計算兩個日期的間隔

+ (NSString *)numberOfDaysWithFromDate:(NSDate *)fromDate toDate:(NSDate *)toDate {
    // 創(chuàng)建一個標準國際時間的日歷
    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
    // 可根據(jù)需要自己設(shè)置時區(qū).
    calendar.timeZone = myTimeZone;
    // 獲取兩個日期的間隔
    NSDateComponents *comp = [calendar components:NSCalendarUnitDay|NSCalendarUnitHour fromDate:fromDate toDate:toDate options:NSCalendarWrapComponents];
    NSInteger hour = (comp.hour - comp.day * 24);
    return [NSString stringWithFormat:@"%ld天%ld小時", comp.day, hour];
}

上文中 NSDateComponents 初始化方法中的 components 屬性是一個枚舉, 還可以獲取更多 NSDate 的信息, 配置見下表.

typedef NS_OPTIONS(NSUInteger, NSCalendarUnit) {
        NSCalendarUnitEra                = kCFCalendarUnitEra,
        NSCalendarUnitYear               = kCFCalendarUnitYear,
        NSCalendarUnitMonth              = kCFCalendarUnitMonth,
        NSCalendarUnitDay                = kCFCalendarUnitDay,
        NSCalendarUnitHour               = kCFCalendarUnitHour,
        NSCalendarUnitMinute             = kCFCalendarUnitMinute,
        NSCalendarUnitSecond             = kCFCalendarUnitSecond,
        NSCalendarUnitWeekday            = kCFCalendarUnitWeekday,
        NSCalendarUnitWeekdayOrdinal     = kCFCalendarUnitWeekdayOrdinal,
        NSCalendarUnitQuarter            NS_ENUM_AVAILABLE(10_6, 4_0) = kCFCalendarUnitQuarter,
        NSCalendarUnitWeekOfMonth        NS_ENUM_AVAILABLE(10_7, 5_0) = kCFCalendarUnitWeekOfMonth,
        NSCalendarUnitWeekOfYear         NS_ENUM_AVAILABLE(10_7, 5_0) = kCFCalendarUnitWeekOfYear,
        NSCalendarUnitYearForWeekOfYear  NS_ENUM_AVAILABLE(10_7, 5_0) = kCFCalendarUnitYearForWeekOfYear,
        NSCalendarUnitNanosecond         NS_ENUM_AVAILABLE(10_7, 5_0) = (1 << 15),
        NSCalendarUnitCalendar           NS_ENUM_AVAILABLE(10_7, 4_0) = (1 << 20),
        NSCalendarUnitTimeZone           NS_ENUM_AVAILABLE(10_7, 4_0) = (1 << 21),
};