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 = '0.79';
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 "Class::MOP::class_of(" . $self->name . ") => ("
173 . (ref($self)) . ")" . " is not compatible with the " .
174 "Class::MOP::class_of(".$superclass_name . ") => ("
175 . ($super_meta_type) . ")";
177 # we also need to check that instance metaclasses
178 # are compatibile in the same the class.
179 ($self->instance_metaclass->isa($super_meta->instance_metaclass))
180 || confess "Class::MOP::class_of(" . $self->name . ")->instance_metaclass => (" . ($self->instance_metaclass) . ")" .
181 " is not compatible with the " .
182 "Class::MOP::class_of(" . $superclass_name . ")->instance_metaclass => (" . ($super_meta->instance_metaclass) . ")";
190 # this should be sufficient, if you have a
191 # use case where it is not, write a test and
193 my $ANON_CLASS_SERIAL = 0;
196 # we need a sufficiently annoying prefix
197 # this should suffice for now, this is
198 # used in a couple of places below, so
199 # need to put it up here for now.
200 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
204 no warnings 'uninitialized';
205 $self->name =~ /^$ANON_CLASS_PREFIX/;
208 sub create_anon_class {
209 my ($class, %options) = @_;
210 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
211 return $class->create($package_name, %options);
215 # this will only get called for
216 # anon-classes, all other calls
217 # are assumed to occur during
218 # global destruction and so don't
219 # really need to be handled explicitly
223 return if Class::MOP::in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
225 no warnings 'uninitialized';
226 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
227 # Moose does a weird thing where it replaces the metaclass for
228 # class when fixing metaclass incompatibility. In that case,
229 # we don't want to clean out the namespace now. We can detect
230 # that because Moose will explicitly update the singleton
231 # cache in Class::MOP.
232 my $current_meta = Class::MOP::get_metaclass_by_name($self->name);
233 return if $current_meta ne $self;
235 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
237 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
238 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
240 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
245 # creating classes with MOP ...
248 my ( $class, @args ) = @_;
250 unshift @args, 'package' if @args % 2 == 1;
252 my (%options) = @args;
253 my $package_name = $options{package};
255 (ref $options{superclasses} eq 'ARRAY')
256 || confess "You must pass an ARRAY ref of superclasses"
257 if exists $options{superclasses};
259 (ref $options{attributes} eq 'ARRAY')
260 || confess "You must pass an ARRAY ref of attributes"
261 if exists $options{attributes};
263 (ref $options{methods} eq 'HASH')
264 || confess "You must pass a HASH ref of methods"
265 if exists $options{methods};
267 $class->SUPER::create(%options);
269 my (%initialize_options) = @args;
270 delete @initialize_options{qw(
278 my $meta = $class->initialize( $package_name => %initialize_options );
281 $meta->add_method('meta' => sub {
282 $class->initialize(ref($_[0]) || $_[0]);
285 $meta->superclasses(@{$options{superclasses}})
286 if exists $options{superclasses};
288 # process attributes first, so that they can
289 # install accessors, but locally defined methods
290 # can then overwrite them. It is maybe a little odd, but
291 # I think this should be the order of things.
292 if (exists $options{attributes}) {
293 foreach my $attr (@{$options{attributes}}) {
294 $meta->add_attribute($attr);
297 if (exists $options{methods}) {
298 foreach my $method_name (keys %{$options{methods}}) {
299 $meta->add_method($method_name, $options{methods}->{$method_name});
308 # all these attribute readers will be bootstrapped
309 # away in the Class::MOP bootstrap section
311 sub get_attribute_map { $_[0]->{'attributes'} }
312 sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
313 sub method_metaclass { $_[0]->{'method_metaclass'} }
314 sub wrapped_method_metaclass { $_[0]->{'wrapped_method_metaclass'} }
315 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
317 # Instance Construction & Cloning
323 # we need to protect the integrity of the
324 # Class::MOP::Class singletons here, so we
325 # delegate this to &construct_class_instance
326 # which will deal with the singletons
327 return $class->construct_class_instance(@_)
328 if $class->name->isa('Class::MOP::Class');
329 return $class->construct_instance(@_);
332 sub construct_instance {
334 my $params = @_ == 1 ? $_[0] : {@_};
335 my $meta_instance = $class->get_meta_instance();
336 my $instance = $meta_instance->create_instance();
337 foreach my $attr ($class->compute_all_applicable_attributes()) {
338 $attr->initialize_instance_slot($meta_instance, $instance, $params);
341 # this will only work for a HASH instance type
342 if ($class->is_anon_class) {
343 (Scalar::Util::reftype($instance) eq 'HASH')
344 || confess "Currently only HASH based instances are supported with instance of anon-classes";
346 # At some point we should make this official
347 # as a reserved slot name, but right now I am
348 # going to keep it here.
