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';
14 use B 'svref_2object';
16 our $VERSION = '0.22';
17 our $AUTHORITY = 'cpan:STEVAN';
19 use base 'Class::MOP::Module';
23 sub meta { Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) }
29 my $package_name = shift;
30 (defined $package_name && $package_name && !blessed($package_name))
31 || confess "You must pass a package name and it cannot be blessed";
32 $class->construct_class_instance('package' => $package_name, @_);
37 my $package_name = shift;
38 (defined $package_name && $package_name && !blessed($package_name))
39 || confess "You must pass a package name and it cannot be blessed";
40 Class::MOP::remove_metaclass_by_name($package_name);
41 $class->construct_class_instance('package' => $package_name, @_);
44 # NOTE: (meta-circularity)
45 # this is a special form of &construct_instance
46 # (see below), which is used to construct class
47 # meta-object instances for any Class::MOP::*
48 # class. All other classes will use the more
49 # normal &construct_instance.
50 sub construct_class_instance {
53 my $package_name = $options{'package'};
54 (defined $package_name && $package_name)
55 || confess "You must pass a package name";
57 # return the metaclass if we have it cached,
58 # and it is still defined (it has not been
59 # reaped by DESTROY yet, which can happen
60 # annoyingly enough during global destruction)
61 return Class::MOP::get_metaclass_by_name($package_name)
62 if Class::MOP::does_metaclass_exist($package_name);
65 # we need to deal with the possibility
66 # of class immutability here, and then
67 # get the name of the class appropriately
68 $class = (blessed($class)
69 ? ($class->is_immutable
70 ? $class->get_mutable_metaclass_name()
74 # now create the metaclass
76 if ($class =~ /^Class::MOP::Class$/) {
79 # inherited from Class::MOP::Package
80 '$!package' => $package_name,
83 # since the following attributes will
84 # actually be loaded from the symbol
85 # table, and actually bypass the instance
86 # entirely, we can just leave these things
87 # listed here for reference, because they
88 # should not actually have a value associated
90 '%!namespace' => \undef,
91 # inherited from Class::MOP::Module
92 '$!version' => \undef,
93 '$!authority' => \undef,
94 # defined in Class::MOP::Class
95 '@!superclasses' => \undef,
99 '$!attribute_metaclass' => $options{'attribute_metaclass'} || 'Class::MOP::Attribute',
100 '$!method_metaclass' => $options{'method_metaclass'} || 'Class::MOP::Method',
101 '$!instance_metaclass' => $options{'instance_metaclass'} || 'Class::MOP::Instance',
106 # it is safe to use meta here because
107 # class will always be a subclass of
108 # Class::MOP::Class, which defines meta
109 $meta = $class->meta->construct_instance(%options)
112 # and check the metaclass compatibility
113 $meta->check_metaclass_compatability();
115 Class::MOP::store_metaclass_by_name($package_name, $meta);
118 # we need to weaken any anon classes
119 # so that they can call DESTROY properly
120 Class::MOP::weaken_metaclass($package_name) if $meta->is_anon_class;
125 sub check_metaclass_compatability {
128 # this is always okay ...
129 return if blessed($self) eq 'Class::MOP::Class' &&
130 $self->instance_metaclass eq 'Class::MOP::Instance';
132 my @class_list = $self->class_precedence_list;
133 shift @class_list; # shift off $self->name
135 foreach my $class_name (@class_list) {
136 my $meta = Class::MOP::get_metaclass_by_name($class_name) || next;
139 # we need to deal with the possibility
140 # of class immutability here, and then
141 # get the name of the class appropriately
142 my $meta_type = ($meta->is_immutable
143 ? $meta->get_mutable_metaclass_name()
146 ($self->isa($meta_type))
147 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
148 " is not compatible with the " .
149 $class_name . "->meta => (" . ($meta_type) . ")";
151 # we also need to check that instance metaclasses
152 # are compatabile in the same the class.
153 ($self->instance_metaclass->isa($meta->instance_metaclass))
154 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
155 " is not compatible with the " .
156 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
164 # this should be sufficient, if you have a
165 # use case where it is not, write a test and
167 my $ANON_CLASS_SERIAL = 0;
170 # we need a sufficiently annoying prefix
171 # this should suffice for now, this is
172 # used in a couple of places below, so
173 # need to put it up here for now.
174 my $ANON_CLASS_PREFIX = 'Class::MOP::Class::__ANON__::SERIAL::';
178 no warnings 'uninitialized';
179 $self->name =~ /^$ANON_CLASS_PREFIX/ ? 1 : 0;
182 sub create_anon_class {
183 my ($class, %options) = @_;
184 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
185 return $class->create($package_name, %options);
189 # this will only get called for
190 # anon-classes, all other calls
191 # are assumed to occur during
192 # global destruction and so don't
193 # really need to be handled explicitly
196 no warnings 'uninitialized';
197 return unless $self->name =~ /^$ANON_CLASS_PREFIX/;
198 my ($serial_id) = ($self->name =~ /^$ANON_CLASS_PREFIX(\d+)/);
200 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
201 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
203 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
208 # creating classes with MOP ...
