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 if (Class::MOP::DEBUG_NO_META()) {
497 if (my $meta = try { $self->SUPER::meta }) {
498 return $meta if $meta->isa('Class::MOP::Class');
500 confess "'meta' method called by MOP internals"
501 if caller =~ /Class::MOP|metaclass/;
503 $class->initialize(ref($_[0]) || $_[0]);
506 $meta->superclasses(@{$options{superclasses}})
507 if exists $options{superclasses};
509 # process attributes first, so that they can
510 # install accessors, but locally defined methods
511 # can then overwrite them. It is maybe a little odd, but
512 # I think this should be the order of things.
513 if (exists $options{attributes}) {
514 foreach my $attr (@{$options{attributes}}) {
515 $meta->add_attribute($attr);
518 if (exists $options{methods}) {
519 foreach my $method_name (keys %{$options{methods}}) {
520 $meta->add_method($method_name, $options{methods}->{$method_name});
529 # all these attribute readers will be bootstrapped
530 # away in the Class::MOP bootstrap section
532 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
533 sub immutable_trait { $_[0]->{'immutable_trait'} }
534 sub constructor_class { $_[0]->{'constructor_class'} }
535 sub constructor_name { $_[0]->{'constructor_name'} }
536 sub destructor_class { $_[0]->{'destructor_class'} }
538 # Instance Construction & Cloning
544 # we need to protect the integrity of the
545 # Class::MOP::Class singletons here, so we
546 # delegate this to &construct_class_instance
547 # which will deal with the singletons
548 return $class->_construct_class_instance(@_)
549 if $class->name->isa('Class::MOP::Class');
550 return $class->_construct_instance(@_);
553 sub _construct_instance {
555 my $params = @_ == 1 ? $_[0] : {@_};
556 my $meta_instance = $class->get_meta_instance();
558 # the code below is almost certainly incorrect
559 # but this is foreign inheritance, so we might
560 # have to kludge it in the end.
562 if (my $instance_class = blessed($params->{__INSTANCE__})) {
563 ($instance_class eq $class->name)
564 || confess "Objects passed as the __INSTANCE__ parameter must "
565 . "already be blessed into the correct class, but "
566 . "$params->{__INSTANCE__} is not a " . $class->name;
567 $instance = $params->{__INSTANCE__};
569 elsif (exists $params->{__INSTANCE__}) {
570 confess "The __INSTANCE__ parameter must be a blessed reference, not "
571 . $params->{__INSTANCE__};
574 $instance = $meta_instance->create_instance();
576 foreach my $attr ($class->get_all_attributes()) {
577 $attr->initialize_instance_slot($meta_instance, $instance, $params);
580 # this will only work for a HASH instance type
581 if ($class->is_anon_class) {
582 (reftype($instance) eq 'HASH')
583 || confess "Currently only HASH based instances are supported with instance of anon-classes";
585 # At some point we should make this official
586 # as a reserved slot name, but right now I am
587 # going to keep it here.
588 # my $RESERVED_MOP_SLOT = '__MOP__';
589 $instance->{'__MOP__'} = $class;
595 sub get_meta_instance {
597 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
600 sub _create_meta_instance {
603 my $instance = $self->instance_metaclass->new(
604 associated_metaclass => $self,
605 attributes => [ $self->get_all_attributes() ],
608 $self->add_meta_instance_dependencies()
609 if $instance->is_dependent_on_superclasses();
616 my $instance = shift;
617 (blessed($instance) && $instance->isa($class->name))
618 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
621 # we need to protect the integrity of the
622 # Class::MOP::Class singletons here, they
623 # should not be cloned.
