I'm not sure Ruby is ideal for exploring OO concepts, as fine a language as it is. Missing, for example, are: inheritance of class attributes/methods, constrain

I'm not sure Ruby is ideal for exploring OO concepts, as fine a language as it is. Missing, for example, are: inheritance of class attributes/methods, constraints on overriding methods (e.g. declaring as abstract or un-overridable/final), dynamic attributes. Thankfully it's a very flexible and forgiving language, so there are third-party libraries (e.g. Hashie, ActiveSupport's Concern) to accomplish these kinds of things, but the core language doesn't offer them.