import UIKit

func countVowels(in string: String) -> Int {
    var numberOfVowels = 0
    for vowel in string.lowercased() {
        switch vowel {
        case "a", "e", "i", "o", "u":
            numberOfVowels += 1
            //print(numberOfVowels)
        default:
            break
        }
    }
    //print(numberOfVowels)
    return numberOfVowels
}

countVowels(in: "The lazy sheep jumped over the moon.")