624 return $instance if $instance->isa('Class::MOP::Class');
625 $class->_clone_instance($instance, @_);
628 sub _clone_instance {
629 my ($class, $instance, %params) = @_;
631 || confess "You can only clone instances, ($instance) is not a blessed instance";
632 my $meta_instance = $class->get_meta_instance();
633 my $clone = $meta_instance->clone_instance($instance);
634 foreach my $attr ($class->get_all_attributes()) {
635 if ( defined( my $init_arg = $attr->init_arg ) ) {
636 if (exists $params{$init_arg}) {
637 $attr->set_value($clone, $params{$init_arg});
644 sub rebless_instance {
645 my ($self, $instance, %params) = @_;
647 my $old_metaclass = Class::MOP::class_of($instance);
649 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
650 $self->name->isa($old_class)
651 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
653 $old_metaclass->rebless_instance_away($instance, $self, %params)
656 my $meta_instance = $self->get_meta_instance();
659 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
660 $meta_instance->rebless_instance_structure($_[1], $self);
662 foreach my $attr ( $self->get_all_attributes ) {
663 if ( $attr->has_value($instance) ) {
664 if ( defined( my $init_arg = $attr->init_arg ) ) {
665 $params{$init_arg} = $attr->get_value($instance)
666 unless exists $params{$init_arg};
669 $attr->set_value($instance, $attr->get_value($instance));
674 foreach my $attr ($self->get_all_attributes) {
675 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
681 sub rebless_instance_back {
682 my ( $self, $instance ) = @_;
684 my $old_metaclass = Class::MOP::class_of($instance);
687 = $old_metaclass ? $old_metaclass->name : blessed($instance);
688 $old_class->isa( $self->name )
690 "You may rebless only into a superclass of ($old_class), of which ("
694 $old_metaclass->rebless_instance_away( $instance, $self )
697 my $meta_instance = $self->get_meta_instance;
699 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
700 $meta_instance->rebless_instance_structure( $_[1], $self );
702 for my $attr ( $old_metaclass->get_all_attributes ) {
703 next if $self->has_attribute( $attr->name );
704 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
710 sub rebless_instance_away {
711 # this intentionally does nothing, it is just a hook
714 sub _attach_attribute {
715 my ($self, $attribute) = @_;
716 $attribute->attach_to_class($self);
719 sub _post_add_attribute {
720 my ( $self, $attribute ) = @_;
722 $self->invalidate_meta_instances;
724 # invalidate package flag here
727 $attribute->install_accessors;
730 $self->remove_attribute( $attribute->name );
735 sub remove_attribute {
738 my $removed_attribute = $self->SUPER::remove_attribute(@_)
741 $self->invalidate_meta_instances;
743 $removed_attribute->remove_accessors;
744 $removed_attribute->detach_from_class;
746 return$removed_attribute;
749 sub find_attribute_by_name {
750 my ( $self, $attr_name ) = @_;
752 foreach my $class ( $self->linearized_isa ) {
753 # fetch the meta-class ...
754 my $meta = Class::MOP::Class->initialize($class);
755 return $meta->get_attribute($attr_name)
756 if $meta->has_attribute($attr_name);
762 sub get_all_attributes {
764 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
765 reverse $self->linearized_isa;
766 return values %attrs;
774 my $isa = $self->get_or_add_package_symbol(
775 { sigil => '@', type => 'ARRAY', name => 'ISA' } );
782 # on 5.8 and below, we need to call
783 # a method to get Perl to detect
784 # a cycle in the class hierarchy
785 my $class = $self->name;
789 # we need to check the metaclass
790 # compatibility here so that we can
791 # be sure that the superclass is
792 # not potentially creating an issues
793 # we don't know about
795 $self->_check_metaclass_compatibility();
796 $self->_superclasses_updated();
802 sub _superclasses_updated {
804 $self->update_meta_instance_dependencies();
809 my $super_class = $self->name;
811 return @{ $super_class->mro::get_isarev() };
814 sub direct_subclasses {
816 my $super_class = $self->name;
821 } Class::MOP::Class->initialize($_)->superclasses
826 return @{ mro::get_linear_isa( (shift)->name ) };
829 sub class_precedence_list {
831 my $name = $self->name;
833 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
835 # We need to check for circular inheritance here
836 # if we are are not on 5.10, cause 5.8 detects it
837 # late. This will do nothing if all is well, and
838 # blow up otherwise. Yes, it's an ugly hack, better
839 # suggestions are welcome.
841 ($name || return)->isa('This is a test for circular inheritance')
844 # if our mro is c3, we can
845 # just grab the linear_isa
846 if (mro::get_mro($name) eq 'c3') {
847 return @{ mro::get_linear_isa($name) }
851 # we can't grab the linear_isa for dfs
852 # since it has all the duplicates
857 Class::MOP::Class->initialize($_)->class_precedence_list()
858 } $self->superclasses()
866 my $fetch_and_prepare_method = sub {
867 my ($self, $method_name) = @_;
868 my $wrapped_metaclass = $self->wrapped_method_metaclass;
870 my $method = $self->get_method($method_name);
871 # if we dont have local ...
