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 sub _method_map { $_[0]->{'methods'} }
352 # Instance Construction & Cloning
358 # we need to protect the integrity of the
359 # Class::MOP::Class singletons here, so we
360 # delegate this to &construct_class_instance
361 # which will deal with the singletons
362 return $class->_construct_class_instance(@_)
363 if $class->name->isa('Class::MOP::Class');
364 return $class->_construct_instance(@_);
367 sub construct_instance {
368 Carp::cluck('The construct_instance method has been made private.'
369 . " The public version is deprecated and will be removed in a future release.\n");
370 shift->_construct_instance(@_);
373 sub _construct_instance {
375 my $params = @_ == 1 ? $_[0] : {@_};
376 my $meta_instance = $class->get_meta_instance();
378 # the code below is almost certainly incorrect
379 # but this is foreign inheritance, so we might
380 # have to kludge it in the end.
381 my $instance = $params->{__INSTANCE__} || $meta_instance->create_instance();
382 foreach my $attr ($class->get_all_attributes()) {
383 $attr->initialize_instance_slot($meta_instance, $instance, $params);
386 # this will only work for a HASH instance type
387 if ($class->is_anon_class) {
388 (Scalar::Util::reftype($instance) eq 'HASH')
389 || confess "Currently only HASH based instances are supported with instance of anon-classes";
391 # At some point we should make this official
392 # as a reserved slot name, but right now I am
393 # going to keep it here.
394 # my $RESERVED_MOP_SLOT = '__MOP__';
395 $instance->{'__MOP__'} = $class;
401 sub get_meta_instance {
403 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
406 sub create_meta_instance {
407 Carp::cluck('The create_meta_instance method has been made private.'
408 . " The public version is deprecated and will be removed in a future release.\n");
409 shift->_create_meta_instance(@_);
412 sub _create_meta_instance {
415 my $instance = $self->instance_metaclass->new(
416 associated_metaclass => $self,
417 attributes => [ $self->get_all_attributes() ],
420 $self->add_meta_instance_dependencies()
421 if $instance->is_dependent_on_superclasses();
428 my $instance = shift;
429 (blessed($instance) && $instance->isa($class->name))
430 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
433 # we need to protect the integrity of the
434 # Class::MOP::Class singletons here, they
435 # should not be cloned.
436 return $instance if $instance->isa('Class::MOP::Class');
437 $class->_clone_instance($instance, @_);
441 Carp::cluck('The clone_instance method has been made private.'
442 . " The public version is deprecated and will be removed in a future release.\n");
443 shift->_clone_instance(@_);
446 sub _clone_instance {
447 my ($class, $instance, %params) = @_;
449 || confess "You can only clone instances, ($instance) is not a blessed instance";
450 my $meta_instance = $class->get_meta_instance();
451 my $clone = $meta_instance->clone_instance($instance);
452 foreach my $attr ($class->get_all_attributes()) {
453 if ( defined( my $init_arg = $attr->init_arg ) ) {
454 if (exists $params{$init_arg}) {
455 $attr->set_value($clone, $params{$init_arg});
462 sub rebless_instance {
463 my ($self, $instance, %params) = @_;
465 my $old_metaclass = Class::MOP::class_of($instance);
467 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
468 $self->name->isa($old_class)
469 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
471 $old_metaclass->rebless_instance_away($instance, $self, %params)
474 my $meta_instance = $self->get_meta_instance();
477 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
478 $meta_instance->rebless_instance_structure($_[1], $self);
480 foreach my $attr ( $self->get_all_attributes ) {
481 if ( $attr->has_value($instance) ) {
482 if ( defined( my $init_arg = $attr->init_arg ) ) {
483 $params{$init_arg} = $attr->get_value($instance)
484 unless exists $params{$init_arg};
487 $attr->set_value($instance, $attr->get_value($instance));
492 foreach my $attr ($self->get_all_attributes) {
493 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
499 sub rebless_instance_away {
500 # this intentionally does nothing, it is just a hook
507 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
510 @{$self->get_package_symbol($var_spec)} = @supers;
513 # on 5.8 and below, we need to call
514 # a method to get Perl to detect
515 # a cycle in the class hierarchy
516 my $class = $self->name;
520 # we need to check the metaclass
521 # compatibility here so that we can
522 # be sure that the superclass is
523 # not potentially creating an issues
524 # we don't know about
526 $self->_check_metaclass_compatibility();
527 $self->_superclasses_updated();
529 @{$self->get_package_symbol($var_spec)};
532 sub _superclasses_updated {
534 $self->update_meta_instance_dependencies();
539 my $super_class = $self->name;
541 return @{ $super_class->mro::get_isarev() };
544 sub direct_subclasses {
546 my $super_class = $self->name;
551 } Class::MOP::Class->initialize($_)->superclasses
556 return @{ mro::get_linear_isa( (shift)->name ) };
559 sub class_precedence_list {
561 my $name = $self->name;
563 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
565 # We need to check for circular inheritance here
566 # if we are are not on 5.10, cause 5.8 detects it
567 # late. This will do nothing if all is well, and
568 # blow up otherwise. Yes, it's an ugly hack, better
569 # suggestions are welcome.
