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);
421 foreach my $attr ( $self->compute_all_applicable_attributes ) {
422 if ( $attr->has_value($instance) ) {
423 if ( defined( my $init_arg = $attr->init_arg ) ) {
424 $params{$init_arg} = $attr->get_value($instance);
426 $attr->set_value($instance);
431 foreach my $attr ($self->compute_all_applicable_attributes) {
432 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
442 @{$self->get_package_symbol('@ISA')} = @supers;
444 # we need to check the metaclass
445 # compatibility here so that we can
446 # be sure that the superclass is
447 # not potentially creating an issues
448 # we don't know about
449 $self->check_metaclass_compatability();
451 @{$self->get_package_symbol('@ISA')};
457 my $super_class = $self->name;
460 my $find_derived_classes;
461 $find_derived_classes = sub {
462 my ($outer_class) = @_;
464 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
467 for my $symbol ( keys %$symbol_table_hashref ) {
468 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
469 my $inner_class = $1;
471 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
475 ? "${outer_class}::$inner_class"
478 if ( $class->isa($super_class) and $class ne $super_class ) {
479 push @derived_classes, $class;
482 next SYMBOL if $class eq 'main'; # skip 'main::*'
484 $find_derived_classes->($class);
488 my $root_class = q{};
489 $find_derived_classes->($root_class);
491 undef $find_derived_classes;
493 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
495 return @derived_classes;
500 if (Class::MOP::IS_RUNNING_ON_5_10()) {
501 return @{ mro::get_linear_isa( (shift)->name ) };
505 return grep { !($seen{$_}++) } (shift)->class_precedence_list;
509 sub class_precedence_list {
512 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
514 # We need to check for circular inheritance here
515 # if we are are not on 5.10, cause 5.8 detects it
516 # late. This will do nothing if all is well, and
517 # blow up otherwise. Yes, it's an ugly hack, better
518 # suggestions are welcome.
520 ($self->name || return)->isa('This is a test for circular inheritance')
526 $self->initialize($_)->class_precedence_list()
527 } $self->superclasses()
534 my ($self, $method_name, $method) = @_;
535 (defined $method_name && $method_name)
536 || confess "You must define a method name";
539 if (blessed($method)) {
540 $body = $method->body;
544 ('CODE' eq (reftype($body) || ''))
545 || confess "Your code block must be a CODE reference";
546 $method = $self->method_metaclass->wrap($body);
548 $self->get_method_map->{$method_name} = $method;
550 my $full_method_name = ($self->name . '::' . $method_name);
551 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
552 $self->update_package_cache_flag;
556 my $fetch_and_prepare_method = sub {
557 my ($self, $method_name) = @_;
559 my $method = $self->get_method($method_name);
560 # if we dont have local ...
562 # try to find the next method
563 $method = $self->find_next_method_by_name($method_name);
564 # die if it does not exist
566 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
567 # and now make sure to wrap it
568 # even if it is already wrapped
569 # because we need a new sub ref
570 $method = Class::MOP::Method::Wrapped->wrap($method);
573 # now make sure we wrap it properly
574 $method = Class::MOP::Method::Wrapped->wrap($method)
575 unless $method->isa('Class::MOP::Method::Wrapped');
577 $self->add_method($method_name => $method);
581 sub add_before_method_modifier {
582 my ($self, $method_name, $method_modifier) = @_;
583 (defined $method_name && $method_name)
584 || confess "You must pass in a method name";
585 my $method = $fetch_and_prepare_method->($self, $method_name);
586 $method->add_before_modifier(subname ':before' => $method_modifier);
589 sub add_after_method_modifier {
590 my ($self, $method_name, $method_modifier) = @_;
591 (defined $method_name && $method_name)
592 || confess "You must pass in a method name";
593 my $method = $fetch_and_prepare_method->($self, $method_name);
594 $method->add_after_modifier(subname ':after' => $method_modifier);
597 sub add_around_method_modifier {
598 my ($self, $method_name, $method_modifier) = @_;
599 (defined $method_name && $method_name)
600 || confess "You must pass in a method name";
601 my $method = $fetch_and_prepare_method->($self, $method_name);
602 $method->add_around_modifier(subname ':around' => $method_modifier);
606 # the methods above used to be named like this:
607 # ${pkg}::${method}:(before|after|around)
608 # but this proved problematic when using one modifier
609 # to wrap multiple methods (something which is likely
610 # to happen pretty regularly IMO). So instead of naming
611 # it like this, I have chosen to just name them purely
612 # with their modifier names, like so:
613 # :(before|after|around)
614 # The fact is that in a stack trace, it will be fairly
615 # evident from the context what method they are attached
616 # to, and so don't need the fully qualified name.
