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 = '0.27';
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 ( defined( my $init_arg = $attr->init_arg ) ) {
390 if (exists $params{$init_arg}) {
391 $attr->set_value($clone, $params{$init_arg});
398 sub rebless_instance {
399 my ($self, $instance) = @_;
402 if ($instance->can('meta')) {
403 ($instance->meta->isa('Class::MOP::Class'))
404 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
405 $old_metaclass = $instance->meta;
408 $old_metaclass = $self->initialize(blessed($instance));
411 my $meta_instance = $self->get_meta_instance();
413 $self->name->isa($old_metaclass->name)
414 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
417 $meta_instance->rebless_instance_structure($instance, $self);
419 # check and upgrade all attributes
420 foreach my $attr ( $self->compute_all_applicable_attributes ) {
421 if ( $attr->has_value($instance) ) {
422 $attr->set_value($instance, $attr->get_value($instance) );
433 @{$self->get_package_symbol('@ISA')} = @supers;
435 # we need to check the metaclass
436 # compatibility here so that we can
437 # be sure that the superclass is
438 # not potentially creating an issues
439 # we don't know about
440 $self->check_metaclass_compatability();
442 @{$self->get_package_symbol('@ISA')};
448 my $super_class = $self->name;
451 my $find_derived_classes;
452 $find_derived_classes = sub {
453 my ($outer_class) = @_;
455 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
458 for my $symbol ( keys %$symbol_table_hashref ) {
459 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
460 my $inner_class = $1;
462 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
466 ? "${outer_class}::$inner_class"
469 if ( $class->isa($super_class) and $class ne $super_class ) {
470 push @derived_classes, $class;
473 next SYMBOL if $class eq 'main'; # skip 'main::*'
475 $find_derived_classes->($class);
479 my $root_class = q{};
480 $find_derived_classes->($root_class);
482 undef $find_derived_classes;
484 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
486 return @derived_classes;
491 if (Class::MOP::IS_RUNNING_ON_5_10()) {
492 return @{ mro::get_linear_isa( (shift)->name ) };
496 return grep { !($seen{$_}++) } (shift)->class_precedence_list;
500 sub class_precedence_list {
503 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
505 # We need to check for circular inheritance here
506 # if we are are not on 5.10, cause 5.8 detects it
507 # late. This will do nothing if all is well, and
508 # blow up otherwise. Yes, it's an ugly hack, better
509 # suggestions are welcome.
511 ($self->name || return)->isa('This is a test for circular inheritance')
517 $self->initialize($_)->class_precedence_list()
518 } $self->superclasses()
525 my ($self, $method_name, $method) = @_;
526 (defined $method_name && $method_name)
527 || confess "You must define a method name";
530 if (blessed($method)) {
531 $body = $method->body;
535 ('CODE' eq (reftype($body) || ''))
536 || confess "Your code block must be a CODE reference";
537 $method = $self->method_metaclass->wrap($body);
539 $self->get_method_map->{$method_name} = $method;
541 my $full_method_name = ($self->name . '::' . $method_name);
542 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
543 $self->update_package_cache_flag;
547 my $fetch_and_prepare_method = sub {
548 my ($self, $method_name) = @_;
550 my $method = $self->get_method($method_name);
551 # if we dont have local ...
