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 = '0.90';
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 sub construct_class_instance {
45 Carp::cluck('The construct_class_instance method has been made private.'
46 . " The public version is deprecated and will be removed in a future release.\n");
47 shift->_construct_class_instance(@_);
50 # NOTE: (meta-circularity)
51 # this is a special form of _construct_instance
52 # (see below), which is used to construct class
53 # meta-object instances for any Class::MOP::*
54 # class. All other classes will use the more
55 # normal &construct_instance.
56 sub _construct_class_instance {
58 my $options = @_ == 1 ? $_[0] : {@_};
59 my $package_name = $options->{package};
60 (defined $package_name && $package_name)
61 || confess "You must pass a package name";
63 # return the metaclass if we have it cached,
64 # and it is still defined (it has not been
65 # reaped by DESTROY yet, which can happen
66 # annoyingly enough during global destruction)
68 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
73 # we need to deal with the possibility
74 # of class immutability here, and then
75 # get the name of the class appropriately
77 ? ($class->is_immutable
78 ? $class->get_mutable_metaclass_name()
82 # now create the metaclass
84 if ($class eq 'Class::MOP::Class') {
85 $meta = $class->_new($options);
89 # it is safe to use meta here because
90 # class will always be a subclass of
91 # Class::MOP::Class, which defines meta
92 $meta = $class->meta->_construct_instance($options)
95 # and check the metaclass compatibility
96 $meta->_check_metaclass_compatibility();
98 Class::MOP::store_metaclass_by_name($package_name, $meta);
101 # we need to weaken any anon classes
102 # so that they can call DESTROY properly
103 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
111 return Class::MOP::Class->initialize($class)->new_object(@_)
112 if $class ne __PACKAGE__;
114 my $options = @_ == 1 ? $_[0] : {@_};
117 # inherited from Class::MOP::Package
118 'package' => $options->{package},
121 # since the following attributes will
122 # actually be loaded from the symbol
123 # table, and actually bypass the instance
124 # entirely, we can just leave these things
125 # listed here for reference, because they
126 # should not actually have a value associated
128 'namespace' => \undef,
130 # inherited from Class::MOP::Module
132 'authority' => \undef,
134 # defined in Class::MOP::Class
135 'superclasses' => \undef,
139 'attribute_metaclass' =>
140 ( $options->{'attribute_metaclass'} || 'Class::MOP::Attribute' ),
141 'method_metaclass' =>
142 ( $options->{'method_metaclass'} || 'Class::MOP::Method' ),
143 'wrapped_method_metaclass' => (
144 $options->{'wrapped_method_metaclass'}
145 || 'Class::MOP::Method::Wrapped'
147 'instance_metaclass' =>
148 ( $options->{'instance_metaclass'} || 'Class::MOP::Instance' ),
149 'immutable_trait' => (
150 $options->{'immutable_trait'}
151 || 'Class::MOP::Class::Immutable::Trait'
153 'constructor_name' => ( $options->{constructor_name} || 'new' ),
154 'constructor_class' => (
155 $options->{constructor_class} || 'Class::MOP::Method::Constructor'
157 'destructor_class' => $options->{destructor_class},
161 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
162 sub update_package_cache_flag {
165 # we can manually update the cache number
166 # since we are actually adding the method
167 # to our cache as well. This avoids us
168 # having to regenerate the method_map.
170 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
174 sub check_metaclass_compatibility {
175 Carp::cluck('The check_metaclass_compatibility method has been made private.'
176 . " The public version is deprecated and will be removed in a future release.\n");
177 shift->_check_metaclass_compatibility(@_);
180 sub _check_metaclass_compatibility {
183 # this is always okay ...
184 return if ref($self) eq 'Class::MOP::Class' &&
185 $self->instance_metaclass eq 'Class::MOP::Instance';
187 my @class_list = $self->linearized_isa;
188 shift @class_list; # shift off $self->name
190 foreach my $superclass_name (@class_list) {
191 my $super_meta = Class::MOP::get_metaclass_by_name($superclass_name) || next;
194 # we need to deal with the possibility
195 # of class immutability here, and then
196 # get the name of the class appropriately
198 = $super_meta->is_immutable
199 ? $super_meta->get_mutable_metaclass_name()
202 ($self->isa($super_meta_type))
203 || confess "The metaclass of " . $self->name . " ("
204 . (ref($self)) . ")" . " is not compatible with the " .
205 "metaclass of its superclass, ".$superclass_name . " ("
206 . ($super_meta_type) . ")";
208 # we also need to check that instance metaclasses
209 # are compatibile in the same the class.
210 ($self->instance_metaclass->isa($super_meta->instance_metaclass))
211 || confess "The instance metaclass for " . $self->name . " (" . ($self->instance_metaclass) . ")" .
212 " is not compatible with the " .
213 "instance metaclass of its superclass, " . $superclass_name . " (" . ($super_meta->instance_metaclass) . ")";
221 # this should be sufficient, if you have a
222 # use case where it is not, write a test and
224 my $ANON_CLASS_SERIAL = 0;
227 # we need a sufficiently annoying prefix
228 # this should suffice for now, this is
229 # used in a couple of places below, so
230 # need to put it up here for now.
