2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken';
11 our $VERSION = '0.26';
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 $options->{is}) {
213 is => ro, writer => _foo # turns into (reader => foo, writer => _foo) as before
214 is => rw, writer => _foo # turns into (reader => foo, writer => _foo)
215 is => rw, accessor => _foo # turns into (accessor => _foo)
216 is => ro, accessor => _foo # error, accesor is rw
220 if ($options->{is} eq 'ro') {
221 confess "Cannot define an accessor name on a read-only attribute, accessors are read/write"
222 if exists $options->{accessor};
223 $options->{reader} ||= $name;
225 elsif ($options->{is} eq 'rw') {
226 if ($options->{writer}) {
227 $options->{reader} ||= $name;
230 $options->{accessor} ||= $name;
234 confess "I do not understand this option (is => " . $options->{is} . ") on attribute $name"
238 if (exists $options->{isa}) {
239 if (exists $options->{does}) {
240 if (eval { $options->{isa}->can('does') }) {
241 ($options->{isa}->does($options->{does}))
242 || confess "Cannot have an isa option and a does option if the isa does not do the does on attribute $name";
245 confess "Cannot have an isa option which cannot ->does() on attribute $name";
249 # allow for anon-subtypes here ...
250 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
251 $options->{type_constraint} = $options->{isa};
254 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options->{isa});
257 elsif (exists $options->{does}) {
258 # allow for anon-subtypes here ...
259 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
260 $options->{type_constraint} = $options->{does};
263 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options->{does});
267 if (exists $options->{coerce} && $options->{coerce}) {
268 (exists $options->{type_constraint})
269 || confess "You cannot have coercion without specifying a type constraint on attribute $name";
270 confess "You cannot have a weak reference to a coerced value on attribute $name"
271 if $options->{weak_ref};
274 if (exists $options->{trigger}) {
275 ('CODE' eq ref $options->{trigger})
276 || confess "Trigger must be a CODE ref";
279 if (exists $options->{auto_deref} && $options->{auto_deref}) {
280 (exists $options->{type_constraint})
281 || confess "You cannot auto-dereference without specifying a type constraint on attribute $name";
282 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
283 $options->{type_constraint}->is_a_type_of('HashRef'))
284 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute $name";
287 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
288 confess("You can not use lazy_build and default for the same attribute $name")
289 if exists $options->{default};
290 $options->{lazy} = 1;
291 $options->{required} = 1;
292 $options->{builder} ||= "_build_${name}";
294 $options->{clearer} ||= "_clear${name}";
295 $options->{predicate} ||= "_has${name}";
298 $options->{clearer} ||= "clear_${name}";
299 $options->{predicate} ||= "has_${name}";
303 if (exists $options->{lazy} && $options->{lazy}) {
304 (exists $options->{default} || defined $options->{builder} )
305 || confess "You cannot have lazy attribute ($name) without specifying a default value for it";
308 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
309 confess "You cannot have a required attribute ($name) without a default, builder, or an init_arg";
314 sub initialize_instance_slot {
315 my ($self, $meta_instance, $instance, $params) = @_;
316 my $init_arg = $self->init_arg();
317 # try to fetch the init arg from the %params ...
321 if ( defined($init_arg) and exists $params->{$init_arg}) {
322 $val = $params->{$init_arg};
326 # skip it if it's lazy
327 return if $self->is_lazy;
328 # and die if it's required and doesn't have a default value
329 confess "Attribute (" . $self->name . ") is required"
330 if $self->is_required && !$self->has_default && !$self->has_builder;
332 # if nothing was in the %params, we can use the
333 # attribute's default value (if it has one)
334 if ($self->has_default) {
335 $val = $self->default($instance);
338 elsif ($self->has_builder) {
339 if (my $builder = $instance->can($self->builder)){
340 $val = $instance->$builder;
344 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
349 return unless $value_is_set;
351 if ($self->has_type_constraint) {
352 my $type_constraint = $self->type_constraint;
353 if ($self->should_coerce && $type_constraint->has_coercion) {
354 $val = $type_constraint->coerce($val);
356 $type_constraint->check($val)
357 || confess "Attribute ("
359 . ") does not pass the type constraint because: "
360 . $type_constraint->get_message($val);
363 $self->set_initial_value($instance, $val);
364 $meta_instance->weaken_slot_value($instance, $self->name)
365 if ref $val && $self->is_weak_ref;
371 # this duplicates too much code from
372 # Class::MOP::Attribute, we need to
373 # refactor these bits eventually.
