2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
9 use Sub::Name 'subname';
12 our $VERSION = '0.22';
13 our $AUTHORITY = 'cpan:STEVAN';
15 use Moose::Meta::Method::Accessor;
16 use Moose::Util::TypeConstraints ();
18 use base 'Class::MOP::Attribute';
20 # options which are not directly used
21 # but we store them for metadata purposes
22 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
23 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
24 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
26 # these are actual options for the attrs
27 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
28 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
29 __PACKAGE__->meta->add_attribute('lazy_build' => (reader => 'is_lazy_build' ));
30 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
31 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
32 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
33 __PACKAGE__->meta->add_attribute('type_constraint' => (
34 reader => 'type_constraint',
35 predicate => 'has_type_constraint',
37 __PACKAGE__->meta->add_attribute('trigger' => (
39 predicate => 'has_trigger',
41 __PACKAGE__->meta->add_attribute('handles' => (
43 predicate => 'has_handles',
45 __PACKAGE__->meta->add_attribute('documentation' => (
46 reader => 'documentation',
47 predicate => 'has_documentation',
51 # we need to have a ->does method in here to
52 # more easily support traits, and the introspection
53 # of those traits. So in order to do this we
54 # just alias Moose::Object's version of it.
56 *does = \&Moose::Object::does;
59 my ($class, $name, %options) = @_;
60 $class->_process_options($name, \%options);
61 return $class->SUPER::new($name, %options);
64 sub clone_and_inherit_options {
65 my ($self, %options) = @_;
66 # you can change default, required, coerce, documentation and lazy
68 foreach my $legal_option (qw(default coerce required documentation lazy)) {
69 if (exists $options{$legal_option}) {
70 $actual_options{$legal_option} = $options{$legal_option};
71 delete $options{$legal_option};
75 # handles can only be added, not changed
76 if ($options{handles}) {
77 confess "You can only add the 'handles' option, you cannot change it"
78 if $self->has_handles;
79 $actual_options{handles} = $options{handles};
80 delete $options{handles};
83 # handles can only be added, not changed
84 if ($options{builder}) {
85 confess "You can only add the 'builder' option, you cannot change it"
86 if $self->has_builder;
87 $actual_options{builder} = $options{builder};
88 delete $options{builder};
91 # isa can be changed, but only if the
92 # new type is a subtype
95 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
96 $type_constraint = $options{isa};
99 $type_constraint = Moose::Util::TypeConstraints::find_or_create_type_constraint(
102 (defined $type_constraint)
103 || confess "Could not find the type constraint '" . $options{isa} . "'";
106 # check here to see if the new type
107 # is a subtype of the old one
108 ($type_constraint->is_subtype_of($self->type_constraint->name))
109 || confess "New type constraint setting must be a subtype of inherited one"
110 # iff we have a type constraint that is ...
111 if $self->has_type_constraint;
113 $actual_options{type_constraint} = $type_constraint;
114 delete $options{isa};
116 (scalar keys %options == 0)
117 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
118 $self->clone(%actual_options);
121 sub _process_options {
122 my ($class, $name, $options) = @_;
124 if (exists $options->{is}) {
125 if ($options->{is} eq 'ro') {
126 $options->{reader} ||= $name;
127 (!exists $options->{trigger})
128 || confess "Cannot have a trigger on a read-only attribute";
130 elsif ($options->{is} eq 'rw') {
131 $options->{accessor} = $name;
132 ((reftype($options->{trigger}) || '') eq 'CODE')
133 || confess "Trigger must be a CODE ref"
134 if exists $options->{trigger};
137 confess "I do not understand this option (is => " . $options->{is} . ")"
141 if (exists $options->{isa}) {
142 if (exists $options->{does}) {
143 if (eval { $options->{isa}->can('does') }) {
144 ($options->{isa}->does($options->{does}))
145 || confess "Cannot have an isa option and a does option if the isa does not do the does";
148 confess "Cannot have an isa option which cannot ->does()";
152 # allow for anon-subtypes here ...
153 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
154 $options->{type_constraint} = $options->{isa};
157 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
159 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
160 constraint => sub { $_[0]->isa($options->{isa}) }
165 elsif (exists $options->{does}) {
166 # allow for anon-subtypes here ...