212 my $package_name = shift;
214 (defined $package_name && $package_name)
215 || confess "You must pass a package name";
218 || confess "You much pass all parameters as name => value pairs " .
219 "(I found an uneven number of params in \@_)";
223 my $code = "package $package_name;";
224 $code .= "\$$package_name\:\:VERSION = '" . $options{version} . "';"
225 if exists $options{version};
226 $code .= "\$$package_name\:\:AUTHORITY = '" . $options{authority} . "';"
227 if exists $options{authority};
230 confess "creation of $package_name failed : $@" if $@;
232 my $meta = $class->initialize($package_name);
234 $meta->add_method('meta' => sub {
235 $class->initialize(blessed($_[0]) || $_[0]);
238 $meta->superclasses(@{$options{superclasses}})
239 if exists $options{superclasses};
241 # process attributes first, so that they can
242 # install accessors, but locally defined methods
243 # can then overwrite them. It is maybe a little odd, but
244 # I think this should be the order of things.
245 if (exists $options{attributes}) {
246 foreach my $attr (@{$options{attributes}}) {
247 $meta->add_attribute($attr);
250 if (exists $options{methods}) {
251 foreach my $method_name (keys %{$options{methods}}) {
252 $meta->add_method($method_name, $options{methods}->{$method_name});
261 # all these attribute readers will be bootstrapped
262 # away in the Class::MOP bootstrap section
264 sub get_attribute_map { $_[0]->{'%!attributes'} }
265 sub attribute_metaclass { $_[0]->{'$!attribute_metaclass'} }
266 sub method_metaclass { $_[0]->{'$!method_metaclass'} }
267 sub instance_metaclass { $_[0]->{'$!instance_metaclass'} }
270 # this is a prime canidate for conversion to XS
273 my $map = $self->{'%!methods'};
275 my $class_name = $self->name;
276 my $method_metaclass = $self->method_metaclass;
278 foreach my $symbol ($self->list_all_package_symbols('CODE')) {
279 my $code = $self->get_package_symbol('&' . $symbol);
281 next if exists $map->{$symbol} &&
282 defined $map->{$symbol} &&
283 $map->{$symbol}->body == $code;
285 my $gv = svref_2object($code)->GV;
286 next if ($gv->STASH->NAME || '') ne $class_name &&
287 ($gv->NAME || '') ne '__ANON__';
289 $map->{$symbol} = $method_metaclass->wrap($code);
295 # Instance Construction & Cloning
300 # we need to protect the integrity of the
301 # Class::MOP::Class singletons here, so we
302 # delegate this to &construct_class_instance
303 # which will deal with the singletons
304 return $class->construct_class_instance(@_)
305 if $class->name->isa('Class::MOP::Class');
306 return $class->construct_instance(@_);
309 sub construct_instance {
310 my ($class, %params) = @_;
311 my $meta_instance = $class->get_meta_instance();
312 my $instance = $meta_instance->create_instance();
313 foreach my $attr ($class->compute_all_applicable_attributes()) {
314 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
317 # this will only work for a HASH instance type
318 if ($class->is_anon_class) {
319 (reftype($instance) eq 'HASH')
320 || confess "Currently only HASH based instances are supported with instance of anon-classes";
322 # At some point we should make this official
323 # as a reserved slot name, but right now I am
324 # going to keep it here.
325 # my $RESERVED_MOP_SLOT = '__MOP__';
326 $instance->{'__MOP__'} = $class;
331 sub get_meta_instance {
333 return $class->instance_metaclass->new(
335 $class->compute_all_applicable_attributes()
341 my $instance = shift;
342 (blessed($instance) && $instance->isa($class->name))
343 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
345 # we need to protect the integrity of the
346 # Class::MOP::Class singletons here, they
347 # should not be cloned.
348 return $instance if $instance->isa('Class::MOP::Class');
349 $class->clone_instance($instance, @_);
353 my ($class, $instance, %params) = @_;
355 || confess "You can only clone instances, \$self is not a blessed instance";
356 my $meta_instance = $class->get_meta_instance();
357 my $clone = $meta_instance->clone_instance($instance);
358 foreach my $attr ($class->compute_all_applicable_attributes()) {
359 if (exists $params{$attr->init_arg}) {
360 $meta_instance->set_slot_value($clone, $attr->name, $params{$attr->init_arg});
372 @{$self->get_package_symbol('@ISA')} = @supers;
374 # we need to check the metaclass
375 # compatability here so that we can
376 # be sure that the superclass is
377 # not potentially creating an issues
378 # we don't know about
379 $self->check_metaclass_compatability();
381 @{$self->get_package_symbol('@ISA')};
384 sub class_precedence_list {
387 # We need to check for ciruclar inheirtance here.
388 # This will do nothing if all is well, and blow
389 # up otherwise. Yes, it's an ugly hack, better
390 # suggestions are welcome.