231 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
235 no warnings 'uninitialized';
236 $self->name =~ /^$ANON_CLASS_PREFIX/o;
239 sub create_anon_class {
240 my ($class, %options) = @_;
241 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
242 return $class->create($package_name, %options);
246 # this will only get called for
247 # anon-classes, all other calls
248 # are assumed to occur during
249 # global destruction and so don't
250 # really need to be handled explicitly
254 return if in_global_destruction(); # it'll happen soon anyway and this just makes things more complicated
256 no warnings 'uninitialized';
257 my $name = $self->name;
258 return unless $name =~ /^$ANON_CLASS_PREFIX/o;
259 # Moose does a weird thing where it replaces the metaclass for
260 # class when fixing metaclass incompatibility. In that case,
261 # we don't want to clean out the namespace now. We can detect
262 # that because Moose will explicitly update the singleton
263 # cache in Class::MOP.
264 my $current_meta = Class::MOP::get_metaclass_by_name($name);
265 return if $current_meta ne $self;
267 my ($serial_id) = ($name =~ /^$ANON_CLASS_PREFIX(\d+)/o);
269 @{$name . '::ISA'} = ();
270 %{$name . '::'} = ();
271 delete ${$ANON_CLASS_PREFIX}{$serial_id . '::'};
273 Class::MOP::remove_metaclass_by_name($name);
278 # creating classes with MOP ...
281 my ( $class, @args ) = @_;
283 unshift @args, 'package' if @args % 2 == 1;
285 my (%options) = @args;
286 my $package_name = $options{package};
288 (ref $options{superclasses} eq 'ARRAY')
289 || confess "You must pass an ARRAY ref of superclasses"
290 if exists $options{superclasses};
292 (ref $options{attributes} eq 'ARRAY')
293 || confess "You must pass an ARRAY ref of attributes"
294 if exists $options{attributes};
296 (ref $options{methods} eq 'HASH')
297 || confess "You must pass a HASH ref of methods"
298 if exists $options{methods};
300 my (%initialize_options) = @args;
301 delete @initialize_options{qw(
309 my $meta = $class->initialize( $package_name => %initialize_options );
311 $meta->_instantiate_module( $options{version}, $options{authority} );
314 $meta->add_method('meta' => sub {
315 $class->initialize(ref($_[0]) || $_[0]);
318 $meta->superclasses(@{$options{superclasses}})
319 if exists $options{superclasses};
321 # process attributes first, so that they can
322 # install accessors, but locally defined methods
323 # can then overwrite them. It is maybe a little odd, but
324 # I think this should be the order of things.
325 if (exists $options{attributes}) {
326 foreach my $attr (@{$options{attributes}}) {
327 $meta->add_attribute($attr);
330 if (exists $options{methods}) {
331 foreach my $method_name (keys %{$options{methods}}) {
332 $meta->add_method($method_name, $options{methods}->{$method_name});
341 # all these attribute readers will be bootstrapped
342 # away in the Class::MOP bootstrap section
344 sub get_attribute_map { $_[0]->{'attributes'} }
345 sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
346 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
347 sub immutable_trait { $_[0]->{'immutable_trait'} }
348 sub constructor_class { $_[0]->{'constructor_class'} }
349 sub constructor_name { $_[0]->{'constructor_name'} }
350 sub destructor_class { $_[0]->{'destructor_class'} }
352 # Instance Construction & Cloning
358 # we need to protect the integrity of the
359 # Class::MOP::Class singletons here, so we
360 # delegate this to &construct_class_instance
361 # which will deal with the singletons
362 return $class->_construct_class_instance(@_)
363 if $class->name->isa('Class::MOP::Class');
364 return $class->_construct_instance(@_);
367 sub construct_instance {
368 Carp::cluck('The construct_instance method has been made private.'
369 . " The public version is deprecated and will be removed in a future release.\n");
370 shift->_construct_instance(@_);
373 sub _construct_instance {
375 my $params = @_ == 1 ? $_[0] : {@_};
376 my $meta_instance = $class->get_meta_instance();
378 # the code below is almost certainly incorrect
379 # but this is foreign inheritance, so we might
380 # have to kludge it in the end.
381 my $instance = $params->{__INSTANCE__} || $meta_instance->create_instance();
382 foreach my $attr ($class->get_all_attributes()) {
383 $attr->initialize_instance_slot($meta_instance, $instance, $params);
386 # this will only work for a HASH instance type
387 if ($class->is_anon_class) {
388 (reftype($instance) eq 'HASH')
389 || confess "Currently only HASH based instances are supported with instance of anon-classes";
391 # At some point we should make this official
392 # as a reserved slot name, but right now I am
393 # going to keep it here.
394 # my $RESERVED_MOP_SLOT = '__MOP__';
395 $instance->{'__MOP__'} = $class;
401 sub get_meta_instance {
403 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
406 sub create_meta_instance {
407 Carp::cluck('The create_meta_instance method has been made private.'
408 . " The public version is deprecated and will be removed in a future release.\n");
409 shift->_create_meta_instance(@_);
412 sub _create_meta_instance {
415 my $instance = $self->instance_metaclass->new(
416 associated_metaclass => $self,
417 attributes => [ $self->get_all_attributes() ],
420 $self->add_meta_instance_dependencies()
421 if $instance->is_dependent_on_superclasses();
428 my $instance = shift;
429 (blessed($instance) && $instance->isa($class->name))
430 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
433 # we need to protect the integrity of the
434 # Class::MOP::Class singletons here, they
435 # should not be cloned.