620 my ($self, $method_name, $method) = @_;
621 (defined $method_name && $method_name)
622 || confess "You must define a method name";
624 my $body = (blessed($method) ? $method->body : $method);
625 ('CODE' eq (reftype($body) || ''))
626 || confess "Your code block must be a CODE reference";
628 $self->add_package_symbol("&${method_name}" => $body);
629 $self->update_package_cache_flag;
633 my ($self, $method_name) = @_;
634 (defined $method_name && $method_name)
635 || confess "You must define a method name";
637 return 0 unless exists $self->get_method_map->{$method_name};
642 my ($self, $method_name) = @_;
643 (defined $method_name && $method_name)
644 || confess "You must define a method name";
647 # I don't really need this here, because
648 # if the method_map is missing a key it
649 # will just return undef for me now
650 # return unless $self->has_method($method_name);
652 return $self->get_method_map->{$method_name};
656 my ($self, $method_name) = @_;
657 (defined $method_name && $method_name)
658 || confess "You must define a method name";
660 my $removed_method = delete $self->get_method_map->{$method_name};
662 $self->remove_package_symbol("&${method_name}");
664 $self->update_package_cache_flag;
666 return $removed_method;
669 sub get_method_list {
671 keys %{$self->get_method_map};
674 sub find_method_by_name {
675 my ($self, $method_name) = @_;
676 (defined $method_name && $method_name)
677 || confess "You must define a method name to find";
678 foreach my $class ($self->linearized_isa) {
679 # fetch the meta-class ...
680 my $meta = $self->initialize($class);
681 return $meta->get_method($method_name)
682 if $meta->has_method($method_name);
687 sub compute_all_applicable_methods {
689 my (@methods, %seen_method);
690 foreach my $class ($self->linearized_isa) {
691 # fetch the meta-class ...
692 my $meta = $self->initialize($class);
693 foreach my $method_name ($meta->get_method_list()) {
694 next if exists $seen_method{$method_name};
695 $seen_method{$method_name}++;
697 name => $method_name,
699 code => $meta->get_method($method_name)
706 sub find_all_methods_by_name {
707 my ($self, $method_name) = @_;
708 (defined $method_name && $method_name)
709 || confess "You must define a method name to find";
711 foreach my $class ($self->linearized_isa) {
712 # fetch the meta-class ...
713 my $meta = $self->initialize($class);
715 name => $method_name,
717 code => $meta->get_method($method_name)
718 } if $meta->has_method($method_name);
723 sub find_next_method_by_name {
724 my ($self, $method_name) = @_;
725 (defined $method_name && $method_name)
726 || confess "You must define a method name to find";
727 my @cpl = $self->linearized_isa;
728 shift @cpl; # discard ourselves
729 foreach my $class (@cpl) {
730 # fetch the meta-class ...
731 my $meta = $self->initialize($class);
732 return $meta->get_method($method_name)
733 if $meta->has_method($method_name);
742 # either we have an attribute object already
743 # or we need to create one from the args provided
744 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
745 # make sure it is derived from the correct type though
746 ($attribute->isa('Class::MOP::Attribute'))
747 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
749 # first we attach our new attribute
750 # because it might need certain information
751 # about the class which it is attached to
752 $attribute->attach_to_class($self);
754 # then we remove attributes of a conflicting
755 # name here so that we can properly detach
756 # the old attr object, and remove any
757 # accessors it would have generated
758 $self->remove_attribute($attribute->name)
759 if $self->has_attribute($attribute->name);
761 # then onto installing the new accessors
762 $attribute->install_accessors();
763 $self->get_attribute_map->{$attribute->name} = $attribute;
767 my ($self, $attribute_name) = @_;
768 (defined $attribute_name && $attribute_name)
769 || confess "You must define an attribute name";
770 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
774 my ($self, $attribute_name) = @_;
775 (defined $attribute_name && $attribute_name)
776 || confess "You must define an attribute name";
777 return $self->get_attribute_map->{$attribute_name}
779 # this will return undef anyway, so no need ...
