BloomAsyncValidator<T> typedef

BloomAsyncValidator<T> = Future<String?> Function(T value)

Signature for an asynchronous validator callback on a single value of type T.

Returns a Future completing with an error message string when validation fails, or null when the value is valid.

Both browser DOM mounting and SSR evaluate async validators seamlessly.

Future<String?> checkUsername(String value) async {
  final taken = await api.isUsernameTaken(value);
  return taken ? 'Username is already taken.' : null;
}

Implementation

typedef BloomAsyncValidator<T> = Future<String?> Function(T value);