571 ($name || return)->isa('This is a test for circular inheritance')
574 # if our mro is c3, we can
575 # just grab the linear_isa
576 if (mro::get_mro($name) eq 'c3') {
577 return @{ mro::get_linear_isa($name) }
581 # we can't grab the linear_isa for dfs
582 # since it has all the duplicates
587 $self->initialize($_)->class_precedence_list()
588 } $self->superclasses()
595 sub wrap_method_body {
596 my ( $self, %args ) = @_;
598 ('CODE' eq ref $args{body})
599 || confess "Your code block must be a CODE reference";
601 $self->method_metaclass->wrap(
602 package_name => $self->name,
608 my ($self, $method_name, $method) = @_;
609 (defined $method_name && $method_name)
610 || confess "You must define a method name";
613 if (blessed($method)) {
614 $body = $method->body;
615 if ($method->package_name ne $self->name) {
616 $method = $method->clone(
617 package_name => $self->name,
619 ) if $method->can('clone');
622 $method->attach_to_class($self);
623 $self->_method_map->{$method_name} = $method;
626 # If a raw code reference is supplied, its method object is not created.
627 # The method object won't be created until required.
632 my ( $current_package, $current_name ) = Class::MOP::get_code_info($body);
634 if ( !defined $current_name || $current_name eq '__ANON__' ) {
635 my $full_method_name = ($self->name . '::' . $method_name);
636 subname($full_method_name => $body);
639 $self->add_package_symbol(
640 { sigil => '&', type => 'CODE', name => $method_name },
646 my $fetch_and_prepare_method = sub {
647 my ($self, $method_name) = @_;
648 my $wrapped_metaclass = $self->wrapped_method_metaclass;
650 my $method = $self->get_method($method_name);
651 # if we dont have local ...
653 # try to find the next method
654 $method = $self->find_next_method_by_name($method_name);
655 # die if it does not exist
657 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
658 # and now make sure to wrap it
659 # even if it is already wrapped
660 # because we need a new sub ref
661 $method = $wrapped_metaclass->wrap($method);
664 # now make sure we wrap it properly
665 $method = $wrapped_metaclass->wrap($method)
666 unless $method->isa($wrapped_metaclass);
668 $self->add_method($method_name => $method);
672 sub add_before_method_modifier {
673 my ($self, $method_name, $method_modifier) = @_;
674 (defined $method_name && $method_name)
675 || confess "You must pass in a method name";
676 my $method = $fetch_and_prepare_method->($self, $method_name);
677 $method->add_before_modifier(
678 subname(':before' => $method_modifier)
682 sub add_after_method_modifier {
683 my ($self, $method_name, $method_modifier) = @_;
684 (defined $method_name && $method_name)
685 || confess "You must pass in a method name";
686 my $method = $fetch_and_prepare_method->($self, $method_name);
687 $method->add_after_modifier(
688 subname(':after' => $method_modifier)
692 sub add_around_method_modifier {
693 my ($self, $method_name, $method_modifier) = @_;
694 (defined $method_name && $method_name)
695 || confess "You must pass in a method name";
696 my $method = $fetch_and_prepare_method->($self, $method_name);
697 $method->add_around_modifier(
698 subname(':around' => $method_modifier)
703 # the methods above used to be named like this:
704 # ${pkg}::${method}:(before|after|around)
705 # but this proved problematic when using one modifier
706 # to wrap multiple methods (something which is likely
707 # to happen pretty regularly IMO). So instead of naming
708 # it like this, I have chosen to just name them purely
709 # with their modifier names, like so:
710 # :(before|after|around)
711 # The fact is that in a stack trace, it will be fairly
712 # evident from the context what method they are attached
713 # to, and so don't need the fully qualified name.
