2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken';
10 our $VERSION = '0.72';
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) } $self->meta->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 $value_is_set;
406 if ($self->has_type_constraint) {
407 my $type_constraint = $self->type_constraint;
408 if ($self->should_coerce && $type_constraint->has_coercion) {
409 $val = $type_constraint->coerce($val);
411 $self->verify_against_type_constraint($val, instance => $instance);
414 $self->set_initial_value($instance, $val);
415 $meta_instance->weaken_slot_value($instance, $self->name)
416 if ref $val && $self->is_weak_ref;
420 my ( $self, $instance ) = @_;
422 my $builder = $self->builder();
424 return $instance->$builder()
425 if $instance->can( $self->builder );
427 $self->throw_error( blessed($instance)
428 . " does not support builder method '"
430 . "' for attribute '"
440 # this duplicates too much code from
441 # Class::MOP::Attribute, we need to
442 # refactor these bits eventually.
444 sub _set_initial_slot_value {
445 my ($self, $meta_instance, $instance, $value) = @_;
447 my $slot_name = $self->name;
449 return $meta_instance->set_slot_value($instance, $slot_name, $value)
450 unless $self->has_initializer;
452 my ($type_constraint, $can_coerce);
453 if ($self->has_type_constraint) {
454 $type_constraint = $self->type_constraint;
455 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
460 if ($type_constraint) {
461 $val = $type_constraint->coerce($val)
463 $self->verify_against_type_constraint($val, object => $instance);
465 $meta_instance->set_slot_value($instance, $slot_name, $val);
468 my $initializer = $self->initializer;
470 # most things will just want to set a value, so make it first arg
471 $instance->$initializer($value, $callback, $self);
475 my ($self, $instance, @args) = @_;
476 my $value = $args[0];
478 my $attr_name = $self->name;
480 if ($self->is_required and not @args) {
481 $self->throw_error("Attribute ($attr_name) is required", object => $instance);
484 if ($self->has_type_constraint) {
486 my $type_constraint = $self->type_constraint;
488 if ($self->should_coerce) {
489 $value = $type_constraint->coerce($value);
491 $type_constraint->_compiled_type_constraint->($value)
492 || $self->throw_error("Attribute ("
494 . ") does not pass the type constraint because "
495 . $type_constraint->get_message($value), object => $instance, data => $value);
498 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
501 $meta_instance->set_slot_value($instance, $attr_name, $value);
503 if (ref $value && $self->is_weak_ref) {
504 $meta_instance->weaken_slot_value($instance, $attr_name);
507 if ($self->has_trigger) {
508 $self->trigger->($instance, $value);
513 my ($self, $instance) = @_;
515 if ($self->is_lazy) {
516 unless ($self->has_value($instance)) {
518 if ($self->has_default) {
519 $value = $self->default($instance);
520 } elsif ( $self->has_builder ) {
521 $value = $self->_call_builder($instance);
523 if ($self->has_type_constraint) {
524 my $type_constraint = $self->type_constraint;
525 $value = $type_constraint->coerce($value)
526 if ($self->should_coerce);
527 $self->verify_against_type_constraint($value);
529 $self->set_initial_value($instance, $value);
533 if ($self->should_auto_deref) {
535 my $type_constraint = $self->type_constraint;
537 if ($type_constraint->is_a_type_of('ArrayRef')) {
538 my $rv = $self->SUPER::get_value($instance);
539 return unless defined $rv;
540 return wantarray ? @{ $rv } : $rv;
542 elsif ($type_constraint->is_a_type_of('HashRef')) {
543 my $rv = $self->SUPER::get_value($instance);
544 return unless defined $rv;
545 return wantarray ? %{ $rv } : $rv;
548 $self->throw_error("Can not auto de-reference the type constraint '" . $type_constraint->name . "'", object => $instance, type_constraint => $type_constraint);
554 return $self->SUPER::get_value($instance);
558 ## installing accessors
560 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
562 sub install_accessors {
564 $self->SUPER::install_accessors(@_);
565 $self->install_delegation if $self->has_handles;
569 sub remove_accessors {
571 $self->SUPER::remove_accessors(@_);
572 $self->remove_delegation if $self->has_handles;
576 sub install_delegation {
580 # Here we canonicalize the 'handles' option
581 # this will sort out any details and always
582 # return an hash of methods which we want
583 # to delagate to, see that method for details
584 my %handles = $self->_canonicalize_handles;
587 # install the delegation ...
