FutureProvider<T> constructor

FutureProvider<T>(Create<Future<T>, ProviderReference> _create, { String? name, })

A provider that asynchronously creates a single value.

FutureProvider can be considered as a combination of Provider and FutureBuilder. By using FutureProvider, the UI will be able to read the state of the future synchronously, handle the loading/error states, and rebuild when the future completes.

A common use-case for FutureProvider is to represent an asynchronous operation such as reading a file or making an HTTP request, that is then listened by the UI.

It can then be combined with:

• FutureProvider.family, for parameterizing the http request based on external parameters, such as fetching a User from its id.
• FutureProvider.autoDispose, to cancel the HTTP request if the user leaves the screen before the Future completed.

Usage example: reading a configuration file

FutureProvider can be a convenient way to expose a Configuration object created by reading a JSON file.

Creating the configuration would be done with your typical async/await syntax, but inside the provider. Using Flutter's asset system, this would be:

final configProvider = FutureProvider<Configuration>((ref) async {
  final content = json.decode(
    await rootBundle.loadString('assets/configurations.json'),
  ) as Map<String, Object?>;

  return Configuration.fromJson(content);
});

Then, the UI can listen to configurations like so:

Widget build(BuildContext, ScopedReader watch) {
  AsyncValue<Configuration> config = watch(configProvider);

  return config.when(
    loading: () => const CircularProgressIndicator(),
    error: (err, stack) => Text('Error: $err'),
    data: (config) {
      return Text(config.host);
    },
  );
}

This will automatically rebuild the UI when the Future completes.

As you can see, listening to a FutureProvider inside a widget returns an AsyncValue – which allows handling the error/loading states.

See also:

• Provider, a provider that synchronously creates a value
• StreamProvider, a provider that asynchronously expose a value which can change over time.
• FutureProvider.family, to create a FutureProvider from external parameters
• FutureProvider.autoDispose, to destroy the state of a FutureProvider when no-longer needed.

Implementation

FutureProvider(this._create, {String? name}) : super(name);