436 return $instance if $instance->isa('Class::MOP::Class');
437 $class->_clone_instance($instance, @_);
441 Carp::cluck('The clone_instance method has been made private.'
442 . " The public version is deprecated and will be removed in a future release.\n");
443 shift->_clone_instance(@_);
446 sub _clone_instance {
447 my ($class, $instance, %params) = @_;
449 || confess "You can only clone instances, ($instance) is not a blessed instance";
450 my $meta_instance = $class->get_meta_instance();
451 my $clone = $meta_instance->clone_instance($instance);
452 foreach my $attr ($class->get_all_attributes()) {
453 if ( defined( my $init_arg = $attr->init_arg ) ) {
454 if (exists $params{$init_arg}) {
455 $attr->set_value($clone, $params{$init_arg});
462 sub rebless_instance {
463 my ($self, $instance, %params) = @_;
465 my $old_metaclass = Class::MOP::class_of($instance);
467 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
468 $self->name->isa($old_class)
469 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
471 $old_metaclass->rebless_instance_away($instance, $self, %params)
474 my $meta_instance = $self->get_meta_instance();
477 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
478 $meta_instance->rebless_instance_structure($_[1], $self);
480 foreach my $attr ( $self->get_all_attributes ) {
481 if ( $attr->has_value($instance) ) {
482 if ( defined( my $init_arg = $attr->init_arg ) ) {
483 $params{$init_arg} = $attr->get_value($instance)
484 unless exists $params{$init_arg};
487 $attr->set_value($instance, $attr->get_value($instance));
492 foreach my $attr ($self->get_all_attributes) {
493 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
499 sub rebless_instance_away {
500 # this intentionally does nothing, it is just a hook
507 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
510 @{$self->get_package_symbol($var_spec)} = @supers;
513 # on 5.8 and below, we need to call
514 # a method to get Perl to detect
515 # a cycle in the class hierarchy
516 my $class = $self->name;
520 # we need to check the metaclass
521 # compatibility here so that we can
522 # be sure that the superclass is
523 # not potentially creating an issues
524 # we don't know about
526 $self->_check_metaclass_compatibility();
527 $self->_superclasses_updated();
529 @{$self->get_package_symbol($var_spec)};
532 sub _superclasses_updated {
534 $self->update_meta_instance_dependencies();
539 my $super_class = $self->name;
541 return @{ $super_class->mro::get_isarev() };
544 sub direct_subclasses {
546 my $super_class = $self->name;
551 } Class::MOP::Class->initialize($_)->superclasses
556 return @{ mro::get_linear_isa( (shift)->name ) };
559 sub class_precedence_list {
561 my $name = $self->name;
563 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
565 # We need to check for circular inheritance here
566 # if we are are not on 5.10, cause 5.8 detects it
567 # late. This will do nothing if all is well, and
568 # blow up otherwise. Yes, it's an ugly hack, better
569 # suggestions are welcome.
571 ($name || return)->isa('This is a test for circular inheritance')
574 # if our mro is c3, we can
575 # just grab the linear_isa
576 if (mro::get_mro($name) eq 'c3') {
577 return @{ mro::get_linear_isa($name) }
581 # we can't grab the linear_isa for dfs
582 # since it has all the duplicates
587 $self->initialize($_)->class_precedence_list()
588 } $self->superclasses()
596 my $fetch_and_prepare_method = sub {
597 my ($self, $method_name) = @_;
598 my $wrapped_metaclass = $self->wrapped_method_metaclass;
600 my $method = $self->get_method($method_name);
601 # if we dont have local ...
603 # try to find the next method
604 $method = $self->find_next_method_by_name($method_name);
605 # die if it does not exist
607 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
608 # and now make sure to wrap it
609 # even if it is already wrapped
610 # because we need a new sub ref
611 $method = $wrapped_metaclass->wrap($method,
612 package_name => $self->name,
613 name => $method_name,
617 # now make sure we wrap it properly
618 $method = $wrapped_metaclass->wrap($method,
619 package_name => $self->name,
620 name => $method_name,
621 ) unless $method->isa($wrapped_metaclass);
623 $self->add_method($method_name => $method);
627 sub add_before_method_modifier {
628 my ($self, $method_name, $method_modifier) = @_;
629 (defined $method_name && $method_name)
630 || confess "You must pass in a method name";
631 my $method = $fetch_and_prepare_method->($self, $method_name);
632 $method->add_before_modifier(
633 subname(':before' => $method_modifier)
637 sub add_after_method_modifier {
638 my ($self, $method_name, $method_modifier) = @_;
639 (defined $method_name && $method_name)
640 || confess "You must pass in a method name";
641 my $method = $fetch_and_prepare_method->($self, $method_name);
642 $method->add_after_modifier(
643 subname(':after' => $method_modifier)
647 sub add_around_method_modifier {
648 my ($self, $method_name, $method_modifier) = @_;
649 (defined $method_name && $method_name)
650 || confess "You must pass in a method name";
651 my $method = $fetch_and_prepare_method->($self, $method_name);
652 $method->add_around_modifier(
653 subname(':around' => $method_modifier)
658 # the methods above used to be named like this:
659 # ${pkg}::${method}:(before|after|around)
660 # but this proved problematic when using one modifier
661 # to wrap multiple methods (something which is likely
662 # to happen pretty regularly IMO). So instead of naming
663 # it like this, I have chosen to just name them purely
664 # with their modifier names, like so:
665 # :(before|after|around)
666 # The fact is that in a stack trace, it will be fairly
667 # evident from the context what method they are attached
668 # to, and so don't need the fully qualified name.
