this is not needed now
[gitmo/Moose.git] / lib / Moose.pm
CommitLineData
fcd84ca9 1
2package Moose;
3
4use strict;
5use warnings;
6
32dd4a95 7our $VERSION = '0.34';
d44714be 8our $AUTHORITY = 'cpan:STEVAN';
fcd84ca9 9
cc65ead0 10use Scalar::Util 'blessed', 'reftype';
3796382a 11use Carp 'confess';
12use Sub::Name 'subname';
fcd84ca9 13
2d562421 14use Sub::Exporter;
7f18097c 15
d7d8a8c7 16use Class::MOP 0.51;
ef1d5f4b 17
c0e30cf5 18use Moose::Meta::Class;
7415b2cb 19use Moose::Meta::TypeConstraint;
3fef8ce8 20use Moose::Meta::TypeConstraint::Class;
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;
d7d8a8c7 29use Moose::Util ();
a15dff8d 30
a3c7e2fe 31{
be33e4f3 32 my $CALLER;
9bcfbab1 33
34 sub init_meta {
35 my ( $class, $base_class, $metaclass ) = @_;
72bbc189 36 $base_class = $class unless defined $base_class;
26fbace8 37 $metaclass = 'Moose::Meta::Class' unless defined $metaclass;
9bcfbab1 38
39 confess
97e11ef5 40 "The Metaclass $metaclass must be a subclass of Moose::Meta::Class."
41 unless $metaclass->isa('Moose::Meta::Class');
a3c7e2fe 42
a3c7e2fe 43 # make a subtype for each Moose class
3fef8ce8 44 class_type($class)
45 unless find_type_constraint($class);
a3c7e2fe 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') )
1edfdf1c 55 || confess "You already have a &meta function, but it does not return a Moose::Meta::Class";
a3c7e2fe 56 }
57 else {
fcec2383 58 # NOTE:
9bcfbab1 59 # this is broken currently, we actually need
60 # to allow the possiblity of an inherited
61 # meta, which will not be visible until the
62 # user 'extends' first. This needs to have
63 # more intelligence to it
64 $meta = $metaclass->initialize($class);
65 $meta->add_method(
66 'meta' => sub {
9bcfbab1 67 # re-initialize so it inherits properly
68 $metaclass->initialize( blessed( $_[0] ) || $_[0] );
69 }
70 );
a3c7e2fe 71 }
72
73 # make sure they inherit from Moose::Object
72bbc189 74 $meta->superclasses($base_class)
9bcfbab1 75 unless $meta->superclasses();
a3c7e2fe 76 }
77
78 my %exports = (
79 extends => sub {
be33e4f3 80 my $class = $CALLER;
68117c45 81 return subname 'Moose::extends' => sub (@) {
82 confess "Must derive at least one class" unless @_;
1eaed09d 83 Class::MOP::load_class($_) for @_;
9bcfbab1 84
85 # this checks the metaclass to make sure
86 # it is correct, sometimes it can get out
1341f10c 87 # of sync when the classes are being built
88 my $meta = $class->meta->_fix_metaclass_incompatability(@_);
be33e4f3 89 $meta->superclasses(@_);
a3c7e2fe 90 };
91 },
92 with => sub {
be33e4f3 93 my $class = $CALLER;
68117c45 94 return subname 'Moose::with' => sub (@) {
d7d8a8c7 95 Moose::Util::apply_all_roles($class->meta, @_)
a3c7e2fe 96 };
97 },
98 has => sub {
be33e4f3 99 my $class = $CALLER;
2c0cbef7 100 return subname 'Moose::has' => sub ($;%) {
9bcfbab1 101 my ( $name, %options ) = @_;
102 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
d7d8a8c7 103 $class->meta->add_attribute( $_, %options ) for @$attrs;
a3c7e2fe 104 };
105 },