553 # try to find the next method
554 $method = $self->find_next_method_by_name($method_name);
555 # die if it does not exist
557 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
558 # and now make sure to wrap it
559 # even if it is already wrapped
560 # because we need a new sub ref
561 $method = Class::MOP::Method::Wrapped->wrap($method);
564 # now make sure we wrap it properly
565 $method = Class::MOP::Method::Wrapped->wrap($method)
566 unless $method->isa('Class::MOP::Method::Wrapped');
568 $self->add_method($method_name => $method);
572 sub add_before_method_modifier {
573 my ($self, $method_name, $method_modifier) = @_;
574 (defined $method_name && $method_name)
575 || confess "You must pass in a method name";
576 my $method = $fetch_and_prepare_method->($self, $method_name);
577 $method->add_before_modifier(subname ':before' => $method_modifier);
580 sub add_after_method_modifier {
581 my ($self, $method_name, $method_modifier) = @_;
582 (defined $method_name && $method_name)
583 || confess "You must pass in a method name";
584 my $method = $fetch_and_prepare_method->($self, $method_name);
585 $method->add_after_modifier(subname ':after' => $method_modifier);
588 sub add_around_method_modifier {
589 my ($self, $method_name, $method_modifier) = @_;
590 (defined $method_name && $method_name)
591 || confess "You must pass in a method name";
592 my $method = $fetch_and_prepare_method->($self, $method_name);
593 $method->add_around_modifier(subname ':around' => $method_modifier);
597 # the methods above used to be named like this:
598 # ${pkg}::${method}:(before|after|around)
599 # but this proved problematic when using one modifier
600 # to wrap multiple methods (something which is likely
601 # to happen pretty regularly IMO). So instead of naming
602 # it like this, I have chosen to just name them purely
603 # with their modifier names, like so:
604 # :(before|after|around)
605 # The fact is that in a stack trace, it will be fairly
606 # evident from the context what method they are attached
607 # to, and so don't need the fully qualified name.
611 my ($self, $method_name, $method) = @_;
612 (defined $method_name && $method_name)
613 || confess "You must define a method name";
615 my $body = (blessed($method) ? $method->body : $method);
616 ('CODE' eq (reftype($body) || ''))
617 || confess "Your code block must be a CODE reference";
619 $self->add_package_symbol("&${method_name}" => $body);
620 $self->update_package_cache_flag;
624 my ($self, $method_name) = @_;
625 (defined $method_name && $method_name)
626 || confess "You must define a method name";
628 return 0 unless exists $self->get_method_map->{$method_name};
633 my ($self, $method_name) = @_;
634 (defined $method_name && $method_name)
635 || confess "You must define a method name";
638 # I don't really need this here, because
639 # if the method_map is missing a key it
640 # will just return undef for me now
641 # return unless $self->has_method($method_name);
643 return $self->get_method_map->{$method_name};
647 my ($self, $method_name) = @_;
648 (defined $method_name && $method_name)
649 || confess "You must define a method name";
651 my $removed_method = delete $self->get_method_map->{$method_name};
653 $self->remove_package_symbol("&${method_name}");
655 $self->update_package_cache_flag;
657 return $removed_method;
660 sub get_method_list {
662 keys %{$self->get_method_map};
665 sub find_method_by_name {
666 my ($self, $method_name) = @_;
667 (defined $method_name && $method_name)
668 || confess "You must define a method name to find";
669 foreach my $class ($self->linearized_isa) {
670 # fetch the meta-class ...
671 my $meta = $self->initialize($class);
672 return $meta->get_method($method_name)
673 if $meta->has_method($method_name);
678 sub compute_all_applicable_methods {
680 my (@methods, %seen_method);
681 foreach my $class ($self->linearized_isa) {
682 # fetch the meta-class ...
683 my $meta = $self->initialize($class);
684 foreach my $method_name ($meta->get_method_list()) {
685 next if exists $seen_method{$method_name};
686 $seen_method{$method_name}++;
688 name => $method_name,
690 code => $meta->get_method($method_name)
697 sub find_all_methods_by_name {
698 my ($self, $method_name) = @_;
699 (defined $method_name && $method_name)
700 || confess "You must define a method name to find";
702 foreach my $class ($self->linearized_isa) {
703 # fetch the meta-class ...
704 my $meta = $self->initialize($class);
706 name => $method_name,
708 code => $meta->get_method($method_name)
709 } if $meta->has_method($method_name);
714 sub find_next_method_by_name {
715 my ($self, $method_name) = @_;
716 (defined $method_name && $method_name)
717 || confess "You must define a method name to find";
718 my @cpl = $self->linearized_isa;
719 shift @cpl; # discard ourselves
720 foreach my $class (@cpl) {
721 # fetch the meta-class ...