588 my $associated_class = $self->associated_class;
589 foreach my $handle (keys %handles) {
590 my $method_to_call = $handles{$handle};
591 my $class_name = $associated_class->name;
592 my $name = "${class_name}::${handle}";
594 (!$associated_class->has_method($handle))
595 || $self->throw_error("You cannot overwrite a locally defined method ($handle) with a delegation", method_name => $handle);
598 # handles is not allowed to delegate
599 # any of these methods, as they will
600 # override the ones in your class, which
601 # is almost certainly not what you want.
603 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
604 #cluck("Not delegating method '$handle' because it is a core method") and
605 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
607 my $method = $self->_make_delegation_method($handle, $method_to_call);
609 $self->associated_class->add_method($method->name, $method);
613 sub remove_delegation {
615 my %handles = $self->_canonicalize_handles;
616 my $associated_class = $self->associated_class;
617 foreach my $handle (keys %handles) {
618 $self->associated_class->remove_method($handle);
622 # private methods to help delegation ...
624 sub _canonicalize_handles {
626 my $handles = $self->handles;
627 if (my $handle_type = ref($handles)) {
628 if ($handle_type eq 'HASH') {
631 elsif ($handle_type eq 'ARRAY') {
632 return map { $_ => $_ } @{$handles};
634 elsif ($handle_type eq 'Regexp') {
635 ($self->has_type_constraint)
636 || $self->throw_error("Cannot delegate methods based on a Regexp without a type constraint (isa)", data => $handles);
637 return map { ($_ => $_) }
638 grep { /$handles/ } $self->_get_delegate_method_list;
640 elsif ($handle_type eq 'CODE') {
641 return $handles->($self, $self->_find_delegate_metaclass);
644 $self->throw_error("Unable to canonicalize the 'handles' option with $handles", data => $handles);
648 Class::MOP::load_class($handles)
649 unless Class::MOP::is_class_loaded($handles);
651 my $role_meta = eval { $handles->meta };
653 $self->throw_error("Unable to canonicalize the 'handles' option with $handles because : $@", data => $handles, error => $@);
656 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
657 || $self->throw_error("Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role", data => $handles);
659 return map { $_ => $_ } (
660 $role_meta->get_method_list,
661 $role_meta->get_required_method_list
666 sub _find_delegate_metaclass {
668 if (my $class = $self->_isa_metadata) {
669 # if the class does have
670 # a meta method, use it
671 return $class->meta if $class->can('meta');
672 # otherwise we might be
673 # dealing with a non-Moose
674 # class, and need to make
676 return Moose::Meta::Class->initialize($class);
678 elsif (my $role = $self->_does_metadata) {
679 # our role will always have
684 $self->throw_error("Cannot find delegate metaclass for attribute " . $self->name);
688 sub _get_delegate_method_list {
690 my $meta = $self->_find_delegate_metaclass;
691 if ($meta->isa('Class::MOP::Class')) {
692 return map { $_->name } # NOTE: !never! delegate &meta
693 grep { $_->package_name ne 'Moose::Object' && $_->name ne 'meta' }
694 $meta->get_all_methods;
696 elsif ($meta->isa('Moose::Meta::Role')) {
697 return $meta->get_method_list;
700 $self->throw_error("Unable to recognize the delegate metaclass '$meta'", data => $meta);
704 sub delegation_metaclass { 'Moose::Meta::Method::Delegation' }
706 sub _make_delegation_method {
707 my ( $self, $handle_name, $method_to_call ) = @_;
711 $method_body = $method_to_call
712 if 'CODE' eq ref($method_to_call);
714 return $self->delegation_metaclass->new(
715 name => $handle_name,
716 package_name => $self->associated_class->name,
718 delegate_to_method => $method_to_call,
722 sub verify_against_type_constraint {
726 return 1 if !$self->has_type_constraint;
728 my $type_constraint = $self->type_constraint;
730 $type_constraint->check($val)
731 || $self->throw_error("Attribute ("
733 . ") does not pass the type constraint because: "
734 . $type_constraint->get_message($val), data => $val, @_);
737 package Moose::Meta::Attribute::Custom::Moose;
738 sub register_implementation { 'Moose::Meta::Attribute' }
748 Moose::Meta::Attribute - The Moose attribute metaclass
752 This class is a subclass of L<Class::MOP::Attribute> that provides
753 additional Moose-specific functionality.
