last minute stupidness
[gitmo/Moose.git] / lib / Moose.pm
CommitLineData
fcd84ca9 1
2package Moose;
3
4use strict;
5use warnings;
6
6f5b731e 7our $VERSION = '0.27';
d44714be 8our $AUTHORITY = 'cpan:STEVAN';
fcd84ca9 9
cc65ead0 10use Scalar::Util 'blessed', 'reftype';
3796382a 11use Carp 'confess';
12use Sub::Name 'subname';
13use B 'svref_2object';
fcd84ca9 14
2d562421 15use Sub::Exporter;
7f18097c 16
ec8b7bd4 17use Class::MOP 0.43;
ef1d5f4b 18
c0e30cf5 19use Moose::Meta::Class;
7415b2cb 20use Moose::Meta::TypeConstraint;
7c13858b 21use Moose::Meta::TypeCoercion;
78cd1d3b 22use Moose::Meta::Attribute;
ddd0ec20 23use Moose::Meta::Instance;
c0e30cf5 24
d67145ed 25use Moose::Meta::Role;
26
fcd84ca9 27use Moose::Object;
7415b2cb 28use Moose::Util::TypeConstraints;
a15dff8d 29
a3c7e2fe 30{
be33e4f3 31 my $CALLER;
9bcfbab1 32
33 sub init_meta {
34 my ( $class, $base_class, $metaclass ) = @_;
72bbc189 35 $base_class = $class unless defined $base_class;
26fbace8 36 $metaclass = 'Moose::Meta::Class' unless defined $metaclass;
9bcfbab1 37
38 confess
39 "The Metaclass $metaclass must be a subclass of Moose::Meta::Class."
40 unless $metaclass->isa('Moose::Meta::Class');
a3c7e2fe 41
a3c7e2fe 42 # make a subtype for each Moose class
9bcfbab1 43 subtype $class => as 'Object' => where { $_->isa($class) } =>
44 optimize_as { blessed( $_[0] ) && $_[0]->isa($class) }
a3c7e2fe 45 unless find_type_constraint($class);
46
47 my $meta;
9bcfbab1 48 if ( $class->can('meta') ) {
fcec2383 49 # NOTE:
9bcfbab1 50 # this is the case where the metaclass pragma
51 # was used before the 'use Moose' statement to
fcec2383 52 # override a specific class
a3c7e2fe 53 $meta = $class->meta();
9bcfbab1 54 ( blessed($meta) && $meta->isa('Moose::Meta::Class') )
55 || confess
56"You already have a &meta function, but it does not return a Moose::Meta::Class";
a3c7e2fe 57 }
58 else {
fcec2383 59 # NOTE:
9bcfbab1 60 # this is broken currently, we actually need
61 # to allow the possiblity of an inherited
62 # meta, which will not be visible until the
63 # user 'extends' first. This needs to have
64 # more intelligence to it
65 $meta = $metaclass->initialize($class);
66 $meta->add_method(
67 'meta' => sub {
68
69 # re-initialize so it inherits properly
70 $metaclass->initialize( blessed( $_[0] ) || $_[0] );
71 }
72 );
a3c7e2fe 73 }
74
75 # make sure they inherit from Moose::Object
72bbc189 76 $meta->superclasses($base_class)
9bcfbab1 77 unless $meta->superclasses();
a3c7e2fe 78 }
79
80 my %exports = (
81 extends => sub {
be33e4f3 82 my $class = $CALLER;
68117c45 83 return subname 'Moose::extends' => sub (@) {
84 confess "Must derive at least one class" unless @_;
1eaed09d 85 Class::MOP::load_class($_) for @_;
9bcfbab1 86
87 # this checks the metaclass to make sure
88 # it is correct, sometimes it can get out
1341f10c 89 # of sync when the classes are being built
90 my $meta = $class->meta->_fix_metaclass_incompatability(@_);
be33e4f3 91 $meta->superclasses(@_);
a3c7e2fe 92 };
93 },
94 with => sub {
be33e4f3 95 my $class = $CALLER;
68117c45 96 return subname 'Moose::with' => sub (@) {
db1ab48d 97 my (@roles) = @_;
68117c45 98 confess "Must specify at least one role" unless @roles;
1eaed09d 99 Class::MOP::load_class($_) for @roles;
1341f10c 100 $class->meta->_apply_all_roles(@roles);
a3c7e2fe 101 };
102 },
103 has => sub {
be33e4f3 104 my $class = $CALLER;
2c0cbef7 105 return subname 'Moose::has' => sub ($;%) {
9bcfbab1 106 my ( $name, %options ) = @_;
107 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
108 $class->meta->_process_attribute( $_, %options ) for @$attrs;
a3c7e2fe 109 };
110 },
111 before => sub {
