92

我正在学习 Swift 3，我正在尝试使用NSNotificationCenter. 这是我的代码：

func savePost(){
    let postData = NSKeyedArchiver.archivedData(withRootObject: _loadedpost)
    UserDefaults.standard().object(forKey: KEY_POST)
}
func loadPost(){
    if let postData = UserDefaults.standard().object(forKey: KEY_POST) as? NSData{
        if let postArray = NSKeyedUnarchiver.unarchiveObject(with: postData as Data) as? [Post]{
                _loadedpost = postArray
        }
    }
    //codeerror
    NotificationCenter.default().post(NSNotification(name: "loadedPost" as NSNotification.Name, object: nil) as Notification)
}

这是观察者：

override func viewDidLoad() {
    super.viewDidLoad()
//codeerorr
    NotificationCenter.default().addObserver(self, selector: Selector(("onPostLoaded")), name: "loadedPost", object: nil)
}

func numberOfSections(in tableView: UITableView) -> Int {
    return 1
}

它总是给我错误“信号 SIGBRT”。当我尝试在观察者中更改名称时，这不是错误，但显然它没有显示任何内容。我该如何解决？

4

4 回答 4

328

斯威夫特 3 & 4

Swift 3 和现在的 Swift 4 已经用struct“包装器类型”替换了许多“字符串类型”的 API，NotificationCenter 就是这种情况。通知现在由 astruct Notfication.Name而不是由标识String。有关更多详细信息，请参阅现在遗留的迁移到 Swift 3 指南

斯威夫特 2.2用法：

// Define identifier
let notificationIdentifier: String = "NotificationIdentifier"

// Register to receive notification
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(YourClassName.methodOfReceivedNotification(_:)), name: notificationIdentifier, object: nil)

// Post a notification
NSNotificationCenter.defaultCenter().postNotificationName(notificationIdentifier, object: nil)

Swift 3 & 4用法：

// Define identifier
let notificationName = Notification.Name("NotificationIdentifier")

// Register to receive notification
NotificationCenter.default.addObserver(self, selector: #selector(YourClassName.methodOfReceivedNotification), name: notificationName, object: nil)

// Post notification
NotificationCenter.default.post(name: notificationName, object: nil)

// Stop listening notification
NotificationCenter.default.removeObserver(self, name: notificationName, object: nil)

所有系统通知类型现在都定义为静态常量 on Notification.Name; 即.UIApplicationDidFinishLaunching,.UITextFieldTextDidChange等

您可以Notification.Name使用自己的自定义通知进行扩展，以与系统通知保持一致：

// Definition:
extension Notification.Name {
    static let yourCustomNotificationName = Notification.Name("yourCustomNotificationName")
}

// Usage:
NotificationCenter.default.post(name: .yourCustomNotificationName, object: nil)

斯威夫特 4.2用法：

与 Swift 4 相同，除了现在系统通知名称是 UIApplication 的一部分。因此，为了与系统通知保持一致，您可以UIApplication使用自己的自定义通知而不是 Notification.Name 进行扩展：

// Definition:
UIApplication {
    public static let yourCustomNotificationName = Notification.Name("yourCustomNotificationName")
}

// Usage:
NotificationCenter.default.post(name: UIApplication.yourCustomNotificationName, object: nil)
于 2016-07-27T14:03:20.840 回答
18

通知似乎再次更改（2016 年 10 月）。

//注册接收通知

NotificationCenter.default.addObserver(self, selector: #selector(yourClass.yourMethod), name: NSNotification.Name(rawValue: "yourNotificatioName"), object: nil)

// 发布通知

NotificationCenter.default.post(name: NSNotification.Name(rawValue: "yourNotificationName"), object: nil)
于 2016-10-09T17:29:23.117 回答
18

对于所有在 Swift 3 或 Swift 4 中纠结于#selector 的人，这里有一个完整的代码示例：

// WE NEED A CLASS THAT SHOULD RECEIVE NOTIFICATIONS
    class MyReceivingClass {

    // ---------------------------------------------
    // INIT -> GOOD PLACE FOR REGISTERING
    // ---------------------------------------------
    init() {
        // WE REGISTER FOR SYSTEM NOTIFICATION (APP WILL RESIGN ACTIVE)

        // Register without parameter
        NotificationCenter.default.addObserver(self, selector: #selector(MyReceivingClass.handleNotification), name: .UIApplicationWillResignActive, object: nil)

        // Register WITH parameter
        NotificationCenter.default.addObserver(self, selector: #selector(MyReceivingClass.handle(withNotification:)), name: .UIApplicationWillResignActive, object: nil)
    }

    // ---------------------------------------------
    // DE-INIT -> LAST OPTION FOR RE-REGISTERING
    // ---------------------------------------------
    deinit {
        NotificationCenter.default.removeObserver(self)
    }

    // either "MyReceivingClass" must be a subclass of NSObject OR selector-methods MUST BE signed with '@objc'

    // ---------------------------------------------
    // HANDLE NOTIFICATION WITHOUT PARAMETER
    // ---------------------------------------------
    @objc func handleNotification() {
        print("RECEIVED ANY NOTIFICATION")
    }

    // ---------------------------------------------
    // HANDLE NOTIFICATION WITH PARAMETER
    // ---------------------------------------------
    @objc func handle(withNotification notification : NSNotification) {
        print("RECEIVED SPECIFIC NOTIFICATION: \(notification)")
    }
}

在这个例子中，我们尝试从 AppDelegate 获取 POST（所以在 AppDelegate 中实现这个）：

// ---------------------------------------------
// WHEN APP IS GOING TO BE INACTIVE
// ---------------------------------------------
func applicationWillResignActive(_ application: UIApplication) {

    print("POSTING")

    // Define identifiyer
    let notificationName = Notification.Name.UIApplicationWillResignActive

    // Post notification
    NotificationCenter.default.post(name: notificationName, object: nil)
}
于 2016-10-22T19:12:03.587 回答
5

我想它又变了。

在 Xcode 8.2 中发布此作品。

NotificationCenter.default.post(Notification(name:.UIApplicationWillResignActive)
于 2017-01-06T00:50:51.323 回答