2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
11 our $VERSION = '0.15';
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.
397 next if $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
399 if ((reftype($method_to_call) || '') eq 'CODE') {
400 $associated_class->add_method($handle => $method_to_call);
403 $associated_class->add_method($handle => sub {
405 # we should check for lack of
406 # a callable return value from
408 my $proxy = (shift)->$accessor();
410 goto &{ $proxy->can($method_to_call) };
419 # private methods to help delegation ...
421 sub _canonicalize_handles {
423 my $handles = $self->handles;
424 if (my $handle_type = ref($handles)) {
425 if ($handle_type eq 'HASH') {
428 elsif ($handle_type eq 'ARRAY') {
429 return map { $_ => $_ } @{$handles};
431 elsif ($handle_type eq 'Regexp') {
432 ($self->has_type_constraint)
433 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
434 return map { ($_ => $_) }
435 grep { /$handles/ } $self->_get_delegate_method_list;
437 elsif ($handle_type eq 'CODE') {
438 return $handles->($self, $self->_find_delegate_metaclass);
441 confess "Unable to canonicalize the 'handles' option with $handles";
445 my $role_meta = eval { $handles->meta };
447 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
450 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
451 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
453 return map { $_ => $_ } (
454 $role_meta->get_method_list,
455 $role_meta->get_required_method_list
460 sub _find_delegate_metaclass {
462 if (my $class = $self->_isa_metadata) {
463 # if the class does have
464 # a meta method, use it
465 return $class->meta if $class->can('meta');
466 # otherwise we might be
467 # dealing with a non-Moose
468 # class, and need to make
470 return Moose::Meta::Class->initialize($class);
472 elsif (my $role = $self->_does_metadata) {
473 # our role will always have
478 confess "Cannot find delegate metaclass for attribute " . $self->name;
482 sub _get_delegate_method_list {
484 my $meta = $self->_find_delegate_metaclass;
485 if ($meta->isa('Class::MOP::Class')) {
486 return map { $_->{name} } # NOTE: !never! delegate &meta
487 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
488 $meta->compute_all_applicable_methods;
490 elsif ($meta->isa('Moose::Meta::Role')) {
491 return $meta->get_method_list;
494 confess "Unable to recognize the delegate metaclass '$meta'";
506 Moose::Meta::Attribute - The Moose attribute metaclass
510 This is a subclass of L<Class::MOP::Attribute> with Moose specific
513 For the most part, the only time you will ever encounter an
514 instance of this class is if you are doing some serious deep
515 introspection. To really understand this class, you need to refer
516 to the L<Class::MOP::Attribute> documentation.
520 =head2 Overridden methods
522 These methods override methods in L<Class::MOP::Attribute> and add
523 Moose specific features. You can safely assume though that they
524 will behave just as L<Class::MOP::Attribute> does.
530 =item B<initialize_instance_slot>
532 =item B<install_accessors>
534 =item B<accessor_metaclass>
540 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
545 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
547 Before setting the value, a check is made on the type constraint of
548 the attribute, if it has one, to see if the value passes it. If the
549 value fails to pass, the set operation dies with a L<Carp/confess>.
551 Any coercion to convert values is done before checking the type constraint.
553 To check a value against a type constraint before setting it, fetch the
554 attribute instance using L<Moose::Meta::Attribute/find_attribute_by_name>,
555 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
556 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
561 =head2 Additional Moose features
563 Moose attributes support type-constraint checking, weak reference
564 creation and type coercion.
568 =item B<clone_and_inherit_options>
570 This is to support the C<has '+foo'> feature, it clones an attribute
571 from a superclass and allows a very specific set of changes to be made
574 =item B<has_type_constraint>
576 Returns true if this meta-attribute has a type constraint.
578 =item B<type_constraint>
580 A read-only accessor for this meta-attribute's type constraint. For
581 more information on what you can do with this, see the documentation
582 for L<Moose::Meta::TypeConstraint>.
586 Returns true if this meta-attribute performs delegation.
590 This returns the value which was passed into the handles option.
594 Returns true if this meta-attribute produces a weak reference.
598 Returns true if this meta-attribute is required to have a value.
602 Returns true if this meta-attribute should be initialized lazily.
604 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
606 =item B<is_lazy_build>
608 Returns true if this meta-attribute should be initialized lazily through
609 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
610 make your attribute required and lazy. In addition it will set the builder, clearer
611 and predicate options for you using the following convention.
613 #If your attribute name starts with an underscore:
614 has '_foo' => (lazy_build => 1);
616 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
618 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
620 #If your attribute name does not start with an underscore:
621 has 'foo' => (lazy_build => 1);
623 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
625 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
627 The reason for the different naming of the C<builder> is that the C<builder>
628 method is a private method while the C<clearer> and C<predicate> methods
631 NOTE: This means your class should provide a method whose name matches the value
632 of the builder part, in this case _build__foo or _build_foo.
634 =item B<should_coerce>
636 Returns true if this meta-attribute should perform type coercion.
638 =item B<should_auto_deref>
640 Returns true if this meta-attribute should perform automatic
643 NOTE: This can only be done for attributes whose type constraint is
644 either I<ArrayRef> or I<HashRef>.
648 Returns true if this meta-attribute has a trigger set.
652 This is a CODE reference which will be executed every time the
653 value of an attribute is assigned. The CODE ref will get two values,
654 the invocant and the new value. This can be used to handle I<basic>
655 bi-directional relations.
657 =item B<documentation>
659 This is a string which contains the documentation for this attribute.
660 It serves no direct purpose right now, but it might in the future
661 in some kind of automated documentation system perhaps.
663 =item B<has_documentation>
665 Returns true if this meta-attribute has any documentation.
671 All complex software has bugs lurking in it, and this module is no
672 exception. If you find a bug please either email me, or add the bug
677 Stevan Little E<lt>stevan@iinteractive.comE<gt>
679 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
681 =head1 COPYRIGHT AND LICENSE
683 Copyright 2006, 2007 by Infinity Interactive, Inc.
685 L<http://www.iinteractive.com>
687 This library is free software; you can redistribute it and/or modify
688 it under the same terms as Perl itself.