167 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
168 $options->{type_constraint} = $options->{does};
171 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
172 $options->{does} => {
173 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
175 Moose::Util::does_role($_[0], $options->{does})
182 if (exists $options->{coerce} && $options->{coerce}) {
183 (exists $options->{type_constraint})
184 || confess "You cannot have coercion without specifying a type constraint";
185 confess "You cannot have a weak reference to a coerced value"
186 if $options->{weak_ref};
189 if (exists $options->{auto_deref} && $options->{auto_deref}) {
190 (exists $options->{type_constraint})
191 || confess "You cannot auto-dereference without specifying a type constraint";
192 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
193 $options->{type_constraint}->is_a_type_of('HashRef'))
194 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
197 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
198 confess("You can not use lazy_build and default for the same attribute")
199 if exists $options->{default};
200 $options->{lazy} = 1;
201 $options->{required} = 1;
202 $options->{builder} ||= "_build_${name}";
204 $options->{clearer} ||= "_clear${name}";
205 $options->{predicate} ||= "_has${name}";
208 $options->{clearer} ||= "clear_${name}";
209 $options->{predicate} ||= "has_${name}";
213 if (exists $options->{lazy} && $options->{lazy}) {
214 (exists $options->{default} || defined $options->{builder} )
215 || confess "You cannot have lazy attribute without specifying a default value for it";
218 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
219 confess "You cannot have a required attribute without a default, builder, or an init_arg";
224 sub initialize_instance_slot {
225 my ($self, $meta_instance, $instance, $params) = @_;
226 my $init_arg = $self->init_arg();
227 # try to fetch the init arg from the %params ...
231 if ( defined($init_arg) and exists $params->{$init_arg}) {
232 $val = $params->{$init_arg};
236 # skip it if it's lazy
237 return if $self->is_lazy;
238 # and die if it's required and doesn't have a default value
239 confess "Attribute (" . $self->name . ") is required"
240 if $self->is_required && !$self->has_default && !$self->has_builder;
242 # if nothing was in the %params, we can use the
243 # attribute's default value (if it has one)
244 if ($self->has_default) {
245 $val = $self->default($instance);
248 elsif ($self->has_builder) {
249 if (my $builder = $instance->can($self->builder)){
250 $val = $instance->$builder;
254 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
259 return unless $value_is_set;
261 if ($self->has_type_constraint) {
262 my $type_constraint = $self->type_constraint;
263 if ($self->should_coerce && $type_constraint->has_coercion) {
264 $val = $type_constraint->coerce($val);
266 $type_constraint->check($val)
267 || confess "Attribute ("
269 . ") does not pass the type constraint because: "
270 . $type_constraint->get_message($val);
273 $self->set_initial_value($instance, $val);
274 $meta_instance->weaken_slot_value($instance, $self->name)
275 if ref $val && $self->is_weak_ref;
281 # this duplicates too much code from
282 # Class::MOP::Attribute, we need to
283 # refactor these bits eventually.
285 sub _set_initial_slot_value {
286 my ($self, $meta_instance, $instance, $value) = @_;
288 my $slot_name = $self->name;
290 return $meta_instance->set_slot_value($instance, $slot_name, $value)
291 unless $self->has_initializer;
293 my ($type_constraint, $can_coerce);
294 if ($self->has_type_constraint) {
295 $type_constraint = $self->type_constraint;
296 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
301 if ($type_constraint) {
302 $val = $type_constraint->coerce($val)
304 $type_constraint->check($val)
305 || confess "Attribute ("
307 . ") does not pass the type constraint because: "
308 . $type_constraint->get_message($val);
310 $meta_instance->set_slot_value($instance, $slot_name, $val);
313 my $initializer = $self->initializer;
315 # most things will just want to set a value, so make it first arg
316 $instance->$initializer($value, $callback, $self);
320 my ($self, $instance, $value) = @_;
322 my $attr_name = $self->name;
324 if ($self->is_required) {
326 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
329 if ($self->has_type_constraint) {
331 my $type_constraint = $self->type_constraint;
333 if ($self->should_coerce) {
334 $value = $type_constraint->coerce($value);
336 $type_constraint->_compiled_type_constraint->($value)
337 || confess "Attribute ("
339 . ") does not pass the type constraint because "
340 . $type_constraint->get_message($value);
343 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
346 $meta_instance->set_slot_value($instance, $attr_name, $value);
348 if (ref $value && $self->is_weak_ref) {
349 $meta_instance->weaken_slot_value($instance, $attr_name);
352 if ($self->has_trigger) {
353 $self->trigger->($instance, $value, $self);
358 my ($self, $instance) = @_;
360 if ($self->is_lazy) {
361 unless ($self->has_value($instance)) {
362 if ($self->has_default) {
363 my $default = $self->default($instance);
364 $self->set_initial_value($instance, $default);
