support into and into_level better, and make _init_meta useable by others

[gitmo/Moose.git] / lib / Moose.pm

package Moose;

use strict;
use warnings;

our $VERSION   = '0.26';
our $AUTHORITY = 'cpan:STEVAN';

use Scalar::Util 'blessed', 'reftype';
use Carp         'confess';
use Sub::Name    'subname';
use B            'svref_2object';

use Sub::Exporter;

use Class::MOP 0.39;

use Moose::Meta::Class;
use Moose::Meta::TypeConstraint;
use Moose::Meta::TypeCoercion;
use Moose::Meta::Attribute;
use Moose::Meta::Instance;

use Moose::Meta::Role;

use Moose::Object;
use Moose::Util::TypeConstraints;

{
    my $CALLER;
    
    sub _init_meta {
        my ($class, $base_class) = @_;
        $base_class = $class unless defined $base_class;

        # make a subtype for each Moose class
        subtype $class
            => as 'Object'
            => where { $_->isa($class) }
            => optimize_as { blessed($_[0]) && $_[0]->isa($class) }
        unless find_type_constraint($class);

        my $meta;
        if ($class->can('meta')) {
            # NOTE:
            # this is the case where the metaclass pragma 
            # was used before the 'use Moose' statement to 
            # override a specific class
            $meta = $class->meta();
            (blessed($meta) && $meta->isa('Moose::Meta::Class'))
                || confess "You already have a &meta function, but it does not return a Moose::Meta::Class";
        }
        else {
            # NOTE:
            # this is broken currently, we actually need 
            # to allow the possiblity of an inherited 
            # meta, which will not be visible until the 
            # user 'extends' first. This needs to have 
            # more intelligence to it 
            $meta = Moose::Meta::Class->initialize($class);
            $meta->add_method('meta' => sub {
                # re-initialize so it inherits properly
                Moose::Meta::Class->initialize(blessed($_[0]) || $_[0]);
            })
        }

        # make sure they inherit from Moose::Object
        $meta->superclasses($base_class)
           unless $meta->superclasses();
    }

    my %exports = (
        extends => sub {
            my $class = $CALLER;
            return subname 'Moose::extends' => sub (@) {
                confess "Must derive at least one class" unless @_;
                Class::MOP::load_class($_) for @_;
                # this checks the metaclass to make sure 
                # it is correct, sometimes it can get out 
                # of sync when the classes are being built
                my $meta = $class->meta->_fix_metaclass_incompatability(@_);
                $meta->superclasses(@_);
            };
        },
        with => sub {
            my $class = $CALLER;
            return subname 'Moose::with' => sub (@) {
                my (@roles) = @_;
                confess "Must specify at least one role" unless @roles;
                Class::MOP::load_class($_) for @roles;
                $class->meta->_apply_all_roles(@roles);
            };
        },
        has => sub {
            my $class = $CALLER;
            return subname 'Moose::has' => sub ($;%) {
                my ($name, %options) = @_;
                my $attrs = (ref($name) eq 'ARRAY') ? $name : [($name)];
                $class->meta->_process_attribute($_, %options) for @$attrs;
            };
        },
        before => sub {
            my $class = $CALLER;
            return subname 'Moose::before' => sub (@&) {
                my $code = pop @_;
                my $meta = $class->meta;
                $meta->add_before_method_modifier($_, $code) for @_;
            };
        },
        after => sub {
            my $class = $CALLER;
            return subname 'Moose::after' => sub (@&) {
                my $code = pop @_;
                my $meta = $class->meta;
                $meta->add_after_method_modifier($_, $code) for @_;
            };
        },
        around => sub {
            my $class = $CALLER;            
            return subname 'Moose::around' => sub (@&) {
                my $code = pop @_;
                my $meta = $class->meta;
                $meta->add_around_method_modifier($_, $code) for @_;
            };
        },
        super => sub {
            {
              our %SUPER_SLOT;
              no strict 'refs';
              $SUPER_SLOT{$CALLER} = \*{"${CALLER}::super"};
            }
            return subname 'Moose::super' => sub {};
        },
        override => sub {
            my $class = $CALLER;
            return subname 'Moose::override' => sub ($&) {
                my ($name, $method) = @_;
                $class->meta->add_override_method_modifier($name => $method);
            };
        },
        inner => sub {
            {
              our %INNER_SLOT;
              no strict 'refs';
              $INNER_SLOT{$CALLER} = \*{"${CALLER}::inner"};
            }
            return subname 'Moose::inner' => sub {};
        },
        augment => sub {
            my $class = $CALLER;
            return subname 'Moose::augment' => sub (@&) {
                my ($name, $method) = @_;
                $class->meta->add_augment_method_modifier($name => $method);
            };
        },
        
