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 = '0.95';
18 $VERSION = eval $VERSION;
19 our $AUTHORITY = 'cpan:STEVAN';
21 use base 'Class::MOP::Module', 'Class::MOP::HasAttributes';
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 instance_metaclass { $_[0]->{'instance_metaclass'} }
332 sub immutable_trait { $_[0]->{'immutable_trait'} }
333 sub constructor_class { $_[0]->{'constructor_class'} }
334 sub constructor_name { $_[0]->{'constructor_name'} }
335 sub destructor_class { $_[0]->{'destructor_class'} }
337 # Instance Construction & Cloning
343 # we need to protect the integrity of the
344 # Class::MOP::Class singletons here, so we
345 # delegate this to &construct_class_instance
346 # which will deal with the singletons
347 return $class->_construct_class_instance(@_)
348 if $class->name->isa('Class::MOP::Class');
349 return $class->_construct_instance(@_);
352 sub _construct_instance {
354 my $params = @_ == 1 ? $_[0] : {@_};
355 my $meta_instance = $class->get_meta_instance();
357 # the code below is almost certainly incorrect
358 # but this is foreign inheritance, so we might
359 # have to kludge it in the end.
360 my $instance = $params->{__INSTANCE__} || $meta_instance->create_instance();
361 foreach my $attr ($class->get_all_attributes()) {
362 $attr->initialize_instance_slot($meta_instance, $instance, $params);
365 # this will only work for a HASH instance type
366 if ($class->is_anon_class) {
367 (reftype($instance) eq 'HASH')
368 || confess "Currently only HASH based instances are supported with instance of anon-classes";
370 # At some point we should make this official
371 # as a reserved slot name, but right now I am
372 # going to keep it here.
373 # my $RESERVED_MOP_SLOT = '__MOP__';
374 $instance->{'__MOP__'} = $class;
380 sub get_meta_instance {
382 $self->{'_meta_instance'} ||= $self->_create_meta_instance();
385 sub _create_meta_instance {
388 my $instance = $self->instance_metaclass->new(
389 associated_metaclass => $self,
390 attributes => [ $self->get_all_attributes() ],
393 $self->add_meta_instance_dependencies()
394 if $instance->is_dependent_on_superclasses();
401 my $instance = shift;
402 (blessed($instance) && $instance->isa($class->name))
403 || confess "You must pass an instance of the metaclass (" . (ref $class ? $class->name : $class) . "), not ($instance)";
406 # we need to protect the integrity of the
407 # Class::MOP::Class singletons here, they
408 # should not be cloned.
409 return $instance if $instance->isa('Class::MOP::Class');
410 $class->_clone_instance($instance, @_);
413 sub _clone_instance {
414 my ($class, $instance, %params) = @_;
416 || confess "You can only clone instances, ($instance) is not a blessed instance";
417 my $meta_instance = $class->get_meta_instance();
418 my $clone = $meta_instance->clone_instance($instance);
419 foreach my $attr ($class->get_all_attributes()) {
420 if ( defined( my $init_arg = $attr->init_arg ) ) {
421 if (exists $params{$init_arg}) {
422 $attr->set_value($clone, $params{$init_arg});
429 sub rebless_instance {
430 my ($self, $instance, %params) = @_;
432 my $old_metaclass = Class::MOP::class_of($instance);
434 my $old_class = $old_metaclass ? $old_metaclass->name : blessed($instance);
435 $self->name->isa($old_class)
436 || confess "You may rebless only into a subclass of ($old_class), of which (". $self->name .") isn't.";
438 $old_metaclass->rebless_instance_away($instance, $self, %params)
441 my $meta_instance = $self->get_meta_instance();
444 # we use $_[1] here because of t/306_rebless_overload.t regressions on 5.8.8
445 $meta_instance->rebless_instance_structure($_[1], $self);
447 foreach my $attr ( $self->get_all_attributes ) {
448 if ( $attr->has_value($instance) ) {
449 if ( defined( my $init_arg = $attr->init_arg ) ) {
450 $params{$init_arg} = $attr->get_value($instance)
451 unless exists $params{$init_arg};
454 $attr->set_value($instance, $attr->get_value($instance));
459 foreach my $attr ($self->get_all_attributes) {
460 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
466 sub rebless_instance_away {
467 # this intentionally does nothing, it is just a hook
474 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
477 @{$self->get_package_symbol($var_spec)} = @supers;
480 # on 5.8 and below, we need to call
481 # a method to get Perl to detect
482 # a cycle in the class hierarchy
483 my $class = $self->name;
487 # we need to check the metaclass
488 # compatibility here so that we can
489 # be sure that the superclass is
490 # not potentially creating an issues
491 # we don't know about
493 $self->_check_metaclass_compatibility();
494 $self->_superclasses_updated();
496 @{$self->get_package_symbol($var_spec)};
499 sub _superclasses_updated {
501 $self->update_meta_instance_dependencies();
506 my $super_class = $self->name;
508 return @{ $super_class->mro::get_isarev() };
511 sub direct_subclasses {
513 my $super_class = $self->name;
518 } Class::MOP::Class->initialize($_)->superclasses
523 return @{ mro::get_linear_isa( (shift)->name ) };
526 sub class_precedence_list {
528 my $name = $self->name;
530 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
532 # We need to check for circular inheritance here
533 # if we are are not on 5.10, cause 5.8 detects it
534 # late. This will do nothing if all is well, and
535 # blow up otherwise. Yes, it's an ugly hack, better
536 # suggestions are welcome.
