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', 'weaken';
14 use Sub::Name 'subname';
15 use Devel::GlobalDestruction 'in_global_destruction';
17 our $VERSION = '0.88';
18 $VERSION = eval $VERSION;
19 our $AUTHORITY = 'cpan:STEVAN';
21 use base 'Class::MOP::Module';
31 $package_name = shift;
34 $package_name = $options{package};
37 (defined $package_name && $package_name && !ref($package_name))
38 || confess "You must pass a package name and it cannot be blessed";
40 return Class::MOP::get_metaclass_by_name($package_name)
41 || $class->_construct_class_instance(package => $package_name, @_);
44 sub construct_class_instance {
45 Carp::cluck('The construct_class_instance method has been made private.'
46 . " The public version is deprecated and will be removed in a future release.\n");
47 shift->_construct_class_instance(@_);
50 # NOTE: (meta-circularity)
51 # this is a special form of _construct_instance
52 # (see below), which is used to construct class
53 # meta-object instances for any Class::MOP::*
54 # class. All other classes will use the more
55 # normal &construct_instance.
56 sub _construct_class_instance {
58 my $options = @_ == 1 ? $_[0] : {@_};
59 my $package_name = $options->{package};
60 (defined $package_name && $package_name)
61 || confess "You must pass a package name";
63 # return the metaclass if we have it cached,
64 # and it is still defined (it has not been
65 # reaped by DESTROY yet, which can happen
66 # annoyingly enough during global destruction)
68 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
73 # we need to deal with the possibility
74 # of class immutability here, and then
75 # get the name of the class appropriately
77 ? ($class->is_immutable
78 ? $class->get_mutable_metaclass_name()
82 # now create the metaclass
84 if ($class eq 'Class::MOP::Class') {
85 $meta = $class->_new($options);
89 # it is safe to use meta here because
90 # class will always be a subclass of
91 # Class::MOP::Class, which defines meta
92 $meta = $class->meta->_construct_instance($options)
95 # and check the metaclass compatibility
96 $meta->_check_metaclass_compatibility();
98 Class::MOP::store_metaclass_by_name($package_name, $meta);
101 # we need to weaken any anon classes
102 # so that they can call DESTROY properly
103 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
110 my $options = @_ == 1 ? $_[0] : {@_};
113 # inherited from Class::MOP::Package
114 'package' => $options->{package},
117 # since the following attributes will
118 # actually be loaded from the symbol
119 # table, and actually bypass the instance
120 # entirely, we can just leave these things
121 # listed here for reference, because they
122 # should not actually have a value associated
124 'namespace' => \undef,
126 # inherited from Class::MOP::Module
128 'authority' => \undef,
130 # defined in Class::MOP::Class
131 'superclasses' => \undef,
135 'attribute_metaclass' =>
136 ( $options->{'attribute_metaclass'} || 'Class::MOP::Attribute' ),
137 'method_metaclass' =>
138 ( $options->{'method_metaclass'} || 'Class::MOP::Method' ),
139 'wrapped_method_metaclass' => (
140 $options->{'wrapped_method_metaclass'}
141 || 'Class::MOP::Method::Wrapped'
143 'instance_metaclass' =>
144 ( $options->{'instance_metaclass'} || 'Class::MOP::Instance' ),
145 'immutable_trait' => (
146 $options->{'immutable_trait'}
147 || 'Class::MOP::Class::Immutable::Trait'
149 'constructor_name' => ( $options->{constructor_name} || 'new' ),
150 'constructor_class' => (
151 $options->{constructor_class} || 'Class::MOP::Method::Constructor'
153 'destructor_class' => $options->{destructor_class},
157 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
158 sub update_package_cache_flag {
161 # we can manually update the cache number
162 # since we are actually adding the method
163 # to our cache as well. This avoids us
164 # having to regenerate the method_map.
166 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
170 sub check_metaclass_compatibility {
171 Carp::cluck('The check_metaclass_compatibility method has been made private.'
172 . " The public version is deprecated and will be removed in a future release.\n");
173 shift->_check_metaclass_compatibility(@_);
176 sub _check_metaclass_compatibility {
179 # this is always okay ...
180 return if ref($self) eq 'Class::MOP::Class' &&
181 $self->instance_metaclass eq 'Class::MOP::Instance';
183 return if $self->can('get_mutable_metaclass_name');
185 my @class_list = $self->linearized_isa;
186 shift @class_list; # shift off $self->name
188 foreach my $superclass_name (@class_list) {
189 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name) || next;
192 # we need to deal with the possibility
193 # of class immutability here, and then
194 # get the name of the class appropriately
196 = $super_meta->is_immutable
197 ? $super_meta->get_mutable_metaclass_name()
200 ($self->isa($super_meta_type))
201 || confess "The metaclass of " . $self->name . " ("
202 . (ref($self)) . ")" . " is not compatible with the " .
203 "metaclass of its superclass, ".$superclass_name . " ("
204 . ($super_meta_type) . ")";
206 # we also need to check that instance metaclasses
207 # are compatibile in the same the class.
208 ($self->instance_metaclass->isa($super_meta->instance_metaclass))
209 || confess "The instance metaclass for " . $self->name . " (" . ($self->instance_metaclass) . ")" .
210 " is not compatible with the " .
211 "instance metaclass of its superclass, " . $superclass_name . " (" . ($super_meta->instance_metaclass) . ")";
219 # this should be sufficient, if you have a
220 # use case where it is not, write a test and
222 my $ANON_CLASS_SERIAL = 0;
225 # we need a sufficiently annoying prefix
226 # this should suffice for now, this is
227 # used in a couple of places below, so
228 # need to put it up here for now.
