2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken';
11 our $VERSION = '0.50';
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 $options->{is}) {
211 ### -------------------------
212 ## is => ro, writer => _foo # turns into (reader => foo, writer => _foo) as before
213 ## is => rw, writer => _foo # turns into (reader => foo, writer => _foo)
214 ## is => rw, accessor => _foo # turns into (accessor => _foo)
215 ## is => ro, accessor => _foo # error, accesor is rw
216 ### -------------------------
218 if ($options->{is} eq 'ro') {
219 confess "Cannot define an accessor name on a read-only attribute, accessors are read/write"
220 if exists $options->{accessor};
221 $options->{reader} ||= $name;
223 elsif ($options->{is} eq 'rw') {
224 if ($options->{writer}) {
225 $options->{reader} ||= $name;
228 $options->{accessor} ||= $name;
232 confess "I do not understand this option (is => " . $options->{is} . ") on attribute $name"
236 if (exists $options->{isa}) {
237 if (exists $options->{does}) {
238 if (eval { $options->{isa}->can('does') }) {
239 ($options->{isa}->does($options->{does}))
240 || confess "Cannot have an isa option and a does option if the isa does not do the does on attribute $name";
243 confess "Cannot have an isa option which cannot ->does() on attribute $name";
247 # allow for anon-subtypes here ...
248 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
249 $options->{type_constraint} = $options->{isa};
252 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options->{isa});
255 elsif (exists $options->{does}) {
256 # allow for anon-subtypes here ...
257 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
258 $options->{type_constraint} = $options->{does};
261 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options->{does});
265 if (exists $options->{coerce} && $options->{coerce}) {
266 (exists $options->{type_constraint})
267 || confess "You cannot have coercion without specifying a type constraint on attribute $name";
268 confess "You cannot have a weak reference to a coerced value on attribute $name"
269 if $options->{weak_ref};
272 if (exists $options->{trigger}) {
273 ('CODE' eq ref $options->{trigger})
274 || confess "Trigger must be a CODE ref";
277 if (exists $options->{auto_deref} && $options->{auto_deref}) {
278 (exists $options->{type_constraint})
279 || confess "You cannot auto-dereference without specifying a type constraint on attribute $name";
280 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
281 $options->{type_constraint}->is_a_type_of('HashRef'))
282 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute $name";
285 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
286 confess("You can not use lazy_build and default for the same attribute $name")
287 if exists $options->{default};
288 $options->{lazy} = 1;
289 $options->{required} = 1;
290 $options->{builder} ||= "_build_${name}";
292 $options->{clearer} ||= "_clear${name}";
293 $options->{predicate} ||= "_has${name}";
296 $options->{clearer} ||= "clear_${name}";
297 $options->{predicate} ||= "has_${name}";
301 if (exists $options->{lazy} && $options->{lazy}) {
302 (exists $options->{default} || defined $options->{builder} )
303 || confess "You cannot have lazy attribute ($name) without specifying a default value for it";
306 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
307 confess "You cannot have a required attribute ($name) without a default, builder, or an init_arg";
312 sub initialize_instance_slot {
313 my ($self, $meta_instance, $instance, $params) = @_;
314 my $init_arg = $self->init_arg();
315 # try to fetch the init arg from the %params ...
319 if ( defined($init_arg) and exists $params->{$init_arg}) {
320 $val = $params->{$init_arg};
324 # skip it if it's lazy
325 return if $self->is_lazy;
326 # and die if it's required and doesn't have a default value
327 confess "Attribute (" . $self->name . ") is required"
328 if $self->is_required && !$self->has_default && !$self->has_builder;
330 # if nothing was in the %params, we can use the
331 # attribute's default value (if it has one)
332 if ($self->has_default) {
333 $val = $self->default($instance);
336 elsif ($self->has_builder) {
337 if (my $builder = $instance->can($self->builder)){
338 $val = $instance->$builder;
342 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
347 return unless $value_is_set;
349 if ($self->has_type_constraint) {
350 my $type_constraint = $self->type_constraint;
351 if ($self->should_coerce && $type_constraint->has_coercion) {
352 $val = $type_constraint->coerce($val);
354 $type_constraint->check($val)
355 || confess "Attribute ("
357 . ") does not pass the type constraint because: "
358 . $type_constraint->get_message($val);
361 $self->set_initial_value($instance, $val);
362 $meta_instance->weaken_slot_value($instance, $self->name)
363 if ref $val && $self->is_weak_ref;
369 # this duplicates too much code from
370 # Class::MOP::Attribute, we need to
371 # refactor these bits eventually.