538 ($name || return)->isa('This is a test for circular inheritance')
541 # if our mro is c3, we can
542 # just grab the linear_isa
543 if (mro::get_mro($name) eq 'c3') {
544 return @{ mro::get_linear_isa($name) }
548 # we can't grab the linear_isa for dfs
549 # since it has all the duplicates
554 $self->initialize($_)->class_precedence_list()
555 } $self->superclasses()
563 my $fetch_and_prepare_method = sub {
564 my ($self, $method_name) = @_;
565 my $wrapped_metaclass = $self->wrapped_method_metaclass;
567 my $method = $self->get_method($method_name);
568 # if we dont have local ...
570 # try to find the next method
571 $method = $self->find_next_method_by_name($method_name);
572 # die if it does not exist
574 || confess "The method '$method_name' was not found in the inheritance hierarchy for " . $self->name;
575 # and now make sure to wrap it
576 # even if it is already wrapped
577 # because we need a new sub ref
578 $method = $wrapped_metaclass->wrap($method,
579 package_name => $self->name,
580 name => $method_name,
584 # now make sure we wrap it properly
585 $method = $wrapped_metaclass->wrap($method,
586 package_name => $self->name,
587 name => $method_name,
588 ) unless $method->isa($wrapped_metaclass);
590 $self->add_method($method_name => $method);
594 sub add_before_method_modifier {
595 my ($self, $method_name, $method_modifier) = @_;
596 (defined $method_name && length $method_name)
597 || confess "You must pass in a method name";
598 my $method = $fetch_and_prepare_method->($self, $method_name);
599 $method->add_before_modifier(
600 subname(':before' => $method_modifier)
604 sub add_after_method_modifier {
605 my ($self, $method_name, $method_modifier) = @_;
606 (defined $method_name && length $method_name)
607 || confess "You must pass in a method name";
608 my $method = $fetch_and_prepare_method->($self, $method_name);
609 $method->add_after_modifier(
610 subname(':after' => $method_modifier)
614 sub add_around_method_modifier {
615 my ($self, $method_name, $method_modifier) = @_;
616 (defined $method_name && length $method_name)
617 || confess "You must pass in a method name";
618 my $method = $fetch_and_prepare_method->($self, $method_name);
619 $method->add_around_modifier(
620 subname(':around' => $method_modifier)
625 # the methods above used to be named like this:
626 # ${pkg}::${method}:(before|after|around)
627 # but this proved problematic when using one modifier
628 # to wrap multiple methods (something which is likely
629 # to happen pretty regularly IMO). So instead of naming
630 # it like this, I have chosen to just name them purely
631 # with their modifier names, like so:
632 # :(before|after|around)
633 # The fact is that in a stack trace, it will be fairly
634 # evident from the context what method they are attached
635 # to, and so don't need the fully qualified name.
