2 package Class::MOP::Class;
7 use Class::MOP::Immutable;
8 use Class::MOP::Instance;
9 use Class::MOP::Method::Wrapped;
12 use Scalar::Util 'blessed', 'reftype', 'weaken';
13 use Sub::Name 'subname';
15 our $VERSION = '0.26';
16 our $AUTHORITY = 'cpan:STEVAN';
18 use base 'Class::MOP::Module';
22 sub meta { Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) }
28 my $package_name = shift;
29 (defined $package_name && $package_name && !blessed($package_name))
30 || confess "You must pass a package name and it cannot be blessed";
31 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
34 $class->construct_class_instance('package' => $package_name, @_);
39 my $package_name = shift;
40 (defined $package_name && $package_name && !blessed($package_name))
41 || confess "You must pass a package name and it cannot be blessed";
42 Class::MOP::remove_metaclass_by_name($package_name);
43 $class->construct_class_instance('package' => $package_name, @_);
46 # NOTE: (meta-circularity)
47 # this is a special form of &construct_instance
48 # (see below), which is used to construct class
49 # meta-object instances for any Class::MOP::*
50 # class. All other classes will use the more
51 # normal &construct_instance.
52 sub construct_class_instance {
55 my $package_name = $options{'package'};
56 (defined $package_name && $package_name)
57 || confess "You must pass a package name";
59 # return the metaclass if we have it cached,
60 # and it is still defined (it has not been
61 # reaped by DESTROY yet, which can happen
62 # annoyingly enough during global destruction)
64 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
69 # we need to deal with the possibility
70 # of class immutability here, and then
71 # get the name of the class appropriately
72 $class = (blessed($class)
73 ? ($class->is_immutable
74 ? $class->get_mutable_metaclass_name()
78 # now create the metaclass
80 if ($class eq 'Class::MOP::Class') {
83 # inherited from Class::MOP::Package
84 '$!package' => $package_name,
87 # since the following attributes will
88 # actually be loaded from the symbol
89 # table, and actually bypass the instance
90 # entirely, we can just leave these things
91 # listed here for reference, because they
92 # should not actually have a value associated
94 '%!namespace' => \undef,
95 # inherited from Class::MOP::Module
96 '$!version' => \undef,
97 '$!authority' => \undef,
98 # defined in Class::MOP::Class
99 '@!superclasses' => \undef,
102 '%!attributes' => {},
103 '$!attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
104 '$!method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
105 '$!instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
107 ## uber-private variables
109 # this starts out as undef so that
110 # we can tell the first time the
111 # methods are fetched
113 '$!_package_cache_flag' => undef,
118 # it is safe to use meta here because
119 # class will always be a subclass of
120 # Class::MOP::Class, which defines meta
121 $meta = $class->meta->construct_instance(%options)
124 # and check the metaclass compatibility
125 $meta->check_metaclass_compatability();
127 Class::MOP::store_metaclass_by_name($package_name, $meta);
130 # we need to weaken any anon classes
131 # so that they can call DESTROY properly
132 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
137 sub reset_package_cache_flag { (shift)->{'$!_package_cache_flag'} = undef }
138 sub update_package_cache_flag {
141 # we can manually update the cache number
142 # since we are actually adding the method
143 # to our cache as well. This avoids us
144 # having to regenerate the method_map.
146 $self->{'$!_package_cache_flag'} = Class::MOP::check_package_cache_flag($self->name);
149 sub check_metaclass_compatability {
152 # this is always okay ...
153 return if blessed($self) eq 'Class::MOP::Class' &&
154 $self->instance_metaclass eq 'Class::MOP::Instance';
156 my @class_list = $self->linearized_isa;
157 shift @class_list; # shift off $self->name
159 foreach my $class_name (@class_list) {
160 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
163 # we need to deal with the possibility
164 # of class immutability here, and then
165 # get the name of the class appropriately
166 my $meta_type = ($meta->is_immutable
167 ? $meta->get_mutable_metaclass_name()
170 ($self->isa($meta_type))
171 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
172 " is not compatible with the " .
173 $class_name . "->meta => (" . ($meta_type) . ")";
175 # we also need to check that instance metaclasses
176 # are compatabile in the same the class.
177 ($self->instance_metaclass->isa($meta->instance_metaclass))
178 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
179 " is not compatible with the " .
180 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
188 # this should be sufficient, if you have a
189 # use case where it is not, write a test and
191 my $ANON_CLASS_SERIAL = 0;
194 # we need a sufficiently annoying prefix
195 # this should suffice for now, this is
196 # used in a couple of places below, so
197 # need to put it up here for now.
198 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
202 no warnings 'uninitialized';
203 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
206 sub create_anon_class {
207 my ($class, %options) = @_;
208 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
209 return $class->create($package_name, %options);
213 # this will only get called for
214 # anon-classes, all other calls
215 # are assumed to occur during
216 # global destruction and so don't
217 # really need to be handled explicitly
220 no warnings 'uninitialized';
221 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
222 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
224 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
225 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
227 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
232 # creating classes with MOP ...
