2 package Class::MOP::Class;
7 use Class::MOP::Immutable;
8 use Class::MOP::Instance;
9 use Class::MOP::Method::Wrapped;
12 use Scalar::Util 'blessed', 'weaken';
14 our $VERSION = '0.65';
15 our $AUTHORITY = 'cpan:STEVAN';
17 use base 'Class::MOP::Module';
23 my $package_name = shift;
24 (defined $package_name && $package_name && !blessed($package_name))
25 || confess "You must pass a package name and it cannot be blessed";
26 return Class::MOP::get_metaclass_by_name($package_name)
27 || $class->construct_class_instance('package' => $package_name, @_);
32 my $package_name = shift;
33 (defined $package_name && $package_name && !blessed($package_name))
34 || confess "You must pass a package name and it cannot be blessed";
35 Class::MOP::remove_metaclass_by_name($package_name);
36 $class->construct_class_instance('package' => $package_name, @_);
39 # NOTE: (meta-circularity)
40 # this is a special form of &construct_instance
41 # (see below), which is used to construct class
42 # meta-object instances for any Class::MOP::*
43 # class. All other classes will use the more
44 # normal &construct_instance.
45 sub construct_class_instance {
48 my $package_name = $options{'package'};
49 (defined $package_name && $package_name)
50 || confess "You must pass a package name";
52 # return the metaclass if we have it cached,
53 # and it is still defined (it has not been
54 # reaped by DESTROY yet, which can happen
55 # annoyingly enough during global destruction)
57 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
62 # we need to deal with the possibility
63 # of class immutability here, and then
64 # get the name of the class appropriately
65 $class = (blessed($class)
66 ? ($class->is_immutable
67 ? $class->get_mutable_metaclass_name()
71 # now create the metaclass
73 if ($class eq 'Class::MOP::Class') {
76 # inherited from Class::MOP::Package
77 'package' => $package_name,
80 # since the following attributes will
81 # actually be loaded from the symbol
82 # table, and actually bypass the instance
83 # entirely, we can just leave these things
84 # listed here for reference, because they
85 # should not actually have a value associated
87 'namespace' => \undef,
88 # inherited from Class::MOP::Module
90 'authority' => \undef,
91 # defined in Class::MOP::Class
92 'superclasses' => \undef,
96 'attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
97 'method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
98 'instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
100 ## uber-private variables
102 # this starts out as undef so that
103 # we can tell the first time the
104 # methods are fetched
106 '_package_cache_flag' => undef,
107 '_meta_instance' => undef,
112 # it is safe to use meta here because
113 # class will always be a subclass of
114 # Class::MOP::Class, which defines meta
115 $meta = $class->meta->construct_instance(%options)
118 # and check the metaclass compatibility
119 $meta->check_metaclass_compatability();
121 Class::MOP::store_metaclass_by_name($package_name, $meta);
124 # we need to weaken any anon classes
125 # so that they can call DESTROY properly
126 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
131 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
132 sub update_package_cache_flag {
135 # we can manually update the cache number
136 # since we are actually adding the method
137 # to our cache as well. This avoids us
138 # having to regenerate the method_map.
140 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
143 sub check_metaclass_compatability {
146 # this is always okay ...
147 return if blessed($self) eq 'Class::MOP::Class' &&
148 $self->instance_metaclass eq 'Class::MOP::Instance';
150 my @class_list = $self->linearized_isa;
151 shift @class_list; # shift off $self->name
153 foreach my $class_name (@class_list) {
154 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
157 # we need to deal with the possibility
158 # of class immutability here, and then
159 # get the name of the class appropriately
160 my $meta_type = ($meta->is_immutable
161 ? $meta->get_mutable_metaclass_name()
164 ($self->isa($meta_type))
165 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
166 " is not compatible with the " .
167 $class_name . "->meta => (" . ($meta_type) . ")";
169 # we also need to check that instance metaclasses
170 # are compatabile in the same the class.
171 ($self->instance_metaclass->isa($meta->instance_metaclass))
172 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
173 " is not compatible with the " .
174 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
182 # this should be sufficient, if you have a
183 # use case where it is not, write a test and
185 my $ANON_CLASS_SERIAL = 0;
188 # we need a sufficiently annoying prefix
189 # this should suffice for now, this is
190 # used in a couple of places below, so
191 # need to put it up here for now.
192 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
196 no warnings 'uninitialized';
197 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
200 sub create_anon_class {
201 my ($class, %options) = @_;
202 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
203 return $class->create($package_name, %options);
207 # this will only get called for
208 # anon-classes, all other calls
209 # are assumed to occur during
210 # global destruction and so don't
211 # really need to be handled explicitly
214 no warnings 'uninitialized';
215 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
216 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
218 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
219 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
221 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
226 # creating classes with MOP ...
229 my ( $class, @args ) = @_;
231 unshift @args, 'name' if @args % 2 == 1;
233 my (%options) = @args;
234 my $package_name = $options{name};
236 (defined $package_name && $package_name)
237 || confess "You must pass a package name";
239 (ref $options{superclasses} eq 'ARRAY')
240 || confess "You must pass an ARRAY ref of superclasses"
241 if exists $options{superclasses};
243 (ref $options{attributes} eq 'ARRAY')
244 || confess "You must pass an ARRAY ref of attributes"
245 if exists $options{attributes};
247 (ref $options{methods} eq 'HASH')
248 || confess "You must pass an HASH ref of methods"
249 if exists $options{methods};
251 my $code = "package $package_name;";
252 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
253 if exists $options{version};
254 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
255 if exists $options{authority};
258 confess "creation of $package_name failed : $@" if $@;
260 my $meta = $class->initialize($package_name);
263 $meta->add_method('meta' => sub {
264 $class->initialize(blessed($_[0]) || $_[0]);
267 $meta->superclasses(@{$options{superclasses}})
268 if exists $options{superclasses};
270 # process attributes first, so that they can
271 # install accessors, but locally defined methods
272 # can then overwrite them. It is maybe a little odd, but
273 # I think this should be the order of things.