638 sub find_method_by_name {
639 my ($self, $method_name) = @_;
640 (defined $method_name && length $method_name)
641 || confess "You must define a method name to find";
642 foreach my $class ($self->linearized_isa) {
643 my $method = $self->initialize($class)->get_method($method_name);
644 return $method if defined $method;
649 sub get_all_methods {
653 for my $class ( reverse $self->linearized_isa ) {
654 my $meta = $self->initialize($class);
656 $methods{$_} = $meta->get_method($_)
657 for $meta->get_method_list;
660 return values %methods;
663 sub get_all_method_names {
666 return grep { !$uniq{$_}++ } map { $self->initialize($_)->get_method_list } $self->linearized_isa;
669 sub find_all_methods_by_name {
670 my ($self, $method_name) = @_;
671 (defined $method_name && length $method_name)
672 || confess "You must define a method name to find";
674 foreach my $class ($self->linearized_isa) {
675 # fetch the meta-class ...
676 my $meta = $self->initialize($class);
678 name => $method_name,
680 code => $meta->get_method($method_name)
681 } if $meta->has_method($method_name);
686 sub find_next_method_by_name {
687 my ($self, $method_name) = @_;
688 (defined $method_name && length $method_name)
689 || confess "You must define a method name to find";
690 my @cpl = $self->linearized_isa;
691 shift @cpl; # discard ourselves
692 foreach my $class (@cpl) {
693 my $method = $self->initialize($class)->get_method($method_name);
694 return $method if defined $method;
699 sub update_meta_instance_dependencies {
702 if ( $self->{meta_instance_dependencies} ) {
703 return $self->add_meta_instance_dependencies;
707 sub add_meta_instance_dependencies {
710 $self->remove_meta_instance_dependencies;
712 my @attrs = $self->get_all_attributes();
715 my @classes = grep { not $seen{ $_->name }++ }
716 map { $_->associated_class } @attrs;
718 foreach my $class (@classes) {
719 $class->add_dependent_meta_instance($self);
722 $self->{meta_instance_dependencies} = \@classes;
725 sub remove_meta_instance_dependencies {
728 if ( my $classes = delete $self->{meta_instance_dependencies} ) {
729 foreach my $class (@$classes) {
730 $class->remove_dependent_meta_instance($self);
740 sub add_dependent_meta_instance {
741 my ( $self, $metaclass ) = @_;
742 push @{ $self->{dependent_meta_instances} }, $metaclass;
745 sub remove_dependent_meta_instance {
746 my ( $self, $metaclass ) = @_;
747 my $name = $metaclass->name;
748 @$_ = grep { $_->name ne $name } @$_
749 for $self->{dependent_meta_instances};
752 sub invalidate_meta_instances {
754 $_->invalidate_meta_instance()
755 for $self, @{ $self->{dependent_meta_instances} };
758 sub invalidate_meta_instance {
760 undef $self->{_meta_instance};
763 # check if we can reinitialize
767 # if any local attr is defined
768 return if $self->get_attribute_list;
770 # or any non-declared methods
771 for my $method ( map { $self->get_method($_) } $self->get_method_list ) {
772 return if $method->isa("Class::MOP::Method::Generated");
773 # FIXME do we need to enforce this too? return unless $method->isa( $self->method_metaclass );
782 sub is_immutable { 0 }
784 sub immutable_options { %{ $_[0]{__immutable}{options} || {} } }
786 sub _immutable_options {
787 my ( $self, @args ) = @_;
790 inline_accessors => 1,
791 inline_constructor => 1,
792 inline_destructor => 0,
794 immutable_trait => $self->immutable_trait,
795 constructor_name => $self->constructor_name,
796 constructor_class => $self->constructor_class,
797 destructor_class => $self->destructor_class,
803 my ( $self, @args ) = @_;
805 if ( $self->is_mutable ) {
806 $self->_initialize_immutable( $self->_immutable_options(@args) );
807 $self->_rebless_as_immutable(@args);
818 if ( $self->is_immutable ) {
819 my @args = $self->immutable_options;
820 $self->_rebless_as_mutable();
821 $self->_remove_inlined_code(@args);
822 delete $self->{__immutable};
830 sub _rebless_as_immutable {
831 my ( $self, @args ) = @_;
833 $self->{__immutable}{original_class} = ref $self;
835 bless $self => $self->_immutable_metaclass(@args);
838 sub _immutable_metaclass {
839 my ( $self, %args ) = @_;
841 if ( my $class = $args{immutable_metaclass} ) {
845 my $trait = $args{immutable_trait} = $self->immutable_trait
846 || confess "no immutable trait specified for $self";
848 my $meta = $self->meta;
849 my $meta_attr = $meta->find_attribute_by_name("immutable_trait");
853 if ( $meta_attr and $trait eq $meta_attr->default ) {
854 # if the trait is the same as the default we try and pick a
855 # predictable name for the immutable metaclass
856 $class_name = 'Class::MOP::Class::Immutable::' . ref($self);
859 $class_name = join '::', 'Class::MOP::Class::Immutable::CustomTrait',
860 $trait, 'ForMetaClass', ref($self);
864 if Class::MOP::is_class_loaded($class_name);
866 # If the metaclass is a subclass of CMOP::Class which has had
867 # metaclass roles applied (via Moose), then we want to make sure
868 # that we preserve that anonymous class (see Fey::ORM for an
869 # example of where this matters).
