在Swift 4.2中反转字符串

str 设置newStr之前的变量:

guard let unwrappedStr = str else { return }
let newStr = String(unwrappedStr.reversed())

str .

if let str = self.label?.text {
    let newStr = String(str.reversed())
}

extension Optional where Wrapped == String {
    func reversed() -> String? {
        guard let str = self else { return nil }
        return String(str.reversed())
    }
}

用法:

str?.reversed()

str 是可选的。我们将再添加几个(guard&map free;-)。。。

对于那些在C中梦想的人:

let newStr = str == nil ? nil : String(str!.reversed())

nil 和/或想要一个 String

let newStr = String((str ?? "").reversed())

这大概是你能做的最短的了。

反转文本值 可以通过反转将textfield值传递给另一个textfield

  class ViewController: UIViewController {

  var str = NSString()


@IBOutlet weak var txt1: UITextField!

override func viewDidLoad() {
    super.viewDidLoad()

}

@IBAction func button1(_ sender: Any) {


    let story: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
    let new = story.instantiateViewController(withIdentifier: "RevViewController")as! RevViewController


    let str = txt1.text!
    new.txtvalue = String(str.reversed())


    self.navigationController?.pushViewController(new, animated: true)


    }

   }

第二视图控制器

   class RevViewController: UIViewController {

 var txtvalue = String()

@IBOutlet weak var textfld2: UITextField!



override func viewDidLoad() {
    super.viewDidLoad()

    textfld2.text = txtvalue

}


}