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 = '0.89';
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 my @class_list = $self->linearized_isa;
184 shift @class_list; # shift off $self->name
186 foreach my $superclass_name (@class_list) {
187 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name) || next;
190 # we need to deal with the possibility
191 # of class immutability here, and then
192 # get the name of the class appropriately
194 = $super_meta->is_immutable
195 ? $super_meta->get_mutable_metaclass_name()
198 ($self->isa($super_meta_type))
199 || confess "The metaclass of " . $self->name . " ("
200 . (ref($self)) . ")" . " is not compatible with the " .
201 "metaclass of its superclass, ".$superclass_name . " ("
202 . ($super_meta_type) . ")";
204 # we also need to check that instance metaclasses
205 # are compatibile in the same the class.
206 ($self->instance_metaclass->isa($super_meta->instance_metaclass))
207 || confess "The instance metaclass for " . $self->name . " (" . ($self->instance_metaclass) . ")" .
208 " is not compatible with the " .
209 "instance metaclass of its superclass, " . $superclass_name . " (" . ($super_meta->instance_metaclass) . ")";
217 # this should be sufficient, if you have a
218 # use case where it is not, write a test and
220 my $ANON_CLASS_SERIAL = 0;
223 # we need a sufficiently annoying prefix
224 # this should suffice for now, this is
225 # used in a couple of places below, so
226 # need to put it up here for now.
227 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
231 no warnings 'uninitialized';
232 $self->name =~ /^$ANON_CLASS_PREFIX/;
235 sub create_anon_class {
236 my ($class, %options) = @_;
237 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
238 return $class->create($package_name, %options);
242 # this will only get called for
243 # anon-classes, all other calls
244 # are assumed to occur during
245 # global destruction and so don't
246 # really need to be handled explicitly
250 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
252 no warnings 'uninitialized';
253 my $name = $self->name;
254 return unless $name =~ /^$ANON_CLASS_PREFIX/;
255 # Moose does a weird thing where it replaces the metaclass for
256 # class when fixing metaclass incompatibility. In that case,
257 # we don't want to clean out the namespace now. We can detect
258 # that because Moose will explicitly update the singleton
259 # cache in Class::MOP.
260 my $current_meta = Class::MOP::get_metaclass_by_name($name);
261 return if $current_meta ne $self;
263 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/);
265 @{$name . '::ISA'} = ();
266 %{$name . '::'} = ();
267 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
269 Class::MOP::remove_metaclass_by_name($name);
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 my $attr_name = $attribute->name;
846 # then we remove attributes of a conflicting
847 # name here so that we can properly detach
848 # the old attr object, and remove any
849 # accessors it would have generated
850 if ( $self->has_attribute($attr_name) ) {
851 $self->remove_attribute($attr_name);
853 $self->invalidate_meta_instances();
856 # get our count of previously inserted attributes and
857 # increment by one so this attribute knows its order
858 my $order = (scalar keys %{$self->get_attribute_map});
859 $attribute->_set_insertion_order($order);
861 # then onto installing the new accessors
862 $self->get_attribute_map->{$attr_name} = $attribute;
864 # invalidate package flag here
868 eval { $attribute->install_accessors() };
872 $self->remove_attribute($attr_name);
879 sub update_meta_instance_dependencies {
882 if ( $self->{meta_instance_dependencies} ) {
883 return $self->add_meta_instance_dependencies;
887 sub add_meta_instance_dependencies {
890 $self->remove_meta_instance_dependencies;
892 my @attrs = $self->get_all_attributes();
895 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
897 foreach my $class ( @classes ) {
898 $class->add_dependent_meta_instance($self);
901 $self->{meta_instance_dependencies} = \@classes;
904 sub remove_meta_instance_dependencies {
907 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
908 foreach my $class ( @$classes ) {
909 $class->remove_dependent_meta_instance($self);
919 sub add_dependent_meta_instance {
920 my ( $self, $metaclass ) = @_;
921 push @{ $self->{dependent_meta_instances} }, $metaclass;
924 sub remove_dependent_meta_instance {
925 my ( $self, $metaclass ) = @_;
926 my $name = $metaclass->name;
927 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
930 sub invalidate_meta_instances {
932 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
935 sub invalidate_meta_instance {
937 undef $self->{_meta_instance};
941 my ($self, $attribute_name) = @_;
942 (defined $attribute_name && $attribute_name)
943 || confess "You must define an attribute name";
944 exists $self->get_attribute_map->{$attribute_name};
948 my ($self, $attribute_name) = @_;
949 (defined $attribute_name && $attribute_name)
950 || confess "You must define an attribute name";
951 return $self->get_attribute_map->{$attribute_name}
953 # this will return undef anyway, so no need ...
