Fix up the Pod tests
[gitmo/Moose.git] / lib / Moose.pm
CommitLineData
fcd84ca9 1package Moose;
d1e17c7f 2use strict;
3use warnings;
fcd84ca9 4
ecb1297a 5use 5.008;
6
6d0815b5 7our $VERSION = '0.93';
75b95414 8$VERSION = eval $VERSION;
d44714be 9our $AUTHORITY = 'cpan:STEVAN';
fcd84ca9 10
21f1e231 11use Scalar::Util 'blessed';
e2095e4a 12use Carp 'confess';
fcd84ca9 13
5bd4db9b 14use Moose::Exporter;
7f18097c 15
28036bc4 16use Class::MOP 0.94;
ef1d5f4b 17
c0e30cf5 18use Moose::Meta::Class;
7415b2cb 19use Moose::Meta::TypeConstraint;
7c13858b 20use Moose::Meta::TypeCoercion;
78cd1d3b 21use Moose::Meta::Attribute;
ddd0ec20 22use Moose::Meta::Instance;
c0e30cf5 23
0779da92 24use Moose::Object;
25
d67145ed 26use Moose::Meta::Role;
0779da92 27use Moose::Meta::Role::Composite;
28use Moose::Meta::Role::Application;
29use Moose::Meta::Role::Application::RoleSummation;
30use Moose::Meta::Role::Application::ToClass;
31use Moose::Meta::Role::Application::ToRole;
32use Moose::Meta::Role::Application::ToInstance;
d67145ed 33
7415b2cb 34use Moose::Util::TypeConstraints;
d7d8a8c7 35use Moose::Util ();
a15dff8d 36
17e5e226 37use Moose::Meta::Attribute::Native;
fafc8b9b 38
c245d69b 39sub throw_error {
d03bd989 40 # FIXME This
c245d69b 41 shift;
42 goto \&confess
43}
4c0b3599 44
5bd4db9b 45sub extends {
d5447d26 46 my $meta = shift;
3d544ed5 47
e2095e4a 48 Moose->throw_error("Must derive at least one class") unless @_;
9bcfbab1 49
5bd4db9b 50 # this checks the metaclass to make sure
51 # it is correct, sometimes it can get out
52 # of sync when the classes are being built
d5447d26 53 $meta->superclasses(@_);
5bd4db9b 54}
a3c7e2fe 55
5bd4db9b 56sub with {
d5447d26 57 Moose::Util::apply_all_roles(shift, @_);
5bd4db9b 58}
9bcfbab1 59
5bd4db9b 60sub has {
d5447d26 61 my $meta = shift;
62 my $name = shift;
e2095e4a 63
64 Moose->throw_error('Usage: has \'name\' => ( key => value, ... )')
db532c7d 65 if @_ % 2 == 1;
e2095e4a 66
833b56a7 67 my %options = ( definition_context => Moose::Util::_caller_info(), @_ );
5bd4db9b 68 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
d5447d26 69 $meta->add_attribute( $_, %options ) for @$attrs;
5bd4db9b 70}
9bcfbab1 71
5bd4db9b 72sub before {
d5447d26 73 Moose::Util::add_method_modifier(shift, 'before', \@_);
5bd4db9b 74}
75
76sub after {
d5447d26 77 Moose::Util::add_method_modifier(shift, 'after', \@_);
5bd4db9b 78}
79
80sub around {
d5447d26 81 Moose::Util::add_method_modifier(shift, 'around', \@_);
5bd4db9b 82}
83
991933fb 84our $SUPER_PACKAGE;
85our $SUPER_BODY;
86our @SUPER_ARGS;
87
5bd4db9b 88sub super {
991933fb 89 # This check avoids a recursion loop - see
90 # t/100_bugs/020_super_recursion.t
91 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
92 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
5bd4db9b 93}
9bcfbab1 94
5bd4db9b 95sub override {
d5447d26 96 my $meta = shift;
5bd4db9b 97 my ( $name, $method ) = @_;
d5447d26 98 $meta->add_override_method_modifier( $name => $method );
5bd4db9b 99}
9bcfbab1 100
5bd4db9b 101sub inner {
102 my $pkg = caller();
103 our ( %INNER_BODY, %INNER_ARGS );
104
105 if ( my $body = $INNER_BODY{$pkg} ) {
106 my @args = @{ $INNER_ARGS{$pkg} };
107 local $INNER_ARGS{$pkg};
108 local $INNER_BODY{$pkg};
109 return $body->(@args);
110 } else {
111 return;
ce265cc3 112 }
5bd4db9b 113}
9bcfbab1 114
5bd4db9b 115sub augment {
d5447d26 116 my $meta = shift;
5bd4db9b 117 my ( $name, $method ) = @_;
d5447d26 118 $meta->add_augment_method_modifier( $name => $method );
ce265cc3 119}
9bcfbab1 120
aedcb7d9 121Moose::Exporter->setup_import_methods(
d5447d26 122 with_meta => [
348715c4 123 qw( extends with has before after around override augment )
97a93056 124 ],
125 as_is => [
126 qw( super inner ),
5bd4db9b 127 \&Carp::confess,
128 \&Scalar::Util::blessed,
129 ],
130);
131
cc841c0e 132sub init_meta {
085fba61 133 # This used to be called as a function. This hack preserves
134 # backwards compatibility.
