判断日期是否是昨天、今天、明天、后天

由于项目需要，整理出来以供大家参考，请各位大神指教，多谢🤝

方法一：NSCalendar 自带方法判断是否是昨天、今天、明天

+ (NSString *)dateStrToStrWithDateStr:(NSString *)dateStr {
    NSString *flagString = @"";
    // 目标日期
    NSDate *tarDate = [self getDateFromDateStr:dateStr];
    if ([[NSCalendar currentCalendar] isDateInYesterday:tarDate]) {
        flagString = @"昨天";
    }else if ([[NSCalendar currentCalendar] isDateInToday:tarDate]) {
        flagString = @"今天";
    }else if ([[NSCalendar currentCalendar] isDateInTomorrow:tarDate]) {
        flagString = @"明天";
    }
    return flagString;
}      

方法二：只适用于判断同一个月份的昨天、今天、明天、后天

+ (NSString *)dateStrToStrWithNowDateStr:(NSString *)nowDateStr dateStr:(NSString *)dateStr {
    NSString *flagString = @"";
    // 当前日期
    int currentDateInt = [self getIntegerFromDateStr:nowDateStr];
    // 目标日期
    int tarInt = [self getIntegerFromDateStr:dateStr];
    // 时间差
    int diff = tarInt - currentDateInt;
    
    if ( diff < 3 && diff >= 0) {
        switch (diff) {
            case 0:
                flagString = @"今天";
                break;
            case 1:
                flagString = @"明天";
                break;
            case 2:
                flagString = @"后天";
                break;
            default:
                break;
        }
    }else if (diff == -1) {
        flagString = @"昨天";
    }
    return flagString;
}

方法三：获取到当前日期的昨天、今天、明天、后天。。。来跟目标日期进行判断，适用于同一个月份和不同月份

+ (NSString *)dateStrToStrWithNowDateStr:(NSString *)nowDateStr dateStr:(NSString *)dateStr {
    NSString *flagString = @"";
    ///
    if ([dateStr isEqualToString:[self getTheDayAfterDay:nowDateStr addDay:-1]]) {
        flagString = @"昨天";
    }else if ([dateStr isEqualToString:[self getTheDayAfterDay:nowDateStr addDay:0]]) {
        flagString = @"今天";
    }else if ([dateStr isEqualToString:[self getTheDayAfterDay:nowDateStr addDay:1]]) {
        flagString = @"明天";
    }else if ([dateStr isEqualToString:[self getTheDayAfterDay:nowDateStr addDay:2]]) {
        flagString = @"后天";
    }
    return flagString;
}
+ (NSString *)getTheDayAfterDay:(NSString *)theDayStr addDay:(int)addDay {
    NSDateFormatter *format = [[NSDateFormatter alloc]init];
    [format setDateFormat:@"yyyy-MM-dd"];
    NSDate *theDay = [format dateFromString:theDayStr];
    NSCalendar *cal = [NSCalendar currentCalendar];
    unsigned int time = NSCalendarUnitYear|NSCalendarUnitMonth|NSCalendarUnitDay;
    NSDateComponents *t = [cal components:time fromDate:theDay];
    int year = (int)[t year];
    int month = (int)[t month];
    int day = (int)[t day];
    day = day + (addDay);
    int monthDays = [self daysCountOfMonth:month andYear:year];
    if (day > monthDays) {
        month += 1;
        day = day - monthDays;
    }else {
        ///不做任何处理
    }
    NSString *resultStr = [NSString stringWithFormat:@"%02d-%02d-%02d",year,month,day];
    return resultStr;
}
+ (int)daysCountOfMonth:(NSInteger)month andYear:(NSInteger)year {
    if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12) {
        return 31;
    }else if (month == 4 || month == 6 || month == 9 || month == 11) {
        return 30;
    }
    if((year%4 != 0) || (year%100 == 0 && year%400 != 0)) {
        return 28;
    }
    return 29;
}

方法四：综合上述所有方法的判断

+ (NSString *)dateStrToStrWithNowDateStr:(NSString *)nowDateStr dateStr:(NSString *)dateStr {
    NSString *flagString = @"";
    // 当前日期
    int currentDateInt = [self getIntegerFromDateStr:nowDateStr];
    // 目标日期
    int tarInt = [self getIntegerFromDateStr:dateStr];
    NSDate *tarDate = [self getDateFromDateStr:dateStr];
    // 时间差
    int diff = tarInt - currentDateInt;
    
    if ( diff < 3 && diff >= 0) {
        switch (diff) {
            case 0:
                flagString = @"今天";
                break;
            case 1:
                flagString = @"明天";
                break;
            case 2:
                flagString = @"后天";
                break;
            default:
                break;
        }
    }else if (diff == -1) {
        flagString = @"昨天";
    }else {
        if ([[NSCalendar currentCalendar] isDateInYesterday:tarDate]) {
            flagString = @"昨天";
        }else if ([[NSCalendar currentCalendar] isDateInToday:tarDate]) {
            flagString = @"今天";
        }else if ([[NSCalendar currentCalendar] isDateInTomorrow:tarDate]) {
            flagString = @"明天";
        }else if ([dateStr isEqualToString:[self getTheDayAfterDay:nowDateStr addDay:2]]) {
            flagString = @"后天";
        }
    }
    return flagString;
}

其中公共方法如下：

+ (NSDate *)getDateFromDateStr:(NSString *)dateStr {
    NSDateFormatter *format = [[NSDateFormatter alloc]init];
    [format setDateFormat:@"yyyy-MM-dd"];
    NSDate *date = [format dateFromString:dateStr];
    return date;
}
+ (int)getIntegerFromDateStr:(NSString *)dateStr {
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"yyyy-MM-dd"];
    NSDate *date = [formatter dateFromString:dateStr];
    NSDateFormatter *formatter1 = [[NSDateFormatter alloc]init];
    [formatter1 setDateFormat:@"yyyyMMdd"];
    NSString *todayStr = [formatter1 stringFromDate:date];
    int presentDay = [todayStr intValue];
    return presentDay;
}