2 package Class::MOP::Class;
8 use Scalar::Util 'blessed', 'reftype';
9 use Sub::Name 'subname';
10 use B 'svref_2object';
12 our $VERSION = '0.14';
14 use Class::MOP::Instance;
18 sub meta { Class::MOP::Class->initialize(blessed($_[0]) || $_[0]) }
23 # Metaclasses are singletons, so we cache them here.
24 # there is no need to worry about destruction though
25 # because they should die only when the program dies.
26 # After all, do package definitions even get reaped?
29 # means of accessing all the metaclasses that have
30 # been initialized thus far (for mugwumps obj browser)
31 sub get_all_metaclasses { %METAS }
32 sub get_all_metaclass_instances { values %METAS }
33 sub get_all_metaclass_names { keys %METAS }
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->construct_class_instance(':package' => $package_name, @_);
45 my $package_name = shift;
46 (defined $package_name && $package_name && !blessed($package_name))
47 || confess "You must pass a package name and it cannot be blessed";
48 $METAS{$package_name} = undef;
49 $class->construct_class_instance(':package' => $package_name, @_);
52 # NOTE: (meta-circularity)
53 # this is a special form of &construct_instance
54 # (see below), which is used to construct class
55 # meta-object instances for any Class::MOP::*
56 # class. All other classes will use the more
57 # normal &construct_instance.
58 sub construct_class_instance {
61 my $package_name = $options{':package'};
62 (defined $package_name && $package_name)
63 || confess "You must pass a package name";
65 # return the metaclass if we have it cached,
66 # and it is still defined (it has not been
67 # reaped by DESTROY yet, which can happen
68 # annoyingly enough during global destruction)
69 return $METAS{$package_name}
70 if exists $METAS{$package_name} && defined $METAS{$package_name};
71 $class = blessed($class) || $class;
72 # now create the metaclass
74 if ($class =~ /^Class::MOP::/) {
76 '$:package' => $package_name,
78 '$:attribute_metaclass' => $options{':attribute_metaclass'} || 'Class::MOP::Attribute',
79 '$:method_metaclass' => $options{':method_metaclass'} || 'Class::MOP::Method',
80 '$:instance_metaclass' => $options{':instance_metaclass'} || 'Class::MOP::Instance',
85 # it is safe to use meta here because
86 # class will always be a subclass of
87 # Class::MOP::Class, which defines meta
88 $meta = $class->meta->construct_instance(%options)
90 # and check the metaclass compatibility
91 $meta->check_metaclass_compatability();
92 $METAS{$package_name} = $meta;
95 sub check_metaclass_compatability {
98 # this is always okay ...
99 return if blessed($self) eq 'Class::MOP::Class' &&
100 $self->instance_metaclass eq 'Class::MOP::Instance';
102 my @class_list = $self->class_precedence_list;
103 shift @class_list; # shift off $self->name
105 foreach my $class_name (@class_list) {
106 my $meta = $METAS{$class_name} || next;
107 ($self->isa(blessed($meta)))
108 || confess $self->name . "->meta => (" . (blessed($self)) . ")" .
109 " is not compatible with the " .
110 $class_name . "->meta => (" . (blessed($meta)) . ")";
112 # we also need to check that instance metaclasses
113 # are compatabile in the same the class.
114 ($self->instance_metaclass->isa($meta->instance_metaclass))
115 || confess $self->name . "->meta => (" . ($self->instance_metaclass) . ")" .
116 " is not compatible with the " .
117 $class_name . "->meta => (" . ($meta->instance_metaclass) . ")";
123 my ($class, $package_name, $package_version, %options) = @_;
124 (defined $package_name && $package_name)
125 || confess "You must pass a package name";
126 my $code = "package $package_name;";
127 $code .= "\$$package_name\:\:VERSION = '$package_version';"
128 if defined $package_version;
130 confess "creation of $package_name failed : $@" if $@;
131 my $meta = $class->initialize($package_name);
133 $meta->add_method('meta' => sub {
134 Class::MOP::Class->initialize(blessed($_[0]) || $_[0]);
137 $meta->superclasses(@{$options{superclasses}})
138 if exists $options{superclasses};
140 # process attributes first, so that they can
141 # install accessors, but locally defined methods
142 # can then overwrite them. It is maybe a little odd, but
143 # I think this should be the order of things.
