I have a strange issue. I register and unregister my Notification like so:
func doRegisterNotificationListener() {
NotificationCenter.default.addObserver(forName: Notification.Name(rawValue: "RateAlertRated"), object: nil, queue: nil, using: rateDidRate)
}
func doUnregisterNotificationListener() {
NotificationCenter.default.removeObserver(self, name: Notification.Name(rawValue: "RateAlertRated"), object: nil)
}
func rateDidRate(notification: Notification) {
let rating = notification.userInfo?["score"] as? Int
let message = notification.userInfo?["message"] as? String
let response = Response(rating: rating, message: message)
output.presentRated(response)
}
This view controller is in a UITabBarController. doRegisterNotificationListener is called in viewDidAppear and doUnregisterNotificationListener is called in viewDidDisappear. When I switch between tabs the register and unregister methods are being called correctly (I tested using a print statement). However if I fire a notification it will still be received even though doUnregisterNotificationListener was called last. Any ideas what I might be doing wrong here?
Quick note:
Also tried:
NotificationCenter.default.removeObserver(self)
This also doesn't work.
I have tested your code and once i register observer with this type it is not called when you doUnregister it. please try this.
NotificationCenter.default.addObserver(self, selector: #selector(rateDidRate(notification:)), name: Notification.Name(rawValue: "RateAlertRated"), object: nil)
If you are working with addObserver(forName:object:queue:using:) you should remove it in this way:
Create:
let center = NSNotificationCenter.defaultCenter()
let mainQueue = NSOperationQueue.mainQueue()
self.localeChangeObserver = center.addObserverForName(NSCurrentLocaleDidChangeNotification, object: nil, queue: mainQueue) { (note) in
print("The user's locale changed to: \(NSLocale.currentLocale().localeIdentifier)")
}
Remove:
center.removeObserver(self.localeChangeObserver)
This approach is taken from the documentation.
Hi i am new in iOS application development. I am using Swift 3.0 code.
In my application I'm fetching the device token and I'm passing to my server. to pass token value from Appdelegate to UIViewController i am using UserDefaults.standard. and it's working fine. During first application load i am showing system's push notification prompt. If user click OK (allow) or Don't allow. application check it using following code.
//Checking Notification State
let isRegisteredForLocalNotifications = UIApplication.shared.currentUserNotificationSettings?.types.contains(UIUserNotificationType.alert) ?? false
if isRegisteredForLocalNotifications{
print("Notification allow")
}else{
print("Notification Don't allow")
}
Note: The above code is working fine in didRegisterForRemoteNotificationsWithDeviceToken.
I am having following issue with above code.
1) if i am using same code in ViewController its working but my application not waiting for system's push notification prompt result. i am getting results in AppDelegate.
So how to reload ViewController from didRegisterForRemoteNotificationsWithDeviceToken? is there any way to do that.
2) can i pause viewController until user response to system's push notification prompt. But i am not sure above code will work in ViewController or not.
Please advise.
Thanks for help.
For first part of your problem, you can create an Observer:
NotificationCenter.default.addObserver(self, selector: #selector(YourClassName.methodOfReceivedNotification(notification:)), name: Notification.Name("NotificationIdentifier"), object: nil)
the function that handle it will be like this:
func methodOfReceivedNotification(notification: Notification){
//Take Action on Notification
}
and then you can call it as follows:
NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: nil)
you can call the above code whenever you want to update your viewController
You can update view controller from didRegisterForRemoteNotificationsWithDeviceToken? by post notification.
let notificationIdentifier: String = "NotificationIdentifier"
//write this to didRegisterForRemoteNotificationsWithDeviceToken
// Post notification
NotificationCenter.default.post(name: notificationName, object: nil)
//write this to your View Controller
let notificationIdentifier: String = "NotificationIdentifier"
// Register to receive notification
NotificationCenter.default.addObserver(self, selector:#selector(YourClassName.methodOfReceivedNotification), name: notificationName, object: nil)
// Stop listening notification
NotificationCenter.default.removeObserver(self, name: notificationName, object: nil);
func methodOfReceivedNotification(notification: Notification) {
}
This question already has answers here:
NSNotificationCenter addObserver in Swift
(16 answers)
Closed 6 years ago.
I'm learning Swift 3 and I'm trying to using NSNotificationCenter. Here is my code:
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)
}
and this is the observer:
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
}
It always gives me the error "signal SIGBRT". When I try to change the name in the observer, it's not an error, but obviously it didn't show anything. How do I fix this?
Swift 3 & 4
Swift 3, and now Swift 4, have replaced many "stringly-typed" APIs with struct "wrapper types", as is the case with NotificationCenter. Notifications are now identified by a struct Notfication.Name rather than by String. For more details see the now legacy Migrating to Swift 3 guide
Swift 2.2 usage:
// 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 usage:
// 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)
All of the system notification types are now defined as static constants on Notification.Name; i.e. .UIApplicationDidFinishLaunching, .UITextFieldTextDidChange, etc.
