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 our $VERSION = '0.92';
18 $VERSION = eval $VERSION;
19 our $AUTHORITY = 'cpan:STEVAN';
21 use base 'Class::MOP::Module';
31 $package_name = shift;
34 $package_name = $options{package};
37 ($package_name && !ref($package_name))
38 || confess "You must pass a package name and it cannot be blessed";
40 return Class::MOP::get_metaclass_by_name($package_name)
41 || $class->_construct_class_instance(package => $package_name, @_);
44 # NOTE: (meta-circularity)
45 # this is a special form of _construct_instance
46 # (see below), which is used to construct class
47 # meta-object instances for any Class::MOP::*
48 # class. All other classes will use the more
49 # normal &construct_instance.
50 sub _construct_class_instance {
52 my $options = @_ == 1 ? $_[0] : {@_};
53 my $package_name = $options->{package};
54 (defined $package_name && $package_name)
55 || confess "You must pass a package name";
57 # return the metaclass if we have it cached,
58 # and it is still defined (it has not been
59 # reaped by DESTROY yet, which can happen
60 # annoyingly enough during global destruction)
62 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
67 # we need to deal with the possibility
68 # of class immutability here, and then
69 # get the name of the class appropriately
71 ? ($class->is_immutable
72 ? $class->get_mutable_metaclass_name()
76 # now create the metaclass
78 if ($class eq 'Class::MOP::Class') {
79 $meta = $class->_new($options);
83 # it is safe to use meta here because
84 # class will always be a subclass of
85 # Class::MOP::Class, which defines meta
86 $meta = $class->meta->_construct_instance($options)
89 # and check the metaclass compatibility
90 $meta->_check_metaclass_compatibility();
92 Class::MOP::store_metaclass_by_name($package_name, $meta);
95 # we need to weaken any anon classes
96 # so that they can call DESTROY properly
97 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
105 return Class::MOP::Class->initialize($class)->new_object(@_)
106 if $class ne __PACKAGE__;
108 my $options = @_ == 1 ? $_[0] : {@_};
111 # inherited from Class::MOP::Package
112 'package' => $options->{package},
115 # since the following attributes will
116 # actually be loaded from the symbol
117 # table, and actually bypass the instance
118 # entirely, we can just leave these things
119 # listed here for reference, because they
120 # should not actually have a value associated
122 'namespace' => \undef,
124 # inherited from Class::MOP::Module
126 'authority' => \undef,
128 # defined in Class::MOP::Class
129 'superclasses' => \undef,
133 'attribute_metaclass' =>
134 ( $options->{'attribute_metaclass'} || 'Class::MOP::Attribute' ),
135 'method_metaclass' =>
136 ( $options->{'method_metaclass'} || 'Class::MOP::Method' ),
137 'wrapped_method_metaclass' => (
138 $options->{'wrapped_method_metaclass'}
139 || 'Class::MOP::Method::Wrapped'
141 'instance_metaclass' =>
142 ( $options->{'instance_metaclass'} || 'Class::MOP::Instance' ),
143 'immutable_trait' => (
144 $options->{'immutable_trait'}
145 || 'Class::MOP::Class::Immutable::Trait'
147 'constructor_name' => ( $options->{constructor_name} || 'new' ),
148 'constructor_class' => (
149 $options->{constructor_class} || 'Class::MOP::Method::Constructor'
151 'destructor_class' => $options->{destructor_class},
155 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
156 sub update_package_cache_flag {
159 # we can manually update the cache number
160 # since we are actually adding the method
161 # to our cache as well. This avoids us
162 # having to regenerate the method_map.
164 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
167 sub _check_metaclass_compatibility {
170 # this is always okay ...
171 return if ref($self) eq 'Class::MOP::Class' &&
172 $self->instance_metaclass eq 'Class::MOP::Instance';
174 my @class_list = $self->linearized_isa;
175 shift @class_list; # shift off $self->name
177 foreach my $superclass_name (@class_list) {
178 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name) || next;
181 # we need to deal with the possibility
182 # of class immutability here, and then
183 # get the name of the class appropriately
185 = $super_meta->is_immutable
186 ? $super_meta->get_mutable_metaclass_name()
189 ($self->isa($super_meta_type))
190 || confess "The metaclass of " . $self->name . " ("
191 . (ref($self)) . ")" . " is not compatible with the " .
192 "metaclass of its superclass, ".$superclass_name . " ("
193 . ($super_meta_type) . ")";
195 # we also need to check that instance metaclasses
196 # are compatibile in the same the class.
197 ($self->instance_metaclass->isa($super_meta->instance_metaclass))
198 || confess "The instance metaclass for " . $self->name . " (" . ($self->instance_metaclass) . ")" .
199 " is not compatible with the " .
200 "instance metaclass of its superclass, " . $superclass_name . " (" . ($super_meta->instance_metaclass) . ")";
208 # this should be sufficient, if you have a
209 # use case where it is not, write a test and
211 my $ANON_CLASS_SERIAL = 0;
214 # we need a sufficiently annoying prefix
215 # this should suffice for now, this is
216 # used in a couple of places below, so
217 # need to put it up here for now.
