为什么无法识别的选择器被发送到实例？

Question

我正在尝试为uiview功能制作一个方便的Binding键盘。我无法克服这个错误

***由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：' - [Twitter.LoginVC handleKeyboard：]：无法识别的选择器发送到实例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notificationService：

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到vc;但它是一个UIViewController实际上没有一个叫做handleKeyboard(_:)的方法。您应该更改为您的注册方法：

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(_:)))

你可以看到你现在告诉你在self上触发选择器，因为它实际上是self有这种方法。作为一般规则：将选择器发送到实例，因此该实例必须具有所选方法。

---

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

extension UIViewController {

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

然后，在注册时做：

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)
}