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 {
387 # just about any fiddling with @ISA or
388 # any fiddling with attributes will
389 # also fiddle with the symbol table
390 # and therefore invalidate the package
391 # cache, in which case we should blow
392 # away the meta-instance cache. Of course
393 # this will invalidate it more often then
394 # is probably needed, but better safe
397 $self->{'_meta_instance'} = undef
398 if defined $self->{'_package_cache_flag'} &&
399 $self->{'_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name);
400 $self->{'_meta_instance'} ||= $self->instance_metaclass->new(
401 associated_metaclass => $self,
402 attributes => [ $self->compute_all_applicable_attributes() ],
408 my $instance = shift;
409 (blessed($instance) && $instance->isa($class->name))
410 || confess "You must pass an instance of the metaclass (" . $class->name . "), not ($instance)";
413 # we need to protect the integrity of the
414 # Class::MOP::Class singletons here, they
415 # should not be cloned.
416 return $instance if $instance->isa('Class::MOP::Class');
417 $class->clone_instance($instance, @_);
421 my ($class, $instance, %params) = @_;
423 || confess "You can only clone instances, ($instance) is not a blessed instance";
424 my $meta_instance = $class->get_meta_instance();
425 my $clone = $meta_instance->clone_instance($instance);
426 foreach my $attr ($class->compute_all_applicable_attributes()) {
427 if ( defined( my $init_arg = $attr->init_arg ) ) {
428 if (exists $params{$init_arg}) {
429 $attr->set_value($clone, $params{$init_arg});
436 sub rebless_instance {
437 my ($self, $instance, %params) = @_;
440 if ($instance->can('meta')) {
441 ($instance->meta->isa('Class::MOP::Class'))
442 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
443 $old_metaclass = $instance->meta;
446 $old_metaclass = $self->initialize(blessed($instance));
449 my $meta_instance = $self->get_meta_instance();
451 $self->name->isa($old_metaclass->name)
452 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
455 $meta_instance->rebless_instance_structure($instance, $self);
457 foreach my $attr ( $self->compute_all_applicable_attributes ) {
458 if ( $attr->has_value($instance) ) {
459 if ( defined( my $init_arg = $attr->init_arg ) ) {
460 $params{$init_arg} = $attr->get_value($instance)
461 unless exists $params{$init_arg};
464 $attr->set_value($instance, $attr->get_value($instance));
469 foreach my $attr ($self->compute_all_applicable_attributes) {
470 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
480 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
483 @{$self->get_package_symbol($var_spec)} = @supers;
485 # we need to check the metaclass
486 # compatibility here so that we can
487 # be sure that the superclass is
488 # not potentially creating an issues
489 # we don't know about
490 $self->check_metaclass_compatability();
492 @{$self->get_package_symbol($var_spec)};
498 my $super_class = $self->name;
501 my $find_derived_classes;
502 $find_derived_classes = sub {
503 my ($outer_class) = @_;
505 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
508 for my $symbol ( keys %$symbol_table_hashref ) {
509 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
510 my $inner_class = $1;
512 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
516 ? "${outer_class}::$inner_class"
519 if ( $class->isa($super_class) and $class ne $super_class ) {
520 push @derived_classes, $class;
523 next SYMBOL if $class eq 'main'; # skip 'main::*'
525 $find_derived_classes->($class);
529 my $root_class = q{};
530 $find_derived_classes->($root_class);
532 undef $find_derived_classes;
534 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
536 return @derived_classes;
541 return @{ mro::get_linear_isa( (shift)->name ) };
544 sub class_precedence_list {
546 my $name = $self->name;
548 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
550 # We need to check for circular inheritance here
551 # if we are are not on 5.10, cause 5.8 detects it
552 # late. This will do nothing if all is well, and
553 # blow up otherwise. Yes, it's an ugly hack, better
554 # suggestions are welcome.
556 ($name || return)->isa('This is a test for circular inheritance')
559 # if our mro is c3, we can
560 # just grab the linear_isa
561 if (mro::get_mro($name) eq 'c3') {
562 return @{ mro::get_linear_isa($name) }
566 # we can't grab the linear_isa for dfs
567 # since it has all the duplicates
572 $self->initialize($_)->class_precedence_list()
573 } $self->superclasses()
581 my ($self, $method_name, $method) = @_;
582 (defined $method_name && $method_name)
583 || confess "You must define a method name";
586 if (blessed($method)) {
587 $body = $method->body;
588 if ($method->package_name ne $self->name &&
589 $method->name ne $method_name) {
590 warn "Hello there, got something for you."
