2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
9 use Sub::Name 'subname';
12 our $VERSION = '0.16';
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->{isa};
155 $options->{type_constraint} = Moose::Util::TypeConstraints::find_or_create_type_constraint(
156 $options->{does} => {
157 parent => Moose::Util::TypeConstraints::find_type_constraint('Role'),
158 constraint => sub { $_[0]->does($options->{does}) }
164 if (exists $options->{coerce} && $options->{coerce}) {
165 (exists $options->{type_constraint})
166 || confess "You cannot have coercion without specifying a type constraint";
167 confess "You cannot have a weak reference to a coerced value"
168 if $options->{weak_ref};
171 if (exists $options->{auto_deref} && $options->{auto_deref}) {
172 (exists $options->{type_constraint})
173 || confess "You cannot auto-dereference without specifying a type constraint";
174 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
175 $options->{type_constraint}->is_a_type_of('HashRef'))
176 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
179 if (exists $options->{lazy_build} && $options->{lazy_build} == 1) {
180 confess("You can not use lazy_build and default for the same attribute")
181 if exists $options->{default};
182 $options->{lazy} = 1;
183 $options->{required} = 1;
184 $options->{builder} ||= "_build_${name}";
186 $options->{clearer} ||= "_clear${name}";
187 $options->{predicate} ||= "_has${name}";
190 $options->{clearer} ||= "clear_${name}";
191 $options->{predicate} ||= "has_${name}";
195 if (exists $options->{lazy} && $options->{lazy}) {
196 (exists $options->{default} || exists $options->{builder} )
197 || confess "You cannot have lazy attribute without specifying a default value for it";
202 sub initialize_instance_slot {
203 my ($self, $meta_instance, $instance, $params) = @_;
204 my $init_arg = $self->init_arg();
205 # try to fetch the init arg from the %params ...
209 if (exists $params->{$init_arg}) {
210 $val = $params->{$init_arg};
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 && !$self->has_builder;
220 # if nothing was in the %params, we can use the
221 # attribute's default value (if it has one)
222 if ($self->has_default) {
223 $val = $self->default($instance);
226 elsif ($self->has_builder) {
227 if (my $builder = $instance->can($self->builder)){
228 $val = $instance->$builder;
232 confess(blessed($instance)." does not support builder method '".$self->builder."' for attribute '" . $self->name . "'");
237 return unless $value_is_set;
239 if ($self->has_type_constraint) {
240 my $type_constraint = $self->type_constraint;
241 if ($self->should_coerce && $type_constraint->has_coercion) {
242 $val = $type_constraint->coerce($val);
244 (defined($type_constraint->check($val)))
245 || confess "Attribute (" .
247 ") does not pass the type constraint (" .
248 $type_constraint->name .
251 ? (blessed($val) && overload::Overloaded($val)
252 ? overload::StrVal($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 defined($type_constraint->_compiled_type_constraint->($value))
283 || confess "Attribute ($attr_name) does not pass the type constraint ("
284 . $type_constraint->name
288 (blessed($value) && overload::Overloaded($value)
289 ? overload::StrVal($value)
296 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
299 $meta_instance->set_slot_value($instance, $attr_name, $value);
301 if (ref $value && $self->is_weak_ref) {
302 $meta_instance->weaken_slot_value($instance, $attr_name);
305 if ($self->has_trigger) {
306 $self->trigger->($instance, $value, $self);
311 my ($self, $instance) = @_;
313 if ($self->is_lazy) {
314 unless ($self->has_value($instance)) {
315 if ($self->has_default) {
316 my $default = $self->default($instance);
317 $self->set_value($instance, $default);
319 if ( $self->has_builder ){
320 if (my $builder = $instance->can($self->builder)){
321 $self->set_value($instance, $instance->$builder);
324 confess(blessed($instance)
325 . " does not support builder method '"
327 . "' for attribute '"
333 $self->set_value($instance, undef);
338 if ($self->should_auto_deref) {
340 my $type_constraint = $self->type_constraint;
342 if ($type_constraint->is_a_type_of('ArrayRef')) {
343 my $rv = $self->SUPER::get_value($instance);
344 return unless defined $rv;
345 return wantarray ? @{ $rv } : $rv;
347 elsif ($type_constraint->is_a_type_of('HashRef')) {
348 my $rv = $self->SUPER::get_value($instance);
349 return unless defined $rv;
350 return wantarray ? %{ $rv } : $rv;
353 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
359 return $self->SUPER::get_value($instance);
363 ## installing accessors
365 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
367 sub install_accessors {
369 $self->SUPER::install_accessors(@_);
371 if ($self->has_handles) {
374 # Here we canonicalize the 'handles' option
375 # this will sort out any details and always
376 # return an hash of methods which we want
377 # to delagate to, see that method for details
378 my %handles = $self->_canonicalize_handles();
380 # find the accessor method for this attribute
381 my $accessor = $self->get_read_method_ref;
382 # then unpack it if we need too ...
