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 = '1.08';
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;
766 my $isa = $self->get_or_add_package_symbol(
767 { sigil => '@', type => 'ARRAY', name => 'ISA' } );
774 # on 5.8 and below, we need to call
775 # a method to get Perl to detect
776 # a cycle in the class hierarchy
777 my $class = $self->name;
781 # we need to check the metaclass
782 # compatibility here so that we can
783 # be sure that the superclass is
784 # not potentially creating an issues
785 # we don't know about
787 $self->_check_metaclass_compatibility();
788 $self->_superclasses_updated();
794 sub _superclasses_updated {
796 $self->update_meta_instance_dependencies();
801 my $super_class = $self->name;
803 return @{ $super_class->mro::get_isarev() };
806 sub direct_subclasses {
808 my $super_class = $self->name;
813 } Class::MOP::Class->initialize($_)->superclasses
818 return @{ mro::get_linear_isa( (shift)->name ) };
821 sub class_precedence_list {
823 my $name = $self->name;
825 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
827 # We need to check for circular inheritance here
828 # if we are are not on 5.10, cause 5.8 detects it
829 # late. This will do nothing if all is well, and
830 # blow up otherwise. Yes, it's an ugly hack, better
831 # suggestions are welcome.
833 ($name || return)->isa('This is a test for circular inheritance')
836 # if our mro is c3, we can
837 # just grab the linear_isa
838 if (mro::get_mro($name) eq 'c3') {
839 return @{ mro::get_linear_isa($name) }
843 # we can't grab the linear_isa for dfs
844 # since it has all the duplicates
849 Class::MOP::Class->initialize($_)->class_precedence_list()
850 } $self->superclasses()
858 my $fetch_and_prepare_method = sub {
859 my ($self, $method_name) = @_;
860 my $wrapped_metaclass = $self->wrapped_method_metaclass;
862 my $method = $self->get_method($method_name);
863 # if we dont have local ...
865 # try to find the next method
866 $method = $self->find_next_method_by_name($method_name);
867 # die if it does not exist
869 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
870 # and now make sure to wrap it
871 # even if it is already wrapped
872 # because we need a new sub ref
873 $method = $wrapped_metaclass->wrap($method,
874 package_name => $self->name,
875 name => $method_name,
879 # now make sure we wrap it properly
880 $method = $wrapped_metaclass->wrap($method,
881 package_name => $self->name,
882 name => $method_name,
883 ) unless $method->isa($wrapped_metaclass);
885 $self->add_method($method_name => $method);
889 sub add_before_method_modifier {
890 my ($self, $method_name, $method_modifier) = @_;
891 (defined $method_name && length $method_name)
892 || confess "You must pass in a method name";
893 my $method = $fetch_and_prepare_method->($self, $method_name);
894 $method->add_before_modifier(
895 subname(':before' => $method_modifier)
899 sub add_after_method_modifier {
900 my ($self, $method_name, $method_modifier) = @_;
901 (defined $method_name && length $method_name)
902 || confess "You must pass in a method name";
903 my $method = $fetch_and_prepare_method->($self, $method_name);
904 $method->add_after_modifier(
905 subname(':after' => $method_modifier)
909 sub add_around_method_modifier {
910 my ($self, $method_name, $method_modifier) = @_;
911 (defined $method_name && length $method_name)
912 || confess "You must pass in a method name";
913 my $method = $fetch_and_prepare_method->($self, $method_name);
914 $method->add_around_modifier(
915 subname(':around' => $method_modifier)
920 # the methods above used to be named like this:
921 # ${pkg}::${method}:(before|after|around)
922 # but this proved problematic when using one modifier
923 # to wrap multiple methods (something which is likely
924 # to happen pretty regularly IMO). So instead of naming
925 # it like this, I have chosen to just name them purely
926 # with their modifier names, like so:
927 # :(before|after|around)
928 # The fact is that in a stack trace, it will be fairly
929 # evident from the context what method they are attached
930 # to, and so don't need the fully qualified name.
933 sub find_method_by_name {
934 my ($self, $method_name) = @_;
935 (defined $method_name && length $method_name)
936 || confess "You must define a method name to find";
937 foreach my $class ($self->linearized_isa) {
938 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
939 return $method if defined $method;
944 sub get_all_methods {
948 for my $class ( reverse $self->linearized_isa ) {
949 my $meta = Class::MOP::Class->initialize($class);
951 $methods{ $_->name } = $_ for $meta->_get_local_methods;
954 return values %methods;
957 sub get_all_method_names {
960 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
963 sub find_all_methods_by_name {
964 my ($self, $method_name) = @_;
965 (defined $method_name && length $method_name)
966 || confess "You must define a method name to find";
968 foreach my $class ($self->linearized_isa) {
969 # fetch the meta-class ...
