Usage

Dependencies

To use go_router_builder, you need to have the following dependencies in pubspec.yaml.

dependencies:
  # ...along with your other dependencies
  go_router: ^9.0.3

dev_dependencies:
  # ...along with your other dev-dependencies
  build_runner: ^2.0.0
  go_router_builder: ^2.3.0

Source code

Instructions below explain how to create and annotate types to use this builder. Along with importing the go_router.dart library, it's essential to also include a part directive that references the generated Dart file. The generated file will always have the name [source_file].g.dart.

import 'package:go_router/go_router.dart';

part 'readme_excerpts.g.dart';

Running build_runner

To do a one-time build:

dart run build_runner build

Read more about using build_runner on pub.dev.

Overview

go_router fundamentally relies on the ability to match a string-based location in a URI format into one or more page builders, each that require zero or more arguments that are passed as path and query parameters as part of the location. go_router does a good job of making the path and query parameters available via the pathParameters and queryParameters properties of the GoRouterState object, but often the page builder must first parse the parameters into types that aren't Strings, e.g.

GoRoute(
  path: ':familyId',
  builder: (BuildContext context, GoRouterState state) {
    // Require the familyId to be present and be an integer.
    final int familyId = int.parse(state.pathParameters['familyId']!);
    return FamilyScreen(familyId);
  },
);

In this example, the familyId parameter is a) required and b) must be an int. However, neither of these requirements are checked until run-time, making it easy to write code that is not type-safe, e.g.

void tap() =>
    context.go('/familyId/a42'); // This is an error: `a42` is not an `int`.

Dart's type system allows mistakes to be caught at compile-time instead of run-time. The goal of the routing is to provide a way to define the required and optional parameters that a specific route consumes and to use code generation to take out the drudgery of writing a bunch of go, push and location boilerplate code implementations ourselves.

Defining a route

Define each route as a class extending GoRouteData and overriding the build method.

class HomeRoute extends GoRouteData {
  const HomeRoute();

  @override
  Widget build(BuildContext context, GoRouterState state) => const HomeScreen();
}

Route tree

The tree of routes is defined as an attribute on each of the top-level routes:

@TypedGoRoute<HomeRoute>(
  path: '/',
  routes: <TypedGoRoute<GoRouteData>>[
    TypedGoRoute<FamilyRoute>(
      path: 'family/:fid',
    ),
  ],
)
class HomeRoute extends GoRouteData {
  const HomeRoute();

  @override
  Widget build(BuildContext context, GoRouterState state) => const HomeScreen();
}

class RedirectRoute extends GoRouteData {
  // There is no need to implement [build] when this [redirect] is unconditional.
  @override
  String? redirect(BuildContext context, GoRouterState state) {
    return const HomeRoute().location;
  }
}

@TypedGoRoute<LoginRoute>(path: '/login')
class LoginRoute extends GoRouteData {
  LoginRoute({this.from});
  final String? from;

  @override
  Widget build(BuildContext context, GoRouterState state) {
    return LoginScreen(from: from);
  }
}

GoRouter initialization

The code generator aggregates all top-level routes into a single list called $appRoutes for use in initializing the GoRouter instance:

final GoRouter router = GoRouter(routes: $appRoutes);

Error builder

One can use typed routes to provide an error builder as well:

class ErrorRoute extends GoRouteData {
  ErrorRoute({required this.error});
  final Exception error;

  @override
  Widget build(BuildContext context, GoRouterState state) {
    return ErrorScreen(error: error);
  }
}

With this in place, you can provide the errorBuilder parameter like so:

final GoRouter routerWithErrorBuilder = GoRouter(
  routes: $appRoutes,
  errorBuilder: (BuildContext context, GoRouterState state) {
    return ErrorRoute(error: state.error!).build(context, state);
  },
);

Navigation

Navigate using the go or push methods provided by the code generator:

void onTap() => const FamilyRoute(fid: 'f2').go(context);

If you get this wrong, the compiler will complain:

// This is an error: missing required parameter 'fid'.
void errorTap() => const FamilyRoute().go(context);

This is the point of typed routing: the error is found statically.

Return value

Starting from go_router 6.5.0, pushing a route and subsequently popping it, can produce a return value. The generated routes also follow this functionality.

final bool? result =
    await const FamilyRoute(fid: 'John').push<bool>(context);

Query parameters

Parameters (named or positional) not listed in the path of TypedGoRoute indicate query parameters:

@TypedGoRoute<LoginRoute>(path: '/login')
class LoginRoute extends GoRouteData {
  LoginRoute({this.from});
  final String? from;

  @override
  Widget build(BuildContext context, GoRouterState state) {
    return LoginScreen(from: from);
  }
}

Default values

For query parameters with a non-nullable type, you can define a default value:

@TypedGoRoute<MyRoute>(path: '/my-route')
class MyRoute extends GoRouteData {
  MyRoute({this.queryParameter = 'defaultValue'});
  final String queryParameter;

  @override
  Widget build(BuildContext context, GoRouterState state) {
    return MyScreen(queryParameter: queryParameter);
  }
}

A query parameter that equals to its default value is not included in the location.