722 my $meta = $self->initialize($class);
723 return $meta->get_method($method_name)
724 if $meta->has_method($method_name);
733 # either we have an attribute object already
734 # or we need to create one from the args provided
735 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
736 # make sure it is derived from the correct type though
737 ($attribute->isa('Class::MOP::Attribute'))
738 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
740 # first we attach our new attribute
741 # because it might need certain information
742 # about the class which it is attached to
743 $attribute->attach_to_class($self);
745 # then we remove attributes of a conflicting
746 # name here so that we can properly detach
747 # the old attr object, and remove any
748 # accessors it would have generated
749 $self->remove_attribute($attribute->name)
750 if $self->has_attribute($attribute->name);
752 # then onto installing the new accessors
753 $attribute->install_accessors();
754 $self->get_attribute_map->{$attribute->name} = $attribute;
758 my ($self, $attribute_name) = @_;
759 (defined $attribute_name && $attribute_name)
760 || confess "You must define an attribute name";
761 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
765 my ($self, $attribute_name) = @_;
766 (defined $attribute_name && $attribute_name)
767 || confess "You must define an attribute name";
768 return $self->get_attribute_map->{$attribute_name}
770 # this will return undef anyway, so no need ...
771 # if $self->has_attribute($attribute_name);
775 sub remove_attribute {
776 my ($self, $attribute_name) = @_;
777 (defined $attribute_name && $attribute_name)
778 || confess "You must define an attribute name";
779 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
780 return unless defined $removed_attribute;
781 delete $self->get_attribute_map->{$attribute_name};
782 $removed_attribute->remove_accessors();
783 $removed_attribute->detach_from_class();
784 return $removed_attribute;
787 sub get_attribute_list {
789 keys %{$self->get_attribute_map};
792 sub compute_all_applicable_attributes {
794 my (@attrs, %seen_attr);
795 foreach my $class ($self->linearized_isa) {
796 # fetch the meta-class ...
797 my $meta = $self->initialize($class);
798 foreach my $attr_name ($meta->get_attribute_list()) {
799 next if exists $seen_attr{$attr_name};
800 $seen_attr{$attr_name}++;
801 push @attrs => $meta->get_attribute($attr_name);
807 sub find_attribute_by_name {
808 my ($self, $attr_name) = @_;
809 foreach my $class ($self->linearized_isa) {
810 # fetch the meta-class ...
811 my $meta = $self->initialize($class);
812 return $meta->get_attribute($attr_name)
813 if $meta->has_attribute($attr_name);
821 sub is_immutable { 0 }
824 # Why I changed this (groditi)
825 # - One Metaclass may have many Classes through many Metaclass instances
826 # - One Metaclass should only have one Immutable Transformer instance
827 # - Each Class may have different Immutabilizing options
828 # - Therefore each Metaclass instance may have different Immutabilizing options
829 # - We need to store one Immutable Transformer instance per Metaclass
830 # - We need to store one set of Immutable Transformer options per Class
831 # - Upon make_mutable we may delete the Immutabilizing options
832 # - We could clean the immutable Transformer instance when there is no more
833 # immutable Classes of that type, but we can also keep it in case
834 # another class with this same Metaclass becomes immutable. It is a case
835 # of trading of storing an instance to avoid unnecessary instantiations of
836 # Immutable Transformers. You may view this as a memory leak, however
837 # Because we have few Metaclasses, in practice it seems acceptable
838 # - To allow Immutable Transformers instances to be cleaned up we could weaken
839 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
842 my %IMMUTABLE_TRANSFORMERS;
843 my %IMMUTABLE_OPTIONS;
847 my $class = blessed $self || $self;
849 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
850 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
852 $transformer->make_metaclass_immutable($self, \%options);
853 $IMMUTABLE_OPTIONS{$self->name} =
854 { %options, IMMUTABLE_TRANSFORMER => $transformer };
856 if( exists $options{debug} && $options{debug} ){
857 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
858 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
864 return if $self->is_mutable;
865 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
866 confess "unable to find immutabilizing options" unless ref $options;
867 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
868 $transformer->make_metaclass_mutable($self, $options);
872 sub create_immutable_transformer {
874 my $class = Class::MOP::Immutable->new($self, {
875 read_only => [qw/superclasses/],
883 remove_package_symbol
886 class_precedence_list => 'ARRAY',
887 linearized_isa => 'ARRAY',
888 compute_all_applicable_attributes => 'ARRAY',
889 get_meta_instance => 'SCALAR',
890 get_method_map => 'SCALAR',
904 Class::MOP::Class - Class Meta Object
908 # assuming that class Foo
909 # has been defined, you can
911 # use this for introspection ...
