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 = '0.25';
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});
402 @{$self->get_package_symbol('@ISA')} = @supers;
404 # we need to check the metaclass
405 # compatibility here so that we can
406 # be sure that the superclass is
407 # not potentially creating an issues
408 # we don't know about
409 $self->check_metaclass_compatability();
411 @{$self->get_package_symbol('@ISA')};
417 my $super_class = $self->name;
420 my $find_derived_classes;
421 $find_derived_classes = sub {
422 my ($outer_class) = @_;
424 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
427 for my $symbol ( keys %$symbol_table_hashref ) {
428 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
429 my $inner_class = $1;
431 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
435 ? "${outer_class}::$inner_class"
438 if ( $class->isa($super_class) and $class ne $super_class ) {
439 push @derived_classes, $class;
442 next SYMBOL if $class eq 'main'; # skip 'main::*'
444 $find_derived_classes->($class);
448 my $root_class = q{};
449 $find_derived_classes->($root_class);
451 undef $find_derived_classes;
453 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
455 return @derived_classes;
461 grep { !($seen{$_}++) } (shift)->class_precedence_list
464 sub class_precedence_list {
467 # We need to check for circular inheritance here.
468 # This will do nothing if all is well, and blow
469 # up otherwise. Yes, it's an ugly hack, better
470 # suggestions are welcome.
471 { ($self->name || return)->isa('This is a test for circular inheritance') }
476 $self->initialize($_)->class_precedence_list()
477 } $self->superclasses()
484 my ($self, $method_name, $method) = @_;
485 (defined $method_name && $method_name)
486 || confess "You must define a method name";
489 if (blessed($method)) {
490 $body = $method->body;
494 ('CODE' eq (reftype($body) || ''))
495 || confess "Your code block must be a CODE reference";
496 $method = $self->method_metaclass->wrap($body);
498 $self->get_method_map->{$method_name} = $method;
500 my $full_method_name = ($self->name . '::' . $method_name);
501 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
502 $self->update_package_cache_flag;
506 my $fetch_and_prepare_method = sub {
507 my ($self, $method_name) = @_;
509 my $method = $self->get_method($method_name);
510 # if we dont have local ...
512 # try to find the next method
513 $method = $self->find_next_method_by_name($method_name);
514 # die if it does not exist
516 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
517 # and now make sure to wrap it
518 # even if it is already wrapped
519 # because we need a new sub ref
520 $method = Class::MOP::Method::Wrapped->wrap($method);
523 # now make sure we wrap it properly
524 $method = Class::MOP::Method::Wrapped->wrap($method)
525 unless $method->isa('Class::MOP::Method::Wrapped');
527 $self->add_method($method_name => $method);
531 sub add_before_method_modifier {
532 my ($self, $method_name, $method_modifier) = @_;
533 (defined $method_name && $method_name)
534 || confess "You must pass in a method name";
535 my $method = $fetch_and_prepare_method->($self, $method_name);
536 $method->add_before_modifier(subname ':before' => $method_modifier);
539 sub add_after_method_modifier {
540 my ($self, $method_name, $method_modifier) = @_;
541 (defined $method_name && $method_name)
542 || confess "You must pass in a method name";
543 my $method = $fetch_and_prepare_method->($self, $method_name);
544 $method->add_after_modifier(subname ':after' => $method_modifier);
547 sub add_around_method_modifier {
548 my ($self, $method_name, $method_modifier) = @_;
549 (defined $method_name && $method_name)
550 || confess "You must pass in a method name";
551 my $method = $fetch_and_prepare_method->($self, $method_name);
552 $method->add_around_modifier(subname ':around' => $method_modifier);
556 # the methods above used to be named like this:
557 # ${pkg}::${method}:(before|after|around)
558 # but this proved problematic when using one modifier
559 # to wrap multiple methods (something which is likely
560 # to happen pretty regularly IMO). So instead of naming
561 # it like this, I have chosen to just name them purely
562 # with their modifier names, like so:
563 # :(before|after|around)
564 # The fact is that in a stack trace, it will be fairly
565 # evident from the context what method they are attached
566 # to, and so don't need the fully qualified name.
