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How do you add an observer in Swift to the default notification center? I'm trying to port this line of code that sends a notification when the battery level changes.
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(batteryLevelChanged:) name:UIDeviceBatteryLevelDidChangeNotification object:nil]; 
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A notification dispatch mechanism that enables the broadcast of information to registered observers. iOS 2.0+ iPadOS 2.0+ macOS 10.0+ Mac Catalyst 13.0+ tvOS 9.0+ watchOS 2.0+
addObserver(_:selector:name:object:)Adds an entry to the notification center to call the provided selector with the notification. iOS 2.0+ iPadOS 2.0+ macOS 10.0+ Mac Catalyst 13.0+ tvOS 9.0+ watchOS 2.0+
default — This is the notification variable you can create it globally inside your class if you having more notifications. addObserver(self, — This is for the class where we are going to observer notification.
Send(Post) Notification:
NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: nil) OR
NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: nil, userInfo: ["Renish":"Dadhaniya"]) Receive(Get) Notification:
NotificationCenter.default.addObserver(self, selector: #selector(self.methodOfReceivedNotification(notification:)), name: Notification.Name("NotificationIdentifier"), object: nil) Function-Method handler for received Notification:
@objc func methodOfReceivedNotification(notification: Notification) {} Send(Post) Notification:
NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: nil) Receive(Get) Notification:
NotificationCenter.default.addObserver(self, selector: #selector(YourClassName.methodOfReceivedNotification(notification:)), name: Notification.Name("NotificationIdentifier"), object: nil) Method handler for received Notification:
func methodOfReceivedNotification(notification: Notification) { // Take Action on Notification } Remove Notification:
deinit { NotificationCenter.default.removeObserver(self, name: Notification.Name("NotificationIdentifier"), object: nil) } Send(Post) Notification
NSNotificationCenter.defaultCenter().postNotificationName("NotificationIdentifier", object: nil) Receive(Get) Notification
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(YourClassName.methodOfReceivedNotification(_:)), name:"NotificationIdentifier", object: nil) Method handler for received Notification
func methodOfReceivedNotification(notification: NSNotification){ // Take Action on Notification } For historic Xcode versions...
Send(Post) Notification
NSNotificationCenter.defaultCenter().postNotificationName("NotificationIdentifier", object: nil) Receive(Get) Notification
NSNotificationCenter.defaultCenter().addObserver(self, selector: "methodOfReceivedNotification:", name:"NotificationIdentifier", object: nil) Remove Notification
NSNotificationCenter.defaultCenter().removeObserver(self, name: "NotificationIdentifier", object: nil) NSNotificationCenter.defaultCenter().removeObserver(self) // Remove from all notifications being observed Method handler for received Notification
func methodOfReceivedNotification(notification: NSNotification) { // Take Action on Notification } Annotate either the class or the target method with @objc
@objc private func methodOfReceivedNotification(notification: NSNotification) { // Take Action on Notification } // Or dynamic private func methodOfReceivedNotification(notification: NSNotification) { // Take Action on Notification } If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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