871 = $meta->is_immutable
872 ? $meta->_get_mutable_metaclass_name
875 my $immutable_meta = $meta_name->create(
877 superclasses => [ ref $self ],
880 Class::MOP::load_class($trait);
881 for my $meth ( Class::MOP::Class->initialize($trait)->get_all_methods ) {
882 my $meth_name = $meth->name;
884 if ( $immutable_meta->find_method_by_name( $meth_name ) ) {
885 $immutable_meta->add_around_method_modifier( $meth_name, $meth->body );
888 $immutable_meta->add_method( $meth_name, $meth->clone );
892 $immutable_meta->make_immutable(
893 inline_constructor => 0,
894 inline_accessors => 0,
900 sub _remove_inlined_code {
903 $self->remove_method( $_->name ) for $self->_inlined_methods;
905 delete $self->{__immutable}{inlined_methods};
908 sub _inlined_methods { @{ $_[0]{__immutable}{inlined_methods} || [] } }
910 sub _add_inlined_method {
911 my ( $self, $method ) = @_;
913 push @{ $self->{__immutable}{inlined_methods} ||= [] }, $method;
916 sub _initialize_immutable {
917 my ( $self, %args ) = @_;
919 $self->{__immutable}{options} = \%args;
920 $self->_install_inlined_code(%args);
923 sub _install_inlined_code {
924 my ( $self, %args ) = @_;
927 $self->_inline_accessors(%args) if $args{inline_accessors};
928 $self->_inline_constructor(%args) if $args{inline_constructor};
929 $self->_inline_destructor(%args) if $args{inline_destructor};
932 sub _rebless_as_mutable {
935 bless $self, $self->_get_mutable_metaclass_name;
940 sub _inline_accessors {
943 foreach my $attr_name ( $self->get_attribute_list ) {
944 $self->get_attribute($attr_name)->install_accessors(1);
948 sub _inline_constructor {
949 my ( $self, %args ) = @_;
951 my $name = $args{constructor_name};
952 # A class may not even have a constructor, and that's okay.
953 return unless defined $name;
955 if ( $self->has_method($name) && !$args{replace_constructor} ) {
956 my $class = $self->name;
957 warn "Not inlining a constructor for $class since it defines"
958 . " its own constructor.\n"
959 . "If you are certain you don't need to inline your"
960 . " constructor, specify inline_constructor => 0 in your"
961 . " call to $class->meta->make_immutable\n";
965 my $constructor_class = $args{constructor_class};
967 Class::MOP::load_class($constructor_class);
969 my $constructor = $constructor_class->new(
973 package_name => $self->name,
977 if ( $args{replace_constructor} or $constructor->can_be_inlined ) {
978 $self->add_method( $name => $constructor );
979 $self->_add_inlined_method($constructor);
983 sub _inline_destructor {
984 my ( $self, %args ) = @_;
986 ( exists $args{destructor_class} && defined $args{destructor_class} )
987 || confess "The 'inline_destructor' option is present, but "
988 . "no destructor class was specified";
990 if ( $self->has_method('DESTROY') && ! $args{replace_destructor} ) {
991 my $class = $self->name;
992 warn "Not inlining a destructor for $class since it defines"
993 . " its own destructor.\n";
997 my $destructor_class = $args{destructor_class};
999 Class::MOP::load_class($destructor_class);
1001 return unless $destructor_class->is_needed($self);
1003 my $destructor = $destructor_class->new(
1006 package_name => $self->name,
1010 if ( $args{replace_destructor} or $destructor->can_be_inlined ) {
1011 $self->add_method( 'DESTROY' => $destructor );
1012 $self->_add_inlined_method($destructor);
1024 Class::MOP::Class - Class Meta Object
1028 # assuming that class Foo
1029 # has been defined, you can
1031 # use this for introspection ...