You can extend Notification.Name with your own custom notifications in order to stay consistent with the system notifications:
// Definition:
extension Notification.Name {
static let yourCustomNotificationName = Notification.Name("yourCustomNotificationName")
}
// Usage:
NotificationCenter.default.post(name: .yourCustomNotificationName, object: nil)
Swift 4.2 usage:
Same as Swift 4, except now system notifications names are part of UIApplication. So in order to stay consistent with the system notifications you can extend UIApplication with your own custom notifications instead of Notification.Name :
// Definition:
UIApplication {
public static let yourCustomNotificationName = Notification.Name("yourCustomNotificationName")
}
// Usage:
NotificationCenter.default.post(name: UIApplication.yourCustomNotificationName, object: nil)
Notifications appear to have changed again (October 2016).
// Register to receive notification
NotificationCenter.default.addObserver(self, selector: #selector(yourClass.yourMethod), name: NSNotification.Name(rawValue: "yourNotificatioName"), object: nil)
// Post notification
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "yourNotificationName"), object: nil)
For all struggling around with the #selector in Swift 3 or Swift 4, here a full code example:
// 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)")
}
}
In this example we try to get POSTs from AppDelegate (so in AppDelegate implement this):
// ---------------------------------------------
// 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)
}
I think it has changed again.
For posting this works in Xcode 8.2.
NotificationCenter.default.post(Notification(name:.UIApplicationWillResignActive)
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];
Swift 4.0 & Xcode 9.0+:
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) {}
Swift 3.0 & Xcode 8.0+:
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)
}
Swift 2.3 & Xcode 7:
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
}
It's the same as the Objective-C API, but uses Swift's syntax.
Swift 4.2 & Swift 5:
NotificationCenter.default.addObserver(
self,
selector: #selector(self.batteryLevelChanged),
name: UIDevice.batteryLevelDidChangeNotification,
object: nil)
If your observer does not inherit from an Objective-C object, you must prefix your method with #objc in order to use it as a selector.
#objc private func batteryLevelChanged(notification: NSNotification){
//do stuff using the userInfo property of the notification object
}
See NSNotificationCenter Class Reference, Interacting with Objective-C APIs
A nice way of doing this is to use the addObserver(forName:object:queue:using:) method rather than the addObserver(_:selector:name:object:) method that is often used from Objective-C code. The advantage of the first variant is that you don't have to use the #objc attribute on your method:
func batteryLevelChanged(notification: Notification) {
// do something useful with this information
}
let observer = NotificationCenter.default.addObserver(
forName: NSNotification.Name.UIDeviceBatteryLevelDidChange,
object: nil, queue: nil,
using: batteryLevelChanged)
and you can even just use a closure instead of a method if you want:
let observer = NotificationCenter.default.addObserver(
forName: NSNotification.Name.UIDeviceBatteryLevelDidChange,
object: nil, queue: nil) { _ in print("🔋") }
You can use the returned value to stop listening for the notification later:
NotificationCenter.default.removeObserver(observer)
There used to be another advantage in using this method, which was that it doesn't require you to use selector strings which couldn't be statically checked by the compiler and so were fragile to breaking if the method is renamed, but Swift 2.2 and later include #selector expressions that fix that problem.
Declare a notification name
extension Notification.Name {
static let purchaseDidFinish = Notification.Name("purchaseDidFinish")
}
You can add observer in two ways:
Using Selector
NotificationCenter.default.addObserver(self, selector: #selector(myFunction), name: .purchaseDidFinish, object: nil)
#objc func myFunction(notification: Notification) {
print(notification.object ?? "") //myObject
print(notification.userInfo ?? "") //[AnyHashable("key"): "Value"]
}
or using block
NotificationCenter.default.addObserver(forName: .purchaseDidFinish, object: nil, queue: nil) { [weak self] (notification) in
guard let strongSelf = self else {
return
}
strongSelf.myFunction(notification: notification)
}
func myFunction(notification: Notification) {
print(notification.object ?? "") //myObject
print(notification.userInfo ?? "") //[AnyHashable("key"): "Value"]
}
Post your notification
NotificationCenter.default.post(name: .purchaseDidFinish, object: "myObject", userInfo: ["key": "Value"])
from iOS 9 and OS X 10.11. It is no longer necessary for an
NSNotificationCenter observer to un-register itself when being
deallocated. more info
For a block based implementation you need to do a weak-strong dance if you want to use self inside the block. more info
Block based observers need to be removed more info
let center = NSNotificationCenter.defaultCenter()
center.removeObserver(self.localeChangeObserver)
Swift 3.0 in Xcode 8
Swift 3.0 has replaced many "stringly-typed" APIs with struct "wrapper types", as is the case with NotificationCenter. Notifications are now identified by a struct Notfication.Name rather than by String. See the Migrating to Swift 3 guide.
Previous usage:
// 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)
New Swift 3.0 usage:
// 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)
All of the system notification types are now defined as static constants on Notification.Name; i.e. .UIDeviceBatteryLevelDidChange, .UIApplicationDidFinishLaunching, .UITextFieldTextDidChange, etc.
