2 package Class::MOP::Class;
7 use Class::MOP::Immutable;
8 use Class::MOP::Instance;
9 use Class::MOP::Method::Wrapped;
12 use Scalar::Util 'blessed', 'weaken';
14 our $VERSION = '0.65';
15 our $AUTHORITY = 'cpan:STEVAN';
17 use base 'Class::MOP::Module';
22 my ( $class, @args ) = @_;
24 unshift @args, 'package' if @args % 2 == 1;
26 my (%options) = @args;
27 my $package_name = $options{package};
29 (defined $package_name && $package_name && !blessed($package_name))
30 || confess "You must pass a package name and it cannot be blessed";
32 return Class::MOP::get_metaclass_by_name($package_name)
33 || $class->construct_class_instance(%options);
38 my $package_name = shift;
39 (defined $package_name && $package_name && !blessed($package_name))
40 || confess "You must pass a package name and it cannot be blessed";
41 Class::MOP::remove_metaclass_by_name($package_name);
42 $class->construct_class_instance('package' => $package_name, @_);
45 # NOTE: (meta-circularity)
46 # this is a special form of &construct_instance
47 # (see below), which is used to construct class
48 # meta-object instances for any Class::MOP::*
49 # class. All other classes will use the more
50 # normal &construct_instance.
51 sub construct_class_instance {
54 my $package_name = $options{'package'};
55 (defined $package_name && $package_name)
56 || confess "You must pass a package name";
58 # return the metaclass if we have it cached,
59 # and it is still defined (it has not been
60 # reaped by DESTROY yet, which can happen
61 # annoyingly enough during global destruction)
63 if (defined(my $meta = Class::MOP::get_metaclass_by_name($package_name))) {
68 # we need to deal with the possibility
69 # of class immutability here, and then
70 # get the name of the class appropriately
71 $class = (blessed($class)
72 ? ($class->is_immutable
73 ? $class->get_mutable_metaclass_name()
77 # now create the metaclass
79 if ($class eq 'Class::MOP::Class') {
82 # inherited from Class::MOP::Package
83 'package' => $package_name,
86 # since the following attributes will
87 # actually be loaded from the symbol
88 # table, and actually bypass the instance
89 # entirely, we can just leave these things
90 # listed here for reference, because they
91 # should not actually have a value associated
93 'namespace' => \undef,
94 # inherited from Class::MOP::Module
96 'authority' => \undef,
97 # defined in Class::MOP::Class
98 'superclasses' => \undef,
102 'attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
103 'method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
104 'instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
106 ## uber-private variables
108 # this starts out as undef so that
109 # we can tell the first time the
110 # methods are fetched
112 '_package_cache_flag' => undef,
113 '_meta_instance' => 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 ...
235 my ( $class, @args ) = @_;
237 unshift @args, 'package' if @args % 2 == 1;
239 my (%options) = @args;
240 my $package_name = $options{package};
242 (defined $package_name && $package_name)
243 || confess "You must pass a package name";
245 (ref $options{superclasses} eq 'ARRAY')
246 || confess "You must pass an ARRAY ref of superclasses"
247 if exists $options{superclasses};
249 (ref $options{attributes} eq 'ARRAY')
250 || confess "You must pass an ARRAY ref of attributes"
251 if exists $options{attributes};
253 (ref $options{methods} eq 'HASH')
254 || confess "You must pass an HASH ref of methods"
255 if exists $options{methods};
257 my $code = "package $package_name;";
258 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
259 if exists $options{version};
260 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
261 if exists $options{authority};
264 confess "creation of $package_name failed : $@" if $@;
266 my $meta = $class->initialize($package_name);
269 $meta->add_method('meta' => sub {
270 $class->initialize(blessed($_[0]) || $_[0]);
273 $meta->superclasses(@{$options{superclasses}})
274 if exists $options{superclasses};
276 # process attributes first, so that they can
277 # install accessors, but locally defined methods
278 # can then overwrite them. It is maybe a little odd, but
279 # I think this should be the order of things.
280 if (exists $options{attributes}) {
281 foreach my $attr (@{$options{attributes}}) {
282 $meta->add_attribute($attr);
285 if (exists $options{methods}) {
286 foreach my $method_name (keys %{$options{methods}}) {
287 $meta->add_method($method_name, $options{methods}->{$method_name});
296 # all these attribute readers will be bootstrapped
297 # away in the Class::MOP bootstrap section
299 sub get_attribute_map { $_[0]->{'attributes'} }
300 sub attribute_metaclass { $_[0]->{'attribute_metaclass'} }
301 sub method_metaclass { $_[0]->{'method_metaclass'} }
302 sub instance_metaclass { $_[0]->{'instance_metaclass'} }
305 # this is a prime canidate for conversion to XS
309 if (defined $self->{'_package_cache_flag'} &&
310 $self->{'_package_cache_flag'} == Class::MOP::check_package_cache_flag($self->name)) {
311 return $self->{'methods'};
314 my $map = $self->{'methods'};
316 my $class_name = $self->name;
317 my $method_metaclass = $self->method_metaclass;
319 my %all_code = $self->get_all_package_symbols('CODE');
321 foreach my $symbol (keys %all_code) {
322 my $code = $all_code{$symbol};
324 next if exists $map->{$symbol} &&
325 defined $map->{$symbol} &&
326 $map->{$symbol}->body == $code;
328 my ($pkg, $name) = Class::MOP::get_code_info($code);
331 # in 5.10 constant.pm the constants show up
332 # as being in the right package, but in pre-5.10
333 # they show up as constant::__ANON__ so we
334 # make an exception here to be sure that things
335 # work as expected in both.
