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', 'reftype', 'weaken';
13 use Sub::Name 'subname';
15 our $VERSION = '0.26';
16 our $AUTHORITY = 'cpan:STEVAN';
18 use base 'Class::MOP::Module';
22 sub meta { Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) }
28 my $package_name = shift;
29 (defined $package_name && $package_name && !blessed($package_name))
30 || confess "You must pass a package name and it cannot be blessed";
31 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
34 $class->construct_class_instance('package' => $package_name, @_);
39 my $package_name = shift;
40 (defined $package_name && $package_name && !blessed($package_name))
41 || confess "You must pass a package name and it cannot be blessed";
42 Class::MOP::remove_metaclass_by_name($package_name);
43 $class->construct_class_instance('package' => $package_name, @_);
46 # NOTE: (meta-circularity)
47 # this is a special form of &construct_instance
48 # (see below), which is used to construct class
49 # meta-object instances for any Class::MOP::*
50 # class. All other classes will use the more
51 # normal &construct_instance.
52 sub construct_class_instance {
55 my $package_name = $options{'package'};
56 (defined $package_name && $package_name)
57 || confess "You must pass a package name";
59 # return the metaclass if we have it cached,
60 # and it is still defined (it has not been
61 # reaped by DESTROY yet, which can happen
62 # annoyingly enough during global destruction)
64 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
69 # we need to deal with the possibility
70 # of class immutability here, and then
71 # get the name of the class appropriately
72 $class = (blessed($class)
73 ? ($class->is_immutable
74 ? $class->get_mutable_metaclass_name()
78 # now create the metaclass
80 if ($class eq 'Class::MOP::Class') {
83 # inherited from Class::MOP::Package
84 '$!package' => $package_name,
87 # since the following attributes will
88 # actually be loaded from the symbol
89 # table, and actually bypass the instance
90 # entirely, we can just leave these things
91 # listed here for reference, because they
92 # should not actually have a value associated
94 '%!namespace' => \undef,
95 # inherited from Class::MOP::Module
96 '$!version' => \undef,
97 '$!authority' => \undef,
98 # defined in Class::MOP::Class
99 '@!superclasses' => \undef,
102 '%!attributes' => {},
103 '$!attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
104 '$!method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
105 '$!instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
107 ## uber-private variables
109 # this starts out as undef so that
110 # we can tell the first time the
111 # methods are fetched
113 '$!_package_cache_flag' => 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);
213 # this will only get called for
214 # anon-classes, all other calls
215 # are assumed to occur during
216 # global destruction and so don't
217 # really need to be handled explicitly
220 no warnings 'uninitialized';
221 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
222 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
224 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
225 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
227 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
232 # creating classes with MOP ...
236 my $package_name = shift;
238 (defined $package_name && $package_name)
239 || confess "You must pass a package name";
242 || confess "You much pass all parameters as name => value pairs " .
243 "(I found an uneven number of params in \@_)";
247 my $code = "package $package_name;";
248 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
249 if exists $options{version};
250 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
251 if exists $options{authority};
254 confess "creation of $package_name failed : $@" if $@;
256 my $meta = $class->initialize($package_name);
258 $meta->add_method('meta' => sub {
259 $class->initialize(blessed($_[0]) || $_[0]);
262 $meta->superclasses(@{$options{superclasses}})
263 if exists $options{superclasses};
265 # process attributes first, so that they can
266 # install accessors, but locally defined methods
267 # can then overwrite them. It is maybe a little odd, but
268 # I think this should be the order of things.
269 if (exists $options{attributes}) {
270 foreach my $attr (@{$options{attributes}}) {
271 $meta->add_attribute($attr);
274 if (exists $options{methods}) {
275 foreach my $method_name (keys %{$options{methods}}) {
276 $meta->add_method($method_name, $options{methods}->{$method_name});
285 # all these attribute readers will be bootstrapped
286 # away in the Class::MOP bootstrap section
288 sub get_attribute_map { $_[0]->{'%!attributes'} }
289 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
290 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
291 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
294 # this is a prime canidate for conversion to XS
298 if (defined $self->{'$!_package_cache_flag'} &&
299 $self->{'$!_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
300 return $self->{'%!methods'};
303 my $map = $self->{'%!methods'};
305 my $class_name = $self->name;
306 my $method_metaclass = $self->method_metaclass;
308 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
309 my $code = $self->get_package_symbol('&' . $symbol);
311 next if exists $map->{$symbol} &&
312 defined $map->{$symbol} &&
313 $map->{$symbol}->body == $code;
315 my ($pkg, $name) = Class::MOP::get_code_info($code);
316 next if ($pkg || '') ne $class_name &&
317 ($name || '') ne '__ANON__';
319 $map->{$symbol} = $method_metaclass->wrap($code);
325 # Instance Construction & Cloning
330 # we need to protect the integrity of the
331 # Class::MOP::Class singletons here, so we
332 # delegate this to &construct_class_instance
333 # which will deal with the singletons
334 return $class->construct_class_instance(@_)
335 if $class->name->isa('Class::MOP::Class');
336 return $class->construct_instance(@_);
339 sub construct_instance {
340 my ($class, %params) = @_;
341 my $meta_instance = $class->get_meta_instance();
342 my $instance = $meta_instance->create_instance();
343 foreach my $attr ($class->compute_all_applicable_attributes()) {
344 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
347 # this will only work for a HASH instance type
348 if ($class->is_anon_class) {
349 (reftype($instance) eq 'HASH')
350 || confess "Currently only HASH based instances are supported with instance of anon-classes";
352 # At some point we should make this official
353 # as a reserved slot name, but right now I am
354 # going to keep it here.
