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';
22 my ( $class, @args ) = @_;
24 unshift @args, 'package' if @args % 2 == 1;
26 my (%options) = @args;
27 my $package_name = $options{package};
29 (defined $package_name && $package_name && !blessed($package_name))
30 || confess "You must pass a package name and it cannot be blessed";
32 return Class::MOP::get_metaclass_by_name($package_name)
33 || $class->construct_class_instance(%options);
38 my $package_name = shift;
39 (defined $package_name && $package_name && !blessed($package_name))
40 || confess "You must pass a package name and it cannot be blessed";
41 Class::MOP::remove_metaclass_by_name($package_name);
42 $class->construct_class_instance('package' => $package_name, @_);
45 # NOTE: (meta-circularity)
46 # this is a special form of &construct_instance
47 # (see below), which is used to construct class
48 # meta-object instances for any Class::MOP::*
49 # class. All other classes will use the more
50 # normal &construct_instance.
51 sub construct_class_instance {
54 my $package_name = $options{'package'};
55 (defined $package_name && $package_name)
56 || confess "You must pass a package name";
58 # return the metaclass if we have it cached,
59 # and it is still defined (it has not been
60 # reaped by DESTROY yet, which can happen
61 # annoyingly enough during global destruction)
63 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
68 # we need to deal with the possibility
69 # of class immutability here, and then
70 # get the name of the class appropriately
71 $class = (blessed($class)
72 ? ($class->is_immutable
73 ? $class->get_mutable_metaclass_name()
77 # now create the metaclass
79 if ($class eq 'Class::MOP::Class') {
82 # inherited from Class::MOP::Package
83 'package' => $package_name,
86 # since the following attributes will
87 # actually be loaded from the symbol
88 # table, and actually bypass the instance
89 # entirely, we can just leave these things
90 # listed here for reference, because they
91 # should not actually have a value associated
93 'namespace' => \undef,
94 # inherited from Class::MOP::Module
96 'authority' => \undef,
97 # defined in Class::MOP::Class
98 'superclasses' => \undef,
102 'attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
103 'method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
104 'instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
106 ## uber-private variables
108 # this starts out as undef so that
109 # we can tell the first time the
110 # methods are fetched
112 '_package_cache_flag' => undef,
113 '_meta_instance' => undef,
118 # it is safe to use meta here because
119 # class will always be a subclass of
120 # Class::MOP::Class, which defines meta
121 $meta = $class->meta->construct_instance(%options)
124 # and check the metaclass compatibility
125 $meta->check_metaclass_compatability();
127 Class::MOP::store_metaclass_by_name($package_name, $meta);
130 # we need to weaken any anon classes
131 # so that they can call DESTROY properly
132 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
137 sub reset_package_cache_flag { (shift)->{'_package_cache_flag'} = undef }
138 sub update_package_cache_flag {
141 # we can manually update the cache number
142 # since we are actually adding the method
143 # to our cache as well. This avoids us
144 # having to regenerate the method_map.
146 $self->{'_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
149 sub check_metaclass_compatability {
152 # this is always okay ...
153 return if blessed($self) eq 'Class::MOP::Class' &&
154 $self->instance_metaclass eq 'Class::MOP::Instance';
156 my @class_list = $self->linearized_isa;
157 shift @class_list; # shift off $self->name
159 foreach my $class_name (@class_list) {
160 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
163 # we need to deal with the possibility
164 # of class immutability here, and then
165 # get the name of the class appropriately
166 my $meta_type = ($meta->is_immutable
167 ? $meta->get_mutable_metaclass_name()
170 ($self->isa($meta_type))
171 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
172 " is not compatible with the " .
173 $class_name . "->meta => (" . ($meta_type) . ")";
175 # we also need to check that instance metaclasses
176 # are compatabile in the same the class.
177 ($self->instance_metaclass->isa($meta->instance_metaclass))
178 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
179 " is not compatible with the " .
180 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
188 # this should be sufficient, if you have a
189 # use case where it is not, write a test and
191 my $ANON_CLASS_SERIAL = 0;
194 # we need a sufficiently annoying prefix
195 # this should suffice for now, this is
196 # used in a couple of places below, so
197 # need to put it up here for now.
198 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
202 no warnings 'uninitialized';
203 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
206 sub create_anon_class {
207 my ($class, %options) = @_;
208 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
209 return $class->create($package_name, %options);
215 require Devel::GlobalDestruction;
216 Devel::GlobalDestruction->import("in_global_destruction");
218 } or *in_global_destruction = sub () { '' };
222 # this will only get called for
223 # anon-classes, all other calls
224 # are assumed to occur during
225 # global destruction and so don't
226 # really need to be handled explicitly
230 return if in_global_destruction; # it'll happen soon anyway and this just makes things more complicated
232 no warnings 'uninitialized';
233 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
234 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
236 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
237 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
239 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
244 # creating classes with MOP ...
247 my ( $class, @args ) = @_;
249 unshift @args, 'package' if @args % 2 == 1;
251 my (%options) = @args;
252 my $package_name = $options{package};
254 (defined $package_name && $package_name)
255 || confess "You must pass a package name";
257 (ref $options{superclasses} eq 'ARRAY')
258 || confess "You must pass an ARRAY ref of superclasses"
259 if exists $options{superclasses};
261 (ref $options{attributes} eq 'ARRAY')
262 || confess "You must pass an ARRAY ref of attributes"
263 if exists $options{attributes};
265 (ref $options{methods} eq 'HASH')
266 || confess "You must pass an HASH ref of methods"
267 if exists $options{methods};
269 my $code = "package $package_name;";
270 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
271 if exists $options{version};
272 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
273 if exists $options{authority};
276 confess "creation of $package_name failed : $@" if $@;
278 my $meta = $class->initialize($package_name);
281 $meta->add_method('meta' => sub {
282 $class->initialize(blessed($_[0]) || $_[0]);
285 $meta->superclasses(@{$options{superclasses}})
286 if exists $options{superclasses};
288 # process attributes first, so that they can
289 # install accessors, but locally defined methods
290 # can then overwrite them. It is maybe a little odd, but
291 # I think this should be the order of things.
