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 = $self->_isa_metadata) {
641 # we might be dealing with a non-Moose class,
642 # and need to make our own metaclass. if there's
643 # already a metaclass, it will be returned
644 return Moose::Meta::Class->initialize($class);
646 elsif (my $role = $self->_does_metadata) {
647 # our role will always have
652 $self->throw_error("Cannot find delegate metaclass for attribute " . $self->name);
656 sub _get_delegate_method_list {
658 my $meta = $self->_find_delegate_metaclass;
659 if ($meta->isa('Class::MOP::Class')) {
660 return map { $_->name } # NOTE: !never! delegate &meta
661 grep { $_->package_name ne 'Moose::Object' && $_->name ne 'meta' }
662 $meta->get_all_methods;
664 elsif ($meta->isa('Moose::Meta::Role')) {
665 return $meta->get_method_list;
668 $self->throw_error("Unable to recognize the delegate metaclass '$meta'", data => $meta);
672 sub delegation_metaclass { 'Moose::Meta::Method::Delegation' }
674 sub _make_delegation_method {
675 my ( $self, $handle_name, $method_to_call ) = @_;
679 $method_body = $method_to_call
680 if 'CODE' eq ref($method_to_call);
682 return $self->delegation_metaclass->new(
683 name => $handle_name,
684 package_name => $self->associated_class->name,
686 delegate_to_method => $method_to_call,
690 sub _coerce_and_verify {
693 my $instance = shift;
695 return $val unless $self->has_type_constraint;
697 my $type_constraint = $self->type_constraint;
698 if ($self->should_coerce && $type_constraint->has_coercion) {
699 $val = $type_constraint->coerce($val);
702 $self->verify_against_type_constraint($val, instance => $instance);
707 sub verify_against_type_constraint {
711 return 1 if !$self->has_type_constraint;
713 my $type_constraint = $self->type_constraint;
715 $type_constraint->check($val)
716 || $self->throw_error("Attribute ("
718 . ") does not pass the type constraint because: "
719 . $type_constraint->get_message($val), data => $val, @_);
722 package Moose::Meta::Attribute::Custom::Moose;
723 sub register_implementation { 'Moose::Meta::Attribute' }
733 Moose::Meta::Attribute - The Moose attribute metaclass
737 This class is a subclass of L<Class::MOP::Attribute> that provides
738 additional Moose-specific functionality.
740 To really understand this class, you will need to start with the
741 L<Class::MOP::Attribute> documentation. This class can be understood
742 as a set of additional features on top of the basic feature provided
743 by that parent class.
747 C<Moose::Meta::Attribute> is a subclass of L<Class::MOP::Attribute>.
751 Many of the documented below override methods in
752 L<Class::MOP::Attribute> and add Moose specific features.
758 =item B<< Moose::Meta::Attribute->new(%options) >>
760 This method overrides the L<Class::MOP::Attribute> constructor.
762 Many of the options below are described in more detail in the
763 L<Moose::Manual::Attributes> document.
765 It adds the following options to the constructor:
769 =item * is => 'ro' or 'rw'
771 This provides a shorthand for specifying the C<reader>, C<writer>, or
772 C<accessor> names. If the attribute is read-only ('ro') then it will
773 have a C<reader> method with the same attribute as the name.
775 If it is read-write ('rw') then it will have an C<accessor> method
776 with the same name. If you provide an explicit C<writer> for a
777 read-write attribute, then you will have a C<reader> with the same
778 name as the attribute, and a C<writer> with the name you provided.
782 This option accepts a type. The type can be a string, which should be
783 a type name. If the type name is unknown, it is assumed to be a class
786 This option can also accept a L<Moose::Meta::TypeConstraint> object.
788 If you I<also> provide a C<does> option, then your C<isa> option must
789 be a class name, and that class must do the role specified with
792 =item * does => $role
794 This is short-hand for saying that the attribute's type must be an
795 object which does the named role.
797 =item * coerce => $bool
799 This option is only valid for objects with a type constraint
800 (C<isa>). If this is true, then coercions will be applied whenever
801 this attribute is set.
803 You can make both this and the C<weak_ref> option true.
805 =item * trigger => $sub
807 This option accepts a subroutine reference, which will be called after
808 the attribute is set.
810 =item * required => $bool
812 An attribute which is required must be provided to the constructor. An
813 attribute which is required can also have a C<default> or C<builder>,
814 which will satisfy its required-ness.
816 A required attribute must have a C<default>, C<builder> or a
817 non-C<undef> C<init_arg>
819 =item * lazy => $bool
821 A lazy attribute must have a C<default> or C<builder>. When an
822 attribute is lazy, the default value will not be calculated until the
825 =item * weak_ref => $bool
827 If this is true, the attribute's value will be stored as a weak
830 =item * auto_deref => $bool
832 If this is true, then the reader will dereference the value when it is
833 called. The attribute must have a type constraint which defines the
834 attribute as an array or hash reference.
836 =item * lazy_build => $bool
838 Setting this to true makes the attribute lazy and provides a number of
846 is equivalent to this:
851 builder => '_build_size',
852 clearer => 'clear_size',
853 predicate => 'has_size',
856 =item * documentation
858 An arbitrary string that can be retrieved later by calling C<<
859 $attr->documentation >>.
863 =item B<< $attr->clone(%options) >>
865 This creates a new attribute based on attribute being cloned. You must
866 supply a C<name> option to provide a new name for the attribute.