337 unless ($pkg eq 'constant' && $name eq '__ANON__') {
338 next if ($pkg || '') ne $class_name ||
339 (($name || '') ne '__ANON__' && ($pkg || '') ne $class_name);
342 $map->{$symbol} = $method_metaclass->wrap(
344 package_name => $class_name,
352 # Instance Construction & Cloning
358 # we need to protect the integrity of the
359 # Class::MOP::Class singletons here, so we
360 # delegate this to &construct_class_instance
361 # which will deal with the singletons
362 return $class->construct_class_instance(@_)
363 if $class->name->isa('Class::MOP::Class');
364 return $class->construct_instance(@_);
367 sub construct_instance {
368 my ($class, %params) = @_;
369 my $meta_instance = $class->get_meta_instance();
370 my $instance = $meta_instance->create_instance();
371 foreach my $attr ($class->compute_all_applicable_attributes()) {
372 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
375 # this will only work for a HASH instance type
376 if ($class->is_anon_class) {
377 (Scalar::Util::reftype($instance) eq 'HASH')
378 || confess "Currently only HASH based instances are supported with instance of anon-classes";
380 # At some point we should make this official
381 # as a reserved slot name, but right now I am
382 # going to keep it here.
383 # my $RESERVED_MOP_SLOT = '__MOP__';
384 $instance->{'__MOP__'} = $class;
390 sub get_meta_instance {
392 $self->{'_meta_instance'} ||= $self->instance_metaclass->new(
393 associated_metaclass => $self,
394 attributes => [ $self->compute_all_applicable_attributes() ],
400 my $instance = shift;
401 (blessed($instance) && $instance->isa($class->name))
402 || confess "You must pass an instance of the metaclass (" . $class->name . "), not ($instance)";
405 # we need to protect the integrity of the
406 # Class::MOP::Class singletons here, they
407 # should not be cloned.
408 return $instance if $instance->isa('Class::MOP::Class');
409 $class->clone_instance($instance, @_);
413 my ($class, $instance, %params) = @_;
415 || confess "You can only clone instances, ($instance) is not a blessed instance";
416 my $meta_instance = $class->get_meta_instance();
417 my $clone = $meta_instance->clone_instance($instance);
418 foreach my $attr ($class->compute_all_applicable_attributes()) {
419 if ( defined( my $init_arg = $attr->init_arg ) ) {
420 if (exists $params{$init_arg}) {
421 $attr->set_value($clone, $params{$init_arg});
428 sub rebless_instance {
429 my ($self, $instance, %params) = @_;
432 if ($instance->can('meta')) {
433 ($instance->meta->isa('Class::MOP::Class'))
434 || confess 'Cannot rebless instance if ->meta is not an instance of Class::MOP::Class';
435 $old_metaclass = $instance->meta;
438 $old_metaclass = $self->initialize(blessed($instance));
441 my $meta_instance = $self->get_meta_instance();
443 $self->name->isa($old_metaclass->name)
444 || confess "You may rebless only into a subclass of (". $old_metaclass->name ."), of which (". $self->name .") isn't.";
447 $meta_instance->rebless_instance_structure($instance, $self);
449 foreach my $attr ( $self->compute_all_applicable_attributes ) {
450 if ( $attr->has_value($instance) ) {
451 if ( defined( my $init_arg = $attr->init_arg ) ) {
452 $params{$init_arg} = $attr->get_value($instance)
453 unless exists $params{$init_arg};
456 $attr->set_value($instance, $attr->get_value($instance));
461 foreach my $attr ($self->compute_all_applicable_attributes) {
462 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
472 my $var_spec = { sigil => '@', type => 'ARRAY', name => 'ISA' };
475 @{$self->get_package_symbol($var_spec)} = @supers;
477 # we need to check the metaclass
478 # compatibility here so that we can
479 # be sure that the superclass is
480 # not potentially creating an issues
481 # we don't know about
482 $self->check_metaclass_compatability();
484 @{$self->get_package_symbol($var_spec)};
490 my $super_class = $self->name;
492 if ( Class::MOP::HAVE_ISAREV() ) {
493 return @{ $super_class->mro::get_isarev() };
497 my $find_derived_classes;
498 $find_derived_classes = sub {
499 my ($outer_class) = @_;
501 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
504 for my $symbol ( keys %$symbol_table_hashref ) {
505 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
506 my $inner_class = $1;
508 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
512 ? "${outer_class}::$inner_class"
515 if ( $class->isa($super_class) and $class ne $super_class ) {
516 push @derived_classes, $class;
519 next SYMBOL if $class eq 'main'; # skip 'main::*'
521 $find_derived_classes->($class);
525 my $root_class = q{};
526 $find_derived_classes->($root_class);
528 undef $find_derived_classes;
530 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
532 return @derived_classes;
538 return @{ mro::get_linear_isa( (shift)->name ) };
541 sub class_precedence_list {
543 my $name = $self->name;
545 unless (Class::MOP::IS_RUNNING_ON_5_10()) {
547 # We need to check for circular inheritance here
548 # if we are are not on 5.10, cause 5.8 detects it
549 # late. This will do nothing if all is well, and
550 # blow up otherwise. Yes, it's an ugly hack, better
551 # suggestions are welcome.