913 # add a method to Foo ...
914 Foo->meta->add_method('bar' => sub { ... })
916 # get a list of all the classes searched
917 # the method dispatcher in the correct order
918 Foo->meta->class_precedence_list()
920 # remove a method from Foo
921 Foo->meta->remove_method('bar');
923 # or use this to actually create classes ...
925 Class::MOP::Class->create('Bar' => (
927 superclasses => [ 'Foo' ],
929 Class::MOP:::Attribute->new('$bar'),
930 Class::MOP:::Attribute->new('$baz'),
933 calculate_bar => sub { ... },
934 construct_baz => sub { ... }
940 This is the largest and currently most complex part of the Perl 5
941 meta-object protocol. It controls the introspection and
942 manipulation of Perl 5 classes (and it can create them too). The
943 best way to understand what this module can do, is to read the
944 documentation for each of it's methods.
948 =head2 Self Introspection
954 This will return a B<Class::MOP::Class> instance which is related
955 to this class. Thereby allowing B<Class::MOP::Class> to actually
958 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
959 bootstrap this module by installing a number of attribute meta-objects
960 into it's metaclass. This will allow this class to reap all the benifits
961 of the MOP when subclassing it.
965 =head2 Class construction
967 These methods will handle creating B<Class::MOP::Class> objects,
968 which can be used to both create new classes, and analyze
969 pre-existing classes.
971 This module will internally store references to all the instances
972 you create with these methods, so that they do not need to be
973 created any more than nessecary. Basically, they are singletons.
977 =item B<create ($package_name,
978 version =E<gt> ?$version,
979 authority =E<gt> ?$authority,
980 superclasses =E<gt> ?@superclasses,
981 methods =E<gt> ?%methods,
982 attributes =E<gt> ?%attributes)>
984 This returns a B<Class::MOP::Class> object, bringing the specified
985 C<$package_name> into existence and adding any of the C<$version>,
986 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
989 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
990 methods =E<gt> ?%methods,
991 attributes =E<gt> ?%attributes)>
993 This will create an anonymous class, it works much like C<create> but
994 it does not need a C<$package_name>. Instead it will create a suitably
995 unique package name for you to stash things into.
997 On very important distinction is that anon classes are destroyed once
998 the metaclass they are attached to goes out of scope. In the DESTROY
999 method, the created package will be removed from the symbol table.
1001 It is also worth noting that any instances created with an anon-class
1002 will keep a special reference to the anon-meta which will prevent the
1003 anon-class from going out of scope until all instances of it have also
1004 been destroyed. This however only works for HASH based instance types,
1005 as we use a special reserved slot (C<__MOP__>) to store this.
1007 =item B<initialize ($package_name, %options)>
1009 This initializes and returns returns a B<Class::MOP::Class> object
1010 for a given a C<$package_name>.
1012 =item B<reinitialize ($package_name, %options)>
1014 This removes the old metaclass, and creates a new one in it's place.
1015 Do B<not> use this unless you really know what you are doing, it could
1016 very easily make a very large mess of your program.
