Navigator

0.2.0

Navigation library for SwiftUI
flopshot/Navigator

What's New

0.2.0

2022-03-02T22:14:09Z

Changes:

  • Added NavigationView.with(_:) method for better library initialization
  • Updated ScreenView protocol with better naming

Navigator

ci workflow swift v5.5 Platforms: iOS, watchOS deployment target iOS 14, watchOS 7

A navigation library that decouples Navigation logic in SwiftUI from the View and allows you to dynamically navigate to other Views programatically in your app.

  • Uses native SwiftUI navigation
  • No custom 3rd party navigation
  • Retains Navigation back button
  • Retains swipe-to-dismiss
  • Light weight, no wrapper views

Features

  1. Navigation Stack: Stores the state of SwiftUI navigation for your app
  2. Dynamic Navigation: Full programatic navigation at runtime. No static hardcoded view destinations necessary
  3. Simple navigation APIs out of the box: navigate(to:) pop() popToRoot()
struct DetailScreen: ScreenView {
    @EnvironmentObject var navigator: Navigator<ScreenID, AppViewFactory>    
    @State var showNextScreen: Bool = false
    var screenId: ScreenID
    
    var body: some View {
        Button("Next") {
            navigator.navigate(to: anotherScreen())
        }
        .navigationTitle("Detail Screen")
        .bindNavigation(self, binding: $showNextScreen)
    }
}

Setup

1. Create a ViewFactory

Create an enum that that maps to the screens in your app along with any needed values. Ensure that it conforms to Hashable

enum ScreenID: Hashable {
    case rootScreen
    case detailScreen(detailID: String)
}

Then create a class that conforms to ViewFactory and implement makeView(screenType:) so that the given ScreenID enum returns the associated View.

class AppViewFactory: ViewFactory {
    
    @ViewBuilder
    func makeView(screenType: ScreenWrapper<ScreenID>) -> some View {
        switch screenType {
        case .screenWrapper(let screenId):
            switch screenId {
            case .rootScreen:
                RootScreen()
            case .detailScreen:
                DetailScreen(currentScreen: screenId!)
            case .none:
            // EmptyView is fine in the exhaustive case
            // as this is just a placeholder until the 
            // Navigation state is instantiated. The
            // app will never need to navigate to this
                EmptyView()
            }
        }
    }
}

2. Initialize Library

In the @main app delcaration, where your root view is the top level view in the navigation stack (or wherever you'd like to place a NavigationView with programatic navigation) initialize the NavigationView using the with(_:) method to inject your instance of Navigator

@main
struct MyApp: App {
    var body: some Scene {
        WindowGroup {
            NavigationView.with(Navigator(rootScreen: ScreenID.rootScreen, viewFactory: AppViewFactory()) {
                RootScreen()
            }    
        }
    }
}

3. Conform app top level views to ScreenView

For each top level view, conform them to ScreenView and apply the bindNavigation(_:binding:) view modifier

struct RootScreen: ScreenView {
    @EnvironmentObject var navigator: Navigator<ScreenID, AppViewFactory>    
    @State var showNextScreen: Bool = false
    var screenId = .rootScreen
    
    var body: some View {
        List {
            Button("Navigate to Deatil Screen") {
                // TODO
            }
        }
        .navigationTitle("Root Screen")
        .bindNavigation(self, binding: $showNextScreen)
    }
}
struct DetailScreen: ScreenView {
    @EnvironmentObject var navigator: Navigator<ScreenID, AppViewFactory>    
    @State var showNextScreen: Bool = false
    var screenId: ScreenID
    
    var body: some View {
        VStack {
            Text("Here is some amazing detail.")
            
            Button("Go Back") {
                // TODO
            }
            .tint(.red)
            .buttonStyle(.borderedProminent)
            .buttonBorderShape(.automatic)
            .controlSize(.large)
        }
        .navigationTitle("Detail Screen")
        .bindNavigation(self, binding: $showNextScreen)
    }
}

Note that except for the RootScreen all other screens should have an id in their ScreenID enum value in order to differentiate same screens in the navigation stack. This can be in the form of a business logic id detailID or some deafult id that has no business logic but merely used to id the screen

enum ScreenID: Hashable {
    // ...
    case anotherScreen(id: UUID = UUID())
}

4. Use the Navigator instance for navigation

Now that all the setup is done, we can use the Navigator instance in the ScreenView View to execute system level View navigation

struct RootScreen: ScreenView {
    @EnvironmentObject var navigator: Navigator<ScreenID, AppViewFactory>
    @State var showNextScreen: Bool = false
    var screenId = .rootScreen
    
    var body: some View {
        List {
            Button("Navigate to Deatil Screen") {
                // Use navigate(to:) to navigate to another ScreenView
                
