining a destructor. This defaults to false.
1837 =item B<< $metaclass->immutable_options >>
1839 Returns a hash of the options used when making the class immutable, including
1840 both defaults and anything supplied by the user in the call to C<<
1841 $metaclass->make_immutable >>. This is useful if you need to temporarily make
1842 a class mutable and then restore immutability as it was before.
1844 =item B<< $metaclass->make_mutable >>
1846 Calling this method reverse the immutabilization transformation.
1850 =head2 Method Modifiers
1852 Method modifiers are hooks which allow a method to be wrapped with
1853 I<before>, I<after> and I<around> method modifiers. Every time a
1854 method is called, its modifiers are also called.
1856 A class can modify its own methods, as well as methods defined in
1859 =head3 How method modifiers work?
1861 Method modifiers work by wrapping the original method and then
1862 replacing it in the class's symbol table. The wrappers will handle
1863 calling all the modifiers in the appropriate order and preserving the
1864 calling context for the original method.
1866 The return values of C<before> and C<after> modifiers are
1867 ignored. This is because their purpose is B<not> to filter the input
1868 and output of the primary method (this is done with an I<around>
1871 This may seem like an odd restriction to some, but doing this allows
1872 for simple code to be added at the beginning or end of a method call
1873 without altering the function of the wrapped method or placing any
1874 extra responsibility on the code of the modifier.
1876 Of course if you have more complex needs, you can use the C<around>
1877 modifier which allows you to change both the parameters passed to the
1878 wrapped method, as well as its return value.
1880 Before and around modifiers are called in last-defined-first-called
1881 order, while after modifiers are called in first-defined-first-called
1882 order. So the call tree might looks something like this:
1894 =head3 What is the performance impact?
1896 Of course there is a performance cost associated with method
1897 modifiers, but we have made every effort to make that cost directly
1898 proportional to the number of modifier features you use.
1900 The wrapping method does its best to B<only> do as much work as it
1901 absolutely needs to. In order to do this we have moved some of the
1902 performance costs to set-up time, where they are easier to amortize.
1904 All this said, our benchmarks have indicated the following:
1906 simple wrapper with no modifiers 100% slower
1907 simple wrapper with simple before modifier 400% slower
1908 simple wrapper with simple after modifier 450% slower
1909 simple wrapper with simple around modifier 500-550% slower
1910 simple wrapper with all 3 modifiers 1100% slower
1912 These numbers may seem daunting, but you must remember, every feature
1913 comes with some cost. To put things in perspective, just doing a
1914 simple C<AUTOLOAD> which does nothing but extract the name of the
1915 method called and return it costs about 400% over a normal method
1920 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1922 This wraps the specified method with the supplied subroutine
1923 reference. The modifier will be called as a method itself, and will
1924 receive the same arguments as are passed to the method.
1926 When the modifier exits, the wrapped method will be called.
1928 The return value of the modifier will be ignored.
1930 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1932 This wraps the specified method with the supplied subroutine
1933 reference. The modifier will be called as a method itself, and will
1934 receive the same arguments as are passed to the method.
1936 When the wrapped methods exits, the modifier will be called.
1938 The return value of the modifier will be ignored.
1940 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1942 This wraps the specified method with the supplied subroutine
1945 The first argument passed to the modifier will be a subroutine
1946 reference to the wrapped method. The second argument is the object,
1947 and after that come any arguments passed when the method is called.
1949 The around modifier can choose to call the original method, as well as
1950 what arguments to pass if it does so.
1952 The return value of the modifier is what will be seen by the caller.
1956 =head2 Introspection
1960 =item B<< Class::MOP::Class->meta >>
1962 This will return a L<Class::MOP::Class> instance for this class.
1964 It should also be noted that L<Class::MOP> will actually bootstrap
1965 this module by installing a number of attribute meta-objects into its
1972 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1974 =head1 COPYRIGHT AND LICENSE
1976 Copyright 2006-2010 by Infinity Interactive, Inc.
1978 L<http://www.iinteractive.com>
1980 This library is free software; you can redistribute it and/or modify
1981 it under the same terms as Perl itself.