No override function in ValueTransformer?

Question

Since my last question I went on trying to make a ValueTransformer transform the values of a NSSlider into Integer.

Background: I have an NSSlider which is bound to Shared User Defaults Controller. A textlabel is also bound to the Shared User Defaults Controller with the same key. I need the textfield to only show Int.

Now my code looks like this:

class IntegerTransformmer: ValueTransformer {

    override class func transformedValueClass() -> AnyClass {
        return NSNumber.self
    }

    override class func allowsReverseTransformation() -> Bool {
        return true
    }

    // as far as I know, here is an override function required. But doing override in the following line, i´m getting error.
      func transformedValue(value: Any?) -> Int? {
        let int = value as! Int
        return int
    }
}

For both, NSSlider and the label I set in bindingsInspector the the Value Transformer on IntegerTransformmer.

In AppDelegate I initialize the ValueTransformer like this:

 override class func initialize() {
        let newTransformer = IntegerTransformmer()
        ValueTransformer.setValueTransformer(newTransformer, forName: NSValueTransformerName(rawValue: "IntegerTransformmer"))

    }

The building works without error, but in my label, I´m still getting DoubleValues. Why I´m not allowed to make transformedValue(value: Any?)as override? Is this the reason why it´s not working? Help of any kind would be much appreciated.