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;
182 $options->{builder} ||= "_build_${name}";
184 $options->{clearer} ||= "_clear${name}";
185 $options->{predicate} ||= "_has${name}";
187 $options->{clearer} ||= "clear_${name}";
188 $options->{predicate} ||= "has_${name}";
192 if (exists $options->{lazy} && $options->{lazy}) {
193 (exists $options->{default} || exists $options->{builder} )
194 || confess "You cannot have lazy attribute without specifying a default value for it";
199 sub initialize_instance_slot {
200 my ($self, $meta_instance, $instance, $params) = @_;
201 my $init_arg = $self->init_arg();
202 # try to fetch the init arg from the %params ...
206 if (exists $params->{$init_arg}) {
207 $val = $params->{$init_arg};
211 # skip it if it's lazy
212 return if $self->is_lazy;
213 # and die if it's required and doesn't have a default value
214 confess "Attribute (" . $self->name . ") is required"
215 if $self->is_required && !$self->has_default && !$self->has_builder;
217 # if nothing was in the %params, we can use the
218 # attribute's default value (if it has one)
219 if ($self->has_default) {
220 $val = $self->default($instance);
222 } elsif ($self->has_builder) {
223 my $builder = $self->builder;
224 if($builder = $instance->can($builder)){
225 $val = $instance->$builder;
228 confess(blessed($instance)." does not support builder method '$builder' for attribute '" . $self->name . "'");
233 return unless $value_is_set;
235 if ($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)
254 $meta_instance->set_slot_value($instance, $self->name, $val);
255 $meta_instance->weaken_slot_value($instance, $self->name)
256 if ref $val && $self->is_weak_ref;
262 my ($self, $instance, $value) = @_;
264 my $attr_name = $self->name;
266 if ($self->is_required) {
268 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
271 if ($self->has_type_constraint) {
273 my $type_constraint = $self->type_constraint;
275 if ($self->should_coerce) {
276 $value = $type_constraint->coerce($value);
278 defined($type_constraint->_compiled_type_constraint->($value))
279 || confess "Attribute ($attr_name) does not pass the type constraint ("
280 . $type_constraint->name
284 (blessed($value) && overload::Overloaded($value)
285 ? overload::StrVal($value)
292 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
295 $meta_instance->set_slot_value($instance, $attr_name, $value);
297 if (ref $value && $self->is_weak_ref) {
298 $meta_instance->weaken_slot_value($instance, $attr_name);
301 if ($self->has_trigger) {
302 $self->trigger->($instance, $value, $self);
307 my ($self, $instance) = @_;
309 if ($self->is_lazy) {
310 unless ($self->has_value($instance)) {
311 if ($self->has_default) {
312 my $default = $self->default($instance);
313 $self->set_value($instance, $default);
315 if ( $self->has_builder ){
316 my $builder = $self->builder;
317 if($builder = $instance->can($builder)){
318 $self->set_value($instance, $instance->$builder);
320 confess(blessed($instance)." does not support builder method '$builder' for attribute '" . $self->name . "'");
323 $self->set_value($instance, undef);
328 if ($self->should_auto_deref) {
330 my $type_constraint = $self->type_constraint;
332 if ($type_constraint->is_a_type_of('ArrayRef')) {
333 my $rv = $self->SUPER::get_value($instance);
334 return unless defined $rv;
335 return wantarray ? @{ $rv } : $rv;
337 elsif ($type_constraint->is_a_type_of('HashRef')) {
338 my $rv = $self->SUPER::get_value($instance);
339 return unless defined $rv;
340 return wantarray ? %{ $rv } : $rv;
343 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
349 return $self->SUPER::get_value($instance);
353 ## installing accessors
355 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
357 sub install_accessors {
359 $self->SUPER::install_accessors(@_);
361 if ($self->has_handles) {
364 # Here we canonicalize the 'handles' option
365 # this will sort out any details and always
366 # return an hash of methods which we want
367 # to delagate to, see that method for details
368 my %handles = $self->_canonicalize_handles();
370 # find the name of the accessor for this attribute
371 my $accessor_name = $self->reader || $self->accessor;
372 (defined $accessor_name)
373 || confess "You cannot install delegation without a reader or accessor for the attribute";
375 # make sure we handle HASH accessors correctly
376 ($accessor_name) = keys %{$accessor_name}
377 if ref($accessor_name) eq 'HASH';
379 # install the delegation ...
380 my $associated_class = $self->associated_class;
381 foreach my $handle (keys %handles) {
382 my $method_to_call = $handles{$handle};
384 (!$associated_class->has_method($handle))
385 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
388 # handles is not allowed to delegate
389 # any of these methods, as they will
390 # override the ones in your class, which
391 # is almost certainly not what you want.
392 next if $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
394 if ((reftype($method_to_call) || '') eq 'CODE') {
395 $associated_class->add_method($handle => $method_to_call);
398 $associated_class->add_method($handle => sub {
400 # we should check for lack of
401 # a callable return value from
403 my $proxy = (shift)->$accessor_name();
405 goto &{ $proxy->can($method_to_call)};
414 # private methods to help delegation ...
