Select Markers of different types on SwiftUI Map

In the view described in the following code, I would like to be able to select a marker, no matter if the marker is a Place or an Accommodation. Both Place and Accommodation are defined as classes with different fields. Both of them have latitude, and longitude. But I can only make one of them selectable depending on which one I put on this line

Map(position: $cameraPosition, selection: $selectedAccommodation) 

or

Map(position: $cameraPosition, selection: $selectedAccommodation) 

import SwiftUI
import MapKit

struct DestinationMapView: View {
    var destination: Destination
    @State private var cameraPosition: MapCameraPosition = .automatic
    @State private var selectedPlace: Place?
    @State private var selectedAccommodation: Accommodation?
    //@State private var selectedPlace: SelectablePlace?
    var body: some View {
        Map(position: $cameraPosition, selection: $selectedPlace) {
            ForEach(destination.accommodations ?? []) { accommodation in
                Group {
                    if let lat = accommodation.latitude, let lon = accommodation.longitude {
                        Marker(accommodation.name, systemImage: "bed.double.fill", coordinate: CLLocationCoordinate2D(latitude: lat, longitude: lon))
                            .tint(.blue)
                    }
                }
                .tag(accommodation)
            }
            ForEach(destination.places ?? []) { place in
                Group {
                    if let lat = place.latitude, let lon = place.longitude {
                        Marker(place.name, systemImage: place.placeType.systemImage, coordinate: CLLocationCoordinate2D(latitude: lat, longitude: lon))
                    }
                }
                .tag(place)
            }
        }
        .sheet(item: $selectedPlace) { selectedPlace in
            Text("Selected Place")
                .presentationDetents([.medium, .large])
                .presentationDragIndicator(.visible)
        }
        .sheet(item: $selectedAccommodation) { selectedAccommodation in
            Text("Selected Accommodation")
                .presentationDetents([.medium, .large])
                .presentationDragIndicator(.visible)
        }
        .onAppear {
            if let coordinateRegion = destination.coordinateRegion {
                cameraPosition = MapCameraPosition.region(coordinateRegion)
            }
        }
    }
}

How can add the capability to select the marker no matter if it's of Place type or Accommodation type?

Try this approach using a dedicated Selection that holds the kind and the id of the selected Accommodation or Place. Adjust the code as required.

enum MarkerType { // <--- here
    case place
    case accommodation
}

struct Selection: Identifiable, Hashable { // <--- here
    let id: UUID
    let kind: MarkerType
}

struct DestinationMapView: View {
    var destination: Destination
    @State private var cameraPosition: MapCameraPosition = .automatic
    @State private var selectedPlace: Place?
    @State private var selectedAccommodation: Accommodation?
    
    @State private var selection: Selection?  // <--- here
    
    var body: some View {
        Map(position: $cameraPosition, selection: $selection) {  // <--- here
            ForEach(destination.accommodations ?? []) { accommodation in
                Group {
                    if let lat = accommodation.latitude, let lon = accommodation.longitude {
                        Marker(accommodation.name, systemImage: "bed.double.fill", coordinate: CLLocationCoordinate2D(latitude: lat, longitude: lon))
                            .tint(.blue)
                    }
                }
                .tag(Selection(id: accommodation.id, kind: .accommodation))
            }
            ForEach(destination.places ?? []) { place in
                Group {
                    if let lat = place.latitude, let lon = place.longitude {
                        Marker(place.name, systemImage: place.placeType, coordinate: CLLocationCoordinate2D(latitude: lat, longitude: lon))
                    }
                }
                .tag(Selection(id: place.id, kind: .place))
            }
        }
        .sheet(item: $selection) { selection in  // <--- here
            if selection.kind == .accommodation {
                Text("Selected Accommodation: \(getAccomodation(selection)?.name ?? "no name")")
                    .presentationDetents([.medium, .large])
                    .presentationDragIndicator(.visible)
            } else {
                Text("Selected Place: \(getPlace(selection)?.name ?? "no name")")
                    .presentationDetents([.medium, .large])
                    .presentationDragIndicator(.visible)
            }
        }
        .onAppear {
            if let coordinateRegion = destination.coordinateRegion {
                cameraPosition = MapCameraPosition.region(coordinateRegion)
            }
        }
    }
    
    // --- here
    func getAccomodation(_ selection: Selection?) -> Accommodation? {
        if let select = selection, let acc = destination.accommodations?.first(where: {$0.id == select.id})
        {
            return acc
        }
        return nil
    }
    
    func getPlace(_ selection: Selection?) -> Place? {
        if let select = selection, let place = destination.places?.first(where: {$0.id == select.id})
        {
            return place
        }
        return nil
    }

}

// --- for testing
struct ContentView: View {
    let destination = Destination(accommodations: [ Accommodation(name: "acc-1", latitude: 51.515, longitude: -0.117),
                                                    Accommodation(name: "acc-2", latitude: 51.516, longitude: -0.118),
                                                    Accommodation(name: "acc-3", latitude: 51.517, longitude: -0.119)],
                                  places: [ Place(name: "place-1", latitude: 51.525, longitude: -0.127),
                                            Place(name: "place-2", latitude: 51.526, longitude: -0.128),
                                            Place(name: "place-3", latitude: 51.527, longitude: -0.129)],
                                  coordinateRegion: MKCoordinateRegion(center: CLLocationCoordinate2D(latitude: 51.52, longitude: -0.116), latitudinalMeters: 3500, longitudinalMeters: 3500))
    
    var body: some View {
        DestinationMapView(destination: destination)
    }
}

struct Place: Identifiable {
    let id = UUID()
    var name: String
    var latitude: Double?
    var longitude: Double?
    var placeType: String = "house" // <--- for testing
}

struct Accommodation: Identifiable {
    let id = UUID()
    var name: String
    var latitude: Double?
    var longitude: Double?
}

struct Destination: Identifiable {
    let id = UUID()
    var accommodations: [Accommodation]?
    var places: [Place]?
    var coordinateRegion: MKCoordinateRegion?
}