135 if ( $_[0] ne __PACKAGE__ ) {
136 return __PACKAGE__->init_meta(
137 for_class => $_[0],
138 base_class => $_[1],
139 metaclass => $_[2],
140 );
141 }
7c4676ef 142
0338a411 143 shift;
144 my %args = @_;
145
146 my $class = $args{for_class}
c245d69b 147 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
085fba61 148 my $base_class = $args{base_class} || 'Moose::Object';
149 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
cc841c0e 150
c245d69b 151 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
cc841c0e 152 unless $metaclass->isa('Moose::Meta::Class');
153
154 # make a subtype for each Moose class
155 class_type($class)
156 unless find_type_constraint($class);
157
158 my $meta;
50d5df60 159
160 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
161 unless ( $meta->isa("Moose::Meta::Class") ) {
677eafe2 162 my $error_message = "$class already has a metaclass, but it does not inherit $metaclass ($meta).";
163 if ( $meta->isa('Moose::Meta::Role') ) {
164 Moose->throw_error($error_message . ' You cannot make the same thing a role and a class. Remove either Moose or Moose::Role.');
165 } else {
166 Moose->throw_error($error_message);
167 }
50d5df60 168 }
169 } else {
170 # no metaclass, no 'meta' method
171
172 # now we check whether our ancestors have metaclass, and if so borrow that
173 my ( undef, @isa ) = @{ $class->mro::get_linear_isa };
174
175 foreach my $ancestor ( @isa ) {
176 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
177
178 my $ancestor_meta_class = ($ancestor_meta->is_immutable
989263ad 179 ? $ancestor_meta->_get_mutable_metaclass_name
50d5df60 180 : ref($ancestor_meta));
181
182 # if we have an ancestor metaclass that inherits $metaclass, we use
41419b9e 183 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
50d5df60 184
185 # the case of having an ancestry is not very common, but arises in
186 # e.g. Reaction
187 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
188 if ( $ancestor_meta_class->isa($metaclass) ) {
189 $metaclass = $ancestor_meta_class;
190 }
191 }
192 }
193
194 $meta = $metaclass->initialize($class);
195 }
196
cc841c0e 197 if ( $class->can('meta') ) {
50d5df60 198 # check 'meta' method
199
200 # it may be inherited
201
cc841c0e 202 # NOTE:
203 # this is the case where the metaclass pragma
204 # was used before the 'use Moose' statement to
205 # override a specific class
50d5df60 206 my $method_meta = $class->meta;
207
208 ( blessed($method_meta) && $method_meta->isa('Moose::Meta::Class') )
e7e9a4d8 209 || Moose->throw_error("$class already has a &meta function, but it does not return a Moose::Meta::Class ($method_meta)");
50d5df60 210
211 $meta = $method_meta;
cc841c0e 212 }
50d5df60 213
214 unless ( $meta->has_method("meta") ) { # don't overwrite
215 # also check for inherited non moose 'meta' method?
216 # FIXME also skip this if the user requested by passing an option
cc841c0e 217 $meta->add_method(
218 'meta' => sub {
219 # re-initialize so it inherits properly
50d5df60 220 $metaclass->initialize( ref($_[0]) || $_[0] );
cc841c0e 221 }
222 );
223 }
224
225 # make sure they inherit from Moose::Object
226 $meta->superclasses($base_class)
227 unless $meta->superclasses();
228
229 return $meta;
230}
231
085fba61 232# This may be used in some older MooseX extensions.
233sub _get_caller {
234 goto &Moose::Exporter::_get_caller;
235}
236
8ecb1fa0 237## make 'em all immutable
238
3cae4250 239$_->make_immutable(
0779da92 240 inline_constructor => 1,
241 constructor_name => "_new",
3cae4250 242 # these are Class::MOP accessors, so they need inlining
243 inline_accessors => 1
244 ) for grep { $_->is_mutable }
245 map { $_->meta }
246 qw(
0779da92 247 Moose::Meta::Attribute
248 Moose::Meta::Class
249 Moose::Meta::Instance
250
0779da92 251 Moose::Meta::TypeCoercion
252 Moose::Meta::TypeCoercion::Union
253
254 Moose::Meta::Method
255 Moose::Meta::Method::Accessor
256 Moose::Meta::Method::Constructor
257 Moose::Meta::Method::Destructor
74862722 258 Moose::Meta::Method::Overridden
0779da92 259 Moose::Meta::Method::Augmented
260
261 Moose::Meta::Role
262 Moose::Meta::Role::Method
263 Moose::Meta::Role::Method::Required
bb153262 264 Moose::Meta::Role::Method::Conflicting
0779da92 265
266 Moose::Meta::Role::Composite
267
268 Moose::Meta::Role::Application
269 Moose::Meta::Role::Application::RoleSummation
270 Moose::Meta::Role::Application::ToClass
271 Moose::Meta::Role::Application::ToRole
272 Moose::Meta::Role::Application::ToInstance
3cae4250 273);
8ecb1fa0 274
fcd84ca9 2751;
276
277__END__
278
279=pod
280
281=head1 NAME
282
8bdc7f13 283Moose - A postmodern object system for Perl 5
fcd84ca9 284
285=head1 SYNOPSIS
e522431d 286
287 package Point;
1cd45431 288 use Moose; # automatically turns on strict and warnings
26fbace8 289
43d599e5 290 has 'x' => (is => 'rw', isa => 'Int');
291 has 'y' => (is => 'rw', isa => 'Int');
26fbace8 292
e522431d 293 sub clear {
294 my $self = shift;
295 $self->x(0);
26fbace8 296 $self->y(0);
e522431d 297 }
26fbace8 298
e522431d 299 package Point3D;
300 use Moose;
26fbace8 301
e522431d 302 extends 'Point';
26fbace8 303
43d599e5 304 has 'z' => (is => 'rw', isa => 'Int');
26fbace8 305
e522431d 306 after 'clear' => sub {
307 my $self = shift;
43d599e5 308 $self->z(0);
26fbace8 309 };
2c0cbef7 310
fcd84ca9 311=head1 DESCRIPTION
312
26fbace8 313Moose is an extension of the Perl 5 object system.
e522431d 314
9b9da6f1 315The main goal of Moose is to make Perl 5 Object Oriented programming
316easier, more consistent and less tedious. With Moose you can to think
6f894f30 317more about what you want to do and less about the mechanics of OOP.
fcd84ca9 318
6f894f30 319Additionally, Moose is built on top of L<Class::MOP>, which is a
320metaclass system for Perl 5. This means that Moose not only makes
321building normal Perl 5 objects better, but it provides the power of
322metaclass programming as well.