755 To really understand this class, you will need to start with the
756 L<Class::MOP::Attribute> documentation. This class can be understood
757 as a set of additional features on top of the basic feature provided
758 by that parent class.
762 C<Moose::Meta::Attribute> is a subclass of L<Class::MOP::Attribute>.
766 Many of the documented below override methods in
767 L<Class::MOP::Attribute> and add Moose specific features.
773 =item B<< Moose::Meta::Attribute->new(%options) >>
775 This method overrides the L<Class::MOP::Attribute> constructor.
777 Many of the options below are described in more detail in the
778 L<Moose::Manual::Attributes> document.
780 It adds the following options to the constructor:
784 =item * is => 'ro' or 'rw'
786 This provides a shorthand for specifying the C<reader>, C<writer>, or
787 C<accessor> names. If the attribute is read-only ('ro') then it will
788 have a C<reader> method with the same attribute as the name.
790 If it is read-write ('rw') then it will have an C<accessor> method
791 with the same name. If you provide an explicit C<writer> for a
792 read-write attribute, then you will have a C<reader> with the same
793 name as the attribute, and a C<writer> with the name you provided.
797 This option accepts a type. The type can be a string, which should be
798 a type name. If the type name is unknown, it is assumed to be a class
801 This option can also accept a L<Moose::Meta::TypeConstraint> object.
803 If you I<also> provide a C<does> option, then your C<isa> option must
804 be a class name, and that class must do the role specified with
807 =item * does => $role
809 This is short-hand for saying that the attribute's type must be an
810 object which does the named role.
812 =item * coerce => $bool
814 This option is only valid for objects with a type constraint
815 (C<isa>). If this is true, then coercions will be applied whenever
816 this attribute is set.
818 You can make both this and the C<weak_ref> option true.
820 =item * trigger => $sub
822 This option accepts a subroutine reference, which will be called after
823 the attribute is set.
825 =item * required => $bool
827 An attribute which is required must be provided to the constructor. An
828 attribute which is required can also have a C<default> or C<builder>,
829 which will satisfy its required-ness.
831 A required attribute must have a C<default>, C<builder> or a
832 non-C<undef> C<init_arg>
834 =item * lazy => $bool
836 A lazy attribute must have a C<default> or C<builder>. When an
837 attribute is lazy, the default value will not be calculated until the
840 =item * weak_ref => $bool
842 If this is true, the attribute's value will be stored as a weak
845 =item * auto_deref => $bool
847 If this is true, then the reader will dereference the value when it is
848 called. The attribute must have a type constraint which defines the
849 attribute as an array or hash reference.
851 =item * lazy_build => $bool
853 Setting this to true makes the attribute lazy and provides a number of
861 is equivalent to this:
866 builder => '_build_size',
867 clearer => 'clear_size',
868 predicate => 'has_size',
871 =item * documentation
873 An arbitrary string that can be retrieved later by calling C<<
874 $attr->documentation >>.
878 =item B<< $attr->clone(%options) >>
880 This creates a new attribute based on attribute being cloned. You must
881 supply a C<name> option to provide a new name for the attribute.
883 The C<%options> can only specify options handled by
884 L<Class::MOP::Attribute>.
888 =head2 Value management
892 =item B<< $attr->initialize_instance_slot($meta_instance, $instance, $params) >>
894 This method is used internally to initialize the attribute's slot in
895 the object C<$instance>.
897 This overrides the L<Class::MOP::Attribute> method to handle lazy
898 attributes, weak references, and type constraints.
904 eval { $point->meta->get_attribute('x')->set_value($point, 'forty-two') };
909 I<Attribute (x) does not pass the type constraint (Int) with 'forty-two'>
911 Before setting the value, a check is made on the type constraint of
912 the attribute, if it has one, to see if the value passes it. If the
913 value fails to pass, the set operation dies with a L<throw_error>.
915 Any coercion to convert values is done before checking the type constraint.
917 To check a value against a type constraint before setting it, fetch the
918 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
919 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
920 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::Basics::Recipe4>
925 =head2 Attribute Accessor generation
929 =item B<< $attr->install_accessors >>
931 This method overrides the parent to also install delegation methods.
933 =item B<< $attr->remove_accessors >>
935 This method overrides the parent to also remove delegation methods.
937 =item B<< $attr->install_delegation >>
939 This method adds its delegation methods to the attribute's associated
940 class, if it has any to add.