873 # try to find the next method
874 $method = $self->find_next_method_by_name($method_name);
875 # die if it does not exist
877 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
878 # and now make sure to wrap it
879 # even if it is already wrapped
880 # because we need a new sub ref
881 $method = $wrapped_metaclass->wrap($method,
882 package_name => $self->name,
883 name => $method_name,
887 # now make sure we wrap it properly
888 $method = $wrapped_metaclass->wrap($method,
889 package_name => $self->name,
890 name => $method_name,
891 ) unless $method->isa($wrapped_metaclass);
893 $self->add_method($method_name => $method);
897 sub add_before_method_modifier {
898 my ($self, $method_name, $method_modifier) = @_;
899 (defined $method_name && length $method_name)
900 || confess "You must pass in a method name";
901 my $method = $fetch_and_prepare_method->($self, $method_name);
902 $method->add_before_modifier(
903 subname(':before' => $method_modifier)
907 sub add_after_method_modifier {
908 my ($self, $method_name, $method_modifier) = @_;
909 (defined $method_name && length $method_name)
910 || confess "You must pass in a method name";
911 my $method = $fetch_and_prepare_method->($self, $method_name);
912 $method->add_after_modifier(
913 subname(':after' => $method_modifier)
917 sub add_around_method_modifier {
918 my ($self, $method_name, $method_modifier) = @_;
919 (defined $method_name && length $method_name)
920 || confess "You must pass in a method name";
921 my $method = $fetch_and_prepare_method->($self, $method_name);
922 $method->add_around_modifier(
923 subname(':around' => $method_modifier)
928 # the methods above used to be named like this:
929 # ${pkg}::${method}:(before|after|around)
930 # but this proved problematic when using one modifier
931 # to wrap multiple methods (something which is likely
932 # to happen pretty regularly IMO). So instead of naming
933 # it like this, I have chosen to just name them purely
934 # with their modifier names, like so:
935 # :(before|after|around)
936 # The fact is that in a stack trace, it will be fairly
937 # evident from the context what method they are attached
938 # to, and so don't need the fully qualified name.
941 sub find_method_by_name {
942 my ($self, $method_name) = @_;
943 (defined $method_name && length $method_name)
944 || confess "You must define a method name to find";
945 foreach my $class ($self->linearized_isa) {
946 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
947 return $method if defined $method;
952 sub get_all_methods {
956 for my $class ( reverse $self->linearized_isa ) {
957 my $meta = Class::MOP::Class->initialize($class);
959 $methods{ $_->name } = $_ for $meta->_get_local_methods;
962 return values %methods;
965 sub get_all_method_names {
968 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
971 sub find_all_methods_by_name {
972 my ($self, $method_name) = @_;
973 (defined $method_name && length $method_name)
974 || confess "You must define a method name to find";
976 foreach my $class ($self->linearized_isa) {
977 # fetch the meta-class ...
978 my $meta = Class::MOP::Class->initialize($class);
980 name => $method_name,
982 code => $meta->get_method($method_name)
983 } if $meta->has_method($method_name);
988 sub find_next_method_by_name {
989 my ($self, $method_name) = @_;
990 (defined $method_name && length $method_name)
991 || confess "You must define a method name to find";
992 my @cpl = $self->linearized_isa;
993 shift @cpl; # discard ourselves
994 foreach my $class (@cpl) {
995 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
996 return $method if defined $method;
1001 sub update_meta_instance_dependencies {
1004 if ( $self->{meta_instance_dependencies} ) {
1005 return $self->add_meta_instance_dependencies;
1009 sub add_meta_instance_dependencies {
1012 $self->remove_meta_instance_dependencies;
1014 my @attrs = $self->get_all_attributes();
1017 my @classes = grep { not $seen{ $_->name }++ }
1018 map { $_->associated_class } @attrs;
1020 foreach my $class (@classes) {
1021 $class->add_dependent_meta_instance($self);
1024 $self->{meta_instance_dependencies} = \@classes;
1027 sub remove_meta_instance_dependencies {
1030 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1031 foreach my $class (@$classes) {
1032 $class->remove_dependent_meta_instance($self);
1042 sub add_dependent_meta_instance {
1043 my ( $self, $metaclass ) = @_;
1044 push @{ $self->{dependent_meta_instances} }, $metaclass;
1047 sub remove_dependent_meta_instance {
1048 my ( $self, $metaclass ) = @_;
1049 my $name = $metaclass->name;
1050 @$_ = grep { $_->name ne $name } @$_
1051 for $self->{dependent_meta_instances};
1054 sub invalidate_meta_instances {
1056 $_->invalidate_meta_instance()
1057 for $self, @{ $self->{dependent_meta_instances} };
1060 sub invalidate_meta_instance {
1062 undef $self->{_meta_instance};
1065 # check if we can reinitialize
1069 # if any local attr is defined
1070 return if $self->get_attribute_list;
1072 # or any non-declared methods
1073 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1074 return if $method->isa("Class::MOP::Method::Generated");
1075 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1083 sub is_mutable { 1 }
1084 sub is_immutable { 0 }
