2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken';
10 our $VERSION = '0.73';
11 our $AUTHORITY = 'cpan:STEVAN';
13 use Moose::Meta::Method::Accessor;
14 use Moose::Meta::Method::Delegation;
16 use Moose::Util::TypeConstraints ();
18 use base 'Class::MOP::Attribute';
20 # options which are not directly used
21 # but we store them for metadata purposes
22 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
23 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
24 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
26 # these are actual options for the attrs
27 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
28 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
29 __PACKAGE__->meta->add_attribute('lazy_build' => (reader => 'is_lazy_build' ));
30 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
31 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
32 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
33 __PACKAGE__->meta->add_attribute('type_constraint' => (
34 reader => 'type_constraint',
35 predicate => 'has_type_constraint',
37 __PACKAGE__->meta->add_attribute('trigger' => (
39 predicate => 'has_trigger',
41 __PACKAGE__->meta->add_attribute('handles' => (
43 predicate => 'has_handles',
45 __PACKAGE__->meta->add_attribute('documentation' => (
46 reader => 'documentation',
47 predicate => 'has_documentation',
49 __PACKAGE__->meta->add_attribute('traits' => (
50 reader => 'applied_traits',
51 predicate => 'has_applied_traits',
54 # we need to have a ->does method in here to
55 # more easily support traits, and the introspection
56 # of those traits. We extend the does check to look
57 # for metatrait aliases.
59 my ($self, $role_name) = @_;
61 Moose::Util::resolve_metatrait_alias(Attribute => $role_name)
63 return 0 if !defined($name); # failed to load class
64 return $self->Moose::Object::does($name);
69 my $class = ( ref $self && $self->associated_class ) || "Moose::Meta::Class";
70 unshift @_, "message" if @_ % 2 == 1;
71 unshift @_, attr => $self if ref $self;
73 my $handler = $class->can("throw_error"); # to avoid incrementing depth by 1
78 my ($class, $name, %options) = @_;
79 $class->_process_options($name, \%options) unless $options{__hack_no_process_options}; # used from clone()... YECHKKK FIXME ICKY YUCK GROSS
80 return $class->SUPER::new($name, %options);
83 sub interpolate_class_and_new {
84 my ($class, $name, @args) = @_;
86 my ( $new_class, @traits ) = $class->interpolate_class(@args);
88 $new_class->new($name, @args, ( scalar(@traits) ? ( traits => \@traits ) : () ) );
91 sub interpolate_class {
92 my ($class, %options) = @_;
94 $class = ref($class) || $class;
96 if ( my $metaclass_name = delete $options{metaclass} ) {
97 my $new_class = Moose::Util::resolve_metaclass_alias( Attribute => $metaclass_name );
99 if ( $class ne $new_class ) {
100 if ( $new_class->can("interpolate_class") ) {
101 return $new_class->interpolate_class(%options);
110 if (my $traits = $options{traits}) {
112 while ($i < @$traits) {
113 my $trait = $traits->[$i++];
114 next if ref($trait); # options to a trait we discarded
116 $trait = Moose::Util::resolve_metatrait_alias(Attribute => $trait)
119 next if $class->does($trait);
121 push @traits, $trait;
124 push @traits, $traits->[$i++]
125 if $traits->[$i] && ref($traits->[$i]);
129 my $anon_class = Moose::Meta::Class->create_anon_class(
130 superclasses => [ $class ],
131 roles => [ @traits ],
135 $class = $anon_class->name;
139 return ( wantarray ? ( $class, @traits ) : $class );
144 my @legal_options_for_inheritance = qw(
145 default coerce required
146 documentation lazy handles
147 builder type_constraint
152 sub legal_options_for_inheritance { @legal_options_for_inheritance }
155 # This method *must* be able to handle
156 # Class::MOP::Attribute instances as
157 # well. Yes, I know that is wrong, but
158 # apparently we didn't realize it was
159 # doing that and now we have some code
160 # which is dependent on it. The real
161 # solution of course is to push this
162 # feature back up into Class::MOP::Attribute
163 # but I not right now, I am too lazy.
