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 # initialize some stuff
128 $meta->get_method_map;
129 $meta->reset_package_cache_flag;
131 Class::MOP::store_metaclass_by_name($package_name, $meta);
134 # we need to weaken any anon classes
135 # so that they can call DESTROY properly
136 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
141 sub reset_package_cache_flag {
143 # we can manually update the cache number
144 # since we are actually adding the method
145 # to our cache as well. This avoids us
146 # having to regenerate the method_map.
148 (shift)->{'$!_package_cache_flag'} = Class::MOP::check_package_cache_flag();
151 sub check_metaclass_compatability {
154 # this is always okay ...
155 return if blessed($self) eq 'Class::MOP::Class' &&
156 $self->instance_metaclass eq 'Class::MOP::Instance';
158 my @class_list = $self->linearized_isa;
159 shift @class_list; # shift off $self->name
161 foreach my $class_name (@class_list) {
162 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
165 # we need to deal with the possibility
166 # of class immutability here, and then
167 # get the name of the class appropriately
168 my $meta_type = ($meta->is_immutable
169 ? $meta->get_mutable_metaclass_name()
172 ($self->isa($meta_type))
173 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
174 " is not compatible with the " .
175 $class_name . "->meta => (" . ($meta_type) . ")";
177 # we also need to check that instance metaclasses
178 # are compatabile in the same the class.
179 ($self->instance_metaclass->isa($meta->instance_metaclass))
180 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
181 " is not compatible with the " .
182 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
190 # this should be sufficient, if you have a
191 # use case where it is not, write a test and
193 my $ANON_CLASS_SERIAL = 0;
196 # we need a sufficiently annoying prefix
197 # this should suffice for now, this is
198 # used in a couple of places below, so
199 # need to put it up here for now.
200 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
204 no warnings 'uninitialized';
205 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
208 sub create_anon_class {
209 my ($class, %options) = @_;
210 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
211 return $class->create($package_name, %options);
215 # this will only get called for
216 # anon-classes, all other calls
217 # are assumed to occur during
218 # global destruction and so don't
219 # really need to be handled explicitly
222 no warnings 'uninitialized';
223 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
224 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
226 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
227 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
229 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
234 # creating classes with MOP ...
238 my $package_name = shift;
240 (defined $package_name && $package_name)
241 || confess "You must pass a package name";
244 || confess "You much pass all parameters as name => value pairs " .
245 "(I found an uneven number of params in \@_)";
249 my $code = "package $package_name;";
250 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
251 if exists $options{version};
252 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
253 if exists $options{authority};
256 confess "creation of $package_name failed : $@" if $@;
258 my $meta = $class->initialize($package_name);
260 $meta->add_method('meta' => sub {
261 $class->initialize(blessed($_[0]) || $_[0]);
264 $meta->superclasses(@{$options{superclasses}})
265 if exists $options{superclasses};
267 # process attributes first, so that they can
268 # install accessors, but locally defined methods
269 # can then overwrite them. It is maybe a little odd, but
270 # I think this should be the order of things.
271 if (exists $options{attributes}) {
272 foreach my $attr (@{$options{attributes}}) {
273 $meta->add_attribute($attr);
276 if (exists $options{methods}) {
277 foreach my $method_name (keys %{$options{methods}}) {
278 $meta->add_method($method_name, $options{methods}->{$method_name});
287 # all these attribute readers will be bootstrapped
288 # away in the Class::MOP bootstrap section
290 sub get_attribute_map { $_[0]->{'%!attributes'} }
291 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
292 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
293 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
296 # this is a prime canidate for conversion to XS
300 if (defined $self->{'$!_package_cache_flag'} &&
301 $self->{'$!_package_cache_flag'} == Class::MOP::check_package_cache_flag()) {
302 return $self->{'%!methods'};
305 my $map = $self->{'%!methods'};
307 my $class_name = $self->name;
308 my $method_metaclass = $self->method_metaclass;
310 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
311 my $code = $self->get_package_symbol('&' . $symbol);
313 next if exists $map->{$symbol} &&
314 defined $map->{$symbol} &&
315 $map->{$symbol}->body == $code;
317 my ($pkg, $name) = Class::MOP::get_code_info($code);
318 next if ($pkg || '') ne $class_name &&
319 ($name || '') ne '__ANON__';
321 $map->{$symbol} = $method_metaclass->wrap($code);
327 # Instance Construction & Cloning
332 # we need to protect the integrity of the
333 # Class::MOP::Class singletons here, so we
334 # delegate this to &construct_class_instance
335 # which will deal with the singletons
336 return $class->construct_class_instance(@_)
337 if $class->name->isa('Class::MOP::Class');
338 return $class->construct_instance(@_);
341 sub construct_instance {
342 my ($class, %params) = @_;
343 my $meta_instance = $class->get_meta_instance();
344 my $instance = $meta_instance->create_instance();
345 foreach my $attr ($class->compute_all_applicable_attributes()) {
346 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
349 # this will only work for a HASH instance type
350 if ($class->is_anon_class) {
351 (reftype($instance) eq 'HASH')
352 || confess "Currently only HASH based instances are supported with instance of anon-classes";
354 # At some point we should make this official
355 # as a reserved slot name, but right now I am
356 # going to keep it here.
