2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken';
8 use List::MoreUtils 'any';
12 our $VERSION = '1.08';
13 our $AUTHORITY = 'cpan:STEVAN';
15 use Moose::Meta::Method::Accessor;
16 use Moose::Meta::Method::Delegation;
18 use Moose::Util::TypeConstraints ();
20 use base 'Class::MOP::Attribute', 'Moose::Meta::Mixin::AttributeCore';
22 __PACKAGE__->meta->add_attribute('traits' => (
23 reader => 'applied_traits',
24 predicate => 'has_applied_traits',
27 # we need to have a ->does method in here to
28 # more easily support traits, and the introspection
29 # of those traits. We extend the does check to look
30 # for metatrait aliases.
32 my ($self, $role_name) = @_;
34 Moose::Util::resolve_metatrait_alias(Attribute => $role_name)
36 return 0 if !defined($name); # failed to load class
37 return $self->Moose::Object::does($name);
42 my $class = ( ref $self && $self->associated_class ) || "Moose::Meta::Class";
43 unshift @_, "message" if @_ % 2 == 1;
44 unshift @_, attr => $self if ref $self;
46 my $handler = $class->can("throw_error"); # to avoid incrementing depth by 1
51 my ($class, $name, %options) = @_;
52 $class->_process_options($name, \%options) unless $options{__hack_no_process_options}; # used from clone()... YECHKKK FIXME ICKY YUCK GROSS
54 delete $options{__hack_no_process_options};
59 map { $_->init_arg() }
60 $class->meta()->get_all_attributes()
63 my @bad = sort grep { ! $attrs{$_} } keys %options;
67 Carp::cluck "Found unknown argument(s) passed to '$name' attribute constructor in '$class': @bad";
70 return $class->SUPER::new($name, %options);
73 sub interpolate_class_and_new {
74 my ($class, $name, %args) = @_;
76 my ( $new_class, @traits ) = $class->interpolate_class(\%args);
78 $new_class->new($name, %args, ( scalar(@traits) ? ( traits => \@traits ) : () ) );
81 sub interpolate_class {
82 my ($class, $options) = @_;
84 $class = ref($class) || $class;
86 if ( my $metaclass_name = delete $options->{metaclass} ) {
87 my $new_class = Moose::Util::resolve_metaclass_alias( Attribute => $metaclass_name );
89 if ( $class ne $new_class ) {
90 if ( $new_class->can("interpolate_class") ) {
91 return $new_class->interpolate_class($options);
100 if (my $traits = $options->{traits}) {
102 while ($i < @$traits) {
103 my $trait = $traits->[$i++];
104 next if ref($trait); # options to a trait we discarded
106 $trait = Moose::Util::resolve_metatrait_alias(Attribute => $trait)
109 next if $class->does($trait);
111 push @traits, $trait;
114 push @traits, $traits->[$i++]
115 if $traits->[$i] && ref($traits->[$i]);
119 my $anon_class = Moose::Meta::Class->create_anon_class(
120 superclasses => [ $class ],
121 roles => [ @traits ],
125 $class = $anon_class->name;
129 return ( wantarray ? ( $class, @traits ) : $class );
134 my @legal_options_for_inheritance = qw(
135 default coerce required
136 documentation lazy handles
137 builder type_constraint
142 sub legal_options_for_inheritance { @legal_options_for_inheritance }
145 # This method *must* be able to handle
146 # Class::MOP::Attribute instances as
147 # well. Yes, I know that is wrong, but
148 # apparently we didn't realize it was
149 # doing that and now we have some code
150 # which is dependent on it. The real
151 # solution of course is to push this
152 # feature back up into Class::MOP::Attribute
153 # but I not right now, I am too lazy.
154 # However if you are reading this and
155 # looking for something to do,.. please
158 sub clone_and_inherit_options {
159 my ($self, %options) = @_;
166 # we may want to extends a Class::MOP::Attribute
167 # in which case we need to be able to use the
168 # core set of legal options that have always
169 # been here. But we allows Moose::Meta::Attribute
170 # instances to changes them.