144 if (exists $options{attributes}) {
145 foreach my $attr (@{$options{attributes}}) {
146 $meta->add_attribute($attr);
149 if (exists $options{methods}) {
150 foreach my $method_name (keys %{$options{methods}}) {
151 $meta->add_method($method_name, $options{methods}->{$method_name});
158 sub create_anon_class {
159 my ($class, %options) = @_;
160 return Class::MOP::Class::__ANON__->create(%options);
166 # all these attribute readers will be bootstrapped
167 # away in the Class::MOP bootstrap section
169 sub name { $_[0]->{'$:package'} }
170 sub get_attribute_map { $_[0]->{'%:attributes'} }
171 sub attribute_metaclass { $_[0]->{'$:attribute_metaclass'} }
172 sub method_metaclass { $_[0]->{'$:method_metaclass'} }
173 sub instance_metaclass { $_[0]->{'$:instance_metaclass'} }
175 # Instance Construction & Cloning
180 # we need to protect the integrity of the
181 # Class::MOP::Class singletons here, so we
182 # delegate this to &construct_class_instance
183 # which will deal with the singletons
184 return $class->construct_class_instance(@_)
185 if $class->name->isa('Class::MOP::Class');
186 return $class->construct_instance(@_);
189 sub construct_instance {
190 my ($class, %params) = @_;
191 my $meta_instance = $class->get_meta_instance();
192 my $instance = $meta_instance->create_instance();
193 foreach my $attr ($class->compute_all_applicable_attributes()) {
194 $attr->initialize_instance_slot($meta_instance, $instance, \%params);
199 sub get_meta_instance {
201 return $class->instance_metaclass->new(
203 $class->compute_all_applicable_attributes()
209 my $instance = shift;
210 (blessed($instance) && $instance->isa($class->name))
211 || confess "You must pass an instance ($instance) of the metaclass (" . $class->name . ")";
213 # we need to protect the integrity of the
214 # Class::MOP::Class singletons here, they
215 # should not be cloned.
216 return $instance if $instance->isa('Class::MOP::Class');
217 $class->clone_instance($instance, @_);
221 my ($class, $instance, %params) = @_;
223 || confess "You can only clone instances, \$self is not a blessed instance";
224 my $meta_instance = $class->get_meta_instance();
225 my $clone = $meta_instance->clone_instance($instance);
226 foreach my $key (%params) {
227 next unless $meta_instance->is_valid_slot($key);
228 $meta_instance->set_slot_value($clone, $key, $params{$key});
235 # &name should be here too, but it is above
236 # because it gets bootstrapped away
240 ${$self->get_package_variable('$VERSION')};
250 @{$self->name . '::ISA'} = @supers;
252 # we need to check the metaclass
253 # compatability here so that we can
254 # be sure that the superclass is
255 # not potentially creating an issues
256 # we don't know about
257 $self->check_metaclass_compatability();
259 @{$self->name . '::ISA'};
262 sub class_precedence_list {
265 # We need to check for ciruclar inheirtance here.
266 # This will do nothing if all is well, and blow
267 # up otherwise. Yes, it's an ugly hack, better
268 # suggestions are welcome.
269 { ($self->name || return)->isa('This is a test for circular inheritance') }
270 # ... and now back to our regularly scheduled program
274 $self->initialize($_)->class_precedence_list()
275 } $self->superclasses()
282 my ($self, $method_name, $method) = @_;
283 (defined $method_name && $method_name)
284 || confess "You must define a method name";
285 # use reftype here to allow for blessed subs ...
286 ('CODE' eq (reftype($method) || ''))
287 || confess "Your code block must be a CODE reference";
288 my $full_method_name = ($self->name . '::' . $method_name);
290 $method = $self->method_metaclass->wrap($method) unless blessed($method);
293 no warnings 'redefine';
294 *{$full_method_name} = subname $full_method_name => $method;
298 my $fetch_and_prepare_method = sub {
299 my ($self, $method_name) = @_;
301 my $method = $self->get_method($method_name);
302 # if we dont have local ...
304 # make sure this method even exists ...
305 ($self->find_next_method_by_name($method_name))
306 || confess "The method '$method_name' is not found in the inherience hierarchy for this class";
307 # if so, then create a local which just
308 # calls the next applicable method ...
309 $self->add_method($method_name => sub {
310 $self->find_next_method_by_name($method_name)->(@_);
312 $method = $self->get_method($method_name);
315 # now make sure we wrap it properly
316 # (if it isnt already)
317 unless ($method->isa('Class::MOP::Method::Wrapped')) {
318 $method = Class::MOP::Method::Wrapped->wrap($method);
319 $self->add_method($method_name => $method);
324 sub add_before_method_modifier {
325 my ($self, $method_name, $method_modifier) = @_;
326 (defined $method_name && $method_name)
327 || confess "You must pass in a method name";
328 my $method = $fetch_and_prepare_method->($self, $method_name);
329 $method->add_before_modifier(subname ':before' => $method_modifier);
332 sub add_after_method_modifier {
333 my ($self, $method_name, $method_modifier) = @_;
334 (defined $method_name && $method_name)
335 || confess "You must pass in a method name";
336 my $method = $fetch_and_prepare_method->($self, $method_name);
337 $method->add_after_modifier(subname ':after' => $method_modifier);
340 sub add_around_method_modifier {
341 my ($self, $method_name, $method_modifier) = @_;
342 (defined $method_name && $method_name)
343 || confess "You must pass in a method name";
344 my $method = $fetch_and_prepare_method->($self, $method_name);
345 $method->add_around_modifier(subname ':around' => $method_modifier);
349 # the methods above used to be named like this:
350 # ${pkg}::${method}:(before|after|around)
351 # but this proved problematic when using one modifier
352 # to wrap multiple methods (something which is likely
353 # to happen pretty regularly IMO). So instead of naming
354 # it like this, I have chosen to just name them purely
355 # with their modifier names, like so:
356 # :(before|after|around)
357 # The fact is that in a stack trace, it will be fairly
358 # evident from the context what method they are attached
359 # to, and so don't need the fully qualified name.
