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 = '0.93';
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,
125 # inherited from Class::MOP::Module
127 'authority' => \undef,
129 # defined in Class::MOP::Class
130 '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});
328 # all these attribute readers will be bootstrapped
329 # away in the Class::MOP bootstrap section
331 sub get_attribute_map { $_[0]->{'attributes'} }
332 sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
333 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
334 sub immutable_trait { $_[0]->{'immutable_trait'} }
335 sub constructor_class { $_[0]->{'constructor_class'} }
336 sub constructor_name { $_[0]->{'constructor_name'} }
337 sub destructor_class { $_[0]->{'destructor_class'} }
339 # Instance Construction & Cloning
345 # we need to protect the integrity of the
346 # Class::MOP::Class singletons here, so we
347 # delegate this to &construct_class_instance
348 # which will deal with the singletons
349 return $class->_construct_class_instance(@_)
350 if $class->name->isa('Class::MOP::Class');
351 return $class->_construct_instance(@_);
354 sub _construct_instance {
356 my $params = @_ == 1 ? $_[0] : {@_};
357 my $meta_instance = $class->get_meta_instance();
359 # the code below is almost certainly incorrect
360 # but this is foreign inheritance, so we might
361 # have to kludge it in the end.
362 my $instance = $params->{__INSTANCE__} || $meta_instance->create_instance();
363 foreach my $attr ($class->get_all_attributes()) {
364 $attr->initialize_instance_slot($meta_instance, $instance, $params);
367 # this will only work for a HASH instance type
368 if ($class->is_anon_class) {
369 (reftype($instance) eq 'HASH')
370 || confess "Currently only HASH based instances are supported with instance of anon-classes";
372 # At some point we should make this official
373 # as a reserved slot name, but right now I am
374 # going to keep it here.
375 # my $RESERVED_MOP_SLOT = '__MOP__';
376 $instance->{'__MOP__'} = $class;
382 sub get_meta_instance {
384 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
387 sub _create_meta_instance {
390 my $instance = $self->instance_metaclass->new(
391 associated_metaclass => $self,
392 attributes => [ $self->get_all_attributes() ],
395 $self->add_meta_instance_dependencies()
396 if $instance->is_dependent_on_superclasses();
403 my $instance = shift;
404 (blessed($instance) && $instance->isa($class->name))
405 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
408 # we need to protect the integrity of the
409 # Class::MOP::Class singletons here, they
410 # should not be cloned.
411 return $instance if $instance->isa('Class::MOP::Class');
412 $class->_clone_instance($instance, @_);
415 sub _clone_instance {
416 my ($class, $instance, %params) = @_;
418 || confess "You can only clone instances, ($instance) is not a blessed instance";
419 my $meta_instance = $class->get_meta_instance();
420 my $clone = $meta_instance->clone_instance($instance);
421 foreach my $attr ($class->get_all_attributes()) {
422 if ( defined( my $init_arg = $attr->init_arg ) ) {
423 if (exists $params{$init_arg}) {
424 $attr->set_value($clone, $params{$init_arg});
431 sub rebless_instance {
432 my ($self, $instance, %params) = @_;
434 my $old_metaclass = Class::MOP::class_of($instance);
436 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
437 $self->name->isa($old_class)
438 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
440 $old_metaclass->rebless_instance_away($instance, $self, %params)
443 my $meta_instance = $self->get_meta_instance();
446 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
447 $meta_instance->rebless_instance_structure($_[1], $self);
449 foreach my $attr ( $self->get_all_attributes ) {
450 if ( $attr->has_value($instance) ) {
451 if ( defined( my $init_arg = $attr->init_arg ) ) {
452 $params{$init_arg} = $attr->get_value($instance)
453 unless exists $params{$init_arg};
456 $attr->set_value($instance, $attr->get_value($instance));
461 foreach my $attr ($self->get_all_attributes) {
462 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
468 sub rebless_instance_away {
469 # this intentionally does nothing, it is just a hook
476 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
479 @{$self->get_package_symbol($var_spec)} = @supers;
482 # on 5.8 and below, we need to call
483 # a method to get Perl to detect
484 # a cycle in the class hierarchy
485 my $class = $self->name;
489 # we need to check the metaclass
490 # compatibility here so that we can
491 # be sure that the superclass is
492 # not potentially creating an issues
493 # we don't know about
495 $self->_check_metaclass_compatibility();
496 $self->_superclasses_updated();
498 @{$self->get_package_symbol($var_spec)};
501 sub _superclasses_updated {
503 $self->update_meta_instance_dependencies();
508 my $super_class = $self->name;
510 return @{ $super_class->mro::get_isarev() };
513 sub direct_subclasses {
515 my $super_class = $self->name;
520 } Class::MOP::Class->initialize($_)->superclasses
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()
565 my $fetch_and_prepare_method = sub {
566 my ($self, $method_name) = @_;
567 my $wrapped_metaclass = $self->wrapped_method_metaclass;
569 my $method = $self->get_method($method_name);
570 # if we dont have local ...