1086 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1088 sub _immutable_options {
1089 my ( $self, @args ) = @_;
1092 inline_accessors => 1,
1093 inline_constructor => 1,
1094 inline_destructor => 0,
1096 immutable_trait => $self->immutable_trait,
1097 constructor_name => $self->constructor_name,
1098 constructor_class => $self->constructor_class,
1099 destructor_class => $self->destructor_class,
1104 sub make_immutable {
1105 my ( $self, @args ) = @_;
1107 if ( $self->is_mutable ) {
1108 $self->_initialize_immutable( $self->_immutable_options(@args) );
1109 $self->_rebless_as_immutable(@args);
1120 if ( $self->is_immutable ) {
1121 my @args = $self->immutable_options;
1122 $self->_rebless_as_mutable();
1123 $self->_remove_inlined_code(@args);
1124 delete $self->{__immutable};
1132 sub _rebless_as_immutable {
1133 my ( $self, @args ) = @_;
1135 $self->{__immutable}{original_class} = ref $self;
1137 bless $self => $self->_immutable_metaclass(@args);
1140 sub _immutable_metaclass {
1141 my ( $self, %args ) = @_;
1143 if ( my $class = $args{immutable_metaclass} ) {
1147 my $trait = $args{immutable_trait} = $self->immutable_trait
1148 || confess "no immutable trait specified for $self";
1150 my $meta = $self->meta;
1151 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1155 if ( $meta_attr and $trait eq $meta_attr->default ) {
1156 # if the trait is the same as the default we try and pick a
1157 # predictable name for the immutable metaclass
1158 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1161 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1162 $trait, 'ForMetaClass', ref($self);
1166 if Class::MOP::is_class_loaded($class_name);
1168 # If the metaclass is a subclass of CMOP::Class which has had
1169 # metaclass roles applied (via Moose), then we want to make sure
1170 # that we preserve that anonymous class (see Fey::ORM for an
1171 # example of where this matters).
1172 my $meta_name = $meta->_real_ref_name;
1174 my $immutable_meta = $meta_name->create(
1176 superclasses => [ ref $self ],
1179 Class::MOP::load_class($trait);
1180 for my $meth ( Class::MOP::Class->initialize($trait)->get_all_methods ) {
1181 my $meth_name = $meth->name;
1183 if ( $immutable_meta->find_method_by_name( $meth_name ) ) {
1184 $immutable_meta->add_around_method_modifier( $meth_name, $meth->body );
1187 $immutable_meta->add_method( $meth_name, $meth->clone );
1191 $immutable_meta->make_immutable(
1192 inline_constructor => 0,
1193 inline_accessors => 0,
1199 sub _remove_inlined_code {
1202 $self->remove_method( $_->name ) for $self->_inlined_methods;
1204 delete $self->{__immutable}{inlined_methods};
1207 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1209 sub _add_inlined_method {
1210 my ( $self, $method ) = @_;
1212 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1215 sub _initialize_immutable {
1216 my ( $self, %args ) = @_;
1218 $self->{__immutable}{options} = \%args;
1219 $self->_install_inlined_code(%args);
1222 sub _install_inlined_code {
1223 my ( $self, %args ) = @_;
1226 $self->_inline_accessors(%args) if $args{inline_accessors};
1227 $self->_inline_constructor(%args) if $args{inline_constructor};
1228 $self->_inline_destructor(%args) if $args{inline_destructor};
1231 sub _rebless_as_mutable {
1234 bless $self, $self->_get_mutable_metaclass_name;
1239 sub _inline_accessors {
1242 foreach my $attr_name ( $self->get_attribute_list ) {
1243 $self->get_attribute($attr_name)->install_accessors(1);
1247 sub _inline_constructor {
1248 my ( $self, %args ) = @_;
1250 my $name = $args{constructor_name};
1251 # A class may not even have a constructor, and that's okay.
1252 return unless defined $name;
1254 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1255 my $class = $self->name;
1256 warn "Not inlining a constructor for $class since it defines"
1257 . " its own constructor.\n"
1258 . "If you are certain you don't need to inline your"
1259 . " constructor, specify inline_constructor => 0 in your"
1260 . " call to $class->meta->make_immutable\n";
1264 my $constructor_class = $args{constructor_class};
1266 Class::MOP::load_class($constructor_class);
1268 my $constructor = $constructor_class->new(
1272 package_name => $self->name,
1276 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1277 $self->add_method( $name => $constructor );
1278 $self->_add_inlined_method($constructor);
1282 sub _inline_destructor {
1283 my ( $self, %args ) = @_;
1285 ( exists $args{destructor_class} && defined $args{destructor_class} )
1286 || confess "The 'inline_destructor' option is present, but "
1287 . "no destructor class was specified";
1289 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1290 my $class = $self->name;
1291 warn "Not inlining a destructor for $class since it defines"
1292 . " its own destructor.\n";
1296 my $destructor_class = $args{destructor_class};
1298 Class::MOP::load_class($destructor_class);
1300 return unless $destructor_class->is_needed($self);
1302 my $destructor = $destructor_class->new(
1305 package_name => $self->name,
1309 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1310 $self->add_method( 'DESTROY' => $destructor );
1311 $self->_add_inlined_method($destructor);
1323 Class::MOP::Class - Class Meta Object
1327 # assuming that class Foo
1328 # has been defined, you can
1330 # use this for introspection ...