        # NOTE:
        # this is experimental, but I am not 
        # happy with it. If you want to try 
        # it, you will have to uncomment it 
        # yourself. 
        # There is a really good chance that 
        # this will be deprecated, dont get 
        # too attached
        # self => sub {
        #     return subname 'Moose::self' => sub {};
        # },        
        # method => sub {
        #     my $class = $CALLER;
        #     return subname 'Moose::method' => sub {
        #         my ($name, $method) = @_;
        #         $class->meta->add_method($name, sub {
        #             my $self = shift;
        #             no strict   'refs';
        #             no warnings 'redefine';
        #             local *{$class->meta->name . '::self'} = sub { $self };
        #             $method->(@_);
        #         });
        #     };
        # },                
        
        confess => sub {
            return \&Carp::confess;
        },
        blessed => sub {
            return \&Scalar::Util::blessed;
        },
    );

    my $exporter = Sub::Exporter::build_exporter({ 
        exports => \%exports,
        groups  => {
            default => [':all']
        }
    });
    
    sub import {
        $CALLER
              = ref $_[1] && defined $_[1]->{into}       ? $_[1]->{into}
              : ref $_[1] && defined $_[1]->{into_level} ? caller($_[1]->{into_level})
              :                                            caller();
        strict->import;
        warnings->import;        

        # we should never export to main
        return if $CALLER eq 'main';
    
        _init_meta($CALLER, 'Moose::Object');
        
        goto $exporter;
    }
    
    sub unimport {
        no strict 'refs';        
        my $class = caller();
        # loop through the exports ...
        foreach my $name (keys %exports) {
            
            # if we find one ...
            if (defined &{$class . '::' . $name}) {
                my $keyword = \&{$class . '::' . $name};
                
                # make sure it is from Moose
                my $pkg_name = eval { svref_2object($keyword)->GV->STASH->NAME };
                next if $@;
                next if $pkg_name ne 'Moose';
                
                # and if it is from Moose then undef the slot
                delete ${$class . '::'}{$name};
            }
        }
    }
    
    
}

## make 'em all immutable

$_->meta->make_immutable(
    inline_constructor => 0,
    inline_accessors   => 1,    
) for (
    'Moose::Meta::Attribute',
    'Moose::Meta::Class',
    'Moose::Meta::Instance',

    'Moose::Meta::TypeConstraint',
    'Moose::Meta::TypeConstraint::Union',
    'Moose::Meta::TypeConstraint::Container',    
    'Moose::Meta::TypeCoercion',

    'Moose::Meta::Method',
    'Moose::Meta::Method::Accessor',
    'Moose::Meta::Method::Constructor',
    'Moose::Meta::Method::Destructor',    
    'Moose::Meta::Method::Overriden',

    'Moose::Meta::Role',
    'Moose::Meta::Role::Method',    
    'Moose::Meta::Role::Method::Required',        
);

1;

__END__

=pod

=head1 NAME

Moose - A complete modern object system for Perl 5

=head1 SYNOPSIS

  package Point;
  use Moose; # automatically turns on strict and warnings
        
  has 'x' => (is => 'rw', isa => 'Int');
  has 'y' => (is => 'rw', isa => 'Int');
  
  sub clear {
      my $self = shift;
      $self->x(0);
      $self->y(0);    
  }
  
  package Point3D;
  use Moose;
  
  extends 'Point';
  
  has 'z' => (is => 'rw', isa => 'Int');
  
  after 'clear' => sub {
      my $self = shift;
      $self->z(0);
  }; 

=head1 DESCRIPTION

Moose is an extension of the Perl 5 object system. 

