SwiftUI: ObservableObject does not persist its State over being redrawn

Finally, there is a Solution provided by Apple: @StateObject.

By replacing @ObservedObject with @StateObject everything mentioned in my initial post is working.

Unfortunately, this is only available in ios 14+.

This is my Code from Xcode 12 Beta (Published June 23, 2020)

struct ContentView: View {

    @State var title = 0

    var body: some View {
        NavigationView {
            VStack {
                Button("Test") {
                    self.title = Int.random(in: 0...1000)
                }

                TestView1()

                TestView2()
            }
            .navigationTitle("\(self.title)")
        }
    }
}

struct TestView1: View {

    @ObservedObject var model = ViewModel()

    var body: some View {
        VStack {
            Button("Test1: \(self.model.title)") {
                self.model.title += 1
            }
        }
    }
}

class ViewModel: ObservableObject {

    @Published var title = 0
}

struct TestView2: View {

    @StateObject var model = ViewModel()

    var body: some View {
        VStack {
            Button("StateObject: \(self.model.title)") {
                self.model.title += 1
            }
        }
    }
}

As you can see, the StateObject Keeps it value upon the redraw of the Parent View, while the ObservedObject is being reset.

I agree with you, I think this is one of many major problems with SwiftUI. Here's what I find myself doing, as gross as it is.

struct MyView: View {
  @State var viewModel = MyViewModel()

  var body : some View {
    MyViewImpl(viewModel: viewModel)
  }
}

fileprivate MyViewImpl : View {
  @ObservedObject var viewModel : MyViewModel

  var body : some View {
    ...
  }
}

You can either construct the view model in place or pass it in, and it gets you a view that will maintain your ObservableObject across reconstruction.