572 # try to find the next method
573 $method = $self->find_next_method_by_name($method_name);
574 # die if it does not exist
576 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
577 # and now make sure to wrap it
578 # even if it is already wrapped
579 # because we need a new sub ref
580 $method = $wrapped_metaclass->wrap($method,
581 package_name => $self->name,
582 name => $method_name,
586 # now make sure we wrap it properly
587 $method = $wrapped_metaclass->wrap($method,
588 package_name => $self->name,
589 name => $method_name,
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 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 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 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.
640 sub find_method_by_name {
641 my ($self, $method_name) = @_;
642 (defined $method_name && $method_name)
643 || confess "You must define a method name to find";
644 foreach my $class ($self->linearized_isa) {
645 my $method = $self->initialize($class)->get_method($method_name);
646 return $method if defined $method;
651 sub get_all_methods {
655 for my $class ( reverse $self->linearized_isa ) {
656 my $meta = $self->initialize($class);
658 $methods{$_} = $meta->get_method($_)
659 for $meta->get_method_list;
662 return values %methods;
665 sub get_all_method_names {
668 return grep { !$uniq{$_}++ } map { $self->initialize($_)->get_method_list } $self->linearized_isa;
671 sub find_all_methods_by_name {
672 my ($self, $method_name) = @_;
673 (defined $method_name && $method_name)
674 || confess "You must define a method name to find";
676 foreach my $class ($self->linearized_isa) {
677 # fetch the meta-class ...
678 my $meta = $self->initialize($class);
680 name => $method_name,
682 code => $meta->get_method($method_name)
683 } if $meta->has_method($method_name);
688 sub find_next_method_by_name {
689 my ($self, $method_name) = @_;
690 (defined $method_name && $method_name)
691 || confess "You must define a method name to find";
692 my @cpl = $self->linearized_isa;
693 shift @cpl; # discard ourselves
694 foreach my $class (@cpl) {
695 my $method = $self->initialize($class)->get_method($method_name);
696 return $method if defined $method;
705 # either we have an attribute object already
706 # or we need to create one from the args provided
707 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
708 # make sure it is derived from the correct type though
709 ($attribute->isa('Class::MOP::Attribute'))
710 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
712 # first we attach our new attribute
713 # because it might need certain information
714 # about the class which it is attached to
715 $attribute->attach_to_class($self);
717 my $attr_name = $attribute->name;
719 # then we remove attributes of a conflicting
720 # name here so that we can properly detach
721 # the old attr object, and remove any
722 # accessors it would have generated
723 if ( $self->has_attribute($attr_name) ) {
724 $self->remove_attribute($attr_name);
726 $self->invalidate_meta_instances();
729 # get our count of previously inserted attributes and
730 # increment by one so this attribute knows its order
731 my $order = (scalar keys %{$self->get_attribute_map});
732 $attribute->_set_insertion_order($order);
734 # then onto installing the new accessors
735 $self->get_attribute_map->{$attr_name} = $attribute;
737 # invalidate package flag here
741 eval { $attribute->install_accessors() };
745 $self->remove_attribute($attr_name);
752 sub update_meta_instance_dependencies {
755 if ( $self->{meta_instance_dependencies} ) {
756 return $self->add_meta_instance_dependencies;
760 sub add_meta_instance_dependencies {
763 $self->remove_meta_instance_dependencies;
765 my @attrs = $self->get_all_attributes();
768 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
770 foreach my $class ( @classes ) {
771 $class->add_dependent_meta_instance($self);
774 $self->{meta_instance_dependencies} = \@classes;
777 sub remove_meta_instance_dependencies {
780 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
781 foreach my $class ( @$classes ) {