717 Carp::cluck("The alias_method method is deprecated. Use add_method instead.\n");
719 shift->add_method(@_);
723 my ($self, $method_name) = @_;
724 (defined $method_name && $method_name)
725 || confess "You must define a method name";
727 defined $self->get_method($method_name);
731 my ($self, $method_name) = @_;
732 (defined $method_name && $method_name)
733 || confess "You must define a method name";
735 my $class_name = $self->name;
736 my $method_map = $self->_method_map;
738 my $method_object = $method_map->{$method_name};
741 my $glob = $self->namespace->{$method_name};
748 if(ref(\$glob) eq 'GLOB'){
749 $code = *{$glob}{CODE};
753 my($code_package, $code_name) = Class::MOP::get_code_info($code);
756 || ( !($code_package eq 'constant' && $code_name eq '__ANON__')
757 && $code_package ne $class_name ) ){
761 else{ # stubs or constants
763 $code = \&{$class_name . '::' . $method_name};
765 $method_object = $method_map->{$method_name} = $self->wrap_method_body(
767 name => $method_name,
768 associated_metaclass => $self,
770 $method_object->_update_generation();
772 else{ # $method_object already exists
773 if(!$method_object->_is_valid_generation){
774 my $glob = $self->namespace->{$method_name};
776 delete $method_map->{$method_name};
781 if(ref(\$glob) eq 'GLOB'){
782 $code = *{$glob}{CODE};
784 delete $method_map->{$method_name};
788 else{ # stubs or constants
790 $code = \&{$class_name . '::' . $method_name};
793 if($method_object->body != $code){ # changed for some reason
794 my($code_package, $code_name) = Class::MOP::get_code_info($code);
796 || ( !($code_package eq 'constant' && $code_name eq '__ANON__')
797 && $code_package ne $class_name ) ){
798 delete $method_map->{$method_name};
803 $method_object = $method_map->{$method_name} = $self->wrap_method_body(
805 name => $method_name,
806 associated_metaclass => $self,
809 $method_object->_update_generation();
813 return $method_object;
817 my ($self, $method_name) = @_;
818 (defined $method_name && $method_name)
819 || confess "You must define a method name";
821 my $removed_method = delete $self->get_method_map->{$method_name};
823 $self->remove_package_symbol(
824 { sigil => '&', type => 'CODE', name => $method_name }
827 $removed_method->detach_from_class if $removed_method;
829 $self->update_package_cache_flag; # still valid, since we just removed the method from the map
831 return $removed_method;
834 sub get_method_list {
836 keys %{$self->get_method_map};
839 sub find_method_by_name {
840 my ($self, $method_name) = @_;
841 (defined $method_name && $method_name)
842 || confess "You must define a method name to find";
843 foreach my $class ($self->linearized_isa) {
844 # fetch the meta-class ...
845 my $meta = $self->initialize($class);
846 return $meta->get_method($method_name)
847 if $meta->has_method($method_name);
852 sub get_all_methods {
854 my %methods = map { %{ $self->initialize($_)->get_method_map } } reverse $self->linearized_isa;
855 return values %methods;
858 sub compute_all_applicable_methods {
859 Carp::cluck('The compute_all_applicable_methods method is deprecated.'
860 . " Use get_all_methods instead.\n");
865 class => $_->package_name,
866 code => $_, # sigh, overloading
868 } shift->get_all_methods(@_);
871 sub get_all_method_names {
874 grep { $uniq{$_}++ == 0 } map { $_->name } $self->get_all_methods;
877 sub find_all_methods_by_name {
878 my ($self, $method_name) = @_;
879 (defined $method_name && $method_name)
880 || confess "You must define a method name to find";
882 foreach my $class ($self->linearized_isa) {
883 # fetch the meta-class ...
884 my $meta = $self->initialize($class);
886 name => $method_name,
888 code => $meta->get_method($method_name)
889 } if $meta->has_method($method_name);
894 sub find_next_method_by_name {
895 my ($self, $method_name) = @_;
896 (defined $method_name && $method_name)
897 || confess "You must define a method name to find";
898 my @cpl = $self->linearized_isa;
899 shift @cpl; # discard ourselves
900 foreach my $class (@cpl) {
901 # fetch the meta-class ...
902 my $meta = $self->initialize($class);
903 return $meta->get_method($method_name)
904 if $meta->has_method($method_name);
913 # either we have an attribute object already
914 # or we need to create one from the args provided
915 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
916 # make sure it is derived from the correct type though
917 ($attribute->isa('Class::MOP::Attribute'))
918 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
920 # first we attach our new attribute
921 # because it might need certain information
922 # about the class which it is attached to
923 $attribute->attach_to_class($self);
925 # then we remove attributes of a conflicting
926 # name here so that we can properly detach
927 # the old attr object, and remove any
928 # accessors it would have generated
929 if ( $self->has_attribute($attribute->name) ) {
930 $self->remove_attribute($attribute->name);
932 $self->invalidate_meta_instances();
935 # get our count of previously inserted attributes and
936 # increment by one so this attribute knows its order
937 my $order = (scalar keys %{$self->get_attribute_map}) - 1;
938 $attribute->_set_insertion_order($order + 1);
940 # then onto installing the new accessors
941 $self->get_attribute_map->{$attribute->name} = $attribute;
943 # invalidate package flag here
947 eval { $attribute->install_accessors() };
951 $self->remove_attribute($attribute->name);
958 sub update_meta_instance_dependencies {
961 if ( $self->{meta_instance_dependencies} ) {
962 return $self->add_meta_instance_dependencies;
966 sub add_meta_instance_dependencies {
969 $self->remove_meta_instance_dependencies;
971 my @attrs = $self->get_all_attributes();
974 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
976 foreach my $class ( @classes ) {
977 $class->add_dependent_meta_instance($self);
980 $self->{meta_instance_dependencies} = \@classes;
983 sub remove_meta_instance_dependencies {
986 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
987 foreach my $class ( @$classes ) {
988 $class->remove_dependent_meta_instance($self);
998 sub add_dependent_meta_instance {
999 my ( $self, $metaclass ) = @_;
1000 push @{ $self->{dependent_meta_instances} }, $metaclass;
1003 sub remove_dependent_meta_instance {
1004 my ( $self, $metaclass ) = @_;
1005 my $name = $metaclass->name;
1006 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
1009 sub invalidate_meta_instances {
1011 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
1014 sub invalidate_meta_instance {
1016 undef $self->{_meta_instance};
1020 my ($self, $attribute_name) = @_;
1021 (defined $attribute_name && $attribute_name)
1022 || confess "You must define an attribute name";
1023 exists $self->get_attribute_map->{$attribute_name};
1027 my ($self, $attribute_name) = @_;
1028 (defined $attribute_name && $attribute_name)
1029 || confess "You must define an attribute name";
1030 return $self->get_attribute_map->{$attribute_name}
1032 # this will return undef anyway, so no need ...
