Swift: declaration 'description' cannot override more than one superclass declaration

Question

I have a structure of inheritance similar to the one below. I\'m adopting the Printable protocol and diligently override description property. I have encountered a bizarre error

Answer 1

I had the same problem with SKTiled when overriding SKTiledScene. In my situation I wanted to override a mouse event for OS X.

The error was as follows:

Declaration 'mouseUp(with:)' cannot override more than one superclass declaration

The problem here is that the mouse events are declared in a class extension:

#if os(macOS)
extension SKTiledScene {

    override open func mouseDown(with event: NSEvent) {}

    override open func mouseMoved(with event: NSEvent) {
        guard let cameraNode = cameraNode else { return }
        cameraNode.mouseMoved(with: event)
    }
    override open func mouseUp(with event: NSEvent) {}
    override open func mouseEntered(with event: NSEvent) {}
    override open func mouseExited(with event: NSEvent) {}

    override open func scrollWheel(with event: NSEvent) {
        guard let cameraNode = cameraNode else { return }
        cameraNode.scrollWheel(with: event)
    }
}
#endif

I could solve my issue to override the method in my own SKTiledScene subclass by re-implementing the extension:

extension SKTiledScene {
    open override func mouseUp(with event: NSEvent) {
        try! SceneManager.shared.transitionToScene(MainMenuScene.self, withAnimation: .fade)
    }
}

I do wonder if I can be sure my extension is always loaded instead of the one from the SKTiled framework, but it seems to work well for now.

Answer 2

What is the Printable Protocol? ;-)

You could use a Getter of a property as

var description: String {
    get {
        return "This is a test";
    }
}

Answer 3

I don't have access to my Mac now, but I would try removing the override in First. override is needed when subclassing but not when implementing a protocol.

Answer 4

Same problem for me, solved by doing:

func customDescription() -> String {
    return ""
}

override var description: String {
    return customDescription()
}

so you can override function as many times as you want to