SwiftUI Listeners/Observation Trouble

Question

I'm having an issue where my listener doesn't update my UI correctly when I define my data structure as a class, but works properly when it is a struct.

func addUserListener(owner: Bool) {
    guard let lobby = currentLobby else {
        print("No Current Lobby! | Add Listener")
        return
    }
  
    userListener = LobbyManager.shared.addUsersListener(lobbyNumber: lobby.number, owner: owner) { [weak self] users in
            guard let self = self, self.userActive else {
                return
            }
            
            print("User Listener Fired!")
        DispatchQueue.main.async {
            //print("Current values: \( self.currentLobby?.users)")
            //print("Returned Users: \(users)")
            
            self.currentLobby?.users = users
            
            print("Lobby Users: \(self.currentLobby?.users)")

        }
        
      
        
            
        }
        
    }

In this section the self.currentLobby?.users is being updated correctly but the changes are not displayed to the user unless lobby is a struct.

class Lobby: ObservableObject {
let number : Int
@Published var users : [DBUser]
@Published var userCount : Int

@MainActor
final class LobbyViewModel : ObservableObject {
    //@Published private(set) var currentLobby: Lobby? = nil
    @Published var currentLobby: Lobby? = nil
    @Published var userListener: ListenerRegistration?
    @Published var lobbyListener: ListenerRegistration?
    var live: Bool = true
    var userActive = true
    var lobbyActive = true

Both the lobby and lobbyViewModel are declared as ObservableObjects with published properties. Thanks for any help.

Answer 1

This issue arises because even though the properties of LobbyViewModel change, the reference to the Lobby instance itself does not change. Therefore, LobbyViewModel's @Published var Lobby does not detect changes within Lobby. In other words, it's a form of broken reference, not because of the listener. While this isn't a particularly recommended data structure, if such a structure is necessary, there might be a way to resolve it as follows:

class LobbyViewModel: ObservableObject {
    @Published var lobby: Lobby = Lobby()
    @Published var counter: Int = 0
    
    func updateUserCount(){
        lobby.userCount += 1
        // It's a way to trigger a functionality similar to @Published.
        objectWillChange.send()
    }
  
}

class Lobby: ObservableObject {
    @Published var number : Int = 0
    @Published var userCount : Int = 0
    
}

struct ContentView: View {
    @StateObject var vm :LobbyViewModel = LobbyViewModel()
    
    var body: some View {
        
        VStack{
            Text("\(vm.lobby.userCount)")
            
            Button {
                vm.updateUserCount()
            } label: {
                Text("Click Here")
            }
            
        }
    }
}

This code is an example written based on your code. Use it for reference.