970 my $meta = Class::MOP::Class->initialize($class);
972 name => $method_name,
974 code => $meta->get_method($method_name)
975 } if $meta->has_method($method_name);
980 sub find_next_method_by_name {
981 my ($self, $method_name) = @_;
982 (defined $method_name && length $method_name)
983 || confess "You must define a method name to find";
984 my @cpl = $self->linearized_isa;
985 shift @cpl; # discard ourselves
986 foreach my $class (@cpl) {
987 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
988 return $method if defined $method;
993 sub update_meta_instance_dependencies {
996 if ( $self->{meta_instance_dependencies} ) {
997 return $self->add_meta_instance_dependencies;
1001 sub add_meta_instance_dependencies {
1004 $self->remove_meta_instance_dependencies;
1006 my @attrs = $self->get_all_attributes();
1009 my @classes = grep { not $seen{ $_->name }++ }
1010 map { $_->associated_class } @attrs;
1012 foreach my $class (@classes) {
1013 $class->add_dependent_meta_instance($self);
1016 $self->{meta_instance_dependencies} = \@classes;
1019 sub remove_meta_instance_dependencies {
1022 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1023 foreach my $class (@$classes) {
1024 $class->remove_dependent_meta_instance($self);
1034 sub add_dependent_meta_instance {
1035 my ( $self, $metaclass ) = @_;
1036 push @{ $self->{dependent_meta_instances} }, $metaclass;
1039 sub remove_dependent_meta_instance {
1040 my ( $self, $metaclass ) = @_;
1041 my $name = $metaclass->name;
1042 @$_ = grep { $_->name ne $name } @$_
1043 for $self->{dependent_meta_instances};
1046 sub invalidate_meta_instances {
1048 $_->invalidate_meta_instance()
1049 for $self, @{ $self->{dependent_meta_instances} };
1052 sub invalidate_meta_instance {
1054 undef $self->{_meta_instance};
1057 # check if we can reinitialize
1061 # if any local attr is defined
1062 return if $self->get_attribute_list;
1064 # or any non-declared methods
1065 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1066 return if $method->isa("Class::MOP::Method::Generated");
1067 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1075 sub is_mutable { 1 }
1076 sub is_immutable { 0 }
1078 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1080 sub _immutable_options {
1081 my ( $self, @args ) = @_;
1084 inline_accessors => 1,
1085 inline_constructor => 1,
1086 inline_destructor => 0,
1088 immutable_trait => $self->immutable_trait,
1089 constructor_name => $self->constructor_name,
1090 constructor_class => $self->constructor_class,
1091 destructor_class => $self->destructor_class,
1096 sub make_immutable {
1097 my ( $self, @args ) = @_;
1099 if ( $self->is_mutable ) {
1100 $self->_initialize_immutable( $self->_immutable_options(@args) );
1101 $self->_rebless_as_immutable(@args);
1112 if ( $self->is_immutable ) {
1113 my @args = $self->immutable_options;
1114 $self->_rebless_as_mutable();
1115 $self->_remove_inlined_code(@args);
1116 delete $self->{__immutable};
1124 sub _rebless_as_immutable {
1125 my ( $self, @args ) = @_;
1127 $self->{__immutable}{original_class} = ref $self;
1129 bless $self => $self->_immutable_metaclass(@args);
1132 sub _immutable_metaclass {
1133 my ( $self, %args ) = @_;
1135 if ( my $class = $args{immutable_metaclass} ) {
1139 my $trait = $args{immutable_trait} = $self->immutable_trait
1140 || confess "no immutable trait specified for $self";
1142 my $meta = $self->meta;
1143 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1147 if ( $meta_attr and $trait eq $meta_attr->default ) {
1148 # if the trait is the same as the default we try and pick a
1149 # predictable name for the immutable metaclass
1150 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1153 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1154 $trait, 'ForMetaClass', ref($self);
1158 if Class::MOP::is_class_loaded($class_name);
1160 # If the metaclass is a subclass of CMOP::Class which has had
1161 # metaclass roles applied (via Moose), then we want to make sure
1162 # that we preserve that anonymous class (see Fey::ORM for an
1163 # example of where this matters).
