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 # or if the old one is a union and the
109 # subtype (or a supertype of it) is included
111 $type_constraint->is_subtype_of($self->type_constraint->name)
112 || ($self->type_constraint->can('includes_type') && $self->type_constraint->includes_type($type_constraint))
113 || confess "New type constraint setting must be a subtype of inherited one" . ($self->type_constraint->can('includes_type') ? ", or included in the inherited constraint" : '')
114 # iff we have a type constraint that is ...
115 if $self->has_type_constraint;
117 $actual_options{type_constraint} = $type_constraint;
118 delete $options{isa};
120 (scalar keys %options == 0)
121 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
122 $self->clone(%actual_options);
125 sub _process_options {
126 my ($class, $name, $options) = @_;
128 if (exists $options->{is}) {
129 if ($options->{is} eq 'ro') {
130 $options->{reader} ||= $name;
131 (!exists $options->{trigger})
132 || confess "Cannot have a trigger on a read-only attribute";
134 elsif ($options->{is} eq 'rw') {
135 $options->{accessor} = $name;
136 ((reftype($options->{trigger}) || '') eq 'CODE')
137 || confess "Trigger must be a CODE ref"
138 if exists $options->{trigger};
141 confess "I do not understand this option (is => " . $options->{is} . ")"
145 if (exists $options->{isa}) {
146 if (exists $options->{does}) {
147 if (eval { $options->{isa}->can('does') }) {
148 ($options->{isa}->does($options->{does}))
149 || confess "Cannot have an isa option and a does option if the isa does not do the does";
152 confess "Cannot have an isa option which cannot ->does()";
156 # allow for anon-subtypes here ...
157 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
158 $options->{type_constraint} = $options->{isa};
161 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
163 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
164 constraint => sub { $_[0]->isa($options->{isa}) }
169 elsif (exists $options->{does}) {
170 # allow for anon-subtypes here ...
171 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
172 $options->{type_constraint} = $options->{does};
175 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
176 $options->{does} => {
177 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
179 Moose::Util::does_role($_[0], $options->{does})
186 if (exists $options->{coerce} && $options->{coerce}) {
187 (exists $options->{type_constraint})
188 || confess "You cannot have coercion without specifying a type constraint";
189 confess "You cannot have a weak reference to a coerced value"
190 if $options->{weak_ref};
193 if (exists $options->{auto_deref} && $options->{auto_deref}) {
194 (exists $options->{type_constraint})
195 || confess "You cannot auto-dereference without specifying a type constraint";
196 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
197 $options->{type_constraint}->is_a_type_of('HashRef'))
198 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
201 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
202 confess("You can not use lazy_build and default for the same attribute")
203 if exists $options->{default};
204 $options->{lazy} = 1;
205 $options->{required} = 1;
206 $options->{builder} ||= "_build_${name}";
208 $options->{clearer} ||= "_clear${name}";
209 $options->{predicate} ||= "_has${name}";
212 $options->{clearer} ||= "clear_${name}";
213 $options->{predicate} ||= "has_${name}";
217 if (exists $options->{lazy} && $options->{lazy}) {
218 (exists $options->{default} || defined $options->{builder} )
219 || confess "You cannot have lazy attribute without specifying a default value for it";
222 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
223 confess "You cannot have a required attribute without a default, builder, or an init_arg";
228 sub initialize_instance_slot {
229 my ($self, $meta_instance, $instance, $params) = @_;
230 my $init_arg = $self->init_arg();
231 # try to fetch the init arg from the %params ...
235 if ( defined($init_arg) and exists $params->{$init_arg}) {
236 $val = $params->{$init_arg};
240 # skip it if it's lazy
241 return if $self->is_lazy;
242 # and die if it's required and doesn't have a default value
243 confess "Attribute (" . $self->name . ") is required"
244 if $self->is_required && !$self->has_default && !$self->has_builder;
246 # if nothing was in the %params, we can use the
247 # attribute's default value (if it has one)
248 if ($self->has_default) {
249 $val = $self->default($instance);
252 elsif ($self->has_builder) {
253 if (my $builder = $instance->can($self->builder)){
254 $val = $instance->$builder;
258 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
263 return unless $value_is_set;
265 if ($self->has_type_constraint) {
266 my $type_constraint = $self->type_constraint;
267 if ($self->should_coerce && $type_constraint->has_coercion) {
268 $val = $type_constraint->coerce($val);
270 $type_constraint->check($val)
271 || confess "Attribute ("
273 . ") does not pass the type constraint because: "
274 . $type_constraint->get_message($val);
277 $self->set_initial_value($instance, $val);
278 $meta_instance->weaken_slot_value($instance, $self->name)
279 if ref $val && $self->is_weak_ref;
285 # this duplicates too much code from
286 # Class::MOP::Attribute, we need to
287 # refactor these bits eventually.