383 $accessor = $accessor->body if blessed $accessor;
385 # install the delegation ...
386 my $associated_class = $self->associated_class;
387 foreach my $handle (keys %handles) {
388 my $method_to_call = $handles{$handle};
389 my $class_name = $associated_class->name;
390 my $name = "${class_name}::${handle}";
392 (!$associated_class->has_method($handle))
393 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
396 # handles is not allowed to delegate
397 # any of these methods, as they will
398 # override the ones in your class, which
399 # is almost certainly not what you want.
401 # FIXME warn when $handle was explicitly specified, but not if the source is a regex or something
402 #cluck("Not delegating method '$handle' because it is a core method") and
403 next if $class_name->isa("Moose::Object") and $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
405 if ((reftype($method_to_call) || '') eq 'CODE') {
406 $associated_class->add_method($handle => subname $name, $method_to_call);
409 $associated_class->add_method($handle => subname $name, sub {
410 my $proxy = (shift)->$accessor();
412 goto &{ $proxy->can($method_to_call) || return };
421 # private methods to help delegation ...
423 sub _canonicalize_handles {
425 my $handles = $self->handles;
426 if (my $handle_type = ref($handles)) {
427 if ($handle_type eq 'HASH') {
430 elsif ($handle_type eq 'ARRAY') {
431 return map { $_ => $_ } @{$handles};
433 elsif ($handle_type eq 'Regexp') {
434 ($self->has_type_constraint)
435 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
436 return map { ($_ => $_) }
437 grep { /$handles/ } $self->_get_delegate_method_list;
439 elsif ($handle_type eq 'CODE') {
440 return $handles->($self, $self->_find_delegate_metaclass);
443 confess "Unable to canonicalize the 'handles' option with $handles";
447 my $role_meta = eval { $handles->meta };
449 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
452 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
453 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
455 return map { $_ => $_ } (
456 $role_meta->get_method_list,
457 $role_meta->get_required_method_list
462 sub _find_delegate_metaclass {
464 if (my $class = $self->_isa_metadata) {
465 # if the class does have
466 # a meta method, use it
467 return $class->meta if $class->can('meta');
468 # otherwise we might be
469 # dealing with a non-Moose
470 # class, and need to make
472 return Moose::Meta::Class->initialize($class);
474 elsif (my $role = $self->_does_metadata) {
475 # our role will always have
480 confess "Cannot find delegate metaclass for attribute " . $self->name;
484 sub _get_delegate_method_list {
486 my $meta = $self->_find_delegate_metaclass;
487 if ($meta->isa('Class::MOP::Class')) {
488 return map { $_->{name} } # NOTE: !never! delegate &meta
489 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
490 $meta->compute_all_applicable_methods;
492 elsif ($meta->isa('Moose::Meta::Role')) {
493 return $meta->get_method_list;
496 confess "Unable to recognize the delegate metaclass '$meta'";
508 Moose::Meta::Attribute - The Moose attribute metaclass
512 This is a subclass of L<Class::MOP::Attribute> with Moose specific
515 For the most part, the only time you will ever encounter an
516 instance of this class is if you are doing some serious deep
517 introspection. To really understand this class, you need to refer
518 to the L<Class::MOP::Attribute> documentation.
