NAME

MooseX::FunkyAttributes::Role::Attribute - custom get/set/clear/has coderefs

SYNOPSIS

package Circle;

use Moose;
use MooseX::FunkyAttributes;

has radius => (
   is          => 'rw',
   isa         => 'Num',
   predicate   => 'has_radius',
);

has diameter => (
   traits      => [ FunkyAttribute ],
   is          => 'rw',
   isa         => 'Num',
   custom_get  => sub { 2 * $_->radius },
   custom_set  => sub { $_->radius( $_[-1] / 2 ) },
   custom_has  => sub { $_->has_radius },
);

DESCRIPTION

This is the base trait which the other MooseX::FunkyAttribute traits inherit from. It allows you to provide coderefs to handle the business of storing and retrieving attribute values.

So instead of storing your attribute values in the object's blessed hashref, you could calculate them on the fly, or store them in a file or database, or an external hashref, or whatever.

Options

If your attribute uses this trait, then you must provide at least the following three coderefs:

custom_set => CODE ($meta, $instance, $value)

The code which implements setting an attribute value. Note that this code does not need to implement type constraint checks, etc. $meta is a Moose::Meta::Attribute object describing the attribute; $instance is the object itself.

$_ is available as an alias for the instance.

custom_get => CODE ($meta, $instance)

The code which implements getting an attribute value.

It should return the value.

custom_has => CODE ($meta, $instance)

The code which implements the predicate functionality for an attribute. That is, it should return true if the attribute has been set, and false if the attribute is unset. (Note that Moose does allow attribute values to be set to undefined, so settedness is not the same as definedness.)

The following three additional coderefs are optional:

custom_clear => CODE ($meta, $instance)

The code which clears an attribute value, making it unset.

If you do not provide this, then your attribute cannot be cleared once set.

custom_init => CODE ($meta, $instance, $value)

Like custom_set but used during object construction.

If you do not provide this, then the custom_set coderef will be used in its place.

custom_weaken => CODE ($meta, $instance)

The code which weakens an attribute value that is a reference.

If you do not provide this, then your attribute cannot be a weak ref.

Moose attempts to create inlined attribute accessors whenever possible. The following coderefs can be defined which must return strings of Perl code suitable for inlining the accessors. They are each optional, but unless all of them are defined, your attribute will not be inlined.

custom_inline_set => CODE ($meta, $instance_string, $value_string)

$instance_string is a string representing the name of the instance variable, such as "\$self". $value_string is a string which evaluates to the value.