218 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
222 no warnings 'uninitialized';
223 $self->name =~ /^$ANON_CLASS_PREFIX/o;
226 sub create_anon_class {
227 my ($class, %options) = @_;
228 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
229 return $class->create($package_name, %options);
233 # this will only get called for
234 # anon-classes, all other calls
235 # are assumed to occur during
236 # global destruction and so don't
237 # really need to be handled explicitly
241 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
243 no warnings 'uninitialized';
244 my $name = $self->name;
245 return unless $name =~ /^$ANON_CLASS_PREFIX/o;
246 # Moose does a weird thing where it replaces the metaclass for
247 # class when fixing metaclass incompatibility. In that case,
248 # we don't want to clean out the namespace now. We can detect
249 # that because Moose will explicitly update the singleton
250 # cache in Class::MOP.
251 my $current_meta = Class::MOP::get_metaclass_by_name($name);
252 return if $current_meta ne $self;
254 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/o);
256 @{$name . '::ISA'} = ();
257 %{$name . '::'} = ();
258 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
260 Class::MOP::remove_metaclass_by_name($name);
265 # creating classes with MOP ...
268 my ( $class, @args ) = @_;
270 unshift @args, 'package' if @args % 2 == 1;
272 my (%options) = @args;
273 my $package_name = $options{package};
275 (ref $options{superclasses} eq 'ARRAY')
276 || confess "You must pass an ARRAY ref of superclasses"
277 if exists $options{superclasses};
279 (ref $options{attributes} eq 'ARRAY')
280 || confess "You must pass an ARRAY ref of attributes"
281 if exists $options{attributes};
283 (ref $options{methods} eq 'HASH')
284 || confess "You must pass a HASH ref of methods"
285 if exists $options{methods};
287 my (%initialize_options) = @args;
288 delete @initialize_options{qw(
296 my $meta = $class->initialize( $package_name => %initialize_options );
298 $meta->_instantiate_module( $options{version}, $options{authority} );
301 $meta->add_method('meta' => sub {
302 $class->initialize(ref($_[0]) || $_[0]);
305 $meta->superclasses(@{$options{superclasses}})
306 if exists $options{superclasses};
308 # process attributes first, so that they can
309 # install accessors, but locally defined methods
310 # can then overwrite them. It is maybe a little odd, but
311 # I think this should be the order of things.
312 if (exists $options{attributes}) {
313 foreach my $attr (@{$options{attributes}}) {
314 $meta->add_attribute($attr);
317 if (exists $options{methods}) {
318 foreach my $method_name (keys %{$options{methods}}) {
319 $meta->add_method($method_name, $options{methods}->{$method_name});
327 # Instance Construction & Cloning
333 # we need to protect the integrity of the
334 # Class::MOP::Class singletons here, so we
335 # delegate this to &construct_class_instance
336 # which will deal with the singletons
337 return $class->_construct_class_instance(@_)
338 if $class->name->isa('Class::MOP::Class');
339 return $class->_construct_instance(@_);
342 sub _construct_instance {
344 my $params = @_ == 1 ? $_[0] : {@_};
345 my $meta_instance = $class->get_meta_instance();
347 # the code below is almost certainly incorrect
348 # but this is foreign inheritance, so we might
349 # have to kludge it in the end.
350 my $instance = $params->{__INSTANCE__} || $meta_instance->create_instance();
351 foreach my $attr ($class->get_all_attributes()) {
352 $attr->initialize_instance_slot($meta_instance, $instance, $params);
355 # this will only work for a HASH instance type
356 if ($class->is_anon_class) {
357 (reftype($instance) eq 'HASH')
358 || confess "Currently only HASH based instances are supported with instance of anon-classes";
360 # At some point we should make this official
361 # as a reserved slot name, but right now I am
362 # going to keep it here.
363 # my $RESERVED_MOP_SLOT = '__MOP__';
364 $instance->{'__MOP__'} = $class;
370 sub get_meta_instance {
372 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
375 sub _create_meta_instance {
378 my $instance = $self->instance_metaclass->new(
379 associated_metaclass => $self,
380 attributes => [ $self->get_all_attributes() ],
383 $self->add_meta_instance_dependencies()
384 if $instance->is_dependent_on_superclasses();
391 my $instance = shift;
392 (blessed($instance) && $instance->isa($class->name))
393 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
396 # we need to protect the integrity of the
397 # Class::MOP::Class singletons here, they
398 # should not be cloned.