=head2 Another object system!?!?

Yes, I know there has been an explosion recently of new ways to 
build object's in Perl 5, most of them based on inside-out objects
and other such things. Moose is different because it is not a new 
object system for Perl 5, but instead an extension of the existing 
object system.

Moose is built on top of L<Class::MOP>, which is a metaclass system 
for Perl 5. This means that Moose not only makes building normal 
Perl 5 objects better, but it also provides the power of metaclass 
programming.

=head2 Is this for real? Or is this just an experiment?

Moose is I<based> on the prototypes and experiments I did for the Perl 6
meta-model. However, Moose is B<NOT> an experiment/prototype; it is for B<real>. 

=head2 Is this ready for use in production? 

Yes, I believe that it is. 

I have two medium-to-large-ish web applications which use Moose heavily
and have been in production (without issue) for several months now. At 
$work, we are re-writing our core offering in it. And several people on 
#moose have been using it (in production) for several months now as well.

Of course, in the end, you need to make this call yourself. If you have 
any questions or concerns, please feel free to email me, or even the list 
or just stop by #moose and ask away.

=head2 Is Moose just Perl 6 in Perl 5?

No. While Moose is very much inspired by Perl 6, it is not itself Perl 6.
Instead, it is an OO system for Perl 5. I built Moose because I was tired of
writing the same old boring Perl 5 OO code, and drooling over Perl 6 OO. So
instead of switching to Ruby, I wrote Moose :)

=head1 BUILDING CLASSES WITH MOOSE

Moose makes every attempt to provide as much convenience as possible during
class construction/definition, but still stay out of your way if you want it
to. Here are a few items to note when building classes with Moose.

Unless specified with C<extends>, any class which uses Moose will 
inherit from L<Moose::Object>.

Moose will also manage all attributes (including inherited ones) that are
defined with C<has>. And (assuming you call C<new>, which is inherited from
L<Moose::Object>) this includes properly initializing all instance slots,
setting defaults where appropriate, and performing any type constraint checking
or coercion.

=head1 EXPORTED FUNCTIONS

Moose will export a number of functions into the class's namespace which 
may then be used to set up the class. These functions all work directly 
on the current class.

=over 4

=item B<meta>

This is a method which provides access to the current class's metaclass.

=item B<extends (@superclasses)>

This function will set the superclass(es) for the current class.

This approach is recommended instead of C<use base>, because C<use base> 
actually C<push>es onto the class's C<@ISA>, whereas C<extends> will 
replace it. This is important to ensure that classes which do not have 
superclasses still properly inherit from L<Moose::Object>.

=item B<with (@roles)>

This will apply a given set of C<@roles> to the local class. Role support 
is currently under heavy development; see L<Moose::Role> for more details.

=item B<has $name =E<gt> %options>

This will install an attribute of a given C<$name> into the current class. 
The C<%options> are the same as those provided by 
L<Class::MOP::Attribute>, in addition to the list below which are provided 
by Moose (L<Moose::Meta::Attribute> to be more specific):

=over 4

=item I<is =E<gt> 'rw'|'ro'>

The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read 
only). These will create either a read/write accessor or a read-only 
accessor respectively, using the same name as the C<$name> of the attribute.

If you need more control over how your accessors are named, you can use the
I<reader>, I<writer> and I<accessor> options inherited from
L<Class::MOP::Attribute>.

=item I<isa =E<gt> $type_name>

The I<isa> option uses Moose's type constraint facilities to set up runtime 
type checking for this attribute. Moose will perform the checks during class 
construction, and within any accessors. The C<$type_name> argument must be a 
string. The string may be either a class name or a type defined using 
Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
for information on how to define a new type, and how to retrieve type meta-data).