1033 # if $self->has_attribute($attribute_name);
1037 sub remove_attribute {
1038 my ($self, $attribute_name) = @_;
1039 (defined $attribute_name && $attribute_name)
1040 || confess "You must define an attribute name";
1041 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
1042 return unless defined $removed_attribute;
1043 delete $self->get_attribute_map->{$attribute_name};
1044 $self->invalidate_meta_instances();
1045 $removed_attribute->remove_accessors();
1046 $removed_attribute->detach_from_class();
1047 return $removed_attribute;
1050 sub get_attribute_list {
1052 keys %{$self->get_attribute_map};
1055 sub get_all_attributes {
1057 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
1058 return values %attrs;
1061 sub compute_all_applicable_attributes {
1062 Carp::cluck('The compute_all_applicable_attributes method has been deprecated.'
1063 . " Use get_all_attributes instead.\n");
1065 shift->get_all_attributes(@_);
1068 sub find_attribute_by_name {
1069 my ($self, $attr_name) = @_;
1070 foreach my $class ($self->linearized_isa) {
1071 # fetch the meta-class ...
1072 my $meta = $self->initialize($class);
1073 return $meta->get_attribute($attr_name)
1074 if $meta->has_attribute($attr_name);
1079 # check if we can reinitialize
1083 # if any local attr is defined
1084 return if $self->get_attribute_list;
1086 # or any non-declared methods
1087 if ( my @methods = values %{ $self->get_method_map } ) {
1088 my $metaclass = $self->method_metaclass;
1089 foreach my $method ( @methods ) {
1090 return if $method->isa("Class::MOP::Method::Generated");
1091 # FIXME do we need to enforce this too? return unless $method->isa($metaclass);
1100 sub is_mutable { 1 }
1101 sub is_immutable { 0 }
1103 sub _immutable_options {
1104 my ( $self, @args ) = @_;
1107 inline_accessors => 1,
1108 inline_constructor => 1,
1109 inline_destructor => 0,
1111 immutable_trait => $self->immutable_trait,
1112 constructor_name => $self->constructor_name,
1113 constructor_class => $self->constructor_class,
1114 destructor_class => $self->destructor_class,
1119 sub make_immutable {
1120 my ( $self, @args ) = @_;
1122 if ( $self->is_mutable ) {
1123 $self->_initialize_immutable( $self->_immutable_options(@args) );
1124 $self->_rebless_as_immutable(@args);
1135 if ( $self->is_immutable ) {
1136 my @args = $self->immutable_options;
1137 $self->_rebless_as_mutable();
1138 $self->_remove_inlined_code(@args);
1139 delete $self->{__immutable};
1147 sub _rebless_as_immutable {
1148 my ( $self, @args ) = @_;
1150 $self->{__immutable}{original_class} = ref $self;
1152 bless $self => $self->_immutable_metaclass(@args);
1155 sub _immutable_metaclass {
1156 my ( $self, %args ) = @_;
1158 if ( my $class = $args{immutable_metaclass} ) {
1162 my $trait = $args{immutable_trait} = $self->immutable_trait
1163 || confess "no immutable trait specified for $self";
1165 my $meta_attr = $self->meta->find_attribute_by_name("immutable_trait");
1169 if ( $meta_attr and $trait eq $meta_attr->default ) {
1170 # if the trait is the same as the default we try and pick a
1171 # predictable name for the immutable metaclass
1172 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1175 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1176 $trait, 'ForMetaClass', ref($self);
1180 if Class::MOP::is_class_loaded($class_name);
1182 # If the metaclass is a subclass of CMOP::Class which has had
1183 # metaclass roles applied (via Moose), then we want to make sure
1184 # that we preserve that anonymous class (see Fey::ORM for an
1185 # example of where this matters).