391 { ($self->name || return)->isa('This is a test for circular inheritance') }
396 $self->initialize($_)->class_precedence_list()
397 } $self->superclasses()
404 my ($self, $method_name, $method) = @_;
405 (defined $method_name && $method_name)
406 || confess "You must define a method name";
409 if (blessed($method)) {
410 $body = $method->body;
414 ('CODE' eq (reftype($body) || ''))
415 || confess "Your code block must be a CODE reference";
416 $method = $self->method_metaclass->wrap($body);
418 $self->get_method_map->{$method_name} = $method;
420 my $full_method_name = ($self->name . '::' . $method_name);
421 $self->add_package_symbol("&${method_name}" => subname $full_method_name => $body);
425 my $fetch_and_prepare_method = sub {
426 my ($self, $method_name) = @_;
428 my $method = $self->get_method($method_name);
429 # if we dont have local ...
431 # try to find the next method
432 $method = $self->find_next_method_by_name($method_name);
433 # die if it does not exist
435 || confess "The method '$method_name' is not found in the inheritance hierarchy for class " . $self->name;
436 # and now make sure to wrap it
437 # even if it is already wrapped
438 # because we need a new sub ref
439 $method = Class::MOP::Method::Wrapped->wrap($method);
442 # now make sure we wrap it properly
443 $method = Class::MOP::Method::Wrapped->wrap($method)
444 unless $method->isa('Class::MOP::Method::Wrapped');
446 $self->add_method($method_name => $method);
450 sub add_before_method_modifier {
451 my ($self, $method_name, $method_modifier) = @_;
452 (defined $method_name && $method_name)
453 || confess "You must pass in a method name";
454 my $method = $fetch_and_prepare_method->($self, $method_name);
455 $method->add_before_modifier(subname ':before' => $method_modifier);
458 sub add_after_method_modifier {
459 my ($self, $method_name, $method_modifier) = @_;
460 (defined $method_name && $method_name)
461 || confess "You must pass in a method name";
462 my $method = $fetch_and_prepare_method->($self, $method_name);
463 $method->add_after_modifier(subname ':after' => $method_modifier);
466 sub add_around_method_modifier {
467 my ($self, $method_name, $method_modifier) = @_;
468 (defined $method_name && $method_name)
469 || confess "You must pass in a method name";
470 my $method = $fetch_and_prepare_method->($self, $method_name);
471 $method->add_around_modifier(subname ':around' => $method_modifier);
475 # the methods above used to be named like this:
476 # ${pkg}::${method}:(before|after|around)
477 # but this proved problematic when using one modifier
478 # to wrap multiple methods (something which is likely
479 # to happen pretty regularly IMO). So instead of naming
480 # it like this, I have chosen to just name them purely
481 # with their modifier names, like so:
482 # :(before|after|around)
483 # The fact is that in a stack trace, it will be fairly
484 # evident from the context what method they are attached
485 # to, and so don't need the fully qualified name.
489 my ($self, $method_name, $method) = @_;
490 (defined $method_name && $method_name)
491 || confess "You must define a method name";
493 my $body = (blessed($method) ? $method->body : $method);
494 ('CODE' eq (reftype($body) || ''))
495 || confess "Your code block must be a CODE reference";
497 $self->add_package_symbol("&${method_name}" => $body);
501 my ($self, $method_name) = @_;
502 (defined $method_name && $method_name)
503 || confess "You must define a method name";
505 return 0 unless exists $self->get_method_map->{$method_name};
510 my ($self, $method_name) = @_;
511 (defined $method_name && $method_name)
512 || confess "You must define a method name";
515 # I don't really need this here, because
516 # if the method_map is missing a key it
517 # will just return undef for me now
518 # return unless $self->has_method($method_name);
520 return $self->get_method_map->{$method_name};
524 my ($self, $method_name) = @_;
525 (defined $method_name && $method_name)
526 || confess "You must define a method name";
528 my $removed_method = $self->get_method($method_name);
531 $self->remove_package_symbol("&${method_name}");
532 delete $self->get_method_map->{$method_name};
533 } if defined $removed_method;
535 return $removed_method;
538 sub get_method_list {
540 keys %{$self->get_method_map};
543 sub find_method_by_name {
544 my ($self, $method_name) = @_;
545 (defined $method_name && $method_name)
546 || confess "You must define a method name to find";
547 # keep a record of what we have seen
548 # here, this will handle all the
549 # inheritence issues because we are
550 # using the &class_precedence_list
552 my @cpl = $self->class_precedence_list();
553 foreach my $class (@cpl) {
554 next if $seen_class{$class};
555 $seen_class{$class}++;
556 # fetch the meta-class ...
557 my $meta = $self->initialize($class);
558 return $meta->get_method($method_name)
559 if $meta->has_method($method_name);
564 sub compute_all_applicable_methods {
567 # keep a record of what we have seen
568 # here, this will handle all the
569 # inheritence issues because we are
570 # using the &class_precedence_list
571 my (%seen_class, %seen_method);
572 foreach my $class ($self->class_precedence_list()) {
573 next if $seen_class{$class};
574 $seen_class{$class}++;
575 # fetch the meta-class ...