363 my ($self, $method_name, $method) = @_;
364 (defined $method_name && $method_name)
365 || confess "You must define a method name";
366 # use reftype here to allow for blessed subs ...
367 ('CODE' eq (reftype($method) || ''))
368 || confess "Your code block must be a CODE reference";
369 my $full_method_name = ($self->name . '::' . $method_name);
371 $method = $self->method_metaclass->wrap($method) unless blessed($method);
374 no warnings 'redefine';
375 *{$full_method_name} = $method;
379 my ($self, $method_name) = @_;
380 (defined $method_name && $method_name)
381 || confess "You must define a method name";
383 my $sub_name = ($self->name . '::' . $method_name);
386 return 0 if !defined(&{$sub_name});
387 my $method = \&{$sub_name};
388 return 0 if (svref_2object($method)->GV->STASH->NAME || '') ne $self->name &&
389 (svref_2object($method)->GV->NAME || '') ne '__ANON__';
391 # at this point we are relatively sure
392 # it is our method, so we bless/wrap it
393 $self->method_metaclass->wrap($method) unless blessed($method);
398 my ($self, $method_name) = @_;
399 (defined $method_name && $method_name)
400 || confess "You must define a method name";
402 return unless $self->has_method($method_name);
405 return \&{$self->name . '::' . $method_name};
409 my ($self, $method_name) = @_;
410 (defined $method_name && $method_name)
411 || confess "You must define a method name";
413 my $removed_method = $self->get_method($method_name);
416 delete ${$self->name . '::'}{$method_name}
417 if defined $removed_method;
419 return $removed_method;
422 sub get_method_list {
425 grep { $self->has_method($_) } keys %{$self->name . '::'};
428 sub compute_all_applicable_methods {
431 # keep a record of what we have seen
432 # here, this will handle all the
433 # inheritence issues because we are
434 # using the &class_precedence_list
435 my (%seen_class, %seen_method);
436 foreach my $class ($self->class_precedence_list()) {
437 next if $seen_class{$class};
438 $seen_class{$class}++;
439 # fetch the meta-class ...
440 my $meta = $self->initialize($class);
441 foreach my $method_name ($meta->get_method_list()) {
442 next if exists $seen_method{$method_name};
443 $seen_method{$method_name}++;
445 name => $method_name,
447 code => $meta->get_method($method_name)
454 sub find_all_methods_by_name {
455 my ($self, $method_name) = @_;
456 (defined $method_name && $method_name)
457 || confess "You must define a method name to find";
459 # keep a record of what we have seen
460 # here, this will handle all the
461 # inheritence issues because we are
462 # using the &class_precedence_list
464 foreach my $class ($self->class_precedence_list()) {
465 next if $seen_class{$class};
466 $seen_class{$class}++;
467 # fetch the meta-class ...
468 my $meta = $self->initialize($class);
470 name => $method_name,
472 code => $meta->get_method($method_name)
473 } if $meta->has_method($method_name);
478 sub find_next_method_by_name {
479 my ($self, $method_name) = @_;
480 (defined $method_name && $method_name)
481 || confess "You must define a method name to find";
482 # keep a record of what we have seen
483 # here, this will handle all the
484 # inheritence issues because we are
485 # using the &class_precedence_list
487 my @cpl = $self->class_precedence_list();
488 shift @cpl; # discard ourselves
489 foreach my $class (@cpl) {
490 next if $seen_class{$class};
491 $seen_class{$class}++;
492 # fetch the meta-class ...