=item I<coerce =E<gt> (1|0)>

This will attempt to use coercion with the supplied type constraint to change 
the value passed into any accessors or constructors. You B<must> have supplied 
a type constraint in order for this to work. See L<Moose::Cookbook::Recipe5>
for an example.

=item I<does =E<gt> $role_name>

This will accept the name of a role which the value stored in this attribute 
is expected to have consumed.

=item I<required =E<gt> (1|0)>

This marks the attribute as being required. This means a I<defined> value must be 
supplied during class construction, and the attribute may never be set to 
C<undef> with an accessor. 

=item I<weak_ref =E<gt> (1|0)>

This will tell the class to store the value of this attribute as a weakened
reference. If an attribute is a weakened reference, it B<cannot> also be
coerced.

=item I<lazy =E<gt> (1|0)>

This will tell the class to not create this slot until absolutely necessary. 
If an attribute is marked as lazy it B<must> have a default supplied.

=item I<auto_deref =E<gt> (1|0)>

This tells the accessor whether to automatically dereference the value returned. 
This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.

=item I<metaclass =E<gt> $metaclass_name>

This tells the class to use a custom attribute metaclass for this particular
attribute. Custom attribute metaclasses are useful for extending the
capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
but they are still a fairly advanced topic and too much to cover here. I will
try and write a recipe on them soon.

The default behavior here is to just load C<$metaclass_name>; however, we also
have a way to alias to a shorter name. This will first look to see if
B<Moose::Meta::Attribute::Custom::$metaclass_name> exists. If it does, Moose
will then check to see if that has the method C<register_implemenetation>, which
should return the actual name of the custom attribute metaclass. If there is no
C<register_implemenetation> method, it will fall back to using
B<Moose::Meta::Attribute::Custom::$metaclass_name> as the metaclass name.

=item I<trigger =E<gt> $code>

The I<trigger> option is a CODE reference which will be called after the value of
the attribute is set. The CODE ref will be passed the instance itself, the
updated value and the attribute meta-object (this is for more advanced fiddling
and can typically be ignored). You B<cannot> have a trigger on a read-only
attribute.

=item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | CODE>

The I<handles> option provides Moose classes with automated delegation features. 
This is a pretty complex and powerful option. It accepts many different option 
formats, each with its own benefits and drawbacks. 

B<NOTE:> This feature is no longer experimental, but it may still have subtle
bugs lurking in the deeper corners. If you think you have found a bug, you
probably have, so please report it to me right away. 

B<NOTE:> The class being delegated to does not need to be a Moose based class,
which is why this feature is especially useful when wrapping non-Moose classes.

All I<handles> option formats share the following traits:

You cannot override a locally defined method with a delegated method; an
exception will be thrown if you try. That is to say, if you define C<foo> in
your class, you cannot override it with a delegated C<foo>. This is almost never
something you would want to do, and if it is, you should do it by hand and not
use Moose.

You cannot override any of the methods found in Moose::Object, or the C<BUILD>
and C<DEMOLISH> methods. These will not throw an exception, but will silently
move on to the next method in the list. My reasoning for this is that you would
almost never want to do this, since it usually breaks your class. As with
overriding locally defined methods, if you do want to do this, you should do it
manually, not with Moose.

Below is the documentation for each option format:

=over 4

=item C<ARRAY>

This is the most common usage for I<handles>. You basically pass a list of 
method names to be delegated, and Moose will install a delegation method 
for each one.

=item C<HASH>

This is the second most common usage for I<handles>. Instead of a list of 
method names, you pass a HASH ref where each key is the method name you 
want installed locally, and its value is the name of the original method 
in the class being delegated to. 

