2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
11 our $VERSION = '0.24';
12 our $AUTHORITY = 'cpan:STEVAN';
14 use Moose::Meta::Method::Accessor;
16 use Moose::Util::TypeConstraints ();
18 use base 'Class::MOP::Attribute';
20 # options which are not directly used
21 # but we store them for metadata purposes
22 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
23 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
24 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
26 # these are actual options for the attrs
27 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
28 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
29 __PACKAGE__->meta->add_attribute('lazy_build' => (reader => 'is_lazy_build' ));
30 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
31 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
32 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
33 __PACKAGE__->meta->add_attribute('type_constraint' => (
34 reader => 'type_constraint',
35 predicate => 'has_type_constraint',
37 __PACKAGE__->meta->add_attribute('trigger' => (
39 predicate => 'has_trigger',
41 __PACKAGE__->meta->add_attribute('handles' => (
43 predicate => 'has_handles',
45 __PACKAGE__->meta->add_attribute('documentation' => (
46 reader => 'documentation',
47 predicate => 'has_documentation',
49 __PACKAGE__->meta->add_attribute('traits' => (
50 reader => 'applied_traits',
51 predicate => 'has_applied_traits',
55 # we need to have a ->does method in here to
56 # more easily support traits, and the introspection
57 # of those traits. So in order to do this we
58 # just alias Moose::Object's version of it.
60 *does = \&Moose::Object::does;
63 my ($class, $name, %options) = @_;
64 $class->_process_options($name, \%options) unless $options{__hack_no_process_options}; # used from clone()... YECHKKK FIXME ICKY YUCK GROSS
65 return $class->SUPER::new($name, %options);
68 sub interpolate_class_and_new {
69 my ($class, $name, @args) = @_;
71 my ( $new_class, @traits ) = $class->interpolate_class(@args);
73 $new_class->new($name, @args, ( scalar(@traits) ? ( traits => \@traits ) : () ) );
76 sub interpolate_class {
77 my ($class, %options) = @_;
79 $class = ref($class) || $class;
81 if ( my $metaclass_name = delete $options{metaclass} ) {
82 my $new_class = Moose::Util::resolve_metaclass_alias( Attribute => $metaclass_name );
84 if ( $class ne $new_class ) {
85 if ( $new_class->can("interpolate_class") ) {
86 return $new_class->interpolate_class(%options);
95 if (my $traits = $options{traits}) {
96 if ( @traits = grep { not $class->does($_) } map {
97 Moose::Util::resolve_metatrait_alias( Attribute => $_ )
101 my $anon_class = Moose::Meta::Class->create_anon_class(
102 superclasses => [ $class ],
103 roles => [ @traits ],
107 $class = $anon_class->name;
111 return ( wantarray ? ( $class, @traits ) : $class );
114 sub clone_and_inherit_options {
115 my ($self, %options) = @_;
117 # you can change default, required, coerce, documentation, lazy, handles, builder, type_constraint (explicitly or using isa/does), metaclass and traits
119 foreach my $legal_option (qw(default coerce required documentation lazy handles builder type_constraint)) {
120 if (exists $options{$legal_option}) {
121 $actual_options{$legal_option} = $options{$legal_option};
122 delete $options{$legal_option};
128 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
129 $type_constraint = $options{isa};
132 $type_constraint = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options{isa});
133 (defined $type_constraint)
134 || confess "Could not find the type constraint '" . $options{isa} . "'";
137 $actual_options{type_constraint} = $type_constraint;
138 delete $options{isa};
141 if ($options{does}) {
143 if (blessed($options{does}) && $options{does}->isa('Moose::Meta::TypeConstraint')) {
144 $type_constraint = $options{does};
147 $type_constraint = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options{does});
148 (defined $type_constraint)
149 || confess "Could not find the type constraint '" . $options{does} . "'";
152 $actual_options{type_constraint} = $type_constraint;
153 delete $options{does};
157 # this doesn't apply to Class::MOP::Attributes,
158 # so we can ignore it for them.