1033 # add a method to Foo ...
1034 Foo->meta->add_method( 'bar' => sub {...} )
1036 # get a list of all the classes searched
1037 # the method dispatcher in the correct order
1038 Foo->meta->class_precedence_list()
1040 # remove a method from Foo
1041 Foo->meta->remove_method('bar');
1043 # or use this to actually create classes ...
1045 Class::MOP::Class->create(
1048 superclasses => ['Foo'],
1050 Class::MOP::Attribute->new('$bar'),
1051 Class::MOP::Attribute->new('$baz'),
1054 calculate_bar => sub {...},
1055 construct_baz => sub {...}
1062 The Class Protocol is the largest and most complex part of the
1063 Class::MOP meta-object protocol. It controls the introspection and
1064 manipulation of Perl 5 classes, and it can create them as well. The
1065 best way to understand what this module can do is to read the
1066 documentation for each of its methods.
1070 C<Class::MOP::Class> is a subclass of L<Class::MOP::Module>.
1074 =head2 Class construction
1076 These methods all create new C<Class::MOP::Class> objects. These
1077 objects can represent existing classes or they can be used to create
1078 new classes from scratch.
1080 The metaclass object for a given class is a singleton. If you attempt
1081 to create a metaclass for the same class twice, you will just get the
1086 =item B<< Class::MOP::Class->create($package_name, %options) >>
1088 This method creates a new C<Class::MOP::Class> object with the given
1089 package name. It accepts a number of options:
1095 An optional version number for the newly created package.
1099 An optional authority for the newly created package.
1101 =item * superclasses
1103 An optional array reference of superclass names.
1107 An optional hash reference of methods for the class. The keys of the
1108 hash reference are method names and values are subroutine references.
1112 An optional array reference of L<Class::MOP::Attribute> objects.
1116 =item B<< Class::MOP::Class->create_anon_class(%options) >>
1118 This method works just like C<< Class::MOP::Class->create >> but it
1119 creates an "anonymous" class. In fact, the class does have a name, but
1120 that name is a unique name generated internally by this module.
1122 It accepts the same C<superclasses>, C<methods>, and C<attributes>
1123 parameters that C<create> accepts.
1125 Anonymous classes are destroyed once the metaclass they are attached
1126 to goes out of scope, and will be removed from Perl's internal symbol
1129 All instances of an anonymous class keep a special reference to the
1130 metaclass object, which prevents the metaclass from going out of scope
1131 while any instances exist.
1133 This only works if the instance is based on a hash reference, however.
1135 =item B<< Class::MOP::Class->initialize($package_name, %options) >>
1137 This method will initialize a C<Class::MOP::Class> object for the
1138 named package. Unlike C<create>, this method I<will not> create a new
1141 The purpose of this method is to retrieve a C<Class::MOP::Class>
1142 object for introspecting an existing class.
1144 If an existing C<Class::MOP::Class> object exists for the named
1145 package, it will be returned, and any options provided will be
1148 If the object does not yet exist, it will be created.
1150 The valid options that can be passed to this method are
1151 C<attribute_metaclass>, C<method_metaclass>,
1152 C<wrapped_method_metaclass>, and C<instance_metaclass>. These are all
1153 optional, and default to the appropriate class in the C<Class::MOP>
1158 =head2 Object instance construction and cloning
1160 These methods are all related to creating and/or cloning object
1165 =item B<< $metaclass->clone_object($instance, %params) >>
1167 This method clones an existing object instance. Any parameters you
1168 provide are will override existing attribute values in the object.
1170 This is a convenience method for cloning an object instance, then
1171 blessing it into the appropriate package.