782 $class->remove_dependent_meta_instance($self);
792 sub add_dependent_meta_instance {
793 my ( $self, $metaclass ) = @_;
794 push @{ $self->{dependent_meta_instances} }, $metaclass;
797 sub remove_dependent_meta_instance {
798 my ( $self, $metaclass ) = @_;
799 my $name = $metaclass->name;
800 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
803 sub invalidate_meta_instances {
805 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
808 sub invalidate_meta_instance {
810 undef $self->{_meta_instance};
814 my ($self, $attribute_name) = @_;
815 (defined $attribute_name)
816 || confess "You must define an attribute name";
817 exists $self->get_attribute_map->{$attribute_name};
821 my ($self, $attribute_name) = @_;
822 (defined $attribute_name)
823 || confess "You must define an attribute name";
824 return $self->get_attribute_map->{$attribute_name}
826 # this will return undef anyway, so no need ...
827 # if $self->has_attribute($attribute_name);
831 sub remove_attribute {
832 my ($self, $attribute_name) = @_;
833 (defined $attribute_name)
834 || confess "You must define an attribute name";
835 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
836 return unless defined $removed_attribute;
837 delete $self->get_attribute_map->{$attribute_name};
838 $self->invalidate_meta_instances();
839 $removed_attribute->remove_accessors();
840 $removed_attribute->detach_from_class();
841 return $removed_attribute;
844 sub get_attribute_list {
846 keys %{$self->get_attribute_map};
849 sub get_all_attributes {
851 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
852 return values %attrs;
855 sub find_attribute_by_name {
856 my ($self, $attr_name) = @_;
857 foreach my $class ($self->linearized_isa) {
858 # fetch the meta-class ...
859 my $meta = $self->initialize($class);
860 return $meta->get_attribute($attr_name)
861 if $meta->has_attribute($attr_name);
866 # check if we can reinitialize
870 # if any local attr is defined
871 return if $self->get_attribute_list;
873 # or any non-declared methods
874 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
875 return if $method->isa("Class::MOP::Method::Generated");
876 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
885 sub is_immutable { 0 }
887 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
889 sub _immutable_options {
890 my ( $self, @args ) = @_;
893 inline_accessors => 1,
894 inline_constructor => 1,
895 inline_destructor => 0,
897 immutable_trait => $self->immutable_trait,
898 constructor_name => $self->constructor_name,
899 constructor_class => $self->constructor_class,
900 destructor_class => $self->destructor_class,
906 my ( $self, @args ) = @_;
908 if ( $self->is_mutable ) {
909 $self->_initialize_immutable( $self->_immutable_options(@args) );
910 $self->_rebless_as_immutable(@args);
921 if ( $self->is_immutable ) {
922 my @args = $self->immutable_options;
923 $self->_rebless_as_mutable();
924 $self->_remove_inlined_code(@args);
925 delete $self->{__immutable};
933 sub _rebless_as_immutable {
934 my ( $self, @args ) = @_;
936 $self->{__immutable}{original_class} = ref $self;
938 bless $self => $self->_immutable_metaclass(@args);
941 sub _immutable_metaclass {
942 my ( $self, %args ) = @_;
944 if ( my $class = $args{immutable_metaclass} ) {
948 my $trait = $args{immutable_trait} = $self->immutable_trait
949 || confess "no immutable trait specified for $self";
951 my $meta = $self->meta;
952 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
956 if ( $meta_attr and $trait eq $meta_attr->default ) {
957 # if the trait is the same as the default we try and pick a
958 # predictable name for the immutable metaclass
959 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
962 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
963 $trait, 'ForMetaClass', ref($self);
967 if Class::MOP::is_class_loaded($class_name);
969 # If the metaclass is a subclass of CMOP::Class which has had
970 # metaclass roles applied (via Moose), then we want to make sure
971 # that we preserve that anonymous class (see Fey::ORM for an
972 # example of where this matters).
