2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
9 use Sub::Name 'subname';
12 our $VERSION = '0.22';
13 our $AUTHORITY = 'cpan:STEVAN';
15 use Moose::Meta::Method::Accessor;
16 use Moose::Util::TypeConstraints ();
18 use base 'Class::MOP::Attribute';
20 # options which are not directly used
21 # but we store them for metadata purposes
22 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
23 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
24 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
26 # these are actual options for the attrs
27 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
28 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
29 __PACKAGE__->meta->add_attribute('lazy_build' => (reader => 'is_lazy_build' ));
30 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
31 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
32 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
33 __PACKAGE__->meta->add_attribute('type_constraint' => (
34 reader => 'type_constraint',
35 predicate => 'has_type_constraint',
37 __PACKAGE__->meta->add_attribute('trigger' => (
39 predicate => 'has_trigger',
41 __PACKAGE__->meta->add_attribute('handles' => (
43 predicate => 'has_handles',
45 __PACKAGE__->meta->add_attribute('documentation' => (
46 reader => 'documentation',
47 predicate => 'has_documentation',
49 __PACKAGE__->meta->add_attribute('traits' => (
50 reader => 'applied_traits',
51 predicate => 'has_applied_traits',
55 # we need to have a ->does method in here to
56 # more easily support traits, and the introspection
57 # of those traits. So in order to do this we
58 # just alias Moose::Object's version of it.
60 *does = \&Moose::Object::does;
63 my ($class, $name, %options) = @_;
64 $class->_process_options($name, \%options);
65 return $class->SUPER::new($name, %options);
68 sub clone_and_inherit_options {
69 my ($self, %options) = @_;
70 # you can change default, required, coerce, documentation, lazy, handles, builder, metaclass and traits
72 foreach my $legal_option (qw(default coerce required documentation lazy handles builder metaclass traits)) {
73 if (exists $options{$legal_option}) {
74 $actual_options{$legal_option} = $options{$legal_option};
75 delete $options{$legal_option};
81 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
82 $type_constraint = $options{isa};
85 $type_constraint = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options{isa});
86 (defined $type_constraint)
87 || confess "Could not find the type constraint '" . $options{isa} . "'";
90 $actual_options{type_constraint} = $type_constraint;
96 if (blessed($options{does}) && $options{does}->isa('Moose::Meta::TypeConstraint')) {
97 $type_constraint = $options{does};
100 $type_constraint = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options{does});
101 (defined $type_constraint)
102 || confess "Could not find the type constraint '" . $options{does} . "'";
105 $actual_options{type_constraint} = $type_constraint;
106 delete $options{does};
109 (scalar keys %options == 0)
110 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
111 $self->clone(%actual_options);
114 sub _process_options {
115 my ($class, $name, $options) = @_;
117 if (exists $options->{is}) {
118 if ($options->{is} eq 'ro') {
119 $options->{reader} ||= $name;
120 (!exists $options->{trigger})
121 || confess "Cannot have a trigger on a read-only attribute $name";
123 elsif ($options->{is} eq 'rw') {
124 $options->{accessor} = $name;
125 ((reftype($options->{trigger}) || '') eq 'CODE')
126 || confess "Trigger must be a CODE ref"
127 if exists $options->{trigger};
130 confess "I do not understand this option (is => " . $options->{is} . ") on attribute $name"
134 if (exists $options->{isa}) {
135 if (exists $options->{does}) {
136 if (eval { $options->{isa}->can('does') }) {
137 ($options->{isa}->does($options->{does}))
138 || confess "Cannot have an isa option and a does option if the isa does not do the does on attribute $name";
141 confess "Cannot have an isa option which cannot ->does() on attribute $name";
145 # allow for anon-subtypes here ...
146 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
147 $options->{type_constraint} = $options->{isa};
150 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_isa_type_constraint($options->{isa});
153 elsif (exists $options->{does}) {
154 # allow for anon-subtypes here ...
