🌰:获取现在时间 转换为字符串(NSDate 转为NSString)

-(NSString *)getCurrentTime
{
    NSDate *date = [NSDate date];
    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
    /*设置日期格式*/
    formatter.dateFormat = @"yyyyMMddHHmmss";
    NSString *nowTime = [formatter stringFromDate:date];
    return nowTime;
}

🌰:NSString字符串转化为NSDate

-(NSDate *)getDateWithString:(NSString *) systemTime {

       NSString* sysTime = systemTime;
       NSDateFormatter *dateFomatter = [[NSDateFormatter alloc] init];
       //设置日期格式这里设置为yyyyMMddHH:mm:ss
       dateFomatter.dateFormat = @"yyyyMMddHH:mm:ss";
      //转化为NSDate
       NSDate* nowDate = [dateFomatter dateFromString:sysTime];
       return nowDate;
}

🌰: 获取时间差: systemTime - date
参数1: date:时间日期, NSString 类型,例如20161107070707
参数2: dateFormat:日期格式,例如:yyyyMMddHH:mm:ss
参数3: systemTime:日期时间,NSString 类型,例如20171108080808
注意:参数date和systemTime两个日期字符串的格式一定要和dateFormat的格式相对应

-(NSDateComponents *)getDateComponents:(NSString *)date dateFormat:(NSString *)dateFormat  severSystemTime:(NSString *)systemTime  {

   //  此处添加判断防止出现闪退
   if (![date isEqual:[NSNull null]]) {
    
       //将参数1日期字符串systemTime转化为NSDate
       NSString* sysTime = systemTime;
       NSDateFormatter *dateFomatter = [[NSDateFormatter alloc] init];
       //设置日期格式为传来的字符串dateFormat
       dateFomatter.dateFormat = dateFormat;
       NSDate* nowDate = [dateFomatter dateFromString:sysTime];

       // 将参数2日期类型字符串date转换为NSDate
       NSString *endTime = date;
       // 当前时间字符串格式
       NSDateFormatter *endDateFomatter = [[NSDateFormatter alloc] init];
       //设置日期格式,为传来的参数dateFormat格式
       endDateFomatter.dateFormat = dateFormat;
       //转化为日期格式
       NSDate* endDate = [endDateFomatter dateFromString:endTime];

       // 当前日历
       NSCalendar *calendar = [NSCalendar currentCalendar];
       // 需要对比的时间数据
       NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth
    | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;
       // 对比时间差
       NSDateComponents *dateCom = [calendar components:unit fromDate: endDate toDate:nowDate options:0];
       //打印 如果参数日期格式对不上的话,可能会打印为空
       NSLog(@"------->>年:%d,月:%d,日:%d,时:%d,分:%d,",comp.year, comp.month, comp.day, comp.hour,comp.minute);
       return dateCom;
    }
  return nil;
}