493 my $meta = $self->initialize($class);
494 return $meta->get_method($method_name)
495 if $meta->has_method($method_name);
504 # either we have an attribute object already
505 # or we need to create one from the args provided
506 my $attribute = blessed($_[0]) ? $_[0] : $self->attribute_metaclass->new(@_);
507 # make sure it is derived from the correct type though
508 ($attribute->isa('Class::MOP::Attribute'))
509 || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
510 $attribute->attach_to_class($self);
511 $attribute->install_accessors();
512 $self->get_attribute_map->{$attribute->name} = $attribute;
515 # in theory we have to tell everyone the slot structure may have changed
519 my ($self, $attribute_name) = @_;
520 (defined $attribute_name && $attribute_name)
521 || confess "You must define an attribute name";
522 exists $self->get_attribute_map->{$attribute_name} ? 1 : 0;
526 my ($self, $attribute_name) = @_;
527 (defined $attribute_name && $attribute_name)
528 || confess "You must define an attribute name";
529 return $self->get_attribute_map->{$attribute_name}
530 if $self->has_attribute($attribute_name);
534 sub remove_attribute {
535 my ($self, $attribute_name) = @_;
536 (defined $attribute_name && $attribute_name)
537 || confess "You must define an attribute name";
538 my $removed_attribute = $self->get_attribute_map->{$attribute_name};
539 return unless defined $removed_attribute;
540 delete $self->get_attribute_map->{$attribute_name};
541 $removed_attribute->remove_accessors();
542 $removed_attribute->detach_from_class();
543 return $removed_attribute;
546 sub get_attribute_list {
548 keys %{$self->get_attribute_map};
551 sub compute_all_applicable_attributes {
554 # keep a record of what we have seen
555 # here, this will handle all the
556 # inheritence issues because we are
557 # using the &class_precedence_list
558 my (%seen_class, %seen_attr);
559 foreach my $class ($self->class_precedence_list()) {
560 next if $seen_class{$class};
561 $seen_class{$class}++;
562 # fetch the meta-class ...
563 my $meta = $self->initialize($class);
564 foreach my $attr_name ($meta->get_attribute_list()) {
565 next if exists $seen_attr{$attr_name};
566 $seen_attr{$attr_name}++;
567 push @attrs => $meta->get_attribute($attr_name);
573 sub find_attribute_by_name {
574 my ($self, $attr_name) = @_;
575 # keep a record of what we have seen
576 # here, this will handle all the
577 # inheritence issues because we are
578 # using the &class_precedence_list
580 foreach my $class ($self->class_precedence_list()) {
581 next if $seen_class{$class};
582 $seen_class{$class}++;
583 # fetch the meta-class ...
584 my $meta = $self->initialize($class);
585 return $meta->get_attribute($attr_name)
586 if $meta->has_attribute($attr_name);
593 sub add_package_variable {
594 my ($self, $variable, $initial_value) = @_;
595 (defined $variable && $variable =~ /^[\$\@\%]/)
596 || confess "variable name does not have a sigil";
598 my ($sigil, $name) = ($variable =~ /^(.)(.*)$/);
599 if (defined $initial_value) {
601 *{$self->name . '::' . $name} = $initial_value;
607 # We HAVE to localize $@ or all
608 # hell breaks loose. It is not
609 # good, believe me, not good.
611 eval $sigil . $self->name . '::' . $name;
614 confess "Could not create package variable ($variable) because : $e" if $e;
618 sub has_package_variable {
619 my ($self, $variable) = @_;
620 (defined $variable && $variable =~ /^[\$\@\%]/)
621 || confess "variable name does not have a sigil";
622 my ($sigil, $name) = ($variable =~ /^(.)(.*)$/);
624 defined ${$self->name . '::'}{$name} ? 1 : 0;
627 sub get_package_variable {
628 my ($self, $variable) = @_;
629 (defined $variable && $variable =~ /^[\$\@\%]/)
630 || confess "variable name does not have a sigil";
631 my ($sigil, $name) = ($variable =~ /^(.)(.*)$/);
635 # We HAVE to localize $@ or all
636 # hell breaks loose. It is not
637 # good, believe me, not good.
639 $ref = eval '\\' . $sigil . $self->name . '::' . $name;
642 confess "Could not get the package variable ($variable) because : $e" if $e;
643 # if we didn't die, then we can return it
647 sub remove_package_variable {
648 my ($self, $variable) = @_;
649 (defined $variable && $variable =~ /^[\$\@\%]/)
650 || confess "variable name does not have a sigil";
651 my ($sigil, $name) = ($variable =~ /^(.)(.*)$/);
653 delete ${$self->name . '::'}{$name};
656 package Class::MOP::Class::__ANON__;
661 use Scalar::Util 'weaken';
663 our $VERSION = '0.01';
665 use base 'Class::MOP::Class';
667 # we hold a weakened cache here
671 # this should be sufficient, if you have a
672 # use case where it is not, write a test and
674 my $ANON_CLASS_SERIAL = 0;
676 # prefix for all anon-class names
677 my $ANON_CLASS_PREFIX = __PACKAGE__ . '::SERIAL::';
681 if ($_[0] =~ /^$ANON_CLASS_PREFIX/) {
682 $class->SUPER::initialize(@_);
686 # we need to do this or weird
688 Class::MOP::Class->initialize(@_);
693 my ($class, %options) = @_;
694 my $package_name = $ANON_CLASS_PREFIX . ++$ANON_CLASS_SERIAL;
695 return $class->SUPER::create($package_name, '0.00', %options);
698 sub construct_class_instance {
699 my ($class, %options) = @_;
700 my $package_name = $options{':package'};
702 # we cache the anon metaclasses as well
703 # but we weaken them (see below)
704 return $ANON_METAS{$package_name}
705 if exists $ANON_METAS{$package_name} &&
706 defined $ANON_METAS{$package_name};
707 my $meta = $class->meta->construct_instance(%options);
708 $meta->check_metaclass_compatability();
709 # weaken the metaclass cache so that
710 # DESTROY gets called as expected
711 weaken($ANON_METAS{$package_name} = $meta);
717 my ($serial_id) = ($self->name =~ /$ANON_CLASS_PREFIX(\d+)/);
718 #warn "destroying $prefix => $serial_id\n$self => ". $self->name;
720 foreach my $key (keys %{$ANON_CLASS_PREFIX . $serial_id}) {
721 delete ${$ANON_CLASS_PREFIX . $serial_id}{$key};
723 delete ${'main::' . $ANON_CLASS_PREFIX}{$serial_id . '::'};
734 Class::MOP::Class - Class Meta Object
738 # assuming that class Foo
739 # has been defined, you can
741 # use this for introspection ...
