How do wait for AsyncData using ref.read?

Question

I'm using riverpod and I want to read a Provider<AsyncValue> in a callback (for example a button).

I want to make sure the read value is not AsyncLoading.

onPressed: () {
  final AsyncValue<T> value = ref.read(myProvider); // I want to make sure it is not AsyncLoading
}

Provider<AsyncValue<T>> myProvider is NOT a FutureProvider or a StreamProvider so I cannot use

final T value = await ref.read(myProvider.future); // I cannot do it. myProvider is not a FutureProvider or a StreamProvider

How can I do something similar to await ref.read(myProvider.future) but for a generic Provider<AsyncValue<T>> ?

Answer 1

In the end, I created this extension:

/// An extension on [WidgetRef] with helpful methods to read an [AsyncValue].
extension AwaitAsyncValue on WidgetRef {
  /// Waits for the [AsyncValue] to be resolved and returns the value.
  Future<T> readAsync<T>(ProviderBase<AsyncValue<T>> provider) {
    final completer = Completer<T>();
    final subscription = listenManual(
      provider,
      (previous, next) {
        next.when(
          data: completer.complete,
          loading: () {},
          error: completer.completeError,
        );
      },
      fireImmediately: true,
    );
    completer.future.then((_) => subscription.close(), onError: (_) => subscription.close());
    return completer.future;
  }
}

And I can use it this way:

final T value = await ref.readAsync(myProvider);