274 if (exists $options{attributes}) {
275 foreach my $attr (@{$options{attributes}}) {
276 $meta->add_attribute($attr);
279 if (exists $options{methods}) {
280 foreach my $method_name (keys %{$options{methods}}) {
281 $meta->add_method($method_name, $options{methods}->{$method_name});
290 # all these attribute readers will be bootstrapped
291 # away in the Class::MOP bootstrap section
293 sub get_attribute_map { $_[0]->{'attributes'} }
294 sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
295 sub method_metaclass { $_[0]->{'method_metaclass'} }
296 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
299 # this is a prime canidate for conversion to XS
303 if (defined $self->{'_package_cache_flag'} &&
304 $self->{'_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
305 return $self->{'methods'};
308 my $map = $self->{'methods'};
310 my $class_name = $self->name;
311 my $method_metaclass = $self->method_metaclass;
313 my %all_code = $self->get_all_package_symbols('CODE');
315 foreach my $symbol (keys %all_code) {
316 my $code = $all_code{$symbol};
318 next if exists $map->{$symbol} &&
319 defined $map->{$symbol} &&
320 $map->{$symbol}->body == $code;
322 my ($pkg, $name) = Class::MOP::get_code_info($code);
325 # in 5.10 constant.pm the constants show up
326 # as being in the right package, but in pre-5.10
327 # they show up as constant::__ANON__ so we
328 # make an exception here to be sure that things
329 # work as expected in both.
331 unless ($pkg eq 'constant' && $name eq '__ANON__') {
332 next if ($pkg || '') ne $class_name ||
333 (($name || '') ne '__ANON__' && ($pkg || '') ne $class_name);
336 $map->{$symbol} = $method_metaclass->wrap(
338 package_name => $class_name,
346 # Instance Construction & Cloning
352 # we need to protect the integrity of the
353 # Class::MOP::Class singletons here, so we
354 # delegate this to &construct_class_instance
355 # which will deal with the singletons
356 return $class->construct_class_instance(@_)
357 if $class->name->isa('Class::MOP::Class');
358 return $class->construct_instance(@_);
361 sub construct_instance {
362 my ($class, %params) = @_;
363 my $meta_instance = $class->get_meta_instance();
364 my $instance = $meta_instance->create_instance();
365 foreach my $attr ($class->compute_all_applicable_attributes()) {
366 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
369 # this will only work for a HASH instance type
370 if ($class->is_anon_class) {
371 (Scalar::Util::reftype($instance) eq 'HASH')
372 || confess "Currently only HASH based instances are supported with instance of anon-classes";
374 # At some point we should make this official
375 # as a reserved slot name, but right now I am
376 # going to keep it here.
377 # my $RESERVED_MOP_SLOT = '__MOP__';
378 $instance->{'__MOP__'} = $class;
384 sub get_meta_instance {
386 $self->{'_meta_instance'} ||= $self->instance_metaclass->new(
387 associated_metaclass => $self,
388 attributes => [ $self->compute_all_applicable_attributes() ],
394 my $instance = shift;
395 (blessed($instance) && $instance->isa($class->name))
396 || confess "You must pass an instance of the metaclass (" . $class->name . "), not ($instance)";
399 # we need to protect the integrity of the
400 # Class::MOP::Class singletons here, they
401 # should not be cloned.
402 return $instance if $instance->isa('Class::MOP::Class');
403 $class->clone_instance($instance, @_);
407 my ($class, $instance, %params) = @_;
409 || confess "You can only clone instances, ($instance) is not a blessed instance";
410 my $meta_instance = $class->get_meta_instance();
411 my $clone = $meta_instance->clone_instance($instance);
412 foreach my $attr ($class->compute_all_applicable_attributes()) {
413 if ( defined( my $init_arg = $attr->init_arg ) ) {
414 if (exists $params{$init_arg}) {
415 $attr->set_value($clone, $params{$init_arg});
422 sub rebless_instance {
423 my ($self, $instance, %params) = @_;
426 if ($instance->can('meta')) {
427 ($instance->meta->isa('Class::MOP::Class'))
428 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
429 $old_metaclass = $instance->meta;
432 $old_metaclass = $self->initialize(blessed($instance));
435 my $meta_instance = $self->get_meta_instance();
437 $self->name->isa($old_metaclass->name)
438 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
441 $meta_instance->rebless_instance_structure($instance, $self);
443 foreach my $attr ( $self->compute_all_applicable_attributes ) {
444 if ( $attr->has_value($instance) ) {
445 if ( defined( my $init_arg = $attr->init_arg ) ) {
446 $params{$init_arg} = $attr->get_value($instance)
447 unless exists $params{$init_arg};
450 $attr->set_value($instance, $attr->get_value($instance));
455 foreach my $attr ($self->compute_all_applicable_attributes) {
456 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
466 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
469 @{$self->get_package_symbol($var_spec)} = @supers;
471 # we need to check the metaclass
472 # compatibility here so that we can
473 # be sure that the superclass is
474 # not potentially creating an issues
475 # we don't know about
476 $self->check_metaclass_compatability();
478 @{$self->get_package_symbol($var_spec)};
484 my $super_class = $self->name;
486 if ( Class::MOP::HAVE_ISAREV() ) {
487 return @{ $super_class->mro::get_isarev() };
491 my $find_derived_classes;
492 $find_derived_classes = sub {
493 my ($outer_class) = @_;
495 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
498 for my $symbol ( keys %$symbol_table_hashref ) {
499 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
500 my $inner_class = $1;
502 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
506 ? "${outer_class}::$inner_class"
509 if ( $class->isa($super_class) and $class ne $super_class ) {
510 push @derived_classes, $class;
513 next SYMBOL if $class eq 'main'; # skip 'main::*'
515 $find_derived_classes->($class);
519 my $root_class = q{};
520 $find_derived_classes->($root_class);
522 undef $find_derived_classes;
524 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
526 return @derived_classes;
532 return @{ mro::get_linear_isa( (shift)->name ) };
535 sub class_precedence_list {
537 my $name = $self->name;
539 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
541 # We need to check for circular inheritance here
542 # if we are are not on 5.10, cause 5.8 detects it
543 # late. This will do nothing if all is well, and
544 # blow up otherwise. Yes, it's an ugly hack, better
545 # suggestions are welcome.
