Ah. I see the confusion. I don't know if I'm going about this in the right way. I want to represent a machine. Machines may be different hardware types. It gets a role for the hardware type that supplies methods that might be able to powercycle it. I am applying the hardware-specific role using apply_all_roles to the instance rather than consuming a role in the class. (Since it gets a different role based on which type it is, and each one of these roles supplies the same named method.) I just wanted to double-check when I apply the role to the object that it is the correct type.
But I really wouldn't apply the object to the wrong type, since the base class has a method to figure all that out and apply the right one. So this probably isn't necessary, it would just be a nice cross-check. Mark On Thu, 12 Jan 2012, Edward Allen wrote: > Ok. This doesn't really make sense. Here is the problem: A role is > applied to a class, not an object (technically you can apply it to an > object with Moose::Util::apply_all_roles, but this seems like a Bad > Idea). A class doesn't have attributes (well there's a module for > that, but let's ignore that for the time being). A class has methods. > So you can test if a method exists, but not if that method returns a > particular value. > > -Edward > > On Thu, Jan 12, 2012 at 2:57 PM, Mark Hedges <hed...@formdata.biz> wrote: > > > > Hi. I'm trying to figure out how a role, when applied to an > > object, can verify that the object already has a particular > > attribute and that its conents equal some string. Am I > > missing something in the cookbook? It is sort of backwards > > from the usual way that an object requires the role can do > > something or has an attribute. > > > > I want to cross check when the role gets applied that the > > role has everything in the object that the methods it > > supplies needs to work. > > > > I suppose I can just verify this when methods run and then > > throw an error to say the role got applied to the wrong > > object, but I'd rather throw that from the place that I > > apply the role. > > > > Mark > > >
