Navigation Backport

This package uses the navigation APIs available in older SwiftUI versions (such as NavigationView and NavigationLink) to recreate the new NavigationStack APIs introduced in WWDC22, so that you can start targeting those APIs on older versions of iOS, tvOS, macOS and watchOS. When running on an OS version that supports NavigationStack, NavigationStack will be used under the hood.

✅ NavigationStack -> NBNavigationStack

✅ NavigationLink -> NBNavigationLink

✅ NavigationPath -> NBNavigationPath

✅ navigationDestination -> nbNavigationDestination

✅ NavigationPath.CodableRepresentation -> NBNavigationPath.CodableRepresentation

You can migrate to these APIs now, and when you eventually bump your deployment target, you can remove this library and easily migrate to its SwiftUI equivalent. NavigationStack's full API is replicated, so you can initialise an NBNavigationStack with a binding to an Array, with a binding to an NBNavigationPath binding, or with no binding at all.

import NavigationBackport
import SwiftUI

struct ContentView: View {
  @State var path = NBNavigationPath()

  var body: some View {
    NBNavigationStack(path: $path) {
      HomeView()
        .nbNavigationDestination(for: NumberList.self, destination: { numberList in
          NumberListView(numberList: numberList)
        })
        .nbNavigationDestination(for: Int.self, destination: { number in
          NumberView(number: number)
        })
        .nbNavigationDestination(for: EmojiVisualisation.self, destination: { visualisation in
          EmojiView(visualisation: visualisation)
        })
    }
  }
}

struct HomeView: View {
  var body: some View {
    VStack(spacing: 8) {
      NBNavigationLink(value: NumberList(range: 0 ..< 100), label: { Text("Pick a number") })
    }.navigationTitle("Home")
  }
}

struct NumberList: Hashable {
  let range: Range<Int>
}

struct NumberListView: View {
  let numberList: NumberList
  var body: some View {
    List {
      ForEach(numberList.range, id: \.self) { number in
        NBNavigationLink("\(number)", value: number)
      }
    }.navigationTitle("List")
  }
}

struct NumberView: View {
  @EnvironmentObject var navigator: PathNavigator
  
  let number: Int

  var body: some View {
    VStack(spacing: 8) {
      Text("\(number)")
      NBNavigationLink(
        value: number + 1,
        label: { Text("Show next number") }
      )
      NBNavigationLink(
        value: EmojiVisualisation(emoji: "🐑", count: number),
        label: { Text("Visualise with sheep") }
      )
      Button("Go back to root", action: { navigator.popToRoot() })
    }.navigationTitle("\(number)")
  }
}

struct EmojiVisualisation: Hashable {
  let emoji: String
  let count: Int
  
  var text: String {
    Array(repeating: emoji, count: count).joined()
  }
}

struct EmojiView: View {
  let visualisation: EmojiVisualisation

  var body: some View {
    Text(visualisation.text)
      .navigationTitle("Visualise \(visualisation.count)")
  }
}

As well as replicating the standard features of the new NavigationStack APIs, some helpful utilities have also been added.

A Navigator object is available through the environment, giving access to the current navigation path. The navigator can be accessed via the environment, e.g. for a NBNavigationPath-backed stack:

@EnvironmentObject var navigator: PathNavigator

Or for a stack backed by an Array, e.g. [ScreenType]:

@EnvironmentObject var navigator: Navigator<ScreenType>

As well as allowing you to inspect the path elements, the navigator can be used to push new screens, pop, pop to a specific screen or pop to the root.

Whether interacting with an Array, an NBNavigationPath, or a Navigator, a number of utility functions are available for easier navigation, such as:

path.push(Profile(name: "John"))

path.pop()

path.popToRoot()

path.popTo(Profile.self)

Note that, if you want to use these methods on an Array, ensure the Array's Element conforms to NBScreen, a protocol that inherits from Hashable without adding any additional requirements. This avoids polluting all arrays with APIs specific to navigation.

Before NavigationStack, SwiftUI did not support pushing more than one screen in a single state update, e.g. when deep-linking to a screen multiple layers deep in a navigation hierarchy. NavigationBackport works around this limitation: you can make any such path changes, and the library will, behind the scenes, break down the larger update into a series of smaller updates that SwiftUI supports if necessary, with delays in between. For example, the following code that pushes three screens in one state update will push the screens one by one if needed:

  path.append(Screen.orders)
  path.append(Screen.editOrder(id: id))
  path.append(Screen.confirmChanges(orderId: id))

This only happens when necessary: on versions of SwiftUI that support NavigationStack, all three screens will be pushed successfully in one update.

This library targets iOS/tvOS versions 14 and above, since it uses StateObject, which is unavailable on iOS/tvOS 13. However, there is an ios13 branch, which uses SwiftUIBackports' backported StateObject, so that it works on iOS/tvOS 13 too.