Marking makeUIView func makes view NOT conform to UIViewRepresentable? - ios

Question

I am trying to update my map's style URL immediately when the device changes from light/dark mode in my SwiftUI app.
The error below shows on every line where "mapView" is declared inside func makeUIView...
"Cannot use mutating getter on immutable value: 'self' is immutable. Mark method 'mutating' to make 'self' mutable"
I was instructed to put mapView inside of makeUIView but there is another func called setCenter() that needs to modify the mapView.
However, when I mark the method mutating the view does not conform to UIViewRepresentable and this error shows every where "mapView" is inside of makeUIView
What can I do to fix this?
struct MapboxMapViewRepresentable: UIViewRepresentable {
#Environment(\.colorScheme) var colorScheme
func makeCoordinator() -> Coordinator {
print("Make coordinator")
return Coordinator(control: self)
}
var mapboxStyleUrl: String {
"mapbox://styles/" + (colorScheme == .dark ? "cl0318cec0sdfdsfsfsfnrshos" : "ckwih3sdfsdfdfsfdfiz7403d0h")
}
lazy var mapView: MGLMapView = {
return MGLMapView(frame: .zero, styleURL: URL(string: mapboxStyleUrl)!)
}()
// FUNC CANNOT BE MUTATING BECAUSE VIEW WILL NOT CONFORM TO UIVIEWREPRESENTABLE
func makeUIView(context: Context) -> MGLMapView {
mapView.showsUserLocation = true
mapView.delegate = context.coordinator
mapView.allowsRotating = false
mapView.direction = 0.0
return mapView
}
// NEEDS TO BE ABLE TO ACCESS mapView
func setCenterAt(coordinate : CLLocationCoordinate2D) {
mapView.setCenter(coordinate, zoomLevel: MapViewModel.startAtZoomLevel, animated: false)
}
func updateUIView(_ mapView: MGLMapView, context: Context) {
//print("updateUIView")
// clear spot data of other users only when zoomed out too far to see them
}
}

Answer 1

A view struct cannot be modified from within itself and makeUIView is exactly a place to create a view (life cycle is managed by SwiftUI), so the fix is to move creation inside, like
func makeUIView(context: Context) -> MGLMapView {
// HERE !!
let mapView = MGLMapView(frame: .zero, styleURL: URL(string: mapboxStyleUrl)!)
mapView.showsUserLocation = true
mapView.delegate = context.coordinator
mapView.allowsRotating = false
mapView.direction = 0.0
return mapView
}