8bdc7f13 323
f5909dca 324=head2 New to Moose?
325
60eccd1e 326If you're new to Moose, the best place to start is the
327L<Moose::Manual> docs, followed by the L<Moose::Cookbook>. The intro
328will show you what Moose is, and how it makes Perl 5 OO better.
6f894f30 329
330The cookbook recipes on Moose basics will get you up to speed with
331many of Moose's features quickly. Once you have an idea of what Moose
332can do, you can use the API documentation to get more detail on
333features which interest you.
f5909dca 334
28669f89 335=head2 Moose Extensions
336
12aed9a0 337The C<MooseX::> namespace is the official place to find Moose extensions.
338These extensions can be found on the CPAN. The easiest way to find them
339is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
340or to examine L<Task::Moose> which aims to keep an up-to-date, easily
341installable list of Moose extensions.
28669f89 342
ceb61b4f 343=head1 TRANSLATIONS
344
345Much of the Moose documentation has been translated into other languages.
346
347=over 4
348
52a0d29a 349=item Japanese
350
e24fb7a0 351Japanese docs can be found at L<http://perldoc.perlassociation.org/pod/Moose-Doc-JA/index.html>. The source POD files can be found in GitHub: L<http://github.com/jpa/Moose-Doc-JA>
ceb61b4f 352
353=back
354
6ba6d68c 355=head1 BUILDING CLASSES WITH MOOSE
356
68efb014 357Moose makes every attempt to provide as much convenience as possible during
358class construction/definition, but still stay out of your way if you want it
359to. Here are a few items to note when building classes with Moose.
6ba6d68c 360
26fbace8 361Unless specified with C<extends>, any class which uses Moose will
6ba6d68c 362inherit from L<Moose::Object>.
363
1cd45431 364Moose will also manage all attributes (including inherited ones) that are
365defined with C<has>. And (assuming you call C<new>, which is inherited from
366L<Moose::Object>) this includes properly initializing all instance slots,
367setting defaults where appropriate, and performing any type constraint checking
368or coercion.
6ba6d68c 369
004222dc 370=head1 PROVIDED METHODS
6ba6d68c 371
d03bd989 372Moose provides a number of methods to all your classes, mostly through the
004222dc 373inheritance of L<Moose::Object>. There is however, one exception.
6ba6d68c 374
375=over 4
376
377=item B<meta>
378
379This is a method which provides access to the current class's metaclass.
380
004222dc 381=back
382
383=head1 EXPORTED FUNCTIONS
384
385Moose will export a number of functions into the class's namespace which
386may then be used to set up the class. These functions all work directly
387on the current class.
388
389=over 4
390
6ba6d68c 391=item B<extends (@superclasses)>
392
393This function will set the superclass(es) for the current class.
394
26fbace8 395This approach is recommended instead of C<use base>, because C<use base>
396actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
397replace it. This is important to ensure that classes which do not have
68efb014 398superclasses still properly inherit from L<Moose::Object>.
6ba6d68c 399
43d599e5 400=item B<with (@roles)>
e9ec68d6 401
d03bd989 402This will apply a given set of C<@roles> to the local class.
e9ec68d6 403
b4291ab4 404=item B<has $name|@$names =E<gt> %options>
6ba6d68c 405
b4291ab4 406This will install an attribute of a given C<$name> into the current class. If
407the first parameter is an array reference, it will create an attribute for
408every C<$name> in the list. The C<%options> are the same as those provided by
409L<Class::MOP::Attribute>, in addition to the list below which are provided by
410Moose (L<Moose::Meta::Attribute> to be more specific):
6ba6d68c 411
412=over 4
413
076c81ed 414=item I<is =E<gt> 'rw'|'ro'>
6ba6d68c 415
26fbace8 416The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
417only). These will create either a read/write accessor or a read-only
6ba6d68c 418accessor respectively, using the same name as the C<$name> of the attribute.
419
1b46b845 420If you need more control over how your accessors are named, you can
421use the L<reader|Class::MOP::Attribute/reader>,
422L<writer|Class::MOP::Attribute/writer> and
423L<accessor|Class::MOP::Attribute/accessor> options inherited from
424L<Class::MOP::Attribute>, however if you use those, you won't need the
425I<is> option.
6ba6d68c 426
076c81ed 427=item I<isa =E<gt> $type_name>
6ba6d68c 428
26fbace8 429The I<isa> option uses Moose's type constraint facilities to set up runtime
430type checking for this attribute. Moose will perform the checks during class
431construction, and within any accessors. The C<$type_name> argument must be a
432string. The string may be either a class name or a type defined using
9cca2e9e 433Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
c2a69ef1 434for information on how to define a new type, and how to retrieve type meta-data).
6ba6d68c 435
daea75c9 436=item I<coerce =E<gt> (1|0)>
437
26fbace8 438This will attempt to use coercion with the supplied type constraint to change
439the value passed into any accessors or constructors. You B<must> have supplied
5cfe3805 440a type constraint in order for this to work. See L<Moose::Cookbook::Basics::Recipe5>
1cd45431 441for an example.
daea75c9 442
443=item I<does =E<gt> $role_name>
444
26fbace8 445This will accept the name of a role which the value stored in this attribute
daea75c9 446is expected to have consumed.
