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 = $self->_does_metadata) {
647 return Class::MOP::class_of($role);
650 $self->throw_error("Cannot find delegate metaclass for attribute " . $self->name);
654 sub _get_delegate_method_list {
656 my $meta = $self->_find_delegate_metaclass;
657 if ($meta->isa('Class::MOP::Class')) {
658 return map { $_->name } # NOTE: !never! delegate &meta
659 grep { $_->package_name ne 'Moose::Object' && $_->name ne 'meta' }
660 $meta->get_all_methods;
662 elsif ($meta->isa('Moose::Meta::Role')) {
663 return $meta->get_method_list;
666 $self->throw_error("Unable to recognize the delegate metaclass '$meta'", data => $meta);
670 sub delegation_metaclass { 'Moose::Meta::Method::Delegation' }
672 sub _make_delegation_method {
673 my ( $self, $handle_name, $method_to_call ) = @_;
677 $method_body = $method_to_call
678 if 'CODE' eq ref($method_to_call);
680 return $self->delegation_metaclass->new(
681 name => $handle_name,
682 package_name => $self->associated_class->name,
684 delegate_to_method => $method_to_call,
688 sub _coerce_and_verify {
691 my $instance = shift;
693 return $val unless $self->has_type_constraint;
695 my $type_constraint = $self->type_constraint;
696 if ($self->should_coerce && $type_constraint->has_coercion) {
697 $val = $type_constraint->coerce($val);
700 $self->verify_against_type_constraint($val, instance => $instance);
705 sub verify_against_type_constraint {
709 return 1 if !$self->has_type_constraint;
711 my $type_constraint = $self->type_constraint;
713 $type_constraint->check($val)
714 || $self->throw_error("Attribute ("
716 . ") does not pass the type constraint because: "
717 . $type_constraint->get_message($val), data => $val, @_);
720 package Moose::Meta::Attribute::Custom::Moose;
721 sub register_implementation { 'Moose::Meta::Attribute' }
731 Moose::Meta::Attribute - The Moose attribute metaclass
735 This class is a subclass of L<Class::MOP::Attribute> that provides
736 additional Moose-specific functionality.
738 To really understand this class, you will need to start with the
739 L<Class::MOP::Attribute> documentation. This class can be understood
740 as a set of additional features on top of the basic feature provided
741 by that parent class.
745 C<Moose::Meta::Attribute> is a subclass of L<Class::MOP::Attribute>.
749 Many of the documented below override methods in
750 L<Class::MOP::Attribute> and add Moose specific features.
756 =item B<< Moose::Meta::Attribute->new(%options) >>
758 This method overrides the L<Class::MOP::Attribute> constructor.
760 Many of the options below are described in more detail in the
761 L<Moose::Manual::Attributes> document.
763 It adds the following options to the constructor:
767 =item * is => 'ro' or 'rw'
769 This provides a shorthand for specifying the C<reader>, C<writer>, or
770 C<accessor> names. If the attribute is read-only ('ro') then it will
771 have a C<reader> method with the same attribute as the name.
773 If it is read-write ('rw') then it will have an C<accessor> method
774 with the same name. If you provide an explicit C<writer> for a
775 read-write attribute, then you will have a C<reader> with the same
776 name as the attribute, and a C<writer> with the name you provided.
780 This option accepts a type. The type can be a string, which should be
781 a type name. If the type name is unknown, it is assumed to be a class
784 This option can also accept a L<Moose::Meta::TypeConstraint> object.
786 If you I<also> provide a C<does> option, then your C<isa> option must
787 be a class name, and that class must do the role specified with
790 =item * does => $role
792 This is short-hand for saying that the attribute's type must be an
793 object which does the named role.
795 =item * coerce => $bool
797 This option is only valid for objects with a type constraint
798 (C<isa>). If this is true, then coercions will be applied whenever
799 this attribute is set.
801 You can make both this and the C<weak_ref> option true.
803 =item * trigger => $sub
805 This option accepts a subroutine reference, which will be called after
806 the attribute is set.
808 =item * required => $bool
810 An attribute which is required must be provided to the constructor. An
811 attribute which is required can also have a C<default> or C<builder>,
812 which will satisfy its required-ness.
814 A required attribute must have a C<default>, C<builder> or a
815 non-C<undef> C<init_arg>
817 =item * lazy => $bool
819 A lazy attribute must have a C<default> or C<builder>. When an
820 attribute is lazy, the default value will not be calculated until the
823 =item * weak_ref => $bool
825 If this is true, the attribute's value will be stored as a weak
828 =item * auto_deref => $bool
830 If this is true, then the reader will dereference the value when it is
831 called. The attribute must have a type constraint which defines the
832 attribute as an array or hash reference.
834 =item * lazy_build => $bool
836 Setting this to true makes the attribute lazy and provides a number of
844 is equivalent to this:
849 builder => '_build_size',
850 clearer => 'clear_size',
851 predicate => 'has_size',
854 =item * documentation
856 An arbitrary string that can be retrieved later by calling C<<
857 $attr->documentation >>.
861 =item B<< $attr->clone(%options) >>
863 This creates a new attribute based on attribute being cloned. You must
864 supply a C<name> option to provide a new name for the attribute.