373 sub _set_initial_slot_value {
374 my ($self, $meta_instance, $instance, $value) = @_;
376 my $slot_name = $self->name;
378 return $meta_instance->set_slot_value($instance, $slot_name, $value)
379 unless $self->has_initializer;
381 my ($type_constraint, $can_coerce);
382 if ($self->has_type_constraint) {
383 $type_constraint = $self->type_constraint;
384 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
389 if ($type_constraint) {
390 $val = $type_constraint->coerce($val)
392 $type_constraint->check($val)
393 || confess "Attribute ("
395 . ") does not pass the type constraint because: "
396 . $type_constraint->get_message($val);
398 $meta_instance->set_slot_value($instance, $slot_name, $val);
401 my $initializer = $self->initializer;
403 # most things will just want to set a value, so make it first arg
404 $instance->$initializer($value, $callback, $self);
408 my ($self, $instance, @args) = @_;
409 my $value = $args[0];
411 my $attr_name = $self->name;
413 if ($self->is_required and not @args) {
414 confess "Attribute ($attr_name) is required";
417 if ($self->has_type_constraint) {
419 my $type_constraint = $self->type_constraint;
421 if ($self->should_coerce) {
422 $value = $type_constraint->coerce($value);
424 $type_constraint->_compiled_type_constraint->($value)
425 || confess "Attribute ("
427 . ") does not pass the type constraint because "
428 . $type_constraint->get_message($value);
431 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
434 $meta_instance->set_slot_value($instance, $attr_name, $value);
436 if (ref $value && $self->is_weak_ref) {
437 $meta_instance->weaken_slot_value($instance, $attr_name);
440 if ($self->has_trigger) {
441 $self->trigger->($instance, $value, $self);
446 my ($self, $instance) = @_;
448 if ($self->is_lazy) {
449 unless ($self->has_value($instance)) {
450 if ($self->has_default) {
451 my $default = $self->default($instance);
452 $self->set_initial_value($instance, $default);
453 } elsif ( $self->has_builder ) {
454 if (my $builder = $instance->can($self->builder)){
455 $self->set_initial_value($instance, $instance->$builder);
458 confess(blessed($instance)
459 . " does not support builder method '"
461 . "' for attribute '"
467 $self->set_initial_value($instance, undef);
472 if ($self->should_auto_deref) {
474 my $type_constraint = $self->type_constraint;
476 if ($type_constraint->is_a_type_of('ArrayRef')) {
477 my $rv = $self->SUPER::get_value($instance);
478 return unless defined $rv;
479 return wantarray ? @{ $rv } : $rv;
481 elsif ($type_constraint->is_a_type_of('HashRef')) {
482 my $rv = $self->SUPER::get_value($instance);
483 return unless defined $rv;
484 return wantarray ? %{ $rv } : $rv;
487 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
493 return $self->SUPER::get_value($instance);
497 ## installing accessors
499 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
501 sub install_accessors {
503 $self->SUPER::install_accessors(@_);
505 if ($self->has_handles) {
508 # Here we canonicalize the 'handles' option
509 # this will sort out any details and always
510 # return an hash of methods which we want
511 # to delagate to, see that method for details
512 my %handles = $self->_canonicalize_handles();
514 # find the accessor method for this attribute
515 my $accessor = $self->get_read_method_ref;
516 # then unpack it if we need too ...
517 $accessor = $accessor->body if blessed $accessor;
519 # install the delegation ...
520 my $associated_class = $self->associated_class;
521 foreach my $handle (keys %handles) {
522 my $method_to_call = $handles{$handle};
523 my $class_name = $associated_class->name;
524 my $name = "${class_name}::${handle}";
526 (!$associated_class->has_method($handle))
527 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
530 # handles is not allowed to delegate
531 # any of these methods, as they will
532 # override the ones in your class, which
533 # is almost certainly not what you want.
535 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
536 #cluck("Not delegating method '$handle' because it is a core method") and
537 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
539 if ('CODE' eq ref($method_to_call)) {
540 $associated_class->add_method($handle => Class::MOP::subname($name, $method_to_call));
544 # we used to do a goto here, but the
545 # goto didn't handle failure correctly
546 # (it just returned nothing), so I took
547 # that out. However, the more I thought
548 # about it, the less I liked it doing
549 # the goto, and I prefered the act of
550 # delegation being actually represented
551 # in the stack trace.
553 $associated_class->add_method($handle => Class::MOP::subname($name, sub {
554 my $proxy = (shift)->$accessor();
556 || confess "Cannot delegate $handle to $method_to_call because " .
557 "the value of " . $self->name . " is not defined";
558 $proxy->$method_to_call(@_);
567 # private methods to help delegation ...