672 Carp::cluck("The alias_method method is deprecated. Use add_method instead.\n");
674 shift->add_method(@_);
677 sub find_method_by_name {
678 my ($self, $method_name) = @_;
679 (defined $method_name && $method_name)
680 || confess "You must define a method name to find";
681 foreach my $class ($self->linearized_isa) {
682 my $method = $self->initialize($class)->get_method($method_name);
683 return $method if defined $method;
688 sub get_all_methods {
690 my %methods = map { %{ $self->initialize($_)->get_method_map } } reverse $self->linearized_isa;
691 return values %methods;
694 sub compute_all_applicable_methods {
695 Carp::cluck('The compute_all_applicable_methods method is deprecated.'
696 . " Use get_all_methods instead.\n");
701 class => $_->package_name,
702 code => $_, # sigh, overloading
704 } shift->get_all_methods(@_);
707 sub get_all_method_names {
710 return grep { !$uniq{$_}++ } map { $self->initialize($_)->get_method_list } $self->linearized_isa;
713 sub find_all_methods_by_name {
714 my ($self, $method_name) = @_;
715 (defined $method_name && $method_name)
716 || confess "You must define a method name to find";
718 foreach my $class ($self->linearized_isa) {
719 # fetch the meta-class ...
720 my $meta = $self->initialize($class);
722 name => $method_name,
724 code => $meta->get_method($method_name)
725 } if $meta->has_method($method_name);
730 sub find_next_method_by_name {
731 my ($self, $method_name) = @_;
732 (defined $method_name && $method_name)
733 || confess "You must define a method name to find";
734 my @cpl = $self->linearized_isa;
735 shift @cpl; # discard ourselves
736 foreach my $class (@cpl) {
737 my $method = $self->initialize($class)->get_method($method_name);
738 return $method if defined $method;
747 # either we have an attribute object already
748 # or we need to create one from the args provided
749 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
750 # make sure it is derived from the correct type though
751 ($attribute->isa('Class::MOP::Attribute'))
752 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
754 # first we attach our new attribute
755 # because it might need certain information
756 # about the class which it is attached to
757 $attribute->attach_to_class($self);
759 my $attr_name = $attribute->name;
761 # then we remove attributes of a conflicting
762 # name here so that we can properly detach
763 # the old attr object, and remove any
764 # accessors it would have generated
765 if ( $self->has_attribute($attr_name) ) {
766 $self->remove_attribute($attr_name);
768 $self->invalidate_meta_instances();
771 # get our count of previously inserted attributes and
772 # increment by one so this attribute knows its order
773 my $order = (scalar keys %{$self->get_attribute_map});
774 $attribute->_set_insertion_order($order);
776 # then onto installing the new accessors
777 $self->get_attribute_map->{$attr_name} = $attribute;
779 # invalidate package flag here
783 eval { $attribute->install_accessors() };
787 $self->remove_attribute($attr_name);
794 sub update_meta_instance_dependencies {
797 if ( $self->{meta_instance_dependencies} ) {
798 return $self->add_meta_instance_dependencies;
802 sub add_meta_instance_dependencies {
805 $self->remove_meta_instance_dependencies;
807 my @attrs = $self->get_all_attributes();
810 my @classes = grep { not $seen{$_->name}++ } map { $_->associated_class } @attrs;
812 foreach my $class ( @classes ) {
813 $class->add_dependent_meta_instance($self);
816 $self->{meta_instance_dependencies} = \@classes;
819 sub remove_meta_instance_dependencies {
822 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
823 foreach my $class ( @$classes ) {
824 $class->remove_dependent_meta_instance($self);
834 sub add_dependent_meta_instance {
835 my ( $self, $metaclass ) = @_;
836 push @{ $self->{dependent_meta_instances} }, $metaclass;
839 sub remove_dependent_meta_instance {
840 my ( $self, $metaclass ) = @_;
841 my $name = $metaclass->name;
842 @$_ = grep { $_->name ne $name } @$_ for $self->{dependent_meta_instances};
845 sub invalidate_meta_instances {
847 $_->invalidate_meta_instance() for $self, @{ $self->{dependent_meta_instances} };
850 sub invalidate_meta_instance {
852 undef $self->{_meta_instance};
856 my ($self, $attribute_name) = @_;
857 (defined $attribute_name && $attribute_name)
858 || confess "You must define an attribute name";
859 exists $self->get_attribute_map->{$attribute_name};
863 my ($self, $attribute_name) = @_;
864 (defined $attribute_name && $attribute_name)
865 || confess "You must define an attribute name";
866 return $self->get_attribute_map->{$attribute_name}
868 # this will return undef anyway, so no need ...
869 # if $self->has_attribute($attribute_name);
873 sub remove_attribute {
874 my ($self, $attribute_name) = @_;
875 (defined $attribute_name && $attribute_name)
876 || confess "You must define an attribute name";
877 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
878 return unless defined $removed_attribute;
879 delete $self->get_attribute_map->{$attribute_name};
880 $self->invalidate_meta_instances();
881 $removed_attribute->remove_accessors();
882 $removed_attribute->detach_from_class();
883 return $removed_attribute;
886 sub get_attribute_list {
888 keys %{$self->get_attribute_map};
891 sub get_all_attributes {
893 my %attrs = map { %{ $self->initialize($_)->get_attribute_map } } reverse $self->linearized_isa;
894 return values %attrs;
897 sub compute_all_applicable_attributes {
898 Carp::cluck('The compute_all_applicable_attributes method has been deprecated.'
899 . " Use get_all_attributes instead.\n");
901 shift->get_all_attributes(@_);
904 sub find_attribute_by_name {
905 my ($self, $attr_name) = @_;
906 foreach my $class ($self->linearized_isa) {
907 # fetch the meta-class ...