172 my @legal_options = $self->can('legal_options_for_inheritance')
173 ? $self->legal_options_for_inheritance
174 : @legal_options_for_inheritance;
176 foreach my $legal_option (@legal_options) {
177 if (exists $options{$legal_option}) {
178 $actual_options{$legal_option} = $options{$legal_option};
179 delete $options{$legal_option};
185 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
186 $type_constraint = $options{isa};
189 $type_constraint = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options{isa});
190 (defined $type_constraint)
191 || $self->throw_error("Could not find the type constraint '" . $options{isa} . "'", data => $options{isa});
194 $actual_options{type_constraint} = $type_constraint;
195 delete $options{isa};
198 if ($options{does}) {
200 if (blessed($options{does}) && $options{does}->isa('Moose::Meta::TypeConstraint')) {
201 $type_constraint = $options{does};
204 $type_constraint = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options{does});
205 (defined $type_constraint)
206 || $self->throw_error("Could not find the type constraint '" . $options{does} . "'", data => $options{does});
209 $actual_options{type_constraint} = $type_constraint;
210 delete $options{does};
214 # this doesn't apply to Class::MOP::Attributes,
215 # so we can ignore it for them.
217 if ($self->can('interpolate_class')) {
218 ( $actual_options{metaclass}, my @traits ) = $self->interpolate_class(\%options);
221 my @all_traits = grep { $seen{$_}++ } @{ $self->applied_traits || [] }, @traits;
222 $actual_options{traits} = \@all_traits if @all_traits;
224 delete @options{qw(metaclass traits)};
227 (scalar keys %options == 0)
228 || $self->throw_error("Illegal inherited options => (" . (join ', ' => keys %options) . ")", data => \%options);
231 $self->clone(%actual_options);
235 my ( $self, %params ) = @_;
237 my $class = delete $params{metaclass} || ref $self;
239 my ( @init, @non_init );
241 foreach my $attr ( grep { $_->has_value($self) } Class::MOP::class_of($self)->get_all_attributes ) {
242 push @{ $attr->has_init_arg ? \@init : \@non_init }, $attr;
245 my %new_params = ( ( map { $_->init_arg => $_->get_value($self) } @init ), %params );
247 my $name = delete $new_params{name};
249 my $clone = $class->new($name, %new_params, __hack_no_process_options => 1 );
251 foreach my $attr ( @non_init ) {
252 $attr->set_value($clone, $attr->get_value($self));
258 sub _process_options {
259 my ($class, $name, $options) = @_;
261 if (exists $options->{is}) {
263 ### -------------------------
264 ## is => ro, writer => _foo # turns into (reader => foo, writer => _foo) as before
265 ## is => rw, writer => _foo # turns into (reader => foo, writer => _foo)
266 ## is => rw, accessor => _foo # turns into (accessor => _foo)
267 ## is => ro, accessor => _foo # error, accesor is rw
268 ### -------------------------
270 if ($options->{is} eq 'ro') {
271 $class->throw_error("Cannot define an accessor name on a read-only attribute, accessors are read/write", data => $options)
272 if exists $options->{accessor};
273 $options->{reader} ||= $name;
275 elsif ($options->{is} eq 'rw') {
276 if ($options->{writer}) {
277 $options->{reader} ||= $name;
280 $options->{accessor} ||= $name;
283 elsif ($options->{is} eq 'bare') {
284 # do nothing, but don't complain (later) about missing methods
287 $class->throw_error("I do not understand this option (is => " . $options->{is} . ") on attribute ($name)", data => $options->{is});
291 if (exists $options->{isa}) {
292 if (exists $options->{does}) {
293 if (try { $options->{isa}->can('does') }) {
294 ($options->{isa}->does($options->{does}))
295 || $class->throw_error("Cannot have an isa option and a does option if the isa does not do the does on attribute ($name)", data => $options);
298 $class->throw_error("Cannot have an isa option which cannot ->does() on attribute ($name)", data => $options);
302 # allow for anon-subtypes here ...
303 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
304 $options->{type_constraint} = $options->{isa};
307 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options->{isa});
310 elsif (exists $options->{does}) {
311 # allow for anon-subtypes here ...
