2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
11 our $VERSION = '0.16';
12 our $AUTHORITY = 'cpan:STEVAN';
14 use Moose::Meta::Method::Accessor;
15 use Moose::Util::TypeConstraints ();
17 use base 'Class::MOP::Attribute';
19 # options which are not directly used
20 # but we store them for metadata purposes
21 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
22 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
23 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
25 # these are actual options for the attrs
26 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
27 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
28 __PACKAGE__->meta->add_attribute('lazy_build' => (reader => 'is_lazy_build' ));
29 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
30 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
31 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
32 __PACKAGE__->meta->add_attribute('type_constraint' => (
33 reader => 'type_constraint',
34 predicate => 'has_type_constraint',
36 __PACKAGE__->meta->add_attribute('trigger' => (
38 predicate => 'has_trigger',
40 __PACKAGE__->meta->add_attribute('handles' => (
42 predicate => 'has_handles',
44 __PACKAGE__->meta->add_attribute('documentation' => (
45 reader => 'documentation',
46 predicate => 'has_documentation',
50 my ($class, $name, %options) = @_;
51 $class->_process_options($name, \%options);
52 return $class->SUPER::new($name, %options);
55 sub clone_and_inherit_options {
56 my ($self, %options) = @_;
57 # you can change default, required, coerce, documentation and lazy
59 foreach my $legal_option (qw(default coerce required documentation lazy)) {
60 if (exists $options{$legal_option}) {
61 $actual_options{$legal_option} = $options{$legal_option};
62 delete $options{$legal_option};
66 # handles can only be added, not changed
67 if ($options{handles}) {
68 confess "You can only add the 'handles' option, you cannot change it"
69 if $self->has_handles;
70 $actual_options{handles} = $options{handles};
71 delete $options{handles};
74 # isa can be changed, but only if the
75 # new type is a subtype
78 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
79 $type_constraint = $options{isa};
82 $type_constraint = Moose::Util::TypeConstraints::find_or_create_type_constraint(
85 (defined $type_constraint)
86 || confess "Could not find the type constraint '" . $options{isa} . "'";
89 # check here to see if the new type
90 # is a subtype of the old one
91 ($type_constraint->is_subtype_of($self->type_constraint->name))
92 || confess "New type constraint setting must be a subtype of inherited one"
93 # iff we have a type constraint that is ...
94 if $self->has_type_constraint;
96 $actual_options{type_constraint} = $type_constraint;
99 (scalar keys %options == 0)
100 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
101 $self->clone(%actual_options);
104 sub _process_options {
105 my ($class, $name, $options) = @_;
107 if (exists $options->{is}) {
108 if ($options->{is} eq 'ro') {
109 $options->{reader} ||= $name;
110 (!exists $options->{trigger})
111 || confess "Cannot have a trigger on a read-only attribute";
113 elsif ($options->{is} eq 'rw') {
114 $options->{accessor} = $name;
115 ((reftype($options->{trigger}) || '') eq 'CODE')
116 || confess "Trigger must be a CODE ref"
117 if exists $options->{trigger};
120 confess "I do not understand this option (is => " . $options->{is} . ")"
124 if (exists $options->{isa}) {
125 if (exists $options->{does}) {
126 if (eval { $options->{isa}->can('does') }) {
127 ($options->{isa}->does($options->{does}))
128 || confess "Cannot have an isa option and a does option if the isa does not do the does";
131 confess "Cannot have an isa option which cannot ->does()";
135 # allow for anon-subtypes here ...
136 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
137 $options->{type_constraint} = $options->{isa};
140 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
142 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
143 constraint => sub { $_[0]->isa($options->{isa}) }
148 elsif (exists $options->{does}) {
149 # allow for anon-subtypes here ...
150 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
151 $options->{type_constraint} = $options->{isa};
154 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
155 $options->{does} => {
156 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
157 constraint => sub { $_[0]->does($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";
166 confess "You cannot have a weak reference to a coerced value"
167 if $options->{weak_ref};
170 if (exists $options->{auto_deref} && $options->{auto_deref}) {
171 (exists $options->{type_constraint})
172 || confess "You cannot auto-dereference without specifying a type constraint";
173 ($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";
178 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
179 confess("You can not use lazy_build and default for the same attribute")
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} || exists $options->{builder} )
196 || confess "You cannot have lazy attribute without specifying a default value for it";
201 sub initialize_instance_slot {
202 my ($self, $meta_instance, $instance, $params) = @_;
203 my $init_arg = $self->init_arg();
204 # try to fetch the init arg from the %params ...