591 . " Method says " . $method->package_name . " " . $method->name
592 . " Class says " . $self->name . " " . $method_name;
593 $method = $method->clone(
594 package_name => $self->name,
596 ) if $method->can('clone');
601 ('CODE' eq ref($body))
602 || confess "Your code block must be a CODE reference";
603 $method = $self->method_metaclass->wrap(
605 package_name => $self->name,
610 $self->get_method_map->{$method_name} = $method;
612 my $full_method_name = ($self->name . '::' . $method_name);
613 $self->add_package_symbol(
614 { sigil => '&', type => 'CODE', name => $method_name },
615 Class::MOP::subname($full_method_name => $body)
617 $self->update_package_cache_flag;
621 my $fetch_and_prepare_method = sub {
622 my ($self, $method_name) = @_;
624 my $method = $self->get_method($method_name);
625 # if we dont have local ...
627 # try to find the next method
628 $method = $self->find_next_method_by_name($method_name);
629 # die if it does not exist
631 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
632 # and now make sure to wrap it
633 # even if it is already wrapped
634 # because we need a new sub ref
635 $method = Class::MOP::Method::Wrapped->wrap($method);
638 # now make sure we wrap it properly
639 $method = Class::MOP::Method::Wrapped->wrap($method)
640 unless $method->isa('Class::MOP::Method::Wrapped');
642 $self->add_method($method_name => $method);
646 sub add_before_method_modifier {
647 my ($self, $method_name, $method_modifier) = @_;
648 (defined $method_name && $method_name)
649 || confess "You must pass in a method name";
650 my $method = $fetch_and_prepare_method->($self, $method_name);
651 $method->add_before_modifier(
652 Class::MOP::subname(':before' => $method_modifier)
656 sub add_after_method_modifier {
657 my ($self, $method_name, $method_modifier) = @_;
658 (defined $method_name && $method_name)
659 || confess "You must pass in a method name";
660 my $method = $fetch_and_prepare_method->($self, $method_name);
661 $method->add_after_modifier(
662 Class::MOP::subname(':after' => $method_modifier)
666 sub add_around_method_modifier {
667 my ($self, $method_name, $method_modifier) = @_;
668 (defined $method_name && $method_name)
669 || confess "You must pass in a method name";
670 my $method = $fetch_and_prepare_method->($self, $method_name);
671 $method->add_around_modifier(
672 Class::MOP::subname(':around' => $method_modifier)
677 # the methods above used to be named like this:
678 # ${pkg}::${method}:(before|after|around)
679 # but this proved problematic when using one modifier
680 # to wrap multiple methods (something which is likely
681 # to happen pretty regularly IMO). So instead of naming
682 # it like this, I have chosen to just name them purely
683 # with their modifier names, like so:
684 # :(before|after|around)
685 # The fact is that in a stack trace, it will be fairly
686 # evident from the context what method they are attached
687 # to, and so don't need the fully qualified name.
691 my ($self, $method_name, $method) = @_;
692 (defined $method_name && $method_name)
693 || confess "You must define a method name";
695 my $body = (blessed($method) ? $method->body : $method);
696 ('CODE' eq ref($body))
697 || confess "Your code block must be a CODE reference";
699 $self->add_package_symbol(
700 { sigil => '&', type => 'CODE', name => $method_name } => $body
702 $self->update_package_cache_flag;
706 my ($self, $method_name) = @_;
707 (defined $method_name && $method_name)
708 || confess "You must define a method name";
710 return 0 unless exists $self->get_method_map->{$method_name};
715 my ($self, $method_name) = @_;
716 (defined $method_name && $method_name)
717 || confess "You must define a method name";
720 # I don't really need this here, because
721 # if the method_map is missing a key it
722 # will just return undef for me now
723 # return unless $self->has_method($method_name);
725 return $self->get_method_map->{$method_name};
729 my ($self, $method_name) = @_;
730 (defined $method_name && $method_name)
731 || confess "You must define a method name";
733 my $removed_method = delete $self->get_method_map->{$method_name};
735 $self->remove_package_symbol(
736 { sigil => '&', type => 'CODE', name => $method_name }
739 $self->update_package_cache_flag;
741 return $removed_method;
744 sub get_method_list {
746 keys %{$self->get_method_map};
749 sub find_method_by_name {
750 my ($self, $method_name) = @_;
751 (defined $method_name && $method_name)
752 || confess "You must define a method name to find";
753 foreach my $class ($self->linearized_isa) {
754 # fetch the meta-class ...