                // This can be anywhere at the view level
                
                // This can also be called at an abstraction layer like a ViewModel
                
                navigator.navigate(to: ScreenID.detailScreen(detailID: "detail-123"))
            }
        }
        .navigationTitle("Root Screen")
        .bindNavigation(self, binding: $showNextScreen)
    }
}
struct DetailScreen: ScreenView {
    @EnvironmentObject var navigator: Navigator<ScreenID, AppViewFactory>
    @State var showNextScreen: Bool = false
    var screenId: ScreenID
    
    var body: some View {
        VStack {
            Text("Here is some amazing detail.")
            
            Button("Go Back") {
                // Use pop() to navigate back to the
                // previous view by popping the current
                navigator.pop()
            }
            .tint(.red)
            .buttonStyle(.borderedProminent)
            .buttonBorderShape(.automatic)
            .controlSize(.large)
        }
        .navigationTitle("Detail Screen")
        .bindNavigation(self, binding: $showNextScreen)
    }
}

Advanced

As stated previously, the Navigator class has the property navStack which keeps a stack (OrderedDictionary) of the ScreenView associated ScreenID enum values that are currently active in the NavigationView. Clients can use it to execte custom navigation logic.

    /// Holds the ordered uniqe set of screens that makes up the Navigation State of the client app,
    /// along with its associated Boolean subject, which toggles the NavigationLink.isActive
    var navStack: OrderedDictionary<ScreenIdentifer, CurrentValueSubject<Bool, Never>> { get }
    

As an example, we can use it create an extention funtion on Navigator called popToDetailWithSpecificIdOrRoot(id: String)

extension Navigator where ScreenIdentifer == ScreenID {
    func popToDetailWithSpecificIdOrRoot(id: String) {
    
        // Since all screens that have been pushed onto the NavigationView
        // are stored in the navStack as keys, we can simply search through
        // them for the specific detail screen with the called id
        
        if let detailScreen: ScreenID = navStack.keys.elements.first(where: {
            if case ScreenID.detailScreen(let detailID) = $0 { 
                return detailID == id 
            }
            return false
        }) {
        
            // Using the first(where:) collections function
            // if we find the detail screen with the called id
            // then the navStack Dictionary can be keyed
            // on the found detailScreen to return the Combine subject
            // that controls the NavigationLink.isActive binding
            // for that detailScreen
            let detailScreenIsActiveBinding = navStack[detailScreen]!
            
            // Sending the false flag to the NavigationLink.isActive binding
            // will dismiss all views off the NavigationView stack to reveal
            // the detailScreen
            detailScreenIsActiveBinding.send(false)
        } else {
        
            // if the detail screen is not found in the current stack
            // then we default to pop all views off the stack to reveal the
            // rootScreen view
            let rootScreenNavigationIsActiveBinding = navStack.elements[0]
            rootScreenNavigationIsActiveBinding.value.send(false)
            
            // could also call self.popToRoot()
        }
    }
}

Because the Navigator class can be a singleton not copuled to any specific view, we can call popToDetailWithSpecificIdOrRoot(id:) anywhere in the app.

@main
struct MyApp: App {

    // Keep reference to the navigator, either as a local property or in an abstraction
    // layer, such as an AppCoordinator
    let navigator = Navigator(rootScreen: ScreenID.rootScreen, viewFactory: AppViewFactory())

    var body: some Scene {
        WindowGroup {
            NavigationView.with(navigator) {
                RootScreen()
            }          
            .task {
                // mimic a system event, such as a notification 
                    
                // create an artificial delay of 10 seconds after the app starts up
                try! await Task.sleep(nanoseconds: 10_000_000_000)
                 
                // User navigates to different views, adding to the navStack
                
                // However far along the user is, this will pop to the first 
                // detailScreen with called id, or pop to the root screen
                navigator.popToDetailWithSpecificIdOrRoot(id: "detail-123")
            }
        }
    }
}

Acknowledgements

Big thanks to Obsured Pixels' excellent article, which inspired this library.

Description

  • Swift Tools 5.5.0
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Dependencies

Last updated: Tue Feb 27 2024 13:51:30 GMT-1000 (Hawaii-Aleutian Standard Time)