289 sub _set_initial_slot_value {
290 my ($self, $meta_instance, $instance, $value) = @_;
292 my $slot_name = $self->name;
294 return $meta_instance->set_slot_value($instance, $slot_name, $value)
295 unless $self->has_initializer;
297 my ($type_constraint, $can_coerce);
298 if ($self->has_type_constraint) {
299 $type_constraint = $self->type_constraint;
300 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
305 if ($type_constraint) {
306 $val = $type_constraint->coerce($val)
308 $type_constraint->check($val)
309 || confess "Attribute ("
311 . ") does not pass the type constraint because: "
312 . $type_constraint->get_message($val);
314 $meta_instance->set_slot_value($instance, $slot_name, $val);
317 my $initializer = $self->initializer;
319 # most things will just want to set a value, so make it first arg
320 $instance->$initializer($value, $callback, $self);
324 my ($self, $instance, $value) = @_;
326 my $attr_name = $self->name;
328 if ($self->is_required) {
330 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
333 if ($self->has_type_constraint) {
335 my $type_constraint = $self->type_constraint;
337 if ($self->should_coerce) {
338 $value = $type_constraint->coerce($value);
340 $type_constraint->_compiled_type_constraint->($value)
341 || confess "Attribute ("
343 . ") does not pass the type constraint because "
344 . $type_constraint->get_message($value);
347 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
350 $meta_instance->set_slot_value($instance, $attr_name, $value);
352 if (ref $value && $self->is_weak_ref) {
353 $meta_instance->weaken_slot_value($instance, $attr_name);
356 if ($self->has_trigger) {
357 $self->trigger->($instance, $value, $self);
362 my ($self, $instance) = @_;
364 if ($self->is_lazy) {
365 unless ($self->has_value($instance)) {
366 if ($self->has_default) {
367 my $default = $self->default($instance);
368 $self->set_initial_value($instance, $default);
370 if ( $self->has_builder ){
371 if (my $builder = $instance->can($self->builder)){
372 $self->set_initial_value($instance, $instance->$builder);
375 confess(blessed($instance)
376 . " does not support builder method '"
378 . "' for attribute '"
384 $self->set_initial_value($instance, undef);
389 if ($self->should_auto_deref) {
391 my $type_constraint = $self->type_constraint;
393 if ($type_constraint->is_a_type_of('ArrayRef')) {
394 my $rv = $self->SUPER::get_value($instance);
395 return unless defined $rv;
396 return wantarray ? @{ $rv } : $rv;
398 elsif ($type_constraint->is_a_type_of('HashRef')) {
399 my $rv = $self->SUPER::get_value($instance);
400 return unless defined $rv;
401 return wantarray ? %{ $rv } : $rv;
404 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
410 return $self->SUPER::get_value($instance);
414 ## installing accessors
416 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
418 sub install_accessors {
420 $self->SUPER::install_accessors(@_);
422 if ($self->has_handles) {
425 # Here we canonicalize the 'handles' option
426 # this will sort out any details and always
427 # return an hash of methods which we want
428 # to delagate to, see that method for details
429 my %handles = $self->_canonicalize_handles();
431 # find the accessor method for this attribute
432 my $accessor = $self->get_read_method_ref;
433 # then unpack it if we need too ...
434 $accessor = $accessor->body if blessed $accessor;
436 # install the delegation ...
437 my $associated_class = $self->associated_class;
438 foreach my $handle (keys %handles) {
439 my $method_to_call = $handles{$handle};
440 my $class_name = $associated_class->name;
441 my $name = "${class_name}::${handle}";
443 (!$associated_class->has_method($handle))
444 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
447 # handles is not allowed to delegate
448 # any of these methods, as they will
449 # override the ones in your class, which
450 # is almost certainly not what you want.
452 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
453 #cluck("Not delegating method '$handle' because it is a core method") and
454 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
456 if ((reftype($method_to_call) || '') eq 'CODE') {
457 $associated_class->add_method($handle => subname $name, $method_to_call);
461 # we used to do a goto here, but the
462 # goto didn't handle failure correctly
463 # (it just returned nothing), so I took
464 # that out. However, the more I thought
465 # about it, the less I liked it doing
466 # the goto, and I prefered the act of
467 # delegation being actually represented
468 # in the stack trace.
470 $associated_class->add_method($handle => subname $name, sub {
471 my $proxy = (shift)->$accessor();
473 || confess "Cannot delegate $handle to $method_to_call because " .
474 "the value of " . $self->name . " is not defined";
475 $proxy->$method_to_call(@_);
484 # private methods to help delegation ...