755 my $meta = $self->initialize($class);
756 return $meta->get_method($method_name)
757 if $meta->has_method($method_name);
762 sub compute_all_applicable_methods {
764 my (@methods, %seen_method);
765 foreach my $class ($self->linearized_isa) {
766 # fetch the meta-class ...
767 my $meta = $self->initialize($class);
768 foreach my $method_name ($meta->get_method_list()) {
769 next if exists $seen_method{$method_name};
770 $seen_method{$method_name}++;
772 name => $method_name,
774 code => $meta->get_method($method_name)
781 sub find_all_methods_by_name {
782 my ($self, $method_name) = @_;
783 (defined $method_name && $method_name)
784 || confess "You must define a method name to find";
786 foreach my $class ($self->linearized_isa) {
787 # fetch the meta-class ...
788 my $meta = $self->initialize($class);
790 name => $method_name,
792 code => $meta->get_method($method_name)
793 } if $meta->has_method($method_name);
798 sub find_next_method_by_name {
799 my ($self, $method_name) = @_;
800 (defined $method_name && $method_name)
801 || confess "You must define a method name to find";
802 my @cpl = $self->linearized_isa;
803 shift @cpl; # discard ourselves
804 foreach my $class (@cpl) {
805 # fetch the meta-class ...
806 my $meta = $self->initialize($class);
807 return $meta->get_method($method_name)
808 if $meta->has_method($method_name);
817 # either we have an attribute object already
818 # or we need to create one from the args provided
819 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
820 # make sure it is derived from the correct type though
821 ($attribute->isa('Class::MOP::Attribute'))
822 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
824 # first we attach our new attribute
825 # because it might need certain information
826 # about the class which it is attached to
827 $attribute->attach_to_class($self);
829 # then we remove attributes of a conflicting
830 # name here so that we can properly detach
831 # the old attr object, and remove any
832 # accessors it would have generated
833 $self->remove_attribute($attribute->name)
834 if $self->has_attribute($attribute->name);
836 # then onto installing the new accessors
837 $attribute->install_accessors();
838 $self->get_attribute_map->{$attribute->name} = $attribute;
842 my ($self, $attribute_name) = @_;
843 (defined $attribute_name && $attribute_name)
844 || confess "You must define an attribute name";
845 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
849 my ($self, $attribute_name) = @_;
850 (defined $attribute_name && $attribute_name)
851 || confess "You must define an attribute name";
852 return $self->get_attribute_map->{$attribute_name}
854 # this will return undef anyway, so no need ...
855 # if $self->has_attribute($attribute_name);
859 sub remove_attribute {
860 my ($self, $attribute_name) = @_;
861 (defined $attribute_name && $attribute_name)
862 || confess "You must define an attribute name";
863 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
864 return unless defined $removed_attribute;
865 delete $self->get_attribute_map->{$attribute_name};
866 $removed_attribute->remove_accessors();
867 $removed_attribute->detach_from_class();
868 return $removed_attribute;
871 sub get_attribute_list {
873 keys %{$self->get_attribute_map};
876 sub compute_all_applicable_attributes {
878 my (@attrs, %seen_attr);
879 foreach my $class ($self->linearized_isa) {
880 # fetch the meta-class ...
881 my $meta = $self->initialize($class);
882 foreach my $attr_name ($meta->get_attribute_list()) {
883 next if exists $seen_attr{$attr_name};
884 $seen_attr{$attr_name}++;
885 push @attrs => $meta->get_attribute($attr_name);
891 sub find_attribute_by_name {
892 my ($self, $attr_name) = @_;
893 foreach my $class ($self->linearized_isa) {
894 # fetch the meta-class ...