160 if ($self->can('interpolate_class')) {
161 ( $actual_options{metaclass}, my @traits ) = $self->interpolate_class(%options);
164 my @all_traits = grep { $seen{$_}++ } @{ $self->applied_traits || [] }, @traits;
165 $actual_options{traits} = \@all_traits if @all_traits;
167 delete @options{qw(metaclass traits)};
170 (scalar keys %options == 0)
171 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
174 $self->clone(%actual_options);
178 my ( $self, %params ) = @_;
180 my $class = $params{metaclass} || ref $self;
182 if ( 0 and $class eq ref $self ) {
183 return $self->SUPER::clone(%params);
185 my ( @init, @non_init );
187 foreach my $attr ( grep { $_->has_value($self) } $self->meta->compute_all_applicable_attributes ) {
188 push @{ $attr->has_init_arg ? \@init : \@non_init }, $attr;
191 my %new_params = ( ( map { $_->init_arg => $_->get_value($self) } @init ), %params );
193 my $name = delete $new_params{name};
195 my $clone = $class->new($name, %new_params, __hack_no_process_options => 1 );
197 foreach my $attr ( @non_init ) {
198 $attr->set_value($clone, $attr->get_value($self));
206 sub _process_options {
207 my ($class, $name, $options) = @_;
209 if (exists $options->{is}) {
210 if ($options->{is} eq 'ro') {
211 $options->{reader} ||= $name;
213 elsif ($options->{is} eq 'rw') {
214 $options->{accessor} = $name;
217 confess "I do not understand this option (is => " . $options->{is} . ") on attribute $name"
221 if (exists $options->{isa}) {
222 if (exists $options->{does}) {
223 if (eval { $options->{isa}->can('does') }) {
224 ($options->{isa}->does($options->{does}))
225 || confess "Cannot have an isa option and a does option if the isa does not do the does on attribute $name";
228 confess "Cannot have an isa option which cannot ->does() on attribute $name";
232 # allow for anon-subtypes here ...
233 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
234 $options->{type_constraint} = $options->{isa};
237 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options->{isa});
240 elsif (exists $options->{does}) {
241 # allow for anon-subtypes here ...
242 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
243 $options->{type_constraint} = $options->{does};
246 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options->{does});
250 if (exists $options->{coerce} && $options->{coerce}) {
251 (exists $options->{type_constraint})
252 || confess "You cannot have coercion without specifying a type constraint on attribute $name";
253 confess "You cannot have a weak reference to a coerced value on attribute $name"
254 if $options->{weak_ref};
257 if (exists $options->{trigger}) {
258 (reftype($options->{trigger}) || '') eq 'CODE'
259 || confess "Trigger must be a CODE ref";
262 if (exists $options->{auto_deref} && $options->{auto_deref}) {
263 (exists $options->{type_constraint})
264 || confess "You cannot auto-dereference without specifying a type constraint on attribute $name";
265 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
266 $options->{type_constraint}->is_a_type_of('HashRef'))
267 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute $name";
270 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
271 confess("You can not use lazy_build and default for the same attribute $name")
272 if exists $options->{default};
273 $options->{lazy} = 1;
274 $options->{required} = 1;
275 $options->{builder} ||= "_build_${name}";
277 $options->{clearer} ||= "_clear${name}";
278 $options->{predicate} ||= "_has${name}";
281 $options->{clearer} ||= "clear_${name}";
282 $options->{predicate} ||= "has_${name}";
286 if (exists $options->{lazy} && $options->{lazy}) {
287 (exists $options->{default} || defined $options->{builder} )
288 || confess "You cannot have lazy attribute ($name) without specifying a default value for it";
291 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
292 confess "You cannot have a required attribute ($name) without a default, builder, or an init_arg";
297 sub initialize_instance_slot {
298 my ($self, $meta_instance, $instance, $params) = @_;
299 my $init_arg = $self->init_arg();
300 # try to fetch the init arg from the %params ...