357 # my $RESERVED_MOP_SLOT = '__MOP__';
358 $instance->{'__MOP__'} = $class;
363 sub get_meta_instance {
365 return $class->instance_metaclass->new(
367 $class->compute_all_applicable_attributes()
373 my $instance = shift;
374 (blessed($instance) && $instance->isa($class->name))
375 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
377 # we need to protect the integrity of the
378 # Class::MOP::Class singletons here, they
379 # should not be cloned.
380 return $instance if $instance->isa('Class::MOP::Class');
381 $class->clone_instance($instance, @_);
385 my ($class, $instance, %params) = @_;
387 || confess "You can only clone instances, \$self is not a blessed instance";
388 my $meta_instance = $class->get_meta_instance();
389 my $clone = $meta_instance->clone_instance($instance);
390 foreach my $attr ($class->compute_all_applicable_attributes()) {
391 if (exists $params{$attr->init_arg}) {
392 $meta_instance->set_slot_value($clone, $attr->name, $params{$attr->init_arg});
404 @{$self->get_package_symbol('@ISA')} = @supers;
406 # we need to check the metaclass
407 # compatibility here so that we can
408 # be sure that the superclass is
409 # not potentially creating an issues
410 # we don't know about
411 $self->check_metaclass_compatability();
413 @{$self->get_package_symbol('@ISA')};
419 my $super_class = $self->name;
422 my $find_derived_classes;
423 $find_derived_classes = sub {
424 my ($outer_class) = @_;
426 my $symbol_table_hashref = do { no strict 'refs'; \%{"${outer_class}::"} };
429 for my $symbol ( keys %$symbol_table_hashref ) {
430 next SYMBOL if $symbol !~ /\A (\w+):: \z/x;
431 my $inner_class = $1;
433 next SYMBOL if $inner_class eq 'SUPER'; # skip '*::SUPER'
437 ? "${outer_class}::$inner_class"
440 if ( $class->isa($super_class) and $class ne $super_class ) {
441 push @derived_classes, $class;
444 next SYMBOL if $class eq 'main'; # skip 'main::*'
446 $find_derived_classes->($class);
450 my $root_class = q{};
451 $find_derived_classes->($root_class);
453 undef $find_derived_classes;
455 @derived_classes = sort { $a->isa($b) ? 1 : $b->isa($a) ? -1 : 0 } @derived_classes;
457 return @derived_classes;
463 grep { !($seen{$_}++) } (shift)->class_precedence_list
466 sub class_precedence_list {
469 # We need to check for circular inheritance here.
470 # This will do nothing if all is well, and blow
471 # up otherwise. Yes, it's an ugly hack, better
472 # suggestions are welcome.
473 { ($self->name || return)->isa('This is a test for circular inheritance') }
478 $self->initialize($_)->class_precedence_list()
479 } $self->superclasses()
486 my ($self, $method_name, $method) = @_;
487 (defined $method_name && $method_name)
488 || confess "You must define a method name";
491 if (blessed($method)) {
492 $body = $method->body;
496 ('CODE' eq (reftype($body) || ''))
497 || confess "Your code block must be a CODE reference";
498 $method = $self->method_metaclass->wrap($body);
500 $self->get_method_map->{$method_name} = $method;
502 my $full_method_name = ($self->name . '::' . $method_name);
503 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
504 $self->reset_package_cache_flag;
508 my $fetch_and_prepare_method = sub {
509 my ($self, $method_name) = @_;
511 my $method = $self->get_method($method_name);
512 # if we dont have local ...
