2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken';
10 our $VERSION = '0.83';
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)->get_all_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 $options->{builder} ||= "_build_${name}";
353 $options->{clearer} ||= "_clear${name}";
354 $options->{predicate} ||= "_has${name}";
357 $options->{clearer} ||= "clear_${name}";
358 $options->{predicate} ||= "has_${name}";
362 if (exists $options->{lazy} && $options->{lazy}) {
363 (exists $options->{default} || defined $options->{builder} )
364 || $class->throw_error("You cannot have lazy attribute ($name) without specifying a default value for it", data => $options);
367 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
368 $class->throw_error("You cannot have a required attribute ($name) without a default, builder, or an init_arg", data => $options);
373 sub initialize_instance_slot {
374 my ($self, $meta_instance, $instance, $params) = @_;
375 my $init_arg = $self->init_arg();
376 # try to fetch the init arg from the %params ...
380 if ( defined($init_arg) and exists $params->{$init_arg}) {
381 $val = $params->{$init_arg};
385 # skip it if it's lazy
386 return if $self->is_lazy;
387 # and die if it's required and doesn't have a default value
388 $self->throw_error("Attribute (" . $self->name . ") is required", object => $instance, data => $params)
389 if $self->is_required && !$self->has_default && !$self->has_builder;
391 # if nothing was in the %params, we can use the
392 # attribute's default value (if it has one)
393 if ($self->has_default) {
394 $val = $self->default($instance);
397 elsif ($self->has_builder) {
398 $val = $self->_call_builder($instance);
403 return unless $value_is_set;
405 $val = $self->_coerce_and_verify( $val, $instance );
407 $self->set_initial_value($instance, $val);
408 $meta_instance->weaken_slot_value($instance, $self->name)
409 if ref $val && $self->is_weak_ref;
413 my ( $self, $instance ) = @_;
415 my $builder = $self->builder();
417 return $instance->$builder()
418 if $instance->can( $self->builder );
420 $self->throw_error( blessed($instance)
421 . " does not support builder method '"
423 . "' for attribute '"
433 # this duplicates too much code from
434 # Class::MOP::Attribute, we need to
435 # refactor these bits eventually.
437 sub _set_initial_slot_value {
438 my ($self, $meta_instance, $instance, $value) = @_;
440 my $slot_name = $self->name;
442 return $meta_instance->set_slot_value($instance, $slot_name, $value)
443 unless $self->has_initializer;
445 my ($type_constraint, $can_coerce);
446 if ($self->has_type_constraint) {
447 $type_constraint = $self->type_constraint;
448 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
452 my $val = $self->_coerce_and_verify( shift, $instance );;
454 $meta_instance->set_slot_value($instance, $slot_name, $val);
457 my $initializer = $self->initializer;
459 # most things will just want to set a value, so make it first arg
460 $instance->$initializer($value, $callback, $self);
464 my ($self, $instance, @args) = @_;
465 my $value = $args[0];
467 my $attr_name = $self->name;
469 if ($self->is_required and not @args) {
470 $self->throw_error("Attribute ($attr_name) is required", object => $instance);
473 $value = $self->_coerce_and_verify( $value, $instance );
475 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
478 $meta_instance->set_slot_value($instance, $attr_name, $value);
480 if (ref $value && $self->is_weak_ref) {
481 $meta_instance->weaken_slot_value($instance, $attr_name);
484 if ($self->has_trigger) {
485 $self->trigger->($instance, $value);
490 my ($self, $instance) = @_;
492 if ($self->is_lazy) {
493 unless ($self->has_value($instance)) {
495 if ($self->has_default) {
496 $value = $self->default($instance);
497 } elsif ( $self->has_builder ) {
498 $value = $self->_call_builder($instance);
501 $value = $self->_coerce_and_verify( $value, $instance );
503 $self->set_initial_value($instance, $value);
507 if ($self->should_auto_deref) {
509 my $type_constraint = $self->type_constraint;
511 if ($type_constraint->is_a_type_of('ArrayRef')) {
512 my $rv = $self->SUPER::get_value($instance);
513 return unless defined $rv;
514 return wantarray ? @{ $rv } : $rv;
516 elsif ($type_constraint->is_a_type_of('HashRef')) {
517 my $rv = $self->SUPER::get_value($instance);
518 return unless defined $rv;
519 return wantarray ? %{ $rv } : $rv;
522 $self->throw_error("Can not auto de-reference the type constraint '" . $type_constraint->name . "'", object => $instance, type_constraint => $type_constraint);
528 return $self->SUPER::get_value($instance);
532 ## installing accessors
534 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
536 sub install_accessors {
538 $self->SUPER::install_accessors(@_);
539 $self->install_delegation if $self->has_handles;
541 # XXX handles should be in associated_methods
543 || @{ $self->associated_methods }
544 || ($self->_is_metadata || '') eq 'bare'
547 'Attribute (' . $self->name . ') has no associated methods'
548 . ' (did you mean to provide an "is" argument?)'
