2 package Class::MOP::Class;
7 use Class::MOP::Immutable;
8 use Class::MOP::Instance;
9 use Class::MOP::Method::Wrapped;
12 use Scalar::Util 'blessed', 'weaken';
14 our $VERSION = '0.78_02';
15 $VERSION = eval $VERSION;
16 our $AUTHORITY = 'cpan:STEVAN';
18 use base 'Class::MOP::Module';
28 $package_name = shift;
31 $package_name = $options{package};
34 (defined $package_name && $package_name && !ref($package_name))
35 || confess "You must pass a package name and it cannot be blessed";
37 return Class::MOP::get_metaclass_by_name($package_name)
38 || $class->construct_class_instance(package => $package_name, @_);
41 # NOTE: (meta-circularity)
42 # this is a special form of &construct_instance
43 # (see below), which is used to construct class
44 # meta-object instances for any Class::MOP::*
45 # class. All other classes will use the more
46 # normal &construct_instance.
47 sub construct_class_instance {
49 my $options = @_ == 1 ? $_[0] : {@_};
50 my $package_name = $options->{package};
51 (defined $package_name && $package_name)
52 || confess "You must pass a package name";
54 # return the metaclass if we have it cached,
55 # and it is still defined (it has not been
56 # reaped by DESTROY yet, which can happen
57 # annoyingly enough during global destruction)
59 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
64 # we need to deal with the possibility
65 # of class immutability here, and then
66 # get the name of the class appropriately
68 ? ($class->is_immutable
69 ? $class->get_mutable_metaclass_name()
73 # now create the metaclass
75 if ($class eq 'Class::MOP::Class') {
76 $meta = $class->_new($options);
80 # it is safe to use meta here because
81 # class will always be a subclass of
82 # Class::MOP::Class, which defines meta
83 $meta = $class->meta->construct_instance($options)
86 # and check the metaclass compatibility
87 $meta->check_metaclass_compatibility();
89 Class::MOP::store_metaclass_by_name($package_name, $meta);
92 # we need to weaken any anon classes
93 # so that they can call DESTROY properly
94 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
101 my $options = @_ == 1 ? $_[0] : {@_};
104 # inherited from Class::MOP::Package
105 'package' => $options->{package},
108 # since the following attributes will
109 # actually be loaded from the symbol
110 # table, and actually bypass the instance
111 # entirely, we can just leave these things
112 # listed here for reference, because they
113 # should not actually have a value associated
115 'namespace' => \undef,
117 # inherited from Class::MOP::Module
119 'authority' => \undef,
121 # defined in Class::MOP::Class
122 'superclasses' => \undef,
126 'attribute_metaclass' => $options->{'attribute_metaclass'}
127 || 'Class::MOP::Attribute',
128 'method_metaclass' => $options->{'method_metaclass'}
129 || 'Class::MOP::Method',
130 'wrapped_method_metaclass' => $options->{'wrapped_method_metaclass'}
131 || 'Class::MOP::Method::Wrapped',
132 'instance_metaclass' => $options->{'instance_metaclass'}
133 || 'Class::MOP::Instance',
137 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
138 sub update_package_cache_flag {
141 # we can manually update the cache number
142 # since we are actually adding the method
143 # to our cache as well. This avoids us
144 # having to regenerate the method_map.
146 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
149 sub check_metaclass_compatibility {
152 # this is always okay ...
153 return if ref($self) eq 'Class::MOP::Class' &&
154 $self->instance_metaclass eq 'Class::MOP::Instance';
156 my @class_list = $self->linearized_isa;
157 shift @class_list; # shift off $self->name
159 foreach my $superclass_name (@class_list) {
160 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name) || next;
163 # we need to deal with the possibility
164 # of class immutability here, and then
165 # get the name of the class appropriately
167 = $super_meta->is_immutable
168 ? $super_meta->get_mutable_metaclass_name()
171 ($self->isa($super_meta_type))
172 || confess $self->name . "->meta => (" . (ref($self)) . ")" .
173 " is not compatible with the " .
174 $superclass_name . "->meta => (" . ($super_meta_type) . ")";
176 # we also need to check that instance metaclasses
177 # are compatibile in the same the class.
178 ($self->instance_metaclass->isa($super_meta->instance_metaclass))
179 || confess $self->name . "->meta->instance_metaclass => (" . ($self->instance_metaclass) . ")" .
180 " is not compatible with the " .
181 $superclass_name . "->meta->instance_metaclass => (" . ($super_meta->instance_metaclass) . ")";
189 # this should be sufficient, if you have a
190 # use case where it is not, write a test and
192 my $ANON_CLASS_SERIAL = 0;
195 # we need a sufficiently annoying prefix
196 # this should suffice for now, this is
197 # used in a couple of places below, so
198 # need to put it up here for now.
