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 handles builder)) {
69 if (exists $options{$legal_option}) {
70 $actual_options{$legal_option} = $options{$legal_option};
71 delete $options{$legal_option};
77 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
78 $type_constraint = $options{isa};
81 $type_constraint = Moose::Util::TypeConstraints::find_or_create_type_constraint(
84 (defined $type_constraint)
85 || confess "Could not find the type constraint '" . $options{isa} . "'";
88 $actual_options{type_constraint} = $type_constraint;
91 (scalar keys %options == 0)
92 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
93 $self->clone(%actual_options);
96 sub _process_options {
97 my ($class, $name, $options) = @_;
99 if (exists $options->{is}) {
100 if ($options->{is} eq 'ro') {
101 $options->{reader} ||= $name;
102 (!exists $options->{trigger})
103 || confess "Cannot have a trigger on a read-only attribute $name";
105 elsif ($options->{is} eq 'rw') {
106 $options->{accessor} = $name;
107 ((reftype($options->{trigger}) || '') eq 'CODE')
108 || confess "Trigger must be a CODE ref"
109 if exists $options->{trigger};
112 confess "I do not understand this option (is => " . $options->{is} . ") on attribute $name"
116 if (exists $options->{isa}) {
117 if (exists $options->{does}) {
118 if (eval { $options->{isa}->can('does') }) {
119 ($options->{isa}->does($options->{does}))
120 || confess "Cannot have an isa option and a does option if the isa does not do the does on attribute $name";
123 confess "Cannot have an isa option which cannot ->does() on attribute $name";
127 # allow for anon-subtypes here ...
128 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
129 $options->{type_constraint} = $options->{isa};
132 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
134 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
135 constraint => sub { $_[0]->isa($options->{isa}) }
140 elsif (exists $options->{does}) {
141 # allow for anon-subtypes here ...
142 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
143 $options->{type_constraint} = $options->{does};
146 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
147 $options->{does} => {
148 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
150 Moose::Util::does_role($_[0], $options->{does})
157 if (exists $options->{coerce} && $options->{coerce}) {
158 (exists $options->{type_constraint})
159 || confess "You cannot have coercion without specifying a type constraint on attribute $name";
160 confess "You cannot have a weak reference to a coerced value on attribute $name"
161 if $options->{weak_ref};
164 if (exists $options->{auto_deref} && $options->{auto_deref}) {
165 (exists $options->{type_constraint})
166 || confess "You cannot auto-dereference without specifying a type constraint on attribute $name";
167 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
168 $options->{type_constraint}->is_a_type_of('HashRef'))
169 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute $name";
172 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
173 confess("You can not use lazy_build and default for the same attribute $name")
174 if exists $options->{default};
175 $options->{lazy} = 1;
176 $options->{required} = 1;
177 $options->{builder} ||= "_build_${name}";
179 $options->{clearer} ||= "_clear${name}";
180 $options->{predicate} ||= "_has${name}";
183 $options->{clearer} ||= "clear_${name}";
184 $options->{predicate} ||= "has_${name}";
188 if (exists $options->{lazy} && $options->{lazy}) {
189 (exists $options->{default} || defined $options->{builder} )
190 || confess "You cannot have lazy attribute ($name) without specifying a default value for it";
193 if ( $options->{required} && !( ( !exists $options->{init_arg} || defined $options->{init_arg} ) || exists $options->{default} || defined $options->{builder} ) ) {
194 confess "You cannot have a required attribute ($name) without a default, builder, or an init_arg";
199 sub initialize_instance_slot {
200 my ($self, $meta_instance, $instance, $params) = @_;
201 my $init_arg = $self->init_arg();
202 # try to fetch the init arg from the %params ...
206 if ( defined($init_arg) and 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);
223 elsif ($self->has_builder) {
224 if (my $builder = $instance->can($self->builder)){
225 $val = $instance->$builder;
229 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
234 return unless $value_is_set;
236 if ($self->has_type_constraint) {
237 my $type_constraint = $self->type_constraint;
238 if ($self->should_coerce && $type_constraint->has_coercion) {
239 $val = $type_constraint->coerce($val);
241 $type_constraint->check($val)
242 || confess "Attribute ("
244 . ") does not pass the type constraint because: "
245 . $type_constraint->get_message($val);
248 $self->set_initial_value($instance, $val);
249 $meta_instance->weaken_slot_value($instance, $self->name)
250 if ref $val && $self->is_weak_ref;
256 # this duplicates too much code from
257 # Class::MOP::Attribute, we need to
258 # refactor these bits eventually.