555 sub remove_accessors {
557 $self->SUPER::remove_accessors(@_);
558 $self->remove_delegation if $self->has_handles;
562 sub install_delegation {
566 # Here we canonicalize the 'handles' option
567 # this will sort out any details and always
568 # return an hash of methods which we want
569 # to delagate to, see that method for details
570 my %handles = $self->_canonicalize_handles;
573 # install the delegation ...
574 my $associated_class = $self->associated_class;
575 foreach my $handle (keys %handles) {
576 my $method_to_call = $handles{$handle};
577 my $class_name = $associated_class->name;
578 my $name = "${class_name}::${handle}";
580 (!$associated_class->has_method($handle))
581 || $self->throw_error("You cannot overwrite a locally defined method ($handle) with a delegation", method_name => $handle);
584 # handles is not allowed to delegate
585 # any of these methods, as they will
586 # override the ones in your class, which
587 # is almost certainly not what you want.
589 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
590 #cluck("Not delegating method '$handle' because it is a core method") and
591 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
593 my $method = $self->_make_delegation_method($handle, $method_to_call);
595 $self->associated_class->add_method($method->name, $method);
599 sub remove_delegation {
601 my %handles = $self->_canonicalize_handles;
602 my $associated_class = $self->associated_class;
603 foreach my $handle (keys %handles) {
604 $self->associated_class->remove_method($handle);
608 # private methods to help delegation ...
610 sub _canonicalize_handles {
612 my $handles = $self->handles;
613 if (my $handle_type = ref($handles)) {
614 if ($handle_type eq 'HASH') {
617 elsif ($handle_type eq 'ARRAY') {
618 return map { $_ => $_ } @{$handles};
620 elsif ($handle_type eq 'Regexp') {
621 ($self->has_type_constraint)
622 || $self->throw_error("Cannot delegate methods based on a Regexp without a type constraint (isa)", data => $handles);
623 return map { ($_ => $_) }
624 grep { /$handles/ } $self->_get_delegate_method_list;
626 elsif ($handle_type eq 'CODE') {
627 return $handles->($self, $self->_find_delegate_metaclass);
630 $self->throw_error("Unable to canonicalize the 'handles' option with $handles", data => $handles);
634 Class::MOP::load_class($handles);
635 my $role_meta = Class::MOP::class_of($handles);
637 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
638 || $self->throw_error("Unable to canonicalize the 'handles' option with $handles because its metaclass is not a Moose::Meta::Role", data => $handles);
640 return map { $_ => $_ } (
641 $role_meta->get_method_list,
642 map { $_->name } $role_meta->get_required_method_list,
647 sub _find_delegate_metaclass {
649 if (my $class = $self->_isa_metadata) {
650 # we might be dealing with a non-Moose class,
651 # and need to make our own metaclass. if there's
652 # already a metaclass, it will be returned
653 return Moose::Meta::Class->initialize($class);
655 elsif (my $role = $self->_does_metadata) {
656 return Class::MOP::class_of($role);
659 $self->throw_error("Cannot find delegate metaclass for attribute " . $self->name);
663 sub _get_delegate_method_list {
665 my $meta = $self->_find_delegate_metaclass;
666 if ($meta->isa('Class::MOP::Class')) {
667 return map { $_->name } # NOTE: !never! delegate &meta
668 grep { $_->package_name ne 'Moose::Object' && $_->name ne 'meta' }
669 $meta->get_all_methods;
671 elsif ($meta->isa('Moose::Meta::Role')) {
672 return $meta->get_method_list;
675 $self->throw_error("Unable to recognize the delegate metaclass '$meta'", data => $meta);
679 sub delegation_metaclass { 'Moose::Meta::Method::Delegation' }
681 sub _make_delegation_method {
682 my ( $self, $handle_name, $method_to_call ) = @_;
686 $method_body = $method_to_call
687 if 'CODE' eq ref($method_to_call);
689 return $self->delegation_metaclass->new(
690 name => $handle_name,
691 package_name => $self->associated_class->name,
693 delegate_to_method => $method_to_call,
697 sub _coerce_and_verify {
700 my $instance = shift;
702 return $val unless $self->has_type_constraint;
704 my $type_constraint = $self->type_constraint;
705 if ($self->should_coerce && $type_constraint->has_coercion) {
706 $val = $type_constraint->coerce($val);
709 $self->verify_against_type_constraint($val, instance => $instance);
714 sub verify_against_type_constraint {
718 return 1 if !$self->has_type_constraint;
720 my $type_constraint = $self->type_constraint;
722 $type_constraint->check($val)
723 || $self->throw_error("Attribute ("
725 . ") does not pass the type constraint because: "
726 . $type_constraint->get_message($val), data => $val, @_);
729 package Moose::Meta::Attribute::Custom::Moose;
730 sub register_implementation { 'Moose::Meta::Attribute' }
740 Moose::Meta::Attribute - The Moose attribute metaclass
744 This class is a subclass of L<Class::MOP::Attribute> that provides
745 additional Moose-specific functionality.