199 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
203 no warnings 'uninitialized';
204 $self->name =~ /^$ANON_CLASS_PREFIX/;
207 sub create_anon_class {
208 my ($class, %options) = @_;
209 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
210 return $class->create($package_name, %options);
214 # this will only get called for
215 # anon-classes, all other calls
216 # are assumed to occur during
217 # global destruction and so don't
218 # really need to be handled explicitly
222 return if Class::MOP::in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
224 no warnings 'uninitialized';
225 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
226 # Moose does a weird thing where it replaces the metaclass for
227 # class when fixing metaclass incompatibility. In that case,
228 # we don't want to clean out the namespace now. We can detect
229 # that because Moose will explicitly update the singleton
230 # cache in Class::MOP.
231 my $current_meta = Class::MOP::get_metaclass_by_name($self->name);
232 return if $current_meta ne $self;
234 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
236 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
237 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
239 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
244 # creating classes with MOP ...
247 my ( $class, @args ) = @_;
249 unshift @args, 'package' if @args % 2 == 1;
251 my (%options) = @args;
252 my $package_name = $options{package};
254 (ref $options{superclasses} eq 'ARRAY')
255 || confess "You must pass an ARRAY ref of superclasses"
256 if exists $options{superclasses};
258 (ref $options{attributes} eq 'ARRAY')
259 || confess "You must pass an ARRAY ref of attributes"
260 if exists $options{attributes};
262 (ref $options{methods} eq 'HASH')
263 || confess "You must pass a HASH ref of methods"
264 if exists $options{methods};
266 $class->SUPER::create(%options);
268 my (%initialize_options) = @args;
269 delete @initialize_options{qw(
277 my $meta = $class->initialize( $package_name => %initialize_options );
280 $meta->add_method('meta' => sub {
281 $class->initialize(ref($_[0]) || $_[0]);
284 $meta->superclasses(@{$options{superclasses}})
285 if exists $options{superclasses};
287 # process attributes first, so that they can
288 # install accessors, but locally defined methods
289 # can then overwrite them. It is maybe a little odd, but
290 # I think this should be the order of things.
291 if (exists $options{attributes}) {
292 foreach my $attr (@{$options{attributes}}) {
293 $meta->add_attribute($attr);
296 if (exists $options{methods}) {
297 foreach my $method_name (keys %{$options{methods}}) {
298 $meta->add_method($method_name, $options{methods}->{$method_name});
307 # all these attribute readers will be bootstrapped
308 # away in the Class::MOP bootstrap section
310 sub get_attribute_map { $_[0]->{'attributes'} }
311 sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
312 sub method_metaclass { $_[0]->{'method_metaclass'} }
313 sub wrapped_method_metaclass { $_[0]->{'wrapped_method_metaclass'} }
314 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
316 # Instance Construction & Cloning
322 # we need to protect the integrity of the
323 # Class::MOP::Class singletons here, so we
324 # delegate this to &construct_class_instance
325 # which will deal with the singletons
326 return $class->construct_class_instance(@_)
327 if $class->name->isa('Class::MOP::Class');
328 return $class->construct_instance(@_);
331 sub construct_instance {
333 my $params = @_ == 1 ? $_[0] : {@_};
334 my $meta_instance = $class->get_meta_instance();
335 my $instance = $meta_instance->create_instance();
336 foreach my $attr ($class->compute_all_applicable_attributes()) {
337 $attr->initialize_instance_slot($meta_instance, $instance, $params);
340 # this will only work for a HASH instance type
341 if ($class->is_anon_class) {
342 (Scalar::Util::reftype($instance) eq 'HASH')
343 || confess "Currently only HASH based instances are supported with instance of anon-classes";
345 # At some point we should make this official
346 # as a reserved slot name, but right now I am
347 # going to keep it here.
348 # my $RESERVED_MOP_SLOT = '__MOP__';
349 $instance->{'__MOP__'} = $class;
355 sub get_meta_instance {
357 $self->{'_meta_instance'} ||= $self->create_meta_instance();
360 sub create_meta_instance {
363 my $instance = $self->instance_metaclass->new(
364 associated_metaclass => $self,
365 attributes => [ $self->compute_all_applicable_attributes() ],
368 $self->add_meta_instance_dependencies()
369 if $instance->is_dependent_on_superclasses();
376 my $instance = shift;
377 (blessed($instance) && $instance->isa($class->name))
378 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
381 # we need to protect the integrity of the
382 # Class::MOP::Class singletons here, they
383 # should not be cloned.
