2 package Moose::Meta::Attribute;
7 use Scalar::Util 'blessed', 'weaken', 'reftype';
10 our $VERSION = '0.05';
12 use Moose::Util::TypeConstraints ();
14 use base 'Class::MOP::Attribute';
16 __PACKAGE__->meta->add_attribute('required' => (reader => 'is_required' ));
17 __PACKAGE__->meta->add_attribute('lazy' => (reader => 'is_lazy' ));
18 __PACKAGE__->meta->add_attribute('coerce' => (reader => 'should_coerce'));
19 __PACKAGE__->meta->add_attribute('weak_ref' => (reader => 'is_weak_ref' ));
20 __PACKAGE__->meta->add_attribute('type_constraint' => (
21 reader => 'type_constraint',
22 predicate => 'has_type_constraint',
24 __PACKAGE__->meta->add_attribute('trigger' => (
26 predicate => 'has_trigger',
30 my ($class, $name, %options) = @_;
31 $class->_process_options($name, \%options);
32 $class->SUPER::new($name, %options);
35 sub clone_and_inherit_options {
36 my ($self, %options) = @_;
37 # you can change default, required and coerce
39 foreach my $legal_option (qw(default coerce required)) {
40 if (exists $options{$legal_option}) {
41 $actual_options{$legal_option} = $options{$legal_option};
42 delete $options{$legal_option};
45 # isa can be changed, but only if the
46 # new type is a subtype
49 if (blessed($options{isa}) && $options{isa}->isa('Moose::Meta::TypeConstraint')) {
50 $type_constraint = $options{isa};
53 $type_constraint = Moose::Util::TypeConstraints::find_type_constraint($options{isa});
54 (defined $type_constraint)
55 || confess "Could not find the type constraint '" . $options{isa} . "'";
57 ($type_constraint->is_subtype_of($self->type_constraint->name))
58 || confess "New type constraint setting must be a subtype of inherited one"
59 if $self->has_type_constraint;
60 $actual_options{type_constraint} = $type_constraint;
63 (scalar keys %options == 0)
64 || confess "Illegal inherited options => (" . (join ', ' => keys %options) . ")";
65 $self->clone(%actual_options);
68 sub _process_options {
69 my ($class, $name, $options) = @_;
70 if (exists $options->{is}) {
71 if ($options->{is} eq 'ro') {
72 $options->{reader} = $name;
73 (!exists $options->{trigger})
74 || confess "Cannot have a trigger on a read-only attribute";
76 elsif ($options->{is} eq 'rw') {
77 $options->{accessor} = $name;
78 ((reftype($options->{trigger}) || '') eq 'CODE')
79 || confess "A trigger must be a CODE reference"
80 if exists $options->{trigger};
84 if (exists $options->{isa}) {
86 if (exists $options->{does}) {
87 if (eval { $options->{isa}->can('does') }) {
88 ($options->{isa}->does($options->{does}))
89 || confess "Cannot have an isa option and a does option if the isa does not do the does";
92 confess "Cannot have an isa option which cannot ->does()";
96 # allow for anon-subtypes here ...
97 if (blessed($options->{isa}) && $options->{isa}->isa('Moose::Meta::TypeConstraint')) {
98 $options->{type_constraint} = $options->{isa};
102 if ($options->{isa} =~ /\|/) {
103 my @type_constraints = split /\s*\|\s*/ => $options->{isa};
104 $options->{type_constraint} = Moose::Util::TypeConstraints::create_type_constraint_union(
109 # otherwise assume it is a constraint
110 my $constraint = Moose::Util::TypeConstraints::find_type_constraint($options->{isa});
111 # if the constraing it not found ....
112 unless (defined $constraint) {
113 # assume it is a foreign class, and make
114 # an anon constraint for it
115 $constraint = Moose::Util::TypeConstraints::subtype(
117 Moose::Util::TypeConstraints::where { $_->isa($options->{isa}) }
120 $options->{type_constraint} = $constraint;
124 elsif (exists $options->{does}) {
125 # allow for anon-subtypes here ...