1187 = $self->meta->is_immutable
1188 ? $self->meta->get_mutable_metaclass_name
1191 my $meta = $meta_name->create(
1193 superclasses => [ ref $self ],
1196 Class::MOP::load_class($trait);
1197 for my $meth ( Class::MOP::Class->initialize($trait)->get_all_methods ) {
1198 next if $meta->has_method( $meth->name );
1200 if ( $meta->find_method_by_name( $meth->name ) ) {
1201 $meta->add_around_method_modifier( $meth->name, $meth->body );
1204 $meta->add_method( $meth->name, $meth->clone );
1208 $meta->make_immutable( inline_constructor => 0 );
1213 sub _remove_inlined_code {
1216 $self->remove_method( $_->name ) for $self->_inlined_methods;
1218 delete $self->{__immutable}{inlined_methods};
1221 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1223 sub _add_inlined_method {
1224 my ( $self, $method ) = @_;
1226 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1229 sub _initialize_immutable {
1230 my ( $self, %args ) = @_;
1232 $self->{__immutable}{options} = \%args;
1233 $self->_install_inlined_code(%args);
1236 sub _install_inlined_code {
1237 my ( $self, %args ) = @_;
1240 $self->_inline_accessors(%args) if $args{inline_accessors};
1241 $self->_inline_constructor(%args) if $args{inline_constructor};
1242 $self->_inline_destructor(%args) if $args{inline_destructor};
1245 sub _rebless_as_mutable {
1248 bless $self, $self->get_mutable_metaclass_name;
1253 sub _inline_accessors {
1256 foreach my $attr_name ( $self->get_attribute_list ) {
1257 $self->get_attribute($attr_name)->install_accessors(1);
1261 sub _inline_constructor {
1262 my ( $self, %args ) = @_;
1264 my $name = $args{constructor_name};
1266 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1267 my $class = $self->name;
1268 warn "Not inlining a constructor for $class since it defines"
1269 . " its own constructor.\n"
1270 . "If you are certain you don't need to inline your"
1271 . " constructor, specify inline_constructor => 0 in your"
1272 . " call to $class->meta->make_immutable\n";
1276 my $constructor_class = $args{constructor_class};
1278 Class::MOP::load_class($constructor_class);
1280 my $constructor = $constructor_class->new(
1284 package_name => $self->name,
1288 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1289 $self->add_method( $name => $constructor );
1290 $self->_add_inlined_method($constructor);
1294 sub _inline_destructor {
1295 my ( $self, %args ) = @_;
1297 ( exists $args{destructor_class} && defined $args{destructor_class} )
1298 || confess "The 'inline_destructor' option is present, but "
1299 . "no destructor class was specified";
1301 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1302 my $class = $self->name;
1303 warn "Not inlining a destructor for $class since it defines"
1304 . " its own destructor.\n";
1308 my $destructor_class = $args{destructor_class};
1310 Class::MOP::load_class($destructor_class);
1312 return unless $destructor_class->is_needed($self);
1314 my $destructor = $destructor_class->new(
1317 package_name => $self->name,
1321 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1322 $self->add_method( 'DESTROY' => $destructor );
1323 $self->_add_inlined_method($destructor);
1335 Class::MOP::Class - Class Meta Object
1339 # assuming that class Foo
1340 # has been defined, you can
1342 # use this for introspection ...
1344 # add a method to Foo ...
1345 Foo->meta->add_method( 'bar' => sub {...} )
1347 # get a list of all the classes searched
1348 # the method dispatcher in the correct order
1349 Foo->meta->class_precedence_list()
1351 # remove a method from Foo
1352 Foo->meta->remove_method('bar');
1354 # or use this to actually create classes ...
1356 Class::MOP::Class->create(
1359 superclasses => ['Foo'],
1361 Class::MOP::Attribute->new('$bar'),
1362 Class::MOP::Attribute->new('$baz'),
1365 calculate_bar => sub {...},
1366 construct_baz => sub {...}
1373 The Class Protocol is the largest and most complex part of the
1374 Class::MOP meta-object protocol. It controls the introspection and
1375 manipulation of Perl 5 classes, and it can create them as well. The
1376 best way to understand what this module can do, is to read the
1377 documentation for each of its methods.
1381 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1385 =head2 Class construction
1387 These methods all create new C<Class::MOP::Class> objects. These
1388 objects can represent existing classes, or they can be used to create
1389 new classes from scratch.
1391 The metaclass object for a given class is a singleton. If you attempt
1392 to create a metaclass for the same class twice, you will just get the
1397 =item B<< Class::MOP::Class->create($package_name, %options) >>
1399 This method creates a new C<Class::MOP::Class> object with the given
1400 package name. It accepts a number of options.
1406 An optional version number for the newly created package.
1410 An optional authority for the newly created package.
1412 =item * superclasses
1414 An optional array reference of superclass names.
1418 An optional hash reference of methods for the class. The keys of the
1419 hash reference are method names, and values are subroutine references.
1423 An optional array reference of attributes.
1425 An attribute can be passed as an existing L<Class::MOP::Attribute>
1426 object, I<or> or as a hash reference of options which will be passed
1427 to the attribute metaclass's constructor.
1431 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1433 This method works just like C<< Class::MOP::Class->create >> but it
1434 creates an "anonymous" class. In fact, the class does have a name, but
1435 that name is a unique name generated internally by this module.
1437 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1438 parameters that C<create> accepts.
1440 Anonymous classes are destroyed once the metaclass they are attached
1441 to goes out of scope, and will be removed from Perl's internal symbol
1444 All instances of an anonymous class keep a special reference to the
1445 metaclass object, which prevents the metaclass from going out of scope
1446 while any instances exist.
1448 This only works if the instance if based on a hash reference, however.
1450 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1452 This method will initialize a C<Class::MOP::Class> object for the
1453 named package. Unlike C<create>, this method I<will not> create a new
1456 The purpose of this method is to retrieve a C<Class::MOP::Class>
1457 object for introspecting an existing class.