208 if (exists $params->{$init_arg}) {
209 $val = $params->{$init_arg};
213 # skip it if it's lazy
214 return if $self->is_lazy;
215 # and die if it's required and doesn't have a default value
216 confess "Attribute (" . $self->name . ") is required"
217 if $self->is_required && !$self->has_default && !$self->has_builder;
219 # if nothing was in the %params, we can use the
220 # attribute's default value (if it has one)
221 if ($self->has_default) {
222 $val = $self->default($instance);
225 elsif ($self->has_builder) {
226 if (my $builder = $instance->can($self->builder)){
227 $val = $instance->$builder;
231 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
236 return unless $value_is_set;
238 if ($self->has_type_constraint) {
239 my $type_constraint = $self->type_constraint;
240 if ($self->should_coerce && $type_constraint->has_coercion) {
241 $val = $type_constraint->coerce($val);
243 (defined($type_constraint->check($val)))
244 || confess "Attribute (" .
246 ") does not pass the type constraint (" .
247 $type_constraint->name .
250 ? (blessed($val) && overload::Overloaded($val)
251 ? overload::StrVal($val)
257 $meta_instance->set_slot_value($instance, $self->name, $val);
258 $meta_instance->weaken_slot_value($instance, $self->name)
259 if ref $val && $self->is_weak_ref;
265 my ($self, $instance, $value) = @_;
267 my $attr_name = $self->name;
269 if ($self->is_required) {
271 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
274 if ($self->has_type_constraint) {
276 my $type_constraint = $self->type_constraint;
278 if ($self->should_coerce) {
279 $value = $type_constraint->coerce($value);
281 defined($type_constraint->_compiled_type_constraint->($value))
282 || confess "Attribute ($attr_name) does not pass the type constraint ("
283 . $type_constraint->name
287 (blessed($value) && overload::Overloaded($value)
288 ? overload::StrVal($value)
295 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
298 $meta_instance->set_slot_value($instance, $attr_name, $value);
300 if (ref $value && $self->is_weak_ref) {
301 $meta_instance->weaken_slot_value($instance, $attr_name);
304 if ($self->has_trigger) {
305 $self->trigger->($instance, $value, $self);
310 my ($self, $instance) = @_;
312 if ($self->is_lazy) {
313 unless ($self->has_value($instance)) {
314 if ($self->has_default) {
315 my $default = $self->default($instance);
316 $self->set_value($instance, $default);
318 if ( $self->has_builder ){
319 if (my $builder = $instance->can($self->builder)){
320 $self->set_value($instance, $instance->$builder);
323 confess(blessed($instance)
324 . " does not support builder method '"
326 . "' for attribute '"
332 $self->set_value($instance, undef);
337 if ($self->should_auto_deref) {
339 my $type_constraint = $self->type_constraint;
341 if ($type_constraint->is_a_type_of('ArrayRef')) {
342 my $rv = $self->SUPER::get_value($instance);
343 return unless defined $rv;
344 return wantarray ? @{ $rv } : $rv;
346 elsif ($type_constraint->is_a_type_of('HashRef')) {
347 my $rv = $self->SUPER::get_value($instance);
348 return unless defined $rv;
349 return wantarray ? %{ $rv } : $rv;
352 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
358 return $self->SUPER::get_value($instance);
362 ## installing accessors
364 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
366 sub install_accessors {
368 $self->SUPER::install_accessors(@_);
370 if ($self->has_handles) {
373 # Here we canonicalize the 'handles' option
374 # this will sort out any details and always
375 # return an hash of methods which we want
376 # to delagate to, see that method for details
377 my %handles = $self->_canonicalize_handles();
379 # find the accessor method for this attribute
380 my $accessor = $self->get_read_method_ref;
381 # then unpack it if we need too ...
382 $accessor = $accessor->body if blessed $accessor;
384 # install the delegation ...
385 my $associated_class = $self->associated_class;
386 foreach my $handle (keys %handles) {
387 my $method_to_call = $handles{$handle};
389 (!$associated_class->has_method($handle))
390 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
393 # handles is not allowed to delegate
394 # any of these methods, as they will
395 # override the ones in your class, which
396 # is almost certainly not what you want.
398 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
399 #cluck("Not delegating method '$handle' because it is a core method") and
400 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
402 if ((reftype($method_to_call) || '') eq 'CODE') {
403 $associated_class->add_method($handle => $method_to_call);
406 $associated_class->add_method($handle => sub {
408 # we should check for lack of
409 # a callable return value from
411 my $proxy = (shift)->$accessor();
413 goto &{ $proxy->can($method_to_call) };
422 # private methods to help delegation ...