399 return $instance if $instance->isa('Class::MOP::Class');
400 $class->_clone_instance($instance, @_);
403 sub _clone_instance {
404 my ($class, $instance, %params) = @_;
406 || confess "You can only clone instances, ($instance) is not a blessed instance";
407 my $meta_instance = $class->get_meta_instance();
408 my $clone = $meta_instance->clone_instance($instance);
409 foreach my $attr ($class->get_all_attributes()) {
410 if ( defined( my $init_arg = $attr->init_arg ) ) {
411 if (exists $params{$init_arg}) {
412 $attr->set_value($clone, $params{$init_arg});
419 sub rebless_instance {
420 my ($self, $instance, %params) = @_;
422 my $old_metaclass = Class::MOP::class_of($instance);
424 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
425 $self->name->isa($old_class)
426 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
428 $old_metaclass->rebless_instance_away($instance, $self, %params)
431 my $meta_instance = $self->get_meta_instance();
434 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
435 $meta_instance->rebless_instance_structure($_[1], $self);
437 foreach my $attr ( $self->get_all_attributes ) {
438 if ( $attr->has_value($instance) ) {
439 if ( defined( my $init_arg = $attr->init_arg ) ) {
440 $params{$init_arg} = $attr->get_value($instance)
441 unless exists $params{$init_arg};
444 $attr->set_value($instance, $attr->get_value($instance));
449 foreach my $attr ($self->get_all_attributes) {
450 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
456 sub rebless_instance_away {
457 # this intentionally does nothing, it is just a hook
464 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
467 @{$self->get_package_symbol($var_spec)} = @supers;
470 # on 5.8 and below, we need to call
471 # a method to get Perl to detect
472 # a cycle in the class hierarchy
473 my $class = $self->name;
477 # we need to check the metaclass
478 # compatibility here so that we can
479 # be sure that the superclass is
480 # not potentially creating an issues
481 # we don't know about
483 $self->_check_metaclass_compatibility();
484 $self->_superclasses_updated();
486 @{$self->get_package_symbol($var_spec)};
489 sub _superclasses_updated {
491 $self->update_meta_instance_dependencies();
496 my $super_class = $self->name;
498 return @{ $super_class->mro::get_isarev() };
501 sub direct_subclasses {
503 my $super_class = $self->name;
508 } Class::MOP::Class->initialize($_)->superclasses
513 return @{ mro::get_linear_isa( (shift)->name ) };
516 sub class_precedence_list {
518 my $name = $self->name;
520 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
522 # We need to check for circular inheritance here
523 # if we are are not on 5.10, cause 5.8 detects it
524 # late. This will do nothing if all is well, and
525 # blow up otherwise. Yes, it's an ugly hack, better
526 # suggestions are welcome.
528 ($name || return)->isa('This is a test for circular inheritance')
531 # if our mro is c3, we can
532 # just grab the linear_isa
533 if (mro::get_mro($name) eq 'c3') {
534 return @{ mro::get_linear_isa($name) }
538 # we can't grab the linear_isa for dfs
539 # since it has all the duplicates
544 $self->initialize($_)->class_precedence_list()
545 } $self->superclasses()
553 my $fetch_and_prepare_method = sub {
554 my ($self, $method_name) = @_;
555 my $wrapped_metaclass = $self->wrapped_method_metaclass;
557 my $method = $self->get_method($method_name);
558 # if we dont have local ...
560 # try to find the next method
561 $method = $self->find_next_method_by_name($method_name);
562 # die if it does not exist
564 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
565 # and now make sure to wrap it
566 # even if it is already wrapped
567 # because we need a new sub ref
568 $method = $wrapped_metaclass->wrap($method,
569 package_name => $self->name,
570 name => $method_name,
574 # now make sure we wrap it properly
575 $method = $wrapped_metaclass->wrap($method,
576 package_name => $self->name,
577 name => $method_name,
578 ) unless $method->isa($wrapped_metaclass);
580 $self->add_method($method_name => $method);
584 sub add_before_method_modifier {
585 my ($self, $method_name, $method_modifier) = @_;
586 (defined $method_name && $method_name)
587 || confess "You must pass in a method name";
588 my $method = $fetch_and_prepare_method->($self, $method_name);
589 $method->add_before_modifier(
590 subname(':before' => $method_modifier)
594 sub add_after_method_modifier {
595 my ($self, $method_name, $method_modifier) = @_;
596 (defined $method_name && $method_name)
597 || confess "You must pass in a method name";
598 my $method = $fetch_and_prepare_method->($self, $method_name);
599 $method->add_after_modifier(
600 subname(':after' => $method_modifier)
604 sub add_around_method_modifier {
605 my ($self, $method_name, $method_modifier) = @_;
606 (defined $method_name && $method_name)
607 || confess "You must pass in a method name";
608 my $method = $fetch_and_prepare_method->($self, $method_name);
609 $method->add_around_modifier(
610 subname(':around' => $method_modifier)
615 # the methods above used to be named like this:
616 # ${pkg}::${method}:(before|after|around)
617 # but this proved problematic when using one modifier
618 # to wrap multiple methods (something which is likely
619 # to happen pretty regularly IMO). So instead of naming
620 # it like this, I have chosen to just name them purely
621 # with their modifier names, like so:
622 # :(before|after|around)
623 # The fact is that in a stack trace, it will be fairly
624 # evident from the context what method they are attached
625 # to, and so don't need the fully qualified name.
628 sub find_method_by_name {
629 my ($self, $method_name) = @_;
630 (defined $method_name && $method_name)
631 || confess "You must define a method name to find";
632 foreach my $class ($self->linearized_isa) {
633 my $method = $self->initialize($class)->get_method($method_name);
634 return $method if defined $method;
639 sub get_all_methods {
641 my %methods = map { %{ $self->initialize($_)->get_method_map } } reverse $self->linearized_isa;
642 return values %methods;
645 sub get_all_method_names {
648 return grep { !$uniq{$_}++ } map { $self->initialize($_)->get_method_list } $self->linearized_isa;
651 sub find_all_methods_by_name {
652 my ($self, $method_name) = @_;
653 (defined $method_name && $method_name)
654 || confess "You must define a method name to find";
656 foreach my $class ($self->linearized_isa) {
657 # fetch the meta-class ...