164 # However if you are reading this and
165 # looking for something to do,.. please
168 sub clone_and_inherit_options {
169 my ($self, %options) = @_;
176 # we may want to extends a Class::MOP::Attribute
177 # in which case we need to be able to use the
178 # core set of legal options that have always
179 # been here. But we allows Moose::Meta::Attribute
180 # instances to changes them.
182 my @legal_options = $self->can('legal_options_for_inheritance')
183 ? $self->legal_options_for_inheritance
184 : @legal_options_for_inheritance;
186 foreach my $legal_option (@legal_options) {
187 if (exists $options{$legal_option}) {
188 $actual_options{$legal_option} = $options{$legal_option};
189 delete $options{$legal_option};
195 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
196 $type_constraint = $options{isa};
199 $type_constraint = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options{isa});
200 (defined $type_constraint)
201 || $self->throw_error("Could not find the type constraint '" . $options{isa} . "'", data => $options{isa});
204 $actual_options{type_constraint} = $type_constraint;
205 delete $options{isa};
208 if ($options{does}) {
210 if (blessed($options{does}) && $options{does}->isa('Moose::Meta::TypeConstraint')) {
211 $type_constraint = $options{does};
214 $type_constraint = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options{does});
215 (defined $type_constraint)
216 || $self->throw_error("Could not find the type constraint '" . $options{does} . "'", data => $options{does});
219 $actual_options{type_constraint} = $type_constraint;
220 delete $options{does};
224 # this doesn't apply to Class::MOP::Attributes,
225 # so we can ignore it for them.
227 if ($self->can('interpolate_class')) {
228 ( $actual_options{metaclass}, my @traits ) = $self->interpolate_class(%options);
231 my @all_traits = grep { $seen{$_}++ } @{ $self->applied_traits || [] }, @traits;
232 $actual_options{traits} = \@all_traits if @all_traits;
234 delete @options{qw(metaclass traits)};
237 (scalar keys %options == 0)
238 || $self->throw_error("Illegal inherited options => (" . (join ', ' => keys %options) . ")", data => \%options);
241 $self->clone(%actual_options);
245 my ( $self, %params ) = @_;
247 my $class = $params{metaclass} || ref $self;
249 my ( @init, @non_init );
251 foreach my $attr ( grep { $_->has_value($self) } Class::MOP::class_of($self)->compute_all_applicable_attributes ) {
252 push @{ $attr->has_init_arg ? \@init : \@non_init }, $attr;
255 my %new_params = ( ( map { $_->init_arg => $_->get_value($self) } @init ), %params );
257 my $name = delete $new_params{name};
259 my $clone = $class->new($name, %new_params, __hack_no_process_options => 1 );
261 foreach my $attr ( @non_init ) {
262 $attr->set_value($clone, $attr->get_value($self));
268 sub _process_options {
269 my ($class, $name, $options) = @_;
271 if (exists $options->{is}) {
273 ### -------------------------
274 ## is => ro, writer => _foo # turns into (reader => foo, writer => _foo) as before
275 ## is => rw, writer => _foo # turns into (reader => foo, writer => _foo)
276 ## is => rw, accessor => _foo # turns into (accessor => _foo)
277 ## is => ro, accessor => _foo # error, accesor is rw
278 ### -------------------------
280 if ($options->{is} eq 'ro') {
281 $class->throw_error("Cannot define an accessor name on a read-only attribute, accessors are read/write", data => $options)
282 if exists $options->{accessor};
283 $options->{reader} ||= $name;
285 elsif ($options->{is} eq 'rw') {
286 if ($options->{writer}) {
287 $options->{reader} ||= $name;
290 $options->{accessor} ||= $name;
294 $class->throw_error("I do not understand this option (is => " . $options->{is} . ") on attribute ($name)", data => $options->{is});
298 if (exists $options->{isa}) {
299 if (exists $options->{does}) {
300 if (eval { $options->{isa}->can('does') }) {
301 ($options->{isa}->does($options->{does}))
302 || $class->throw_error("Cannot have an isa option and a does option if the isa does not do the does on attribute ($name)", data => $options);
305 $class->throw_error("Cannot have an isa option which cannot ->does() on attribute ($name)", data => $options);
309 # allow for anon-subtypes here ...
