2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
9 use Sub::Name 'subname';
12 our $VERSION = '0.18';
13 our $AUTHORITY = 'cpan:STEVAN';
15 use Moose::Meta::Method::Accessor;
16 use Moose::Util::TypeConstraints ();
18 use base 'Class::MOP::Attribute';
20 # options which are not directly used
21 # but we store them for metadata purposes
22 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
23 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
24 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
26 # these are actual options for the attrs
27 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
28 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
29 __PACKAGE__->meta->add_attribute('lazy_build' => (reader => 'is_lazy_build' ));
30 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
31 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
32 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
33 __PACKAGE__->meta->add_attribute('type_constraint' => (
34 reader => 'type_constraint',
35 predicate => 'has_type_constraint',
37 __PACKAGE__->meta->add_attribute('trigger' => (
39 predicate => 'has_trigger',
41 __PACKAGE__->meta->add_attribute('handles' => (
43 predicate => 'has_handles',
45 __PACKAGE__->meta->add_attribute('documentation' => (
46 reader => 'documentation',
47 predicate => 'has_documentation',
51 my ($class, $name, %options) = @_;
52 $class->_process_options($name, \%options);
53 return $class->SUPER::new($name, %options);
56 sub clone_and_inherit_options {
57 my ($self, %options) = @_;
58 # you can change default, required, coerce, documentation and lazy
60 foreach my $legal_option (qw(default coerce required documentation lazy)) {
61 if (exists $options{$legal_option}) {
62 $actual_options{$legal_option} = $options{$legal_option};
63 delete $options{$legal_option};
67 # handles can only be added, not changed
68 if ($options{handles}) {
69 confess "You can only add the 'handles' option, you cannot change it"
70 if $self->has_handles;
71 $actual_options{handles} = $options{handles};
72 delete $options{handles};
75 # isa can be changed, but only if the
76 # new type is a subtype
79 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
80 $type_constraint = $options{isa};
83 $type_constraint = Moose::Util::TypeConstraints::find_or_create_type_constraint(
86 (defined $type_constraint)
87 || confess "Could not find the type constraint '" . $options{isa} . "'";
90 # check here to see if the new type
91 # is a subtype of the old one
92 ($type_constraint->is_subtype_of($self->type_constraint->name))
93 || confess "New type constraint setting must be a subtype of inherited one"
94 # iff we have a type constraint that is ...
95 if $self->has_type_constraint;
97 $actual_options{type_constraint} = $type_constraint;
100 (scalar keys %options == 0)
101 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
102 $self->clone(%actual_options);
105 sub _process_options {
106 my ($class, $name, $options) = @_;
108 if (exists $options->{is}) {
109 if ($options->{is} eq 'ro') {
110 $options->{reader} ||= $name;
111 (!exists $options->{trigger})
112 || confess "Cannot have a trigger on a read-only attribute";
114 elsif ($options->{is} eq 'rw') {
115 $options->{accessor} = $name;
116 ((reftype($options->{trigger}) || '') eq 'CODE')
117 || confess "Trigger must be a CODE ref"
118 if exists $options->{trigger};
121 confess "I do not understand this option (is => " . $options->{is} . ")"
125 if (exists $options->{isa}) {
126 if (exists $options->{does}) {
127 if (eval { $options->{isa}->can('does') }) {
128 ($options->{isa}->does($options->{does}))
129 || confess "Cannot have an isa option and a does option if the isa does not do the does";
132 confess "Cannot have an isa option which cannot ->does()";
136 # allow for anon-subtypes here ...
137 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
138 $options->{type_constraint} = $options->{isa};
141 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
143 parent => Moose::Util::TypeConstraints::find_type_constraint('Object'),
144 constraint => sub { $_[0]->isa($options->{isa}) }
149 elsif (exists $options->{does}) {
150 # allow for anon-subtypes here ...
151 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
152 $options->{type_constraint} = $options->{does};
155 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
156 $options->{does} => {
157 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
159 Moose::Util::does_role($_[0], $options->{does})
166 if (exists $options->{coerce} && $options->{coerce}) {
167 (exists $options->{type_constraint})
168 || confess "You cannot have coercion without specifying a type constraint";
169 confess "You cannot have a weak reference to a coerced value"
170 if $options->{weak_ref};
173 if (exists $options->{auto_deref} && $options->{auto_deref}) {
174 (exists $options->{type_constraint})
175 || confess "You cannot auto-dereference without specifying a type constraint";
176 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
177 $options->{type_constraint}->is_a_type_of('HashRef'))
178 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
181 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
182 confess("You can not use lazy_build and default for the same attribute")
183 if exists $options->{default};
184 $options->{lazy} = 1;
185 $options->{required} = 1;
186 $options->{builder} ||= "_build_${name}";
188 $options->{clearer} ||= "_clear${name}";
189 $options->{predicate} ||= "_has${name}";
192 $options->{clearer} ||= "clear_${name}";
193 $options->{predicate} ||= "has_${name}";
197 if (exists $options->{lazy} && $options->{lazy}) {
198 (exists $options->{default} || exists $options->{builder} )
199 || confess "You cannot have lazy attribute without specifying a default value for it";
204 sub initialize_instance_slot {
205 my ($self, $meta_instance, $instance, $params) = @_;
206 my $init_arg = $self->init_arg();
207 # try to fetch the init arg from the %params ...