1018 =item B<construct_class_instance (%options)>
1020 This will construct an instance of B<Class::MOP::Class>, it is
1021 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1022 to use C<construct_instance> once all the bootstrapping is done. This
1023 method is used internally by C<initialize> and should never be called
1024 from outside of that method really.
1026 =item B<check_metaclass_compatability>
1028 This method is called as the very last thing in the
1029 C<construct_class_instance> method. This will check that the
1030 metaclass you are creating is compatible with the metaclasses of all
1031 your ancestors. For more inforamtion about metaclass compatibility
1032 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1034 =item B<update_package_cache_flag>
1036 This will reset the package cache flag for this particular metaclass
1037 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1038 function. This is very rarely needed from outside of C<Class::MOP::Class>
1039 but in some cases you might want to use it, so it is here.
1041 =item B<reset_package_cache_flag>
1043 Clear this flag, used in Moose.
1047 =head2 Object instance construction and cloning
1049 These methods are B<entirely optional>, it is up to you whether you want
1054 =item B<instance_metaclass>
1056 =item B<get_meta_instance>
1058 =item B<new_object (%params)>
1060 This is a convience method for creating a new object of the class, and
1061 blessing it into the appropriate package as well. Ideally your class
1062 would call a C<new> this method like so:
1065 my ($class, %param) = @_;
1066 $class->meta->new_object(%params);
1069 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1070 but that is considered bad style, so we do not do that.
1072 =item B<construct_instance (%params)>
1074 This method is used to construct an instace structure suitable for
1075 C<bless>-ing into your package of choice. It works in conjunction
1076 with the Attribute protocol to collect all applicable attributes.
1078 This will construct and instance using a HASH ref as storage
1079 (currently only HASH references are supported). This will collect all
1080 the applicable attributes and layout out the fields in the HASH ref,
1081 it will then initialize them using either use the corresponding key
1082 in C<%params> or any default value or initializer found in the
1083 attribute meta-object.
1085 =item B<clone_object ($instance, %params)>
1087 This is a convience method for cloning an object instance, then
1088 blessing it into the appropriate package. This method will call
1089 C<clone_instance>, which performs a shallow copy of the object,
1090 see that methods documentation for more details. Ideally your
1091 class would call a C<clone> this method like so:
1093 sub MyClass::clone {
1094 my ($self, %param) = @_;
1095 $self->meta->clone_object($self, %params);
1098 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1099 but that is considered bad style, so we do not do that.
1101 =item B<clone_instance($instance, %params)>
1103 This method is a compliment of C<construct_instance> (which means if
1104 you override C<construct_instance>, you need to override this one too),
1105 and clones the instance shallowly.
1107 The cloned structure returned is (like with C<construct_instance>) an
1108 unC<bless>ed HASH reference, it is your responsibility to then bless
1109 this cloned structure into the right class (which C<clone_object> will
1112 As of 0.11, this method will clone the C<$instance> structure shallowly,
1113 as opposed to the deep cloning implemented in prior versions. After much
1114 thought, research and discussion, I have decided that anything but basic
1115 shallow cloning is outside the scope of the meta-object protocol. I
1116 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1117 is too I<context-specific> to be part of the MOP.
1119 =item B<rebless_instance($instance)>
1121 This will change the class of C<$instance> to the class of the invoking
1122 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1123 itself. This limitation may be relaxed in the future.
1125 This can be useful in a number of situations, such as when you are writing
1126 a program that doesn't know everything at object construction time.
1130 =head2 Informational
1132 These are a few predicate methods for asking information about the class.
1136 =item B<is_anon_class>
1138 This returns true if the class is a C<Class::MOP::Class> created anon class.
1142 This returns true if the class is still mutable.
1144 =item B<is_immutable>
1146 This returns true if the class has been made immutable.
1150 =head2 Inheritance Relationships
1154 =item B<superclasses (?@superclasses)>
1156 This is a read-write attribute which represents the superclass
1157 relationships of the class the B<Class::MOP::Class> instance is
1158 associated with. Basically, it can get and set the C<@ISA> for you.