1164 my $meta_name = $meta->_real_ref_name;
1166 my $immutable_meta = $meta_name->create(
1168 superclasses => [ ref $self ],
1171 Class::MOP::load_class($trait);
1172 for my $meth ( Class::MOP::Class->initialize($trait)->get_all_methods ) {
1173 my $meth_name = $meth->name;
1175 if ( $immutable_meta->find_method_by_name( $meth_name ) ) {
1176 $immutable_meta->add_around_method_modifier( $meth_name, $meth->body );
1179 $immutable_meta->add_method( $meth_name, $meth->clone );
1183 $immutable_meta->make_immutable(
1184 inline_constructor => 0,
1185 inline_accessors => 0,
1191 sub _remove_inlined_code {
1194 $self->remove_method( $_->name ) for $self->_inlined_methods;
1196 delete $self->{__immutable}{inlined_methods};
1199 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1201 sub _add_inlined_method {
1202 my ( $self, $method ) = @_;
1204 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1207 sub _initialize_immutable {
1208 my ( $self, %args ) = @_;
1210 $self->{__immutable}{options} = \%args;
1211 $self->_install_inlined_code(%args);
1214 sub _install_inlined_code {
1215 my ( $self, %args ) = @_;
1218 $self->_inline_accessors(%args) if $args{inline_accessors};
1219 $self->_inline_constructor(%args) if $args{inline_constructor};
1220 $self->_inline_destructor(%args) if $args{inline_destructor};
1223 sub _rebless_as_mutable {
1226 bless $self, $self->_get_mutable_metaclass_name;
1231 sub _inline_accessors {
1234 foreach my $attr_name ( $self->get_attribute_list ) {
1235 $self->get_attribute($attr_name)->install_accessors(1);
1239 sub _inline_constructor {
1240 my ( $self, %args ) = @_;
1242 my $name = $args{constructor_name};
1243 # A class may not even have a constructor, and that's okay.
1244 return unless defined $name;
1246 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1247 my $class = $self->name;
1248 warn "Not inlining a constructor for $class since it defines"
1249 . " its own constructor.\n"
1250 . "If you are certain you don't need to inline your"
1251 . " constructor, specify inline_constructor => 0 in your"
1252 . " call to $class->meta->make_immutable\n";
1256 my $constructor_class = $args{constructor_class};
1258 Class::MOP::load_class($constructor_class);
1260 my $constructor = $constructor_class->new(
1264 package_name => $self->name,
1268 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1269 $self->add_method( $name => $constructor );
1270 $self->_add_inlined_method($constructor);
1274 sub _inline_destructor {
1275 my ( $self, %args ) = @_;
1277 ( exists $args{destructor_class} && defined $args{destructor_class} )
1278 || confess "The 'inline_destructor' option is present, but "
1279 . "no destructor class was specified";
1281 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1282 my $class = $self->name;
1283 warn "Not inlining a destructor for $class since it defines"
1284 . " its own destructor.\n";
1288 my $destructor_class = $args{destructor_class};
1290 Class::MOP::load_class($destructor_class);
1292 return unless $destructor_class->is_needed($self);
1294 my $destructor = $destructor_class->new(
1297 package_name => $self->name,
1301 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1302 $self->add_method( 'DESTROY' => $destructor );
1303 $self->_add_inlined_method($destructor);
1315 Class::MOP::Class - Class Meta Object
1319 # assuming that class Foo
1320 # has been defined, you can
1322 # use this for introspection ...
1324 # add a method to Foo ...
1325 Foo->meta->add_method( 'bar' => sub {...} )
1327 # get a list of all the classes searched
1328 # the method dispatcher in the correct order
1329 Foo->meta->class_precedence_list()
1331 # remove a method from Foo
1332 Foo->meta->remove_method('bar');
1334 # or use this to actually create classes ...
1336 Class::MOP::Class->create(
1339 superclasses => ['Foo'],
1341 Class::MOP::Attribute->new('$bar'),
1342 Class::MOP::Attribute->new('$baz'),
1345 calculate_bar => sub {...},
1346 construct_baz => sub {...}
1353 The Class Protocol is the largest and most complex part of the
1354 Class::MOP meta-object protocol. It controls the introspection and
1355 manipulation of Perl 5 classes, and it can create them as well. The
1356 best way to understand what this module can do is to read the
1357 documentation for each of its methods.