384 return $instance if $instance->isa('Class::MOP::Class');
385 $class->clone_instance($instance, @_);
389 my ($class, $instance, %params) = @_;
391 || confess "You can only clone instances, ($instance) is not a blessed instance";
392 my $meta_instance = $class->get_meta_instance();
393 my $clone = $meta_instance->clone_instance($instance);
394 foreach my $attr ($class->compute_all_applicable_attributes()) {
395 if ( defined( my $init_arg = $attr->init_arg ) ) {
396 if (exists $params{$init_arg}) {
397 $attr->set_value($clone, $params{$init_arg});
404 sub rebless_instance {
405 my ($self, $instance, %params) = @_;
408 if ($instance->can('meta')) {
409 ($instance->meta->isa('Class::MOP::Class'))
410 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
411 $old_metaclass = $instance->meta;
414 $old_metaclass = $self->initialize(blessed($instance));
417 my $meta_instance = $self->get_meta_instance();
419 $self->name->isa($old_metaclass->name)
420 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
423 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
424 $meta_instance->rebless_instance_structure($_[1], $self);
426 foreach my $attr ( $self->compute_all_applicable_attributes ) {
427 if ( $attr->has_value($instance) ) {
428 if ( defined( my $init_arg = $attr->init_arg ) ) {
429 $params{$init_arg} = $attr->get_value($instance)
430 unless exists $params{$init_arg};
433 $attr->set_value($instance, $attr->get_value($instance));
438 foreach my $attr ($self->compute_all_applicable_attributes) {
439 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
449 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
452 @{$self->get_package_symbol($var_spec)} = @supers;
455 # on 5.8 and below, we need to call
456 # a method to get Perl to detect
457 # a cycle in the class hierarchy
458 my $class = $self->name;
462 # we need to check the metaclass
463 # compatibility here so that we can
464 # be sure that the superclass is
465 # not potentially creating an issues
466 # we don't know about
468 $self->check_metaclass_compatibility();
469 $self->update_meta_instance_dependencies();
471 @{$self->get_package_symbol($var_spec)};
477 my $super_class = $self->name;
479 if ( Class::MOP::HAVE_ISAREV() ) {
480 return @{ $super_class->mro::get_isarev() };
484 my $find_derived_classes;
485 $find_derived_classes = sub {
486 my ($outer_class) = @_;
488 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
491 for my $symbol ( keys %$symbol_table_hashref ) {
492 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
493 my $inner_class = $1;
495 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
499 ? "${outer_class}::$inner_class"
502 if ( $class->isa($super_class) and $class ne $super_class ) {
503 push @derived_classes, $class;
506 next SYMBOL if $class eq 'main'; # skip 'main::*'
508 $find_derived_classes->($class);
512 my $root_class = q{};
513 $find_derived_classes->($root_class);
515 undef $find_derived_classes;
517 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
519 return @derived_classes;
525 return @{ mro::get_linear_isa( (shift)->name ) };
528 sub class_precedence_list {
530 my $name = $self->name;
532 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
534 # We need to check for circular inheritance here
535 # if we are are not on 5.10, cause 5.8 detects it
536 # late. This will do nothing if all is well, and
537 # blow up otherwise. Yes, it's an ugly hack, better
538 # suggestions are welcome.
540 ($name || return)->isa('This is a test for circular inheritance')
543 # if our mro is c3, we can
544 # just grab the linear_isa
545 if (mro::get_mro($name) eq 'c3') {
546 return @{ mro::get_linear_isa($name) }
550 # we can't grab the linear_isa for dfs
551 # since it has all the duplicates
556 $self->initialize($_)->class_precedence_list()
557 } $self->superclasses()
564 sub wrap_method_body {
565 my ( $self, %args ) = @_;
567 ('CODE' eq ref $args{body})
568 || confess "Your code block must be a CODE reference";
570 $self->method_metaclass->wrap(
571 package_name => $self->name,
577 my ($self, $method_name, $method) = @_;
578 (defined $method_name && $method_name)
579 || confess "You must define a method name";
582 if (blessed($method)) {
583 $body = $method->body;
584 if ($method->package_name ne $self->name) {
585 $method = $method->clone(
586 package_name => $self->name,
588 ) if $method->can('clone');
593 $method = $self->wrap_method_body( body => $body, name => $method_name );
596 $method->attach_to_class($self);
598 # This used to call get_method_map, which meant we would build all
599 # the method objects for the class just because we added one
600 # method. This is hackier, but quicker too.
601 $self->{methods}{$method_name} = $method;
603 my $full_method_name = ($self->name . '::' . $method_name);
604 $self->add_package_symbol(
605 { sigil => '&', type => 'CODE', name => $method_name },
606 Class::MOP::subname($full_method_name => $body)
611 my $fetch_and_prepare_method = sub {
612 my ($self, $method_name) = @_;
613 my $wrapped_metaclass = $self->wrapped_method_metaclass;
615 my $method = $self->get_method($method_name);
616 # if we dont have local ...
618 # try to find the next method
619 $method = $self->find_next_method_by_name($method_name);
620 # die if it does not exist
622 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
623 # and now make sure to wrap it
624 # even if it is already wrapped
625 # because we need a new sub ref
626 $method = $wrapped_metaclass->wrap($method);
629 # now make sure we wrap it properly
630 $method = $wrapped_metaclass->wrap($method)
631 unless $method->isa($wrapped_metaclass);
633 $self->add_method($method_name => $method);
637 sub add_before_method_modifier {
638 my ($self, $method_name, $method_modifier) = @_;
639 (defined $method_name && $method_name)
640 || confess "You must pass in a method name";
641 my $method = $fetch_and_prepare_method->($self, $method_name);
642 $method->add_before_modifier(
643 Class::MOP::subname(':before' => $method_modifier)
647 sub add_after_method_modifier {
648 my ($self, $method_name, $method_modifier) = @_;
649 (defined $method_name && $method_name)
650 || confess "You must pass in a method name";
651 my $method = $fetch_and_prepare_method->($self, $method_name);
652 $method->add_after_modifier(
653 Class::MOP::subname(':after' => $method_modifier)
657 sub add_around_method_modifier {
658 my ($self, $method_name, $method_modifier) = @_;
659 (defined $method_name && $method_name)
660 || confess "You must pass in a method name";
661 my $method = $fetch_and_prepare_method->($self, $method_name);
662 $method->add_around_modifier(
663 Class::MOP::subname(':around' => $method_modifier)
668 # the methods above used to be named like this:
669 # ${pkg}::${method}:(before|after|around)
670 # but this proved problematic when using one modifier
671 # to wrap multiple methods (something which is likely
672 # to happen pretty regularly IMO). So instead of naming
673 # it like this, I have chosen to just name them purely
674 # with their modifier names, like so:
675 # :(before|after|around)
676 # The fact is that in a stack trace, it will be fairly
677 # evident from the context what method they are attached
678 # to, and so don't need the fully qualified name.