570 my ($self, $method_name, $method) = @_;
571 (defined $method_name && $method_name)
572 || confess "You must define a method name";
574 my $body = (blessed($method) ? $method->body : $method);
575 ('CODE' eq (reftype($body) || ''))
576 || confess "Your code block must be a CODE reference";
578 $self->add_package_symbol("&${method_name}" => $body);
579 $self->update_package_cache_flag;
583 my ($self, $method_name) = @_;
584 (defined $method_name && $method_name)
585 || confess "You must define a method name";
587 return 0 unless exists $self->get_method_map->{$method_name};
592 my ($self, $method_name) = @_;
593 (defined $method_name && $method_name)
594 || confess "You must define a method name";
597 # I don't really need this here, because
598 # if the method_map is missing a key it
599 # will just return undef for me now
600 # return unless $self->has_method($method_name);
602 return $self->get_method_map->{$method_name};
606 my ($self, $method_name) = @_;
607 (defined $method_name && $method_name)
608 || confess "You must define a method name";
610 my $removed_method = delete $self->get_method_map->{$method_name};
612 $self->remove_package_symbol("&${method_name}");
614 $self->update_package_cache_flag;
616 return $removed_method;
619 sub get_method_list {
621 keys %{$self->get_method_map};
624 sub find_method_by_name {
625 my ($self, $method_name) = @_;
626 (defined $method_name && $method_name)
627 || confess "You must define a method name to find";
628 foreach my $class ($self->linearized_isa) {
629 # fetch the meta-class ...
630 my $meta = $self->initialize($class);
631 return $meta->get_method($method_name)
632 if $meta->has_method($method_name);
637 sub compute_all_applicable_methods {
639 my (@methods, %seen_method);
640 foreach my $class ($self->linearized_isa) {
641 # fetch the meta-class ...
642 my $meta = $self->initialize($class);
643 foreach my $method_name ($meta->get_method_list()) {
644 next if exists $seen_method{$method_name};
645 $seen_method{$method_name}++;
647 name => $method_name,
649 code => $meta->get_method($method_name)
656 sub find_all_methods_by_name {
657 my ($self, $method_name) = @_;
658 (defined $method_name && $method_name)
659 || confess "You must define a method name to find";
661 foreach my $class ($self->linearized_isa) {
662 # fetch the meta-class ...
663 my $meta = $self->initialize($class);
665 name => $method_name,
667 code => $meta->get_method($method_name)
668 } if $meta->has_method($method_name);
673 sub find_next_method_by_name {
674 my ($self, $method_name) = @_;
675 (defined $method_name && $method_name)
676 || confess "You must define a method name to find";
677 my @cpl = $self->linearized_isa;
678 shift @cpl; # discard ourselves
679 foreach my $class (@cpl) {
680 # fetch the meta-class ...
681 my $meta = $self->initialize($class);
682 return $meta->get_method($method_name)
683 if $meta->has_method($method_name);
692 # either we have an attribute object already
693 # or we need to create one from the args provided
694 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
695 # make sure it is derived from the correct type though
696 ($attribute->isa('Class::MOP::Attribute'))
697 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
699 # first we attach our new attribute
700 # because it might need certain information
701 # about the class which it is attached to
702 $attribute->attach_to_class($self);
704 # then we remove attributes of a conflicting
705 # name here so that we can properly detach
706 # the old attr object, and remove any
707 # accessors it would have generated
708 $self->remove_attribute($attribute->name)
709 if $self->has_attribute($attribute->name);
711 # then onto installing the new accessors
712 $attribute->install_accessors();
713 $self->get_attribute_map->{$attribute->name} = $attribute;
717 my ($self, $attribute_name) = @_;
718 (defined $attribute_name && $attribute_name)
719 || confess "You must define an attribute name";
720 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
724 my ($self, $attribute_name) = @_;
725 (defined $attribute_name && $attribute_name)
726 || confess "You must define an attribute name";
727 return $self->get_attribute_map->{$attribute_name}
729 # this will return undef anyway, so no need ...
730 # if $self->has_attribute($attribute_name);
734 sub remove_attribute {
735 my ($self, $attribute_name) = @_;
736 (defined $attribute_name && $attribute_name)
737 || confess "You must define an attribute name";
738 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
739 return unless defined $removed_attribute;
740 delete $self->get_attribute_map->{$attribute_name};
741 $removed_attribute->remove_accessors();
742 $removed_attribute->detach_from_class();
743 return $removed_attribute;
746 sub get_attribute_list {
748 keys %{$self->get_attribute_map};
751 sub compute_all_applicable_attributes {
753 my (@attrs, %seen_attr);
754 foreach my $class ($self->linearized_isa) {
755 # fetch the meta-class ...