658 my $meta = $self->initialize($class);
660 name => $method_name,
662 code => $meta->get_method($method_name)
663 } if $meta->has_method($method_name);
668 sub find_next_method_by_name {
669 my ($self, $method_name) = @_;
670 (defined $method_name && $method_name)
671 || confess "You must define a method name to find";
672 my @cpl = $self->linearized_isa;
673 shift @cpl; # discard ourselves
674 foreach my $class (@cpl) {
675 my $method = $self->initialize($class)->get_method($method_name);
676 return $method if defined $method;
685 # either we have an attribute object already
686 # or we need to create one from the args provided
687 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
688 # make sure it is derived from the correct type though
689 ($attribute->isa('Class::MOP::Attribute'))
690 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
692 # first we attach our new attribute
693 # because it might need certain information
694 # about the class which it is attached to
695 $attribute->attach_to_class($self);
697 my $attr_name = $attribute->name;
699 # then we remove attributes of a conflicting
700 # name here so that we can properly detach
701 # the old attr object, and remove any
702 # accessors it would have generated
703 if ( $self->has_attribute($attr_name) ) {
704 $self->remove_attribute($attr_name);
706 $self->invalidate_meta_instances();
709 # get our count of previously inserted attributes and
710 # increment by one so this attribute knows its order
711 my $order = (scalar keys %{$self->get_attribute_map});
712 $attribute->_set_insertion_order($order);
714 # then onto installing the new accessors
715 $self->get_attribute_map->{$attr_name} = $attribute;
717 # invalidate package flag here
721 eval { $attribute->install_accessors() };
725 $self->remove_attribute($attr_name);
732 sub update_meta_instance_dependencies {
735 if ( $self->{meta_instance_dependencies} ) {
736 return $self->add_meta_instance_dependencies;
740 sub add_meta_instance_dependencies {
743 $self->remove_meta_instance_dependencies;
745 my @attrs = $self->get_all_attributes();
748 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
750 foreach my $class ( @classes ) {
751 $class->add_dependent_meta_instance($self);
754 $self->{meta_instance_dependencies} = \@classes;
757 sub remove_meta_instance_dependencies {
760 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
761 foreach my $class ( @$classes ) {
762 $class->remove_dependent_meta_instance($self);
772 sub add_dependent_meta_instance {
773 my ( $self, $metaclass ) = @_;
774 push @{ $self->{dependent_meta_instances} }, $metaclass;
777 sub remove_dependent_meta_instance {
778 my ( $self, $metaclass ) = @_;
779 my $name = $metaclass->name;
780 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
783 sub invalidate_meta_instances {
785 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
788 sub invalidate_meta_instance {
790 undef $self->{_meta_instance};
794 my ($self, $attribute_name) = @_;
795 (defined $attribute_name)
796 || confess "You must define an attribute name";
797 exists $self->get_attribute_map->{$attribute_name};
801 my ($self, $attribute_name) = @_;
802 (defined $attribute_name)
803 || confess "You must define an attribute name";
804 return $self->get_attribute_map->{$attribute_name}
806 # this will return undef anyway, so no need ...
807 # if $self->has_attribute($attribute_name);
811 sub remove_attribute {
812 my ($self, $attribute_name) = @_;
813 (defined $attribute_name)
814 || confess "You must define an attribute name";
815 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
816 return unless defined $removed_attribute;
817 delete $self->get_attribute_map->{$attribute_name};
818 $self->invalidate_meta_instances();
819 $removed_attribute->remove_accessors();
820 $removed_attribute->detach_from_class();
821 return $removed_attribute;
824 sub get_attribute_list {
826 keys %{$self->get_attribute_map};
829 sub get_all_attributes {
831 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
832 return values %attrs;
835 sub find_attribute_by_name {
836 my ($self, $attr_name) = @_;
837 foreach my $class ($self->linearized_isa) {
838 # fetch the meta-class ...