684 $self->add_method(@_);
688 my ($self, $method_name) = @_;
689 (defined $method_name && $method_name)
690 || confess "You must define a method name";
692 exists $self->{methods}{$method_name} || exists $self->get_method_map->{$method_name};
696 my ($self, $method_name) = @_;
697 (defined $method_name && $method_name)
698 || confess "You must define a method name";
700 return $self->{methods}{$method_name} || $self->get_method_map->{$method_name};
704 my ($self, $method_name) = @_;
705 (defined $method_name && $method_name)
706 || confess "You must define a method name";
708 my $removed_method = delete $self->get_method_map->{$method_name};
710 $self->remove_package_symbol(
711 { sigil => '&', type => 'CODE', name => $method_name }
714 $removed_method->detach_from_class if $removed_method;
716 $self->update_package_cache_flag; # still valid, since we just removed the method from the map
718 return $removed_method;
721 sub get_method_list {
723 keys %{$self->get_method_map};
726 sub find_method_by_name {
727 my ($self, $method_name) = @_;
728 (defined $method_name && $method_name)
729 || confess "You must define a method name to find";
730 foreach my $class ($self->linearized_isa) {
731 # fetch the meta-class ...
732 my $meta = $self->initialize($class);
733 return $meta->get_method($method_name)
734 if $meta->has_method($method_name);
739 sub get_all_methods {
741 my %methods = map { %{ $self->initialize($_)->get_method_map } } reverse $self->linearized_isa;
742 return values %methods;
746 sub compute_all_applicable_methods {
750 class => $_->package_name,
751 code => $_, # sigh, overloading
753 } shift->get_all_methods(@_);
756 sub get_all_method_names {
759 grep { $uniq{$_}++ == 0 } map { $_->name } $self->get_all_methods;
762 sub find_all_methods_by_name {
763 my ($self, $method_name) = @_;
764 (defined $method_name && $method_name)
765 || confess "You must define a method name to find";
767 foreach my $class ($self->linearized_isa) {
768 # fetch the meta-class ...
769 my $meta = $self->initialize($class);
771 name => $method_name,
773 code => $meta->get_method($method_name)
774 } if $meta->has_method($method_name);
779 sub find_next_method_by_name {
780 my ($self, $method_name) = @_;
781 (defined $method_name && $method_name)
782 || confess "You must define a method name to find";
783 my @cpl = $self->linearized_isa;
784 shift @cpl; # discard ourselves
785 foreach my $class (@cpl) {
786 # fetch the meta-class ...
787 my $meta = $self->initialize($class);
788 return $meta->get_method($method_name)
789 if $meta->has_method($method_name);
798 # either we have an attribute object already
799 # or we need to create one from the args provided
800 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
801 # make sure it is derived from the correct type though
802 ($attribute->isa('Class::MOP::Attribute'))
803 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
805 # first we attach our new attribute
806 # because it might need certain information
807 # about the class which it is attached to
808 $attribute->attach_to_class($self);
810 # then we remove attributes of a conflicting
811 # name here so that we can properly detach
812 # the old attr object, and remove any
813 # accessors it would have generated
814 if ( $self->has_attribute($attribute->name) ) {
815 $self->remove_attribute($attribute->name);
817 $self->invalidate_meta_instances();
820 # then onto installing the new accessors
821 $self->get_attribute_map->{$attribute->name} = $attribute;
823 # invalidate package flag here
824 my $e = do { local $@; eval { $attribute->install_accessors() }; $@ };
826 $self->remove_attribute($attribute->name);
833 sub update_meta_instance_dependencies {
836 if ( $self->{meta_instance_dependencies} ) {
837 return $self->add_meta_instance_dependencies;
841 sub add_meta_instance_dependencies {
844 $self->remove_meta_instance_dependencies;
846 my @attrs = $self->compute_all_applicable_attributes();
849 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
851 foreach my $class ( @classes ) {
852 $class->add_dependent_meta_instance($self);
855 $self->{meta_instance_dependencies} = \@classes;
858 sub remove_meta_instance_dependencies {
861 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
862 foreach my $class ( @$classes ) {
863 $class->remove_dependent_meta_instance($self);
873 sub add_dependent_meta_instance {
874 my ( $self, $metaclass ) = @_;
875 push @{ $self->{dependent_meta_instances} }, $metaclass;
878 sub remove_dependent_meta_instance {
879 my ( $self, $metaclass ) = @_;
880 my $name = $metaclass->name;
881 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
884 sub invalidate_meta_instances {
886 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
889 sub invalidate_meta_instance {
891 undef $self->{_meta_instance};
895 my ($self, $attribute_name) = @_;
896 (defined $attribute_name && $attribute_name)
897 || confess "You must define an attribute name";
898 exists $self->get_attribute_map->{$attribute_name};
902 my ($self, $attribute_name) = @_;
903 (defined $attribute_name && $attribute_name)
904 || confess "You must define an attribute name";
905 return $self->get_attribute_map->{$attribute_name}
907 # this will return undef anyway, so no need ...
