singleWhere method

Optional<T> singleWhere(bool predicate(T value))

Returns an Optional containing the only element that satisfies the given predicate if there is exactly one, otherwise returns Optional.empty.

Checks elements to see if predicate(element) returns true. If exactly one element satisfies predicate, that element is returned wrapped in an Optional. If none or more than one matching element is found, an Optional.empty is returned.

If the null value satisfies the given predicate, this lookup can not distinguish between not having exactly one element satisfying the predicate and only containing the null value satisfying the predicate. Methods like contains can be used if the distinction is important.

Implementation

Optional<T> singleWhere(bool Function(T value) predicate) {
  try {
    return Optional.ofNullable(_set.singleWhere(predicate));
    // ignore: avoid_catching_errors
  } on Error {
    return const Optional.empty();
  }
}