576 my $meta = $self->initialize($class);
577 foreach my $method_name ($meta->get_method_list()) {
578 next if exists $seen_method{$method_name};
579 $seen_method{$method_name}++;
581 name => $method_name,
583 code => $meta->get_method($method_name)
590 sub find_all_methods_by_name {
591 my ($self, $method_name) = @_;
592 (defined $method_name && $method_name)
593 || confess "You must define a method name to find";
595 # keep a record of what we have seen
596 # here, this will handle all the
597 # inheritence issues because we are
598 # using the &class_precedence_list
600 foreach my $class ($self->class_precedence_list()) {
601 next if $seen_class{$class};
602 $seen_class{$class}++;
603 # fetch the meta-class ...
604 my $meta = $self->initialize($class);
606 name => $method_name,
608 code => $meta->get_method($method_name)
609 } if $meta->has_method($method_name);
614 sub find_next_method_by_name {
615 my ($self, $method_name) = @_;
616 (defined $method_name && $method_name)
617 || confess "You must define a method name to find";
618 # keep a record of what we have seen
619 # here, this will handle all the
620 # inheritence issues because we are
621 # using the &class_precedence_list
623 my @cpl = $self->class_precedence_list();
624 shift @cpl; # discard ourselves
625 foreach my $class (@cpl) {
626 next if $seen_class{$class};
627 $seen_class{$class}++;
628 # fetch the meta-class ...
629 my $meta = $self->initialize($class);
630 return $meta->get_method($method_name)
631 if $meta->has_method($method_name);
640 # either we have an attribute object already
641 # or we need to create one from the args provided
642 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
643 # make sure it is derived from the correct type though
644 ($attribute->isa('Class::MOP::Attribute'))
645 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
647 # first we attach our new attribute
648 # because it might need certain information
649 # about the class which it is attached to
650 $attribute->attach_to_class($self);
652 # then we remove attributes of a conflicting
653 # name here so that we can properly detach
654 # the old attr object, and remove any
655 # accessors it would have generated
656 $self->remove_attribute($attribute->name)
657 if $self->has_attribute($attribute->name);
659 # then onto installing the new accessors
660 $attribute->install_accessors();
661 $self->get_attribute_map->{$attribute->name} = $attribute;
665 my ($self, $attribute_name) = @_;
666 (defined $attribute_name && $attribute_name)
667 || confess "You must define an attribute name";
668 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
672 my ($self, $attribute_name) = @_;
673 (defined $attribute_name && $attribute_name)
674 || confess "You must define an attribute name";
675 return $self->get_attribute_map->{$attribute_name}
677 # this will return undef anyway, so no need ...
678 # if $self->has_attribute($attribute_name);
682 sub remove_attribute {
683 my ($self, $attribute_name) = @_;
684 (defined $attribute_name && $attribute_name)
685 || confess "You must define an attribute name";
686 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
687 return unless defined $removed_attribute;
688 delete $self->get_attribute_map->{$attribute_name};
689 $removed_attribute->remove_accessors();
690 $removed_attribute->detach_from_class();
691 return $removed_attribute;
694 sub get_attribute_list {
696 keys %{$self->get_attribute_map};
699 sub compute_all_applicable_attributes {
702 # keep a record of what we have seen
703 # here, this will handle all the
704 # inheritence issues because we are
705 # using the &class_precedence_list
706 my (%seen_class, %seen_attr);
707 foreach my $class ($self->class_precedence_list()) {
708 next if $seen_class{$class};
709 $seen_class{$class}++;
710 # fetch the meta-class ...
711 my $meta = $self->initialize($class);
712 foreach my $attr_name ($meta->get_attribute_list()) {
713 next if exists $seen_attr{$attr_name};
714 $seen_attr{$attr_name}++;
715 push @attrs => $meta->get_attribute($attr_name);
721 sub find_attribute_by_name {
722 my ($self, $attr_name) = @_;
723 # keep a record of what we have seen
724 # here, this will handle all the
725 # inheritence issues because we are
726 # using the &class_precedence_list
728 foreach my $class ($self->class_precedence_list()) {
729 next if $seen_class{$class};
730 $seen_class{$class}++;
731 # fetch the meta-class ...