312 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
313 $options->{type_constraint} = $options->{does};
316 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options->{does});
320 if (exists $options->{coerce} && $options->{coerce}) {
321 (exists $options->{type_constraint})
322 || $class->throw_error("You cannot have coercion without specifying a type constraint on attribute ($name)", data => $options);
323 $class->throw_error("You cannot have a weak reference to a coerced value on attribute ($name)", data => $options)
324 if $options->{weak_ref};
326 unless ( $options->{type_constraint}->has_coercion ) {
327 my $type = $options->{type_constraint}->name;
328 $class->throw_error("You cannot coerce an attribute ($name) unless its type ($type) has a coercion", data => $options);
332 if (exists $options->{trigger}) {
333 ('CODE' eq ref $options->{trigger})
334 || $class->throw_error("Trigger must be a CODE ref on attribute ($name)", data => $options->{trigger});
337 if (exists $options->{auto_deref} && $options->{auto_deref}) {
338 (exists $options->{type_constraint})
339 || $class->throw_error("You cannot auto-dereference without specifying a type constraint on attribute ($name)", data => $options);
340 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
341 $options->{type_constraint}->is_a_type_of('HashRef'))
342 || $class->throw_error("You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute ($name)", data => $options);
345 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
346 $class->throw_error("You can not use lazy_build and default for the same attribute ($name)", data => $options)
347 if exists $options->{default};
348 $options->{lazy} = 1;
349 $options->{builder} ||= "_build_${name}";
351 $options->{clearer} ||= "_clear${name}";
352 $options->{predicate} ||= "_has${name}";
355 $options->{clearer} ||= "clear_${name}";
356 $options->{predicate} ||= "has_${name}";
360 if (exists $options->{lazy} && $options->{lazy}) {
361 (exists $options->{default} || defined $options->{builder} )
362 || $class->throw_error("You cannot have lazy attribute ($name) without specifying a default value for it", data => $options);
365 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
366 $class->throw_error("You cannot have a required attribute ($name) without a default, builder, or an init_arg", data => $options);
371 sub initialize_instance_slot {
372 my ($self, $meta_instance, $instance, $params) = @_;
373 my $init_arg = $self->init_arg();
374 # try to fetch the init arg from the %params ...
378 if ( defined($init_arg) and exists $params->{$init_arg}) {
379 $val = $params->{$init_arg};
383 # skip it if it's lazy
384 return if $self->is_lazy;
385 # and die if it's required and doesn't have a default value
386 $self->throw_error("Attribute (" . $self->name . ") is required", object => $instance, data => $params)
387 if $self->is_required && !$self->has_default && !$self->has_builder;
389 # if nothing was in the %params, we can use the
390 # attribute's default value (if it has one)
391 if ($self->has_default) {
392 $val = $self->default($instance);
395 elsif ($self->has_builder) {
396 $val = $self->_call_builder($instance);
401 return unless $value_is_set;
403 $val = $self->_coerce_and_verify( $val, $instance );
405 $self->set_initial_value($instance, $val);
407 if ( ref $val && $self->is_weak_ref ) {
408 $self->_weaken_value($instance);
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;
446 my $val = $self->_coerce_and_verify( shift, $instance );;
448 $meta_instance->set_slot_value($instance, $slot_name, $val);
451 my $initializer = $self->initializer;
453 # most things will just want to set a value, so make it first arg
454 $instance->$initializer($value, $callback, $self);
458 my ($self, $instance, @args) = @_;
459 my $value = $args[0];
461 my $attr_name = $self->name;
463 if ($self->is_required and not @args) {
464 $self->throw_error("Attribute ($attr_name) is required", object => $instance);
467 $value = $self->_coerce_and_verify( $value, $instance );
470 if ( $self->has_trigger && $self->has_value($instance) ) {
471 @old = $self->get_value($instance, 'for trigger');
474 $self->SUPER::set_value($instance, $value);
476 if ( ref $value && $self->is_weak_ref ) {