743 # add a method to Foo ...
744 Foo->meta->add_method('bar' => sub { ... })
746 # get a list of all the classes searched
747 # the method dispatcher in the correct order
748 Foo->meta->class_precedence_list()
750 # remove a method from Foo
751 Foo->meta->remove_method('bar');
753 # or use this to actually create classes ...
755 Class::MOP::Class->create('Bar' => '0.01' => (
756 superclasses => [ 'Foo' ],
758 Class::MOP:::Attribute->new('$bar'),
759 Class::MOP:::Attribute->new('$baz'),
762 calculate_bar => sub { ... },
763 construct_baz => sub { ... }
769 This is the largest and currently most complex part of the Perl 5
770 meta-object protocol. It controls the introspection and
771 manipulation of Perl 5 classes (and it can create them too). The
772 best way to understand what this module can do, is to read the
773 documentation for each of it's methods.
777 =head2 Self Introspection
783 This will return a B<Class::MOP::Class> instance which is related
784 to this class. Thereby allowing B<Class::MOP::Class> to actually
787 As with B<Class::MOP::Attribute>, B<Class::MOP> will actually
788 bootstrap this module by installing a number of attribute meta-objects
789 into it's metaclass. This will allow this class to reap all the benifits
790 of the MOP when subclassing it.
792 =item B<get_all_metaclasses>
794 This will return an hash of all the metaclass instances that have
795 been cached by B<Class::MOP::Class> keyed by the package name.
797 =item B<get_all_metaclass_instances>
799 This will return an array of all the metaclass instances that have
800 been cached by B<Class::MOP::Class>.
802 =item B<get_all_metaclass_names>
804 This will return an array of all the metaclass names that have
805 been cached by B<Class::MOP::Class>.
809 =head2 Class construction
811 These methods will handle creating B<Class::MOP::Class> objects,
812 which can be used to both create new classes, and analyze
813 pre-existing classes.
815 This module will internally store references to all the instances
816 you create with these methods, so that they do not need to be
817 created any more than nessecary. Basically, they are singletons.
821 =item B<create ($package_name, ?$package_version,
822 superclasses =E<gt> ?@superclasses,
823 methods =E<gt> ?%methods,
824 attributes =E<gt> ?%attributes)>
826 This returns a B<Class::MOP::Class> object, bringing the specified
827 C<$package_name> into existence and adding any of the
828 C<$package_version>, C<@superclasses>, C<%methods> and C<%attributes>
831 =item B<create_anon_class (superclasses =E<gt> ?@superclasses,
832 methods =E<gt> ?%methods,
833 attributes =E<gt> ?%attributes)>
835 This will create an anonymous class, it works much like C<create> but
836 it does not need a C<$package_name>. Instead it will create a suitably
837 unique package name for you to stash things into.
839 =item B<initialize ($package_name, %options)>
841 This initializes and returns returns a B<Class::MOP::Class> object
842 for a given a C<$package_name>.
844 =item B<reinitialize ($package_name, %options)>
846 This removes the old metaclass, and creates a new one in it's place.
847 Do B<not> use this unless you really know what you are doing, it could
848 very easily make a very large mess of your program.
850 =item B<construct_class_instance (%options)>
852 This will construct an instance of B<Class::MOP::Class>, it is
853 here so that we can actually "tie the knot" for B<Class::MOP::Class>
854 to use C<construct_instance> once all the bootstrapping is done. This
855 method is used internally by C<initialize> and should never be called
856 from outside of that method really.
858 =item B<check_metaclass_compatability>
860 This method is called as the very last thing in the
861 C<construct_class_instance> method. This will check that the
862 metaclass you are creating is compatible with the metaclasses of all
863 your ancestors. For more inforamtion about metaclass compatibility
864 see the C<About Metaclass compatibility> section in L<Class::MOP>.
