catchFutureError<L, R> static method

Future<Either<L, R>> catchFutureError<L, R>(ErrorMapper<L> errorMapper, FutureOr<R> block())

Evaluates the specified block and wrap the result in a Right.

If an error is thrown or block returns a future that completes with an error, calling errorMapper with that error and wrap the result in a Left.

Example

// Result: Left(Exception())
await Either.catchFutureError<Object, String>(
  (e, s) => e,
  () => throw Exception())
);

// Result: Left(Exception())
await Either.catchFutureError<Object, String>(
  (e, s) => e,
  () async => throw Exception())
);

// Result: Right('hoc081098')
await Either.catchFutureError<Object, String>(
  (e, s) => e,
  () => Future.value('hoc081098'))
);

// Result: Right('hoc081098')
await Either.catchFutureError<Object, String>(
  (e, s) => e,
  () async => await Future.value('hoc081098'))
);

Implementation

static Future<Either<L, R>> catchFutureError<L, R>(
  ErrorMapper<L> errorMapper,
  FutureOr<R> Function() block,
) =>
    Future.sync(block)
        .then((value) => Either<L, R>.right(value))
        .onError<Object>(
            (e, s) => Either.left(errorMapper(e.throwIfFatal(), s)));