732 my $meta = $self->initialize($class);
733 return $meta->get_attribute($attr_name)
734 if $meta->has_attribute($attr_name);
742 sub is_immutable { 0 }
745 # Why I changed this (groditi)
746 # - One Metaclass may have many Classes through many Metaclass instances
747 # - One Metaclass should only have one Immutable Transformer instance
748 # - Each Class may have different Immutabilizing options
749 # - Therefore each Metaclass instance may have different Immutabilizing options
750 # - We need to store one Immutable Transformer instance per Metaclass
751 # - We need to store one set of Immutable Transformer options per Class
752 # - Upon make_mutable we may delete the Immutabilizing options
753 # - We could clean the immutable Transformer instance when there is no more
754 # immutable Classes of that type, but we can also keep it in case
755 # another class with this same Metaclass becomes immutable. It is a case
756 # of trading of storing an instance to avoid unnecessary instantiations of
757 # Immutable Transformers. You may view this as a memory leak, however
758 # Because we have few Metaclasses, in practice it seems acceptable
759 # - To allow Immutable Transformers instances to be cleaned up we could weaken
760 # the reference stored in $IMMUTABLE_TRANSFORMERS{$class} and ||= should DWIM
763 my %IMMUTABLE_TRANSFORMERS;
764 my %IMMUTABLE_OPTIONS;
768 my $class = blessed $self || $self;
770 $IMMUTABLE_TRANSFORMERS{$class} ||= $self->create_immutable_transformer;
771 my $transformer = $IMMUTABLE_TRANSFORMERS{$class};
773 $transformer->make_metaclass_immutable($self, %options);
774 $IMMUTABLE_OPTIONS{$self->name} =
775 { %options, IMMUTABLE_TRANSFORMER => $transformer };
777 if( exists $options{debug} && $options{debug} ){
778 print STDERR "# of Metaclass options: ", keys %IMMUTABLE_OPTIONS;
779 print STDERR "# of Immutable transformers: ", keys %IMMUTABLE_TRANSFORMERS;
785 return if $self->is_mutable;
786 my $options = delete $IMMUTABLE_OPTIONS{$self->name};
787 confess "unable to find immutabilizing options" unless $options;
788 my $transformer = delete $options->{IMMUTABLE_TRANSFORMER};
789 $transformer->make_metaclass_mutable($self, %$options);
793 sub create_immutable_transformer {
795 my $class = Class::MOP::Immutable->new($self, {
796 read_only => [qw/superclasses/],
804 remove_package_symbol
807 class_precedence_list => 'ARRAY',
808 compute_all_applicable_attributes => 'ARRAY',
809 get_meta_instance => 'SCALAR',
810 get_method_map => 'SCALAR',
824 Class::MOP::Class - Class Meta Object
828 # assuming that class Foo
829 # has been defined, you can
831 # use this for introspection ...
833 # add a method to Foo ...
834 Foo->meta->add_method('bar' => sub { ... })
836 # get a list of all the classes searched
837 # the method dispatcher in the correct order
838 Foo->meta->class_precedence_list()
840 # remove a method from Foo
841 Foo->meta->remove_method('bar');
843 # or use this to actually create classes ...
845 Class::MOP::Class->create('Bar' => (
847 superclasses => [ 'Foo' ],
849 Class::MOP:::Attribute->new('$bar'),
850 Class::MOP:::Attribute->new('$baz'),
853 calculate_bar => sub { ... },
854 construct_baz => sub { ... }
860 This is the largest and currently most complex part of the Perl 5
861 meta-object protocol. It controls the introspection and
862 manipulation of Perl 5 classes (and it can create them too). The
863 best way to understand what this module can do, is to read the
864 documentation for each of it's methods.
868 =head2 Self Introspection
874 This will return a B<Class::MOP::Class> instance which is related
875 to this class. Thereby allowing B<Class::MOP::Class> to actually
878 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
879 bootstrap this module by installing a number of attribute meta-objects
880 into it's metaclass. This will allow this class to reap all the benifits
881 of the MOP when subclassing it.
885 =head2 Class construction
887 These methods will handle creating B<Class::MOP::Class> objects,
888 which can be used to both create new classes, and analyze
889 pre-existing classes.
891 This module will internally store references to all the instances
892 you create with these methods, so that they do not need to be
893 created any more than nessecary. Basically, they are singletons.
897 =item B<create ($package_name,
898 version =E<gt> ?$version,
899 authority =E<gt> ?$authority,
900 superclasses =E<gt> ?@superclasses,
901 methods =E<gt> ?%methods,
902 attributes =E<gt> ?%attributes)>
904 This returns a B<Class::MOP::Class> object, bringing the specified
905 C<$package_name> into existence and adding any of the C<$version>,
906 C<$authority>, C<@superclasses>, C<%methods> and C<%attributes> to
909 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
910 methods =E<gt> ?%methods,
911 attributes =E<gt> ?%attributes)>
913 This will create an anonymous class, it works much like C<create> but
914 it does not need a C<$package_name>. Instead it will create a suitably
915 unique package name for you to stash things into.
917 On very important distinction is that anon classes are destroyed once
918 the metaclass they are attached to goes out of scope. In the DESTROY
919 method, the created package will be removed from the symbol table.
921 It is also worth noting that any instances created with an anon-class
922 will keep a special reference to the anon-meta which will prevent the
923 anon-class from going out of scope until all instances of it have also
924 been destroyed. This however only works for HASH based instance types,
925 as we use a special reserved slot (C<__MOP__>) to store this.
927 =item B<initialize ($package_name, %options)>
929 This initializes and returns returns a B<Class::MOP::Class> object
930 for a given a C<$package_name>.
932 =item B<reinitialize ($package_name, %options)>
934 This removes the old metaclass, and creates a new one in it's place.
935 Do B<not> use this unless you really know what you are doing, it could
936 very easily make a very large mess of your program.
