toggle method

int toggle(T element, [ bool test(T element)? ])

Implementation

int toggle(T element, [bool Function(T element)? test]) {
  final alreadyAdded =
      test != null ? firstOrDefault(test) != null : contains(element);

  if (alreadyAdded) {
    test != null ? removeWhere(test) : remove(element);
  } else {
    add(element);
  }

  return alreadyAdded ? -1 : 1;
}