522 =head2 Overridden methods
524 These methods override methods in L<Class::MOP::Attribute> and add
525 Moose specific features. You can safely assume though that they
526 will behave just as L<Class::MOP::Attribute> does.
532 =item B<initialize_instance_slot>
534 =item B<install_accessors>
536 =item B<accessor_metaclass>
542 eval { $point->meta->get_attribute('x')->set_value($point, 'fourty-two') };
547 I<Attribute (x) does not pass the type constraint (Int) with 'fourty-two'>
549 Before setting the value, a check is made on the type constraint of
550 the attribute, if it has one, to see if the value passes it. If the
551 value fails to pass, the set operation dies with a L<Carp/confess>.
553 Any coercion to convert values is done before checking the type constraint.
555 To check a value against a type constraint before setting it, fetch the
556 attribute instance using L<Class::MOP::Class/find_attribute_by_name>,
557 fetch the type_constraint from the attribute using L<Moose::Meta::Attribute/type_constraint>
558 and call L<Moose::Meta::TypeConstraint/check>. See L<Moose::Cookbook::RecipeX>
563 =head2 Additional Moose features
565 Moose attributes support type-constraint checking, weak reference
566 creation and type coercion.
570 =item B<clone_and_inherit_options>
572 This is to support the C<has '+foo'> feature, it clones an attribute
573 from a superclass and allows a very specific set of changes to be made
576 =item B<has_type_constraint>
578 Returns true if this meta-attribute has a type constraint.
580 =item B<type_constraint>
582 A read-only accessor for this meta-attribute's type constraint. For
583 more information on what you can do with this, see the documentation
584 for L<Moose::Meta::TypeConstraint>.
588 Returns true if this meta-attribute performs delegation.
592 This returns the value which was passed into the handles option.
596 Returns true if this meta-attribute produces a weak reference.
600 Returns true if this meta-attribute is required to have a value.
604 Returns true if this meta-attribute should be initialized lazily.
606 NOTE: lazy attributes, B<must> have a C<default> or C<builder> field set.
608 =item B<is_lazy_build>
610 Returns true if this meta-attribute should be initialized lazily through
611 the builder generated by lazy_build. Using C<lazy_build =E<gt> 1> will
612 make your attribute required and lazy. In addition it will set the builder, clearer
613 and predicate options for you using the following convention.
615 #If your attribute name starts 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 #If your attribute name does not start with an underscore:
623 has 'foo' => (lazy_build => 1);
625 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', builder => '_build_foo);
627 has 'foo' => (lazy => 1, required => 1, predicate => 'has_foo', clearer => 'clear_foo', default => sub{shift->_build_foo});
629 The reason for the different naming of the C<builder> is that the C<builder>
630 method is a private method while the C<clearer> and C<predicate> methods
633 NOTE: This means your class should provide a method whose name matches the value
634 of the builder part, in this case _build__foo or _build_foo.
636 =item B<should_coerce>
638 Returns true if this meta-attribute should perform type coercion.
640 =item B<should_auto_deref>
642 Returns true if this meta-attribute should perform automatic
645 NOTE: This can only be done for attributes whose type constraint is
646 either I<ArrayRef> or I<HashRef>.
650 Returns true if this meta-attribute has a trigger set.
654 This is a CODE reference which will be executed every time the
655 value of an attribute is assigned. The CODE ref will get two values,
656 the invocant and the new value. This can be used to handle I<basic>
657 bi-directional relations.
659 =item B<documentation>
661 This is a string which contains the documentation for this attribute.
662 It serves no direct purpose right now, but it might in the future
663 in some kind of automated documentation system perhaps.
665 =item B<has_documentation>
667 Returns true if this meta-attribute has any documentation.
673 All complex software has bugs lurking in it, and this module is no
674 exception. If you find a bug please either email me, or add the bug
679 Stevan Little E<lt>stevan@iinteractive.comE<gt>
681 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
683 =head1 COPYRIGHT AND LICENSE
685 Copyright 2006-2008 by Infinity Interactive, Inc.
687 L<http://www.iinteractive.com>
689 This library is free software; you can redistribute it and/or modify
690 it under the same terms as Perl itself.