Updating/Refreshing the contents of a ContainerView - ios

Question

I currently have a view controller that has a container view which functions similar to the bottom drawer in the iOS Maps application. When an image is scanned, the drawer animates onto the screen (it begins hidden off the screen at (0,700)) and displays information that comes from Firebase. Within this container, I have another container that allows me to have a PageViewController setup. This setup allows the user to swipe between 2 different sets of information (all of which needs to be loaded from Firebase).
I don't know how to reset the data within the second PageViewController so that whenever the drawer is dismissed through a button, the PageViewController system resets and I can use my function inside the secondPageViewController to reload the tableView it has inside.
TL;DR / More Information
Scanning an image is what loads the information into the ViewControllers.
I have one independent VC (ViewController) with a container view inside of it (BottomDrawerViewController). The BottomDrawerViewController also has a container inside of it which is a PageViewController with 2 pages (Swipe1ViewController & Swipe2ViewController)
The first page of the PageViewController setup works fine (Most likely because that information is loaded using an NSNotification)
I haven't been able to use an NSNotification to send and refresh this data the same way because this is not the first view controller that shows up after I post my notification.
I can't just load all my information independently in the second PageViewController because I get the pathway to the Firebase information from my original ViewController
Question: How can I reset both this data and the PageViewController so that whenever the user dismisses the bottom drawer the information on the second page is able to be refreshed on the next scan and the PageViewController starts on the first page? I thought maybe by forcing the view to disappear so that ViewDidLoad is called when it appears on screen but I am realizing this isn't possible.
I've attached some of the important code from all of the view controllers and my Firebase code in image and JSON form just in case that helps.
ViewController: -- This is the part that gets information to send to containers and what animates in the main container
ref.child("Directory").child(imageName).observeSingleEvent(of: .value, with: { (snapshot) in
print(snapshot)
let content = ImageInformation(snapshot: snapshot)
// TODO: Deliver Image Metadata here
let imageInfo = ["eventTitle": imageName, "source": content.Source, "date": content.Date] as [String : Any]
NotificationCenter.default.post(name: Notification.Name.drawerVC, object: nil, userInfo: imageInfo)
NotificationCenter.default.post(name: Notification.Name.newsVC, object: nil, userInfo: imageInfo)
})
UIView.animate(withDuration: 0.50) {
self.bottomDrawer.frame = CGRect(x: self.bottomPosition.x, y: self.bottomPosition.y, width: self.bottomDrawer.frame.size.width, height: self.bottomDrawer.frame.size.height)
}
BottomDrawerViewController: -- This gets a notification from ViewController and changes the drawers title. It also sends a notification back to ViewController when the view is pressed so that it can be dismissed.
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(appeared), name: Notification.Name.drawerVC, object: nil)
let tap = UITapGestureRecognizer(target: self, action: #selector(handleTap(_:)))
view.addGestureRecognizer(tap)
}
#objc func appeared(_ notification: NSNotification) {
if let eventTitle = notification.userInfo?["eventTitle"] as? String {
self.eventTitleLabel.text = eventTitle
}
}
#objc func handleTap(_ sender: UITapGestureRecognizer) {
NotificationCenter.default.post(name: Notification.Name.mainVC, object: nil, userInfo: nil)
}
PageViewController: --This controls my PageViewController setup. Since everything is the same as a normal setup I did not include. This line allows me to send a variable from the first page to the second.
var eventTitle: String = ""
Swipe1ViewController: -- Receives a notification from ViewController and uses it to populate the Labels on screen. It also sends the event title ("Test Input" in the database) to the PageViewController to be used by the Swipe2ViewController (No code shown)
Swipe2ViewController: -- As of right now it takes the eventTitle variable from the PageViewController and uses it to get data from Firebase but this doesn't work multiple times because viewDidLoad() only runs once when the BottomDrawerViewController is swiped up. I've also tried putting the fetchHeadlines() function in viewDidAppear() but if the user dismisses and scans a completely different picture it won't update.
override func viewDidLoad() {
super.viewDidLoad()
self.newsTableView.delegate = self
self.newsTableView.dataSource = self
// fetchHeadlines()
}
override func viewDidAppear(_ animated: Bool) {
//
fetchHeadlines()
}
override func viewDidDisappear(_ animated: Bool) {
}
func fetchHeadlines() {
let pageVC = self.parent as! DrawerPageViewController
let eventTitle = pageVC.eventTitle
print("Title: " + eventTitle)
ref.child("Directory").child(eventTitle).child("News").observeSingleEvent(of: .value) { (newsSnapshot) in
for news in newsSnapshot.children.allObjects as! [DataSnapshot] {
print("Key: \(news.key)", "Value: \(news.value)")
//self.headlines.append(news)
DispatchQueue.global().async {
DispatchQueue.main.async {
// self.tableView.reloadData()
}
}
}
}
}

Answer 1

You shouldn't be using notifications to propagate data from one view to another. As you see, it doesn't work that well, it can be error prone, and it can be challenging to debug. Instead, you should embrace the relationship between parent and child view controllers. That is, The ViewController should pass the data to the BottomViewController, who passes the data to the PageViewController, and it's the PageViewController's job to set up the data in the sub-pages. This lets you put the data where it belongs when each view controller is put on screen.
Note that a parent view controller can access a child using the childViewControllers array. So ViewController can access the BottomViewController directly using:
if let bottomViewController = childViewControllers.first as? BottomViewController {
// set up the bottomViewController here
}