954 # if $self->has_attribute($attribute_name);
958 sub remove_attribute {
959 my ($self, $attribute_name) = @_;
960 (defined $attribute_name && $attribute_name)
961 || confess "You must define an attribute name";
962 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
963 return unless defined $removed_attribute;
964 delete $self->get_attribute_map->{$attribute_name};
965 $self->invalidate_meta_instances();
966 $removed_attribute->remove_accessors();
967 $removed_attribute->detach_from_class();
968 return $removed_attribute;
971 sub get_attribute_list {
973 keys %{$self->get_attribute_map};
976 sub get_all_attributes {
978 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
979 return values %attrs;
982 sub compute_all_applicable_attributes {
983 Carp::cluck('The compute_all_applicable_attributes method has been deprecated.'
984 . " Use get_all_attributes instead.\n");
986 shift->get_all_attributes(@_);
989 sub find_attribute_by_name {
990 my ($self, $attr_name) = @_;
991 foreach my $class ($self->linearized_isa) {
992 # fetch the meta-class ...
993 my $meta = $self->initialize($class);
994 return $meta->get_attribute($attr_name)
995 if $meta->has_attribute($attr_name);
1000 # check if we can reinitialize
1004 # if any local attr is defined
1005 return if $self->get_attribute_list;
1007 # or any non-declared methods
1008 if ( my @methods = values %{ $self->get_method_map } ) {
1009 my $metaclass = $self->method_metaclass;
1010 foreach my $method ( @methods ) {
1011 return if $method->isa("Class::MOP::Method::Generated");
1012 # FIXME do we need to enforce this too? return unless $method->isa($metaclass);
1021 sub is_mutable { 1 }
1022 sub is_immutable { 0 }
1024 sub _immutable_options {
1025 my ( $self, @args ) = @_;
1028 inline_accessors => 1,
1029 inline_constructor => 1,
1030 inline_destructor => 0,
1032 immutable_trait => $self->immutable_trait,
1033 constructor_name => $self->constructor_name,
1034 constructor_class => $self->constructor_class,
1035 destructor_class => $self->destructor_class,
1040 sub make_immutable {
1041 my ( $self, @args ) = @_;
1043 if ( $self->is_mutable ) {
1044 $self->_initialize_immutable( $self->_immutable_options(@args) );
1045 $self->_rebless_as_immutable(@args);
1056 if ( $self->is_immutable ) {
1057 my @args = $self->immutable_options;
1058 $self->_rebless_as_mutable();
1059 $self->_remove_inlined_code(@args);
1060 delete $self->{__immutable};
1068 sub _rebless_as_immutable {
1069 my ( $self, @args ) = @_;
1071 $self->{__immutable}{original_class} = ref $self;
1073 bless $self => $self->_immutable_metaclass(@args);
1076 sub _immutable_metaclass {
1077 my ( $self, %args ) = @_;
1079 if ( my $class = $args{immutable_metaclass} ) {
1083 my $trait = $args{immutable_trait} = $self->immutable_trait
1084 || confess "no immutable trait specified for $self";
1086 my $meta_attr = $self->meta->find_attribute_by_name("immutable_trait");
1090 if ( $meta_attr and $trait eq $meta_attr->default ) {
1091 # if the trait is the same as the default we try and pick a
1092 # predictable name for the immutable metaclass
1093 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1096 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1097 $trait, 'ForMetaClass', ref($self);
1101 if Class::MOP::is_class_loaded($class_name);
1103 # If the metaclass is a subclass of CMOP::Class which has had
1104 # metaclass roles applied (via Moose), then we want to make sure
1105 # that we preserve that anonymous class (see Fey::ORM for an
1106 # example of where this matters).