553 ($name || return)->isa('This is a test for circular inheritance')
556 # if our mro is c3, we can
557 # just grab the linear_isa
558 if (mro::get_mro($name) eq 'c3') {
559 return @{ mro::get_linear_isa($name) }
563 # we can't grab the linear_isa for dfs
564 # since it has all the duplicates
569 $self->initialize($_)->class_precedence_list()
570 } $self->superclasses()
578 my ($self, $method_name, $method) = @_;
579 (defined $method_name && $method_name)
580 || confess "You must define a method name";
583 if (blessed($method)) {
584 $body = $method->body;
585 if ($method->package_name ne $self->name &&
586 $method->name ne $method_name) {
587 warn "Hello there, got something for you."
588 . " Method says " . $method->package_name . " " . $method->name
589 . " Class says " . $self->name . " " . $method_name;
590 $method = $method->clone(
591 package_name => $self->name,
593 ) if $method->can('clone');
598 ('CODE' eq ref($body))
599 || confess "Your code block must be a CODE reference";
600 $method = $self->method_metaclass->wrap(
602 package_name => $self->name,
607 $self->get_method_map->{$method_name} = $method;
609 my $full_method_name = ($self->name . '::' . $method_name);
610 $self->add_package_symbol(
611 { sigil => '&', type => 'CODE', name => $method_name },
612 Class::MOP::subname($full_method_name => $body)
614 $self->update_package_cache_flag;
618 my $fetch_and_prepare_method = sub {
619 my ($self, $method_name) = @_;
621 my $method = $self->get_method($method_name);
622 # if we dont have local ...
624 # try to find the next method
625 $method = $self->find_next_method_by_name($method_name);
626 # die if it does not exist
628 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
629 # and now make sure to wrap it
630 # even if it is already wrapped
631 # because we need a new sub ref
632 $method = Class::MOP::Method::Wrapped->wrap($method);
635 # now make sure we wrap it properly
636 $method = Class::MOP::Method::Wrapped->wrap($method)
637 unless $method->isa('Class::MOP::Method::Wrapped');
639 $self->add_method($method_name => $method);
643 sub add_before_method_modifier {
644 my ($self, $method_name, $method_modifier) = @_;
645 (defined $method_name && $method_name)
646 || confess "You must pass in a method name";
647 my $method = $fetch_and_prepare_method->($self, $method_name);
648 $method->add_before_modifier(
649 Class::MOP::subname(':before' => $method_modifier)
653 sub add_after_method_modifier {
654 my ($self, $method_name, $method_modifier) = @_;
655 (defined $method_name && $method_name)
656 || confess "You must pass in a method name";
657 my $method = $fetch_and_prepare_method->($self, $method_name);
658 $method->add_after_modifier(
659 Class::MOP::subname(':after' => $method_modifier)
663 sub add_around_method_modifier {
664 my ($self, $method_name, $method_modifier) = @_;
665 (defined $method_name && $method_name)
666 || confess "You must pass in a method name";
667 my $method = $fetch_and_prepare_method->($self, $method_name);
668 $method->add_around_modifier(
669 Class::MOP::subname(':around' => $method_modifier)
674 # the methods above used to be named like this:
675 # ${pkg}::${method}:(before|after|around)
676 # but this proved problematic when using one modifier
677 # to wrap multiple methods (something which is likely
678 # to happen pretty regularly IMO). So instead of naming
679 # it like this, I have chosen to just name them purely
680 # with their modifier names, like so:
681 # :(before|after|around)
682 # The fact is that in a stack trace, it will be fairly
683 # evident from the context what method they are attached
684 # to, and so don't need the fully qualified name.
688 my ($self, $method_name, $method) = @_;
689 (defined $method_name && $method_name)
690 || confess "You must define a method name";
692 my $body = (blessed($method) ? $method->body : $method);
693 ('CODE' eq ref($body))
694 || confess "Your code block must be a CODE reference";
696 $self->add_package_symbol(
697 { sigil => '&', type => 'CODE', name => $method_name } => $body
699 $self->update_package_cache_flag;
703 my ($self, $method_name) = @_;
704 (defined $method_name && $method_name)
705 || confess "You must define a method name";
707 return 0 unless exists $self->get_method_map->{$method_name};
712 my ($self, $method_name) = @_;
713 (defined $method_name && $method_name)
714 || confess "You must define a method name";
717 # I don't really need this here, because
718 # if the method_map is missing a key it
719 # will just return undef for me now
720 # return unless $self->has_method($method_name);
722 return $self->get_method_map->{$method_name};
726 my ($self, $method_name) = @_;
727 (defined $method_name && $method_name)
728 || confess "You must define a method name";
730 my $removed_method = delete $self->get_method_map->{$method_name};
732 $self->remove_package_symbol(
733 { sigil => '&', type => 'CODE', name => $method_name }
736 $self->update_package_cache_flag;
738 return $removed_method;
741 sub get_method_list {
743 keys %{$self->get_method_map};
746 sub find_method_by_name {
747 my ($self, $method_name) = @_;
748 (defined $method_name && $method_name)
749 || confess "You must define a method name to find";
750 foreach my $class ($self->linearized_isa) {
751 # fetch the meta-class ...
752 my $meta = $self->initialize($class);
753 return $meta->get_method($method_name)
754 if $meta->has_method($method_name);
759 sub compute_all_applicable_methods {
761 my (@methods, %seen_method);
762 foreach my $class ($self->linearized_isa) {
763 # fetch the meta-class ...