1459 If an existing C<Class::MOP::Class> object exists for the named
1460 package, it will be returned, and any options provided will be
1463 If the object does not yet exist, it will be created.
1465 The valid options that can be passed to this method are
1466 C<attribute_metaclass>, C<method_metaclass>,
1467 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1468 optional, and default to the appropriate class in the C<Class::MOP>
1473 =head2 Object instance construction and cloning
1475 These methods are all related to creating and/or cloning object
1480 =item B<< $metaclass->clone_object($instance, %params) >>
1482 This method clones an existing object instance. Any parameters you
1483 provide are will override existing attribute values in the object.
1485 This is a convenience method for cloning an object instance, then
1486 blessing it into the appropriate package.
1488 You could implement a clone method in your class, using this method:
1491 my ($self, %params) = @_;
1492 $self->meta->clone_object($self, %params);
1495 =item B<< $metaclass->rebless_instance($instance, %params) >>
1497 This method changes the class of C<$instance> to the metaclass's class.
1499 You can only rebless an instance into a subclass of its current
1500 class. If you pass any additional parameters, these will be treated
1501 like constructor parameters and used to initialize the object's
1502 attributes. Any existing attributes that are already set will be
1505 Before reblessing the instance, this method will call
1506 C<rebless_instance_away> on the instance's current metaclass. This method
1507 will be passed the instance, the new metaclass, and any parameters
1508 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1509 does nothing; it is merely a hook.
1511 =item B<< $metaclass->new_object(%params) >>
1513 This method is used to create a new object of the metaclass's
1514 class. Any parameters you provide are used to initialize the
1515 instance's attributes. A special C<__INSTANCE__> key can be passed to
1516 provide an already generated instance, rather than having Class::MOP
1517 generate it for you. This is mostly useful for using Class::MOP with
1518 foreign classes, which generally generate instances using their own
1521 =item B<< $metaclass->instance_metaclass >>
1523 Returns the class name of the instance metaclass, see
1524 L<Class::MOP::Instance> for more information on the instance
1527 =item B<< $metaclass->get_meta_instance >>
1529 Returns an instance of the C<instance_metaclass> to be used in the
1530 construction of a new instance of the class.
1534 =head2 Informational predicates
1536 These are a few predicate methods for asking information about the
1541 =item B<< $metaclass->is_anon_class >>
1543 This returns true if the class was created by calling C<<
1544 Class::MOP::Class->create_anon_class >>.
1546 =item B<< $metaclass->is_mutable >>
1548 This returns true if the class is still mutable.
1550 =item B<< $metaclass->is_immutable >>
1552 This returns true if the class has been made immutable.
1554 =item B<< $metaclass->is_pristine >>
1556 A class is I<not> pristine if it has non-inherited attributes or if it
1557 has any generated methods.
1561 =head2 Inheritance Relationships
1565 =item B<< $metaclass->superclasses(@superclasses) >>
1567 This is a read-write accessor which represents the superclass
1568 relationships of the metaclass's class.
1570 This is basically sugar around getting and setting C<@ISA>.
1572 =item B<< $metaclass->class_precedence_list >>
1574 This returns a list of all of the class's ancestor classes. The
1575 classes are returned in method dispatch order.
1577 =item B<< $metaclass->linearized_isa >>
1579 This returns a list based on C<class_precedence_list> but with all
1582 =item B<< $metaclass->subclasses >>
1584 This returns a list of all subclasses for this class, even indirect
1587 =item B<< $metaclass->direct_subclasses >>
1589 This returns a list of immediate subclasses for this class, which does not
1590 include indirect subclasses.
1594 =head2 Method introspection and creation
1596 These methods allow you to introspect a class's methods, as well as
1597 add, remove, or change methods.
1599 Determining what is truly a method in a Perl 5 class requires some
1600 heuristics (aka guessing).
1602 Methods defined outside the package with a fully qualified name (C<sub
1603 Package::name { ... }>) will be included. Similarly, methods named
1604 with a fully qualified name using L<Sub::Name> are also included.
1606 However, we attempt to ignore imported functions.
1608 Ultimately, we are using heuristics to determine what truly is a
1609 method in a class, and these heuristics may get the wrong answer in
1610 some edge cases. However, for most "normal" cases the heuristics work
1615 =item B<< $metaclass->get_method($method_name) >>
1617 This will return a L<Class::MOP::Method> for the specified
1618 C<$method_name>. If the class does not have the specified method, it
1621 =item B<< $metaclass->has_method($method_name) >>
1623 Returns a boolean indicating whether or not the class defines the
1624 named method. It does not include methods inherited from parent
1627 =item B<< $metaclass->get_method_map >>
1629 Returns a hash reference representing the methods defined in this
1630 class. The keys are method names and the values are
1631 L<Class::MOP::Method> objects.
1633 =item B<< $metaclass->get_method_list >>
1635 This will return a list of method I<names> for all methods defined in
1638 =item B<< $metaclass->get_all_methods >>
1640 This will traverse the inheritance hierarchy and return a list of all
1641 the L<Class::MOP::Method> objects for this class and its parents.