155 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
156 $options->{type_constraint} = $options->{does};
159 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_does_type_constraint($options->{does});
163 if (exists $options->{coerce} && $options->{coerce}) {
164 (exists $options->{type_constraint})
165 || confess "You cannot have coercion without specifying a type constraint on attribute $name";
166 confess "You cannot have a weak reference to a coerced value on attribute $name"
167 if $options->{weak_ref};
170 if (exists $options->{auto_deref} && $options->{auto_deref}) {
171 (exists $options->{type_constraint})
172 || confess "You cannot auto-dereference without specifying a type constraint on attribute $name";
173 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
174 $options->{type_constraint}->is_a_type_of('HashRef'))
175 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute $name";
178 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
179 confess("You can not use lazy_build and default for the same attribute $name")
180 if exists $options->{default};
181 $options->{lazy} = 1;
182 $options->{required} = 1;
183 $options->{builder} ||= "_build_${name}";
185 $options->{clearer} ||= "_clear${name}";
186 $options->{predicate} ||= "_has${name}";
189 $options->{clearer} ||= "clear_${name}";
190 $options->{predicate} ||= "has_${name}";
194 if (exists $options->{lazy} && $options->{lazy}) {
195 (exists $options->{default} || defined $options->{builder} )
196 || confess "You cannot have lazy attribute ($name) without specifying a default value for it";
199 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
200 confess "You cannot have a required attribute ($name) without a default, builder, or an init_arg";
205 sub initialize_instance_slot {
206 my ($self, $meta_instance, $instance, $params) = @_;
207 my $init_arg = $self->init_arg();
208 # try to fetch the init arg from the %params ...
212 if ( defined($init_arg) and exists $params->{$init_arg}) {
213 $val = $params->{$init_arg};
217 # skip it if it's lazy
218 return if $self->is_lazy;
219 # and die if it's required and doesn't have a default value
220 confess "Attribute (" . $self->name . ") is required"
221 if $self->is_required && !$self->has_default && !$self->has_builder;
223 # if nothing was in the %params, we can use the
224 # attribute's default value (if it has one)
225 if ($self->has_default) {
226 $val = $self->default($instance);
229 elsif ($self->has_builder) {
230 if (my $builder = $instance->can($self->builder)){
231 $val = $instance->$builder;
235 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
240 return unless $value_is_set;
242 if ($self->has_type_constraint) {
243 my $type_constraint = $self->type_constraint;
244 if ($self->should_coerce && $type_constraint->has_coercion) {
245 $val = $type_constraint->coerce($val);
247 $type_constraint->check($val)
248 || confess "Attribute ("
250 . ") does not pass the type constraint because: "
251 . $type_constraint->get_message($val);
254 $self->set_initial_value($instance, $val);
255 $meta_instance->weaken_slot_value($instance, $self->name)
256 if ref $val && $self->is_weak_ref;
262 # this duplicates too much code from
263 # Class::MOP::Attribute, we need to
264 # refactor these bits eventually.
266 sub _set_initial_slot_value {
267 my ($self, $meta_instance, $instance, $value) = @_;
269 my $slot_name = $self->name;
271 return $meta_instance->set_slot_value($instance, $slot_name, $value)
272 unless $self->has_initializer;
274 my ($type_constraint, $can_coerce);
275 if ($self->has_type_constraint) {
276 $type_constraint = $self->type_constraint;
277 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
282 if ($type_constraint) {
283 $val = $type_constraint->coerce($val)
285 $type_constraint->check($val)
286 || confess "Attribute ("
288 . ") does not pass the type constraint because: "
289 . $type_constraint->get_message($val);
291 $meta_instance->set_slot_value($instance, $slot_name, $val);
294 my $initializer = $self->initializer;
296 # most things will just want to set a value, so make it first arg
297 $instance->$initializer($value, $callback, $self);
301 my ($self, $instance, $value) = @_;
303 my $attr_name = $self->name;
305 if ($self->is_required) {
307 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
310 if ($self->has_type_constraint) {
312 my $type_constraint = $self->type_constraint;
314 if ($self->should_coerce) {
315 $value = $type_constraint->coerce($value);
317 $type_constraint->_compiled_type_constraint->($value)
318 || confess "Attribute ("
320 . ") does not pass the type constraint because "
321 . $type_constraint->get_message($value);
324 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
327 $meta_instance->set_slot_value($instance, $attr_name, $value);
329 if (ref $value && $self->is_weak_ref) {
330 $meta_instance->weaken_slot_value($instance, $attr_name);
333 if ($self->has_trigger) {
334 $self->trigger->($instance, $value, $self);
339 my ($self, $instance) = @_;
341 if ($self->is_lazy) {
342 unless ($self->has_value($instance)) {
343 if ($self->has_default) {
344 my $default = $self->default($instance);
345 $self->set_initial_value($instance, $default);