938 =item B<construct_class_instance (%options)>
940 This will construct an instance of B<Class::MOP::Class>, it is
941 here so that we can actually "tie the knot" for B<Class::MOP::Class>
942 to use C<construct_instance> once all the bootstrapping is done. This
943 method is used internally by C<initialize> and should never be called
944 from outside of that method really.
946 =item B<check_metaclass_compatability>
948 This method is called as the very last thing in the
949 C<construct_class_instance> method. This will check that the
950 metaclass you are creating is compatible with the metaclasses of all
951 your ancestors. For more inforamtion about metaclass compatibility
952 see the C<About Metaclass compatibility> section in L<Class::MOP>.
956 =head2 Object instance construction and cloning
958 These methods are B<entirely optional>, it is up to you whether you want
963 =item B<instance_metaclass>
965 =item B<get_meta_instance>
967 =item B<new_object (%params)>
969 This is a convience method for creating a new object of the class, and
970 blessing it into the appropriate package as well. Ideally your class
971 would call a C<new> this method like so:
974 my ($class, %param) = @_;
975 $class->meta->new_object(%params);
978 Of course the ideal place for this would actually be in C<UNIVERSAL::>
979 but that is considered bad style, so we do not do that.
981 =item B<construct_instance (%params)>
983 This method is used to construct an instace structure suitable for
984 C<bless>-ing into your package of choice. It works in conjunction
985 with the Attribute protocol to collect all applicable attributes.
987 This will construct and instance using a HASH ref as storage
988 (currently only HASH references are supported). This will collect all
989 the applicable attributes and layout out the fields in the HASH ref,
990 it will then initialize them using either use the corresponding key
991 in C<%params> or any default value or initializer found in the
992 attribute meta-object.
994 =item B<clone_object ($instance, %params)>
996 This is a convience method for cloning an object instance, then
997 blessing it into the appropriate package. This method will call
998 C<clone_instance>, which performs a shallow copy of the object,
999 see that methods documentation for more details. Ideally your
1000 class would call a C<clone> this method like so:
1002 sub MyClass::clone {
1003 my ($self, %param) = @_;
1004 $self->meta->clone_object($self, %params);
1007 Of course the ideal place for this would actually be in C<UNIVERSAL::>
1008 but that is considered bad style, so we do not do that.
1010 =item B<clone_instance($instance, %params)>
1012 This method is a compliment of C<construct_instance> (which means if
1013 you override C<construct_instance>, you need to override this one too),
1014 and clones the instance shallowly.
1016 The cloned structure returned is (like with C<construct_instance>) an
1017 unC<bless>ed HASH reference, it is your responsibility to then bless
1018 this cloned structure into the right class (which C<clone_object> will
1021 As of 0.11, this method will clone the C<$instance> structure shallowly,
1022 as opposed to the deep cloning implemented in prior versions. After much
1023 thought, research and discussion, I have decided that anything but basic
1024 shallow cloning is outside the scope of the meta-object protocol. I
1025 think Yuval "nothingmuch" Kogman put it best when he said that cloning
1026 is too I<context-specific> to be part of the MOP.
1030 =head2 Informational
1032 These are a few predicate methods for asking information about the class.
1036 =item B<is_anon_class>
1038 This returns true if the class is a C<Class::MOP::Class> created anon class.
1042 This returns true if the class is still mutable.
1044 =item B<is_immutable>
1046 This returns true if the class has been made immutable.
1050 =head2 Inheritance Relationships
1054 =item B<superclasses (?@superclasses)>
1056 This is a read-write attribute which represents the superclass
1057 relationships of the class the B<Class::MOP::Class> instance is
1058 associated with. Basically, it can get and set the C<@ISA> for you.
1061 Perl will occasionally perform some C<@ISA> and method caching, if
1062 you decide to change your superclass relationship at runtime (which
1063 is quite insane and very much not recommened), then you should be
1064 aware of this and the fact that this module does not make any
1065 attempt to address this issue.
1067 =item B<class_precedence_list>
1069 This computes the a list of all the class's ancestors in the same order
1070 in which method dispatch will be done. This is similair to
1071 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
1079 =item B<get_method_map>
1081 =item B<method_metaclass>
1083 =item B<add_method ($method_name, $method)>
1085 This will take a C<$method_name> and CODE reference to that
1086 C<$method> and install it into the class's package.
1089 This does absolutely nothing special to C<$method>
1090 other than use B<Sub::Name> to make sure it is tagged with the
1091 correct name, and therefore show up correctly in stack traces and
1094 =item B<alias_method ($method_name, $method)>
1096 This will take a C<$method_name> and CODE reference to that
1097 C<$method> and alias the method into the class's package.
1100 Unlike C<add_method>, this will B<not> try to name the
1101 C<$method> using B<Sub::Name>, it only aliases the method in
1102 the class's package.
1104 =item B<has_method ($method_name)>
1106 This just provides a simple way to check if the class implements
1107 a specific C<$method_name>. It will I<not> however, attempt to check
1108 if the class inherits the method (use C<UNIVERSAL::can> for that).