447
448=item I<required =E<gt> (1|0)>
449
81bec8f8 450This marks the attribute as being required. This means a value must be
be1355c0 451supplied during class construction, I<or> the attribute must be lazy
452and have either a default or a builder. Note that c<required> does not
453say anything about the attribute's value, which can be C<undef>.
daea75c9 454
455=item I<weak_ref =E<gt> (1|0)>
456
68efb014 457This will tell the class to store the value of this attribute as a weakened
458reference. If an attribute is a weakened reference, it B<cannot> also be
459coerced.
daea75c9 460
461=item I<lazy =E<gt> (1|0)>
462
26fbace8 463This will tell the class to not create this slot until absolutely necessary.
daea75c9 464If an attribute is marked as lazy it B<must> have a default supplied.
465
9e93dd19 466=item I<auto_deref =E<gt> (1|0)>
467
1668f3d7 468This tells the accessor to automatically dereference the value of this
469attribute when called in list context. The accessor will still return a
470reference when called in scalar context. This is only legal if your C<isa>
471option is either C<ArrayRef> or C<HashRef>.
9e93dd19 472
65e14c86 473=item I<trigger =E<gt> $code>
474
525129a5 475The I<trigger> option is a CODE reference which will be called after
476the value of the attribute is set. The CODE ref will be passed the
3dda07f5 477instance itself and the updated value. If the attribute already had a
478value, this will be passed as the third value to the trigger.
479
480You B<can> have a trigger on a read-only attribute.
010997ca 481
482B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
483either in the constructor, or using the writer. Default and built values will
484B<not> cause the trigger to be fired.
daea75c9 485
e3de240e 486=item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | DUCKTYPE | CODE>
2c0cbef7 487
26fbace8 488The I<handles> option provides Moose classes with automated delegation features.
489This is a pretty complex and powerful option. It accepts many different option
490formats, each with its own benefits and drawbacks.
38e3283b 491
1cd45431 492B<NOTE:> The class being delegated to does not need to be a Moose based class,
493which is why this feature is especially useful when wrapping non-Moose classes.
38e3283b 494
1cd45431 495All I<handles> option formats share the following traits:
38e3283b 496
1cd45431 497You cannot override a locally defined method with a delegated method; an
498exception will be thrown if you try. That is to say, if you define C<foo> in
499your class, you cannot override it with a delegated C<foo>. This is almost never
500something you would want to do, and if it is, you should do it by hand and not
501use Moose.
38e3283b 502
1cd45431 503You cannot override any of the methods found in Moose::Object, or the C<BUILD>
504and C<DEMOLISH> methods. These will not throw an exception, but will silently
505move on to the next method in the list. My reasoning for this is that you would
506almost never want to do this, since it usually breaks your class. As with
507overriding locally defined methods, if you do want to do this, you should do it
508manually, not with Moose.
38e3283b 509
d03bd989 510You do not I<need> to have a reader (or accessor) for the attribute in order
511to delegate to it. Moose will create a means of accessing the value for you,
512however this will be several times B<less> efficient then if you had given
f3c4e20e 513the attribute a reader (or accessor) to use.
514
38e3283b 515Below is the documentation for each option format:
516
517=over 4
518
519=item C<ARRAY>
520
26fbace8 521This is the most common usage for I<handles>. You basically pass a list of
522method names to be delegated, and Moose will install a delegation method
1cd45431 523for each one.
38e3283b 524
525=item C<HASH>
526
26fbace8 527This is the second most common usage for I<handles>. Instead of a list of
528method names, you pass a HASH ref where each key is the method name you
529want installed locally, and its value is the name of the original method
530in the class being delegated to.
fd595040 531
26fbace8 532This can be very useful for recursive classes like trees. Here is a
5cfe3805 533quick example (soon to be expanded into a Moose::Cookbook recipe):
38e3283b 534
1cd45431 535 package Tree;
38e3283b 536 use Moose;
26fbace8 537
38e3283b 538 has 'node' => (is => 'rw', isa => 'Any');
26fbace8 539
38e3283b 540 has 'children' => (
541 is => 'ro',
542 isa => 'ArrayRef',
543 default => sub { [] }
544 );
26fbace8 545
38e3283b 546 has 'parent' => (
547 is => 'rw',
548 isa => 'Tree',
a4e516f6 549 weak_ref => 1,
38e3283b 550 handles => {
551 parent_node => 'node',
26fbace8 552 siblings => 'children',
38e3283b 553 }
554 );
555
1cd45431 556In this example, the Tree package gets C<parent_node> and C<siblings> methods,
557which delegate to the C<node> and C<children> methods (respectively) of the Tree
26fbace8 558instance stored in the C<parent> slot.
38e3283b 559
9218b114 560You may also use an array reference to curry arguments to the original method.
561
562 has 'thing' => (
563 ...
3c573ca4 564 handles => { set_foo => [ set => 'foo' ] },
9218b114 565 );
566
567 # $self->set_foo(...) calls $self->thing->set('foo', ...)
568
569The first element of the array reference is the original method name, and the
3c573ca4 570rest is a list of curried arguments.
9218b114 571
38e3283b 572=item C<REGEXP>
573
26fbace8 574The regexp option works very similar to the ARRAY option, except that it builds
575the list of methods for you. It starts by collecting all possible methods of the
576class being delegated to, then filters that list using the regexp supplied here.
38e3283b 577
26fbace8 578B<NOTE:> An I<isa> option is required when using the regexp option format. This
579is so that we can determine (at compile time) the method list from the class.
38e3283b 580Without an I<isa> this is just not possible.
581
c84f324f 582=item C<ROLE>
583
26fbace8 584With the role option, you specify the name of a role whose "interface" then
585becomes the list of methods to handle. The "interface" can be defined as; the
586methods of the role and any required methods of the role. It should be noted
587that this does B<not> include any method modifiers or generated attribute
c84f324f 588methods (which is consistent with role composition).