349 # my $RESERVED_MOP_SLOT = '__MOP__';
350 $instance->{'__MOP__'} = $class;
356 sub get_meta_instance {
358 $self->{'_meta_instance'} ||= $self->create_meta_instance();
361 sub create_meta_instance {
364 my $instance = $self->instance_metaclass->new(
365 associated_metaclass => $self,
366 attributes => [ $self->compute_all_applicable_attributes() ],
369 $self->add_meta_instance_dependencies()
370 if $instance->is_dependent_on_superclasses();
377 my $instance = shift;
378 (blessed($instance) && $instance->isa($class->name))
379 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
382 # we need to protect the integrity of the
383 # Class::MOP::Class singletons here, they
384 # should not be cloned.
385 return $instance if $instance->isa('Class::MOP::Class');
386 $class->clone_instance($instance, @_);
390 my ($class, $instance, %params) = @_;
392 || confess "You can only clone instances, ($instance) is not a blessed instance";
393 my $meta_instance = $class->get_meta_instance();
394 my $clone = $meta_instance->clone_instance($instance);
395 foreach my $attr ($class->compute_all_applicable_attributes()) {
396 if ( defined( my $init_arg = $attr->init_arg ) ) {
397 if (exists $params{$init_arg}) {
398 $attr->set_value($clone, $params{$init_arg});
405 sub rebless_instance {
406 my ($self, $instance, %params) = @_;
408 my $old_metaclass = Class::MOP::class_of($instance);
410 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
411 $self->name->isa($old_class)
412 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
414 $old_metaclass->rebless_instance_away($instance, $self, %params)
417 my $meta_instance = $self->get_meta_instance();
420 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
421 $meta_instance->rebless_instance_structure($_[1], $self);
423 foreach my $attr ( $self->compute_all_applicable_attributes ) {
424 if ( $attr->has_value($instance) ) {
425 if ( defined( my $init_arg = $attr->init_arg ) ) {
426 $params{$init_arg} = $attr->get_value($instance)
427 unless exists $params{$init_arg};
430 $attr->set_value($instance, $attr->get_value($instance));
435 foreach my $attr ($self->compute_all_applicable_attributes) {
436 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
442 sub rebless_instance_away {
443 # this intentionally does nothing, it is just a hook
450 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
453 @{$self->get_package_symbol($var_spec)} = @supers;
456 # on 5.8 and below, we need to call
457 # a method to get Perl to detect
458 # a cycle in the class hierarchy
459 my $class = $self->name;
463 # we need to check the metaclass
464 # compatibility here so that we can
465 # be sure that the superclass is
466 # not potentially creating an issues
467 # we don't know about
469 $self->check_metaclass_compatibility();
470 $self->update_meta_instance_dependencies();
472 @{$self->get_package_symbol($var_spec)};
477 my $super_class = $self->name;
479 return @{ $super_class->mro::get_isarev() };
484 return @{ mro::get_linear_isa( (shift)->name ) };
487 sub class_precedence_list {
489 my $name = $self->name;
491 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
493 # We need to check for circular inheritance here
494 # if we are are not on 5.10, cause 5.8 detects it
495 # late. This will do nothing if all is well, and
496 # blow up otherwise. Yes, it's an ugly hack, better
497 # suggestions are welcome.
499 ($name || return)->isa('This is a test for circular inheritance')
502 # if our mro is c3, we can
503 # just grab the linear_isa
504 if (mro::get_mro($name) eq 'c3') {
505 return @{ mro::get_linear_isa($name) }
509 # we can't grab the linear_isa for dfs
510 # since it has all the duplicates
515 $self->initialize($_)->class_precedence_list()
516 } $self->superclasses()
523 sub wrap_method_body {
524 my ( $self, %args ) = @_;
526 ('CODE' eq ref $args{body})
527 || confess "Your code block must be a CODE reference";
529 $self->method_metaclass->wrap(
530 package_name => $self->name,
536 my ($self, $method_name, $method) = @_;
537 (defined $method_name && $method_name)
538 || confess "You must define a method name";
541 if (blessed($method)) {
542 $body = $method->body;
543 if ($method->package_name ne $self->name) {
544 $method = $method->clone(
545 package_name => $self->name,
547 ) if $method->can('clone');
552 $method = $self->wrap_method_body( body => $body, name => $method_name );
555 $method->attach_to_class($self);
557 # This used to call get_method_map, which meant we would build all
558 # the method objects for the class just because we added one
559 # method. This is hackier, but quicker too.