756 my $meta = $self->initialize($class);
757 foreach my $attr_name ($meta->get_attribute_list()) {
758 next if exists $seen_attr{$attr_name};
759 $seen_attr{$attr_name}++;
760 push @attrs => $meta->get_attribute($attr_name);
766 sub find_attribute_by_name {
767 my ($self, $attr_name) = @_;
768 foreach my $class ($self->linearized_isa) {
769 # fetch the meta-class ...
770 my $meta = $self->initialize($class);
771 return $meta->get_attribute($attr_name)
772 if $meta->has_attribute($attr_name);
780 sub is_immutable { 0 }
783 # Why I changed this (groditi)
784 # - One Metaclass may have many Classes through many Metaclass instances
785 # - One Metaclass should only have one Immutable Transformer instance
786 # - Each Class may have different Immutabilizing options
787 # - Therefore each Metaclass instance may have different Immutabilizing options
788 # - We need to store one Immutable Transformer instance per Metaclass
789 # - We need to store one set of Immutable Transformer options per Class
790 # - Upon make_mutable we may delete the Immutabilizing options
791 # - We could clean the immutable Transformer instance when there is no more
792 # immutable Classes of that type, but we can also keep it in case
793 # another class with this same Metaclass becomes immutable. It is a case
794 # of trading of storing an instance to avoid unnecessary instantiations of
795 # Immutable Transformers. You may view this as a memory leak, however
796 # Because we have few Metaclasses, in practice it seems acceptable
797 # - To allow Immutable Transformers instances to be cleaned up we could weaken
798 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
801 my %IMMUTABLE_TRANSFORMERS;
802 my %IMMUTABLE_OPTIONS;
806 my $class = blessed $self || $self;
808 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
809 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
811 $transformer->make_metaclass_immutable($self, %options);
812 $IMMUTABLE_OPTIONS{$self->name} =
813 { %options, IMMUTABLE_TRANSFORMER => $transformer };
815 if( exists $options{debug} && $options{debug} ){
816 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
817 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
823 return if $self->is_mutable;
824 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
825 confess "unable to find immutabilizing options" unless ref $options;
826 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
827 $transformer->make_metaclass_mutable($self, %$options);
831 sub create_immutable_transformer {
833 my $class = Class::MOP::Immutable->new($self, {
834 read_only => [qw/superclasses/],
842 remove_package_symbol
845 class_precedence_list => 'ARRAY',
846 linearized_isa => 'ARRAY',
847 compute_all_applicable_attributes => 'ARRAY',
848 get_meta_instance => 'SCALAR',
849 get_method_map => 'SCALAR',
863 Class::MOP::Class - Class Meta Object
867 # assuming that class Foo
868 # has been defined, you can
870 # use this for introspection ...
872 # add a method to Foo ...
873 Foo->meta->add_method('bar' => sub { ... })
875 # get a list of all the classes searched
876 # the method dispatcher in the correct order
877 Foo->meta->class_precedence_list()
879 # remove a method from Foo
880 Foo->meta->remove_method('bar');
882 # or use this to actually create classes ...
884 Class::MOP::Class->create('Bar' => (
886 superclasses => [ 'Foo' ],
888 Class::MOP:::Attribute->new('$bar'),
889 Class::MOP:::Attribute->new('$baz'),
892 calculate_bar => sub { ... },
893 construct_baz => sub { ... }
899 This is the largest and currently most complex part of the Perl 5
900 meta-object protocol. It controls the introspection and
901 manipulation of Perl 5 classes (and it can create them too). The
902 best way to understand what this module can do, is to read the
903 documentation for each of it's methods.
907 =head2 Self Introspection
913 This will return a B<Class::MOP::Class> instance which is related
914 to this class. Thereby allowing B<Class::MOP::Class> to actually
917 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
918 bootstrap this module by installing a number of attribute meta-objects
919 into it's metaclass. This will allow this class to reap all the benifits
920 of the MOP when subclassing it.
924 =head2 Class construction
926 These methods will handle creating B<Class::MOP::Class> objects,
927 which can be used to both create new classes, and analyze
928 pre-existing classes.