106 before => sub {
be33e4f3 107 my $class = $CALLER;
2c0cbef7 108 return subname 'Moose::before' => sub (@&) {
a3c7e2fe 109 my $code = pop @_;
be33e4f3 110 my $meta = $class->meta;
9bcfbab1 111 $meta->add_before_method_modifier( $_, $code ) for @_;
a3c7e2fe 112 };
113 },
114 after => sub {
be33e4f3 115 my $class = $CALLER;
2c0cbef7 116 return subname 'Moose::after' => sub (@&) {
a3c7e2fe 117 my $code = pop @_;
be33e4f3 118 my $meta = $class->meta;
9bcfbab1 119 $meta->add_after_method_modifier( $_, $code ) for @_;
a3c7e2fe 120 };
121 },
122 around => sub {
9bcfbab1 123 my $class = $CALLER;
2c0cbef7 124 return subname 'Moose::around' => sub (@&) {
a3c7e2fe 125 my $code = pop @_;
be33e4f3 126 my $meta = $class->meta;
9bcfbab1 127 $meta->add_around_method_modifier( $_, $code ) for @_;
a3c7e2fe 128 };
129 },
130 super => sub {
52c7c330 131 {
9bcfbab1 132 our %SUPER_SLOT;
133 no strict 'refs';
134 $SUPER_SLOT{$CALLER} = \*{"${CALLER}::super"};
52c7c330 135 }
9bcfbab1 136 return subname 'Moose::super' => sub { };
a3c7e2fe 137 },
138 override => sub {
be33e4f3 139 my $class = $CALLER;
2c0cbef7 140 return subname 'Moose::override' => sub ($&) {
9bcfbab1 141 my ( $name, $method ) = @_;
142 $class->meta->add_override_method_modifier( $name => $method );
a3c7e2fe 143 };
144 },
145 inner => sub {
52c7c330 146 {
9bcfbab1 147 our %INNER_SLOT;
148 no strict 'refs';
149 $INNER_SLOT{$CALLER} = \*{"${CALLER}::inner"};
52c7c330 150 }
9bcfbab1 151 return subname 'Moose::inner' => sub { };
a3c7e2fe 152 },
153 augment => sub {
be33e4f3 154 my $class = $CALLER;
2c0cbef7 155 return subname 'Moose::augment' => sub (@&) {
9bcfbab1 156 my ( $name, $method ) = @_;
157 $class->meta->add_augment_method_modifier( $name => $method );
a3c7e2fe 158 };
159 },
160 confess => sub {
161 return \&Carp::confess;
162 },
163 blessed => sub {
164 return \&Scalar::Util::blessed;
66bcefc1 165 },
a3c7e2fe 166 );
3d544ed5 167
9bcfbab1 168 my $exporter = Sub::Exporter::build_exporter(
169 {
170 exports => \%exports,
171 groups => { default => [':all'] }
a3c7e2fe 172 }
9bcfbab1 173 );
174
c92c1205 175 # 1 extra level because it's called by import so there's a layer of indirection
176 sub _get_caller{
177 my $offset = 1;
26fbace8 178 return
c92c1205 179 ref $_[1] && defined $_[1]->{into}
180 ? $_[1]->{into}
181 : ref $_[1] && defined $_[1]->{into_level}
182 ? caller($offset + $_[1]->{into_level})
183 : caller($offset);
184 }
5bee491d 185
186 sub import {
c92c1205 187 $CALLER = _get_caller(@_);
26fbace8 188
c235cd98 189 strict->import;
9bcfbab1 190 warnings->import;
a3c7e2fe 191
192 # we should never export to main
193 return if $CALLER eq 'main';
9bcfbab1 194
195 init_meta( $CALLER, 'Moose::Object' );
196
a3c7e2fe 197 goto $exporter;
fcb7afc2 198 }
9bcfbab1 199
31f8ec72 200 sub unimport {
9bcfbab1 201 no strict 'refs';
c92c1205 202 my $class = _get_caller(@_);
9bcfbab1 203
31f8ec72 204 # loop through the exports ...
9bcfbab1 205 foreach my $name ( keys %exports ) {
206
31f8ec72 207 # if we find one ...