229 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
233 no warnings 'uninitialized';
234 $self->name =~ /^$ANON_CLASS_PREFIX/;
237 sub create_anon_class {
238 my ($class, %options) = @_;
239 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
240 return $class->create($package_name, %options);
244 # this will only get called for
245 # anon-classes, all other calls
246 # are assumed to occur during
247 # global destruction and so don't
248 # really need to be handled explicitly
252 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
254 no warnings 'uninitialized';
255 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
256 # Moose does a weird thing where it replaces the metaclass for
257 # class when fixing metaclass incompatibility. In that case,
258 # we don't want to clean out the namespace now. We can detect
259 # that because Moose will explicitly update the singleton
260 # cache in Class::MOP.
261 my $current_meta = Class::MOP::get_metaclass_by_name($self->name);
262 return if $current_meta ne $self;
264 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
266 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
267 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
269 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
274 # creating classes with MOP ...
277 my ( $class, @args ) = @_;
279 unshift @args, 'package' if @args % 2 == 1;
281 my (%options) = @args;
282 my $package_name = $options{package};
284 (ref $options{superclasses} eq 'ARRAY')
285 || confess "You must pass an ARRAY ref of superclasses"
286 if exists $options{superclasses};
288 (ref $options{attributes} eq 'ARRAY')
289 || confess "You must pass an ARRAY ref of attributes"
290 if exists $options{attributes};
292 (ref $options{methods} eq 'HASH')
293 || confess "You must pass a HASH ref of methods"
294 if exists $options{methods};
296 my (%initialize_options) = @args;
297 delete @initialize_options{qw(
305 my $meta = $class->initialize( $package_name => %initialize_options );
307 $meta->_instantiate_module( $options{version}, $options{authority} );
310 $meta->add_method('meta' => sub {
311 $class->initialize(ref($_[0]) || $_[0]);
314 $meta->superclasses(@{$options{superclasses}})
315 if exists $options{superclasses};
317 # process attributes first, so that they can
318 # install accessors, but locally defined methods
319 # can then overwrite them. It is maybe a little odd, but
320 # I think this should be the order of things.
321 if (exists $options{attributes}) {
322 foreach my $attr (@{$options{attributes}}) {
323 $meta->add_attribute($attr);
326 if (exists $options{methods}) {
327 foreach my $method_name (keys %{$options{methods}}) {
328 $meta->add_method($method_name, $options{methods}->{$method_name});
337 # all these attribute readers will be bootstrapped
338 # away in the Class::MOP bootstrap section
340 sub get_attribute_map { $_[0]->{'attributes'} }
341 sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
342 sub method_metaclass { $_[0]->{'method_metaclass'} }
343 sub wrapped_method_metaclass { $_[0]->{'wrapped_method_metaclass'} }
344 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
345 sub immutable_trait { $_[0]->{'immutable_trait'} }
346 sub constructor_class { $_[0]->{'constructor_class'} }
347 sub constructor_name { $_[0]->{'constructor_name'} }
348 sub destructor_class { $_[0]->{'destructor_class'} }
350 # Instance Construction & Cloning
356 # we need to protect the integrity of the
357 # Class::MOP::Class singletons here, so we
358 # delegate this to &construct_class_instance
359 # which will deal with the singletons
360 return $class->_construct_class_instance(@_)
361 if $class->name->isa('Class::MOP::Class');
362 return $class->_construct_instance(@_);
365 sub construct_instance {
366 Carp::cluck('The construct_instance method has been made private.'
367 . " The public version is deprecated and will be removed in a future release.\n");
368 shift->_construct_instance(@_);
371 sub _construct_instance {
373 my $params = @_ == 1 ? $_[0] : {@_};
374 my $meta_instance = $class->get_meta_instance();
376 # the code below is almost certainly incorrect
377 # but this is foreign inheritance, so we might
378 # have to kludge it in the end.
379 my $instance = $params->{__INSTANCE__} || $meta_instance->create_instance();
380 foreach my $attr ($class->get_all_attributes()) {
381 $attr->initialize_instance_slot($meta_instance, $instance, $params);
384 # this will only work for a HASH instance type
385 if ($class->is_anon_class) {
386 (Scalar::Util::reftype($instance) eq 'HASH')
387 || confess "Currently only HASH based instances are supported with instance of anon-classes";
389 # At some point we should make this official
390 # as a reserved slot name, but right now I am
391 # going to keep it here.
392 # my $RESERVED_MOP_SLOT = '__MOP__';
393 $instance->{'__MOP__'} = $class;
399 sub get_meta_instance {
401 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
404 sub create_meta_instance {
405 Carp::cluck('The create_meta_instance method has been made private.'
406 . " The public version is deprecated and will be removed in a future release.\n");
407 shift->_create_meta_instance(@_);
410 sub _create_meta_instance {
413 my $instance = $self->instance_metaclass->new(
414 associated_metaclass => $self,
415 attributes => [ $self->get_all_attributes() ],
418 $self->add_meta_instance_dependencies()
419 if $instance->is_dependent_on_superclasses();
426 my $instance = shift;
427 (blessed($instance) && $instance->isa($class->name))
428 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
431 # we need to protect the integrity of the
432 # Class::MOP::Class singletons here, they
433 # should not be cloned.
434 return $instance if $instance->isa('Class::MOP::Class');
435 $class->_clone_instance($instance, @_);