974 = $meta->is_immutable
975 ? $meta->_get_mutable_metaclass_name
978 my $immutable_meta = $meta_name->create(
980 superclasses => [ ref $self ],
983 Class::MOP::load_class($trait);
984 for my $meth ( Class::MOP::Class->initialize($trait)->get_all_methods ) {
985 my $meth_name = $meth->name;
987 if ( $immutable_meta->find_method_by_name( $meth_name ) ) {
988 $immutable_meta->add_around_method_modifier( $meth_name, $meth->body );
991 $immutable_meta->add_method( $meth_name, $meth->clone );
995 $immutable_meta->make_immutable(
996 inline_constructor => 0,
997 inline_accessors => 0,
1003 sub _remove_inlined_code {
1006 $self->remove_method( $_->name ) for $self->_inlined_methods;
1008 delete $self->{__immutable}{inlined_methods};
1011 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1013 sub _add_inlined_method {
1014 my ( $self, $method ) = @_;
1016 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1019 sub _initialize_immutable {
1020 my ( $self, %args ) = @_;
1022 $self->{__immutable}{options} = \%args;
1023 $self->_install_inlined_code(%args);
1026 sub _install_inlined_code {
1027 my ( $self, %args ) = @_;
1030 $self->_inline_accessors(%args) if $args{inline_accessors};
1031 $self->_inline_constructor(%args) if $args{inline_constructor};
1032 $self->_inline_destructor(%args) if $args{inline_destructor};
1035 sub _rebless_as_mutable {
1038 bless $self, $self->_get_mutable_metaclass_name;
1043 sub _inline_accessors {
1046 foreach my $attr_name ( $self->get_attribute_list ) {
1047 $self->get_attribute($attr_name)->install_accessors(1);
1051 sub _inline_constructor {
1052 my ( $self, %args ) = @_;
1054 my $name = $args{constructor_name};
1056 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1057 my $class = $self->name;
1058 warn "Not inlining a constructor for $class since it defines"
1059 . " its own constructor.\n"
1060 . "If you are certain you don't need to inline your"
1061 . " constructor, specify inline_constructor => 0 in your"
1062 . " call to $class->meta->make_immutable\n";
1066 my $constructor_class = $args{constructor_class};
1068 Class::MOP::load_class($constructor_class);
1070 my $constructor = $constructor_class->new(
1074 package_name => $self->name,
1078 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1079 $self->add_method( $name => $constructor );
1080 $self->_add_inlined_method($constructor);
1084 sub _inline_destructor {
1085 my ( $self, %args ) = @_;
1087 ( exists $args{destructor_class} && defined $args{destructor_class} )
1088 || confess "The 'inline_destructor' option is present, but "
1089 . "no destructor class was specified";
1091 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1092 my $class = $self->name;
1093 warn "Not inlining a destructor for $class since it defines"
1094 . " its own destructor.\n";
1098 my $destructor_class = $args{destructor_class};
1100 Class::MOP::load_class($destructor_class);
1102 return unless $destructor_class->is_needed($self);
1104 my $destructor = $destructor_class->new(
1107 package_name => $self->name,
1111 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1112 $self->add_method( 'DESTROY' => $destructor );
1113 $self->_add_inlined_method($destructor);
1125 Class::MOP::Class - Class Meta Object
1129 # assuming that class Foo
1130 # has been defined, you can
1132 # use this for introspection ...
1134 # add a method to Foo ...