236 my $package_name = shift;
238 (defined $package_name && $package_name)
239 || confess "You must pass a package name";
242 || confess "You much pass all parameters as name => value pairs " .
243 "(I found an uneven number of params in \@_)";
247 my $code = "package $package_name;";
248 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
249 if exists $options{version};
250 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
251 if exists $options{authority};
254 confess "creation of $package_name failed : $@" if $@;
256 my $meta = $class->initialize($package_name);
258 $meta->add_method('meta' => sub {
259 $class->initialize(blessed($_[0]) || $_[0]);
262 $meta->superclasses(@{$options{superclasses}})
263 if exists $options{superclasses};
265 # process attributes first, so that they can
266 # install accessors, but locally defined methods
267 # can then overwrite them. It is maybe a little odd, but
268 # I think this should be the order of things.
269 if (exists $options{attributes}) {
270 foreach my $attr (@{$options{attributes}}) {
271 $meta->add_attribute($attr);
274 if (exists $options{methods}) {
275 foreach my $method_name (keys %{$options{methods}}) {
276 $meta->add_method($method_name, $options{methods}->{$method_name});
285 # all these attribute readers will be bootstrapped
286 # away in the Class::MOP bootstrap section
288 sub get_attribute_map { $_[0]->{'%!attributes'} }
289 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
290 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
291 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
294 # this is a prime canidate for conversion to XS
298 if (defined $self->{'$!_package_cache_flag'} &&
299 $self->{'$!_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
300 return $self->{'%!methods'};
303 my $map = $self->{'%!methods'};
305 my $class_name = $self->name;
306 my $method_metaclass = $self->method_metaclass;
308 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
309 my $code = $self->get_package_symbol('&' . $symbol);
311 next if exists $map->{$symbol} &&
312 defined $map->{$symbol} &&
313 $map->{$symbol}->body == $code;
315 my ($pkg, $name) = Class::MOP::get_code_info($code);
316 next if ($pkg || '') ne $class_name &&
317 ($name || '') ne '__ANON__';
319 $map->{$symbol} = $method_metaclass->wrap($code);
325 # Instance Construction & Cloning
330 # we need to protect the integrity of the
331 # Class::MOP::Class singletons here, so we
332 # delegate this to &construct_class_instance
333 # which will deal with the singletons
334 return $class->construct_class_instance(@_)
335 if $class->name->isa('Class::MOP::Class');
336 return $class->construct_instance(@_);
339 sub construct_instance {
340 my ($class, %params) = @_;
341 my $meta_instance = $class->get_meta_instance();
342 my $instance = $meta_instance->create_instance();
343 foreach my $attr ($class->compute_all_applicable_attributes()) {
344 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
347 # this will only work for a HASH instance type
348 if ($class->is_anon_class) {
349 (reftype($instance) eq 'HASH')
350 || confess "Currently only HASH based instances are supported with instance of anon-classes";
352 # At some point we should make this official
353 # as a reserved slot name, but right now I am
354 # going to keep it here.
355 # my $RESERVED_MOP_SLOT = '__MOP__';
356 $instance->{'__MOP__'} = $class;
361 sub get_meta_instance {
363 return $class->instance_metaclass->new(
365 $class->compute_all_applicable_attributes()
371 my $instance = shift;
372 (blessed($instance) && $instance->isa($class->name))
373 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
375 # we need to protect the integrity of the
376 # Class::MOP::Class singletons here, they
377 # should not be cloned.
378 return $instance if $instance->isa('Class::MOP::Class');
379 $class->clone_instance($instance, @_);
383 my ($class, $instance, %params) = @_;
385 || confess "You can only clone instances, \$self is not a blessed instance";
386 my $meta_instance = $class->get_meta_instance();
387 my $clone = $meta_instance->clone_instance($instance);
388 foreach my $attr ($class->compute_all_applicable_attributes()) {
389 if (exists $params{$attr->init_arg}) {
390 $meta_instance->set_slot_value($clone, $attr->name, $params{$attr->init_arg});
396 sub rebless_instance {
397 my ($self, $instance, $new_metaclass) = @_;
399 # it's okay (expected, even) to pass in a package name
400 unless (blessed $new_metaclass) {
401 $new_metaclass = $self->initialize($new_metaclass);
403 my $meta_instance = $self->get_meta_instance();
405 # make sure we're reblessing into a subclass
407 for my $superclass ($new_metaclass->linearized_isa) {
408 if ($superclass eq $self->name) {
415 || confess "You may rebless only into a subclass. (". $new_metaclass->name .") is not a subclass of (". $self->name .").";
418 $meta_instance->rebless_instance_structure($instance, $new_metaclass);