347 if ( $self->has_builder ){
348 if (my $builder = $instance->can($self->builder)){
349 $self->set_initial_value($instance, $instance->$builder);
352 confess(blessed($instance)
353 . " does not support builder method '"
355 . "' for attribute '"
361 $self->set_initial_value($instance, undef);
366 if ($self->should_auto_deref) {
368 my $type_constraint = $self->type_constraint;
370 if ($type_constraint->is_a_type_of('ArrayRef')) {
371 my $rv = $self->SUPER::get_value($instance);
372 return unless defined $rv;
373 return wantarray ? @{ $rv } : $rv;
375 elsif ($type_constraint->is_a_type_of('HashRef')) {
376 my $rv = $self->SUPER::get_value($instance);
377 return unless defined $rv;
378 return wantarray ? %{ $rv } : $rv;
381 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
387 return $self->SUPER::get_value($instance);
391 ## installing accessors
393 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
395 sub install_accessors {
397 $self->SUPER::install_accessors(@_);
399 if ($self->has_handles) {
402 # Here we canonicalize the 'handles' option
403 # this will sort out any details and always
404 # return an hash of methods which we want
405 # to delagate to, see that method for details
406 my %handles = $self->_canonicalize_handles();
408 # find the accessor method for this attribute
409 my $accessor = $self->get_read_method_ref;
410 # then unpack it if we need too ...
411 $accessor = $accessor->body if blessed $accessor;
413 # install the delegation ...
414 my $associated_class = $self->associated_class;
415 foreach my $handle (keys %handles) {
416 my $method_to_call = $handles{$handle};
417 my $class_name = $associated_class->name;
418 my $name = "${class_name}::${handle}";
420 (!$associated_class->has_method($handle))
421 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
424 # handles is not allowed to delegate
425 # any of these methods, as they will
426 # override the ones in your class, which
427 # is almost certainly not what you want.
429 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
430 #cluck("Not delegating method '$handle' because it is a core method") and
431 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
433 if ((reftype($method_to_call) || '') eq 'CODE') {
434 $associated_class->add_method($handle => subname $name, $method_to_call);
438 # we used to do a goto here, but the
439 # goto didn't handle failure correctly
440 # (it just returned nothing), so I took
441 # that out. However, the more I thought
442 # about it, the less I liked it doing
443 # the goto, and I prefered the act of
444 # delegation being actually represented
445 # in the stack trace.
447 $associated_class->add_method($handle => subname $name, sub {
448 my $proxy = (shift)->$accessor();
450 || confess "Cannot delegate $handle to $method_to_call because " .
451 "the value of " . $self->name . " is not defined";
452 $proxy->$method_to_call(@_);
461 # private methods to help delegation ...
463 sub _canonicalize_handles {
465 my $handles = $self->handles;
466 if (my $handle_type = ref($handles)) {
467 if ($handle_type eq 'HASH') {
470 elsif ($handle_type eq 'ARRAY') {
471 return map { $_ => $_ } @{$handles};
473 elsif ($handle_type eq 'Regexp') {
474 ($self->has_type_constraint)
475 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
476 return map { ($_ => $_) }
477 grep { /$handles/ } $self->_get_delegate_method_list;
479 elsif ($handle_type eq 'CODE') {
480 return $handles->($self, $self->_find_delegate_metaclass);
483 confess "Unable to canonicalize the 'handles' option with $handles";
487 my $role_meta = eval { $handles->meta };
489 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
492 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
493 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
495 return map { $_ => $_ } (
496 $role_meta->get_method_list,
497 $role_meta->get_required_method_list
502 sub _find_delegate_metaclass {
504 if (my $class = $self->_isa_metadata) {
505 # if the class does have
506 # a meta method, use it
507 return $class->meta if $class->can('meta');
508 # otherwise we might be
509 # dealing with a non-Moose
510 # class, and need to make
512 return Moose::Meta::Class->initialize($class);
514 elsif (my $role = $self->_does_metadata) {
515 # our role will always have
520 confess "Cannot find delegate metaclass for attribute " . $self->name;
524 sub _get_delegate_method_list {
526 my $meta = $self->_find_delegate_metaclass;
527 if ($meta->isa('Class::MOP::Class')) {
528 return map { $_->{name} } # NOTE: !never! delegate &meta
529 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
530 $meta->compute_all_applicable_methods;
532 elsif ($meta->isa('Moose::Meta::Role')) {
533 return $meta->get_method_list;
536 confess "Unable to recognize the delegate metaclass '$meta'";
548 Moose::Meta::Attribute - The Moose attribute metaclass
552 This is a subclass of L<Class::MOP::Attribute> with Moose specific
555 For the most part, the only time you will ever encounter an
556 instance of this class is if you are doing some serious deep
557 introspection. To really understand this class, you need to refer
558 to the L<Class::MOP::Attribute> documentation.