375 sub _set_initial_slot_value {
376 my ($self, $meta_instance, $instance, $value) = @_;
378 my $slot_name = $self->name;
380 return $meta_instance->set_slot_value($instance, $slot_name, $value)
381 unless $self->has_initializer;
383 my ($type_constraint, $can_coerce);
384 if ($self->has_type_constraint) {
385 $type_constraint = $self->type_constraint;
386 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
391 if ($type_constraint) {
392 $val = $type_constraint->coerce($val)
394 $type_constraint->check($val)
395 || confess "Attribute ("
397 . ") does not pass the type constraint because: "
398 . $type_constraint->get_message($val);
400 $meta_instance->set_slot_value($instance, $slot_name, $val);
403 my $initializer = $self->initializer;
405 # most things will just want to set a value, so make it first arg
406 $instance->$initializer($value, $callback, $self);
410 my ($self, $instance, @args) = @_;
411 my $value = $args[0];
413 my $attr_name = $self->name;
415 if ($self->is_required and not @args) {
416 confess "Attribute ($attr_name) is required";
419 if ($self->has_type_constraint) {
421 my $type_constraint = $self->type_constraint;
423 if ($self->should_coerce) {
424 $value = $type_constraint->coerce($value);
426 $type_constraint->_compiled_type_constraint->($value)
427 || confess "Attribute ("
429 . ") does not pass the type constraint because "
430 . $type_constraint->get_message($value);
433 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
436 $meta_instance->set_slot_value($instance, $attr_name, $value);
438 if (ref $value && $self->is_weak_ref) {
439 $meta_instance->weaken_slot_value($instance, $attr_name);
442 if ($self->has_trigger) {
443 $self->trigger->($instance, $value, $self);
448 my ($self, $instance) = @_;
450 if ($self->is_lazy) {
451 unless ($self->has_value($instance)) {
452 if ($self->has_default) {
453 my $default = $self->default($instance);
454 $self->set_initial_value($instance, $default);
456 if ( $self->has_builder ){
457 if (my $builder = $instance->can($self->builder)){
458 $self->set_initial_value($instance, $instance->$builder);
461 confess(blessed($instance)
462 . " does not support builder method '"
464 . "' for attribute '"
470 $self->set_initial_value($instance, undef);
475 if ($self->should_auto_deref) {
477 my $type_constraint = $self->type_constraint;
479 if ($type_constraint->is_a_type_of('ArrayRef')) {
480 my $rv = $self->SUPER::get_value($instance);
481 return unless defined $rv;
482 return wantarray ? @{ $rv } : $rv;
484 elsif ($type_constraint->is_a_type_of('HashRef')) {
485 my $rv = $self->SUPER::get_value($instance);
486 return unless defined $rv;
487 return wantarray ? %{ $rv } : $rv;
490 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
496 return $self->SUPER::get_value($instance);
500 ## installing accessors
502 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
504 sub install_accessors {
506 $self->SUPER::install_accessors(@_);
508 if ($self->has_handles) {
511 # Here we canonicalize the 'handles' option
512 # this will sort out any details and always
513 # return an hash of methods which we want
514 # to delagate to, see that method for details
515 my %handles = $self->_canonicalize_handles();
517 # find the accessor method for this attribute
518 my $accessor = $self->get_read_method_ref;
519 # then unpack it if we need too ...
520 $accessor = $accessor->body if blessed $accessor;
522 # install the delegation ...
523 my $associated_class = $self->associated_class;
524 foreach my $handle (keys %handles) {
525 my $method_to_call = $handles{$handle};
526 my $class_name = $associated_class->name;
527 my $name = "${class_name}::${handle}";
529 (!$associated_class->has_method($handle))
530 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
533 # handles is not allowed to delegate
534 # any of these methods, as they will
535 # override the ones in your class, which
536 # is almost certainly not what you want.
538 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
539 #cluck("Not delegating method '$handle' because it is a core method") and
540 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
542 if ('CODE' eq ref($method_to_call)) {
543 $associated_class->add_method($handle => Class::MOP::subname($name, $method_to_call));
547 # we used to do a goto here, but the
548 # goto didn't handle failure correctly
549 # (it just returned nothing), so I took
550 # that out. However, the more I thought
551 # about it, the less I liked it doing
552 # the goto, and I prefered the act of
553 # delegation being actually represented
554 # in the stack trace.
556 $associated_class->add_method($handle => Class::MOP::subname($name, sub {
557 my $proxy = (shift)->$accessor();
559 || confess "Cannot delegate $handle to $method_to_call because " .
560 "the value of " . $self->name . " is not defined";
561 $proxy->$method_to_call(@_);
570 # private methods to help delegation ...