477 $self->_weaken_value($instance);
480 if ($self->has_trigger) {
481 $self->trigger->($instance, $value, @old);
486 my ( $self, $instance ) = @_;
488 my $meta_instance = Class::MOP::Class->initialize( blessed($instance) )
491 $meta_instance->weaken_slot_value( $instance, $self->name );
495 my ($self, $instance, $for_trigger) = @_;
497 if ($self->is_lazy) {
498 unless ($self->has_value($instance)) {
500 if ($self->has_default) {
501 $value = $self->default($instance);
502 } elsif ( $self->has_builder ) {
503 $value = $self->_call_builder($instance);
506 $value = $self->_coerce_and_verify( $value, $instance );
508 $self->set_initial_value($instance, $value);
512 if ( $self->should_auto_deref && ! $for_trigger ) {
514 my $type_constraint = $self->type_constraint;
516 if ($type_constraint->is_a_type_of('ArrayRef')) {
517 my $rv = $self->SUPER::get_value($instance);
518 return unless defined $rv;
519 return wantarray ? @{ $rv } : $rv;
521 elsif ($type_constraint->is_a_type_of('HashRef')) {
522 my $rv = $self->SUPER::get_value($instance);
523 return unless defined $rv;
524 return wantarray ? %{ $rv } : $rv;
527 $self->throw_error("Can not auto de-reference the type constraint '" . $type_constraint->name . "'", object => $instance, type_constraint => $type_constraint);
533 return $self->SUPER::get_value($instance);
537 ## installing accessors
539 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
541 sub install_accessors {
543 $self->SUPER::install_accessors(@_);
544 $self->install_delegation if $self->has_handles;
548 sub _check_associated_methods {
551 @{ $self->associated_methods }
552 || ($self->_is_metadata || '') eq 'bare'
555 'Attribute (' . $self->name . ') of class '
556 . $self->associated_class->name
557 . ' has no associated methods'
558 . ' (did you mean to provide an "is" argument?)'
564 sub _process_accessors {
566 my ($type, $accessor, $generate_as_inline_methods) = @_;
567 $accessor = (keys %$accessor)[0] if (ref($accessor)||'') eq 'HASH';
568 my $method = $self->associated_class->get_method($accessor);
569 if ($method && !$method->isa('Class::MOP::Method::Accessor')
570 && (!$self->definition_context
571 || $method->package_name eq $self->definition_context->{package})) {
573 "You are overwriting a locally defined method ($accessor) with "
577 if (!$self->associated_class->has_method($accessor)
578 && $self->associated_class->has_package_symbol('&' . $accessor)) {
580 "You are overwriting a locally defined function ($accessor) with "
584 $self->SUPER::_process_accessors(@_);
587 sub remove_accessors {
589 $self->SUPER::remove_accessors(@_);
590 $self->remove_delegation if $self->has_handles;
594 sub install_delegation {
598 # Here we canonicalize the 'handles' option
599 # this will sort out any details and always
600 # return an hash of methods which we want
601 # to delagate to, see that method for details
602 my %handles = $self->_canonicalize_handles;
605 # install the delegation ...
606 my $associated_class = $self->associated_class;
607 foreach my $handle (keys %handles) {
608 my $method_to_call = $handles{$handle};
609 my $class_name = $associated_class->name;
610 my $name = "${class_name}::${handle}";
612 (!$associated_class->has_method($handle))
613 || $self->throw_error("You cannot overwrite a locally defined method ($handle) with a delegation", method_name => $handle);
616 # handles is not allowed to delegate
617 # any of these methods, as they will
618 # override the ones in your class, which
619 # is almost certainly not what you want.
621 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
622 #cluck("Not delegating method '$handle' because it is a core method") and
623 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
625 my $method = $self->_make_delegation_method($handle, $method_to_call);
627 $self->associated_class->add_method($method->name, $method);
628 $self->associate_method($method);
632 sub remove_delegation {
634 my %handles = $self->_canonicalize_handles;
635 my $associated_class = $self->associated_class;
636 foreach my $handle (keys %handles) {
637 next unless any { $handle eq $_ }
639 @{ $self->associated_methods };
640 $self->associated_class->remove_method($handle);
644 # private methods to help delegation ...