764 my $meta = $self->initialize($class);
765 foreach my $method_name ($meta->get_method_list()) {
766 next if exists $seen_method{$method_name};
767 $seen_method{$method_name}++;
769 name => $method_name,
771 code => $meta->get_method($method_name)
778 sub find_all_methods_by_name {
779 my ($self, $method_name) = @_;
780 (defined $method_name && $method_name)
781 || confess "You must define a method name to find";
783 foreach my $class ($self->linearized_isa) {
784 # fetch the meta-class ...
785 my $meta = $self->initialize($class);
787 name => $method_name,
789 code => $meta->get_method($method_name)
790 } if $meta->has_method($method_name);
795 sub find_next_method_by_name {
796 my ($self, $method_name) = @_;
797 (defined $method_name && $method_name)
798 || confess "You must define a method name to find";
799 my @cpl = $self->linearized_isa;
800 shift @cpl; # discard ourselves
801 foreach my $class (@cpl) {
802 # fetch the meta-class ...
803 my $meta = $self->initialize($class);
804 return $meta->get_method($method_name)
805 if $meta->has_method($method_name);
814 # either we have an attribute object already
815 # or we need to create one from the args provided
816 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
817 # make sure it is derived from the correct type though
818 ($attribute->isa('Class::MOP::Attribute'))
819 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
821 # first we attach our new attribute
822 # because it might need certain information
823 # about the class which it is attached to
824 $attribute->attach_to_class($self);
826 # then we remove attributes of a conflicting
827 # name here so that we can properly detach
828 # the old attr object, and remove any
829 # accessors it would have generated
830 if ( $self->has_attribute($attribute->name) ) {
831 $self->remove_attribute($attribute->name);
833 $self->invalidate_meta_instances();
836 # then onto installing the new accessors
837 $self->get_attribute_map->{$attribute->name} = $attribute;
839 # invalidate package flag here
840 my $e = do { local $@; eval { $attribute->install_accessors() }; $@ };
842 $self->remove_attribute($attribute->name);
849 sub invalidate_meta_instances {
852 my @metas = ( $self, map { Class::MOP::Class->initialize($_) } $self->subclasses );
854 $_->invalidate_meta_instance() for @metas;
857 sub invalidate_meta_instance {
859 undef $self->{_meta_instance};
863 my ($self, $attribute_name) = @_;
864 (defined $attribute_name && $attribute_name)
865 || confess "You must define an attribute name";
866 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
870 my ($self, $attribute_name) = @_;
871 (defined $attribute_name && $attribute_name)
872 || confess "You must define an attribute name";
873 return $self->get_attribute_map->{$attribute_name}
875 # this will return undef anyway, so no need ...
876 # if $self->has_attribute($attribute_name);
880 sub remove_attribute {
881 my ($self, $attribute_name) = @_;
882 (defined $attribute_name && $attribute_name)
883 || confess "You must define an attribute name";
884 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
885 return unless defined $removed_attribute;
886 delete $self->get_attribute_map->{$attribute_name};
887 $self->invalidate_meta_instances();
888 $removed_attribute->remove_accessors();
889 $removed_attribute->detach_from_class();
890 return $removed_attribute;
893 sub get_attribute_list {
895 keys %{$self->get_attribute_map};
898 sub compute_all_applicable_attributes {
900 my (@attrs, %seen_attr);
901 foreach my $class ($self->linearized_isa) {
902 # fetch the meta-class ...
903 my $meta = $self->initialize($class);
904 foreach my $attr_name ($meta->get_attribute_list()) {
905 next if exists $seen_attr{$attr_name};
906 $seen_attr{$attr_name}++;
907 push @attrs => $meta->get_attribute($attr_name);
913 sub find_attribute_by_name {
914 my ($self, $attr_name) = @_;
915 foreach my $class ($self->linearized_isa) {
916 # fetch the meta-class ...