This can be very useful for recursive classes like trees. Here is a 
quick example (soon to be expanded into a Moose::Cookbook::Recipe):

  package Tree;
  use Moose;
  
  has 'node' => (is => 'rw', isa => 'Any');
  
  has 'children' => (
      is      => 'ro',
      isa     => 'ArrayRef',
      default => sub { [] }
  );
  
  has 'parent' => (
      is          => 'rw',
      isa         => 'Tree',
      is_weak_ref => 1,
      handles     => {
          parent_node => 'node',
          siblings    => 'children', 
      }
  );

In this example, the Tree package gets C<parent_node> and C<siblings> methods,
which delegate to the C<node> and C<children> methods (respectively) of the Tree
instance stored in the C<parent> slot. 

=item C<REGEXP>

The regexp option works very similar to the ARRAY option, except that it builds 
the list of methods for you. It starts by collecting all possible methods of the 
class being delegated to, then filters that list using the regexp supplied here. 

B<NOTE:> An I<isa> option is required when using the regexp option format. This 
is so that we can determine (at compile time) the method list from the class. 
Without an I<isa> this is just not possible.

=item C<ROLE>

With the role option, you specify the name of a role whose "interface" then 
becomes the list of methods to handle. The "interface" can be defined as; the 
methods of the role and any required methods of the role. It should be noted 
that this does B<not> include any method modifiers or generated attribute 
methods (which is consistent with role composition).

=item C<CODE>

This is the option to use when you really want to do something funky. You should
only use it if you really know what you are doing, as it involves manual
metaclass twiddling.

This takes a code reference, which should expect two arguments. The first is the
attribute meta-object this I<handles> is attached to. The second is the
metaclass of the class being delegated to. It expects you to return a hash (not
a HASH ref) of the methods you want mapped. 

=back

=back

=item B<has +$name =E<gt> %options>

This is variation on the normal attibute creator C<has> which allows you to 
clone and extend an attribute from a superclass. Here is a quick example:

  package Foo;
  use Moose;
  
  has 'message' => (
      is      => 'rw', 
      isa     => 'Str',
      default => 'Hello, I am a Foo'
  );
  
  package My::Foo;
  use Moose;
  
  extends 'Foo';
  
  has '+message' => (default => 'Hello I am My::Foo');

What is happening here is that B<My::Foo> is cloning the C<message> attribute
from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
'Str'> characteristics, but changing the value in C<default>.

This feature is restricted somewhat, so as to try and force at least I<some>
sanity into it. You are only allowed to change the following attributes:

=over 4

=item I<default> 

Change the default value of an attribute.

=item I<coerce> 

Change whether the attribute attempts to coerce a value passed to it.

=item I<required> 

Change if the attribute is required to have a value.

=item I<documentation>

Change the documentation string associated with the attribute.

=item I<lazy>

Change if the attribute lazily initializes the slot.

=item I<isa>

You I<are> allowed to change the type, B<if and only if> the new type is a
subtype of the old type.

=item I<handles>

You are allowed to B<add> a new C<handles> definition, but you are B<not> 
allowed to I<change> one. 

=back

=item B<before $name|@names =E<gt> sub { ... }>

=item B<after $name|@names =E<gt> sub { ... }>

=item B<around $name|@names =E<gt> sub { ... }>

This three items are syntactic sugar for the before, after, and around method
modifier features that L<Class::MOP> provides. More information on these may be
found in the L<Class::MOP::Class documentation|Class::MOP::Class/"Method
Modifiers"> for now.

=item B<super>

The keyword C<super> is a no-op when called outside of an C<override> method. In  
the context of an C<override> method, it will call the next most appropriate 
superclass method with the same arguments as the original method.

=item B<override ($name, &sub)>

An C<override> method is a way of explicitly saying "I am overriding this 
method from my superclass". You can call C<super> within this method, and 
it will work as expected. The same thing I<can> be accomplished with a normal 
method call and the C<SUPER::> pseudo-package; it is really your choice. 

=item B<inner>

The keyword C<inner>, much like C<super>, is a no-op outside of the context of 
an C<augment> method. You can think of C<inner> as being the inverse of 
C<super>; the details of how C<inner> and C<augment> work is best described in
the L<Moose::Cookbook>.