310 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
311 $options->{type_constraint} = $options->{isa};
314 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options->{isa});
317 elsif (exists $options->{does}) {
318 # allow for anon-subtypes here ...
319 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
320 $options->{type_constraint} = $options->{does};
323 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options->{does});
327 if (exists $options->{coerce} && $options->{coerce}) {
328 (exists $options->{type_constraint})
329 || $class->throw_error("You cannot have coercion without specifying a type constraint on attribute ($name)", data => $options);
330 $class->throw_error("You cannot have a weak reference to a coerced value on attribute ($name)", data => $options)
331 if $options->{weak_ref};
334 if (exists $options->{trigger}) {
335 ('CODE' eq ref $options->{trigger})
336 || $class->throw_error("Trigger must be a CODE ref on attribute ($name)", data => $options->{trigger});
339 if (exists $options->{auto_deref} && $options->{auto_deref}) {
340 (exists $options->{type_constraint})
341 || $class->throw_error("You cannot auto-dereference without specifying a type constraint on attribute ($name)", data => $options);
342 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
343 $options->{type_constraint}->is_a_type_of('HashRef'))
344 || $class->throw_error("You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute ($name)", data => $options);
347 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
348 $class->throw_error("You can not use lazy_build and default for the same attribute ($name)", data => $options)
349 if exists $options->{default};
350 $options->{lazy} = 1;
351 $options->{required} = 1;
352 $options->{builder} ||= "_build_${name}";
354 $options->{clearer} ||= "_clear${name}";
355 $options->{predicate} ||= "_has${name}";
358 $options->{clearer} ||= "clear_${name}";
359 $options->{predicate} ||= "has_${name}";
363 if (exists $options->{lazy} && $options->{lazy}) {
364 (exists $options->{default} || defined $options->{builder} )
365 || $class->throw_error("You cannot have lazy attribute ($name) without specifying a default value for it", data => $options);
368 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
369 $class->throw_error("You cannot have a required attribute ($name) without a default, builder, or an init_arg", data => $options);
374 sub initialize_instance_slot {
375 my ($self, $meta_instance, $instance, $params) = @_;
376 my $init_arg = $self->init_arg();
377 # try to fetch the init arg from the %params ...
381 if ( defined($init_arg) and exists $params->{$init_arg}) {
382 $val = $params->{$init_arg};
386 # skip it if it's lazy
387 return if $self->is_lazy;
388 # and die if it's required and doesn't have a default value
389 $self->throw_error("Attribute (" . $self->name . ") is required", object => $instance, data => $params)
390 if $self->is_required && !$self->has_default && !$self->has_builder;
392 # if nothing was in the %params, we can use the
393 # attribute's default value (if it has one)
394 if ($self->has_default) {
395 $val = $self->default($instance);
398 elsif ($self->has_builder) {
399 $val = $self->_call_builder($instance);
404 return unless $value_is_set;
406 $val = $self->_coerce_and_verify( $val, $instance );
408 $self->set_initial_value($instance, $val);
409 $meta_instance->weaken_slot_value($instance, $self->name)
410 if ref $val && $self->is_weak_ref;
414 my ( $self, $instance ) = @_;
416 my $builder = $self->builder();
418 return $instance->$builder()
419 if $instance->can( $self->builder );
421 $self->throw_error( blessed($instance)
422 . " does not support builder method '"
424 . "' for attribute '"
434 # this duplicates too much code from
435 # Class::MOP::Attribute, we need to
436 # refactor these bits eventually.