917 my $meta = $self->initialize($class);
918 return $meta->get_attribute($attr_name)
919 if $meta->has_attribute($attr_name);
927 sub is_immutable { 0 }
930 # Why I changed this (groditi)
931 # - One Metaclass may have many Classes through many Metaclass instances
932 # - One Metaclass should only have one Immutable Transformer instance
933 # - Each Class may have different Immutabilizing options
934 # - Therefore each Metaclass instance may have different Immutabilizing options
935 # - We need to store one Immutable Transformer instance per Metaclass
936 # - We need to store one set of Immutable Transformer options per Class
937 # - Upon make_mutable we may delete the Immutabilizing options
938 # - We could clean the immutable Transformer instance when there is no more
939 # immutable Classes of that type, but we can also keep it in case
940 # another class with this same Metaclass becomes immutable. It is a case
941 # of trading of storing an instance to avoid unnecessary instantiations of
942 # Immutable Transformers. You may view this as a memory leak, however
943 # Because we have few Metaclasses, in practice it seems acceptable
944 # - To allow Immutable Transformers instances to be cleaned up we could weaken
945 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
949 my %IMMUTABLE_TRANSFORMERS;
950 my %IMMUTABLE_OPTIONS;
952 sub get_immutable_options {
954 return if $self->is_mutable;
955 confess "unable to find immutabilizing options"
956 unless exists $IMMUTABLE_OPTIONS{$self->name};
957 my %options = %{$IMMUTABLE_OPTIONS{$self->name}};
958 delete $options{IMMUTABLE_TRANSFORMER};
962 sub get_immutable_transformer {
964 if( $self->is_mutable ){
965 my $class = blessed $self || $self;
966 return $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
968 confess "unable to find transformer for immutable class"
969 unless exists $IMMUTABLE_OPTIONS{$self->name};
970 return $IMMUTABLE_OPTIONS{$self->name}->{IMMUTABLE_TRANSFORMER};
977 my $transformer = $self->get_immutable_transformer;
978 $transformer->make_metaclass_immutable($self, \%options);
979 $IMMUTABLE_OPTIONS{$self->name} =
980 { %options, IMMUTABLE_TRANSFORMER => $transformer };
982 if( exists $options{debug} && $options{debug} ){
983 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
984 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
992 return if $self->is_mutable;
993 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
994 confess "unable to find immutabilizing options" unless ref $options;
995 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
996 $transformer->make_metaclass_mutable($self, $options);
1001 sub create_immutable_transformer {
1003 my $class = Class::MOP::Immutable->new($self, {
1004 read_only => [qw/superclasses/],
1011 remove_package_symbol
1014 class_precedence_list => 'ARRAY',
1015 linearized_isa => 'ARRAY',
1016 compute_all_applicable_attributes => 'ARRAY',
1017 get_meta_instance => 'SCALAR',
1018 get_method_map => 'SCALAR',
1021 # this is ugly, but so are typeglobs,
1022 # so whattayahgonnadoboutit
1025 add_package_symbol => sub {
1026 my $original = shift;
1027 confess "Cannot add package symbols to an immutable metaclass"
1028 unless (caller(2))[3] eq 'Class::MOP::Package::get_package_symbol';
1029 goto $original->body;
1044 Class::MOP::Class - Class Meta Object
1048 # assuming that class Foo
1049 # has been defined, you can
1051 # use this for introspection ...
1053 # add a method to Foo ...
1054 Foo->meta->add_method('bar' => sub { ... })
1056 # get a list of all the classes searched
1057 # the method dispatcher in the correct order
1058 Foo->meta->class_precedence_list()
1060 # remove a method from Foo
1061 Foo->meta->remove_method('bar');
1063 # or use this to actually create classes ...
1065 Class::MOP::Class->create('Bar' => (
1067 superclasses => [ 'Foo' ],
1069 Class::MOP:::Attribute->new('$bar'),
1070 Class::MOP:::Attribute->new('$baz'),
1073 calculate_bar => sub { ... },
1074 construct_baz => sub { ... }
1080 This is the largest and currently most complex part of the Perl 5
1081 meta-object protocol. It controls the introspection and
1082 manipulation of Perl 5 classes (and it can create them too). The
1083 best way to understand what this module can do, is to read the
1084 documentation for each of it's methods.
1088 =head2 Self Introspection
1094 This will return a B<Class::MOP::Class> instance which is related
1095 to this class. Thereby allowing B<Class::MOP::Class> to actually
1098 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
1099 bootstrap this module by installing a number of attribute meta-objects
1100 into it's metaclass. This will allow this class to reap all the benifits
1101 of the MOP when subclassing it.
1105 =head2 Class construction
1107 These methods will handle creating B<Class::MOP::Class> objects,
1108 which can be used to both create new classes, and analyze
1109 pre-existing classes.
1111 This module will internally store references to all the instances
1112 you create with these methods, so that they do not need to be
1113 created any more than nessecary. Basically, they are singletons.
1117 =item B<create ($package_name,
1118 version =E<gt> ?$version,
1119 authority =E<gt> ?$authority,
1120 superclasses =E<gt> ?@superclasses,
1121 methods =E<gt> ?%methods,
1122 attributes =E<gt> ?%attributes)>
1124 This returns a B<Class::MOP::Class> object, bringing the specified
1125 C<$package_name> into existence and adding any of the C<$version>,
1126 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
1129 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
1130 methods =E<gt> ?%methods,
1131 attributes =E<gt> ?%attributes)>
1133 This will create an anonymous class, it works much like C<create> but
1134 it does not need a C<$package_name>. Instead it will create a suitably
1135 unique package name for you to stash things into.
1137 On very important distinction is that anon classes are destroyed once
1138 the metaclass they are attached to goes out of scope. In the DESTROY
1139 method, the created package will be removed from the symbol table.
1141 It is also worth noting that any instances created with an anon-class
1142 will keep a special reference to the anon-meta which will prevent the
1143 anon-class from going out of scope until all instances of it have also
1144 been destroyed. This however only works for HASH based instance types,
1145 as we use a special reserved slot (C<__MOP__>) to store this.
1147 =item B<initialize ($package_name, %options)>
1149 This initializes and returns returns a B<Class::MOP::Class> object
1150 for a given a C<$package_name>.
1152 =item B<reinitialize ($package_name, %options)>
1154 This removes the old metaclass, and creates a new one in it's place.
1155 Do B<not> use this unless you really know what you are doing, it could
1156 very easily make a very large mess of your program.
1158 =item B<construct_class_instance (%options)>
1160 This will construct an instance of B<Class::MOP::Class>, it is
1161 here so that we can actually "tie the knot" for B<Class::MOP::Class>
1162 to use C<construct_instance> once all the bootstrapping is done. This
1163 method is used internally by C<initialize> and should never be called
1164 from outside of that method really.