292 if (exists $options{attributes}) {
293 foreach my $attr (@{$options{attributes}}) {
294 $meta->add_attribute($attr);
297 if (exists $options{methods}) {
298 foreach my $method_name (keys %{$options{methods}}) {
299 $meta->add_method($method_name, $options{methods}->{$method_name});
308 # all these attribute readers will be bootstrapped
309 # away in the Class::MOP bootstrap section
311 sub get_attribute_map { $_[0]->{'attributes'} }
312 sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
313 sub method_metaclass { $_[0]->{'method_metaclass'} }
314 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
317 # this is a prime canidate for conversion to XS
321 if (defined $self->{'_package_cache_flag'} &&
322 $self->{'_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
323 return $self->{'methods'};
326 my $map = $self->{'methods'};
328 my $class_name = $self->name;
329 my $method_metaclass = $self->method_metaclass;
331 my %all_code = $self->get_all_package_symbols('CODE');
333 foreach my $symbol (keys %all_code) {
334 my $code = $all_code{$symbol};
336 next if exists $map->{$symbol} &&
337 defined $map->{$symbol} &&
338 $map->{$symbol}->body == $code;
340 my ($pkg, $name) = Class::MOP::get_code_info($code);
343 # in 5.10 constant.pm the constants show up
344 # as being in the right package, but in pre-5.10
345 # they show up as constant::__ANON__ so we
346 # make an exception here to be sure that things
347 # work as expected in both.
349 unless ($pkg eq 'constant' && $name eq '__ANON__') {
350 next if ($pkg || '') ne $class_name ||
351 (($name || '') ne '__ANON__' && ($pkg || '') ne $class_name);
354 $map->{$symbol} = $method_metaclass->wrap(
356 package_name => $class_name,
364 # Instance Construction & Cloning
370 # we need to protect the integrity of the
371 # Class::MOP::Class singletons here, so we
372 # delegate this to &construct_class_instance
373 # which will deal with the singletons
374 return $class->construct_class_instance(@_)
375 if $class->name->isa('Class::MOP::Class');
376 return $class->construct_instance(@_);
379 sub construct_instance {
380 my ($class, %params) = @_;
381 my $meta_instance = $class->get_meta_instance();
382 my $instance = $meta_instance->create_instance();
383 foreach my $attr ($class->compute_all_applicable_attributes()) {
384 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
387 # this will only work for a HASH instance type
388 if ($class->is_anon_class) {
389 (Scalar::Util::reftype($instance) eq 'HASH')
390 || confess "Currently only HASH based instances are supported with instance of anon-classes";
392 # At some point we should make this official
393 # as a reserved slot name, but right now I am
394 # going to keep it here.
395 # my $RESERVED_MOP_SLOT = '__MOP__';
396 $instance->{'__MOP__'} = $class;
402 sub get_meta_instance {
404 $self->{'_meta_instance'} ||= $self->instance_metaclass->new(
405 associated_metaclass => $self,
406 attributes => [ $self->compute_all_applicable_attributes() ],
412 my $instance = shift;
413 (blessed($instance) && $instance->isa($class->name))
414 || confess "You must pass an instance of the metaclass (" . $class->name . "), not ($instance)";
417 # we need to protect the integrity of the
418 # Class::MOP::Class singletons here, they
419 # should not be cloned.
420 return $instance if $instance->isa('Class::MOP::Class');
421 $class->clone_instance($instance, @_);
425 my ($class, $instance, %params) = @_;
427 || confess "You can only clone instances, ($instance) is not a blessed instance";
428 my $meta_instance = $class->get_meta_instance();
429 my $clone = $meta_instance->clone_instance($instance);
430 foreach my $attr ($class->compute_all_applicable_attributes()) {
431 if ( defined( my $init_arg = $attr->init_arg ) ) {
432 if (exists $params{$init_arg}) {
433 $attr->set_value($clone, $params{$init_arg});
440 sub rebless_instance {
441 my ($self, $instance, %params) = @_;
444 if ($instance->can('meta')) {
445 ($instance->meta->isa('Class::MOP::Class'))
446 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
447 $old_metaclass = $instance->meta;
450 $old_metaclass = $self->initialize(blessed($instance));
453 my $meta_instance = $self->get_meta_instance();
455 $self->name->isa($old_metaclass->name)
456 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
459 $meta_instance->rebless_instance_structure($instance, $self);
461 foreach my $attr ( $self->compute_all_applicable_attributes ) {
462 if ( $attr->has_value($instance) ) {
463 if ( defined( my $init_arg = $attr->init_arg ) ) {
464 $params{$init_arg} = $attr->get_value($instance)
465 unless exists $params{$init_arg};
468 $attr->set_value($instance, $attr->get_value($instance));
473 foreach my $attr ($self->compute_all_applicable_attributes) {
474 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
484 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
487 @{$self->get_package_symbol($var_spec)} = @supers;
489 # we need to check the metaclass
490 # compatibility here so that we can
491 # be sure that the superclass is
492 # not potentially creating an issues
493 # we don't know about
494 $self->check_metaclass_compatability();
496 @{$self->get_package_symbol($var_spec)};
502 my $super_class = $self->name;
504 if ( Class::MOP::HAVE_ISAREV() ) {
505 return @{ $super_class->mro::get_isarev() };
509 my $find_derived_classes;
510 $find_derived_classes = sub {
511 my ($outer_class) = @_;
513 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
516 for my $symbol ( keys %$symbol_table_hashref ) {
517 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
518 my $inner_class = $1;
520 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
524 ? "${outer_class}::$inner_class"
527 if ( $class->isa($super_class) and $class ne $super_class ) {
528 push @derived_classes, $class;
531 next SYMBOL if $class eq 'main'; # skip 'main::*'
533 $find_derived_classes->($class);
537 my $root_class = q{};
538 $find_derived_classes->($root_class);
540 undef $find_derived_classes;
542 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
544 return @derived_classes;
550 return @{ mro::get_linear_isa( (shift)->name ) };
553 sub class_precedence_list {
555 my $name = $self->name;
557 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
559 # We need to check for circular inheritance here
560 # if we are are not on 5.10, cause 5.8 detects it
561 # late. This will do nothing if all is well, and
562 # blow up otherwise. Yes, it's an ugly hack, better
563 # suggestions are welcome.