930 This module will internally store references to all the instances
931 you create with these methods, so that they do not need to be
932 created any more than nessecary. Basically, they are singletons.
936 =item B<create ($package_name,
937 version =E<gt> ?$version,
938 authority =E<gt> ?$authority,
939 superclasses =E<gt> ?@superclasses,
940 methods =E<gt> ?%methods,
941 attributes =E<gt> ?%attributes)>
943 This returns a B<Class::MOP::Class> object, bringing the specified
944 C<$package_name> into existence and adding any of the C<$version>,
945 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
948 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
949 methods =E<gt> ?%methods,
950 attributes =E<gt> ?%attributes)>
952 This will create an anonymous class, it works much like C<create> but
953 it does not need a C<$package_name>. Instead it will create a suitably
954 unique package name for you to stash things into.
956 On very important distinction is that anon classes are destroyed once
957 the metaclass they are attached to goes out of scope. In the DESTROY
958 method, the created package will be removed from the symbol table.
960 It is also worth noting that any instances created with an anon-class
961 will keep a special reference to the anon-meta which will prevent the
962 anon-class from going out of scope until all instances of it have also
963 been destroyed. This however only works for HASH based instance types,
964 as we use a special reserved slot (C<__MOP__>) to store this.
966 =item B<initialize ($package_name, %options)>
968 This initializes and returns returns a B<Class::MOP::Class> object
969 for a given a C<$package_name>.
971 =item B<reinitialize ($package_name, %options)>
973 This removes the old metaclass, and creates a new one in it's place.
974 Do B<not> use this unless you really know what you are doing, it could
975 very easily make a very large mess of your program.
977 =item B<construct_class_instance (%options)>
979 This will construct an instance of B<Class::MOP::Class>, it is
980 here so that we can actually "tie the knot" for B<Class::MOP::Class>
981 to use C<construct_instance> once all the bootstrapping is done. This
982 method is used internally by C<initialize> and should never be called
983 from outside of that method really.
985 =item B<check_metaclass_compatability>
987 This method is called as the very last thing in the
988 C<construct_class_instance> method. This will check that the
989 metaclass you are creating is compatible with the metaclasses of all
990 your ancestors. For more inforamtion about metaclass compatibility
991 see the C<About Metaclass compatibility> section in L<Class::MOP>.
993 =item B<update_package_cache_flag>
995 This will reset the package cache flag for this particular metaclass
996 it is basically the value of the C<Class::MOP::get_package_cache_flag>
997 function. This is very rarely needed from outside of C<Class::MOP::Class>
998 but in some cases you might want to use it, so it is here.
1000 =item B<reset_package_cache_flag>
1002 Clear this flag, used in Moose.
1006 =head2 Object instance construction and cloning
1008 These methods are B<entirely optional>, it is up to you whether you want
1013 =item B<instance_metaclass>
1015 =item B<get_meta_instance>
1017 =item B<new_object (%params)>
1019 This is a convience method for creating a new object of the class, and
1020 blessing it into the appropriate package as well. Ideally your class
1021 would call a C<new> this method like so:
1024 my ($class, %param) = @_;
1025 $class->meta->new_object(%params);
1028 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1029 but that is considered bad style, so we do not do that.
1031 =item B<construct_instance (%params)>
1033 This method is used to construct an instace structure suitable for
1034 C<bless>-ing into your package of choice. It works in conjunction
1035 with the Attribute protocol to collect all applicable attributes.
1037 This will construct and instance using a HASH ref as storage
1038 (currently only HASH references are supported). This will collect all
1039 the applicable attributes and layout out the fields in the HASH ref,
1040 it will then initialize them using either use the corresponding key
1041 in C<%params> or any default value or initializer found in the
1042 attribute meta-object.
1044 =item B<clone_object ($instance, %params)>
1046 This is a convience method for cloning an object instance, then
1047 blessing it into the appropriate package. This method will call
1048 C<clone_instance>, which performs a shallow copy of the object,
1049 see that methods documentation for more details. Ideally your
1050 class would call a C<clone> this method like so:
1052 sub MyClass::clone {
1053 my ($self, %param) = @_;
1054 $self->meta->clone_object($self, %params);
1057 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1058 but that is considered bad style, so we do not do that.
