2 package Class::MOP::Class;
7 use Class::MOP::Instance;
8 use Class::MOP::Method::Wrapped;
9 use Class::MOP::Method::Accessor;
10 use Class::MOP::Method::Constructor;
13 use Scalar::Util 'blessed', 'reftype', 'weaken';
14 use Sub::Name 'subname';
15 use Devel::GlobalDestruction 'in_global_destruction';
17 use List::MoreUtils 'all';
19 our $VERSION = '1.04';
20 $VERSION = eval $VERSION;
21 our $AUTHORITY = 'cpan:STEVAN';
23 use base 'Class::MOP::Module',
24 'Class::MOP::Mixin::HasAttributes',
25 'Class::MOP::Mixin::HasMethods';
35 $package_name = shift;
38 $package_name = $options{package};
41 ($package_name && !ref($package_name))
42 || confess "You must pass a package name and it cannot be blessed";
44 return Class::MOP::get_metaclass_by_name($package_name)
45 || $class->_construct_class_instance(package => $package_name, @_);
48 # NOTE: (meta-circularity)
49 # this is a special form of _construct_instance
50 # (see below), which is used to construct class
51 # meta-object instances for any Class::MOP::*
52 # class. All other classes will use the more
53 # normal &construct_instance.
54 sub _construct_class_instance {
56 my $options = @_ == 1 ? $_[0] : {@_};
57 my $package_name = $options->{package};
58 (defined $package_name && $package_name)
59 || confess "You must pass a package name";
61 # return the metaclass if we have it cached,
62 # and it is still defined (it has not been
63 # reaped by DESTROY yet, which can happen
64 # annoyingly enough during global destruction)
66 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
72 ? $class->_real_ref_name
75 # now create the metaclass
77 if ($class eq 'Class::MOP::Class') {
78 $meta = $class->_new($options);
82 # it is safe to use meta here because
83 # class will always be a subclass of
84 # Class::MOP::Class, which defines meta
85 $meta = $class->meta->_construct_instance($options)
88 # and check the metaclass compatibility
89 $meta->_check_metaclass_compatibility();
91 Class::MOP::store_metaclass_by_name($package_name, $meta);
94 # we need to weaken any anon classes
95 # so that they can call DESTROY properly
96 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
104 # NOTE: we need to deal with the possibility of class immutability here,
105 # and then get the name of the class appropriately
106 return $self->is_immutable
107 ? $self->_get_mutable_metaclass_name()
114 return Class::MOP::Class->initialize($class)->new_object(@_)
115 if $class ne __PACKAGE__;
117 my $options = @_ == 1 ? $_[0] : {@_};
120 # inherited from Class::MOP::Package
121 'package' => $options->{package},
124 # since the following attributes will
125 # actually be loaded from the symbol
126 # table, and actually bypass the instance
127 # entirely, we can just leave these things
128 # listed here for reference, because they
129 # should not actually have a value associated
131 'namespace' => \undef,
134 # inherited from Class::MOP::Module
136 'authority' => \undef,
138 # defined in Class::MOP::Class
139 'superclasses' => \undef,
142 'attribute_metaclass' =>
143 ( $options->{'attribute_metaclass'} || 'Class::MOP::Attribute' ),
144 'method_metaclass' =>
145 ( $options->{'method_metaclass'} || 'Class::MOP::Method' ),
146 'wrapped_method_metaclass' => (
147 $options->{'wrapped_method_metaclass'}
148 || 'Class::MOP::Method::Wrapped'
150 'instance_metaclass' =>
151 ( $options->{'instance_metaclass'} || 'Class::MOP::Instance' ),
152 'immutable_trait' => (
153 $options->{'immutable_trait'}
154 || 'Class::MOP::Class::Immutable::Trait'
156 'constructor_name' => ( $options->{constructor_name} || 'new' ),
157 'constructor_class' => (
158 $options->{constructor_class} || 'Class::MOP::Method::Constructor'
160 'destructor_class' => $options->{destructor_class},
164 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
165 sub update_package_cache_flag {
168 # we can manually update the cache number
169 # since we are actually adding the method
170 # to our cache as well. This avoids us
171 # having to regenerate the method_map.
173 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
176 ## Metaclass compatibility
178 my %base_metaclass = (
179 attribute_metaclass => 'Class::MOP::Attribute',
180 method_metaclass => 'Class::MOP::Method',
181 wrapped_method_metaclass => 'Class::MOP::Method::Wrapped',
182 instance_metaclass => 'Class::MOP::Instance',
183 constructor_class => 'Class::MOP::Method::Constructor',
184 destructor_class => 'Class::MOP::Method::Destructor',
187 sub _base_metaclasses { %base_metaclass }
190 sub _check_metaclass_compatibility {
193 my @superclasses = $self->superclasses
196 $self->_fix_metaclass_incompatibility(@superclasses);
198 my %base_metaclass = $self->_base_metaclasses;
200 # this is always okay ...