211 if ( defined($init_arg) and exists $params->{$init_arg}) {
212 $val = $params->{$init_arg};
216 # skip it if it's lazy
217 return if $self->is_lazy;
218 # and die if it's required and doesn't have a default value
219 confess "Attribute (" . $self->name . ") is required"
220 if $self->is_required && !$self->has_default && !$self->has_builder;
222 # if nothing was in the %params, we can use the
223 # attribute's default value (if it has one)
224 if ($self->has_default) {
225 $val = $self->default($instance);
228 elsif ($self->has_builder) {
229 if (my $builder = $instance->can($self->builder)){
230 $val = $instance->$builder;
234 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
239 return unless $value_is_set;
241 if ($self->has_type_constraint) {
242 my $type_constraint = $self->type_constraint;
243 if ($self->should_coerce && $type_constraint->has_coercion) {
244 $val = $type_constraint->coerce($val);
246 (defined($type_constraint->check($val)))
247 || confess "Attribute (" .
249 ") does not pass the type constraint (" .
250 $type_constraint->name .
253 ? overload::StrVal($val)
258 $meta_instance->set_slot_value($instance, $self->name, $val);
259 $meta_instance->weaken_slot_value($instance, $self->name)
260 if ref $val && $self->is_weak_ref;
266 my ($self, $instance, $value) = @_;
268 my $attr_name = $self->name;
270 if ($self->is_required) {
272 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
275 if ($self->has_type_constraint) {
277 my $type_constraint = $self->type_constraint;
279 if ($self->should_coerce) {
280 $value = $type_constraint->coerce($value);
282 $type_constraint->_compiled_type_constraint->($value)
283 || confess "Attribute ($attr_name) does not pass the type constraint ("
284 . $type_constraint->name
287 ? ("'" . overload::StrVal($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 if (my $builder = $instance->can($self->builder)){
317 $self->set_value($instance, $instance->$builder);
320 confess(blessed($instance)
321 . " does not support builder method '"
323 . "' for attribute '"
329 $self->set_value($instance, undef);
334 if ($self->should_auto_deref) {
336 my $type_constraint = $self->type_constraint;
338 if ($type_constraint->is_a_type_of('ArrayRef')) {
339 my $rv = $self->SUPER::get_value($instance);
340 return unless defined $rv;
341 return wantarray ? @{ $rv } : $rv;
343 elsif ($type_constraint->is_a_type_of('HashRef')) {
344 my $rv = $self->SUPER::get_value($instance);
345 return unless defined $rv;
346 return wantarray ? %{ $rv } : $rv;
349 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
355 return $self->SUPER::get_value($instance);
359 ## installing accessors
361 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
363 sub install_accessors {
365 $self->SUPER::install_accessors(@_);
367 if ($self->has_handles) {
370 # Here we canonicalize the 'handles' option
371 # this will sort out any details and always
372 # return an hash of methods which we want
373 # to delagate to, see that method for details
374 my %handles = $self->_canonicalize_handles();
376 # find the accessor method for this attribute
377 my $accessor = $self->get_read_method_ref;
378 # then unpack it if we need too ...
379 $accessor = $accessor->body if blessed $accessor;
381 # install the delegation ...
382 my $associated_class = $self->associated_class;
383 foreach my $handle (keys %handles) {
384 my $method_to_call = $handles{$handle};
385 my $class_name = $associated_class->name;
386 my $name = "${class_name}::${handle}";
388 (!$associated_class->has_method($handle))
389 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
392 # handles is not allowed to delegate
393 # any of these methods, as they will
394 # override the ones in your class, which
395 # is almost certainly not what you want.
397 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
398 #cluck("Not delegating method '$handle' because it is a core method") and
399 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
401 if ((reftype($method_to_call) || '') eq 'CODE') {
402 $associated_class->add_method($handle => subname $name, $method_to_call);
405 $associated_class->add_method($handle => subname $name, sub {
406 my $proxy = (shift)->$accessor();
409 || confess "Cannot delegate $handle to $method_to_call because " .
410 "the value of " . $self->name . " is not defined";
411 goto &{ $proxy->can($method_to_call) || return };
420 # private methods to help delegation ...
