strangeliu/navigationbackport

Backported SwiftUI navigation APIs introduced in WWDC22

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 and watchOS.

✅ NavigationStack -> NBNavigationStack

✳️ NavigationSplitView -> NBNavigationSplitView (Only support double column style by now)

✅ NavigationLink -> NBNavigationLink

✅ NavigationPath -> NBNavigationPath

✅ navigationDestination -> nbNavigationDestination

You can migrate to these APIs now, and when you eventually bump your deployment target to iOS 16, you can remove this library and easily migrate to its SwiftUI equivalent. You can initialise NBNavigationStack with a binding to an Array, a NBNavigationPath binding, or neither.

Example

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, goBackToRoot: { path.removeLast(path.count) })
        })
        .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 {
  let number: Int
  let goBackToRoot: () -> Void

  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: goBackToRoot)
    }.navigationTitle("\(number)")
  }
}

struct EmojiVisualisation: Hashable {
  let emoji: Character
  let count: Int
}

struct EmojiView: View {
  let visualisation: EmojiVisualisation

  var body: some View {
    Text(String(Array(repeating: visualisation.emoji, count: visualisation.count)))
      .navigationTitle("Visualise \(visualisation.count)")
  }
}

Deep-linking

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 provides an API to work around this limitation: you can wrap such path changes within a call to withDelaysIfUnsupported, and the library will, if necessary, break down the larger update into a series of smaller updates that SwiftUI supports, with delays in between. For example, the following code that tries to push three screens in one update will not work:

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

However, the following code will successfully push all three screens, one after another:

$path.withDelaysIfUnsupported {
  $0.append(Screen.orders)
  $0.append(Screen.editOrder(id: id))
  $0.append(Screen.confirmChanges(orderId: id))
}

You can make any changes to the path passed into the withDelaysIfUnsupported closure, and the library will calculate the minimal number of state updates required to successfully update the UI.

To do

The package is not yet fully complete. Here are some outstanding tasks:

• Codable support for NavigationPath
• Codable support for NavigationLink
• Backport NavigationSplitView
• Conditionally use SwiftUI Navigation API if available?