202 if ref($self) eq 'Class::MOP::Class'
204 my $meta = $self->$_;
205 !defined($meta) || $meta eq $base_metaclass{$_};
207 keys %base_metaclass;
209 for my $superclass (@superclasses) {
210 $self->_check_class_metaclass_compatibility($superclass);
213 for my $metaclass_type ( keys %base_metaclass ) {
214 next unless defined $self->$metaclass_type;
215 for my $superclass (@superclasses) {
216 $self->_check_single_metaclass_compatibility( $metaclass_type,
222 sub _class_metaclass_is_compatible {
224 my ( $superclass_name ) = @_;
226 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
229 my $super_meta_type = $super_meta->_real_ref_name;
231 return $self->isa($super_meta_type);
234 sub _check_class_metaclass_compatibility {
236 my ( $superclass_name ) = @_;
238 if (!$self->_class_metaclass_is_compatible($superclass_name)) {
239 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
241 my $super_meta_type = $super_meta->_real_ref_name;
243 confess "The metaclass of " . $self->name . " ("
244 . (ref($self)) . ")" . " is not compatible with "
245 . "the metaclass of its superclass, "
246 . $superclass_name . " (" . ($super_meta_type) . ")";
250 sub _single_metaclass_is_compatible {
252 my ( $metaclass_type, $superclass_name ) = @_;
254 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name)
257 # for instance, Moose::Meta::Class has a error_class attribute, but
258 # Class::MOP::Class doesn't - this shouldn't be an error
259 return 1 unless $super_meta->can($metaclass_type);
260 # for instance, Moose::Meta::Class has a destructor_class, but
261 # Class::MOP::Class doesn't - this shouldn't be an error
262 return 1 unless defined $super_meta->$metaclass_type;
263 # if metaclass is defined in superclass but not here, it's not compatible
264 # this is a really odd case
265 return 0 unless defined $self->$metaclass_type;
267 return $self->$metaclass_type->isa($super_meta->$metaclass_type);
270 sub _check_single_metaclass_compatibility {
272 my ( $metaclass_type, $superclass_name ) = @_;
274 if (!$self->_single_metaclass_is_compatible($metaclass_type, $superclass_name)) {
275 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name);
276 my $metaclass_type_name = $metaclass_type;
277 $metaclass_type_name =~ s/_(?:meta)?class$//;
278 $metaclass_type_name =~ s/_/ /g;
279 confess "The $metaclass_type_name metaclass for "
280 . $self->name . " (" . ($self->$metaclass_type)
281 . ")" . " is not compatible with the "
282 . "$metaclass_type_name metaclass of its "
283 . "superclass, " . $superclass_name . " ("
284 . ($super_meta->$metaclass_type) . ")";
288 sub _can_fix_class_metaclass_incompatibility_by_subclassing {
290 my ($super_meta) = @_;
292 my $super_meta_type = $super_meta->_real_ref_name;
294 return $super_meta_type ne blessed($self)
295 && $super_meta->isa(blessed($self));
298 sub _can_fix_single_metaclass_incompatibility_by_subclassing {
300 my ($metaclass_type, $super_meta) = @_;
302 my $specific_meta = $self->$metaclass_type;
303 return unless $super_meta->can($metaclass_type);
304 my $super_specific_meta = $super_meta->$metaclass_type;
306 # for instance, Moose::Meta::Class has a destructor_class, but
307 # Class::MOP::Class doesn't - this shouldn't be an error
308 return unless defined $super_specific_meta;
310 # if metaclass is defined in superclass but not here, it's fixable
311 # this is a really odd case
312 return 1 unless defined $specific_meta;
314 return $specific_meta ne $super_specific_meta
315 && $super_specific_meta->isa($specific_meta);
318 sub _can_fix_metaclass_incompatibility_by_subclassing {
320 my ($super_meta) = @_;
322 return 1 if $self->_can_fix_class_metaclass_incompatibility_by_subclassing($super_meta);
324 my %base_metaclass = $self->_base_metaclasses;
325 for my $metaclass_type (keys %base_metaclass) {
326 return 1 if $self->_can_fix_single_metaclass_incompatibility_by_subclassing($metaclass_type, $super_meta);
332 sub _can_fix_metaclass_incompatibility {
334 return $self->_can_fix_metaclass_incompatibility_by_subclassing(@_);
337 sub _fix_metaclass_incompatibility {
339 my @supers = map { Class::MOP::Class->initialize($_) } @_;
342 for my $super (@supers) {
344 if $self->_can_fix_metaclass_incompatibility($super);
346 return unless $necessary;
348 for my $super (@supers) {
349 if (!$self->_class_metaclass_is_compatible($super->name)) {
350 $self->_fix_class_metaclass_incompatibility($super);
354 my %base_metaclass = $self->_base_metaclasses;
355 for my $metaclass_type (keys %base_metaclass) {
356 for my $super (@supers) {
357 if (!$self->_single_metaclass_is_compatible($metaclass_type, $super->name)) {
358 $self->_fix_single_metaclass_incompatibility(
359 $metaclass_type, $super
366 sub _fix_class_metaclass_incompatibility {
368 my ( $super_meta ) = @_;
370 if ($self->_can_fix_class_metaclass_incompatibility_by_subclassing($super_meta)) {
372 || confess "Can't fix metaclass incompatibility for "
374 . " because it is not pristine.";
376 my $super_meta_name = $super_meta->_real_ref_name;
378 $super_meta_name->meta->rebless_instance($self);
382 sub _fix_single_metaclass_incompatibility {
384 my ( $metaclass_type, $super_meta ) = @_;
386 if ($self->_can_fix_single_metaclass_incompatibility_by_subclassing($metaclass_type, $super_meta)) {
388 || confess "Can't fix metaclass incompatibility for "
390 . " because it is not pristine.";
392 $self->{$metaclass_type} = $super_meta->$metaclass_type;
400 # this should be sufficient, if you have a
401 # use case where it is not, write a test and
403 my $ANON_CLASS_SERIAL = 0;
406 # we need a sufficiently annoying prefix
407 # this should suffice for now, this is
408 # used in a couple of places below, so
409 # need to put it up here for now.
410 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
414 no warnings 'uninitialized';
415 $self->name =~ /^$ANON_CLASS_PREFIX/o;
418 sub create_anon_class {
419 my ($class, %options) = @_;
420 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
421 return $class->create($package_name, %options);
425 # this will only get called for
426 # anon-classes, all other calls
427 # are assumed to occur during
428 # global destruction and so don't
429 # really need to be handled explicitly
433 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
435 no warnings 'uninitialized';
436 my $name = $self->name;
437 return unless $name =~ /^$ANON_CLASS_PREFIX/o;
439 # Moose does a weird thing where it replaces the metaclass for
440 # class when fixing metaclass incompatibility. In that case,
441 # we don't want to clean out the namespace now. We can detect
442 # that because Moose will explicitly update the singleton
443 # cache in Class::MOP.
444 my $current_meta = Class::MOP::get_metaclass_by_name($name);
445 return if $current_meta ne $self;
447 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/o);
449 @{$name . '::ISA'} = ();
450 %{$name . '::'} = ();
451 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
453 Class::MOP::remove_metaclass_by_name($name);
458 # creating classes with MOP ...