1173 You could implement a clone method in your class, using this method:
1176 my ($self, %params) = @_;
1177 $self->meta->clone_object($self, %params);
1180 =item B<< $metaclass->rebless_instance($instance, %params) >>
1182 This method changes the class of C<$instance> to the metaclass's class.
1184 You can only rebless an instance into a subclass of its current
1185 class. If you pass any additional parameters, these will be treated
1186 like constructor parameters and used to initialize the object's
1187 attributes. Any existing attributes that are already set will be
1190 Before reblessing the instance, this method will call
1191 C<rebless_instance_away> on the instance's current metaclass. This method
1192 will be passed the instance, the new metaclass, and any parameters
1193 specified to C<rebless_instance>. By default, C<rebless_instance_away>
1194 does nothing; it is merely a hook.
1196 =item B<< $metaclass->new_object(%params) >>
1198 This method is used to create a new object of the metaclass's
1199 class. Any parameters you provide are used to initialize the
1200 instance's attributes. A special C<__INSTANCE__> key can be passed to
1201 provide an already generated instance, rather than having Class::MOP
1202 generate it for you. This is mostly useful for using Class::MOP with
1203 foreign classes which generate instances using their own constructors.
1205 =item B<< $metaclass->instance_metaclass >>
1207 Returns the class name of the instance metaclass. See
1208 L<Class::MOP::Instance> for more information on the instance
1211 =item B<< $metaclass->get_meta_instance >>
1213 Returns an instance of the C<instance_metaclass> to be used in the
1214 construction of a new instance of the class.
1218 =head2 Informational predicates
1220 These are a few predicate methods for asking information about the
1225 =item B<< $metaclass->is_anon_class >>
1227 This returns true if the class was created by calling C<<
1228 Class::MOP::Class->create_anon_class >>.
1230 =item B<< $metaclass->is_mutable >>
1232 This returns true if the class is still mutable.
1234 =item B<< $metaclass->is_immutable >>
1236 This returns true if the class has been made immutable.
1238 =item B<< $metaclass->is_pristine >>
1240 A class is I<not> pristine if it has non-inherited attributes or if it
1241 has any generated methods.
1245 =head2 Inheritance Relationships
1249 =item B<< $metaclass->superclasses(@superclasses) >>
1251 This is a read-write accessor which represents the superclass
1252 relationships of the metaclass's class.
1254 This is basically sugar around getting and setting C<@ISA>.
1256 =item B<< $metaclass->class_precedence_list >>
1258 This returns a list of all of the class's ancestor classes. The
1259 classes are returned in method dispatch order.
1261 =item B<< $metaclass->linearized_isa >>
1263 This returns a list based on C<class_precedence_list> but with all
1266 =item B<< $metaclass->subclasses >>
1268 This returns a list of all subclasses for this class, even indirect
1271 =item B<< $metaclass->direct_subclasses >>
1273 This returns a list of immediate subclasses for this class, which does not
1274 include indirect subclasses.
1278 =head2 Method introspection
1280 See L<Class::MOP::Package/Method introspection and creation> for
1281 methods that operate only on the current class. Class::MOP::Class adds
1282 introspection capabilities that take inheritance into account.
1286 =item B<< $metaclass->get_all_methods >>
1288 This will traverse the inheritance hierarchy and return a list of all
1289 the L<Class::MOP::Method> objects for this class and its parents.
1291 =item B<< $metaclass->find_method_by_name($method_name) >>
1293 This will return a L<Class::MOP::Method> for the specified
1294 C<$method_name>. If the class does not have the specified method, it
1297 Unlike C<get_method>, this method I<will> look for the named method in
1300 =item B<< $metaclass->get_all_method_names >>
1302 This will return a list of method I<names> for all of this class's
1303 methods, including inherited methods.
1305 =item B<< $metaclass->find_all_methods_by_name($method_name) >>
1307 This method looks for the named method in the class and all of its
1308 parents. It returns every matching method it finds in the inheritance
1309 tree, so it returns a list of methods.
1311 Each method is returned as a hash reference with three keys. The keys
1312 are C<name>, C<class>, and C<code>. The C<code> key has a
1313 L<Class::MOP::Method> object as its value.
1315 The list of methods is distinct.
1317 =item B<< $metaclass->find_next_method_by_name($method_name) >>
1319 This method returns the first method in any superclass matching the
1320 given name. It is effectively the method that C<SUPER::$method_name>
1325 =head2 Attribute introspection and creation
1327 Because Perl 5 does not have a core concept of attributes in classes,
1328 we can only return information about attributes which have been added
1329 via this class's methods. We cannot discover information about
1330 attributes which are defined in terms of "regular" Perl 5 methods.