895 my $meta = $self->initialize($class);
896 return $meta->get_attribute($attr_name)
897 if $meta->has_attribute($attr_name);
905 sub is_immutable { 0 }
908 # Why I changed this (groditi)
909 # - One Metaclass may have many Classes through many Metaclass instances
910 # - One Metaclass should only have one Immutable Transformer instance
911 # - Each Class may have different Immutabilizing options
912 # - Therefore each Metaclass instance may have different Immutabilizing options
913 # - We need to store one Immutable Transformer instance per Metaclass
914 # - We need to store one set of Immutable Transformer options per Class
915 # - Upon make_mutable we may delete the Immutabilizing options
916 # - We could clean the immutable Transformer instance when there is no more
917 # immutable Classes of that type, but we can also keep it in case
918 # another class with this same Metaclass becomes immutable. It is a case
919 # of trading of storing an instance to avoid unnecessary instantiations of
920 # Immutable Transformers. You may view this as a memory leak, however
921 # Because we have few Metaclasses, in practice it seems acceptable
922 # - To allow Immutable Transformers instances to be cleaned up we could weaken
923 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
927 my %IMMUTABLE_TRANSFORMERS;
928 my %IMMUTABLE_OPTIONS;
930 sub get_immutable_options {
932 return if $self->is_mutable;
933 confess "unable to find immutabilizing options"
934 unless exists $IMMUTABLE_OPTIONS{$self->name};
935 my %options = %{$IMMUTABLE_OPTIONS{$self->name}};
936 delete $options{IMMUTABLE_TRANSFORMER};
940 sub get_immutable_transformer {
942 if( $self->is_mutable ){
943 my $class = blessed $self || $self;
944 return $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
946 confess "unable to find transformer for immutable class"
947 unless exists $IMMUTABLE_OPTIONS{$self->name};
948 return $IMMUTABLE_OPTIONS{$self->name}->{IMMUTABLE_TRANSFORMER};
955 my $transformer = $self->get_immutable_transformer;
956 $transformer->make_metaclass_immutable($self, \%options);
957 $IMMUTABLE_OPTIONS{$self->name} =
958 { %options, IMMUTABLE_TRANSFORMER => $transformer };
960 if( exists $options{debug} && $options{debug} ){
961 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
962 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
970 return if $self->is_mutable;
971 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
972 confess "unable to find immutabilizing options" unless ref $options;
973 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
974 $transformer->make_metaclass_mutable($self, $options);
979 sub create_immutable_transformer {
981 my $class = Class::MOP::Immutable->new($self, {
982 read_only => [qw/superclasses/],
989 remove_package_symbol
992 class_precedence_list => 'ARRAY',
993 linearized_isa => 'ARRAY',
994 compute_all_applicable_attributes => 'ARRAY',
995 get_meta_instance => 'SCALAR',
996 get_method_map => 'SCALAR',
999 # this is ugly, but so are typeglobs,
1000 # so whattayahgonnadoboutit
1003 add_package_symbol => sub {
1004 my $original = shift;
1005 confess "Cannot add package symbols to an immutable metaclass"
1006 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
1007 goto $original->body;
1022 Class::MOP::Class - Class Meta Object
1026 # assuming that class Foo
1027 # has been defined, you can
1029 # use this for introspection ...
1031 # add a method to Foo ...
1032 Foo->meta->add_method('bar' => sub { ... })
1034 # get a list of all the classes searched
1035 # the method dispatcher in the correct order
1036 Foo->meta->class_precedence_list()
1038 # remove a method from Foo
1039 Foo->meta->remove_method('bar');
1041 # or use this to actually create classes ...
1043 Class::MOP::Class->create('Bar' => (
1045 superclasses => [ 'Foo' ],
1047 Class::MOP:::Attribute->new('$bar'),
1048 Class::MOP:::Attribute->new('$baz'),
1051 calculate_bar => sub { ... },
1052 construct_baz => sub { ... }
1058 This is the largest and currently most complex part of the Perl 5
1059 meta-object protocol. It controls the introspection and
1060 manipulation of Perl 5 classes (and it can create them too). The
1061 best way to understand what this module can do, is to read the
1062 documentation for each of it's methods.
1066 =head2 Self Introspection
1072 This will return a B<Class::MOP::Class> instance which is related
1073 to this class. Thereby allowing B<Class::MOP::Class> to actually
1076 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1077 bootstrap this module by installing a number of attribute meta-objects
1078 into it's metaclass. This will allow this class to reap all the benifits
1079 of the MOP when subclassing it.
1083 =head2 Class construction
1085 These methods will handle creating B<Class::MOP::Class> objects,
1086 which can be used to both create new classes, and analyze
1087 pre-existing classes.