1361 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1365 =head2 Class construction
1367 These methods all create new C<Class::MOP::Class> objects. These
1368 objects can represent existing classes or they can be used to create
1369 new classes from scratch.
1371 The metaclass object for a given class is a singleton. If you attempt
1372 to create a metaclass for the same class twice, you will just get the
1377 =item B<< Class::MOP::Class->create($package_name, %options) >>
1379 This method creates a new C<Class::MOP::Class> object with the given
1380 package name. It accepts a number of options:
1386 An optional version number for the newly created package.
1390 An optional authority for the newly created package.
1392 =item * superclasses
1394 An optional array reference of superclass names.
1398 An optional hash reference of methods for the class. The keys of the
1399 hash reference are method names and values are subroutine references.
1403 An optional array reference of L<Class::MOP::Attribute> objects.
1407 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1409 This method works just like C<< Class::MOP::Class->create >> but it
1410 creates an "anonymous" class. In fact, the class does have a name, but
1411 that name is a unique name generated internally by this module.
1413 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1414 parameters that C<create> accepts.
1416 Anonymous classes are destroyed once the metaclass they are attached
1417 to goes out of scope, and will be removed from Perl's internal symbol
1420 All instances of an anonymous class keep a special reference to the
1421 metaclass object, which prevents the metaclass from going out of scope
1422 while any instances exist.
1424 This only works if the instance is based on a hash reference, however.
1426 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1428 This method will initialize a C<Class::MOP::Class> object for the
1429 named package. Unlike C<create>, this method I<will not> create a new
1432 The purpose of this method is to retrieve a C<Class::MOP::Class>
1433 object for introspecting an existing class.
1435 If an existing C<Class::MOP::Class> object exists for the named
1436 package, it will be returned, and any options provided will be
1439 If the object does not yet exist, it will be created.
1441 The valid options that can be passed to this method are
1442 C<attribute_metaclass>, C<method_metaclass>,
1443 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1444 optional, and default to the appropriate class in the C<Class::MOP>
1449 =head2 Object instance construction and cloning
1451 These methods are all related to creating and/or cloning object
1456 =item B<< $metaclass->clone_object($instance, %params) >>
1458 This method clones an existing object instance. Any parameters you
1459 provide are will override existing attribute values in the object.
1461 This is a convenience method for cloning an object instance, then
1462 blessing it into the appropriate package.
1464 You could implement a clone method in your class, using this method:
1467 my ($self, %params) = @_;
1468 $self->meta->clone_object($self, %params);
1471 =item B<< $metaclass->rebless_instance($instance, %params) >>
1473 This method changes the class of C<$instance> to the metaclass's class.
1475 You can only rebless an instance into a subclass of its current
1476 class. If you pass any additional parameters, these will be treated
1477 like constructor parameters and used to initialize the object's
1478 attributes. Any existing attributes that are already set will be
1481 Before reblessing the instance, this method will call
1482 C<rebless_instance_away> on the instance's current metaclass. This method
1483 will be passed the instance, the new metaclass, and any parameters
1484 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1485 does nothing; it is merely a hook.
1487 =item B<< $metaclass->rebless_instance_back($instance) >>
1489 Does the same thing as C<rebless_instance>, except that you can only
1490 rebless an instance into one of its superclasses. Any attributes that
1491 do not exist in the superclass will be deinitialized.
1493 This is a much more dangerous operation than C<rebless_instance>,
1494 especially when multiple inheritance is involved, so use this carefully!
1496 =item B<< $metaclass->new_object(%params) >>
1498 This method is used to create a new object of the metaclass's
1499 class. Any parameters you provide are used to initialize the
1500 instance's attributes. A special C<__INSTANCE__> key can be passed to
1501 provide an already generated instance, rather than having Class::MOP
1502 generate it for you. This is mostly useful for using Class::MOP with
1503 foreign classes which generate instances using their own constructors.
1505 =item B<< $metaclass->instance_metaclass >>
1507 Returns the class name of the instance metaclass. See
1508 L<Class::MOP::Instance> for more information on the instance
1511 =item B<< $metaclass->get_meta_instance >>
1513 Returns an instance of the C<instance_metaclass> to be used in the
1514 construction of a new instance of the class.