420 # check and upgrade all attributes
421 my %params = map { $_->name => $meta_instance->get_slot_value($instance, $_->name) }
422 grep { $meta_instance->is_slot_initialized($instance, $_->name) }
423 $new_metaclass->compute_all_applicable_attributes;
425 foreach my $attr ($new_metaclass->compute_all_applicable_attributes) {
426 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
436 @{$self->get_package_symbol('@ISA')} = @supers;
438 # we need to check the metaclass
439 # compatibility here so that we can
440 # be sure that the superclass is
441 # not potentially creating an issues
442 # we don't know about
443 $self->check_metaclass_compatability();
445 @{$self->get_package_symbol('@ISA')};
451 my $super_class = $self->name;
454 my $find_derived_classes;
455 $find_derived_classes = sub {
456 my ($outer_class) = @_;
458 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
461 for my $symbol ( keys %$symbol_table_hashref ) {
462 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
463 my $inner_class = $1;
465 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
469 ? "${outer_class}::$inner_class"
472 if ( $class->isa($super_class) and $class ne $super_class ) {
473 push @derived_classes, $class;
476 next SYMBOL if $class eq 'main'; # skip 'main::*'
478 $find_derived_classes->($class);
482 my $root_class = q{};
483 $find_derived_classes->($root_class);
485 undef $find_derived_classes;
487 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
489 return @derived_classes;
494 if (Class::MOP::IS_RUNNING_ON_5_10()) {
495 return @{ mro::get_linear_isa( (shift)->name ) };
499 return grep { !($seen{$_}++) } (shift)->class_precedence_list;
503 sub class_precedence_list {
506 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
508 # We need to check for circular inheritance here
509 # if we are are not on 5.10, cause 5.8 detects it
510 # late. This will do nothing if all is well, and
511 # blow up otherwise. Yes, it's an ugly hack, better
512 # suggestions are welcome.
514 ($self->name || return)->isa('This is a test for circular inheritance')
520 $self->initialize($_)->class_precedence_list()
521 } $self->superclasses()
528 my ($self, $method_name, $method) = @_;
529 (defined $method_name && $method_name)
530 || confess "You must define a method name";
533 if (blessed($method)) {
534 $body = $method->body;
538 ('CODE' eq (reftype($body) || ''))
539 || confess "Your code block must be a CODE reference";
540 $method = $self->method_metaclass->wrap($body);
542 $self->get_method_map->{$method_name} = $method;
544 my $full_method_name = ($self->name . '::' . $method_name);
545 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
546 $self->update_package_cache_flag;
550 my $fetch_and_prepare_method = sub {
551 my ($self, $method_name) = @_;
553 my $method = $self->get_method($method_name);
554 # if we dont have local ...
556 # try to find the next method
557 $method = $self->find_next_method_by_name($method_name);
558 # die if it does not exist
560 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
561 # and now make sure to wrap it
562 # even if it is already wrapped
563 # because we need a new sub ref
564 $method = Class::MOP::Method::Wrapped->wrap($method);
567 # now make sure we wrap it properly
568 $method = Class::MOP::Method::Wrapped->wrap($method)
569 unless $method->isa('Class::MOP::Method::Wrapped');
571 $self->add_method($method_name => $method);
575 sub add_before_method_modifier {
576 my ($self, $method_name, $method_modifier) = @_;
577 (defined $method_name && $method_name)
578 || confess "You must pass in a method name";
579 my $method = $fetch_and_prepare_method->($self, $method_name);
580 $method->add_before_modifier(subname ':before' => $method_modifier);
583 sub add_after_method_modifier {
584 my ($self, $method_name, $method_modifier) = @_;
585 (defined $method_name && $method_name)
586 || confess "You must pass in a method name";
587 my $method = $fetch_and_prepare_method->($self, $method_name);
588 $method->add_after_modifier(subname ':after' => $method_modifier);
591 sub add_around_method_modifier {
592 my ($self, $method_name, $method_modifier) = @_;
593 (defined $method_name && $method_name)
594 || confess "You must pass in a method name";
595 my $method = $fetch_and_prepare_method->($self, $method_name);
596 $method->add_around_modifier(subname ':around' => $method_modifier);
600 # the methods above used to be named like this:
601 # ${pkg}::${method}:(before|after|around)
602 # but this proved problematic when using one modifier
603 # to wrap multiple methods (something which is likely
604 # to happen pretty regularly IMO). So instead of naming
605 # it like this, I have chosen to just name them purely
606 # with their modifier names, like so:
607 # :(before|after|around)
608 # The fact is that in a stack trace, it will be fairly
609 # evident from the context what method they are attached
610 # to, and so don't need the fully qualified name.