1166 =item B<check_metaclass_compatability>
1168 This method is called as the very last thing in the
1169 C<construct_class_instance> method. This will check that the
1170 metaclass you are creating is compatible with the metaclasses of all
1171 your ancestors. For more inforamtion about metaclass compatibility
1172 see the C<About Metaclass compatibility> section in L<Class::MOP>.
1174 =item B<update_package_cache_flag>
1176 This will reset the package cache flag for this particular metaclass
1177 it is basically the value of the C<Class::MOP::get_package_cache_flag>
1178 function. This is very rarely needed from outside of C<Class::MOP::Class>
1179 but in some cases you might want to use it, so it is here.
1181 =item B<reset_package_cache_flag>
1183 Clears the package cache flag to announce to the internals that we need
1184 to rebuild the method map.
1186 =item B<invalidate_meta_instances>
1188 Clears the cached meta instance for this metaclass and all of its subclasses.
1190 Called by C<add_attribute> and C<remove_attribute> to recalculate the attribute
1193 =item B<invalidate_meta_instance>
1195 Used by C<invalidate_meta_instances>.
1199 =head2 Object instance construction and cloning
1201 These methods are B<entirely optional>, it is up to you whether you want
1206 =item B<instance_metaclass>
1208 Returns the class name of the instance metaclass, see L<Class::MOP::Instance>
1209 for more information on the instance metaclasses.
1211 =item B<get_meta_instance>
1213 Returns an instance of L<Class::MOP::Instance> to be used in the construction
1214 of a new instance of the class.
1216 =item B<new_object (%params)>
1218 This is a convience method for creating a new object of the class, and
1219 blessing it into the appropriate package as well. Ideally your class
1220 would call a C<new> this method like so:
1223 my ($class, %param) = @_;
1224 $class->meta->new_object(%params);
1227 =item B<construct_instance (%params)>
1229 This method is used to construct an instance structure suitable for
1230 C<bless>-ing into your package of choice. It works in conjunction
1231 with the Attribute protocol to collect all applicable attributes.
1233 This will construct and instance using a HASH ref as storage
1234 (currently only HASH references are supported). This will collect all
1235 the applicable attributes and layout out the fields in the HASH ref,
1236 it will then initialize them using either use the corresponding key
1237 in C<%params> or any default value or initializer found in the
1238 attribute meta-object.
1240 =item B<clone_object ($instance, %params)>
1242 This is a convience method for cloning an object instance, then
1243 blessing it into the appropriate package. This method will call
1244 C<clone_instance>, which performs a shallow copy of the object,
1245 see that methods documentation for more details. Ideally your
1246 class would call a C<clone> this method like so:
1248 sub MyClass::clone {
1249 my ($self, %param) = @_;
1250 $self->meta->clone_object($self, %params);
1253 =item B<clone_instance($instance, %params)>
1255 This method is a compliment of C<construct_instance> (which means if
1256 you override C<construct_instance>, you need to override this one too),
1257 and clones the instance shallowly.
1259 The cloned structure returned is (like with C<construct_instance>) an
1260 unC<bless>ed HASH reference, it is your responsibility to then bless
1261 this cloned structure into the right class (which C<clone_object> will
1264 As of 0.11, this method will clone the C<$instance> structure shallowly,
1265 as opposed to the deep cloning implemented in prior versions. After much
1266 thought, research and discussion, I have decided that anything but basic
1267 shallow cloning is outside the scope of the meta-object protocol. I
1268 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1269 is too I<context-specific> to be part of the MOP.
1271 =item B<rebless_instance($instance, ?%params)>
1273 This will change the class of C<$instance> to the class of the invoking
1274 C<Class::MOP::Class>. You may only rebless the instance to a subclass of
1275 itself. You may pass in optional C<%params> which are like constructor
1276 params and will override anything already defined in the instance.
1280 =head2 Informational
1282 These are a few predicate methods for asking information about the class.
1286 =item B<is_anon_class>
1288 This returns true if the class is a C<Class::MOP::Class> created anon class.
1292 This returns true if the class is still mutable.
1294 =item B<is_immutable>
1296 This returns true if the class has been made immutable.
1300 =head2 Inheritance Relationships
1304 =item B<superclasses (?@superclasses)>
1306 This is a read-write attribute which represents the superclass
1307 relationships of the class the B<Class::MOP::Class> instance is
1308 associated with. Basically, it can get and set the C<@ISA> for you.
1310 =item B<class_precedence_list>
1312 This computes the a list of all the class's ancestors in the same order
1313 in which method dispatch will be done. This is similair to what
1314 B<Class::ISA::super_path> does, but we don't remove duplicate names.
1316 =item B<linearized_isa>
1318 This returns a list based on C<class_precedence_list> but with all
1323 This returns a list of subclasses for this class.
1331 =item B<get_method_map>
1333 Returns a HASH ref of name to CODE reference mapping for this class.
1335 =item B<method_metaclass>
1337 Returns the class name of the method metaclass, see L<Class::MOP::Method>
1338 for more information on the method metaclasses.
1340 =item B<add_method ($method_name, $method)>
1342 This will take a C<$method_name> and CODE reference to that
1343 C<$method> and install it into the class's package.
1346 This does absolutely nothing special to C<$method>
1347 other than use B<Sub::Name> to make sure it is tagged with the
1348 correct name, and therefore show up correctly in stack traces and
1351 =item B<alias_method ($method_name, $method)>
1353 This will take a C<$method_name> and CODE reference to that
1354 C<$method> and alias the method into the class's package.
1357 Unlike C<add_method>, this will B<not> try to name the
1358 C<$method> using B<Sub::Name>, it only aliases the method in
1359 the class's package.