=item B<augment ($name, &sub)>

An C<augment> method, is a way of explicitly saying "I am augmenting this 
method from my superclass". Once again, the details of how C<inner> and 
C<augment> work is best described in the L<Moose::Cookbook>.

=item B<confess>

This is the C<Carp::confess> function, and exported here because I use it
all the time. This feature may change in the future, so you have been warned. 

=item B<blessed>

This is the C<Scalar::Util::blessed> function, it is exported here because I
use it all the time. It is highly recommended that this is used instead of 
C<ref> anywhere you need to test for an object's class name.

=back

=head1 UNIMPORTING FUNCTIONS

=head2 B<unimport>

Moose offers a way to remove the keywords it exports, through the C<unimport>
method. You simply have to say C<no Moose> at the bottom of your code for this
to work. Here is an example:

    package Person;
    use Moose;

    has 'first_name' => (is => 'rw', isa => 'Str');
    has 'last_name'  => (is => 'rw', isa => 'Str');
    
    sub full_name { 
        my $self = shift;
        $self->first_name . ' ' . $self->last_name 
    }
    
    no Moose; # keywords are removed from the Person package    

=head1 CAVEATS

=over 4

=item *

It should be noted that C<super> and C<inner> B<cannot> be used in the same
method. However, they may be combined within the same class hierarchy; see
F<t/014_override_augment_inner_super.t> for an example.

The reason for this is that C<super> is only valid within a method 
with the C<override> modifier, and C<inner> will never be valid within an 
C<override> method. In fact, C<augment> will skip over any C<override> methods 
when searching for its appropriate C<inner>.

This might seem like a restriction, but I am of the opinion that keeping these
two features separate (yet interoperable) actually makes them easy to use, since
their behavior is then easier to predict. Time will tell whether I am right or
not (UPDATE: so far so good).

=back

=head1 ACKNOWLEDGEMENTS

=over 4

=item I blame Sam Vilain for introducing me to the insanity that is meta-models.

=item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.

=item Without Yuval "nothingmuch" Kogman this module would not be possible, 
and it certainly wouldn't have this name ;P

=item The basis of the TypeContraints module was Rob Kinyon's idea 
originally, I just ran with it.

=item Thanks to mst & chansen and the whole #moose poose for all the 
early ideas/feature-requests/encouragement/bug-finding.

=item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.

=back

=head1 SEE ALSO

=over 4

=item L<http://www.iinteractive.com/moose>

This is the official web home of Moose, it contains links to our public SVN repo
as well as links to a number of talks and articles on Moose and Moose related 
technologies. 

=item L<Class::MOP> documentation

=item The #moose channel on irc.perl.org

=item The Moose mailing list - moose@perl.org

=item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/5788>

=back

=head2 Papers 

=over 4

=item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>

This paper (suggested by lbr on #moose) was what lead to the implementation 
of the C<super>/C<override> and C<inner>/C<augment> features. If you really 
want to understand them, I suggest you read this.

=back

=head1 BUGS

All complex software has bugs lurking in it, and this module is no 
exception. If you find a bug please either email me, or add the bug
to cpan-RT.

=head1 AUTHOR

Stevan Little E<lt>stevan@iinteractive.comE<gt>

B<with contributions from:>

Aankhen

Adam (Alias) Kennedy

Anders (Debolaz) Nor Berle

Nathan (kolibre) Gray

Christian (chansen) Hansen

Eric (ewilhelm) Wilhelm

Guillermo (groditi) Roditi

Jess (castaway) Robinson

Matt (mst) Trout

Robert (phaylon) Sedlacek

Robert (rlb3) Boone

Scott (konobi) McWhirter

Shlomi (rindolf) Fish

Yuval (nothingmuch) Kogman

Chris (perigrin) Prather

... and many other #moose folks

=head1 COPYRIGHT AND LICENSE

Copyright 2006, 2007 by Infinity Interactive, Inc.

L<http://www.iinteractive.com>

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself. 

=cut