547 ($name || return)->isa('This is a test for circular inheritance')
550 # if our mro is c3, we can
551 # just grab the linear_isa
552 if (mro::get_mro($name) eq 'c3') {
553 return @{ mro::get_linear_isa($name) }
557 # we can't grab the linear_isa for dfs
558 # since it has all the duplicates
563 $self->initialize($_)->class_precedence_list()
564 } $self->superclasses()
572 my ($self, $method_name, $method) = @_;
573 (defined $method_name && $method_name)
574 || confess "You must define a method name";
577 if (blessed($method)) {
578 $body = $method->body;
579 if ($method->package_name ne $self->name &&
580 $method->name ne $method_name) {
581 warn "Hello there, got something for you."
582 . " Method says " . $method->package_name . " " . $method->name
583 . " Class says " . $self->name . " " . $method_name;
584 $method = $method->clone(
585 package_name => $self->name,
587 ) if $method->can('clone');
592 ('CODE' eq ref($body))
593 || confess "Your code block must be a CODE reference";
594 $method = $self->method_metaclass->wrap(
596 package_name => $self->name,
601 $self->get_method_map->{$method_name} = $method;
603 my $full_method_name = ($self->name . '::' . $method_name);
604 $self->add_package_symbol(
605 { sigil => '&', type => 'CODE', name => $method_name },
606 Class::MOP::subname($full_method_name => $body)
608 $self->update_package_cache_flag;
612 my $fetch_and_prepare_method = sub {
613 my ($self, $method_name) = @_;
615 my $method = $self->get_method($method_name);
616 # if we dont have local ...
618 # try to find the next method
619 $method = $self->find_next_method_by_name($method_name);
620 # die if it does not exist
622 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
623 # and now make sure to wrap it
624 # even if it is already wrapped
625 # because we need a new sub ref
626 $method = Class::MOP::Method::Wrapped->wrap($method);
629 # now make sure we wrap it properly
630 $method = Class::MOP::Method::Wrapped->wrap($method)
631 unless $method->isa('Class::MOP::Method::Wrapped');
633 $self->add_method($method_name => $method);
637 sub add_before_method_modifier {
638 my ($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_before_modifier(
643 Class::MOP::subname(':before' => $method_modifier)
647 sub add_after_method_modifier {
648 my ($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_after_modifier(
653 Class::MOP::subname(':after' => $method_modifier)
657 sub add_around_method_modifier {
658 my ($self, $method_name, $method_modifier) = @_;
659 (defined $method_name && $method_name)
660 || confess "You must pass in a method name";
661 my $method = $fetch_and_prepare_method->($self, $method_name);
662 $method->add_around_modifier(
663 Class::MOP::subname(':around' => $method_modifier)
668 # the methods above used to be named like this:
669 # ${pkg}::${method}:(before|after|around)
670 # but this proved problematic when using one modifier
671 # to wrap multiple methods (something which is likely
672 # to happen pretty regularly IMO). So instead of naming
673 # it like this, I have chosen to just name them purely
674 # with their modifier names, like so:
675 # :(before|after|around)
676 # The fact is that in a stack trace, it will be fairly
677 # evident from the context what method they are attached
678 # to, and so don't need the fully qualified name.