1161 Perl will occasionally perform some C<@ISA> and method caching, if
1162 you decide to change your superclass relationship at runtime (which
1163 is quite insane and very much not recommened), then you should be
1164 aware of this and the fact that this module does not make any
1165 attempt to address this issue.
1167 =item B<class_precedence_list>
1169 This computes the a list of all the class's ancestors in the same order
1170 in which method dispatch will be done. This is similair to
1171 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
1173 =item B<linearized_isa>
1175 This returns a list based on C<class_precedence_list> but with all
1180 This returns a list of subclasses for this class.
1188 =item B<get_method_map>
1190 =item B<method_metaclass>
1192 =item B<add_method ($method_name, $method)>
1194 This will take a C<$method_name> and CODE reference to that
1195 C<$method> and install it into the class's package.
1198 This does absolutely nothing special to C<$method>
1199 other than use B<Sub::Name> to make sure it is tagged with the
1200 correct name, and therefore show up correctly in stack traces and
1203 =item B<alias_method ($method_name, $method)>
1205 This will take a C<$method_name> and CODE reference to that
1206 C<$method> and alias the method into the class's package.
1209 Unlike C<add_method>, this will B<not> try to name the
1210 C<$method> using B<Sub::Name>, it only aliases the method in
1211 the class's package.
1213 =item B<has_method ($method_name)>
1215 This just provides a simple way to check if the class implements
1216 a specific C<$method_name>. It will I<not> however, attempt to check
1217 if the class inherits the method (use C<UNIVERSAL::can> for that).
1219 This will correctly handle functions defined outside of the package
1220 that use a fully qualified name (C<sub Package::name { ... }>).
1222 This will correctly handle functions renamed with B<Sub::Name> and
1223 installed using the symbol tables. However, if you are naming the
1224 subroutine outside of the package scope, you must use the fully
1225 qualified name, including the package name, for C<has_method> to
1226 correctly identify it.
1228 This will attempt to correctly ignore functions imported from other
1229 packages using B<Exporter>. It breaks down if the function imported
1230 is an C<__ANON__> sub (such as with C<use constant>), which very well
1231 may be a valid method being applied to the class.
1233 In short, this method cannot always be trusted to determine if the
1234 C<$method_name> is actually a method. However, it will DWIM about
1235 90% of the time, so it's a small trade off I think.
1237 =item B<get_method ($method_name)>
1239 This will return a Class::MOP::Method instance related to the specified
1240 C<$method_name>, or return undef if that method does not exist.
1242 The Class::MOP::Method is codifiable, so you can use it like a normal
1243 CODE reference, see L<Class::MOP::Method> for more information.
1245 =item B<find_method_by_name ($method_name>
1247 This will return a CODE reference of the specified C<$method_name>,
1248 or return undef if that method does not exist.
1250 Unlike C<get_method> this will also look in the superclasses.
1252 =item B<remove_method ($method_name)>
1254 This will attempt to remove a given C<$method_name> from the class.
1255 It will return the CODE reference that it has removed, and will
1256 attempt to use B<Sub::Name> to clear the methods associated name.
1258 =item B<get_method_list>
1260 This will return a list of method names for all I<locally> defined
1261 methods. It does B<not> provide a list of all applicable methods,
1262 including any inherited ones. If you want a list of all applicable
1263 methods, use the C<compute_all_applicable_methods> method.
1265 =item B<compute_all_applicable_methods>
1267 This will return a list of all the methods names this class will
1268 respond to, taking into account inheritance. The list will be a list of
1269 HASH references, each one containing the following information; method
1270 name, the name of the class in which the method lives and a CODE
1271 reference for the actual method.