1135 Foo->meta->add_method( 'bar' => sub {...} )
1137 # get a list of all the classes searched
1138 # the method dispatcher in the correct order
1139 Foo->meta->class_precedence_list()
1141 # remove a method from Foo
1142 Foo->meta->remove_method('bar');
1144 # or use this to actually create classes ...
1146 Class::MOP::Class->create(
1149 superclasses => ['Foo'],
1151 Class::MOP::Attribute->new('$bar'),
1152 Class::MOP::Attribute->new('$baz'),
1155 calculate_bar => sub {...},
1156 construct_baz => sub {...}
1163 The Class Protocol is the largest and most complex part of the
1164 Class::MOP meta-object protocol. It controls the introspection and
1165 manipulation of Perl 5 classes, and it can create them as well. The
1166 best way to understand what this module can do is to read the
1167 documentation for each of its methods.
1171 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1175 =head2 Class construction
1177 These methods all create new C<Class::MOP::Class> objects. These
1178 objects can represent existing classes or they can be used to create
1179 new classes from scratch.
1181 The metaclass object for a given class is a singleton. If you attempt
1182 to create a metaclass for the same class twice, you will just get the
1187 =item B<< Class::MOP::Class->create($package_name, %options) >>
1189 This method creates a new C<Class::MOP::Class> object with the given
1190 package name. It accepts a number of options:
1196 An optional version number for the newly created package.
1200 An optional authority for the newly created package.
1202 =item * superclasses
1204 An optional array reference of superclass names.
1208 An optional hash reference of methods for the class. The keys of the
1209 hash reference are method names and values are subroutine references.
1213 An optional array reference of L<Class::MOP::Attribute> objects.
1217 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1219 This method works just like C<< Class::MOP::Class->create >> but it
1220 creates an "anonymous" class. In fact, the class does have a name, but
1221 that name is a unique name generated internally by this module.
1223 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1224 parameters that C<create> accepts.
1226 Anonymous classes are destroyed once the metaclass they are attached
1227 to goes out of scope, and will be removed from Perl's internal symbol
1230 All instances of an anonymous class keep a special reference to the
1231 metaclass object, which prevents the metaclass from going out of scope
1232 while any instances exist.
1234 This only works if the instance is based on a hash reference, however.
1236 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1238 This method will initialize a C<Class::MOP::Class> object for the
1239 named package. Unlike C<create>, this method I<will not> create a new
1242 The purpose of this method is to retrieve a C<Class::MOP::Class>
1243 object for introspecting an existing class.
1245 If an existing C<Class::MOP::Class> object exists for the named
1246 package, it will be returned, and any options provided will be
1249 If the object does not yet exist, it will be created.
1251 The valid options that can be passed to this method are
1252 C<attribute_metaclass>, C<method_metaclass>,
1253 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1254 optional, and default to the appropriate class in the C<Class::MOP>
1259 =head2 Object instance construction and cloning
1261 These methods are all related to creating and/or cloning object
1266 =item B<< $metaclass->clone_object($instance, %params) >>
1268 This method clones an existing object instance. Any parameters you
1269 provide are will override existing attribute values in the object.
1271 This is a convenience method for cloning an object instance, then
1272 blessing it into the appropriate package.
1274 You could implement a clone method in your class, using this method:
1277 my ($self, %params) = @_;
1278 $self->meta->clone_object($self, %params);
1281 =item B<< $metaclass->rebless_instance($instance, %params) >>
1283 This method changes the class of C<$instance> to the metaclass's class.
1285 You can only rebless an instance into a subclass of its current
1286 class. If you pass any additional parameters, these will be treated
1287 like constructor parameters and used to initialize the object's
1288 attributes. Any existing attributes that are already set will be
1291 Before reblessing the instance, this method will call
1292 C<rebless_instance_away> on the instance's current metaclass. This method
1293 will be passed the instance, the new metaclass, and any parameters
1294 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1295 does nothing; it is merely a hook.
