2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken';
11 our $VERSION = '0.53';
12 our $AUTHORITY = 'cpan:STEVAN';
14 use Moose::Meta::Method::Accessor;
16 use Moose::Util::TypeConstraints ();
18 use base 'Class::MOP::Attribute';
20 # options which are not directly used
21 # but we store them for metadata purposes
22 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
23 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
24 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
26 # these are actual options for the attrs
27 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
28 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
29 __PACKAGE__->meta->add_attribute('lazy_build' => (reader => 'is_lazy_build' ));
30 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
31 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
32 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
33 __PACKAGE__->meta->add_attribute('type_constraint' => (
34 reader => 'type_constraint',
35 predicate => 'has_type_constraint',
37 __PACKAGE__->meta->add_attribute('trigger' => (
39 predicate => 'has_trigger',
41 __PACKAGE__->meta->add_attribute('handles' => (
43 predicate => 'has_handles',
45 __PACKAGE__->meta->add_attribute('documentation' => (
46 reader => 'documentation',
47 predicate => 'has_documentation',
49 __PACKAGE__->meta->add_attribute('traits' => (
50 reader => 'applied_traits',
51 predicate => 'has_applied_traits',
54 # we need to have a ->does method in here to
55 # more easily support traits, and the introspection
56 # of those traits. We extend the does check to look
57 # for metatrait aliases.
59 my ($self, $role_name) = @_;
61 Moose::Util::resolve_metatrait_alias(Attribute => $role_name)
63 return 0 if !defined($name); # failed to load class
64 return Moose::Object::does($self, $name);
68 my ($class, $name, %options) = @_;
69 $class->_process_options($name, \%options) unless $options{__hack_no_process_options}; # used from clone()... YECHKKK FIXME ICKY YUCK GROSS
70 return $class->SUPER::new($name, %options);
73 sub interpolate_class_and_new {
74 my ($class, $name, @args) = @_;
76 my ( $new_class, @traits ) = $class->interpolate_class(@args);
78 $new_class->new($name, @args, ( scalar(@traits) ? ( traits => \@traits ) : () ) );
81 sub interpolate_class {
82 my ($class, %options) = @_;
84 $class = ref($class) || $class;
86 if ( my $metaclass_name = delete $options{metaclass} ) {
87 my $new_class = Moose::Util::resolve_metaclass_alias( Attribute => $metaclass_name );
89 if ( $class ne $new_class ) {
90 if ( $new_class->can("interpolate_class") ) {
91 return $new_class->interpolate_class(%options);
100 if (my $traits = $options{traits}) {
101 if ( @traits = grep { not $class->does($_) } map {
102 Moose::Util::resolve_metatrait_alias( Attribute => $_ )
106 my $anon_class = Moose::Meta::Class->create_anon_class(
107 superclasses => [ $class ],
108 roles => [ @traits ],
112 $class = $anon_class->name;
116 return ( wantarray ? ( $class, @traits ) : $class );
119 # you can change default, required, coerce, documentation, lazy, handles, builder, type_constraint (explicitly or using isa/does), metaclass and traits
120 sub legal_options_for_inheritance {
121 return qw(default coerce required documentation lazy handles builder
125 sub clone_and_inherit_options {
126 my ($self, %options) = @_;
129 foreach my $legal_option ($self->legal_options_for_inheritance) {
130 if (exists $options{$legal_option}) {
131 $actual_options{$legal_option} = $options{$legal_option};
132 delete $options{$legal_option};
138 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
139 $type_constraint = $options{isa};
142 $type_constraint = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options{isa});
143 (defined $type_constraint)
144 || confess "Could not find the type constraint '" . $options{isa} . "'";
147 $actual_options{type_constraint} = $type_constraint;
148 delete $options{isa};
151 if ($options{does}) {
153 if (blessed($options{does}) && $options{does}->isa('Moose::Meta::TypeConstraint')) {
154 $type_constraint = $options{does};
157 $type_constraint = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options{does});
158 (defined $type_constraint)
159 || confess "Could not find the type constraint '" . $options{does} . "'";
162 $actual_options{type_constraint} = $type_constraint;
163 delete $options{does};
167 # this doesn't apply to Class::MOP::Attributes,
168 # so we can ignore it for them.