868 =head2 Object instance construction and cloning
870 These methods are B<entirely optional>, it is up to you whether you want
875 =item B<instance_metaclass>
877 =item B<get_meta_instance>
879 =item B<new_object (%params)>
881 This is a convience method for creating a new object of the class, and
882 blessing it into the appropriate package as well. Ideally your class
883 would call a C<new> this method like so:
886 my ($class, %param) = @_;
887 $class->meta->new_object(%params);
890 Of course the ideal place for this would actually be in C<UNIVERSAL::>
891 but that is considered bad style, so we do not do that.
893 =item B<construct_instance (%params)>
895 This method is used to construct an instace structure suitable for
896 C<bless>-ing into your package of choice. It works in conjunction
897 with the Attribute protocol to collect all applicable attributes.
899 This will construct and instance using a HASH ref as storage
900 (currently only HASH references are supported). This will collect all
901 the applicable attributes and layout out the fields in the HASH ref,
902 it will then initialize them using either use the corresponding key
903 in C<%params> or any default value or initializer found in the
904 attribute meta-object.
906 =item B<clone_object ($instance, %params)>
908 This is a convience method for cloning an object instance, then
909 blessing it into the appropriate package. This method will call
910 C<clone_instance>, which performs a shallow copy of the object,
911 see that methods documentation for more details. Ideally your
912 class would call a C<clone> this method like so:
915 my ($self, %param) = @_;
916 $self->meta->clone_object($self, %params);
919 Of course the ideal place for this would actually be in C<UNIVERSAL::>
920 but that is considered bad style, so we do not do that.
922 =item B<clone_instance($instance, %params)>
924 This method is a compliment of C<construct_instance> (which means if
925 you override C<construct_instance>, you need to override this one too),
926 and clones the instance shallowly.
928 The cloned structure returned is (like with C<construct_instance>) an
929 unC<bless>ed HASH reference, it is your responsibility to then bless
930 this cloned structure into the right class (which C<clone_object> will
933 As of 0.11, this method will clone the C<$instance> structure shallowly,
934 as opposed to the deep cloning implemented in prior versions. After much
935 thought, research and discussion, I have decided that anything but basic
936 shallow cloning is outside the scope of the meta-object protocol. I
937 think Yuval "nothingmuch" Kogman put it best when he said that cloning
938 is too I<context-specific> to be part of the MOP.
948 This is a read-only attribute which returns the package name for the
949 given B<Class::MOP::Class> instance.
953 This is a read-only attribute which returns the C<$VERSION> of the
954 package for the given B<Class::MOP::Class> instance.
958 =head2 Inheritance Relationships
962 =item B<superclasses (?@superclasses)>
964 This is a read-write attribute which represents the superclass
965 relationships of the class the B<Class::MOP::Class> instance is
966 associated with. Basically, it can get and set the C<@ISA> for you.
969 Perl will occasionally perform some C<@ISA> and method caching, if
970 you decide to change your superclass relationship at runtime (which
971 is quite insane and very much not recommened), then you should be
972 aware of this and the fact that this module does not make any
973 attempt to address this issue.
975 =item B<class_precedence_list>
977 This computes the a list of all the class's ancestors in the same order
978 in which method dispatch will be done. This is similair to
979 what B<Class::ISA::super_path> does, but we don't remove duplicate names.
987 =item B<method_metaclass>
989 =item B<add_method ($method_name, $method)>
991 This will take a C<$method_name> and CODE reference to that
992 C<$method> and install it into the class's package.
995 This does absolutely nothing special to C<$method>
996 other than use B<Sub::Name> to make sure it is tagged with the
997 correct name, and therefore show up correctly in stack traces and
1000 =item B<alias_method ($method_name, $method)>
1002 This will take a C<$method_name> and CODE reference to that
1003 C<$method> and alias the method into the class's package.
1006 Unlike C<add_method>, this will B<not> try to name the
1007 C<$method> using B<Sub::Name>, it only aliases the method in
1008 the class's package.
1010 =item B<has_method ($method_name)>
1012 This just provides a simple way to check if the class implements
1013 a specific C<$method_name>. It will I<not> however, attempt to check
1014 if the class inherits the method (use C<UNIVERSAL::can> for that).
1016 This will correctly handle functions defined outside of the package
1017 that use a fully qualified name (C<sub Package::name { ... }>).
1019 This will correctly handle functions renamed with B<Sub::Name> and
1020 installed using the symbol tables. However, if you are naming the
1021 subroutine outside of the package scope, you must use the fully
1022 qualified name, including the package name, for C<has_method> to
1023 correctly identify it.
1025 This will attempt to correctly ignore functions imported from other
1026 packages using B<Exporter>. It breaks down if the function imported
1027 is an C<__ANON__> sub (such as with C<use constant>), which very well
1028 may be a valid method being applied to the class.