1060 =item B<clone_instance($instance, %params)>
1062 This method is a compliment of C<construct_instance> (which means if
1063 you override C<construct_instance>, you need to override this one too),
1064 and clones the instance shallowly.
1066 The cloned structure returned is (like with C<construct_instance>) an
1067 unC<bless>ed HASH reference, it is your responsibility to then bless
1068 this cloned structure into the right class (which C<clone_object> will
1071 As of 0.11, this method will clone the C<$instance> structure shallowly,
1072 as opposed to the deep cloning implemented in prior versions. After much
1073 thought, research and discussion, I have decided that anything but basic
1074 shallow cloning is outside the scope of the meta-object protocol. I
1075 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1076 is too I<context-specific> to be part of the MOP.
1080 =head2 Informational
1082 These are a few predicate methods for asking information about the class.
1086 =item B<is_anon_class>
1088 This returns true if the class is a C<Class::MOP::Class> created anon class.
1092 This returns true if the class is still mutable.
1094 =item B<is_immutable>
1096 This returns true if the class has been made immutable.
1100 =head2 Inheritance Relationships
1104 =item B<superclasses (?@superclasses)>
1106 This is a read-write attribute which represents the superclass
1107 relationships of the class the B<Class::MOP::Class> instance is
1108 associated with. Basically, it can get and set the C<@ISA> for you.
1111 Perl will occasionally perform some C<@ISA> and method caching, if
1112 you decide to change your superclass relationship at runtime (which
1113 is quite insane and very much not recommened), then you should be
1114 aware of this and the fact that this module does not make any
1115 attempt to address this issue.
1117 =item B<class_precedence_list>
1119 This computes the a list of all the class's ancestors in the same order
1120 in which method dispatch will be done. This is similair to
1121 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
1123 =item B<linearized_isa>
1125 This returns a list based on C<class_precedence_list> but with all
1130 This returns a list of subclasses for this class.
1138 =item B<get_method_map>
1140 =item B<method_metaclass>
1142 =item B<add_method ($method_name, $method)>
1144 This will take a C<$method_name> and CODE reference to that
1145 C<$method> and install it into the class's package.
1148 This does absolutely nothing special to C<$method>
1149 other than use B<Sub::Name> to make sure it is tagged with the
1150 correct name, and therefore show up correctly in stack traces and
1153 =item B<alias_method ($method_name, $method)>
1155 This will take a C<$method_name> and CODE reference to that
1156 C<$method> and alias the method into the class's package.
1159 Unlike C<add_method>, this will B<not> try to name the
1160 C<$method> using B<Sub::Name>, it only aliases the method in
1161 the class's package.
1163 =item B<has_method ($method_name)>
1165 This just provides a simple way to check if the class implements
1166 a specific C<$method_name>. It will I<not> however, attempt to check
1167 if the class inherits the method (use C<UNIVERSAL::can> for that).
1169 This will correctly handle functions defined outside of the package
1170 that use a fully qualified name (C<sub Package::name { ... }>).
1172 This will correctly handle functions renamed with B<Sub::Name> and
1173 installed using the symbol tables. However, if you are naming the
1174 subroutine outside of the package scope, you must use the fully
1175 qualified name, including the package name, for C<has_method> to
1176 correctly identify it.
1178 This will attempt to correctly ignore functions imported from other
1179 packages using B<Exporter>. It breaks down if the function imported
1180 is an C<__ANON__> sub (such as with C<use constant>), which very well
1181 may be a valid method being applied to the class.
1183 In short, this method cannot always be trusted to determine if the
1184 C<$method_name> is actually a method. However, it will DWIM about
1185 90% of the time, so it's a small trade off I think.
1187 =item B<get_method ($method_name)>
1189 This will return a Class::MOP::Method instance related to the specified
1190 C<$method_name>, or return undef if that method does not exist.
1192 The Class::MOP::Method is codifiable, so you can use it like a normal
1193 CODE reference, see L<Class::MOP::Method> for more information.
1195 =item B<find_method_by_name ($method_name>
1197 This will return a CODE reference of the specified C<$method_name>,
1198 or return undef if that method does not exist.
1200 Unlike C<get_method> this will also look in the superclasses.
1202 =item B<remove_method ($method_name)>
1204 This will attempt to remove a given C<$method_name> from the class.
1205 It will return the CODE reference that it has removed, and will
1206 attempt to use B<Sub::Name> to clear the methods associated name.