839 my $meta = $self->initialize($class);
840 return $meta->get_attribute($attr_name)
841 if $meta->has_attribute($attr_name);
846 # check if we can reinitialize
850 # if any local attr is defined
851 return if $self->get_attribute_list;
853 # or any non-declared methods
854 if ( my @methods = values %{ $self->get_method_map } ) {
855 my $metaclass = $self->method_metaclass;
856 foreach my $method ( @methods ) {
857 return if $method->isa("Class::MOP::Method::Generated");
858 # FIXME do we need to enforce this too? return unless $method->isa($metaclass);
868 sub is_immutable { 0 }
870 sub _immutable_options {
871 my ( $self, @args ) = @_;
874 inline_accessors => 1,
875 inline_constructor => 1,
876 inline_destructor => 0,
878 immutable_trait => $self->immutable_trait,
879 constructor_name => $self->constructor_name,
880 constructor_class => $self->constructor_class,
881 destructor_class => $self->destructor_class,
887 my ( $self, @args ) = @_;
889 if ( $self->is_mutable ) {
890 $self->_initialize_immutable( $self->_immutable_options(@args) );
891 $self->_rebless_as_immutable(@args);
902 if ( $self->is_immutable ) {
903 my @args = $self->immutable_options;
904 $self->_rebless_as_mutable();
905 $self->_remove_inlined_code(@args);
906 delete $self->{__immutable};
914 sub _rebless_as_immutable {
915 my ( $self, @args ) = @_;
917 $self->{__immutable}{original_class} = ref $self;
919 bless $self => $self->_immutable_metaclass(@args);
922 sub _immutable_metaclass {
923 my ( $self, %args ) = @_;
925 if ( my $class = $args{immutable_metaclass} ) {
929 my $trait = $args{immutable_trait} = $self->immutable_trait
930 || confess "no immutable trait specified for $self";
932 my $meta = $self->meta;
933 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
937 if ( $meta_attr and $trait eq $meta_attr->default ) {
938 # if the trait is the same as the default we try and pick a
939 # predictable name for the immutable metaclass
940 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
943 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
944 $trait, 'ForMetaClass', ref($self);
948 if Class::MOP::is_class_loaded($class_name);
950 # If the metaclass is a subclass of CMOP::Class which has had
951 # metaclass roles applied (via Moose), then we want to make sure
952 # that we preserve that anonymous class (see Fey::ORM for an
953 # example of where this matters).
955 = $meta->is_immutable
956 ? $meta->get_mutable_metaclass_name
959 my $immutable_meta = $meta_name->create(
961 superclasses => [ ref $self ],
964 Class::MOP::load_class($trait);
965 for my $meth ( Class::MOP::Class->initialize($trait)->get_all_methods ) {
966 my $meth_name = $meth->name;
968 if ( $immutable_meta->find_method_by_name( $meth_name ) ) {
969 $immutable_meta->add_around_method_modifier( $meth_name, $meth->body );
972 $immutable_meta->add_method( $meth_name, $meth->clone );
976 $immutable_meta->make_immutable(
977 inline_constructor => 0,
978 inline_accessors => 0,
984 sub _remove_inlined_code {
987 $self->remove_method( $_->name ) for $self->_inlined_methods;
989 delete $self->{__immutable}{inlined_methods};
992 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
994 sub _add_inlined_method {
995 my ( $self, $method ) = @_;
997 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1000 sub _initialize_immutable {
1001 my ( $self, %args ) = @_;
1003 $self->{__immutable}{options} = \%args;
1004 $self->_install_inlined_code(%args);
1007 sub _install_inlined_code {
1008 my ( $self, %args ) = @_;
1011 $self->_inline_accessors(%args) if $args{inline_accessors};
1012 $self->_inline_constructor(%args) if $args{inline_constructor};
1013 $self->_inline_destructor(%args) if $args{inline_destructor};
1016 sub _rebless_as_mutable {
1019 bless $self, $self->get_mutable_metaclass_name;
1024 sub _inline_accessors {
1027 foreach my $attr_name ( $self->get_attribute_list ) {
1028 $self->get_attribute($attr_name)->install_accessors(1);
1032 sub _inline_constructor {
1033 my ( $self, %args ) = @_;
1035 my $name = $args{constructor_name};
1037 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1038 my $class = $self->name;
1039 warn "Not inlining a constructor for $class since it defines"
1040 . " its own constructor.\n"
1041 . "If you are certain you don't need to inline your"
1042 . " constructor, specify inline_constructor => 0 in your"
1043 . " call to $class->meta->make_immutable\n";
1047 my $constructor_class = $args{constructor_class};
1049 Class::MOP::load_class($constructor_class);
1051 my $constructor = $constructor_class->new(
1055 package_name => $self->name,
1059 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1060 $self->add_method( $name => $constructor );
1061 $self->_add_inlined_method($constructor);
1065 sub _inline_destructor {
1066 my ( $self, %args ) = @_;
1068 ( exists $args{destructor_class} && defined $args{destructor_class} )
1069 || confess "The 'inline_destructor' option is present, but "
1070 . "no destructor class was specified";
1072 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1073 my $class = $self->name;
1074 warn "Not inlining a destructor for $class since it defines"
1075 . " its own destructor.\n";
1079 my $destructor_class = $args{destructor_class};
1081 Class::MOP::load_class($destructor_class);
1083 return unless $destructor_class->is_needed($self);
1085 my $destructor = $destructor_class->new(
1088 package_name => $self->name,
1092 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1093 $self->add_method( 'DESTROY' => $destructor );
1094 $self->_add_inlined_method($destructor);
1106 Class::MOP::Class - Class Meta Object
1110 # assuming that class Foo
1111 # has been defined, you can
1113 # use this for introspection ...
1115 # add a method to Foo ...
1116 Foo->meta->add_method( 'bar' => sub {...} )
1118 # get a list of all the classes searched
1119 # the method dispatcher in the correct order
1120 Foo->meta->class_precedence_list()
1122 # remove a method from Foo
1123 Foo->meta->remove_method('bar');
1125 # or use this to actually create classes ...