You can extend Notification.Name with your own custom notifications in order to stay consistent with the system notifications:
// Definition:
extension Notification.Name {
static let yourCustomNotificationName = Notification.Name("yourCustomNotificationName")
}
// Usage:
NotificationCenter.default.post(name: .yourCustomNotificationName, object: nil)
In Swift 5
Let's say if want to Receive Data from ViewControllerB to
ViewControllerA
ViewControllerA (Receiver)
import UIKit
class ViewControllerA: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
//MARK: - - - - - Code for Passing Data through Notification Observer - - - - -
// add observer in controller(s) where you want to receive data
NotificationCenter.default.addObserver(self, selector: #selector(self.methodOfReceivedNotification(notification:)), name: Notification.Name("NotificationIdentifier"), object: nil)
}
//MARK: - - - - - Method for receiving Data through Post Notificaiton - - - - -
#objc func methodOfReceivedNotification(notification: Notification) {
print("Value of notification : ", notification.object ?? "")
}
}
ViewControllerB (Sender)
import UIKit
class ViewControllerB: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
//MARK: - - - - - Set data for Passing Data Post Notification - - - - -
let objToBeSent = "Test Message from Notification"
NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: objToBeSent)
}
}
Pass Data using NSNotificationCenter
You can also pass data using NotificationCentre in swift 3.0 and NSNotificationCenter in swift 2.0.
Swift 2.0 Version
Pass info using userInfo which is a optional Dictionary of type [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 Version
The userInfo now takes [AnyHashable:Any]? as an argument, which we provide as a dictionary literal in Swift
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
}
}
Source pass data using NotificationCentre(swift 3.0) and NSNotificationCenter(swift 2.0)
Swift 5 Notification Observer
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(batteryLevelChanged), name: UIDevice.batteryLevelDidChangeNotification, object: nil)
}
#objc func batteryLevelChanged(notification : NSNotification){
//do here code
}
override func viewWillDisappear(_ animated: Bool) {
NotificationCenter.default.removeObserver(self, name: UIDevice.batteryLevelDidChangeNotification, object: nil)
}
I'm able to do one of the following to successfully use a selector - without annotating anything with #objc:
NSNotificationCenter.defaultCenter().addObserver(self,
selector:"batteryLevelChanged:" as Selector,
name:"UIDeviceBatteryLevelDidChangeNotification",
object:nil)
OR
let notificationSelector: Selector = "batteryLevelChanged:"
NSNotificationCenter.defaultCenter().addObserver(self,
selector: notificationSelector,
name:"UIDeviceBatteryLevelDidChangeNotification",
object:nil)
My xcrun version shows Swift 1.2, and this works on Xcode 6.4 and Xcode 7 beta 2 (which I thought would be using Swift 2.0):
$xcrun swift --version
Apple Swift version 1.2 (swiftlang-602.0.53.1 clang-602.0.53)
This is very simple example of custom notification observer and post
Add Notification Observer
NotificationCenter.default.addObserver(self, selector: #selector(myFunction), name: Notification.Name("CustomeNotificationName"), object: nil)
Add Selector and handle Observer call
#objc func myFunction(notification: Notification) {
//Write you code
}
Post Notification(Observer) when it is required.
NotificationCenter.default.post(name: NSNotification.Name("CustomeNotificationName"), object: "Object", userInfo: ["key":"Value"])
Notes:- Make user when you leave screen you need to remove observer. e.g.
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
NotificationCenter.default.removeObserver(self);
}
Create an objc function which you want to execute when notification is called.
#objc func reloadNotification(_ notification: Notification) {
tblview.reloadData()
}
Add the notification observer in view did load.
NotificationCenter.default.addObserver(self, selector:#selector(reloadNotification(_:)), name: Notification.Name("reloadSideMenuDataNS"),object: nil)
post your notification where you want to call the function.
NotificationCenter.default.post(name: Notification.Name("reloadSideMenuDataNS"), object: nil)
you can remove your notification in view did disappear with below.
NotificationCenter.default.removeObserver(self, name: Notification.Name("reloadSideMenuDataNS"), object: nil)
In swift 2.2 - XCode 7.3, we use #selector for NSNotificationCenter
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(rotate), name: UIDeviceOrientationDidChangeNotification, object: nil)
We should remove notification also.
Ex.
deinit
{
NotificationCenter.default.removeObserver(self, name:NSNotification.Name(rawValue: "notify"), object: nil)
}
In swift 3, Xcode 8.2:- checking battery state level
//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
}
NSNotificationCenter add observer syntax in Swift 4.0 for iOS 11
NotificationCenter.default.addObserver(self, selector: #selector(keyboardShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
This is for keyboardWillShow notification name type. Other type can be selected from the available option
the Selector is of type #objc func which handle how the keyboard will show ( this is your user function )
Swift 5 & Xcode 10.2:
NotificationCenter.default.addObserver(
self,
selector: #selector(batteryLevelDidChangeNotification),
name: UIDevice.batteryLevelDidChangeNotification,
object: nil)