614 my ($self, $method_name, $method) = @_;
615 (defined $method_name && $method_name)
616 || confess "You must define a method name";
618 my $body = (blessed($method) ? $method->body : $method);
619 ('CODE' eq (reftype($body) || ''))
620 || confess "Your code block must be a CODE reference";
622 $self->add_package_symbol("&${method_name}" => $body);
623 $self->update_package_cache_flag;
627 my ($self, $method_name) = @_;
628 (defined $method_name && $method_name)
629 || confess "You must define a method name";
631 return 0 unless exists $self->get_method_map->{$method_name};
636 my ($self, $method_name) = @_;
637 (defined $method_name && $method_name)
638 || confess "You must define a method name";
641 # I don't really need this here, because
642 # if the method_map is missing a key it
643 # will just return undef for me now
644 # return unless $self->has_method($method_name);
646 return $self->get_method_map->{$method_name};
650 my ($self, $method_name) = @_;
651 (defined $method_name && $method_name)
652 || confess "You must define a method name";
654 my $removed_method = delete $self->get_method_map->{$method_name};
656 $self->remove_package_symbol("&${method_name}");
658 $self->update_package_cache_flag;
660 return $removed_method;
663 sub get_method_list {
665 keys %{$self->get_method_map};
668 sub find_method_by_name {
669 my ($self, $method_name) = @_;
670 (defined $method_name && $method_name)
671 || confess "You must define a method name to find";
672 foreach my $class ($self->linearized_isa) {
673 # fetch the meta-class ...
674 my $meta = $self->initialize($class);
675 return $meta->get_method($method_name)
676 if $meta->has_method($method_name);
681 sub compute_all_applicable_methods {
683 my (@methods, %seen_method);
684 foreach my $class ($self->linearized_isa) {
685 # fetch the meta-class ...
686 my $meta = $self->initialize($class);
687 foreach my $method_name ($meta->get_method_list()) {
688 next if exists $seen_method{$method_name};
689 $seen_method{$method_name}++;
691 name => $method_name,
693 code => $meta->get_method($method_name)
700 sub find_all_methods_by_name {
701 my ($self, $method_name) = @_;
702 (defined $method_name && $method_name)
703 || confess "You must define a method name to find";
705 foreach my $class ($self->linearized_isa) {
706 # fetch the meta-class ...
707 my $meta = $self->initialize($class);
709 name => $method_name,
711 code => $meta->get_method($method_name)
712 } if $meta->has_method($method_name);
717 sub find_next_method_by_name {
718 my ($self, $method_name) = @_;
719 (defined $method_name && $method_name)
720 || confess "You must define a method name to find";
721 my @cpl = $self->linearized_isa;
722 shift @cpl; # discard ourselves
723 foreach my $class (@cpl) {
724 # fetch the meta-class ...
725 my $meta = $self->initialize($class);
726 return $meta->get_method($method_name)
727 if $meta->has_method($method_name);
736 # either we have an attribute object already
737 # or we need to create one from the args provided
738 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
739 # make sure it is derived from the correct type though
740 ($attribute->isa('Class::MOP::Attribute'))
741 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
743 # first we attach our new attribute
744 # because it might need certain information
745 # about the class which it is attached to
746 $attribute->attach_to_class($self);
748 # then we remove attributes of a conflicting
749 # name here so that we can properly detach
750 # the old attr object, and remove any
751 # accessors it would have generated
752 $self->remove_attribute($attribute->name)
753 if $self->has_attribute($attribute->name);
755 # then onto installing the new accessors
756 $attribute->install_accessors();
757 $self->get_attribute_map->{$attribute->name} = $attribute;
761 my ($self, $attribute_name) = @_;
762 (defined $attribute_name && $attribute_name)
763 || confess "You must define an attribute name";
764 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
768 my ($self, $attribute_name) = @_;
769 (defined $attribute_name && $attribute_name)
770 || confess "You must define an attribute name";
771 return $self->get_attribute_map->{$attribute_name}
773 # this will return undef anyway, so no need ...
774 # if $self->has_attribute($attribute_name);
778 sub remove_attribute {
779 my ($self, $attribute_name) = @_;
780 (defined $attribute_name && $attribute_name)
781 || confess "You must define an attribute name";
782 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
783 return unless defined $removed_attribute;
784 delete $self->get_attribute_map->{$attribute_name};
785 $removed_attribute->remove_accessors();
786 $removed_attribute->detach_from_class();
787 return $removed_attribute;
790 sub get_attribute_list {
792 keys %{$self->get_attribute_map};
795 sub compute_all_applicable_attributes {
797 my (@attrs, %seen_attr);
798 foreach my $class ($self->linearized_isa) {
799 # fetch the meta-class ...
800 my $meta = $self->initialize($class);
801 foreach my $attr_name ($meta->get_attribute_list()) {
802 next if exists $seen_attr{$attr_name};
803 $seen_attr{$attr_name}++;
804 push @attrs => $meta->get_attribute($attr_name);
810 sub find_attribute_by_name {
811 my ($self, $attr_name) = @_;
812 foreach my $class ($self->linearized_isa) {
813 # fetch the meta-class ...