170 if ($self->can('interpolate_class')) {
171 ( $actual_options{metaclass}, my @traits ) = $self->interpolate_class(%options);
174 my @all_traits = grep { $seen{$_}++ } @{ $self->applied_traits || [] }, @traits;
175 $actual_options{traits} = \@all_traits if @all_traits;
177 delete @options{qw(metaclass traits)};
180 (scalar keys %options == 0)
181 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
184 $self->clone(%actual_options);
188 my ( $self, %params ) = @_;
190 my $class = $params{metaclass} || ref $self;
192 if ( 0 and $class eq ref $self ) {
193 return $self->SUPER::clone(%params);
195 my ( @init, @non_init );
197 foreach my $attr ( grep { $_->has_value($self) } $self->meta->compute_all_applicable_attributes ) {
198 push @{ $attr->has_init_arg ? \@init : \@non_init }, $attr;
201 my %new_params = ( ( map { $_->init_arg => $_->get_value($self) } @init ), %params );
203 my $name = delete $new_params{name};
205 my $clone = $class->new($name, %new_params, __hack_no_process_options => 1 );
207 foreach my $attr ( @non_init ) {
208 $attr->set_value($clone, $attr->get_value($self));
216 sub _process_options {
217 my ($class, $name, $options) = @_;
219 if (exists $options->{is}) {
221 ### -------------------------
222 ## is => ro, writer => _foo # turns into (reader => foo, writer => _foo) as before
223 ## is => rw, writer => _foo # turns into (reader => foo, writer => _foo)
224 ## is => rw, accessor => _foo # turns into (accessor => _foo)
225 ## is => ro, accessor => _foo # error, accesor is rw
226 ### -------------------------
228 if ($options->{is} eq 'ro') {
229 confess "Cannot define an accessor name on a read-only attribute, accessors are read/write"
230 if exists $options->{accessor};
231 $options->{reader} ||= $name;
233 elsif ($options->{is} eq 'rw') {
234 if ($options->{writer}) {
235 $options->{reader} ||= $name;
238 $options->{accessor} ||= $name;
242 confess "I do not understand this option (is => " . $options->{is} . ") on attribute ($name)"
246 if (exists $options->{isa}) {
247 if (exists $options->{does}) {
248 if (eval { $options->{isa}->can('does') }) {
249 ($options->{isa}->does($options->{does}))
250 || confess "Cannot have an isa option and a does option if the isa does not do the does on attribute ($name)";
253 confess "Cannot have an isa option which cannot ->does() on attribute ($name)";
257 # allow for anon-subtypes here ...
258 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
259 $options->{type_constraint} = $options->{isa};
262 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options->{isa});
265 elsif (exists $options->{does}) {
266 # allow for anon-subtypes here ...
267 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
268 $options->{type_constraint} = $options->{does};
271 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options->{does});
275 if (exists $options->{coerce} && $options->{coerce}) {
276 (exists $options->{type_constraint})
277 || confess "You cannot have coercion without specifying a type constraint on attribute ($name)";
278 confess "You cannot have a weak reference to a coerced value on attribute ($name)"
279 if $options->{weak_ref};
282 if (exists $options->{trigger}) {
283 ('CODE' eq ref $options->{trigger})
284 || confess "Trigger must be a CODE ref on attribute ($name)";
287 if (exists $options->{auto_deref} && $options->{auto_deref}) {
288 (exists $options->{type_constraint})
289 || confess "You cannot auto-dereference without specifying a type constraint on attribute ($name)";
290 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
291 $options->{type_constraint}->is_a_type_of('HashRef'))
292 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute ($name)";
295 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
296 confess("You can not use lazy_build and default for the same attribute ($name)")
297 if exists $options->{default};
298 $options->{lazy} = 1;
299 $options->{required} = 1;
300 $options->{builder} ||= "_build_${name}";
302 $options->{clearer} ||= "_clear${name}";
303 $options->{predicate} ||= "_has${name}";
306 $options->{clearer} ||= "clear_${name}";
307 $options->{predicate} ||= "has_${name}";
311 if (exists $options->{lazy} && $options->{lazy}) {
312 (exists $options->{default} || defined $options->{builder} )
313 || confess "You cannot have lazy attribute ($name) without specifying a default value for it";
316 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
317 confess "You cannot have a required attribute ($name) without a default, builder, or an init_arg";
322 sub initialize_instance_slot {
323 my ($self, $meta_instance, $instance, $params) = @_;
324 my $init_arg = $self->init_arg();
325 # try to fetch the init arg from the %params ...