514 # try to find the next method
515 $method = $self->find_next_method_by_name($method_name);
516 # die if it does not exist
518 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
519 # and now make sure to wrap it
520 # even if it is already wrapped
521 # because we need a new sub ref
522 $method = Class::MOP::Method::Wrapped->wrap($method);
525 # now make sure we wrap it properly
526 $method = Class::MOP::Method::Wrapped->wrap($method)
527 unless $method->isa('Class::MOP::Method::Wrapped');
529 $self->add_method($method_name => $method);
533 sub add_before_method_modifier {
534 my ($self, $method_name, $method_modifier) = @_;
535 (defined $method_name && $method_name)
536 || confess "You must pass in a method name";
537 my $method = $fetch_and_prepare_method->($self, $method_name);
538 $method->add_before_modifier(subname ':before' => $method_modifier);
541 sub add_after_method_modifier {
542 my ($self, $method_name, $method_modifier) = @_;
543 (defined $method_name && $method_name)
544 || confess "You must pass in a method name";
545 my $method = $fetch_and_prepare_method->($self, $method_name);
546 $method->add_after_modifier(subname ':after' => $method_modifier);
549 sub add_around_method_modifier {
550 my ($self, $method_name, $method_modifier) = @_;
551 (defined $method_name && $method_name)
552 || confess "You must pass in a method name";
553 my $method = $fetch_and_prepare_method->($self, $method_name);
554 $method->add_around_modifier(subname ':around' => $method_modifier);
558 # the methods above used to be named like this:
559 # ${pkg}::${method}:(before|after|around)
560 # but this proved problematic when using one modifier
561 # to wrap multiple methods (something which is likely
562 # to happen pretty regularly IMO). So instead of naming
563 # it like this, I have chosen to just name them purely
564 # with their modifier names, like so:
565 # :(before|after|around)
566 # The fact is that in a stack trace, it will be fairly
567 # evident from the context what method they are attached
568 # to, and so don't need the fully qualified name.
572 my ($self, $method_name, $method) = @_;
573 (defined $method_name && $method_name)
574 || confess "You must define a method name";
576 my $body = (blessed($method) ? $method->body : $method);
577 ('CODE' eq (reftype($body) || ''))
578 || confess "Your code block must be a CODE reference";
580 $self->add_package_symbol("&${method_name}" => $body);
581 $self->reset_package_cache_flag;
585 my ($self, $method_name) = @_;
586 (defined $method_name && $method_name)
587 || confess "You must define a method name";
589 return 0 unless exists $self->get_method_map->{$method_name};
594 my ($self, $method_name) = @_;
595 (defined $method_name && $method_name)
596 || confess "You must define a method name";
599 # I don't really need this here, because
600 # if the method_map is missing a key it
601 # will just return undef for me now
602 # return unless $self->has_method($method_name);
604 return $self->get_method_map->{$method_name};
608 my ($self, $method_name) = @_;
609 (defined $method_name && $method_name)
610 || confess "You must define a method name";
612 my $removed_method = delete $self->get_method_map->{$method_name};
614 $self->remove_package_symbol("&${method_name}");
616 $self->reset_package_cache_flag;
618 return $removed_method;
621 sub get_method_list {
623 keys %{$self->get_method_map};
626 sub find_method_by_name {
627 my ($self, $method_name) = @_;
628 (defined $method_name && $method_name)
629 || confess "You must define a method name to find";
630 foreach my $class ($self->linearized_isa) {
631 # fetch the meta-class ...
632 my $meta = $self->initialize($class);
633 return $meta->get_method($method_name)
634 if $meta->has_method($method_name);
639 sub compute_all_applicable_methods {
641 my (@methods, %seen_method);
642 foreach my $class ($self->linearized_isa) {
643 # fetch the meta-class ...
644 my $meta = $self->initialize($class);
645 foreach my $method_name ($meta->get_method_list()) {
646 next if exists $seen_method{$method_name};
647 $seen_method{$method_name}++;
649 name => $method_name,
651 code => $meta->get_method($method_name)
658 sub find_all_methods_by_name {
659 my ($self, $method_name) = @_;
660 (defined $method_name && $method_name)
661 || confess "You must define a method name to find";
663 foreach my $class ($self->linearized_isa) {
664 # fetch the meta-class ...
665 my $meta = $self->initialize($class);
667 name => $method_name,
669 code => $meta->get_method($method_name)
670 } if $meta->has_method($method_name);
675 sub find_next_method_by_name {
676 my ($self, $method_name) = @_;
677 (defined $method_name && $method_name)
678 || confess "You must define a method name to find";
679 my @cpl = $self->linearized_isa;
680 shift @cpl; # discard ourselves
681 foreach my $class (@cpl) {
682 # fetch the meta-class ...