1297 =item B<< $metaclass->new_object(%params) >>
1299 This method is used to create a new object of the metaclass's
1300 class. Any parameters you provide are used to initialize the
1301 instance's attributes. A special C<__INSTANCE__> key can be passed to
1302 provide an already generated instance, rather than having Class::MOP
1303 generate it for you. This is mostly useful for using Class::MOP with
1304 foreign classes which generate instances using their own constructors.
1306 =item B<< $metaclass->instance_metaclass >>
1308 Returns the class name of the instance metaclass. See
1309 L<Class::MOP::Instance> for more information on the instance
1312 =item B<< $metaclass->get_meta_instance >>
1314 Returns an instance of the C<instance_metaclass> to be used in the
1315 construction of a new instance of the class.
1319 =head2 Informational predicates
1321 These are a few predicate methods for asking information about the
1326 =item B<< $metaclass->is_anon_class >>
1328 This returns true if the class was created by calling C<<
1329 Class::MOP::Class->create_anon_class >>.
1331 =item B<< $metaclass->is_mutable >>
1333 This returns true if the class is still mutable.
1335 =item B<< $metaclass->is_immutable >>
1337 This returns true if the class has been made immutable.
1339 =item B<< $metaclass->is_pristine >>
1341 A class is I<not> pristine if it has non-inherited attributes or if it
1342 has any generated methods.
1346 =head2 Inheritance Relationships
1350 =item B<< $metaclass->superclasses(@superclasses) >>
1352 This is a read-write accessor which represents the superclass
1353 relationships of the metaclass's class.
1355 This is basically sugar around getting and setting C<@ISA>.
1357 =item B<< $metaclass->class_precedence_list >>
1359 This returns a list of all of the class's ancestor classes. The
1360 classes are returned in method dispatch order.
1362 =item B<< $metaclass->linearized_isa >>
1364 This returns a list based on C<class_precedence_list> but with all
1367 =item B<< $metaclass->subclasses >>
1369 This returns a list of all subclasses for this class, even indirect
1372 =item B<< $metaclass->direct_subclasses >>
1374 This returns a list of immediate subclasses for this class, which does not
1375 include indirect subclasses.
1379 =head2 Method introspection
1381 See L<Class::MOP::Package/Method introspection and creation> for
1382 methods that operate only on the current class. Class::MOP::Class adds
1383 introspection capabilities that take inheritance into account.
1387 =item B<< $metaclass->get_all_methods >>
1389 This will traverse the inheritance hierarchy and return a list of all
1390 the L<Class::MOP::Method> objects for this class and its parents.
1392 =item B<< $metaclass->find_method_by_name($method_name) >>
1394 This will return a L<Class::MOP::Method> for the specified
1395 C<$method_name>. If the class does not have the specified method, it
1398 Unlike C<get_method>, this method I<will> look for the named method in
1401 =item B<< $metaclass->get_all_method_names >>
1403 This will return a list of method I<names> for all of this class's
1404 methods, including inherited methods.
1406 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1408 This method looks for the named method in the class and all of its
1409 parents. It returns every matching method it finds in the inheritance
1410 tree, so it returns a list of methods.
1412 Each method is returned as a hash reference with three keys. The keys
1413 are C<name>, C<class>, and C<code>. The C<code> key has a
1414 L<Class::MOP::Method> object as its value.
1416 The list of methods is distinct.
1418 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1420 This method returns the first method in any superclass matching the
1421 given name. It is effectively the method that C<SUPER::$method_name>
1426 =head2 Attribute introspection and creation
1428 Because Perl 5 does not have a core concept of attributes in classes,
1429 we can only return information about attributes which have been added
1430 via this class's methods. We cannot discover information about
1431 attributes which are defined in terms of "regular" Perl 5 methods.
1435 =item B<< $metaclass->get_attribute($attribute_name) >>
1437 This will return a L<Class::MOP::Attribute> for the specified
1438 C<$attribute_name>. If the class does not have the specified
1439 attribute, it returns C<undef>.
1441 NOTE that get_attribute does not search superclasses, for that you
1442 need to use C<find_attribute_by_name>.