565 ($name || return)->isa('This is a test for circular inheritance')
568 # if our mro is c3, we can
569 # just grab the linear_isa
570 if (mro::get_mro($name) eq 'c3') {
571 return @{ mro::get_linear_isa($name) }
575 # we can't grab the linear_isa for dfs
576 # since it has all the duplicates
581 $self->initialize($_)->class_precedence_list()
582 } $self->superclasses()
590 my ($self, $method_name, $method) = @_;
591 (defined $method_name && $method_name)
592 || confess "You must define a method name";
595 if (blessed($method)) {
596 $body = $method->body;
597 if ($method->package_name ne $self->name &&
598 $method->name ne $method_name) {
599 warn "Hello there, got something for you."
600 . " Method says " . $method->package_name . " " . $method->name
601 . " Class says " . $self->name . " " . $method_name;
602 $method = $method->clone(
603 package_name => $self->name,
605 ) if $method->can('clone');
610 ('CODE' eq ref($body))
611 || confess "Your code block must be a CODE reference";
612 $method = $self->method_metaclass->wrap(
614 package_name => $self->name,
619 $self->get_method_map->{$method_name} = $method;
621 my $full_method_name = ($self->name . '::' . $method_name);
622 $self->add_package_symbol(
623 { sigil => '&', type => 'CODE', name => $method_name },
624 Class::MOP::subname($full_method_name => $body)
626 $self->update_package_cache_flag;
630 my $fetch_and_prepare_method = sub {
631 my ($self, $method_name) = @_;
633 my $method = $self->get_method($method_name);
634 # if we dont have local ...
636 # try to find the next method
637 $method = $self->find_next_method_by_name($method_name);
638 # die if it does not exist
640 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
641 # and now make sure to wrap it
642 # even if it is already wrapped
643 # because we need a new sub ref
644 $method = Class::MOP::Method::Wrapped->wrap($method);
647 # now make sure we wrap it properly
648 $method = Class::MOP::Method::Wrapped->wrap($method)
649 unless $method->isa('Class::MOP::Method::Wrapped');
651 $self->add_method($method_name => $method);
655 sub add_before_method_modifier {
656 my ($self, $method_name, $method_modifier) = @_;
657 (defined $method_name && $method_name)
658 || confess "You must pass in a method name";
659 my $method = $fetch_and_prepare_method->($self, $method_name);
660 $method->add_before_modifier(
661 Class::MOP::subname(':before' => $method_modifier)
665 sub add_after_method_modifier {
666 my ($self, $method_name, $method_modifier) = @_;
667 (defined $method_name && $method_name)
668 || confess "You must pass in a method name";
669 my $method = $fetch_and_prepare_method->($self, $method_name);
670 $method->add_after_modifier(
671 Class::MOP::subname(':after' => $method_modifier)
675 sub add_around_method_modifier {
676 my ($self, $method_name, $method_modifier) = @_;
677 (defined $method_name && $method_name)
678 || confess "You must pass in a method name";
679 my $method = $fetch_and_prepare_method->($self, $method_name);
680 $method->add_around_modifier(
681 Class::MOP::subname(':around' => $method_modifier)
686 # the methods above used to be named like this:
687 # ${pkg}::${method}:(before|after|around)
688 # but this proved problematic when using one modifier
689 # to wrap multiple methods (something which is likely
690 # to happen pretty regularly IMO). So instead of naming
691 # it like this, I have chosen to just name them purely
692 # with their modifier names, like so:
693 # :(before|after|around)
694 # The fact is that in a stack trace, it will be fairly
695 # evident from the context what method they are attached
696 # to, and so don't need the fully qualified name.
