Selection sort in Swift

Question

I'm creating a simple selection sort in Swift. In my sort method I'm getting an error when calling method for exchanging values within the array.

    class func sort(a:[String]) {
       var N = a.count
       for(var i = 0; i < N; i++) {
         var min = i
         for(var j = i+1; j < N; j++) {
             if(less(a[i], str2:a[j])) {
                min = j
             }
         }
         exch(&a, i, min) // Error: [String] not convertible to @value inout $T3
       }
    }

Exch method:

    class func exch(inout a:[String], i:Int, j:Int) {
       let temp = a[i]
       a[i] = a[j]
       a[j] = temp
    }

Thanks for the help! :)

Answer 1

arguments are immutable by default, whereas inout parameters are mutable, so the problem is that you can't convert immutable a to mutable inout parameter. you need to declare it with var to make it mutable

class func sort(var a:[String]) { // declare a with var. by default it is using let
   var N = a.count
   for(var i = 0; i < N; i++) {
     var min = i
     for(var j = i+1; j < N; j++) {
         if(less(a[i], str2:a[j])) {
            min = j
         }
     }
     exch(&a, i, min) // Error: [String] not convertible to @value inout $T3
   }