1108 = $self->meta->is_immutable
1109 ? $self->meta->get_mutable_metaclass_name
1112 my $meta = $meta_name->create(
1114 superclasses => [ ref $self ],
1117 Class::MOP::load_class($trait);
1118 for my $meth ( Class::MOP::Class->initialize($trait)->get_all_methods ) {
1119 next if $meta->has_method( $meth->name );
1121 if ( $meta->find_method_by_name( $meth->name ) ) {
1122 $meta->add_around_method_modifier( $meth->name, $meth->body );
1125 $meta->add_method( $meth->name, $meth->clone );
1129 $meta->make_immutable( inline_constructor => 0 );
1134 sub _remove_inlined_code {
1137 $self->remove_method( $_->name ) for $self->_inlined_methods;
1139 delete $self->{__immutable}{inlined_methods};
1142 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1144 sub _add_inlined_method {
1145 my ( $self, $method ) = @_;
1147 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1150 sub _initialize_immutable {
1151 my ( $self, %args ) = @_;
1153 $self->{__immutable}{options} = \%args;
1154 $self->_install_inlined_code(%args);
1157 sub _install_inlined_code {
1158 my ( $self, %args ) = @_;
1161 $self->_inline_accessors(%args) if $args{inline_accessors};
1162 $self->_inline_constructor(%args) if $args{inline_constructor};
1163 $self->_inline_destructor(%args) if $args{inline_destructor};
1166 sub _rebless_as_mutable {
1169 bless $self, $self->get_mutable_metaclass_name;
1174 sub _inline_accessors {
1177 foreach my $attr_name ( $self->get_attribute_list ) {
1178 $self->get_attribute($attr_name)->install_accessors(1);
1182 sub _inline_constructor {
1183 my ( $self, %args ) = @_;
1185 my $name = $args{constructor_name};
1187 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1188 my $class = $self->name;
1189 warn "Not inlining a constructor for $class since it defines"
1190 . " its own constructor.\n"
1191 . "If you are certain you don't need to inline your"
1192 . " constructor, specify inline_constructor => 0 in your"
1193 . " call to $class->meta->make_immutable\n";
1197 my $constructor_class = $args{constructor_class};
1199 Class::MOP::load_class($constructor_class);
1201 my $constructor = $constructor_class->new(
1205 package_name => $self->name,
1209 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1210 $self->add_method( $name => $constructor );
1211 $self->_add_inlined_method($constructor);
1215 sub _inline_destructor {
1216 my ( $self, %args ) = @_;
1218 ( exists $args{destructor_class} && defined $args{destructor_class} )
1219 || confess "The 'inline_destructor' option is present, but "
1220 . "no destructor class was specified";
1222 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1223 my $class = $self->name;
1224 warn "Not inlining a destructor for $class since it defines"
1225 . " its own destructor.\n";
1229 my $destructor_class = $args{destructor_class};
1231 Class::MOP::load_class($destructor_class);
1233 return unless $destructor_class->is_needed($self);
1235 my $destructor = $destructor_class->new(
1238 package_name => $self->name,
1242 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1243 $self->add_method( 'DESTROY' => $destructor );
1244 $self->_add_inlined_method($destructor);
1256 Class::MOP::Class - Class Meta Object
1260 # assuming that class Foo
1261 # has been defined, you can
1263 # use this for introspection ...
1265 # add a method to Foo ...
1266 Foo->meta->add_method( 'bar' => sub {...} )
1268 # get a list of all the classes searched
1269 # the method dispatcher in the correct order
1270 Foo->meta->class_precedence_list()
1272 # remove a method from Foo
1273 Foo->meta->remove_method('bar');
1275 # or use this to actually create classes ...
1277 Class::MOP::Class->create(
1280 superclasses => ['Foo'],
1282 Class::MOP::Attribute->new('$bar'),
1283 Class::MOP::Attribute->new('$baz'),
1286 calculate_bar => sub {...},
1287 construct_baz => sub {...}
1294 The Class Protocol is the largest and most complex part of the
1295 Class::MOP meta-object protocol. It controls the introspection and
1296 manipulation of Perl 5 classes, and it can create them as well. The
1297 best way to understand what this module can do, is to read the
1298 documentation for each of its methods.
1302 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1306 =head2 Class construction
1308 These methods all create new C<Class::MOP::Class> objects. These
1309 objects can represent existing classes, or they can be used to create
1310 new classes from scratch.
