How to update UIViewRepresentable with ObservableObject

I'm gonna provide a general solution for any UI/NS view representable using combine. There are performance benefits to my method.

1. Created an Observable Object and wrap the desired properties with @Published wrapper
2. Inject the Observed object via the updateView method in the view representable using a method you'll make in step 3
3. Subclass the desired view with the view model as a parameter. Create an addViewModel method and use combine operators/ subscribers and add them to cancellable.

Note - Works great with environment objects.

    struct swiftUIView : View {
      @EnvironmentObject var env : yourViewModel
      ...
      ...
          UIViewRep(wm : env)
     }

    struct UIViewRep : UIViewRepresentable {

     var wm : yourViewModel
     
     func makeUIView {
      let yv = yourView()
      yv.addViewModel(wm)
      return yv
      }}

    class yourView : UIView {
     var viewModel : yourViewModel?
     var cancellable = Set<AnyCancellable>()
     ...
     ...
     func addViewModel( _ wm : yourViewModel) {
     self.viewModel = wm

      self.viewModel?.desiredProperty
          .sink(receiveValue: { [unowned self] w in
        print("Make changes with ", w)
       }).store(in: &cancellable)
      }
    }

this solution worked for me but with EnvironmentObject https://gist.github.com/svanimpe/152e6539cd371a9ae0cfee42b374d7c4

To make sure your ObservedObject does not get created multiple times (you only want one copy of it), you can put it outside your UIViewRepresentable:

import SwiftUI
import MapKit

struct ContentView: View {
    @ObservedObject var dataSource = DataSource()

    var body: some View {
        MyView(locationCoordinates: dataSource.locationCoordinates, value: dataSource.value)
    }
}
class DataSource: ObservableObject {
    @Published var locationCoordinates = [CLLocationCoordinate2D]()
    var value: Int = 0

    init() {
        Timer.scheduledTimer(withTimeInterval: 3, repeats: true) { timer in
            self.value += 1
            self.locationCoordinates.append(CLLocationCoordinate2D(latitude: 52, longitude: 16+0.1*Double(self.value)))
        }
    }
}

struct MyView: UIViewRepresentable {
    var locationCoordinates: [CLLocationCoordinate2D]
    var value: Int

    func makeUIView(context: Context) -> MKMapView {
        MKMapView(frame: .zero)
    }

    func updateUIView(_ view: MKMapView, context: Context) {
        print("I am being called!")
        let newestCoordinate = locationCoordinates.last ?? CLLocationCoordinate2D(latitude: 52, longitude: 16)
        let annotation = MKPointAnnotation()
        annotation.coordinate = newestCoordinate
        annotation.title = "Test #\(value)"
        view.addAnnotation(annotation)
    }
}