2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
11 our $VERSION = '0.11';
12 our $AUTHORITY = 'cpan:STEVAN';
14 use Moose::Meta::Method::Accessor;
15 use Moose::Util::TypeConstraints ();
17 use base 'Class::MOP::Attribute';
19 # options which are not directly used
20 # but we store them for metadata purposes
21 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
22 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
23 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
25 # these are actual options for the attrs
26 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
27 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
28 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
29 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
30 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
31 __PACKAGE__->meta->add_attribute('type_constraint' => (
32 reader => 'type_constraint',
33 predicate => 'has_type_constraint',
35 __PACKAGE__->meta->add_attribute('trigger' => (
37 predicate => 'has_trigger',
39 __PACKAGE__->meta->add_attribute('handles' => (
41 predicate => 'has_handles',
43 __PACKAGE__->meta->add_attribute('documentation' => (
44 reader => 'documentation',
45 predicate => 'has_documentation',
49 my ($class, $name, %options) = @_;
50 $class->_process_options($name, \%options);
51 return $class->SUPER::new($name, %options);
54 sub clone_and_inherit_options {
55 my ($self, %options) = @_;
56 # you can change default, required, coerce, documentation and lazy
58 foreach my $legal_option (qw(default coerce required documentation lazy)) {
59 if (exists $options{$legal_option}) {
60 $actual_options{$legal_option} = $options{$legal_option};
61 delete $options{$legal_option};
65 # handles can only be added, not changed
66 if ($options{handles}) {
67 confess "You can only add the 'handles' option, you cannot change it"
68 if $self->has_handles;
69 $actual_options{handles} = $options{handles};
70 delete $options{handles};
73 # isa can be changed, but only if the
74 # new type is a subtype
77 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
78 $type_constraint = $options{isa};
81 $type_constraint = Moose::Util::TypeConstraints::find_type_constraint($options{isa});
82 (defined $type_constraint)
83 || confess "Could not find the type constraint '" . $options{isa} . "'";
86 # check here to see if the new type
87 # is a subtype of the old one
88 ($type_constraint->is_subtype_of($self->type_constraint->name))
89 || confess "New type constraint setting must be a subtype of inherited one"
90 # iff we have a type constraint that is ...
91 if $self->has_type_constraint;
93 $actual_options{type_constraint} = $type_constraint;
96 (scalar keys %options == 0)
97 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
98 $self->clone(%actual_options);
101 sub _process_options {
102 my ($class, $name, $options) = @_;
104 if (exists $options->{is}) {
105 if ($options->{is} eq 'ro') {
106 $options->{reader} ||= $name;
107 (!exists $options->{trigger})
108 || confess "Cannot have a trigger on a read-only attribute";
110 elsif ($options->{is} eq 'rw') {
111 $options->{accessor} = $name;
112 ((reftype($options->{trigger}) || '') eq 'CODE')
113 || confess "Trigger must be a CODE ref"
114 if exists $options->{trigger};
117 confess "I do not understand this option (is => " . $options->{is} . ")"
121 if (exists $options->{isa}) {
123 if (exists $options->{does}) {
124 if (eval { $options->{isa}->can('does') }) {
125 ($options->{isa}->does($options->{does}))
126 || confess "Cannot have an isa option and a does option if the isa does not do the does";
129 confess "Cannot have an isa option which cannot ->does()";
133 # allow for anon-subtypes here ...
134 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
135 $options->{type_constraint} = $options->{isa};
139 if ($options->{isa} =~ /\|/) {
140 my @type_constraints = split /\s*\|\s*/ => $options->{isa};
141 $options->{type_constraint} = Moose::Util::TypeConstraints::create_type_constraint_union(
146 # otherwise assume it is a constraint
147 my $constraint = Moose::Util::TypeConstraints::find_type_constraint($options->{isa});
148 # if the constraing it not found ....
149 unless (defined $constraint) {
150 # assume it is a foreign class, and make
151 # an anon constraint for it
152 $constraint = Moose::Util::TypeConstraints::subtype(
154 Moose::Util::TypeConstraints::where { $_->isa($options->{isa}) }
157 $options->{type_constraint} = $constraint;
161 elsif (exists $options->{does}) {
162 # allow for anon-subtypes here ...
163 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
164 $options->{type_constraint} = $options->{isa};
167 # otherwise assume it is a constraint
168 my $constraint = Moose::Util::TypeConstraints::find_type_constraint($options->{does});
169 # if the constraing it not found ....