be33e4f3 112 my $class = $CALLER;
2c0cbef7 113 return subname 'Moose::before' => sub (@&) {
a3c7e2fe 114 my $code = pop @_;
be33e4f3 115 my $meta = $class->meta;
9bcfbab1 116 $meta->add_before_method_modifier( $_, $code ) for @_;
a3c7e2fe 117 };
118 },
119 after => sub {
be33e4f3 120 my $class = $CALLER;
2c0cbef7 121 return subname 'Moose::after' => sub (@&) {
a3c7e2fe 122 my $code = pop @_;
be33e4f3 123 my $meta = $class->meta;
9bcfbab1 124 $meta->add_after_method_modifier( $_, $code ) for @_;
a3c7e2fe 125 };
126 },
127 around => sub {
9bcfbab1 128 my $class = $CALLER;
2c0cbef7 129 return subname 'Moose::around' => sub (@&) {
a3c7e2fe 130 my $code = pop @_;
be33e4f3 131 my $meta = $class->meta;
9bcfbab1 132 $meta->add_around_method_modifier( $_, $code ) for @_;
a3c7e2fe 133 };
134 },
135 super => sub {
52c7c330 136 {
9bcfbab1 137 our %SUPER_SLOT;
138 no strict 'refs';
139 $SUPER_SLOT{$CALLER} = \*{"${CALLER}::super"};
52c7c330 140 }
9bcfbab1 141 return subname 'Moose::super' => sub { };
a3c7e2fe 142 },
143 override => sub {
be33e4f3 144 my $class = $CALLER;
2c0cbef7 145 return subname 'Moose::override' => sub ($&) {
9bcfbab1 146 my ( $name, $method ) = @_;
147 $class->meta->add_override_method_modifier( $name => $method );
a3c7e2fe 148 };
149 },
150 inner => sub {
52c7c330 151 {
9bcfbab1 152 our %INNER_SLOT;
153 no strict 'refs';
154 $INNER_SLOT{$CALLER} = \*{"${CALLER}::inner"};
52c7c330 155 }
9bcfbab1 156 return subname 'Moose::inner' => sub { };
a3c7e2fe 157 },
158 augment => sub {
be33e4f3 159 my $class = $CALLER;
2c0cbef7 160 return subname 'Moose::augment' => sub (@&) {
9bcfbab1 161 my ( $name, $method ) = @_;
162 $class->meta->add_augment_method_modifier( $name => $method );
a3c7e2fe 163 };
164 },
9bcfbab1 165
68efb014 166 # NOTE:
9bcfbab1 167 # this is experimental, but I am not
168 # happy with it. If you want to try
169 # it, you will have to uncomment it
170 # yourself.
171 # There is a really good chance that
172 # this will be deprecated, dont get
2a0f3bd3 173 # too attached
174 # self => sub {
175 # return subname 'Moose::self' => sub {};
9bcfbab1 176 # },
2a0f3bd3 177 # method => sub {
178 # my $class = $CALLER;
179 # return subname 'Moose::method' => sub {
180 # my ($name, $method) = @_;
181 # $class->meta->add_method($name, sub {
182 # my $self = shift;
183 # no strict 'refs';
184 # no warnings 'redefine';
185 # local *{$class->meta->name . '::self'} = sub { $self };
186 # $method->(@_);
187 # });
188 # };
9bcfbab1 189 # },
190
a3c7e2fe 191 confess => sub {
192 return \&Carp::confess;
193 },
194 blessed => sub {
195 return \&Scalar::Util::blessed;
66bcefc1 196 },
a3c7e2fe 197 );
3d544ed5 198
9bcfbab1 199 my $exporter = Sub::Exporter::build_exporter(
200 {
201 exports => \%exports,
202 groups => { default => [':all'] }
a3c7e2fe 203 }
9bcfbab1 204 );
205
c92c1205 206 # 1 extra level because it's called by import so there's a layer of indirection
207 sub _get_caller{
208 my $offset = 1;
26fbace8 209 return
c92c1205 210 ref $_[1] && defined $_[1]->{into}
211 ? $_[1]->{into}
212 : ref $_[1] && defined $_[1]->{into_level}
213 ? caller($offset + $_[1]->{into_level})
214 : caller($offset);
215 }
5bee491d 216
217 sub import {
c92c1205 218 $CALLER = _get_caller(@_);
26fbace8 219
c235cd98 220 strict->import;
9bcfbab1 221 warnings->import;
a3c7e2fe 222
223 # we should never export to main
224 return if $CALLER eq 'main';
9bcfbab1 225
226 init_meta( $CALLER, 'Moose::Object' );
227
a3c7e2fe 228 goto $exporter;
fcb7afc2 229 }
9bcfbab1 230
31f8ec72 231 sub unimport {
9bcfbab1 232 no strict 'refs';
c92c1205 233 my $class = _get_caller(@_);
9bcfbab1 234
31f8ec72 235 # loop through the exports ...
