2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
10 our $VERSION = '0.10';
11 our $AUTHORITY = 'cpan:STEVAN';
13 use Moose::Meta::Method::Accessor;
14 use Moose::Util::TypeConstraints ();
16 use base 'Class::MOP::Attribute';
18 # options which are not directly used
19 # but we store them for metadata purposes
20 __PACKAGE__->meta->add_attribute('isa' => (reader => '_isa_metadata'));
21 __PACKAGE__->meta->add_attribute('does' => (reader => '_does_metadata'));
22 __PACKAGE__->meta->add_attribute('is' => (reader => '_is_metadata'));
24 # these are actual options for the attrs
25 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
26 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
27 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce' ));
28 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
29 __PACKAGE__->meta->add_attribute('auto_deref' => (reader => 'should_auto_deref'));
30 __PACKAGE__->meta->add_attribute('type_constraint' => (
31 reader => 'type_constraint',
32 predicate => 'has_type_constraint',
34 __PACKAGE__->meta->add_attribute('trigger' => (
36 predicate => 'has_trigger',
38 __PACKAGE__->meta->add_attribute('handles' => (
40 predicate => 'has_handles',
42 __PACKAGE__->meta->add_attribute('documentation' => (
43 reader => 'documentation',
44 predicate => 'has_documentation',
48 my ($class, $name, %options) = @_;
49 $class->_process_options($name, \%options);
50 return $class->SUPER::new($name, %options);
53 sub clone_and_inherit_options {
54 my ($self, %options) = @_;
55 # you can change default, required, coerce and documentation
57 foreach my $legal_option (qw(default coerce required documentation)) {
58 if (exists $options{$legal_option}) {
59 $actual_options{$legal_option} = $options{$legal_option};
60 delete $options{$legal_option};
63 # isa can be changed, but only if the
64 # new type is a subtype
67 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
68 $type_constraint = $options{isa};
71 $type_constraint = Moose::Util::TypeConstraints::find_type_constraint($options{isa});
72 (defined $type_constraint)
73 || confess "Could not find the type constraint '" . $options{isa} . "'";
76 # check here to see if the new type
77 # is a subtype of the old one
78 ($type_constraint->is_subtype_of($self->type_constraint->name))
79 || confess "New type constraint setting must be a subtype of inherited one"
80 # iff we have a type constraint that is ...
81 if $self->has_type_constraint;
83 $actual_options{type_constraint} = $type_constraint;
86 (scalar keys %options == 0)
87 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
88 $self->clone(%actual_options);
91 sub _process_options {
92 my ($class, $name, $options) = @_;
94 if (exists $options->{is}) {
95 if ($options->{is} eq 'ro') {
96 $options->{reader} = $name;
97 (!exists $options->{trigger})
98 || confess "Cannot have a trigger on a read-only attribute";
100 elsif ($options->{is} eq 'rw') {
101 $options->{accessor} = $name;
102 ((reftype($options->{trigger}) || '') eq 'CODE')
103 || confess "Trigger must be a CODE ref"
104 if exists $options->{trigger};
107 confess "I do not understand this option (is => " . $options->{is} . ")"
111 if (exists $options->{isa}) {
113 if (exists $options->{does}) {
114 if (eval { $options->{isa}->can('does') }) {
115 ($options->{isa}->does($options->{does}))
116 || confess "Cannot have an isa option and a does option if the isa does not do the does";
119 confess "Cannot have an isa option which cannot ->does()";
123 # allow for anon-subtypes here ...
124 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
125 $options->{type_constraint} = $options->{isa};
129 if ($options->{isa} =~ /\|/) {
130 my @type_constraints = split /\s*\|\s*/ => $options->{isa};
131 $options->{type_constraint} = Moose::Util::TypeConstraints::create_type_constraint_union(
136 # otherwise assume it is a constraint
137 my $constraint = Moose::Util::TypeConstraints::find_type_constraint($options->{isa});
138 # if the constraing it not found ....
139 unless (defined $constraint) {
140 # assume it is a foreign class, and make
141 # an anon constraint for it
142 $constraint = Moose::Util::TypeConstraints::subtype(
144 Moose::Util::TypeConstraints::where { $_->isa($options->{isa}) }
147 $options->{type_constraint} = $constraint;
151 elsif (exists $options->{does}) {
152 # allow for anon-subtypes here ...
153 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
154 $options->{type_constraint} = $options->{isa};
157 # otherwise assume it is a constraint
158 my $constraint = Moose::Util::TypeConstraints::find_type_constraint($options->{does});
159 # if the constraing it not found ....