1273 =item B<find_all_methods_by_name ($method_name)>
1275 This will traverse the inheritence hierarchy and locate all methods
1276 with a given C<$method_name>. Similar to
1277 C<compute_all_applicable_methods> it returns a list of HASH references
1278 with the following information; method name (which will always be the
1279 same as C<$method_name>), the name of the class in which the method
1280 lives and a CODE reference for the actual method.
1282 The list of methods produced is a distinct list, meaning there are no
1283 duplicates in it. This is especially useful for things like object
1284 initialization and destruction where you only want the method called
1285 once, and in the correct order.
1287 =item B<find_next_method_by_name ($method_name)>
1289 This will return the first method to match a given C<$method_name> in
1290 the superclasses, this is basically equivalent to calling
1291 C<SUPER::$method_name>, but it can be dispatched at runtime.
1295 =head2 Method Modifiers
1297 Method modifiers are a concept borrowed from CLOS, in which a method
1298 can be wrapped with I<before>, I<after> and I<around> method modifiers
1299 that will be called everytime the method is called.
1301 =head3 How method modifiers work?
1303 Method modifiers work by wrapping the original method and then replacing
1304 it in the classes symbol table. The wrappers will handle calling all the
1305 modifiers in the appropariate orders and preserving the calling context
1306 for the original method.
1308 Each method modifier serves a particular purpose, which may not be
1309 obvious to users of other method wrapping modules. To start with, the
1310 return values of I<before> and I<after> modifiers are ignored. This is
1311 because thier purpose is B<not> to filter the input and output of the
1312 primary method (this is done with an I<around> modifier). This may seem
1313 like an odd restriction to some, but doing this allows for simple code
1314 to be added at the begining or end of a method call without jeapordizing
1315 the normal functioning of the primary method or placing any extra
1316 responsibility on the code of the modifier. Of course if you have more
1317 complex needs, then use the I<around> modifier, which uses a variation
1318 of continutation passing style to allow for a high degree of flexibility.
1320 Before and around modifiers are called in last-defined-first-called order,
1321 while after modifiers are called in first-defined-first-called order. So
1322 the call tree might looks something like this:
1332 To see examples of using method modifiers, see the following examples
1333 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1334 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1335 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1337 =head3 What is the performance impact?
1339 Of course there is a performance cost associated with method modifiers,
1340 but we have made every effort to make that cost be directly proportional
1341 to the amount of modifier features you utilize.
1343 The wrapping method does it's best to B<only> do as much work as it
1344 absolutely needs to. In order to do this we have moved some of the
1345 performance costs to set-up time, where they are easier to amortize.
1347 All this said, my benchmarks have indicated the following:
1349 simple wrapper with no modifiers 100% slower
1350 simple wrapper with simple before modifier 400% slower
1351 simple wrapper with simple after modifier 450% slower
1352 simple wrapper with simple around modifier 500-550% slower
1353 simple wrapper with all 3 modifiers 1100% slower
1355 These numbers may seem daunting, but you must remember, every feature
1356 comes with some cost. To put things in perspective, just doing a simple
1357 C<AUTOLOAD> which does nothing but extract the name of the method called
1358 and return it costs about 400% over a normal method call.
1362 =item B<add_before_method_modifier ($method_name, $code)>
1364 This will wrap the method at C<$method_name> and the supplied C<$code>
1365 will be passed the C<@_> arguments, and called before the original
1366 method is called. As specified above, the return value of the I<before>
1367 method modifiers is ignored, and it's ability to modify C<@_> is
1368 fairly limited. If you need to do either of these things, use an
1369 C<around> method modifier.
1371 =item B<add_after_method_modifier ($method_name, $code)>
1373 This will wrap the method at C<$method_name> so that the original
1374 method will be called, it's return values stashed, and then the
1375 supplied C<$code> will be passed the C<@_> arguments, and called.
