How to return an undefined value for NSPoint

Question

I am learning swift and I am trying to make a simple app where I move an object (The default ship) with the keyboard. I am designing an event to represent the left keypress. Since I do not need the mouse to be at a specific place, NSLocation is of no real use to me. The official documentation tells me to return the variable locationInWindow, which is my NSPoint for NSLocation, as undefined.

I am not sure to grasp what they mean by this. I tried to use the _undefined keyword, but then this comes up :

Cannot convert value of type '(@autoclosure () -> String, StaticString, UInt) -> _' to specified type 'NSPoint' (aka 'CGPoint')

Here is my code

        var locationInWindow : NSPoint{
        return _undefined
    }

    let movingLeftEvent = NSEvent.keyEvent(with:NSEvent.EventType.keyDown, location: nil, modifierFlags:[], timestamp: [], windowNumber: 0, context: nil , characters: <#String#>, charactersIgnoringModifiers: <#String#>, isARepeat: false, keyCode: <#UInt16#>)

Answer 1

You just need to addLocalMonitorForEvents to your view controller

NSEvent.addLocalMonitorForEvents(matching: .keyDown) {
    self.keyDown(with: $0)
    return $0
}

and implement your custom keyDown method:

override func keyDown(with event: NSEvent) {
    switch event.keyCode {
    case  123:
        // run left arrow code action
        ship.runAction(
            SCNAction.repeatForever(
                SCNAction.rotateBy(x: 0, y: -2, z: 0, duration: 1)
            )
        )
    case  124:
        // run right arrow code action
        ship.runAction(
            SCNAction.repeatForever(
                SCNAction.rotateBy(x: 0, y: 2, z: 0, duration: 1)
            )
        )
    default:
        print("event.keyCode:", event.keyCode)
    }
}

Sample