1361 =item B<has_method ($method_name)>
1363 This just provides a simple way to check if the class implements
1364 a specific C<$method_name>. It will I<not> however, attempt to check
1365 if the class inherits the method (use C<UNIVERSAL::can> for that).
1367 This will correctly handle functions defined outside of the package
1368 that use a fully qualified name (C<sub Package::name { ... }>).
1370 This will correctly handle functions renamed with B<Sub::Name> and
1371 installed using the symbol tables. However, if you are naming the
1372 subroutine outside of the package scope, you must use the fully
1373 qualified name, including the package name, for C<has_method> to
1374 correctly identify it.
1376 This will attempt to correctly ignore functions imported from other
1377 packages using B<Exporter>. It breaks down if the function imported
1378 is an C<__ANON__> sub (such as with C<use constant>), which very well
1379 may be a valid method being applied to the class.
1381 In short, this method cannot always be trusted to determine if the
1382 C<$method_name> is actually a method. However, it will DWIM about
1383 90% of the time, so it's a small trade off I think.
1385 =item B<get_method ($method_name)>
1387 This will return a Class::MOP::Method instance related to the specified
1388 C<$method_name>, or return undef if that method does not exist.
1390 The Class::MOP::Method is codifiable, so you can use it like a normal
1391 CODE reference, see L<Class::MOP::Method> for more information.
1393 =item B<find_method_by_name ($method_name)>
1395 This will return a CODE reference of the specified C<$method_name>,
1396 or return undef if that method does not exist.
1398 Unlike C<get_method> this will also look in the superclasses.
1400 =item B<remove_method ($method_name)>
1402 This will attempt to remove a given C<$method_name> from the class.
1403 It will return the CODE reference that it has removed, and will
1404 attempt to use B<Sub::Name> to clear the methods associated name.
1406 =item B<get_method_list>
1408 This will return a list of method names for all I<locally> defined
1409 methods. It does B<not> provide a list of all applicable methods,
1410 including any inherited ones. If you want a list of all applicable
1411 methods, use the C<compute_all_applicable_methods> method.
1413 =item B<compute_all_applicable_methods>
1415 This will return a list of all the methods names this class will
1416 respond to, taking into account inheritance. The list will be a list of
1417 HASH references, each one containing the following information; method
1418 name, the name of the class in which the method lives and a CODE
1419 reference for the actual method.
1421 =item B<find_all_methods_by_name ($method_name)>
1423 This will traverse the inheritence hierarchy and locate all methods
1424 with a given C<$method_name>. Similar to
1425 C<compute_all_applicable_methods> it returns a list of HASH references
1426 with the following information; method name (which will always be the
1427 same as C<$method_name>), the name of the class in which the method
1428 lives and a CODE reference for the actual method.
1430 The list of methods produced is a distinct list, meaning there are no
1431 duplicates in it. This is especially useful for things like object
1432 initialization and destruction where you only want the method called
1433 once, and in the correct order.
1435 =item B<find_next_method_by_name ($method_name)>
1437 This will return the first method to match a given C<$method_name> in
1438 the superclasses, this is basically equivalent to calling
1439 C<SUPER::$method_name>, but it can be dispatched at runtime.
1443 =head2 Method Modifiers
1445 Method modifiers are a concept borrowed from CLOS, in which a method
1446 can be wrapped with I<before>, I<after> and I<around> method modifiers
1447 that will be called everytime the method is called.
1449 =head3 How method modifiers work?
1451 Method modifiers work by wrapping the original method and then replacing
1452 it in the classes symbol table. The wrappers will handle calling all the
1453 modifiers in the appropariate orders and preserving the calling context
1454 for the original method.
1456 Each method modifier serves a particular purpose, which may not be
1457 obvious to users of other method wrapping modules. To start with, the
1458 return values of I<before> and I<after> modifiers are ignored. This is
1459 because thier purpose is B<not> to filter the input and output of the
1460 primary method (this is done with an I<around> modifier). This may seem
1461 like an odd restriction to some, but doing this allows for simple code
1462 to be added at the begining or end of a method call without jeapordizing
1463 the normal functioning of the primary method or placing any extra
1464 responsibility on the code of the modifier. Of course if you have more
1465 complex needs, then use the I<around> modifier, which uses a variation
1466 of continutation passing style to allow for a high degree of flexibility.
1468 Before and around modifiers are called in last-defined-first-called order,
1469 while after modifiers are called in first-defined-first-called order. So
1470 the call tree might looks something like this:
1480 To see examples of using method modifiers, see the following examples
1481 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1482 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1483 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1485 =head3 What is the performance impact?
1487 Of course there is a performance cost associated with method modifiers,
1488 but we have made every effort to make that cost be directly proportional
1489 to the amount of modifier features you utilize.
1491 The wrapping method does it's best to B<only> do as much work as it
1492 absolutely needs to. In order to do this we have moved some of the
1493 performance costs to set-up time, where they are easier to amortize.
1495 All this said, my benchmarks have indicated the following:
1497 simple wrapper with no modifiers 100% slower
1498 simple wrapper with simple before modifier 400% slower
1499 simple wrapper with simple after modifier 450% slower
1500 simple wrapper with simple around modifier 500-550% slower
1501 simple wrapper with all 3 modifiers 1100% slower
1503 These numbers may seem daunting, but you must remember, every feature
1504 comes with some cost. To put things in perspective, just doing a simple
1505 C<AUTOLOAD> which does nothing but extract the name of the method called
1506 and return it costs about 400% over a normal method call.
