Clear SwiftUI list in NavigationView does not properly go back to default - swift

Question

The simple navigation demo below demonstrate an example of my issue:
A SwiftUI list inside a NavigationView is filled up with data from the data model Model.
The list items can be selected and the NavigationView is linking another view on the right (demonstrated here with destination)
There is the possibility to clear the data from the model - the SwiftUI list gets empty
The model data can be filled with new data at a later point in time
import SwiftUI
// Data model
class Model: ObservableObject {
// Example data
#Published var example: [String] = ["Data 1", "Data 2", "Data 3"]
#Published var selected: String?
}
// View
struct ContentView: View {
#ObservedObject var data: Model = Model()
var body: some View {
VStack {
// button to empty data set
Button(action: {
data.selected = nil
data.example.removeAll()
}) {
Text("Empty Example data")
}
NavigationView {
// data list
List {
ForEach(data.example, id: \.self) { element in
// navigation to "destination"
NavigationLink(destination: destination(element: element), tag: element, selection: $data.selected) {
Text(element)
}
}
}
// default view when nothing is selected
Text("Nothing selected")
}
}
}
func destination(element: String) -> some View {
return Text("\(element) selected")
}
}
What happens when I click the "Empty Example data" button is that the list will be properly cleared up. However, the selection is somehow persistent and the NavigationView will not jump back to the default view when nothing is selected:
I would expect the view Text("Nothing selected") being loaded.
Do I overlook something important?

Answer 1

When you change the data.example
in the button, the left panel changes because the List has changed.
However the right side do not, because no change has occurred there, only the List has changed.
The ForEach does not re-paint the "destination" views.
You have an "ObservedObject" and its purpose is to keep track of the changes, so using that
you can achieve what you want, like this:
import SwiftUI
#main
struct TestApp: App {
var body: some Scene {
WindowGroup {
ContentView()
}
}
}
class Model: ObservableObject {
#Published var example: [String] = ["Data 1", "Data 2", "Data 3"]
#Published var selected: String?
}
struct ContentView: View {
#StateObject var data: Model = Model()
var body: some View {
VStack {
Button(action: {
data.selected = nil
data.example.removeAll()
}) {
Text("Empty Example data")
}
NavigationView {
List {
ForEach(data.example, id: \.self) { element in
NavigationLink(destination: DestinationView(),
tag: element,
selection: $data.selected) {
Text(element)
}
}
}
Text("Nothing selected")
}.environmentObject(data)
}
}
}
struct DestinationView: View {
#EnvironmentObject var data: Model
var body: some View {
Text("\(data.selected ?? "")")
}
}