1444 =item B<< $metaclass->has_attribute($attribute_name) >>
1446 Returns a boolean indicating whether or not the class defines the
1447 named attribute. It does not include attributes inherited from parent
1450 =item B<< $metaclass->get_attribute_map >>
1452 Returns a hash reference representing the attributes defined in this
1453 class. The keys are attribute names and the values are
1454 L<Class::MOP::Attribute> objects.
1456 =item B<< $metaclass->get_attribute_list >>
1458 This will return a list of attributes I<names> for all attributes
1459 defined in this class.
1461 =item B<< $metaclass->get_all_attributes >>
1463 This will traverse the inheritance hierarchy and return a list of all
1464 the L<Class::MOP::Attribute> objects for this class and its parents.
1466 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1468 This will return a L<Class::MOP::Attribute> for the specified
1469 C<$attribute_name>. If the class does not have the specified
1470 attribute, it returns C<undef>.
1472 Unlike C<get_attribute>, this attribute I<will> look for the named
1473 attribute in superclasses.
1475 =item B<< $metaclass->add_attribute(...) >>
1477 This method accepts either an existing L<Class::MOP::Attribute>
1478 object or parameters suitable for passing to that class's C<new>
1481 The attribute provided will be added to the class.
1483 Any accessor methods defined by the attribute will be added to the
1484 class when the attribute is added.
1486 If an attribute of the same name already exists, the old attribute
1487 will be removed first.
1489 =item B<< $metaclass->remove_attribute($attribute_name) >>
1491 This will remove the named attribute from the class, and
1492 L<Class::MOP::Attribute> object.
1494 Removing an attribute also removes any accessor methods defined by the
1497 However, note that removing an attribute will only affect I<future>
1498 object instances created for this class, not existing instances.
1500 =item B<< $metaclass->attribute_metaclass >>
1502 Returns the class name of the attribute metaclass for this class. By
1503 default, this is L<Class::MOP::Attribute>.
1507 =head2 Class Immutability
1509 Making a class immutable "freezes" the class definition. You can no
1510 longer call methods which alter the class, such as adding or removing
1511 methods or attributes.
1513 Making a class immutable lets us optimize the class by inlining some
1514 methods, and also allows us to optimize some methods on the metaclass
1517 After immutabilization, the metaclass object will cache most informational
1518 methods that returns information about methods or attributes. Methods which
1519 would alter the class, such as C<add_attribute> and C<add_method>, will
1520 throw an error on an immutable metaclass object.
1522 The immutabilization system in L<Moose> takes much greater advantage
1523 of the inlining features than Class::MOP itself does.
1527 =item B<< $metaclass->make_immutable(%options) >>
1529 This method will create an immutable transformer and use it to make
1530 the class and its metaclass object immutable.
1532 This method accepts the following options:
1536 =item * inline_accessors
1538 =item * inline_constructor
1540 =item * inline_destructor
1542 These are all booleans indicating whether the specified method(s)
1545 By default, accessors and the constructor are inlined, but not the
1548 =item * immutable_trait
1550 The name of a class which will be used as a parent class for the
1551 metaclass object being made immutable. This "trait" implements the
1552 post-immutability functionality of the metaclass (but not the
1553 transformation itself).
1555 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1557 =item * constructor_name
1559 This is the constructor method name. This defaults to "new".
1561 =item * constructor_class
1563 The name of the method metaclass for constructors. It will be used to
1564 generate the inlined constructor. This defaults to
1565 "Class::MOP::Method::Constructor".
1567 =item * replace_constructor
1569 This is a boolean indicating whether an existing constructor should be
1570 replaced when inlining a constructor. This defaults to false.
1572 =item * destructor_class
1574 The name of the method metaclass for destructors. It will be used to
1575 generate the inlined destructor. This defaults to
1576 "Class::MOP::Method::Denstructor".
1578 =item * replace_destructor
1580 This is a boolean indicating whether an existing destructor should be
1581 replaced when inlining a destructor. This defaults to false.