1332 # add a method to Foo ...
1333 Foo->meta->add_method( 'bar' => sub {...} )
1335 # get a list of all the classes searched
1336 # the method dispatcher in the correct order
1337 Foo->meta->class_precedence_list()
1339 # remove a method from Foo
1340 Foo->meta->remove_method('bar');
1342 # or use this to actually create classes ...
1344 Class::MOP::Class->create(
1347 superclasses => ['Foo'],
1349 Class::MOP::Attribute->new('$bar'),
1350 Class::MOP::Attribute->new('$baz'),
1353 calculate_bar => sub {...},
1354 construct_baz => sub {...}
1361 The Class Protocol is the largest and most complex part of the
1362 Class::MOP meta-object protocol. It controls the introspection and
1363 manipulation of Perl 5 classes, and it can create them as well. The
1364 best way to understand what this module can do is to read the
1365 documentation for each of its methods.
1369 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1373 =head2 Class construction
1375 These methods all create new C<Class::MOP::Class> objects. These
1376 objects can represent existing classes or they can be used to create
1377 new classes from scratch.
1379 The metaclass object for a given class is a singleton. If you attempt
1380 to create a metaclass for the same class twice, you will just get the
1385 =item B<< Class::MOP::Class->create($package_name, %options) >>
1387 This method creates a new C<Class::MOP::Class> object with the given
1388 package name. It accepts a number of options:
1394 An optional version number for the newly created package.
1398 An optional authority for the newly created package.
1400 =item * superclasses
1402 An optional array reference of superclass names.
1406 An optional hash reference of methods for the class. The keys of the
1407 hash reference are method names and values are subroutine references.
1411 An optional array reference of L<Class::MOP::Attribute> objects.
1415 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1417 This method works just like C<< Class::MOP::Class->create >> but it
1418 creates an "anonymous" class. In fact, the class does have a name, but
1419 that name is a unique name generated internally by this module.
1421 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1422 parameters that C<create> accepts.
1424 Anonymous classes are destroyed once the metaclass they are attached
1425 to goes out of scope, and will be removed from Perl's internal symbol
1428 All instances of an anonymous class keep a special reference to the
1429 metaclass object, which prevents the metaclass from going out of scope
1430 while any instances exist.
1432 This only works if the instance is based on a hash reference, however.
1434 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1436 This method will initialize a C<Class::MOP::Class> object for the
1437 named package. Unlike C<create>, this method I<will not> create a new
1440 The purpose of this method is to retrieve a C<Class::MOP::Class>
1441 object for introspecting an existing class.
1443 If an existing C<Class::MOP::Class> object exists for the named
1444 package, it will be returned, and any options provided will be
1447 If the object does not yet exist, it will be created.
1449 The valid options that can be passed to this method are
1450 C<attribute_metaclass>, C<method_metaclass>,
1451 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1452 optional, and default to the appropriate class in the C<Class::MOP>
1457 =head2 Object instance construction and cloning
1459 These methods are all related to creating and/or cloning object
1464 =item B<< $metaclass->clone_object($instance, %params) >>
1466 This method clones an existing object instance. Any parameters you
1467 provide are will override existing attribute values in the object.
1469 This is a convenience method for cloning an object instance, then
1470 blessing it into the appropriate package.
1472 You could implement a clone method in your class, using this method:
1475 my ($self, %params) = @_;
1476 $self->meta->clone_object($self, %params);
1479 =item B<< $metaclass->rebless_instance($instance, %params) >>
1481 This method changes the class of C<$instance> to the metaclass's class.
1483 You can only rebless an instance into a subclass of its current
1484 class. If you pass any additional parameters, these will be treated
1485 like constructor parameters and used to initialize the object's
1486 attributes. Any existing attributes that are already set will be
1489 Before reblessing the instance, this method will call
1490 C<rebless_instance_away> on the instance's current metaclass. This method
1491 will be passed the instance, the new metaclass, and any parameters
1492 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1493 does nothing; it is merely a hook.
1495 =item B<< $metaclass->rebless_instance_back($instance) >>
1497 Does the same thing as C<rebless_instance>, except that you can only
1498 rebless an instance into one of its superclasses. Any attributes that
1499 do not exist in the superclass will be deinitialized.