683 my $meta = $self->initialize($class);
684 return $meta->get_method($method_name)
685 if $meta->has_method($method_name);
694 # either we have an attribute object already
695 # or we need to create one from the args provided
696 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
697 # make sure it is derived from the correct type though
698 ($attribute->isa('Class::MOP::Attribute'))
699 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
701 # first we attach our new attribute
702 # because it might need certain information
703 # about the class which it is attached to
704 $attribute->attach_to_class($self);
706 # then we remove attributes of a conflicting
707 # name here so that we can properly detach
708 # the old attr object, and remove any
709 # accessors it would have generated
710 $self->remove_attribute($attribute->name)
711 if $self->has_attribute($attribute->name);
713 # then onto installing the new accessors
714 $attribute->install_accessors();
715 $self->get_attribute_map->{$attribute->name} = $attribute;
719 my ($self, $attribute_name) = @_;
720 (defined $attribute_name && $attribute_name)
721 || confess "You must define an attribute name";
722 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
726 my ($self, $attribute_name) = @_;
727 (defined $attribute_name && $attribute_name)
728 || confess "You must define an attribute name";
729 return $self->get_attribute_map->{$attribute_name}
731 # this will return undef anyway, so no need ...
732 # if $self->has_attribute($attribute_name);
736 sub remove_attribute {
737 my ($self, $attribute_name) = @_;
738 (defined $attribute_name && $attribute_name)
739 || confess "You must define an attribute name";
740 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
741 return unless defined $removed_attribute;
742 delete $self->get_attribute_map->{$attribute_name};
743 $removed_attribute->remove_accessors();
744 $removed_attribute->detach_from_class();
745 return $removed_attribute;
748 sub get_attribute_list {
750 keys %{$self->get_attribute_map};
753 sub compute_all_applicable_attributes {
755 my (@attrs, %seen_attr);
756 foreach my $class ($self->linearized_isa) {
757 # fetch the meta-class ...
758 my $meta = $self->initialize($class);
759 foreach my $attr_name ($meta->get_attribute_list()) {
760 next if exists $seen_attr{$attr_name};
761 $seen_attr{$attr_name}++;
762 push @attrs => $meta->get_attribute($attr_name);
768 sub find_attribute_by_name {
769 my ($self, $attr_name) = @_;
770 foreach my $class ($self->linearized_isa) {
771 # fetch the meta-class ...
772 my $meta = $self->initialize($class);
773 return $meta->get_attribute($attr_name)
774 if $meta->has_attribute($attr_name);
782 sub is_immutable { 0 }
785 # Why I changed this (groditi)
786 # - One Metaclass may have many Classes through many Metaclass instances
787 # - One Metaclass should only have one Immutable Transformer instance
788 # - Each Class may have different Immutabilizing options
789 # - Therefore each Metaclass instance may have different Immutabilizing options
790 # - We need to store one Immutable Transformer instance per Metaclass
791 # - We need to store one set of Immutable Transformer options per Class
792 # - Upon make_mutable we may delete the Immutabilizing options
793 # - We could clean the immutable Transformer instance when there is no more
794 # immutable Classes of that type, but we can also keep it in case
795 # another class with this same Metaclass becomes immutable. It is a case
796 # of trading of storing an instance to avoid unnecessary instantiations of
797 # Immutable Transformers. You may view this as a memory leak, however
798 # Because we have few Metaclasses, in practice it seems acceptable
799 # - To allow Immutable Transformers instances to be cleaned up we could weaken
800 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
803 my %IMMUTABLE_TRANSFORMERS;
804 my %IMMUTABLE_OPTIONS;
808 my $class = blessed $self || $self;
810 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
811 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
813 $transformer->make_metaclass_immutable($self, %options);
814 $IMMUTABLE_OPTIONS{$self->name} =
815 { %options, IMMUTABLE_TRANSFORMER => $transformer };
817 if( exists $options{debug} && $options{debug} ){
818 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
819 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
825 return if $self->is_mutable;
826 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
827 confess "unable to find immutabilizing options" unless ref $options;
828 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
829 $transformer->make_metaclass_mutable($self, %$options);
833 sub create_immutable_transformer {
835 my $class = Class::MOP::Immutable->new($self, {
836 read_only => [qw/superclasses/],
844 remove_package_symbol
847 class_precedence_list => 'ARRAY',
848 linearized_isa => 'ARRAY',
849 compute_all_applicable_attributes => 'ARRAY',
850 get_meta_instance => 'SCALAR',
851 get_method_map => 'SCALAR',
865 Class::MOP::Class - Class Meta Object
869 # assuming that class Foo
870 # has been defined, you can
872 # use this for introspection ...
874 # add a method to Foo ...