366 if ( $self->has_builder ){
367 if (my $builder = $instance->can($self->builder)){
368 $self->set_initial_value($instance, $instance->$builder);
371 confess(blessed($instance)
372 . " does not support builder method '"
374 . "' for attribute '"
380 $self->set_initial_value($instance, undef);
385 if ($self->should_auto_deref) {
387 my $type_constraint = $self->type_constraint;
389 if ($type_constraint->is_a_type_of('ArrayRef')) {
390 my $rv = $self->SUPER::get_value($instance);
391 return unless defined $rv;
392 return wantarray ? @{ $rv } : $rv;
394 elsif ($type_constraint->is_a_type_of('HashRef')) {
395 my $rv = $self->SUPER::get_value($instance);
396 return unless defined $rv;
397 return wantarray ? %{ $rv } : $rv;
400 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
406 return $self->SUPER::get_value($instance);
410 ## installing accessors
412 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
414 sub install_accessors {
416 $self->SUPER::install_accessors(@_);
418 if ($self->has_handles) {
421 # Here we canonicalize the 'handles' option
422 # this will sort out any details and always
423 # return an hash of methods which we want
424 # to delagate to, see that method for details
425 my %handles = $self->_canonicalize_handles();
427 # find the accessor method for this attribute
428 my $accessor = $self->get_read_method_ref;
429 # then unpack it if we need too ...
430 $accessor = $accessor->body if blessed $accessor;
432 # install the delegation ...
433 my $associated_class = $self->associated_class;
434 foreach my $handle (keys %handles) {
435 my $method_to_call = $handles{$handle};
436 my $class_name = $associated_class->name;
437 my $name = "${class_name}::${handle}";
439 (!$associated_class->has_method($handle))
440 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
443 # handles is not allowed to delegate
444 # any of these methods, as they will
445 # override the ones in your class, which
446 # is almost certainly not what you want.
448 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
449 #cluck("Not delegating method '$handle' because it is a core method") and
450 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
452 if ((reftype($method_to_call) || '') eq 'CODE') {
453 $associated_class->add_method($handle => subname $name, $method_to_call);
457 # we used to do a goto here, but the
458 # goto didn't handle failure correctly
459 # (it just returned nothing), so I took
460 # that out. However, the more I thought
461 # about it, the less I liked it doing
462 # the goto, and I prefered the act of
463 # delegation being actually represented
464 # in the stack trace.
466 $associated_class->add_method($handle => subname $name, sub {
467 my $proxy = (shift)->$accessor();
469 || confess "Cannot delegate $handle to $method_to_call because " .
470 "the value of " . $self->name . " is not defined";
471 $proxy->$method_to_call(@_);
480 # private methods to help delegation ...
482 sub _canonicalize_handles {
484 my $handles = $self->handles;
485 if (my $handle_type = ref($handles)) {
486 if ($handle_type eq 'HASH') {
489 elsif ($handle_type eq 'ARRAY') {
490 return map { $_ => $_ } @{$handles};
492 elsif ($handle_type eq 'Regexp') {
493 ($self->has_type_constraint)
494 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
495 return map { ($_ => $_) }
496 grep { /$handles/ } $self->_get_delegate_method_list;
498 elsif ($handle_type eq 'CODE') {
499 return $handles->($self, $self->_find_delegate_metaclass);
502 confess "Unable to canonicalize the 'handles' option with $handles";
506 my $role_meta = eval { $handles->meta };
508 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
511 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
512 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
514 return map { $_ => $_ } (
515 $role_meta->get_method_list,
516 $role_meta->get_required_method_list
521 sub _find_delegate_metaclass {
523 if (my $class = $self->_isa_metadata) {
524 # if the class does have
525 # a meta method, use it
526 return $class->meta if $class->can('meta');
527 # otherwise we might be
528 # dealing with a non-Moose
529 # class, and need to make
531 return Moose::Meta::Class->initialize($class);
533 elsif (my $role = $self->_does_metadata) {
534 # our role will always have
539 confess "Cannot find delegate metaclass for attribute " . $self->name;
543 sub _get_delegate_method_list {
545 my $meta = $self->_find_delegate_metaclass;
546 if ($meta->isa('Class::MOP::Class')) {
547 return map { $_->{name} } # NOTE: !never! delegate &meta
548 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
549 $meta->compute_all_applicable_methods;
551 elsif ($meta->isa('Moose::Meta::Role')) {
552 return $meta->get_method_list;
555 confess "Unable to recognize the delegate metaclass '$meta'";
567 Moose::Meta::Attribute - The Moose attribute metaclass
571 This is a subclass of L<Class::MOP::Attribute> with Moose specific
574 For the most part, the only time you will ever encounter an
575 instance of this class is if you are doing some serious deep
576 introspection. To really understand this class, you need to refer
577 to the L<Class::MOP::Attribute> documentation.