1501 This is a much more dangerous operation than C<rebless_instance>,
1502 especially when multiple inheritance is involved, so use this carefully!
1504 =item B<< $metaclass->new_object(%params) >>
1506 This method is used to create a new object of the metaclass's
1507 class. Any parameters you provide are used to initialize the
1508 instance's attributes. A special C<__INSTANCE__> key can be passed to
1509 provide an already generated instance, rather than having Class::MOP
1510 generate it for you. This is mostly useful for using Class::MOP with
1511 foreign classes which generate instances using their own constructors.
1513 =item B<< $metaclass->instance_metaclass >>
1515 Returns the class name of the instance metaclass. See
1516 L<Class::MOP::Instance> for more information on the instance
1519 =item B<< $metaclass->get_meta_instance >>
1521 Returns an instance of the C<instance_metaclass> to be used in the
1522 construction of a new instance of the class.
1526 =head2 Informational predicates
1528 These are a few predicate methods for asking information about the
1533 =item B<< $metaclass->is_anon_class >>
1535 This returns true if the class was created by calling C<<
1536 Class::MOP::Class->create_anon_class >>.
1538 =item B<< $metaclass->is_mutable >>
1540 This returns true if the class is still mutable.
1542 =item B<< $metaclass->is_immutable >>
1544 This returns true if the class has been made immutable.
1546 =item B<< $metaclass->is_pristine >>
1548 A class is I<not> pristine if it has non-inherited attributes or if it
1549 has any generated methods.
1553 =head2 Inheritance Relationships
1557 =item B<< $metaclass->superclasses(@superclasses) >>
1559 This is a read-write accessor which represents the superclass
1560 relationships of the metaclass's class.
1562 This is basically sugar around getting and setting C<@ISA>.
1564 =item B<< $metaclass->class_precedence_list >>
1566 This returns a list of all of the class's ancestor classes. The
1567 classes are returned in method dispatch order.
1569 =item B<< $metaclass->linearized_isa >>
1571 This returns a list based on C<class_precedence_list> but with all
1574 =item B<< $metaclass->subclasses >>
1576 This returns a list of all subclasses for this class, even indirect
1579 =item B<< $metaclass->direct_subclasses >>
1581 This returns a list of immediate subclasses for this class, which does not
1582 include indirect subclasses.
1586 =head2 Method introspection and creation
1588 These methods allow you to introspect a class's methods, as well as
1589 add, remove, or change methods.
1591 Determining what is truly a method in a Perl 5 class requires some
1592 heuristics (aka guessing).
1594 Methods defined outside the package with a fully qualified name (C<sub
1595 Package::name { ... }>) will be included. Similarly, methods named
1596 with a fully qualified name using L<Sub::Name> are also included.
1598 However, we attempt to ignore imported functions.
1600 Ultimately, we are using heuristics to determine what truly is a
1601 method in a class, and these heuristics may get the wrong answer in
1602 some edge cases. However, for most "normal" cases the heuristics work
1607 =item B<< $metaclass->get_method($method_name) >>
1609 This will return a L<Class::MOP::Method> for the specified
1610 C<$method_name>. If the class does not have the specified method, it
1613 =item B<< $metaclass->has_method($method_name) >>
1615 Returns a boolean indicating whether or not the class defines the
1616 named method. It does not include methods inherited from parent
1619 =item B<< $metaclass->get_method_list >>
1621 This will return a list of method I<names> for all methods defined in
1624 =item B<< $metaclass->add_method($method_name, $method) >>
1626 This method takes a method name and a subroutine reference, and adds
1627 the method to the class.
1629 The subroutine reference can be a L<Class::MOP::Method>, and you are
1630 strongly encouraged to pass a meta method object instead of a code
1631 reference. If you do so, that object gets stored as part of the
1632 class's method map directly. If not, the meta information will have to
1633 be recreated later, and may be incorrect.
1635 If you provide a method object, this method will clone that object if
1636 the object's package name does not match the class name. This lets us
1637 track the original source of any methods added from other classes
1638 (notably Moose roles).
1640 =item B<< $metaclass->remove_method($method_name) >>
1642 Remove the named method from the class. This method returns the
1643 L<Class::MOP::Method> object for the method.
1645 =item B<< $metaclass->method_metaclass >>
1647 Returns the class name of the method metaclass, see
1648 L<Class::MOP::Method> for more information on the method metaclass.
1650 =item B<< $metaclass->wrapped_method_metaclass >>
1652 Returns the class name of the wrapped method metaclass, see
1653 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1656 =item B<< $metaclass->get_all_methods >>
1658 This will traverse the inheritance hierarchy and return a list of all
1659 the L<Class::MOP::Method> objects for this class and its parents.