569 sub _canonicalize_handles {
571 my $handles = $self->handles;
572 if (my $handle_type = ref($handles)) {
573 if ($handle_type eq 'HASH') {
576 elsif ($handle_type eq 'ARRAY') {
577 return map { $_ => $_ } @{$handles};
579 elsif ($handle_type eq 'Regexp') {
580 ($self->has_type_constraint)
581 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
582 return map { ($_ => $_) }
583 grep { /$handles/ } $self->_get_delegate_method_list;
585 elsif ($handle_type eq 'CODE') {
586 return $handles->($self, $self->_find_delegate_metaclass);
589 confess "Unable to canonicalize the 'handles' option with $handles";
593 my $role_meta = eval { $handles->meta };
595 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
598 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
599 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
601 return map { $_ => $_ } (
602 $role_meta->get_method_list,
603 $role_meta->get_required_method_list
608 sub _find_delegate_metaclass {
610 if (my $class = $self->_isa_metadata) {
611 # if the class does have
612 # a meta method, use it
613 return $class->meta if $class->can('meta');
614 # otherwise we might be
615 # dealing with a non-Moose
616 # class, and need to make
618 return Moose::Meta::Class->initialize($class);
620 elsif (my $role = $self->_does_metadata) {
621 # our role will always have
626 confess "Cannot find delegate metaclass for attribute " . $self->name;
630 sub _get_delegate_method_list {
632 my $meta = $self->_find_delegate_metaclass;
633 if ($meta->isa('Class::MOP::Class')) {
634 return map { $_->{name} } # NOTE: !never! delegate &meta
635 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
636 $meta->compute_all_applicable_methods;
638 elsif ($meta->isa('Moose::Meta::Role')) {
639 return $meta->get_method_list;
642 confess "Unable to recognize the delegate metaclass '$meta'";
646 package Moose::Meta::Attribute::Custom::Moose;
647 sub register_implementation { 'Moose::Meta::Attribute' }
657 Moose::Meta::Attribute - The Moose attribute metaclass
661 This is a subclass of L<Class::MOP::Attribute> with Moose specific
664 For the most part, the only time you will ever encounter an
665 instance of this class is if you are doing some serious deep
666 introspection. To really understand this class, you need to refer
667 to the L<Class::MOP::Attribute> documentation.
671 =head2 Overridden methods
673 These methods override methods in L<Class::MOP::Attribute> and add
674 Moose specific features. You can safely assume though that they
675 will behave just as L<Class::MOP::Attribute> does.
685 =item B<initialize_instance_slot>
687 =item B<install_accessors>
689 =item B<accessor_metaclass>
695 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
700 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
702 Before setting the value, a check is made on the type constraint of
703 the attribute, if it has one, to see if the value passes it. If the
704 value fails to pass, the set operation dies with a L<Carp/confess>.
706 Any coercion to convert values is done before checking the type constraint.
708 To check a value against a type constraint before setting it, fetch the
709 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
710 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
711 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
716 =head2 Additional Moose features
718 Moose attributes support type-constraint checking, weak reference
719 creation and type coercion.
723 =item B<interpolate_class_and_new>
725 =item B<interpolate_class>
727 When called as a class method causes interpretation of the C<metaclass> and
730 =item B<clone_and_inherit_options>
732 This is to support the C<has '+foo'> feature, it clones an attribute
733 from a superclass and allows a very specific set of changes to be made
736 =item B<has_type_constraint>
738 Returns true if this meta-attribute has a type constraint.
740 =item B<type_constraint>
742 A read-only accessor for this meta-attribute's type constraint. For
743 more information on what you can do with this, see the documentation
744 for L<Moose::Meta::TypeConstraint>.
748 Returns true if this meta-attribute performs delegation.
752 This returns the value which was passed into the handles option.
756 Returns true if this meta-attribute produces a weak reference.
760 Returns true if this meta-attribute is required to have a value.
764 Returns true if this meta-attribute should be initialized lazily.
766 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
768 =item B<is_lazy_build>
770 Returns true if this meta-attribute should be initialized lazily through
771 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
772 make your attribute required and lazy. In addition it will set the builder, clearer
773 and predicate options for you using the following convention.
775 #If your attribute name starts with an underscore:
776 has '_foo' => (lazy_build => 1);
778 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
780 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
782 #If your attribute name does not start with an underscore:
783 has 'foo' => (lazy_build => 1);
785 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
787 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
789 The reason for the different naming of the C<builder> is that the C<builder>
790 method is a private method while the C<clearer> and C<predicate> methods
793 NOTE: This means your class should provide a method whose name matches the value
794 of the builder part, in this case _build__foo or _build_foo.
796 =item B<should_coerce>
798 Returns true if this meta-attribute should perform type coercion.
800 =item B<should_auto_deref>
802 Returns true if this meta-attribute should perform automatic
805 NOTE: This can only be done for attributes whose type constraint is
806 either I<ArrayRef> or I<HashRef>.
810 Returns true if this meta-attribute has a trigger set.
814 This is a CODE reference which will be executed every time the
815 value of an attribute is assigned. The CODE ref will get two values,
816 the invocant and the new value. This can be used to handle I<basic>
817 bi-directional relations.
819 =item B<documentation>
821 This is a string which contains the documentation for this attribute.
822 It serves no direct purpose right now, but it might in the future
823 in some kind of automated documentation system perhaps.
825 =item B<has_documentation>
827 Returns true if this meta-attribute has any documentation.
829 =item B<applied_traits>
831 This will return the ARRAY ref of all the traits applied to this
832 attribute, or if no traits have been applied, it returns C<undef>.
834 =item B<has_applied_traits>
836 Returns true if this meta-attribute has any traits applied.
842 All complex software has bugs lurking in it, and this module is no
843 exception. If you find a bug please either email me, or add the bug
848 Stevan Little E<lt>stevan@iinteractive.comE<gt>
850 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
852 =head1 COPYRIGHT AND LICENSE
854 Copyright 2006-2008 by Infinity Interactive, Inc.
856 L<http://www.iinteractive.com>
858 This library is free software; you can redistribute it and/or modify
859 it under the same terms as Perl itself.