1585 =item B<< $metaclass->immutable_options >>
1587 Returns a hash of the options used when making the class immutable, including
1588 both defaults and anything supplied by the user in the call to C<<
1589 $metaclass->make_immutable >>. This is useful if you need to temporarily make
1590 a class mutable and then restore immutability as it was before.
1592 =item B<< $metaclass->make_mutable >>
1594 Calling this method reverse the immutabilization transformation.
1598 =head2 Method Modifiers
1600 Method modifiers are hooks which allow a method to be wrapped with
1601 I<before>, I<after> and I<around> method modifiers. Every time a
1602 method is called, its modifiers are also called.
1604 A class can modify its own methods, as well as methods defined in
1607 =head3 How method modifiers work?
1609 Method modifiers work by wrapping the original method and then
1610 replacing it in the class's symbol table. The wrappers will handle
1611 calling all the modifiers in the appropriate order and preserving the
1612 calling context for the original method.
1614 The return values of C<before> and C<after> modifiers are
1615 ignored. This is because their purpose is B<not> to filter the input
1616 and output of the primary method (this is done with an I<around>
1619 This may seem like an odd restriction to some, but doing this allows
1620 for simple code to be added at the beginning or end of a method call
1621 without altering the function of the wrapped method or placing any
1622 extra responsibility on the code of the modifier.
1624 Of course if you have more complex needs, you can use the C<around>
1625 modifier which allows you to change both the parameters passed to the
1626 wrapped method, as well as its return value.
1628 Before and around modifiers are called in last-defined-first-called
1629 order, while after modifiers are called in first-defined-first-called
1630 order. So the call tree might looks something like this:
1642 =head3 What is the performance impact?
1644 Of course there is a performance cost associated with method
1645 modifiers, but we have made every effort to make that cost directly
1646 proportional to the number of modifier features you use.
1648 The wrapping method does its best to B<only> do as much work as it
1649 absolutely needs to. In order to do this we have moved some of the
1650 performance costs to set-up time, where they are easier to amortize.
1652 All this said, our benchmarks have indicated the following:
1654 simple wrapper with no modifiers 100% slower
1655 simple wrapper with simple before modifier 400% slower
1656 simple wrapper with simple after modifier 450% slower
1657 simple wrapper with simple around modifier 500-550% slower
1658 simple wrapper with all 3 modifiers 1100% slower
1660 These numbers may seem daunting, but you must remember, every feature
1661 comes with some cost. To put things in perspective, just doing a
1662 simple C<AUTOLOAD> which does nothing but extract the name of the
1663 method called and return it costs about 400% over a normal method
1668 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1670 This wraps the specified method with the supplied subroutine
1671 reference. The modifier will be called as a method itself, and will
1672 receive the same arguments as are passed to the method.
1674 When the modifier exits, the wrapped method will be called.
1676 The return value of the modifier will be ignored.
1678 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1680 This wraps the specified method with the supplied subroutine
1681 reference. The modifier will be called as a method itself, and will
1682 receive the same arguments as are passed to the method.
1684 When the wrapped methods exits, the modifier will be called.
1686 The return value of the modifier will be ignored.
1688 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1690 This wraps the specified method with the supplied subroutine
1693 The first argument passed to the modifier will be a subroutine
1694 reference to the wrapped method. The second argument is the object,
1695 and after that come any arguments passed when the method is called.
1697 The around modifier can choose to call the original method, as well as
1698 what arguments to pass if it does so.
1700 The return value of the modifier is what will be seen by the caller.
1704 =head2 Introspection
1708 =item B<< Class::MOP::Class->meta >>
1710 This will return a L<Class::MOP::Class> instance for this class.
1712 It should also be noted that L<Class::MOP> will actually bootstrap
1713 this module by installing a number of attribute meta-objects into its
1720 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1722 =head1 COPYRIGHT AND LICENSE
1724 Copyright 2006-2009 by Infinity Interactive, Inc.
1726 L<http://www.iinteractive.com>
1728 This library is free software; you can redistribute it and/or modify
1729 it under the same terms as Perl itself.