为什么无法识别的选择器发送到实例？

Question

我正在尝试制作一个方便的绑定键盘到 uiview 函数。我无法解决这个错误

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Twitter.LoginVC handleKeyboard:]: unrecognized selector sent to instance 0x7ffbf142e970'

class KeyboardService {

var constraint: NSLayoutConstraint!
var vc: UIViewController!

func bind(bottomConstraint: NSLayoutConstraint, vc: UIViewController) {
    constraint = bottomConstraint
    self.vc = vc
    NotificationService.instance.addKeyboardObservers(onVC: vc, handleKeyboardSelector: #selector(self.handleKeyboard(_:))) // **CRASHES HERE**
}

@objc func handleKeyboard(_ notification: NSNotification) {
    NotificationService.instance.handleKeyboard(notification: notification, bottomConstraint: constraint, vc: vc)
} 
}

这是我的通知服务：

class NotificationService {
static let instance  = NotificationService()

func addKeyboardObservers(onVC vc: UIViewController, handleKeyboardSelector: Selector) {
    NotificationCenter.default.addObserver(vc, selector: handleKeyboardSelector, name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.addObserver(vc, selector: handleKeyboardSelector, name: UIResponder.keyboardWillHideNotification, object: nil)
}
}

编辑：

class KeyboardService {

var constraint: NSLayoutConstraint!
var vc: UIViewController!

func bind(bottomConstraint: NSLayoutConstraint, vc: UIViewController) {
    constraint = bottomConstraint
    self.vc = vc
    NotificationService.instance.addKeyboardObservers(self, handleKeyboardSelector: #selector(self.handleKeyboard(_:)))
}

@objc func handleKeyboard(_ notification: NSNotification) {
    NotificationService.instance.handleKeyboard(notification: notification, bottomConstraint: constraint, vc: vc)
}

}

编辑 2：

class KeyboardService {

var constraint: NSLayoutConstraint!
var vc: UIViewController!

func bind(bottomConstraint: NSLayoutConstraint, vc: UIViewController) {
    constraint = bottomConstraint
    self.vc = vc
    NotificationService.instance.addKeyboardObservers(self, handleKeyboardSelector: #selector(handleKeyboard(_:)))
}

@objc func handleKeyboard(_ notification: NSNotification) {
    NotificationService.instance.handleKeyboard(notification: notification, bottomConstraint: constraint, vc: vc)
}
}

在 vc 的 viewDidLoad() 中：

KeyboardService().bind(bottomConstraint: loginBtnBackViewBottomConstraint, vc: self)

Answer 1

您正在尝试将选择器发送至 vc；但它是一个 UIViewController 实际上并没有名为 handleKeyboard(_:) 的方法。您应该将您的注册方式更改为：

func addKeyboardObservers(_ observer: Any, handleKeyboardSelector: Selector) {
    NotificationCenter.default.addObserver(observer, selector: handleKeyboardSelector, name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.addObserver(observer, selector: handleKeyboardSelector, name: UIResponder.keyboardWillHideNotification, object: nil)
}

然后当你使用它时，你会做：

NotificationService.instance.addKeyboardObservers(self, handleKeyboardSelector: #selector(self.handleKeyboard(_:)))

如您所见，您现在要触发 self 上的选择器，因为它实际上是 self 具有该方法。作为一般规则：选择器被发送到一个实例，因此该实例必须具有所选方法。

如果您真的想将选择器发送到 viewController 实例，您可以创建一个 extension 将方法添加到每个 UIViewController

extension UIViewController {

    @objc func handleKeyboard(_ notification: NSNotification) {
        // do your stuff here
    }
}

然后，在注册时执行：

NotificationService.instance.addKeyboardObservers(onVC: vc, handleKeyboardSelector: #selector(vc.handleKeyboard(_:))) // notice the vc.handleKeyboard instead of self.handleKeyboard

编辑尝试在视图控制器中保留键盘服务：

let keyboardService = KeyboardService()

override func viewDidLoad() {
    super.viewDidLoad()
    keyboardService.bind(bottomConstraint: loginBtnBackViewBottomConstraint, vc: self)
}

为什么无法识别的选择器发送到实例？

Why Unrecognized selector sent to instance?

iphone

xcode

ios

swift

swift4.2