1334 =item B<< $metaclass->get_attribute($attribute_name) >>
1336 This will return a L<Class::MOP::Attribute> for the specified
1337 C<$attribute_name>. If the class does not have the specified
1338 attribute, it returns C<undef>.
1340 NOTE that get_attribute does not search superclasses, for that you
1341 need to use C<find_attribute_by_name>.
1343 =item B<< $metaclass->has_attribute($attribute_name) >>
1345 Returns a boolean indicating whether or not the class defines the
1346 named attribute. It does not include attributes inherited from parent
1349 =item B<< $metaclass->get_attribute_list >>
1351 This will return a list of attributes I<names> for all attributes
1352 defined in this class.
1354 =item B<< $metaclass->get_all_attributes >>
1356 This will traverse the inheritance hierarchy and return a list of all
1357 the L<Class::MOP::Attribute> objects for this class and its parents.
1359 =item B<< $metaclass->find_attribute_by_name($attribute_name) >>
1361 This will return a L<Class::MOP::Attribute> for the specified
1362 C<$attribute_name>. If the class does not have the specified
1363 attribute, it returns C<undef>.
1365 Unlike C<get_attribute>, this attribute I<will> look for the named
1366 attribute in superclasses.
1368 =item B<< $metaclass->add_attribute(...) >>
1370 This method accepts either an existing L<Class::MOP::Attribute>
1371 object or parameters suitable for passing to that class's C<new>
1374 The attribute provided will be added to the class.
1376 Any accessor methods defined by the attribute will be added to the
1377 class when the attribute is added.
1379 If an attribute of the same name already exists, the old attribute
1380 will be removed first.
1382 =item B<< $metaclass->remove_attribute($attribute_name) >>
1384 This will remove the named attribute from the class, and
1385 L<Class::MOP::Attribute> object.
1387 Removing an attribute also removes any accessor methods defined by the
1390 However, note that removing an attribute will only affect I<future>
1391 object instances created for this class, not existing instances.
1393 =item B<< $metaclass->attribute_metaclass >>
1395 Returns the class name of the attribute metaclass for this class. By
1396 default, this is L<Class::MOP::Attribute>.
1400 =head2 Class Immutability
1402 Making a class immutable "freezes" the class definition. You can no
1403 longer call methods which alter the class, such as adding or removing
1404 methods or attributes.
1406 Making a class immutable lets us optimize the class by inlining some
1407 methods, and also allows us to optimize some methods on the metaclass
1410 After immutabilization, the metaclass object will cache most informational
1411 methods that returns information about methods or attributes. Methods which
1412 would alter the class, such as C<add_attribute> and C<add_method>, will
1413 throw an error on an immutable metaclass object.
1415 The immutabilization system in L<Moose> takes much greater advantage
1416 of the inlining features than Class::MOP itself does.
1420 =item B<< $metaclass->make_immutable(%options) >>
1422 This method will create an immutable transformer and use it to make
1423 the class and its metaclass object immutable.
1425 This method accepts the following options:
1429 =item * inline_accessors
1431 =item * inline_constructor
1433 =item * inline_destructor
1435 These are all booleans indicating whether the specified method(s)
1438 By default, accessors and the constructor are inlined, but not the
1441 =item * immutable_trait
1443 The name of a class which will be used as a parent class for the
1444 metaclass object being made immutable. This "trait" implements the
1445 post-immutability functionality of the metaclass (but not the
1446 transformation itself).
1448 This defaults to L<Class::MOP::Class::Immutable::Trait>.
1450 =item * constructor_name
1452 This is the constructor method name. This defaults to "new".
1454 =item * constructor_class
1456 The name of the method metaclass for constructors. It will be used to
1457 generate the inlined constructor. This defaults to
1458 "Class::MOP::Method::Constructor".
1460 =item * replace_constructor
1462 This is a boolean indicating whether an existing constructor should be
1463 replaced when inlining a constructor. This defaults to false.
1465 =item * destructor_class
1467 The name of the method metaclass for destructors. It will be used to
1468 generate the inlined destructor. This defaults to
1469 "Class::MOP::Method::Denstructor".
1471 =item * replace_destructor
1473 This is a boolean indicating whether an existing destructor should be
1474 replaced when inlining a destructor. This defaults to false.