1643 =item B<< $metaclass->find_method_by_name($method_name) >>
1645 This will return a L<Class::MOP::Method> for the specified
1646 C<$method_name>. If the class does not have the specified method, it
1649 Unlike C<get_method>, this method I<will> look for the named method in
1652 =item B<< $metaclass->get_all_method_names >>
1654 This will return a list of method I<names> for all of this class's
1655 methods, including inherited methods.
1657 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1659 This method looks for the named method in the class and all of its
1660 parents. It returns every matching method it finds in the inheritance
1661 tree, so it returns a list of methods.
1663 Each method is returned as a hash reference with three keys. The keys
1664 are C<name>, C<class>, and C<code>. The C<code> key has a
1665 L<Class::MOP::Method> object as its value.
1667 The list of methods is distinct.
1669 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1671 This method returns the first method in any superclass matching the
1672 given name. It is effectively the method that C<SUPER::$method_name>
1675 =item B<< $metaclass->add_method($method_name, $method) >>
1677 This method takes a method name and a subroutine reference, and adds
1678 the method to the class.
1680 The subroutine reference can be a L<Class::MOP::Method>, and you are
1681 strongly encouraged to pass a meta method object instead of a code
1682 reference. If you do so, that object gets stored as part of the
1683 class's method map directly. If not, the meta information will have to
1684 be recreated later, and may be incorrect.
1686 If you provide a method object, this method will clone that object if
1687 the object's package name does not match the class name. This lets us
1688 track the original source of any methods added from other classes
1689 (notably Moose roles).
1691 =item B<< $metaclass->remove_method($method_name) >>
1693 Remove the named method from the class. This method returns the
1694 L<Class::MOP::Method> object for the method.
1696 =item B<< $metaclass->method_metaclass >>
1698 Returns the class name of the method metaclass, see
1699 L<Class::MOP::Method> for more information on the method metaclass.
1701 =item B<< $metaclass->wrapped_method_metaclass >>
1703 Returns the class name of the wrapped method metaclass, see
1704 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1709 =head2 Attribute introspection and creation
1711 Because Perl 5 does not have a core concept of attributes in classes,
1712 we can only return information about attributes which have been added
1713 via this class's methods. We cannot discover information about
1714 attributes which are defined in terms of "regular" Perl 5 methods.
1718 =item B<< $metaclass->get_attribute($attribute_name) >>
1720 This will return a L<Class::MOP::Attribute> for the specified
1721 C<$attribute_name>. If the class does not have the specified
1722 attribute, it returns C<undef>.
1724 NOTE that get_attribute does not search superclasses, for that you
1725 need to use C<find_attribute_by_name>.
1727 =item B<< $metaclass->has_attribute($attribute_name) >>
1729 Returns a boolean indicating whether or not the class defines the
1730 named attribute. It does not include attributes inherited from parent
1733 =item B<< $metaclass->get_attribute_map >>
1735 Returns a hash reference representing the attributes defined in this
1736 class. The keys are attribute names and the values are
1737 L<Class::MOP::Attribute> objects.
1739 =item B<< $metaclass->get_attribute_list >>
1741 This will return a list of attributes I<names> for all attributes
1742 defined in this class.
1744 =item B<< $metaclass->get_all_attributes >>
1746 This will traverse the inheritance hierarchy and return a list of all
1747 the L<Class::MOP::Attribute> objects for this class and its parents.
1749 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1751 This will return a L<Class::MOP::Attribute> for the specified
1752 C<$attribute_name>. If the class does not have the specified
1753 attribute, it returns C<undef>
1755 Unlike C<get_attribute>, this attribute I<will> look for the named
1756 attribute in superclasses.
1758 =item B<< $metaclass->add_attribute(...) >>
1760 This method accepts either an existing L<Class::MOP::Attribute>
1761 object, or parameters suitable for passing to that class's C<new>
1764 The attribute provided will be added to the class.
1766 Any accessor methods defined by the attribute will be added to the
1767 class when the attribute is added.
1769 If an attribute of the same name already exists, the old attribute
1770 will be removed first.
1772 =item B<< $metaclass->remove_attribute($attribute_name) >>
1774 This will remove the named attribute from the class, and
1775 L<Class::MOP::Attribute> object.
1777 Removing an attribute also removes any accessor methods defined by the
1780 However, note that removing an attribute will only affect I<future>
1781 object instances created for this class, not existing instances.
1783 =item B<< $metaclass->attribute_metaclass >>
1785 Returns the class name of the attribute metaclass for this class. By
1786 default, this is L<Class::MOP::Attribute>. for more information on
1790 =head2 Class Immutability
1792 Making a class immutable "freezes" the class definition. You can no
1793 longer call methods which alter the class, such as adding or removing
1794 methods or attributes.
1796 Making a class immutable lets us optimize the class by inlining some
1797 methods, and also allows us to optimize some methods on the metaclass
1800 After immutabilization, the metaclass object will cache most
1801 informational methods such as C<get_method_map> and
1802 C<get_all_attributes>. Methods which would alter the class, such as
1803 C<add_attribute>, C<add_method>, and so on will throw an error on an
1804 immutable metaclass object.
1806 The immutabilization system in L<Moose> takes much greater advantage
1807 of the inlining features than Class::MOP itself does.
