currentAsString property Null safety
A string containing the current rune.
For runes outside the basic multilingual plane, this will be a String of length 2, containing two code units.
Returns an empty string if there is no current value.
Implementation
String get currentAsString {
if (_position == _nextPosition) return "";
if (_position + 1 == _nextPosition) return string[_position];
return string.substring(_position, _nextPosition);
}