170 unless (defined $constraint) {
171 # assume it is a foreign class, and make
172 # an anon constraint for it
173 $constraint = Moose::Util::TypeConstraints::subtype(
175 Moose::Util::TypeConstraints::where { $_->does($options->{does}) }
178 $options->{type_constraint} = $constraint;
182 if (exists $options->{coerce} && $options->{coerce}) {
183 (exists $options->{type_constraint})
184 || confess "You cannot have coercion without specifying a type constraint";
185 confess "You cannot have a weak reference to a coerced value"
186 if $options->{weak_ref};
189 if (exists $options->{auto_deref} && $options->{auto_deref}) {
190 (exists $options->{type_constraint})
191 || confess "You cannot auto-dereference without specifying a type constraint";
192 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
193 $options->{type_constraint}->is_a_type_of('HashRef'))
194 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
197 if (exists $options->{lazy} && $options->{lazy}) {
198 (exists $options->{default})
199 || confess "You cannot have lazy attribute without specifying a default value for it";
203 sub initialize_instance_slot {
204 my ($self, $meta_instance, $instance, $params) = @_;
205 my $init_arg = $self->init_arg();
206 # try to fetch the init arg from the %params ...
209 if (exists $params->{$init_arg}) {
210 $val = $params->{$init_arg};
212 if (!defined $val && $self->is_required) {
213 confess "Attribute (" . $self->name . ") is required and cannot be undef";
217 # skip it if it's lazy
218 return if $self->is_lazy;
219 # and die if it's required and doesn't have a default value
220 confess "Attribute (" . $self->name . ") is required"
221 if $self->is_required && !$self->has_default;
224 # if nothing was in the %params, we can use the
225 # attribute's default value (if it has one)
226 if (!defined $val && $self->has_default) {
227 $val = $self->default($instance);
230 if (defined $val || $self->has_default) {
231 if ($self->has_type_constraint) {
232 my $type_constraint = $self->type_constraint;
233 if ($self->should_coerce && $type_constraint->has_coercion) {
234 $val = $type_constraint->coerce($val);
236 (defined($type_constraint->check($val)))
237 || confess "Attribute (" .
239 ") does not pass the type constraint (" .
240 $type_constraint->name .
243 ? (overload::Overloaded($val)
244 ? overload::StrVal($val)
251 $meta_instance->set_slot_value($instance, $self->name, $val);
252 $meta_instance->weaken_slot_value($instance, $self->name)
253 if ref $val && $self->is_weak_ref;
259 my ($self, $instance, $value) = @_;
261 my $attr_name = $self->name;
263 if ($self->is_required) {
265 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
268 if ($self->has_type_constraint) {
270 my $type_constraint = $self->type_constraint;
272 if ($self->should_coerce) {
273 $value = $type_constraint->coerce($value);
275 defined($type_constraint->_compiled_type_constraint->($value))
276 || confess "Attribute ($attr_name) does not pass the type constraint ("
277 . $type_constraint->name
280 ? ("'" . (overload::Overloaded($value) ? overload::StrVal($value) : $value) . "'")
285 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
288 $meta_instance->set_slot_value($instance, $attr_name, $value);
290 if (ref $value && $self->is_weak_ref) {
291 $meta_instance->weaken_slot_value($instance, $attr_name);
294 if ($self->has_trigger) {
295 $self->trigger->($instance, $value, $self);
300 my ($self, $instance) = @_;
302 if ($self->is_lazy) {
303 unless ($self->has_value($instance)) {
304 if ($self->has_default) {
305 my $default = $self->default($instance);
306 $self->set_value($instance, $default);
309 $self->set_value($instance, undef);
314 if ($self->should_auto_deref) {
316 my $type_constraint = $self->type_constraint;
318 if ($type_constraint->is_a_type_of('ArrayRef')) {
319 my $rv = $self->SUPER::get_value($instance);
320 return unless defined $rv;
321 return wantarray ? @{ $rv } : $rv;
323 elsif ($type_constraint->is_a_type_of('HashRef')) {
324 my $rv = $self->SUPER::get_value($instance);
325 return unless defined $rv;
326 return wantarray ? %{ $rv } : $rv;
329 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
335 return $self->SUPER::get_value($instance);
339 ## installing accessors
341 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
343 sub install_accessors {
345 $self->SUPER::install_accessors(@_);
347 if ($self->has_handles) {
350 # Here we canonicalize the 'handles' option
351 # this will sort out any details and always
352 # return an hash of methods which we want
353 # to delagate to, see that method for details
354 my %handles = $self->_canonicalize_handles();
356 # find the name of the accessor for this attribute
357 my $accessor_name = $self->reader || $self->accessor;
358 (defined $accessor_name)
359 || confess "You cannot install delegation without a reader or accessor for the attribute";
361 # make sure we handle HASH accessors correctly
362 ($accessor_name) = keys %{$accessor_name}
363 if ref($accessor_name) eq 'HASH';
365 # install the delegation ...
366 my $associated_class = $self->associated_class;
367 foreach my $handle (keys %handles) {
368 my $method_to_call = $handles{$handle};
370 (!$associated_class->has_method($handle))
371 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
374 # handles is not allowed to delegate
375 # any of these methods, as they will
376 # override the ones in your class, which
377 # is almost certainly not what you want.
378 next if $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
380 if ((reftype($method_to_call) || '') eq 'CODE') {
381 $associated_class->add_method($handle => $method_to_call);
384 $associated_class->add_method($handle => sub {
386 # we should check for lack of
387 # a callable return value from
389 my $proxy = (shift)->$accessor_name();
391 goto &{ $proxy->can($method_to_call)};
400 # private methods to help delegation ...
