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It's difficult to get roles and attributes to play nice. Attributes basically have two parts to the implementation:

  1. They need to be initialized in the constructor; and

  2. You need to provide accessors for them.

The accessors are easy. But your role framework doesn't have any control over the constructor; the constructor gets built by the class framework!

That's why if you look at Perl implementations of roles, you'll see them fall into two neat categories:

  • Moose::Role, Mouse::Role, Moo::Role, and p5-mop roles all allow you to define attributes in roles.

    These role implementations are all part of larger frameworks that include a class builder.

  • Role::Tiny and Role::Tiny do not allow you to define attributes in roles.

    These role implementations are stand-alone.

So basically, if you want to write a role implementation that supports attributes, you'll need to write a class implementation to support it.

I'm not saying you shouldn't do it. It's a good learning experience.

use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name

In reply to Re^3: Object::InsideOut and Roles/Mixins by tobyink
in thread Object::InsideOut and Roles/Mixins by Yary

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