439 Carp::cluck('The clone_instance method has been made private.'
440 . " The public version is deprecated and will be removed in a future release.\n");
441 shift->_clone_instance(@_);
444 sub _clone_instance {
445 my ($class, $instance, %params) = @_;
447 || confess "You can only clone instances, ($instance) is not a blessed instance";
448 my $meta_instance = $class->get_meta_instance();
449 my $clone = $meta_instance->clone_instance($instance);
450 foreach my $attr ($class->get_all_attributes()) {
451 if ( defined( my $init_arg = $attr->init_arg ) ) {
452 if (exists $params{$init_arg}) {
453 $attr->set_value($clone, $params{$init_arg});
460 sub rebless_instance {
461 my ($self, $instance, %params) = @_;
463 my $old_metaclass = Class::MOP::class_of($instance);
465 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
466 $self->name->isa($old_class)
467 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
469 $old_metaclass->rebless_instance_away($instance, $self, %params)
472 my $meta_instance = $self->get_meta_instance();
475 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
476 $meta_instance->rebless_instance_structure($_[1], $self);
478 foreach my $attr ( $self->get_all_attributes ) {
479 if ( $attr->has_value($instance) ) {
480 if ( defined( my $init_arg = $attr->init_arg ) ) {
481 $params{$init_arg} = $attr->get_value($instance)
482 unless exists $params{$init_arg};
485 $attr->set_value($instance, $attr->get_value($instance));
490 foreach my $attr ($self->get_all_attributes) {
491 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
497 sub rebless_instance_away {
498 # this intentionally does nothing, it is just a hook
505 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
508 @{$self->get_package_symbol($var_spec)} = @supers;
511 # on 5.8 and below, we need to call
512 # a method to get Perl to detect
513 # a cycle in the class hierarchy
514 my $class = $self->name;
518 # we need to check the metaclass
519 # compatibility here so that we can
520 # be sure that the superclass is
521 # not potentially creating an issues
522 # we don't know about
524 $self->_check_metaclass_compatibility();
525 $self->_superclasses_updated();
527 @{$self->get_package_symbol($var_spec)};
530 sub _superclasses_updated {
532 $self->update_meta_instance_dependencies();
537 my $super_class = $self->name;
539 return @{ $super_class->mro::get_isarev() };
542 sub direct_subclasses {
544 my $super_class = $self->name;
549 } Class::MOP::Class->initialize($_)->superclasses
554 return @{ mro::get_linear_isa( (shift)->name ) };
557 sub class_precedence_list {
559 my $name = $self->name;
561 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
563 # We need to check for circular inheritance here
564 # if we are are not on 5.10, cause 5.8 detects it
565 # late. This will do nothing if all is well, and
566 # blow up otherwise. Yes, it's an ugly hack, better
567 # suggestions are welcome.
569 ($name || return)->isa('This is a test for circular inheritance')
572 # if our mro is c3, we can
573 # just grab the linear_isa
574 if (mro::get_mro($name) eq 'c3') {
575 return @{ mro::get_linear_isa($name) }
579 # we can't grab the linear_isa for dfs
580 # since it has all the duplicates
585 $self->initialize($_)->class_precedence_list()
586 } $self->superclasses()
593 sub wrap_method_body {
594 my ( $self, %args ) = @_;
596 ('CODE' eq ref $args{body})
597 || confess "Your code block must be a CODE reference";
599 $self->method_metaclass->wrap(
600 package_name => $self->name,
606 my ($self, $method_name, $method) = @_;
607 (defined $method_name && $method_name)
608 || confess "You must define a method name";
611 if (blessed($method)) {
612 $body = $method->body;
613 if ($method->package_name ne $self->name) {
614 $method = $method->clone(
615 package_name => $self->name,
617 ) if $method->can('clone');
622 $method = $self->wrap_method_body( body => $body, name => $method_name );
625 $method->attach_to_class($self);
627 $self->get_method_map->{$method_name} = $method;
629 my ( $current_package, $current_name ) = Class::MOP::get_code_info($body);
631 if ( !defined $current_name || $current_name eq '__ANON__' ) {
632 my $full_method_name = ($self->name . '::' . $method_name);
633 subname($full_method_name => $body);
636 $self->add_package_symbol(
637 { sigil => '&', type => 'CODE', name => $method_name },
643 my $fetch_and_prepare_method = sub {
644 my ($self, $method_name) = @_;
645 my $wrapped_metaclass = $self->wrapped_method_metaclass;
647 my $method = $self->get_method($method_name);
648 # if we dont have local ...
650 # try to find the next method
651 $method = $self->find_next_method_by_name($method_name);
652 # die if it does not exist
654 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
655 # and now make sure to wrap it
656 # even if it is already wrapped
657 # because we need a new sub ref
658 $method = $wrapped_metaclass->wrap($method);
661 # now make sure we wrap it properly
662 $method = $wrapped_metaclass->wrap($method)
663 unless $method->isa($wrapped_metaclass);
665 $self->add_method($method_name => $method);
669 sub add_before_method_modifier {
670 my ($self, $method_name, $method_modifier) = @_;
671 (defined $method_name && $method_name)
672 || confess "You must pass in a method name";
673 my $method = $fetch_and_prepare_method->($self, $method_name);
674 $method->add_before_modifier(
675 subname(':before' => $method_modifier)
679 sub add_after_method_modifier {
680 my ($self, $method_name, $method_modifier) = @_;
681 (defined $method_name && $method_name)
682 || confess "You must pass in a method name";
683 my $method = $fetch_and_prepare_method->($self, $method_name);
684 $method->add_after_modifier(
685 subname(':after' => $method_modifier)
689 sub add_around_method_modifier {
690 my ($self, $method_name, $method_modifier) = @_;
691 (defined $method_name && $method_name)
692 || confess "You must pass in a method name";
693 my $method = $fetch_and_prepare_method->($self, $method_name);
694 $method->add_around_modifier(
695 subname(':around' => $method_modifier)
700 # the methods above used to be named like this:
701 # ${pkg}::${method}:(before|after|around)
702 # but this proved problematic when using one modifier
703 # to wrap multiple methods (something which is likely
704 # to happen pretty regularly IMO). So instead of naming
705 # it like this, I have chosen to just name them purely
706 # with their modifier names, like so:
707 # :(before|after|around)
708 # The fact is that in a stack trace, it will be fairly
709 # evident from the context what method they are attached
710 # to, and so don't need the fully qualified name.
