check if mapView has finished rendering? - swift

Question

So I know swift has mapViewDidFinishRenderingMap(_:fullyRendered:), but I have no clue how I can use that function to only add my mapView onto the view hierarchy when it finishes rendering.
Right now, even with the DispatchGroup .enter() and .leave(), the view.addSubview(mapView) is getting called before it finishes rendering, which results in my MKPolylines not showing up on the map when it loads.
How can I make sure that the map finishes rendering before view.addSubview(mapView) is called?
#Koen basically what my viedDidLoad() is doing:
override func viewDidLoad() {
super.viewDidLoad()
mapView = MKMapView()
let leftMargin:CGFloat = 0
let topMargin:CGFloat = 0
let mapWidth:CGFloat = view.frame.size.width
let mapHeight:CGFloat = view.frame.size.height
mapView?.frame = CGRect(x: leftMargin, y: topMargin, width: mapWidth, height: mapHeight)
mapView?.mapType = MKMapType.standard
mapView?.isZoomEnabled = true
mapView?.isScrollEnabled = true
mapView?.delegate = self
mapView?.showsScale = true
// I have this to make sure they run in order only after the previous block is finished because of dependencies
let group = DispatchGroup()
group.enter()
DispatchQueue.main.async {
// gets the routes as polylines and adds to mapView
self.fetchRoutes()
group.leave()
}
goup.notify(queue: .main) {
group.enter()
DispatchQueue.main.async {
// depending on the route data, adds the stops as annotations to mapView
self.fetchAnnotations()
group.leave()
}
group.notify(queue: .main) {
// the idea was that once both route and stops are added to the mapView, display mapView to screen
self.view.addSubview(mapView)
}
}
}

Answer 1

Issue was solved by moving all of my data fetching code into a single function and using DispatchGroup to only call addSubview(mapView) after the fetching finishes.
Was not able to find out the root cause, but the issue was solved.