461 my ( $class, @args ) = @_;
463 unshift @args, 'package' if @args % 2 == 1;
465 my (%options) = @args;
466 my $package_name = $options{package};
468 (ref $options{superclasses} eq 'ARRAY')
469 || confess "You must pass an ARRAY ref of superclasses"
470 if exists $options{superclasses};
472 (ref $options{attributes} eq 'ARRAY')
473 || confess "You must pass an ARRAY ref of attributes"
474 if exists $options{attributes};
476 (ref $options{methods} eq 'HASH')
477 || confess "You must pass a HASH ref of methods"
478 if exists $options{methods};
480 my (%initialize_options) = @args;
481 delete @initialize_options{qw(
489 my $meta = $class->initialize( $package_name => %initialize_options );
491 $meta->_instantiate_module( $options{version}, $options{authority} );
494 $meta->add_method('meta' => sub {
495 $class->initialize(ref($_[0]) || $_[0]);
498 $meta->superclasses(@{$options{superclasses}})
499 if exists $options{superclasses};
501 # process attributes first, so that they can
502 # install accessors, but locally defined methods
503 # can then overwrite them. It is maybe a little odd, but
504 # I think this should be the order of things.
505 if (exists $options{attributes}) {
506 foreach my $attr (@{$options{attributes}}) {
507 $meta->add_attribute($attr);
510 if (exists $options{methods}) {
511 foreach my $method_name (keys %{$options{methods}}) {
512 $meta->add_method($method_name, $options{methods}->{$method_name});
521 # all these attribute readers will be bootstrapped
522 # away in the Class::MOP bootstrap section
524 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
525 sub immutable_trait { $_[0]->{'immutable_trait'} }
526 sub constructor_class { $_[0]->{'constructor_class'} }
527 sub constructor_name { $_[0]->{'constructor_name'} }
528 sub destructor_class { $_[0]->{'destructor_class'} }
530 # Instance Construction & Cloning
536 # we need to protect the integrity of the
537 # Class::MOP::Class singletons here, so we
538 # delegate this to &construct_class_instance
539 # which will deal with the singletons
540 return $class->_construct_class_instance(@_)
541 if $class->name->isa('Class::MOP::Class');
542 return $class->_construct_instance(@_);
545 sub _construct_instance {
547 my $params = @_ == 1 ? $_[0] : {@_};
548 my $meta_instance = $class->get_meta_instance();
550 # the code below is almost certainly incorrect
551 # but this is foreign inheritance, so we might
552 # have to kludge it in the end.
554 if (my $instance_class = blessed($params->{__INSTANCE__})) {
555 ($instance_class eq $class->name)
556 || confess "Objects passed as the __INSTANCE__ parameter must "
557 . "already be blessed into the correct class, but "
558 . "$params->{__INSTANCE__} is not a " . $class->name;
559 $instance = $params->{__INSTANCE__};
561 elsif (exists $params->{__INSTANCE__}) {
562 confess "The __INSTANCE__ parameter must be a blessed reference, not "
563 . $params->{__INSTANCE__};
566 $instance = $meta_instance->create_instance();
568 foreach my $attr ($class->get_all_attributes()) {
569 $attr->initialize_instance_slot($meta_instance, $instance, $params);
572 # this will only work for a HASH instance type
573 if ($class->is_anon_class) {
574 (reftype($instance) eq 'HASH')
575 || confess "Currently only HASH based instances are supported with instance of anon-classes";
577 # At some point we should make this official
578 # as a reserved slot name, but right now I am
579 # going to keep it here.
580 # my $RESERVED_MOP_SLOT = '__MOP__';
581 $instance->{'__MOP__'} = $class;
587 sub get_meta_instance {
589 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
592 sub _create_meta_instance {
595 my $instance = $self->instance_metaclass->new(
596 associated_metaclass => $self,
597 attributes => [ $self->get_all_attributes() ],
600 $self->add_meta_instance_dependencies()
601 if $instance->is_dependent_on_superclasses();
608 my $instance = shift;
609 (blessed($instance) && $instance->isa($class->name))
610 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
613 # we need to protect the integrity of the
614 # Class::MOP::Class singletons here, they
615 # should not be cloned.
616 return $instance if $instance->isa('Class::MOP::Class');
617 $class->_clone_instance($instance, @_);
620 sub _clone_instance {
621 my ($class, $instance, %params) = @_;
623 || confess "You can only clone instances, ($instance) is not a blessed instance";
624 my $meta_instance = $class->get_meta_instance();
625 my $clone = $meta_instance->clone_instance($instance);
626 foreach my $attr ($class->get_all_attributes()) {
627 if ( defined( my $init_arg = $attr->init_arg ) ) {
628 if (exists $params{$init_arg}) {
629 $attr->set_value($clone, $params{$init_arg});
636 sub rebless_instance {
637 my ($self, $instance, %params) = @_;
639 my $old_metaclass = Class::MOP::class_of($instance);
641 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
642 $self->name->isa($old_class)
643 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
645 $old_metaclass->rebless_instance_away($instance, $self, %params)
648 my $meta_instance = $self->get_meta_instance();
651 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
652 $meta_instance->rebless_instance_structure($_[1], $self);
654 foreach my $attr ( $self->get_all_attributes ) {
655 if ( $attr->has_value($instance) ) {
656 if ( defined( my $init_arg = $attr->init_arg ) ) {
657 $params{$init_arg} = $attr->get_value($instance)
658 unless exists $params{$init_arg};
661 $attr->set_value($instance, $attr->get_value($instance));
666 foreach my $attr ($self->get_all_attributes) {
667 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
673 sub rebless_instance_back {
674 my ( $self, $instance ) = @_;
676 my $old_metaclass = Class::MOP::class_of($instance);
679 = $old_metaclass ? $old_metaclass->name : blessed($instance);
680 $old_class->isa( $self->name )
682 "You may rebless only into a superclass of ($old_class), of which ("
686 $old_metaclass->rebless_instance_away( $instance, $self )
689 my $meta_instance = $self->get_meta_instance;
691 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
692 $meta_instance->rebless_instance_structure( $_[1], $self );
694 for my $attr ( $old_metaclass->get_all_attributes ) {
695 next if $self->has_attribute( $attr->name );
696 $meta_instance->deinitialize_slot( $instance, $_ ) for $attr->slots;
702 sub rebless_instance_away {
703 # this intentionally does nothing, it is just a hook
706 sub _attach_attribute {
707 my ($self, $attribute) = @_;
708 $attribute->attach_to_class($self);
711 sub _post_add_attribute {
712 my ( $self, $attribute ) = @_;
714 $self->invalidate_meta_instances;
716 # invalidate package flag here
719 $attribute->install_accessors;
722 $self->remove_attribute( $attribute->name );
727 sub remove_attribute {
730 my $removed_attribute = $self->SUPER::remove_attribute(@_)
733 $self->invalidate_meta_instances;
735 $removed_attribute->remove_accessors;
736 $removed_attribute->detach_from_class;
738 return$removed_attribute;
741 sub find_attribute_by_name {
742 my ( $self, $attr_name ) = @_;
744 foreach my $class ( $self->linearized_isa ) {
745 # fetch the meta-class ...