402 sub _canonicalize_handles {
404 my $handles = $self->handles;
405 if (my $handle_type = ref($handles)) {
406 if ($handle_type eq 'HASH') {
409 elsif ($handle_type eq 'ARRAY') {
410 return map { $_ => $_ } @{$handles};
412 elsif ($handle_type eq 'Regexp') {
413 ($self->has_type_constraint)
414 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
415 return map { ($_ => $_) }
416 grep { /$handles/ } $self->_get_delegate_method_list;
418 elsif ($handle_type eq 'CODE') {
419 return $handles->($self, $self->_find_delegate_metaclass);
422 confess "Unable to canonicalize the 'handles' option with $handles";
426 my $role_meta = eval { $handles->meta };
428 confess "Unable to canonicalize the 'handles' option with $handles because : $@";
431 (blessed $role_meta && $role_meta->isa('Moose::Meta::Role'))
432 || confess "Unable to canonicalize the 'handles' option with $handles because ->meta is not a Moose::Meta::Role";
434 return map { $_ => $_ } (
435 $role_meta->get_method_list,
436 $role_meta->get_required_method_list
441 sub _find_delegate_metaclass {
443 if (my $class = $self->_isa_metadata) {
444 # if the class does have
445 # a meta method, use it
446 return $class->meta if $class->can('meta');
447 # otherwise we might be
448 # dealing with a non-Moose
449 # class, and need to make
451 return Moose::Meta::Class->initialize($class);
453 elsif (my $role = $self->_does_metadata) {
454 # our role will always have
459 confess "Cannot find delegate metaclass for attribute " . $self->name;
463 sub _get_delegate_method_list {
465 my $meta = $self->_find_delegate_metaclass;
466 if ($meta->isa('Class::MOP::Class')) {
467 return map { $_->{name} } # NOTE: !never! delegate &meta
468 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
469 $meta->compute_all_applicable_methods;
471 elsif ($meta->isa('Moose::Meta::Role')) {
472 return $meta->get_method_list;
475 confess "Unable to recognize the delegate metaclass '$meta'";
487 Moose::Meta::Attribute - The Moose attribute metaclass
491 This is a subclass of L<Class::MOP::Attribute> with Moose specific
494 For the most part, the only time you will ever encounter an
495 instance of this class is if you are doing some serious deep
496 introspection. To really understand this class, you need to refer
497 to the L<Class::MOP::Attribute> documentation.
501 =head2 Overridden methods
503 These methods override methods in L<Class::MOP::Attribute> and add
504 Moose specific features. You can safely assume though that they
505 will behave just as L<Class::MOP::Attribute> does.
511 =item B<initialize_instance_slot>
513 =item B<install_accessors>
515 =item B<accessor_metaclass>
523 =head2 Additional Moose features
525 Moose attributes support type-constraint checking, weak reference
526 creation and type coercion.
530 =item B<clone_and_inherit_options>
532 This is to support the C<has '+foo'> feature, it clones an attribute
533 from a superclass and allows a very specific set of changes to be made
536 =item B<has_type_constraint>
538 Returns true if this meta-attribute has a type constraint.
540 =item B<type_constraint>
542 A read-only accessor for this meta-attribute's type constraint. For
543 more information on what you can do with this, see the documentation
544 for L<Moose::Meta::TypeConstraint>.
548 Returns true if this meta-attribute performs delegation.
552 This returns the value which was passed into the handles option.
556 Returns true if this meta-attribute produces a weak reference.
560 Returns true if this meta-attribute is required to have a value.
564 Returns true if this meta-attribute should be initialized lazily.
566 NOTE: lazy attributes, B<must> have a C<default> field set.
568 =item B<should_coerce>
570 Returns true if this meta-attribute should perform type coercion.
572 =item B<should_auto_deref>
574 Returns true if this meta-attribute should perform automatic
577 NOTE: This can only be done for attributes whose type constraint is
578 either I<ArrayRef> or I<HashRef>.
582 Returns true if this meta-attribute has a trigger set.
586 This is a CODE reference which will be executed every time the
587 value of an attribute is assigned. The CODE ref will get two values,
588 the invocant and the new value. This can be used to handle I<basic>
589 bi-directional relations.
591 =item B<documentation>
593 This is a string which contains the documentation for this attribute.
594 It serves no direct purpose right now, but it might in the future
595 in some kind of automated documentation system perhaps.
597 =item B<has_documentation>
599 Returns true if this meta-attribute has any documentation.
605 All complex software has bugs lurking in it, and this module is no
606 exception. If you find a bug please either email me, or add the bug
611 Stevan Little E<lt>stevan@iinteractive.comE<gt>
613 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
615 =head1 COPYRIGHT AND LICENSE
617 Copyright 2006, 2007 by Infinity Interactive, Inc.
619 L<http://www.iinteractive.com>
621 This library is free software; you can redistribute it and/or modify
622 it under the same terms as Perl itself.