814 my $meta = $self->initialize($class);
815 return $meta->get_attribute($attr_name)
816 if $meta->has_attribute($attr_name);
824 sub is_immutable { 0 }
827 # Why I changed this (groditi)
828 # - One Metaclass may have many Classes through many Metaclass instances
829 # - One Metaclass should only have one Immutable Transformer instance
830 # - Each Class may have different Immutabilizing options
831 # - Therefore each Metaclass instance may have different Immutabilizing options
832 # - We need to store one Immutable Transformer instance per Metaclass
833 # - We need to store one set of Immutable Transformer options per Class
834 # - Upon make_mutable we may delete the Immutabilizing options
835 # - We could clean the immutable Transformer instance when there is no more
836 # immutable Classes of that type, but we can also keep it in case
837 # another class with this same Metaclass becomes immutable. It is a case
838 # of trading of storing an instance to avoid unnecessary instantiations of
839 # Immutable Transformers. You may view this as a memory leak, however
840 # Because we have few Metaclasses, in practice it seems acceptable
841 # - To allow Immutable Transformers instances to be cleaned up we could weaken
842 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
845 my %IMMUTABLE_TRANSFORMERS;
846 my %IMMUTABLE_OPTIONS;
850 my $class = blessed $self || $self;
852 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
853 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
855 $transformer->make_metaclass_immutable($self, \%options);
856 $IMMUTABLE_OPTIONS{$self->name} =
857 { %options, IMMUTABLE_TRANSFORMER => $transformer };
859 if( exists $options{debug} && $options{debug} ){
860 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
861 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
867 return if $self->is_mutable;
868 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
869 confess "unable to find immutabilizing options" unless ref $options;
870 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
871 $transformer->make_metaclass_mutable($self, $options);
875 sub create_immutable_transformer {
877 my $class = Class::MOP::Immutable->new($self, {
878 read_only => [qw/superclasses/],
886 remove_package_symbol
889 class_precedence_list => 'ARRAY',
890 linearized_isa => 'ARRAY',
891 compute_all_applicable_attributes => 'ARRAY',
892 get_meta_instance => 'SCALAR',
893 get_method_map => 'SCALAR',
907 Class::MOP::Class - Class Meta Object
911 # assuming that class Foo
912 # has been defined, you can
914 # use this for introspection ...
916 # add a method to Foo ...
917 Foo->meta->add_method('bar' => sub { ... })
919 # get a list of all the classes searched
920 # the method dispatcher in the correct order
921 Foo->meta->class_precedence_list()
923 # remove a method from Foo
924 Foo->meta->remove_method('bar');
926 # or use this to actually create classes ...
928 Class::MOP::Class->create('Bar' => (
930 superclasses => [ 'Foo' ],
932 Class::MOP:::Attribute->new('$bar'),
933 Class::MOP:::Attribute->new('$baz'),
936 calculate_bar => sub { ... },
937 construct_baz => sub { ... }
943 This is the largest and currently most complex part of the Perl 5
944 meta-object protocol. It controls the introspection and
945 manipulation of Perl 5 classes (and it can create them too). The
946 best way to understand what this module can do, is to read the
947 documentation for each of it's methods.
951 =head2 Self Introspection
957 This will return a B<Class::MOP::Class> instance which is related
958 to this class. Thereby allowing B<Class::MOP::Class> to actually
961 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
962 bootstrap this module by installing a number of attribute meta-objects
963 into it's metaclass. This will allow this class to reap all the benifits
964 of the MOP when subclassing it.
968 =head2 Class construction
970 These methods will handle creating B<Class::MOP::Class> objects,
971 which can be used to both create new classes, and analyze
972 pre-existing classes.
974 This module will internally store references to all the instances
975 you create with these methods, so that they do not need to be
976 created any more than nessecary. Basically, they are singletons.
980 =item B<create ($package_name,
981 version =E<gt> ?$version,
982 authority =E<gt> ?$authority,
983 superclasses =E<gt> ?@superclasses,
984 methods =E<gt> ?%methods,
985 attributes =E<gt> ?%attributes)>
987 This returns a B<Class::MOP::Class> object, bringing the specified
988 C<$package_name> into existence and adding any of the C<$version>,
989 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
992 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
993 methods =E<gt> ?%methods,
994 attributes =E<gt> ?%attributes)>
996 This will create an anonymous class, it works much like C<create> but
997 it does not need a C<$package_name>. Instead it will create a suitably
998 unique package name for you to stash things into.
1000 On very important distinction is that anon classes are destroyed once
1001 the metaclass they are attached to goes out of scope. In the DESTROY
1002 method, the created package will be removed from the symbol table.
1004 It is also worth noting that any instances created with an anon-class
1005 will keep a special reference to the anon-meta which will prevent the
1006 anon-class from going out of scope until all instances of it have also
1007 been destroyed. This however only works for HASH based instance types,
1008 as we use a special reserved slot (C<__MOP__>) to store this.
1010 =item B<initialize ($package_name, %options)>
1012 This initializes and returns returns a B<Class::MOP::Class> object
1013 for a given a C<$package_name>.
1015 =item B<reinitialize ($package_name, %options)>
1017 This removes the old metaclass, and creates a new one in it's place.
1018 Do B<not> use this unless you really know what you are doing, it could
1019 very easily make a very large mess of your program.
1021 =item B<construct_class_instance (%options)>
1023 This will construct an instance of B<Class::MOP::Class>, it is
1024 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1025 to use C<construct_instance> once all the bootstrapping is done. This
1026 method is used internally by C<initialize> and should never be called
1027 from outside of that method really.
