func digitSum(var n : Int) -> Int {
    var sum = 0
    while n > 0 {
        sum += n % 10 // Add least significant digit ...
        n /= 10   // ... and remove it from the number.
    }
    return sum
}

println(digitSum(845)) // 17

func digitSum(_ n : Int) -> Int {
    var n = n
    var sum = 0
    while n > 0 {
        sum += n % 10 // Add least significant digit ...
        n /= 10   // ... and remove it from the number.
    }
    return sum
}

print(digitSum(845)) // 17

let myString = "845"
let sum = myString.characters.flatMap{Int(String($0))}.reduce(0, +)
print(sum) // 17

let myInteger = 845
let sumInt = String(myInteger).characters.flatMap{Int(String($0))}.reduce(0, +)
print(sumInt) // 17

func sumDigits(var i : Int) -> Int {
    var sum = 0
    var nDigits = floor(log10(Double(i))) + 1
    for var r = nDigits; r > 0; r-- {
        var p = pow(10, r - 1)
        var d = floor(Double(i) / p)
        sum += Int(d)
        i -= Int(d * p)
    }
    return sum
}

func digitSum(of number: Int) -> Int
{
if(number < 10)
    {
    return number
    }
    else
        {
        return number % 10 + digitSum(of: (number/10))
        }
}