9bcfbab1 236 foreach my $name ( keys %exports ) {
237
31f8ec72 238 # if we find one ...
9bcfbab1 239 if ( defined &{ $class . '::' . $name } ) {
240 my $keyword = \&{ $class . '::' . $name };
241
31f8ec72 242 # make sure it is from Moose
9bcfbab1 243 my $pkg_name =
244 eval { svref_2object($keyword)->GV->STASH->NAME };
31f8ec72 245 next if $@;
246 next if $pkg_name ne 'Moose';
9bcfbab1 247
31f8ec72 248 # and if it is from Moose then undef the slot
9bcfbab1 249 delete ${ $class . '::' }{$name};
31f8ec72 250 }
251 }
252 }
9bcfbab1 253
fcd84ca9 254}
255
8ecb1fa0 256## make 'em all immutable
257
258$_->meta->make_immutable(
259 inline_constructor => 0,
77a18c28 260 inline_accessors => 1, # these are Class::MOP accessors, so they need inlining
9bcfbab1 261 )
262 for (
8ecb1fa0 263 'Moose::Meta::Attribute',
264 'Moose::Meta::Class',
265 'Moose::Meta::Instance',
266
267 'Moose::Meta::TypeConstraint',
268 'Moose::Meta::TypeConstraint::Union',
0fbd4b0a 269 'Moose::Meta::TypeConstraint::Parameterized',
8ecb1fa0 270 'Moose::Meta::TypeCoercion',
271
272 'Moose::Meta::Method',
273 'Moose::Meta::Method::Accessor',
274 'Moose::Meta::Method::Constructor',
9bcfbab1 275 'Moose::Meta::Method::Destructor',
8ecb1fa0 276 'Moose::Meta::Method::Overriden',
d67145ed 277
278 'Moose::Meta::Role',
9bcfbab1 279 'Moose::Meta::Role::Method',
280 'Moose::Meta::Role::Method::Required',
281 );
8ecb1fa0 282
fcd84ca9 2831;
284
285__END__
286
287=pod
288
289=head1 NAME
290
31f8ec72 291Moose - A complete modern object system for Perl 5
fcd84ca9 292
293=head1 SYNOPSIS
e522431d 294
295 package Point;
1cd45431 296 use Moose; # automatically turns on strict and warnings
26fbace8 297
43d599e5 298 has 'x' => (is => 'rw', isa => 'Int');
299 has 'y' => (is => 'rw', isa => 'Int');
26fbace8 300
e522431d 301 sub clear {
302 my $self = shift;
303 $self->x(0);
26fbace8 304 $self->y(0);
e522431d 305 }
26fbace8 306
e522431d 307 package Point3D;
308 use Moose;
26fbace8 309
e522431d 310 extends 'Point';
26fbace8 311
43d599e5 312 has 'z' => (is => 'rw', isa => 'Int');
26fbace8 313
e522431d 314 after 'clear' => sub {
315 my $self = shift;
43d599e5 316 $self->z(0);
26fbace8 317 };
2c0cbef7 318
fcd84ca9 319=head1 DESCRIPTION
320
26fbace8 321Moose is an extension of the Perl 5 object system.
e522431d 322
323=head2 Another object system!?!?
fcd84ca9 324
26fbace8 325Yes, I know there has been an explosion recently of new ways to
68efb014 326build object's in Perl 5, most of them based on inside-out objects
26fbace8 327and other such things. Moose is different because it is not a new
328object system for Perl 5, but instead an extension of the existing
e522431d 329object system.