646 sub _canonicalize_handles {
648 my $handles = $self->handles;
649 if (my $handle_type = ref($handles)) {
650 if ($handle_type eq 'HASH') {
653 elsif ($handle_type eq 'ARRAY') {
654 return map { $_ => $_ } @{$handles};
656 elsif ($handle_type eq 'Regexp') {
657 ($self->has_type_constraint)
658 || $self->throw_error("Cannot delegate methods based on a Regexp without a type constraint (isa)", data => $handles);
659 return map { ($_ => $_) }
660 grep { /$handles/ } $self->_get_delegate_method_list;
662 elsif ($handle_type eq 'CODE') {
663 return $handles->($self, $self->_find_delegate_metaclass);
665 elsif (blessed($handles) && $handles->isa('Moose::Meta::TypeConstraint::DuckType')) {
666 return map { $_ => $_ } @{ $handles->methods };
668 elsif (blessed($handles) && $handles->isa('Moose::Meta::TypeConstraint::Role')) {
669 $handles = $handles->role;
672 $self->throw_error("Unable to canonicalize the 'handles' option with $handles", data => $handles);
676 Class::MOP::load_class($handles);
677 my $role_meta = Class::MOP::class_of($handles);
679 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
680 || $self->throw_error("Unable to canonicalize the 'handles' option with $handles because its metaclass is not a Moose::Meta::Role", data => $handles);
682 return map { $_ => $_ }
683 grep { $_ ne 'meta' } (
684 $role_meta->get_method_list,
685 map { $_->name } $role_meta->get_required_method_list,
689 sub _find_delegate_metaclass {
691 if (my $class = $self->_isa_metadata) {
692 # we might be dealing with a non-Moose class,
693 # and need to make our own metaclass. if there's
694 # already a metaclass, it will be returned
695 return Class::MOP::Class->initialize($class);
697 elsif (my $role = $self->_does_metadata) {
698 return Class::MOP::class_of($role);
701 $self->throw_error("Cannot find delegate metaclass for attribute " . $self->name);
705 sub _get_delegate_method_list {
707 my $meta = $self->_find_delegate_metaclass;
708 if ($meta->isa('Class::MOP::Class')) {
709 return map { $_->name } # NOTE: !never! delegate &meta
710 grep { $_->package_name ne 'Moose::Object' && $_->name ne 'meta' }
711 $meta->get_all_methods;
713 elsif ($meta->isa('Moose::Meta::Role')) {
714 return $meta->get_method_list;
717 $self->throw_error("Unable to recognize the delegate metaclass '$meta'", data => $meta);
721 sub delegation_metaclass { 'Moose::Meta::Method::Delegation' }
723 sub _make_delegation_method {
724 my ( $self, $handle_name, $method_to_call ) = @_;
726 my @curried_arguments;
728 ($method_to_call, @curried_arguments) = @$method_to_call
729 if 'ARRAY' eq ref($method_to_call);
731 return $self->delegation_metaclass->new(
732 name => $handle_name,
733 package_name => $self->associated_class->name,
735 delegate_to_method => $method_to_call,
736 curried_arguments => \@curried_arguments,
740 sub _coerce_and_verify {
743 my $instance = shift;
745 return $val unless $self->has_type_constraint;
747 $val = $self->type_constraint->coerce($val)
748 if $self->should_coerce;
750 $self->verify_against_type_constraint($val, instance => $instance);
755 sub verify_against_type_constraint {
759 return 1 if !$self->has_type_constraint;
761 my $type_constraint = $self->type_constraint;
763 $type_constraint->check($val)
764 || $self->throw_error("Attribute ("
766 . ") does not pass the type constraint because: "
767 . $type_constraint->get_message($val), data => $val, @_);
770 package Moose::Meta::Attribute::Custom::Moose;
771 sub register_implementation { 'Moose::Meta::Attribute' }
781 Moose::Meta::Attribute - The Moose attribute metaclass
785 This class is a subclass of L<Class::MOP::Attribute> that provides
786 additional Moose-specific functionality.
788 To really understand this class, you will need to start with the
789 L<Class::MOP::Attribute> documentation. This class can be understood
790 as a set of additional features on top of the basic feature provided
791 by that parent class.
795 C<Moose::Meta::Attribute> is a subclass of L<Class::MOP::Attribute>.
799 Many of the documented below override methods in
800 L<Class::MOP::Attribute> and add Moose specific features.
806 =item B<< Moose::Meta::Attribute->new(%options) >>
808 This method overrides the L<Class::MOP::Attribute> constructor.
810 Many of the options below are described in more detail in the
811 L<Moose::Manual::Attributes> document.
813 It adds the following options to the constructor:
817 =item * is => 'ro', 'rw', 'bare'
819 This provides a shorthand for specifying the C<reader>, C<writer>, or
820 C<accessor> names. If the attribute is read-only ('ro') then it will
821 have a C<reader> method with the same attribute as the name.
