反轉字串

Version = 2.2

let aString = "This is a test string."

// first, reverse the String's characters 
let reversedCharacters = aString.characters.reverse()

// then convert back to a String with the String() initializer
let reversedString = String(reversedCharacters)

print(reversedString) // ".gnirts tset a si sihT"

Version = 3.0

let reversedCharacters = aString.characters.reversed()
let reversedString = String(reversedCharacters)