1110 This will correctly handle functions defined outside of the package
1111 that use a fully qualified name (C<sub Package::name { ... }>).
1113 This will correctly handle functions renamed with B<Sub::Name> and
1114 installed using the symbol tables. However, if you are naming the
1115 subroutine outside of the package scope, you must use the fully
1116 qualified name, including the package name, for C<has_method> to
1117 correctly identify it.
1119 This will attempt to correctly ignore functions imported from other
1120 packages using B<Exporter>. It breaks down if the function imported
1121 is an C<__ANON__> sub (such as with C<use constant>), which very well
1122 may be a valid method being applied to the class.
1124 In short, this method cannot always be trusted to determine if the
1125 C<$method_name> is actually a method. However, it will DWIM about
1126 90% of the time, so it's a small trade off I think.
1128 =item B<get_method ($method_name)>
1130 This will return a Class::MOP::Method instance related to the specified
1131 C<$method_name>, or return undef if that method does not exist.
1133 The Class::MOP::Method is codifiable, so you can use it like a normal
1134 CODE reference, see L<Class::MOP::Method> for more information.
1136 =item B<find_method_by_name ($method_name>
1138 This will return a CODE reference of the specified C<$method_name>,
1139 or return undef if that method does not exist.
1141 Unlike C<get_method> this will also look in the superclasses.
1143 =item B<remove_method ($method_name)>
1145 This will attempt to remove a given C<$method_name> from the class.
1146 It will return the CODE reference that it has removed, and will
1147 attempt to use B<Sub::Name> to clear the methods associated name.
1149 =item B<get_method_list>
1151 This will return a list of method names for all I<locally> defined
1152 methods. It does B<not> provide a list of all applicable methods,
1153 including any inherited ones. If you want a list of all applicable
1154 methods, use the C<compute_all_applicable_methods> method.
1156 =item B<compute_all_applicable_methods>
1158 This will return a list of all the methods names this class will
1159 respond to, taking into account inheritance. The list will be a list of
1160 HASH references, each one containing the following information; method
1161 name, the name of the class in which the method lives and a CODE
1162 reference for the actual method.
1164 =item B<find_all_methods_by_name ($method_name)>
1166 This will traverse the inheritence hierarchy and locate all methods
1167 with a given C<$method_name>. Similar to
1168 C<compute_all_applicable_methods> it returns a list of HASH references
1169 with the following information; method name (which will always be the
1170 same as C<$method_name>), the name of the class in which the method
1171 lives and a CODE reference for the actual method.
1173 The list of methods produced is a distinct list, meaning there are no
1174 duplicates in it. This is especially useful for things like object
1175 initialization and destruction where you only want the method called
1176 once, and in the correct order.
1178 =item B<find_next_method_by_name ($method_name)>
1180 This will return the first method to match a given C<$method_name> in
1181 the superclasses, this is basically equivalent to calling
1182 C<SUPER::$method_name>, but it can be dispatched at runtime.
1186 =head2 Method Modifiers
1188 Method modifiers are a concept borrowed from CLOS, in which a method
1189 can be wrapped with I<before>, I<after> and I<around> method modifiers
1190 that will be called everytime the method is called.
1192 =head3 How method modifiers work?
1194 Method modifiers work by wrapping the original method and then replacing
1195 it in the classes symbol table. The wrappers will handle calling all the
1196 modifiers in the appropariate orders and preserving the calling context
1197 for the original method.
1199 Each method modifier serves a particular purpose, which may not be
1200 obvious to users of other method wrapping modules. To start with, the
1201 return values of I<before> and I<after> modifiers are ignored. This is
1202 because thier purpose is B<not> to filter the input and output of the
1203 primary method (this is done with an I<around> modifier). This may seem
1204 like an odd restriction to some, but doing this allows for simple code
1205 to be added at the begining or end of a method call without jeapordizing
1206 the normal functioning of the primary method or placing any extra
1207 responsibility on the code of the modifier. Of course if you have more
1208 complex needs, then use the I<around> modifier, which uses a variation
1209 of continutation passing style to allow for a high degree of flexibility.
1211 Before and around modifiers are called in last-defined-first-called order,
1212 while after modifiers are called in first-defined-first-called order. So
1213 the call tree might looks something like this:
1223 To see examples of using method modifiers, see the following examples
1224 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1225 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1226 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1228 =head3 What is the performance impact?
1230 Of course there is a performance cost associated with method modifiers,
1231 but we have made every effort to make that cost be directly proportional
1232 to the amount of modifier features you utilize.
1234 The wrapping method does it's best to B<only> do as much work as it
1235 absolutely needs to. In order to do this we have moved some of the
1236 performance costs to set-up time, where they are easier to amortize.
1238 All this said, my benchmarks have indicated the following:
1240 simple wrapper with no modifiers 100% slower
1241 simple wrapper with simple before modifier 400% slower
1242 simple wrapper with simple after modifier 450% slower
1243 simple wrapper with simple around modifier 500-550% slower
1244 simple wrapper with all 3 modifiers 1100% slower
1246 These numbers may seem daunting, but you must remember, every feature
1247 comes with some cost. To put things in perspective, just doing a simple
1248 C<AUTOLOAD> which does nothing but extract the name of the method called
1249 and return it costs about 400% over a normal method call.
