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

It is possible to return a real sum-value after you have tested for the int-type in sum(). Doing so I would solve the problem as follows:

import Cocoa

extension Array {
    func sum() -> Int {
        if !(self[0] is Int) { return 0; }
        var sum = 0;
        for value in self { sum += value as Int }
        return sum;
    }
}

let array = [1,2,3,4,5]
array.sum() // =15

let otherArray = ["StringValue"]
otherArray.sum() // =0