908 my $meta = $self->initialize($class);
909 return $meta->get_attribute($attr_name)
910 if $meta->has_attribute($attr_name);
915 # check if we can reinitialize
919 # if any local attr is defined
920 return if $self->get_attribute_list;
922 # or any non-declared methods
923 if ( my @methods = values %{ $self->get_method_map } ) {
924 my $metaclass = $self->method_metaclass;
925 foreach my $method ( @methods ) {
926 return if $method->isa("Class::MOP::Method::Generated");
927 # FIXME do we need to enforce this too? return unless $method->isa($metaclass);
937 sub is_immutable { 0 }
939 sub _immutable_options {
940 my ( $self, @args ) = @_;
943 inline_accessors => 1,
944 inline_constructor => 1,
945 inline_destructor => 0,
947 immutable_trait => $self->immutable_trait,
948 constructor_name => $self->constructor_name,
949 constructor_class => $self->constructor_class,
950 destructor_class => $self->destructor_class,
956 my ( $self, @args ) = @_;
958 if ( $self->is_mutable ) {
959 $self->_initialize_immutable( $self->_immutable_options(@args) );
960 $self->_rebless_as_immutable(@args);
971 if ( $self->is_immutable ) {
972 my @args = $self->immutable_options;
973 $self->_rebless_as_mutable();
974 $self->_remove_inlined_code(@args);
975 delete $self->{__immutable};
983 sub _rebless_as_immutable {
984 my ( $self, @args ) = @_;
986 $self->{__immutable}{original_class} = ref $self;
988 bless $self => $self->_immutable_metaclass(@args);
991 sub _immutable_metaclass {
992 my ( $self, %args ) = @_;
994 if ( my $class = $args{immutable_metaclass} ) {
998 my $trait = $args{immutable_trait} = $self->immutable_trait
999 || confess "no immutable trait specified for $self";
1001 my $meta = $self->meta;
1002 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
1006 if ( $meta_attr and $trait eq $meta_attr->default ) {
1007 # if the trait is the same as the default we try and pick a
1008 # predictable name for the immutable metaclass
1009 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
1012 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
1013 $trait, 'ForMetaClass', ref($self);
1017 if Class::MOP::is_class_loaded($class_name);
1019 # If the metaclass is a subclass of CMOP::Class which has had
1020 # metaclass roles applied (via Moose), then we want to make sure
1021 # that we preserve that anonymous class (see Fey::ORM for an
1022 # example of where this matters).
1024 = $meta->is_immutable
1025 ? $meta->get_mutable_metaclass_name
1028 my $immutable_meta = $meta_name->create(
1030 superclasses => [ ref $self ],
1033 Class::MOP::load_class($trait);
1034 for my $meth ( Class::MOP::Class->initialize($trait)->get_all_methods ) {
1035 my $meth_name = $meth->name;
1037 if ( $immutable_meta->find_method_by_name( $meth_name ) ) {
1038 $immutable_meta->add_around_method_modifier( $meth_name, $meth->body );
1041 $immutable_meta->add_method( $meth_name, $meth->clone );
1045 $immutable_meta->make_immutable(
1046 inline_constructor => 0,
1047 inline_accessors => 0,
1053 sub _remove_inlined_code {
1056 $self->remove_method( $_->name ) for $self->_inlined_methods;
1058 delete $self->{__immutable}{inlined_methods};
1061 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
1063 sub _add_inlined_method {
1064 my ( $self, $method ) = @_;
1066 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
1069 sub _initialize_immutable {
1070 my ( $self, %args ) = @_;
1072 $self->{__immutable}{options} = \%args;
1073 $self->_install_inlined_code(%args);
1076 sub _install_inlined_code {
1077 my ( $self, %args ) = @_;
1080 $self->_inline_accessors(%args) if $args{inline_accessors};
1081 $self->_inline_constructor(%args) if $args{inline_constructor};
1082 $self->_inline_destructor(%args) if $args{inline_destructor};
1085 sub _rebless_as_mutable {
1088 bless $self, $self->get_mutable_metaclass_name;
1093 sub _inline_accessors {
1096 foreach my $attr_name ( $self->get_attribute_list ) {
1097 $self->get_attribute($attr_name)->install_accessors(1);
1101 sub _inline_constructor {
1102 my ( $self, %args ) = @_;
1104 my $name = $args{constructor_name};
1106 if ( $self->has_method($name) && !$args{replace_constructor} ) {
1107 my $class = $self->name;
1108 warn "Not inlining a constructor for $class since it defines"
1109 . " its own constructor.\n"
1110 . "If you are certain you don't need to inline your"
1111 . " constructor, specify inline_constructor => 0 in your"
1112 . " call to $class->meta->make_immutable\n";
1116 my $constructor_class = $args{constructor_class};
1118 Class::MOP::load_class($constructor_class);
1120 my $constructor = $constructor_class->new(
1124 package_name => $self->name,
1128 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
1129 $self->add_method( $name => $constructor );
1130 $self->_add_inlined_method($constructor);
1134 sub _inline_destructor {
1135 my ( $self, %args ) = @_;
1137 ( exists $args{destructor_class} && defined $args{destructor_class} )
1138 || confess "The 'inline_destructor' option is present, but "
1139 . "no destructor class was specified";
1141 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
1142 my $class = $self->name;
1143 warn "Not inlining a destructor for $class since it defines"
1144 . " its own destructor.\n";
1148 my $destructor_class = $args{destructor_class};
1150 Class::MOP::load_class($destructor_class);
1152 return unless $destructor_class->is_needed($self);
1154 my $destructor = $destructor_class->new(
1157 package_name => $self->name,
1161 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1162 $self->add_method( 'DESTROY' => $destructor );
1163 $self->_add_inlined_method($destructor);
1175 Class::MOP::Class - Class Meta Object
1179 # assuming that class Foo
1180 # has been defined, you can
1182 # use this for introspection ...