3c7278fb 330
26fbace8 331Moose is built on top of L<Class::MOP>, which is a metaclass system
332for Perl 5. This means that Moose not only makes building normal
333Perl 5 objects better, but it also provides the power of metaclass
505c6fac 334programming.
e522431d 335
734d1752 336=head2 Is this for real? Or is this just an experiment?
e522431d 337
2c0cbef7 338Moose is I<based> on the prototypes and experiments I did for the Perl 6
26fbace8 339meta-model. However, Moose is B<NOT> an experiment/prototype; it is for B<real>.
734d1752 340
26fbace8 341=head2 Is this ready for use in production?
d44714be 342
26fbace8 343Yes, I believe that it is.
734d1752 344
26fbace8 345Moose has been used successfully in production environemnts by several people
346and companies (including the one I work for). There are Moose applications
347which have been in production with little or no issue now for over a year.
348I consider it highly stable and we are commited to keeping it stable.
e522431d 349
26fbace8 350Of course, in the end, you need to make this call yourself. If you have
351any questions or concerns, please feel free to email me, or even the list
d44714be 352or just stop by #moose and ask away.
353
43d599e5 354=head2 Is Moose just Perl 6 in Perl 5?
e522431d 355
68efb014 356No. While Moose is very much inspired by Perl 6, it is not itself Perl 6.
1cd45431 357Instead, it is an OO system for Perl 5. I built Moose because I was tired of
68efb014 358writing the same old boring Perl 5 OO code, and drooling over Perl 6 OO. So
359instead of switching to Ruby, I wrote Moose :)
3c7278fb 360
28669f89 361=head2 Moose Extensions
362
363The L<MooseX::> namespace is the official place to find Moose extensions.
6f5b731e 364There are a number of these modules out on CPAN right now the best way to
365find them is to search for MooseX:: on search.cpan.org.
28669f89 366
6ba6d68c 367=head1 BUILDING CLASSES WITH MOOSE
368
68efb014 369Moose makes every attempt to provide as much convenience as possible during
370class construction/definition, but still stay out of your way if you want it
371to. Here are a few items to note when building classes with Moose.
6ba6d68c 372
26fbace8 373Unless specified with C<extends>, any class which uses Moose will
6ba6d68c 374inherit from L<Moose::Object>.
375
1cd45431 376Moose will also manage all attributes (including inherited ones) that are
377defined with C<has>. And (assuming you call C<new>, which is inherited from
378L<Moose::Object>) this includes properly initializing all instance slots,
379setting defaults where appropriate, and performing any type constraint checking
380or coercion.
6ba6d68c 381
382=head1 EXPORTED FUNCTIONS
383
26fbace8 384Moose will export a number of functions into the class's namespace which
385may then be used to set up the class. These functions all work directly
6ba6d68c 386on the current class.
387
388=over 4
389
390=item B<meta>
391
392This is a method which provides access to the current class's metaclass.
393
394=item B<extends (@superclasses)>
395
396This function will set the superclass(es) for the current class.
397
26fbace8 398This approach is recommended instead of C<use base>, because C<use base>
399actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
400replace it. This is important to ensure that classes which do not have
68efb014 401superclasses still properly inherit from L<Moose::Object>.
6ba6d68c 402
43d599e5 403=item B<with (@roles)>
e9ec68d6 404
26fbace8 405This will apply a given set of C<@roles> to the local class. Role support
68efb014 406is currently under heavy development; see L<Moose::Role> for more details.
e9ec68d6 407
cd7eeaf5 408=item B<has $name =E<gt> %options>
6ba6d68c 409
26fbace8 410This will install an attribute of a given C<$name> into the current class.
411The C<%options> are the same as those provided by
412L<Class::MOP::Attribute>, in addition to the list below which are provided
43d599e5 413by Moose (L<Moose::Meta::Attribute> to be more specific):
6ba6d68c 414
415=over 4
416
076c81ed 417=item I<is =E<gt> 'rw'|'ro'>
6ba6d68c 418
26fbace8 419The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
420only). These will create either a read/write accessor or a read-only
6ba6d68c 421accessor respectively, using the same name as the C<$name> of the attribute.
422
1cd45431 423If you need more control over how your accessors are named, you can use the
424I<reader>, I<writer> and I<accessor> options inherited from
425L<Class::MOP::Attribute>.
