overrideWithValue method

@override Override overrideWithValue(AsyncValue<T> value)

Overrides the behavior of a provider with a value.

Some common use-cases are:

• testing, by replacing a service with a fake implementation, or to reach a very specific state easily.
• multiple environments, by changing the implementation of a class based on the platform or other parameters.

This function should be used in combination with ProviderScope.overrides or ProviderContainer.overrides:

final myService = Provider((ref) => MyService());

runApp(
  ProviderScope(
    overrides: [
      myService.overrideWithProvider(
        // Replace the implementation of MyService with a fake implementation
        Provider((ref) => MyFakeService())
      ),
    ],
    child: MyApp(),
  ),
);

Implementation

@override
Override overrideWithValue(AsyncValue<T> value) {
  return ProviderOverride(
    ValueProvider<Stream<T>, AsyncValue<T>>((ref) {
      AsyncValue<T>? lastValue;
      final controller = StreamController<T>();
      ref.onDispose(controller.close);

      ref.onChange = (newValue) {
        newValue.when(
          data: controller.add,
          loading: () {
            if (lastValue != null && lastValue is! AsyncLoading) {
              ref.markMustRecomputeState();
            }
          },
          error: controller.addError,
        );
        lastValue = newValue;
      };

      ref.onChange!(value);

      return controller.stream.asBroadcastStream();
    }, value),
    this,
  );
}