438 sub _set_initial_slot_value {
439 my ($self, $meta_instance, $instance, $value) = @_;
441 my $slot_name = $self->name;
443 return $meta_instance->set_slot_value($instance, $slot_name, $value)
444 unless $self->has_initializer;
446 my ($type_constraint, $can_coerce);
447 if ($self->has_type_constraint) {
448 $type_constraint = $self->type_constraint;
449 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
453 my $val = $self->_coerce_and_verify( shift, $instance );;
455 $meta_instance->set_slot_value($instance, $slot_name, $val);
458 my $initializer = $self->initializer;
460 # most things will just want to set a value, so make it first arg
461 $instance->$initializer($value, $callback, $self);
465 my ($self, $instance, @args) = @_;
466 my $value = $args[0];
468 my $attr_name = $self->name;
470 if ($self->is_required and not @args) {
471 $self->throw_error("Attribute ($attr_name) is required", object => $instance);
474 $value = $self->_coerce_and_verify( $value, $instance );
476 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
479 $meta_instance->set_slot_value($instance, $attr_name, $value);
481 if (ref $value && $self->is_weak_ref) {
482 $meta_instance->weaken_slot_value($instance, $attr_name);
485 if ($self->has_trigger) {
486 $self->trigger->($instance, $value);
491 my ($self, $instance) = @_;
493 if ($self->is_lazy) {
494 unless ($self->has_value($instance)) {
496 if ($self->has_default) {
497 $value = $self->default($instance);
498 } elsif ( $self->has_builder ) {
499 $value = $self->_call_builder($instance);
502 $value = $self->_coerce_and_verify( $value, $instance );
504 $self->set_initial_value($instance, $value);
508 if ($self->should_auto_deref) {
510 my $type_constraint = $self->type_constraint;
512 if ($type_constraint->is_a_type_of('ArrayRef')) {
513 my $rv = $self->SUPER::get_value($instance);
514 return unless defined $rv;
515 return wantarray ? @{ $rv } : $rv;
517 elsif ($type_constraint->is_a_type_of('HashRef')) {
518 my $rv = $self->SUPER::get_value($instance);
519 return unless defined $rv;
520 return wantarray ? %{ $rv } : $rv;
523 $self->throw_error("Can not auto de-reference the type constraint '" . $type_constraint->name . "'", object => $instance, type_constraint => $type_constraint);
529 return $self->SUPER::get_value($instance);
533 ## installing accessors
535 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
537 sub install_accessors {
539 $self->SUPER::install_accessors(@_);
540 $self->install_delegation if $self->has_handles;
544 sub remove_accessors {
546 $self->SUPER::remove_accessors(@_);
547 $self->remove_delegation if $self->has_handles;
551 sub install_delegation {
555 # Here we canonicalize the 'handles' option
556 # this will sort out any details and always
557 # return an hash of methods which we want
558 # to delagate to, see that method for details
559 my %handles = $self->_canonicalize_handles;
562 # install the delegation ...
563 my $associated_class = $self->associated_class;
564 foreach my $handle (keys %handles) {
565 my $method_to_call = $handles{$handle};
566 my $class_name = $associated_class->name;
567 my $name = "${class_name}::${handle}";
569 (!$associated_class->has_method($handle))
570 || $self->throw_error("You cannot overwrite a locally defined method ($handle) with a delegation", method_name => $handle);
573 # handles is not allowed to delegate
574 # any of these methods, as they will
575 # override the ones in your class, which
576 # is almost certainly not what you want.
578 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
579 #cluck("Not delegating method '$handle' because it is a core method") and
580 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
582 my $method = $self->_make_delegation_method($handle, $method_to_call);
584 $self->associated_class->add_method($method->name, $method);
588 sub remove_delegation {
590 my %handles = $self->_canonicalize_handles;
591 my $associated_class = $self->associated_class;
592 foreach my $handle (keys %handles) {
593 $self->associated_class->remove_method($handle);
597 # private methods to help delegation ...