355 # my $RESERVED_MOP_SLOT = '__MOP__';
356 $instance->{'__MOP__'} = $class;
361 sub get_meta_instance {
363 return $class->instance_metaclass->new(
365 $class->compute_all_applicable_attributes()
371 my $instance = shift;
372 (blessed($instance) && $instance->isa($class->name))
373 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
375 # we need to protect the integrity of the
376 # Class::MOP::Class singletons here, they
377 # should not be cloned.
378 return $instance if $instance->isa('Class::MOP::Class');
379 $class->clone_instance($instance, @_);
383 my ($class, $instance, %params) = @_;
385 || confess "You can only clone instances, \$self is not a blessed instance";
386 my $meta_instance = $class->get_meta_instance();
387 my $clone = $meta_instance->clone_instance($instance);
388 foreach my $attr ($class->compute_all_applicable_attributes()) {
389 if (exists $params{$attr->init_arg}) {
390 $meta_instance->set_slot_value($clone, $attr->name, $params{$attr->init_arg});
396 sub rebless_instance {
397 my ($self, $instance) = @_;
398 my $old_metaclass = $instance->meta();
399 my $meta_instance = $self->get_meta_instance();
401 $self->name->isa($old_metaclass->name)
402 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
405 $meta_instance->rebless_instance_structure($instance, $self);
407 # check and upgrade all attributes
408 my %params = map { $_->name => $meta_instance->get_slot_value($instance, $_->name) }
409 grep { $meta_instance->is_slot_initialized($instance, $_->name) }
410 $self->compute_all_applicable_attributes;
412 foreach my $attr ($self->compute_all_applicable_attributes) {
413 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
423 @{$self->get_package_symbol('@ISA')} = @supers;
425 # we need to check the metaclass
426 # compatibility here so that we can
427 # be sure that the superclass is
428 # not potentially creating an issues
429 # we don't know about
430 $self->check_metaclass_compatability();
432 @{$self->get_package_symbol('@ISA')};
438 my $super_class = $self->name;
441 my $find_derived_classes;
442 $find_derived_classes = sub {
443 my ($outer_class) = @_;
445 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
448 for my $symbol ( keys %$symbol_table_hashref ) {
449 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
450 my $inner_class = $1;
452 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
456 ? "${outer_class}::$inner_class"
459 if ( $class->isa($super_class) and $class ne $super_class ) {
460 push @derived_classes, $class;
463 next SYMBOL if $class eq 'main'; # skip 'main::*'
465 $find_derived_classes->($class);
469 my $root_class = q{};
470 $find_derived_classes->($root_class);
472 undef $find_derived_classes;
474 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
476 return @derived_classes;
481 if (Class::MOP::IS_RUNNING_ON_5_10()) {
482 return @{ mro::get_linear_isa( (shift)->name ) };
486 return grep { !($seen{$_}++) } (shift)->class_precedence_list;
490 sub class_precedence_list {
493 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
495 # We need to check for circular inheritance here
496 # if we are are not on 5.10, cause 5.8 detects it
497 # late. This will do nothing if all is well, and
498 # blow up otherwise. Yes, it's an ugly hack, better
499 # suggestions are welcome.
501 ($self->name || return)->isa('This is a test for circular inheritance')
507 $self->initialize($_)->class_precedence_list()
508 } $self->superclasses()
515 my ($self, $method_name, $method) = @_;
516 (defined $method_name && $method_name)
517 || confess "You must define a method name";
520 if (blessed($method)) {
521 $body = $method->body;
525 ('CODE' eq (reftype($body) || ''))
526 || confess "Your code block must be a CODE reference";
527 $method = $self->method_metaclass->wrap($body);
529 $self->get_method_map->{$method_name} = $method;
531 my $full_method_name = ($self->name . '::' . $method_name);
532 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
533 $self->update_package_cache_flag;
537 my $fetch_and_prepare_method = sub {
538 my ($self, $method_name) = @_;
540 my $method = $self->get_method($method_name);
541 # if we dont have local ...
