CODEWITHSUNDEEP
swiftoverriding
Karl Kivi
Karl Kivi

Reputation: 145

Method-overriding from its superclass

I am getting this Swift error:

Method does not override any method from its superclass!

Why is this appearing? The relevant code is below:

class TouchyView: UIView {

override func touchesBegan(touches: NSSet?, withEvent event: UIEvent) {
    updateTouches(event.allTouches())
}
override func touchesMoved(touches: NSSet?, withEvent event: UIEvent) {
    updateTouches(event.allTouches())
}
override func touchesEnded(touches: NSSet?, withEvent event: UIEvent) {
    updateTouches(event.allTouches())
}
override func touchesCancelled(touches: NSSet!!, withEvent event: UIEvent) {
    updateTouches(event.allTouches())
}

var touchPoints = [CGPoint]()

func updateTouches( touches: NSSet? ) {
    touchPoints = []
    touches?.enumerateObjectsUsingBlock() { (element,stop) in
        if let touch = element as? UITouch {
            switch touch.phase {
                case .Began, .Moved, .Stationary:
                    self.touchPoints.append(touch.locationInView(self))
                default:
                    break
            }
        }
     }
    setNeedsDisplay()
}

Upvotes: 2

Views: 427

Answers (1)

Glenn
Glenn

Reputation: 2806

Inheritance : If you have a class with a method

class myClass {

func abc () {
   // do something
}

and you make another class which inherits from the first :

class myOtherClass :myClass {

// do whatever stuff in this class

}

that second class will also have that abc method from the first class. If you want however to change the functionality of abc in that second class you have to use the

override

keyword.

class myOtherClass :myClass {

override func abc () {
    // do something else
}


// do whatever stuff in this class

}

It's great that swift makes you add that override keyword, you won't accidentally override methods from the first class (which often happens if the name is quite generic).

You can not however use override (and it's of no use) if the method doesn't exists in the first class. And this is your case.

Hope this helps and if this is not clear I advise you to read a book on Object Oriented Programming

Upvotes: 1

Related Questions