780 # if $self->has_attribute($attribute_name);
784 sub remove_attribute {
785 my ($self, $attribute_name) = @_;
786 (defined $attribute_name && $attribute_name)
787 || confess "You must define an attribute name";
788 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
789 return unless defined $removed_attribute;
790 delete $self->get_attribute_map->{$attribute_name};
791 $removed_attribute->remove_accessors();
792 $removed_attribute->detach_from_class();
793 return $removed_attribute;
796 sub get_attribute_list {
798 keys %{$self->get_attribute_map};
801 sub compute_all_applicable_attributes {
803 my (@attrs, %seen_attr);
804 foreach my $class ($self->linearized_isa) {
805 # fetch the meta-class ...
806 my $meta = $self->initialize($class);
807 foreach my $attr_name ($meta->get_attribute_list()) {
808 next if exists $seen_attr{$attr_name};
809 $seen_attr{$attr_name}++;
810 push @attrs => $meta->get_attribute($attr_name);
816 sub find_attribute_by_name {
817 my ($self, $attr_name) = @_;
818 foreach my $class ($self->linearized_isa) {
819 # fetch the meta-class ...
820 my $meta = $self->initialize($class);
821 return $meta->get_attribute($attr_name)
822 if $meta->has_attribute($attr_name);
830 sub is_immutable { 0 }
833 # Why I changed this (groditi)
834 # - One Metaclass may have many Classes through many Metaclass instances
835 # - One Metaclass should only have one Immutable Transformer instance
836 # - Each Class may have different Immutabilizing options
837 # - Therefore each Metaclass instance may have different Immutabilizing options
838 # - We need to store one Immutable Transformer instance per Metaclass
839 # - We need to store one set of Immutable Transformer options per Class
840 # - Upon make_mutable we may delete the Immutabilizing options
841 # - We could clean the immutable Transformer instance when there is no more
842 # immutable Classes of that type, but we can also keep it in case
843 # another class with this same Metaclass becomes immutable. It is a case
844 # of trading of storing an instance to avoid unnecessary instantiations of
845 # Immutable Transformers. You may view this as a memory leak, however
846 # Because we have few Metaclasses, in practice it seems acceptable
847 # - To allow Immutable Transformers instances to be cleaned up we could weaken
848 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
851 my %IMMUTABLE_TRANSFORMERS;
852 my %IMMUTABLE_OPTIONS;
856 my $class = blessed $self || $self;
858 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
859 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
861 $transformer->make_metaclass_immutable($self, \%options);
862 $IMMUTABLE_OPTIONS{$self->name} =
863 { %options, IMMUTABLE_TRANSFORMER => $transformer };
865 if( exists $options{debug} && $options{debug} ){
866 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
867 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
873 return if $self->is_mutable;
874 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
875 confess "unable to find immutabilizing options" unless ref $options;
876 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
877 $transformer->make_metaclass_mutable($self, $options);
881 sub create_immutable_transformer {
883 my $class = Class::MOP::Immutable->new($self, {
884 read_only => [qw/superclasses/],
892 remove_package_symbol
895 class_precedence_list => 'ARRAY',
896 linearized_isa => 'ARRAY',
897 compute_all_applicable_attributes => 'ARRAY',
898 get_meta_instance => 'SCALAR',
899 get_method_map => 'SCALAR',
913 Class::MOP::Class - Class Meta Object
917 # assuming that class Foo
918 # has been defined, you can
920 # use this for introspection ...
922 # add a method to Foo ...
923 Foo->meta->add_method('bar' => sub { ... })
925 # get a list of all the classes searched
926 # the method dispatcher in the correct order
927 Foo->meta->class_precedence_list()
929 # remove a method from Foo
930 Foo->meta->remove_method('bar');
932 # or use this to actually create classes ...
934 Class::MOP::Class->create('Bar' => (
936 superclasses => [ 'Foo' ],
938 Class::MOP:::Attribute->new('$bar'),
939 Class::MOP:::Attribute->new('$baz'),
942 calculate_bar => sub { ... },
943 construct_baz => sub { ... }
949 This is the largest and currently most complex part of the Perl 5
950 meta-object protocol. It controls the introspection and
951 manipulation of Perl 5 classes (and it can create them too). The
952 best way to understand what this module can do, is to read the
953 documentation for each of it's methods.
957 =head2 Self Introspection
963 This will return a B<Class::MOP::Class> instance which is related
964 to this class. Thereby allowing B<Class::MOP::Class> to actually
967 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
968 bootstrap this module by installing a number of attribute meta-objects
969 into it's metaclass. This will allow this class to reap all the benifits
970 of the MOP when subclassing it.