1376 As specified above, the return value of the I<after> method
1377 modifiers is ignored, and it cannot modify the return values of
1378 the original method. If you need to do either of these things, use an
1379 C<around> method modifier.
1381 =item B<add_around_method_modifier ($method_name, $code)>
1383 This will wrap the method at C<$method_name> so that C<$code>
1384 will be called and passed the original method as an extra argument
1385 at the begining of the C<@_> argument list. This is a variation of
1386 continuation passing style, where the function prepended to C<@_>
1387 can be considered a continuation. It is up to C<$code> if it calls
1388 the original method or not, there is no restriction on what the
1389 C<$code> can or cannot do.
1395 It should be noted that since there is no one consistent way to define
1396 the attributes of a class in Perl 5. These methods can only work with
1397 the information given, and can not easily discover information on
1398 their own. See L<Class::MOP::Attribute> for more details.
1402 =item B<attribute_metaclass>
1404 =item B<get_attribute_map>
1406 =item B<add_attribute ($attribute_meta_object | $attribute_name, %attribute_spec)>
1408 This stores the C<$attribute_meta_object> (or creates one from the
1409 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1410 instance associated with the given class. Unlike methods, attributes
1411 within the MOP are stored as meta-information only. They will be used
1412 later to construct instances from (see C<construct_instance> above).
1413 More details about the attribute meta-objects can be found in the
1414 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1417 It should be noted that any accessor, reader/writer or predicate
1418 methods which the C<$attribute_meta_object> has will be installed
1419 into the class at this time.
1422 If an attribute already exists for C<$attribute_name>, the old one
1423 will be removed (as well as removing all it's accessors), and then
1426 =item B<has_attribute ($attribute_name)>
1428 Checks to see if this class has an attribute by the name of
1429 C<$attribute_name> and returns a boolean.
1431 =item B<get_attribute ($attribute_name)>
1433 Returns the attribute meta-object associated with C<$attribute_name>,
1434 if none is found, it will return undef.
1436 =item B<remove_attribute ($attribute_name)>
1438 This will remove the attribute meta-object stored at
1439 C<$attribute_name>, then return the removed attribute meta-object.
1442 Removing an attribute will only affect future instances of
1443 the class, it will not make any attempt to remove the attribute from
1444 any existing instances of the class.
1446 It should be noted that any accessor, reader/writer or predicate
1447 methods which the attribute meta-object stored at C<$attribute_name>
1448 has will be removed from the class at this time. This B<will> make
1449 these attributes somewhat inaccessable in previously created
1450 instances. But if you are crazy enough to do this at runtime, then
1451 you are crazy enough to deal with something like this :).
1453 =item B<get_attribute_list>
1455 This returns a list of attribute names which are defined in the local
1456 class. If you want a list of all applicable attributes for a class,
1457 use the C<compute_all_applicable_attributes> method.
1459 =item B<compute_all_applicable_attributes>
1461 This will traverse the inheritance heirachy and return a list of all
1462 the applicable attributes for this class. It does not construct a
1463 HASH reference like C<compute_all_applicable_methods> because all
1464 that same information is discoverable through the attribute
1467 =item B<find_attribute_by_name ($attr_name)>
1469 This method will traverse the inheritance heirachy and find the
1470 first attribute whose name matches C<$attr_name>, then return it.
1471 It will return undef if nothing is found.
1475 =head2 Class Immutability
1479 =item B<make_immutable (%options)>
1481 This method will invoke a tranforamtion upon the class which will
1482 make it immutable. Details of this transformation can be found in
1483 the L<Class::MOP::Immutable> documentation.
1485 =item B<make_mutable>
1487 This method will reverse tranforamtion upon the class which
1490 =item B<create_immutable_transformer>
1492 Create a transformer suitable for making this class immutable
1498 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1500 =head1 COPYRIGHT AND LICENSE
1502 Copyright 2006-2008 by Infinity Interactive, Inc.
1504 L<http://www.iinteractive.com>
1506 This library is free software; you can redistribute it and/or modify
1507 it under the same terms as Perl itself.