543 # try to find the next method
544 $method = $self->find_next_method_by_name($method_name);
545 # die if it does not exist
547 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
548 # and now make sure to wrap it
549 # even if it is already wrapped
550 # because we need a new sub ref
551 $method = Class::MOP::Method::Wrapped->wrap($method);
554 # now make sure we wrap it properly
555 $method = Class::MOP::Method::Wrapped->wrap($method)
556 unless $method->isa('Class::MOP::Method::Wrapped');
558 $self->add_method($method_name => $method);
562 sub add_before_method_modifier {
563 my ($self, $method_name, $method_modifier) = @_;
564 (defined $method_name && $method_name)
565 || confess "You must pass in a method name";
566 my $method = $fetch_and_prepare_method->($self, $method_name);
567 $method->add_before_modifier(subname ':before' => $method_modifier);
570 sub add_after_method_modifier {
571 my ($self, $method_name, $method_modifier) = @_;
572 (defined $method_name && $method_name)
573 || confess "You must pass in a method name";
574 my $method = $fetch_and_prepare_method->($self, $method_name);
575 $method->add_after_modifier(subname ':after' => $method_modifier);
578 sub add_around_method_modifier {
579 my ($self, $method_name, $method_modifier) = @_;
580 (defined $method_name && $method_name)
581 || confess "You must pass in a method name";
582 my $method = $fetch_and_prepare_method->($self, $method_name);
583 $method->add_around_modifier(subname ':around' => $method_modifier);
587 # the methods above used to be named like this:
588 # ${pkg}::${method}:(before|after|around)
589 # but this proved problematic when using one modifier
590 # to wrap multiple methods (something which is likely
591 # to happen pretty regularly IMO). So instead of naming
592 # it like this, I have chosen to just name them purely
593 # with their modifier names, like so:
594 # :(before|after|around)
595 # The fact is that in a stack trace, it will be fairly
596 # evident from the context what method they are attached
597 # to, and so don't need the fully qualified name.
601 my ($self, $method_name, $method) = @_;
602 (defined $method_name && $method_name)
603 || confess "You must define a method name";
605 my $body = (blessed($method) ? $method->body : $method);
606 ('CODE' eq (reftype($body) || ''))
607 || confess "Your code block must be a CODE reference";
609 $self->add_package_symbol("&${method_name}" => $body);
610 $self->update_package_cache_flag;
614 my ($self, $method_name) = @_;
615 (defined $method_name && $method_name)
616 || confess "You must define a method name";
618 return 0 unless exists $self->get_method_map->{$method_name};
623 my ($self, $method_name) = @_;
624 (defined $method_name && $method_name)
625 || confess "You must define a method name";
628 # I don't really need this here, because
629 # if the method_map is missing a key it
630 # will just return undef for me now
631 # return unless $self->has_method($method_name);
633 return $self->get_method_map->{$method_name};
637 my ($self, $method_name) = @_;
638 (defined $method_name && $method_name)
639 || confess "You must define a method name";
641 my $removed_method = delete $self->get_method_map->{$method_name};
643 $self->remove_package_symbol("&${method_name}");
645 $self->update_package_cache_flag;
647 return $removed_method;
650 sub get_method_list {
652 keys %{$self->get_method_map};
655 sub find_method_by_name {
656 my ($self, $method_name) = @_;
657 (defined $method_name && $method_name)
658 || confess "You must define a method name to find";
659 foreach my $class ($self->linearized_isa) {
660 # fetch the meta-class ...
661 my $meta = $self->initialize($class);
662 return $meta->get_method($method_name)
663 if $meta->has_method($method_name);
668 sub compute_all_applicable_methods {
670 my (@methods, %seen_method);
671 foreach my $class ($self->linearized_isa) {
672 # fetch the meta-class ...
673 my $meta = $self->initialize($class);
674 foreach my $method_name ($meta->get_method_list()) {
675 next if exists $seen_method{$method_name};
676 $seen_method{$method_name}++;
678 name => $method_name,
680 code => $meta->get_method($method_name)
687 sub find_all_methods_by_name {
688 my ($self, $method_name) = @_;
689 (defined $method_name && $method_name)
690 || confess "You must define a method name to find";
692 foreach my $class ($self->linearized_isa) {
693 # fetch the meta-class ...