1127 Class::MOP::Class->create(
1130 superclasses => ['Foo'],
1132 Class::MOP::Attribute->new('$bar'),
1133 Class::MOP::Attribute->new('$baz'),
1136 calculate_bar => sub {...},
1137 construct_baz => sub {...}
1144 The Class Protocol is the largest and most complex part of the
1145 Class::MOP meta-object protocol. It controls the introspection and
1146 manipulation of Perl 5 classes, and it can create them as well. The
1147 best way to understand what this module can do, is to read the
1148 documentation for each of its methods.
1152 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1156 =head2 Class construction
1158 These methods all create new C<Class::MOP::Class> objects. These
1159 objects can represent existing classes, or they can be used to create
1160 new classes from scratch.
1162 The metaclass object for a given class is a singleton. If you attempt
1163 to create a metaclass for the same class twice, you will just get the
1168 =item B<< Class::MOP::Class->create($package_name, %options) >>
1170 This method creates a new C<Class::MOP::Class> object with the given
1171 package name. It accepts a number of options.
1177 An optional version number for the newly created package.
1181 An optional authority for the newly created package.
1183 =item * superclasses
1185 An optional array reference of superclass names.
1189 An optional hash reference of methods for the class. The keys of the
1190 hash reference are method names, and values are subroutine references.
1194 An optional array reference of L<Class::MOP::Attribute> objects.
1198 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1200 This method works just like C<< Class::MOP::Class->create >> but it
1201 creates an "anonymous" class. In fact, the class does have a name, but
1202 that name is a unique name generated internally by this module.
1204 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1205 parameters that C<create> accepts.
1207 Anonymous classes are destroyed once the metaclass they are attached
1208 to goes out of scope, and will be removed from Perl's internal symbol
1211 All instances of an anonymous class keep a special reference to the
1212 metaclass object, which prevents the metaclass from going out of scope
1213 while any instances exist.
1215 This only works if the instance if based on a hash reference, however.
1217 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1219 This method will initialize a C<Class::MOP::Class> object for the
1220 named package. Unlike C<create>, this method I<will not> create a new
1223 The purpose of this method is to retrieve a C<Class::MOP::Class>
1224 object for introspecting an existing class.
1226 If an existing C<Class::MOP::Class> object exists for the named
1227 package, it will be returned, and any options provided will be
1230 If the object does not yet exist, it will be created.
1232 The valid options that can be passed to this method are
1233 C<attribute_metaclass>, C<method_metaclass>,
1234 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1235 optional, and default to the appropriate class in the C<Class::MOP>
1240 =head2 Object instance construction and cloning
1242 These methods are all related to creating and/or cloning object
1247 =item B<< $metaclass->clone_object($instance, %params) >>
1249 This method clones an existing object instance. Any parameters you
1250 provide are will override existing attribute values in the object.
1252 This is a convenience method for cloning an object instance, then
1253 blessing it into the appropriate package.
1255 You could implement a clone method in your class, using this method:
1258 my ($self, %params) = @_;
1259 $self->meta->clone_object($self, %params);
1262 =item B<< $metaclass->rebless_instance($instance, %params) >>
1264 This method changes the class of C<$instance> to the metaclass's class.
1266 You can only rebless an instance into a subclass of its current
1267 class. If you pass any additional parameters, these will be treated
1268 like constructor parameters and used to initialize the object's
1269 attributes. Any existing attributes that are already set will be
1272 Before reblessing the instance, this method will call
1273 C<rebless_instance_away> on the instance's current metaclass. This method
1274 will be passed the instance, the new metaclass, and any parameters
1275 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1276 does nothing; it is merely a hook.
1278 =item B<< $metaclass->new_object(%params) >>
1280 This method is used to create a new object of the metaclass's
1281 class. Any parameters you provide are used to initialize the
1282 instance's attributes. A special C<__INSTANCE__> key can be passed to
1283 provide an already generated instance, rather than having Class::MOP
1284 generate it for you. This is mostly useful for using Class::MOP with
1285 foreign classes, which generally generate instances using their own
1288 =item B<< $metaclass->instance_metaclass >>
1290 Returns the class name of the instance metaclass, see
1291 L<Class::MOP::Instance> for more information on the instance
1294 =item B<< $metaclass->get_meta_instance >>
1296 Returns an instance of the C<instance_metaclass> to be used in the
1297 construction of a new instance of the class.
1301 =head2 Informational predicates
1303 These are a few predicate methods for asking information about the
1308 =item B<< $metaclass->is_anon_class >>
1310 This returns true if the class was created by calling C<<
1311 Class::MOP::Class->create_anon_class >>.
1313 =item B<< $metaclass->is_mutable >>
1315 This returns true if the class is still mutable.
1317 =item B<< $metaclass->is_immutable >>
1319 This returns true if the class has been made immutable.
1321 =item B<< $metaclass->is_pristine >>
1323 A class is I<not> pristine if it has non-inherited attributes or if it
1324 has any generated methods.
1328 =head2 Inheritance Relationships
1332 =item B<< $metaclass->superclasses(@superclasses) >>
1334 This is a read-write accessor which represents the superclass
1335 relationships of the metaclass's class.