9bcfbab1 208 if ( defined &{ $class . '::' . $name } ) {
209 my $keyword = \&{ $class . '::' . $name };
210
31f8ec72 211 # make sure it is from Moose
53dd42d8 212 my ($pkg_name) = Class::MOP::get_code_info($keyword);
31f8ec72 213 next if $@;
214 next if $pkg_name ne 'Moose';
9bcfbab1 215
31f8ec72 216 # and if it is from Moose then undef the slot
9bcfbab1 217 delete ${ $class . '::' }{$name};
31f8ec72 218 }
219 }
220 }
9bcfbab1 221
fcd84ca9 222}
223
8ecb1fa0 224## make 'em all immutable
225
226$_->meta->make_immutable(
227 inline_constructor => 0,
77a18c28 228 inline_accessors => 1, # these are Class::MOP accessors, so they need inlining
9bcfbab1 229 )
230 for (
8ecb1fa0 231 'Moose::Meta::Attribute',
232 'Moose::Meta::Class',
233 'Moose::Meta::Instance',
234
235 'Moose::Meta::TypeConstraint',
236 'Moose::Meta::TypeConstraint::Union',
0fbd4b0a 237 'Moose::Meta::TypeConstraint::Parameterized',
8ecb1fa0 238 'Moose::Meta::TypeCoercion',
239
240 'Moose::Meta::Method',
241 'Moose::Meta::Method::Accessor',
242 'Moose::Meta::Method::Constructor',
9bcfbab1 243 'Moose::Meta::Method::Destructor',
8ecb1fa0 244 'Moose::Meta::Method::Overriden',
d67145ed 245
246 'Moose::Meta::Role',
9bcfbab1 247 'Moose::Meta::Role::Method',
248 'Moose::Meta::Role::Method::Required',
249 );
8ecb1fa0 250
fcd84ca9 2511;
252
253__END__
254
255=pod
256
257=head1 NAME
258
8bdc7f13 259Moose - A postmodern object system for Perl 5
fcd84ca9 260
261=head1 SYNOPSIS
e522431d 262
263 package Point;
1cd45431 264 use Moose; # automatically turns on strict and warnings
26fbace8 265
43d599e5 266 has 'x' => (is => 'rw', isa => 'Int');
267 has 'y' => (is => 'rw', isa => 'Int');
26fbace8 268
e522431d 269 sub clear {
270 my $self = shift;
271 $self->x(0);
26fbace8 272 $self->y(0);
e522431d 273 }
26fbace8 274
e522431d 275 package Point3D;
276 use Moose;
26fbace8 277
e522431d 278 extends 'Point';
26fbace8 279
43d599e5 280 has 'z' => (is => 'rw', isa => 'Int');
26fbace8 281
e522431d 282 after 'clear' => sub {
283 my $self = shift;
43d599e5 284 $self->z(0);
26fbace8 285 };
2c0cbef7 286
fcd84ca9 287=head1 DESCRIPTION
288
26fbace8 289Moose is an extension of the Perl 5 object system.
e522431d 290
291=head2 Another object system!?!?
fcd84ca9 292
26fbace8 293Yes, I know there has been an explosion recently of new ways to
68efb014 294build object's in Perl 5, most of them based on inside-out objects
26fbace8 295and other such things. Moose is different because it is not a new
296object system for Perl 5, but instead an extension of the existing
e522431d 297object system.
3c7278fb 298
26fbace8 299Moose is built on top of L<Class::MOP>, which is a metaclass system
300for Perl 5. This means that Moose not only makes building normal
301Perl 5 objects better, but it also provides the power of metaclass
505c6fac 302programming.
e522431d 303
734d1752 304=head2 Is this for real? Or is this just an experiment?
e522431d 305
2c0cbef7 306Moose is I<based> on the prototypes and experiments I did for the Perl 6
26fbace8 307meta-model. However, Moose is B<NOT> an experiment/prototype; it is for B<real>.
734d1752 308
26fbace8 309=head2 Is this ready for use in production?
d44714be 310
26fbace8 311Yes, I believe that it is.
734d1752 312
26fbace8 313Moose has been used successfully in production environemnts by several people
314and companies (including the one I work for). There are Moose applications
8bdc7f13 315which have been in production with little or no issue now for well over a year.
26fbace8 316I consider it highly stable and we are commited to keeping it stable.
e522431d 317
26fbace8 318Of course, in the end, you need to make this call yourself. If you have
319any questions or concerns, please feel free to email me, or even the list
d44714be 320or just stop by #moose and ask away.
321
43d599e5 322=head2 Is Moose just Perl 6 in Perl 5?
e522431d 323
68efb014 324No. While Moose is very much inspired by Perl 6, it is not itself Perl 6.
1cd45431 325Instead, it is an OO system for Perl 5. I built Moose because I was tired of
68efb014 326writing the same old boring Perl 5 OO code, and drooling over Perl 6 OO. So
327instead of switching to Ruby, I wrote Moose :)
3c7278fb 328
8bdc7f13 329=head2 Wait, I<post> modern, I thought it was just I<modern>?