1312 The metaclass object for a given class is a singleton. If you attempt
1313 to create a metaclass for the same class twice, you will just get the
1318 =item B<< Class::MOP::Class->create($package_name, %options) >>
1320 This method creates a new C<Class::MOP::Class> object with the given
1321 package name. It accepts a number of options.
1327 An optional version number for the newly created package.
1331 An optional authority for the newly created package.
1333 =item * superclasses
1335 An optional array reference of superclass names.
1339 An optional hash reference of methods for the class. The keys of the
1340 hash reference are method names, and values are subroutine references.
1344 An optional array reference of L<Class::MOP::Attribute> objects.
1348 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1350 This method works just like C<< Class::MOP::Class->create >> but it
1351 creates an "anonymous" class. In fact, the class does have a name, but
1352 that name is a unique name generated internally by this module.
1354 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1355 parameters that C<create> accepts.
1357 Anonymous classes are destroyed once the metaclass they are attached
1358 to goes out of scope, and will be removed from Perl's internal symbol
1361 All instances of an anonymous class keep a special reference to the
1362 metaclass object, which prevents the metaclass from going out of scope
1363 while any instances exist.
1365 This only works if the instance if based on a hash reference, however.
1367 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1369 This method will initialize a C<Class::MOP::Class> object for the
1370 named package. Unlike C<create>, this method I<will not> create a new
1373 The purpose of this method is to retrieve a C<Class::MOP::Class>
1374 object for introspecting an existing class.
1376 If an existing C<Class::MOP::Class> object exists for the named
1377 package, it will be returned, and any options provided will be
1380 If the object does not yet exist, it will be created.
1382 The valid options that can be passed to this method are
1383 C<attribute_metaclass>, C<method_metaclass>,
1384 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1385 optional, and default to the appropriate class in the C<Class::MOP>
1390 =head2 Object instance construction and cloning
1392 These methods are all related to creating and/or cloning object
1397 =item B<< $metaclass->clone_object($instance, %params) >>
1399 This method clones an existing object instance. Any parameters you
1400 provide are will override existing attribute values in the object.
1402 This is a convenience method for cloning an object instance, then
1403 blessing it into the appropriate package.
1405 You could implement a clone method in your class, using this method:
1408 my ($self, %params) = @_;
1409 $self->meta->clone_object($self, %params);
1412 =item B<< $metaclass->rebless_instance($instance, %params) >>
1414 This method changes the class of C<$instance> to the metaclass's class.
1416 You can only rebless an instance into a subclass of its current
1417 class. If you pass any additional parameters, these will be treated
1418 like constructor parameters and used to initialize the object's
1419 attributes. Any existing attributes that are already set will be
1422 Before reblessing the instance, this method will call
1423 C<rebless_instance_away> on the instance's current metaclass. This method
1424 will be passed the instance, the new metaclass, and any parameters
1425 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1426 does nothing; it is merely a hook.
1428 =item B<< $metaclass->new_object(%params) >>
1430 This method is used to create a new object of the metaclass's
1431 class. Any parameters you provide are used to initialize the
1432 instance's attributes. A special C<__INSTANCE__> key can be passed to
1433 provide an already generated instance, rather than having Class::MOP
1434 generate it for you. This is mostly useful for using Class::MOP with
1435 foreign classes, which generally generate instances using their own
1438 =item B<< $metaclass->instance_metaclass >>
1440 Returns the class name of the instance metaclass, see
1441 L<Class::MOP::Instance> for more information on the instance
1444 =item B<< $metaclass->get_meta_instance >>
1446 Returns an instance of the C<instance_metaclass> to be used in the
1447 construction of a new instance of the class.
1451 =head2 Informational predicates
1453 These are a few predicate methods for asking information about the
1458 =item B<< $metaclass->is_anon_class >>
1460 This returns true if the class was created by calling C<<
1461 Class::MOP::Class->create_anon_class >>.
1463 =item B<< $metaclass->is_mutable >>
1465 This returns true if the class is still mutable.
1467 =item B<< $metaclass->is_immutable >>
1469 This returns true if the class has been made immutable.
1471 =item B<< $metaclass->is_pristine >>
1473 A class is I<not> pristine if it has non-inherited attributes or if it
1474 has any generated methods.
