Moose::Meta::Attribute::Native

Section: User Contributed Perl Documentation (3)
Updated: 2018-05-16
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NAME

Moose::Meta::Attribute::Native - Delegate to native Perl types

VERSION

version 2.2011

SYNOPSIS

  package MyClass;
  use Moose;

  has 'mapping' => (
      traits  => ['Hash'],
      is      => 'rw',
      isa     => 'HashRef[Str]',
      default => sub { {} },
      handles => {
          exists_in_mapping => 'exists',
          ids_in_mapping    => 'keys',
          get_mapping       => 'get',
          set_mapping       => 'set',
          set_quantity      => [ set => 'quantity' ],
      },
  );

  my $obj = MyClass->new;
  $obj->set_quantity(10);      # quantity => 10
  $obj->set_mapping('foo', 4); # foo => 4
  $obj->set_mapping('bar', 5); # bar => 5
  $obj->set_mapping('baz', 6); # baz => 6

  # prints 5
  print $obj->get_mapping('bar') if $obj->exists_in_mapping('bar');

  # prints 'quantity, foo, bar, baz'
  print join ', ', $obj->ids_in_mapping;

DESCRIPTION

Native delegations allow you to delegate to native Perl data structures as if they were objects. For example, in the ``SYNOPSIS'' you can see a hash reference being treated as if it has methods named "exists()", "keys()", "get()", and "set()".

The delegation methods (mostly) map to Perl builtins and operators. The return values of these delegations should be the same as the corresponding Perl operation. Any deviations will be explicitly documented.

API

Native delegations are enabled by passing certain options to "has" when creating an attribute.

traits

To enable this feature, pass the appropriate name in the "traits" array reference for the attribute. For example, to enable this feature for hash reference, we include 'Hash' in the list of traits.

isa

You will need to make sure that the attribute has an appropriate type. For example, to use this with a Hash you must specify that your attribute is some sort of "HashRef".

handles

This is just like any other delegation, but only a hash reference is allowed when defining native delegations. The keys are the methods to be created in the class which contains the attribute. The values are the methods provided by the associated trait. Currying works the same way as it does with any other delegation.

See the docs for each native trait for details on what methods are available.

TRAITS FOR NATIVE DELEGATIONS

Below are some simple examples of each native trait. More features are available than what is shown here; this is just a quick synopsis.

Array (Moose::Meta::Attribute::Native::Trait::Array)

    has 'queue' => (
        traits  => ['Array'],
        is      => 'ro',
        isa     => 'ArrayRef[Str]',
        default => sub { [] },
        handles => {
            add_item  => 'push',
            next_item => 'shift',
            # ...
        }
    );

Bool (Moose::Meta::Attribute::Native::Trait::Bool)

    has 'is_lit' => (
        traits  => ['Bool'],
        is      => 'ro',
        isa     => 'Bool',
        default => 0,
        handles => {
            illuminate  => 'set',
            darken      => 'unset',
            flip_switch => 'toggle',
            is_dark     => 'not',
            # ...
        }
    );

Code (Moose::Meta::Attribute::Native::Trait::Code)

    has 'callback' => (
        traits  => ['Code'],
        is      => 'ro',
        isa     => 'CodeRef',
        default => sub {
            sub {'called'}
        },
        handles => {
            call => 'execute',
            # ...
        }
    );

Counter (Moose::Meta::Attribute::Native::Trait::Counter)

    has 'counter' => (
        traits  => ['Counter'],
        is      => 'ro',
        isa     => 'Num',
        default => 0,
        handles => {
            inc_counter   => 'inc',
            dec_counter   => 'dec',
            reset_counter => 'reset',
            # ...
        }
    );

Hash (Moose::Meta::Attribute::Native::Trait::Hash)

    has 'options' => (
        traits  => ['Hash'],
        is      => 'ro',
        isa     => 'HashRef[Str]',
        default => sub { {} },
        handles => {
            set_option => 'set',
            get_option => 'get',
            has_option => 'exists',
            # ...
        }
    );

Number (Moose::Meta::Attribute::Native::Trait::Number)

    has 'integer' => (
        traits  => ['Number'],
        is      => 'ro',
        isa     => 'Int',
        default => 5,
        handles => {
            set => 'set',
            add => 'add',
            sub => 'sub',
            mul => 'mul',
            div => 'div',
            mod => 'mod',
            abs => 'abs',
            # ...
        }
    );

String (Moose::Meta::Attribute::Native::Trait::String)

    has 'text' => (
        traits  => ['String'],
        is      => 'ro',
        isa     => 'Str',
        default => q{},
        handles => {
            add_text     => 'append',
            replace_text => 'replace',
            # ...
        }
    );

COMPATIBILITY WITH MooseX::AttributeHelpers

This feature used to be a separated CPAN distribution called MooseX::AttributeHelpers.

When the feature was incorporated into the Moose core, some of the API details were changed. The underlying capabilities are the same, but some details of the API were changed.

BUGS

See ``BUGS'' in Moose for details on reporting bugs.

AUTHORS

•: Stevan Little <stevan.little@iinteractive.com>
•: Dave Rolsky <autarch@urth.org>
•: Jesse Luehrs <doy@tozt.net>
•: Shawn M Moore <code@sartak.org>
•: יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>
•: Karen Etheridge <ether@cpan.org>
•: Florian Ragwitz <rafl@debian.org>
•: Hans Dieter Pearcey <hdp@weftsoar.net>
•: Chris Prather <chris@prather.org>
•: Matt S Trout <mst@shadowcat.co.uk>

COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.