714 Carp::cluck("The alias_method method is deprecated. Use add_method instead.\n");
716 shift->add_method(@_);
720 my ($self, $method_name) = @_;
721 (defined $method_name && $method_name)
722 || confess "You must define a method name";
724 exists $self->get_method_map->{$method_name};
728 my ($self, $method_name) = @_;
729 (defined $method_name && $method_name)
730 || confess "You must define a method name";
732 return $self->get_method_map->{$method_name};
736 my ($self, $method_name) = @_;
737 (defined $method_name && $method_name)
738 || confess "You must define a method name";
740 my $removed_method = delete $self->get_method_map->{$method_name};
742 $self->remove_package_symbol(
743 { sigil => '&', type => 'CODE', name => $method_name }
746 $removed_method->detach_from_class if $removed_method;
748 $self->update_package_cache_flag; # still valid, since we just removed the method from the map
750 return $removed_method;
753 sub get_method_list {
755 keys %{$self->get_method_map};
758 sub find_method_by_name {
759 my ($self, $method_name) = @_;
760 (defined $method_name && $method_name)
761 || confess "You must define a method name to find";
762 foreach my $class ($self->linearized_isa) {
763 # fetch the meta-class ...
764 my $meta = $self->initialize($class);
765 return $meta->get_method($method_name)
766 if $meta->has_method($method_name);
771 sub get_all_methods {
773 my %methods = map { %{ $self->initialize($_)->get_method_map } } reverse $self->linearized_isa;
774 return values %methods;
777 sub compute_all_applicable_methods {
778 Carp::cluck('The compute_all_applicable_methods method is deprecated.'
779 . " Use get_all_methods instead.\n");
784 class => $_->package_name,
785 code => $_, # sigh, overloading
787 } shift->get_all_methods(@_);
790 sub get_all_method_names {
793 grep { $uniq{$_}++ == 0 } map { $_->name } $self->get_all_methods;
796 sub find_all_methods_by_name {
797 my ($self, $method_name) = @_;
798 (defined $method_name && $method_name)
799 || confess "You must define a method name to find";
801 foreach my $class ($self->linearized_isa) {
802 # fetch the meta-class ...
803 my $meta = $self->initialize($class);
805 name => $method_name,
807 code => $meta->get_method($method_name)
808 } if $meta->has_method($method_name);
813 sub find_next_method_by_name {
814 my ($self, $method_name) = @_;
815 (defined $method_name && $method_name)
816 || confess "You must define a method name to find";
817 my @cpl = $self->linearized_isa;
818 shift @cpl; # discard ourselves
819 foreach my $class (@cpl) {
820 # fetch the meta-class ...
821 my $meta = $self->initialize($class);
822 return $meta->get_method($method_name)
823 if $meta->has_method($method_name);
832 # either we have an attribute object already
833 # or we need to create one from the args provided
834 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
835 # make sure it is derived from the correct type though
836 ($attribute->isa('Class::MOP::Attribute'))
837 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
839 # first we attach our new attribute
840 # because it might need certain information
841 # about the class which it is attached to
842 $attribute->attach_to_class($self);
844 # then we remove attributes of a conflicting
845 # name here so that we can properly detach
846 # the old attr object, and remove any
847 # accessors it would have generated
848 if ( $self->has_attribute($attribute->name) ) {
849 $self->remove_attribute($attribute->name);
851 $self->invalidate_meta_instances();
854 # get our count of previously inserted attributes and
855 # increment by one so this attribute knows its order
856 my $order = (scalar keys %{$self->get_attribute_map}) - 1;
857 $attribute->_set_insertion_order($order + 1);
859 # then onto installing the new accessors
860 $self->get_attribute_map->{$attribute->name} = $attribute;
862 # invalidate package flag here
866 eval { $attribute->install_accessors() };
870 $self->remove_attribute($attribute->name);
877 sub update_meta_instance_dependencies {
880 if ( $self->{meta_instance_dependencies} ) {
881 return $self->add_meta_instance_dependencies;
885 sub add_meta_instance_dependencies {
888 $self->remove_meta_instance_dependencies;
890 my @attrs = $self->get_all_attributes();
893 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
895 foreach my $class ( @classes ) {
896 $class->add_dependent_meta_instance($self);
899 $self->{meta_instance_dependencies} = \@classes;
902 sub remove_meta_instance_dependencies {
905 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
906 foreach my $class ( @$classes ) {
907 $class->remove_dependent_meta_instance($self);
917 sub add_dependent_meta_instance {
918 my ( $self, $metaclass ) = @_;
919 push @{ $self->{dependent_meta_instances} }, $metaclass;
922 sub remove_dependent_meta_instance {
923 my ( $self, $metaclass ) = @_;
924 my $name = $metaclass->name;
925 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
928 sub invalidate_meta_instances {
930 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
933 sub invalidate_meta_instance {
935 undef $self->{_meta_instance};
939 my ($self, $attribute_name) = @_;
940 (defined $attribute_name && $attribute_name)
941 || confess "You must define an attribute name";
942 exists $self->get_attribute_map->{$attribute_name};
946 my ($self, $attribute_name) = @_;
947 (defined $attribute_name && $attribute_name)
948 || confess "You must define an attribute name";
949 return $self->get_attribute_map->{$attribute_name}
951 # this will return undef anyway, so no need ...
952 # if $self->has_attribute($attribute_name);
956 sub remove_attribute {
957 my ($self, $attribute_name) = @_;
958 (defined $attribute_name && $attribute_name)
959 || confess "You must define an attribute name";
960 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
961 return unless defined $removed_attribute;
962 delete $self->get_attribute_map->{$attribute_name};
963 $self->invalidate_meta_instances();
964 $removed_attribute->remove_accessors();
965 $removed_attribute->detach_from_class();
966 return $removed_attribute;
969 sub get_attribute_list {
971 keys %{$self->get_attribute_map};
974 sub get_all_attributes {
976 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
977 return values %attrs;
980 sub compute_all_applicable_attributes {
981 Carp::cluck('The compute_all_applicable_attributes method has been deprecated.'
982 . " Use get_all_attributes instead.\n");
984 shift->get_all_attributes(@_);
987 sub find_attribute_by_name {
988 my ($self, $attr_name) = @_;
989 foreach my $class ($self->linearized_isa) {
990 # fetch the meta-class ...
