combineAsync<T extends Object> function

Async<List<T>> combineAsync<T extends Object>(Iterable<Async<T>> asyncs, { @noFutures Err<List<T>> onErr(List<Result<T>> allResults)?, })

Combines an iterable of Asyncs into one containing a list of their values.

The inputs are awaited concurrently. If any resolves to an Err, applies the onErr function to combine errors.

Implementation

Async<List<T>> combineAsync<T extends Object>(
  Iterable<Async<T>> asyncs, {
  @noFutures Err<List<T>> Function(List<Result<T>> allResults)? onErr,
}) {
  if (asyncs.isEmpty) {
    return Async.okValue([]);
  }

  return Async(() async {
    final results = await Future.wait(asyncs.map((a) => a.value));
    final combined = combineResult(results, onErr: onErr);
    switch (combined) {
      case Ok(value: final value):
        return value;
      case Err err:
        throw err;
    }
  });
}