SwiftUI changes in model not updating view

Question

I use URLSession to connect to a websocket server. With the callback functions I update the var "isConnectionOpen" inside the Model/Service. Even though I use the @Published modifier the update is not redrawing my view. Below you can find a short overview.

Model

var isConnectionOpen = false
func openConnection()

    // callback functions
    func urlSession(_ session: URLSession, webSocketTask: URLSessionWebSocketTask, didOpenWithProtocol protocol: String?) {
        print("WebSocket connection opened")
isConnectionOpen = true
}

ViewModel

@Published var model = Model()

View

@ObservedObject var vm: VM

var body: some View {
    Text(vm.model.isConnectionOpen ? "Connected" : "Not connected")
}

Is you model a struct or a class?

cedricbahirwe
– cedricbahirwe

2022-04-25 15:47:27 +00:00
Commented Apr 25, 2022 at 15:47 — cedricbahirwe
– cedricbahirwe, Commented Apr 25, 2022 at 15:47

Afrcvn · Accepted Answer · 2022-04-25 20:22:57Z

here is an example of using @ObservedObject in the parent view you have to declare the object as @StateObject

 class Model: ObservableObject{
    @Published var isConnectionOpen = false
    
    func openConnection(){
        // ...
        // if is completed set isConnectionOpen = true
        isConnectionOpen = true

    }
}

struct ChildView: View{
    @ObservedObject var model: Model

    var body: some View {
        VStack{
            Button("tap-to-connect"){
                model.openConnection()
            }
            Text(model.isConnectionOpen ? "Connected" : "Not connected")

        }
    }
}

struct ParentView: View {
    @StateObject var model = Model()
    var body: some View{
        ChildView(model: model)
//            .onAppear(perform: {
//                // Mark: Connect to server
//                model.openConnection()
//            })
    }

}

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