2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
11 our $VERSION = '0.13';
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 $type_constraint = Moose::Util::TypeConstraints::find_type_constraint($options{isa});
83 (defined $type_constraint)
84 || confess "Could not find the type constraint '" . $options{isa} . "'";
87 # check here to see if the new type
88 # is a subtype of the old one
89 ($type_constraint->is_subtype_of($self->type_constraint->name))
90 || confess "New type constraint setting must be a subtype of inherited one"
91 # iff we have a type constraint that is ...
92 if $self->has_type_constraint;
94 $actual_options{type_constraint} = $type_constraint;
97 (scalar keys %options == 0)
98 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
99 $self->clone(%actual_options);
102 sub _process_options {
103 my ($class, $name, $options) = @_;
105 if (exists $options->{is}) {
106 if ($options->{is} eq 'ro') {
107 $options->{reader} ||= $name;
108 (!exists $options->{trigger})
109 || confess "Cannot have a trigger on a read-only attribute";
111 elsif ($options->{is} eq 'rw') {
112 $options->{accessor} = $name;
113 ((reftype($options->{trigger}) || '') eq 'CODE')
114 || confess "Trigger must be a CODE ref"
115 if exists $options->{trigger};
118 confess "I do not understand this option (is => " . $options->{is} . ")"
122 if (exists $options->{isa}) {
124 if (exists $options->{does}) {
125 if (eval { $options->{isa}->can('does') }) {
126 ($options->{isa}->does($options->{does}))
127 || confess "Cannot have an isa option and a does option if the isa does not do the does";
130 confess "Cannot have an isa option which cannot ->does()";
134 # allow for anon-subtypes here ...
135 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
136 $options->{type_constraint} = $options->{isa};
139 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
141 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
142 constraint => sub { $_[0]->isa($options->{isa}) }
147 elsif (exists $options->{does}) {
148 # allow for anon-subtypes here ...
149 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
150 $options->{type_constraint} = $options->{isa};
153 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
154 $options->{does} => {
155 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
156 constraint => sub { $_[0]->does($options->{does}) }
162 if (exists $options->{coerce} && $options->{coerce}) {
163 (exists $options->{type_constraint})
164 || confess "You cannot have coercion without specifying a type constraint";
165 confess "You cannot have a weak reference to a coerced value"
166 if $options->{weak_ref};
169 if (exists $options->{auto_deref} && $options->{auto_deref}) {
170 (exists $options->{type_constraint})
171 || confess "You cannot auto-dereference without specifying a type constraint";
172 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
173 $options->{type_constraint}->is_a_type_of('HashRef'))
174 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
177 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
178 confess("You can not use lazy_build and default for the same attribute")
179 if exists $options->{default};
180 $options->{lazy} = 1;
181 $options->{required} = 1;
183 $options->{builder} ||= "_build${name}";
184 $options->{clearer} ||= "_clear${name}";
185 $options->{predicate} ||= "_has${name}";
187 $options->{builder} ||= "build_${name}";
188 $options->{clearer} ||= "clear_${name}";
189 $options->{predicate} ||= "has_${name}";
193 if (exists $options->{lazy} && $options->{lazy}) {
194 (exists $options->{default} || exists $options->{builder} )
195 || confess "You cannot have lazy attribute without specifying a default value for it";
200 sub initialize_instance_slot {
201 my ($self, $meta_instance, $instance, $params) = @_;
202 my $init_arg = $self->init_arg();
203 # try to fetch the init arg from the %params ...
206 if (exists $params->{$init_arg}) {
207 $val = $params->{$init_arg};
209 if (!defined $val && $self->is_required) {
210 confess "Attribute (" . $self->name . ") is required and cannot be undef";
214 # skip it if it's lazy
215 return if $self->is_lazy;
216 # and die if it's required and doesn't have a default value
217 confess "Attribute (" . $self->name . ") is required"
218 if $self->is_required && !$self->has_default && !$self->has_builder;
221 # if nothing was in the %params, we can use the
222 # attribute's default value (if it has one)
223 if (!defined $val && $self->has_default) {
224 $val = $self->default($instance);
225 } elsif (!defined $val && $self->has_builder) {
226 my $builder = $self->builder;
227 if($builder = $instance->can($builder)){
228 $val = $instance->$builder;
230 confess(blessed($instance)." does not support builder method '$builder' for attribute '" . $self->name . "'");
234 if (defined $val || $self->has_default) {
235 if ($self->has_type_constraint) {
236 my $type_constraint = $self->type_constraint;
237 if ($self->should_coerce && $type_constraint->has_coercion) {
238 $val = $type_constraint->coerce($val);
240 (defined($type_constraint->check($val)))
241 || confess "Attribute (" .
243 ") does not pass the type constraint (" .
244 $type_constraint->name .
