Cross navigation with NavigationView - swiftui

Question

I have the following structure
enum Page {
case chapter1
case chapter2
}
struct ContentView: View {
#State var page: Page? = nil
var body: some View {
NavigationView {
VStack {
NavigationLink(destination: Chapter1(page: self.$page),
tag: .chapter1,
selection: self.$page) {
Text("Chapter 1")
}
NavigationLink(destination: Chapter2(page: self.$page),
tag: .chapter2,
selection: self.$page) {
Text("Chapter 2")
}
}
}
}
}
struct Chapter1: View {
#Binding var page: Page?
var body: some View {
VStack {
Button("Back to Overview") {
self.page = nil
}
Button("Chapter 2") {
self.page = .chapter2
}
}
}
}
struct Chapter2: View {
#Binding var page: Page?
var body: some View {
VStack {
Button("Back to Overview") {
self.page = nil
}
}
}
}
The moment I go from Chapter1 directly to Chapter2 it breaks the backlink in Chaper2.
Firstly, what is the reason for that?
Secondly, is there a way to transition from Chapter1 to Chapter2 with a different kind of animation, instead of duplicate back-and-forth flip?

Answer 1

The NavigationView manger links on per-level base, so modifying other stack level can result it unexpected behaviour.
Here is a solution for the described use-case. Tested with Xcode 11.4 / iOS 13.4
struct TestNavigationByEnum: View {
#State var page: Page? = nil
var body: some View {
NavigationView {
VStack {
NavigationLink(destination: Chapter1(page: self.$page),
tag: .chapter1,
selection: self.$page) {
Text("Chapter 1")
}.isDetailLink(false) // important !!
NavigationLink(destination: Chapter2(page: self.$page),
tag: .chapter2,
selection: self.$page) {
Text("Chapter 2")
}.isDetailLink(false)
}
}
}
}
struct Chapter1: View {
#Binding var page: Page?
var body: some View {
VStack {
Button("Back to Overview") {
self.page = nil
}
// own level link
NavigationLink(destination: Chapter2(page: self.$page)) {
Text("Chapter 2")
}.isDetailLink(false)
}
}
}