416 sub _canonicalize_handles {
418 my $handles = $self->handles;
419 if (my $handle_type = ref($handles)) {
420 if ($handle_type eq 'HASH') {
423 elsif ($handle_type eq 'ARRAY') {
424 return map { $_ => $_ } @{$handles};
426 elsif ($handle_type eq 'Regexp') {
427 ($self->has_type_constraint)
428 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
429 return map { ($_ => $_) }
430 grep { /$handles/ } $self->_get_delegate_method_list;
432 elsif ($handle_type eq 'CODE') {
433 return $handles->($self, $self->_find_delegate_metaclass);
436 confess "Unable to canonicalize the 'handles' option with $handles";
440 my $role_meta = eval { $handles->meta };
442 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
445 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
446 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
448 return map { $_ => $_ } (
449 $role_meta->get_method_list,
450 $role_meta->get_required_method_list
455 sub _find_delegate_metaclass {
457 if (my $class = $self->_isa_metadata) {
458 # if the class does have
459 # a meta method, use it
460 return $class->meta if $class->can('meta');
461 # otherwise we might be
462 # dealing with a non-Moose
463 # class, and need to make
465 return Moose::Meta::Class->initialize($class);
467 elsif (my $role = $self->_does_metadata) {
468 # our role will always have
473 confess "Cannot find delegate metaclass for attribute " . $self->name;
477 sub _get_delegate_method_list {
479 my $meta = $self->_find_delegate_metaclass;
480 if ($meta->isa('Class::MOP::Class')) {
481 return map { $_->{name} } # NOTE: !never! delegate &meta
482 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
483 $meta->compute_all_applicable_methods;
485 elsif ($meta->isa('Moose::Meta::Role')) {
486 return $meta->get_method_list;
489 confess "Unable to recognize the delegate metaclass '$meta'";
501 Moose::Meta::Attribute - The Moose attribute metaclass
505 This is a subclass of L<Class::MOP::Attribute> with Moose specific
508 For the most part, the only time you will ever encounter an
509 instance of this class is if you are doing some serious deep
510 introspection. To really understand this class, you need to refer
511 to the L<Class::MOP::Attribute> documentation.
515 =head2 Overridden methods
517 These methods override methods in L<Class::MOP::Attribute> and add
518 Moose specific features. You can safely assume though that they
519 will behave just as L<Class::MOP::Attribute> does.
525 =item B<initialize_instance_slot>
527 =item B<install_accessors>
529 =item B<accessor_metaclass>
535 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
540 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
542 Before setting the value, a check is made on the type constraint of
543 the attribute, if it has one, to see if the value passes it. If the
544 value fails to pass, the set operation dies with a L<Carp/confess>.
546 Any coercion to convert values is done before checking the type constraint.
548 To check a value against a type constraint before setting it, fetch the
549 attribute instance using L<Moose::Meta::Attribute/find_attribute_by_name>,
550 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
551 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
556 =head2 Additional Moose features
558 Moose attributes support type-constraint checking, weak reference
559 creation and type coercion.
563 =item B<clone_and_inherit_options>
565 This is to support the C<has '+foo'> feature, it clones an attribute
566 from a superclass and allows a very specific set of changes to be made
569 =item B<has_type_constraint>
571 Returns true if this meta-attribute has a type constraint.
573 =item B<type_constraint>
575 A read-only accessor for this meta-attribute's type constraint. For
576 more information on what you can do with this, see the documentation
577 for L<Moose::Meta::TypeConstraint>.
581 Returns true if this meta-attribute performs delegation.
585 This returns the value which was passed into the handles option.
589 Returns true if this meta-attribute produces a weak reference.
593 Returns true if this meta-attribute is required to have a value.
597 Returns true if this meta-attribute should be initialized lazily.
599 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
601 =item B<is_lazy_build>
603 Returns true if this meta-attribute should be initialized lazily through
604 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
605 make your attribute required and lazy. In addition it will set the builder, clearer
606 and predicate options for you using the following convention.
608 #If your attribute name starts with an underscore:
609 has '_foo' => (lazy_build => 1);
611 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
613 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
615 #If your attribute name does not start with an underscore:
616 has 'foo' => (lazy_build => 1);
618 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
620 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
622 The reason for the different naming of the C<builder> is that the C<builder>
623 method is a private method while the C<clearer> and C<predicate> methods
626 NOTE: This means your class should provide a method whose name matches the value
627 of the builder part, in this case _build__foo or _build_foo.
629 =item B<should_coerce>
631 Returns true if this meta-attribute should perform type coercion.
633 =item B<should_auto_deref>
635 Returns true if this meta-attribute should perform automatic
638 NOTE: This can only be done for attributes whose type constraint is
639 either I<ArrayRef> or I<HashRef>.
643 Returns true if this meta-attribute has a trigger set.
647 This is a CODE reference which will be executed every time the
648 value of an attribute is assigned. The CODE ref will get two values,
649 the invocant and the new value. This can be used to handle I<basic>
650 bi-directional relations.
652 =item B<documentation>
654 This is a string which contains the documentation for this attribute.
655 It serves no direct purpose right now, but it might in the future
656 in some kind of automated documentation system perhaps.
658 =item B<has_documentation>
660 Returns true if this meta-attribute has any documentation.
666 All complex software has bugs lurking in it, and this module is no
667 exception. If you find a bug please either email me, or add the bug
672 Stevan Little E<lt>stevan@iinteractive.comE<gt>
674 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
676 =head1 COPYRIGHT AND LICENSE
678 Copyright 2006, 2007 by Infinity Interactive, Inc.
680 L<http://www.iinteractive.com>
682 This library is free software; you can redistribute it and/or modify
683 it under the same terms as Perl itself.