694 my $meta = $self->initialize($class);
696 name => $method_name,
698 code => $meta->get_method($method_name)
699 } if $meta->has_method($method_name);
704 sub find_next_method_by_name {
705 my ($self, $method_name) = @_;
706 (defined $method_name && $method_name)
707 || confess "You must define a method name to find";
708 my @cpl = $self->linearized_isa;
709 shift @cpl; # discard ourselves
710 foreach my $class (@cpl) {
711 # fetch the meta-class ...
712 my $meta = $self->initialize($class);
713 return $meta->get_method($method_name)
714 if $meta->has_method($method_name);
723 # either we have an attribute object already
724 # or we need to create one from the args provided
725 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
726 # make sure it is derived from the correct type though
727 ($attribute->isa('Class::MOP::Attribute'))
728 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
730 # first we attach our new attribute
731 # because it might need certain information
732 # about the class which it is attached to
733 $attribute->attach_to_class($self);
735 # then we remove attributes of a conflicting
736 # name here so that we can properly detach
737 # the old attr object, and remove any
738 # accessors it would have generated
739 $self->remove_attribute($attribute->name)
740 if $self->has_attribute($attribute->name);
742 # then onto installing the new accessors
743 $attribute->install_accessors();
744 $self->get_attribute_map->{$attribute->name} = $attribute;
748 my ($self, $attribute_name) = @_;
749 (defined $attribute_name && $attribute_name)
750 || confess "You must define an attribute name";
751 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
755 my ($self, $attribute_name) = @_;
756 (defined $attribute_name && $attribute_name)
757 || confess "You must define an attribute name";
758 return $self->get_attribute_map->{$attribute_name}
760 # this will return undef anyway, so no need ...
761 # if $self->has_attribute($attribute_name);
765 sub remove_attribute {
766 my ($self, $attribute_name) = @_;
767 (defined $attribute_name && $attribute_name)
768 || confess "You must define an attribute name";
769 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
770 return unless defined $removed_attribute;
771 delete $self->get_attribute_map->{$attribute_name};
772 $removed_attribute->remove_accessors();
773 $removed_attribute->detach_from_class();
774 return $removed_attribute;
777 sub get_attribute_list {
779 keys %{$self->get_attribute_map};
782 sub compute_all_applicable_attributes {
784 my (@attrs, %seen_attr);
785 foreach my $class ($self->linearized_isa) {
786 # fetch the meta-class ...
787 my $meta = $self->initialize($class);
788 foreach my $attr_name ($meta->get_attribute_list()) {
789 next if exists $seen_attr{$attr_name};
790 $seen_attr{$attr_name}++;
791 push @attrs => $meta->get_attribute($attr_name);
797 sub find_attribute_by_name {
798 my ($self, $attr_name) = @_;
799 foreach my $class ($self->linearized_isa) {
800 # fetch the meta-class ...
801 my $meta = $self->initialize($class);
802 return $meta->get_attribute($attr_name)
803 if $meta->has_attribute($attr_name);
811 sub is_immutable { 0 }
814 # Why I changed this (groditi)
815 # - One Metaclass may have many Classes through many Metaclass instances
816 # - One Metaclass should only have one Immutable Transformer instance
817 # - Each Class may have different Immutabilizing options
818 # - Therefore each Metaclass instance may have different Immutabilizing options
819 # - We need to store one Immutable Transformer instance per Metaclass
820 # - We need to store one set of Immutable Transformer options per Class
821 # - Upon make_mutable we may delete the Immutabilizing options
822 # - We could clean the immutable Transformer instance when there is no more
823 # immutable Classes of that type, but we can also keep it in case
824 # another class with this same Metaclass becomes immutable. It is a case
825 # of trading of storing an instance to avoid unnecessary instantiations of
826 # Immutable Transformers. You may view this as a memory leak, however
827 # Because we have few Metaclasses, in practice it seems acceptable
828 # - To allow Immutable Transformers instances to be cleaned up we could weaken
829 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
832 my %IMMUTABLE_TRANSFORMERS;
833 my %IMMUTABLE_OPTIONS;
837 my $class = blessed $self || $self;
839 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
840 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
842 $transformer->make_metaclass_immutable($self, \%options);
843 $IMMUTABLE_OPTIONS{$self->name} =
844 { %options, IMMUTABLE_TRANSFORMER => $transformer };
846 if( exists $options{debug} && $options{debug} ){
847 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
848 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
854 return if $self->is_mutable;
855 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
856 confess "unable to find immutabilizing options" unless ref $options;
857 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
858 $transformer->make_metaclass_mutable($self, $options);
862 sub create_immutable_transformer {
864 my $class = Class::MOP::Immutable->new($self, {
865 read_only => [qw/superclasses/],
873 remove_package_symbol
876 class_precedence_list => 'ARRAY',
877 linearized_isa => 'ARRAY',
878 compute_all_applicable_attributes => 'ARRAY',
879 get_meta_instance => 'SCALAR',
880 get_method_map => 'SCALAR',
894 Class::MOP::Class - Class Meta Object
898 # assuming that class Foo
899 # has been defined, you can
901 # use this for introspection ...