599 sub _canonicalize_handles {
601 my $handles = $self->handles;
602 if (my $handle_type = ref($handles)) {
603 if ($handle_type eq 'HASH') {
606 elsif ($handle_type eq 'ARRAY') {
607 return map { $_ => $_ } @{$handles};
609 elsif ($handle_type eq 'Regexp') {
610 ($self->has_type_constraint)
611 || $self->throw_error("Cannot delegate methods based on a Regexp without a type constraint (isa)", data => $handles);
612 return map { ($_ => $_) }
613 grep { /$handles/ } $self->_get_delegate_method_list;
615 elsif ($handle_type eq 'CODE') {
616 return $handles->($self, $self->_find_delegate_metaclass);
619 $self->throw_error("Unable to canonicalize the 'handles' option with $handles", data => $handles);
623 Class::MOP::load_class($handles)
624 unless Class::MOP::is_class_loaded($handles);
626 my $role_meta = Class::MOP::class_of($handles);
628 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
629 || $self->throw_error("Unable to canonicalize the 'handles' option with $handles because its metaclass is not a Moose::Meta::Role", data => $handles);
631 return map { $_ => $_ } (
632 $role_meta->get_method_list,
633 $role_meta->get_required_method_list
638 sub _find_delegate_metaclass {
640 if (my $class = $self->_isa_metadata) {
641 # if the class does have
642 # a meta method, use it
643 return $class->meta if $class->can('meta');
644 # otherwise we might be
645 # dealing with a non-Moose
646 # class, and need to make
648 return Moose::Meta::Class->initialize($class);
650 elsif (my $role = $self->_does_metadata) {
651 # our role will always have
656 $self->throw_error("Cannot find delegate metaclass for attribute " . $self->name);
660 sub _get_delegate_method_list {
662 my $meta = $self->_find_delegate_metaclass;
663 if ($meta->isa('Class::MOP::Class')) {
664 return map { $_->name } # NOTE: !never! delegate &meta
665 grep { $_->package_name ne 'Moose::Object' && $_->name ne 'meta' }
666 $meta->get_all_methods;
668 elsif ($meta->isa('Moose::Meta::Role')) {
669 return $meta->get_method_list;
672 $self->throw_error("Unable to recognize the delegate metaclass '$meta'", data => $meta);
676 sub delegation_metaclass { 'Moose::Meta::Method::Delegation' }
678 sub _make_delegation_method {
679 my ( $self, $handle_name, $method_to_call ) = @_;
683 $method_body = $method_to_call
684 if 'CODE' eq ref($method_to_call);
686 return $self->delegation_metaclass->new(
687 name => $handle_name,
688 package_name => $self->associated_class->name,
690 delegate_to_method => $method_to_call,
694 sub _coerce_and_verify {
697 my $instance = shift;
699 return $val unless $self->has_type_constraint;
701 my $type_constraint = $self->type_constraint;
702 if ($self->should_coerce && $type_constraint->has_coercion) {
703 $val = $type_constraint->coerce($val);
706 $self->verify_against_type_constraint($val, instance => $instance);
711 sub verify_against_type_constraint {
715 return 1 if !$self->has_type_constraint;
717 my $type_constraint = $self->type_constraint;
719 $type_constraint->check($val)
720 || $self->throw_error("Attribute ("
722 . ") does not pass the type constraint because: "
723 . $type_constraint->get_message($val), data => $val, @_);
726 package Moose::Meta::Attribute::Custom::Moose;
727 sub register_implementation { 'Moose::Meta::Attribute' }
737 Moose::Meta::Attribute - The Moose attribute metaclass
741 This class is a subclass of L<Class::MOP::Attribute> that provides
742 additional Moose-specific functionality.
744 To really understand this class, you will need to start with the
745 L<Class::MOP::Attribute> documentation. This class can be understood
746 as a set of additional features on top of the basic feature provided
747 by that parent class.