1518 =head2 Informational predicates
1520 These are a few predicate methods for asking information about the
1525 =item B<< $metaclass->is_anon_class >>
1527 This returns true if the class was created by calling C<<
1528 Class::MOP::Class->create_anon_class >>.
1530 =item B<< $metaclass->is_mutable >>
1532 This returns true if the class is still mutable.
1534 =item B<< $metaclass->is_immutable >>
1536 This returns true if the class has been made immutable.
1538 =item B<< $metaclass->is_pristine >>
1540 A class is I<not> pristine if it has non-inherited attributes or if it
1541 has any generated methods.
1545 =head2 Inheritance Relationships
1549 =item B<< $metaclass->superclasses(@superclasses) >>
1551 This is a read-write accessor which represents the superclass
1552 relationships of the metaclass's class.
1554 This is basically sugar around getting and setting C<@ISA>.
1556 =item B<< $metaclass->class_precedence_list >>
1558 This returns a list of all of the class's ancestor classes. The
1559 classes are returned in method dispatch order.
1561 =item B<< $metaclass->linearized_isa >>
1563 This returns a list based on C<class_precedence_list> but with all
1566 =item B<< $metaclass->subclasses >>
1568 This returns a list of all subclasses for this class, even indirect
1571 =item B<< $metaclass->direct_subclasses >>
1573 This returns a list of immediate subclasses for this class, which does not
1574 include indirect subclasses.
1578 =head2 Method introspection and creation
1580 These methods allow you to introspect a class's methods, as well as
1581 add, remove, or change methods.
1583 Determining what is truly a method in a Perl 5 class requires some
1584 heuristics (aka guessing).
1586 Methods defined outside the package with a fully qualified name (C<sub
1587 Package::name { ... }>) will be included. Similarly, methods named
1588 with a fully qualified name using L<Sub::Name> are also included.
1590 However, we attempt to ignore imported functions.
1592 Ultimately, we are using heuristics to determine what truly is a
1593 method in a class, and these heuristics may get the wrong answer in
1594 some edge cases. However, for most "normal" cases the heuristics work
1599 =item B<< $metaclass->get_method($method_name) >>
1601 This will return a L<Class::MOP::Method> for the specified
1602 C<$method_name>. If the class does not have the specified method, it
1605 =item B<< $metaclass->has_method($method_name) >>
1607 Returns a boolean indicating whether or not the class defines the
1608 named method. It does not include methods inherited from parent
1611 =item B<< $metaclass->get_method_list >>
1613 This will return a list of method I<names> for all methods defined in
1616 =item B<< $metaclass->add_method($method_name, $method) >>
1618 This method takes a method name and a subroutine reference, and adds
1619 the method to the class.
1621 The subroutine reference can be a L<Class::MOP::Method>, and you are
1622 strongly encouraged to pass a meta method object instead of a code
1623 reference. If you do so, that object gets stored as part of the
1624 class's method map directly. If not, the meta information will have to
1625 be recreated later, and may be incorrect.
1627 If you provide a method object, this method will clone that object if
1628 the object's package name does not match the class name. This lets us
1629 track the original source of any methods added from other classes
1630 (notably Moose roles).
1632 =item B<< $metaclass->remove_method($method_name) >>
1634 Remove the named method from the class. This method returns the
1635 L<Class::MOP::Method> object for the method.
1637 =item B<< $metaclass->method_metaclass >>
1639 Returns the class name of the method metaclass, see
1640 L<Class::MOP::Method> for more information on the method metaclass.
1642 =item B<< $metaclass->wrapped_method_metaclass >>
1644 Returns the class name of the wrapped method metaclass, see
1645 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1648 =item B<< $metaclass->get_all_methods >>
1650 This will traverse the inheritance hierarchy and return a list of all
1651 the L<Class::MOP::Method> objects for this class and its parents.
1653 =item B<< $metaclass->find_method_by_name($method_name) >>
1655 This will return a L<Class::MOP::Method> for the specified
1656 C<$method_name>. If the class does not have the specified method, it
1659 Unlike C<get_method>, this method I<will> look for the named method in
1662 =item B<< $metaclass->get_all_method_names >>
1664 This will return a list of method I<names> for all of this class's
1665 methods, including inherited methods.
1667 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1669 This method looks for the named method in the class and all of its
1670 parents. It returns every matching method it finds in the inheritance
1671 tree, so it returns a list of methods.