1661 =item B<< $metaclass->find_method_by_name($method_name) >>
1663 This will return a L<Class::MOP::Method> for the specified
1664 C<$method_name>. If the class does not have the specified method, it
1667 Unlike C<get_method>, this method I<will> look for the named method in
1670 =item B<< $metaclass->get_all_method_names >>
1672 This will return a list of method I<names> for all of this class's
1673 methods, including inherited methods.
1675 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1677 This method looks for the named method in the class and all of its
1678 parents. It returns every matching method it finds in the inheritance
1679 tree, so it returns a list of methods.
1681 Each method is returned as a hash reference with three keys. The keys
1682 are C<name>, C<class>, and C<code>. The C<code> key has a
1683 L<Class::MOP::Method> object as its value.
1685 The list of methods is distinct.
1687 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1689 This method returns the first method in any superclass matching the
1690 given name. It is effectively the method that C<SUPER::$method_name>
1695 =head2 Attribute introspection and creation
1697 Because Perl 5 does not have a core concept of attributes in classes,
1698 we can only return information about attributes which have been added
1699 via this class's methods. We cannot discover information about
1700 attributes which are defined in terms of "regular" Perl 5 methods.
1704 =item B<< $metaclass->get_attribute($attribute_name) >>
1706 This will return a L<Class::MOP::Attribute> for the specified
1707 C<$attribute_name>. If the class does not have the specified
1708 attribute, it returns C<undef>.
1710 NOTE that get_attribute does not search superclasses, for that you
1711 need to use C<find_attribute_by_name>.
1713 =item B<< $metaclass->has_attribute($attribute_name) >>
1715 Returns a boolean indicating whether or not the class defines the
1716 named attribute. It does not include attributes inherited from parent
1719 =item B<< $metaclass->get_attribute_list >>
1721 This will return a list of attributes I<names> for all attributes
1722 defined in this class. Note that this operates on the current class
1723 only, it does not traverse the inheritance hierarchy.
1725 =item B<< $metaclass->get_all_attributes >>
1727 This will traverse the inheritance hierarchy and return a list of all
1728 the L<Class::MOP::Attribute> objects for this class and its parents.
1730 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1732 This will return a L<Class::MOP::Attribute> for the specified
1733 C<$attribute_name>. If the class does not have the specified
1734 attribute, it returns C<undef>.
1736 Unlike C<get_attribute>, this attribute I<will> look for the named
1737 attribute in superclasses.
1739 =item B<< $metaclass->add_attribute(...) >>
1741 This method accepts either an existing L<Class::MOP::Attribute>
1742 object or parameters suitable for passing to that class's C<new>
1745 The attribute provided will be added to the class.
1747 Any accessor methods defined by the attribute will be added to the
1748 class when the attribute is added.
1750 If an attribute of the same name already exists, the old attribute
1751 will be removed first.
1753 =item B<< $metaclass->remove_attribute($attribute_name) >>
1755 This will remove the named attribute from the class, and
1756 L<Class::MOP::Attribute> object.
1758 Removing an attribute also removes any accessor methods defined by the
1761 However, note that removing an attribute will only affect I<future>
1762 object instances created for this class, not existing instances.
1764 =item B<< $metaclass->attribute_metaclass >>
1766 Returns the class name of the attribute metaclass for this class. By
1767 default, this is L<Class::MOP::Attribute>.
1771 =head2 Class Immutability
1773 Making a class immutable "freezes" the class definition. You can no
1774 longer call methods which alter the class, such as adding or removing
1775 methods or attributes.
1777 Making a class immutable lets us optimize the class by inlining some
1778 methods, and also allows us to optimize some methods on the metaclass
1781 After immutabilization, the metaclass object will cache most informational
1782 methods that returns information about methods or attributes. Methods which
1783 would alter the class, such as C<add_attribute> and C<add_method>, will
1784 throw an error on an immutable metaclass object.
1786 The immutabilization system in L<Moose> takes much greater advantage
1787 of the inlining features than Class::MOP itself does.
1791 =item B<< $metaclass->make_immutable(%options) >>
1793 This method will create an immutable transformer and use it to make
1794 the class and its metaclass object immutable.
1796 This method accepts the following options:
1800 =item * inline_accessors
1802 =item * inline_constructor
1804 =item * inline_destructor
1806 These are all booleans indicating whether the specified method(s)
1809 By default, accessors and the constructor are inlined, but not the
1812 =item * immutable_trait
1814 The name of a class which will be used as a parent class for the
1815 metaclass object being made immutable. This "trait" implements the
1816 post-immutability functionality of the metaclass (but not the
1817 transformation itself).