589
e3de240e 590=item C<DUCKTYPE>
591
a6d8545f 592With the duck type option, you pass a duck type object whose "interface" then
593becomes the list of methods to handle. The "interface" can be defined as; the
594list of methods passed to C<duck_type> to create a duck type object. For more
595information on C<duck_type> please check
e9c2746e 596L<Moose::Util::TypeConstraints>.
e3de240e 597
38e3283b 598=item C<CODE>
599
1cd45431 600This is the option to use when you really want to do something funky. You should
601only use it if you really know what you are doing, as it involves manual
602metaclass twiddling.
38e3283b 603
1cd45431 604This takes a code reference, which should expect two arguments. The first is the
605attribute meta-object this I<handles> is attached to. The second is the
606metaclass of the class being delegated to. It expects you to return a hash (not
26fbace8 607a HASH ref) of the methods you want mapped.
38e3283b 608
609=back
2c0cbef7 610
004222dc 611=item I<metaclass =E<gt> $metaclass_name>
612
613This tells the class to use a custom attribute metaclass for this particular
614attribute. Custom attribute metaclasses are useful for extending the
615capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
d03bd989 616but they are still a fairly advanced topic and too much to cover here, see
5cfe3805 617L<Moose::Cookbook::Meta::Recipe1> for more information.
004222dc 618
8a8856de 619See L<Metaclass and Trait Name Resolution> for details on how a metaclass name
620is resolved to a class name.
004222dc 621
622=item I<traits =E<gt> [ @role_names ]>
623
d03bd989 624This tells Moose to take the list of C<@role_names> and apply them to the
625attribute meta-object. This is very similar to the I<metaclass> option, but
54f2996d 626allows you to use more than one extension at a time.
004222dc 627
8a8856de 628See L<Metaclass and Trait Name Resolution> for details on how a trait name is
629resolved to a role name.
54f2996d 630
631Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
632example.
004222dc 633
019f031d 634=item I<builder> => Str
010997ca 635
1b46b845 636The value of this key is the name of the method that will be called to
637obtain the value used to initialize the attribute. See the L<builder
638option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
0bb2cc8a 639 and/or L<Moose::Cookbook::Basics::Recipe8> for more information.
010997ca 640
019f031d 641=item I<default> => SCALAR | CODE
010997ca 642
643The value of this key is the default value which will initialize the attribute.
644
1b46b845 645NOTE: If the value is a simple scalar (string or number), then it can
646be just passed as is. However, if you wish to initialize it with a
647HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
648See the L<default option docs in
649Class::MOP::Attribute|Class::MOP::Attribute/default> for more
650information.
010997ca 651
019f031d 652=item I<clearer> => Str
010997ca 653
afd72e0c 654Creates a method allowing you to clear the value, see the L<clearer option
655docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
1b46b845 656information.
010997ca 657
019f031d 658=item I<predicate> => Str
010997ca 659
afd72e0c 660Creates a method to perform a basic test to see if a value has been set in the
661attribute, see the L<predicate option docs in
662Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
010997ca 663
019f031d 664=item I<lazy_build> => (0|1)
665
666Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
667"clear_$attr', predicate => 'has_$attr' unless they are already defined.
668
8c63a5c8 669=item I<initializer> => Str
670
671This may be a method name (referring to a method on the class with
672this attribute) or a CODE ref. The initializer is used to set the
673attribute value on an instance when the attribute is set during
674instance initialization (but not when the value is being assigned
675to). See the L<initializer option docs in
676Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
677information.
019f031d 678
60dcf673 679=item I<documentation> => $string
680
681An arbitrary string that can be retrieved later by calling C<<
682$attr->documentation >>.
683
684
685
6ba6d68c 686=back
687
cd7eeaf5 688=item B<has +$name =E<gt> %options>
689
c7874946 690This is variation on the normal attribute creator C<has> which allows you to
d03bd989 691clone and extend an attribute from a superclass or from a role. Here is an
8d62bf6d 692example of the superclass usage:
cd7eeaf5 693
694 package Foo;
695 use Moose;
26fbace8 696
cd7eeaf5 697 has 'message' => (
26fbace8 698 is => 'rw',
cd7eeaf5 699 isa => 'Str',
700 default => 'Hello, I am a Foo'
701 );
26fbace8 702
cd7eeaf5 703 package My::Foo;
704 use Moose;
26fbace8 705
cd7eeaf5 706 extends 'Foo';
26fbace8 707
cd7eeaf5 708 has '+message' => (default => 'Hello I am My::Foo');
709
1cd45431 710What is happening here is that B<My::Foo> is cloning the C<message> attribute
711from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
712'Str'> characteristics, but changing the value in C<default>.
cd7eeaf5 713
8d62bf6d 714Here is another example, but within the context of a role:
715
716 package Foo::Role;
717 use Moose::Role;
986d175a 718
8d62bf6d 719 has 'message' => (
720 is => 'rw',
721 isa => 'Str',
722 default => 'Hello, I am a Foo'
723 );
986d175a 724
8d62bf6d 725 package My::Foo;
726 use Moose;
986d175a 727
8d62bf6d 728 with 'Foo::Role';
986d175a 729
8d62bf6d 730 has '+message' => (default => 'Hello I am My::Foo');
731
d03bd989 732In this case, we are basically taking the attribute which the role supplied
733and altering it within the bounds of this feature.
8d62bf6d 734
73f70bdf 735Note that you can only extend an attribute from either a superclass or a role,
736you cannot extend an attribute in a role that composes over an attribute from
737another role.