1337 This is basically sugar around getting and setting C<@ISA>.
1339 =item B<< $metaclass->class_precedence_list >>
1341 This returns a list of all of the class's ancestor classes. The
1342 classes are returned in method dispatch order.
1344 =item B<< $metaclass->linearized_isa >>
1346 This returns a list based on C<class_precedence_list> but with all
1349 =item B<< $metaclass->subclasses >>
1351 This returns a list of all subclasses for this class, even indirect
1354 =item B<< $metaclass->direct_subclasses >>
1356 This returns a list of immediate subclasses for this class, which does not
1357 include indirect subclasses.
1361 =head2 Method introspection
1363 See L<Class::MOP::Package/Method introspection and creation> for
1364 methods that operate only on the current class. Class::MOP::Class adds
1365 introspection capabilities that take inheritance into account.
1369 =item B<< $metaclass->get_all_methods >>
1371 This will traverse the inheritance hierarchy and return a list of all
1372 the L<Class::MOP::Method> objects for this class and its parents.
1374 =item B<< $metaclass->find_method_by_name($method_name) >>
1376 This will return a L<Class::MOP::Method> for the specified
1377 C<$method_name>. If the class does not have the specified method, it
1380 Unlike C<get_method>, this method I<will> look for the named method in
1383 =item B<< $metaclass->get_all_method_names >>
1385 This will return a list of method I<names> for all of this class's
1386 methods, including inherited methods.
1388 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1390 This method looks for the named method in the class and all of its
1391 parents. It returns every matching method it finds in the inheritance
1392 tree, so it returns a list of methods.
1394 Each method is returned as a hash reference with three keys. The keys
1395 are C<name>, C<class>, and C<code>. The C<code> key has a
1396 L<Class::MOP::Method> object as its value.
1398 The list of methods is distinct.
1400 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1402 This method returns the first method in any superclass matching the
1403 given name. It is effectively the method that C<SUPER::$method_name>
1408 =head2 Attribute introspection and creation
1410 Because Perl 5 does not have a core concept of attributes in classes,
1411 we can only return information about attributes which have been added
1412 via this class's methods. We cannot discover information about
1413 attributes which are defined in terms of "regular" Perl 5 methods.
1417 =item B<< $metaclass->get_attribute($attribute_name) >>
1419 This will return a L<Class::MOP::Attribute> for the specified
1420 C<$attribute_name>. If the class does not have the specified
1421 attribute, it returns C<undef>.
1423 NOTE that get_attribute does not search superclasses, for that you
1424 need to use C<find_attribute_by_name>.
1426 =item B<< $metaclass->has_attribute($attribute_name) >>
1428 Returns a boolean indicating whether or not the class defines the
1429 named attribute. It does not include attributes inherited from parent
1432 =item B<< $metaclass->get_attribute_map >>
1434 Returns a hash reference representing the attributes defined in this
1435 class. The keys are attribute names and the values are
1436 L<Class::MOP::Attribute> objects.
1438 =item B<< $metaclass->get_attribute_list >>
1440 This will return a list of attributes I<names> for all attributes
1441 defined in this class.
1443 =item B<< $metaclass->get_all_attributes >>
1445 This will traverse the inheritance hierarchy and return a list of all
1446 the L<Class::MOP::Attribute> objects for this class and its parents.
1448 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1450 This will return a L<Class::MOP::Attribute> for the specified
1451 C<$attribute_name>. If the class does not have the specified
1452 attribute, it returns C<undef>
1454 Unlike C<get_attribute>, this attribute I<will> look for the named
1455 attribute in superclasses.
1457 =item B<< $metaclass->add_attribute(...) >>
1459 This method accepts either an existing L<Class::MOP::Attribute>
1460 object, or parameters suitable for passing to that class's C<new>
1463 The attribute provided will be added to the class.
1465 Any accessor methods defined by the attribute will be added to the
1466 class when the attribute is added.
1468 If an attribute of the same name already exists, the old attribute
1469 will be removed first.
1471 =item B<< $metaclass->remove_attribute($attribute_name) >>
1473 This will remove the named attribute from the class, and
1474 L<Class::MOP::Attribute> object.
1476 Removing an attribute also removes any accessor methods defined by the
1479 However, note that removing an attribute will only affect I<future>
1480 object instances created for this class, not existing instances.
1482 =item B<< $metaclass->attribute_metaclass >>
1484 Returns the class name of the attribute metaclass for this class. By
1485 default, this is L<Class::MOP::Attribute>.
1489 =head2 Class Immutability
1491 Making a class immutable "freezes" the class definition. You can no
1492 longer call methods which alter the class, such as adding or removing
1493 methods or attributes.
1495 Making a class immutable lets us optimize the class by inlining some
1496 methods, and also allows us to optimize some methods on the metaclass
1499 After immutabilization, the metaclass object will cache most
1500 informational methods such as C<get_method_map> and
1501 C<get_all_attributes>. Methods which would alter the class, such as
1502 C<add_attribute>, C<add_method>, and so on will throw an error on an
1503 immutable metaclass object.
1505 The immutabilization system in L<Moose> takes much greater advantage
1506 of the inlining features than Class::MOP itself does.