991 my $meta = $self->initialize($class);
992 return $meta->get_attribute($attr_name)
993 if $meta->has_attribute($attr_name);
998 # check if we can reinitialize
1002 # if any local attr is defined
1003 return if $self->get_attribute_list;
1005 # or any non-declared methods
1006 if ( my @methods = values %{ $self->get_method_map } ) {
1007 my $metaclass = $self->method_metaclass;
1008 foreach my $method ( @methods ) {
1009 return if $method->isa("Class::MOP::Method::Generated");
1010 # FIXME do we need to enforce this too? return unless $method->isa($metaclass);
1019 sub is_mutable { 1 }
1020 sub is_immutable { 0 }
1022 sub _immutable_options {
1023 my ( $self, @args ) = @_;
1026 inline_accessors => 1,
1027 inline_constructor => 1,
1028 inline_destructor => 0,
1030 immutable_trait => $self->immutable_trait,
1031 constructor_name => $self->constructor_name,
1032 constructor_class => $self->constructor_class,
1033 destructor_class => $self->destructor_class,
1038 sub make_immutable {
1039 my ( $self, @args ) = @_;
1041 if ( $self->is_mutable ) {
1042 $self->_initialize_immutable( $self->_immutable_options(@args) );
1043 $self->_rebless_as_immutable(@args);
1054 if ( $self->is_immutable ) {
1055 my @args = $self->immutable_options;
1056 $self->_rebless_as_mutable();
1057 $self->_remove_inlined_code(@args);
1058 delete $self->{__immutable};
1066 sub _rebless_as_immutable {
1067 my ( $self, @args ) = @_;
1069 $self->{__immutable}{original_class} = ref $self;
1071 bless $self => $self->_immutable_metaclass(@args);
1074 sub _immutable_metaclass {
1075 my ( $self, %args ) = @_;
1077 if ( my $class = $args{immutable_metaclass} ) {
1081 my $trait = $args{immutable_trait} = $self->immutable_trait
1082 || confess "no immutable trait specified for $self";
1084 my $meta_attr = $self->meta->find_attribute_by_name("immutable_trait");
1088 if ( $meta_attr and $trait eq $meta_attr->default ) {
1089 # if the trait is the same as the default we try and pick a
1090 # predictable name for the immutable metaclass
1091 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1094 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1095 $trait, 'ForMetaClass', ref($self);
1099 if Class::MOP::is_class_loaded($class_name);
1101 my $meta = Class::MOP::Class->create(
1103 superclasses => [ ref $self ],
1106 Class::MOP::load_class($trait);
1107 for my $meth ( Class::MOP::Class->initialize($trait)->get_all_methods ) {
1108 next if $meta->has_method( $meth->name );
1110 if ( $meta->find_method_by_name( $meth->name ) ) {
1111 $meta->add_around_method_modifier( $meth->name, $meth->body );
1114 $meta->add_method( $meth->name, $meth->clone );
1121 sub _remove_inlined_code {
1124 $self->remove_method( $_->name ) for $self->_inlined_methods;
1126 delete $self->{__immutable}{inlined_methods};
1129 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1131 sub _add_inlined_method {
1132 my ( $self, $method ) = @_;
1134 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1137 sub _initialize_immutable {
1138 my ( $self, %args ) = @_;
1140 $self->{__immutable}{options} = \%args;
1141 $self->_install_inlined_code(%args);
1144 sub _install_inlined_code {
1145 my ( $self, %args ) = @_;
1148 $self->_inline_accessors(%args) if $args{inline_accessors};
1149 $self->_inline_constructor(%args) if $args{inline_constructor};
1150 $self->_inline_destructor(%args) if $args{inline_destructor};
1153 sub _rebless_as_mutable {
1156 bless $self, $self->get_mutable_metaclass_name;
1161 sub _inline_accessors {
1164 foreach my $attr_name ( $self->get_attribute_list ) {
1165 $self->get_attribute($attr_name)->install_accessors(1);
1169 sub _inline_constructor {
1170 my ( $self, %args ) = @_;
1172 my $name = $args{constructor_name};
1174 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1175 my $class = $self->name;
1176 warn "Not inlining a constructor for $class since it defines"
1177 . " its own constructor.\n"
1178 . "If you are certain you don't need to inline your"
1179 . " constructor, specify inline_constructor => 0 in your"
1180 . " call to $class->meta->make_immutable\n";
1184 my $constructor_class = $args{constructor_class};
1186 Class::MOP::load_class($constructor_class);
1188 my $constructor = $constructor_class->new(
1192 package_name => $self->name,
1196 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1197 $self->add_method( $name => $constructor );
1198 $self->_add_inlined_method($constructor);
1202 sub _inline_destructor {
1203 my ( $self, %args ) = @_;
1205 ( exists $args{destructor_class} && defined $args{destructor_class} )
1206 || confess "The 'inline_destructor' option is present, but "
1207 . "no destructor class was specified";
1209 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1210 my $class = $self->name;
1211 warn "Not inlining a destructor for $class since it defines"
1212 . " its own destructor.\n";
1216 my $destructor_class = $args{destructor_class};
1218 Class::MOP::load_class($destructor_class);
1220 return unless $destructor_class->is_needed($self);
1222 my $destructor = $destructor_class->new(
1225 package_name => $self->name,
1229 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1230 $self->add_method( 'DESTROY' => $destructor );
1231 $self->_add_inlined_method($destructor);
1243 Class::MOP::Class - Class Meta Object
1247 # assuming that class Foo
1248 # has been defined, you can
1250 # use this for introspection ...
1252 # add a method to Foo ...
1253 Foo->meta->add_method( 'bar' => sub {...} )
1255 # get a list of all the classes searched
1256 # the method dispatcher in the correct order
1257 Foo->meta->class_precedence_list()
1259 # remove a method from Foo
1260 Foo->meta->remove_method('bar');
1262 # or use this to actually create classes ...