260 sub _set_initial_slot_value {
261 my ($self, $meta_instance, $instance, $value) = @_;
263 my $slot_name = $self->name;
265 return $meta_instance->set_slot_value($instance, $slot_name, $value)
266 unless $self->has_initializer;
268 my ($type_constraint, $can_coerce);
269 if ($self->has_type_constraint) {
270 $type_constraint = $self->type_constraint;
271 $can_coerce = ($self->should_coerce && $type_constraint->has_coercion);
276 if ($type_constraint) {
277 $val = $type_constraint->coerce($val)
279 $type_constraint->check($val)
280 || confess "Attribute ("
282 . ") does not pass the type constraint because: "
283 . $type_constraint->get_message($val);
285 $meta_instance->set_slot_value($instance, $slot_name, $val);
288 my $initializer = $self->initializer;
290 # most things will just want to set a value, so make it first arg
291 $instance->$initializer($value, $callback, $self);
295 my ($self, $instance, $value) = @_;
297 my $attr_name = $self->name;
299 if ($self->is_required) {
301 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
304 if ($self->has_type_constraint) {
306 my $type_constraint = $self->type_constraint;
308 if ($self->should_coerce) {
309 $value = $type_constraint->coerce($value);
311 $type_constraint->_compiled_type_constraint->($value)
312 || confess "Attribute ("
314 . ") does not pass the type constraint because "
315 . $type_constraint->get_message($value);
318 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
321 $meta_instance->set_slot_value($instance, $attr_name, $value);
323 if (ref $value && $self->is_weak_ref) {
324 $meta_instance->weaken_slot_value($instance, $attr_name);
327 if ($self->has_trigger) {
328 $self->trigger->($instance, $value, $self);
333 my ($self, $instance) = @_;
335 if ($self->is_lazy) {
336 unless ($self->has_value($instance)) {
337 if ($self->has_default) {
338 my $default = $self->default($instance);
339 $self->set_initial_value($instance, $default);
341 if ( $self->has_builder ){
342 if (my $builder = $instance->can($self->builder)){
343 $self->set_initial_value($instance, $instance->$builder);
346 confess(blessed($instance)
347 . " does not support builder method '"
349 . "' for attribute '"
355 $self->set_initial_value($instance, undef);
360 if ($self->should_auto_deref) {
362 my $type_constraint = $self->type_constraint;
364 if ($type_constraint->is_a_type_of('ArrayRef')) {
365 my $rv = $self->SUPER::get_value($instance);
366 return unless defined $rv;
367 return wantarray ? @{ $rv } : $rv;
369 elsif ($type_constraint->is_a_type_of('HashRef')) {
370 my $rv = $self->SUPER::get_value($instance);
371 return unless defined $rv;
372 return wantarray ? %{ $rv } : $rv;
375 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
381 return $self->SUPER::get_value($instance);
385 ## installing accessors
387 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
389 sub install_accessors {
391 $self->SUPER::install_accessors(@_);
393 if ($self->has_handles) {
396 # Here we canonicalize the 'handles' option
397 # this will sort out any details and always
398 # return an hash of methods which we want
399 # to delagate to, see that method for details
400 my %handles = $self->_canonicalize_handles();
402 # find the accessor method for this attribute
403 my $accessor = $self->get_read_method_ref;
404 # then unpack it if we need too ...
405 $accessor = $accessor->body if blessed $accessor;
407 # install the delegation ...
408 my $associated_class = $self->associated_class;
409 foreach my $handle (keys %handles) {
410 my $method_to_call = $handles{$handle};
411 my $class_name = $associated_class->name;
412 my $name = "${class_name}::${handle}";
414 (!$associated_class->has_method($handle))
415 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
418 # handles is not allowed to delegate
419 # any of these methods, as they will
420 # override the ones in your class, which
421 # is almost certainly not what you want.
423 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
424 #cluck("Not delegating method '$handle' because it is a core method") and
425 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
427 if ((reftype($method_to_call) || '') eq 'CODE') {
428 $associated_class->add_method($handle => subname $name, $method_to_call);
432 # we used to do a goto here, but the
433 # goto didn't handle failure correctly
434 # (it just returned nothing), so I took
435 # that out. However, the more I thought
436 # about it, the less I liked it doing
437 # the goto, and I prefered the act of
438 # delegation being actually represented
439 # in the stack trace.
441 $associated_class->add_method($handle => subname $name, sub {
442 my $proxy = (shift)->$accessor();
444 || confess "Cannot delegate $handle to $method_to_call because " .
445 "the value of " . $self->name . " is not defined";
446 $proxy->$method_to_call(@_);
455 # private methods to help delegation ...
