IOS比较两个日期的大小获取当前月份天数（今天、明天、后天）

项目中有一个时间选择期，需要显示今天、明天、后天。对于需要跨月的情况要对日期本月天数进行判断。

/** 获取当前月份的最后一天 */-(void)_getDateBtnValue{    NSInteger year = [[NSDate date] getYear]; //获取年份    NSInteger month = [[NSDate date] getMonth];//获取月份    NSInteger day = [[NSDate date] getDay];//获取日期        //判断当前月分的天数    int endDate = 0;    switch (month) {        case 1:        case 3:        case 5:        case 7:        case 8:        case 10:        case 12:            endDate = 31;            break;            break;        case 4:        case 6:        case 9:        case 11:            endDate = 30;            break;        case 2:            // 是否为闰年            if (year % 400 == 0) {                endDate = 29;                break;            } else {                if (year % 100 != 0 && year %4 ==4) {                    endDate = 29;                } else {                    endDate = 28;                }                break;            }            break;        default:            break;    }        NSDictionary *dic =  [self calculateDateWithEndDate:endDate withDay:day withMonth:month];    dateDic = dic;    //更新Button内容    [self.todayBtn setTitle:[NSString stringWithFormat:@"今天(%@/%@)",dic[@"month"],dic[@"day"]] forState:UIControlStateNormal];    [self.tomorrowBtn setTitle:[NSString stringWithFormat:@"明天(%@/%@)",dic[@"tomorrowMonth"],dic[@"tomorrow"]] forState:UIControlStateNormal];    [self.afterDayBtn setTitle:[NSString stringWithFormat:@"后天(%@/%@)",dic[@"afterDayMonth"],dic[@"afterDay"]] forState:UIControlStateNormal];}/** *  判断当前今天明天后天在跨月的时候天数和月份数 *  @parma endDate:当月最后一天 *  @parma day:今天的日期 *  @parma month:当前月份 *  @parma weekday:当前是周几 */-(NSDictionary *)calculateDateWithEndDate:(int)endDate withDay:(NSInteger)day withMonth:(NSInteger)month{    NSInteger tomorrow = 0; //明天    NSInteger afterDay = 0;  //后天    NSInteger tomorrowMonth = 0;    NSInteger afterDayMonth = 0;    NSInteger currentYear = [[NSDate date] getYear];    NSInteger nextYear = currentYear;    NSInteger lastYear = nextYear;        if(endDate - day <= 0)    {        tomorrow = 1;        afterDay = tomorrow + 1;        tomorrowMonth = month + 1;        if(tomorrowMonth > 12)        {            tomorrowMonth = 1;            nextYear=nextYear + 1;            lastYear = nextYear;        }        afterDayMonth = tomorrowMonth;    }        else if(endDate - day == 1)    {        tomorrow = endDate;        afterDay = 1;        tomorrowMonth = month;        afterDayMonth = month + 1;        if(month == 12)        {            afterDayMonth = 1;            lastYear = nextYear + 1;        }    }        else    {        tomorrow = day+1;        afterDay = tomorrow + 1;        tomorrowMonth = month;        afterDayMonth = month;    }        NSMutableDictionary *dic = [NSMutableDictionary dictionary];    [dic setObject:[NSNumber numberWithInteger:day] forKey:@"day"];    [dic setObject:[NSNumber numberWithInteger:month] forKey:@"month"];    [dic setObject:[NSNumber numberWithInteger:currentYear] forKey:@"year"];        [dic setObject:[NSNumber numberWithInteger:tomorrow] forKey:@"tomorrow"];    [dic setObject:[NSNumber numberWithInteger:tomorrowMonth] forKey:@"tomorrowMonth"];    [dic setObject:[NSNumber numberWithInteger:nextYear] forKey:@"nextYear"];        [dic setObject:[NSNumber numberWithInteger:afterDay] forKey:@"afterDay"];    [dic setObject:[NSNumber numberWithInteger:lastYear] forKey:@"lastYear"];    [dic setObject:[NSNumber numberWithInteger:afterDayMonth] forKey:@"afterDayMonth"];        return dic;    }/** *  判断两个时间的大小 *  @parma selectDate:选择的日期 *  @return 1:大于当前日期 -1:小于当前时间 0:等于当前时间 */-(int)compareDateWithSelectDate:(NSString *)selectDate{    NSDate *currentDate = [NSDate date];    NSDateFormatter *fomatter = [[NSDateFormatter alloc] init];    [fomatter setDateFormat:@"YYYY-MM-dd HH:mm"];    NSString *curentDateStr = [fomatter stringFromDate:currentDate];    currentDate = [fomatter dateFromString:curentDateStr];        int result = [[fomatter dateFromString:selectDate] compare:currentDate];    if(result == NSOrderedDescending)    {        return 1;    }    else if(result == NSOrderedAscending)    {        return -1;    }    return 0;}/** 获取今天是周几 **/-(NSString *)_getWeakDay:(UIButton *)sender{    NSInteger weakday = [[NSDate date] weekday];//周末为第一天    NSString *selectWeakDay = @"";    NSInteger tmpWeakday = weakday;    switch (sender.tag) {        case 100://今天        {            tmpWeakday = weakday;        }            break;        case 101://明天        {            tmpWeakday = weakday+1;            if(tmpWeakday>7)            {                tmpWeakday = 1;            }        }            break;        case 102://后天        {            tmpWeakday = weakday + 2;            if(tmpWeakday - 7 > 0)            {                (tmpWeakday == 8) ? (tmpWeakday = 1) : (tmpWeakday = 2);            }        }            break;        default:            break;    }        switch (tmpWeakday) {        case 1:            selectWeakDay = @"星期天";            break;                    case 2:            selectWeakDay = @"星期一";            break;                    case 3:            selectWeakDay = @"星期二";            break;                    case 4:            selectWeakDay = @"星期三";            break;                    case 5:            selectWeakDay = @"星期四";            break;                    case 6:            selectWeakDay = @"星期五";            break;                    case 7:            selectWeakDay = @"星期六";            break;        default:            break;    }        return selectWeakDay;}