Excerpts from Ovid's message of Mon Oct 12 11:53:23 -0400 2009:
> So instead of this:
>
> package Thing;
> use Moose;
> with (
> DoesRobot => { excludes => 'draw', aliases => { draw => 'draw_with_arm' }
> },
> 'DoesDrawable'
> );
>
> You recommend this:
>
> package Thing;
> use Moose;
> has robot_arm => (
> is => 'ro',
> isa => 'RobotArm',
> default => sub { RobotArm->new({ to_draw => shift }) },
> handles => { draw_with_arm => 'draw' },
> );
>
> This is interesting in a couple of ways. Aside from the fact that we have
> more scaffolding code we have to write, we no longer get our
> composition-time safety from 'requires' which roles provide. With
> delegation, if $self doesn't provide the methods you need, you get your
> failures at runtime instead of composition time. This is a problem when
> delegation requires bi-directional in the sending and receiving
> objects.
The fact that a hammer's no good for washing clothes doesn't mean you can't
still bash nails with it.
package HasRobot;
use Moose::Role;
requires @some_methods;
has robot_arm => (
is => 'ro',
isa => 'RobotArm',
lazy => 1,
default => sub { RobotArm->new({ to_draw => shift }) },
handles => { draw_with_arm => 'draw' },
);
(If you don't like hardcoding draw_with_arm, use MooseX::Role::Parameterized to
refactor it.)
Alternately, make a RobotArm::Drawable role that just requires @some_methods.
hdp.