682 my ($self, $method_name, $method) = @_;
683 (defined $method_name && $method_name)
684 || confess "You must define a method name";
686 my $body = (blessed($method) ? $method->body : $method);
687 ('CODE' eq ref($body))
688 || confess "Your code block must be a CODE reference";
690 $self->add_package_symbol(
691 { sigil => '&', type => 'CODE', name => $method_name } => $body
693 $self->update_package_cache_flag;
697 my ($self, $method_name) = @_;
698 (defined $method_name && $method_name)
699 || confess "You must define a method name";
701 return 0 unless exists $self->get_method_map->{$method_name};
706 my ($self, $method_name) = @_;
707 (defined $method_name && $method_name)
708 || confess "You must define a method name";
711 # I don't really need this here, because
712 # if the method_map is missing a key it
713 # will just return undef for me now
714 # return unless $self->has_method($method_name);
716 return $self->get_method_map->{$method_name};
720 my ($self, $method_name) = @_;
721 (defined $method_name && $method_name)
722 || confess "You must define a method name";
724 my $removed_method = delete $self->get_method_map->{$method_name};
726 $self->remove_package_symbol(
727 { sigil => '&', type => 'CODE', name => $method_name }
730 $self->update_package_cache_flag;
732 return $removed_method;
735 sub get_method_list {
737 keys %{$self->get_method_map};
740 sub find_method_by_name {
741 my ($self, $method_name) = @_;
742 (defined $method_name && $method_name)
743 || confess "You must define a method name to find";
744 foreach my $class ($self->linearized_isa) {
745 # fetch the meta-class ...
746 my $meta = $self->initialize($class);
747 return $meta->get_method($method_name)
748 if $meta->has_method($method_name);
753 sub compute_all_applicable_methods {
755 my (@methods, %seen_method);
756 foreach my $class ($self->linearized_isa) {
757 # fetch the meta-class ...
758 my $meta = $self->initialize($class);
759 foreach my $method_name ($meta->get_method_list()) {
760 next if exists $seen_method{$method_name};
761 $seen_method{$method_name}++;
763 name => $method_name,
765 code => $meta->get_method($method_name)
772 sub find_all_methods_by_name {
773 my ($self, $method_name) = @_;
774 (defined $method_name && $method_name)
775 || confess "You must define a method name to find";
777 foreach my $class ($self->linearized_isa) {
778 # fetch the meta-class ...
779 my $meta = $self->initialize($class);
781 name => $method_name,
783 code => $meta->get_method($method_name)
784 } if $meta->has_method($method_name);
789 sub find_next_method_by_name {
790 my ($self, $method_name) = @_;
791 (defined $method_name && $method_name)
792 || confess "You must define a method name to find";
793 my @cpl = $self->linearized_isa;
794 shift @cpl; # discard ourselves
795 foreach my $class (@cpl) {
796 # fetch the meta-class ...
797 my $meta = $self->initialize($class);
798 return $meta->get_method($method_name)
799 if $meta->has_method($method_name);
808 # either we have an attribute object already
809 # or we need to create one from the args provided
810 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
811 # make sure it is derived from the correct type though
812 ($attribute->isa('Class::MOP::Attribute'))
813 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
815 # first we attach our new attribute
816 # because it might need certain information
817 # about the class which it is attached to
818 $attribute->attach_to_class($self);
820 # then we remove attributes of a conflicting
821 # name here so that we can properly detach
822 # the old attr object, and remove any
823 # accessors it would have generated
824 if ( $self->has_attribute($attribute->name) ) {
825 $self->remove_attribute($attribute->name);
827 $self->invalidate_meta_instances();
830 # then onto installing the new accessors
831 $self->get_attribute_map->{$attribute->name} = $attribute;
833 # invalidate package flag here
834 $attribute->install_accessors();
839 sub invalidate_meta_instances {
842 my @metas = ( $self, map { Class::MOP::Class->initialize($_) } $self->subclasses );
844 $_->invalidate_meta_instance() for @metas;
847 sub invalidate_meta_instance {
849 undef $self->{_meta_instance};
853 my ($self, $attribute_name) = @_;
854 (defined $attribute_name && $attribute_name)
855 || confess "You must define an attribute name";
856 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
860 my ($self, $attribute_name) = @_;
861 (defined $attribute_name && $attribute_name)
862 || confess "You must define an attribute name";
863 return $self->get_attribute_map->{$attribute_name}
865 # this will return undef anyway, so no need ...
866 # if $self->has_attribute($attribute_name);
870 sub remove_attribute {
871 my ($self, $attribute_name) = @_;
872 (defined $attribute_name && $attribute_name)
873 || confess "You must define an attribute name";
874 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
875 return unless defined $removed_attribute;
876 delete $self->get_attribute_map->{$attribute_name};
877 $self->invalidate_meta_instances();
878 $removed_attribute->remove_accessors();
879 $removed_attribute->detach_from_class();
880 return $removed_attribute;
883 sub get_attribute_list {
885 keys %{$self->get_attribute_map};
888 sub compute_all_applicable_attributes {
890 my (@attrs, %seen_attr);
891 foreach my $class ($self->linearized_isa) {
892 # fetch the meta-class ...
893 my $meta = $self->initialize($class);
894 foreach my $attr_name ($meta->get_attribute_list()) {
895 next if exists $seen_attr{$attr_name};
896 $seen_attr{$attr_name}++;
897 push @attrs => $meta->get_attribute($attr_name);
903 sub find_attribute_by_name {
904 my ($self, $attr_name) = @_;
905 foreach my $class ($self->linearized_isa) {
906 # fetch the meta-class ...