1089 This module will internally store references to all the instances
1090 you create with these methods, so that they do not need to be
1091 created any more than nessecary. Basically, they are singletons.
1095 =item B<create ($package_name,
1096 version =E<gt> ?$version,
1097 authority =E<gt> ?$authority,
1098 superclasses =E<gt> ?@superclasses,
1099 methods =E<gt> ?%methods,
1100 attributes =E<gt> ?%attributes)>
1102 This returns a B<Class::MOP::Class> object, bringing the specified
1103 C<$package_name> into existence and adding any of the C<$version>,
1104 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1107 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1108 methods =E<gt> ?%methods,
1109 attributes =E<gt> ?%attributes)>
1111 This will create an anonymous class, it works much like C<create> but
1112 it does not need a C<$package_name>. Instead it will create a suitably
1113 unique package name for you to stash things into.
1115 On very important distinction is that anon classes are destroyed once
1116 the metaclass they are attached to goes out of scope. In the DESTROY
1117 method, the created package will be removed from the symbol table.
1119 It is also worth noting that any instances created with an anon-class
1120 will keep a special reference to the anon-meta which will prevent the
1121 anon-class from going out of scope until all instances of it have also
1122 been destroyed. This however only works for HASH based instance types,
1123 as we use a special reserved slot (C<__MOP__>) to store this.
1125 =item B<initialize ($package_name, %options)>
1127 This initializes and returns returns a B<Class::MOP::Class> object
1128 for a given a C<$package_name>.
1130 =item B<reinitialize ($package_name, %options)>
1132 This removes the old metaclass, and creates a new one in it's place.
1133 Do B<not> use this unless you really know what you are doing, it could
1134 very easily make a very large mess of your program.
1136 =item B<construct_class_instance (%options)>
1138 This will construct an instance of B<Class::MOP::Class>, it is
1139 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1140 to use C<construct_instance> once all the bootstrapping is done. This
1141 method is used internally by C<initialize> and should never be called
1142 from outside of that method really.
1144 =item B<check_metaclass_compatability>
1146 This method is called as the very last thing in the
1147 C<construct_class_instance> method. This will check that the
1148 metaclass you are creating is compatible with the metaclasses of all
1149 your ancestors. For more inforamtion about metaclass compatibility
1150 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1152 =item B<update_package_cache_flag>
1154 This will reset the package cache flag for this particular metaclass
1155 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1156 function. This is very rarely needed from outside of C<Class::MOP::Class>
1157 but in some cases you might want to use it, so it is here.
1159 =item B<reset_package_cache_flag>
1161 Clears the package cache flag to announce to the internals that we need
1162 to rebuild the method map.
1166 =head2 Object instance construction and cloning
1168 These methods are B<entirely optional>, it is up to you whether you want
1173 =item B<instance_metaclass>
1175 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1176 for more information on the instance metaclasses.
1178 =item B<get_meta_instance>
1180 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1181 of a new instance of the class.
1183 =item B<new_object (%params)>
1185 This is a convience method for creating a new object of the class, and
1186 blessing it into the appropriate package as well. Ideally your class
1187 would call a C<new> this method like so:
1190 my ($class, %param) = @_;
1191 $class->meta->new_object(%params);
1194 =item B<construct_instance (%params)>
1196 This method is used to construct an instance structure suitable for
1197 C<bless>-ing into your package of choice. It works in conjunction
1198 with the Attribute protocol to collect all applicable attributes.
1200 This will construct and instance using a HASH ref as storage
1201 (currently only HASH references are supported). This will collect all
1202 the applicable attributes and layout out the fields in the HASH ref,
1203 it will then initialize them using either use the corresponding key
1204 in C<%params> or any default value or initializer found in the
1205 attribute meta-object.
1207 =item B<clone_object ($instance, %params)>
1209 This is a convience method for cloning an object instance, then
1210 blessing it into the appropriate package. This method will call
1211 C<clone_instance>, which performs a shallow copy of the object,
1212 see that methods documentation for more details. Ideally your
1213 class would call a C<clone> this method like so:
1215 sub MyClass::clone {
1216 my ($self, %param) = @_;
1217 $self->meta->clone_object($self, %params);
1220 =item B<clone_instance($instance, %params)>
1222 This method is a compliment of C<construct_instance> (which means if
1223 you override C<construct_instance>, you need to override this one too),
1224 and clones the instance shallowly.