903 # add a method to Foo ...
904 Foo->meta->add_method('bar' => sub { ... })
906 # get a list of all the classes searched
907 # the method dispatcher in the correct order
908 Foo->meta->class_precedence_list()
910 # remove a method from Foo
911 Foo->meta->remove_method('bar');
913 # or use this to actually create classes ...
915 Class::MOP::Class->create('Bar' => (
917 superclasses => [ 'Foo' ],
919 Class::MOP:::Attribute->new('$bar'),
920 Class::MOP:::Attribute->new('$baz'),
923 calculate_bar => sub { ... },
924 construct_baz => sub { ... }
930 This is the largest and currently most complex part of the Perl 5
931 meta-object protocol. It controls the introspection and
932 manipulation of Perl 5 classes (and it can create them too). The
933 best way to understand what this module can do, is to read the
934 documentation for each of it's methods.
938 =head2 Self Introspection
944 This will return a B<Class::MOP::Class> instance which is related
945 to this class. Thereby allowing B<Class::MOP::Class> to actually
948 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
949 bootstrap this module by installing a number of attribute meta-objects
950 into it's metaclass. This will allow this class to reap all the benifits
951 of the MOP when subclassing it.
955 =head2 Class construction
957 These methods will handle creating B<Class::MOP::Class> objects,
958 which can be used to both create new classes, and analyze
959 pre-existing classes.
961 This module will internally store references to all the instances
962 you create with these methods, so that they do not need to be
963 created any more than nessecary. Basically, they are singletons.
967 =item B<create ($package_name,
968 version =E<gt> ?$version,
969 authority =E<gt> ?$authority,
970 superclasses =E<gt> ?@superclasses,
971 methods =E<gt> ?%methods,
972 attributes =E<gt> ?%attributes)>
974 This returns a B<Class::MOP::Class> object, bringing the specified
975 C<$package_name> into existence and adding any of the C<$version>,
976 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
979 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
980 methods =E<gt> ?%methods,
981 attributes =E<gt> ?%attributes)>
983 This will create an anonymous class, it works much like C<create> but
984 it does not need a C<$package_name>. Instead it will create a suitably
985 unique package name for you to stash things into.
987 On very important distinction is that anon classes are destroyed once
988 the metaclass they are attached to goes out of scope. In the DESTROY
989 method, the created package will be removed from the symbol table.
991 It is also worth noting that any instances created with an anon-class
992 will keep a special reference to the anon-meta which will prevent the
993 anon-class from going out of scope until all instances of it have also
994 been destroyed. This however only works for HASH based instance types,
995 as we use a special reserved slot (C<__MOP__>) to store this.
997 =item B<initialize ($package_name, %options)>
999 This initializes and returns returns a B<Class::MOP::Class> object
1000 for a given a C<$package_name>.
1002 =item B<reinitialize ($package_name, %options)>
1004 This removes the old metaclass, and creates a new one in it's place.
1005 Do B<not> use this unless you really know what you are doing, it could
1006 very easily make a very large mess of your program.
1008 =item B<construct_class_instance (%options)>
1010 This will construct an instance of B<Class::MOP::Class>, it is
1011 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1012 to use C<construct_instance> once all the bootstrapping is done. This
1013 method is used internally by C<initialize> and should never be called
1014 from outside of that method really.
1016 =item B<check_metaclass_compatability>
1018 This method is called as the very last thing in the
1019 C<construct_class_instance> method. This will check that the
1020 metaclass you are creating is compatible with the metaclasses of all
1021 your ancestors. For more inforamtion about metaclass compatibility
1022 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1024 =item B<update_package_cache_flag>
1026 This will reset the package cache flag for this particular metaclass
1027 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1028 function. This is very rarely needed from outside of C<Class::MOP::Class>
1029 but in some cases you might want to use it, so it is here.
1031 =item B<reset_package_cache_flag>
1033 Clear this flag, used in Moose.
1037 =head2 Object instance construction and cloning
1039 These methods are B<entirely optional>, it is up to you whether you want
1044 =item B<instance_metaclass>
1046 =item B<get_meta_instance>
1048 =item B<new_object (%params)>
1050 This is a convience method for creating a new object of the class, and
1051 blessing it into the appropriate package as well. Ideally your class
1052 would call a C<new> this method like so:
1055 my ($class, %param) = @_;
1056 $class->meta->new_object(%params);
1059 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1060 but that is considered bad style, so we do not do that.