974 =head2 Class construction
976 These methods will handle creating B<Class::MOP::Class> objects,
977 which can be used to both create new classes, and analyze
978 pre-existing classes.
980 This module will internally store references to all the instances
981 you create with these methods, so that they do not need to be
982 created any more than nessecary. Basically, they are singletons.
986 =item B<create ($package_name,
987 version =E<gt> ?$version,
988 authority =E<gt> ?$authority,
989 superclasses =E<gt> ?@superclasses,
990 methods =E<gt> ?%methods,
991 attributes =E<gt> ?%attributes)>
993 This returns a B<Class::MOP::Class> object, bringing the specified
994 C<$package_name> into existence and adding any of the C<$version>,
995 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
998 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
999 methods =E<gt> ?%methods,
1000 attributes =E<gt> ?%attributes)>
1002 This will create an anonymous class, it works much like C<create> but
1003 it does not need a C<$package_name>. Instead it will create a suitably
1004 unique package name for you to stash things into.
1006 On very important distinction is that anon classes are destroyed once
1007 the metaclass they are attached to goes out of scope. In the DESTROY
1008 method, the created package will be removed from the symbol table.
1010 It is also worth noting that any instances created with an anon-class
1011 will keep a special reference to the anon-meta which will prevent the
1012 anon-class from going out of scope until all instances of it have also
1013 been destroyed. This however only works for HASH based instance types,
1014 as we use a special reserved slot (C<__MOP__>) to store this.
1016 =item B<initialize ($package_name, %options)>
1018 This initializes and returns returns a B<Class::MOP::Class> object
1019 for a given a C<$package_name>.
1021 =item B<reinitialize ($package_name, %options)>
1023 This removes the old metaclass, and creates a new one in it's place.
1024 Do B<not> use this unless you really know what you are doing, it could
1025 very easily make a very large mess of your program.
1027 =item B<construct_class_instance (%options)>
1029 This will construct an instance of B<Class::MOP::Class>, it is
1030 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1031 to use C<construct_instance> once all the bootstrapping is done. This
1032 method is used internally by C<initialize> and should never be called
1033 from outside of that method really.
1035 =item B<check_metaclass_compatability>
1037 This method is called as the very last thing in the
1038 C<construct_class_instance> method. This will check that the
1039 metaclass you are creating is compatible with the metaclasses of all
1040 your ancestors. For more inforamtion about metaclass compatibility
1041 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1043 =item B<update_package_cache_flag>
1045 This will reset the package cache flag for this particular metaclass
1046 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1047 function. This is very rarely needed from outside of C<Class::MOP::Class>
1048 but in some cases you might want to use it, so it is here.
1050 =item B<reset_package_cache_flag>
1052 Clear this flag, used in Moose.
1056 =head2 Object instance construction and cloning
1058 These methods are B<entirely optional>, it is up to you whether you want
1063 =item B<instance_metaclass>
1065 =item B<get_meta_instance>
1067 =item B<new_object (%params)>
1069 This is a convience method for creating a new object of the class, and
1070 blessing it into the appropriate package as well. Ideally your class
1071 would call a C<new> this method like so:
1074 my ($class, %param) = @_;
1075 $class->meta->new_object(%params);
1078 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1079 but that is considered bad style, so we do not do that.
1081 =item B<construct_instance (%params)>
1083 This method is used to construct an instace structure suitable for
1084 C<bless>-ing into your package of choice. It works in conjunction
1085 with the Attribute protocol to collect all applicable attributes.
1087 This will construct and instance using a HASH ref as storage
1088 (currently only HASH references are supported). This will collect all
1089 the applicable attributes and layout out the fields in the HASH ref,
1090 it will then initialize them using either use the corresponding key
1091 in C<%params> or any default value or initializer found in the
1092 attribute meta-object.
1094 =item B<clone_object ($instance, %params)>
1096 This is a convience method for cloning an object instance, then
1097 blessing it into the appropriate package. This method will call
1098 C<clone_instance>, which performs a shallow copy of the object,
1099 see that methods documentation for more details. Ideally your
1100 class would call a C<clone> this method like so:
1102 sub MyClass::clone {
1103 my ($self, %param) = @_;
1104 $self->meta->clone_object($self, %params);
1107 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1108 but that is considered bad style, so we do not do that.