560 $self->{methods}{$method_name} = $method;
562 my $full_method_name = ($self->name . '::' . $method_name);
563 $self->add_package_symbol(
564 { sigil => '&', type => 'CODE', name => $method_name },
565 Class::MOP::subname($full_method_name => $body)
570 my $fetch_and_prepare_method = sub {
571 my ($self, $method_name) = @_;
572 my $wrapped_metaclass = $self->wrapped_method_metaclass;
574 my $method = $self->get_method($method_name);
575 # if we dont have local ...
577 # try to find the next method
578 $method = $self->find_next_method_by_name($method_name);
579 # die if it does not exist
581 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
582 # and now make sure to wrap it
583 # even if it is already wrapped
584 # because we need a new sub ref
585 $method = $wrapped_metaclass->wrap($method);
588 # now make sure we wrap it properly
589 $method = $wrapped_metaclass->wrap($method)
590 unless $method->isa($wrapped_metaclass);
592 $self->add_method($method_name => $method);
596 sub add_before_method_modifier {
597 my ($self, $method_name, $method_modifier) = @_;
598 (defined $method_name && $method_name)
599 || confess "You must pass in a method name";
600 my $method = $fetch_and_prepare_method->($self, $method_name);
601 $method->add_before_modifier(
602 Class::MOP::subname(':before' => $method_modifier)
606 sub add_after_method_modifier {
607 my ($self, $method_name, $method_modifier) = @_;
608 (defined $method_name && $method_name)
609 || confess "You must pass in a method name";
610 my $method = $fetch_and_prepare_method->($self, $method_name);
611 $method->add_after_modifier(
612 Class::MOP::subname(':after' => $method_modifier)
616 sub add_around_method_modifier {
617 my ($self, $method_name, $method_modifier) = @_;
618 (defined $method_name && $method_name)
619 || confess "You must pass in a method name";
620 my $method = $fetch_and_prepare_method->($self, $method_name);
621 $method->add_around_modifier(
622 Class::MOP::subname(':around' => $method_modifier)
627 # the methods above used to be named like this:
628 # ${pkg}::${method}:(before|after|around)
629 # but this proved problematic when using one modifier
630 # to wrap multiple methods (something which is likely
631 # to happen pretty regularly IMO). So instead of naming
632 # it like this, I have chosen to just name them purely
633 # with their modifier names, like so:
634 # :(before|after|around)
635 # The fact is that in a stack trace, it will be fairly
636 # evident from the context what method they are attached
637 # to, and so don't need the fully qualified name.
643 $self->add_method(@_);
647 my ($self, $method_name) = @_;
648 (defined $method_name && $method_name)
649 || confess "You must define a method name";
651 exists $self->{methods}{$method_name} || exists $self->get_method_map->{$method_name};
655 my ($self, $method_name) = @_;
656 (defined $method_name && $method_name)
657 || confess "You must define a method name";
659 return $self->{methods}{$method_name} || $self->get_method_map->{$method_name};
663 my ($self, $method_name) = @_;
664 (defined $method_name && $method_name)
665 || confess "You must define a method name";
667 my $removed_method = delete $self->get_method_map->{$method_name};
669 $self->remove_package_symbol(
670 { sigil => '&', type => 'CODE', name => $method_name }
673 $removed_method->detach_from_class if $removed_method;
675 $self->update_package_cache_flag; # still valid, since we just removed the method from the map
677 return $removed_method;
680 sub get_method_list {
682 keys %{$self->get_method_map};
685 sub find_method_by_name {
686 my ($self, $method_name) = @_;
687 (defined $method_name && $method_name)
688 || confess "You must define a method name to find";
689 foreach my $class ($self->linearized_isa) {
690 # fetch the meta-class ...
691 my $meta = $self->initialize($class);
692 return $meta->get_method($method_name)
693 if $meta->has_method($method_name);
698 sub get_all_methods {
700 my %methods = map { %{ $self->initialize($_)->get_method_map } } reverse $self->linearized_isa;
701 return values %methods;
705 sub compute_all_applicable_methods {
709 class => $_->package_name,
710 code => $_, # sigh, overloading
712 } shift->get_all_methods(@_);
715 sub get_all_method_names {
718 grep { $uniq{$_}++ == 0 } map { $_->name } $self->get_all_methods;
721 sub find_all_methods_by_name {
722 my ($self, $method_name) = @_;
723 (defined $method_name && $method_name)
724 || confess "You must define a method name to find";
726 foreach my $class ($self->linearized_isa) {
727 # fetch the meta-class ...
