警报中的 Swift 4 UITextField 最大长度

Question

如何在 Alert 中设置 UITextField 的最大长度？

Swift 4 中这方面的最新最佳实践是什么？

这是我的代码示例，但它会崩溃，因为 UITextField 一开始不存在。

class ViewController: UIViewController, UITextFieldDelegate {
@IBOutlet weak var textField: UITextField!
let limitLength = 10
@IBOutlet weak var player1: UIButton!


func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    guard let text = textField.text else { return true }
    let newLength = text.characters.count + string.characters.count - range.length
    return newLength <= limitLength
}

@IBAction func player1Action(_ sender: UIButton) {
    let alertController = UIAlertController(title: "Please enter you name", message: "Maximum 10 characters", preferredStyle: .alert)
    alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: {
        alert -> Void in
        let textField = alertController.textFields![0] as UITextField
        // do something with textField
        self.player1.setTitle("\(textField.text!)", for: .normal)
    }))
    alertController.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))

    alertController.addTextField(configurationHandler: {(textField : UITextField!) -> Void in
        textField.placeholder = "Name"
    })
    self.present(alertController, animated: true, completion: nil)

}


override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    textField.delegate = self

}

非常感谢您的宝贵时间。

Answer 1

您实际上不需要创建 UITextField 的实例。 addTextField 闭包将为您返回 UITextField。您需要做的就是在闭包中设置该文本字段的委托(delegate)。

class ViewController: UIViewController, UITextFieldDelegate {
    let limitLength = 10
    @IBOutlet weak var player1: UIButton!

    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        guard let text = textField.text else { return true }
        let newLength = text.characters.count + string.characters.count - range.length
        return newLength <= limitLength
    }

    @IBAction func player1Action(_ sender: UIButton) {
        let alertController = UIAlertController(title: "Please enter you name", message: "Maximum 10 characters", preferredStyle: .alert)
        alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: {
            alert -> Void in
            let textField = alertController.textFields![0] as UITextField
            self.player1.setTitle("\(textField.text!)", for: .normal)
        }))
        alertController.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))

        alertController.addTextField(configurationHandler: {(textField : UITextField!) -> Void in
            textField.placeholder = "Name"
            textField.delegate = self // Set the delegate
        })

        present(alertController, animated: true, completion: nil)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
    }
}