1030 In short, this method cannot always be trusted to determine if the
1031 C<$method_name> is actually a method. However, it will DWIM about
1032 90% of the time, so it's a small trade off I think.
1034 =item B<get_method ($method_name)>
1036 This will return a CODE reference of the specified C<$method_name>,
1037 or return undef if that method does not exist.
1039 =item B<remove_method ($method_name)>
1041 This will attempt to remove a given C<$method_name> from the class.
1042 It will return the CODE reference that it has removed, and will
1043 attempt to use B<Sub::Name> to clear the methods associated name.
1045 =item B<get_method_list>
1047 This will return a list of method names for all I<locally> defined
1048 methods. It does B<not> provide a list of all applicable methods,
1049 including any inherited ones. If you want a list of all applicable
1050 methods, use the C<compute_all_applicable_methods> method.
1052 =item B<compute_all_applicable_methods>
1054 This will return a list of all the methods names this class will
1055 respond to, taking into account inheritance. The list will be a list of
1056 HASH references, each one containing the following information; method
1057 name, the name of the class in which the method lives and a CODE
1058 reference for the actual method.
1060 =item B<find_all_methods_by_name ($method_name)>
1062 This will traverse the inheritence hierarchy and locate all methods
1063 with a given C<$method_name>. Similar to
1064 C<compute_all_applicable_methods> it returns a list of HASH references
1065 with the following information; method name (which will always be the
1066 same as C<$method_name>), the name of the class in which the method
1067 lives and a CODE reference for the actual method.
1069 The list of methods produced is a distinct list, meaning there are no
1070 duplicates in it. This is especially useful for things like object
1071 initialization and destruction where you only want the method called
1072 once, and in the correct order.
1074 =item B<find_next_method_by_name ($method_name)>
1076 This will return the first method to match a given C<$method_name> in
1077 the superclasses, this is basically equivalent to calling
1078 C<SUPER::$method_name>, but it can be dispatched at runtime.
1082 =head2 Method Modifiers
1084 Method modifiers are a concept borrowed from CLOS, in which a method
1085 can be wrapped with I<before>, I<after> and I<around> method modifiers
1086 that will be called everytime the method is called.
1088 =head3 How method modifiers work?
1090 Method modifiers work by wrapping the original method and then replacing
1091 it in the classes symbol table. The wrappers will handle calling all the
1092 modifiers in the appropariate orders and preserving the calling context
1093 for the original method.
1095 Each method modifier serves a particular purpose, which may not be
1096 obvious to users of other method wrapping modules. To start with, the
1097 return values of I<before> and I<after> modifiers are ignored. This is
1098 because thier purpose is B<not> to filter the input and output of the
1099 primary method (this is done with an I<around> modifier). This may seem
1100 like an odd restriction to some, but doing this allows for simple code
1101 to be added at the begining or end of a method call without jeapordizing
1102 the normal functioning of the primary method or placing any extra
1103 responsibility on the code of the modifier. Of course if you have more
1104 complex needs, then use the I<around> modifier, which uses a variation
1105 of continutation passing style to allow for a high degree of flexibility.
1107 Before and around modifiers are called in last-defined-first-called order,
1108 while after modifiers are called in first-defined-first-called order. So
1109 the call tree might looks something like this:
1119 To see examples of using method modifiers, see the following examples
1120 included in the distribution; F<InstanceCountingClass>, F<Perl6Attribute>,
1121 F<AttributesWithHistory> and F<C3MethodDispatchOrder>. There is also a
1122 classic CLOS usage example in the test F<017_add_method_modifier.t>.
1124 =head3 What is the performance impact?
1126 Of course there is a performance cost associated with method modifiers,
1127 but we have made every effort to make that cost be directly proportional
1128 to the amount of modifier features you utilize.
1130 The wrapping method does it's best to B<only> do as much work as it
1131 absolutely needs to. In order to do this we have moved some of the
1132 performance costs to set-up time, where they are easier to amortize.
1134 All this said, my benchmarks have indicated the following:
1136 simple wrapper with no modifiers 100% slower
1137 simple wrapper with simple before modifier 400% slower
1138 simple wrapper with simple after modifier 450% slower
1139 simple wrapper with simple around modifier 500-550% slower
1140 simple wrapper with all 3 modifiers 1100% slower
1142 These numbers may seem daunting, but you must remember, every feature
1143 comes with some cost. To put things in perspective, just doing a simple
1144 C<AUTOLOAD> which does nothing but extract the name of the method called
1145 and return it costs about 400% over a normal method call.
1149 =item B<add_before_method_modifier ($method_name, $code)>
1151 This will wrap the method at C<$method_name> and the supplied C<$code>
1152 will be passed the C<@_> arguments, and called before the original
1153 method is called. As specified above, the return value of the I<before>
1154 method modifiers is ignored, and it's ability to modify C<@_> is
1155 fairly limited. If you need to do either of these things, use an
1156 C<around> method modifier.
1158 =item B<add_after_method_modifier ($method_name, $code)>
1160 This will wrap the method at C<$method_name> so that the original
1161 method will be called, it's return values stashed, and then the
1162 supplied C<$code> will be passed the C<@_> arguments, and called.
