这是一个非常简单的自定义通知观察者和post的例子

添加通知观察员

NotificationCenter.default.addObserver(self, selector: #selector(myFunction), name: Notification.Name("CustomeNotificationName"), object: nil)

添加选择器并处理观察者调用

@objc func myFunction(notification: Notification) {
    
    //Write you code
}

在需要时发布通知(观察员)。

NotificationCenter.default.post(name: NSNotification.Name("CustomeNotificationName"), object: "Object", userInfo: ["key":"Value"])

注意:-当你离开屏幕时，你需要删除观察者。如。

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    NotificationCenter.default.removeObserver(self);
}

使用NSNotificationCenter传递数据

也支持通过swift 3.0中的NotificationCentre和swift 2.0中的NSNotificationCenter进行数据传递。

Swift 2.0版本

使用userInfo传递信息，userInfo是一个可选的字典类型[NSObject: AnyObject]?

let imageDataDict:[String: UIImage] = ["image": image]

// Post a notification
 NSNotificationCenter.defaultCenter().postNotificationName(notificationName, object: nil, userInfo: imageDataDict)

// Register to receive notification in your class
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(self.showSpinningWheel(_:)), name: notificationName, object: nil)

// handle notification
func showSpinningWheel(notification: NSNotification) {
  if let image = notification.userInfo?["image"] as? UIImage {
  // do something with your image   
  }
}

Swift 3.0版本

userInfo现在需要[AnyHashable:Any]?作为一个参数，我们在Swift中作为字典字面量提供

let imageDataDict:[String: UIImage] = ["image": image]

// post a notification
 NotificationCenter.default.post(name: NSNotification.Name(rawValue: "notificationName"), object: nil, userInfo: imageDataDict) 
// `default` is now a property, not a method call

// Register to receive notification in your class
NotificationCenter.default.addObserver(self, selector: #selector(self.showSpinningWheel(_:)), name: NSNotification.Name(rawValue: "notificationName"), object: nil)

// handle notification
func showSpinningWheel(_ notification: NSNotification) {

  if let image = notification.userInfo?["image"] as? UIImage {
  // do something with your image   
  }
}

使用NotificationCentre(swift 3.0)和NSNotificationCenter(swift 2.0)传递源数据

Xcode 8中的Swift 3.0

Swift 3.0已经用结构“包装器类型”取代了许多“字符串类型”的api, NotificationCenter也是如此。通知现在由struct notification标识。名称而不是字符串。参见迁移到Swift 3指南。

以前的用法:

// 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 3.0的新用法:

// 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)

所有系统通知类型现在都定义为notification . name上的静态常量;例如。uidevicebatteryleveldidchange， . uiapplicationdidfinishlaunching， . uitextfieldtextdidchange等。

您可以扩展通知。使用您自己的自定义通知命名，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)

在swift 3, Xcode 8.2:-检查电池状态水平

//Add observer
NotificationCenter.default.addObserver(self, selector: #selector(batteryStateDidChange), name: NSNotification.Name.UIDeviceBatteryStateDidChange, object: nil)


 //Fired when battery level changes

 func batteryStateDidChange(notification: NSNotification){
        //perform manipulation here
    }

这是一个非常简单的自定义通知观察者和post的例子

添加通知观察员

NotificationCenter.default.addObserver(self, selector: #selector(myFunction), name: Notification.Name("CustomeNotificationName"), object: nil)

添加选择器并处理观察者调用

@objc func myFunction(notification: Notification) {
    
    //Write you code
}

在需要时发布通知(观察员)。

NotificationCenter.default.post(name: NSNotification.Name("CustomeNotificationName"), object: "Object", userInfo: ["key":"Value"])

注意:-当你离开屏幕时，你需要删除观察者。如。

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    NotificationCenter.default.removeObserver(self);
}

它与Objective-C API相同，但使用了Swift的语法。

Swift 4.2和Swift 5:

NotificationCenter.default.addObserver(
    self,
    selector: #selector(self.batteryLevelChanged),
    name: UIDevice.batteryLevelDidChangeNotification,
    object: nil)

如果你的观察者没有从Objective-C对象继承，你必须用@objc作为你的方法的前缀来使用它作为选择器。

@objc private func batteryLevelChanged(notification: NSNotification){     
    //do stuff using the userInfo property of the notification object
}

参见NSNotificationCenter类参考，与Objective-C api交互