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[gitmo/Moose.git] / lib / Moose / Meta / Role / Attribute.pm

package Moose::Meta::Role::Attribute;

use strict;
use warnings;

use Carp 'confess';
use List::MoreUtils 'all';
use Scalar::Util 'blessed', 'weaken';

use base 'Moose::Meta::Mixin::AttributeCore', 'Class::MOP::Object';

__PACKAGE__->meta->add_attribute(
    'metaclass' => (
        reader => 'metaclass',
    )
);

__PACKAGE__->meta->add_attribute(
    'associated_role' => (
        reader => 'associated_role',
    )
);

__PACKAGE__->meta->add_attribute(
    'is' => (
        reader => 'is',
    )
);

__PACKAGE__->meta->add_attribute(
    'original_options' => (
        reader => 'original_options',
    )
);

sub new {
    my ( $class, $name, %options ) = @_;

    (defined $name)
        || confess "You must provide a name for the attribute";

    return bless {
        name             => $name,
        original_options => \%options,
        %options,
    }, $class;
}

sub attach_to_role {
    my ( $self, $role ) = @_;

    ( blessed($role) && $role->isa('Moose::Meta::Role') )
        || confess
        "You must pass a Moose::Meta::Role instance (or a subclass)";

    weaken( $self->{'associated_role'} = $role );
}

sub attribute_for_class {
    my $self      = shift;
    my $metaclass = shift;

    return $metaclass->interpolate_class_and_new(
        $self->name => %{ $self->original_options } );
}

sub clone {
    my $self = shift;

    return ( ref $self )->new( $self->name, %{ $self->original_options } );
}

sub is_same_as {
    my $self = shift;
    my $attr = shift;

    my $self_options = $self->original_options;
    my $other_options = $attr->original_options;

    return 0
        unless ( join q{|}, sort keys %{$self_options} ) eq ( join q{|}, sort keys %{$other_options} );

    for my $key ( keys %{$self_options} ) {
        return 0 if defined $self_options->{$key} && ! defined $other_options->{$key};
        return 0 if ! defined $self_options->{$key} && defined $other_options->{$key};

        next if all { ! defined } $self_options->{$key}, $other_options->{$key};

        return 0 unless $self_options->{$key} eq $other_options->{$key};
    }

    return 1;
}

1;

=pod

=head1 DESCRIPTION

This class implements the API for attributes in roles. Attributes in roles are
more like attribute prototypes than full blown attributes. While they are
introspectable, they have very little behavior.

=head1 METHODS

This class provides the following methods:

=over 4

=item B<< Moose::Meta::Role::Attribute->new(...) >>

This method accepts all the options that would be passed to the constructor
for L<Moose::Meta::Attribute>.

=item B<< $attr->metaclass >>

=item B<< $attr->is >>

Returns the option as passed to the constructor.

=item B<< $attr->associated_role >>

Returns the L<Moose::Meta::Role> to which this attribute belongs, if any.

=item B<< $attr->original_options >>

Returns a hash reference of options passed to the constructor. This is used
when creating a L<Moose::Meta::Attribute> object from this object.

=item B<< $attr->attach_to_role($role) >>

Attaches the attribute to the given L<Moose::Meta::Role>.

=item B<< $attr->attribute_for_class($metaclass) >>

Given an attribute metaclass name, this method calls C<<
$metaclass->interpolate_class_and_new >> to construct an attribute object
which can be added to a L<Moose::Meta::Class>.

=item B<< $attr->clone >>

Creates a new object identical to the object on which the method is called.

=item B<< $attr->is_same_as($other_attr) >>

Compares two role attributes and returns true if they are identical.

=back

In addition, this class implements all informational predicates implements by
L<Moose::Meta::Attribute> (and L<Class::MOP::Attribute>).

=head1 BUGS

See L<Moose/BUGS> for details on reporting bugs.

=cut