1819 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1821 =item * constructor_name
1823 This is the constructor method name. This defaults to "new".
1825 =item * constructor_class
1827 The name of the method metaclass for constructors. It will be used to
1828 generate the inlined constructor. This defaults to
1829 "Class::MOP::Method::Constructor".
1831 =item * replace_constructor
1833 This is a boolean indicating whether an existing constructor should be
1834 replaced when inlining a constructor. This defaults to false.
1836 =item * destructor_class
1838 The name of the method metaclass for destructors. It will be used to
1839 generate the inlined destructor. This defaults to
1840 "Class::MOP::Method::Denstructor".
1842 =item * replace_destructor
1844 This is a boolean indicating whether an existing destructor should be
1845 replaced when inlining a destructor. This defaults to false.
1849 =item B<< $metaclass->immutable_options >>
1851 Returns a hash of the options used when making the class immutable, including
1852 both defaults and anything supplied by the user in the call to C<<
1853 $metaclass->make_immutable >>. This is useful if you need to temporarily make
1854 a class mutable and then restore immutability as it was before.
1856 =item B<< $metaclass->make_mutable >>
1858 Calling this method reverse the immutabilization transformation.
1862 =head2 Method Modifiers
1864 Method modifiers are hooks which allow a method to be wrapped with
1865 I<before>, I<after> and I<around> method modifiers. Every time a
1866 method is called, its modifiers are also called.
1868 A class can modify its own methods, as well as methods defined in
1871 =head3 How method modifiers work?
1873 Method modifiers work by wrapping the original method and then
1874 replacing it in the class's symbol table. The wrappers will handle
1875 calling all the modifiers in the appropriate order and preserving the
1876 calling context for the original method.
1878 The return values of C<before> and C<after> modifiers are
1879 ignored. This is because their purpose is B<not> to filter the input
1880 and output of the primary method (this is done with an I<around>
1883 This may seem like an odd restriction to some, but doing this allows
1884 for simple code to be added at the beginning or end of a method call
1885 without altering the function of the wrapped method or placing any
1886 extra responsibility on the code of the modifier.
1888 Of course if you have more complex needs, you can use the C<around>
1889 modifier which allows you to change both the parameters passed to the
1890 wrapped method, as well as its return value.
1892 Before and around modifiers are called in last-defined-first-called
1893 order, while after modifiers are called in first-defined-first-called
1894 order. So the call tree might looks something like this:
1906 =head3 What is the performance impact?
1908 Of course there is a performance cost associated with method
1909 modifiers, but we have made every effort to make that cost directly
1910 proportional to the number of modifier features you use.
1912 The wrapping method does its best to B<only> do as much work as it
1913 absolutely needs to. In order to do this we have moved some of the
1914 performance costs to set-up time, where they are easier to amortize.
1916 All this said, our benchmarks have indicated the following:
1918 simple wrapper with no modifiers 100% slower
1919 simple wrapper with simple before modifier 400% slower
1920 simple wrapper with simple after modifier 450% slower
1921 simple wrapper with simple around modifier 500-550% slower
1922 simple wrapper with all 3 modifiers 1100% slower
1924 These numbers may seem daunting, but you must remember, every feature
1925 comes with some cost. To put things in perspective, just doing a
1926 simple C<AUTOLOAD> which does nothing but extract the name of the
1927 method called and return it costs about 400% over a normal method
1932 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1934 This wraps the specified method with the supplied subroutine
1935 reference. The modifier will be called as a method itself, and will
1936 receive the same arguments as are passed to the method.
1938 When the modifier exits, the wrapped method will be called.
1940 The return value of the modifier will be ignored.
1942 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1944 This wraps the specified method with the supplied subroutine
1945 reference. The modifier will be called as a method itself, and will
1946 receive the same arguments as are passed to the method.
1948 When the wrapped methods exits, the modifier will be called.
1950 The return value of the modifier will be ignored.
1952 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1954 This wraps the specified method with the supplied subroutine
1957 The first argument passed to the modifier will be a subroutine
1958 reference to the wrapped method. The second argument is the object,
1959 and after that come any arguments passed when the method is called.
1961 The around modifier can choose to call the original method, as well as
1962 what arguments to pass if it does so.
1964 The return value of the modifier is what will be seen by the caller.
1968 =head2 Introspection
1972 =item B<< Class::MOP::Class->meta >>
1974 This will return a L<Class::MOP::Class> instance for this class.
1976 It should also be noted that L<Class::MOP> will actually bootstrap
1977 this module by installing a number of attribute meta-objects into its
1984 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1986 =head1 COPYRIGHT AND LICENSE
1988 Copyright 2006-2010 by Infinity Interactive, Inc.
1990 L<http://www.iinteractive.com>
1992 This library is free software; you can redistribute it and/or modify
1993 it under the same terms as Perl itself.