907 my $meta = $self->initialize($class);
908 return $meta->get_attribute($attr_name)
909 if $meta->has_attribute($attr_name);
917 sub is_immutable { 0 }
920 # Why I changed this (groditi)
921 # - One Metaclass may have many Classes through many Metaclass instances
922 # - One Metaclass should only have one Immutable Transformer instance
923 # - Each Class may have different Immutabilizing options
924 # - Therefore each Metaclass instance may have different Immutabilizing options
925 # - We need to store one Immutable Transformer instance per Metaclass
926 # - We need to store one set of Immutable Transformer options per Class
927 # - Upon make_mutable we may delete the Immutabilizing options
928 # - We could clean the immutable Transformer instance when there is no more
929 # immutable Classes of that type, but we can also keep it in case
930 # another class with this same Metaclass becomes immutable. It is a case
931 # of trading of storing an instance to avoid unnecessary instantiations of
932 # Immutable Transformers. You may view this as a memory leak, however
933 # Because we have few Metaclasses, in practice it seems acceptable
934 # - To allow Immutable Transformers instances to be cleaned up we could weaken
935 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
939 my %IMMUTABLE_TRANSFORMERS;
940 my %IMMUTABLE_OPTIONS;
942 sub get_immutable_options {
944 return if $self->is_mutable;
945 confess "unable to find immutabilizing options"
946 unless exists $IMMUTABLE_OPTIONS{$self->name};
947 my %options = %{$IMMUTABLE_OPTIONS{$self->name}};
948 delete $options{IMMUTABLE_TRANSFORMER};
952 sub get_immutable_transformer {
954 if( $self->is_mutable ){
955 my $class = blessed $self || $self;
956 return $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
958 confess "unable to find transformer for immutable class"
959 unless exists $IMMUTABLE_OPTIONS{$self->name};
960 return $IMMUTABLE_OPTIONS{$self->name}->{IMMUTABLE_TRANSFORMER};
967 my $transformer = $self->get_immutable_transformer;
968 $transformer->make_metaclass_immutable($self, \%options);
969 $IMMUTABLE_OPTIONS{$self->name} =
970 { %options, IMMUTABLE_TRANSFORMER => $transformer };
972 if( exists $options{debug} && $options{debug} ){
973 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
974 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
982 return if $self->is_mutable;
983 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
984 confess "unable to find immutabilizing options" unless ref $options;
985 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
986 $transformer->make_metaclass_mutable($self, $options);
991 sub create_immutable_transformer {
993 my $class = Class::MOP::Immutable->new($self, {
994 read_only => [qw/superclasses/],
1001 remove_package_symbol
1004 class_precedence_list => 'ARRAY',
1005 linearized_isa => 'ARRAY',
1006 compute_all_applicable_attributes => 'ARRAY',
1007 get_meta_instance => 'SCALAR',
1008 get_method_map => 'SCALAR',
1011 # this is ugly, but so are typeglobs,
1012 # so whattayahgonnadoboutit
1015 add_package_symbol => sub {
1016 my $original = shift;
1017 confess "Cannot add package symbols to an immutable metaclass"
1018 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
1019 goto $original->body;
1034 Class::MOP::Class - Class Meta Object
1038 # assuming that class Foo
1039 # has been defined, you can
1041 # use this for introspection ...
1043 # add a method to Foo ...
1044 Foo->meta->add_method('bar' => sub { ... })
1046 # get a list of all the classes searched
1047 # the method dispatcher in the correct order
1048 Foo->meta->class_precedence_list()
1050 # remove a method from Foo
1051 Foo->meta->remove_method('bar');
1053 # or use this to actually create classes ...
1055 Class::MOP::Class->create('Bar' => (
1057 superclasses => [ 'Foo' ],
1059 Class::MOP:::Attribute->new('$bar'),
1060 Class::MOP:::Attribute->new('$baz'),
1063 calculate_bar => sub { ... },
1064 construct_baz => sub { ... }
1070 This is the largest and currently most complex part of the Perl 5
1071 meta-object protocol. It controls the introspection and
1072 manipulation of Perl 5 classes (and it can create them too). The
1073 best way to understand what this module can do, is to read the
1074 documentation for each of it's methods.
1078 =head2 Self Introspection
1084 This will return a B<Class::MOP::Class> instance which is related
1085 to this class. Thereby allowing B<Class::MOP::Class> to actually
1088 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1089 bootstrap this module by installing a number of attribute meta-objects
1090 into it's metaclass. This will allow this class to reap all the benifits
1091 of the MOP when subclassing it.
1095 =head2 Class construction
1097 These methods will handle creating B<Class::MOP::Class> objects,
1098 which can be used to both create new classes, and analyze
1099 pre-existing classes.
1101 This module will internally store references to all the instances
1102 you create with these methods, so that they do not need to be
1103 created any more than nessecary. Basically, they are singletons.
1107 =item B<create ($package_name,
1108 version =E<gt> ?$version,
1109 authority =E<gt> ?$authority,
1110 superclasses =E<gt> ?@superclasses,
1111 methods =E<gt> ?%methods,
1112 attributes =E<gt> ?%attributes)>
1114 This returns a B<Class::MOP::Class> object, bringing the specified
1115 C<$package_name> into existence and adding any of the C<$version>,
1116 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1119 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1120 methods =E<gt> ?%methods,
1121 attributes =E<gt> ?%attributes)>
1123 This will create an anonymous class, it works much like C<create> but
1124 it does not need a C<$package_name>. Instead it will create a suitably
1125 unique package name for you to stash things into.
1127 On very important distinction is that anon classes are destroyed once
1128 the metaclass they are attached to goes out of scope. In the DESTROY
1129 method, the created package will be removed from the symbol table.
1131 It is also worth noting that any instances created with an anon-class
1132 will keep a special reference to the anon-meta which will prevent the
1133 anon-class from going out of scope until all instances of it have also
1134 been destroyed. This however only works for HASH based instance types,
1135 as we use a special reserved slot (C<__MOP__>) to store this.