875 Foo->meta->add_method('bar' => sub { ... })
877 # get a list of all the classes searched
878 # the method dispatcher in the correct order
879 Foo->meta->class_precedence_list()
881 # remove a method from Foo
882 Foo->meta->remove_method('bar');
884 # or use this to actually create classes ...
886 Class::MOP::Class->create('Bar' => (
888 superclasses => [ 'Foo' ],
890 Class::MOP:::Attribute->new('$bar'),
891 Class::MOP:::Attribute->new('$baz'),
894 calculate_bar => sub { ... },
895 construct_baz => sub { ... }
901 This is the largest and currently most complex part of the Perl 5
902 meta-object protocol. It controls the introspection and
903 manipulation of Perl 5 classes (and it can create them too). The
904 best way to understand what this module can do, is to read the
905 documentation for each of it's methods.
909 =head2 Self Introspection
915 This will return a B<Class::MOP::Class> instance which is related
916 to this class. Thereby allowing B<Class::MOP::Class> to actually
919 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
920 bootstrap this module by installing a number of attribute meta-objects
921 into it's metaclass. This will allow this class to reap all the benifits
922 of the MOP when subclassing it.
926 =head2 Class construction
928 These methods will handle creating B<Class::MOP::Class> objects,
929 which can be used to both create new classes, and analyze
930 pre-existing classes.
932 This module will internally store references to all the instances
933 you create with these methods, so that they do not need to be
934 created any more than nessecary. Basically, they are singletons.
938 =item B<create ($package_name,
939 version =E<gt> ?$version,
940 authority =E<gt> ?$authority,
941 superclasses =E<gt> ?@superclasses,
942 methods =E<gt> ?%methods,
943 attributes =E<gt> ?%attributes)>
945 This returns a B<Class::MOP::Class> object, bringing the specified
946 C<$package_name> into existence and adding any of the C<$version>,
947 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
950 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
951 methods =E<gt> ?%methods,
952 attributes =E<gt> ?%attributes)>
954 This will create an anonymous class, it works much like C<create> but
955 it does not need a C<$package_name>. Instead it will create a suitably
956 unique package name for you to stash things into.
958 On very important distinction is that anon classes are destroyed once
959 the metaclass they are attached to goes out of scope. In the DESTROY
960 method, the created package will be removed from the symbol table.
962 It is also worth noting that any instances created with an anon-class
963 will keep a special reference to the anon-meta which will prevent the
964 anon-class from going out of scope until all instances of it have also
965 been destroyed. This however only works for HASH based instance types,
966 as we use a special reserved slot (C<__MOP__>) to store this.
968 =item B<initialize ($package_name, %options)>
970 This initializes and returns returns a B<Class::MOP::Class> object
971 for a given a C<$package_name>.
973 =item B<reinitialize ($package_name, %options)>
975 This removes the old metaclass, and creates a new one in it's place.
976 Do B<not> use this unless you really know what you are doing, it could
977 very easily make a very large mess of your program.
979 =item B<construct_class_instance (%options)>
981 This will construct an instance of B<Class::MOP::Class>, it is
982 here so that we can actually "tie the knot" for B<Class::MOP::Class>
983 to use C<construct_instance> once all the bootstrapping is done. This
984 method is used internally by C<initialize> and should never be called
985 from outside of that method really.
987 =item B<check_metaclass_compatability>
989 This method is called as the very last thing in the
990 C<construct_class_instance> method. This will check that the
991 metaclass you are creating is compatible with the metaclasses of all
992 your ancestors. For more inforamtion about metaclass compatibility
993 see the C<About Metaclass compatibility> section in L<Class::MOP>.
995 =item B<reset_package_cache_flag>
997 This will reset the package cache flag for this particular metaclass
998 it is basically the value of the C<Class::MOP::get_package_cache_flag>
999 function. This is very rarely needed from outside of C<Class::MOP::Class>
1000 but in some cases you might want to use it, so it is here.
1004 =head2 Object instance construction and cloning
1006 These methods are B<entirely optional>, it is up to you whether you want
1011 =item B<instance_metaclass>
1013 =item B<get_meta_instance>
1015 =item B<new_object (%params)>
1017 This is a convience method for creating a new object of the class, and
1018 blessing it into the appropriate package as well. Ideally your class
1019 would call a C<new> this method like so:
1022 my ($class, %param) = @_;
1023 $class->meta->new_object(%params);
1026 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1027 but that is considered bad style, so we do not do that.
1029 =item B<construct_instance (%params)>
1031 This method is used to construct an instace structure suitable for
1032 C<bless>-ing into your package of choice. It works in conjunction
1033 with the Attribute protocol to collect all applicable attributes.
