I had this function to move certain textfields upwards, when the keyboards would block their view - I'm sure you all know about this:
override func viewDidLoad() {
super.viewDidLoad()
let center: NotificationCenter = NotificationCenter.default
center.addObserver(self, selector: #selector(keyboardDidShow(notification:)), name: NSNotification.Name?.UIKeyboardDidShow, object: nil)
center.addObserver(self, selector: #selector(keyboardWillHide(notification:)), name: NSNotification.Name?.UIKeyboardWillHide, object: nil)
}
But when I recently updated to swift 4.2, these stopped working, and these suggestions came up:
Replace 'UIKeyboardDidShow' with 'UIResponder.keyboardDidShowNotification' &
Replace 'UIKeyboardWillHide' with 'UIResponder.keyboardWillHideNotification
But when I pressed "fix", I get the error (x2):
Type 'NSNotification.Name' has no member 'UIResponder'
It kind of seems like a bug to me? That xCode can't accept it's own changes?? Anybody came across this and knows what to do?
Thanks!
Try this
let notificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector: #selector(adjustForKeyboard), name: UIResponder.keyboardWillHideNotification, object: nil)
notificationCenter.addObserver(self, selector: #selector(adjustForKeyboard), name: UIResponder.keyboardWillChangeFrameNotification object: nil)
More info use this link :- enter link description here
I hope this will help you :D
Thanks
I have a function with default parameter value like this:
#objc func myFunc(theFlag: Bool = false) {
}
This function is called via notification center
NotificationCenter.default.addObserver(self, selector: #selector(myFunc), name: MyNotificationName, object: nil)
When MyNotificationName is posted, myFunc is called via notification center.
I assumed that the default value of theFlag is set to "false" and it works as I expected on most devices.
However, I found that theFlag is set to "true" on 32bit devices.
I wonder if this was not a correct way to call a function with default value via notification center. Is there any official manner to do that?
I'm testing on Swift 4.1, Xcode 9.4.1
The correct way is
#objc func myFunc(_ notification:Notification) // OR NSNotification also
Don't expect the NotificationCenter.default to set a value for theFlag: Bool = false , with
NotificationCenter.default.addObserver(self, selector: #selector(myFunc), name: MyNotificationName, object: nil)
OR
NotificationCenter.default.addObserver(self, selector: #selector(myFunc(_:)), name: MyNotificationName, object: nil)
//
If you want to send a value then insert it inside object / userInfo
NotificationCenter.default.post(name:MyNotificationName, object:<#Here#>, userInfo:<#OrHere#>)
i am trying to post notification NotificationCenter from appdelegate and receive notification in another view but notification not received.
Post notification :-
func xmppStream(_ sender: XMPPStream, didReceive message: XMPPMessage)
{
print("did receive message isss-->\(message)")
NotificationCenter.default.post(name: Notification.Name("MessageReceived"), object: message)
}
Received Notification in viewdidload :-
NotificationCenter.default.addObserver(self, selector: #selector(self.messagereceived(notification:)), name: Notification.Name("MessageReceived"), object: nil)
Method :-
#objc func messagereceived(notification:Notification)
{
let message = notification.object as? XMPPMessage
print("chat conversion message is----->\(message)")
}
My "messagereceived" Method not called.
so any one have solution related to this then please help me.
Thanks in advance.
Change the notification post from
NotificationCenter.default.post(name: Notification.Name("MessageReceived"), object: message)
to
NotificationCenter.default.post(Notification(name: Notification.Name(rawValue: "MessageReceived"),object: message))
and the observer from
NotificationCenter.default.addObserver(self, selector: #selector(self.messagereceived(notification:)), name: Notification.Name("MessageReceived"), object: nil)
to
NotificationCenter.default.addObserver(self, selector: #selector(self.messagereceived(notification:)), name: NSNotification.Name(rawValue: "MessageReceived"), object: nil)
In my case i can't get NotificationCenter in some situation in my app .
and problem was that using
NotificationCenter.default.addObserver(self, selector: #selector(btnRegister(_:)), name: Notification.Name(rawValue: "btnRegister"), object: nil)
in my viewDidLoad() func, And when i set above code in my viewWillAppear() func, that's work perfectly.
According to your code logic , move above code to other func or other section of your code and try to fix your problem.
NotificationCenter.default.addObserver(self, selector: Selector(("uploaded")), name: NSNotification.Name(rawValue: "uploaded"), object: nil)
I was writing name: "uploaded:" and xcode corrected it to the above code. The problem is when running the app i get unrecognized selector.
Any one know how to fix this to work with swift 3
Use the (identifier checking) #selector syntax:
Without parameter:
#selector(uploaded)
With parameter:
#selector(uploaded(_:))
NotificationCenter.default.addObserver(self, selector: #selector(ViewController.update), name: NSNotification.Name(rawValue: "uploaded"), object: nil)
func update() {
// do what you want
}
please note that "ViewController" is the class name where your function is
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)