304 if ( defined($init_arg) and exists $params->{$init_arg}) {
305 $val = $params->{$init_arg};
309 # skip it if it's lazy
310 return if $self->is_lazy;
311 # and die if it's required and doesn't have a default value
312 confess "Attribute (" . $self->name . ") is required"
313 if $self->is_required && !$self->has_default && !$self->has_builder;
315 # if nothing was in the %params, we can use the
316 # attribute's default value (if it has one)
317 if ($self->has_default) {
318 $val = $self->default($instance);
321 elsif ($self->has_builder) {
322 if (my $builder = $instance->can($self->builder)){
323 $val = $instance->$builder;
327 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
332 return unless $value_is_set;
334 if ($self->has_type_constraint) {
335 my $type_constraint = $self->type_constraint;
336 if ($self->should_coerce && $type_constraint->has_coercion) {
337 $val = $type_constraint->coerce($val);
339 $type_constraint->check($val)
340 || confess "Attribute ("
342 . ") does not pass the type constraint because: "
343 . $type_constraint->get_message($val);
346 $self->set_initial_value($instance, $val);
347 $meta_instance->weaken_slot_value($instance, $self->name)
348 if ref $val && $self->is_weak_ref;
354 # this duplicates too much code from
355 # Class::MOP::Attribute, we need to
356 # refactor these bits eventually.
358 sub _set_initial_slot_value {
359 my ($self, $meta_instance, $instance, $value) = @_;
361 my $slot_name = $self->name;
363 return $meta_instance->set_slot_value($instance, $slot_name, $value)
364 unless $self->has_initializer;
366 my ($type_constraint, $can_coerce);
367 if ($self->has_type_constraint) {
368 $type_constraint = $self->type_constraint;
369 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
374 if ($type_constraint) {
375 $val = $type_constraint->coerce($val)
377 $type_constraint->check($val)
378 || confess "Attribute ("
380 . ") does not pass the type constraint because: "
381 . $type_constraint->get_message($val);
383 $meta_instance->set_slot_value($instance, $slot_name, $val);
386 my $initializer = $self->initializer;
388 # most things will just want to set a value, so make it first arg
389 $instance->$initializer($value, $callback, $self);
393 my ($self, $instance, @args) = @_;
394 my $value = $args[0];
396 my $attr_name = $self->name;
398 if ($self->is_required and not @args) {
399 confess "Attribute ($attr_name) is required";
402 if ($self->has_type_constraint) {
404 my $type_constraint = $self->type_constraint;
406 if ($self->should_coerce) {
407 $value = $type_constraint->coerce($value);
409 $type_constraint->_compiled_type_constraint->($value)
410 || confess "Attribute ("
412 . ") does not pass the type constraint because "
413 . $type_constraint->get_message($value);
416 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
419 $meta_instance->set_slot_value($instance, $attr_name, $value);
421 if (ref $value && $self->is_weak_ref) {
422 $meta_instance->weaken_slot_value($instance, $attr_name);
425 if ($self->has_trigger) {
426 $self->trigger->($instance, $value, $self);
431 my ($self, $instance) = @_;
433 if ($self->is_lazy) {
434 unless ($self->has_value($instance)) {
435 if ($self->has_default) {
436 my $default = $self->default($instance);
437 $self->set_initial_value($instance, $default);
439 if ( $self->has_builder ){
440 if (my $builder = $instance->can($self->builder)){
441 $self->set_initial_value($instance, $instance->$builder);
444 confess(blessed($instance)
445 . " does not support builder method '"
447 . "' for attribute '"
453 $self->set_initial_value($instance, undef);
458 if ($self->should_auto_deref) {
460 my $type_constraint = $self->type_constraint;
462 if ($type_constraint->is_a_type_of('ArrayRef')) {
463 my $rv = $self->SUPER::get_value($instance);
464 return unless defined $rv;
465 return wantarray ? @{ $rv } : $rv;
467 elsif ($type_constraint->is_a_type_of('HashRef')) {
468 my $rv = $self->SUPER::get_value($instance);
469 return unless defined $rv;
470 return wantarray ? %{ $rv } : $rv;
473 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
479 return $self->SUPER::get_value($instance);
483 ## installing accessors
485 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
487 sub install_accessors {
489 $self->SUPER::install_accessors(@_);
491 if ($self->has_handles) {
494 # Here we canonicalize the 'handles' option
495 # this will sort out any details and always
496 # return an hash of methods which we want
497 # to delagate to, see that method for details
498 my %handles = $self->_canonicalize_handles();
500 # find the accessor method for this attribute
501 my $accessor = $self->get_read_method_ref;
502 # then unpack it if we need too ...
