restorablePush<T extends Object?> method Null safety

  1. @optionalTypeArgs
String restorablePush<T extends Object?>(
  1. RestorableRouteBuilder<T> routeBuilder,
  2. {Object? arguments}
)
optionalTypeArgs">@optionalTypeArgs

Push a new route onto the navigator.

Unlike Routes pushed via push, Routes pushed with this method are restored during state restoration according to the rules outlined in the "State Restoration" section of Navigator.

The new route and the previous route (if any) are notified (see Route.didPush and Route.didChangeNext). If the Navigator has any Navigator.observers, they will be notified as well (see NavigatorObserver.didPush).

Ongoing gestures within the current route are canceled when a new route is pushed.

The T type argument is the type of the return value of the route.

The method takes a static RestorableRouteBuilder as argument, which must instantiate and return a new Route object that will be added to the navigator. The provided arguments object is passed to the routeBuilder. The navigator calls the static routeBuilder function again during state restoration to re-create the route object.

Any object that is serializable via the StandardMessageCodec can be passed as arguments. Often, a Map is used to pass key-value pairs.

The method returns an opaque ID for the pushed route that can be used by the RestorableRouteFuture to gain access to the actual Route object added to the navigator and its return value. You can ignore the return value of this method, if you do not care about the route object or the route's return value.

link
Typical usage is as follows:
To create a local project with this code sample, run:
flutter create --sample=widgets.NavigatorState.restorablePush.1 mysample

Implementation

@optionalTypeArgs
String restorablePush<T extends Object?>(RestorableRouteBuilder<T> routeBuilder, {Object? arguments}) {
  assert(routeBuilder != null);
  assert(_debugIsStaticCallback(routeBuilder), 'The provided routeBuilder must be a static function.');
  assert(debugIsSerializableForRestoration(arguments), 'The arguments object must be serializable via the StandardMessageCodec.');
  final _RouteEntry entry = _RestorationInformation.anonymous(
    routeBuilder: routeBuilder,
    arguments: arguments,
    restorationScopeId: _nextPagelessRestorationScopeId,
  ).toRouteEntry(this, initialState: _RouteLifecycle.push);
  _pushEntry(entry);
  return entry.restorationId!;
}