How do I reload UIScrollView containing ViewControllers to add/remove view controllers - swift

Question

I have a scrollView that contains a dynamic amount of WeatherViewControllers each displaying the weather data of a different city the user has saved. The user can segue from the WeatherViewControllers to a CityListViewController. Where they can add and remove cities from their list which in turn should add and remove WeatherViewControllers from the scrollView upon dismissing the CityListViewController, this is where I am running into a problem.
Currently I am trying to use a protocol to call viewDidLoad in the scrollViewController upon dismissing the CityListViewController but am getting an error:
Fatal error: Unexpectedly found nil while unwrapping an Optional
value: file)
when it gets to:
let weatherScreen = storyboard!.instantiateViewController(identifier: "View Controller") as! ViewController
Side Note: Upon initially opening the app the scrollView loads properly with all the correct WeatherViewControllers in the UIScrollView and the correct cities in the list.
class ScrollViewController: UIViewController, ScrollReloadProtocol {
func reloadScrollView() {
print("SCROLL RELOADED!!!!!*******")
self.viewDidLoad()
}
#IBOutlet weak var totalScrollView: UIScrollView!
var pages = [ViewController]()
var x = 0
var weatherScreensArray = [SavedCityEntity]()
var weatherScreenStringArray = [String]()
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
var horizString = "H:|[page1(==view)]"
let defaults = UserDefaults.standard
override func viewDidLoad() {
super.viewDidLoad()
//userDefaults used to keep track of which screen is which to put different cities on different viewControllers
defaults.set(0, forKey: "screenNumber")
//load cities to get number of cities saved
loadCities()
var views : [String: UIView] = ["view": view]
//create all weatherWeatherControllers
while x <= weatherScreensArray.count {
pages.append(createAndAddWeatherScreen(number: x))
weatherScreenStringArray.append("page\(x+1)")
views["\(weatherScreenStringArray[x])"] = pages[x].view
let addToHoriz = "[\(weatherScreenStringArray[x])(==view)]"
horizString.append(addToHoriz)
x+=1
}
horizString.append("|")
let verticalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:|[page1(==view)]|", options: [], metrics: nil, views: views)
let horizontalConstraints = NSLayoutConstraint.constraints(withVisualFormat: horizString, options: [.alignAllTop, .alignAllBottom], metrics: nil, views: views)
NSLayoutConstraint.activate(verticalConstraints + horizontalConstraints)
}
//Function to create and add weatherViewController
func createAndAddWeatherScreen(number: Int) -> ViewController {
defaults.set(number, forKey: "screenNumber")
let weatherScreen = storyboard!.instantiateViewController(identifier: "View Controller") as! ViewController
weatherScreen.view.translatesAutoresizingMaskIntoConstraints = false
totalScrollView.addSubview(weatherScreen.view)
addChild(weatherScreen)
weatherScreen.didMove(toParent: self)
return weatherScreen
}
}

Answer 1

You could try something like this:
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let weatherScreen = storyboard.instantiateViewController(withIdentifier: "View Controller") as! ViewController
It's also probably better to use one word for the identifier: "ViewController", and give it the same name as the class. Make sure to set these values also in your actual storyboard.