傳遞和返回功能

以下函式返回另一個函式作為其結果，稍後可以將其分配給變數並呼叫：

func jediTrainer () -> ((String, Int) -> String) {
  func train(name: String, times: Int) -> (String) {
    return "\(name) has been trained in the Force \(times) times"
  }
  return train
}

let train = jediTrainer()
train("Obi Wan", 3)