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
daea75c9 440a type constraint in order for this to work. See L<Moose::Cookbook::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
26fbace8 450This marks the attribute as being required. This means a I<defined> value must be
451supplied during class construction, and the attribute may never be set to
452C<undef> with an accessor.
daea75c9 453
454=item I<weak_ref =E<gt> (1|0)>
455
68efb014 456This will tell the class to store the value of this attribute as a weakened
457reference. If an attribute is a weakened reference, it B<cannot> also be
458coerced.
daea75c9 459
460=item I<lazy =E<gt> (1|0)>
461
26fbace8 462This will tell the class to not create this slot until absolutely necessary.
daea75c9 463If an attribute is marked as lazy it B<must> have a default supplied.
464
9e93dd19 465=item I<auto_deref =E<gt> (1|0)>
466
26fbace8 467This tells the accessor whether to automatically dereference the value returned.
1cd45431 468This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.
9e93dd19 469
c1935ade 470=item I<metaclass =E<gt> $metaclass_name>
471
1cd45431 472This tells the class to use a custom attribute metaclass for this particular
473attribute. Custom attribute metaclasses are useful for extending the
474capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
475but they are still a fairly advanced topic and too much to cover here. I will
476try and write a recipe on them soon.
477
478The default behavior here is to just load C<$metaclass_name>; however, we also
479have a way to alias to a shorter name. This will first look to see if
480B<Moose::Meta::Attribute::Custom::$metaclass_name> exists. If it does, Moose
481will then check to see if that has the method C<register_implemenetation>, which
482should return the actual name of the custom attribute metaclass. If there is no
483C<register_implemenetation> method, it will fall back to using
c1935ade 484B<Moose::Meta::Attribute::Custom::$metaclass_name> as the metaclass name.
485
daea75c9 486=item I<trigger =E<gt> $code>
487
1cd45431 488The I<trigger> option is a CODE reference which will be called after the value of
489the attribute is set. The CODE ref will be passed the instance itself, the
daea75c9 490updated value and the attribute meta-object (this is for more advanced fiddling
1cd45431 491and can typically be ignored). You B<cannot> have a trigger on a read-only
492attribute.
daea75c9 493
c84f324f 494=item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | CODE>
2c0cbef7 495
26fbace8 496The I<handles> option provides Moose classes with automated delegation features.
497This is a pretty complex and powerful option. It accepts many different option
498formats, each with its own benefits and drawbacks.
38e3283b 499
1cd45431 500B<NOTE:> This feature is no longer experimental, but it may still have subtle
501bugs lurking in the deeper corners. If you think you have found a bug, you
26fbace8 502probably have, so please report it to me right away.
38e3283b 503
1cd45431 504B<NOTE:> The class being delegated to does not need to be a Moose based class,
505which is why this feature is especially useful when wrapping non-Moose classes.
38e3283b 506
1cd45431 507All I<handles> option formats share the following traits:
38e3283b 508
1cd45431 509You cannot override a locally defined method with a delegated method; an
510exception will be thrown if you try. That is to say, if you define C<foo> in
511your class, you cannot override it with a delegated C<foo>. This is almost never
512something you would want to do, and if it is, you should do it by hand and not
513use Moose.
38e3283b 514
1cd45431 515You cannot override any of the methods found in Moose::Object, or the C<BUILD>
516and C<DEMOLISH> methods. These will not throw an exception, but will silently
517move on to the next method in the list. My reasoning for this is that you would
518almost never want to do this, since it usually breaks your class. As with
519overriding locally defined methods, if you do want to do this, you should do it
520manually, not with Moose.
38e3283b 521
522Below is the documentation for each option format:
523
524=over 4
525
526=item C<ARRAY>
527
26fbace8 528This is the most common usage for I<handles>. You basically pass a list of
529method names to be delegated, and Moose will install a delegation method
1cd45431 530for each one.