1062 =item B<construct_instance (%params)>
1064 This method is used to construct an instace structure suitable for
1065 C<bless>-ing into your package of choice. It works in conjunction
1066 with the Attribute protocol to collect all applicable attributes.
1068 This will construct and instance using a HASH ref as storage
1069 (currently only HASH references are supported). This will collect all
1070 the applicable attributes and layout out the fields in the HASH ref,
1071 it will then initialize them using either use the corresponding key
1072 in C<%params> or any default value or initializer found in the
1073 attribute meta-object.
1075 =item B<clone_object ($instance, %params)>
1077 This is a convience method for cloning an object instance, then
1078 blessing it into the appropriate package. This method will call
1079 C<clone_instance>, which performs a shallow copy of the object,
1080 see that methods documentation for more details. Ideally your
1081 class would call a C<clone> this method like so:
1083 sub MyClass::clone {
1084 my ($self, %param) = @_;
1085 $self->meta->clone_object($self, %params);
1088 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1089 but that is considered bad style, so we do not do that.
1091 =item B<clone_instance($instance, %params)>
1093 This method is a compliment of C<construct_instance> (which means if
1094 you override C<construct_instance>, you need to override this one too),
1095 and clones the instance shallowly.
1097 The cloned structure returned is (like with C<construct_instance>) an
1098 unC<bless>ed HASH reference, it is your responsibility to then bless
1099 this cloned structure into the right class (which C<clone_object> will
1102 As of 0.11, this method will clone the C<$instance> structure shallowly,
1103 as opposed to the deep cloning implemented in prior versions. After much
1104 thought, research and discussion, I have decided that anything but basic
1105 shallow cloning is outside the scope of the meta-object protocol. I
1106 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1107 is too I<context-specific> to be part of the MOP.
1109 =item B<rebless_instance($instance)>
1111 This will change the class of C<$instance> to the class of the invoking
1112 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1113 itself. This limitation may be relaxed in the future.
1115 This can be useful in a number of situations, such as when you are writing
1116 a program that doesn't know everything at object construction time.
1120 =head2 Informational
1122 These are a few predicate methods for asking information about the class.
1126 =item B<is_anon_class>
1128 This returns true if the class is a C<Class::MOP::Class> created anon class.
1132 This returns true if the class is still mutable.
1134 =item B<is_immutable>
1136 This returns true if the class has been made immutable.
1140 =head2 Inheritance Relationships
1144 =item B<superclasses (?@superclasses)>
1146 This is a read-write attribute which represents the superclass
1147 relationships of the class the B<Class::MOP::Class> instance is
1148 associated with. Basically, it can get and set the C<@ISA> for you.
1151 Perl will occasionally perform some C<@ISA> and method caching, if
1152 you decide to change your superclass relationship at runtime (which
1153 is quite insane and very much not recommened), then you should be
1154 aware of this and the fact that this module does not make any
1155 attempt to address this issue.
1157 =item B<class_precedence_list>
1159 This computes the a list of all the class's ancestors in the same order
1160 in which method dispatch will be done. This is similair to
1161 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
1163 =item B<linearized_isa>
1165 This returns a list based on C<class_precedence_list> but with all
1170 This returns a list of subclasses for this class.
1178 =item B<get_method_map>
1180 =item B<method_metaclass>
1182 =item B<add_method ($method_name, $method)>
1184 This will take a C<$method_name> and CODE reference to that
1185 C<$method> and install it into the class's package.
1188 This does absolutely nothing special to C<$method>
1189 other than use B<Sub::Name> to make sure it is tagged with the
1190 correct name, and therefore show up correctly in stack traces and
1193 =item B<alias_method ($method_name, $method)>
1195 This will take a C<$method_name> and CODE reference to that
1196 C<$method> and alias the method into the class's package.
1199 Unlike C<add_method>, this will B<not> try to name the
1200 C<$method> using B<Sub::Name>, it only aliases the method in
1201 the class's package.
1203 =item B<has_method ($method_name)>
1205 This just provides a simple way to check if the class implements
1206 a specific C<$method_name>. It will I<not> however, attempt to check
1207 if the class inherits the method (use C<UNIVERSAL::can> for that).
1209 This will correctly handle functions defined outside of the package
1210 that use a fully qualified name (C<sub Package::name { ... }>).
1212 This will correctly handle functions renamed with B<Sub::Name> and
1213 installed using the symbol tables. However, if you are naming the
1214 subroutine outside of the package scope, you must use the fully
1215 qualified name, including the package name, for C<has_method> to
1216 correctly identify it.
1218 This will attempt to correctly ignore functions imported from other
1219 packages using B<Exporter>. It breaks down if the function imported
1220 is an C<__ANON__> sub (such as with C<use constant>), which very well
1221 may be a valid method being applied to the class.