700 my ($self, $method_name, $method) = @_;
701 (defined $method_name && $method_name)
702 || confess "You must define a method name";
704 my $body = (blessed($method) ? $method->body : $method);
705 ('CODE' eq ref($body))
706 || confess "Your code block must be a CODE reference";
708 $self->add_package_symbol(
709 { sigil => '&', type => 'CODE', name => $method_name } => $body
711 $self->update_package_cache_flag;
715 my ($self, $method_name) = @_;
716 (defined $method_name && $method_name)
717 || confess "You must define a method name";
719 return 0 unless exists $self->get_method_map->{$method_name};
724 my ($self, $method_name) = @_;
725 (defined $method_name && $method_name)
726 || confess "You must define a method name";
729 # I don't really need this here, because
730 # if the method_map is missing a key it
731 # will just return undef for me now
732 # return unless $self->has_method($method_name);
734 return $self->get_method_map->{$method_name};
738 my ($self, $method_name) = @_;
739 (defined $method_name && $method_name)
740 || confess "You must define a method name";
742 my $removed_method = delete $self->get_method_map->{$method_name};
744 $self->remove_package_symbol(
745 { sigil => '&', type => 'CODE', name => $method_name }
748 $self->update_package_cache_flag;
750 return $removed_method;
753 sub get_method_list {
755 keys %{$self->get_method_map};
758 sub find_method_by_name {
759 my ($self, $method_name) = @_;
760 (defined $method_name && $method_name)
761 || confess "You must define a method name to find";
762 foreach my $class ($self->linearized_isa) {
763 # fetch the meta-class ...
764 my $meta = $self->initialize($class);
765 return $meta->get_method($method_name)
766 if $meta->has_method($method_name);
771 sub compute_all_applicable_methods {
773 my (@methods, %seen_method);
774 foreach my $class ($self->linearized_isa) {
775 # fetch the meta-class ...
776 my $meta = $self->initialize($class);
777 foreach my $method_name ($meta->get_method_list()) {
778 next if exists $seen_method{$method_name};
779 $seen_method{$method_name}++;
781 name => $method_name,
783 code => $meta->get_method($method_name)
790 sub find_all_methods_by_name {
791 my ($self, $method_name) = @_;
792 (defined $method_name && $method_name)
793 || confess "You must define a method name to find";
795 foreach my $class ($self->linearized_isa) {
796 # fetch the meta-class ...
797 my $meta = $self->initialize($class);
799 name => $method_name,
801 code => $meta->get_method($method_name)
802 } if $meta->has_method($method_name);
807 sub find_next_method_by_name {
808 my ($self, $method_name) = @_;
809 (defined $method_name && $method_name)
810 || confess "You must define a method name to find";
811 my @cpl = $self->linearized_isa;
812 shift @cpl; # discard ourselves
813 foreach my $class (@cpl) {
814 # fetch the meta-class ...
815 my $meta = $self->initialize($class);
816 return $meta->get_method($method_name)
817 if $meta->has_method($method_name);
826 # either we have an attribute object already
827 # or we need to create one from the args provided
828 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
829 # make sure it is derived from the correct type though
830 ($attribute->isa('Class::MOP::Attribute'))
831 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
833 # first we attach our new attribute
834 # because it might need certain information
835 # about the class which it is attached to
836 $attribute->attach_to_class($self);
838 # then we remove attributes of a conflicting
839 # name here so that we can properly detach
840 # the old attr object, and remove any
841 # accessors it would have generated
842 if ( $self->has_attribute($attribute->name) ) {
843 $self->remove_attribute($attribute->name);
845 $self->invalidate_meta_instances();
848 # then onto installing the new accessors
849 $self->get_attribute_map->{$attribute->name} = $attribute;
851 # invalidate package flag here
852 my $e = do { local $@; eval { $attribute->install_accessors() }; $@ };
854 $self->remove_attribute($attribute->name);
861 sub invalidate_meta_instances {
864 my @metas = ( $self, map { Class::MOP::Class->initialize($_) } $self->subclasses );
866 $_->invalidate_meta_instance() for @metas;
869 sub invalidate_meta_instance {
871 undef $self->{_meta_instance};
875 my ($self, $attribute_name) = @_;
876 (defined $attribute_name && $attribute_name)
877 || confess "You must define an attribute name";
878 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
882 my ($self, $attribute_name) = @_;
883 (defined $attribute_name && $attribute_name)
884 || confess "You must define an attribute name";
885 return $self->get_attribute_map->{$attribute_name}
887 # this will return undef anyway, so no need ...
888 # if $self->has_attribute($attribute_name);
892 sub remove_attribute {
893 my ($self, $attribute_name) = @_;
894 (defined $attribute_name && $attribute_name)
895 || confess "You must define an attribute name";
896 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
897 return unless defined $removed_attribute;
898 delete $self->get_attribute_map->{$attribute_name};
899 $self->invalidate_meta_instances();
900 $removed_attribute->remove_accessors();
901 $removed_attribute->detach_from_class();
902 return $removed_attribute;
905 sub get_attribute_list {
907 keys %{$self->get_attribute_map};
910 sub compute_all_applicable_attributes {
912 my (@attrs, %seen_attr);
913 foreach my $class ($self->linearized_isa) {
914 # fetch the meta-class ...
915 my $meta = $self->initialize($class);
916 foreach my $attr_name ($meta->get_attribute_list()) {
917 next if exists $seen_attr{$attr_name};
918 $seen_attr{$attr_name}++;
919 push @attrs => $meta->get_attribute($attr_name);
925 sub find_attribute_by_name {
926 my ($self, $attr_name) = @_;
927 foreach my $class ($self->linearized_isa) {
928 # fetch the meta-class ...