38e3283b 531
532=item C<HASH>
533
26fbace8 534This is the second most common usage for I<handles>. Instead of a list of
535method names, you pass a HASH ref where each key is the method name you
536want installed locally, and its value is the name of the original method
537in the class being delegated to.
fd595040 538
26fbace8 539This can be very useful for recursive classes like trees. Here is a
fd595040 540quick example (soon to be expanded into a Moose::Cookbook::Recipe):
38e3283b 541
1cd45431 542 package Tree;
38e3283b 543 use Moose;
26fbace8 544
38e3283b 545 has 'node' => (is => 'rw', isa => 'Any');
26fbace8 546
38e3283b 547 has 'children' => (
548 is => 'ro',
549 isa => 'ArrayRef',
550 default => sub { [] }
551 );
26fbace8 552
38e3283b 553 has 'parent' => (
554 is => 'rw',
555 isa => 'Tree',
556 is_weak_ref => 1,
557 handles => {
558 parent_node => 'node',
26fbace8 559 siblings => 'children',
38e3283b 560 }
561 );
562
1cd45431 563In this example, the Tree package gets C<parent_node> and C<siblings> methods,
564which delegate to the C<node> and C<children> methods (respectively) of the Tree
26fbace8 565instance stored in the C<parent> slot.
38e3283b 566
567=item C<REGEXP>
568
26fbace8 569The regexp option works very similar to the ARRAY option, except that it builds
570the list of methods for you. It starts by collecting all possible methods of the
571class being delegated to, then filters that list using the regexp supplied here.
38e3283b 572
26fbace8 573B<NOTE:> An I<isa> option is required when using the regexp option format. This
574is so that we can determine (at compile time) the method list from the class.
38e3283b 575Without an I<isa> this is just not possible.
576
c84f324f 577=item C<ROLE>
578
26fbace8 579With the role option, you specify the name of a role whose "interface" then
580becomes the list of methods to handle. The "interface" can be defined as; the
581methods of the role and any required methods of the role. It should be noted
582that this does B<not> include any method modifiers or generated attribute
c84f324f 583methods (which is consistent with role composition).
584
38e3283b 585=item C<CODE>
586
1cd45431 587This is the option to use when you really want to do something funky. You should
588only use it if you really know what you are doing, as it involves manual
589metaclass twiddling.
38e3283b 590
1cd45431 591This takes a code reference, which should expect two arguments. The first is the
592attribute meta-object this I<handles> is attached to. The second is the
593metaclass of the class being delegated to. It expects you to return a hash (not
26fbace8 594a HASH ref) of the methods you want mapped.
38e3283b 595
596=back
2c0cbef7 597
6ba6d68c 598=back
599
cd7eeaf5 600=item B<has +$name =E<gt> %options>
601
26fbace8 602This is variation on the normal attibute creator C<has> which allows you to
cd7eeaf5 603clone and extend an attribute from a superclass. Here is a quick example:
604
605 package Foo;
606 use Moose;
26fbace8 607
cd7eeaf5 608 has 'message' => (
26fbace8 609 is => 'rw',
cd7eeaf5 610 isa => 'Str',
611 default => 'Hello, I am a Foo'
612 );
26fbace8 613
cd7eeaf5 614 package My::Foo;
615 use Moose;
26fbace8 616
cd7eeaf5 617 extends 'Foo';
26fbace8 618
cd7eeaf5 619 has '+message' => (default => 'Hello I am My::Foo');
620
1cd45431 621What is happening here is that B<My::Foo> is cloning the C<message> attribute
622from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
623'Str'> characteristics, but changing the value in C<default>.
cd7eeaf5 624
83cc9094 625This feature is restricted somewhat, so as to try and force at least I<some>
cd7eeaf5 626sanity into it. You are only allowed to change the following attributes:
627
628=over 4
629
26fbace8 630=item I<default>
cd7eeaf5 631
632Change the default value of an attribute.
633
26fbace8 634=item I<coerce>
cd7eeaf5 635
636Change whether the attribute attempts to coerce a value passed to it.
637
26fbace8 638=item I<required>
cd7eeaf5 639
640Change if the attribute is required to have a value.
641
642=item I<documentation>
643
644Change the documentation string associated with the attribute.
645
83cc9094 646=item I<lazy>
647
648Change if the attribute lazily initializes the slot.
649
cd7eeaf5 650=item I<isa>
651
1cd45431 652You I<are> allowed to change the type, B<if and only if> the new type is a
653subtype of the old type.
cd7eeaf5 654
83cc9094 655=item I<handles>
656
26fbace8 657You are allowed to B<add> a new C<handles> definition, but you are B<not>
658allowed to I<change> one.
83cc9094 659
cd7eeaf5 660=back
661
076c81ed 662=item B<before $name|@names =E<gt> sub { ... }>
6ba6d68c 663
076c81ed 664=item B<after $name|@names =E<gt> sub { ... }>
6ba6d68c 665
076c81ed 666=item B<around $name|@names =E<gt> sub { ... }>
6ba6d68c 667
d8af92ae 668This three items are syntactic sugar for the before, after, and around method
669modifier features that L<Class::MOP> provides. More information on these may be
670found in the L<Class::MOP::Class documentation|Class::MOP::Class/"Method
671Modifiers"> for now.