1223 In short, this method cannot always be trusted to determine if the
1224 C<$method_name> is actually a method. However, it will DWIM about
1225 90% of the time, so it's a small trade off I think.
1227 =item B<get_method ($method_name)>
1229 This will return a Class::MOP::Method instance related to the specified
1230 C<$method_name>, or return undef if that method does not exist.
1232 The Class::MOP::Method is codifiable, so you can use it like a normal
1233 CODE reference, see L<Class::MOP::Method> for more information.
1235 =item B<find_method_by_name ($method_name>
1237 This will return a CODE reference of the specified C<$method_name>,
1238 or return undef if that method does not exist.
1240 Unlike C<get_method> this will also look in the superclasses.
1242 =item B<remove_method ($method_name)>
1244 This will attempt to remove a given C<$method_name> from the class.
1245 It will return the CODE reference that it has removed, and will
1246 attempt to use B<Sub::Name> to clear the methods associated name.
1248 =item B<get_method_list>
1250 This will return a list of method names for all I<locally> defined
1251 methods. It does B<not> provide a list of all applicable methods,
1252 including any inherited ones. If you want a list of all applicable
1253 methods, use the C<compute_all_applicable_methods> method.
1255 =item B<compute_all_applicable_methods>
1257 This will return a list of all the methods names this class will
1258 respond to, taking into account inheritance. The list will be a list of
1259 HASH references, each one containing the following information; method
1260 name, the name of the class in which the method lives and a CODE
1261 reference for the actual method.
1263 =item B<find_all_methods_by_name ($method_name)>
1265 This will traverse the inheritence hierarchy and locate all methods
1266 with a given C<$method_name>. Similar to
1267 C<compute_all_applicable_methods> it returns a list of HASH references
1268 with the following information; method name (which will always be the
1269 same as C<$method_name>), the name of the class in which the method
1270 lives and a CODE reference for the actual method.
1272 The list of methods produced is a distinct list, meaning there are no
1273 duplicates in it. This is especially useful for things like object
1274 initialization and destruction where you only want the method called
1275 once, and in the correct order.
1277 =item B<find_next_method_by_name ($method_name)>
1279 This will return the first method to match a given C<$method_name> in
1280 the superclasses, this is basically equivalent to calling
1281 C<SUPER::$method_name>, but it can be dispatched at runtime.
1285 =head2 Method Modifiers
1287 Method modifiers are a concept borrowed from CLOS, in which a method
1288 can be wrapped with I<before>, I<after> and I<around> method modifiers
1289 that will be called everytime the method is called.
1291 =head3 How method modifiers work?
1293 Method modifiers work by wrapping the original method and then replacing
1294 it in the classes symbol table. The wrappers will handle calling all the
1295 modifiers in the appropariate orders and preserving the calling context
1296 for the original method.
1298 Each method modifier serves a particular purpose, which may not be
1299 obvious to users of other method wrapping modules. To start with, the
1300 return values of I<before> and I<after> modifiers are ignored. This is
1301 because thier purpose is B<not> to filter the input and output of the
1302 primary method (this is done with an I<around> modifier). This may seem
1303 like an odd restriction to some, but doing this allows for simple code
1304 to be added at the begining or end of a method call without jeapordizing
1305 the normal functioning of the primary method or placing any extra
1306 responsibility on the code of the modifier. Of course if you have more
1307 complex needs, then use the I<around> modifier, which uses a variation
1308 of continutation passing style to allow for a high degree of flexibility.
1310 Before and around modifiers are called in last-defined-first-called order,
1311 while after modifiers are called in first-defined-first-called order. So
1312 the call tree might looks something like this:
1322 To see examples of using method modifiers, see the following examples
1323 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1324 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1325 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1327 =head3 What is the performance impact?
1329 Of course there is a performance cost associated with method modifiers,
1330 but we have made every effort to make that cost be directly proportional
1331 to the amount of modifier features you utilize.
1333 The wrapping method does it's best to B<only> do as much work as it
1334 absolutely needs to. In order to do this we have moved some of the
1335 performance costs to set-up time, where they are easier to amortize.
1337 All this said, my benchmarks have indicated the following:
1339 simple wrapper with no modifiers 100% slower
1340 simple wrapper with simple before modifier 400% slower
1341 simple wrapper with simple after modifier 450% slower
1342 simple wrapper with simple around modifier 500-550% slower
1343 simple wrapper with all 3 modifiers 1100% slower
1345 These numbers may seem daunting, but you must remember, every feature
1346 comes with some cost. To put things in perspective, just doing a simple
1347 C<AUTOLOAD> which does nothing but extract the name of the method called
1348 and return it costs about 400% over a normal method call.
