Extension of constructed generic type in Swift

Question

Is it possible to extend an generic class for a specialised/constructed generic type? I would like to extend Int Arrays with a method to calculate the sum of its elements.

Answer 1

you can do it as well

extension Array {
    func sum () -> Int? {
        guard self.count > 0  && self.first is Int  else {
            return nil
        }
        var s = 0
        forEach {
            s += $0 as! Int
        }
        return s
    }
}