1478 =head2 Inheritance Relationships
1482 =item B<< $metaclass->superclasses(@superclasses) >>
1484 This is a read-write accessor which represents the superclass
1485 relationships of the metaclass's class.
1487 This is basically sugar around getting and setting C<@ISA>.
1489 =item B<< $metaclass->class_precedence_list >>
1491 This returns a list of all of the class's ancestor classes. The
1492 classes are returned in method dispatch order.
1494 =item B<< $metaclass->linearized_isa >>
1496 This returns a list based on C<class_precedence_list> but with all
1499 =item B<< $metaclass->subclasses >>
1501 This returns a list of all subclasses for this class, even indirect
1504 =item B<< $metaclass->direct_subclasses >>
1506 This returns a list of immediate subclasses for this class, which does not
1507 include indirect subclasses.
1511 =head2 Method introspection and creation
1513 These methods allow you to introspect a class's methods, as well as
1514 add, remove, or change methods.
1516 Determining what is truly a method in a Perl 5 class requires some
1517 heuristics (aka guessing).
1519 Methods defined outside the package with a fully qualified name (C<sub
1520 Package::name { ... }>) will be included. Similarly, methods named
1521 with a fully qualified name using L<Sub::Name> are also included.
1523 However, we attempt to ignore imported functions.
1525 Ultimately, we are using heuristics to determine what truly is a
1526 method in a class, and these heuristics may get the wrong answer in
1527 some edge cases. However, for most "normal" cases the heuristics work
1532 =item B<< $metaclass->get_method($method_name) >>
1534 This will return a L<Class::MOP::Method> for the specified
1535 C<$method_name>. If the class does not have the specified method, it
1538 =item B<< $metaclass->has_method($method_name) >>
1540 Returns a boolean indicating whether or not the class defines the
1541 named method. It does not include methods inherited from parent
1544 =item B<< $metaclass->get_method_map >>
1546 Returns a hash reference representing the methods defined in this
1547 class. The keys are method names and the values are
1548 L<Class::MOP::Method> objects.
1550 =item B<< $metaclass->get_method_list >>
1552 This will return a list of method I<names> for all methods defined in
1555 =item B<< $metaclass->get_all_methods >>
1557 This will traverse the inheritance hierarchy and return a list of all
1558 the L<Class::MOP::Method> objects for this class and its parents.
1560 =item B<< $metaclass->find_method_by_name($method_name) >>
1562 This will return a L<Class::MOP::Method> for the specified
1563 C<$method_name>. If the class does not have the specified method, it
1566 Unlike C<get_method>, this method I<will> look for the named method in
1569 =item B<< $metaclass->get_all_method_names >>
1571 This will return a list of method I<names> for all of this class's
1572 methods, including inherited methods.
1574 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1576 This method looks for the named method in the class and all of its
1577 parents. It returns every matching method it finds in the inheritance
1578 tree, so it returns a list of methods.
1580 Each method is returned as a hash reference with three keys. The keys
1581 are C<name>, C<class>, and C<code>. The C<code> key has a
1582 L<Class::MOP::Method> object as its value.
1584 The list of methods is distinct.
1586 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1588 This method returns the first method in any superclass matching the
1589 given name. It is effectively the method that C<SUPER::$method_name>
1592 =item B<< $metaclass->add_method($method_name, $method) >>
1594 This method takes a method name and a subroutine reference, and adds
1595 the method to the class.
1597 The subroutine reference can be a L<Class::MOP::Method>, and you are
1598 strongly encouraged to pass a meta method object instead of a code
1599 reference. If you do so, that object gets stored as part of the
1600 class's method map directly. If not, the meta information will have to
1601 be recreated later, and may be incorrect.
1603 If you provide a method object, this method will clone that object if
1604 the object's package name does not match the class name. This lets us
1605 track the original source of any methods added from other classes
1606 (notably Moose roles).
1608 =item B<< $metaclass->remove_method($method_name) >>
1610 Remove the named method from the class. This method returns the
1611 L<Class::MOP::Method> object for the method.
1613 =item B<< $metaclass->method_metaclass >>
1615 Returns the class name of the method metaclass, see
1616 L<Class::MOP::Method> for more information on the method metaclass.
1618 =item B<< $metaclass->wrapped_method_metaclass >>
1620 Returns the class name of the wrapped method metaclass, see
1621 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1626 =head2 Attribute introspection and creation
1628 Because Perl 5 does not have a core concept of attributes in classes,
1629 we can only return information about attributes which have been added
1630 via this class's methods. We cannot discover information about
1631 attributes which are defined in terms of "regular" Perl 5 methods.