823 If it is read-write ('rw') then it will have an C<accessor> method
824 with the same name. If you provide an explicit C<writer> for a
825 read-write attribute, then you will have a C<reader> with the same
826 name as the attribute, and a C<writer> with the name you provided.
828 Use 'bare' when you are deliberately not installing any methods
829 (accessor, reader, etc.) associated with this attribute; otherwise,
830 Moose will issue a deprecation warning when this attribute is added to a
835 This option accepts a type. The type can be a string, which should be
836 a type name. If the type name is unknown, it is assumed to be a class
839 This option can also accept a L<Moose::Meta::TypeConstraint> object.
841 If you I<also> provide a C<does> option, then your C<isa> option must
842 be a class name, and that class must do the role specified with
845 =item * does => $role
847 This is short-hand for saying that the attribute's type must be an
848 object which does the named role.
850 =item * coerce => $bool
852 This option is only valid for objects with a type constraint
853 (C<isa>). If this is true, then coercions will be applied whenever
854 this attribute is set.
856 You can make both this and the C<weak_ref> option true.
858 =item * trigger => $sub
860 This option accepts a subroutine reference, which will be called after
861 the attribute is set.
863 =item * required => $bool
865 An attribute which is required must be provided to the constructor. An
866 attribute which is required can also have a C<default> or C<builder>,
867 which will satisfy its required-ness.
869 A required attribute must have a C<default>, C<builder> or a
870 non-C<undef> C<init_arg>
872 =item * lazy => $bool
874 A lazy attribute must have a C<default> or C<builder>. When an
875 attribute is lazy, the default value will not be calculated until the
878 =item * weak_ref => $bool
880 If this is true, the attribute's value will be stored as a weak
883 =item * auto_deref => $bool
885 If this is true, then the reader will dereference the value when it is
886 called. The attribute must have a type constraint which defines the
887 attribute as an array or hash reference.
889 =item * lazy_build => $bool
891 Setting this to true makes the attribute lazy and provides a number of
899 is equivalent to this:
904 builder => '_build_size',
905 clearer => 'clear_size',
906 predicate => 'has_size',
909 =item * documentation
911 An arbitrary string that can be retrieved later by calling C<<
912 $attr->documentation >>.
916 =item B<< $attr->clone(%options) >>
918 This creates a new attribute based on attribute being cloned. You must
919 supply a C<name> option to provide a new name for the attribute.
921 The C<%options> can only specify options handled by
922 L<Class::MOP::Attribute>.
926 =head2 Value management
930 =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >>
932 This method is used internally to initialize the attribute's slot in
933 the object C<$instance>.
935 This overrides the L<Class::MOP::Attribute> method to handle lazy
936 attributes, weak references, and type constraints.
942 eval { $point->meta->get_attribute('x')->set_value($point, 'forty-two') };
947 I<Attribute (x) does not pass the type constraint (Int) with 'forty-two'>
949 Before setting the value, a check is made on the type constraint of
950 the attribute, if it has one, to see if the value passes it. If the
951 value fails to pass, the set operation dies with a L</throw_error>.
953 Any coercion to convert values is done before checking the type constraint.
955 To check a value against a type constraint before setting it, fetch the
956 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
957 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
958 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::Basics::Recipe4>
963 =head2 Attribute Accessor generation
967 =item B<< $attr->install_accessors >>
969 This method overrides the parent to also install delegation methods.
971 If, after installing all methods, the attribute object has no associated
972 methods, it throws an error unless C<< is => 'bare' >> was passed to the
973 attribute constructor. (Trying to add an attribute that has no associated
974 methods is almost always an error.)
976 =item B<< $attr->remove_accessors >>
978 This method overrides the parent to also remove delegation methods.
980 =item B<< $attr->install_delegation >>
982 This method adds its delegation methods to the attribute's associated
983 class, if it has any to add.