572 sub _canonicalize_handles {
574 my $handles = $self->handles;
575 if (my $handle_type = ref($handles)) {
576 if ($handle_type eq 'HASH') {
579 elsif ($handle_type eq 'ARRAY') {
580 return map { $_ => $_ } @{$handles};
582 elsif ($handle_type eq 'Regexp') {
583 ($self->has_type_constraint)
584 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
585 return map { ($_ => $_) }
586 grep { /$handles/ } $self->_get_delegate_method_list;
588 elsif ($handle_type eq 'CODE') {
589 return $handles->($self, $self->_find_delegate_metaclass);
592 confess "Unable to canonicalize the 'handles' option with $handles";
596 my $role_meta = eval { $handles->meta };
598 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
601 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
602 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
604 return map { $_ => $_ } (
605 $role_meta->get_method_list,
606 $role_meta->get_required_method_list
611 sub _find_delegate_metaclass {
613 if (my $class = $self->_isa_metadata) {
614 # if the class does have
615 # a meta method, use it
616 return $class->meta if $class->can('meta');
617 # otherwise we might be
618 # dealing with a non-Moose
619 # class, and need to make
621 return Moose::Meta::Class->initialize($class);
623 elsif (my $role = $self->_does_metadata) {
624 # our role will always have
629 confess "Cannot find delegate metaclass for attribute " . $self->name;
633 sub _get_delegate_method_list {
635 my $meta = $self->_find_delegate_metaclass;
636 if ($meta->isa('Class::MOP::Class')) {
637 return map { $_->{name} } # NOTE: !never! delegate &meta
638 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
639 $meta->compute_all_applicable_methods;
641 elsif ($meta->isa('Moose::Meta::Role')) {
642 return $meta->get_method_list;
645 confess "Unable to recognize the delegate metaclass '$meta'";
649 package Moose::Meta::Attribute::Custom::Moose;
650 sub register_implementation { 'Moose::Meta::Attribute' }
660 Moose::Meta::Attribute - The Moose attribute metaclass
664 This is a subclass of L<Class::MOP::Attribute> with Moose specific
667 For the most part, the only time you will ever encounter an
668 instance of this class is if you are doing some serious deep
669 introspection. To really understand this class, you need to refer
670 to the L<Class::MOP::Attribute> documentation.
674 =head2 Overridden methods
676 These methods override methods in L<Class::MOP::Attribute> and add
677 Moose specific features. You can safely assume though that they
678 will behave just as L<Class::MOP::Attribute> does.
688 =item B<initialize_instance_slot>
690 =item B<install_accessors>
692 =item B<accessor_metaclass>
698 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
703 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
705 Before setting the value, a check is made on the type constraint of
706 the attribute, if it has one, to see if the value passes it. If the
707 value fails to pass, the set operation dies with a L<Carp/confess>.
709 Any coercion to convert values is done before checking the type constraint.
711 To check a value against a type constraint before setting it, fetch the
712 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
713 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
714 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
719 =head2 Additional Moose features
721 Moose attributes support type-constraint checking, weak reference
722 creation and type coercion.
726 =item B<interpolate_class_and_new>
728 =item B<interpolate_class>
730 When called as a class method causes interpretation of the C<metaclass> and
733 =item B<clone_and_inherit_options>
735 This is to support the C<has '+foo'> feature, it clones an attribute
736 from a superclass and allows a very specific set of changes to be made
739 =item B<has_type_constraint>
741 Returns true if this meta-attribute has a type constraint.
743 =item B<type_constraint>
745 A read-only accessor for this meta-attribute's type constraint. For
746 more information on what you can do with this, see the documentation
747 for L<Moose::Meta::TypeConstraint>.
751 Returns true if this meta-attribute performs delegation.
755 This returns the value which was passed into the handles option.
759 Returns true if this meta-attribute produces a weak reference.
763 Returns true if this meta-attribute is required to have a value.
767 Returns true if this meta-attribute should be initialized lazily.
769 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
771 =item B<is_lazy_build>
773 Returns true if this meta-attribute should be initialized lazily through
774 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
775 make your attribute required and lazy. In addition it will set the builder, clearer
776 and predicate options for you using the following convention.
778 #If your attribute name starts with an underscore:
779 has '_foo' => (lazy_build => 1);
781 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
783 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
785 #If your attribute name does not start with an underscore:
786 has 'foo' => (lazy_build => 1);
788 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
790 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
792 The reason for the different naming of the C<builder> is that the C<builder>
793 method is a private method while the C<clearer> and C<predicate> methods
796 NOTE: This means your class should provide a method whose name matches the value
797 of the builder part, in this case _build__foo or _build_foo.
799 =item B<should_coerce>
801 Returns true if this meta-attribute should perform type coercion.
803 =item B<should_auto_deref>
805 Returns true if this meta-attribute should perform automatic
808 NOTE: This can only be done for attributes whose type constraint is
809 either I<ArrayRef> or I<HashRef>.
813 Returns true if this meta-attribute has a trigger set.
817 This is a CODE reference which will be executed every time the
818 value of an attribute is assigned. The CODE ref will get two values,
819 the invocant and the new value. This can be used to handle I<basic>
820 bi-directional relations.
822 =item B<documentation>
824 This is a string which contains the documentation for this attribute.
825 It serves no direct purpose right now, but it might in the future
826 in some kind of automated documentation system perhaps.
828 =item B<has_documentation>
830 Returns true if this meta-attribute has any documentation.
832 =item B<applied_traits>
834 This will return the ARRAY ref of all the traits applied to this
835 attribute, or if no traits have been applied, it returns C<undef>.
837 =item B<has_applied_traits>
839 Returns true if this meta-attribute has any traits applied.
845 All complex software has bugs lurking in it, and this module is no
846 exception. If you find a bug please either email me, or add the bug
851 Stevan Little E<lt>stevan@iinteractive.comE<gt>
853 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
855 =head1 COPYRIGHT AND LICENSE
857 Copyright 2006-2008 by Infinity Interactive, Inc.
859 L<http://www.iinteractive.com>
861 This library is free software; you can redistribute it and/or modify
862 it under the same terms as Perl itself.