1184 # add a method to Foo ...
1185 Foo->meta->add_method( 'bar' => sub {...} )
1187 # get a list of all the classes searched
1188 # the method dispatcher in the correct order
1189 Foo->meta->class_precedence_list()
1191 # remove a method from Foo
1192 Foo->meta->remove_method('bar');
1194 # or use this to actually create classes ...
1196 Class::MOP::Class->create(
1199 superclasses => ['Foo'],
1201 Class::MOP::Attribute->new('$bar'),
1202 Class::MOP::Attribute->new('$baz'),
1205 calculate_bar => sub {...},
1206 construct_baz => sub {...}
1213 The Class Protocol is the largest and most complex part of the
1214 Class::MOP meta-object protocol. It controls the introspection and
1215 manipulation of Perl 5 classes, and it can create them as well. The
1216 best way to understand what this module can do, is to read the
1217 documentation for each of its methods.
1221 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1225 =head2 Class construction
1227 These methods all create new C<Class::MOP::Class> objects. These
1228 objects can represent existing classes, or they can be used to create
1229 new classes from scratch.
1231 The metaclass object for a given class is a singleton. If you attempt
1232 to create a metaclass for the same class twice, you will just get the
1237 =item B<< Class::MOP::Class->create($package_name, %options) >>
1239 This method creates a new C<Class::MOP::Class> object with the given
1240 package name. It accepts a number of options.
1246 An optional version number for the newly created package.
1250 An optional authority for the newly created package.
1252 =item * superclasses
1254 An optional array reference of superclass names.
1258 An optional hash reference of methods for the class. The keys of the
1259 hash reference are method names, and values are subroutine references.
1263 An optional array reference of L<Class::MOP::Attribute> objects.
1267 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1269 This method works just like C<< Class::MOP::Class->create >> but it
1270 creates an "anonymous" class. In fact, the class does have a name, but
1271 that name is a unique name generated internally by this module.
1273 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1274 parameters that C<create> accepts.
1276 Anonymous classes are destroyed once the metaclass they are attached
1277 to goes out of scope, and will be removed from Perl's internal symbol
1280 All instances of an anonymous class keep a special reference to the
1281 metaclass object, which prevents the metaclass from going out of scope
1282 while any instances exist.
1284 This only works if the instance if based on a hash reference, however.
1286 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1288 This method will initialize a C<Class::MOP::Class> object for the
1289 named package. Unlike C<create>, this method I<will not> create a new
1292 The purpose of this method is to retrieve a C<Class::MOP::Class>
1293 object for introspecting an existing class.
1295 If an existing C<Class::MOP::Class> object exists for the named
1296 package, it will be returned, and any options provided will be
1299 If the object does not yet exist, it will be created.
1301 The valid options that can be passed to this method are
1302 C<attribute_metaclass>, C<method_metaclass>,
1303 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1304 optional, and default to the appropriate class in the C<Class::MOP>
1309 =head2 Object instance construction and cloning
1311 These methods are all related to creating and/or cloning object
1316 =item B<< $metaclass->clone_object($instance, %params) >>
1318 This method clones an existing object instance. Any parameters you
1319 provide are will override existing attribute values in the object.
1321 This is a convenience method for cloning an object instance, then
1322 blessing it into the appropriate package.
1324 You could implement a clone method in your class, using this method:
1327 my ($self, %params) = @_;
1328 $self->meta->clone_object($self, %params);
1331 =item B<< $metaclass->rebless_instance($instance, %params) >>
1333 This method changes the class of C<$instance> to the metaclass's class.
1335 You can only rebless an instance into a subclass of its current
1336 class. If you pass any additional parameters, these will be treated
1337 like constructor parameters and used to initialize the object's
1338 attributes. Any existing attributes that are already set will be
1341 Before reblessing the instance, this method will call
1342 C<rebless_instance_away> on the instance's current metaclass. This method
1343 will be passed the instance, the new metaclass, and any parameters
1344 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1345 does nothing; it is merely a hook.
1347 =item B<< $metaclass->new_object(%params) >>
1349 This method is used to create a new object of the metaclass's
1350 class. Any parameters you provide are used to initialize the
1351 instance's attributes. A special C<__INSTANCE__> key can be passed to
1352 provide an already generated instance, rather than having Class::MOP
1353 generate it for you. This is mostly useful for using Class::MOP with
1354 foreign classes, which generally generate instances using their own
1357 =item B<< $metaclass->instance_metaclass >>
1359 Returns the class name of the instance metaclass, see
1360 L<Class::MOP::Instance> for more information on the instance
1363 =item B<< $metaclass->get_meta_instance >>
1365 Returns an instance of the C<instance_metaclass> to be used in the
1366 construction of a new instance of the class.