929 my $meta = $self->initialize($class);
930 return $meta->get_attribute($attr_name)
931 if $meta->has_attribute($attr_name);
939 sub is_immutable { 0 }
942 # Why I changed this (groditi)
943 # - One Metaclass may have many Classes through many Metaclass instances
944 # - One Metaclass should only have one Immutable Transformer instance
945 # - Each Class may have different Immutabilizing options
946 # - Therefore each Metaclass instance may have different Immutabilizing options
947 # - We need to store one Immutable Transformer instance per Metaclass
948 # - We need to store one set of Immutable Transformer options per Class
949 # - Upon make_mutable we may delete the Immutabilizing options
950 # - We could clean the immutable Transformer instance when there is no more
951 # immutable Classes of that type, but we can also keep it in case
952 # another class with this same Metaclass becomes immutable. It is a case
953 # of trading of storing an instance to avoid unnecessary instantiations of
954 # Immutable Transformers. You may view this as a memory leak, however
955 # Because we have few Metaclasses, in practice it seems acceptable
956 # - To allow Immutable Transformers instances to be cleaned up we could weaken
957 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
961 my %IMMUTABLE_TRANSFORMERS;
962 my %IMMUTABLE_OPTIONS;
964 sub get_immutable_options {
966 return if $self->is_mutable;
967 confess "unable to find immutabilizing options"
968 unless exists $IMMUTABLE_OPTIONS{$self->name};
969 my %options = %{$IMMUTABLE_OPTIONS{$self->name}};
970 delete $options{IMMUTABLE_TRANSFORMER};
974 sub get_immutable_transformer {
976 if( $self->is_mutable ){
977 my $class = blessed $self || $self;
978 return $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
980 confess "unable to find transformer for immutable class"
981 unless exists $IMMUTABLE_OPTIONS{$self->name};
982 return $IMMUTABLE_OPTIONS{$self->name}->{IMMUTABLE_TRANSFORMER};
989 my $transformer = $self->get_immutable_transformer;
990 $transformer->make_metaclass_immutable($self, \%options);
991 $IMMUTABLE_OPTIONS{$self->name} =
992 { %options, IMMUTABLE_TRANSFORMER => $transformer };
994 if( exists $options{debug} && $options{debug} ){
995 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
996 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
1004 return if $self->is_mutable;
1005 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
1006 confess "unable to find immutabilizing options" unless ref $options;
1007 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
1008 $transformer->make_metaclass_mutable($self, $options);
1013 sub create_immutable_transformer {
1015 my $class = Class::MOP::Immutable->new($self, {
1016 read_only => [qw/superclasses/],
1023 remove_package_symbol
1026 class_precedence_list => 'ARRAY',
1027 linearized_isa => 'ARRAY',
1028 compute_all_applicable_attributes => 'ARRAY',
1029 get_meta_instance => 'SCALAR',
1030 get_method_map => 'SCALAR',
1033 # this is ugly, but so are typeglobs,
1034 # so whattayahgonnadoboutit
1037 add_package_symbol => sub {
1038 my $original = shift;
1039 confess "Cannot add package symbols to an immutable metaclass"
1040 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
1041 goto $original->body;
1056 Class::MOP::Class - Class Meta Object
1060 # assuming that class Foo
1061 # has been defined, you can
1063 # use this for introspection ...
1065 # add a method to Foo ...
1066 Foo->meta->add_method('bar' => sub { ... })
1068 # get a list of all the classes searched
1069 # the method dispatcher in the correct order
1070 Foo->meta->class_precedence_list()
1072 # remove a method from Foo
1073 Foo->meta->remove_method('bar');
1075 # or use this to actually create classes ...
1077 Class::MOP::Class->create('Bar' => (
1079 superclasses => [ 'Foo' ],
1081 Class::MOP:::Attribute->new('$bar'),
1082 Class::MOP:::Attribute->new('$baz'),
1085 calculate_bar => sub { ... },
1086 construct_baz => sub { ... }
1092 This is the largest and currently most complex part of the Perl 5
1093 meta-object protocol. It controls the introspection and
1094 manipulation of Perl 5 classes (and it can create them too). The
1095 best way to understand what this module can do, is to read the
1096 documentation for each of it's methods.
1100 =head2 Self Introspection
1106 This will return a B<Class::MOP::Class> instance which is related
1107 to this class. Thereby allowing B<Class::MOP::Class> to actually
1110 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1111 bootstrap this module by installing a number of attribute meta-objects
1112 into it's metaclass. This will allow this class to reap all the benifits
1113 of the MOP when subclassing it.
1117 =head2 Class construction
1119 These methods will handle creating B<Class::MOP::Class> objects,
1120 which can be used to both create new classes, and analyze
1121 pre-existing classes.
1123 This module will internally store references to all the instances
1124 you create with these methods, so that they do not need to be
1125 created any more than nessecary. Basically, they are singletons.
1129 =item B<create ($package_name,
1130 version =E<gt> ?$version,
1131 authority =E<gt> ?$authority,
1132 superclasses =E<gt> ?@superclasses,
1133 methods =E<gt> ?%methods,
1134 attributes =E<gt> ?%attributes)>
1136 This returns a B<Class::MOP::Class> object, bringing the specified
1137 C<$package_name> into existence and adding any of the C<$version>,
1138 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1141 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1142 methods =E<gt> ?%methods,
1143 attributes =E<gt> ?%attributes)>
1145 This will create an anonymous class, it works much like C<create> but
1146 it does not need a C<$package_name>. Instead it will create a suitably
1147 unique package name for you to stash things into.
1149 On very important distinction is that anon classes are destroyed once
1150 the metaclass they are attached to goes out of scope. In the DESTROY
1151 method, the created package will be removed from the symbol table.
