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

In Swift you just add the var keyword before the variable name in the function declaration:

func reduceToZero(var x:Int) -> Int { // notice the "var" keyword
    while (x != 0) {
        x = x-1            
    }
    return x
}

Refer to the subsection "Constant and Variable Parameters" in the "Functions" chapter of the Swift book (page 210 of the iBook as it is today).