1264 Class::MOP::Class->create(
1267 superclasses => ['Foo'],
1269 Class::MOP::Attribute->new('$bar'),
1270 Class::MOP::Attribute->new('$baz'),
1273 calculate_bar => sub {...},
1274 construct_baz => sub {...}
1281 The Class Protocol is the largest and most complex part of the
1282 Class::MOP meta-object protocol. It controls the introspection and
1283 manipulation of Perl 5 classes, and it can create them as well. The
1284 best way to understand what this module can do, is to read the
1285 documentation for each of its methods.
1289 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1293 =head2 Class construction
1295 These methods all create new C<Class::MOP::Class> objects. These
1296 objects can represent existing classes, or they can be used to create
1297 new classes from scratch.
1299 The metaclass object for a given class is a singleton. If you attempt
1300 to create a metaclass for the same class twice, you will just get the
1305 =item B<< Class::MOP::Class->create($package_name, %options) >>
1307 This method creates a new C<Class::MOP::Class> object with the given
1308 package name. It accepts a number of options.
1314 An optional version number for the newly created package.
1318 An optional authority for the newly created package.
1320 =item * superclasses
1322 An optional array reference of superclass names.
1326 An optional hash reference of methods for the class. The keys of the
1327 hash reference are method names, and values are subroutine references.
1331 An optional array reference of attributes.
1333 An attribute can be passed as an existing L<Class::MOP::Attribute>
1334 object, I<or> or as a hash reference of options which will be passed
1335 to the attribute metaclass's constructor.
1339 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1341 This method works just like C<< Class::MOP::Class->create >> but it
1342 creates an "anonymous" class. In fact, the class does have a name, but
1343 that name is a unique name generated internally by this module.
1345 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1346 parameters that C<create> accepts.
1348 Anonymous classes are destroyed once the metaclass they are attached
1349 to goes out of scope, and will be removed from Perl's internal symbol
1352 All instances of an anonymous class keep a special reference to the
1353 metaclass object, which prevents the metaclass from going out of scope
1354 while any instances exist.
1356 This only works if the instance if based on a hash reference, however.
1358 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1360 This method will initialize a C<Class::MOP::Class> object for the
1361 named package. Unlike C<create>, this method I<will not> create a new
1364 The purpose of this method is to retrieve a C<Class::MOP::Class>
1365 object for introspecting an existing class.
1367 If an existing C<Class::MOP::Class> object exists for the named
1368 package, it will be returned, and any options provided will be
1371 If the object does not yet exist, it will be created.
1373 The valid options that can be passed to this method are
1374 C<attribute_metaclass>, C<method_metaclass>,
1375 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1376 optional, and default to the appropriate class in the C<Class::MOP>
1381 =head2 Object instance construction and cloning
1383 These methods are all related to creating and/or cloning object
1388 =item B<< $metaclass->clone_object($instance, %params) >>
1390 This method clones an existing object instance. Any parameters you
1391 provide are will override existing attribute values in the object.
1393 This is a convenience method for cloning an object instance, then
1394 blessing it into the appropriate package.
1396 You could implement a clone method in your class, using this method:
1399 my ($self, %params) = @_;
1400 $self->meta->clone_object($self, %params);
1403 =item B<< $metaclass->rebless_instance($instance, %params) >>
1405 This method changes the class of C<$instance> to the metaclass's class.
1407 You can only rebless an instance into a subclass of its current
1408 class. If you pass any additional parameters, these will be treated
1409 like constructor parameters and used to initialize the object's
1410 attributes. Any existing attributes that are already set will be
1413 Before reblessing the instance, this method will call
1414 C<rebless_instance_away> on the instance's current metaclass. This method
1415 will be passed the instance, the new metaclass, and any parameters
1416 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1417 does nothing; it is merely a hook.
1419 =item B<< $metaclass->new_object(%params) >>
1421 This method is used to create a new object of the metaclass's
1422 class. Any parameters you provide are used to initialize the
1423 instance's attributes. A special C<__INSTANCE__> key can be passed to
1424 provide an already generated instance, rather than having Class::MOP
1425 generate it for you. This is mostly useful for using Class::MOP with
1426 foreign classes, which generally generate instances using their own
1429 =item B<< $metaclass->instance_metaclass >>
1431 Returns the class name of the instance metaclass, see
1432 L<Class::MOP::Instance> for more information on the instance
1435 =item B<< $metaclass->get_meta_instance >>
1437 Returns an instance of the C<instance_metaclass> to be used in the
1438 construction of a new instance of the class.
1442 =head2 Informational predicates
1444 These are a few predicate methods for asking information about the
1449 =item B<< $metaclass->is_anon_class >>
1451 This returns true if the class was created by calling C<<
1452 Class::MOP::Class->create_anon_class >>.
1454 =item B<< $metaclass->is_mutable >>
1456 This returns true if the class is still mutable.
1458 =item B<< $metaclass->is_immutable >>
1460 This returns true if the class has been made immutable.
1462 =item B<< $metaclass->is_pristine >>
1464 A class is I<not> pristine if it has non-inherited attributes or if it
1465 has any generated methods.
1469 =head2 Inheritance Relationships
1473 =item B<< $metaclass->superclasses(@superclasses) >>
1475 This is a read-write accessor which represents the superclass
1476 relationships of the metaclass's class.
1478 This is basically sugar around getting and setting C<@ISA>.
1480 =item B<< $metaclass->class_precedence_list >>
1482 This returns a list of all of the class's ancestor classes. The
1483 classes are returned in method dispatch order.
1485 =item B<< $metaclass->linearized_isa >>
1487 This returns a list based on C<class_precedence_list> but with all
1490 =item B<< $metaclass->subclasses >>
1492 This returns a list of all subclasses for this class, even indirect
1495 =item B<< $metaclass->direct_subclasses >>
1497 This returns a list of immediate subclasses for this class, which does not
1498 include indirect subclasses.