1226 The cloned structure returned is (like with C<construct_instance>) an
1227 unC<bless>ed HASH reference, it is your responsibility to then bless
1228 this cloned structure into the right class (which C<clone_object> will
1231 As of 0.11, this method will clone the C<$instance> structure shallowly,
1232 as opposed to the deep cloning implemented in prior versions. After much
1233 thought, research and discussion, I have decided that anything but basic
1234 shallow cloning is outside the scope of the meta-object protocol. I
1235 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1236 is too I<context-specific> to be part of the MOP.
1238 =item B<rebless_instance($instance, ?%params)>
1240 This will change the class of C<$instance> to the class of the invoking
1241 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1242 itself. You may pass in optional C<%params> which are like constructor
1243 params and will override anything already defined in the instance.
1247 =head2 Informational
1249 These are a few predicate methods for asking information about the class.
1253 =item B<is_anon_class>
1255 This returns true if the class is a C<Class::MOP::Class> created anon class.
1259 This returns true if the class is still mutable.
1261 =item B<is_immutable>
1263 This returns true if the class has been made immutable.
1267 =head2 Inheritance Relationships
1271 =item B<superclasses (?@superclasses)>
1273 This is a read-write attribute which represents the superclass
1274 relationships of the class the B<Class::MOP::Class> instance is
1275 associated with. Basically, it can get and set the C<@ISA> for you.
1277 =item B<class_precedence_list>
1279 This computes the a list of all the class's ancestors in the same order
1280 in which method dispatch will be done. This is similair to what
1281 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1283 =item B<linearized_isa>
1285 This returns a list based on C<class_precedence_list> but with all
1290 This returns a list of subclasses for this class.
1298 =item B<get_method_map>
1300 Returns a HASH ref of name to CODE reference mapping for this class.
1302 =item B<method_metaclass>
1304 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1305 for more information on the method metaclasses.
1307 =item B<add_method ($method_name, $method)>
1309 This will take a C<$method_name> and CODE reference to that
1310 C<$method> and install it into the class's package.
1313 This does absolutely nothing special to C<$method>
1314 other than use B<Sub::Name> to make sure it is tagged with the
1315 correct name, and therefore show up correctly in stack traces and
1318 =item B<alias_method ($method_name, $method)>
1320 This will take a C<$method_name> and CODE reference to that
1321 C<$method> and alias the method into the class's package.
1324 Unlike C<add_method>, this will B<not> try to name the
1325 C<$method> using B<Sub::Name>, it only aliases the method in
1326 the class's package.
1328 =item B<has_method ($method_name)>
1330 This just provides a simple way to check if the class implements
1331 a specific C<$method_name>. It will I<not> however, attempt to check
1332 if the class inherits the method (use C<UNIVERSAL::can> for that).
1334 This will correctly handle functions defined outside of the package
1335 that use a fully qualified name (C<sub Package::name { ... }>).
1337 This will correctly handle functions renamed with B<Sub::Name> and
1338 installed using the symbol tables. However, if you are naming the
1339 subroutine outside of the package scope, you must use the fully
1340 qualified name, including the package name, for C<has_method> to
1341 correctly identify it.
1343 This will attempt to correctly ignore functions imported from other
1344 packages using B<Exporter>. It breaks down if the function imported
1345 is an C<__ANON__> sub (such as with C<use constant>), which very well
1346 may be a valid method being applied to the class.
1348 In short, this method cannot always be trusted to determine if the
1349 C<$method_name> is actually a method. However, it will DWIM about
1350 90% of the time, so it's a small trade off I think.
1352 =item B<get_method ($method_name)>
1354 This will return a Class::MOP::Method instance related to the specified
1355 C<$method_name>, or return undef if that method does not exist.
1357 The Class::MOP::Method is codifiable, so you can use it like a normal
1358 CODE reference, see L<Class::MOP::Method> for more information.
1360 =item B<find_method_by_name ($method_name)>
1362 This will return a CODE reference of the specified C<$method_name>,
1363 or return undef if that method does not exist.
1365 Unlike C<get_method> this will also look in the superclasses.
1367 =item B<remove_method ($method_name)>
1369 This will attempt to remove a given C<$method_name> from the class.
1370 It will return the CODE reference that it has removed, and will
1371 attempt to use B<Sub::Name> to clear the methods associated name.