503 $accessor = $accessor->body if blessed $accessor;
505 # install the delegation ...
506 my $associated_class = $self->associated_class;
507 foreach my $handle (keys %handles) {
508 my $method_to_call = $handles{$handle};
509 my $class_name = $associated_class->name;
510 my $name = "${class_name}::${handle}";
512 (!$associated_class->has_method($handle))
513 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
516 # handles is not allowed to delegate
517 # any of these methods, as they will
518 # override the ones in your class, which
519 # is almost certainly not what you want.
521 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
522 #cluck("Not delegating method '$handle' because it is a core method") and
523 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
525 if ((reftype($method_to_call) || '') eq 'CODE') {
526 $associated_class->add_method($handle => Class::MOP::subname($name, $method_to_call));
530 # we used to do a goto here, but the
531 # goto didn't handle failure correctly
532 # (it just returned nothing), so I took
533 # that out. However, the more I thought
534 # about it, the less I liked it doing
535 # the goto, and I prefered the act of
536 # delegation being actually represented
537 # in the stack trace.
539 $associated_class->add_method($handle => Class::MOP::subname($name, sub {
540 my $proxy = (shift)->$accessor();
542 || confess "Cannot delegate $handle to $method_to_call because " .
543 "the value of " . $self->name . " is not defined";
544 $proxy->$method_to_call(@_);
553 # private methods to help delegation ...
555 sub _canonicalize_handles {
557 my $handles = $self->handles;
558 if (my $handle_type = ref($handles)) {
559 if ($handle_type eq 'HASH') {
562 elsif ($handle_type eq 'ARRAY') {
563 return map { $_ => $_ } @{$handles};
565 elsif ($handle_type eq 'Regexp') {
566 ($self->has_type_constraint)
567 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
568 return map { ($_ => $_) }
569 grep { /$handles/ } $self->_get_delegate_method_list;
571 elsif ($handle_type eq 'CODE') {
572 return $handles->($self, $self->_find_delegate_metaclass);
575 confess "Unable to canonicalize the 'handles' option with $handles";
579 my $role_meta = eval { $handles->meta };
581 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
584 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
585 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
587 return map { $_ => $_ } (
588 $role_meta->get_method_list,
589 $role_meta->get_required_method_list
594 sub _find_delegate_metaclass {
596 if (my $class = $self->_isa_metadata) {
597 # if the class does have
598 # a meta method, use it
599 return $class->meta if $class->can('meta');
600 # otherwise we might be
601 # dealing with a non-Moose
602 # class, and need to make
604 return Moose::Meta::Class->initialize($class);
606 elsif (my $role = $self->_does_metadata) {
607 # our role will always have
612 confess "Cannot find delegate metaclass for attribute " . $self->name;
616 sub _get_delegate_method_list {
618 my $meta = $self->_find_delegate_metaclass;
619 if ($meta->isa('Class::MOP::Class')) {
620 return map { $_->{name} } # NOTE: !never! delegate &meta
621 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
622 $meta->compute_all_applicable_methods;
624 elsif ($meta->isa('Moose::Meta::Role')) {
625 return $meta->get_method_list;
628 confess "Unable to recognize the delegate metaclass '$meta'";
640 Moose::Meta::Attribute - The Moose attribute metaclass
644 This is a subclass of L<Class::MOP::Attribute> with Moose specific
647 For the most part, the only time you will ever encounter an
648 instance of this class is if you are doing some serious deep
649 introspection. To really understand this class, you need to refer
650 to the L<Class::MOP::Attribute> documentation.