126 if (blessed($options->{does}) && $options->{does}->isa('Moose::Meta::TypeConstraint')) {
127 $options->{type_constraint} = $options->{isa};
130 # otherwise assume it is a constraint
131 my $constraint = Moose::Util::TypeConstraints::find_type_constraint($options->{does});
132 # if the constraing it not found ....
133 unless (defined $constraint) {
134 # assume it is a foreign class, and make
135 # an anon constraint for it
136 $constraint = Moose::Util::TypeConstraints::subtype(
138 Moose::Util::TypeConstraints::where { $_->does($options->{does}) }
141 $options->{type_constraint} = $constraint;
145 if (exists $options->{coerce} && $options->{coerce}) {
146 (exists $options->{type_constraint})
147 || confess "You cannot have coercion without specifying a type constraint";
148 (!$options->{type_constraint}->isa('Moose::Meta::TypeConstraint::Union'))
149 || confess "You cannot have coercion with a type constraint union";
150 confess "You cannot have a weak reference to a coerced value"
151 if $options->{weak_ref};
154 if (exists $options->{lazy} && $options->{lazy}) {
155 (exists $options->{default})
156 || confess "You cannot have lazy attribute without specifying a default value for it";
160 sub initialize_instance_slot {
161 my ($self, $meta_instance, $instance, $params) = @_;
162 my $init_arg = $self->init_arg();
163 # try to fetch the init arg from the %params ...
166 if (exists $params->{$init_arg}) {
167 $val = $params->{$init_arg};
170 # skip it if it's lazy
171 return if $self->is_lazy;
172 # and die if it's required and doesn't have a default value
173 confess "Attribute (" . $self->name . ") is required"
174 if $self->is_required && !$self->has_default;
177 # if nothing was in the %params, we can use the
178 # attribute's default value (if it has one)
179 if (!defined $val && $self->has_default) {
180 $val = $self->default($instance);
183 if ($self->has_type_constraint) {
184 my $type_constraint = $self->type_constraint;
185 if ($self->should_coerce && $type_constraint->has_coercion) {
186 $val = $type_constraint->coercion->coerce($val);
188 (defined($type_constraint->check($val)))
189 || confess "Attribute (" .
191 ") does not pass the type contraint (" .
192 $type_constraint->name .
197 $meta_instance->set_slot_value($instance, $self->name, $val);
198 $meta_instance->weaken_slot_value($instance, $self->name)
199 if ref $val && $self->is_weak_ref;
202 sub _inline_check_constraint {
203 my ($self, $value) = @_;
204 return '' unless $self->has_type_constraint;
206 # FIXME - remove 'unless defined($value) - constraint Undef
207 return sprintf <<'EOF', $value, $value, $value, $value
208 defined($attr->type_constraint->check(%s))
209 || confess "Attribute (" . $attr->name . ") does not pass the type contraint ("
210 . $attr->type_constraint->name . ") with " . (defined(%s) ? "'%s'" : "undef")
216 my ($self, $instance, $value) = @_;
218 my $mi = $self->associated_class->get_meta_instance;
219 my $slot_name = sprintf "'%s'", $self->slots;
221 my $code = $mi->inline_set_slot_value($instance, $slot_name, $value) . ";";
222 $code .= $mi->inline_weaken_slot_value($instance, $slot_name, $value) . ";"
223 if $self->is_weak_ref;
227 sub _inline_trigger {
228 my ($self, $instance, $value) = @_;
229 return '' unless $self->has_trigger;
230 return sprintf('$attr->trigger->(%s, %s, $attr);', $instance, $value);
234 my ($self, $instance) = @_;
236 my $mi = $self->associated_class->get_meta_instance;
237 my $slot_name = sprintf "'%s'", $self->slots;
239 return $mi->inline_get_slot_value($instance, $slot_name);
242 sub generate_accessor_method {
243 my ($attr, $attr_name) = @_;
244 my $value_name = $attr->should_coerce ? '$val' : '$_[1]';
245 my $mi = $attr->associated_class->get_meta_instance;
246 my $slot_name = sprintf "'%s'", $attr->slots;
249 . 'if (scalar(@_) == 2) {'
250 . ($attr->is_required ?
251 'defined($_[1]) || confess "Attribute ($attr_name) is required, so cannot be set to undef";'
253 . ($attr->should_coerce ?