Extra parameter

A route can consume an extra parameter by taking it as a typed constructor parameter with the special name $extra:

class PersonRouteWithExtra extends GoRouteData {
  PersonRouteWithExtra(this.$extra);
  final Person? $extra;

  @override
  Widget build(BuildContext context, GoRouterState state) {
    return PersonScreen($extra);
  }
}

Pass the extra param as a typed object:

void tapWithExtra() {
  PersonRouteWithExtra(Person(id: 1, name: 'Marvin', age: 42)).go(context);
}

The $extra parameter is still passed outside the location, still defeats dynamic and deep linking (including the browser back button) and is still not recommended when targeting Flutter web.

Mixed parameters

You can, of course, combine the use of path, query and $extra parameters:

@TypedGoRoute<HotdogRouteWithEverything>(path: '/:ketchup')
class HotdogRouteWithEverything extends GoRouteData {
  HotdogRouteWithEverything(this.ketchup, this.mustard, this.$extra);
  final bool ketchup; // A required path parameter.
  final String? mustard; // An optional query parameter.
  final Sauce $extra; // A special $extra parameter.

  @override
  Widget build(BuildContext context, GoRouterState state) {
    return HotdogScreen(ketchup, mustard, $extra);
  }
}

This seems kinda silly, but it works.

Redirection

Redirect using the location property on a route provided by the code generator:

redirect: (BuildContext context, GoRouterState state) {
  final bool loggedIn = loginInfo.loggedIn;
  final bool loggingIn = state.matchedLocation == LoginRoute().location;
  if (!loggedIn && !loggingIn) {
    return LoginRoute(from: state.matchedLocation).location;
  }
  if (loggedIn && loggingIn) {
    return const HomeRoute().location;
  }
  return null;
},

Route-level redirection

Handle route-level redirects by implementing the redirect method on the route:

class RedirectRoute extends GoRouteData {
  // There is no need to implement [build] when this [redirect] is unconditional.
  @override
  String? redirect(BuildContext context, GoRouterState state) {
    return const HomeRoute().location;
  }
}

Type conversions

The code generator can convert simple types like int and enum to/from the String type of the underlying pathParameters:

enum BookKind { all, popular, recent }

class BooksRoute extends GoRouteData {
  BooksRoute({this.kind = BookKind.popular});
  final BookKind kind;

  @override
  Widget build(BuildContext context, GoRouterState state) {
    return BooksScreen(kind: kind);
  }
}

Transitions

By default, the GoRouter will use the app it finds in the widget tree, e.g. MaterialApp, CupertinoApp, WidgetApp, etc. and use the corresponding page type to create the page that wraps the Widget returned by the route's build method, e.g. MaterialPage, CupertinoPage, NoTransitionPage, etc. Furthermore, it will use the state.pageKey property to set the key property of the page and the restorationId of the page.

Transition override

If you'd like to change how the page is created, e.g. to use a different page type, pass non-default parameters when creating the page (like a custom key) or access the GoRouteState object, you can override the buildPage method of the base class instead of the build method:

class MyMaterialRouteWithKey extends GoRouteData {
  static const LocalKey _key = ValueKey<String>('my-route-with-key');
  @override
  MaterialPage<void> buildPage(BuildContext context, GoRouterState state) {
    return const MaterialPage<void>(
      key: _key,
      child: MyPage(),
    );
  }
}

Custom transitions

Overriding the buildPage method is also useful for custom transitions:

class FancyRoute extends GoRouteData {
  @override
  CustomTransitionPage<void> buildPage(
    BuildContext context,
    GoRouterState state,
  ) {
    return CustomTransitionPage<void>(
        key: state.pageKey,
        child: const MyPage(),
        transitionsBuilder: (BuildContext context, Animation<double> animation,
            Animation<double> secondaryAnimation, Widget child) {
          return RotationTransition(turns: animation, child: child);
        });
  }
}

TypedShellRoute and navigator keys

There may be situations where a child route of a shell needs to be displayed on a different navigator. This kind of scenarios can be achieved by declaring a static navigator key named:

• $navigatorKey for ShellRoutes
• $parentNavigatorKey for GoRoutes

Example:

final GlobalKey<NavigatorState> shellNavigatorKey = GlobalKey<NavigatorState>();
final GlobalKey<NavigatorState> rootNavigatorKey = GlobalKey<NavigatorState>();

class MyShellRouteData extends ShellRouteData {
  const MyShellRouteData();

  static final GlobalKey<NavigatorState> $navigatorKey = shellNavigatorKey;

  @override
  Widget builder(BuildContext context, GoRouterState state, Widget navigator) {
    return MyShellRoutePage(navigator);
  }
}

// For GoRoutes:
class MyGoRouteData extends GoRouteData {
  const MyGoRouteData();

  static final GlobalKey<NavigatorState> $parentNavigatorKey = rootNavigatorKey;

  @override
  Widget build(BuildContext context, GoRouterState state) => const MyPage();
}

An example is available here.

Run tests

To run unit tests, run command dart tool/run_tests.dart from packages/go_router_builder/.

To run tests in examples, run flutter test from packages/go_router_builder/example.