between static method
在两个 rank 之间生成一个新的 rank
Implementation
static String between(String? prevRank, String? nextRank) {
if (prevRank == null && nextRank == null) {
return generateInitialRank();
}
if (prevRank == null) {
return _getPrevRank(nextRank!);
}
if (nextRank == null) {
return _getNextRank(prevRank);
}
return _getMidRank(prevRank, nextRank);
}