1035 This will construct and instance using a HASH ref as storage
1036 (currently only HASH references are supported). This will collect all
1037 the applicable attributes and layout out the fields in the HASH ref,
1038 it will then initialize them using either use the corresponding key
1039 in C<%params> or any default value or initializer found in the
1040 attribute meta-object.
1042 =item B<clone_object ($instance, %params)>
1044 This is a convience method for cloning an object instance, then
1045 blessing it into the appropriate package. This method will call
1046 C<clone_instance>, which performs a shallow copy of the object,
1047 see that methods documentation for more details. Ideally your
1048 class would call a C<clone> this method like so:
1050 sub MyClass::clone {
1051 my ($self, %param) = @_;
1052 $self->meta->clone_object($self, %params);
1055 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1056 but that is considered bad style, so we do not do that.
1058 =item B<clone_instance($instance, %params)>
1060 This method is a compliment of C<construct_instance> (which means if
1061 you override C<construct_instance>, you need to override this one too),
1062 and clones the instance shallowly.
1064 The cloned structure returned is (like with C<construct_instance>) an
1065 unC<bless>ed HASH reference, it is your responsibility to then bless
1066 this cloned structure into the right class (which C<clone_object> will
1069 As of 0.11, this method will clone the C<$instance> structure shallowly,
1070 as opposed to the deep cloning implemented in prior versions. After much
1071 thought, research and discussion, I have decided that anything but basic
1072 shallow cloning is outside the scope of the meta-object protocol. I
1073 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1074 is too I<context-specific> to be part of the MOP.
1078 =head2 Informational
1080 These are a few predicate methods for asking information about the class.
1084 =item B<is_anon_class>
1086 This returns true if the class is a C<Class::MOP::Class> created anon class.
1090 This returns true if the class is still mutable.
1092 =item B<is_immutable>
1094 This returns true if the class has been made immutable.
1098 =head2 Inheritance Relationships
1102 =item B<superclasses (?@superclasses)>
1104 This is a read-write attribute which represents the superclass
1105 relationships of the class the B<Class::MOP::Class> instance is
1106 associated with. Basically, it can get and set the C<@ISA> for you.
1109 Perl will occasionally perform some C<@ISA> and method caching, if
1110 you decide to change your superclass relationship at runtime (which
1111 is quite insane and very much not recommened), then you should be
1112 aware of this and the fact that this module does not make any
1113 attempt to address this issue.
1115 =item B<class_precedence_list>
1117 This computes the a list of all the class's ancestors in the same order
1118 in which method dispatch will be done. This is similair to
1119 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
1121 =item B<linearized_isa>
1123 This returns a list based on C<class_precedence_list> but with all
1128 This returns a list of subclasses for this class.
1136 =item B<get_method_map>
1138 =item B<method_metaclass>
1140 =item B<add_method ($method_name, $method)>
1142 This will take a C<$method_name> and CODE reference to that
1143 C<$method> and install it into the class's package.
1146 This does absolutely nothing special to C<$method>
1147 other than use B<Sub::Name> to make sure it is tagged with the
1148 correct name, and therefore show up correctly in stack traces and
1151 =item B<alias_method ($method_name, $method)>
1153 This will take a C<$method_name> and CODE reference to that
1154 C<$method> and alias the method into the class's package.
1157 Unlike C<add_method>, this will B<not> try to name the
1158 C<$method> using B<Sub::Name>, it only aliases the method in
1159 the class's package.
1161 =item B<has_method ($method_name)>
1163 This just provides a simple way to check if the class implements
1164 a specific C<$method_name>. It will I<not> however, attempt to check
1165 if the class inherits the method (use C<UNIVERSAL::can> for that).
1167 This will correctly handle functions defined outside of the package
1168 that use a fully qualified name (C<sub Package::name { ... }>).
1170 This will correctly handle functions renamed with B<Sub::Name> and
1171 installed using the symbol tables. However, if you are naming the
1172 subroutine outside of the package scope, you must use the fully
1173 qualified name, including the package name, for C<has_method> to
1174 correctly identify it.
1176 This will attempt to correctly ignore functions imported from other
1177 packages using B<Exporter>. It breaks down if the function imported
1178 is an C<__ANON__> sub (such as with C<use constant>), which very well
1179 may be a valid method being applied to the class.
1181 In short, this method cannot always be trusted to determine if the
1182 C<$method_name> is actually a method. However, it will DWIM about
1183 90% of the time, so it's a small trade off I think.