422 sub _canonicalize_handles {
424 my $handles = $self->handles;
425 if (my $handle_type = ref($handles)) {
426 if ($handle_type eq 'HASH') {
429 elsif ($handle_type eq 'ARRAY') {
430 return map { $_ => $_ } @{$handles};
432 elsif ($handle_type eq 'Regexp') {
433 ($self->has_type_constraint)
434 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
435 return map { ($_ => $_) }
436 grep { /$handles/ } $self->_get_delegate_method_list;
438 elsif ($handle_type eq 'CODE') {
439 return $handles->($self, $self->_find_delegate_metaclass);
442 confess "Unable to canonicalize the 'handles' option with $handles";
446 my $role_meta = eval { $handles->meta };
448 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
451 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
452 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
454 return map { $_ => $_ } (
455 $role_meta->get_method_list,
456 $role_meta->get_required_method_list
461 sub _find_delegate_metaclass {
463 if (my $class = $self->_isa_metadata) {
464 # if the class does have
465 # a meta method, use it
466 return $class->meta if $class->can('meta');
467 # otherwise we might be
468 # dealing with a non-Moose
469 # class, and need to make
471 return Moose::Meta::Class->initialize($class);
473 elsif (my $role = $self->_does_metadata) {
474 # our role will always have
479 confess "Cannot find delegate metaclass for attribute " . $self->name;
483 sub _get_delegate_method_list {
485 my $meta = $self->_find_delegate_metaclass;
486 if ($meta->isa('Class::MOP::Class')) {
487 return map { $_->{name} } # NOTE: !never! delegate &meta
488 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
489 $meta->compute_all_applicable_methods;
491 elsif ($meta->isa('Moose::Meta::Role')) {
492 return $meta->get_method_list;
495 confess "Unable to recognize the delegate metaclass '$meta'";
507 Moose::Meta::Attribute - The Moose attribute metaclass
511 This is a subclass of L<Class::MOP::Attribute> with Moose specific
514 For the most part, the only time you will ever encounter an
515 instance of this class is if you are doing some serious deep
516 introspection. To really understand this class, you need to refer
517 to the L<Class::MOP::Attribute> documentation.
521 =head2 Overridden methods
523 These methods override methods in L<Class::MOP::Attribute> and add
524 Moose specific features. You can safely assume though that they
525 will behave just as L<Class::MOP::Attribute> does.
531 =item B<initialize_instance_slot>
533 =item B<install_accessors>
535 =item B<accessor_metaclass>
541 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
546 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
548 Before setting the value, a check is made on the type constraint of
549 the attribute, if it has one, to see if the value passes it. If the
550 value fails to pass, the set operation dies with a L<Carp/confess>.
552 Any coercion to convert values is done before checking the type constraint.
554 To check a value against a type constraint before setting it, fetch the
555 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
556 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
557 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
562 =head2 Additional Moose features
564 Moose attributes support type-constraint checking, weak reference
565 creation and type coercion.
569 =item B<clone_and_inherit_options>
571 This is to support the C<has '+foo'> feature, it clones an attribute
572 from a superclass and allows a very specific set of changes to be made
575 =item B<has_type_constraint>
577 Returns true if this meta-attribute has a type constraint.
579 =item B<type_constraint>
581 A read-only accessor for this meta-attribute's type constraint. For
582 more information on what you can do with this, see the documentation
583 for L<Moose::Meta::TypeConstraint>.
587 Returns true if this meta-attribute performs delegation.
591 This returns the value which was passed into the handles option.
595 Returns true if this meta-attribute produces a weak reference.
599 Returns true if this meta-attribute is required to have a value.
603 Returns true if this meta-attribute should be initialized lazily.
605 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
607 =item B<is_lazy_build>
609 Returns true if this meta-attribute should be initialized lazily through
610 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
611 make your attribute required and lazy. In addition it will set the builder, clearer
612 and predicate options for you using the following convention.
614 #If your attribute name starts with an underscore:
615 has '_foo' => (lazy_build => 1);
617 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', builder => '_build__foo);
619 has '_foo' => (lazy => 1, required => 1, predicate => '_has_foo', clearer => '_clear_foo', default => sub{shift->_build__foo});
621 #If your attribute name does not start with an underscore:
622 has 'foo' => (lazy_build => 1);
624 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
626 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
628 The reason for the different naming of the C<builder> is that the C<builder>
629 method is a private method while the C<clearer> and C<predicate> methods
632 NOTE: This means your class should provide a method whose name matches the value
633 of the builder part, in this case _build__foo or _build_foo.
635 =item B<should_coerce>
637 Returns true if this meta-attribute should perform type coercion.
639 =item B<should_auto_deref>
641 Returns true if this meta-attribute should perform automatic
644 NOTE: This can only be done for attributes whose type constraint is
645 either I<ArrayRef> or I<HashRef>.
649 Returns true if this meta-attribute has a trigger set.
653 This is a CODE reference which will be executed every time the
654 value of an attribute is assigned. The CODE ref will get two values,
655 the invocant and the new value. This can be used to handle I<basic>
656 bi-directional relations.
658 =item B<documentation>
660 This is a string which contains the documentation for this attribute.
661 It serves no direct purpose right now, but it might in the future
662 in some kind of automated documentation system perhaps.
664 =item B<has_documentation>
666 Returns true if this meta-attribute has any documentation.
672 All complex software has bugs lurking in it, and this module is no
673 exception. If you find a bug please either email me, or add the bug
678 Stevan Little E<lt>stevan@iinteractive.comE<gt>
680 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
682 =head1 COPYRIGHT AND LICENSE
684 Copyright 2006-2008 by Infinity Interactive, Inc.
686 L<http://www.iinteractive.com>
688 This library is free software; you can redistribute it and/or modify
689 it under the same terms as Perl itself.