1 package Mouse::Meta::Attribute;
2 use Mouse::Util qw(:meta); # enables strict and warnings
6 use Mouse::Meta::TypeConstraint;
9 my($class, $name, $args) = @_;
11 # taken from Class::MOP::Attribute::new
14 or $class->throw_error('You must provide a name for the attribute');
16 if(!exists $args->{init_arg}){
17 $args->{init_arg} = $name;
20 # 'required' requires eigher 'init_arg', 'builder', or 'default'
21 my $can_be_required = defined( $args->{init_arg} );
23 if(exists $args->{builder}){
25 # Moose refuses a CODE ref builder, but Mouse doesn't for backward compatibility
26 # This feature will be changed in a future. (gfx)
27 $class->throw_error('builder must be a defined scalar value which is a method name')
28 #if ref $args->{builder} || !defined $args->{builder};
29 if !defined $args->{builder};
33 elsif(exists $args->{default}){
34 if(ref $args->{default} && ref($args->{default}) ne 'CODE'){
35 $class->throw_error("References are not allowed as default values, you must "
36 . "wrap the default of '$name' in a CODE reference (ex: sub { [] } and not [])");
41 if( $args->{required} && !$can_be_required ) {
42 $class->throw_error("You cannot have a required attribute ($name) without a default, builder, or an init_arg");
45 # taken from Mouse::Meta::Attribute->new and _process_args->
47 if(exists $args->{is}){
51 $args->{reader} ||= $name;
54 if(exists $args->{writer}){
55 $args->{reader} ||= $name;
58 $args->{accessor} ||= $name;
62 # do nothing, but don't complain (later) about missing methods
65 $is = 'undef' if !defined $is;
66 $class->throw_error("I do not understand this option (is => $is) on attribute ($name)");
71 if(exists $args->{isa}){
72 $args->{type_constraint} = Mouse::Util::TypeConstraints::find_or_create_isa_type_constraint($args->{isa});
74 elsif(exists $args->{does}){
75 $args->{type_constraint} = Mouse::Util::TypeConstraints::find_or_create_does_type_constraint($args->{does});
77 $tc = $args->{type_constraint};
81 || $class->throw_error("You cannot have coercion without specifying a type constraint on attribute ($name)");
84 && $class->throw_error("You cannot have a weak reference to a coerced value on attribute ($name)");
87 if ($args->{lazy_build}) {
88 exists($args->{default})
89 && $class->throw_error("You can not use lazy_build and default for the same attribute ($name)");
92 $args->{builder} ||= "_build_${name}";
94 $args->{clearer} ||= "_clear${name}";
95 $args->{predicate} ||= "_has${name}";
98 $args->{clearer} ||= "clear_${name}";
99 $args->{predicate} ||= "has_${name}";
103 if ($args->{auto_deref}) {
105 || $class->throw_error("You cannot auto-dereference without specifying a type constraint on attribute ($name)");
107 ( $tc->is_a_type_of('ArrayRef') || $tc->is_a_type_of('HashRef') )
108 || $class->throw_error("You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute ($name)");
111 if (exists $args->{trigger}) {
112 ('CODE' eq ref $args->{trigger})
113 || $class->throw_error("Trigger must be a CODE ref on attribute ($name)");
117 (exists $args->{default} || defined $args->{builder})
118 || $class->throw_error("You cannot have lazy attribute ($name) without specifying a default value for it");
128 my %args = (@_ == 1) ? %{ $_[0] } : @_;
130 $class->_process_options($name, \%args);
134 my $self = bless \%args, $class;
137 if($class ne __PACKAGE__){
138 $class->meta->_initialize_object($self, \%args);
141 # XXX: there is no fast way to check attribute validity
145 # Carp::cluck("Found unknown argument(s) passed to '$name' attribute constructor in '$class': @bad");
151 sub has_read_method { $_[0]->has_reader || $_[0]->has_accessor }
152 sub has_write_method { $_[0]->has_writer || $_[0]->has_accessor }
154 sub interpolate_class{
155 my($class, $args) = @_;
157 if(my $metaclass = delete $args->{metaclass}){
158 $class = Mouse::Util::resolve_metaclass_alias( Attribute => $metaclass );
162 if(my $traits_ref = delete $args->{traits}){
164 for (my $i = 0; $i < @{$traits_ref}; $i++) {
165 my $trait = Mouse::Util::resolve_metaclass_alias(Attribute => $traits_ref->[$i], trait => 1);
167 next if $class->does($trait);
169 push @traits, $trait;
172 push @traits, $traits_ref->[++$i]
173 if ref($traits_ref->[$i+1]);
177 $class = Mouse::Meta::Class->create_anon_class(
178 superclasses => [ $class ],
185 return( $class, @traits );
188 sub _coerce_and_verify {
189 my($self, $value, $instance) = @_;
191 my $type_constraint = $self->{type_constraint};