1185 =item B<get_method ($method_name)>
1187 This will return a Class::MOP::Method instance related to the specified
1188 C<$method_name>, or return undef if that method does not exist.
1190 The Class::MOP::Method is codifiable, so you can use it like a normal
1191 CODE reference, see L<Class::MOP::Method> for more information.
1193 =item B<find_method_by_name ($method_name>
1195 This will return a CODE reference of the specified C<$method_name>,
1196 or return undef if that method does not exist.
1198 Unlike C<get_method> this will also look in the superclasses.
1200 =item B<remove_method ($method_name)>
1202 This will attempt to remove a given C<$method_name> from the class.
1203 It will return the CODE reference that it has removed, and will
1204 attempt to use B<Sub::Name> to clear the methods associated name.
1206 =item B<get_method_list>
1208 This will return a list of method names for all I<locally> defined
1209 methods. It does B<not> provide a list of all applicable methods,
1210 including any inherited ones. If you want a list of all applicable
1211 methods, use the C<compute_all_applicable_methods> method.
1213 =item B<compute_all_applicable_methods>
1215 This will return a list of all the methods names this class will
1216 respond to, taking into account inheritance. The list will be a list of
1217 HASH references, each one containing the following information; method
1218 name, the name of the class in which the method lives and a CODE
1219 reference for the actual method.
1221 =item B<find_all_methods_by_name ($method_name)>
1223 This will traverse the inheritence hierarchy and locate all methods
1224 with a given C<$method_name>. Similar to
1225 C<compute_all_applicable_methods> it returns a list of HASH references
1226 with the following information; method name (which will always be the
1227 same as C<$method_name>), the name of the class in which the method
1228 lives and a CODE reference for the actual method.
1230 The list of methods produced is a distinct list, meaning there are no
1231 duplicates in it. This is especially useful for things like object
1232 initialization and destruction where you only want the method called
1233 once, and in the correct order.
1235 =item B<find_next_method_by_name ($method_name)>
1237 This will return the first method to match a given C<$method_name> in
1238 the superclasses, this is basically equivalent to calling
1239 C<SUPER::$method_name>, but it can be dispatched at runtime.
1243 =head2 Method Modifiers
1245 Method modifiers are a concept borrowed from CLOS, in which a method
1246 can be wrapped with I<before>, I<after> and I<around> method modifiers
1247 that will be called everytime the method is called.
1249 =head3 How method modifiers work?
1251 Method modifiers work by wrapping the original method and then replacing
1252 it in the classes symbol table. The wrappers will handle calling all the
1253 modifiers in the appropariate orders and preserving the calling context
1254 for the original method.
1256 Each method modifier serves a particular purpose, which may not be
1257 obvious to users of other method wrapping modules. To start with, the
1258 return values of I<before> and I<after> modifiers are ignored. This is
1259 because thier purpose is B<not> to filter the input and output of the
1260 primary method (this is done with an I<around> modifier). This may seem
1261 like an odd restriction to some, but doing this allows for simple code
1262 to be added at the begining or end of a method call without jeapordizing
1263 the normal functioning of the primary method or placing any extra
1264 responsibility on the code of the modifier. Of course if you have more
1265 complex needs, then use the I<around> modifier, which uses a variation
1266 of continutation passing style to allow for a high degree of flexibility.
1268 Before and around modifiers are called in last-defined-first-called order,
1269 while after modifiers are called in first-defined-first-called order. So
1270 the call tree might looks something like this:
1280 To see examples of using method modifiers, see the following examples
1281 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1282 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1283 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1285 =head3 What is the performance impact?
1287 Of course there is a performance cost associated with method modifiers,
1288 but we have made every effort to make that cost be directly proportional
1289 to the amount of modifier features you utilize.
1291 The wrapping method does it's best to B<only> do as much work as it
1292 absolutely needs to. In order to do this we have moved some of the
1293 performance costs to set-up time, where they are easier to amortize.
1295 All this said, my benchmarks have indicated the following:
1297 simple wrapper with no modifiers 100% slower
1298 simple wrapper with simple before modifier 400% slower
1299 simple wrapper with simple after modifier 450% slower
1300 simple wrapper with simple around modifier 500-550% slower
1301 simple wrapper with all 3 modifiers 1100% slower
1303 These numbers may seem daunting, but you must remember, every feature
1304 comes with some cost. To put things in perspective, just doing a simple
1305 C<AUTOLOAD> which does nothing but extract the name of the method called
1306 and return it costs about 400% over a normal method call.