1373 =item B<get_method_list>
1375 This will return a list of method names for all I<locally> defined
1376 methods. It does B<not> provide a list of all applicable methods,
1377 including any inherited ones. If you want a list of all applicable
1378 methods, use the C<compute_all_applicable_methods> method.
1380 =item B<compute_all_applicable_methods>
1382 This will return a list of all the methods names this class will
1383 respond to, taking into account inheritance. The list will be a list of
1384 HASH references, each one containing the following information; method
1385 name, the name of the class in which the method lives and a CODE
1386 reference for the actual method.
1388 =item B<find_all_methods_by_name ($method_name)>
1390 This will traverse the inheritence hierarchy and locate all methods
1391 with a given C<$method_name>. Similar to
1392 C<compute_all_applicable_methods> it returns a list of HASH references
1393 with the following information; method name (which will always be the
1394 same as C<$method_name>), the name of the class in which the method
1395 lives and a CODE reference for the actual method.
1397 The list of methods produced is a distinct list, meaning there are no
1398 duplicates in it. This is especially useful for things like object
1399 initialization and destruction where you only want the method called
1400 once, and in the correct order.
1402 =item B<find_next_method_by_name ($method_name)>
1404 This will return the first method to match a given C<$method_name> in
1405 the superclasses, this is basically equivalent to calling
1406 C<SUPER::$method_name>, but it can be dispatched at runtime.
1410 =head2 Method Modifiers
1412 Method modifiers are a concept borrowed from CLOS, in which a method
1413 can be wrapped with I<before>, I<after> and I<around> method modifiers
1414 that will be called everytime the method is called.
1416 =head3 How method modifiers work?
1418 Method modifiers work by wrapping the original method and then replacing
1419 it in the classes symbol table. The wrappers will handle calling all the
1420 modifiers in the appropariate orders and preserving the calling context
1421 for the original method.
1423 Each method modifier serves a particular purpose, which may not be
1424 obvious to users of other method wrapping modules. To start with, the
1425 return values of I<before> and I<after> modifiers are ignored. This is
1426 because thier purpose is B<not> to filter the input and output of the
1427 primary method (this is done with an I<around> modifier). This may seem
1428 like an odd restriction to some, but doing this allows for simple code
1429 to be added at the begining or end of a method call without jeapordizing
1430 the normal functioning of the primary method or placing any extra
1431 responsibility on the code of the modifier. Of course if you have more
1432 complex needs, then use the I<around> modifier, which uses a variation
1433 of continutation passing style to allow for a high degree of flexibility.
1435 Before and around modifiers are called in last-defined-first-called order,
1436 while after modifiers are called in first-defined-first-called order. So
1437 the call tree might looks something like this:
1447 To see examples of using method modifiers, see the following examples
1448 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1449 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1450 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1452 =head3 What is the performance impact?
1454 Of course there is a performance cost associated with method modifiers,
1455 but we have made every effort to make that cost be directly proportional
1456 to the amount of modifier features you utilize.
1458 The wrapping method does it's best to B<only> do as much work as it
1459 absolutely needs to. In order to do this we have moved some of the
1460 performance costs to set-up time, where they are easier to amortize.
1462 All this said, my benchmarks have indicated the following:
1464 simple wrapper with no modifiers 100% slower
1465 simple wrapper with simple before modifier 400% slower
1466 simple wrapper with simple after modifier 450% slower
1467 simple wrapper with simple around modifier 500-550% slower
1468 simple wrapper with all 3 modifiers 1100% slower
1470 These numbers may seem daunting, but you must remember, every feature
1471 comes with some cost. To put things in perspective, just doing a simple
1472 C<AUTOLOAD> which does nothing but extract the name of the method called
1473 and return it costs about 400% over a normal method call.
1477 =item B<add_before_method_modifier ($method_name, $code)>
1479 This will wrap the method at C<$method_name> and the supplied C<$code>
1480 will be passed the C<@_> arguments, and called before the original
1481 method is called. As specified above, the return value of the I<before>
1482 method modifiers is ignored, and it's ability to modify C<@_> is
1483 fairly limited. If you need to do either of these things, use an
1484 C<around> method modifier.
1486 =item B<add_after_method_modifier ($method_name, $code)>
1488 This will wrap the method at C<$method_name> so that the original
1489 method will be called, it's return values stashed, and then the
1490 supplied C<$code> will be passed the C<@_> arguments, and called.