1370 =head2 Informational predicates
1372 These are a few predicate methods for asking information about the
1377 =item B<< $metaclass->is_anon_class >>
1379 This returns true if the class was created by calling C<<
1380 Class::MOP::Class->create_anon_class >>.
1382 =item B<< $metaclass->is_mutable >>
1384 This returns true if the class is still mutable.
1386 =item B<< $metaclass->is_immutable >>
1388 This returns true if the class has been made immutable.
1390 =item B<< $metaclass->is_pristine >>
1392 A class is I<not> pristine if it has non-inherited attributes or if it
1393 has any generated methods.
1397 =head2 Inheritance Relationships
1401 =item B<< $metaclass->superclasses(@superclasses) >>
1403 This is a read-write accessor which represents the superclass
1404 relationships of the metaclass's class.
1406 This is basically sugar around getting and setting C<@ISA>.
1408 =item B<< $metaclass->class_precedence_list >>
1410 This returns a list of all of the class's ancestor classes. The
1411 classes are returned in method dispatch order.
1413 =item B<< $metaclass->linearized_isa >>
1415 This returns a list based on C<class_precedence_list> but with all
1418 =item B<< $metaclass->subclasses >>
1420 This returns a list of all subclasses for this class, even indirect
1423 =item B<< $metaclass->direct_subclasses >>
1425 This returns a list of immediate subclasses for this class, which does not
1426 include indirect subclasses.
1430 =head2 Method introspection
1432 See L<Class::MOP::Package/Method introspection and creation> for
1433 methods that operate only on the current class. Class::MOP::Class adds
1434 introspection capabilities that take inheritance into account.
1438 =item B<< $metaclass->get_all_methods >>
1440 This will traverse the inheritance hierarchy and return a list of all
1441 the L<Class::MOP::Method> objects for this class and its parents.
1443 =item B<< $metaclass->find_method_by_name($method_name) >>
1445 This will return a L<Class::MOP::Method> for the specified
1446 C<$method_name>. If the class does not have the specified method, it
1449 Unlike C<get_method>, this method I<will> look for the named method in
1452 =item B<< $metaclass->get_all_method_names >>
1454 This will return a list of method I<names> for all of this class's
1455 methods, including inherited methods.
1457 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1459 This method looks for the named method in the class and all of its
1460 parents. It returns every matching method it finds in the inheritance
1461 tree, so it returns a list of methods.
1463 Each method is returned as a hash reference with three keys. The keys
1464 are C<name>, C<class>, and C<code>. The C<code> key has a
1465 L<Class::MOP::Method> object as its value.
1467 The list of methods is distinct.
1469 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1471 This method returns the first method in any superclass matching the
1472 given name. It is effectively the method that C<SUPER::$method_name>
1477 =head2 Attribute introspection and creation
1479 Because Perl 5 does not have a core concept of attributes in classes,
1480 we can only return information about attributes which have been added
1481 via this class's methods. We cannot discover information about
1482 attributes which are defined in terms of "regular" Perl 5 methods.
1486 =item B<< $metaclass->get_attribute($attribute_name) >>
1488 This will return a L<Class::MOP::Attribute> for the specified
1489 C<$attribute_name>. If the class does not have the specified
1490 attribute, it returns C<undef>.
1492 NOTE that get_attribute does not search superclasses, for that you
1493 need to use C<find_attribute_by_name>.
1495 =item B<< $metaclass->has_attribute($attribute_name) >>
1497 Returns a boolean indicating whether or not the class defines the
1498 named attribute. It does not include attributes inherited from parent
1501 =item B<< $metaclass->get_attribute_map >>
1503 Returns a hash reference representing the attributes defined in this
1504 class. The keys are attribute names and the values are
1505 L<Class::MOP::Attribute> objects.
1507 =item B<< $metaclass->get_attribute_list >>
1509 This will return a list of attributes I<names> for all attributes
1510 defined in this class.
1512 =item B<< $metaclass->get_all_attributes >>
1514 This will traverse the inheritance hierarchy and return a list of all
1515 the L<Class::MOP::Attribute> objects for this class and its parents.
1517 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1519 This will return a L<Class::MOP::Attribute> for the specified
1520 C<$attribute_name>. If the class does not have the specified
1521 attribute, it returns C<undef>
1523 Unlike C<get_attribute>, this attribute I<will> look for the named
1524 attribute in superclasses.
1526 =item B<< $metaclass->add_attribute(...) >>
1528 This method accepts either an existing L<Class::MOP::Attribute>
1529 object, or parameters suitable for passing to that class's C<new>
1532 The attribute provided will be added to the class.
1534 Any accessor methods defined by the attribute will be added to the
1535 class when the attribute is added.
1537 If an attribute of the same name already exists, the old attribute
1538 will be removed first.
1540 =item B<< $metaclass->remove_attribute($attribute_name) >>
1542 This will remove the named attribute from the class, and
1543 L<Class::MOP::Attribute> object.
1545 Removing an attribute also removes any accessor methods defined by the
1548 However, note that removing an attribute will only affect I<future>
1549 object instances created for this class, not existing instances.
1551 =item B<< $metaclass->attribute_metaclass >>
1553 Returns the class name of the attribute metaclass for this class. By
1554 default, this is L<Class::MOP::Attribute>. for more information on
1558 =head2 Class Immutability
1560 Making a class immutable "freezes" the class definition. You can no
1561 longer call methods which alter the class, such as adding or removing
1562 methods or attributes.