654 =head2 Overridden methods
656 These methods override methods in L<Class::MOP::Attribute> and add
657 Moose specific features. You can safely assume though that they
658 will behave just as L<Class::MOP::Attribute> does.
668 =item B<initialize_instance_slot>
670 =item B<install_accessors>
672 =item B<accessor_metaclass>
678 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
683 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
685 Before setting the value, a check is made on the type constraint of
686 the attribute, if it has one, to see if the value passes it. If the
687 value fails to pass, the set operation dies with a L<Carp/confess>.
689 Any coercion to convert values is done before checking the type constraint.
691 To check a value against a type constraint before setting it, fetch the
692 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
693 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
694 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
699 =head2 Additional Moose features
701 Moose attributes support type-constraint checking, weak reference
702 creation and type coercion.
706 =item B<interpolate_class_and_new>
708 =item B<interpolate_class>
710 When called as a class method causes interpretation of the C<metaclass> and
713 =item B<clone_and_inherit_options>
715 This is to support the C<has '+foo'> feature, it clones an attribute
716 from a superclass and allows a very specific set of changes to be made
719 =item B<has_type_constraint>
721 Returns true if this meta-attribute has a type constraint.
723 =item B<type_constraint>
725 A read-only accessor for this meta-attribute's type constraint. For
726 more information on what you can do with this, see the documentation
727 for L<Moose::Meta::TypeConstraint>.
731 Returns true if this meta-attribute performs delegation.
735 This returns the value which was passed into the handles option.
739 Returns true if this meta-attribute produces a weak reference.
743 Returns true if this meta-attribute is required to have a value.
747 Returns true if this meta-attribute should be initialized lazily.
749 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
751 =item B<is_lazy_build>
753 Returns true if this meta-attribute should be initialized lazily through
754 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
755 make your attribute required and lazy. In addition it will set the builder, clearer
756 and predicate options for you using the following convention.
758 #If your attribute name starts with an underscore:
759 has '_foo' => (lazy_build => 1);
761 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
763 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
765 #If your attribute name does not start with an underscore:
766 has 'foo' => (lazy_build => 1);
768 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
770 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
772 The reason for the different naming of the C<builder> is that the C<builder>
773 method is a private method while the C<clearer> and C<predicate> methods
776 NOTE: This means your class should provide a method whose name matches the value
777 of the builder part, in this case _build__foo or _build_foo.
779 =item B<should_coerce>
781 Returns true if this meta-attribute should perform type coercion.
783 =item B<should_auto_deref>
785 Returns true if this meta-attribute should perform automatic
788 NOTE: This can only be done for attributes whose type constraint is
789 either I<ArrayRef> or I<HashRef>.
793 Returns true if this meta-attribute has a trigger set.
797 This is a CODE reference which will be executed every time the
798 value of an attribute is assigned. The CODE ref will get two values,
799 the invocant and the new value. This can be used to handle I<basic>
800 bi-directional relations.
802 =item B<documentation>
804 This is a string which contains the documentation for this attribute.
805 It serves no direct purpose right now, but it might in the future
806 in some kind of automated documentation system perhaps.
808 =item B<has_documentation>
810 Returns true if this meta-attribute has any documentation.
812 =item B<applied_traits>
814 This will return the ARRAY ref of all the traits applied to this
815 attribute, or if no traits have been applied, it returns C<undef>.
817 =item B<has_applied_traits>
819 Returns true if this meta-attribute has any traits applied.
825 All complex software has bugs lurking in it, and this module is no
826 exception. If you find a bug please either email me, or add the bug
831 Stevan Little E<lt>stevan@iinteractive.comE<gt>
833 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
835 =head1 COPYRIGHT AND LICENSE
837 Copyright 2006-2008 by Infinity Interactive, Inc.
839 L<http://www.iinteractive.com>
841 This library is free software; you can redistribute it and/or modify
842 it under the same terms as Perl itself.