1137 =item B<initialize ($package_name, %options)>
1139 This initializes and returns returns a B<Class::MOP::Class> object
1140 for a given a C<$package_name>.
1142 =item B<reinitialize ($package_name, %options)>
1144 This removes the old metaclass, and creates a new one in it's place.
1145 Do B<not> use this unless you really know what you are doing, it could
1146 very easily make a very large mess of your program.
1148 =item B<construct_class_instance (%options)>
1150 This will construct an instance of B<Class::MOP::Class>, it is
1151 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1152 to use C<construct_instance> once all the bootstrapping is done. This
1153 method is used internally by C<initialize> and should never be called
1154 from outside of that method really.
1156 =item B<check_metaclass_compatability>
1158 This method is called as the very last thing in the
1159 C<construct_class_instance> method. This will check that the
1160 metaclass you are creating is compatible with the metaclasses of all
1161 your ancestors. For more inforamtion about metaclass compatibility
1162 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1164 =item B<update_package_cache_flag>
1166 This will reset the package cache flag for this particular metaclass
1167 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1168 function. This is very rarely needed from outside of C<Class::MOP::Class>
1169 but in some cases you might want to use it, so it is here.
1171 =item B<reset_package_cache_flag>
1173 Clears the package cache flag to announce to the internals that we need
1174 to rebuild the method map.
1176 =item B<invalidate_meta_instances>
1178 Clears the cached meta instance for this metaclass and all of its subclasses.
1180 Called by C<add_attribute> and C<remove_attribute> to recalculate the attribute
1183 =item B<invalidate_meta_instance>
1185 Used by C<invalidate_meta_instances>.
1189 =head2 Object instance construction and cloning
1191 These methods are B<entirely optional>, it is up to you whether you want
1196 =item B<instance_metaclass>
1198 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1199 for more information on the instance metaclasses.
1201 =item B<get_meta_instance>
1203 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1204 of a new instance of the class.
1206 =item B<new_object (%params)>
1208 This is a convience method for creating a new object of the class, and
1209 blessing it into the appropriate package as well. Ideally your class
1210 would call a C<new> this method like so:
1213 my ($class, %param) = @_;
1214 $class->meta->new_object(%params);
1217 =item B<construct_instance (%params)>
1219 This method is used to construct an instance structure suitable for
1220 C<bless>-ing into your package of choice. It works in conjunction
1221 with the Attribute protocol to collect all applicable attributes.
1223 This will construct and instance using a HASH ref as storage
1224 (currently only HASH references are supported). This will collect all
1225 the applicable attributes and layout out the fields in the HASH ref,
1226 it will then initialize them using either use the corresponding key
1227 in C<%params> or any default value or initializer found in the
1228 attribute meta-object.
1230 =item B<clone_object ($instance, %params)>
1232 This is a convience method for cloning an object instance, then
1233 blessing it into the appropriate package. This method will call
1234 C<clone_instance>, which performs a shallow copy of the object,
1235 see that methods documentation for more details. Ideally your
1236 class would call a C<clone> this method like so:
1238 sub MyClass::clone {
1239 my ($self, %param) = @_;
1240 $self->meta->clone_object($self, %params);
1243 =item B<clone_instance($instance, %params)>
1245 This method is a compliment of C<construct_instance> (which means if
1246 you override C<construct_instance>, you need to override this one too),
1247 and clones the instance shallowly.
1249 The cloned structure returned is (like with C<construct_instance>) an
1250 unC<bless>ed HASH reference, it is your responsibility to then bless
1251 this cloned structure into the right class (which C<clone_object> will
1254 As of 0.11, this method will clone the C<$instance> structure shallowly,
1255 as opposed to the deep cloning implemented in prior versions. After much
1256 thought, research and discussion, I have decided that anything but basic
1257 shallow cloning is outside the scope of the meta-object protocol. I
1258 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1259 is too I<context-specific> to be part of the MOP.
1261 =item B<rebless_instance($instance, ?%params)>
1263 This will change the class of C<$instance> to the class of the invoking
1264 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1265 itself. You may pass in optional C<%params> which are like constructor
1266 params and will override anything already defined in the instance.
1270 =head2 Informational
1272 These are a few predicate methods for asking information about the class.
1276 =item B<is_anon_class>
1278 This returns true if the class is a C<Class::MOP::Class> created anon class.
1282 This returns true if the class is still mutable.
1284 =item B<is_immutable>
1286 This returns true if the class has been made immutable.
1290 =head2 Inheritance Relationships
1294 =item B<superclasses (?@superclasses)>
1296 This is a read-write attribute which represents the superclass
1297 relationships of the class the B<Class::MOP::Class> instance is
1298 associated with. Basically, it can get and set the C<@ISA> for you.
1300 =item B<class_precedence_list>
1302 This computes the a list of all the class's ancestors in the same order
1303 in which method dispatch will be done. This is similair to what
1304 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1306 =item B<linearized_isa>
1308 This returns a list based on C<class_precedence_list> but with all
1313 This returns a list of subclasses for this class.
1321 =item B<get_method_map>
1323 Returns a HASH ref of name to CODE reference mapping for this class.
1325 =item B<method_metaclass>
1327 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1328 for more information on the method metaclasses.
