ios返回当前时间，精确到毫秒。

- (NSString *)getTimeNow
{
NSString* date;

NSDateFormatter * formatter = [[NSDateFormatter alloc ] init];
//[formatter setDateFormat:@"YYYY.MM.dd.hh.mm.ss"];
[formatter setDateFormat:@"YYYY-MM-dd hh:mm:ss:SSS"];
date = [formatter stringFromDate:[NSDate date]];
timeNow = [[NSString alloc] initWithFormat:@"%@", date];
NSLog(@"%@", timeNow);
return timeNow;
}