746 my $meta = Class::MOP::Class->initialize($class);
747 return $meta->get_attribute($attr_name)
748 if $meta->has_attribute($attr_name);
754 sub get_all_attributes {
756 my %attrs = map { %{ Class::MOP::Class->initialize($_)->_attribute_map } }
757 reverse $self->linearized_isa;
758 return values %attrs;
765 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
768 @{$self->get_package_symbol($var_spec)} = @supers;
771 # on 5.8 and below, we need to call
772 # a method to get Perl to detect
773 # a cycle in the class hierarchy
774 my $class = $self->name;
778 # we need to check the metaclass
779 # compatibility here so that we can
780 # be sure that the superclass is
781 # not potentially creating an issues
782 # we don't know about
784 $self->_check_metaclass_compatibility();
785 $self->_superclasses_updated();
787 @{$self->get_package_symbol($var_spec)};
790 sub _superclasses_updated {
792 $self->update_meta_instance_dependencies();
797 my $super_class = $self->name;
799 return @{ $super_class->mro::get_isarev() };
802 sub direct_subclasses {
804 my $super_class = $self->name;
809 } Class::MOP::Class->initialize($_)->superclasses
814 return @{ mro::get_linear_isa( (shift)->name ) };
817 sub class_precedence_list {
819 my $name = $self->name;
821 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
823 # We need to check for circular inheritance here
824 # if we are are not on 5.10, cause 5.8 detects it
825 # late. This will do nothing if all is well, and
826 # blow up otherwise. Yes, it's an ugly hack, better
827 # suggestions are welcome.
829 ($name || return)->isa('This is a test for circular inheritance')
832 # if our mro is c3, we can
833 # just grab the linear_isa
834 if (mro::get_mro($name) eq 'c3') {
835 return @{ mro::get_linear_isa($name) }
839 # we can't grab the linear_isa for dfs
840 # since it has all the duplicates
845 Class::MOP::Class->initialize($_)->class_precedence_list()
846 } $self->superclasses()
854 my $fetch_and_prepare_method = sub {
855 my ($self, $method_name) = @_;
856 my $wrapped_metaclass = $self->wrapped_method_metaclass;
858 my $method = $self->get_method($method_name);
859 # if we dont have local ...
861 # try to find the next method
862 $method = $self->find_next_method_by_name($method_name);
863 # die if it does not exist
865 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
866 # and now make sure to wrap it
867 # even if it is already wrapped
868 # because we need a new sub ref
869 $method = $wrapped_metaclass->wrap($method,
870 package_name => $self->name,
871 name => $method_name,
875 # now make sure we wrap it properly
876 $method = $wrapped_metaclass->wrap($method,
877 package_name => $self->name,
878 name => $method_name,
879 ) unless $method->isa($wrapped_metaclass);
881 $self->add_method($method_name => $method);
885 sub add_before_method_modifier {
886 my ($self, $method_name, $method_modifier) = @_;
887 (defined $method_name && length $method_name)
888 || confess "You must pass in a method name";
889 my $method = $fetch_and_prepare_method->($self, $method_name);
890 $method->add_before_modifier(
891 subname(':before' => $method_modifier)
895 sub add_after_method_modifier {
896 my ($self, $method_name, $method_modifier) = @_;
897 (defined $method_name && length $method_name)
898 || confess "You must pass in a method name";
899 my $method = $fetch_and_prepare_method->($self, $method_name);
900 $method->add_after_modifier(
901 subname(':after' => $method_modifier)
905 sub add_around_method_modifier {
906 my ($self, $method_name, $method_modifier) = @_;
907 (defined $method_name && length $method_name)
908 || confess "You must pass in a method name";
909 my $method = $fetch_and_prepare_method->($self, $method_name);
910 $method->add_around_modifier(
911 subname(':around' => $method_modifier)
916 # the methods above used to be named like this:
917 # ${pkg}::${method}:(before|after|around)
918 # but this proved problematic when using one modifier
919 # to wrap multiple methods (something which is likely
920 # to happen pretty regularly IMO). So instead of naming
921 # it like this, I have chosen to just name them purely
922 # with their modifier names, like so:
923 # :(before|after|around)
924 # The fact is that in a stack trace, it will be fairly
925 # evident from the context what method they are attached
926 # to, and so don't need the fully qualified name.
929 sub find_method_by_name {
930 my ($self, $method_name) = @_;
931 (defined $method_name && length $method_name)
932 || confess "You must define a method name to find";
933 foreach my $class ($self->linearized_isa) {
934 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
935 return $method if defined $method;
940 sub get_all_methods {
944 for my $class ( reverse $self->linearized_isa ) {
945 my $meta = Class::MOP::Class->initialize($class);
947 $methods{$_} = $meta->get_method($_)
948 for $meta->get_method_list;
951 return values %methods;
954 sub get_all_method_names {
957 return grep { !$uniq{$_}++ } map { Class::MOP::Class->initialize($_)->get_method_list } $self->linearized_isa;
960 sub find_all_methods_by_name {
961 my ($self, $method_name) = @_;
962 (defined $method_name && length $method_name)
963 || confess "You must define a method name to find";
965 foreach my $class ($self->linearized_isa) {
966 # fetch the meta-class ...