1478 =item B<< $metaclass->immutable_options >>
1480 Returns a hash of the options used when making the class immutable, including
1481 both defaults and anything supplied by the user in the call to C<<
1482 $metaclass->make_immutable >>. This is useful if you need to temporarily make
1483 a class mutable and then restore immutability as it was before.
1485 =item B<< $metaclass->make_mutable >>
1487 Calling this method reverse the immutabilization transformation.
1491 =head2 Method Modifiers
1493 Method modifiers are hooks which allow a method to be wrapped with
1494 I<before>, I<after> and I<around> method modifiers. Every time a
1495 method is called, its modifiers are also called.
1497 A class can modify its own methods, as well as methods defined in
1500 =head3 How method modifiers work?
1502 Method modifiers work by wrapping the original method and then
1503 replacing it in the class's symbol table. The wrappers will handle
1504 calling all the modifiers in the appropriate order and preserving the
1505 calling context for the original method.
1507 The return values of C<before> and C<after> modifiers are
1508 ignored. This is because their purpose is B<not> to filter the input
1509 and output of the primary method (this is done with an I<around>
1512 This may seem like an odd restriction to some, but doing this allows
1513 for simple code to be added at the beginning or end of a method call
1514 without altering the function of the wrapped method or placing any
1515 extra responsibility on the code of the modifier.
1517 Of course if you have more complex needs, you can use the C<around>
1518 modifier which allows you to change both the parameters passed to the
1519 wrapped method, as well as its return value.
1521 Before and around modifiers are called in last-defined-first-called
1522 order, while after modifiers are called in first-defined-first-called
1523 order. So the call tree might looks something like this:
1535 =head3 What is the performance impact?
1537 Of course there is a performance cost associated with method
1538 modifiers, but we have made every effort to make that cost directly
1539 proportional to the number of modifier features you use.
1541 The wrapping method does its best to B<only> do as much work as it
1542 absolutely needs to. In order to do this we have moved some of the
1543 performance costs to set-up time, where they are easier to amortize.
1545 All this said, our benchmarks have indicated the following:
1547 simple wrapper with no modifiers 100% slower
1548 simple wrapper with simple before modifier 400% slower
1549 simple wrapper with simple after modifier 450% slower
1550 simple wrapper with simple around modifier 500-550% slower
1551 simple wrapper with all 3 modifiers 1100% slower
1553 These numbers may seem daunting, but you must remember, every feature
1554 comes with some cost. To put things in perspective, just doing a
1555 simple C<AUTOLOAD> which does nothing but extract the name of the
1556 method called and return it costs about 400% over a normal method
1561 =item B<< $metaclass->add_before_method_modifier($method_name, $code) >>
1563 This wraps the specified method with the supplied subroutine
1564 reference. The modifier will be called as a method itself, and will
1565 receive the same arguments as are passed to the method.
1567 When the modifier exits, the wrapped method will be called.
1569 The return value of the modifier will be ignored.
1571 =item B<< $metaclass->add_after_method_modifier($method_name, $code) >>
1573 This wraps the specified method with the supplied subroutine
1574 reference. The modifier will be called as a method itself, and will
1575 receive the same arguments as are passed to the method.
1577 When the wrapped methods exits, the modifier will be called.
1579 The return value of the modifier will be ignored.
1581 =item B<< $metaclass->add_around_method_modifier($method_name, $code) >>
1583 This wraps the specified method with the supplied subroutine
1586 The first argument passed to the modifier will be a subroutine
1587 reference to the wrapped method. The second argument is the object,
1588 and after that come any arguments passed when the method is called.
1590 The around modifier can choose to call the original method, as well as
1591 what arguments to pass if it does so.
1593 The return value of the modifier is what will be seen by the caller.
1597 =head2 Introspection
1601 =item B<< Class::MOP::Class->meta >>
1603 This will return a L<Class::MOP::Class> instance for this class.
1605 It should also be noted that L<Class::MOP> will actually bootstrap
1606 this module by installing a number of attribute meta-objects into its
1613 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1615 =head1 COPYRIGHT AND LICENSE
1617 Copyright 2006-2009 by Infinity Interactive, Inc.
1619 L<http://www.iinteractive.com>
1621 This library is free software; you can redistribute it and/or modify
1622 it under the same terms as Perl itself.