908 # if $self->has_attribute($attribute_name);
912 sub remove_attribute {
913 my ($self, $attribute_name) = @_;
914 (defined $attribute_name && $attribute_name)
915 || confess "You must define an attribute name";
916 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
917 return unless defined $removed_attribute;
918 delete $self->get_attribute_map->{$attribute_name};
919 $self->invalidate_meta_instances();
920 $removed_attribute->remove_accessors();
921 $removed_attribute->detach_from_class();
922 return $removed_attribute;
925 sub get_attribute_list {
927 keys %{$self->get_attribute_map};
930 sub get_all_attributes {
931 shift->compute_all_applicable_attributes(@_);
934 sub compute_all_applicable_attributes {
936 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
937 return values %attrs;
940 sub find_attribute_by_name {
941 my ($self, $attr_name) = @_;
942 foreach my $class ($self->linearized_isa) {
943 # fetch the meta-class ...
944 my $meta = $self->initialize($class);
945 return $meta->get_attribute($attr_name)
946 if $meta->has_attribute($attr_name);
951 # check if we can reinitialize
955 # if any local attr is defined
956 return if $self->get_attribute_list;
958 # or any non-declared methods
959 if ( my @methods = values %{ $self->get_method_map } ) {
960 my $metaclass = $self->method_metaclass;
961 foreach my $method ( @methods ) {
962 return if $method->isa("Class::MOP::Method::Generated");
963 # FIXME do we need to enforce this too? return unless $method->isa($metaclass);
973 sub is_immutable { 0 }
975 sub immutable_transformer { $_[0]->{immutable_transformer} }
976 sub _set_immutable_transformer { $_[0]->{immutable_transformer} = $_[1] }
981 return if $self->is_immutable;
983 my $transformer = $self->immutable_transformer
984 || $self->_make_immutable_transformer(@_);
986 $self->_set_immutable_transformer($transformer);
988 $transformer->make_metaclass_immutable;
992 my %Default_Immutable_Options = (
993 read_only => [qw/superclasses/],
1001 remove_package_symbol
1005 class_precedence_list => 'ARRAY',
1006 # FIXME perl 5.10 memoizes this on its own, no need?
1007 linearized_isa => 'ARRAY',
1008 get_all_methods => 'ARRAY',
1009 get_all_method_names => 'ARRAY',
1010 compute_all_applicable_attributes => 'ARRAY',
1011 get_meta_instance => 'SCALAR',
1012 get_method_map => 'SCALAR',
1016 # this is ugly, but so are typeglobs,
1017 # so whattayahgonnadoboutit
1020 add_package_symbol => sub {
1021 my $original = shift;
1022 confess "Cannot add package symbols to an immutable metaclass"
1023 unless ( caller(2) )[3] eq
1024 'Class::MOP::Package::get_package_symbol';
1026 # This is a workaround for a bug in 5.8.1 which thinks that
1027 # goto $original->body
1028 # is trying to go to a label
1029 my $body = $original->body;
1035 sub _default_immutable_transformer_options {
1036 return %Default_Immutable_Options;
1040 sub _make_immutable_transformer {
1043 Class::MOP::Immutable->new(
1045 $self->_default_immutable_transformer_options,
1053 return if $self->is_mutable;
1055 $self->immutable_transformer->make_metaclass_mutable;
1066 Class::MOP::Class - Class Meta Object
1070 # assuming that class Foo
1071 # has been defined, you can
1073 # use this for introspection ...
1075 # add a method to Foo ...
1076 Foo->meta->add_method( 'bar' => sub {...} )
1078 # get a list of all the classes searched
1079 # the method dispatcher in the correct order
1080 Foo->meta->class_precedence_list()
1082 # remove a method from Foo
1083 Foo->meta->remove_method('bar');
1085 # or use this to actually create classes ...
1087 Class::MOP::Class->create(
1090 superclasses => ['Foo'],
1092 Class::MOP:: : Attribute->new('$bar'),
1093 Class::MOP:: : Attribute->new('$baz'),
1096 calculate_bar => sub {...},
1097 construct_baz => sub {...}
1104 The Class Protocol is the largest and most complex part of the
1105 Class::MOP meta-object protocol. It controls the introspection and
1106 manipulation of Perl 5 classes, and it can create them as well. The
1107 best way to understand what this module can do, is to read the
1108 documentation for each of its methods.