751 C<Moose::Meta::Attribute> is a subclass of L<Class::MOP::Attribute>.
755 Many of the documented below override methods in
756 L<Class::MOP::Attribute> and add Moose specific features.
762 =item B<< Moose::Meta::Attribute->new(%options) >>
764 This method overrides the L<Class::MOP::Attribute> constructor.
766 Many of the options below are described in more detail in the
767 L<Moose::Manual::Attributes> document.
769 It adds the following options to the constructor:
773 =item * is => 'ro' or 'rw'
775 This provides a shorthand for specifying the C<reader>, C<writer>, or
776 C<accessor> names. If the attribute is read-only ('ro') then it will
777 have a C<reader> method with the same attribute as the name.
779 If it is read-write ('rw') then it will have an C<accessor> method
780 with the same name. If you provide an explicit C<writer> for a
781 read-write attribute, then you will have a C<reader> with the same
782 name as the attribute, and a C<writer> with the name you provided.
786 This option accepts a type. The type can be a string, which should be
787 a type name. If the type name is unknown, it is assumed to be a class
790 This option can also accept a L<Moose::Meta::TypeConstraint> object.
792 If you I<also> provide a C<does> option, then your C<isa> option must
793 be a class name, and that class must do the role specified with
796 =item * does => $role
798 This is short-hand for saying that the attribute's type must be an
799 object which does the named role.
801 =item * coerce => $bool
803 This option is only valid for objects with a type constraint
804 (C<isa>). If this is true, then coercions will be applied whenever
805 this attribute is set.
807 You can make both this and the C<weak_ref> option true.
809 =item * trigger => $sub
811 This option accepts a subroutine reference, which will be called after
812 the attribute is set.
814 =item * required => $bool
816 An attribute which is required must be provided to the constructor. An
817 attribute which is required can also have a C<default> or C<builder>,
818 which will satisfy its required-ness.
820 A required attribute must have a C<default>, C<builder> or a
821 non-C<undef> C<init_arg>
823 =item * lazy => $bool
825 A lazy attribute must have a C<default> or C<builder>. When an
826 attribute is lazy, the default value will not be calculated until the
829 =item * weak_ref => $bool
831 If this is true, the attribute's value will be stored as a weak
834 =item * auto_deref => $bool
836 If this is true, then the reader will dereference the value when it is
837 called. The attribute must have a type constraint which defines the
838 attribute as an array or hash reference.
840 =item * lazy_build => $bool
842 Setting this to true makes the attribute lazy and provides a number of
850 is equivalent to this:
855 builder => '_build_size',
856 clearer => 'clear_size',
857 predicate => 'has_size',
860 =item * documentation
862 An arbitrary string that can be retrieved later by calling C<<
863 $attr->documentation >>.
867 =item B<< $attr->clone(%options) >>
869 This creates a new attribute based on attribute being cloned. You must
870 supply a C<name> option to provide a new name for the attribute.
872 The C<%options> can only specify options handled by
873 L<Class::MOP::Attribute>.
877 =head2 Value management
881 =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >>
883 This method is used internally to initialize the attribute's slot in
884 the object C<$instance>.
886 This overrides the L<Class::MOP::Attribute> method to handle lazy
887 attributes, weak references, and type constraints.
893 eval { $point->meta->get_attribute('x')->set_value($point, 'forty-two') };
898 I<Attribute (x) does not pass the type constraint (Int) with 'forty-two'>
900 Before setting the value, a check is made on the type constraint of
901 the attribute, if it has one, to see if the value passes it. If the
902 value fails to pass, the set operation dies with a L<throw_error>.
904 Any coercion to convert values is done before checking the type constraint.
906 To check a value against a type constraint before setting it, fetch the
907 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
908 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
909 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::Basics::Recipe4>
914 =head2 Attribute Accessor generation
918 =item B<< $attr->install_accessors >>
920 This method overrides the parent to also install delegation methods.
922 =item B<< $attr->remove_accessors >>
924 This method overrides the parent to also remove delegation methods.
926 =item B<< $attr->install_delegation >>
928 This method adds its delegation methods to the attribute's associated
929 class, if it has any to add.
