Swift view reload when app becomes active - ios

Question

I have values that are being updated from firebase, I am calling the functions that update the values inside viewdidload(), when the app is installed the values are updated, then I send an update that is basically requiring me to close the app twice until the value are update, not sure if iphone keeps it in memory even after 1 close?
I tried adding viewWillAppear and viewDidAppear to try and fix this but neither did anything. Is there a way to reload the view when the app is opened even if it was not closed and was in the background.
Will this work through app delegate? how can i Update the viewcontroller from there?
Thank you.

Answer 1

It is better to listen for UIApplication.didBecomeActiveNotification The iOS sends this notification when the app goes from background to foreground.
You can install handler for that notification for example in viewDidLoad method of your controller.
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self,
selector: #selector(handleAppDidBecomeActiveNotification(notification:)),
name: UIApplication.didBecomeActiveNotification,
object: nil)
}
Your handler will be just a method in the same view controller to call when receive this notification. In that method you can reload the data or do anything you'd like
#objc func handleAppDidBecomeActiveNotification(notification: Notification) {
reloadData()
}
And of course do not forget to unregister for UIApplication.didBecomeActiveNotification when the view controller is closed. For example in the deinit method of the controller
deinit {
NotificationCenter.default.removeObserver(self)
}
In that way the logic for reload and what triggers the reload will be capsulated in each view controller and the app delegate will not know about this which is better.

Answer 2

You could handle it from AppDelegate.
Use optional application did become active method.
func applicationDidBecomeActive(_ application: UIApplication)
This method is called to let your app know that it moved from the inactive to active state. You should use this method to restart any tasks that were paused (or not yet started) while the app was inactive.
Edited to show how to get desired controller.
Check controller inside it:
func applicationDidBecomeActive(_ application: UIApplication) {
let appDelegate: AppDelegate? = UIApplication.shared.delegate as? AppDelegate
if let controller = appDelegate?.window?.rootViewController {
if let navigationController: UINavigationController = controller as? UINavigationController {
let viewControllers: [UIViewController] = navigationController.viewControllers
for viewController in viewControllers {
// Check for your view controller here
}
} else if let viewController: UIViewController = controller as? UIViewController {
// Check for your view controller here
} else if let tabController: UITabBarController = controller as? UITabBarController {
// Narrow the hierarchy and check for your view controller here
}
}
}

Answer 3

You have to call method tableView.reloadData() in the viewDidLoad() after loading data from firebase.
For instance have a look on my example:
// no matter what you have collectionView or tableView
#IBOutlet private weak var cardsCollectionView: UICollectionView!
// data from firebase stored in the array
private var cards: [Card]?
override func viewDidLoad() {
super.viewDidLoad()
DatabaseService.shared.loadDataFromDb { (cards) in
DispatchQueue.main.async {
// update of array with new data
self.cards = cards
// update of view
self.cardsCollectionView.reloadData()
}
}
}