192 return $value if !defined $type_constraint;
194 if ($self->should_coerce && $type_constraint->has_coercion) {
195 $value = $type_constraint->coerce($value);
198 $self->verify_against_type_constraint($value);
203 sub verify_against_type_constraint {
204 my ($self, $value) = @_;
206 my $type_constraint = $self->{type_constraint};
207 return 1 if !$type_constraint;
208 return 1 if $type_constraint->check($value);
210 $self->_throw_type_constraint_error($value, $type_constraint);
213 sub _throw_type_constraint_error {
214 my($self, $value, $type) = @_;
217 sprintf q{Attribute (%s) does not pass the type constraint because: %s},
219 $type->get_message($value),
223 sub clone_and_inherit_options{
224 my($self, %args) = @_;
226 my($attribute_class, @traits) = ref($self)->interpolate_class(\%args);
228 $args{traits} = \@traits if @traits;
229 # do not inherit the 'handles' attribute
230 foreach my $name(keys %{$self}){
231 if(!exists $args{$name} && $name ne 'handles'){
232 $args{$name} = $self->{$name};
235 return $attribute_class->new($self->name, %args);
238 sub get_read_method {
239 return $_[0]->reader || $_[0]->accessor
241 sub get_write_method {
242 return $_[0]->writer || $_[0]->accessor
245 sub _get_accessor_method_ref {
246 my($self, $type, $generator) = @_;
248 my $metaclass = $self->associated_class
249 || $self->throw_error('No asocciated class for ' . $self->name);
251 my $accessor = $self->$type();
253 return $metaclass->get_method_body($accessor);
256 return $self->accessor_metaclass->$generator($self, $metaclass);
260 sub get_read_method_ref{
262 return $self->{_read_method_ref} ||= $self->_get_accessor_method_ref('get_read_method', '_generate_reader');
265 sub get_write_method_ref{
267 return $self->{_write_method_ref} ||= $self->_get_accessor_method_ref('get_write_method', '_generate_writer');
271 my($self, $object, $value) = @_;
272 return $self->get_write_method_ref()->($object, $value);
276 my($self, $object) = @_;
277 return $self->get_read_method_ref()->($object);
281 my($self, $object) = @_;
282 my $accessor_ref = $self->{_predicate_ref}
283 ||= $self->_get_accessor_method_ref('predicate', '_generate_predicate');
285 return $accessor_ref->($object);
289 my($self, $object) = @_;
290 my $accessor_ref = $self->{_crealer_ref}
291 ||= $self->_get_accessor_method_ref('clearer', '_generate_clearer');
293 return $accessor_ref->($object);
297 sub associate_method{
298 my ($attribute, $method_name) = @_;
299 $attribute->{associated_methods}++;
303 sub install_accessors{
306 my $metaclass = $attribute->associated_class;
307 my $accessor_class = $attribute->accessor_metaclass;
309 foreach my $type(qw(accessor reader writer predicate clearer)){
310 if(exists $attribute->{$type}){
311 my $generator = '_generate_' . $type;
312 my $code = $accessor_class->$generator($attribute, $metaclass);
313 $metaclass->add_method($attribute->{$type} => $code);
314 $attribute->associate_method($attribute->{$type});
319 if(exists $attribute->{handles}){
320 my %handles = $attribute->_canonicalize_handles($attribute->{handles});
322 while(my($handle, $method_to_call) = each %handles){
323 $metaclass->add_method($handle =>
324 $attribute->_make_delegation_method(
325 $handle, $method_to_call));
327 $attribute->associate_method($handle);
334 sub delegation_metaclass() { 'Mouse::Meta::Method::Delegation' }
336 sub _canonicalize_handles {
337 my($self, $handles) = @_;
339 if (ref($handles) eq 'HASH') {
342 elsif (ref($handles) eq 'ARRAY') {
343 return map { $_ => $_ } @$handles;
345 elsif (ref($handles) eq 'Regexp') {
346 my $class_or_role = ($self->{isa} || $self->{does})
347 || $self->throw_error("Cannot delegate methods based on a Regexp without a type constraint (isa)");
349 my $meta = Mouse::Meta::Class->initialize("$class_or_role"); # "" for stringify
350 return map { $_ => $_ }
351 grep { !Mouse::Object->can($_) && $_ =~ $handles }
352 Mouse::Util::is_a_metarole($meta)
353 ? $meta->get_method_list
354 : $meta->get_all_method_names;
357 $self->throw_error("Unable to canonicalize the 'handles' option with $handles");
361 sub _make_delegation_method {
362 my($self, $handle, $method_to_call) = @_;
363 my $delegator = $self->delegation_metaclass;
364 Mouse::Util::load_class($delegator);
366 return $delegator->_generate_delegation($self, $handle, $method_to_call);
372 my $metaclass = (ref $self && $self->associated_class) || 'Mouse::Meta::Class';
373 $metaclass->throw_error(@_, depth => 1);