738
d03bd989 739Aside from where the attributes come from (one from superclass, the other
740from a role), this feature works exactly the same. This feature is restricted
741somewhat, so as to try and force at least I<some> sanity into it. You are only
4032c9bb 742allowed to change the following attributes:
cd7eeaf5 743
744=over 4
745
26fbace8 746=item I<default>
cd7eeaf5 747
748Change the default value of an attribute.
749
26fbace8 750=item I<coerce>
cd7eeaf5 751
752Change whether the attribute attempts to coerce a value passed to it.
753
26fbace8 754=item I<required>
cd7eeaf5 755
756Change if the attribute is required to have a value.
757
758=item I<documentation>
759
760Change the documentation string associated with the attribute.
761
83cc9094 762=item I<lazy>
763
764Change if the attribute lazily initializes the slot.
765
cd7eeaf5 766=item I<isa>
767
d03bd989 768You I<are> allowed to change the type without restriction.
aed87761 769
d03bd989 770It is recommended that you use this freedom with caution. We used to
771only allow for extension only if the type was a subtype of the parent's
772type, but we felt that was too restrictive and is better left as a
773policy decision.
cd7eeaf5 774
83cc9094 775=item I<handles>
776
26fbace8 777You are allowed to B<add> a new C<handles> definition, but you are B<not>
778allowed to I<change> one.
83cc9094 779
8d62bf6d 780=item I<builder>
781
782You are allowed to B<add> a new C<builder> definition, but you are B<not>
783allowed to I<change> one.
784
13284479 785=item I<metaclass>
786
787You are allowed to B<add> a new C<metaclass> definition, but you are
788B<not> allowed to I<change> one.
789
790=item I<traits>
791
792You are allowed to B<add> additional traits to the C<traits> definition.
6549b0d1 793These traits will be composed into the attribute, but preexisting traits
13284479 794B<are not> overridden, or removed.
795
cd7eeaf5 796=back
797
076c81ed 798=item B<before $name|@names =E<gt> sub { ... }>
6ba6d68c 799
076c81ed 800=item B<after $name|@names =E<gt> sub { ... }>
6ba6d68c 801
076c81ed 802=item B<around $name|@names =E<gt> sub { ... }>
6ba6d68c 803
e9f7d5c5 804These three items are syntactic sugar for the before, after, and around method
d8af92ae 805modifier features that L<Class::MOP> provides. More information on these may be
9b75e4b6 806found in L<Moose::Manual::MethodModifiers> and the
807L<Class::MOP::Class documentation|Class::MOP::Class/"Method Modifiers">.
6ba6d68c 808
159da176 809=item B<super>
810
26fbace8 811The keyword C<super> is a no-op when called outside of an C<override> method. In
812the context of an C<override> method, it will call the next most appropriate
159da176 813superclass method with the same arguments as the original method.
814
815=item B<override ($name, &sub)>
816
26fbace8 817An C<override> method is a way of explicitly saying "I am overriding this
818method from my superclass". You can call C<super> within this method, and
819it will work as expected. The same thing I<can> be accomplished with a normal
820method call and the C<SUPER::> pseudo-package; it is really your choice.
159da176 821
822=item B<inner>
823
26fbace8 824The keyword C<inner>, much like C<super>, is a no-op outside of the context of
825an C<augment> method. You can think of C<inner> as being the inverse of
68efb014 826C<super>; the details of how C<inner> and C<augment> work is best described in
5cfe3805 827the L<Moose::Cookbook::Basics::Recipe6>.
159da176 828
829=item B<augment ($name, &sub)>
830
26fbace8 831An C<augment> method, is a way of explicitly saying "I am augmenting this
832method from my superclass". Once again, the details of how C<inner> and
5cfe3805 833C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
159da176 834
6ba6d68c 835=item B<confess>
836
68efb014 837This is the C<Carp::confess> function, and exported here because I use it
d03bd989 838all the time.
6ba6d68c 839
840=item B<blessed>
841
1cd45431 842This is the C<Scalar::Util::blessed> function, it is exported here because I
26fbace8 843use it all the time. It is highly recommended that this is used instead of
6ba6d68c 844C<ref> anywhere you need to test for an object's class name.
845
846=back
847
c1381000 848=head1 METACLASS
54f2996d 849
c1381000 850When you use Moose, you can specify which metaclass to use:
851
852 use Moose -metaclass => 'My::Meta::Class';
853
854You can also specify traits which will be applied to your metaclass:
54f2996d 855
856 use Moose -traits => 'My::Trait';
857
858This is very similar to the attribute traits feature. When you do
859this, your class's C<meta> object will have the specified traits
8a8856de 860applied to it. See L<Metaclass and Trait Name Resolution> for more
861details.
54f2996d 862
8a8856de 863=head2 Metaclass and Trait Name Resolution
54f2996d 864
865By default, when given a trait name, Moose simply tries to load a
866class of the same name. If such a class does not exist, it then looks
867for for a class matching
868B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
869variable here will be one of B<Attribute> or B<Class>, depending on
870what the trait is being applied to.
871
872If a class with this long name exists, Moose checks to see if it has
873the method C<register_implementation>. This method is expected to
874return the I<real> class name of the trait. If there is no
875C<register_implementation> method, it will fall back to using
876B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
877
8a8856de 878The lookup method for metaclasses is the same, except that it looks
879for a class matching B<Moose::Meta::$type::Custom::$metaclass_name>.
880
54f2996d 881If all this is confusing, take a look at
882L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
883attribute trait.
