SwiftUI: detecting the NavigationView back button press

Question

In SwiftUI I couldn't find a way to detect when the user taps on the default back button of the navigation view when I am inside DetailView1 in this code:

struct RootView: View {
    @State private var showDetails: Bool = false
    var body: some View {
        NavigationView {
            VStack {
                NavigationLink(destination: DetailView1(), isActive: $showDetails) {
                    Text("show DetailView1")
                }
            }
            .navigationBarTitle("RootView")
        }
    }
}

struct DetailView1: View {
    @State private var showDetails: Bool = false
    var body: some View {
        NavigationLink(destination: DetailView2(), isActive: $showDetails) {
            Text("show DetailView2")
        }
        .navigationBarTitle("DetailView1")
    }
}

struct DetailView2: View {
    var body: some View {
        Text("")
            .navigationBarTitle("DetailView2")
    }
}

Using .onDisappear doesn't solve the problem as its closure is called when the view is popped off or a new view is pushed.

Answer 1

The quick solution is to create a custom back button because right now the framework have not this possibility.

struct DetailView : View {

    @Environment(\.presentationMode) var mode: Binding<PresentationMode>

    var body : some View {
        Text("Detail View")
            .navigationBarBackButtonHidden(true)
            .navigationBarItems(leading: Button(action : {
                self.mode.wrappedValue.dismiss()
            }){
                Image(systemName: "arrow.left")
            })
    }
}

Answer 2

As soon as you press the back button, the view sets isPresented to false, so you can use an observer on that value to trigger code when the back button is pressed. Assume this view is presented inside a navigation controller:

struct MyView: View {
    @Environment(\.isPresented) var isPresented

    var body: some View {
        Rectangle().onChange(of: isPresented) { newValue in
            if !newValue {
                print("detail view is dismissed")
            }
        }
    }
}