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我试图UITextFieldDelegate在单独的类中实现，但它不起作用：

class ViewController: UIViewController {

    @IBOutlet var TextField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()
        let restrictor = TextFieldRestrictController()
        TextField.delegate = restrictor
    }
}

class TextFieldRestrictController : NSObject, UITextFieldDelegate {

    public func textField(_ textField: UITextField,
                          shouldChangeCharactersIn range: NSRange,
                          replacementString string: String) -> Bool {
        let inverseSet = NSCharacterSet(
            charactersIn:"0123456789.").inverted

        let components = string.components(separatedBy: inverseSet)

        let filtered = components.joined(separator:"")
        return string == filtered
    }
}

但这正在起作用：

class ViewController: UIViewController {

    @IBOutlet var TextField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()
        TextField.delegate …