1029 =item B<check_metaclass_compatability>
1031 This method is called as the very last thing in the
1032 C<construct_class_instance> method. This will check that the
1033 metaclass you are creating is compatible with the metaclasses of all
1034 your ancestors. For more inforamtion about metaclass compatibility
1035 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1037 =item B<update_package_cache_flag>
1039 This will reset the package cache flag for this particular metaclass
1040 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1041 function. This is very rarely needed from outside of C<Class::MOP::Class>
1042 but in some cases you might want to use it, so it is here.
1044 =item B<reset_package_cache_flag>
1046 Clear this flag, used in Moose.
1050 =head2 Object instance construction and cloning
1052 These methods are B<entirely optional>, it is up to you whether you want
1057 =item B<instance_metaclass>
1059 =item B<get_meta_instance>
1061 =item B<new_object (%params)>
1063 This is a convience method for creating a new object of the class, and
1064 blessing it into the appropriate package as well. Ideally your class
1065 would call a C<new> this method like so:
1068 my ($class, %param) = @_;
1069 $class->meta->new_object(%params);
1072 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1073 but that is considered bad style, so we do not do that.
1075 =item B<construct_instance (%params)>
1077 This method is used to construct an instace structure suitable for
1078 C<bless>-ing into your package of choice. It works in conjunction
1079 with the Attribute protocol to collect all applicable attributes.
1081 This will construct and instance using a HASH ref as storage
1082 (currently only HASH references are supported). This will collect all
1083 the applicable attributes and layout out the fields in the HASH ref,
1084 it will then initialize them using either use the corresponding key
1085 in C<%params> or any default value or initializer found in the
1086 attribute meta-object.
1088 =item B<clone_object ($instance, %params)>
1090 This is a convience method for cloning an object instance, then
1091 blessing it into the appropriate package. This method will call
1092 C<clone_instance>, which performs a shallow copy of the object,
1093 see that methods documentation for more details. Ideally your
1094 class would call a C<clone> this method like so:
1096 sub MyClass::clone {
1097 my ($self, %param) = @_;
1098 $self->meta->clone_object($self, %params);
1101 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1102 but that is considered bad style, so we do not do that.
1104 =item B<clone_instance($instance, %params)>
1106 This method is a compliment of C<construct_instance> (which means if
1107 you override C<construct_instance>, you need to override this one too),
1108 and clones the instance shallowly.
1110 The cloned structure returned is (like with C<construct_instance>) an
1111 unC<bless>ed HASH reference, it is your responsibility to then bless
1112 this cloned structure into the right class (which C<clone_object> will
1115 As of 0.11, this method will clone the C<$instance> structure shallowly,
1116 as opposed to the deep cloning implemented in prior versions. After much
1117 thought, research and discussion, I have decided that anything but basic
1118 shallow cloning is outside the scope of the meta-object protocol. I
1119 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1120 is too I<context-specific> to be part of the MOP.
1124 =head2 Informational
1126 These are a few predicate methods for asking information about the class.
1130 =item B<is_anon_class>
1132 This returns true if the class is a C<Class::MOP::Class> created anon class.
1136 This returns true if the class is still mutable.
1138 =item B<is_immutable>
1140 This returns true if the class has been made immutable.
1144 =head2 Inheritance Relationships
1148 =item B<superclasses (?@superclasses)>
1150 This is a read-write attribute which represents the superclass
1151 relationships of the class the B<Class::MOP::Class> instance is
1152 associated with. Basically, it can get and set the C<@ISA> for you.
1155 Perl will occasionally perform some C<@ISA> and method caching, if
1156 you decide to change your superclass relationship at runtime (which
1157 is quite insane and very much not recommened), then you should be
1158 aware of this and the fact that this module does not make any
1159 attempt to address this issue.
1161 =item B<class_precedence_list>
1163 This computes the a list of all the class's ancestors in the same order
1164 in which method dispatch will be done. This is similair to
1165 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
1167 =item B<linearized_isa>
1169 This returns a list based on C<class_precedence_list> but with all
1174 This returns a list of subclasses for this class.
1182 =item B<get_method_map>
1184 =item B<method_metaclass>
1186 =item B<add_method ($method_name, $method)>
1188 This will take a C<$method_name> and CODE reference to that
1189 C<$method> and install it into the class's package.
1192 This does absolutely nothing special to C<$method>
1193 other than use B<Sub::Name> to make sure it is tagged with the
1194 correct name, and therefore show up correctly in stack traces and
1197 =item B<alias_method ($method_name, $method)>
1199 This will take a C<$method_name> and CODE reference to that
1200 C<$method> and alias the method into the class's package.
1203 Unlike C<add_method>, this will B<not> try to name the
1204 C<$method> using B<Sub::Name>, it only aliases the method in
1205 the class's package.
1207 =item B<has_method ($method_name)>
1209 This just provides a simple way to check if the class implements
1210 a specific C<$method_name>. It will I<not> however, attempt to check
1211 if the class inherits the method (use C<UNIVERSAL::can> for that).
