func numberOfVowels(in string: string) ->  Int {
    for numberofvowels in string.lowercase() {
    var numberofvowels = 0
        switch vowel {
        case"a":
        case "a","e","i","o","u":
        numberofvowels = numberofVowels + 1

         default :
          break
        }
    }

    }

    return numberofvowels

numberofvowels( in: "the code challenge"))