884
1cd45431 885=head1 UNIMPORTING FUNCTIONS
31f8ec72 886
887=head2 B<unimport>
888
1cd45431 889Moose offers a way to remove the keywords it exports, through the C<unimport>
31f8ec72 890method. You simply have to say C<no Moose> at the bottom of your code for this
891to work. Here is an example:
892
893 package Person;
894 use Moose;
895
896 has 'first_name' => (is => 'rw', isa => 'Str');
897 has 'last_name' => (is => 'rw', isa => 'Str');
26fbace8 898
899 sub full_name {
31f8ec72 900 my $self = shift;
26fbace8 901 $self->first_name . ' ' . $self->last_name
31f8ec72 902 }
26fbace8 903
904 no Moose; # keywords are removed from the Person package
31f8ec72 905
9bcfbab1 906=head1 EXTENDING AND EMBEDDING MOOSE
907
5e86efbe 908To learn more about extending Moose, we recommend checking out the
909"Extending" recipes in the L<Moose::Cookbook>, starting with
910L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
911all the different ways you might extend Moose.
554b7648 912
913=head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
9bcfbab1 914
554b7648 915The C<init_meta> method sets up the metaclass object for the class
b143539e 916specified by C<for_class>. This method injects a a C<meta> accessor
917into the class so you can get at this object. It also sets the class's
554b7648 918superclass to C<base_class>, with L<Moose::Object> as the default.
9bcfbab1 919
a8de959b 920C<init_meta> returns the metaclass object for C<$class>.
921
16fb3624 922You can specify an alternate metaclass with the C<metaclass> option.
26fbace8 923
80837fe1 924For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
925
554b7648 926This method used to be documented as a function which accepted
927positional parameters. This calling style will still work for
4a66a4b3 928backwards compatibility, but is deprecated.
554b7648 929
930=head2 B<import>
931
932Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
933and C<{into_level =E<gt> 1}>.
934
935B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
936instead, which lets you stack multiple C<Moose.pm>-alike modules
937sanely. It handles getting the exported functions into the right place
938for you.
939
23d3fe84 940=head2 B<throw_error>
4c0b3599 941
942An alias for C<confess>, used by internally by Moose.
943
6ea5491a 944=head1 METACLASS COMPATIBILITY AND MOOSE
945
946Metaclass compatibility is a thorny subject. You should start by
947reading the "About Metaclass compatibility" section in the
948C<Class::MOP> docs.
949
950Moose will attempt to resolve a few cases of metaclass incompatibility
951when you set the superclasses for a class, unlike C<Class::MOP>, which
952simply dies if the metaclasses are incompatible.
953
954In actuality, Moose fixes incompatibility for I<all> of a class's
955metaclasses, not just the class metaclass. That includes the instance
956metaclass, attribute metaclass, as well as its constructor class and
957destructor class. However, for simplicity this discussion will just
958refer to "metaclass", meaning the class metaclass, most of the time.
959
960Moose has two algorithms for fixing metaclass incompatibility.
961
962The first algorithm is very simple. If all the metaclass for the
963parent is a I<subclass> of the child's metaclass, then we simply
964replace the child's metaclass with the parent's.
965
966The second algorithm is more complicated. It tries to determine if the
967metaclasses only "differ by roles". This means that the parent and
968child's metaclass share a common ancestor in their respective
969hierarchies, and that the subclasses under the common ancestor are
970only different because of role applications. This case is actually
971fairly common when you mix and match various C<MooseX::*> modules,
972many of which apply roles to the metaclass.
973
974If the parent and child do differ by roles, Moose replaces the
975metaclass in the child with a newly created metaclass. This metaclass
976is a subclass of the parent's metaclass, does all of the roles that
977the child's metaclass did before being replaced. Effectively, this
978means the new metaclass does all of the roles done by both the
979parent's and child's original metaclasses.
980
981Ultimately, this is all transparent to you except in the case of an
982unresolvable conflict.
983
fafec530 984=head2 The MooseX:: namespace
985
d03bd989 986Generally if you're writing an extension I<for> Moose itself you'll want
987to put your extension in the C<MooseX::> namespace. This namespace is
988specifically for extensions that make Moose better or different in some
989fundamental way. It is traditionally B<not> for a package that just happens
990to use Moose. This namespace follows from the examples of the C<LWPx::>
fafec530 991and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
992respectively.
993
05d9eaf6 994=head1 CAVEATS
995
996=over 4
997
998=item *
999
1cd45431 1000It should be noted that C<super> and C<inner> B<cannot> be used in the same
1001method. However, they may be combined within the same class hierarchy; see
1002F<t/014_override_augment_inner_super.t> for an example.
05d9eaf6 1003
26fbace8 1004The reason for this is that C<super> is only valid within a method
1005with the C<override> modifier, and C<inner> will never be valid within an
1006C<override> method. In fact, C<augment> will skip over any C<override> methods
68efb014 1007when searching for its appropriate C<inner>.
05d9eaf6 1008
1cd45431 1009This might seem like a restriction, but I am of the opinion that keeping these
1010two features separate (yet interoperable) actually makes them easy to use, since
1011their behavior is then easier to predict. Time will tell whether I am right or
c84f324f 1012not (UPDATE: so far so good).
05d9eaf6 1013
9b9da6f1 1014=back
1015
e49c11d2 1016=head1 GETTING HELP
1017
1018We offer both a mailing list and a very active IRC channel.
1019
1020The mailing list is L<moose@perl.org>. You must be subscribed to send
1021a message. To subscribe, send an empty message to
1022L<moose-subscribe@perl.org>
1023
60cbb35f 1024You can also visit us at C<#moose> on C<< irc://irc.perl.org/#moose >>
1025This channel is quite active, and questions at all levels (on Moose-related
1026topics ;) are welcome.
e49c11d2 1027
5569c072 1028=head1 ACKNOWLEDGEMENTS
1029
1030=over 4
1031
54c189df 1032=item I blame Sam Vilain for introducing me to the insanity that is meta-models.