1112 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1116 =head2 Class construction
1118 These methods all create new C<Class::MOP::Class> objects. These
1119 objects can represent existing classes, or they can be used to create
1120 new classes from scratch.
1122 The metaclass object for a given class is a singleton. If you attempt
1123 to create a metaclass for the same class twice, you will just get the
1128 =item B<< Class::MOP::Class->create($package_name, %options) >>
1130 This method creates a new C<Class::MOP::Class> object with the given
1131 package name. It accepts a number of options.
1137 An optional version number for the newly created package.
1141 An optional authority for the newly created package.
1143 =item * superclasses
1145 An optional array reference of superclass names.
1149 An optional hash reference of methods for the class. The keys of the
1150 hash reference are method names, and values are subroutine references.
1154 An optional array reference of attributes.
1156 An attribute can be passed as an existing L<Class::MOP::Attribute>
1157 object, I<or> or as a hash reference of options which will be passed
1158 to the attribute metaclass's constructor.
1162 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1164 This method works just like C<< Class::MOP::Class->create >> but it
1165 creates an "anonymous" class. In fact, the class does have a name, but
1166 that name is a unique name generated internally by this module.
1168 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1169 parameters that C<create> accepts.
1171 Anonymous classes are destroyed once the metaclass they are attached
1172 to goes out of scope, and will be removed from Perl's internal symbol
1175 All instances of an anonymous class keep a special reference to the
1176 metaclass object, which prevents the metaclass from going out of scope
1177 while any instances exist.
1179 This only works if the instance if based on a hash reference, however.
1181 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1183 This method will initialize a C<Class::MOP::Class> object for the
1184 named package. Unlike C<create>, this method I<will not> create a new
1187 The purpose of this method is to retrieve a C<Class::MOP::Class>
1188 object for introspecting an existing class.
1190 If an existing C<Class::MOP::Class> object exists for the named
1191 package, it will be returned, and any options provided will be
1194 If the object does not yet exist, it will be created.
1196 The valid options that can be passed to this method are
1197 C<attribute_metaclass>, C<method_metaclass>,
1198 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1199 optional, and default to the appropriate class in the C<Class::MOP>
1204 =head2 Object instance construction and cloning
1206 These methods are all related to creating and/or cloning object
1211 =item B<< $metaclass->clone_object($instance, %params) >>
1213 This method clones an existing object instance. Any parameters you
1214 provide are will override existing attribute values in the object.
1216 This is a convenience method for cloning an object instance, then
1217 blessing it into the appropriate package.
1219 You could implement a clone method in your class, using this method:
1222 my ($self, %params) = @_;
1223 $self->meta->clone_object($self, %params);
1226 =item B<< $metaclass->rebless_instance($instance, %params) >>
1228 This method changes the class of C<$instance> to the metaclass's class.
1230 You can only rebless an instance into a subclass of its current
1231 class. If you pass any additional parameters, these will be treated
1232 like constructor parameters and used to initialize the object's
1233 attributes. Any existing attributes that are already set will be
1236 =item B<< $metaclass->new_object(%params) >>
1238 This method is used to create a new object of the metaclass's
1239 class. Any parameters you provide are used to initialize the
1240 instance's attributes.
1242 =item B<< $metaclass->instance_metaclass >>
1244 Returns the class name of the instance metaclass, see
1245 L<Class::MOP::Instance> for more information on the instance
1248 =item B<< $metaclass->get_meta_instance >>
1250 Returns an instance of the C<instance_metaclass> to be used in the
1251 construction of a new instance of the class.
1255 =head2 Informational predicates
1257 These are a few predicate methods for asking information about the
1262 =item B<< $metaclass->is_anon_class >>
1264 This returns true if the class was created by calling C<<
1265 Class::MOP::Class->create_anon_class >>.
1267 =item B<< $metaclass->is_mutable >>
1269 This returns true if the class is still mutable.
1271 =item B<< $metaclass->is_immutable >>
1273 This returns true if the class has been made immutable.
1275 =item B<< $metaclass->is_pristine >>
1277 A class is I<not> pristine if it has non-inherited attributes or if it
1278 has any generated methods.
1282 =head2 Inheritance Relationships
1286 =item B<< $metaclass->superclasses(@superclasses) >>
1288 This is a read-write accessor which represents the superclass
1289 relationships of the metaclass's class.
1291 This is basically sugar around getting and setting C<@ISA>.
1293 =item B<< $metaclass->class_precedence_list >>
1295 This returns a list of all of the class's ancestor classes. The
1296 classes are returned in method dispatch order.
1298 =item B<< $metaclass->linearized_isa >>
1300 This returns a list based on C<class_precedence_list> but with all
1303 =item B<< $metaclass->subclasses >>
1305 This returns a list of subclasses for this class.
1309 =head2 Method introspection and creation
1311 These methods allow you to introspect a class's methods, as well as
1312 add, remove, or change methods.
1314 Determining what is truly a method in a Perl 5 class requires some
1315 heuristics (aka guessing).
1317 Methods defined outside the package with a fully qualified name (C<sub
1318 Package::name { ... }>) will be included. Similarly, methods named
1319 with a fully qualified name using L<Sub::Name> are also included.