728 my $meta = $self->initialize($class);
730 name => $method_name,
732 code => $meta->get_method($method_name)
733 } if $meta->has_method($method_name);
738 sub find_next_method_by_name {
739 my ($self, $method_name) = @_;
740 (defined $method_name && $method_name)
741 || confess "You must define a method name to find";
742 my @cpl = $self->linearized_isa;
743 shift @cpl; # discard ourselves
744 foreach my $class (@cpl) {
745 # fetch the meta-class ...
746 my $meta = $self->initialize($class);
747 return $meta->get_method($method_name)
748 if $meta->has_method($method_name);
757 # either we have an attribute object already
758 # or we need to create one from the args provided
759 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
760 # make sure it is derived from the correct type though
761 ($attribute->isa('Class::MOP::Attribute'))
762 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
764 # first we attach our new attribute
765 # because it might need certain information
766 # about the class which it is attached to
767 $attribute->attach_to_class($self);
769 # then we remove attributes of a conflicting
770 # name here so that we can properly detach
771 # the old attr object, and remove any
772 # accessors it would have generated
773 if ( $self->has_attribute($attribute->name) ) {
774 $self->remove_attribute($attribute->name);
776 $self->invalidate_meta_instances();
779 # then onto installing the new accessors
780 $self->get_attribute_map->{$attribute->name} = $attribute;
782 # invalidate package flag here
783 my $e = do { local $@; eval { $attribute->install_accessors() }; $@ };
785 $self->remove_attribute($attribute->name);
792 sub update_meta_instance_dependencies {
795 if ( $self->{meta_instance_dependencies} ) {
796 return $self->add_meta_instance_dependencies;
800 sub add_meta_instance_dependencies {
803 $self->remove_meta_instance_dependencies;
805 my @attrs = $self->compute_all_applicable_attributes();
808 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
810 foreach my $class ( @classes ) {
811 $class->add_dependent_meta_instance($self);
814 $self->{meta_instance_dependencies} = \@classes;
817 sub remove_meta_instance_dependencies {
820 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
821 foreach my $class ( @$classes ) {
822 $class->remove_dependent_meta_instance($self);
832 sub add_dependent_meta_instance {
833 my ( $self, $metaclass ) = @_;
834 push @{ $self->{dependent_meta_instances} }, $metaclass;
837 sub remove_dependent_meta_instance {
838 my ( $self, $metaclass ) = @_;
839 my $name = $metaclass->name;
840 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
843 sub invalidate_meta_instances {
845 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
848 sub invalidate_meta_instance {
850 undef $self->{_meta_instance};
854 my ($self, $attribute_name) = @_;
855 (defined $attribute_name && $attribute_name)
856 || confess "You must define an attribute name";
857 exists $self->get_attribute_map->{$attribute_name};
861 my ($self, $attribute_name) = @_;
862 (defined $attribute_name && $attribute_name)
863 || confess "You must define an attribute name";
864 return $self->get_attribute_map->{$attribute_name}
866 # this will return undef anyway, so no need ...
867 # if $self->has_attribute($attribute_name);
871 sub remove_attribute {
872 my ($self, $attribute_name) = @_;
873 (defined $attribute_name && $attribute_name)
874 || confess "You must define an attribute name";
875 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
876 return unless defined $removed_attribute;
877 delete $self->get_attribute_map->{$attribute_name};
878 $self->invalidate_meta_instances();
879 $removed_attribute->remove_accessors();
880 $removed_attribute->detach_from_class();
881 return $removed_attribute;
884 sub get_attribute_list {
886 keys %{$self->get_attribute_map};
889 sub get_all_attributes {
890 shift->compute_all_applicable_attributes(@_);
893 sub compute_all_applicable_attributes {
895 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
896 return values %attrs;
899 sub find_attribute_by_name {
900 my ($self, $attr_name) = @_;
901 foreach my $class ($self->linearized_isa) {
902 # fetch the meta-class ...
903 my $meta = $self->initialize($class);
904 return $meta->get_attribute($attr_name)
905 if $meta->has_attribute($attr_name);
910 # check if we can reinitialize
914 # if any local attr is defined
915 return if $self->get_attribute_list;
917 # or any non-declared methods
918 if ( my @methods = values %{ $self->get_method_map } ) {
919 my $metaclass = $self->method_metaclass;
920 foreach my $method ( @methods ) {
921 return if $method->isa("Class::MOP::Method::Generated");
922 # FIXME do we need to enforce this too? return unless $method->isa($metaclass);
932 sub is_immutable { 0 }
934 sub immutable_transformer { $_[0]->{immutable_transformer} }
935 sub _set_immutable_transformer { $_[0]->{immutable_transformer} = $_[1] }
940 return if $self->is_immutable;
942 my $transformer = $self->immutable_transformer
943 || $self->_make_immutable_transformer(@_);
945 $self->_set_immutable_transformer($transformer);
947 $transformer->make_metaclass_immutable;
951 my %Default_Immutable_Options = (
952 read_only => [qw/superclasses/],
960 remove_package_symbol
964 class_precedence_list => 'ARRAY',
965 # FIXME perl 5.10 memoizes this on its own, no need?