1673 Each method is returned as a hash reference with three keys. The keys
1674 are C<name>, C<class>, and C<code>. The C<code> key has a
1675 L<Class::MOP::Method> object as its value.
1677 The list of methods is distinct.
1679 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1681 This method returns the first method in any superclass matching the
1682 given name. It is effectively the method that C<SUPER::$method_name>
1687 =head2 Attribute introspection and creation
1689 Because Perl 5 does not have a core concept of attributes in classes,
1690 we can only return information about attributes which have been added
1691 via this class's methods. We cannot discover information about
1692 attributes which are defined in terms of "regular" Perl 5 methods.
1696 =item B<< $metaclass->get_attribute($attribute_name) >>
1698 This will return a L<Class::MOP::Attribute> for the specified
1699 C<$attribute_name>. If the class does not have the specified
1700 attribute, it returns C<undef>.
1702 NOTE that get_attribute does not search superclasses, for that you
1703 need to use C<find_attribute_by_name>.
1705 =item B<< $metaclass->has_attribute($attribute_name) >>
1707 Returns a boolean indicating whether or not the class defines the
1708 named attribute. It does not include attributes inherited from parent
1711 =item B<< $metaclass->get_attribute_list >>
1713 This will return a list of attributes I<names> for all attributes
1714 defined in this class. Note that this operates on the current class
1715 only, it does not traverse the inheritance hierarchy.
1717 =item B<< $metaclass->get_all_attributes >>
1719 This will traverse the inheritance hierarchy and return a list of all
1720 the L<Class::MOP::Attribute> objects for this class and its parents.
1722 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1724 This will return a L<Class::MOP::Attribute> for the specified
1725 C<$attribute_name>. If the class does not have the specified
1726 attribute, it returns C<undef>.
1728 Unlike C<get_attribute>, this attribute I<will> look for the named
1729 attribute in superclasses.
1731 =item B<< $metaclass->add_attribute(...) >>
1733 This method accepts either an existing L<Class::MOP::Attribute>
1734 object or parameters suitable for passing to that class's C<new>
1737 The attribute provided will be added to the class.
1739 Any accessor methods defined by the attribute will be added to the
1740 class when the attribute is added.
1742 If an attribute of the same name already exists, the old attribute
1743 will be removed first.
1745 =item B<< $metaclass->remove_attribute($attribute_name) >>
1747 This will remove the named attribute from the class, and
1748 L<Class::MOP::Attribute> object.
1750 Removing an attribute also removes any accessor methods defined by the
1753 However, note that removing an attribute will only affect I<future>
1754 object instances created for this class, not existing instances.
1756 =item B<< $metaclass->attribute_metaclass >>
1758 Returns the class name of the attribute metaclass for this class. By
1759 default, this is L<Class::MOP::Attribute>.
1763 =head2 Class Immutability
1765 Making a class immutable "freezes" the class definition. You can no
1766 longer call methods which alter the class, such as adding or removing
1767 methods or attributes.
1769 Making a class immutable lets us optimize the class by inlining some
1770 methods, and also allows us to optimize some methods on the metaclass
1773 After immutabilization, the metaclass object will cache most informational
1774 methods that returns information about methods or attributes. Methods which
1775 would alter the class, such as C<add_attribute> and C<add_method>, will
1776 throw an error on an immutable metaclass object.
1778 The immutabilization system in L<Moose> takes much greater advantage
1779 of the inlining features than Class::MOP itself does.
1783 =item B<< $metaclass->make_immutable(%options) >>
1785 This method will create an immutable transformer and use it to make
1786 the class and its metaclass object immutable.
1788 This method accepts the following options:
1792 =item * inline_accessors
1794 =item * inline_constructor
1796 =item * inline_destructor
1798 These are all booleans indicating whether the specified method(s)
1801 By default, accessors and the constructor are inlined, but not the
1804 =item * immutable_trait
1806 The name of a class which will be used as a parent class for the
1807 metaclass object being made immutable. This "trait" implements the
1808 post-immutability functionality of the metaclass (but not the
1809 transformation itself).
1811 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1813 =item * constructor_name
1815 This is the constructor method name. This defaults to "new".
1817 =item * constructor_class
1819 The name of the method metaclass for constructors. It will be used to
1820 generate the inlined constructor. This defaults to
1821 "Class::MOP::Method::Constructor".
1823 =item * replace_constructor
1825 This is a boolean indicating whether an existing constructor should be
1826 replaced when inlining a constructor. This defaults to false.