967 my $meta = Class::MOP::Class->initialize($class);
969 name => $method_name,
971 code => $meta->get_method($method_name)
972 } if $meta->has_method($method_name);
977 sub find_next_method_by_name {
978 my ($self, $method_name) = @_;
979 (defined $method_name && length $method_name)
980 || confess "You must define a method name to find";
981 my @cpl = $self->linearized_isa;
982 shift @cpl; # discard ourselves
983 foreach my $class (@cpl) {
984 my $method = Class::MOP::Class->initialize($class)->get_method($method_name);
985 return $method if defined $method;
990 sub update_meta_instance_dependencies {
993 if ( $self->{meta_instance_dependencies} ) {
994 return $self->add_meta_instance_dependencies;
998 sub add_meta_instance_dependencies {
1001 $self->remove_meta_instance_dependencies;
1003 my @attrs = $self->get_all_attributes();
1006 my @classes = grep { not $seen{ $_->name }++ }
1007 map { $_->associated_class } @attrs;
1009 foreach my $class (@classes) {
1010 $class->add_dependent_meta_instance($self);
1013 $self->{meta_instance_dependencies} = \@classes;
1016 sub remove_meta_instance_dependencies {
1019 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
1020 foreach my $class (@$classes) {
1021 $class->remove_dependent_meta_instance($self);
1031 sub add_dependent_meta_instance {
1032 my ( $self, $metaclass ) = @_;
1033 push @{ $self->{dependent_meta_instances} }, $metaclass;
1036 sub remove_dependent_meta_instance {
1037 my ( $self, $metaclass ) = @_;
1038 my $name = $metaclass->name;
1039 @$_ = grep { $_->name ne $name } @$_
1040 for $self->{dependent_meta_instances};
1043 sub invalidate_meta_instances {
1045 $_->invalidate_meta_instance()
1046 for $self, @{ $self->{dependent_meta_instances} };
1049 sub invalidate_meta_instance {
1051 undef $self->{_meta_instance};
1054 # check if we can reinitialize
1058 # if any local attr is defined
1059 return if $self->get_attribute_list;
1061 # or any non-declared methods
1062 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
1063 return if $method->isa("Class::MOP::Method::Generated");
1064 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
1072 sub is_mutable { 1 }
1073 sub is_immutable { 0 }
1075 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
1077 sub _immutable_options {
1078 my ( $self, @args ) = @_;
1081 inline_accessors => 1,
1082 inline_constructor => 1,
1083 inline_destructor => 0,
1085 immutable_trait => $self->immutable_trait,
1086 constructor_name => $self->constructor_name,
1087 constructor_class => $self->constructor_class,
1088 destructor_class => $self->destructor_class,
1093 sub make_immutable {
1094 my ( $self, @args ) = @_;
1096 if ( $self->is_mutable ) {
1097 $self->_initialize_immutable( $self->_immutable_options(@args) );
1098 $self->_rebless_as_immutable(@args);
1109 if ( $self->is_immutable ) {
1110 my @args = $self->immutable_options;
1111 $self->_rebless_as_mutable();
1112 $self->_remove_inlined_code(@args);
1113 delete $self->{__immutable};
1121 sub _rebless_as_immutable {
1122 my ( $self, @args ) = @_;
1124 $self->{__immutable}{original_class} = ref $self;
1126 bless $self => $self->_immutable_metaclass(@args);
1129 sub _immutable_metaclass {
1130 my ( $self, %args ) = @_;
1132 if ( my $class = $args{immutable_metaclass} ) {
1136 my $trait = $args{immutable_trait} = $self->immutable_trait
1137 || confess "no immutable trait specified for $self";
1139 my $meta = $self->meta;
1140 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1144 if ( $meta_attr and $trait eq $meta_attr->default ) {
1145 # if the trait is the same as the default we try and pick a
1146 # predictable name for the immutable metaclass
1147 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1150 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1151 $trait, 'ForMetaClass', ref($self);
1155 if Class::MOP::is_class_loaded($class_name);
1157 # If the metaclass is a subclass of CMOP::Class which has had
1158 # metaclass roles applied (via Moose), then we want to make sure
1159 # that we preserve that anonymous class (see Fey::ORM for an
1160 # example of where this matters).
1161 my $meta_name = $meta->_real_ref_name;
1163 my $immutable_meta = $meta_name->create(
1165 superclasses => [ ref $self ],
1168 Class::MOP::load_class($trait);
1169 for my $meth ( Class::MOP::Class->initialize($trait)->get_all_methods ) {
1170 my $meth_name = $meth->name;
1172 if ( $immutable_meta->find_method_by_name( $meth_name ) ) {
1173 $immutable_meta->add_around_method_modifier( $meth_name, $meth->body );
1176 $immutable_meta->add_method( $meth_name, $meth->clone );
1180 $immutable_meta->make_immutable(
1181 inline_constructor => 0,
1182 inline_accessors => 0,
1188 sub _remove_inlined_code {
1191 $self->remove_method( $_->name ) for $self->_inlined_methods;
1193 delete $self->{__immutable}{inlined_methods};
1196 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1198 sub _add_inlined_method {
1199 my ( $self, $method ) = @_;
1201 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1204 sub _initialize_immutable {
1205 my ( $self, %args ) = @_;
1207 $self->{__immutable}{options} = \%args;
1208 $self->_install_inlined_code(%args);
1211 sub _install_inlined_code {
1212 my ( $self, %args ) = @_;
1215 $self->_inline_accessors(%args) if $args{inline_accessors};
1216 $self->_inline_constructor(%args) if $args{inline_constructor};
1217 $self->_inline_destructor(%args) if $args{inline_destructor};
1220 sub _rebless_as_mutable {
1223 bless $self, $self->_get_mutable_metaclass_name;
1228 sub _inline_accessors {
1231 foreach my $attr_name ( $self->get_attribute_list ) {
1232 $self->get_attribute($attr_name)->install_accessors(1);
1236 sub _inline_constructor {
1237 my ( $self, %args ) = @_;
1239 my $name = $args{constructor_name};
1240 # A class may not even have a constructor, and that's okay.
1241 return unless defined $name;
1243 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1244 my $class = $self->name;
1245 warn "Not inlining a constructor for $class since it defines"
1246 . " its own constructor.\n"
1247 . "If you are certain you don't need to inline your"
1248 . " constructor, specify inline_constructor => 0 in your"
1249 . " call to $class->meta->make_immutable\n";
1253 my $constructor_class = $args{constructor_class};
1255 Class::MOP::load_class($constructor_class);
1257 my $constructor = $constructor_class->new(
1261 package_name => $self->name,
1265 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1266 $self->add_method( $name => $constructor );
1267 $self->_add_inlined_method($constructor);
1271 sub _inline_destructor {
1272 my ( $self, %args ) = @_;
1274 ( exists $args{destructor_class} && defined $args{destructor_class} )
1275 || confess "The 'inline_destructor' option is present, but "
1276 . "no destructor class was specified";
1278 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1279 my $class = $self->name;
1280 warn "Not inlining a destructor for $class since it defines"
1281 . " its own destructor.\n";
1285 my $destructor_class = $args{destructor_class};
1287 Class::MOP::load_class($destructor_class);
1289 return unless $destructor_class->is_needed($self);
1291 my $destructor = $destructor_class->new(
1294 package_name => $self->name,
1298 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1299 $self->add_method( 'DESTROY' => $destructor );
1300 $self->_add_inlined_method($destructor);
1312 Class::MOP::Class - Class Meta Object
1316 # assuming that class Foo
1317 # has been defined, you can
1319 # use this for introspection ...
