How to get access to underlying GMSMapView from UIRepresentable MapView - swift

Question

In my app I have a ViewModel(MapViewModel) class, a UIRepresentable class and ContentView. I am looking for a way to get access to GMSMapView view in the ViewModel that is created as a UIRepresentable class.
ContentView.swift:
import SwiftUI
import Combine
struct ContentView: View {
#State private var selection = 0
#State private var dragOffset = CGSize.zero
#ObservedObject var mapViewModel : MapViewModel = MapViewModel()
var body: some View {
GeometryReader { geo in
TabView(selection: self.$selection) {
MapView()
.edgesIgnoringSafeArea(.all)
.tabItem {
VStack {
Image(systemName: "house")
Text("Home")
}
}
.tag(0)
Text("Second Page")
.tabItem {
VStack {
Image(systemName: "gear")
Text("Settings")
}
}
.tag(1)
Text("Third Page")
.tabItem {
VStack {
Image(systemName: "gear")
Text("Third Page")
}
}
.tag(2)
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
MapViewModel.swift:
import Foundation
import Combine
import GoogleMaps
import os
class MapViewModel: NSObject, ObservableObject {
let lm = CLLocationManager()
var myLocations = [CLLocation]()
override init() {
super.init()
lm.delegate = self
lm.desiredAccuracy = kCLLocationAccuracyBest
lm.requestWhenInUseAuthorization()
lm.pausesLocationUpdatesAutomatically = false
lm.allowsBackgroundLocationUpdates = true
lm.startUpdatingLocation()
}
}
extension MapViewModel: CLLocationManagerDelegate {
func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
//self.status = status
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
os_log("locationManager:didUpdateLocations: received location",log: Log.general, type: .debug)
}
}
MapView.swift:
import UIKit
import SwiftUI
import GoogleMaps
struct MapView: UIViewRepresentable {
func makeUIView(context: Context) -> GMSMapView {
let camera = GMSCameraPosition.camera(withLatitude: 30.267153, longitude: -97.7430608, zoom: 6.0)
let gmsMapView = GMSMapView.map(withFrame: CGRect.zero, camera: camera)
gmsMapView.delegate = context.coordinator
return gmsMapView
}
func updateUIView(_ mapView: GMSMapView, context: Self.Context) {
}
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
class Coordinator: NSObject, GMSMapViewDelegate {
var parent: MapView
init(_ parent: MapView) {
self.parent = parent
}
}
}
struct GoogleMapView_Previews: PreviewProvider {
static var previews: some View {
MapView()
}
}
So any idea on how I can access the gmsMapView object in MapViewModel. I need access to draw lines on the map...Thanks!

Answer 1

I was able to get past this issue by defining the polyline overly value as #Published and accessing it via viewmodel in updateUI. So instead of trying to access the mapview from the viewmodel, I let the view add the polyline overlay. Hope this helps someone else. Thanks
ContentView.swift:
struct ContentView: View {
#State private var selection = 0
#State private var dragOffset = CGSize.zero
#ObservedObject var mapViewModel: MapViewModel
var body: some View {
GeometryReader { geo in
TabView(selection: self.$selection) {
MapView()
.edgesIgnoringSafeArea(.all)
.tabItem {
VStack {
Image(systemName: "house")
Text("Home")
}
}
.tag(0)
Text("Second Page")
.tabItem {
VStack {
Image(systemName: "gear")
Text("Settings")
}
}
.tag(1)
Text("Third Page")
.tabItem {
VStack {
Image(systemName: "gear")
Text("Third Page")
}
}
.tag(2)
}
}
}
}
MapView:
struct MapView: UIViewRepresentable {
#ObservedObject var mapViewModel = MapViewModel()
func makeUIView(context: Context) -> GMSMapView {
let camera = GMSCameraPosition.camera(withLatitude: 30.5986015, longitude: -97.8210401, zoom: 20.0)
let mapView = GMSMapView.map(withFrame: CGRect.zero, camera: camera)
mapView.isMyLocationEnabled = true
mapView.animate(toViewingAngle: 45)
mapView.delegate = context.coordinator
return mapView
}
func updateUIView(_ mapView: GMSMapView, context: Self.Context) {
if (mapViewModel.polyline != nil) {
print("updateUIView: Polyline = \(mapViewModel.polyline!.description)")
os_log("updateUIView: Polyline = %{Public}s",log: Log.general, type: .debug, mapViewModel.polyline!.description)
mapViewModel.polyline!.strokeColor = UIColor.red
mapViewModel.polyline!.strokeWidth = 5.0
mapViewModel.polyline!.map = mapView
}
if (mapViewModel.locChanged && mapViewModel.myLocations.count > 0) {
print("updateUIView: Refocus camera on last location")
os_log("updateUIView: Refocus camera on last location",log: Log.general, type: .debug, mapViewModel.polyline!.description)
let camera = GMSCameraPosition.camera(withLatitude: (mapViewModel.myLocations.last?.coordinate.latitude)!, longitude: (mapViewModel.myLocations.last?.coordinate.longitude)!, zoom: 20.0)
let _ = GMSMapView.map(withFrame: CGRect.zero, camera: camera)
}
}
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
class Coordinator: NSObject, GMSMapViewDelegate {
var parent: MapView
init(_ parent: MapView) {
self.parent = parent
}
}
}
MapViewModel:
class MapViewModel: NSObject, ObservableObject {
.
.
.
#Published var polyline: GMSPolyline?
#Published var locChanged: Bool = false
override init() {
super.init()
.
.
.
polyline = nil
}
.
.
.
func draw(myLocations: [CLLocation], color: UIColor) {
os_log("MapViewController: Drawing Track for last two Locations",log: Log.general, type: .info)
print("MapViewController: Drawing Track for last two Locations")
let path = GMSMutablePath()
let c1 = myLocations[myLocations.count - 1].coordinate
let c2 = myLocations[myLocations.count - 2].coordinate
path.add(c1)
path.add(c2)
polyline = GMSPolyline(path: path)
print("draw: Polyline = \(polyline!.description)")
polyline!.strokeColor = color
polyline!.strokeWidth = 5.0
}
.
.
.
extension MapViewModel: CLLocationManagerDelegate {
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
os_log("locationManager:didUpdateLocations: received location",log: Log.general, type: .debug)
guard let lastLocation: CLLocation = locations.last else {
os_log("locationManager:didUpdateLocations: received null location",log: Log.general, type: .debug)
return
}
if (myLocations.count >= 2) {
os_log("MapViewController: updateLocation: Calling draw method with count = %{Public}s",log: Log.general, type: .debug, myLocations.count.description)
self.draw(myLocations: self.myLocations, color:.red)
}
.
.
.
} else {
os_log("LocationManager: Bad Location...",log: Log.general, type: .error)
badLocationCount += 1
locChanged = false
}
}
}