1352 =item B<add_before_method_modifier ($method_name, $code)>
1354 This will wrap the method at C<$method_name> and the supplied C<$code>
1355 will be passed the C<@_> arguments, and called before the original
1356 method is called. As specified above, the return value of the I<before>
1357 method modifiers is ignored, and it's ability to modify C<@_> is
1358 fairly limited. If you need to do either of these things, use an
1359 C<around> method modifier.
1361 =item B<add_after_method_modifier ($method_name, $code)>
1363 This will wrap the method at C<$method_name> so that the original
1364 method will be called, it's return values stashed, and then the
1365 supplied C<$code> will be passed the C<@_> arguments, and called.
1366 As specified above, the return value of the I<after> method
1367 modifiers is ignored, and it cannot modify the return values of
1368 the original method. If you need to do either of these things, use an
1369 C<around> method modifier.
1371 =item B<add_around_method_modifier ($method_name, $code)>
1373 This will wrap the method at C<$method_name> so that C<$code>
1374 will be called and passed the original method as an extra argument
1375 at the begining of the C<@_> argument list. This is a variation of
1376 continuation passing style, where the function prepended to C<@_>
1377 can be considered a continuation. It is up to C<$code> if it calls
1378 the original method or not, there is no restriction on what the
1379 C<$code> can or cannot do.
1385 It should be noted that since there is no one consistent way to define
1386 the attributes of a class in Perl 5. These methods can only work with
1387 the information given, and can not easily discover information on
1388 their own. See L<Class::MOP::Attribute> for more details.
1392 =item B<attribute_metaclass>
1394 =item B<get_attribute_map>
1396 =item B<add_attribute ($attribute_meta_object | $attribute_name, %attribute_spec)>
1398 This stores the C<$attribute_meta_object> (or creates one from the
1399 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1400 instance associated with the given class. Unlike methods, attributes
1401 within the MOP are stored as meta-information only. They will be used
1402 later to construct instances from (see C<construct_instance> above).
1403 More details about the attribute meta-objects can be found in the
1404 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1407 It should be noted that any accessor, reader/writer or predicate
1408 methods which the C<$attribute_meta_object> has will be installed
1409 into the class at this time.
1412 If an attribute already exists for C<$attribute_name>, the old one
1413 will be removed (as well as removing all it's accessors), and then
1416 =item B<has_attribute ($attribute_name)>
1418 Checks to see if this class has an attribute by the name of
1419 C<$attribute_name> and returns a boolean.
1421 =item B<get_attribute ($attribute_name)>
1423 Returns the attribute meta-object associated with C<$attribute_name>,
1424 if none is found, it will return undef.
1426 =item B<remove_attribute ($attribute_name)>
1428 This will remove the attribute meta-object stored at
1429 C<$attribute_name>, then return the removed attribute meta-object.
1432 Removing an attribute will only affect future instances of
1433 the class, it will not make any attempt to remove the attribute from
1434 any existing instances of the class.
1436 It should be noted that any accessor, reader/writer or predicate
1437 methods which the attribute meta-object stored at C<$attribute_name>
1438 has will be removed from the class at this time. This B<will> make
1439 these attributes somewhat inaccessable in previously created
1440 instances. But if you are crazy enough to do this at runtime, then
1441 you are crazy enough to deal with something like this :).
1443 =item B<get_attribute_list>
1445 This returns a list of attribute names which are defined in the local
1446 class. If you want a list of all applicable attributes for a class,
1447 use the C<compute_all_applicable_attributes> method.
1449 =item B<compute_all_applicable_attributes>
1451 This will traverse the inheritance heirachy and return a list of all
1452 the applicable attributes for this class. It does not construct a
1453 HASH reference like C<compute_all_applicable_methods> because all
1454 that same information is discoverable through the attribute
1457 =item B<find_attribute_by_name ($attr_name)>
1459 This method will traverse the inheritance heirachy and find the
1460 first attribute whose name matches C<$attr_name>, then return it.
1461 It will return undef if nothing is found.
1465 =head2 Class Immutability
1469 =item B<make_immutable (%options)>
1471 This method will invoke a tranforamtion upon the class which will
1472 make it immutable. Details of this transformation can be found in
1473 the L<Class::MOP::Immutable> documentation.
1475 =item B<make_mutable>
1477 This method will reverse tranforamtion upon the class which
1480 =item B<create_immutable_transformer>
1482 Create a transformer suitable for making this class immutable
1488 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1490 =head1 COPYRIGHT AND LICENSE
1492 Copyright 2006-2008 by Infinity Interactive, Inc.
1494 L<http://www.iinteractive.com>
1496 This library is free software; you can redistribute it and/or modify
1497 it under the same terms as Perl itself.