iphone - 判断当前本地时间是否在两个时间之间(忽略日期部分)

Question

考虑到 Cocoa-Touch(iPhone 上的 Objective-C)中没有 NSTime，并且给定两次作为 NSStrings 和一个时区作为 NSString，你如何计算当前本地时间是否在这两个时间之间.请记住，时间字符串中的日期无关紧要，并且填充了虚拟日期。

例如:

 TimeZone: Pacific Time (US & Canada)
 Start Time: 2000-01-01T10:00:00Z
 End Time: 2000-01-01T17:00:00Z

 Local Time: now

如何确认本地时间是否在指定的时间范围内(确保首先将开始/结束时间转换为正确的时区)？

Answer 1

最大的问题似乎是时间可能跨越两天(最初它们可能不会，但是当您进行时区转换时，之后它们可能)。因此，如果我们要完全忽略给定的日期信息，则必须对如何处理这些日期跨度做出一些假设。你的问题不完全是关于如何处理这个问题(即我不知道你想要达到什么目的)所以这只是一种解决方法，这可能不是你想要的，但是希望它将引导您朝着正确的方向前进:

• 将给定的字符串解析为 NSDate 对象，忽略日期信息(结果:时间被处理为假定它们是同一天)并执行时区转换
• 获取从较早的NSDate到较晚的NSDate的时间间隔
• 为“今天在较早的给定时间”和“昨天在较早的给定时间”创建 NSDate 对象
• 比较从这两个 NSDate 到当前日期/时间的时间间隔与两个给定日期/时间之间的时间间隔

另请注意，NSTimeZone 无法理解您所提供格式的时区字符串("Pacific Time (US & Canada)")，因此您需要在那里做一些转换。

这是一个代码示例(我是在 OS X 上写的，因为我没有 iPhone SDK，所以希望所有使用的 API 也能在 iPhone 上使用):

- (BOOL)checkTimes
{
    // won't work:
    //NSString *tzs = @"Pacific Time (US & Canada)";
    // 
    // will work (need to translate given timezone information
    // to abbreviations accepted by NSTimeZone -- won't cover
    // that here):
    NSString *tzs = @"PST";

    NSString *ds1 = @"2000-01-01T10:00:00Z";
    NSString *ds2 = @"2000-01-01T17:00:00Z";

    // remove dates from given strings (requirement was to ignore
    // the dates completely)
    ds1 = [ds1 substringFromIndex:11];
    ds2 = [ds2 substringFromIndex:11];

    // remove the UTC time zone designator from the end (don't know
    // what it's doing there since the time zone is given as a
    // separate field but I'll assume for the sake of this example
    // that the time zone designator for the given dates will
    // always be 'Z' and we'll always ignore it)
    ds1 = [ds1 substringToIndex:8];
    ds2 = [ds2 substringToIndex:8];

    // parse given dates into NSDate objects
    NSDateFormatter *df = [[[NSDateFormatter alloc] init] autorelease];
    [df setDateFormat:@"HH:mm:ss"];
    [df setTimeZone:[NSTimeZone timeZoneWithAbbreviation:tzs]];
    NSDate *date1 = [df dateFromString:ds1];
    NSDate *date2 = [df dateFromString:ds2];

    // get time interval from earlier to later given date
    NSDate *earlierDate = date1;
    NSTimeInterval ti = [date2 timeIntervalSinceDate:date1];
    if (ti < 0)
    {
        earlierDate = date2;
        ti = [date1 timeIntervalSinceDate:date2];
    }

    // get current date/time
    NSDate *now = [NSDate date];

    // create an NSDate for today at the earlier given time
    NSDateComponents *todayDateComps = [[NSCalendar currentCalendar]
                                        components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit
                                        fromDate:now];
    NSDateComponents *earlierTimeComps = [[NSCalendar currentCalendar]
                                          components:NSHourCalendarUnit|NSMinuteCalendarUnit|NSSecondCalendarUnit
                                          fromDate:earlierDate];
    NSDateComponents *todayEarlierTimeComps = [[[NSDateComponents alloc] init] autorelease];
    [todayEarlierTimeComps setYear:[todayDateComps year]];
    [todayEarlierTimeComps setMonth:[todayDateComps month]];
    [todayEarlierTimeComps setDay:[todayDateComps day]];
    [todayEarlierTimeComps setHour:[earlierTimeComps hour]];
    [todayEarlierTimeComps setMinute:[earlierTimeComps minute]];
    [todayEarlierTimeComps setSecond:[earlierTimeComps second]];
    NSDate *todayEarlierTime = [[NSCalendar currentCalendar]
                                dateFromComponents:todayEarlierTimeComps];

    // create an NSDate for yesterday at the earlier given time
    NSDateComponents *minusOneDayComps = [[[NSDateComponents alloc] init] autorelease];
    [minusOneDayComps setDay:-1];
    NSDate *yesterday = [[NSCalendar currentCalendar]
                         dateByAddingComponents:minusOneDayComps
                         toDate:now
                         options:0];
    NSDateComponents *yesterdayDateComps = [[NSCalendar currentCalendar]
                                            components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit
                                            fromDate:yesterday];
    NSDateComponents *yesterdayEarlierTimeComps = [[[NSDateComponents alloc] init] autorelease];
    [yesterdayEarlierTimeComps setYear:[yesterdayDateComps year]];
    [yesterdayEarlierTimeComps setMonth:[yesterdayDateComps month]];
    [yesterdayEarlierTimeComps setDay:[yesterdayDateComps day]];
    [yesterdayEarlierTimeComps setHour:[earlierTimeComps hour]];
    [yesterdayEarlierTimeComps setMinute:[earlierTimeComps minute]];
    [yesterdayEarlierTimeComps setSecond:[earlierTimeComps second]];
    NSDate *yesterdayEarlierTime = [[NSCalendar currentCalendar]
                                dateFromComponents:yesterdayEarlierTimeComps];

    // check time interval from [today at the earlier given time] to [now]
    NSTimeInterval ti_todayEarlierTimeTillNow = [now timeIntervalSinceDate:todayEarlierTime];
    if (0 <= ti_todayEarlierTimeTillNow && ti_todayEarlierTimeTillNow <= ti)
        return YES;

    // check time interval from [yesterday at the earlier given time] to [now]
    NSTimeInterval ti_yesterdayEarlierTimeTillNow = [now timeIntervalSinceDate:yesterdayEarlierTime];
    if (0 <= ti_yesterdayEarlierTimeTillNow && ti_yesterdayEarlierTimeTillNow <= ti)
        return YES;

    return NO;
}