5569c072 1033
54c189df 1034=item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
5569c072 1035
26fbace8 1036=item Without Yuval "nothingmuch" Kogman this module would not be possible,
54c189df 1037and it certainly wouldn't have this name ;P
5569c072 1038
26fbace8 1039=item The basis of the TypeContraints module was Rob Kinyon's idea
5569c072 1040originally, I just ran with it.
1041
638585e1 1042=item Thanks to mst & chansen and the whole #moose posse for all the
c84f324f 1043early ideas/feature-requests/encouragement/bug-finding.
d46a48f3 1044
68efb014 1045=item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1046
5569c072 1047=back
1048
e90c03d0 1049=head1 SEE ALSO
1050
1051=over 4
1052
c84f324f 1053=item L<http://www.iinteractive.com/moose>
1054
6549b0d1 1055This is the official web home of Moose, it contains links to our public SVN repository
26fbace8 1056as well as links to a number of talks and articles on Moose and Moose related
1057technologies.
c84f324f 1058
196064ab 1059=item The Moose is flying, a tutorial by Randal Schwartz
1060
1061Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1062
1063Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1064
12aed9a0 1065=item Several Moose extension modules in the C<MooseX::> namespace.
1066
1067See L<http://search.cpan.org/search?query=MooseX::> for extensions.
28669f89 1068
e49c11d2 1069=item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1070
c84f324f 1071=back
1072
004222dc 1073=head2 Books
1074
1075=over 4
1076
1077=item The Art of the MetaObject Protocol
1078
d03bd989 1079I mention this in the L<Class::MOP> docs too, this book was critical in
004222dc 1080the development of both modules and is highly recommended.
1081
1082=back
1083
26fbace8 1084=head2 Papers
c84f324f 1085
1086=over 4
e90c03d0 1087
159da176 1088=item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1089
26fbace8 1090This paper (suggested by lbr on #moose) was what lead to the implementation
1091of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1cd45431 1092want to understand them, I suggest you read this.
159da176 1093
e90c03d0 1094=back
1095
fcd84ca9 1096=head1 BUGS
1097
26fbace8 1098All complex software has bugs lurking in it, and this module is no
7efc4307 1099exception.
1100
1101Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1102interface at L<http://rt.cpan.org>.
fcd84ca9 1103
47b19570 1104=head1 FEATURE REQUESTS
1105
d03bd989 1106We are very strict about what features we add to the Moose core, especially
1107the user-visible features. Instead we have made sure that the underlying
1108meta-system of Moose is as extensible as possible so that you can add your
854b298d 1109own features easily.
1110
1111That said, occasionally there is a feature needed in the meta-system
1112to support your planned extension, in which case you should either
1113email the mailing list (moose@perl.org) or join us on IRC at
1114L<irc://irc.perl.org/#moose> to discuss. The
1115L<Moose::Manual::Contributing> has more detail about how and when you
1116can contribute.
47b19570 1117
fcd84ca9 1118=head1 AUTHOR
1119
d03bd989 1120Moose is an open project, there are at this point dozens of people who have
1121contributed, and can contribute. If you have added anything to the Moose
862ae2c4 1122project you have a commit bit on this file and can add your name to the list.
fcd84ca9 1123
862ae2c4 1124=head2 CABAL
1125
d03bd989 1126However there are only a few people with the rights to release a new version
862ae2c4 1127of Moose. The Moose Cabal are the people to go to with questions regarding
a4869d1e 1128the wider purview of Moose, and help out maintaining not just the code
958dc4e3 1129but the community as well.
862ae2c4 1130
1131Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1132
862ae2c4 1133Yuval (nothingmuch) Kogman
1134
69ba075f 1135Shawn (sartak) Moore E<lt>sartak@bestpractical.comE<gt>
862ae2c4 1136
7a706548 1137Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
5c5e5480 1138
4c6410bf 1139Jesse (doy) Luehrs E<lt>doy at tozt dot netE<gt>
1140
fd995afb 1141Hans Dieter (confound) Pearcey E<lt>hdp@pobox.comE<gt>
1142
d209e3ad 1143Chris (perigrin) Prather
1144
36edf31b 1145Florian Ragwitz E<lt>rafl@debian.orgE<gt>
d209e3ad 1146
862ae2c4 1147=head2 OTHER CONTRIBUTORS
db1ab48d 1148
9af1d28b 1149Aankhen
1150
1151Adam (Alias) Kennedy
1152
1153Anders (Debolaz) Nor Berle
1154
6549b0d1 1155Nathan (kolibrie) Gray
5868294f 1156
9af1d28b 1157Christian (chansen) Hansen
1158
1159Eric (ewilhelm) Wilhelm
1160
1161Guillermo (groditi) Roditi
1162
1163Jess (castaway) Robinson
1164
1165Matt (mst) Trout
1166
1167Robert (phaylon) Sedlacek
1168
1169Robert (rlb3) Boone
1170
1171Scott (konobi) McWhirter
1172
f44ae52f 1173Shlomi (rindolf) Fish
1174
68b6146c 1175Wallace (wreis) Reis
1176
e46f5cc2 1177Jonathan (jrockway) Rockway
1178
3ccdc84a 1179Piotr (dexter) Roszatycki
1180
26fbace8 1181Sam (mugwump) Vilain
f1917f58 1182
2f7e4042 1183Cory (gphat) Watson
1184
0be258b5 1185Dylan Hardison (doc fixes)
1186
9af1d28b 1187... and many other #moose folks
98aae381 1188
fcd84ca9 1189=head1 COPYRIGHT AND LICENSE
1190
2840a3b2 1191Copyright 2006-2009 by Infinity Interactive, Inc.
fcd84ca9 1192
1193L<http://www.iinteractive.com>
1194
1195This library is free software; you can redistribute it and/or modify
26fbace8 1196it under the same terms as Perl itself.
fcd84ca9 1197
ddd0ec20 1198=cut