1828 =item * destructor_class
1830 The name of the method metaclass for destructors. It will be used to
1831 generate the inlined destructor. This defaults to
1832 "Class::MOP::Method::Denstructor".
1834 =item * replace_destructor
1836 This is a boolean indicating whether an existing destructor should be
1837 replaced when inlining a destructor. This defaults to false.
1841 =item B<< $metaclass->immutable_options >>
1843 Returns a hash of the options used when making the class immutable, including
1844 both defaults and anything supplied by the user in the call to C<<
1845 $metaclass->make_immutable >>. This is useful if you need to temporarily make
1846 a class mutable and then restore immutability as it was before.
1848 =item B<< $metaclass->make_mutable >>
1850 Calling this method reverse the immutabilization transformation.
1854 =head2 Method Modifiers
1856 Method modifiers are hooks which allow a method to be wrapped with
1857 I<before>, I<after> and I<around> method modifiers. Every time a
1858 method is called, its modifiers are also called.
1860 A class can modify its own methods, as well as methods defined in
1863 =head3 How method modifiers work?
1865 Method modifiers work by wrapping the original method and then
1866 replacing it in the class's symbol table. The wrappers will handle
1867 calling all the modifiers in the appropriate order and preserving the
1868 calling context for the original method.
1870 The return values of C<before> and C<after> modifiers are
1871 ignored. This is because their purpose is B<not> to filter the input
1872 and output of the primary method (this is done with an I<around>
1875 This may seem like an odd restriction to some, but doing this allows
1876 for simple code to be added at the beginning or end of a method call
1877 without altering the function of the wrapped method or placing any
1878 extra responsibility on the code of the modifier.
1880 Of course if you have more complex needs, you can use the C<around>
1881 modifier which allows you to change both the parameters passed to the
1882 wrapped method, as well as its return value.
1884 Before and around modifiers are called in last-defined-first-called
1885 order, while after modifiers are called in first-defined-first-called
1886 order. So the call tree might looks something like this:
1898 =head3 What is the performance impact?
1900 Of course there is a performance cost associated with method
1901 modifiers, but we have made every effort to make that cost directly
1902 proportional to the number of modifier features you use.
1904 The wrapping method does its best to B<only> do as much work as it
1905 absolutely needs to. In order to do this we have moved some of the
1906 performance costs to set-up time, where they are easier to amortize.
1908 All this said, our benchmarks have indicated the following:
1910 simple wrapper with no modifiers 100% slower
1911 simple wrapper with simple before modifier 400% slower
1912 simple wrapper with simple after modifier 450% slower
1913 simple wrapper with simple around modifier 500-550% slower
1914 simple wrapper with all 3 modifiers 1100% slower
1916 These numbers may seem daunting, but you must remember, every feature
1917 comes with some cost. To put things in perspective, just doing a
1918 simple C<AUTOLOAD> which does nothing but extract the name of the
1919 method called and return it costs about 400% over a normal method
1924 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1926 This wraps the specified method with the supplied subroutine
1927 reference. The modifier will be called as a method itself, and will
1928 receive the same arguments as are passed to the method.
1930 When the modifier exits, the wrapped method will be called.
1932 The return value of the modifier will be ignored.
1934 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1936 This wraps the specified method with the supplied subroutine
1937 reference. The modifier will be called as a method itself, and will
1938 receive the same arguments as are passed to the method.
1940 When the wrapped methods exits, the modifier will be called.
1942 The return value of the modifier will be ignored.
1944 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1946 This wraps the specified method with the supplied subroutine
1949 The first argument passed to the modifier will be a subroutine
1950 reference to the wrapped method. The second argument is the object,
1951 and after that come any arguments passed when the method is called.
1953 The around modifier can choose to call the original method, as well as
1954 what arguments to pass if it does so.
1956 The return value of the modifier is what will be seen by the caller.
1960 =head2 Introspection
1964 =item B<< Class::MOP::Class->meta >>
1966 This will return a L<Class::MOP::Class> instance for this class.
1968 It should also be noted that L<Class::MOP> will actually bootstrap
1969 this module by installing a number of attribute meta-objects into its
1976 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1978 =head1 COPYRIGHT AND LICENSE
1980 Copyright 2006-2010 by Infinity Interactive, Inc.
1982 L<http://www.iinteractive.com>
1984 This library is free software; you can redistribute it and/or modify
1985 it under the same terms as Perl itself.