866 The C<%options> can only specify options handled by
867 L<Class::MOP::Attribute>.
871 =head2 Value management
875 =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >>
877 This method is used internally to initialize the attribute's slot in
878 the object C<$instance>.
880 This overrides the L<Class::MOP::Attribute> method to handle lazy
881 attributes, weak references, and type constraints.
887 eval { $point->meta->get_attribute('x')->set_value($point, 'forty-two') };
892 I<Attribute (x) does not pass the type constraint (Int) with 'forty-two'>
894 Before setting the value, a check is made on the type constraint of
895 the attribute, if it has one, to see if the value passes it. If the
896 value fails to pass, the set operation dies with a L<throw_error>.
898 Any coercion to convert values is done before checking the type constraint.
900 To check a value against a type constraint before setting it, fetch the
901 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
902 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
903 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::Basics::Recipe4>
908 =head2 Attribute Accessor generation
912 =item B<< $attr->install_accessors >>
914 This method overrides the parent to also install delegation methods.
916 =item B<< $attr->remove_accessors >>
918 This method overrides the parent to also remove delegation methods.
920 =item B<< $attr->install_delegation >>
922 This method adds its delegation methods to the attribute's associated
923 class, if it has any to add.
925 =item B<< $attr->remove_delegation >>
927 This method remove its delegation methods from the attribute's
930 =item B<< $attr->accessor_metaclass >>
932 Returns the accessor metaclass name, which defaults to
933 L<Moose::Meta::Method::Accessor>.
935 =item B<< $attr->delegation_metaclass >>
937 Returns the delegation metaclass name, which defaults to
938 L<Moose::Meta::Method::Delegation>.
942 =head2 Additional Moose features
944 These methods are not found in the superclass. They support features
949 =item B<< $attr->does($role) >>
951 This indicates whether the I<attribute itself> does the given
952 role. The role can be given as a full class name, or as a resolvable
955 Note that this checks the attribute itself, not its type constraint,
956 so it is checking the attribute's metaclass and any traits applied to
959 =item B<< Moose::Meta::Class->interpolate_class_and_new($name, %options) >>
961 This is an alternate constructor that handles the C<metaclass> and
964 Effectively, this method is a factory that finds or creates the
965 appropriate class for the given C<metaclass> and/or C<traits>.
967 Once it has the appropriate class, it will call C<< $class->new($name,
968 %options) >> on that class.
970 =item B<< $attr->clone_and_inherit_options(%options) >>
972 This method supports the C<has '+foo'> feature. It does various bits
973 of processing on the supplied C<%options> before ultimately calling
976 One of its main tasks is to make sure that the C<%options> provided
977 only includes the options returned by the
978 C<legal_options_for_inheritance> method.
980 =item B<< $attr->legal_options_for_inheritance >>
982 This returns a whitelist of options that can be overridden in a
983 subclass's attribute definition.
985 This exists to allow a custom metaclass to change or add to the list
986 of options which can be changed.
988 =item B<< $attr->type_constraint >>
990 Returns the L<Moose::Meta::TypeConstraint> object for this attribute,
993 =item B<< $attr->has_type_constraint >>
995 Returns true if this attribute has a type constraint.
997 =item B<< $attr->verify_against_type_constraint($value) >>
999 Given a value, this method returns true if the value is valid for the
1000 attribute's type constraint. If the value is not valid, it throws an
1003 =item B<< $attr->handles >>
1005 This returns the value of the C<handles> option passed to the
1008 =item B<< $attr->has_handles >>
1010 Returns true if this attribute performs delegation.
1012 =item B<< $attr->is_weak_ref >>
1014 Returns true if this attribute stores its value as a weak reference.
1016 =item B<< $attr->is_required >>
1018 Returns true if this attribute is required to have a value.
1020 =item B<< $attr->is_lazy >>
1022 Returns true if this attribute is lazy.
1024 =item B<< $attr->is_lazy_build >>
1026 Returns true if the C<lazy_build> option was true when passed to the
1029 =item B<< $attr->should_coerce >>
1031 Returns true if the C<coerce> option passed to the constructor was
1034 =item B<< $attr->should_auto_deref >>
1036 Returns true if the C<auto_deref> option passed to the constructor was
1039 =item B<< $attr->trigger >>
1041 This is the subroutine reference that was in the C<trigger> option
1042 passed to the constructor, if any.
1044 =item B<< $attr->has_trigger >>
1046 Returns true if this attribute has a trigger set.
1048 =item B<< $attr->documentation >>
1050 Returns the value that was in the C<documentation> option passed to
1051 the constructor, if any.
1053 =item B<< $attr->has_documentation >>
1055 Returns true if this attribute has any documentation.
1057 =item B<< $attr->applied_traits >>
1059 This returns an array reference of all the traits which were applied
1060 to this attribute. If none were applied, this returns C<undef>.
1062 =item B<< $attr->has_applied_traits >>
1064 Returns true if this attribute has any traits applied.
1070 All complex software has bugs lurking in it, and this module is no
1071 exception. If you find a bug please either email me, or add the bug
1076 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1078 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
1080 =head1 COPYRIGHT AND LICENSE
1082 Copyright 2006-2009 by Infinity Interactive, Inc.
1084 L<http://www.iinteractive.com>
1086 This library is free software; you can redistribute it and/or modify
1087 it under the same terms as Perl itself.