1213 This will correctly handle functions defined outside of the package
1214 that use a fully qualified name (C<sub Package::name { ... }>).
1216 This will correctly handle functions renamed with B<Sub::Name> and
1217 installed using the symbol tables. However, if you are naming the
1218 subroutine outside of the package scope, you must use the fully
1219 qualified name, including the package name, for C<has_method> to
1220 correctly identify it.
1222 This will attempt to correctly ignore functions imported from other
1223 packages using B<Exporter>. It breaks down if the function imported
1224 is an C<__ANON__> sub (such as with C<use constant>), which very well
1225 may be a valid method being applied to the class.
1227 In short, this method cannot always be trusted to determine if the
1228 C<$method_name> is actually a method. However, it will DWIM about
1229 90% of the time, so it's a small trade off I think.
1231 =item B<get_method ($method_name)>
1233 This will return a Class::MOP::Method instance related to the specified
1234 C<$method_name>, or return undef if that method does not exist.
1236 The Class::MOP::Method is codifiable, so you can use it like a normal
1237 CODE reference, see L<Class::MOP::Method> for more information.
1239 =item B<find_method_by_name ($method_name>
1241 This will return a CODE reference of the specified C<$method_name>,
1242 or return undef if that method does not exist.
1244 Unlike C<get_method> this will also look in the superclasses.
1246 =item B<remove_method ($method_name)>
1248 This will attempt to remove a given C<$method_name> from the class.
1249 It will return the CODE reference that it has removed, and will
1250 attempt to use B<Sub::Name> to clear the methods associated name.
1252 =item B<get_method_list>
1254 This will return a list of method names for all I<locally> defined
1255 methods. It does B<not> provide a list of all applicable methods,
1256 including any inherited ones. If you want a list of all applicable
1257 methods, use the C<compute_all_applicable_methods> method.
1259 =item B<compute_all_applicable_methods>
1261 This will return a list of all the methods names this class will
1262 respond to, taking into account inheritance. The list will be a list of
1263 HASH references, each one containing the following information; method
1264 name, the name of the class in which the method lives and a CODE
1265 reference for the actual method.
1267 =item B<find_all_methods_by_name ($method_name)>
1269 This will traverse the inheritence hierarchy and locate all methods
1270 with a given C<$method_name>. Similar to
1271 C<compute_all_applicable_methods> it returns a list of HASH references
1272 with the following information; method name (which will always be the
1273 same as C<$method_name>), the name of the class in which the method
1274 lives and a CODE reference for the actual method.
1276 The list of methods produced is a distinct list, meaning there are no
1277 duplicates in it. This is especially useful for things like object
1278 initialization and destruction where you only want the method called
1279 once, and in the correct order.
1281 =item B<find_next_method_by_name ($method_name)>
1283 This will return the first method to match a given C<$method_name> in
1284 the superclasses, this is basically equivalent to calling
1285 C<SUPER::$method_name>, but it can be dispatched at runtime.
1289 =head2 Method Modifiers
1291 Method modifiers are a concept borrowed from CLOS, in which a method
1292 can be wrapped with I<before>, I<after> and I<around> method modifiers
1293 that will be called everytime the method is called.
1295 =head3 How method modifiers work?
1297 Method modifiers work by wrapping the original method and then replacing
1298 it in the classes symbol table. The wrappers will handle calling all the
1299 modifiers in the appropariate orders and preserving the calling context
1300 for the original method.
1302 Each method modifier serves a particular purpose, which may not be
1303 obvious to users of other method wrapping modules. To start with, the
1304 return values of I<before> and I<after> modifiers are ignored. This is
1305 because thier purpose is B<not> to filter the input and output of the
1306 primary method (this is done with an I<around> modifier). This may seem
1307 like an odd restriction to some, but doing this allows for simple code
1308 to be added at the begining or end of a method call without jeapordizing
1309 the normal functioning of the primary method or placing any extra
1310 responsibility on the code of the modifier. Of course if you have more
1311 complex needs, then use the I<around> modifier, which uses a variation
1312 of continutation passing style to allow for a high degree of flexibility.
1314 Before and around modifiers are called in last-defined-first-called order,
1315 while after modifiers are called in first-defined-first-called order. So
1316 the call tree might looks something like this:
1326 To see examples of using method modifiers, see the following examples
1327 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1328 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1329 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1331 =head3 What is the performance impact?
1333 Of course there is a performance cost associated with method modifiers,
1334 but we have made every effort to make that cost be directly proportional
1335 to the amount of modifier features you utilize.
1337 The wrapping method does it's best to B<only> do as much work as it
1338 absolutely needs to. In order to do this we have moved some of the
1339 performance costs to set-up time, where they are easier to amortize.