966 linearized_isa => 'ARRAY',
967 get_all_methods => 'ARRAY',
968 get_all_method_names => 'ARRAY',
969 compute_all_applicable_attributes => 'ARRAY',
970 get_meta_instance => 'SCALAR',
971 get_method_map => 'SCALAR',
975 # this is ugly, but so are typeglobs,
976 # so whattayahgonnadoboutit
979 add_package_symbol => sub {
980 my $original = shift;
981 confess "Cannot add package symbols to an immutable metaclass"
982 unless ( caller(2) )[3] eq
983 'Class::MOP::Package::get_package_symbol';
985 # This is a workaround for a bug in 5.8.1 which thinks that
986 # goto $original->body
987 # is trying to go to a label
988 my $body = $original->body;
994 sub _default_immutable_transformer_options {
995 return %Default_Immutable_Options;
999 sub _make_immutable_transformer {
1002 Class::MOP::Immutable->new(
1004 $self->_default_immutable_transformer_options,
1012 return if $self->is_mutable;
1014 $self->immutable_transformer->make_metaclass_mutable;
1025 Class::MOP::Class - Class Meta Object
1029 # assuming that class Foo
1030 # has been defined, you can
1032 # use this for introspection ...
1034 # add a method to Foo ...
1035 Foo->meta->add_method( 'bar' => sub {...} )
1037 # get a list of all the classes searched
1038 # the method dispatcher in the correct order
1039 Foo->meta->class_precedence_list()
1041 # remove a method from Foo
1042 Foo->meta->remove_method('bar');
1044 # or use this to actually create classes ...
1046 Class::MOP::Class->create(
1049 superclasses => ['Foo'],
1051 Class::MOP:: : Attribute->new('$bar'),
1052 Class::MOP:: : Attribute->new('$baz'),
1055 calculate_bar => sub {...},
1056 construct_baz => sub {...}
1063 The Class Protocol is the largest and most complex part of the
1064 Class::MOP meta-object protocol. It controls the introspection and
1065 manipulation of Perl 5 classes, and it can create them as well. The
1066 best way to understand what this module can do, is to read the
1067 documentation for each of its methods.
1071 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1075 =head2 Class construction
1077 These methods all create new C<Class::MOP::Class> objects. These
1078 objects can represent existing classes, or they can be used to create
1079 new classes from scratch.
1081 The metaclass object for a given class is a singleton. If you attempt
1082 to create a metaclass for the same class twice, you will just get the
1087 =item B<< Class::MOP::Class->create($package_name, %options) >>
1089 This method creates a new C<Class::MOP::Class> object with the given
1090 package name. It accepts a number of options.
1096 An optional version number for the newly created package.
1100 An optional authority for the newly created package.
1102 =item * superclasses
1104 An optional array reference of superclass names.
1108 An optional hash reference of methods for the class. The keys of the
1109 hash reference are method names, and values are subroutine references.
1113 An optional array reference of attributes.
1115 An attribute can be passed as an existing L<Class::MOP::Attribute>
1116 object, I<or> or as a hash reference of options which will be passed
1117 to the attribute metaclass's constructor.
1121 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1123 This method works just like C<< Class::MOP::Class->create >> but it
1124 creates an "anonymous" class. In fact, the class does have a name, but
1125 that name is a unique name generated internally by this module.
1127 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1128 parameters that C<create> accepts.
1130 Anonymous classes are destroyed once the metaclass they are attached
1131 to goes out of scope, and will be removed from Perl's internal symbol
1134 All instances of an anonymous class keep a special reference to the
1135 metaclass object, which prevents the metaclass from going out of scope
1136 while any instances exist.
1138 This only works if the instance if based on a hash reference, however.
1140 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1142 This method will initialize a C<Class::MOP::Class> object for the
1143 named package. Unlike C<create>, this method I<will not> create a new
1146 The purpose of this method is to retrieve a C<Class::MOP::Class>
1147 object for introspecting an existing class.