329 if ( defined($init_arg) and exists $params->{$init_arg}) {
330 $val = $params->{$init_arg};
334 # skip it if it's lazy
335 return if $self->is_lazy;
336 # and die if it's required and doesn't have a default value
337 confess "Attribute (" . $self->name . ") is required"
338 if $self->is_required && !$self->has_default && !$self->has_builder;
340 # if nothing was in the %params, we can use the
341 # attribute's default value (if it has one)
342 if ($self->has_default) {
343 $val = $self->default($instance);
346 elsif ($self->has_builder) {
347 if (my $builder = $instance->can($self->builder)){
348 $val = $instance->$builder;
352 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
357 return unless $value_is_set;
359 if ($self->has_type_constraint) {
360 my $type_constraint = $self->type_constraint;
361 if ($self->should_coerce && $type_constraint->has_coercion) {
362 $val = $type_constraint->coerce($val);
364 $type_constraint->check($val)
365 || confess "Attribute ("
367 . ") does not pass the type constraint because: "
368 . $type_constraint->get_message($val);
371 $self->set_initial_value($instance, $val);
372 $meta_instance->weaken_slot_value($instance, $self->name)
373 if ref $val && $self->is_weak_ref;
379 # this duplicates too much code from
380 # Class::MOP::Attribute, we need to
381 # refactor these bits eventually.
383 sub _set_initial_slot_value {
384 my ($self, $meta_instance, $instance, $value) = @_;
386 my $slot_name = $self->name;
388 return $meta_instance->set_slot_value($instance, $slot_name, $value)
389 unless $self->has_initializer;
391 my ($type_constraint, $can_coerce);
392 if ($self->has_type_constraint) {
393 $type_constraint = $self->type_constraint;
394 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
399 if ($type_constraint) {
400 $val = $type_constraint->coerce($val)
402 $type_constraint->check($val)
403 || confess "Attribute ("
405 . ") does not pass the type constraint because: "
406 . $type_constraint->get_message($val);
408 $meta_instance->set_slot_value($instance, $slot_name, $val);
411 my $initializer = $self->initializer;
413 # most things will just want to set a value, so make it first arg
414 $instance->$initializer($value, $callback, $self);
418 my ($self, $instance, @args) = @_;
419 my $value = $args[0];
421 my $attr_name = $self->name;
423 if ($self->is_required and not @args) {
424 confess "Attribute ($attr_name) is required";
427 if ($self->has_type_constraint) {
429 my $type_constraint = $self->type_constraint;
431 if ($self->should_coerce) {
432 $value = $type_constraint->coerce($value);
434 $type_constraint->_compiled_type_constraint->($value)
435 || confess "Attribute ("
437 . ") does not pass the type constraint because "
438 . $type_constraint->get_message($value);
441 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
444 $meta_instance->set_slot_value($instance, $attr_name, $value);
446 if (ref $value && $self->is_weak_ref) {
447 $meta_instance->weaken_slot_value($instance, $attr_name);
450 if ($self->has_trigger) {
451 $self->trigger->($instance, $value, $self);
456 my ($self, $instance) = @_;
458 if ($self->is_lazy) {
459 unless ($self->has_value($instance)) {
460 if ($self->has_default) {
461 my $default = $self->default($instance);
462 $self->set_initial_value($instance, $default);
463 } elsif ( $self->has_builder ) {
464 if (my $builder = $instance->can($self->builder)){
465 $self->set_initial_value($instance, $instance->$builder);
468 confess(blessed($instance)
469 . " does not support builder method '"
471 . "' for attribute '"
477 $self->set_initial_value($instance, undef);
482 if ($self->should_auto_deref) {
484 my $type_constraint = $self->type_constraint;
486 if ($type_constraint->is_a_type_of('ArrayRef')) {
487 my $rv = $self->SUPER::get_value($instance);
488 return unless defined $rv;
489 return wantarray ? @{ $rv } : $rv;
491 elsif ($type_constraint->is_a_type_of('HashRef')) {
492 my $rv = $self->SUPER::get_value($instance);
493 return unless defined $rv;
494 return wantarray ? %{ $rv } : $rv;
497 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
503 return $self->SUPER::get_value($instance);
507 ## installing accessors
509 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
511 sub install_accessors {
513 $self->SUPER::install_accessors(@_);
514 $self->install_delegation if $self->has_handles;
518 sub install_delegation {
522 # Here we canonicalize the 'handles' option
523 # this will sort out any details and always
524 # return an hash of methods which we want
525 # to delagate to, see that method for details
526 my %handles = $self->_canonicalize_handles();
528 # find the accessor method for this attribute
529 my $accessor = $self->get_read_method_ref;
530 # then unpack it if we need too ...