1321 However, we attempt to ignore imported functions.
1323 Ultimately, we are using heuristics to determine what truly is a
1324 method in a class, and these heuristics may get the wrong answer in
1325 some edge cases. However, for most "normal" cases the heuristics work
1330 =item B<< $metaclass->get_method($method_name) >>
1332 This will return a L<Class::MOP::Method> for the specified
1333 C<$method_name>. If the class does not have the specified method, it
1336 =item B<< $metaclass->has_method($method_name) >>
1338 Returns a boolean indicating whether or not the class defines the
1339 named method. It does not include methods inherited from parent
1342 =item B<< $metaclass->get_method_map >>
1344 Returns a hash reference representing the methods defined in this
1345 class. The keys are method names and the values are
1346 L<Class::MOP::Method> objects.
1348 =item B<< $metaclass->get_method_list >>
1350 This will return a list of method I<names> for all methods defined in
1353 =item B<< $metaclass->get_all_methods >>
1355 This will traverse the inheritance hierarchy and return a list of all
1356 the L<Class::MOP::Method> objects for this class and its parents.
1358 =item B<< $metaclass->find_method_by_name($method_name) >>
1360 This will return a L<Class::MOP::Method> for the specified
1361 C<$method_name>. If the class does not have the specified method, it
1364 Unlike C<get_method>, this method I<will> look for the named method in
1367 =item B<< $metaclass->get_all_method_names >>
1369 This will return a list of method I<names> for all of this class's
1370 methods, including inherited methods.
1372 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1374 This method looks for the named method in the class and all of its
1375 parents. It returns every matching method it finds in the inheritance
1376 tree, so it returns a list of methods.
1378 Each method is returned as a hash reference with three keys. The keys
1379 are C<name>, C<class>, and C<code>. The C<code> key has a
1380 L<Class::MOP::Method> object as its value.
1382 The list of methods is distinct.
1384 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1386 This method returns the first method in any superclass matching the
1387 given name. It is effectively the method that C<SUPER::$method_name>
1390 =item B<< $metaclass->add_method($method_name, $method) >>
1392 This method takes a method name and a subroutine reference, and adds
1393 the method to the class.
1395 The subroutine reference can be a L<Class::MOP::Method>, and you are
1396 strongly encouraged to pass a meta method object instead of a code
1397 reference. If you do so, that object gets stored as part of the
1398 class's method map directly. If not, the meta information will have to
1399 be recreated later, and may be incorrect.
1401 If you provide a method object, this method will clone that object if
1402 the object's package name does not match the class name. This lets us
1403 track the original source of any methods added from other classes
1404 (notably Moose roles).
1406 =item B<< $metaclass->remove_method($method_name) >>
1408 Remove the named method from the class. This method returns the
1409 L<Class::MOP::Method> object for the method.
1411 =item B<< $metaclass->method_metaclass >>
1413 Returns the class name of the method metaclass, see
1414 L<Class::MOP::Method> for more information on the method metaclass.
1416 =item B<< $metaclass->wrapped_method_metaclass >>
1418 Returns the class name of the wrapped method metaclass, see
1419 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1424 =head2 Attribute introspection and creation
1426 Because Perl 5 does not have a core concept of attributes in classes,
1427 we can only return information about attributes which have been added
1428 via this class's methods. We cannot discover information about
1429 attributes which are defined in terms of "regular" Perl 5 methods.
1433 =item B<< $metaclass->get_attribute($attribute_name) >>
1435 This will return a L<Class::MOP::Attribute> for the specified
1436 C<$attribute_name>. If the class does not have the specified
1437 attribute, it returns C<undef>
1439 =item B<< $metaclass->has_attribute($attribute_name) >>
1441 Returns a boolean indicating whether or not the class defines the
1442 named attribute. It does not include attributes inherited from parent
1445 =item B<< $metaclass->get_attribute_map >>
1447 Returns a hash reference representing the attributes defined in this
1448 class. The keys are attribute names and the values are
1449 L<Class::MOP::Attribute> objects.
1451 =item B<< $metaclass->get_attribute_list >>
1453 This will return a list of attributes I<names> for all attributes
1454 defined in this class.
1456 =item B<< $metaclass->get_all_attributes >>
1458 This will traverse the inheritance hierarchy and return a list of all
1459 the L<Class::MOP::Attribute> objects for this class and its parents.
1461 This method can also be called as C<compute_all_applicable_attributes>.
1463 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1465 This will return a L<Class::MOP::Attribute> for the specified
1466 C<$attribute_name>. If the class does not have the specified
1467 attribute, it returns C<undef>
1469 Unlike C<get_attribute>, this attribute I<will> look for the named
1470 attribute in superclasses.
1472 =item B<< $metaclass->add_attribute(...) >>
1474 This method accepts either an existing L<Class::MOP::Attribute>
1475 object, or parameters suitable for passing to that class's C<new>
1478 The attribute provided will be added to the class.
1480 Any accessor methods defined by the attribute will be added to the
1481 class when the attribute is added.
1483 If an attribute of the same name already exists, the old attribute
1484 will be removed first.