1491 As specified above, the return value of the I<after> method
1492 modifiers is ignored, and it cannot modify the return values of
1493 the original method. If you need to do either of these things, use an
1494 C<around> method modifier.
1496 =item B<add_around_method_modifier ($method_name, $code)>
1498 This will wrap the method at C<$method_name> so that C<$code>
1499 will be called and passed the original method as an extra argument
1500 at the begining of the C<@_> argument list. This is a variation of
1501 continuation passing style, where the function prepended to C<@_>
1502 can be considered a continuation. It is up to C<$code> if it calls
1503 the original method or not, there is no restriction on what the
1504 C<$code> can or cannot do.
1510 It should be noted that since there is no one consistent way to define
1511 the attributes of a class in Perl 5. These methods can only work with
1512 the information given, and can not easily discover information on
1513 their own. See L<Class::MOP::Attribute> for more details.
1517 =item B<attribute_metaclass>
1519 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1520 for more information on the attribute metaclasses.
1522 =item B<get_attribute_map>
1524 This returns a HASH ref of name to attribute meta-object mapping.
1526 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1528 This stores the C<$attribute_meta_object> (or creates one from the
1529 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1530 instance associated with the given class. Unlike methods, attributes
1531 within the MOP are stored as meta-information only. They will be used
1532 later to construct instances from (see C<construct_instance> above).
1533 More details about the attribute meta-objects can be found in the
1534 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1537 It should be noted that any accessor, reader/writer or predicate
1538 methods which the C<$attribute_meta_object> has will be installed
1539 into the class at this time.
1542 If an attribute already exists for C<$attribute_name>, the old one
1543 will be removed (as well as removing all it's accessors), and then
1546 =item B<has_attribute ($attribute_name)>
1548 Checks to see if this class has an attribute by the name of
1549 C<$attribute_name> and returns a boolean.
1551 =item B<get_attribute ($attribute_name)>
1553 Returns the attribute meta-object associated with C<$attribute_name>,
1554 if none is found, it will return undef.
1556 =item B<remove_attribute ($attribute_name)>
1558 This will remove the attribute meta-object stored at
1559 C<$attribute_name>, then return the removed attribute meta-object.
1562 Removing an attribute will only affect future instances of
1563 the class, it will not make any attempt to remove the attribute from
1564 any existing instances of the class.
1566 It should be noted that any accessor, reader/writer or predicate
1567 methods which the attribute meta-object stored at C<$attribute_name>
1568 has will be removed from the class at this time. This B<will> make
1569 these attributes somewhat inaccessable in previously created
1570 instances. But if you are crazy enough to do this at runtime, then
1571 you are crazy enough to deal with something like this :).
1573 =item B<get_attribute_list>
1575 This returns a list of attribute names which are defined in the local
1576 class. If you want a list of all applicable attributes for a class,
1577 use the C<compute_all_applicable_attributes> method.
1579 =item B<compute_all_applicable_attributes>
1581 This will traverse the inheritance heirachy and return a list of all
1582 the applicable attributes for this class. It does not construct a
1583 HASH reference like C<compute_all_applicable_methods> because all
1584 that same information is discoverable through the attribute
1587 =item B<find_attribute_by_name ($attr_name)>
1589 This method will traverse the inheritance heirachy and find the
1590 first attribute whose name matches C<$attr_name>, then return it.
1591 It will return undef if nothing is found.
1595 =head2 Class Immutability
1599 =item B<make_immutable (%options)>
1601 This method will invoke a tranforamtion upon the class which will
1602 make it immutable. Details of this transformation can be found in
1603 the L<Class::MOP::Immutable> documentation.
1605 =item B<make_mutable>
1607 This method will reverse tranforamtion upon the class which
1610 =item B<get_immutable_transformer>
1612 Return a transformer suitable for making this class immutable or, if this
1613 class is immutable, the transformer used to make it immutable.
1615 =item B<get_immutable_options>
1617 If the class is immutable, return the options used to make it immutable.
1619 =item B<create_immutable_transformer>
1621 Create a transformer suitable for making this class immutable
1627 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1629 =head1 COPYRIGHT AND LICENSE
1631 Copyright 2006-2008 by Infinity Interactive, Inc.
1633 L<http://www.iinteractive.com>
1635 This library is free software; you can redistribute it and/or modify
1636 it under the same terms as Perl itself.