330
331So I was reading Larry Wall's talk from the 1999 Linux World entitled
332"Perl, the first postmodern computer language" in which he talks about how
333he picked the features for Perl because he thought they were cool and he
334threw out the ones that he thought sucked. This got me thinking about how
335we have done the same thing in Moose. For Moose, we have "borrowed" features
336from Perl 6, CLOS (LISP), Smalltalk, Java, BETA, OCaml, Ruby and more, and
337the bits we didn't like (cause they sucked) we tossed aside. So for this
338reason (and a few others) I have re-dubbed Moose a I<postmodern> object system.
339
340Nuff Said.
341
28669f89 342=head2 Moose Extensions
343
344The L<MooseX::> namespace is the official place to find Moose extensions.
0b26305c 345There are a number of these modules out on CPAN right now the best way to
346find them is to search for MooseX:: on search.cpan.org.
28669f89 347
6ba6d68c 348=head1 BUILDING CLASSES WITH MOOSE
349
68efb014 350Moose makes every attempt to provide as much convenience as possible during
351class construction/definition, but still stay out of your way if you want it
352to. Here are a few items to note when building classes with Moose.
6ba6d68c 353
26fbace8 354Unless specified with C<extends>, any class which uses Moose will
6ba6d68c 355inherit from L<Moose::Object>.
356
1cd45431 357Moose will also manage all attributes (including inherited ones) that are
358defined with C<has>. And (assuming you call C<new>, which is inherited from
359L<Moose::Object>) this includes properly initializing all instance slots,
360setting defaults where appropriate, and performing any type constraint checking
361or coercion.
6ba6d68c 362
363=head1 EXPORTED FUNCTIONS
364
26fbace8 365Moose will export a number of functions into the class's namespace which
366may then be used to set up the class. These functions all work directly
6ba6d68c 367on the current class.
368
369=over 4
370
371=item B<meta>
372
373This is a method which provides access to the current class's metaclass.
374
375=item B<extends (@superclasses)>
376
377This function will set the superclass(es) for the current class.
378
26fbace8 379This approach is recommended instead of C<use base>, because C<use base>
380actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
381replace it. This is important to ensure that classes which do not have
68efb014 382superclasses still properly inherit from L<Moose::Object>.
6ba6d68c 383
43d599e5 384=item B<with (@roles)>
e9ec68d6 385
26fbace8 386This will apply a given set of C<@roles> to the local class. Role support
68efb014 387is currently under heavy development; see L<Moose::Role> for more details.
e9ec68d6 388
cd7eeaf5 389=item B<has $name =E<gt> %options>
6ba6d68c 390
26fbace8 391This will install an attribute of a given C<$name> into the current class.
392The C<%options> are the same as those provided by
393L<Class::MOP::Attribute>, in addition to the list below which are provided
43d599e5 394by Moose (L<Moose::Meta::Attribute> to be more specific):
6ba6d68c 395
396=over 4
397
076c81ed 398=item I<is =E<gt> 'rw'|'ro'>
6ba6d68c 399
26fbace8 400The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
401only). These will create either a read/write accessor or a read-only
6ba6d68c 402accessor respectively, using the same name as the C<$name> of the attribute.
403
1cd45431 404If you need more control over how your accessors are named, you can use the
405I<reader>, I<writer> and I<accessor> options inherited from
406L<Class::MOP::Attribute>.
6ba6d68c 407
076c81ed 408=item I<isa =E<gt> $type_name>
6ba6d68c 409
26fbace8 410The I<isa> option uses Moose's type constraint facilities to set up runtime
411type checking for this attribute. Moose will perform the checks during class
412construction, and within any accessors. The C<$type_name> argument must be a
413string. The string may be either a class name or a type defined using
9cca2e9e 414Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
c2a69ef1 415for information on how to define a new type, and how to retrieve type meta-data).
6ba6d68c 416
daea75c9 417=item I<coerce =E<gt> (1|0)>
418
26fbace8 419This will attempt to use coercion with the supplied type constraint to change
420the value passed into any accessors or constructors. You B<must> have supplied
daea75c9 421a type constraint in order for this to work. See L<Moose::Cookbook::Recipe5>
1cd45431 422for an example.
daea75c9 423
424=item I<does =E<gt> $role_name>
425
26fbace8 426This will accept the name of a role which the value stored in this attribute
daea75c9 427is expected to have consumed.