247 ? (blessed($val) && overload::Overloaded($val)
248 ? overload::StrVal($val)
255 $meta_instance->set_slot_value($instance, $self->name, $val);
256 $meta_instance->weaken_slot_value($instance, $self->name)
257 if ref $val && $self->is_weak_ref;
263 my ($self, $instance, $value) = @_;
265 my $attr_name = $self->name;
267 if ($self->is_required) {
269 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
272 if ($self->has_type_constraint) {
274 my $type_constraint = $self->type_constraint;
276 if ($self->should_coerce) {
277 $value = $type_constraint->coerce($value);
279 defined($type_constraint->_compiled_type_constraint->($value))
280 || confess "Attribute ($attr_name) does not pass the type constraint ("
281 . $type_constraint->name
285 (blessed($value) && overload::Overloaded($value)
286 ? overload::StrVal($value)
293 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
296 $meta_instance->set_slot_value($instance, $attr_name, $value);
298 if (ref $value && $self->is_weak_ref) {
299 $meta_instance->weaken_slot_value($instance, $attr_name);
302 if ($self->has_trigger) {
303 $self->trigger->($instance, $value, $self);
308 my ($self, $instance) = @_;
310 if ($self->is_lazy) {
311 unless ($self->has_value($instance)) {
312 if ($self->has_default) {
313 my $default = $self->default($instance);
314 $self->set_value($instance, $default);
316 if ( $self->has_builder ){
317 my $builder = $self->builder;
318 if($builder = $instance->can($builder)){
319 $self->set_value($instance, $instance->$builder);
321 confess(blessed($instance)." does not support builder method '$builder' for attribute '" . $self->name . "'");
324 $self->set_value($instance, undef);
329 if ($self->should_auto_deref) {
331 my $type_constraint = $self->type_constraint;
333 if ($type_constraint->is_a_type_of('ArrayRef')) {
334 my $rv = $self->SUPER::get_value($instance);
335 return unless defined $rv;
336 return wantarray ? @{ $rv } : $rv;
338 elsif ($type_constraint->is_a_type_of('HashRef')) {
339 my $rv = $self->SUPER::get_value($instance);
340 return unless defined $rv;
341 return wantarray ? %{ $rv } : $rv;
344 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
350 return $self->SUPER::get_value($instance);
354 ## installing accessors
356 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
358 sub install_accessors {
360 $self->SUPER::install_accessors(@_);
362 if ($self->has_handles) {
365 # Here we canonicalize the 'handles' option
366 # this will sort out any details and always
367 # return an hash of methods which we want
368 # to delagate to, see that method for details
369 my %handles = $self->_canonicalize_handles();
371 # find the name of the accessor for this attribute
372 my $accessor_name = $self->reader || $self->accessor;
373 (defined $accessor_name)
374 || confess "You cannot install delegation without a reader or accessor for the attribute";
376 # make sure we handle HASH accessors correctly
377 ($accessor_name) = keys %{$accessor_name}
378 if ref($accessor_name) eq 'HASH';
380 # install the delegation ...
381 my $associated_class = $self->associated_class;
382 foreach my $handle (keys %handles) {
383 my $method_to_call = $handles{$handle};
385 (!$associated_class->has_method($handle))
386 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
389 # handles is not allowed to delegate
390 # any of these methods, as they will
391 # override the ones in your class, which
392 # is almost certainly not what you want.
393 next if $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
395 if ((reftype($method_to_call) || '') eq 'CODE') {
396 $associated_class->add_method($handle => $method_to_call);
399 $associated_class->add_method($handle => sub {
401 # we should check for lack of
402 # a callable return value from
404 my $proxy = (shift)->$accessor_name();
406 goto &{ $proxy->can($method_to_call)};
415 # private methods to help delegation ...
417 sub _canonicalize_handles {
419 my $handles = $self->handles;
420 if (my $handle_type = ref($handles)) {
421 if ($handle_type eq 'HASH') {
424 elsif ($handle_type eq 'ARRAY') {
425 return map { $_ => $_ } @{$handles};
427 elsif ($handle_type eq 'Regexp') {
428 ($self->has_type_constraint)
429 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
430 return map { ($_ => $_) }
431 grep { /$handles/ } $self->_get_delegate_method_list;
433 elsif ($handle_type eq 'CODE') {
434 return $handles->($self, $self->_find_delegate_metaclass);
437 confess "Unable to canonicalize the 'handles' option with $handles";
441 my $role_meta = eval { $handles->meta };
443 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
446 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
447 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
449 return map { $_ => $_ } (
450 $role_meta->get_method_list,
451 $role_meta->get_required_method_list
456 sub _find_delegate_metaclass {
458 if (my $class = $self->_isa_metadata) {
459 # if the class does have
460 # a meta method, use it
461 return $class->meta if $class->can('meta');
462 # otherwise we might be
463 # dealing with a non-Moose
464 # class, and need to make
466 return Moose::Meta::Class->initialize($class);
468 elsif (my $role = $self->_does_metadata) {
469 # our role will always have
474 confess "Cannot find delegate metaclass for attribute " . $self->name;
478 sub _get_delegate_method_list {
480 my $meta = $self->_find_delegate_metaclass;
481 if ($meta->isa('Class::MOP::Class')) {
482 return map { $_->{name} } # NOTE: !never! delegate &meta
483 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
484 $meta->compute_all_applicable_methods;
486 elsif ($meta->isa('Moose::Meta::Role')) {
487 return $meta->get_method_list;
490 confess "Unable to recognize the delegate metaclass '$meta'";
502 Moose::Meta::Attribute - The Moose attribute metaclass
506 This is a subclass of L<Class::MOP::Attribute> with Moose specific
509 For the most part, the only time you will ever encounter an
510 instance of this class is if you are doing some serious deep
511 introspection. To really understand this class, you need to refer
512 to the L<Class::MOP::Attribute> documentation.