1208 =item B<get_method_list>
1210 This will return a list of method names for all I<locally> defined
1211 methods. It does B<not> provide a list of all applicable methods,
1212 including any inherited ones. If you want a list of all applicable
1213 methods, use the C<compute_all_applicable_methods> method.
1215 =item B<compute_all_applicable_methods>
1217 This will return a list of all the methods names this class will
1218 respond to, taking into account inheritance. The list will be a list of
1219 HASH references, each one containing the following information; method
1220 name, the name of the class in which the method lives and a CODE
1221 reference for the actual method.
1223 =item B<find_all_methods_by_name ($method_name)>
1225 This will traverse the inheritence hierarchy and locate all methods
1226 with a given C<$method_name>. Similar to
1227 C<compute_all_applicable_methods> it returns a list of HASH references
1228 with the following information; method name (which will always be the
1229 same as C<$method_name>), the name of the class in which the method
1230 lives and a CODE reference for the actual method.
1232 The list of methods produced is a distinct list, meaning there are no
1233 duplicates in it. This is especially useful for things like object
1234 initialization and destruction where you only want the method called
1235 once, and in the correct order.
1237 =item B<find_next_method_by_name ($method_name)>
1239 This will return the first method to match a given C<$method_name> in
1240 the superclasses, this is basically equivalent to calling
1241 C<SUPER::$method_name>, but it can be dispatched at runtime.
1245 =head2 Method Modifiers
1247 Method modifiers are a concept borrowed from CLOS, in which a method
1248 can be wrapped with I<before>, I<after> and I<around> method modifiers
1249 that will be called everytime the method is called.
1251 =head3 How method modifiers work?
1253 Method modifiers work by wrapping the original method and then replacing
1254 it in the classes symbol table. The wrappers will handle calling all the
1255 modifiers in the appropariate orders and preserving the calling context
1256 for the original method.
1258 Each method modifier serves a particular purpose, which may not be
1259 obvious to users of other method wrapping modules. To start with, the
1260 return values of I<before> and I<after> modifiers are ignored. This is
1261 because thier purpose is B<not> to filter the input and output of the
1262 primary method (this is done with an I<around> modifier). This may seem
1263 like an odd restriction to some, but doing this allows for simple code
1264 to be added at the begining or end of a method call without jeapordizing
1265 the normal functioning of the primary method or placing any extra
1266 responsibility on the code of the modifier. Of course if you have more
1267 complex needs, then use the I<around> modifier, which uses a variation
1268 of continutation passing style to allow for a high degree of flexibility.
1270 Before and around modifiers are called in last-defined-first-called order,
1271 while after modifiers are called in first-defined-first-called order. So
1272 the call tree might looks something like this:
1282 To see examples of using method modifiers, see the following examples
1283 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1284 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1285 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1287 =head3 What is the performance impact?
1289 Of course there is a performance cost associated with method modifiers,
1290 but we have made every effort to make that cost be directly proportional
1291 to the amount of modifier features you utilize.
1293 The wrapping method does it's best to B<only> do as much work as it
1294 absolutely needs to. In order to do this we have moved some of the
1295 performance costs to set-up time, where they are easier to amortize.
1297 All this said, my benchmarks have indicated the following:
1299 simple wrapper with no modifiers 100% slower
1300 simple wrapper with simple before modifier 400% slower
1301 simple wrapper with simple after modifier 450% slower
1302 simple wrapper with simple around modifier 500-550% slower
1303 simple wrapper with all 3 modifiers 1100% slower
1305 These numbers may seem daunting, but you must remember, every feature
1306 comes with some cost. To put things in perspective, just doing a simple
1307 C<AUTOLOAD> which does nothing but extract the name of the method called
1308 and return it costs about 400% over a normal method call.
1312 =item B<add_before_method_modifier ($method_name, $code)>
1314 This will wrap the method at C<$method_name> and the supplied C<$code>
1315 will be passed the C<@_> arguments, and called before the original
1316 method is called. As specified above, the return value of the I<before>
1317 method modifiers is ignored, and it's ability to modify C<@_> is
1318 fairly limited. If you need to do either of these things, use an
1319 C<around> method modifier.
1321 =item B<add_after_method_modifier ($method_name, $code)>
1323 This will wrap the method at C<$method_name> so that the original
1324 method will be called, it's return values stashed, and then the
1325 supplied C<$code> will be passed the C<@_> arguments, and called.