6ba6d68c 672
159da176 673=item B<super>
674
26fbace8 675The keyword C<super> is a no-op when called outside of an C<override> method. In
676the context of an C<override> method, it will call the next most appropriate
159da176 677superclass method with the same arguments as the original method.
678
679=item B<override ($name, &sub)>
680
26fbace8 681An C<override> method is a way of explicitly saying "I am overriding this
682method from my superclass". You can call C<super> within this method, and
683it will work as expected. The same thing I<can> be accomplished with a normal
684method call and the C<SUPER::> pseudo-package; it is really your choice.
159da176 685
686=item B<inner>
687
26fbace8 688The keyword C<inner>, much like C<super>, is a no-op outside of the context of
689an C<augment> method. You can think of C<inner> as being the inverse of
68efb014 690C<super>; the details of how C<inner> and C<augment> work is best described in
159da176 691the L<Moose::Cookbook>.
692
693=item B<augment ($name, &sub)>
694
26fbace8 695An C<augment> method, is a way of explicitly saying "I am augmenting this
696method from my superclass". Once again, the details of how C<inner> and
159da176 697C<augment> work is best described in the L<Moose::Cookbook>.
698
6ba6d68c 699=item B<confess>
700
68efb014 701This is the C<Carp::confess> function, and exported here because I use it
26fbace8 702all the time. This feature may change in the future, so you have been warned.
6ba6d68c 703
704=item B<blessed>
705
1cd45431 706This is the C<Scalar::Util::blessed> function, it is exported here because I
26fbace8 707use it all the time. It is highly recommended that this is used instead of
6ba6d68c 708C<ref> anywhere you need to test for an object's class name.
709
710=back
711
1cd45431 712=head1 UNIMPORTING FUNCTIONS
31f8ec72 713
714=head2 B<unimport>
715
1cd45431 716Moose offers a way to remove the keywords it exports, through the C<unimport>
31f8ec72 717method. You simply have to say C<no Moose> at the bottom of your code for this
718to work. Here is an example:
719
720 package Person;
721 use Moose;
722
723 has 'first_name' => (is => 'rw', isa => 'Str');
724 has 'last_name' => (is => 'rw', isa => 'Str');
26fbace8 725
726 sub full_name {
31f8ec72 727 my $self = shift;
26fbace8 728 $self->first_name . ' ' . $self->last_name
31f8ec72 729 }
26fbace8 730
731 no Moose; # keywords are removed from the Person package
31f8ec72 732
9bcfbab1 733=head1 EXTENDING AND EMBEDDING MOOSE
734
26fbace8 735Moose also offers some options for extending or embedding it into your own
9bcfbab1 736framework. The basic premise is to have something that sets up your class'
26fbace8 737metaclass and export the moose declarators (C<has>, C<with>, C<extends>,...).
9bcfbab1 738Here is an example:
739
740 package MyFramework;
741 use Moose;
26fbace8 742
9bcfbab1 743 sub import {
744 my $CALLER = caller();
745
746 strict->import;
747 warnings->import;
748
749 # we should never export to main
750 return if $CALLER eq 'main';
751 Moose::init_meta( $CALLER, 'MyFramework::Base' );
752 Moose->import({into => $CALLER});
753
754 # Do my custom framework stuff
26fbace8 755
9bcfbab1 756 return 1;
757 }
26fbace8 758
9bcfbab1 759=head2 B<import>
760
77a18c28 761Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
9bcfbab1 762and C<{into_level =E<gt> 1}>
763
764=head2 B<init_meta ($class, $baseclass, $metaclass)>
765
26fbace8 766Moose does some boot strapping: it creates a metaclass object for your class,
767and then injects a C<meta> accessor into your class to retrieve it. Then it
768sets your baseclass to Moose::Object or the value you pass in unless you already
769have one. This is all done via C<init_meta> which takes the name of your class
2bbba362 770and optionally a baseclass and a metaclass as arguments.
26fbace8 771
05d9eaf6 772=head1 CAVEATS
773
774=over 4
775
776=item *
777
1cd45431 778It should be noted that C<super> and C<inner> B<cannot> be used in the same
779method. However, they may be combined within the same class hierarchy; see
780F<t/014_override_augment_inner_super.t> for an example.
