I have an pagMenuController on did select method I am passing the index. And in another vc I am getting that index values and I needs to show the view respective with incoming index value.
Code in my FirstVC:
func pageMenuController(_ pageMenuController: PageMenuController, didSelectMenuItem index: Int, direction: PageMenuNavigationDirection) {
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "updateView"), object: nil, userInfo: ["indexValue": index])
}
Code in my SecondVC:
override func viewWillAppear(_ animated: Bool) {
NotificationCenter.default.addObserver(self, selector: #selector(ContViewController.incomingNotification(_:)), name: NSNotification.Name(rawValue: "updateView"), object: nil)
}
#objc func incomingNotification(_ notification: Notification) {
if let indexVal = notification.userInfo?["indexValue"] as? Int {
print(indexVal)
}
}
When ever my screen appears, I needs to get the index values. But when I click on my menu items first, second time index values in not showing. 3rd, and above time its coming. what I have missed.
Any solutions?
Thank you
move your observer to viewdidload
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(ContViewController.incomingNotification(_:)), name: NSNotification.Name(rawValue: "updateView"), object: nil)
}
Related
I have a problem when I try to pass an array from a UITableView to another one using NotificationCenter Design Pattern (because I don't have a segue between this 2 UIViewControllers). I don't know what I'm doing wrong but I don't receive any data in my second view controller.
My functions looks like this:
* First VC - The Sender Controller (From where I send data) *
class ProductsViewController: UIViewController{
var selectedProductsArray = [Product]()
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
// Implement Notification Design Pattern to send data
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "productsToLoad"), object: selectedProductsArray)
print(selectedProductsArray) // Here I have some data in this array (Photo here: https://ibb.co/k8hoEy)
}
* Second ViewController - The Receiver Controller (Where I will receive the data) *
class CartViewController: UIViewController {
var productsInCartArray = [Product]()
// We retrieve data from "selectedProductsArray" and we append all the products into "productsInCartArray"
#objc func notificationRecevied(notification: Notification) {
productsInCartArray = notification.object as! [Product]
print(productsInCartArray)
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
// Add observer to watch when something was changed in "selectedProductsArray"
NotificationCenter.default.addObserver(self, selector: #selector(notificationRecevied(notification:)), name: NSNotification.Name(rawValue: "productsToLoad"), object: nil)
print(productsInCartArray) // Output: []
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
// We remove the observer from the memory
NotificationCenter.default.removeObserver(self, name: NSNotification.Name(rawValue: "productsToLoad"), object: nil)
}
}
Screenshot:
Thank you for your time if you are reading this !
You need to remove this from viewWillDisappear of CartViewController
NotificationCenter.default.removeObserver(self, name: NSNotification.Name(rawValue: "productsToLoad"), object: nil)
as when you post in products the cards are not shown so there is no listener inside it , beside that CartViewController should be opened at least once before you post any data from ProductsViewController
//
you can completely remove the NotificationCenter work , and do this in CartViewController
let products = ((self.tabBarController?.viewControllers![0] as! UINavigationController).topViewController as! ProductsViewController).selectedProductsArray
Note : Don't worry for ! unwrapping it won't crash
I'm having some trouble understanding why the reloadData() line crashes with the following error 'unexpected found nil while unwrapping optional value'(also, why is it an optional?). Basically, when user taps a button it fires an API request, second VC(recipesVC) is shown and when data is retrieved from the API, in receivedRecipes method (previous VC) I want to reloadData from recipesVC (currentVC)
As my data is correctly passed to recipesVC, I don't see why reloadData() won't work on the same VC. Could you please give me a little help with this?
thank you.
override func viewDidLoad() {
super.viewDidLoad()
let recipes = Notification.Name(rawValue: "gotRecipes")
NotificationCenter.default.addObserver(self, selector: #selector(receivedRecipes),name: recipes, object: nil)
}
#objc func receivedRecipes() {
let recipesVC = storyboard?.instantiateViewController(withIdentifier: "recipesList") as! RecipesViewController
recipesVC.recipesList = request.recipeDetails
recipesVC.recipes.reloadData()
}
#objc func receivedRecipes() {
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "recipes"), object: nil, userInfo: ["data":request.recipeDetails])
}
In your currentVC
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(receivedRecipes(notification:)),name: NSNotification.Name(rawValue: "recipes"), object: nil)
}
#objc func receivedRecipes(notification: Notification) {
recipesList = notification.userInfo
recipes.reloadData()
}
Add validation to your data:
func receivedRecipes() {
guard let details = request.recipeDetails else { return }
let recipesVC = storyboard?.instantiateViewController(withIdentifier: "recipesList") as! RecipesViewController
recipesVC.recipesList = details
recipesVC.recipes.reloadData()
}
The next tip, you can update your notification and get recipes from the notification.object, but previously you should paste them into:
let parsedRecipes = Recipes()
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "gotRecipes"), object: parsedRecipes, userInfo: nil)
Also show recipesVC after it initialization with:
self.present(...) or self.navigationController?.show(...)
I'm trying to enable segue into a specific view upon opening a local notification by using NotificationCenter.addObserver(...)
My code is
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self,
selector: #selector(LocalNotificationViewController.test), name: ???, object: nil)
}
With test method to perform the segue to ViewController with identifier NotificationView which I'm not sure what to put...
#objc func SomeNotificationAct(notification: NSNotification){
DispatchQueue.main.async() {
self.performSegue(withIdentifier: "NotificationView", sender: self)
}
}
My main question is how do I know the name of my local notification to put into the NotificationCenter.addObserver(...) method?