985 =item B<< $attr->remove_delegation >>
987 This method remove its delegation methods from the attribute's
990 =item B<< $attr->accessor_metaclass >>
992 Returns the accessor metaclass name, which defaults to
993 L<Moose::Meta::Method::Accessor>.
995 =item B<< $attr->delegation_metaclass >>
997 Returns the delegation metaclass name, which defaults to
998 L<Moose::Meta::Method::Delegation>.
1002 =head2 Additional Moose features
1004 These methods are not found in the superclass. They support features
1009 =item B<< $attr->does($role) >>
1011 This indicates whether the I<attribute itself> does the given
1012 role. The role can be given as a full class name, or as a resolvable
1015 Note that this checks the attribute itself, not its type constraint,
1016 so it is checking the attribute's metaclass and any traits applied to
1019 =item B<< Moose::Meta::Class->interpolate_class_and_new($name, %options) >>
1021 This is an alternate constructor that handles the C<metaclass> and
1024 Effectively, this method is a factory that finds or creates the
1025 appropriate class for the given C<metaclass> and/or C<traits>.
1027 Once it has the appropriate class, it will call C<< $class->new($name,
1028 %options) >> on that class.
1030 =item B<< $attr->clone_and_inherit_options(%options) >>
1032 This method supports the C<has '+foo'> feature. It does various bits
1033 of processing on the supplied C<%options> before ultimately calling
1034 the C<clone> method.
1036 One of its main tasks is to make sure that the C<%options> provided
1037 only includes the options returned by the
1038 C<legal_options_for_inheritance> method.
1040 =item B<< $attr->legal_options_for_inheritance >>
1042 This returns a whitelist of options that can be overridden in a
1043 subclass's attribute definition.
1045 This exists to allow a custom metaclass to change or add to the list
1046 of options which can be changed.
1048 =item B<< $attr->type_constraint >>
1050 Returns the L<Moose::Meta::TypeConstraint> object for this attribute,
1053 =item B<< $attr->has_type_constraint >>
1055 Returns true if this attribute has a type constraint.
1057 =item B<< $attr->verify_against_type_constraint($value) >>
1059 Given a value, this method returns true if the value is valid for the
1060 attribute's type constraint. If the value is not valid, it throws an
1063 =item B<< $attr->handles >>
1065 This returns the value of the C<handles> option passed to the
1068 =item B<< $attr->has_handles >>
1070 Returns true if this attribute performs delegation.
1072 =item B<< $attr->is_weak_ref >>
1074 Returns true if this attribute stores its value as a weak reference.
1076 =item B<< $attr->is_required >>
1078 Returns true if this attribute is required to have a value.
1080 =item B<< $attr->is_lazy >>
1082 Returns true if this attribute is lazy.
1084 =item B<< $attr->is_lazy_build >>
1086 Returns true if the C<lazy_build> option was true when passed to the
1089 =item B<< $attr->should_coerce >>
1091 Returns true if the C<coerce> option passed to the constructor was
1094 =item B<< $attr->should_auto_deref >>
1096 Returns true if the C<auto_deref> option passed to the constructor was
1099 =item B<< $attr->trigger >>
1101 This is the subroutine reference that was in the C<trigger> option
1102 passed to the constructor, if any.
1104 =item B<< $attr->has_trigger >>
1106 Returns true if this attribute has a trigger set.
1108 =item B<< $attr->documentation >>
1110 Returns the value that was in the C<documentation> option passed to
1111 the constructor, if any.
1113 =item B<< $attr->has_documentation >>
1115 Returns true if this attribute has any documentation.
1117 =item B<< $attr->applied_traits >>
1119 This returns an array reference of all the traits which were applied
1120 to this attribute. If none were applied, this returns C<undef>.
1122 =item B<< $attr->has_applied_traits >>
1124 Returns true if this attribute has any traits applied.
1130 See L<Moose/BUGS> for details on reporting bugs.
1134 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1136 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
1138 =head1 COPYRIGHT AND LICENSE
1140 Copyright 2006-2010 by Infinity Interactive, Inc.
1142 L<http://www.iinteractive.com>
1144 This library is free software; you can redistribute it and/or modify
1145 it under the same terms as Perl itself.