NSString 得到当前日期

-(NSString *) get_current_date_time
{
   
NSDate *now = [NSDate
date];

    

    NSCalendar *cal = [NSCalendar
currentCalendar];

    unsigned
int unitFlags =
NSYearCalendarUnit | NSMonthCalendarUnit |
NSDayCalendarUnit | NSHourCalendarUnit |
NSMinuteCalendarUnit | NSSecondCalendarUnit |
NSWeekdayCalendarUnit;
   
NSDateComponents *dd = [cal
components:unitFlags fromDate:now];
   
int y = [dd year];
   
int m = [dd month];
   
int d = [dd day];
   
int week = [dd weekday];

    
   
int hour = [dd hour];
   
int minute = [dd minute];
   
int second = [dd second];

    
   
NSString *date_time=@"";
    date_time =[
NSString stringWithFormat:@"%02d-%02d-%02d %02d:%02d:%02d",y,m,d,hour,minute,second ];
   
return date_time;
}