1341 All this said, my benchmarks have indicated the following:
1343 simple wrapper with no modifiers 100% slower
1344 simple wrapper with simple before modifier 400% slower
1345 simple wrapper with simple after modifier 450% slower
1346 simple wrapper with simple around modifier 500-550% slower
1347 simple wrapper with all 3 modifiers 1100% slower
1349 These numbers may seem daunting, but you must remember, every feature
1350 comes with some cost. To put things in perspective, just doing a simple
1351 C<AUTOLOAD> which does nothing but extract the name of the method called
1352 and return it costs about 400% over a normal method call.
1356 =item B<add_before_method_modifier ($method_name, $code)>
1358 This will wrap the method at C<$method_name> and the supplied C<$code>
1359 will be passed the C<@_> arguments, and called before the original
1360 method is called. As specified above, the return value of the I<before>
1361 method modifiers is ignored, and it's ability to modify C<@_> is
1362 fairly limited. If you need to do either of these things, use an
1363 C<around> method modifier.
1365 =item B<add_after_method_modifier ($method_name, $code)>
1367 This will wrap the method at C<$method_name> so that the original
1368 method will be called, it's return values stashed, and then the
1369 supplied C<$code> will be passed the C<@_> arguments, and called.
1370 As specified above, the return value of the I<after> method
1371 modifiers is ignored, and it cannot modify the return values of
1372 the original method. If you need to do either of these things, use an
1373 C<around> method modifier.
1375 =item B<add_around_method_modifier ($method_name, $code)>
1377 This will wrap the method at C<$method_name> so that C<$code>
1378 will be called and passed the original method as an extra argument
1379 at the begining of the C<@_> argument list. This is a variation of
1380 continuation passing style, where the function prepended to C<@_>
1381 can be considered a continuation. It is up to C<$code> if it calls
1382 the original method or not, there is no restriction on what the
1383 C<$code> can or cannot do.
1389 It should be noted that since there is no one consistent way to define
1390 the attributes of a class in Perl 5. These methods can only work with
1391 the information given, and can not easily discover information on
1392 their own. See L<Class::MOP::Attribute> for more details.
1396 =item B<attribute_metaclass>
1398 =item B<get_attribute_map>
1400 =item B<add_attribute ($attribute_meta_object | $attribute_name, %attribute_spec)>
1402 This stores the C<$attribute_meta_object> (or creates one from the
1403 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1404 instance associated with the given class. Unlike methods, attributes
1405 within the MOP are stored as meta-information only. They will be used
1406 later to construct instances from (see C<construct_instance> above).
1407 More details about the attribute meta-objects can be found in the
1408 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1411 It should be noted that any accessor, reader/writer or predicate
1412 methods which the C<$attribute_meta_object> has will be installed
1413 into the class at this time.
1416 If an attribute already exists for C<$attribute_name>, the old one
1417 will be removed (as well as removing all it's accessors), and then
1420 =item B<has_attribute ($attribute_name)>
1422 Checks to see if this class has an attribute by the name of
1423 C<$attribute_name> and returns a boolean.
1425 =item B<get_attribute ($attribute_name)>
1427 Returns the attribute meta-object associated with C<$attribute_name>,
1428 if none is found, it will return undef.
1430 =item B<remove_attribute ($attribute_name)>
1432 This will remove the attribute meta-object stored at
1433 C<$attribute_name>, then return the removed attribute meta-object.
1436 Removing an attribute will only affect future instances of
1437 the class, it will not make any attempt to remove the attribute from
1438 any existing instances of the class.
1440 It should be noted that any accessor, reader/writer or predicate
1441 methods which the attribute meta-object stored at C<$attribute_name>
1442 has will be removed from the class at this time. This B<will> make
1443 these attributes somewhat inaccessable in previously created
1444 instances. But if you are crazy enough to do this at runtime, then
1445 you are crazy enough to deal with something like this :).
1447 =item B<get_attribute_list>
1449 This returns a list of attribute names which are defined in the local
1450 class. If you want a list of all applicable attributes for a class,
1451 use the C<compute_all_applicable_attributes> method.
1453 =item B<compute_all_applicable_attributes>
1455 This will traverse the inheritance heirachy and return a list of all
1456 the applicable attributes for this class. It does not construct a
1457 HASH reference like C<compute_all_applicable_methods> because all
1458 that same information is discoverable through the attribute
1461 =item B<find_attribute_by_name ($attr_name)>
1463 This method will traverse the inheritance heirachy and find the
1464 first attribute whose name matches C<$attr_name>, then return it.
1465 It will return undef if nothing is found.
1469 =head2 Class Immutability
1473 =item B<make_immutable (%options)>
1475 This method will invoke a tranforamtion upon the class which will
1476 make it immutable. Details of this transformation can be found in
1477 the L<Class::MOP::Immutable> documentation.
1479 =item B<make_mutable>
1481 This method will reverse tranforamtion upon the class which
1484 =item B<create_immutable_transformer>
1486 Create a transformer suitable for making this class immutable
1492 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1494 =head1 COPYRIGHT AND LICENSE
1496 Copyright 2006-2008 by Infinity Interactive, Inc.
1498 L<http://www.iinteractive.com>
1500 This library is free software; you can redistribute it and/or modify
1501 it under the same terms as Perl itself.