1149 If an existing C<Class::MOP::Class> object exists for the named
1150 package, it will be returned, and any options provided will be
1153 If the object does not yet exist, it will be created.
1155 The valid options that can be passed to this method are
1156 C<attribute_metaclass>, C<method_metaclass>,
1157 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1158 optional, and default to the appropriate class in the C<Class::MOP>
1163 =head2 Object instance construction and cloning
1165 These methods are all related to creating and/or cloning object
1170 =item B<< $metaclass->clone_object($instance, %params) >>
1172 This method clones an existing object instance. Any parameters you
1173 provide are will override existing attribute values in the object.
1175 This is a convenience method for cloning an object instance, then
1176 blessing it into the appropriate package.
1178 You could implement a clone method in your class, using this method:
1181 my ($self, %params) = @_;
1182 $self->meta->clone_object($self, %params);
1185 =item B<< $metaclass->rebless_instance($instance, %params) >>
1187 This method changes the class of C<$instance> to the metaclass's class.
1189 You can only rebless an instance into a subclass of its current
1190 class. If you pass any additional parameters, these will be treated
1191 like constructor parameters and used to initialize the object's
1192 attributes. Any existing attributes that are already set will be
1195 Before reblessing the instance, this method will call
1196 C<rebless_instance_away> on the instance's current metaclass. This method
1197 will be passed the instance, the new metaclass, and any parameters
1198 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1199 does nothing; it is merely a hook.
1201 =item B<< $metaclass->new_object(%params) >>
1203 This method is used to create a new object of the metaclass's
1204 class. Any parameters you provide are used to initialize the
1205 instance's attributes.
1207 =item B<< $metaclass->instance_metaclass >>
1209 Returns the class name of the instance metaclass, see
1210 L<Class::MOP::Instance> for more information on the instance
1213 =item B<< $metaclass->get_meta_instance >>
1215 Returns an instance of the C<instance_metaclass> to be used in the
1216 construction of a new instance of the class.
1220 =head2 Informational predicates
1222 These are a few predicate methods for asking information about the
1227 =item B<< $metaclass->is_anon_class >>
1229 This returns true if the class was created by calling C<<
1230 Class::MOP::Class->create_anon_class >>.
1232 =item B<< $metaclass->is_mutable >>
1234 This returns true if the class is still mutable.
1236 =item B<< $metaclass->is_immutable >>
1238 This returns true if the class has been made immutable.
1240 =item B<< $metaclass->is_pristine >>
1242 A class is I<not> pristine if it has non-inherited attributes or if it
1243 has any generated methods.
1247 =head2 Inheritance Relationships
1251 =item B<< $metaclass->superclasses(@superclasses) >>
1253 This is a read-write accessor which represents the superclass
1254 relationships of the metaclass's class.
1256 This is basically sugar around getting and setting C<@ISA>.
1258 =item B<< $metaclass->class_precedence_list >>
1260 This returns a list of all of the class's ancestor classes. The
1261 classes are returned in method dispatch order.
1263 =item B<< $metaclass->linearized_isa >>
1265 This returns a list based on C<class_precedence_list> but with all
1268 =item B<< $metaclass->subclasses >>
1270 This returns a list of subclasses for this class.
1274 =head2 Method introspection and creation
1276 These methods allow you to introspect a class's methods, as well as
1277 add, remove, or change methods.
1279 Determining what is truly a method in a Perl 5 class requires some
1280 heuristics (aka guessing).
1282 Methods defined outside the package with a fully qualified name (C<sub
1283 Package::name { ... }>) will be included. Similarly, methods named
1284 with a fully qualified name using L<Sub::Name> are also included.
1286 However, we attempt to ignore imported functions.
1288 Ultimately, we are using heuristics to determine what truly is a
1289 method in a class, and these heuristics may get the wrong answer in
1290 some edge cases. However, for most "normal" cases the heuristics work
1295 =item B<< $metaclass->get_method($method_name) >>
1297 This will return a L<Class::MOP::Method> for the specified
1298 C<$method_name>. If the class does not have the specified method, it
1301 =item B<< $metaclass->has_method($method_name) >>
1303 Returns a boolean indicating whether or not the class defines the
1304 named method. It does not include methods inherited from parent
1307 =item B<< $metaclass->get_method_map >>
1309 Returns a hash reference representing the methods defined in this
1310 class. The keys are method names and the values are
1311 L<Class::MOP::Method> objects.
1313 =item B<< $metaclass->get_method_list >>
1315 This will return a list of method I<names> for all methods defined in
1318 =item B<< $metaclass->get_all_methods >>
1320 This will traverse the inheritance hierarchy and return a list of all
1321 the L<Class::MOP::Method> objects for this class and its parents.
