Code Snippet: Print All Integers in a String

Within these castle walls be forged Mavens of Computer Science ...

— Merlin, The Coder

var line : String? repeat {

   line = readLine()
   if let text = line {
       for character in text {
           if ("0" ... "9").contains(character) {
               print(character)
           }
       }
   }

} while line != nil