Swift make method parameter mutable?

Question

How can I deal with this error without creating additional variable?

func reduceToZero(x:Int) -> Int {
    while (x != 0) {
        x = x-1            //         


        

Answer 1

For Swift 1 and 2 (for Swift 3 see answer by achi using an inout parameter): Argument of a function in Swift is let by default so change it to var if you need to alter the value i.e,

func reduceToZero(var x:Int) -> Int {
    while (x != 0) {
        x = x-1     
    }
    return x
}