486 sub _canonicalize_handles {
488 my $handles = $self->handles;
489 if (my $handle_type = ref($handles)) {
490 if ($handle_type eq 'HASH') {
493 elsif ($handle_type eq 'ARRAY') {
494 return map { $_ => $_ } @{$handles};
496 elsif ($handle_type eq 'Regexp') {
497 ($self->has_type_constraint)
498 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
499 return map { ($_ => $_) }
500 grep { /$handles/ } $self->_get_delegate_method_list;
502 elsif ($handle_type eq 'CODE') {
503 return $handles->($self, $self->_find_delegate_metaclass);
506 confess "Unable to canonicalize the 'handles' option with $handles";
510 my $role_meta = eval { $handles->meta };
512 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
515 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
516 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
518 return map { $_ => $_ } (
519 $role_meta->get_method_list,
520 $role_meta->get_required_method_list
525 sub _find_delegate_metaclass {
527 if (my $class = $self->_isa_metadata) {
528 # if the class does have
529 # a meta method, use it
530 return $class->meta if $class->can('meta');
531 # otherwise we might be
532 # dealing with a non-Moose
533 # class, and need to make
535 return Moose::Meta::Class->initialize($class);
537 elsif (my $role = $self->_does_metadata) {
538 # our role will always have
543 confess "Cannot find delegate metaclass for attribute " . $self->name;
547 sub _get_delegate_method_list {
549 my $meta = $self->_find_delegate_metaclass;
550 if ($meta->isa('Class::MOP::Class')) {
551 return map { $_->{name} } # NOTE: !never! delegate &meta
552 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
553 $meta->compute_all_applicable_methods;
555 elsif ($meta->isa('Moose::Meta::Role')) {
556 return $meta->get_method_list;
559 confess "Unable to recognize the delegate metaclass '$meta'";
571 Moose::Meta::Attribute - The Moose attribute metaclass
575 This is a subclass of L<Class::MOP::Attribute> with Moose specific
578 For the most part, the only time you will ever encounter an
579 instance of this class is if you are doing some serious deep
580 introspection. To really understand this class, you need to refer
581 to the L<Class::MOP::Attribute> documentation.
585 =head2 Overridden methods
587 These methods override methods in L<Class::MOP::Attribute> and add
588 Moose specific features. You can safely assume though that they
589 will behave just as L<Class::MOP::Attribute> does.
597 =item B<initialize_instance_slot>
599 =item B<install_accessors>
601 =item B<accessor_metaclass>
607 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
612 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
614 Before setting the value, a check is made on the type constraint of
615 the attribute, if it has one, to see if the value passes it. If the
616 value fails to pass, the set operation dies with a L<Carp/confess>.
618 Any coercion to convert values is done before checking the type constraint.
620 To check a value against a type constraint before setting it, fetch the
621 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
622 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
623 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
628 =head2 Additional Moose features
630 Moose attributes support type-constraint checking, weak reference
631 creation and type coercion.
635 =item B<clone_and_inherit_options>
637 This is to support the C<has '+foo'> feature, it clones an attribute
638 from a superclass and allows a very specific set of changes to be made
641 =item B<has_type_constraint>
643 Returns true if this meta-attribute has a type constraint.
645 =item B<type_constraint>
647 A read-only accessor for this meta-attribute's type constraint. For
648 more information on what you can do with this, see the documentation
649 for L<Moose::Meta::TypeConstraint>.
653 Returns true if this meta-attribute performs delegation.
657 This returns the value which was passed into the handles option.
661 Returns true if this meta-attribute produces a weak reference.
665 Returns true if this meta-attribute is required to have a value.
669 Returns true if this meta-attribute should be initialized lazily.
671 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
673 =item B<is_lazy_build>
675 Returns true if this meta-attribute should be initialized lazily through
676 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
677 make your attribute required and lazy. In addition it will set the builder, clearer
678 and predicate options for you using the following convention.
680 #If your attribute name starts with an underscore:
681 has '_foo' => (lazy_build => 1);
683 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
685 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
687 #If your attribute name does not start with an underscore:
688 has 'foo' => (lazy_build => 1);
690 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
692 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
694 The reason for the different naming of the C<builder> is that the C<builder>
695 method is a private method while the C<clearer> and C<predicate> methods
698 NOTE: This means your class should provide a method whose name matches the value
699 of the builder part, in this case _build__foo or _build_foo.
701 =item B<should_coerce>
703 Returns true if this meta-attribute should perform type coercion.
705 =item B<should_auto_deref>
707 Returns true if this meta-attribute should perform automatic
710 NOTE: This can only be done for attributes whose type constraint is
711 either I<ArrayRef> or I<HashRef>.
715 Returns true if this meta-attribute has a trigger set.
719 This is a CODE reference which will be executed every time the
720 value of an attribute is assigned. The CODE ref will get two values,
721 the invocant and the new value. This can be used to handle I<basic>
722 bi-directional relations.
724 =item B<documentation>
726 This is a string which contains the documentation for this attribute.
727 It serves no direct purpose right now, but it might in the future
728 in some kind of automated documentation system perhaps.
730 =item B<has_documentation>
732 Returns true if this meta-attribute has any documentation.
738 All complex software has bugs lurking in it, and this module is no
739 exception. If you find a bug please either email me, or add the bug
744 Stevan Little E<lt>stevan@iinteractive.comE<gt>
746 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
748 =head1 COPYRIGHT AND LICENSE
750 Copyright 2006-2008 by Infinity Interactive, Inc.
752 L<http://www.iinteractive.com>
754 This library is free software; you can redistribute it and/or modify
755 it under the same terms as Perl itself.