1321 # add a method to Foo ...
1322 Foo->meta->add_method( 'bar' => sub {...} )
1324 # get a list of all the classes searched
1325 # the method dispatcher in the correct order
1326 Foo->meta->class_precedence_list()
1328 # remove a method from Foo
1329 Foo->meta->remove_method('bar');
1331 # or use this to actually create classes ...
1333 Class::MOP::Class->create(
1336 superclasses => ['Foo'],
1338 Class::MOP::Attribute->new('$bar'),
1339 Class::MOP::Attribute->new('$baz'),
1342 calculate_bar => sub {...},
1343 construct_baz => sub {...}
1350 The Class Protocol is the largest and most complex part of the
1351 Class::MOP meta-object protocol. It controls the introspection and
1352 manipulation of Perl 5 classes, and it can create them as well. The
1353 best way to understand what this module can do is to read the
1354 documentation for each of its methods.
1358 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1362 =head2 Class construction
1364 These methods all create new C<Class::MOP::Class> objects. These
1365 objects can represent existing classes or they can be used to create
1366 new classes from scratch.
1368 The metaclass object for a given class is a singleton. If you attempt
1369 to create a metaclass for the same class twice, you will just get the
1374 =item B<< Class::MOP::Class->create($package_name, %options) >>
1376 This method creates a new C<Class::MOP::Class> object with the given
1377 package name. It accepts a number of options:
1383 An optional version number for the newly created package.
1387 An optional authority for the newly created package.
1389 =item * superclasses
1391 An optional array reference of superclass names.
1395 An optional hash reference of methods for the class. The keys of the
1396 hash reference are method names and values are subroutine references.
1400 An optional array reference of L<Class::MOP::Attribute> objects.
1404 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1406 This method works just like C<< Class::MOP::Class->create >> but it
1407 creates an "anonymous" class. In fact, the class does have a name, but
1408 that name is a unique name generated internally by this module.
1410 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1411 parameters that C<create> accepts.
1413 Anonymous classes are destroyed once the metaclass they are attached
1414 to goes out of scope, and will be removed from Perl's internal symbol
1417 All instances of an anonymous class keep a special reference to the
1418 metaclass object, which prevents the metaclass from going out of scope
1419 while any instances exist.
1421 This only works if the instance is based on a hash reference, however.
1423 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1425 This method will initialize a C<Class::MOP::Class> object for the
1426 named package. Unlike C<create>, this method I<will not> create a new
1429 The purpose of this method is to retrieve a C<Class::MOP::Class>
1430 object for introspecting an existing class.
1432 If an existing C<Class::MOP::Class> object exists for the named
1433 package, it will be returned, and any options provided will be
1436 If the object does not yet exist, it will be created.
1438 The valid options that can be passed to this method are
1439 C<attribute_metaclass>, C<method_metaclass>,
1440 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1441 optional, and default to the appropriate class in the C<Class::MOP>
1446 =head2 Object instance construction and cloning
1448 These methods are all related to creating and/or cloning object
1453 =item B<< $metaclass->clone_object($instance, %params) >>
1455 This method clones an existing object instance. Any parameters you
1456 provide are will override existing attribute values in the object.
1458 This is a convenience method for cloning an object instance, then
1459 blessing it into the appropriate package.
1461 You could implement a clone method in your class, using this method:
1464 my ($self, %params) = @_;
1465 $self->meta->clone_object($self, %params);
1468 =item B<< $metaclass->rebless_instance($instance, %params) >>
1470 This method changes the class of C<$instance> to the metaclass's class.
1472 You can only rebless an instance into a subclass of its current
1473 class. If you pass any additional parameters, these will be treated
1474 like constructor parameters and used to initialize the object's
1475 attributes. Any existing attributes that are already set will be
1478 Before reblessing the instance, this method will call
1479 C<rebless_instance_away> on the instance's current metaclass. This method
1480 will be passed the instance, the new metaclass, and any parameters
1481 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1482 does nothing; it is merely a hook.
1484 =item B<< $metaclass->rebless_instance_back($instance) >>
1486 Does the same thing as C<rebless_instance>, except that you can only
1487 rebless an instance into one of its superclasses. Any attributes that
1488 do not exist in the superclass will be deinitialized.
1490 This is a much more dangerous operation than C<rebless_instance>,
1491 especially when multiple inheritance is involved, so use this carefully!
1493 =item B<< $metaclass->new_object(%params) >>
1495 This method is used to create a new object of the metaclass's
1496 class. Any parameters you provide are used to initialize the
1497 instance's attributes. A special C<__INSTANCE__> key can be passed to
1498 provide an already generated instance, rather than having Class::MOP
1499 generate it for you. This is mostly useful for using Class::MOP with
1500 foreign classes which generate instances using their own constructors.
1502 =item B<< $metaclass->instance_metaclass >>
1504 Returns the class name of the instance metaclass. See
1505 L<Class::MOP::Instance> for more information on the instance
1508 =item B<< $metaclass->get_meta_instance >>
1510 Returns an instance of the C<instance_metaclass> to be used in the
1511 construction of a new instance of the class.
1515 =head2 Informational predicates
1517 These are a few predicate methods for asking information about the
1522 =item B<< $metaclass->is_anon_class >>
1524 This returns true if the class was created by calling C<<
1525 Class::MOP::Class->create_anon_class >>.
1527 =item B<< $metaclass->is_mutable >>
1529 This returns true if the class is still mutable.
1531 =item B<< $metaclass->is_immutable >>
1533 This returns true if the class has been made immutable.
1535 =item B<< $metaclass->is_pristine >>
1537 A class is I<not> pristine if it has non-inherited attributes or if it
1538 has any generated methods.