1110 =item B<clone_instance($instance, %params)>
1112 This method is a compliment of C<construct_instance> (which means if
1113 you override C<construct_instance>, you need to override this one too),
1114 and clones the instance shallowly.
1116 The cloned structure returned is (like with C<construct_instance>) an
1117 unC<bless>ed HASH reference, it is your responsibility to then bless
1118 this cloned structure into the right class (which C<clone_object> will
1121 As of 0.11, this method will clone the C<$instance> structure shallowly,
1122 as opposed to the deep cloning implemented in prior versions. After much
1123 thought, research and discussion, I have decided that anything but basic
1124 shallow cloning is outside the scope of the meta-object protocol. I
1125 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1126 is too I<context-specific> to be part of the MOP.
1128 =item B<rebless_instance($instance)>
1130 This will change the class of C<$instance> to the class of the invoking
1131 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1132 itself. This limitation may be relaxed in the future.
1134 This can be useful in a number of situations, such as when you are writing
1135 a program that doesn't know everything at object construction time.
1139 =head2 Informational
1141 These are a few predicate methods for asking information about the class.
1145 =item B<is_anon_class>
1147 This returns true if the class is a C<Class::MOP::Class> created anon class.
1151 This returns true if the class is still mutable.
1153 =item B<is_immutable>
1155 This returns true if the class has been made immutable.
1159 =head2 Inheritance Relationships
1163 =item B<superclasses (?@superclasses)>
1165 This is a read-write attribute which represents the superclass
1166 relationships of the class the B<Class::MOP::Class> instance is
1167 associated with. Basically, it can get and set the C<@ISA> for you.
1170 Perl will occasionally perform some C<@ISA> and method caching, if
1171 you decide to change your superclass relationship at runtime (which
1172 is quite insane and very much not recommened), then you should be
1173 aware of this and the fact that this module does not make any
1174 attempt to address this issue.
1176 =item B<class_precedence_list>
1178 This computes the a list of all the class's ancestors in the same order
1179 in which method dispatch will be done. This is similair to
1180 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
1182 =item B<linearized_isa>
1184 This returns a list based on C<class_precedence_list> but with all
1189 This returns a list of subclasses for this class.
1197 =item B<get_method_map>
1199 =item B<method_metaclass>
1201 =item B<add_method ($method_name, $method)>
1203 This will take a C<$method_name> and CODE reference to that
1204 C<$method> and install it into the class's package.
1207 This does absolutely nothing special to C<$method>
1208 other than use B<Sub::Name> to make sure it is tagged with the
1209 correct name, and therefore show up correctly in stack traces and
1212 =item B<alias_method ($method_name, $method)>
1214 This will take a C<$method_name> and CODE reference to that
1215 C<$method> and alias the method into the class's package.
1218 Unlike C<add_method>, this will B<not> try to name the
1219 C<$method> using B<Sub::Name>, it only aliases the method in
1220 the class's package.
1222 =item B<has_method ($method_name)>
1224 This just provides a simple way to check if the class implements
1225 a specific C<$method_name>. It will I<not> however, attempt to check
1226 if the class inherits the method (use C<UNIVERSAL::can> for that).
1228 This will correctly handle functions defined outside of the package
1229 that use a fully qualified name (C<sub Package::name { ... }>).
1231 This will correctly handle functions renamed with B<Sub::Name> and
1232 installed using the symbol tables. However, if you are naming the
1233 subroutine outside of the package scope, you must use the fully
1234 qualified name, including the package name, for C<has_method> to
1235 correctly identify it.
1237 This will attempt to correctly ignore functions imported from other
1238 packages using B<Exporter>. It breaks down if the function imported
1239 is an C<__ANON__> sub (such as with C<use constant>), which very well
1240 may be a valid method being applied to the class.
1242 In short, this method cannot always be trusted to determine if the
1243 C<$method_name> is actually a method. However, it will DWIM about
1244 90% of the time, so it's a small trade off I think.
1246 =item B<get_method ($method_name)>
1248 This will return a Class::MOP::Method instance related to the specified
1249 C<$method_name>, or return undef if that method does not exist.
1251 The Class::MOP::Method is codifiable, so you can use it like a normal
1252 CODE reference, see L<Class::MOP::Method> for more information.
1254 =item B<find_method_by_name ($method_name>
1256 This will return a CODE reference of the specified C<$method_name>,
1257 or return undef if that method does not exist.