You will need to create extension for Notification name like,
extension Notification.Name {
static let hello1 = Notification.Name("HelloNotifcationName")
static let hello2 = Notification.Name("HelloNotifcationName2")
}
and use it like this,
NotificationCenter.default.addObserver(self, selector: #selector(setToHelloName1(notification:)), name: .hello1, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(setToHelloName2(notfication:)), name: .hello2, object: nil)
You can find further reference or tutorial,here
I have mainViewController and inside have scrollView and I have secondViewController I want to change scrollView offset to top from secondViewController when I want to try it with NSNotificationCenter gives me ;
: unrecognized selector sent to instance 0x7ff83e024200'
How can I fix it ?
My codes under below.
mainViewController
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: "gotop:", name: NSNotification.Name(rawValue: "gotop"), object: nil)
}
func gotop(){
scrollView.setContentOffset(CGPoint(x:0, y:0), animated: false)
}
secondViewController
#IBAction func goButton (sender : UIButton){
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "gotop"), object: nil)
}
check your addObserver code, selector should have below signature
NotificationCenter.default.addObserver(self, selector: #selector(MainViewController.goTop(notification:)), name: Notification.Name("gotop"), object: nil)
Method handler for received Notification:
func goTop(notification: Notification){
scrollView.setContentOffset(CGPoint(x:0, y:0), animated: false)
}
For posting notification
NotificationCenter.default.post(name: Notification.Name("gotop"), object: nil)
Remove Notification in denit
deinit {
NotificationCenter.default.removeObserver((self, name: Notification.Name("gotop"), object: nil)
}
I have used below code in my project to add notification :
NotificationCenter.default.addObserver(self, selector: #selector(YourViewController.gotop), name: NSNotification.Name(rawValue: "gotop"), object: nil)
Try if it works in your scenario.
the definition of your "goTop" func is wrong :
instead of
func gotop(){
//do your stuff
}
try this :
func gotop(notification : NSNotification){
//do your stuff
}
let me know if this solve your problem.
I have two controllers
class CtrlA: UIViewController {
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
NotificationCenter.default.addObserver(CtrlB.self, selector: #selector(CtrlB.badge(notification:)), name: NSNotification.Name(rawValue: "badge"), object: nil)
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
NotificationCenter.default.removeObserver(CtrlB.self, name: NSNotification.Name(rawValue: "badge"), object: nil)
}
}
class CtrlB: UIViewController {
static func badge (notification: NSNotification) {
// blah blah
}
}
Whats the correct way to unregister the notification listener above?
I'm not certain this is correct:
NotificationCenter.default.removeObserver(CtrlB.self, name: NSNotification.Name(rawValue: "badge"), object: nil)
I don't think I can use self either, since it was registered on CtrlB.self
So the best way to implement the notification in your project is create one class called NotificationManager inside that declare one dictionary in which you can always update the observers
class NotificationManager {
var observers = [String: AnyObject]()
}
Create addObserver method, post notification method and remove
observer method inside the same class.
func postNotification(_ name: String, userInfo: [AnyHashable: Any]? = nil) {
NotificationCenter.default.post(name: name, object: nil, userInfo: userInfo)
}
func addObserver(_ name: String, block: #escaping (Notification) -> Void) {
//if observer is already in place for this name, remove it
removeObserverForName(name)
let observer = NotificationCenter.default.addObserver(forName: name), object: nil, queue: OperationQueue.main, using: block)
self.observers[name] = observer
}
func removeObserver(_ name: name) {
guard let observer = self.observers[name] else { return }
NotificationCenter.default.removeObserver(observer)
self.observers.removeValue(forKey: name)
}
//Removes all observers
func removeAllObservers() {
for observer in self.observers.values {
NotificationCenter.default.removeObserver(observer)
}self.observers = [:]
}
So access the above method in any of your class wherever its required and it will take care of everything. This will also prevent crash in your code. If try to remove the same observer more than one time.
I am not sure why you are registering/unregistering to notifications with a class and not an instance. 'CtrlB.self' - will not give you an instance of the CtrlB class, in fact it will return a class itself.
Instead you should use something like this:
class CtrlA {
let ctrlBInstance = CtrlB()
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
NotificationCenter.default.addObserver(ctrlBInstance, selector: #selector(CtrlB.badge(notification:)), name: NSNotification.Name(rawValue: "badge"), object: nil)
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
NotificationCenter.default.removeObserver(ctrlBInstance, name: NSNotification.Name(rawValue: "badge"), object: nil)
}
}
And your ClassB should look like this in this case:
class CtrlB {
func badge (notification: NSNotification) {
// blah blah
}
}
You need to get the instance of the observer,which you haven't declared...
for instance you need to set class variable secondA...
class CtrlA: UIViewController {
var secondController: CtrlB?
override func viewDidLoad()
{
super.viewDidLoad()
if let unwrappedController = storyboard.instantiateViewController(withIdentifier: "someViewController") as? CtrlB
{
secondController = unwrappedController
}
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
if let secondController = secondController
{
NotificationCenter.default.addObserver(CtrlB.self, selector: #selector(CtrlB.badge(notification:)), name: NSNotification.Name(rawValue: "badge"), object: nil)
}
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if let secondController = secondController
{
NotificationCenter.default.removeObserver(CtrlB.self, name: NSNotification.Name(rawValue: "badge"), object: nil)
}
}
//Also don't forget to remove listening on deinit
deinit
{
if let secondController = secondController
{
NotificationCenter.default.removeObserver(secondController, name: NSNotification.Name(rawValue: "badge"), object: nil)
}
}
}
class CtrlB: UIViewController {
//Here you go with notification...
static func badge (notification: NSNotification) {
// blah blah
}
}