424 sub _canonicalize_handles {
426 my $handles = $self->handles;
427 if (my $handle_type = ref($handles)) {
428 if ($handle_type eq 'HASH') {
431 elsif ($handle_type eq 'ARRAY') {
432 return map { $_ => $_ } @{$handles};
434 elsif ($handle_type eq 'Regexp') {
435 ($self->has_type_constraint)
436 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
437 return map { ($_ => $_) }
438 grep { /$handles/ } $self->_get_delegate_method_list;
440 elsif ($handle_type eq 'CODE') {
441 return $handles->($self, $self->_find_delegate_metaclass);
444 confess "Unable to canonicalize the 'handles' option with $handles";
448 my $role_meta = eval { $handles->meta };
450 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
453 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
454 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
456 return map { $_ => $_ } (
457 $role_meta->get_method_list,
458 $role_meta->get_required_method_list
463 sub _find_delegate_metaclass {
465 if (my $class = $self->_isa_metadata) {
466 # if the class does have
467 # a meta method, use it
468 return $class->meta if $class->can('meta');
469 # otherwise we might be
470 # dealing with a non-Moose
471 # class, and need to make
473 return Moose::Meta::Class->initialize($class);
475 elsif (my $role = $self->_does_metadata) {
476 # our role will always have
481 confess "Cannot find delegate metaclass for attribute " . $self->name;
485 sub _get_delegate_method_list {
487 my $meta = $self->_find_delegate_metaclass;
488 if ($meta->isa('Class::MOP::Class')) {
489 return map { $_->{name} } # NOTE: !never! delegate &meta
490 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
491 $meta->compute_all_applicable_methods;
493 elsif ($meta->isa('Moose::Meta::Role')) {
494 return $meta->get_method_list;
497 confess "Unable to recognize the delegate metaclass '$meta'";
509 Moose::Meta::Attribute - The Moose attribute metaclass
513 This is a subclass of L<Class::MOP::Attribute> with Moose specific
516 For the most part, the only time you will ever encounter an
517 instance of this class is if you are doing some serious deep
518 introspection. To really understand this class, you need to refer
519 to the L<Class::MOP::Attribute> documentation.
523 =head2 Overridden methods
525 These methods override methods in L<Class::MOP::Attribute> and add
526 Moose specific features. You can safely assume though that they
527 will behave just as L<Class::MOP::Attribute> does.
533 =item B<initialize_instance_slot>
535 =item B<install_accessors>
537 =item B<accessor_metaclass>
543 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
548 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
550 Before setting the value, a check is made on the type constraint of
551 the attribute, if it has one, to see if the value passes it. If the
552 value fails to pass, the set operation dies with a L<Carp/confess>.
554 Any coercion to convert values is done before checking the type constraint.
556 To check a value against a type constraint before setting it, fetch the
557 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
558 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
559 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
564 =head2 Additional Moose features
566 Moose attributes support type-constraint checking, weak reference
567 creation and type coercion.
571 =item B<clone_and_inherit_options>
573 This is to support the C<has '+foo'> feature, it clones an attribute
574 from a superclass and allows a very specific set of changes to be made
577 =item B<has_type_constraint>
579 Returns true if this meta-attribute has a type constraint.
581 =item B<type_constraint>
583 A read-only accessor for this meta-attribute's type constraint. For
584 more information on what you can do with this, see the documentation
585 for L<Moose::Meta::TypeConstraint>.
589 Returns true if this meta-attribute performs delegation.
593 This returns the value which was passed into the handles option.
597 Returns true if this meta-attribute produces a weak reference.
601 Returns true if this meta-attribute is required to have a value.
605 Returns true if this meta-attribute should be initialized lazily.
607 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
609 =item B<is_lazy_build>
611 Returns true if this meta-attribute should be initialized lazily through
612 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
613 make your attribute required and lazy. In addition it will set the builder, clearer
614 and predicate options for you using the following convention.
616 #If your attribute name starts with an underscore:
617 has '_foo' => (lazy_build => 1);
619 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
621 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
623 #If your attribute name does not start with an underscore:
624 has 'foo' => (lazy_build => 1);
626 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
628 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
630 The reason for the different naming of the C<builder> is that the C<builder>
631 method is a private method while the C<clearer> and C<predicate> methods
634 NOTE: This means your class should provide a method whose name matches the value
635 of the builder part, in this case _build__foo or _build_foo.
637 =item B<should_coerce>
639 Returns true if this meta-attribute should perform type coercion.
641 =item B<should_auto_deref>
643 Returns true if this meta-attribute should perform automatic
646 NOTE: This can only be done for attributes whose type constraint is
647 either I<ArrayRef> or I<HashRef>.
651 Returns true if this meta-attribute has a trigger set.
655 This is a CODE reference which will be executed every time the
656 value of an attribute is assigned. The CODE ref will get two values,
657 the invocant and the new value. This can be used to handle I<basic>
658 bi-directional relations.
660 =item B<documentation>
662 This is a string which contains the documentation for this attribute.
663 It serves no direct purpose right now, but it might in the future
664 in some kind of automated documentation system perhaps.
666 =item B<has_documentation>
668 Returns true if this meta-attribute has any documentation.
674 All complex software has bugs lurking in it, and this module is no
675 exception. If you find a bug please either email me, or add the bug
680 Stevan Little E<lt>stevan@iinteractive.comE<gt>
682 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
684 =head1 COPYRIGHT AND LICENSE
686 Copyright 2006-2008 by Infinity Interactive, Inc.
688 L<http://www.iinteractive.com>
690 This library is free software; you can redistribute it and/or modify
691 it under the same terms as Perl itself.