Swift 4-通知中心addObserver发行

Question

每当一个unrecognized selector到达并且应用程序尝试执行它相关的方法时，我都会崩溃并得到一个Notification错误。这是我的代码--在viewDidLoad中

let notificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector: Selector(("sayHello")), name:NSNotification.Name(rawValue: "dataDownloadCompleted"), object: nil)

sayHello()方法非常简单-如下所示：

func sayHello() {
    print("Hello")
}

我已经证实了Notification已经成功发布，并且它已经成功到达--所以这不是问题所在。当应用程序在Notification到达时(通过执行sayHello()方法)采取行动时，就会发生崩溃。它一直给我unrecognized selector错误。

知道我做错什么了吗？(顺便说一句，这在Swift 3& Xcode 8中非常有效，但是现在对于Swift 4和Xcode 9，语法已经改变了，Xcode帮助我完成了必要的代码修复/更新--但是崩溃仍在发生。)

Answer 1

您可以通过以下步骤改进代码：

extension Notification.Name {
    static let dataDownloadCompleted = Notification.Name(
       rawValue: "dataDownloadCompleted")
}

像这样使用它：

let notificationCenter = NotificationCenter.default
notificationCenter.addObserver(self,
                               selector: #selector(YourClass.sayHello),
                               name: .dataDownloadCompleted,
                               object: nil)

但是，正如已经指出的，通过更改为#选择器可以解决问题

Answer 2

Data Receiving - Add observer:

override func viewDidLoad() {
     super.viewDidLoad()
     NotificationCenter.default.addObserver(self, selector: #selector(yourfunction(notfication:)), name: .postNotifi, object: nil)
}

@objc func yourfunction(notfication: NSNotification) {
     print("xxx")
}

Sending Data - Post Notification:

override func viewWillDisappear(_ animated: Bool) {
      super.viewWillDisappear(animated)
      NotificationCenter.default.removeObserver(self, name: .postNotifi, object: nil)
}

extension Notification.Name {
      static let postNotifi = Notification.Name("postNotifi")
}

Answer 3

SWIFT4.0& Xcode 9.0+:

发送(邮寄)通知：

NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: nil)

或

NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: nil, userInfo: ["Renish":"Dadhaniya"])

接收(获取)通知：

NotificationCenter.default.addObserver(self, selector: #selector(self.methodOfReceivedNotification(notification:)), name: Notification.Name("NotificationIdentifier"), object: nil)

接收通知的函数-方法处理程序：

@objc func methodOfReceivedNotification(notification: Notification) {}

SWIFT3.0& Xcode 8.0+:

发送(邮寄)通知：

NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: nil)

接收(获取)通知：

NotificationCenter.default.addObserver(self, selector: #selector(YourClassName.methodOfReceivedNotification(notification:)), name: Notification.Name("NotificationIdentifier"), object: nil)

接收通知的方法处理程序：

func methodOfReceivedNotification(notification: Notification) {
  // Take Action on Notification
}

删除通知：

deinit {
  NotificationCenter.default.removeObserver(self, name: Notification.Name("NotificationIdentifier"), object: nil)
}

Swift 2.3 & Xcode 7:

发送(邮寄)通知

NSNotificationCenter.defaultCenter().postNotificationName("NotificationIdentifier", object: nil)

收到(收到)通知

NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(YourClassName.methodOfReceivedNotification(_:)), name:"NotificationIdentifier", object: nil)

接收通知的方法处理程序

func methodOfReceivedNotification(notification: NSNotification){
  // Take Action on Notification
}

参考文献：https://medium.com/@javedmultani16/notification-in-swift-4-8b0db631f49d