516 =head2 Overridden methods
518 These methods override methods in L<Class::MOP::Attribute> and add
519 Moose specific features. You can safely assume though that they
520 will behave just as L<Class::MOP::Attribute> does.
526 =item B<initialize_instance_slot>
528 =item B<install_accessors>
530 =item B<accessor_metaclass>
536 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
541 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
543 Before setting the value, a check is made on the type constraint of
544 the attribute, if it has one, to see if the value passes it. If the
545 value fails to pass, the set operation dies with a L<Carp/confess>.
547 Any coercion to convert values is done before checking the type constraint.
549 To check a value against a type constraint before setting it, fetch the
550 attribute instance using L<Moose::Meta::Attribute/find_attribute_by_name>,
551 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
552 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
557 =head2 Additional Moose features
559 Moose attributes support type-constraint checking, weak reference
560 creation and type coercion.
564 =item B<clone_and_inherit_options>
566 This is to support the C<has '+foo'> feature, it clones an attribute
567 from a superclass and allows a very specific set of changes to be made
570 =item B<has_type_constraint>
572 Returns true if this meta-attribute has a type constraint.
574 =item B<type_constraint>
576 A read-only accessor for this meta-attribute's type constraint. For
577 more information on what you can do with this, see the documentation
578 for L<Moose::Meta::TypeConstraint>.
582 Returns true if this meta-attribute performs delegation.
586 This returns the value which was passed into the handles option.
590 Returns true if this meta-attribute produces a weak reference.
594 Returns true if this meta-attribute is required to have a value.
598 Returns true if this meta-attribute should be initialized lazily.
600 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
602 =item B<is_lazy_build>
604 Returns true if this meta-attribute should be initialized lazily through
605 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
606 make your attribute required and lazy. In addition it will set the builder, clearer
607 and predicate options for you using the following convention.
609 #If your attribute name starts with an underscore:
610 has '_foo' => (lazy_build => 1);
612 has '_foo' => (lazy => 1, required => 1, builder => '_build_foo', predicate => '_has_foo', clearer => '_clear_foo');
614 has '_foo' => (lazy => 1, required => 1, builder => '_build_foo', default => sub{shift->_build_foo}, clearer => '_clear_foo');
616 #If your attribute name does not start with an underscore:
617 has 'foo' => (lazy => 1, required => 1, builder => 'build_foo', predicate => 'has_foo', clearer => 'clear_foo');
619 has '_foo' => (lazy => 1, required => 1, builder => '_build_foo', default => sub{shift->build_foo}, clearer => '_clear_foo');
621 NOTE: This means your class should provide a method whose name matches the value
622 of the builder part, in this case _build_foo or build_foo.
624 =item B<should_coerce>
626 Returns true if this meta-attribute should perform type coercion.
628 =item B<should_auto_deref>
630 Returns true if this meta-attribute should perform automatic
633 NOTE: This can only be done for attributes whose type constraint is
634 either I<ArrayRef> or I<HashRef>.
638 Returns true if this meta-attribute has a trigger set.
642 This is a CODE reference which will be executed every time the
643 value of an attribute is assigned. The CODE ref will get two values,
644 the invocant and the new value. This can be used to handle I<basic>
645 bi-directional relations.
647 =item B<documentation>
649 This is a string which contains the documentation for this attribute.
650 It serves no direct purpose right now, but it might in the future
651 in some kind of automated documentation system perhaps.
653 =item B<has_documentation>
655 Returns true if this meta-attribute has any documentation.
661 All complex software has bugs lurking in it, and this module is no
662 exception. If you find a bug please either email me, or add the bug
667 Stevan Little E<lt>stevan@iinteractive.comE<gt>
669 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
671 =head1 COPYRIGHT AND LICENSE
673 Copyright 2006, 2007 by Infinity Interactive, Inc.
675 L<http://www.iinteractive.com>
677 This library is free software; you can redistribute it and/or modify
678 it under the same terms as Perl itself.