1163 As specified above, the return value of the I<after> method
1164 modifiers is ignored, and it cannot modify the return values of
1165 the original method. If you need to do either of these things, use an
1166 C<around> method modifier.
1168 =item B<add_around_method_modifier ($method_name, $code)>
1170 This will wrap the method at C<$method_name> so that C<$code>
1171 will be called and passed the original method as an extra argument
1172 at the begining of the C<@_> argument list. This is a variation of
1173 continuation passing style, where the function prepended to C<@_>
1174 can be considered a continuation. It is up to C<$code> if it calls
1175 the original method or not, there is no restriction on what the
1176 C<$code> can or cannot do.
1182 It should be noted that since there is no one consistent way to define
1183 the attributes of a class in Perl 5. These methods can only work with
1184 the information given, and can not easily discover information on
1185 their own. See L<Class::MOP::Attribute> for more details.
1189 =item B<attribute_metaclass>
1191 =item B<get_attribute_map>
1193 =item B<add_attribute ($attribute_name, $attribute_meta_object)>
1195 This stores a C<$attribute_meta_object> in the B<Class::MOP::Class>
1196 instance associated with the given class, and associates it with
1197 the C<$attribute_name>. Unlike methods, attributes within the MOP
1198 are stored as meta-information only. They will be used later to
1199 construct instances from (see C<construct_instance> above).
1200 More details about the attribute meta-objects can be found in the
1201 L<Class::MOP::Attribute> or the L<Class::MOP/The Attribute protocol>
1204 It should be noted that any accessor, reader/writer or predicate
1205 methods which the C<$attribute_meta_object> has will be installed
1206 into the class at this time.
1208 =item B<has_attribute ($attribute_name)>
1210 Checks to see if this class has an attribute by the name of
1211 C<$attribute_name> and returns a boolean.
1213 =item B<get_attribute ($attribute_name)>
1215 Returns the attribute meta-object associated with C<$attribute_name>,
1216 if none is found, it will return undef.
1218 =item B<remove_attribute ($attribute_name)>
1220 This will remove the attribute meta-object stored at
1221 C<$attribute_name>, then return the removed attribute meta-object.
1224 Removing an attribute will only affect future instances of
1225 the class, it will not make any attempt to remove the attribute from
1226 any existing instances of the class.
1228 It should be noted that any accessor, reader/writer or predicate
1229 methods which the attribute meta-object stored at C<$attribute_name>
1230 has will be removed from the class at this time. This B<will> make
1231 these attributes somewhat inaccessable in previously created
1232 instances. But if you are crazy enough to do this at runtime, then
1233 you are crazy enough to deal with something like this :).
1235 =item B<get_attribute_list>
1237 This returns a list of attribute names which are defined in the local
1238 class. If you want a list of all applicable attributes for a class,
1239 use the C<compute_all_applicable_attributes> method.
1241 =item B<compute_all_applicable_attributes>
1243 This will traverse the inheritance heirachy and return a list of all
1244 the applicable attributes for this class. It does not construct a
1245 HASH reference like C<compute_all_applicable_methods> because all
1246 that same information is discoverable through the attribute
1249 =item B<find_attribute_by_name ($attr_name)>
1251 This method will traverse the inheritance heirachy and find the
1252 first attribute whose name matches C<$attr_name>, then return it.
1253 It will return undef if nothing is found.
1257 =head2 Package Variables
1259 Since Perl's classes are built atop the Perl package system, it is
1260 fairly common to use package scoped variables for things like static
1261 class variables. The following methods are convience methods for
1262 the creation and inspection of package scoped variables.
1266 =item B<add_package_variable ($variable_name, ?$initial_value)>
1268 Given a C<$variable_name>, which must contain a leading sigil, this
1269 method will create that variable within the package which houses the
1270 class. It also takes an optional C<$initial_value>, which must be a
1271 reference of the same type as the sigil of the C<$variable_name>
1274 =item B<get_package_variable ($variable_name)>
1276 This will return a reference to the package variable in
1279 =item B<has_package_variable ($variable_name)>
1281 Returns true (C<1>) if there is a package variable defined for
1282 C<$variable_name>, and false (C<0>) otherwise.
1284 =item B<remove_package_variable ($variable_name)>
1286 This will attempt to remove the package variable at C<$variable_name>.
1292 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1294 =head1 COPYRIGHT AND LICENSE
1296 Copyright 2006 by Infinity Interactive, Inc.
1298 L<http://www.iinteractive.com>
1300 This library is free software; you can redistribute it and/or modify
1301 it under the same terms as Perl itself.