1259 Unlike C<get_method> this will also look in the superclasses.
1261 =item B<remove_method ($method_name)>
1263 This will attempt to remove a given C<$method_name> from the class.
1264 It will return the CODE reference that it has removed, and will
1265 attempt to use B<Sub::Name> to clear the methods associated name.
1267 =item B<get_method_list>
1269 This will return a list of method names for all I<locally> defined
1270 methods. It does B<not> provide a list of all applicable methods,
1271 including any inherited ones. If you want a list of all applicable
1272 methods, use the C<compute_all_applicable_methods> method.
1274 =item B<compute_all_applicable_methods>
1276 This will return a list of all the methods names this class will
1277 respond to, taking into account inheritance. The list will be a list of
1278 HASH references, each one containing the following information; method
1279 name, the name of the class in which the method lives and a CODE
1280 reference for the actual method.
1282 =item B<find_all_methods_by_name ($method_name)>
1284 This will traverse the inheritence hierarchy and locate all methods
1285 with a given C<$method_name>. Similar to
1286 C<compute_all_applicable_methods> it returns a list of HASH references
1287 with the following information; method name (which will always be the
1288 same as C<$method_name>), the name of the class in which the method
1289 lives and a CODE reference for the actual method.
1291 The list of methods produced is a distinct list, meaning there are no
1292 duplicates in it. This is especially useful for things like object
1293 initialization and destruction where you only want the method called
1294 once, and in the correct order.
1296 =item B<find_next_method_by_name ($method_name)>
1298 This will return the first method to match a given C<$method_name> in
1299 the superclasses, this is basically equivalent to calling
1300 C<SUPER::$method_name>, but it can be dispatched at runtime.
1304 =head2 Method Modifiers
1306 Method modifiers are a concept borrowed from CLOS, in which a method
1307 can be wrapped with I<before>, I<after> and I<around> method modifiers
1308 that will be called everytime the method is called.
1310 =head3 How method modifiers work?
1312 Method modifiers work by wrapping the original method and then replacing
1313 it in the classes symbol table. The wrappers will handle calling all the
1314 modifiers in the appropariate orders and preserving the calling context
1315 for the original method.
1317 Each method modifier serves a particular purpose, which may not be
1318 obvious to users of other method wrapping modules. To start with, the
1319 return values of I<before> and I<after> modifiers are ignored. This is
1320 because thier purpose is B<not> to filter the input and output of the
1321 primary method (this is done with an I<around> modifier). This may seem
1322 like an odd restriction to some, but doing this allows for simple code
1323 to be added at the begining or end of a method call without jeapordizing
1324 the normal functioning of the primary method or placing any extra
1325 responsibility on the code of the modifier. Of course if you have more
1326 complex needs, then use the I<around> modifier, which uses a variation
1327 of continutation passing style to allow for a high degree of flexibility.
1329 Before and around modifiers are called in last-defined-first-called order,
1330 while after modifiers are called in first-defined-first-called order. So
1331 the call tree might looks something like this:
1341 To see examples of using method modifiers, see the following examples
1342 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1343 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1344 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1346 =head3 What is the performance impact?
1348 Of course there is a performance cost associated with method modifiers,
1349 but we have made every effort to make that cost be directly proportional
1350 to the amount of modifier features you utilize.
1352 The wrapping method does it's best to B<only> do as much work as it
1353 absolutely needs to. In order to do this we have moved some of the
1354 performance costs to set-up time, where they are easier to amortize.
1356 All this said, my benchmarks have indicated the following:
1358 simple wrapper with no modifiers 100% slower
1359 simple wrapper with simple before modifier 400% slower
1360 simple wrapper with simple after modifier 450% slower
1361 simple wrapper with simple around modifier 500-550% slower
1362 simple wrapper with all 3 modifiers 1100% slower
1364 These numbers may seem daunting, but you must remember, every feature
1365 comes with some cost. To put things in perspective, just doing a simple
1366 C<AUTOLOAD> which does nothing but extract the name of the method called
1367 and return it costs about 400% over a normal method call.