1510 =item B<add_before_method_modifier ($method_name, $code)>
1512 This will wrap the method at C<$method_name> and the supplied C<$code>
1513 will be passed the C<@_> arguments, and called before the original
1514 method is called. As specified above, the return value of the I<before>
1515 method modifiers is ignored, and it's ability to modify C<@_> is
1516 fairly limited. If you need to do either of these things, use an
1517 C<around> method modifier.
1519 =item B<add_after_method_modifier ($method_name, $code)>
1521 This will wrap the method at C<$method_name> so that the original
1522 method will be called, it's return values stashed, and then the
1523 supplied C<$code> will be passed the C<@_> arguments, and called.
1524 As specified above, the return value of the I<after> method
1525 modifiers is ignored, and it cannot modify the return values of
1526 the original method. If you need to do either of these things, use an
1527 C<around> method modifier.
1529 =item B<add_around_method_modifier ($method_name, $code)>
1531 This will wrap the method at C<$method_name> so that C<$code>
1532 will be called and passed the original method as an extra argument
1533 at the begining of the C<@_> argument list. This is a variation of
1534 continuation passing style, where the function prepended to C<@_>
1535 can be considered a continuation. It is up to C<$code> if it calls
1536 the original method or not, there is no restriction on what the
1537 C<$code> can or cannot do.
1543 It should be noted that since there is no one consistent way to define
1544 the attributes of a class in Perl 5. These methods can only work with
1545 the information given, and can not easily discover information on
1546 their own. See L<Class::MOP::Attribute> for more details.
1550 =item B<attribute_metaclass>
1552 Returns the class name of the attribute metaclass, see L<Class::MOP::Attribute>
1553 for more information on the attribute metaclasses.
1555 =item B<get_attribute_map>
1557 This returns a HASH ref of name to attribute meta-object mapping.
1559 =item B<add_attribute ($attribute_meta_object | ($attribute_name, %attribute_spec))>
1561 This stores the C<$attribute_meta_object> (or creates one from the
1562 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1563 instance associated with the given class. Unlike methods, attributes
1564 within the MOP are stored as meta-information only. They will be used
1565 later to construct instances from (see C<construct_instance> above).
1566 More details about the attribute meta-objects can be found in the
1567 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1570 It should be noted that any accessor, reader/writer or predicate
1571 methods which the C<$attribute_meta_object> has will be installed
1572 into the class at this time.
1575 If an attribute already exists for C<$attribute_name>, the old one
1576 will be removed (as well as removing all it's accessors), and then
1579 =item B<has_attribute ($attribute_name)>
1581 Checks to see if this class has an attribute by the name of
1582 C<$attribute_name> and returns a boolean.
1584 =item B<get_attribute ($attribute_name)>
1586 Returns the attribute meta-object associated with C<$attribute_name>,
1587 if none is found, it will return undef.
1589 =item B<remove_attribute ($attribute_name)>
1591 This will remove the attribute meta-object stored at
1592 C<$attribute_name>, then return the removed attribute meta-object.
1595 Removing an attribute will only affect future instances of
1596 the class, it will not make any attempt to remove the attribute from
1597 any existing instances of the class.
1599 It should be noted that any accessor, reader/writer or predicate
1600 methods which the attribute meta-object stored at C<$attribute_name>
1601 has will be removed from the class at this time. This B<will> make
1602 these attributes somewhat inaccessable in previously created
1603 instances. But if you are crazy enough to do this at runtime, then
1604 you are crazy enough to deal with something like this :).
1606 =item B<get_attribute_list>
1608 This returns a list of attribute names which are defined in the local
1609 class. If you want a list of all applicable attributes for a class,
1610 use the C<compute_all_applicable_attributes> method.
1612 =item B<compute_all_applicable_attributes>
1614 This will traverse the inheritance heirachy and return a list of all
1615 the applicable attributes for this class. It does not construct a
1616 HASH reference like C<compute_all_applicable_methods> because all
1617 that same information is discoverable through the attribute
1620 =item B<find_attribute_by_name ($attr_name)>
1622 This method will traverse the inheritance heirachy and find the
1623 first attribute whose name matches C<$attr_name>, then return it.
1624 It will return undef if nothing is found.
1628 =head2 Class Immutability
1632 =item B<make_immutable (%options)>
1634 This method will invoke a tranforamtion upon the class which will
1635 make it immutable. Details of this transformation can be found in
1636 the L<Class::MOP::Immutable> documentation.
1638 =item B<make_mutable>
1640 This method will reverse tranforamtion upon the class which
1643 =item B<get_immutable_transformer>
1645 Return a transformer suitable for making this class immutable or, if this
1646 class is immutable, the transformer used to make it immutable.
1648 =item B<get_immutable_options>
1650 If the class is immutable, return the options used to make it immutable.
1652 =item B<create_immutable_transformer>
1654 Create a transformer suitable for making this class immutable
1660 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1662 =head1 COPYRIGHT AND LICENSE
1664 Copyright 2006-2008 by Infinity Interactive, Inc.
1666 L<http://www.iinteractive.com>
1668 This library is free software; you can redistribute it and/or modify
1669 it under the same terms as Perl itself.