428
429=item I<required =E<gt> (1|0)>
430
26fbace8 431This marks the attribute as being required. This means a I<defined> value must be
432supplied during class construction, and the attribute may never be set to
433C<undef> with an accessor.
daea75c9 434
435=item I<weak_ref =E<gt> (1|0)>
436
68efb014 437This will tell the class to store the value of this attribute as a weakened
438reference. If an attribute is a weakened reference, it B<cannot> also be
439coerced.
daea75c9 440
441=item I<lazy =E<gt> (1|0)>
442
26fbace8 443This will tell the class to not create this slot until absolutely necessary.
daea75c9 444If an attribute is marked as lazy it B<must> have a default supplied.
445
9e93dd19 446=item I<auto_deref =E<gt> (1|0)>
447
26fbace8 448This tells the accessor whether to automatically dereference the value returned.
1cd45431 449This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.
9e93dd19 450
c1935ade 451=item I<metaclass =E<gt> $metaclass_name>
452
1cd45431 453This tells the class to use a custom attribute metaclass for this particular
454attribute. Custom attribute metaclasses are useful for extending the
455capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
456but they are still a fairly advanced topic and too much to cover here. I will
457try and write a recipe on them soon.
458
459The default behavior here is to just load C<$metaclass_name>; however, we also
460have a way to alias to a shorter name. This will first look to see if
461B<Moose::Meta::Attribute::Custom::$metaclass_name> exists. If it does, Moose
32dd4a95 462will then check to see if that has the method C<register_implementation>, which
1cd45431 463should return the actual name of the custom attribute metaclass. If there is no
32dd4a95 464C<register_implementation> method, it will fall back to using
c1935ade 465B<Moose::Meta::Attribute::Custom::$metaclass_name> as the metaclass name.
466
daea75c9 467=item I<trigger =E<gt> $code>
468
1cd45431 469The I<trigger> option is a CODE reference which will be called after the value of
470the attribute is set. The CODE ref will be passed the instance itself, the
daea75c9 471updated value and the attribute meta-object (this is for more advanced fiddling
1cd45431 472and can typically be ignored). You B<cannot> have a trigger on a read-only
473attribute.
daea75c9 474
c84f324f 475=item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | CODE>
2c0cbef7 476
26fbace8 477The I<handles> option provides Moose classes with automated delegation features.
478This is a pretty complex and powerful option. It accepts many different option
479formats, each with its own benefits and drawbacks.
38e3283b 480
1cd45431 481B<NOTE:> This feature is no longer experimental, but it may still have subtle
482bugs lurking in the deeper corners. If you think you have found a bug, you
26fbace8 483probably have, so please report it to me right away.
38e3283b 484
1cd45431 485B<NOTE:> The class being delegated to does not need to be a Moose based class,
486which is why this feature is especially useful when wrapping non-Moose classes.
38e3283b 487
1cd45431 488All I<handles> option formats share the following traits:
38e3283b 489
1cd45431 490You cannot override a locally defined method with a delegated method; an
491exception will be thrown if you try. That is to say, if you define C<foo> in
492your class, you cannot override it with a delegated C<foo>. This is almost never
493something you would want to do, and if it is, you should do it by hand and not
494use Moose.
38e3283b 495
1cd45431 496You cannot override any of the methods found in Moose::Object, or the C<BUILD>
497and C<DEMOLISH> methods. These will not throw an exception, but will silently
498move on to the next method in the list. My reasoning for this is that you would
499almost never want to do this, since it usually breaks your class. As with
500overriding locally defined methods, if you do want to do this, you should do it
501manually, not with Moose.
38e3283b 502
f3c4e20e 503You do not I<need> to have a reader (or accessor) for the attribute in order
504to delegate to it. Moose will create a means of accessing the value for you,
505however this will be several times B<less> efficient then if you had given
506the attribute a reader (or accessor) to use.
507
38e3283b 508Below is the documentation for each option format:
509
510=over 4
511
512=item C<ARRAY>
513
26fbace8 514This is the most common usage for I<handles>. You basically pass a list of
515method names to be delegated, and Moose will install a delegation method
1cd45431 516for each one.