747 To really understand this class, you will need to start with the
748 L<Class::MOP::Attribute> documentation. This class can be understood
749 as a set of additional features on top of the basic feature provided
750 by that parent class.
754 C<Moose::Meta::Attribute> is a subclass of L<Class::MOP::Attribute>.
758 Many of the documented below override methods in
759 L<Class::MOP::Attribute> and add Moose specific features.
765 =item B<< Moose::Meta::Attribute->new(%options) >>
767 This method overrides the L<Class::MOP::Attribute> constructor.
769 Many of the options below are described in more detail in the
770 L<Moose::Manual::Attributes> document.
772 It adds the following options to the constructor:
776 =item * is => 'ro' or 'rw'
778 This provides a shorthand for specifying the C<reader>, C<writer>, or
779 C<accessor> names. If the attribute is read-only ('ro') then it will
780 have a C<reader> method with the same attribute as the name.
782 If it is read-write ('rw') then it will have an C<accessor> method
783 with the same name. If you provide an explicit C<writer> for a
784 read-write attribute, then you will have a C<reader> with the same
785 name as the attribute, and a C<writer> with the name you provided.
789 This option accepts a type. The type can be a string, which should be
790 a type name. If the type name is unknown, it is assumed to be a class
793 This option can also accept a L<Moose::Meta::TypeConstraint> object.
795 If you I<also> provide a C<does> option, then your C<isa> option must
796 be a class name, and that class must do the role specified with
799 =item * does => $role
801 This is short-hand for saying that the attribute's type must be an
802 object which does the named role.
804 =item * coerce => $bool
806 This option is only valid for objects with a type constraint
807 (C<isa>). If this is true, then coercions will be applied whenever
808 this attribute is set.
810 You can make both this and the C<weak_ref> option true.
812 =item * trigger => $sub
814 This option accepts a subroutine reference, which will be called after
815 the attribute is set.
817 =item * required => $bool
819 An attribute which is required must be provided to the constructor. An
820 attribute which is required can also have a C<default> or C<builder>,
821 which will satisfy its required-ness.
823 A required attribute must have a C<default>, C<builder> or a
824 non-C<undef> C<init_arg>
826 =item * lazy => $bool
828 A lazy attribute must have a C<default> or C<builder>. When an
829 attribute is lazy, the default value will not be calculated until the
832 =item * weak_ref => $bool
834 If this is true, the attribute's value will be stored as a weak
837 =item * auto_deref => $bool
839 If this is true, then the reader will dereference the value when it is
840 called. The attribute must have a type constraint which defines the
841 attribute as an array or hash reference.
843 =item * lazy_build => $bool
845 Setting this to true makes the attribute lazy and provides a number of
853 is equivalent to this:
858 builder => '_build_size',
859 clearer => 'clear_size',
860 predicate => 'has_size',
863 =item * documentation
865 An arbitrary string that can be retrieved later by calling C<<
866 $attr->documentation >>.
870 =item B<< $attr->clone(%options) >>
872 This creates a new attribute based on attribute being cloned. You must
873 supply a C<name> option to provide a new name for the attribute.
875 The C<%options> can only specify options handled by
876 L<Class::MOP::Attribute>.
880 =head2 Value management
884 =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >>
886 This method is used internally to initialize the attribute's slot in
887 the object C<$instance>.
889 This overrides the L<Class::MOP::Attribute> method to handle lazy
890 attributes, weak references, and type constraints.
896 eval { $point->meta->get_attribute('x')->set_value($point, 'forty-two') };
901 I<Attribute (x) does not pass the type constraint (Int) with 'forty-two'>
903 Before setting the value, a check is made on the type constraint of
904 the attribute, if it has one, to see if the value passes it. If the
905 value fails to pass, the set operation dies with a L<throw_error>.