381 Mouse::Meta::Attribute - The Mouse attribute metaclass
385 This document describes Mouse version 0.45
389 =head2 C<< new(%options) -> Mouse::Meta::Attribute >>
391 Instantiates a new Mouse::Meta::Attribute. Does nothing else.
393 It adds the following options to the constructor:
397 =item C<< is => 'ro', 'rw', 'bare' >>
399 This provides a shorthand for specifying the C<reader>, C<writer>, or
400 C<accessor> names. If the attribute is read-only ('ro') then it will
401 have a C<reader> method with the same attribute as the name.
403 If it is read-write ('rw') then it will have an C<accessor> method
404 with the same name. If you provide an explicit C<writer> for a
405 read-write attribute, then you will have a C<reader> with the same
406 name as the attribute, and a C<writer> with the name you provided.
408 Use 'bare' when you are deliberately not installing any methods
409 (accessor, reader, etc.) associated with this attribute; otherwise,
410 Moose will issue a deprecation warning when this attribute is added to a
413 =item C<< isa => Type >>
415 This option accepts a type. The type can be a string, which should be
416 a type name. If the type name is unknown, it is assumed to be a class
419 This option can also accept a L<Moose::Meta::TypeConstraint> object.
421 If you I<also> provide a C<does> option, then your C<isa> option must
422 be a class name, and that class must do the role specified with
425 =item C<< does => Role >>
427 This is short-hand for saying that the attribute's type must be an
428 object which does the named role.
430 B<This option is not yet supported.>
432 =item C<< coerce => Bool >>
434 This option is only valid for objects with a type constraint
435 (C<isa>). If this is true, then coercions will be applied whenever
436 this attribute is set.
438 You can make both this and the C<weak_ref> option true.
440 =item C<< trigger => CodeRef >>
442 This option accepts a subroutine reference, which will be called after
443 the attribute is set.
445 =item C<< required => Bool >>
447 An attribute which is required must be provided to the constructor. An
448 attribute which is required can also have a C<default> or C<builder>,
449 which will satisfy its required-ness.
451 A required attribute must have a C<default>, C<builder> or a
452 non-C<undef> C<init_arg>
454 =item C<< lazy => Bool >>
456 A lazy attribute must have a C<default> or C<builder>. When an
457 attribute is lazy, the default value will not be calculated until the
460 =item C<< weak_ref => Bool >>
462 If this is true, the attribute's value will be stored as a weak
465 =item C<< auto_deref => Bool >>
467 If this is true, then the reader will dereference the value when it is
468 called. The attribute must have a type constraint which defines the
469 attribute as an array or hash reference.
471 =item C<< lazy_build => Bool >>
473 Setting this to true makes the attribute lazy and provides a number of
481 is equivalent to this:
486 builder => '_build_size',
487 clearer => 'clear_size',
488 predicate => 'has_size',
493 =head2 C<< associate_method(MethodName) >>
495 Associates a method with the attribute. Typically, this is called internally
496 when an attribute generates its accessors.
498 Currently the argument I<MethodName> is ignored in Mouse.
500 =head2 C<< verify_against_type_constraint(Item) -> TRUE | ERROR >>
502 Checks that the given value passes this attribute's type constraint. Returns C<true>
503 on success, otherwise C<confess>es.
505 =head2 C<< clone_and_inherit_options(options) -> Mouse::Meta::Attribute >>
507 Creates a new attribute in the owner class, inheriting options from parent classes.
508 Accessors and helper methods are installed. Some error checking is done.
510 =head2 C<< get_read_method_ref >>
512 =head2 C<< get_write_method_ref >>
514 Returns the subroutine reference of a method suitable for reading or
515 writing the attribute's value in the associated class. These methods
516 always return a subroutine reference, regardless of whether or not the
517 attribute is read- or write-only.
521 L<Moose::Meta::Attribute>
523 L<Class::MOP::Attribute>