1486 =item B<< $metaclass->remove_attribute($attribute_name) >>
1488 This will remove the named attribute from the class, and
1489 L<Class::MOP::Attribute> object.
1491 Removing an attribute also removes any accessor methods defined by the
1494 However, note that removing an attribute will only affect I<future>
1495 object instances created for this class, not existing instances.
1497 =item B<< $metaclass->attribute_metaclass >>
1499 Returns the class name of the attribute metaclass for this class. By
1500 default, this is L<Class::MOP::Attribute>. for more information on
1504 =head2 Class Immutability
1506 Making a class immutable "freezes" the class definition. You can no
1507 longer call methods which alter the class, such as adding or removing
1508 methods or attributes.
1510 Making a class immutable lets us optimize the class by inlining some
1511 methods, and also allows us to optimize some methods on the metaclass
1514 The immutabilization system in L<Moose> takes much greater advantage
1515 of the inlining features than Class::MOP itself does.
1519 =item B<< $metaclass->make_immutable(%options) >>
1521 This method will create an immutable transformer and uses it to make
1522 the class and its metaclass object immutable.
1524 Details of how immutabilization works are in L<Class::MOP::Immutable>
1527 =item B<< $metaclass->make_mutable >>
1529 Calling this method reverse the immutabilization transformation.
1531 =item B<< $metaclass->immutable_transformer >>
1533 If the class has been made immutable previously, this returns the
1534 L<Class::MOP::Immutable> object that was created to do the
1537 If the class was never made immutable, this method will die.
1541 =head2 Method Modifiers
1543 Method modifiers are hooks which allow a method to be wrapped with
1544 I<before>, I<after> and I<around> method modifiers. Every time a
1545 method is called, it's modifiers are also called.
1547 A class can modify its own methods, as well as methods defined in
1550 =head3 How method modifiers work?
1552 Method modifiers work by wrapping the original method and then
1553 replacing it in the class's symbol table. The wrappers will handle
1554 calling all the modifiers in the appropriate order and preserving the
1555 calling context for the original method.
1557 The return values of C<before> and C<after> modifiers are
1558 ignored. This is because their purpose is B<not> to filter the input
1559 and output of the primary method (this is done with an I<around>
1562 This may seem like an odd restriction to some, but doing this allows
1563 for simple code to be added at the beginning or end of a method call
1564 without altering the function of the wrapped method or placing any
1565 extra responsibility on the code of the modifier.
1567 Of course if you have more complex needs, you can use the C<around>
1568 modifier which allows you to change both the parameters passed to the
1569 wrapped method, as well as its return value.
1571 Before and around modifiers are called in last-defined-first-called
1572 order, while after modifiers are called in first-defined-first-called
1573 order. So the call tree might looks something like this:
1585 =head3 What is the performance impact?
1587 Of course there is a performance cost associated with method
1588 modifiers, but we have made every effort to make that cost directly
1589 proportional to the number of modifier features you utilize.
1591 The wrapping method does it's best to B<only> do as much work as it
1592 absolutely needs to. In order to do this we have moved some of the
1593 performance costs to set-up time, where they are easier to amortize.
1595 All this said, our benchmarks have indicated the following:
1597 simple wrapper with no modifiers 100% slower
1598 simple wrapper with simple before modifier 400% slower
1599 simple wrapper with simple after modifier 450% slower
1600 simple wrapper with simple around modifier 500-550% slower
1601 simple wrapper with all 3 modifiers 1100% slower
1603 These numbers may seem daunting, but you must remember, every feature
1604 comes with some cost. To put things in perspective, just doing a
1605 simple C<AUTOLOAD> which does nothing but extract the name of the
1606 method called and return it costs about 400% over a normal method
1611 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1613 This wraps the specified method with the supplied subroutine
1614 reference. The modifier will be called as a method itself, and will
1615 receive the same arguments as are passed to the method.
1617 When the modifier exits, the wrapped method will be called.
1619 The return value of the modifier will be ignored.
1621 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1623 This wraps the specified method with the supplied subroutine
1624 reference. The modifier will be called as a method itself, and will
1625 receive the same arguments as are passed to the method.
1627 When the wrapped methods exits, the modifier will be called.
1629 The return value of the modifier will be ignored.
1631 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1633 This wraps the specified method with the supplied subroutine
1636 The first argument passed to the modifier will be a subroutine
1637 reference to the wrapped method. The second argument is the object,
1638 and after that come any arguments passed when the method is called.
1640 The around modifier can choose to call the original method, as well as
1641 what arguments to pass if it does so.
1643 The return value of the modifier is what will be seen by the caller.
1647 =head2 Introspection
1651 =item B<< Class::MOP::Class->meta >>
1653 This will return a L<Class::MOP::Class> instance for this class.
1655 It should also be noted that L<Class::MOP> will actually bootstrap
1656 this module by installing a number of attribute meta-objects into its
1663 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1665 =head1 COPYRIGHT AND LICENSE
1667 Copyright 2006-2009 by Infinity Interactive, Inc.
1669 L<http://www.iinteractive.com>
1671 This library is free software; you can redistribute it and/or modify
1672 it under the same terms as Perl itself.