1153 It is also worth noting that any instances created with an anon-class
1154 will keep a special reference to the anon-meta which will prevent the
1155 anon-class from going out of scope until all instances of it have also
1156 been destroyed. This however only works for HASH based instance types,
1157 as we use a special reserved slot (C<__MOP__>) to store this.
1159 =item B<initialize ($package_name, %options)>
1161 This initializes and returns returns a B<Class::MOP::Class> object
1162 for a given a C<$package_name>.
1164 =item B<reinitialize ($package_name, %options)>
1166 This removes the old metaclass, and creates a new one in it's place.
1167 Do B<not> use this unless you really know what you are doing, it could
1168 very easily make a very large mess of your program.
1170 =item B<construct_class_instance (%options)>
1172 This will construct an instance of B<Class::MOP::Class>, it is
1173 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1174 to use C<construct_instance> once all the bootstrapping is done. This
1175 method is used internally by C<initialize> and should never be called
1176 from outside of that method really.
1178 =item B<check_metaclass_compatability>
1180 This method is called as the very last thing in the
1181 C<construct_class_instance> method. This will check that the
1182 metaclass you are creating is compatible with the metaclasses of all
1183 your ancestors. For more inforamtion about metaclass compatibility
1184 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1186 =item B<update_package_cache_flag>
1188 This will reset the package cache flag for this particular metaclass
1189 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1190 function. This is very rarely needed from outside of C<Class::MOP::Class>
1191 but in some cases you might want to use it, so it is here.
1193 =item B<reset_package_cache_flag>
1195 Clears the package cache flag to announce to the internals that we need
1196 to rebuild the method map.
1198 =item B<invalidate_meta_instances>
1200 Clears the cached meta instance for this metaclass and all of its subclasses.
1202 Called by C<add_attribute> and C<remove_attribute> to recalculate the attribute
1205 =item B<invalidate_meta_instance>
1207 Used by C<invalidate_meta_instances>.
1211 =head2 Object instance construction and cloning
1213 These methods are B<entirely optional>, it is up to you whether you want
1218 =item B<instance_metaclass>
1220 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1221 for more information on the instance metaclasses.
1223 =item B<get_meta_instance>
1225 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1226 of a new instance of the class.
1228 =item B<new_object (%params)>
1230 This is a convience method for creating a new object of the class, and
1231 blessing it into the appropriate package as well. Ideally your class
1232 would call a C<new> this method like so:
1235 my ($class, %param) = @_;
1236 $class->meta->new_object(%params);
1239 =item B<construct_instance (%params)>
1241 This method is used to construct an instance structure suitable for
1242 C<bless>-ing into your package of choice. It works in conjunction
1243 with the Attribute protocol to collect all applicable attributes.
1245 This will construct and instance using a HASH ref as storage
1246 (currently only HASH references are supported). This will collect all
1247 the applicable attributes and layout out the fields in the HASH ref,
1248 it will then initialize them using either use the corresponding key
1249 in C<%params> or any default value or initializer found in the
1250 attribute meta-object.
1252 =item B<clone_object ($instance, %params)>
1254 This is a convience method for cloning an object instance, then
1255 blessing it into the appropriate package. This method will call
1256 C<clone_instance>, which performs a shallow copy of the object,
1257 see that methods documentation for more details. Ideally your
1258 class would call a C<clone> this method like so:
1260 sub MyClass::clone {
1261 my ($self, %param) = @_;
1262 $self->meta->clone_object($self, %params);
1265 =item B<clone_instance($instance, %params)>
1267 This method is a compliment of C<construct_instance> (which means if
1268 you override C<construct_instance>, you need to override this one too),
1269 and clones the instance shallowly.
1271 The cloned structure returned is (like with C<construct_instance>) an
1272 unC<bless>ed HASH reference, it is your responsibility to then bless
1273 this cloned structure into the right class (which C<clone_object> will
1276 As of 0.11, this method will clone the C<$instance> structure shallowly,
1277 as opposed to the deep cloning implemented in prior versions. After much
1278 thought, research and discussion, I have decided that anything but basic
1279 shallow cloning is outside the scope of the meta-object protocol. I
1280 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1281 is too I<context-specific> to be part of the MOP.
1283 =item B<rebless_instance($instance, ?%params)>
1285 This will change the class of C<$instance> to the class of the invoking
1286 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1287 itself. You may pass in optional C<%params> which are like constructor
1288 params and will override anything already defined in the instance.
1292 =head2 Informational
1294 These are a few predicate methods for asking information about the class.
1298 =item B<is_anon_class>
1300 This returns true if the class is a C<Class::MOP::Class> created anon class.
1304 This returns true if the class is still mutable.
1306 =item B<is_immutable>
1308 This returns true if the class has been made immutable.
1312 =head2 Inheritance Relationships
1316 =item B<superclasses (?@superclasses)>
1318 This is a read-write attribute which represents the superclass
1319 relationships of the class the B<Class::MOP::Class> instance is
1320 associated with. Basically, it can get and set the C<@ISA> for you.
1322 =item B<class_precedence_list>
1324 This computes the a list of all the class's ancestors in the same order
1325 in which method dispatch will be done. This is similair to what
1326 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1328 =item B<linearized_isa>
1330 This returns a list based on C<class_precedence_list> but with all
1335 This returns a list of subclasses for this class.
1343 =item B<get_method_map>
1345 Returns a HASH ref of name to CODE reference mapping for this class.
1347 =item B<method_metaclass>
1349 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1350 for more information on the method metaclasses.