1323 =item B<< $metaclass->find_method_by_name($method_name) >>
1325 This will return a L<Class::MOP::Method> for the specified
1326 C<$method_name>. If the class does not have the specified method, it
1329 Unlike C<get_method>, this method I<will> look for the named method in
1332 =item B<< $metaclass->get_all_method_names >>
1334 This will return a list of method I<names> for all of this class's
1335 methods, including inherited methods.
1337 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1339 This method looks for the named method in the class and all of its
1340 parents. It returns every matching method it finds in the inheritance
1341 tree, so it returns a list of methods.
1343 Each method is returned as a hash reference with three keys. The keys
1344 are C<name>, C<class>, and C<code>. The C<code> key has a
1345 L<Class::MOP::Method> object as its value.
1347 The list of methods is distinct.
1349 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1351 This method returns the first method in any superclass matching the
1352 given name. It is effectively the method that C<SUPER::$method_name>
1355 =item B<< $metaclass->add_method($method_name, $method) >>
1357 This method takes a method name and a subroutine reference, and adds
1358 the method to the class.
1360 The subroutine reference can be a L<Class::MOP::Method>, and you are
1361 strongly encouraged to pass a meta method object instead of a code
1362 reference. If you do so, that object gets stored as part of the
1363 class's method map directly. If not, the meta information will have to
1364 be recreated later, and may be incorrect.
1366 If you provide a method object, this method will clone that object if
1367 the object's package name does not match the class name. This lets us
1368 track the original source of any methods added from other classes
1369 (notably Moose roles).
1371 =item B<< $metaclass->remove_method($method_name) >>
1373 Remove the named method from the class. This method returns the
1374 L<Class::MOP::Method> object for the method.
1376 =item B<< $metaclass->method_metaclass >>
1378 Returns the class name of the method metaclass, see
1379 L<Class::MOP::Method> for more information on the method metaclass.
1381 =item B<< $metaclass->wrapped_method_metaclass >>
1383 Returns the class name of the wrapped method metaclass, see
1384 L<Class::MOP::Method::Wrapped> for more information on the wrapped
1389 =head2 Attribute introspection and creation
1391 Because Perl 5 does not have a core concept of attributes in classes,
1392 we can only return information about attributes which have been added
1393 via this class's methods. We cannot discover information about
1394 attributes which are defined in terms of "regular" Perl 5 methods.
1398 =item B<< $metaclass->get_attribute($attribute_name) >>
1400 This will return a L<Class::MOP::Attribute> for the specified
1401 C<$attribute_name>. If the class does not have the specified
1402 attribute, it returns C<undef>
1404 =item B<< $metaclass->has_attribute($attribute_name) >>
1406 Returns a boolean indicating whether or not the class defines the
1407 named attribute. It does not include attributes inherited from parent
1410 =item B<< $metaclass->get_attribute_map >>
1412 Returns a hash reference representing the attributes defined in this
1413 class. The keys are attribute names and the values are
1414 L<Class::MOP::Attribute> objects.
1416 =item B<< $metaclass->get_attribute_list >>
1418 This will return a list of attributes I<names> for all attributes
1419 defined in this class.
1421 =item B<< $metaclass->get_all_attributes >>
1423 This will traverse the inheritance hierarchy and return a list of all
1424 the L<Class::MOP::Attribute> objects for this class and its parents.
1426 This method can also be called as C<compute_all_applicable_attributes>.
1428 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1430 This will return a L<Class::MOP::Attribute> for the specified
1431 C<$attribute_name>. If the class does not have the specified
1432 attribute, it returns C<undef>
1434 Unlike C<get_attribute>, this attribute I<will> look for the named
1435 attribute in superclasses.
1437 =item B<< $metaclass->add_attribute(...) >>
1439 This method accepts either an existing L<Class::MOP::Attribute>
1440 object, or parameters suitable for passing to that class's C<new>
1443 The attribute provided will be added to the class.
1445 Any accessor methods defined by the attribute will be added to the
1446 class when the attribute is added.
1448 If an attribute of the same name already exists, the old attribute
1449 will be removed first.
1451 =item B<< $metaclass->remove_attribute($attribute_name) >>
1453 This will remove the named attribute from the class, and
1454 L<Class::MOP::Attribute> object.
1456 Removing an attribute also removes any accessor methods defined by the
1459 However, note that removing an attribute will only affect I<future>
1460 object instances created for this class, not existing instances.
1462 =item B<< $metaclass->attribute_metaclass >>
1464 Returns the class name of the attribute metaclass for this class. By
1465 default, this is L<Class::MOP::Attribute>. for more information on
1469 =head2 Class Immutability
1471 Making a class immutable "freezes" the class definition. You can no
1472 longer call methods which alter the class, such as adding or removing
1473 methods or attributes.