05d9eaf6 781
26fbace8 782The reason for this is that C<super> is only valid within a method
783with the C<override> modifier, and C<inner> will never be valid within an
784C<override> method. In fact, C<augment> will skip over any C<override> methods
68efb014 785when searching for its appropriate C<inner>.
05d9eaf6 786
1cd45431 787This might seem like a restriction, but I am of the opinion that keeping these
788two features separate (yet interoperable) actually makes them easy to use, since
789their behavior is then easier to predict. Time will tell whether I am right or
c84f324f 790not (UPDATE: so far so good).
05d9eaf6 791
792=back
793
5569c072 794=head1 ACKNOWLEDGEMENTS
795
796=over 4
797
54c189df 798=item I blame Sam Vilain for introducing me to the insanity that is meta-models.
5569c072 799
54c189df 800=item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
5569c072 801
26fbace8 802=item Without Yuval "nothingmuch" Kogman this module would not be possible,
54c189df 803and it certainly wouldn't have this name ;P
5569c072 804
26fbace8 805=item The basis of the TypeContraints module was Rob Kinyon's idea
5569c072 806originally, I just ran with it.
807
26fbace8 808=item Thanks to mst & chansen and the whole #moose poose for all the
c84f324f 809early ideas/feature-requests/encouragement/bug-finding.
d46a48f3 810
68efb014 811=item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
812
5569c072 813=back
814
e90c03d0 815=head1 SEE ALSO
816
817=over 4
818
c84f324f 819=item L<http://www.iinteractive.com/moose>
820
821This is the official web home of Moose, it contains links to our public SVN repo
26fbace8 822as well as links to a number of talks and articles on Moose and Moose related
823technologies.
c84f324f 824
6ba6d68c 825=item L<Class::MOP> documentation
826
827=item The #moose channel on irc.perl.org
828
e67a0fca 829=item The Moose mailing list - moose@perl.org
830
c84f324f 831=item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/5788>
832
28669f89 833=item Several Moose extension modules in the L<MooseX::> namespace.
834
c84f324f 835=back
836
26fbace8 837=head2 Papers
c84f324f 838
839=over 4
e90c03d0 840
159da176 841=item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
842
26fbace8 843This paper (suggested by lbr on #moose) was what lead to the implementation
844of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1cd45431 845want to understand them, I suggest you read this.
159da176 846
e90c03d0 847=back
848
fcd84ca9 849=head1 BUGS
850
26fbace8 851All complex software has bugs lurking in it, and this module is no
fcd84ca9 852exception. If you find a bug please either email me, or add the bug
853to cpan-RT.
854
fcd84ca9 855=head1 AUTHOR
856
857Stevan Little E<lt>stevan@iinteractive.comE<gt>
858
9af1d28b 859B<with contributions from:>
db1ab48d 860
9af1d28b 861Aankhen
862
863Adam (Alias) Kennedy
864
865Anders (Debolaz) Nor Berle
866
5868294f 867Nathan (kolibre) Gray
868
9af1d28b 869Christian (chansen) Hansen
870
e7f8d0c2 871Hans Dieter (confound) Pearcey
872
9af1d28b 873Eric (ewilhelm) Wilhelm
874
875Guillermo (groditi) Roditi
876
877Jess (castaway) Robinson
878
879Matt (mst) Trout
880
881Robert (phaylon) Sedlacek
882
883Robert (rlb3) Boone
884
885Scott (konobi) McWhirter
886
f44ae52f 887Shlomi (rindolf) Fish
888
9af1d28b 889Yuval (nothingmuch) Kogman
890
cbe25729 891Chris (perigrin) Prather
892
e46f5cc2 893Jonathan (jrockway) Rockway
894
3ccdc84a 895Piotr (dexter) Roszatycki
896
26fbace8 897Sam (mugwump) Vilain
f1917f58 898
9af1d28b 899... and many other #moose folks
98aae381 900
fcd84ca9 901=head1 COPYRIGHT AND LICENSE
902
b77fdbed 903Copyright 2006, 2007 by Infinity Interactive, Inc.
fcd84ca9 904
905L<http://www.iinteractive.com>
906
907This library is free software; you can redistribute it and/or modify
26fbace8 908it under the same terms as Perl itself.
fcd84ca9 909
ddd0ec20 910=cut