931 =item B<< $attr->remove_delegation >>
933 This method remove its delegation methods from the attribute's
936 =item B<< $attr->accessor_metaclass >>
938 Returns the accessor metaclass name, which defaults to
939 L<Moose::Meta::Method::Accessor>.
941 =item B<< $attr->delegation_metaclass >>
943 Returns the delegation metaclass name, which defaults to
944 L<Moose::Meta::Method::Delegation>.
948 =head2 Additional Moose features
950 These methods are not found in the superclass. They support features
955 =item B<< $attr->does($role) >>
957 This indicates whether the I<attribute itself> does the given
958 role. The role can be given as a full class name, or as a resolvable
961 Note that this checks the attribute itself, not its type constraint,
962 so it is checking the attribute's metaclass and any traits applied to
965 =item B<< Moose::Meta::Class->interpolate_class_and_new($name, %options) >>
967 This is an alternate constructor that handles the C<metaclass> and
970 Effectively, this method is a factory that finds or creates the
971 appropriate class for the given C<metaclass> and/or C<traits>.
973 Once it has the appropriate class, it will call C<< $class->new($name,
974 %options) >> on that class.
976 =item B<< $attr->clone_and_inherit_options(%options) >>
978 This method supports the C<has '+foo'> feature. It does various bits
979 of processing on the supplied C<%options> before ultimately calling
982 One of its main tasks is to make sure that the C<%options> provided
983 only includes the options returned by the
984 C<legal_options_for_inheritance> method.
986 =item B<< $attr->legal_options_for_inheritance >>
988 This returns a whitelist of options that can be overridden in a
989 subclass's attribute definition.
991 This exists to allow a custom metaclass to change or add to the list
992 of options which can be changed.
994 =item B<< $attr->type_constraint >>
996 Returns the L<Moose::Meta::TypeConstraint> object for this attribute,
999 =item B<< $attr->has_type_constraint >>
1001 Returns true if this attribute has a type constraint.
1003 =item B<< $attr->verify_against_type_constraint($value) >>
1005 Given a value, this method returns true if the value is valid for the
1006 attribute's type constraint. If the value is not valid, it throws an
1009 =item B<< $attr->handles >>
1011 This returns the value of the C<handles> option passed to the
1014 =item B<< $attr->has_handles >>
1016 Returns true if this attribute performs delegation.
1018 =item B<< $attr->is_weak_ref >>
1020 Returns true if this attribute stores its value as a weak reference.
1022 =item B<< $attr->is_required >>
1024 Returns true if this attribute is required to have a value.
1026 =item B<< $attr->is_lazy >>
1028 Returns true if this attribute is lazy.
1030 =item B<< $attr->is_lazy_build >>
1032 Returns true if the C<lazy_build> option was true when passed to the
1035 =item B<< $attr->should_coerce >>
1037 Returns true if the C<coerce> option passed to the constructor was
1040 =item B<< $attr->should_auto_deref >>
1042 Returns true if the C<auto_deref> option passed to the constructor was
1045 =item B<< $attr->trigger >>
1047 This is the subroutine reference that was in the C<trigger> option
1048 passed to the constructor, if any.
1050 =item B<< $attr->has_trigger >>
1052 Returns true if this attribute has a trigger set.
1054 =item B<< $attr->documentation >>
1056 Returns the value that was in the C<documentation> option passed to
1057 the constructor, if any.
1059 =item B<< $attr->has_documentation >>
1061 Returns true if this attribute has any documentation.
1063 =item B<< $attr->applied_traits >>
1065 This returns an array reference of all the traits which were applied
1066 to this attribute. If none were applied, this returns C<undef>.
1068 =item B<< $attr->has_applied_traits >>
1070 Returns true if this attribute has any traits applied.
1076 All complex software has bugs lurking in it, and this module is no
1077 exception. If you find a bug please either email me, or add the bug
1082 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1084 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
1086 =head1 COPYRIGHT AND LICENSE
1088 Copyright 2006-2009 by Infinity Interactive, Inc.
1090 L<http://www.iinteractive.com>
1092 This library is free software; you can redistribute it and/or modify
1093 it under the same terms as Perl itself.