1475 Making a class immutable lets us optimize the class by inlining some
1476 methods, and also allows us to optimize some methods on the metaclass
1479 The immutabilization system in L<Moose> takes much greater advantage
1480 of the inlining features than Class::MOP itself does.
1484 =item B<< $metaclass->make_immutable(%options) >>
1486 This method will create an immutable transformer and uses it to make
1487 the class and its metaclass object immutable.
1489 Details of how immutabilization works are in L<Class::MOP::Immutable>
1492 =item B<< $metaclass->make_mutable >>
1494 Calling this method reverse the immutabilization transformation.
1496 =item B<< $metaclass->immutable_transformer >>
1498 If the class has been made immutable previously, this returns the
1499 L<Class::MOP::Immutable> object that was created to do the
1502 If the class was never made immutable, this method will die.
1506 =head2 Method Modifiers
1508 Method modifiers are hooks which allow a method to be wrapped with
1509 I<before>, I<after> and I<around> method modifiers. Every time a
1510 method is called, it's modifiers are also called.
1512 A class can modify its own methods, as well as methods defined in
1515 =head3 How method modifiers work?
1517 Method modifiers work by wrapping the original method and then
1518 replacing it in the class's symbol table. The wrappers will handle
1519 calling all the modifiers in the appropriate order and preserving the
1520 calling context for the original method.
1522 The return values of C<before> and C<after> modifiers are
1523 ignored. This is because their purpose is B<not> to filter the input
1524 and output of the primary method (this is done with an I<around>
1527 This may seem like an odd restriction to some, but doing this allows
1528 for simple code to be added at the beginning or end of a method call
1529 without altering the function of the wrapped method or placing any
1530 extra responsibility on the code of the modifier.
1532 Of course if you have more complex needs, you can use the C<around>
1533 modifier which allows you to change both the parameters passed to the
1534 wrapped method, as well as its return value.
1536 Before and around modifiers are called in last-defined-first-called
1537 order, while after modifiers are called in first-defined-first-called
1538 order. So the call tree might looks something like this:
1550 =head3 What is the performance impact?
1552 Of course there is a performance cost associated with method
1553 modifiers, but we have made every effort to make that cost directly
1554 proportional to the number of modifier features you utilize.
1556 The wrapping method does it's best to B<only> do as much work as it
1557 absolutely needs to. In order to do this we have moved some of the
1558 performance costs to set-up time, where they are easier to amortize.
1560 All this said, our benchmarks have indicated the following:
1562 simple wrapper with no modifiers 100% slower
1563 simple wrapper with simple before modifier 400% slower
1564 simple wrapper with simple after modifier 450% slower
1565 simple wrapper with simple around modifier 500-550% slower
1566 simple wrapper with all 3 modifiers 1100% slower
1568 These numbers may seem daunting, but you must remember, every feature
1569 comes with some cost. To put things in perspective, just doing a
1570 simple C<AUTOLOAD> which does nothing but extract the name of the
1571 method called and return it costs about 400% over a normal method
1576 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1578 This wraps the specified method with the supplied subroutine
1579 reference. The modifier will be called as a method itself, and will
1580 receive the same arguments as are passed to the method.
1582 When the modifier exits, the wrapped method will be called.
1584 The return value of the modifier will be ignored.
1586 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1588 This wraps the specified method with the supplied subroutine
1589 reference. The modifier will be called as a method itself, and will
1590 receive the same arguments as are passed to the method.
1592 When the wrapped methods exits, the modifier will be called.
1594 The return value of the modifier will be ignored.
1596 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1598 This wraps the specified method with the supplied subroutine
1601 The first argument passed to the modifier will be a subroutine
1602 reference to the wrapped method. The second argument is the object,
1603 and after that come any arguments passed when the method is called.
1605 The around modifier can choose to call the original method, as well as
1606 what arguments to pass if it does so.
1608 The return value of the modifier is what will be seen by the caller.
1612 =head2 Introspection
1616 =item B<< Class::MOP::Class->meta >>
1618 This will return a L<Class::MOP::Class> instance for this class.
1620 It should also be noted that L<Class::MOP> will actually bootstrap
1621 this module by installing a number of attribute meta-objects into its
1628 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1630 =head1 COPYRIGHT AND LICENSE
1632 Copyright 2006-2009 by Infinity Interactive, Inc.
1634 L<http://www.iinteractive.com>
1636 This library is free software; you can redistribute it and/or modify
1637 it under the same terms as Perl itself.