获取上周的周一和周日的时间

-(NSString *)getLastMondayTime{          NSDate *nowDate = [NSDate date];     NSCalendar *calendar = [NSCalendar currentCalendar];     NSDateComponents *comp = [calendar components:NSYearCalendarUnit| NSDayCalendarUnit|NSWeekdayCalendarUnit|NSDayCalendarUnit fromDate:nowDate];          //获取今天是周几     NSInteger weekDay = [comp weekday];     //获取某天是几号     NSInteger day = [comp day];          //计算当前日期和上周的星期一和星期天相差天数     long firstDiff,lastDiff;     if (weekDay == 1) {                  firstDiff = -13;         lastDiff = 0;     }     else{                  firstDiff = [calendar firstWeekday] - weekDay +1-7;         lastDiff = 8 - weekDay;     }          //在当前日期基础上加上时间差的天数     NSDateComponents *firstDayComp = [calendar components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:nowDate];     [firstDayComp setDay:day + firstDiff];     NSDate *firstDayOfWeek = [calendar dateFromComponents:firstDayComp];          NSDateComponents *lastDayComp = [calendar components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:nowDate];     [lastDayComp setDay:day + lastDiff];     NSDate *lastDayOfWeek = [calendar dateFromComponents:lastDayComp];          NSDateFormatter *formatter = [[NSDateFormatter alloc]init];     [formatter setDateFormat:@"MM月dd日"];     NSString *firstDay = [formatter stringFromDate:firstDayOfWeek];     NSString *lastDay = [formatter stringFromDate:lastDayOfWeek];          NSString *dateStr = [NSString stringWithFormat:@"%@-%@",firstDay,lastDay];          return dateStr; }