1352 =item B<add_method ($method_name, $method)>
1354 This will take a C<$method_name> and CODE reference to that
1355 C<$method> and install it into the class's package.
1358 This does absolutely nothing special to C<$method>
1359 other than use B<Sub::Name> to make sure it is tagged with the
1360 correct name, and therefore show up correctly in stack traces and
1363 =item B<alias_method ($method_name, $method)>
1365 This will take a C<$method_name> and CODE reference to that
1366 C<$method> and alias the method into the class's package.
1369 Unlike C<add_method>, this will B<not> try to name the
1370 C<$method> using B<Sub::Name>, it only aliases the method in
1371 the class's package.
1373 =item B<has_method ($method_name)>
1375 This just provides a simple way to check if the class implements
1376 a specific C<$method_name>. It will I<not> however, attempt to check
1377 if the class inherits the method (use C<UNIVERSAL::can> for that).
1379 This will correctly handle functions defined outside of the package
1380 that use a fully qualified name (C<sub Package::name { ... }>).
1382 This will correctly handle functions renamed with B<Sub::Name> and
1383 installed using the symbol tables. However, if you are naming the
1384 subroutine outside of the package scope, you must use the fully
1385 qualified name, including the package name, for C<has_method> to
1386 correctly identify it.
1388 This will attempt to correctly ignore functions imported from other
1389 packages using B<Exporter>. It breaks down if the function imported
1390 is an C<__ANON__> sub (such as with C<use constant>), which very well
1391 may be a valid method being applied to the class.
1393 In short, this method cannot always be trusted to determine if the
1394 C<$method_name> is actually a method. However, it will DWIM about
1395 90% of the time, so it's a small trade off I think.
1397 =item B<get_method ($method_name)>
1399 This will return a Class::MOP::Method instance related to the specified
1400 C<$method_name>, or return undef if that method does not exist.
1402 The Class::MOP::Method is codifiable, so you can use it like a normal
1403 CODE reference, see L<Class::MOP::Method> for more information.
1405 =item B<find_method_by_name ($method_name)>
1407 This will return a CODE reference of the specified C<$method_name>,
1408 or return undef if that method does not exist.
1410 Unlike C<get_method> this will also look in the superclasses.
1412 =item B<remove_method ($method_name)>
1414 This will attempt to remove a given C<$method_name> from the class.
1415 It will return the CODE reference that it has removed, and will
1416 attempt to use B<Sub::Name> to clear the methods associated name.
1418 =item B<get_method_list>
1420 This will return a list of method names for all I<locally> defined
1421 methods. It does B<not> provide a list of all applicable methods,
1422 including any inherited ones. If you want a list of all applicable
1423 methods, use the C<compute_all_applicable_methods> method.
1425 =item B<compute_all_applicable_methods>
1427 This will return a list of all the methods names this class will
1428 respond to, taking into account inheritance. The list will be a list of
1429 HASH references, each one containing the following information; method
1430 name, the name of the class in which the method lives and a CODE
1431 reference for the actual method.
1433 =item B<find_all_methods_by_name ($method_name)>
1435 This will traverse the inheritence hierarchy and locate all methods
1436 with a given C<$method_name>. Similar to
1437 C<compute_all_applicable_methods> it returns a list of HASH references
1438 with the following information; method name (which will always be the
1439 same as C<$method_name>), the name of the class in which the method
1440 lives and a CODE reference for the actual method.
1442 The list of methods produced is a distinct list, meaning there are no
1443 duplicates in it. This is especially useful for things like object
1444 initialization and destruction where you only want the method called
1445 once, and in the correct order.
1447 =item B<find_next_method_by_name ($method_name)>
1449 This will return the first method to match a given C<$method_name> in
1450 the superclasses, this is basically equivalent to calling
1451 C<SUPER::$method_name>, but it can be dispatched at runtime.
1455 =head2 Method Modifiers
1457 Method modifiers are a concept borrowed from CLOS, in which a method
1458 can be wrapped with I<before>, I<after> and I<around> method modifiers
1459 that will be called everytime the method is called.
1461 =head3 How method modifiers work?
1463 Method modifiers work by wrapping the original method and then replacing
1464 it in the classes symbol table. The wrappers will handle calling all the
1465 modifiers in the appropariate orders and preserving the calling context
1466 for the original method.
1468 Each method modifier serves a particular purpose, which may not be
1469 obvious to users of other method wrapping modules. To start with, the
1470 return values of I<before> and I<after> modifiers are ignored. This is
1471 because thier purpose is B<not> to filter the input and output of the
1472 primary method (this is done with an I<around> modifier). This may seem
1473 like an odd restriction to some, but doing this allows for simple code
1474 to be added at the begining or end of a method call without jeapordizing
1475 the normal functioning of the primary method or placing any extra
1476 responsibility on the code of the modifier. Of course if you have more
1477 complex needs, then use the I<around> modifier, which uses a variation
1478 of continutation passing style to allow for a high degree of flexibility.
1480 Before and around modifiers are called in last-defined-first-called order,
1481 while after modifiers are called in first-defined-first-called order. So
1482 the call tree might looks something like this:
1492 To see examples of using method modifiers, see the following examples
1493 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1494 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1495 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1497 =head3 What is the performance impact?
1499 Of course there is a performance cost associated with method modifiers,
1500 but we have made every effort to make that cost be directly proportional
1501 to the amount of modifier features you utilize.
1503 The wrapping method does it's best to B<only> do as much work as it
1504 absolutely needs to. In order to do this we have moved some of the
1505 performance costs to set-up time, where they are easier to amortize.