1542 =head2 Inheritance Relationships
1546 =item B<< $metaclass->superclasses(@superclasses) >>
1548 This is a read-write accessor which represents the superclass
1549 relationships of the metaclass's class.
1551 This is basically sugar around getting and setting C<@ISA>.
1553 =item B<< $metaclass->class_precedence_list >>
1555 This returns a list of all of the class's ancestor classes. The
1556 classes are returned in method dispatch order.
1558 =item B<< $metaclass->linearized_isa >>
1560 This returns a list based on C<class_precedence_list> but with all
1563 =item B<< $metaclass->subclasses >>
1565 This returns a list of all subclasses for this class, even indirect
1568 =item B<< $metaclass->direct_subclasses >>
1570 This returns a list of immediate subclasses for this class, which does not
1571 include indirect subclasses.
1575 =head2 Method introspection and creation
1577 These methods allow you to introspect a class's methods, as well as
1578 add, remove, or change methods.
1580 Determining what is truly a method in a Perl 5 class requires some
1581 heuristics (aka guessing).
1583 Methods defined outside the package with a fully qualified name (C<sub
1584 Package::name { ... }>) will be included. Similarly, methods named
1585 with a fully qualified name using L<Sub::Name> are also included.
1587 However, we attempt to ignore imported functions.
1589 Ultimately, we are using heuristics to determine what truly is a
1590 method in a class, and these heuristics may get the wrong answer in
1591 some edge cases. However, for most "normal" cases the heuristics work
1596 =item B<< $metaclass->get_method($method_name) >>
1598 This will return a L<Class::MOP::Method> for the specified
1599 C<$method_name>. If the class does not have the specified method, it
1602 =item B<< $metaclass->has_method($method_name) >>
1604 Returns a boolean indicating whether or not the class defines the
1605 named method. It does not include methods inherited from parent
1608 =item B<< $metaclass->get_method_list >>
1610 This will return a list of method I<names> for all methods defined in
1613 =item B<< $metaclass->add_method($method_name, $method) >>
1615 This method takes a method name and a subroutine reference, and adds
1616 the method to the class.
1618 The subroutine reference can be a L<Class::MOP::Method>, and you are
1619 strongly encouraged to pass a meta method object instead of a code
1620 reference. If you do so, that object gets stored as part of the
1621 class's method map directly. If not, the meta information will have to
1622 be recreated later, and may be incorrect.
1624 If you provide a method object, this method will clone that object if
1625 the object's package name does not match the class name. This lets us
1626 track the original source of any methods added from other classes
1627 (notably Moose roles).
1629 =item B<< $metaclass->remove_method($method_name) >>
1631 Remove the named method from the class. This method returns the
1632 L<Class::MOP::Method> object for the method.
1634 =item B<< $metaclass->method_metaclass >>
1636 Returns the class name of the method metaclass, see
1637 L<Class::MOP::Method> for more information on the method metaclass.
1639 =item B<< $metaclass->wrapped_method_metaclass >>
1641 Returns the class name of the wrapped method metaclass, see
1642 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1645 =item B<< $metaclass->get_all_methods >>
1647 This will traverse the inheritance hierarchy and return a list of all
1648 the L<Class::MOP::Method> objects for this class and its parents.
1650 =item B<< $metaclass->find_method_by_name($method_name) >>
1652 This will return a L<Class::MOP::Method> for the specified
1653 C<$method_name>. If the class does not have the specified method, it
1656 Unlike C<get_method>, this method I<will> look for the named method in
1659 =item B<< $metaclass->get_all_method_names >>
1661 This will return a list of method I<names> for all of this class's
1662 methods, including inherited methods.
1664 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1666 This method looks for the named method in the class and all of its
1667 parents. It returns every matching method it finds in the inheritance
1668 tree, so it returns a list of methods.
1670 Each method is returned as a hash reference with three keys. The keys
1671 are C<name>, C<class>, and C<code>. The C<code> key has a
1672 L<Class::MOP::Method> object as its value.
1674 The list of methods is distinct.
1676 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1678 This method returns the first method in any superclass matching the
1679 given name. It is effectively the method that C<SUPER::$method_name>
1684 =head2 Attribute introspection and creation
1686 Because Perl 5 does not have a core concept of attributes in classes,
1687 we can only return information about attributes which have been added
1688 via this class's methods. We cannot discover information about
1689 attributes which are defined in terms of "regular" Perl 5 methods.
1693 =item B<< $metaclass->get_attribute($attribute_name) >>
1695 This will return a L<Class::MOP::Attribute> for the specified
1696 C<$attribute_name>. If the class does not have the specified
1697 attribute, it returns C<undef>.
1699 NOTE that get_attribute does not search superclasses, for that you
1700 need to use C<find_attribute_by_name>.
1702 =item B<< $metaclass->has_attribute($attribute_name) >>
1704 Returns a boolean indicating whether or not the class defines the
1705 named attribute. It does not include attributes inherited from parent
1708 =item B<< $metaclass->get_attribute_list >>
1710 This will return a list of attributes I<names> for all attributes
1711 defined in this class. Note that this operates on the current class
1712 only, it does not traverse the inheritance hierarchy.
1714 =item B<< $metaclass->get_all_attributes >>
1716 This will traverse the inheritance hierarchy and return a list of all
1717 the L<Class::MOP::Attribute> objects for this class and its parents.
1719 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1721 This will return a L<Class::MOP::Attribute> for the specified
1722 C<$attribute_name>. If the class does not have the specified
1723 attribute, it returns C<undef>.
1725 Unlike C<get_attribute>, this attribute I<will> look for the named
1726 attribute in superclasses.
1728 =item B<< $metaclass->add_attribute(...) >>
1730 This method accepts either an existing L<Class::MOP::Attribute>
1731 object or parameters suitable for passing to that class's C<new>
1734 The attribute provided will be added to the class.
1736 Any accessor methods defined by the attribute will be added to the
1737 class when the attribute is added.
1739 If an attribute of the same name already exists, the old attribute
1740 will be removed first.
1742 =item B<< $metaclass->remove_attribute($attribute_name) >>
1744 This will remove the named attribute from the class, and
1745 L<Class::MOP::Attribute> object.
1747 Removing an attribute also removes any accessor methods defined by the
1750 However, note that removing an attribute will only affect I<future>
1751 object instances created for this class, not existing instances.