1510 =item B<< $metaclass->make_immutable(%options) >>
1512 This method will create an immutable transformer and uses it to make
1513 the class and its metaclass object immutable.
1515 This method accepts the following options:
1519 =item * inline_accessors
1521 =item * inline_constructor
1523 =item * inline_destructor
1525 These are all booleans indicating whether the specified method(s)
1528 By default, accessors and the constructor are inlined, but not the
1531 =item * immutable_trait
1533 The name of a class which will be used as a parent class for the
1534 metaclass object being made immutable. This "trait" implements the
1535 post-immutability functionality of the metaclass (but not the
1536 transformation itself).
1538 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1540 =item * constructor_name
1542 This is the constructor method name. This defaults to "new".
1544 =item * constructor_class
1546 The name of the method metaclass for constructors. It will be used to
1547 generate the inlined constructor. This defaults to
1548 "Class::MOP::Method::Constructor".
1550 =item * replace_constructor
1552 This is a boolean indicating whether an existing constructor should be
1553 replaced when inlining a constructor. This defaults to false.
1555 =item * destructor_class
1557 The name of the method metaclass for destructors. It will be used to
1558 generate the inlined destructor. This defaults to
1559 "Class::MOP::Method::Denstructor".
1561 =item * replace_destructor
1563 This is a boolean indicating whether an existing destructor should be
1564 replaced when inlining a destructor. This defaults to false.
1568 =item B<< $metaclass->make_mutable >>
1570 Calling this method reverse the immutabilization transformation.
1574 =head2 Method Modifiers
1576 Method modifiers are hooks which allow a method to be wrapped with
1577 I<before>, I<after> and I<around> method modifiers. Every time a
1578 method is called, it's modifiers are also called.
1580 A class can modify its own methods, as well as methods defined in
1583 =head3 How method modifiers work?
1585 Method modifiers work by wrapping the original method and then
1586 replacing it in the class's symbol table. The wrappers will handle
1587 calling all the modifiers in the appropriate order and preserving the
1588 calling context for the original method.
1590 The return values of C<before> and C<after> modifiers are
1591 ignored. This is because their purpose is B<not> to filter the input
1592 and output of the primary method (this is done with an I<around>
1595 This may seem like an odd restriction to some, but doing this allows
1596 for simple code to be added at the beginning or end of a method call
1597 without altering the function of the wrapped method or placing any
1598 extra responsibility on the code of the modifier.
1600 Of course if you have more complex needs, you can use the C<around>
1601 modifier which allows you to change both the parameters passed to the
1602 wrapped method, as well as its return value.
1604 Before and around modifiers are called in last-defined-first-called
1605 order, while after modifiers are called in first-defined-first-called
1606 order. So the call tree might looks something like this:
1618 =head3 What is the performance impact?
1620 Of course there is a performance cost associated with method
1621 modifiers, but we have made every effort to make that cost directly
1622 proportional to the number of modifier features you utilize.
1624 The wrapping method does it's best to B<only> do as much work as it
1625 absolutely needs to. In order to do this we have moved some of the
1626 performance costs to set-up time, where they are easier to amortize.
1628 All this said, our benchmarks have indicated the following:
1630 simple wrapper with no modifiers 100% slower
1631 simple wrapper with simple before modifier 400% slower
1632 simple wrapper with simple after modifier 450% slower
1633 simple wrapper with simple around modifier 500-550% slower
1634 simple wrapper with all 3 modifiers 1100% slower
1636 These numbers may seem daunting, but you must remember, every feature
1637 comes with some cost. To put things in perspective, just doing a
1638 simple C<AUTOLOAD> which does nothing but extract the name of the
1639 method called and return it costs about 400% over a normal method
1644 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1646 This wraps the specified method with the supplied subroutine
1647 reference. The modifier will be called as a method itself, and will
1648 receive the same arguments as are passed to the method.
1650 When the modifier exits, the wrapped method will be called.
1652 The return value of the modifier will be ignored.
1654 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1656 This wraps the specified method with the supplied subroutine
1657 reference. The modifier will be called as a method itself, and will
1658 receive the same arguments as are passed to the method.
1660 When the wrapped methods exits, the modifier will be called.
1662 The return value of the modifier will be ignored.
1664 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1666 This wraps the specified method with the supplied subroutine
1669 The first argument passed to the modifier will be a subroutine
1670 reference to the wrapped method. The second argument is the object,
1671 and after that come any arguments passed when the method is called.
1673 The around modifier can choose to call the original method, as well as
1674 what arguments to pass if it does so.
1676 The return value of the modifier is what will be seen by the caller.
1680 =head2 Introspection
1684 =item B<< Class::MOP::Class->meta >>
1686 This will return a L<Class::MOP::Class> instance for this class.
1688 It should also be noted that L<Class::MOP> will actually bootstrap
1689 this module by installing a number of attribute meta-objects into its
1696 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1698 =head1 COPYRIGHT AND LICENSE
1700 Copyright 2006-2009 by Infinity Interactive, Inc.
1702 L<http://www.iinteractive.com>
1704 This library is free software; you can redistribute it and/or modify
1705 it under the same terms as Perl itself.