38e3283b 517
518=item C<HASH>
519
26fbace8 520This is the second most common usage for I<handles>. Instead of a list of
521method names, you pass a HASH ref where each key is the method name you
522want installed locally, and its value is the name of the original method
523in the class being delegated to.
fd595040 524
26fbace8 525This can be very useful for recursive classes like trees. Here is a
fd595040 526quick example (soon to be expanded into a Moose::Cookbook::Recipe):
38e3283b 527
1cd45431 528 package Tree;
38e3283b 529 use Moose;
26fbace8 530
38e3283b 531 has 'node' => (is => 'rw', isa => 'Any');
26fbace8 532
38e3283b 533 has 'children' => (
534 is => 'ro',
535 isa => 'ArrayRef',
536 default => sub { [] }
537 );
26fbace8 538
38e3283b 539 has 'parent' => (
540 is => 'rw',
541 isa => 'Tree',
a4e516f6 542 weak_ref => 1,
38e3283b 543 handles => {
544 parent_node => 'node',
26fbace8 545 siblings => 'children',
38e3283b 546 }
547 );
548
1cd45431 549In this example, the Tree package gets C<parent_node> and C<siblings> methods,
550which delegate to the C<node> and C<children> methods (respectively) of the Tree
26fbace8 551instance stored in the C<parent> slot.
38e3283b 552
553=item C<REGEXP>
554
26fbace8 555The regexp option works very similar to the ARRAY option, except that it builds
556the list of methods for you. It starts by collecting all possible methods of the
557class being delegated to, then filters that list using the regexp supplied here.
38e3283b 558
26fbace8 559B<NOTE:> An I<isa> option is required when using the regexp option format. This
560is so that we can determine (at compile time) the method list from the class.
38e3283b 561Without an I<isa> this is just not possible.
562
c84f324f 563=item C<ROLE>
564
26fbace8 565With the role option, you specify the name of a role whose "interface" then
566becomes the list of methods to handle. The "interface" can be defined as; the
567methods of the role and any required methods of the role. It should be noted
568that this does B<not> include any method modifiers or generated attribute
c84f324f 569methods (which is consistent with role composition).
570
38e3283b 571=item C<CODE>
572
1cd45431 573This is the option to use when you really want to do something funky. You should
574only use it if you really know what you are doing, as it involves manual
575metaclass twiddling.
38e3283b 576
1cd45431 577This takes a code reference, which should expect two arguments. The first is the
578attribute meta-object this I<handles> is attached to. The second is the
579metaclass of the class being delegated to. It expects you to return a hash (not
26fbace8 580a HASH ref) of the methods you want mapped.
38e3283b 581
582=back
2c0cbef7 583
6ba6d68c 584=back
585
cd7eeaf5 586=item B<has +$name =E<gt> %options>
587
26fbace8 588This is variation on the normal attibute creator C<has> which allows you to
cd7eeaf5 589clone and extend an attribute from a superclass. Here is a quick example:
590
591 package Foo;
592 use Moose;
26fbace8 593
cd7eeaf5 594 has 'message' => (
26fbace8 595 is => 'rw',
cd7eeaf5 596 isa => 'Str',
597 default => 'Hello, I am a Foo'
598 );
26fbace8 599
cd7eeaf5 600 package My::Foo;
601 use Moose;
26fbace8 602
cd7eeaf5 603 extends 'Foo';
26fbace8 604
cd7eeaf5 605 has '+message' => (default => 'Hello I am My::Foo');
606
1cd45431 607What is happening here is that B<My::Foo> is cloning the C<message> attribute
608from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
609'Str'> characteristics, but changing the value in C<default>.
cd7eeaf5 610
83cc9094 611This feature is restricted somewhat, so as to try and force at least I<some>
cd7eeaf5 612sanity into it. You are only allowed to change the following attributes:
613
614=over 4
615
26fbace8 616=item I<default>
cd7eeaf5 617
618Change the default value of an attribute.
619
26fbace8 620=item I<coerce>
cd7eeaf5 621
622Change whether the attribute attempts to coerce a value passed to it.
623
26fbace8 624=item I<required>
cd7eeaf5 625
626Change if the attribute is required to have a value.
627
628=item I<documentation>
629
630Change the documentation string associated with the attribute.
631
83cc9094 632=item I<lazy>
633
634Change if the attribute lazily initializes the slot.
635
cd7eeaf5 636=item I<isa>
637
1cd45431 638You I<are> allowed to change the type, B<if and only if> the new type is a
639subtype of the old type.
cd7eeaf5 640
83cc9094 641=item I<handles>
642
26fbace8 643You are allowed to B<add> a new C<handles> definition, but you are B<not>
644allowed to I<change> one.
83cc9094 645
cd7eeaf5 646=back
647
076c81ed 648=item B<before $name|@names =E<gt> sub { ... }>
6ba6d68c 649
076c81ed 650=item B<after $name|@names =E<gt> sub { ... }>
6ba6d68c 651
076c81ed 652=item B<around $name|@names =E<gt> sub { ... }>
6ba6d68c 653
d8af92ae 654This three items are syntactic sugar for the before, after, and around method
655modifier features that L<Class::MOP> provides. More information on these may be
656found in the L<Class::MOP::Class documentation|Class::MOP::Class/"Method
657Modifiers"> for now.