1753 =item B<< $metaclass->attribute_metaclass >>
1755 Returns the class name of the attribute metaclass for this class. By
1756 default, this is L<Class::MOP::Attribute>.
1760 =head2 Class Immutability
1762 Making a class immutable "freezes" the class definition. You can no
1763 longer call methods which alter the class, such as adding or removing
1764 methods or attributes.
1766 Making a class immutable lets us optimize the class by inlining some
1767 methods, and also allows us to optimize some methods on the metaclass
1770 After immutabilization, the metaclass object will cache most informational
1771 methods that returns information about methods or attributes. Methods which
1772 would alter the class, such as C<add_attribute> and C<add_method>, will
1773 throw an error on an immutable metaclass object.
1775 The immutabilization system in L<Moose> takes much greater advantage
1776 of the inlining features than Class::MOP itself does.
1780 =item B<< $metaclass->make_immutable(%options) >>
1782 This method will create an immutable transformer and use it to make
1783 the class and its metaclass object immutable.
1785 This method accepts the following options:
1789 =item * inline_accessors
1791 =item * inline_constructor
1793 =item * inline_destructor
1795 These are all booleans indicating whether the specified method(s)
1798 By default, accessors and the constructor are inlined, but not the
1801 =item * immutable_trait
1803 The name of a class which will be used as a parent class for the
1804 metaclass object being made immutable. This "trait" implements the
1805 post-immutability functionality of the metaclass (but not the
1806 transformation itself).
1808 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1810 =item * constructor_name
1812 This is the constructor method name. This defaults to "new".
1814 =item * constructor_class
1816 The name of the method metaclass for constructors. It will be used to
1817 generate the inlined constructor. This defaults to
1818 "Class::MOP::Method::Constructor".
1820 =item * replace_constructor
1822 This is a boolean indicating whether an existing constructor should be
1823 replaced when inlining a constructor. This defaults to false.
1825 =item * destructor_class
1827 The name of the method metaclass for destructors. It will be used to
1828 generate the inlined destructor. This defaults to
1829 "Class::MOP::Method::Denstructor".
1831 =item * replace_destructor
1833 This is a boolean indicating whether an existing destructor should be
1834 replaced when inlining a destructor. This defaults to false.
1838 =item B<< $metaclass->immutable_options >>
1840 Returns a hash of the options used when making the class immutable, including
1841 both defaults and anything supplied by the user in the call to C<<
1842 $metaclass->make_immutable >>. This is useful if you need to temporarily make
1843 a class mutable and then restore immutability as it was before.
1845 =item B<< $metaclass->make_mutable >>
1847 Calling this method reverse the immutabilization transformation.
1851 =head2 Method Modifiers
1853 Method modifiers are hooks which allow a method to be wrapped with
1854 I<before>, I<after> and I<around> method modifiers. Every time a
1855 method is called, its modifiers are also called.
1857 A class can modify its own methods, as well as methods defined in
1860 =head3 How method modifiers work?
1862 Method modifiers work by wrapping the original method and then
1863 replacing it in the class's symbol table. The wrappers will handle
1864 calling all the modifiers in the appropriate order and preserving the
1865 calling context for the original method.
1867 The return values of C<before> and C<after> modifiers are
1868 ignored. This is because their purpose is B<not> to filter the input
1869 and output of the primary method (this is done with an I<around>
1872 This may seem like an odd restriction to some, but doing this allows
1873 for simple code to be added at the beginning or end of a method call
1874 without altering the function of the wrapped method or placing any
1875 extra responsibility on the code of the modifier.
1877 Of course if you have more complex needs, you can use the C<around>
1878 modifier which allows you to change both the parameters passed to the
1879 wrapped method, as well as its return value.
1881 Before and around modifiers are called in last-defined-first-called
1882 order, while after modifiers are called in first-defined-first-called
1883 order. So the call tree might looks something like this:
1895 =head3 What is the performance impact?
1897 Of course there is a performance cost associated with method
1898 modifiers, but we have made every effort to make that cost directly
1899 proportional to the number of modifier features you use.
1901 The wrapping method does its best to B<only> do as much work as it
1902 absolutely needs to. In order to do this we have moved some of the
1903 performance costs to set-up time, where they are easier to amortize.
1905 All this said, our benchmarks have indicated the following:
1907 simple wrapper with no modifiers 100% slower
1908 simple wrapper with simple before modifier 400% slower
1909 simple wrapper with simple after modifier 450% slower
1910 simple wrapper with simple around modifier 500-550% slower
1911 simple wrapper with all 3 modifiers 1100% slower
1913 These numbers may seem daunting, but you must remember, every feature
1914 comes with some cost. To put things in perspective, just doing a
1915 simple C<AUTOLOAD> which does nothing but extract the name of the
1916 method called and return it costs about 400% over a normal method
1921 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1923 This wraps the specified method with the supplied subroutine
1924 reference. The modifier will be called as a method itself, and will
1925 receive the same arguments as are passed to the method.
1927 When the modifier exits, the wrapped method will be called.
1929 The return value of the modifier will be ignored.
1931 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1933 This wraps the specified method with the supplied subroutine
1934 reference. The modifier will be called as a method itself, and will
1935 receive the same arguments as are passed to the method.
1937 When the wrapped methods exits, the modifier will be called.
1939 The return value of the modifier will be ignored.
1941 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1943 This wraps the specified method with the supplied subroutine
1946 The first argument passed to the modifier will be a subroutine
1947 reference to the wrapped method. The second argument is the object,
1948 and after that come any arguments passed when the method is called.
1950 The around modifier can choose to call the original method, as well as
1951 what arguments to pass if it does so.
1953 The return value of the modifier is what will be seen by the caller.
1957 =head2 Introspection
1961 =item B<< Class::MOP::Class->meta >>
1963 This will return a L<Class::MOP::Class> instance for this class.
1965 It should also be noted that L<Class::MOP> will actually bootstrap
1966 this module by installing a number of attribute meta-objects into its
1973 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1975 =head1 COPYRIGHT AND LICENSE
1977 Copyright 2006-2010 by Infinity Interactive, Inc.
1979 L<http://www.iinteractive.com>
1981 This library is free software; you can redistribute it and/or modify
1982 it under the same terms as Perl itself.