581 =head2 Overridden methods
583 These methods override methods in L<Class::MOP::Attribute> and add
584 Moose specific features. You can safely assume though that they
585 will behave just as L<Class::MOP::Attribute> does.
593 =item B<initialize_instance_slot>
595 =item B<install_accessors>
597 =item B<accessor_metaclass>
603 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
608 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
610 Before setting the value, a check is made on the type constraint of
611 the attribute, if it has one, to see if the value passes it. If the
612 value fails to pass, the set operation dies with a L<Carp/confess>.
614 Any coercion to convert values is done before checking the type constraint.
616 To check a value against a type constraint before setting it, fetch the
617 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
618 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
619 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
624 =head2 Additional Moose features
626 Moose attributes support type-constraint checking, weak reference
627 creation and type coercion.
631 =item B<clone_and_inherit_options>
633 This is to support the C<has '+foo'> feature, it clones an attribute
634 from a superclass and allows a very specific set of changes to be made
637 =item B<has_type_constraint>
639 Returns true if this meta-attribute has a type constraint.
641 =item B<type_constraint>
643 A read-only accessor for this meta-attribute's type constraint. For
644 more information on what you can do with this, see the documentation
645 for L<Moose::Meta::TypeConstraint>.
649 Returns true if this meta-attribute performs delegation.
653 This returns the value which was passed into the handles option.
657 Returns true if this meta-attribute produces a weak reference.
661 Returns true if this meta-attribute is required to have a value.
665 Returns true if this meta-attribute should be initialized lazily.
667 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
669 =item B<is_lazy_build>
671 Returns true if this meta-attribute should be initialized lazily through
672 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
673 make your attribute required and lazy. In addition it will set the builder, clearer
674 and predicate options for you using the following convention.
676 #If your attribute name starts with an underscore:
677 has '_foo' => (lazy_build => 1);
679 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
681 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
683 #If your attribute name does not start with an underscore:
684 has 'foo' => (lazy_build => 1);
686 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
688 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
690 The reason for the different naming of the C<builder> is that the C<builder>
691 method is a private method while the C<clearer> and C<predicate> methods
694 NOTE: This means your class should provide a method whose name matches the value
695 of the builder part, in this case _build__foo or _build_foo.
697 =item B<should_coerce>
699 Returns true if this meta-attribute should perform type coercion.
701 =item B<should_auto_deref>
703 Returns true if this meta-attribute should perform automatic
706 NOTE: This can only be done for attributes whose type constraint is
707 either I<ArrayRef> or I<HashRef>.
711 Returns true if this meta-attribute has a trigger set.
715 This is a CODE reference which will be executed every time the
716 value of an attribute is assigned. The CODE ref will get two values,
717 the invocant and the new value. This can be used to handle I<basic>
718 bi-directional relations.
720 =item B<documentation>
722 This is a string which contains the documentation for this attribute.
723 It serves no direct purpose right now, but it might in the future
724 in some kind of automated documentation system perhaps.
726 =item B<has_documentation>
728 Returns true if this meta-attribute has any documentation.
734 All complex software has bugs lurking in it, and this module is no
735 exception. If you find a bug please either email me, or add the bug
740 Stevan Little E<lt>stevan@iinteractive.comE<gt>
742 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
744 =head1 COPYRIGHT AND LICENSE
746 Copyright 2006-2008 by Infinity Interactive, Inc.
748 L<http://www.iinteractive.com>
750 This library is free software; you can redistribute it and/or modify
751 it under the same terms as Perl itself.