942 =item B<< $attr->remove_delegation >>
944 This method remove its delegation methods from the attribute's
947 =item B<< $attr->accessor_metaclass >>
949 Returns the accessor metaclass name, which defaults to
950 L<Moose::Meta::Method::Accessor>.
952 =item B<< $attr->delegation_metaclass >>
954 Returns the delegation metaclass name, which defaults to
955 L<Moose::Meta::Method::Delegation>.
959 =head2 Additional Moose features
961 These methods are not found in the superclass. They support features
966 =item B<< $attr->does($role) >>
968 This indicates whether the I<attribute itself> does the given
969 role. The role can be given as a full class name, or as a resolvable
972 Note that this checks the attribute itself, not its type constraint,
973 so it is checking the attribute's metaclass and any traits applied to
976 =item B<< Moose::Meta::Class->interpolate_class_and_new($name, %options) >>
978 This is an alternate constructor that handles the C<metaclass> and
981 Effectively, this method is a factory that finds or creates the
982 appropriate class for the given C<metaclass> and/or C<traits>.
984 Once it has the appropriate class, it will call C<< $class->new($name,
985 %options) >> on that class.
987 =item B<< $attr->clone_and_inherit_options(%options) >>
989 This method supports the C<has '+foo'> feature. It does various bits
990 of processing on the supplied C<%options> before ultimately calling
993 One of its main tasks is to make sure that the C<%options> provided
994 only includes the options returned by the
995 C<legal_options_for_inheritance> method.
997 =item B<< $attr->legal_options_for_inheritance >>
999 This returns a whitelist of options that can be overridden in a
1000 subclass's attribute definition.
1002 This exists to allow a custom metaclass to change or add to the list
1003 of options which can be changed.
1005 =item B<< $attr->type_constraint >>
1007 Returns the L<Moose::Meta::TypeConstraint> object for this attribute,
1010 =item B<< $attr->has_type_constraint >>
1012 Returns true if this attribute has a type constraint.
1014 =item B<< $attr->verify_against_type_constraint($value) >>
1016 Given a value, this method returns true if the value is valid for the
1017 attribute's type constraint. If the value is not valid, it throws an
1020 =item B<< $attr->handles >>
1022 This returns the value of the C<handles> option passed to the
1025 =item B<< $attr->has_handles >>
1027 Returns true if this attribute performs delegation.
1029 =item B<< $attr->is_weak_ref >>
1031 Returns true if this attribute stores its value as a weak reference.
1033 =item B<< $attr->is_required >>
1035 Returns true if this attribute is required to have a value.
1037 =item B<< $attr->is_lazy >>
1039 Returns true if this attribute is lazy.
1041 =item B<< $attr->is_lazy_build >>
1043 Returns true if the C<lazy_build> option was true when passed to the
1046 =item B<< $attr->should_coerce >>
1048 Returns true if the C<coerce> option passed to the constructor was
1051 =item B<< $attr->should_auto_deref >>
1053 Returns true if the C<auto_deref> option passed to the constructor was
1056 =item B<< $attr->trigger >>
1058 This is the subroutine reference that was in the C<trigger> option
1059 passed to the constructor, if any.
1061 =item B<< $attr->has_trigger >>
1063 Returns true if this attribute has a trigger set.
1065 =item B<< $attr->documentation >>
1067 Returns the value that was in the C<documentation> option passed to
1068 the constructor, if any.
1070 =item B<< $attr->has_documentation >>
1072 Returns true if this attribute has any documentation.
1074 =item B<< $attr->applied_traits >>
1076 This returns an array reference of all the traits which were applied
1077 to this attribute. If none were applied, this returns C<undef>.
1079 =item B<< $attr->has_applied_traits >>
1081 Returns true if this attribute has any traits applied.
1087 All complex software has bugs lurking in it, and this module is no
1088 exception. If you find a bug please either email me, or add the bug
1093 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1095 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
1097 =head1 COPYRIGHT AND LICENSE
1099 Copyright 2006-2009 by Infinity Interactive, Inc.
1101 L<http://www.iinteractive.com>
1103 This library is free software; you can redistribute it and/or modify
1104 it under the same terms as Perl itself.