1507 All this said, my benchmarks have indicated the following:
1509 simple wrapper with no modifiers 100% slower
1510 simple wrapper with simple before modifier 400% slower
1511 simple wrapper with simple after modifier 450% slower
1512 simple wrapper with simple around modifier 500-550% slower
1513 simple wrapper with all 3 modifiers 1100% slower
1515 These numbers may seem daunting, but you must remember, every feature
1516 comes with some cost. To put things in perspective, just doing a simple
1517 C<AUTOLOAD> which does nothing but extract the name of the method called
1518 and return it costs about 400% over a normal method call.
1522 =item B<add_before_method_modifier ($method_name, $code)>
1524 This will wrap the method at C<$method_name> and the supplied C<$code>
1525 will be passed the C<@_> arguments, and called before the original
1526 method is called. As specified above, the return value of the I<before>
1527 method modifiers is ignored, and it's ability to modify C<@_> is
1528 fairly limited. If you need to do either of these things, use an
1529 C<around> method modifier.
1531 =item B<add_after_method_modifier ($method_name, $code)>
1533 This will wrap the method at C<$method_name> so that the original
1534 method will be called, it's return values stashed, and then the
1535 supplied C<$code> will be passed the C<@_> arguments, and called.
1536 As specified above, the return value of the I<after> method
1537 modifiers is ignored, and it cannot modify the return values of
1538 the original method. If you need to do either of these things, use an
1539 C<around> method modifier.
1541 =item B<add_around_method_modifier ($method_name, $code)>
1543 This will wrap the method at C<$method_name> so that C<$code>
1544 will be called and passed the original method as an extra argument
1545 at the begining of the C<@_> argument list. This is a variation of
1546 continuation passing style, where the function prepended to C<@_>
1547 can be considered a continuation. It is up to C<$code> if it calls
1548 the original method or not, there is no restriction on what the
1549 C<$code> can or cannot do.
1555 It should be noted that since there is no one consistent way to define
1556 the attributes of a class in Perl 5. These methods can only work with
1557 the information given, and can not easily discover information on
1558 their own. See L<Class::MOP::Attribute> for more details.
1562 =item B<attribute_metaclass>
1564 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1565 for more information on the attribute metaclasses.
1567 =item B<get_attribute_map>
1569 This returns a HASH ref of name to attribute meta-object mapping.
1571 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1573 This stores the C<$attribute_meta_object> (or creates one from the
1574 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1575 instance associated with the given class. Unlike methods, attributes
1576 within the MOP are stored as meta-information only. They will be used
1577 later to construct instances from (see C<construct_instance> above).
1578 More details about the attribute meta-objects can be found in the
1579 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1582 It should be noted that any accessor, reader/writer or predicate
1583 methods which the C<$attribute_meta_object> has will be installed
1584 into the class at this time.
1587 If an attribute already exists for C<$attribute_name>, the old one
1588 will be removed (as well as removing all it's accessors), and then
1591 =item B<has_attribute ($attribute_name)>
1593 Checks to see if this class has an attribute by the name of
1594 C<$attribute_name> and returns a boolean.
1596 =item B<get_attribute ($attribute_name)>
1598 Returns the attribute meta-object associated with C<$attribute_name>,
1599 if none is found, it will return undef.
1601 =item B<remove_attribute ($attribute_name)>
1603 This will remove the attribute meta-object stored at
1604 C<$attribute_name>, then return the removed attribute meta-object.
1607 Removing an attribute will only affect future instances of
1608 the class, it will not make any attempt to remove the attribute from
1609 any existing instances of the class.
1611 It should be noted that any accessor, reader/writer or predicate
1612 methods which the attribute meta-object stored at C<$attribute_name>
1613 has will be removed from the class at this time. This B<will> make
1614 these attributes somewhat inaccessable in previously created
1615 instances. But if you are crazy enough to do this at runtime, then
1616 you are crazy enough to deal with something like this :).
1618 =item B<get_attribute_list>
1620 This returns a list of attribute names which are defined in the local
1621 class. If you want a list of all applicable attributes for a class,
1622 use the C<compute_all_applicable_attributes> method.
1624 =item B<compute_all_applicable_attributes>
1626 This will traverse the inheritance heirachy and return a list of all
1627 the applicable attributes for this class. It does not construct a
1628 HASH reference like C<compute_all_applicable_methods> because all
1629 that same information is discoverable through the attribute
1632 =item B<find_attribute_by_name ($attr_name)>
1634 This method will traverse the inheritance heirachy and find the
1635 first attribute whose name matches C<$attr_name>, then return it.
1636 It will return undef if nothing is found.
1640 =head2 Class Immutability
1644 =item B<make_immutable (%options)>
1646 This method will invoke a tranforamtion upon the class which will
1647 make it immutable. Details of this transformation can be found in
1648 the L<Class::MOP::Immutable> documentation.
1650 =item B<make_mutable>
1652 This method will reverse tranforamtion upon the class which
1655 =item B<get_immutable_transformer>
1657 Return a transformer suitable for making this class immutable or, if this
1658 class is immutable, the transformer used to make it immutable.
1660 =item B<get_immutable_options>
1662 If the class is immutable, return the options used to make it immutable.
1664 =item B<create_immutable_transformer>
1666 Create a transformer suitable for making this class immutable
1672 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1674 =head1 COPYRIGHT AND LICENSE
1676 Copyright 2006-2008 by Infinity Interactive, Inc.
1678 L<http://www.iinteractive.com>
1680 This library is free software; you can redistribute it and/or modify
1681 it under the same terms as Perl itself.