1811 =item B<< $metaclass->make_immutable(%options) >>
1813 This method will create an immutable transformer and uses it to make
1814 the class and its metaclass object immutable.
1816 This method accepts the following options:
1820 =item * inline_accessors
1822 =item * inline_constructor
1824 =item * inline_destructor
1826 These are all booleans indicating whether the specified method(s)
1829 By default, accessors and the constructor are inlined, but not the
1832 =item * immutable_trait
1834 The name of a class which will be used as a parent class for the
1835 metaclass object being made immutable. This "trait" implements the
1836 post-immutability functionality of the metaclass (but not the
1837 transformation itself).
1839 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1841 =item * constructor_name
1843 This is the constructor method name. This defaults to "new".
1845 =item * constructor_class
1847 The name of the method metaclass for constructors. It will be used to
1848 generate the inlined constructor. This defaults to
1849 "Class::MOP::Method::Constructor".
1851 =item * replace_constructor
1853 This is a boolean indicating whether an existing constructor should be
1854 replaced when inlining a constructor. This defaults to false.
1856 =item * destructor_class
1858 The name of the method metaclass for destructors. It will be used to
1859 generate the inlined destructor. This defaults to
1860 "Class::MOP::Method::Denstructor".
1862 =item * replace_destructor
1864 This is a boolean indicating whether an existing destructor should be
1865 replaced when inlining a destructor. This defaults to false.
1869 =item B<< $metaclass->make_mutable >>
1871 Calling this method reverse the immutabilization transformation.
1875 =head2 Method Modifiers
1877 Method modifiers are hooks which allow a method to be wrapped with
1878 I<before>, I<after> and I<around> method modifiers. Every time a
1879 method is called, it's modifiers are also called.
1881 A class can modify its own methods, as well as methods defined in
1884 =head3 How method modifiers work?
1886 Method modifiers work by wrapping the original method and then
1887 replacing it in the class's symbol table. The wrappers will handle
1888 calling all the modifiers in the appropriate order and preserving the
1889 calling context for the original method.
1891 The return values of C<before> and C<after> modifiers are
1892 ignored. This is because their purpose is B<not> to filter the input
1893 and output of the primary method (this is done with an I<around>
1896 This may seem like an odd restriction to some, but doing this allows
1897 for simple code to be added at the beginning or end of a method call
1898 without altering the function of the wrapped method or placing any
1899 extra responsibility on the code of the modifier.
1901 Of course if you have more complex needs, you can use the C<around>
1902 modifier which allows you to change both the parameters passed to the
1903 wrapped method, as well as its return value.
1905 Before and around modifiers are called in last-defined-first-called
1906 order, while after modifiers are called in first-defined-first-called
1907 order. So the call tree might looks something like this:
1919 =head3 What is the performance impact?
1921 Of course there is a performance cost associated with method
1922 modifiers, but we have made every effort to make that cost directly
1923 proportional to the number of modifier features you utilize.
1925 The wrapping method does it's best to B<only> do as much work as it
1926 absolutely needs to. In order to do this we have moved some of the
1927 performance costs to set-up time, where they are easier to amortize.
1929 All this said, our benchmarks have indicated the following:
1931 simple wrapper with no modifiers 100% slower
1932 simple wrapper with simple before modifier 400% slower
1933 simple wrapper with simple after modifier 450% slower
1934 simple wrapper with simple around modifier 500-550% slower
1935 simple wrapper with all 3 modifiers 1100% slower
1937 These numbers may seem daunting, but you must remember, every feature
1938 comes with some cost. To put things in perspective, just doing a
1939 simple C<AUTOLOAD> which does nothing but extract the name of the
1940 method called and return it costs about 400% over a normal method
1945 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1947 This wraps the specified method with the supplied subroutine
1948 reference. The modifier will be called as a method itself, and will
1949 receive the same arguments as are passed to the method.
1951 When the modifier exits, the wrapped method will be called.
1953 The return value of the modifier will be ignored.
1955 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1957 This wraps the specified method with the supplied subroutine
1958 reference. The modifier will be called as a method itself, and will
1959 receive the same arguments as are passed to the method.
1961 When the wrapped methods exits, the modifier will be called.
1963 The return value of the modifier will be ignored.
1965 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1967 This wraps the specified method with the supplied subroutine
1970 The first argument passed to the modifier will be a subroutine
1971 reference to the wrapped method. The second argument is the object,
1972 and after that come any arguments passed when the method is called.
1974 The around modifier can choose to call the original method, as well as
1975 what arguments to pass if it does so.
1977 The return value of the modifier is what will be seen by the caller.
1981 =head2 Introspection
1985 =item B<< Class::MOP::Class->meta >>
1987 This will return a L<Class::MOP::Class> instance for this class.
1989 It should also be noted that L<Class::MOP> will actually bootstrap
1990 this module by installing a number of attribute meta-objects into its
1997 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1999 =head1 COPYRIGHT AND LICENSE
2001 Copyright 2006-2009 by Infinity Interactive, Inc.
2003 L<http://www.iinteractive.com>
2005 This library is free software; you can redistribute it and/or modify
2006 it under the same terms as Perl itself.