1635 =item B<< $metaclass->get_attribute($attribute_name) >>
1637 This will return a L<Class::MOP::Attribute> for the specified
1638 C<$attribute_name>. If the class does not have the specified
1639 attribute, it returns C<undef>.
1641 NOTE that get_attribute does not search superclasses, for that you
1642 need to use C<find_attribute_by_name>.
1644 =item B<< $metaclass->has_attribute($attribute_name) >>
1646 Returns a boolean indicating whether or not the class defines the
1647 named attribute. It does not include attributes inherited from parent
1650 =item B<< $metaclass->get_attribute_map >>
1652 Returns a hash reference representing the attributes defined in this
1653 class. The keys are attribute names and the values are
1654 L<Class::MOP::Attribute> objects.
1656 =item B<< $metaclass->get_attribute_list >>
1658 This will return a list of attributes I<names> for all attributes
1659 defined in this class.
1661 =item B<< $metaclass->get_all_attributes >>
1663 This will traverse the inheritance hierarchy and return a list of all
1664 the L<Class::MOP::Attribute> objects for this class and its parents.
1666 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1668 This will return a L<Class::MOP::Attribute> for the specified
1669 C<$attribute_name>. If the class does not have the specified
1670 attribute, it returns C<undef>
1672 Unlike C<get_attribute>, this attribute I<will> look for the named
1673 attribute in superclasses.
1675 =item B<< $metaclass->add_attribute(...) >>
1677 This method accepts either an existing L<Class::MOP::Attribute>
1678 object, or parameters suitable for passing to that class's C<new>
1681 The attribute provided will be added to the class.
1683 Any accessor methods defined by the attribute will be added to the
1684 class when the attribute is added.
1686 If an attribute of the same name already exists, the old attribute
1687 will be removed first.
1689 =item B<< $metaclass->remove_attribute($attribute_name) >>
1691 This will remove the named attribute from the class, and
1692 L<Class::MOP::Attribute> object.
1694 Removing an attribute also removes any accessor methods defined by the
1697 However, note that removing an attribute will only affect I<future>
1698 object instances created for this class, not existing instances.
1700 =item B<< $metaclass->attribute_metaclass >>
1702 Returns the class name of the attribute metaclass for this class. By
1703 default, this is L<Class::MOP::Attribute>. for more information on
1707 =head2 Class Immutability
1709 Making a class immutable "freezes" the class definition. You can no
1710 longer call methods which alter the class, such as adding or removing
1711 methods or attributes.
1713 Making a class immutable lets us optimize the class by inlining some
1714 methods, and also allows us to optimize some methods on the metaclass
1717 After immutabilization, the metaclass object will cache most
1718 informational methods such as C<get_method_map> and
1719 C<get_all_attributes>. Methods which would alter the class, such as
1720 C<add_attribute>, C<add_method>, and so on will throw an error on an
1721 immutable metaclass object.
1723 The immutabilization system in L<Moose> takes much greater advantage
1724 of the inlining features than Class::MOP itself does.
1728 =item B<< $metaclass->make_immutable(%options) >>
1730 This method will create an immutable transformer and uses it to make
1731 the class and its metaclass object immutable.
1733 This method accepts the following options:
1737 =item * inline_accessors
1739 =item * inline_constructor
1741 =item * inline_destructor
1743 These are all booleans indicating whether the specified method(s)
1746 By default, accessors and the constructor are inlined, but not the
1749 =item * immutable_trait
1751 The name of a class which will be used as a parent class for the
1752 metaclass object being made immutable. This "trait" implements the
1753 post-immutability functionality of the metaclass (but not the
1754 transformation itself).
1756 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1758 =item * constructor_name
1760 This is the constructor method name. This defaults to "new".
1762 =item * constructor_class
1764 The name of the method metaclass for constructors. It will be used to
1765 generate the inlined constructor. This defaults to
1766 "Class::MOP::Method::Constructor".