531 $accessor = $accessor->body if blessed $accessor;
533 # install the delegation ...
534 my $associated_class = $self->associated_class;
535 foreach my $handle (keys %handles) {
536 my $method_to_call = $handles{$handle};
537 my $class_name = $associated_class->name;
538 my $name = "${class_name}::${handle}";
540 (!$associated_class->has_method($handle))
541 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
544 # handles is not allowed to delegate
545 # any of these methods, as they will
546 # override the ones in your class, which
547 # is almost certainly not what you want.
549 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
550 #cluck("Not delegating method '$handle' because it is a core method") and
551 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
553 if ('CODE' eq ref($method_to_call)) {
554 $associated_class->add_method($handle => Class::MOP::subname($name, $method_to_call));
558 # we used to do a goto here, but the
559 # goto didn't handle failure correctly
560 # (it just returned nothing), so I took
561 # that out. However, the more I thought
562 # about it, the less I liked it doing
563 # the goto, and I prefered the act of
564 # delegation being actually represented
565 # in the stack trace.
567 $associated_class->add_method($handle => Class::MOP::subname($name, sub {
568 my $proxy = (shift)->$accessor();
570 || confess "Cannot delegate $handle to $method_to_call because " .
571 "the value of " . $self->name . " is not defined";
572 $proxy->$method_to_call(@_);
578 # private methods to help delegation ...
580 sub _canonicalize_handles {
582 my $handles = $self->handles;
583 if (my $handle_type = ref($handles)) {
584 if ($handle_type eq 'HASH') {
587 elsif ($handle_type eq 'ARRAY') {
588 return map { $_ => $_ } @{$handles};
590 elsif ($handle_type eq 'Regexp') {
591 ($self->has_type_constraint)
592 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
593 return map { ($_ => $_) }
594 grep { /$handles/ } $self->_get_delegate_method_list;
596 elsif ($handle_type eq 'CODE') {
597 return $handles->($self, $self->_find_delegate_metaclass);
600 confess "Unable to canonicalize the 'handles' option with $handles";
604 my $role_meta = eval { $handles->meta };
606 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
609 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
610 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
612 return map { $_ => $_ } (
613 $role_meta->get_method_list,
614 $role_meta->get_required_method_list
619 sub _find_delegate_metaclass {
621 if (my $class = $self->_isa_metadata) {
622 # if the class does have
623 # a meta method, use it
624 return $class->meta if $class->can('meta');
625 # otherwise we might be
626 # dealing with a non-Moose
627 # class, and need to make
629 return Moose::Meta::Class->initialize($class);
631 elsif (my $role = $self->_does_metadata) {
632 # our role will always have
637 confess "Cannot find delegate metaclass for attribute " . $self->name;
641 sub _get_delegate_method_list {
643 my $meta = $self->_find_delegate_metaclass;
644 if ($meta->isa('Class::MOP::Class')) {
645 return map { $_->{name} } # NOTE: !never! delegate &meta
646 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
647 $meta->compute_all_applicable_methods;
649 elsif ($meta->isa('Moose::Meta::Role')) {
650 return $meta->get_method_list;
653 confess "Unable to recognize the delegate metaclass '$meta'";
657 package Moose::Meta::Attribute::Custom::Moose;
658 sub register_implementation { 'Moose::Meta::Attribute' }
668 Moose::Meta::Attribute - The Moose attribute metaclass
672 This is a subclass of L<Class::MOP::Attribute> with Moose specific
675 For the most part, the only time you will ever encounter an
676 instance of this class is if you are doing some serious deep
677 introspection. To really understand this class, you need to refer
678 to the L<Class::MOP::Attribute> documentation.
