riverpod_navigator_core 0.22.0

Navigation state management using the riverpod

Riverpod navigation

Simple but powerfull Flutter navigation with riverpod, freezed and Navigator 2.0 that solves the following:

• Strictly typed navigation:
  you can use navigate([HomeSegment(),BookSegment(id: 2)]); instead of navigate('home/book;id:2'); in your code.
• asynchronous navigation
  is the case when changing the navigation state requires asynchronous actions (such as loading or saving data from the Internet)
• multiple providers
  is the case when the navigation state depends on multiple providers
• easier coding:
  the problem of navigation is reduced to manipulation an immutable collection.
• better separation of concerns: UI x Model (thanks to riverpod 👍):
  navigation logic can be developed and tested without typing a single flutter widget.
• nested navigation
  just use the nested riverpod ProviderScope()

Two packages

Use riverpod_navigator package to develop in Flutter.

Note: Most of the code is in the riverpod_navigator_core dart library thai is independent of Flutter. riverpod_navigator addresses the connection to Flutter Navigator 2.0.

Terminology used

Take a look at the following terms related to url path home/book;id=2

• string-path: final stringPath = 'home/book;id=2';
• string-segment - the string-path consists of two slash-delimited string-segments: home and book;id=2
• typed-segment - the typed-segment (aka class TypedSegment {} ) defines string-segment: HomeSegment() and BookSegment(id:2) in this case
• typed-path: typed-path (aka typedef TypedPath = List<TypedSegment>) : [HomeSegment(), BookSegment(id:2)];
• Flutter Navigator 2.0 navigation-stack is specified by TypedPath, where each TypedPath's TypedSegment instance corresponds to a screen and page instance
  [MaterialPage (child: HomeScreen(HomeSegment())), MaterialPage (child: BookScreen(BookSegment(id:2)))].

Navigator Data Flow Diagram:

As you can see, changing the Input state starts the async calculation. The result of the calculations is Output state in navigationStackProvider and possibly app specific Side effects. Connecting navigationStackProvider to Flutter Navigator 2.0 is then easy.

The appLogic procedure returns the future with the new navigationStack and its signature is as follows:

FutureOr<TypedPath> appNavigationLogic(TypedPath oldNavigationStack, TypedPath ongoingPath)

Simple example

Step1 - imutable classes for typed-segment

We use freezed-package to generate immutable TypedSegment descendant classes.

It's a good idea to be familiar with the freezed-package (including support for JSON serialization).

From the following SegmentGrp class declaration, the freezed generates two classes: HomeSegment and PageSegment.

@freezed
class Segments with _$Segments, TypedSegment {
  Segments._();
  factory Segments.home() = HomeSegment;
  factory Segments.page({required String title}) = PageSegment;

  factory Segments.fromJson(Map<String, dynamic> json) => _$SegmentsFromJson(json);
}

Step2 - navigator parameterization

Extends the RNavigator class as follows.

class AppNavigator extends RNavigator {
  AppNavigator(Ref ref)
      : super(
          ref,
          [
            RRoutes<Segments>(Segments.fromJson, [ // json deserialize to HomeSegment or PageSegment
              RRoute<HomeSegment>(HomeScreen.new), // assign HomeScreen builder for HomeSegment
              RRoute<PageSegment>(PageScreen.new), // assign PageScreen builder for PageSegment
            ])
          ],
        );
}

Step3 - the AppNavigator in MaterialApp.router

If you are familiar with the Flutter Navigator 2.0 and the riverpod, the following code is clear:

class App extends ConsumerWidget {
  const App({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context, WidgetRef ref) => MaterialApp.router(
        title: 'Riverpod Navigator Example',
        routerDelegate: ref.navigator.routerDelegate,
        routeInformationParser: ref.navigator.routeInformationParser,
      );
}

Step4 - main entry point

void main() => runApp(
      ProviderScope(
        overrides: RNavigatorCore.providerOverrides([HomeSegment()], AppNavigator.new),
        child: const App(),
      ),
    );

And that's all

HomeScreen and PageScreen widgets and test are in the source code:

• simple.dart
• simple_test.dart

Testing

Before developing a GUI, it's a good idea to develop and test an invisible application core.

  test('navigation test', () async {
    final container = ProviderContainer(overrides: RNavigatorCore.providerOverrides([HomeSegment()], AppNavigator.new));
    final navigator = container.read(riverpodNavigatorProvider);

    Future navigTest(Future action(), String expected) async {
      await action();
      await container.pump();
      expect(navigator.navigationStack2Url, expected);
    }

    await navigTest(() => navigator.navigate([HomeSegment()]), 'home');

    await navigTest(() => navigator.navigate([HomeSegment(), PageSegment(title: 'Page')]), 'home/page;title=Page');

    await navigTest(() => navigator.pop(), 'home');

    await navigTest(() => navigator.push(PageSegment(title: 'Page2')), 'home/page;title=Page2');

    await navigTest(() => navigator.replaceLast((_) => PageSegment(title: 'Page3')), 'home/page;title=Page3');
  });

Full source code:

simple.dart, simple_test.dart

Other features doc and samples

Note: The following examples are prepared using a functional_widget package that simplifies writing widgets. The use of functional_widget is optional.

• Async navigation and splash screen
• Login flow
• More TypedSegment roots
• Nested navigation

Installation of examples

After clonning repository, go to examples\doc subdirectory and execute:

• flutter create .
• flutter pub get

You can then run the examples in the /lib subdirectory of project.

Roadmap

I prepared this package for my new project. Its further development depends on whether it will be used by the community.

• proofreading because my English is not good. Community help is warmly welcomed.
• BlockGUI widget (block the GUI while asynchronous navigation is waiting to complete)
• parameterization allowing cupertino