Swift 4 - 通知中心 addObserver 问题

Question

每次 Notification 到达并且应用程序尝试执行其关联方法时，我都会崩溃并收到 unrecognized selector 错误。这是我的代码 - 在 viewDidLoad:

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")
}

我已确认 Notification 已成功发布并且 已成功到达 - 所以这不是问题所在。当应用程序希望在 Notification 到达时采取行动 - 通过执行 sayHello() 方法时，就会发生崩溃。它一直给我 unrecognized selector 错误。

知道我做错了什么吗？（顺便说一句，这与 Swift 3 & Xcode 8 完美配合，但现在 Swift 4 和 Xcode 9 语法已更改 [Xcode walked我通过必要的代码 fixes/updates] - 但崩溃不断发生。）

Answer 1

您可以通过以下步骤改进您的代码：

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

并像这样使用它：

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

但是正如已经指出的那样，通过更改为 #selector

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

Swift 4.0 & Xcode 9.0+:

发送(Post)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)

收到通知的函数方法处理程序：


@objc func methodOfReceivedNotification(notification: Notification) {}

Swift 3.0 & Xcode 8.0+:

发送(Post)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)

收到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(Post)通知

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

接收（获取）通知


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

收到通知的方法处理程序

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

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

Swift 4 - 通知中心 addObserver 问题

Swift 4 - Notification Center addObserver issue

addobserver

nsnotificationcenter

swift

xcode9