1330 =item B<add_method ($method_name, $method)>
1332 This will take a C<$method_name> and CODE reference to that
1333 C<$method> and install it into the class's package.
1336 This does absolutely nothing special to C<$method>
1337 other than use B<Sub::Name> to make sure it is tagged with the
1338 correct name, and therefore show up correctly in stack traces and
1341 =item B<alias_method ($method_name, $method)>
1343 This will take a C<$method_name> and CODE reference to that
1344 C<$method> and alias the method into the class's package.
1347 Unlike C<add_method>, this will B<not> try to name the
1348 C<$method> using B<Sub::Name>, it only aliases the method in
1349 the class's package.
1351 =item B<has_method ($method_name)>
1353 This just provides a simple way to check if the class implements
1354 a specific C<$method_name>. It will I<not> however, attempt to check
1355 if the class inherits the method (use C<UNIVERSAL::can> for that).
1357 This will correctly handle functions defined outside of the package
1358 that use a fully qualified name (C<sub Package::name { ... }>).
1360 This will correctly handle functions renamed with B<Sub::Name> and
1361 installed using the symbol tables. However, if you are naming the
1362 subroutine outside of the package scope, you must use the fully
1363 qualified name, including the package name, for C<has_method> to
1364 correctly identify it.
1366 This will attempt to correctly ignore functions imported from other
1367 packages using B<Exporter>. It breaks down if the function imported
1368 is an C<__ANON__> sub (such as with C<use constant>), which very well
1369 may be a valid method being applied to the class.
1371 In short, this method cannot always be trusted to determine if the
1372 C<$method_name> is actually a method. However, it will DWIM about
1373 90% of the time, so it's a small trade off I think.
1375 =item B<get_method ($method_name)>
1377 This will return a Class::MOP::Method instance related to the specified
1378 C<$method_name>, or return undef if that method does not exist.
1380 The Class::MOP::Method is codifiable, so you can use it like a normal
1381 CODE reference, see L<Class::MOP::Method> for more information.
1383 =item B<find_method_by_name ($method_name)>
1385 This will return a CODE reference of the specified C<$method_name>,
1386 or return undef if that method does not exist.
1388 Unlike C<get_method> this will also look in the superclasses.
1390 =item B<remove_method ($method_name)>
1392 This will attempt to remove a given C<$method_name> from the class.
1393 It will return the CODE reference that it has removed, and will
1394 attempt to use B<Sub::Name> to clear the methods associated name.
1396 =item B<get_method_list>
1398 This will return a list of method names for all I<locally> defined
1399 methods. It does B<not> provide a list of all applicable methods,
1400 including any inherited ones. If you want a list of all applicable
1401 methods, use the C<compute_all_applicable_methods> method.
1403 =item B<compute_all_applicable_methods>
1405 This will return a list of all the methods names this class will
1406 respond to, taking into account inheritance. The list will be a list of
1407 HASH references, each one containing the following information; method
1408 name, the name of the class in which the method lives and a CODE
1409 reference for the actual method.
1411 =item B<find_all_methods_by_name ($method_name)>
1413 This will traverse the inheritence hierarchy and locate all methods
1414 with a given C<$method_name>. Similar to
1415 C<compute_all_applicable_methods> it returns a list of HASH references
1416 with the following information; method name (which will always be the
1417 same as C<$method_name>), the name of the class in which the method
1418 lives and a CODE reference for the actual method.
1420 The list of methods produced is a distinct list, meaning there are no
1421 duplicates in it. This is especially useful for things like object
1422 initialization and destruction where you only want the method called
1423 once, and in the correct order.
1425 =item B<find_next_method_by_name ($method_name)>
1427 This will return the first method to match a given C<$method_name> in
1428 the superclasses, this is basically equivalent to calling
1429 C<SUPER::$method_name>, but it can be dispatched at runtime.
1433 =head2 Method Modifiers
1435 Method modifiers are a concept borrowed from CLOS, in which a method
1436 can be wrapped with I<before>, I<after> and I<around> method modifiers
1437 that will be called everytime the method is called.
1439 =head3 How method modifiers work?
1441 Method modifiers work by wrapping the original method and then replacing
1442 it in the classes symbol table. The wrappers will handle calling all the
1443 modifiers in the appropariate orders and preserving the calling context
1444 for the original method.
1446 Each method modifier serves a particular purpose, which may not be
1447 obvious to users of other method wrapping modules. To start with, the
1448 return values of I<before> and I<after> modifiers are ignored. This is
1449 because thier purpose is B<not> to filter the input and output of the
1450 primary method (this is done with an I<around> modifier). This may seem
1451 like an odd restriction to some, but doing this allows for simple code
1452 to be added at the begining or end of a method call without jeapordizing
1453 the normal functioning of the primary method or placing any extra
1454 responsibility on the code of the modifier. Of course if you have more
1455 complex needs, then use the I<around> modifier, which uses a variation
1456 of continutation passing style to allow for a high degree of flexibility.
1458 Before and around modifiers are called in last-defined-first-called order,
1459 while after modifiers are called in first-defined-first-called order. So
1460 the call tree might looks something like this:
1470 To see examples of using method modifiers, see the following examples
1471 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1472 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1473 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1475 =head3 What is the performance impact?
1477 Of course there is a performance cost associated with method modifiers,
1478 but we have made every effort to make that cost be directly proportional
1479 to the amount of modifier features you utilize.
1481 The wrapping method does it's best to B<only> do as much work as it
1482 absolutely needs to. In order to do this we have moved some of the
1483 performance costs to set-up time, where they are easier to amortize.