254 'my $val = $attr->type_constraint->coercion->coerce($_[1]);'
256 . $attr->_inline_check_constraint($value_name)
257 . $attr->_inline_store($inv, $value_name)
258 . $attr->_inline_trigger($inv, $value_name)
261 '$_[0]->{$attr_name} = ($attr->has_default ? $attr->default($_[0]) : undef)'
262 . 'unless exists $_[0]->{$attr_name};'
264 . 'return ' . $attr->_inline_get( $inv )
266 my $sub = eval $code;
267 warn "Could not create accessor for '$attr_name' because $@ \n code: $code" if $@;
268 confess "Could not create accessor for '$attr_name' because $@ \n code: $code" if $@;
272 sub generate_writer_method {
273 my ($attr, $attr_name) = @_;
274 my $value_name = $attr->should_coerce ? '$val' : '$_[1]';
277 . ($attr->is_required ?
278 'defined($_[1]) || confess "Attribute ($attr_name) is required, so cannot be set to undef";'
280 . ($attr->should_coerce ?
281 'my $val = $attr->type_constraint->coercion->coerce($_[1]);'
283 . $attr->_inline_check_constraint($value_name)
284 . $attr->_inline_store($inv, $value_name)
285 . $attr->_inline_trigger($inv, $value_name)
287 my $sub = eval $code;
288 confess "Could not create writer for '$attr_name' because $@ \n code: $code" if $@;
292 sub generate_reader_method {
294 my $attr_name = $self->slots;
296 . 'confess "Cannot assign a value to a read-only accessor" if @_ > 1;'
298 '$_[0]->{$attr_name} = ($self->has_default ? $self->default($_[0]) : undef)'
299 . 'unless exists $_[0]->{$attr_name};'
301 . 'return $_[0]->{$attr_name};'
303 my $sub = eval $code;
304 confess "Could not create reader for '$attr_name' because $@ \n code: $code" if $@;
316 Moose::Meta::Attribute - The Moose attribute metaclass
320 This is a subclass of L<Class::MOP::Attribute> with Moose specific
323 For the most part, the only time you will ever encounter an
324 instance of this class is if you are doing some serious deep
325 introspection. To really understand this class, you need to refer
326 to the L<Class::MOP::Attribute> documentation.
330 =head2 Overridden methods
332 These methods override methods in L<Class::MOP::Attribute> and add
333 Moose specific features. You can safely assume though that they
334 will behave just as L<Class::MOP::Attribute> does.
340 =item B<clone_and_inherit_options>
342 =item B<initialize_instance_slot>
344 =item B<generate_accessor_method>
346 =item B<generate_writer_method>
348 =item B<generate_reader_method>
352 =head2 Additional Moose features
354 Moose attributes support type-contstraint checking, weak reference
355 creation and type coercion.
359 =item B<has_type_constraint>
361 Returns true if this meta-attribute has a type constraint.
363 =item B<type_constraint>
365 A read-only accessor for this meta-attribute's type constraint. For
366 more information on what you can do with this, see the documentation
367 for L<Moose::Meta::TypeConstraint>.
371 Returns true if this meta-attribute produces a weak reference.
375 Returns true if this meta-attribute is required to have a value.
379 Returns true if this meta-attribute should be initialized lazily.
381 NOTE: lazy attributes, B<must> have a C<default> field set.
383 =item B<should_coerce>
385 Returns true if this meta-attribute should perform type coercion.
389 Returns true if this meta-attribute has a trigger set.
393 This is a CODE reference which will be executed every time the
394 value of an attribute is assigned. The CODE ref will get two values,
395 the invocant and the new value. This can be used to handle I<basic>
396 bi-directional relations.
402 All complex software has bugs lurking in it, and this module is no
403 exception. If you find a bug please either email me, or add the bug
408 Stevan Little E<lt>stevan@iinteractive.comE<gt>
410 =head1 COPYRIGHT AND LICENSE
412 Copyright 2006 by Infinity Interactive, Inc.
414 L<http://www.iinteractive.com>
416 This library is free software; you can redistribute it and/or modify
417 it under the same terms as Perl itself.