Swift算法2-Reverse a String

Write a function that takes a string as input and returns the string reversed.

Example:
Given s = "hello", return "olleh".

ok this is the solution i got:

class Solution {
    func reverseString(s: String) -> String {
        var stringArray = [s]
        let reversedStr = stringArray.map() { String($0.characters.reverse()) }
        return reversedStr[0]
    }
}

and this is the version i made before, and it cannot be compiled at leetcode. whyyyyyyyyyyy??????
well i know this code is ugly but it is the first solution i got for the reversing.....

class Solution {
    func reverseString(s: String) -> String {
        var stringArray = [Character]()
        var newS = ""
        if (s == "") {return s}
        for c: Character in s.characters {
            stringArray += [c]
        }
        var l = stringArray.count - 1
        for (l; l >= 0; l--) {
        /*
        for i in 0..<l/2 {
          var j: Character
          j = stringArray[l-i]
          stringArray[l-i] = stringArray[i]
          stringArray[i] = j
        }
        */
        let e = stringArray.removeAtIndex(l)
        newS.append(e)
        }
        return newS
    }
}```