Swift — Require classes implementing protocol to be subclasses of a certain class

Question

I\'m creating several NSView classes, all of which support a special operation, which we\'ll call transmogrify. At first glance, this seems like t

Answer 1

As per definition a protocol just declares requirements of "methods, properties an other requirements". And by "other requirements" it means a superclass is not a part of it.

A protocol defines a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality.

Right now, I don't see a clean solution. It's possible to use a where-clause to define a type which is a NSView and conforms to the TransmogrifiableView like this:

class MyClass {
    var aTransmogrifiableNSView: T
}

Or you could use another superclass:

protocol TransmogrifiableViewProtocol {
    func transmogrify()
}

class TransmogrifiableView: NSView, TransmogrifiableViewProtocol {
    func transmogrify() {
        assert(false, "transmogrify() must be overwritten!")
    }
}

class AnImplementedTransmogrifiableView: TransmogrifiableView {
    func transmogrify() {
        println("Do the transmogrification...")
    }
}

In the end both solutions aren't clean and wouldn't satisfy myself. Maybe an abstract-keyword will be added to Swift someday?