1253 =item B<add_before_method_modifier ($method_name, $code)>
1255 This will wrap the method at C<$method_name> and the supplied C<$code>
1256 will be passed the C<@_> arguments, and called before the original
1257 method is called. As specified above, the return value of the I<before>
1258 method modifiers is ignored, and it's ability to modify C<@_> is
1259 fairly limited. If you need to do either of these things, use an
1260 C<around> method modifier.
1262 =item B<add_after_method_modifier ($method_name, $code)>
1264 This will wrap the method at C<$method_name> so that the original
1265 method will be called, it's return values stashed, and then the
1266 supplied C<$code> will be passed the C<@_> arguments, and called.
1267 As specified above, the return value of the I<after> method
1268 modifiers is ignored, and it cannot modify the return values of
1269 the original method. If you need to do either of these things, use an
1270 C<around> method modifier.
1272 =item B<add_around_method_modifier ($method_name, $code)>
1274 This will wrap the method at C<$method_name> so that C<$code>
1275 will be called and passed the original method as an extra argument
1276 at the begining of the C<@_> argument list. This is a variation of
1277 continuation passing style, where the function prepended to C<@_>
1278 can be considered a continuation. It is up to C<$code> if it calls
1279 the original method or not, there is no restriction on what the
1280 C<$code> can or cannot do.
1286 It should be noted that since there is no one consistent way to define
1287 the attributes of a class in Perl 5. These methods can only work with
1288 the information given, and can not easily discover information on
1289 their own. See L<Class::MOP::Attribute> for more details.
1293 =item B<attribute_metaclass>
1295 =item B<get_attribute_map>
1297 =item B<add_attribute ($attribute_meta_object | $attribute_name, %attribute_spec)>
1299 This stores the C<$attribute_meta_object> (or creates one from the
1300 C<$attribute_name> and C<%attribute_spec>) in the B<Class::MOP::Class>
1301 instance associated with the given class. Unlike methods, attributes
1302 within the MOP are stored as meta-information only. They will be used
1303 later to construct instances from (see C<construct_instance> above).
1304 More details about the attribute meta-objects can be found in the
1305 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1308 It should be noted that any accessor, reader/writer or predicate
1309 methods which the C<$attribute_meta_object> has will be installed
1310 into the class at this time.
1313 If an attribute already exists for C<$attribute_name>, the old one
1314 will be removed (as well as removing all it's accessors), and then
1317 =item B<has_attribute ($attribute_name)>
1319 Checks to see if this class has an attribute by the name of
1320 C<$attribute_name> and returns a boolean.
1322 =item B<get_attribute ($attribute_name)>
1324 Returns the attribute meta-object associated with C<$attribute_name>,
1325 if none is found, it will return undef.
1327 =item B<remove_attribute ($attribute_name)>
1329 This will remove the attribute meta-object stored at
1330 C<$attribute_name>, then return the removed attribute meta-object.
1333 Removing an attribute will only affect future instances of
1334 the class, it will not make any attempt to remove the attribute from
1335 any existing instances of the class.
1337 It should be noted that any accessor, reader/writer or predicate
1338 methods which the attribute meta-object stored at C<$attribute_name>
1339 has will be removed from the class at this time. This B<will> make
1340 these attributes somewhat inaccessable in previously created
1341 instances. But if you are crazy enough to do this at runtime, then
1342 you are crazy enough to deal with something like this :).
1344 =item B<get_attribute_list>
1346 This returns a list of attribute names which are defined in the local
1347 class. If you want a list of all applicable attributes for a class,
1348 use the C<compute_all_applicable_attributes> method.
1350 =item B<compute_all_applicable_attributes>
1352 This will traverse the inheritance heirachy and return a list of all
1353 the applicable attributes for this class. It does not construct a
1354 HASH reference like C<compute_all_applicable_methods> because all
1355 that same information is discoverable through the attribute
1358 =item B<find_attribute_by_name ($attr_name)>
1360 This method will traverse the inheritance heirachy and find the
1361 first attribute whose name matches C<$attr_name>, then return it.
1362 It will return undef if nothing is found.
1366 =head2 Class Immutability
1370 =item B<make_immutable (%options)>
1372 This method will invoke a tranforamtion upon the class which will
1373 make it immutable. Details of this transformation can be found in
1374 the L<Class::MOP::Immutable> documentation.
1376 =item B<make_mutable>
1378 This method will reverse tranforamtion upon the class which
1381 =item B<create_immutable_transformer>
1383 Create a transformer suitable for making this class immutable
1389 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1391 =head1 COPYRIGHT AND LICENSE
1393 Copyright 2006, 2007 by Infinity Interactive, Inc.
1395 L<http://www.iinteractive.com>
1397 This library is free software; you can redistribute it and/or modify
1398 it under the same terms as Perl itself.