1310 =item B<add_before_method_modifier ($method_name, $code)>
1312 This will wrap the method at C<$method_name> and the supplied C<$code>
1313 will be passed the C<@_> arguments, and called before the original
1314 method is called. As specified above, the return value of the I<before>
1315 method modifiers is ignored, and it's ability to modify C<@_> is
1316 fairly limited. If you need to do either of these things, use an
1317 C<around> method modifier.
1319 =item B<add_after_method_modifier ($method_name, $code)>
1321 This will wrap the method at C<$method_name> so that the original
1322 method will be called, it's return values stashed, and then the
1323 supplied C<$code> will be passed the C<@_> arguments, and called.
1324 As specified above, the return value of the I<after> method
1325 modifiers is ignored, and it cannot modify the return values of
1326 the original method. If you need to do either of these things, use an
1327 C<around> method modifier.
1329 =item B<add_around_method_modifier ($method_name, $code)>
1331 This will wrap the method at C<$method_name> so that C<$code>
1332 will be called and passed the original method as an extra argument
1333 at the begining of the C<@_> argument list. This is a variation of
1334 continuation passing style, where the function prepended to C<@_>
1335 can be considered a continuation. It is up to C<$code> if it calls
1336 the original method or not, there is no restriction on what the
1337 C<$code> can or cannot do.
1343 It should be noted that since there is no one consistent way to define
1344 the attributes of a class in Perl 5. These methods can only work with
1345 the information given, and can not easily discover information on
1346 their own. See L<Class::MOP::Attribute> for more details.
1350 =item B<attribute_metaclass>
1352 =item B<get_attribute_map>
1354 =item B<add_attribute ($attribute_meta_object | $attribute_name, %attribute_spec)>
1356 This stores the C<$attribute_meta_object> (or creates one from the
1357 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1358 instance associated with the given class. Unlike methods, attributes
1359 within the MOP are stored as meta-information only. They will be used
1360 later to construct instances from (see C<construct_instance> above).
1361 More details about the attribute meta-objects can be found in the
1362 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1365 It should be noted that any accessor, reader/writer or predicate
1366 methods which the C<$attribute_meta_object> has will be installed
1367 into the class at this time.
1370 If an attribute already exists for C<$attribute_name>, the old one
1371 will be removed (as well as removing all it's accessors), and then
1374 =item B<has_attribute ($attribute_name)>
1376 Checks to see if this class has an attribute by the name of
1377 C<$attribute_name> and returns a boolean.
1379 =item B<get_attribute ($attribute_name)>
1381 Returns the attribute meta-object associated with C<$attribute_name>,
1382 if none is found, it will return undef.
1384 =item B<remove_attribute ($attribute_name)>
1386 This will remove the attribute meta-object stored at
1387 C<$attribute_name>, then return the removed attribute meta-object.
1390 Removing an attribute will only affect future instances of
1391 the class, it will not make any attempt to remove the attribute from
1392 any existing instances of the class.
1394 It should be noted that any accessor, reader/writer or predicate
1395 methods which the attribute meta-object stored at C<$attribute_name>
1396 has will be removed from the class at this time. This B<will> make
1397 these attributes somewhat inaccessable in previously created
1398 instances. But if you are crazy enough to do this at runtime, then
1399 you are crazy enough to deal with something like this :).
1401 =item B<get_attribute_list>
1403 This returns a list of attribute names which are defined in the local
1404 class. If you want a list of all applicable attributes for a class,
1405 use the C<compute_all_applicable_attributes> method.
1407 =item B<compute_all_applicable_attributes>
1409 This will traverse the inheritance heirachy and return a list of all
1410 the applicable attributes for this class. It does not construct a
1411 HASH reference like C<compute_all_applicable_methods> because all
1412 that same information is discoverable through the attribute
1415 =item B<find_attribute_by_name ($attr_name)>
1417 This method will traverse the inheritance heirachy and find the
1418 first attribute whose name matches C<$attr_name>, then return it.
1419 It will return undef if nothing is found.
1423 =head2 Class Immutability
1427 =item B<make_immutable (%options)>
1429 This method will invoke a tranforamtion upon the class which will
1430 make it immutable. Details of this transformation can be found in
1431 the L<Class::MOP::Immutable> documentation.
1433 =item B<make_mutable>
1435 This method will reverse tranforamtion upon the class which
1438 =item B<create_immutable_transformer>
1440 Create a transformer suitable for making this class immutable
1446 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1448 =head1 COPYRIGHT AND LICENSE
1450 Copyright 2006, 2007 by Infinity Interactive, Inc.
1452 L<http://www.iinteractive.com>
1454 This library is free software; you can redistribute it and/or modify
1455 it under the same terms as Perl itself.