6ba6d68c 658
159da176 659=item B<super>
660
26fbace8 661The keyword C<super> is a no-op when called outside of an C<override> method. In
662the context of an C<override> method, it will call the next most appropriate
159da176 663superclass method with the same arguments as the original method.
664
665=item B<override ($name, &sub)>
666
26fbace8 667An C<override> method is a way of explicitly saying "I am overriding this
668method from my superclass". You can call C<super> within this method, and
669it will work as expected. The same thing I<can> be accomplished with a normal
670method call and the C<SUPER::> pseudo-package; it is really your choice.
159da176 671
672=item B<inner>
673
26fbace8 674The keyword C<inner>, much like C<super>, is a no-op outside of the context of
675an C<augment> method. You can think of C<inner> as being the inverse of
68efb014 676C<super>; the details of how C<inner> and C<augment> work is best described in
159da176 677the L<Moose::Cookbook>.
678
679=item B<augment ($name, &sub)>
680
26fbace8 681An C<augment> method, is a way of explicitly saying "I am augmenting this
682method from my superclass". Once again, the details of how C<inner> and
159da176 683C<augment> work is best described in the L<Moose::Cookbook>.
684
6ba6d68c 685=item B<confess>
686
68efb014 687This is the C<Carp::confess> function, and exported here because I use it
26fbace8 688all the time. This feature may change in the future, so you have been warned.
6ba6d68c 689
690=item B<blessed>
691
1cd45431 692This is the C<Scalar::Util::blessed> function, it is exported here because I
26fbace8 693use it all the time. It is highly recommended that this is used instead of
6ba6d68c 694C<ref> anywhere you need to test for an object's class name.
695
696=back
697
1cd45431 698=head1 UNIMPORTING FUNCTIONS
31f8ec72 699
700=head2 B<unimport>
701
1cd45431 702Moose offers a way to remove the keywords it exports, through the C<unimport>
31f8ec72 703method. You simply have to say C<no Moose> at the bottom of your code for this
704to work. Here is an example:
705
706 package Person;
707 use Moose;
708
709 has 'first_name' => (is => 'rw', isa => 'Str');
710 has 'last_name' => (is => 'rw', isa => 'Str');
26fbace8 711
712 sub full_name {
31f8ec72 713 my $self = shift;
26fbace8 714 $self->first_name . ' ' . $self->last_name
31f8ec72 715 }
26fbace8 716
717 no Moose; # keywords are removed from the Person package
31f8ec72 718
9bcfbab1 719=head1 EXTENDING AND EMBEDDING MOOSE
720
26fbace8 721Moose also offers some options for extending or embedding it into your own
9bcfbab1 722framework. The basic premise is to have something that sets up your class'
26fbace8 723metaclass and export the moose declarators (C<has>, C<with>, C<extends>,...).
9bcfbab1 724Here is an example:
725
726 package MyFramework;
727 use Moose;
26fbace8 728
9bcfbab1 729 sub import {
730 my $CALLER = caller();
731
732 strict->import;
733 warnings->import;
734
735 # we should never export to main
736 return if $CALLER eq 'main';
737 Moose::init_meta( $CALLER, 'MyFramework::Base' );
738 Moose->import({into => $CALLER});
739
740 # Do my custom framework stuff
26fbace8 741
9bcfbab1 742 return 1;
743 }
26fbace8 744
9bcfbab1 745=head2 B<import>
746
77a18c28 747Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
9bcfbab1 748and C<{into_level =E<gt> 1}>
749
750=head2 B<init_meta ($class, $baseclass, $metaclass)>
751
26fbace8 752Moose does some boot strapping: it creates a metaclass object for your class,
753and then injects a C<meta> accessor into your class to retrieve it. Then it
754sets your baseclass to Moose::Object or the value you pass in unless you already
755have one. This is all done via C<init_meta> which takes the name of your class
2bbba362 756and optionally a baseclass and a metaclass as arguments.
26fbace8 757
05d9eaf6 758=head1 CAVEATS
759
760=over 4
761
762=item *
763
1cd45431 764It should be noted that C<super> and C<inner> B<cannot> be used in the same
765method. However, they may be combined within the same class hierarchy; see
766F<t/014_override_augment_inner_super.t> for an example.