1502 =head2 Method introspection and creation
1504 These methods allow you to introspect a class's methods, as well as
1505 add, remove, or change methods.
1507 Determining what is truly a method in a Perl 5 class requires some
1508 heuristics (aka guessing).
1510 Methods defined outside the package with a fully qualified name (C<sub
1511 Package::name { ... }>) will be included. Similarly, methods named
1512 with a fully qualified name using L<Sub::Name> are also included.
1514 However, we attempt to ignore imported functions.
1516 Ultimately, we are using heuristics to determine what truly is a
1517 method in a class, and these heuristics may get the wrong answer in
1518 some edge cases. However, for most "normal" cases the heuristics work
1523 =item B<< $metaclass->get_method($method_name) >>
1525 This will return a L<Class::MOP::Method> for the specified
1526 C<$method_name>. If the class does not have the specified method, it
1529 =item B<< $metaclass->has_method($method_name) >>
1531 Returns a boolean indicating whether or not the class defines the
1532 named method. It does not include methods inherited from parent
1535 =item B<< $metaclass->get_method_map >>
1537 Returns a hash reference representing the methods defined in this
1538 class. The keys are method names and the values are
1539 L<Class::MOP::Method> objects.
1541 =item B<< $metaclass->get_method_list >>
1543 This will return a list of method I<names> for all methods defined in
1546 =item B<< $metaclass->get_all_methods >>
1548 This will traverse the inheritance hierarchy and return a list of all
1549 the L<Class::MOP::Method> objects for this class and its parents.
1551 =item B<< $metaclass->find_method_by_name($method_name) >>
1553 This will return a L<Class::MOP::Method> for the specified
1554 C<$method_name>. If the class does not have the specified method, it
1557 Unlike C<get_method>, this method I<will> look for the named method in
1560 =item B<< $metaclass->get_all_method_names >>
1562 This will return a list of method I<names> for all of this class's
1563 methods, including inherited methods.
1565 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1567 This method looks for the named method in the class and all of its
1568 parents. It returns every matching method it finds in the inheritance
1569 tree, so it returns a list of methods.
1571 Each method is returned as a hash reference with three keys. The keys
1572 are C<name>, C<class>, and C<code>. The C<code> key has a
1573 L<Class::MOP::Method> object as its value.
1575 The list of methods is distinct.
1577 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1579 This method returns the first method in any superclass matching the
1580 given name. It is effectively the method that C<SUPER::$method_name>
1583 =item B<< $metaclass->add_method($method_name, $method) >>
1585 This method takes a method name and a subroutine reference, and adds
1586 the method to the class.
1588 The subroutine reference can be a L<Class::MOP::Method>, and you are
1589 strongly encouraged to pass a meta method object instead of a code
1590 reference. If you do so, that object gets stored as part of the
1591 class's method map directly. If not, the meta information will have to
1592 be recreated later, and may be incorrect.
1594 If you provide a method object, this method will clone that object if
1595 the object's package name does not match the class name. This lets us
1596 track the original source of any methods added from other classes
1597 (notably Moose roles).
1599 =item B<< $metaclass->remove_method($method_name) >>
1601 Remove the named method from the class. This method returns the
1602 L<Class::MOP::Method> object for the method.
1604 =item B<< $metaclass->method_metaclass >>
1606 Returns the class name of the method metaclass, see
1607 L<Class::MOP::Method> for more information on the method metaclass.
1609 =item B<< $metaclass->wrapped_method_metaclass >>
1611 Returns the class name of the wrapped method metaclass, see
1612 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1617 =head2 Attribute introspection and creation
1619 Because Perl 5 does not have a core concept of attributes in classes,
1620 we can only return information about attributes which have been added
1621 via this class's methods. We cannot discover information about
1622 attributes which are defined in terms of "regular" Perl 5 methods.
1626 =item B<< $metaclass->get_attribute($attribute_name) >>
1628 This will return a L<Class::MOP::Attribute> for the specified
1629 C<$attribute_name>. If the class does not have the specified
1630 attribute, it returns C<undef>.
1632 NOTE that get_attribute does not search superclasses, for that you
1633 need to use C<find_attribute_by_name>.
1635 =item B<< $metaclass->has_attribute($attribute_name) >>
1637 Returns a boolean indicating whether or not the class defines the
1638 named attribute. It does not include attributes inherited from parent
1641 =item B<< $metaclass->get_attribute_map >>
1643 Returns a hash reference representing the attributes defined in this
1644 class. The keys are attribute names and the values are
1645 L<Class::MOP::Attribute> objects.
1647 =item B<< $metaclass->get_attribute_list >>
1649 This will return a list of attributes I<names> for all attributes
1650 defined in this class.
1652 =item B<< $metaclass->get_all_attributes >>
1654 This will traverse the inheritance hierarchy and return a list of all
1655 the L<Class::MOP::Attribute> objects for this class and its parents.
1657 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1659 This will return a L<Class::MOP::Attribute> for the specified
1660 C<$attribute_name>. If the class does not have the specified
1661 attribute, it returns C<undef>
1663 Unlike C<get_attribute>, this attribute I<will> look for the named
1664 attribute in superclasses.
1666 =item B<< $metaclass->add_attribute(...) >>
1668 This method accepts either an existing L<Class::MOP::Attribute>
1669 object, or parameters suitable for passing to that class's C<new>
1672 The attribute provided will be added to the class.
1674 Any accessor methods defined by the attribute will be added to the
1675 class when the attribute is added.
1677 If an attribute of the same name already exists, the old attribute
1678 will be removed first.
1680 =item B<< $metaclass->remove_attribute($attribute_name) >>
1682 This will remove the named attribute from the class, and
1683 L<Class::MOP::Attribute> object.
1685 Removing an attribute also removes any accessor methods defined by the
1688 However, note that removing an attribute will only affect I<future>
1689 object instances created for this class, not existing instances.