160 unless (defined $constraint) {
161 # assume it is a foreign class, and make
162 # an anon constraint for it
163 $constraint = Moose::Util::TypeConstraints::subtype(
165 Moose::Util::TypeConstraints::where { $_->does($options->{does}) }
168 $options->{type_constraint} = $constraint;
172 if (exists $options->{coerce} && $options->{coerce}) {
173 (exists $options->{type_constraint})
174 || confess "You cannot have coercion without specifying a type constraint";
175 confess "You cannot have a weak reference to a coerced value"
176 if $options->{weak_ref};
179 if (exists $options->{auto_deref} && $options->{auto_deref}) {
180 (exists $options->{type_constraint})
181 || confess "You cannot auto-dereference without specifying a type constraint";
182 ($options->{type_constraint}->is_a_type_of('ArrayRef') ||
183 $options->{type_constraint}->is_a_type_of('HashRef'))
184 || confess "You cannot auto-dereference anything other than a ArrayRef or HashRef";
187 if (exists $options->{lazy} && $options->{lazy}) {
188 (exists $options->{default})
189 || confess "You cannot have lazy attribute without specifying a default value for it";
193 sub initialize_instance_slot {
194 my ($self, $meta_instance, $instance, $params) = @_;
195 my $init_arg = $self->init_arg();
196 # try to fetch the init arg from the %params ...
199 if (exists $params->{$init_arg}) {
200 $val = $params->{$init_arg};
203 # skip it if it's lazy
204 return if $self->is_lazy;
205 # and die if it's required and doesn't have a default value
206 confess "Attribute (" . $self->name . ") is required"
207 if $self->is_required && !$self->has_default;
210 # if nothing was in the %params, we can use the
211 # attribute's default value (if it has one)
212 if (!defined $val && $self->has_default) {
213 $val = $self->default($instance);
217 if ($self->has_type_constraint) {
218 my $type_constraint = $self->type_constraint;
219 if ($self->should_coerce && $type_constraint->has_coercion) {
220 $val = $type_constraint->coerce($val);
222 (defined($type_constraint->check($val)))
223 || confess "Attribute (" .
225 ") does not pass the type constraint (" .
226 $type_constraint->name .
231 $meta_instance->set_slot_value($instance, $self->name, $val);
232 $meta_instance->weaken_slot_value($instance, $self->name)
233 if ref $val && $self->is_weak_ref;
239 my ($self, $instance, $value) = @_;
241 my $attr_name = $self->name;
243 if ($self->is_required) {
245 || confess "Attribute ($attr_name) is required, so cannot be set to undef";
248 if ($self->has_type_constraint) {
250 my $type_constraint = $self->type_constraint;
252 if ($self->should_coerce) {
253 $value = $type_constraint->coerce($value);
255 defined($type_constraint->_compiled_type_constraint->($value))
256 || confess "Attribute ($attr_name) does not pass the type constraint ("
257 . $type_constraint->name . ") with " . (defined($value) ? ("'" . $value . "'") : "undef")
261 my $meta_instance = Class::MOP::Class->initialize(blessed($instance))
264 $meta_instance->set_slot_value($instance, $attr_name, $value);
266 if (ref $value && $self->is_weak_ref) {
267 $meta_instance->weaken_slot_value($instance, $attr_name);
270 if ($self->has_trigger) {
271 $self->trigger->($instance, $value, $self);
276 my ($self, $instance) = @_;
278 if ($self->is_lazy) {
279 unless ($self->has_value($instance)) {
280 if ($self->has_default) {
281 my $default = $self->default($instance);
282 $self->set_value($instance, $default);
285 $self->set_value($instance, undef);
290 if ($self->should_auto_deref) {
292 my $type_constraint = $self->type_constraint;
294 if ($type_constraint->is_a_type_of('ArrayRef')) {
295 my $rv = $self->SUPER::get_value($instance);
296 return unless defined $rv;
297 return wantarray ? @{ $rv } : $rv;
299 elsif ($type_constraint->is_a_type_of('HashRef')) {
300 my $rv = $self->SUPER::get_value($instance);
301 return unless defined $rv;
302 return wantarray ? %{ $rv } : $rv;
305 confess "Can not auto de-reference the type constraint '" . $type_constraint->name . "'";
311 return $self->SUPER::get_value($instance);
315 ## installing accessors
317 sub accessor_metaclass { 'Moose::Meta::Method::Accessor' }
319 sub install_accessors {
321 $self->SUPER::install_accessors(@_);
323 if ($self->has_handles) {
326 # Here we canonicalize the 'handles' option
327 # this will sort out any details and always
328 # return an hash of methods which we want
329 # to delagate to, see that method for details
330 my %handles = $self->_canonicalize_handles();
332 # find the name of the accessor for this attribute
333 my $accessor_name = $self->reader || $self->accessor;
334 (defined $accessor_name)
335 || confess "You cannot install delegation without a reader or accessor for the attribute";
337 # make sure we handle HASH accessors correctly
338 ($accessor_name) = keys %{$accessor_name}
339 if ref($accessor_name) eq 'HASH';
341 # install the delegation ...
342 my $associated_class = $self->associated_class;
343 foreach my $handle (keys %handles) {
344 my $method_to_call = $handles{$handle};
346 (!$associated_class->has_method($handle))
347 || confess "You cannot overwrite a locally defined method ($handle) with a delegation";
350 # handles is not allowed to delegate
351 # any of these methods, as they will
352 # override the ones in your class, which
353 # is almost certainly not what you want.