1371 =item B<add_before_method_modifier ($method_name, $code)>
1373 This will wrap the method at C<$method_name> and the supplied C<$code>
1374 will be passed the C<@_> arguments, and called before the original
1375 method is called. As specified above, the return value of the I<before>
1376 method modifiers is ignored, and it's ability to modify C<@_> is
1377 fairly limited. If you need to do either of these things, use an
1378 C<around> method modifier.
1380 =item B<add_after_method_modifier ($method_name, $code)>
1382 This will wrap the method at C<$method_name> so that the original
1383 method will be called, it's return values stashed, and then the
1384 supplied C<$code> will be passed the C<@_> arguments, and called.
1385 As specified above, the return value of the I<after> method
1386 modifiers is ignored, and it cannot modify the return values of
1387 the original method. If you need to do either of these things, use an
1388 C<around> method modifier.
1390 =item B<add_around_method_modifier ($method_name, $code)>
1392 This will wrap the method at C<$method_name> so that C<$code>
1393 will be called and passed the original method as an extra argument
1394 at the begining of the C<@_> argument list. This is a variation of
1395 continuation passing style, where the function prepended to C<@_>
1396 can be considered a continuation. It is up to C<$code> if it calls
1397 the original method or not, there is no restriction on what the
1398 C<$code> can or cannot do.
1404 It should be noted that since there is no one consistent way to define
1405 the attributes of a class in Perl 5. These methods can only work with
1406 the information given, and can not easily discover information on
1407 their own. See L<Class::MOP::Attribute> for more details.
1411 =item B<attribute_metaclass>
1413 =item B<get_attribute_map>
1415 =item B<add_attribute ($attribute_meta_object | $attribute_name, %attribute_spec)>
1417 This stores the C<$attribute_meta_object> (or creates one from the
1418 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1419 instance associated with the given class. Unlike methods, attributes
1420 within the MOP are stored as meta-information only. They will be used
1421 later to construct instances from (see C<construct_instance> above).
1422 More details about the attribute meta-objects can be found in the
1423 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1426 It should be noted that any accessor, reader/writer or predicate
1427 methods which the C<$attribute_meta_object> has will be installed
1428 into the class at this time.
1431 If an attribute already exists for C<$attribute_name>, the old one
1432 will be removed (as well as removing all it's accessors), and then
1435 =item B<has_attribute ($attribute_name)>
1437 Checks to see if this class has an attribute by the name of
1438 C<$attribute_name> and returns a boolean.
1440 =item B<get_attribute ($attribute_name)>
1442 Returns the attribute meta-object associated with C<$attribute_name>,
1443 if none is found, it will return undef.
1445 =item B<remove_attribute ($attribute_name)>
1447 This will remove the attribute meta-object stored at
1448 C<$attribute_name>, then return the removed attribute meta-object.
1451 Removing an attribute will only affect future instances of
1452 the class, it will not make any attempt to remove the attribute from
1453 any existing instances of the class.
1455 It should be noted that any accessor, reader/writer or predicate
1456 methods which the attribute meta-object stored at C<$attribute_name>
1457 has will be removed from the class at this time. This B<will> make
1458 these attributes somewhat inaccessable in previously created
1459 instances. But if you are crazy enough to do this at runtime, then
1460 you are crazy enough to deal with something like this :).
1462 =item B<get_attribute_list>
1464 This returns a list of attribute names which are defined in the local
1465 class. If you want a list of all applicable attributes for a class,
1466 use the C<compute_all_applicable_attributes> method.
1468 =item B<compute_all_applicable_attributes>
1470 This will traverse the inheritance heirachy and return a list of all
1471 the applicable attributes for this class. It does not construct a
1472 HASH reference like C<compute_all_applicable_methods> because all
1473 that same information is discoverable through the attribute
1476 =item B<find_attribute_by_name ($attr_name)>
1478 This method will traverse the inheritance heirachy and find the
1479 first attribute whose name matches C<$attr_name>, then return it.
1480 It will return undef if nothing is found.
1484 =head2 Class Immutability
1488 =item B<make_immutable (%options)>
1490 This method will invoke a tranforamtion upon the class which will
1491 make it immutable. Details of this transformation can be found in
1492 the L<Class::MOP::Immutable> documentation.
1494 =item B<make_mutable>
1496 This method will reverse tranforamtion upon the class which
1499 =item B<create_immutable_transformer>
1501 Create a transformer suitable for making this class immutable
1507 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1509 =head1 COPYRIGHT AND LICENSE
1511 Copyright 2006-2008 by Infinity Interactive, Inc.
1513 L<http://www.iinteractive.com>
1515 This library is free software; you can redistribute it and/or modify
1516 it under the same terms as Perl itself.