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 probably need to start with
756 the L<Class::MOP::Attribute> documentation. This class can be
757 understood as a set of additional features on top of the basic feature
758 provided by that parent class.
762 Many of the documented below override methods in
763 L<Class::MOP::Attribute> and add Moose specific features.
769 =item B<< Moose::Meta::Attribute->new(%options) >>
771 This method overrides the L<Class::MOP::Attribute> constructor.
773 Many of the options below are described in more detail in the
774 L<Moose::Manual::Attributes> document.
776 It adds the following options to the constructor:
780 =item * is => 'ro' or 'rw'
782 This provides a shorthand for specifying the C<reader>, C<writer>, or
783 C<accessor> names. If the attribute is read-only ('ro') then it will
784 have a C<reader> method with the same attribute as the name.
786 If it is read-write ('rw') then it will have an C<accessor> method
787 with the same name. If you provide an explicit C<writer> for a
788 read-write attribute, then you will have a C<reader> with the same
789 name as the attribute, and a C<writer> with the name you provided.
793 This option accepts a type. The type can be a string, which should be
794 a type name. If the type name is unknown, it is assumed to be a class
797 This option can also accept a L<Moose::Meta::TypeConstraint> object.
799 If you I<also> provide a C<does> option, then your C<isa> option must
800 be a class name, and that class must do the role specified with
803 =item * does => $role
805 This is short-hand for saying that the attribute's type must be an
806 object which does the named role.
808 =item * coerce => $bool
810 This option is only valid for objects with a type constraint
811 (C<isa>). If this is true, then coercions will be applied whenever
812 this attribute is set.
814 You can make both this and the C<weak_ref> option true.
816 =item * trigger => $sub
818 This option accepts a subroutine reference, which will be called after
819 the attribute is set.
821 =item * required => $bool
823 An attribute which is required must be provided to the constructor. An
824 attribute which is required can also have a C<default> or C<builder>,
825 which will satisy its required-ness.
827 A required attribute must have a C<default>, C<builder> or a
828 non-C<undef> C<init_arg>
830 =item * lazy => $bool
832 A lazy attribute must have a C<default> or C<builder>. When an
833 attribute is lazy, the default value will not be calculated until the
836 =item * weak_ref => $bool
838 If this is true, the attribute's value will be stored as a weak
841 =item * auto_deref => $bool
843 If this is true, then the reader will dereference the value when it is
844 called. The attribute must have a type constraint which defines the
845 attribute as an array or hash reference.
847 =item * lazy_build => $bool
849 Setting this to true makes the attribute lazy and provides a number of
857 is equivalent to this:
862 builder => '_build_size',
863 clearer => 'clear_size',
864 predicate => 'has_size',
867 =item * documentation
869 An arbitrary string that can be retrieved later by calling C<<
870 $attr->documentation >>.
874 =item B<< $attr->clone(%options) >>
876 This creates a new attribute based on attribute being cloned. You must
877 supply a C<name> option to provide a new name for the attribute.
879 The C<%options> can only specify options handled by
880 L<Class::MOP::Attribute>.
882 =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 =item B<< $attr->remove_accessors>>
927 This method overrides the parent to also remove delegation methods.
929 =item B<< $attr->install_delegation >>
931 This method adds its delegation methods to the attribute's associated
932 class, if it has any to add.
934 =item B<< $attr->remove_delegation >>
936 This method remove its delegation methods from the attribute's
939 =item B<< $attr->accessor_metaclass >>
941 Returns the accessor metaclass name, which defaults to
942 L<Moose::Meta::Method::Accessor>.
944 =item B<< $attr->delegation_metaclass >>
946 Returns the delegation metaclass name, which defaults to
947 L<Moose::Meta::Method::Delegation>.
951 =head2 Additional Moose features
953 These methods are not found in the superclass. They support features
956 =item B<< $attr->does($role) >>
958 This indicates whether the I<attribute itself> does the given
959 role. The role can be given as a full class name, or as a resolveable
962 Note that this checks the attribute itself, not its type constraint,
963 so it is checking the attribute's metaclass and any traits applied to
966 =item B<< Moose::Meta::Class->interpolate_class_and_new($name, %options) >>
968 This is an alternate constructor that handles the C<metaclass> and
971 Effectively, this method is a factory that finds or creates the
972 appropriate class for the given C<metaclass> and/or C<traits.
974 Once it has the appropriate class, it will call C<< $class->new($name,
975 %options) >> on that class.
977 =item B<< $attr->clone_and_inherit_options(%options) >>
979 This method supports the C<has '+foo'> feature. It does various bits
980 of processing on the supplied C<%options> before ultimately calling
983 One of its main tasks is to make sure that the C<%options> provided
984 only includes the options returned by the
985 C<legal_options_for_inheritance> method.
987 =item B<< $attr->legal_options_for_inheritance >>
989 This returns a whitelist of options that can be overridden in a
990 subclass's attribute definition.
992 This exists to allow a custom metaclass to change or add to the list
993 of options which can be changed.
995 =item B<< $attr->type_constraint >>
997 Returns the L<Moose::Meta::TypeConstraint> object for this attribute,
1000 =item B<< $attr->has_type_constraint >>
1002 Returns true if this attribute has a type constraint.
1004 =item B<< $attr->verify_against_type_constraint($value) >>
1006 Given a value, this method returns true if the value is valid for the
1007 attribute's type constraint. If the value is not valid, it throws an
1010 =item B<< $attr->handles >>
1012 This returns the value of the C<handles> option passed to the
1015 =item B<< $attr->has_handles >>
1017 Returns true if this attribute performs delegation.
1019 =item B<< $attr->is_weak_ref >>
1021 Returns true if this attribute stores its value as a weak reference.
1023 =item B<< $attr->is_required >>
1025 Returns true if this attribute is required to have a value.
1027 =item B<< $attr->is_lazy >>
1029 Returns true if this attribute is lazy.
1031 =item B<< $attr->is_lazy_build >>
1033 Returns true if the C<lazy_build> option was true when passed to the
1036 =item B<< $attr->should_coerce >>
1038 Returns true if the C<coerce> option passed to the constructor was
1041 =item B<< $attr->should_auto_deref >>
1043 Returns true if the C<auto_deref> option passed to the constructor was
1046 =item B<< $attr->trigger >>
1048 This is the subroutine reference that was in the C<trigger> option
1049 passed to the constructor, if any.
1051 =item B<< $attr->has_trigger>>
1053 Returns true if this attribute has a trigger set.
1055 =item B<< $attr->documentation >>
1057 Returns the value that was in the C<documentation> option passed to
1058 the constructor, if any.
1060 =item B<< $attr->has_documentation >>
1062 Returns true if this attribute has any documentation.
1064 =item B<< $attr->applied_traits >>
1066 This returns an array reference of all the traits which were applied
1067 to this attribute. If none were applied, this returns C<undef>.
1069 =item B<< $attr->has_applied_traits >>
1071 Returns true if this attribute has any traits applied.
1077 All complex software has bugs lurking in it, and this module is no
1078 exception. If you find a bug please either email me, or add the bug
1083 Stevan Little E<lt>stevan@iinteractive.comE<gt>
1085 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
1087 =head1 COPYRIGHT AND LICENSE
1089 Copyright 2006-2009 by Infinity Interactive, Inc.
1091 L<http://www.iinteractive.com>
1093 This library is free software; you can redistribute it and/or modify
1094 it under the same terms as Perl itself.