1564 Making a class immutable lets us optimize the class by inlining some
1565 methods, and also allows us to optimize some methods on the metaclass
1568 After immutabilization, the metaclass object will cache most
1569 informational methods such as C<get_method_map> and
1570 C<get_all_attributes>. Methods which would alter the class, such as
1571 C<add_attribute>, C<add_method>, and so on will throw an error on an
1572 immutable metaclass object.
1574 The immutabilization system in L<Moose> takes much greater advantage
1575 of the inlining features than Class::MOP itself does.
1579 =item B<< $metaclass->make_immutable(%options) >>
1581 This method will create an immutable transformer and uses it to make
1582 the class and its metaclass object immutable.
1584 This method accepts the following options:
1588 =item * inline_accessors
1590 =item * inline_constructor
1592 =item * inline_destructor
1594 These are all booleans indicating whether the specified method(s)
1597 By default, accessors and the constructor are inlined, but not the
1600 =item * immutable_trait
1602 The name of a class which will be used as a parent class for the
1603 metaclass object being made immutable. This "trait" implements the
1604 post-immutability functionality of the metaclass (but not the
1605 transformation itself).
1607 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1609 =item * constructor_name
1611 This is the constructor method name. This defaults to "new".
1613 =item * constructor_class
1615 The name of the method metaclass for constructors. It will be used to
1616 generate the inlined constructor. This defaults to
1617 "Class::MOP::Method::Constructor".
1619 =item * replace_constructor
1621 This is a boolean indicating whether an existing constructor should be
1622 replaced when inlining a constructor. This defaults to false.
1624 =item * destructor_class
1626 The name of the method metaclass for destructors. It will be used to
1627 generate the inlined destructor. This defaults to
1628 "Class::MOP::Method::Denstructor".
1630 =item * replace_destructor
1632 This is a boolean indicating whether an existing destructor should be
1633 replaced when inlining a destructor. This defaults to false.
1637 =item B<< $metaclass->make_mutable >>
1639 Calling this method reverse the immutabilization transformation.
1643 =head2 Method Modifiers
1645 Method modifiers are hooks which allow a method to be wrapped with
1646 I<before>, I<after> and I<around> method modifiers. Every time a
1647 method is called, it's modifiers are also called.
1649 A class can modify its own methods, as well as methods defined in
1652 =head3 How method modifiers work?
1654 Method modifiers work by wrapping the original method and then
1655 replacing it in the class's symbol table. The wrappers will handle
1656 calling all the modifiers in the appropriate order and preserving the
1657 calling context for the original method.
1659 The return values of C<before> and C<after> modifiers are
1660 ignored. This is because their purpose is B<not> to filter the input
1661 and output of the primary method (this is done with an I<around>
1664 This may seem like an odd restriction to some, but doing this allows
1665 for simple code to be added at the beginning or end of a method call
1666 without altering the function of the wrapped method or placing any
1667 extra responsibility on the code of the modifier.
1669 Of course if you have more complex needs, you can use the C<around>
1670 modifier which allows you to change both the parameters passed to the
1671 wrapped method, as well as its return value.
1673 Before and around modifiers are called in last-defined-first-called
1674 order, while after modifiers are called in first-defined-first-called
1675 order. So the call tree might looks something like this:
1687 =head3 What is the performance impact?
1689 Of course there is a performance cost associated with method
1690 modifiers, but we have made every effort to make that cost directly
1691 proportional to the number of modifier features you utilize.
1693 The wrapping method does it's best to B<only> do as much work as it
1694 absolutely needs to. In order to do this we have moved some of the
1695 performance costs to set-up time, where they are easier to amortize.
1697 All this said, our benchmarks have indicated the following:
1699 simple wrapper with no modifiers 100% slower
1700 simple wrapper with simple before modifier 400% slower
1701 simple wrapper with simple after modifier 450% slower
1702 simple wrapper with simple around modifier 500-550% slower
1703 simple wrapper with all 3 modifiers 1100% slower
1705 These numbers may seem daunting, but you must remember, every feature
1706 comes with some cost. To put things in perspective, just doing a
1707 simple C<AUTOLOAD> which does nothing but extract the name of the
1708 method called and return it costs about 400% over a normal method
1713 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1715 This wraps the specified method with the supplied subroutine
1716 reference. The modifier will be called as a method itself, and will
1717 receive the same arguments as are passed to the method.
1719 When the modifier exits, the wrapped method will be called.
1721 The return value of the modifier will be ignored.
1723 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1725 This wraps the specified method with the supplied subroutine
1726 reference. The modifier will be called as a method itself, and will
1727 receive the same arguments as are passed to the method.
1729 When the wrapped methods exits, the modifier will be called.
1731 The return value of the modifier will be ignored.
1733 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1735 This wraps the specified method with the supplied subroutine
1738 The first argument passed to the modifier will be a subroutine
1739 reference to the wrapped method. The second argument is the object,
1740 and after that come any arguments passed when the method is called.
1742 The around modifier can choose to call the original method, as well as
1743 what arguments to pass if it does so.
1745 The return value of the modifier is what will be seen by the caller.
1749 =head2 Introspection
1753 =item B<< Class::MOP::Class->meta >>
1755 This will return a L<Class::MOP::Class> instance for this class.
1757 It should also be noted that L<Class::MOP> will actually bootstrap
1758 this module by installing a number of attribute meta-objects into its
1765 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1767 =head1 COPYRIGHT AND LICENSE
1769 Copyright 2006-2009 by Infinity Interactive, Inc.
1771 L<http://www.iinteractive.com>
1773 This library is free software; you can redistribute it and/or modify
1774 it under the same terms as Perl itself.