 public class Generator {
 
   public struct Constants {
-    public static let uppercaseLetters = Array(arrayLiteral: "ABCDEFGHIJKLMNOPQRSTUVWXYZ")
-    public static let letters = Array(arrayLiteral: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
-    public static let numbers = Array(arrayLiteral: "0123456789")
+    public static let uppercaseLetters = Array("ABCDEFGHIJKLMNOPQRSTUVWXYZ".characters)
+    public static let letters = Array("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".characters)
+    public static let numbers = Array("0123456789".characters)
   }
 
   let parser: Parser

    return String(string.characters.enumerate().map {
      (index, item) in
      let count = UInt32(Constants.uppercaseLetters.count)
      let char = Constants.uppercaseLetters[Int(arc4random_uniform(count))].characters.first!
      return String(item) == "?" ? char : item
      })
  }

      (index, item) in
      let numberIndex = index == 0 ? arc4random_uniform(count - 1) :
        arc4random_uniform(count)
      let char = Constants.numbers[Int(numberIndex)]
      return String(item) == "#" ? char : item
      })
  }