562 =head2 Overridden methods
564 These methods override methods in L<Class::MOP::Attribute> and add
565 Moose specific features. You can safely assume though that they
566 will behave just as L<Class::MOP::Attribute> does.
574 =item B<initialize_instance_slot>
576 =item B<install_accessors>
578 =item B<accessor_metaclass>
584 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
589 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
591 Before setting the value, a check is made on the type constraint of
592 the attribute, if it has one, to see if the value passes it. If the
593 value fails to pass, the set operation dies with a L<Carp/confess>.
595 Any coercion to convert values is done before checking the type constraint.
597 To check a value against a type constraint before setting it, fetch the
598 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
599 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
600 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
605 =head2 Additional Moose features
607 Moose attributes support type-constraint checking, weak reference
608 creation and type coercion.
612 =item B<clone_and_inherit_options>
614 This is to support the C<has '+foo'> feature, it clones an attribute
615 from a superclass and allows a very specific set of changes to be made
618 =item B<has_type_constraint>
620 Returns true if this meta-attribute has a type constraint.
622 =item B<type_constraint>
624 A read-only accessor for this meta-attribute's type constraint. For
625 more information on what you can do with this, see the documentation
626 for L<Moose::Meta::TypeConstraint>.
630 Returns true if this meta-attribute performs delegation.
634 This returns the value which was passed into the handles option.
638 Returns true if this meta-attribute produces a weak reference.
642 Returns true if this meta-attribute is required to have a value.
646 Returns true if this meta-attribute should be initialized lazily.
648 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
650 =item B<is_lazy_build>
652 Returns true if this meta-attribute should be initialized lazily through
653 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
654 make your attribute required and lazy. In addition it will set the builder, clearer
655 and predicate options for you using the following convention.
657 #If your attribute name starts with an underscore:
658 has '_foo' => (lazy_build => 1);
660 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
662 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
664 #If your attribute name does not start with an underscore:
665 has 'foo' => (lazy_build => 1);
667 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
669 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
671 The reason for the different naming of the C<builder> is that the C<builder>
672 method is a private method while the C<clearer> and C<predicate> methods
675 NOTE: This means your class should provide a method whose name matches the value
676 of the builder part, in this case _build__foo or _build_foo.
678 =item B<should_coerce>
680 Returns true if this meta-attribute should perform type coercion.
682 =item B<should_auto_deref>
684 Returns true if this meta-attribute should perform automatic
687 NOTE: This can only be done for attributes whose type constraint is
688 either I<ArrayRef> or I<HashRef>.
692 Returns true if this meta-attribute has a trigger set.
696 This is a CODE reference which will be executed every time the
697 value of an attribute is assigned. The CODE ref will get two values,
698 the invocant and the new value. This can be used to handle I<basic>
699 bi-directional relations.
701 =item B<documentation>
703 This is a string which contains the documentation for this attribute.
704 It serves no direct purpose right now, but it might in the future
705 in some kind of automated documentation system perhaps.
707 =item B<has_documentation>
709 Returns true if this meta-attribute has any documentation.
711 =item B<applied_traits>
713 This will return the ARRAY ref of all the traits applied to this
714 attribute, or if no traits have been applied, it returns C<undef>.
716 =item B<has_applied_traits>
718 Returns true if this meta-attribute has any traits applied.
724 All complex software has bugs lurking in it, and this module is no
725 exception. If you find a bug please either email me, or add the bug
730 Stevan Little E<lt>stevan@iinteractive.comE<gt>
732 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
734 =head1 COPYRIGHT AND LICENSE
736 Copyright 2006-2008 by Infinity Interactive, Inc.
738 L<http://www.iinteractive.com>
740 This library is free software; you can redistribute it and/or modify
741 it under the same terms as Perl itself.