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Comment by Joeri | Hacker News Reader

Maybe it's just me, but I've never seen a use for traits. Any time I need to reuse logic across classes, I'll make it a proper class and compose it in as a member.

What sort of functionality do you use traits for?

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That's a delegation strategy, which is a very limited form of composition.

A class with a trait/role can be queried for that interface:

  smile() if $my_object->does('SomeTrait');

Methods provided by a trait/role have direct access to $self.

Also, Moose gives you the ability to apply traits to classes that are not predefined with those traits:

  use Moose::Util;
  my $instance = Moose::Util::with_traits('MooseClass', 'MyTrait')->new(%params);

You can parameterize roles (as in, pass parameters that affect what the role provides). If you put some method modifiers into your roles, you can enhance existing functionality; for example, you can add logging, memoization, and persistence, all without the class having those features beforehand.

In other words, roles/traits make your OOP functionality much more composable.

> I'll make it a proper class and compose it in as a member.

You've just implemented traits.

In PHP traits override methods which is something other than being a member object (though you can use traits to do that as well). http://php.net/manual/en/language.oop5.traits.php

I used traits to extract common functionality from POPOs.

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