1326 As specified above, the return value of the I<after> method
1327 modifiers is ignored, and it cannot modify the return values of
1328 the original method. If you need to do either of these things, use an
1329 C<around> method modifier.
1331 =item B<add_around_method_modifier ($method_name, $code)>
1333 This will wrap the method at C<$method_name> so that C<$code>
1334 will be called and passed the original method as an extra argument
1335 at the begining of the C<@_> argument list. This is a variation of
1336 continuation passing style, where the function prepended to C<@_>
1337 can be considered a continuation. It is up to C<$code> if it calls
1338 the original method or not, there is no restriction on what the
1339 C<$code> can or cannot do.
1345 It should be noted that since there is no one consistent way to define
1346 the attributes of a class in Perl 5. These methods can only work with
1347 the information given, and can not easily discover information on
1348 their own. See L<Class::MOP::Attribute> for more details.
1352 =item B<attribute_metaclass>
1354 =item B<get_attribute_map>
1356 =item B<add_attribute ($attribute_meta_object | $attribute_name, %attribute_spec)>
1358 This stores the C<$attribute_meta_object> (or creates one from the
1359 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1360 instance associated with the given class. Unlike methods, attributes
1361 within the MOP are stored as meta-information only. They will be used
1362 later to construct instances from (see C<construct_instance> above).
1363 More details about the attribute meta-objects can be found in the
1364 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1367 It should be noted that any accessor, reader/writer or predicate
1368 methods which the C<$attribute_meta_object> has will be installed
1369 into the class at this time.
1372 If an attribute already exists for C<$attribute_name>, the old one
1373 will be removed (as well as removing all it's accessors), and then
1376 =item B<has_attribute ($attribute_name)>
1378 Checks to see if this class has an attribute by the name of
1379 C<$attribute_name> and returns a boolean.
1381 =item B<get_attribute ($attribute_name)>
1383 Returns the attribute meta-object associated with C<$attribute_name>,
1384 if none is found, it will return undef.
1386 =item B<remove_attribute ($attribute_name)>
1388 This will remove the attribute meta-object stored at
1389 C<$attribute_name>, then return the removed attribute meta-object.
1392 Removing an attribute will only affect future instances of
1393 the class, it will not make any attempt to remove the attribute from
1394 any existing instances of the class.
1396 It should be noted that any accessor, reader/writer or predicate
1397 methods which the attribute meta-object stored at C<$attribute_name>
1398 has will be removed from the class at this time. This B<will> make
1399 these attributes somewhat inaccessable in previously created
1400 instances. But if you are crazy enough to do this at runtime, then
1401 you are crazy enough to deal with something like this :).
1403 =item B<get_attribute_list>
1405 This returns a list of attribute names which are defined in the local
1406 class. If you want a list of all applicable attributes for a class,
1407 use the C<compute_all_applicable_attributes> method.
1409 =item B<compute_all_applicable_attributes>
1411 This will traverse the inheritance heirachy and return a list of all
1412 the applicable attributes for this class. It does not construct a
1413 HASH reference like C<compute_all_applicable_methods> because all
1414 that same information is discoverable through the attribute
1417 =item B<find_attribute_by_name ($attr_name)>
1419 This method will traverse the inheritance heirachy and find the
1420 first attribute whose name matches C<$attr_name>, then return it.
1421 It will return undef if nothing is found.
1425 =head2 Class Immutability
1429 =item B<make_immutable (%options)>
1431 This method will invoke a tranforamtion upon the class which will
1432 make it immutable. Details of this transformation can be found in
1433 the L<Class::MOP::Immutable> documentation.
1435 =item B<make_mutable>
1437 This method will reverse tranforamtion upon the class which
1440 =item B<create_immutable_transformer>
1442 Create a transformer suitable for making this class immutable
1448 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1450 =head1 COPYRIGHT AND LICENSE
1452 Copyright 2006, 2007 by Infinity Interactive, Inc.
1454 L<http://www.iinteractive.com>
1456 This library is free software; you can redistribute it and/or modify
1457 it under the same terms as Perl itself.