Swift 3＆amp; 4

Question

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。我该如何解决这个问题？

Answer 1

Swift 3＆amp; 4

Swift 3，现在是Swift 4，已经用struct“包装类型”取代了许多“带字符串类型”的API，就像NotificationCenter一样。现在，通知由struct Notfication.Name而不是String标识。有关详细信息，请参阅现在的遗留Migrating to Swift 3 guide

Swift 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＆amp; 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)

现在，所有系统通知类型都定义为Notification.Name上的静态常量;即.UIApplicationDidFinishLaunching，.UITextFieldTextDidChange等

您可以使用自己的自定义通知扩展Notification.Name，以便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)

Swift 4.2 用法：

与Swift 4相同，但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，您可以使用自己的自定义通知而不是Notification.Name扩展UIApplication：

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

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

Answer 2

对于所有在Swift 3或Swift 4中使用#selector的人来说，这是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)")
    }
}

在此示例中，我们尝试从AppDelegate获取POST（因此在AppDelegate中实现此操作）：

// ---------------------------------------------
// 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)
}

Answer 3

通知似乎再次发生变化（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)

Answer 4

我认为它已经改变了。

发布此内容适用于Xcode 8.2。

NotificationCenter.default.post(Notification(name:.UIApplicationWillResignActive)

Swift 3上的NotificationCenter问题

4 个答案:

Swift 3＆amp; 4