1691 =item B<< $metaclass->attribute_metaclass >>
1693 Returns the class name of the attribute metaclass for this class. By
1694 default, this is L<Class::MOP::Attribute>. for more information on
1698 =head2 Class Immutability
1700 Making a class immutable "freezes" the class definition. You can no
1701 longer call methods which alter the class, such as adding or removing
1702 methods or attributes.
1704 Making a class immutable lets us optimize the class by inlining some
1705 methods, and also allows us to optimize some methods on the metaclass
1708 After immutabilization, the metaclass object will cache most
1709 informational methods such as C<get_method_map> and
1710 C<get_all_attributes>. Methods which would alter the class, such as
1711 C<add_attribute>, C<add_method>, and so on will throw an error on an
1712 immutable metaclass object.
1714 The immutabilization system in L<Moose> takes much greater advantage
1715 of the inlining features than Class::MOP itself does.
1719 =item B<< $metaclass->make_immutable(%options) >>
1721 This method will create an immutable transformer and uses it to make
1722 the class and its metaclass object immutable.
1724 This method accepts the following options:
1728 =item * inline_accessors
1730 =item * inline_constructor
1732 =item * inline_destructor
1734 These are all booleans indicating whether the specified method(s)
1737 By default, accessors and the constructor are inlined, but not the
1740 =item * immutable_trait
1742 The name of a class which will be used as a parent class for the
1743 metaclass object being made immutable. This "trait" implements the
1744 post-immutability functionality of the metaclass (but not the
1745 transformation itself).
1747 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1749 =item * constructor_name
1751 This is the constructor method name. This defaults to "new".
1753 =item * constructor_class
1755 The name of the method metaclass for constructors. It will be used to
1756 generate the inlined constructor. This defaults to
1757 "Class::MOP::Method::Constructor".
1759 =item * replace_constructor
1761 This is a boolean indicating whether an existing constructor should be
1762 replaced when inlining a constructor. This defaults to false.
1764 =item * destructor_class
1766 The name of the method metaclass for destructors. It will be used to
1767 generate the inlined destructor. This defaults to
1768 "Class::MOP::Method::Denstructor".
1770 =item * replace_destructor
1772 This is a boolean indicating whether an existing destructor should be
1773 replaced when inlining a destructor. This defaults to false.
1777 =item B<< $metaclass->make_mutable >>
1779 Calling this method reverse the immutabilization transformation.
1783 =head2 Method Modifiers
1785 Method modifiers are hooks which allow a method to be wrapped with
1786 I<before>, I<after> and I<around> method modifiers. Every time a
1787 method is called, it's modifiers are also called.
1789 A class can modify its own methods, as well as methods defined in
1792 =head3 How method modifiers work?
1794 Method modifiers work by wrapping the original method and then
1795 replacing it in the class's symbol table. The wrappers will handle
1796 calling all the modifiers in the appropriate order and preserving the
1797 calling context for the original method.
1799 The return values of C<before> and C<after> modifiers are
1800 ignored. This is because their purpose is B<not> to filter the input
1801 and output of the primary method (this is done with an I<around>
1804 This may seem like an odd restriction to some, but doing this allows
1805 for simple code to be added at the beginning or end of a method call
1806 without altering the function of the wrapped method or placing any
1807 extra responsibility on the code of the modifier.
1809 Of course if you have more complex needs, you can use the C<around>
1810 modifier which allows you to change both the parameters passed to the
1811 wrapped method, as well as its return value.
1813 Before and around modifiers are called in last-defined-first-called
1814 order, while after modifiers are called in first-defined-first-called
1815 order. So the call tree might looks something like this:
1827 =head3 What is the performance impact?
1829 Of course there is a performance cost associated with method
1830 modifiers, but we have made every effort to make that cost directly
1831 proportional to the number of modifier features you utilize.
1833 The wrapping method does it's best to B<only> do as much work as it
1834 absolutely needs to. In order to do this we have moved some of the
1835 performance costs to set-up time, where they are easier to amortize.
1837 All this said, our benchmarks have indicated the following:
1839 simple wrapper with no modifiers 100% slower
1840 simple wrapper with simple before modifier 400% slower
1841 simple wrapper with simple after modifier 450% slower
1842 simple wrapper with simple around modifier 500-550% slower
1843 simple wrapper with all 3 modifiers 1100% slower
1845 These numbers may seem daunting, but you must remember, every feature
1846 comes with some cost. To put things in perspective, just doing a
1847 simple C<AUTOLOAD> which does nothing but extract the name of the
1848 method called and return it costs about 400% over a normal method
1853 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1855 This wraps the specified method with the supplied subroutine
1856 reference. The modifier will be called as a method itself, and will
1857 receive the same arguments as are passed to the method.
1859 When the modifier exits, the wrapped method will be called.
1861 The return value of the modifier will be ignored.
1863 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1865 This wraps the specified method with the supplied subroutine
1866 reference. The modifier will be called as a method itself, and will
1867 receive the same arguments as are passed to the method.
1869 When the wrapped methods exits, the modifier will be called.
1871 The return value of the modifier will be ignored.
1873 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1875 This wraps the specified method with the supplied subroutine
1878 The first argument passed to the modifier will be a subroutine
1879 reference to the wrapped method. The second argument is the object,
1880 and after that come any arguments passed when the method is called.
1882 The around modifier can choose to call the original method, as well as
1883 what arguments to pass if it does so.
1885 The return value of the modifier is what will be seen by the caller.
1889 =head2 Introspection
1893 =item B<< Class::MOP::Class->meta >>
1895 This will return a L<Class::MOP::Class> instance for this class.
1897 It should also be noted that L<Class::MOP> will actually bootstrap
1898 this module by installing a number of attribute meta-objects into its
1905 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1907 =head1 COPYRIGHT AND LICENSE
1909 Copyright 2006-2009 by Infinity Interactive, Inc.
1911 L<http://www.iinteractive.com>
1913 This library is free software; you can redistribute it and/or modify
1914 it under the same terms as Perl itself.