traceNo property
get always new traceNo
Implementation
Future<String> get traceNo async {
int? lastTraceNo = (await _prefs).getInt(_keyTraceNo);
int traceNo = (lastTraceNo ?? 0) + 1;
await (await _prefs).setInt(_keyTraceNo, traceNo >= 999999 ? 0 : traceNo);
return "$traceNo".padLeft(6, "0");
}