1485 All this said, my benchmarks have indicated the following:
1487 simple wrapper with no modifiers 100% slower
1488 simple wrapper with simple before modifier 400% slower
1489 simple wrapper with simple after modifier 450% slower
1490 simple wrapper with simple around modifier 500-550% slower
1491 simple wrapper with all 3 modifiers 1100% slower
1493 These numbers may seem daunting, but you must remember, every feature
1494 comes with some cost. To put things in perspective, just doing a simple
1495 C<AUTOLOAD> which does nothing but extract the name of the method called
1496 and return it costs about 400% over a normal method call.
1500 =item B<add_before_method_modifier ($method_name, $code)>
1502 This will wrap the method at C<$method_name> and the supplied C<$code>
1503 will be passed the C<@_> arguments, and called before the original
1504 method is called. As specified above, the return value of the I<before>
1505 method modifiers is ignored, and it's ability to modify C<@_> is
1506 fairly limited. If you need to do either of these things, use an
1507 C<around> method modifier.
1509 =item B<add_after_method_modifier ($method_name, $code)>
1511 This will wrap the method at C<$method_name> so that the original
1512 method will be called, it's return values stashed, and then the
1513 supplied C<$code> will be passed the C<@_> arguments, and called.
1514 As specified above, the return value of the I<after> method
1515 modifiers is ignored, and it cannot modify the return values of
1516 the original method. If you need to do either of these things, use an
1517 C<around> method modifier.
1519 =item B<add_around_method_modifier ($method_name, $code)>
1521 This will wrap the method at C<$method_name> so that C<$code>
1522 will be called and passed the original method as an extra argument
1523 at the begining of the C<@_> argument list. This is a variation of
1524 continuation passing style, where the function prepended to C<@_>
1525 can be considered a continuation. It is up to C<$code> if it calls
1526 the original method or not, there is no restriction on what the
1527 C<$code> can or cannot do.
1533 It should be noted that since there is no one consistent way to define
1534 the attributes of a class in Perl 5. These methods can only work with
1535 the information given, and can not easily discover information on
1536 their own. See L<Class::MOP::Attribute> for more details.
1540 =item B<attribute_metaclass>
1542 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1543 for more information on the attribute metaclasses.
1545 =item B<get_attribute_map>
1547 This returns a HASH ref of name to attribute meta-object mapping.
1549 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1551 This stores the C<$attribute_meta_object> (or creates one from the
1552 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1553 instance associated with the given class. Unlike methods, attributes
1554 within the MOP are stored as meta-information only. They will be used
1555 later to construct instances from (see C<construct_instance> above).
1556 More details about the attribute meta-objects can be found in the
1557 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1560 It should be noted that any accessor, reader/writer or predicate
1561 methods which the C<$attribute_meta_object> has will be installed
1562 into the class at this time.
1565 If an attribute already exists for C<$attribute_name>, the old one
1566 will be removed (as well as removing all it's accessors), and then
1569 =item B<has_attribute ($attribute_name)>
1571 Checks to see if this class has an attribute by the name of
1572 C<$attribute_name> and returns a boolean.
1574 =item B<get_attribute ($attribute_name)>
1576 Returns the attribute meta-object associated with C<$attribute_name>,
1577 if none is found, it will return undef.
1579 =item B<remove_attribute ($attribute_name)>
1581 This will remove the attribute meta-object stored at
1582 C<$attribute_name>, then return the removed attribute meta-object.
1585 Removing an attribute will only affect future instances of
1586 the class, it will not make any attempt to remove the attribute from
1587 any existing instances of the class.
1589 It should be noted that any accessor, reader/writer or predicate
1590 methods which the attribute meta-object stored at C<$attribute_name>
1591 has will be removed from the class at this time. This B<will> make
1592 these attributes somewhat inaccessable in previously created
1593 instances. But if you are crazy enough to do this at runtime, then
1594 you are crazy enough to deal with something like this :).
1596 =item B<get_attribute_list>
1598 This returns a list of attribute names which are defined in the local
1599 class. If you want a list of all applicable attributes for a class,
1600 use the C<compute_all_applicable_attributes> method.
1602 =item B<compute_all_applicable_attributes>
1604 This will traverse the inheritance heirachy and return a list of all
1605 the applicable attributes for this class. It does not construct a
1606 HASH reference like C<compute_all_applicable_methods> because all
1607 that same information is discoverable through the attribute
1610 =item B<find_attribute_by_name ($attr_name)>
1612 This method will traverse the inheritance heirachy and find the
1613 first attribute whose name matches C<$attr_name>, then return it.
1614 It will return undef if nothing is found.
1618 =head2 Class Immutability
1622 =item B<make_immutable (%options)>
1624 This method will invoke a tranforamtion upon the class which will
1625 make it immutable. Details of this transformation can be found in
1626 the L<Class::MOP::Immutable> documentation.
1628 =item B<make_mutable>
1630 This method will reverse tranforamtion upon the class which
1633 =item B<get_immutable_transformer>
1635 Return a transformer suitable for making this class immutable or, if this
1636 class is immutable, the transformer used to make it immutable.
1638 =item B<get_immutable_options>
1640 If the class is immutable, return the options used to make it immutable.
1642 =item B<create_immutable_transformer>
1644 Create a transformer suitable for making this class immutable
1650 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1652 =head1 COPYRIGHT AND LICENSE
1654 Copyright 2006-2008 by Infinity Interactive, Inc.
1656 L<http://www.iinteractive.com>
1658 This library is free software; you can redistribute it and/or modify
1659 it under the same terms as Perl itself.