868 The C<%options> can only specify options handled by
869 L<Class::MOP::Attribute>.
873 =head2 Value management
877 =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >>
879 This method is used internally to initialize the attribute's slot in
880 the object C<$instance>.
882 This overrides the L<Class::MOP::Attribute> method to handle lazy
883 attributes, weak references, and type constraints.
889 eval { $point->meta->get_attribute('x')->set_value($point, 'forty-two') };
894 I<Attribute (x) does not pass the type constraint (Int) with 'forty-two'>
896 Before setting the value, a check is made on the type constraint of
897 the attribute, if it has one, to see if the value passes it. If the
898 value fails to pass, the set operation dies with a L<throw_error>.
900 Any coercion to convert values is done before checking the type constraint.
902 To check a value against a type constraint before setting it, fetch the
903 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
904 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
905 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::Basics::Recipe4>
910 =head2 Attribute Accessor generation
914 =item B<< $attr->install_accessors >>
916 This method overrides the parent to also install delegation methods.
918 =item B<< $attr->remove_accessors >>
920 This method overrides the parent to also remove delegation methods.
922 =item B<< $attr->install_delegation >>
924 This method adds its delegation methods to the attribute's associated
925 class, if it has any to add.
927 =item B<< $attr->remove_delegation >>
929 This method remove its delegation methods from the attribute's
932 =item B<< $attr->accessor_metaclass >>
934 Returns the accessor metaclass name, which defaults to
935 L<Moose::Meta::Method::Accessor>.
937 =item B<< $attr->delegation_metaclass >>
939 Returns the delegation metaclass name, which defaults to
940 L<Moose::Meta::Method::Delegation>.
944 =head2 Additional Moose features
946 These methods are not found in the superclass. They support features
951 =item B<< $attr->does($role) >>
953 This indicates whether the I<attribute itself> does the given
954 role. The role can be given as a full class name, or as a resolvable
957 Note that this checks the attribute itself, not its type constraint,
958 so it is checking the attribute's metaclass and any traits applied to
961 =item B<< Moose::Meta::Class->interpolate_class_and_new($name, %options) >>
963 This is an alternate constructor that handles the C<metaclass> and
966 Effectively, this method is a factory that finds or creates the
967 appropriate class for the given C<metaclass> and/or C<traits>.
969 Once it has the appropriate class, it will call C<< $class->new($name,
970 %options) >> on that class.
972 =item B<< $attr->clone_and_inherit_options(%options) >>
974 This method supports the C<has '+foo'> feature. It does various bits
975 of processing on the supplied C<%options> before ultimately calling
978 One of its main tasks is to make sure that the C<%options> provided
979 only includes the options returned by the
980 C<legal_options_for_inheritance> method.
982 =item B<< $attr->legal_options_for_inheritance >>
984 This returns a whitelist of options that can be overridden in a
985 subclass's attribute definition.
987 This exists to allow a custom metaclass to change or add to the list
988 of options which can be changed.
990 =item B<< $attr->type_constraint >>
992 Returns the L<Moose::Meta::TypeConstraint> object for this attribute,
995 =item B<< $attr->has_type_constraint >>
997 Returns true if this attribute has a type constraint.
999 =item B<< $attr->verify_against_type_constraint($value) >>
1001 Given a value, this method returns true if the value is valid for the
1002 attribute's type constraint. If the value is not valid, it throws an
1005 =item B<< $attr->handles >>
1007 This returns the value of the C<handles> option passed to the
1010 =item B<< $attr->has_handles >>
1012 Returns true if this attribute performs delegation.
1014 =item B<< $attr->is_weak_ref >>
1016 Returns true if this attribute stores its value as a weak reference.
1018 =item B<< $attr->is_required >>
1020 Returns true if this attribute is required to have a value.
1022 =item B<< $attr->is_lazy >>
1024 Returns true if this attribute is lazy.
1026 =item B<< $attr->is_lazy_build >>
1028 Returns true if the C<lazy_build> option was true when passed to the
1031 =item B<< $attr->should_coerce >>
1033 Returns true if the C<coerce> option passed to the constructor was
1036 =item B<< $attr->should_auto_deref >>
1038 Returns true if the C<auto_deref> option passed to the constructor was
1041 =item B<< $attr->trigger >>
1043 This is the subroutine reference that was in the C<trigger> option
1044 passed to the constructor, if any.
1046 =item B<< $attr->has_trigger >>
1048 Returns true if this attribute has a trigger set.
1050 =item B<< $attr->documentation >>
1052 Returns the value that was in the C<documentation> option passed to
1053 the constructor, if any.
1055 =item B<< $attr->has_documentation >>
1057 Returns true if this attribute has any documentation.
1059 =item B<< $attr->applied_traits >>
1061 This returns an array reference of all the traits which were applied
1062 to this attribute. If none were applied, this returns C<undef>.
1064 =item B<< $attr->has_applied_traits >>
1066 Returns true if this attribute has any traits applied.
1072 All complex software has bugs lurking in it, and this module is no
1073 exception. If you find a bug please either email me, or add the bug
1078 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1080 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
1082 =head1 COPYRIGHT AND LICENSE
1084 Copyright 2006-2009 by Infinity Interactive, Inc.
1086 L<http://www.iinteractive.com>
1088 This library is free software; you can redistribute it and/or modify
1089 it under the same terms as Perl itself.