682 =head2 Overridden methods
684 These methods override methods in L<Class::MOP::Attribute> and add
685 Moose specific features. You can safely assume though that they
686 will behave just as L<Class::MOP::Attribute> does.
696 =item B<initialize_instance_slot>
698 =item B<install_accessors>
700 =item B<install_delegation>
702 =item B<accessor_metaclass>
708 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
713 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
715 Before setting the value, a check is made on the type constraint of
716 the attribute, if it has one, to see if the value passes it. If the
717 value fails to pass, the set operation dies with a L<Carp/confess>.
719 Any coercion to convert values is done before checking the type constraint.
721 To check a value against a type constraint before setting it, fetch the
722 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
723 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
724 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
729 =head2 Additional Moose features
731 Moose attributes support type-constraint checking, weak reference
732 creation and type coercion.
736 =item B<interpolate_class_and_new>
738 =item B<interpolate_class>
740 When called as a class method causes interpretation of the C<metaclass> and
743 =item B<clone_and_inherit_options>
745 This is to support the C<has '+foo'> feature, it clones an attribute
746 from a superclass and allows a very specific set of changes to be made
749 =item B<legal_options_for_inheritance>
751 Whitelist with options you can change. You can overload it in your custom
752 metaclass to allow your options be inheritable.
754 =item B<has_type_constraint>
756 Returns true if this meta-attribute has a type constraint.
758 =item B<type_constraint>
760 A read-only accessor for this meta-attribute's type constraint. For
761 more information on what you can do with this, see the documentation
762 for L<Moose::Meta::TypeConstraint>.
766 Returns true if this meta-attribute performs delegation.
770 This returns the value which was passed into the handles option.
774 Returns true if this meta-attribute produces a weak reference.
778 Returns true if this meta-attribute is required to have a value.
782 Returns true if this meta-attribute should be initialized lazily.
784 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
786 =item B<is_lazy_build>
788 Returns true if this meta-attribute should be initialized lazily through
789 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
790 make your attribute required and lazy. In addition it will set the builder, clearer
791 and predicate options for you using the following convention.
793 #If your attribute name starts with an underscore:
794 has '_foo' => (lazy_build => 1);
796 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
798 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
800 #If your attribute name does not start with an underscore:
801 has 'foo' => (lazy_build => 1);
803 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
805 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
807 The reason for the different naming of the C<builder> is that the C<builder>
808 method is a private method while the C<clearer> and C<predicate> methods
811 NOTE: This means your class should provide a method whose name matches the value
812 of the builder part, in this case _build__foo or _build_foo.
814 =item B<should_coerce>
816 Returns true if this meta-attribute should perform type coercion.
818 =item B<should_auto_deref>
820 Returns true if this meta-attribute should perform automatic
823 NOTE: This can only be done for attributes whose type constraint is
824 either I<ArrayRef> or I<HashRef>.
828 Returns true if this meta-attribute has a trigger set.
832 This is a CODE reference which will be executed every time the
833 value of an attribute is assigned. The CODE ref will get two values,
834 the invocant and the new value. This can be used to handle I<basic>
835 bi-directional relations.
837 =item B<documentation>
839 This is a string which contains the documentation for this attribute.
840 It serves no direct purpose right now, but it might in the future
841 in some kind of automated documentation system perhaps.
843 =item B<has_documentation>
845 Returns true if this meta-attribute has any documentation.
847 =item B<applied_traits>
849 This will return the ARRAY ref of all the traits applied to this
850 attribute, or if no traits have been applied, it returns C<undef>.
852 =item B<has_applied_traits>
854 Returns true if this meta-attribute has any traits applied.
860 All complex software has bugs lurking in it, and this module is no
861 exception. If you find a bug please either email me, or add the bug
866 Stevan Little E<lt>stevan@iinteractive.comE<gt>
868 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
870 =head1 COPYRIGHT AND LICENSE
872 Copyright 2006-2008 by Infinity Interactive, Inc.
874 L<http://www.iinteractive.com>
876 This library is free software; you can redistribute it and/or modify
877 it under the same terms as Perl itself.