1768 =item * replace_constructor
1770 This is a boolean indicating whether an existing constructor should be
1771 replaced when inlining a constructor. This defaults to false.
1773 =item * destructor_class
1775 The name of the method metaclass for destructors. It will be used to
1776 generate the inlined destructor. This defaults to
1777 "Class::MOP::Method::Denstructor".
1779 =item * replace_destructor
1781 This is a boolean indicating whether an existing destructor should be
1782 replaced when inlining a destructor. This defaults to false.
1786 =item B<< $metaclass->make_mutable >>
1788 Calling this method reverse the immutabilization transformation.
1792 =head2 Method Modifiers
1794 Method modifiers are hooks which allow a method to be wrapped with
1795 I<before>, I<after> and I<around> method modifiers. Every time a
1796 method is called, it's modifiers are also called.
1798 A class can modify its own methods, as well as methods defined in
1801 =head3 How method modifiers work?
1803 Method modifiers work by wrapping the original method and then
1804 replacing it in the class's symbol table. The wrappers will handle
1805 calling all the modifiers in the appropriate order and preserving the
1806 calling context for the original method.
1808 The return values of C<before> and C<after> modifiers are
1809 ignored. This is because their purpose is B<not> to filter the input
1810 and output of the primary method (this is done with an I<around>
1813 This may seem like an odd restriction to some, but doing this allows
1814 for simple code to be added at the beginning or end of a method call
1815 without altering the function of the wrapped method or placing any
1816 extra responsibility on the code of the modifier.
1818 Of course if you have more complex needs, you can use the C<around>
1819 modifier which allows you to change both the parameters passed to the
1820 wrapped method, as well as its return value.
1822 Before and around modifiers are called in last-defined-first-called
1823 order, while after modifiers are called in first-defined-first-called
1824 order. So the call tree might looks something like this:
1836 =head3 What is the performance impact?
1838 Of course there is a performance cost associated with method
1839 modifiers, but we have made every effort to make that cost directly
1840 proportional to the number of modifier features you utilize.
1842 The wrapping method does it's best to B<only> do as much work as it
1843 absolutely needs to. In order to do this we have moved some of the
1844 performance costs to set-up time, where they are easier to amortize.
1846 All this said, our benchmarks have indicated the following:
1848 simple wrapper with no modifiers 100% slower
1849 simple wrapper with simple before modifier 400% slower
1850 simple wrapper with simple after modifier 450% slower
1851 simple wrapper with simple around modifier 500-550% slower
1852 simple wrapper with all 3 modifiers 1100% slower
1854 These numbers may seem daunting, but you must remember, every feature
1855 comes with some cost. To put things in perspective, just doing a
1856 simple C<AUTOLOAD> which does nothing but extract the name of the
1857 method called and return it costs about 400% over a normal method
1862 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1864 This wraps the specified method with the supplied subroutine
1865 reference. The modifier will be called as a method itself, and will
1866 receive the same arguments as are passed to the method.
1868 When the modifier exits, the wrapped method will be called.
1870 The return value of the modifier will be ignored.
1872 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1874 This wraps the specified method with the supplied subroutine
1875 reference. The modifier will be called as a method itself, and will
1876 receive the same arguments as are passed to the method.
1878 When the wrapped methods exits, the modifier will be called.
1880 The return value of the modifier will be ignored.
1882 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1884 This wraps the specified method with the supplied subroutine
1887 The first argument passed to the modifier will be a subroutine
1888 reference to the wrapped method. The second argument is the object,
1889 and after that come any arguments passed when the method is called.
1891 The around modifier can choose to call the original method, as well as
1892 what arguments to pass if it does so.
1894 The return value of the modifier is what will be seen by the caller.
1898 =head2 Introspection
1902 =item B<< Class::MOP::Class->meta >>
1904 This will return a L<Class::MOP::Class> instance for this class.
1906 It should also be noted that L<Class::MOP> will actually bootstrap
1907 this module by installing a number of attribute meta-objects into its
1914 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1916 =head1 COPYRIGHT AND LICENSE
1918 Copyright 2006-2009 by Infinity Interactive, Inc.
1920 L<http://www.iinteractive.com>
1922 This library is free software; you can redistribute it and/or modify
1923 it under the same terms as Perl itself.