907 Any coercion to convert values is done before checking the type constraint.
909 To check a value against a type constraint before setting it, fetch the
910 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
911 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
912 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::Basics::Recipe4>
917 =head2 Attribute Accessor generation
921 =item B<< $attr->install_accessors >>
923 This method overrides the parent to also install delegation methods.
925 If, after installing all methods, the attribute object has no associated
926 methods, it throws an error unless C<< is => 'bare' >> was passed to the
927 attribute constructor. (Trying to add an attribute that has no associated
928 methods is almost always an error.)
930 =item B<< $attr->remove_accessors >>
932 This method overrides the parent to also remove delegation methods.
934 =item B<< $attr->install_delegation >>
936 This method adds its delegation methods to the attribute's associated
937 class, if it has any to add.
939 =item B<< $attr->remove_delegation >>
941 This method remove its delegation methods from the attribute's
944 =item B<< $attr->accessor_metaclass >>
946 Returns the accessor metaclass name, which defaults to
947 L<Moose::Meta::Method::Accessor>.
949 =item B<< $attr->delegation_metaclass >>
951 Returns the delegation metaclass name, which defaults to
952 L<Moose::Meta::Method::Delegation>.
956 =head2 Additional Moose features
958 These methods are not found in the superclass. They support features
963 =item B<< $attr->does($role) >>
965 This indicates whether the I<attribute itself> does the given
966 role. The role can be given as a full class name, or as a resolvable
969 Note that this checks the attribute itself, not its type constraint,
970 so it is checking the attribute's metaclass and any traits applied to
973 =item B<< Moose::Meta::Class->interpolate_class_and_new($name, %options) >>
975 This is an alternate constructor that handles the C<metaclass> and
978 Effectively, this method is a factory that finds or creates the
979 appropriate class for the given C<metaclass> and/or C<traits>.
981 Once it has the appropriate class, it will call C<< $class->new($name,
982 %options) >> on that class.
984 =item B<< $attr->clone_and_inherit_options(%options) >>
986 This method supports the C<has '+foo'> feature. It does various bits
987 of processing on the supplied C<%options> before ultimately calling
990 One of its main tasks is to make sure that the C<%options> provided
991 only includes the options returned by the
992 C<legal_options_for_inheritance> method.
994 =item B<< $attr->legal_options_for_inheritance >>
996 This returns a whitelist of options that can be overridden in a
997 subclass's attribute definition.
999 This exists to allow a custom metaclass to change or add to the list
1000 of options which can be changed.
1002 =item B<< $attr->type_constraint >>
1004 Returns the L<Moose::Meta::TypeConstraint> object for this attribute,
1007 =item B<< $attr->has_type_constraint >>
1009 Returns true if this attribute has a type constraint.
1011 =item B<< $attr->verify_against_type_constraint($value) >>
1013 Given a value, this method returns true if the value is valid for the
1014 attribute's type constraint. If the value is not valid, it throws an
1017 =item B<< $attr->handles >>
1019 This returns the value of the C<handles> option passed to the
1022 =item B<< $attr->has_handles >>
1024 Returns true if this attribute performs delegation.
1026 =item B<< $attr->is_weak_ref >>
1028 Returns true if this attribute stores its value as a weak reference.
1030 =item B<< $attr->is_required >>
1032 Returns true if this attribute is required to have a value.
1034 =item B<< $attr->is_lazy >>
1036 Returns true if this attribute is lazy.
1038 =item B<< $attr->is_lazy_build >>
1040 Returns true if the C<lazy_build> option was true when passed to the
1043 =item B<< $attr->should_coerce >>
1045 Returns true if the C<coerce> option passed to the constructor was
1048 =item B<< $attr->should_auto_deref >>
1050 Returns true if the C<auto_deref> option passed to the constructor was
1053 =item B<< $attr->trigger >>
1055 This is the subroutine reference that was in the C<trigger> option
1056 passed to the constructor, if any.
1058 =item B<< $attr->has_trigger >>
1060 Returns true if this attribute has a trigger set.
1062 =item B<< $attr->documentation >>
1064 Returns the value that was in the C<documentation> option passed to
1065 the constructor, if any.
1067 =item B<< $attr->has_documentation >>
1069 Returns true if this attribute has any documentation.
1071 =item B<< $attr->applied_traits >>
1073 This returns an array reference of all the traits which were applied
1074 to this attribute. If none were applied, this returns C<undef>.
1076 =item B<< $attr->has_applied_traits >>
1078 Returns true if this attribute has any traits applied.
1084 All complex software has bugs lurking in it, and this module is no
1085 exception. If you find a bug please either email me, or add the bug
1090 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1092 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
1094 =head1 COPYRIGHT AND LICENSE
1096 Copyright 2006-2009 by Infinity Interactive, Inc.
1098 L<http://www.iinteractive.com>
1100 This library is free software; you can redistribute it and/or modify
1101 it under the same terms as Perl itself.