457 sub _canonicalize_handles {
459 my $handles = $self->handles;
460 if (my $handle_type = ref($handles)) {
461 if ($handle_type eq 'HASH') {
464 elsif ($handle_type eq 'ARRAY') {
465 return map { $_ => $_ } @{$handles};
467 elsif ($handle_type eq 'Regexp') {
468 ($self->has_type_constraint)
469 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
470 return map { ($_ => $_) }
471 grep { /$handles/ } $self->_get_delegate_method_list;
473 elsif ($handle_type eq 'CODE') {
474 return $handles->($self, $self->_find_delegate_metaclass);
477 confess "Unable to canonicalize the 'handles' option with $handles";
481 my $role_meta = eval { $handles->meta };
483 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
486 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
487 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
489 return map { $_ => $_ } (
490 $role_meta->get_method_list,
491 $role_meta->get_required_method_list
496 sub _find_delegate_metaclass {
498 if (my $class = $self->_isa_metadata) {
499 # if the class does have
500 # a meta method, use it
501 return $class->meta if $class->can('meta');
502 # otherwise we might be
503 # dealing with a non-Moose
504 # class, and need to make
506 return Moose::Meta::Class->initialize($class);
508 elsif (my $role = $self->_does_metadata) {
509 # our role will always have
514 confess "Cannot find delegate metaclass for attribute " . $self->name;
518 sub _get_delegate_method_list {
520 my $meta = $self->_find_delegate_metaclass;
521 if ($meta->isa('Class::MOP::Class')) {
522 return map { $_->{name} } # NOTE: !never! delegate &meta
523 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
524 $meta->compute_all_applicable_methods;
526 elsif ($meta->isa('Moose::Meta::Role')) {
527 return $meta->get_method_list;
530 confess "Unable to recognize the delegate metaclass '$meta'";
542 Moose::Meta::Attribute - The Moose attribute metaclass
546 This is a subclass of L<Class::MOP::Attribute> with Moose specific
549 For the most part, the only time you will ever encounter an
550 instance of this class is if you are doing some serious deep
551 introspection. To really understand this class, you need to refer
552 to the L<Class::MOP::Attribute> documentation.
556 =head2 Overridden methods
558 These methods override methods in L<Class::MOP::Attribute> and add
559 Moose specific features. You can safely assume though that they
560 will behave just as L<Class::MOP::Attribute> does.
568 =item B<initialize_instance_slot>
570 =item B<install_accessors>
572 =item B<accessor_metaclass>
578 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
583 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
585 Before setting the value, a check is made on the type constraint of
586 the attribute, if it has one, to see if the value passes it. If the
587 value fails to pass, the set operation dies with a L<Carp/confess>.
589 Any coercion to convert values is done before checking the type constraint.
591 To check a value against a type constraint before setting it, fetch the
592 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
593 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
594 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
599 =head2 Additional Moose features
601 Moose attributes support type-constraint checking, weak reference
602 creation and type coercion.
606 =item B<clone_and_inherit_options>
608 This is to support the C<has '+foo'> feature, it clones an attribute
609 from a superclass and allows a very specific set of changes to be made
612 =item B<has_type_constraint>
614 Returns true if this meta-attribute has a type constraint.
616 =item B<type_constraint>
618 A read-only accessor for this meta-attribute's type constraint. For
619 more information on what you can do with this, see the documentation
620 for L<Moose::Meta::TypeConstraint>.
624 Returns true if this meta-attribute performs delegation.
628 This returns the value which was passed into the handles option.
632 Returns true if this meta-attribute produces a weak reference.
636 Returns true if this meta-attribute is required to have a value.
640 Returns true if this meta-attribute should be initialized lazily.
642 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
644 =item B<is_lazy_build>
646 Returns true if this meta-attribute should be initialized lazily through
647 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
648 make your attribute required and lazy. In addition it will set the builder, clearer
649 and predicate options for you using the following convention.
651 #If your attribute name starts with an underscore:
652 has '_foo' => (lazy_build => 1);
654 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
656 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
658 #If your attribute name does not start with an underscore:
659 has 'foo' => (lazy_build => 1);
661 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
663 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
665 The reason for the different naming of the C<builder> is that the C<builder>
666 method is a private method while the C<clearer> and C<predicate> methods
669 NOTE: This means your class should provide a method whose name matches the value
670 of the builder part, in this case _build__foo or _build_foo.
672 =item B<should_coerce>
674 Returns true if this meta-attribute should perform type coercion.
676 =item B<should_auto_deref>
678 Returns true if this meta-attribute should perform automatic
681 NOTE: This can only be done for attributes whose type constraint is
682 either I<ArrayRef> or I<HashRef>.
686 Returns true if this meta-attribute has a trigger set.
690 This is a CODE reference which will be executed every time the
691 value of an attribute is assigned. The CODE ref will get two values,
692 the invocant and the new value. This can be used to handle I<basic>
693 bi-directional relations.
695 =item B<documentation>
697 This is a string which contains the documentation for this attribute.
698 It serves no direct purpose right now, but it might in the future
699 in some kind of automated documentation system perhaps.
701 =item B<has_documentation>
703 Returns true if this meta-attribute has any documentation.
709 All complex software has bugs lurking in it, and this module is no
710 exception. If you find a bug please either email me, or add the bug
715 Stevan Little E<lt>stevan@iinteractive.comE<gt>
717 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
719 =head1 COPYRIGHT AND LICENSE
721 Copyright 2006-2008 by Infinity Interactive, Inc.
723 L<http://www.iinteractive.com>
725 This library is free software; you can redistribute it and/or modify
726 it under the same terms as Perl itself.