05d9eaf6 767
26fbace8 768The reason for this is that C<super> is only valid within a method
769with the C<override> modifier, and C<inner> will never be valid within an
770C<override> method. In fact, C<augment> will skip over any C<override> methods
68efb014 771when searching for its appropriate C<inner>.
05d9eaf6 772
1cd45431 773This might seem like a restriction, but I am of the opinion that keeping these
774two features separate (yet interoperable) actually makes them easy to use, since
775their behavior is then easier to predict. Time will tell whether I am right or
c84f324f 776not (UPDATE: so far so good).
05d9eaf6 777
778=back
779
5569c072 780=head1 ACKNOWLEDGEMENTS
781
782=over 4
783
54c189df 784=item I blame Sam Vilain for introducing me to the insanity that is meta-models.
5569c072 785
54c189df 786=item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
5569c072 787
26fbace8 788=item Without Yuval "nothingmuch" Kogman this module would not be possible,
54c189df 789and it certainly wouldn't have this name ;P
5569c072 790
26fbace8 791=item The basis of the TypeContraints module was Rob Kinyon's idea
5569c072 792originally, I just ran with it.
793
26fbace8 794=item Thanks to mst & chansen and the whole #moose poose for all the
c84f324f 795early ideas/feature-requests/encouragement/bug-finding.
d46a48f3 796
68efb014 797=item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
798
5569c072 799=back
800
e90c03d0 801=head1 SEE ALSO
802
803=over 4
804
c84f324f 805=item L<http://www.iinteractive.com/moose>
806
807This is the official web home of Moose, it contains links to our public SVN repo
26fbace8 808as well as links to a number of talks and articles on Moose and Moose related
809technologies.
c84f324f 810
6ba6d68c 811=item L<Class::MOP> documentation
812
813=item The #moose channel on irc.perl.org
814
e67a0fca 815=item The Moose mailing list - moose@perl.org
816
c84f324f 817=item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/5788>
818
28669f89 819=item Several Moose extension modules in the L<MooseX::> namespace.
820
c84f324f 821=back
822
26fbace8 823=head2 Papers
c84f324f 824
825=over 4
e90c03d0 826
159da176 827=item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
828
26fbace8 829This paper (suggested by lbr on #moose) was what lead to the implementation
830of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1cd45431 831want to understand them, I suggest you read this.
159da176 832
e90c03d0 833=back
834
fcd84ca9 835=head1 BUGS
836
26fbace8 837All complex software has bugs lurking in it, and this module is no
fcd84ca9 838exception. If you find a bug please either email me, or add the bug
839to cpan-RT.
840
fcd84ca9 841=head1 AUTHOR
842
843Stevan Little E<lt>stevan@iinteractive.comE<gt>
844
9af1d28b 845B<with contributions from:>
db1ab48d 846
9af1d28b 847Aankhen
848
849Adam (Alias) Kennedy
850
851Anders (Debolaz) Nor Berle
852
5868294f 853Nathan (kolibre) Gray
854
9af1d28b 855Christian (chansen) Hansen
856
e7f8d0c2 857Hans Dieter (confound) Pearcey
858
9af1d28b 859Eric (ewilhelm) Wilhelm
860
861Guillermo (groditi) Roditi
862
863Jess (castaway) Robinson
864
865Matt (mst) Trout
866
867Robert (phaylon) Sedlacek
868
869Robert (rlb3) Boone
870
871Scott (konobi) McWhirter
872
f44ae52f 873Shlomi (rindolf) Fish
874
9af1d28b 875Yuval (nothingmuch) Kogman
876
cbe25729 877Chris (perigrin) Prather
878
e46f5cc2 879Jonathan (jrockway) Rockway
880
3ccdc84a 881Piotr (dexter) Roszatycki
882
26fbace8 883Sam (mugwump) Vilain
f1917f58 884
ac211120 885Shawn (sartak) Moore
886
9af1d28b 887... and many other #moose folks
98aae381 888
fcd84ca9 889=head1 COPYRIGHT AND LICENSE
890
778db3ac 891Copyright 2006-2008 by Infinity Interactive, Inc.
fcd84ca9 892
893L<http://www.iinteractive.com>
894
895This library is free software; you can redistribute it and/or modify
26fbace8 896it under the same terms as Perl itself.
fcd84ca9 897
ddd0ec20 898=cut