354 next if $handle =~ /^BUILD|DEMOLISH$/ || Moose::Object->can($handle);
356 if ((reftype($method_to_call) || '') eq 'CODE') {
357 $associated_class->add_method($handle => $method_to_call);
360 $associated_class->add_method($handle => sub {
362 # we should check for lack of
363 # a callable return value from
365 ((shift)->$accessor_name())->$method_to_call(@_);
374 # private methods to help delegation ...
376 sub _canonicalize_handles {
378 my $handles = $self->handles;
379 if (ref($handles) eq 'HASH') {
382 elsif (ref($handles) eq 'ARRAY') {
383 return map { $_ => $_ } @{$handles};
385 elsif (ref($handles) eq 'Regexp') {
386 ($self->has_type_constraint)
387 || confess "Cannot delegate methods based on a RegExpr without a type constraint (isa)";
388 return map { ($_ => $_) }
389 grep { /$handles/ } $self->_get_delegate_method_list;
391 elsif (ref($handles) eq 'CODE') {
392 return $handles->($self, $self->_find_delegate_metaclass);
395 confess "Unable to canonicalize the 'handles' option with $handles";
399 sub _find_delegate_metaclass {
401 if (my $class = $self->_isa_metadata) {
402 # if the class does have
403 # a meta method, use it
404 return $class->meta if $class->can('meta');
405 # otherwise we might be
406 # dealing with a non-Moose
407 # class, and need to make
409 return Moose::Meta::Class->initialize($class);
411 elsif (my $role = $self->_does_metadata) {
412 # our role will always have
417 confess "Cannot find delegate metaclass for attribute " . $self->name;
421 sub _get_delegate_method_list {
423 my $meta = $self->_find_delegate_metaclass;
424 if ($meta->isa('Class::MOP::Class')) {
425 return map { $_->{name} } # NOTE: !never! delegate &meta
426 grep { $_->{class} ne 'Moose::Object' && $_->{name} ne 'meta' }
427 $meta->compute_all_applicable_methods;
429 elsif ($meta->isa('Moose::Meta::Role')) {
430 return $meta->get_method_list;
433 confess "Unable to recognize the delegate metaclass '$meta'";
445 Moose::Meta::Attribute - The Moose attribute metaclass
449 This is a subclass of L<Class::MOP::Attribute> with Moose specific
452 For the most part, the only time you will ever encounter an
453 instance of this class is if you are doing some serious deep
454 introspection. To really understand this class, you need to refer
455 to the L<Class::MOP::Attribute> documentation.
459 =head2 Overridden methods
461 These methods override methods in L<Class::MOP::Attribute> and add
462 Moose specific features. You can safely assume though that they
463 will behave just as L<Class::MOP::Attribute> does.
469 =item B<initialize_instance_slot>
471 =item B<install_accessors>
473 =item B<accessor_metaclass>
481 =head2 Additional Moose features
483 Moose attributes support type-constraint checking, weak reference
484 creation and type coercion.
488 =item B<clone_and_inherit_options>
490 This is to support the C<has '+foo'> feature, it clones an attribute
491 from a superclass and allows a very specific set of changes to be made
494 =item B<has_type_constraint>
496 Returns true if this meta-attribute has a type constraint.
498 =item B<type_constraint>
500 A read-only accessor for this meta-attribute's type constraint. For
501 more information on what you can do with this, see the documentation
502 for L<Moose::Meta::TypeConstraint>.
506 Returns true if this meta-attribute performs delegation.
510 This returns the value which was passed into the handles option.
514 Returns true if this meta-attribute produces a weak reference.
518 Returns true if this meta-attribute is required to have a value.
522 Returns true if this meta-attribute should be initialized lazily.
524 NOTE: lazy attributes, B<must> have a C<default> field set.
526 =item B<should_coerce>
528 Returns true if this meta-attribute should perform type coercion.
530 =item B<should_auto_deref>
532 Returns true if this meta-attribute should perform automatic
535 NOTE: This can only be done for attributes whose type constraint is
536 either I<ArrayRef> or I<HashRef>.
540 Returns true if this meta-attribute has a trigger set.
544 This is a CODE reference which will be executed every time the
545 value of an attribute is assigned. The CODE ref will get two values,
546 the invocant and the new value. This can be used to handle I<basic>
547 bi-directional relations.
549 =item B<documentation>
551 This is a string which contains the documentation for this attribute.
552 It serves no direct purpose right now, but it might in the future
553 in some kind of automated documentation system perhaps.
555 =item B<has_documentation>
557 Returns true if this meta-attribute has any documentation.
563 All complex software has bugs lurking in it, and this module is no
564 exception. If you find a bug please either email me, or add the bug
569 Stevan Little E<lt>stevan@iinteractive.comE<gt>
571 Yuval Kogman E<lt>nothingmuch@woobling.comE<gt>
573 =head1 COPYRIGHT AND LICENSE
575 Copyright 2006, 2007 by Infinity Interactive, Inc.
577 L<http://www.iinteractive.com>
579 This library is free software; you can redistribute it and/or modify
580 it under the same terms as Perl itself.