当我尝试输出最接近的时间时，为什么输出显示为空？

Question

输出是：

测试首班车时间：2000-01-01 11:40:00 +0000

最近的时间：(null)

为什么我设置为 6:40 时数组中的第一个巴士时间显示为 11:40？为什么最后它说空？谢谢。

        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        formatter.dateFormat = @"H:mm:ss";

        NSDate *bus500_monday_To_Friday_T1 = [formatter dateFromString:@"06:40:00"]; // 6:40 AM
        NSDate *bus500_monday_To_Friday_T2 = [formatter dateFromString:@"07:50:00"]; // 7:50 AM
        NSDate *bus500_monday_To_Friday_T3 = [formatter dateFromString:@"08:20:00"]; // 8:20 AM
        NSDate *bus500_monday_To_Friday_T4 = [formatter dateFromString:@"08:50:00"]; // 8:50 AM
        NSDate *bus500_monday_To_Friday_T5 = [formatter dateFromString:@"09:20:00"]; // 9:20 AM
        NSDate *bus500_monday_To_Friday_T6 = [formatter dateFromString:@"09:50:00"]; // 9:50 AM
        NSDate *bus500_monday_To_Friday_T7 = [formatter dateFromString:@"10:20:00"]; // 10:20 AM
        NSDate *bus500_monday_To_Friday_T8 = [formatter dateFromString:@"10:50:00"]; // 10:50 AM
        NSDate *bus500_monday_To_Friday_T9 = [formatter dateFromString:@"11:20:00"]; // 11:20 AM
        NSDate *bus500_monday_To_Friday_T10 = [formatter dateFromString:@"11:50:00"]; // 11:50 AM
        NSDate *bus500_monday_To_Friday_T11 = [formatter dateFromString:@"12:20:00"]; // 12:20 PM
        NSDate *bus500_monday_To_Friday_T12 = [formatter dateFromString:@"12:50:00"]; // 12:50 PM
        NSDate *bus500_monday_To_Friday_T13 = [formatter dateFromString:@"13:20:00"]; // 1:20 PM
        NSDate *bus500_monday_To_Friday_T14 = [formatter dateFromString:@"13:50:00"]; // 1:50 PM
        NSDate *bus500_monday_To_Friday_T15 = [formatter dateFromString:@"14:20:00"]; // 2:20 PM
        NSDate *bus500_monday_To_Friday_T16 = [formatter dateFromString:@"14:50:00"]; // 2:50 PM
        NSDate *bus500_monday_To_Friday_T17 = [formatter dateFromString:@"15:20:00"]; // 3:20 PM
        NSDate *bus500_monday_To_Friday_T18 = [formatter dateFromString:@"15:50:00"]; // 3:50 PM
        NSDate *bus500_monday_To_Friday_T19 = [formatter dateFromString:@"16:20:00"]; // 4:20 PM
        NSDate *bus500_monday_To_Friday_T20 = [formatter dateFromString:@"16:50:00"]; // 4:50 PM
        NSDate *bus500_monday_To_Friday_T21 = [formatter dateFromString:@"17:20:00"]; // 5:20 PM
        NSDate *bus500_monday_To_Friday_T22 = [formatter dateFromString:@"17:50:00"]; // 5:50 PM
        NSDate *bus500_monday_To_Friday_T23 = [formatter dateFromString:@"18:20:00"]; // 6:20 PM
        NSDate *bus500_monday_To_Friday_T24 = [formatter dateFromString:@"19:05:00"]; // 7:05 PM

        NSArray *bus500Times = @[bus500_monday_To_Friday_T1,
                                 bus500_monday_To_Friday_T2,
                                 bus500_monday_To_Friday_T3,
                                 bus500_monday_To_Friday_T4,
                                 bus500_monday_To_Friday_T5,
                                 bus500_monday_To_Friday_T6,
                                 bus500_monday_To_Friday_T7,
                                 bus500_monday_To_Friday_T8,
                                 bus500_monday_To_Friday_T9,
                                 bus500_monday_To_Friday_T10,
                                 bus500_monday_To_Friday_T11,
                                 bus500_monday_To_Friday_T12,
                                 bus500_monday_To_Friday_T13,
                                 bus500_monday_To_Friday_T14,
                                 bus500_monday_To_Friday_T15,
                                 bus500_monday_To_Friday_T16,
                                 bus500_monday_To_Friday_T17,
                                 bus500_monday_To_Friday_T18,
                                 bus500_monday_To_Friday_T19,
                                 bus500_monday_To_Friday_T20,
                                 bus500_monday_To_Friday_T21,
                                 bus500_monday_To_Friday_T22,
                                 bus500_monday_To_Friday_T23,
                                 bus500_monday_To_Friday_T24];

        NSDate *currentTime = [NSDate dateWithTimeInterval:[[NSTimeZone localTimeZone] secondsFromGMT]
                                                 sinceDate:[NSDate date]];;
        NSDate *closestTime500;

        for(NSDate *date in bus500Times)
        {
            if([date timeIntervalSinceDate:currentTime] > 0)
            {
                closestTime500 = date;
                break;
            }
        }

        NSLog(@"Testing first bus time: %@", bus500_monday_To_Friday_T1);
        NSLog(@"Closest time: %@", closestTime500);

Answer 1

这样做：

转储 NSDates 数组并保留一个 NSStrings 数组。

NSArray* busTimes = @[@"06:40:00", @"07:50:00", ...];

NSDateFormatter* fmtr = [[NSDateFormatter alloc] init];
[fmtr setFormat:@"HH:mm:ss"];
NSDate nowDate = [NSDate date];
NSString* nowString = [fmtr stringFromDate:nowDate];

NSString* closestTime = nil;

for (NSString* busTime in busTimes) {
    if ([busTime compare:nowString] == NSOrderedDescending ) {
        closestTime = busTime;
        break;
    }
}

（请注意，我没有更改循环中的逻辑，这看起来有点可疑，这取决于您是否假设数据是有序的。）

另一种方法：

NSArray* busTimes = @[@"06:40:00", @"07:50:00", ...];
NSDateFormatter* fmtr = [[NSDateFormatter alloc] init];
[fmtr setFormat:@"HH:mm:ss"];
NSMutableArray* busMinutes = [NSMutableArray array];
for (NSString* time in busTimes) {
    NSTimeInterval doubleTime = [[fmtr dateFromString:time] timeIntervalSinceReferenceDate];
    [busMinutes addObject: [NSNumber numberWithDouble:doubleTime]];
}

NSDate* nowDate = [NSDate date];
NSString* nowString = [fmtr stringFromDate:nowDate];
NSDate* nowDate2 = [fmtr dateFromString:nowString];
NSTimeInterval nowInterval = [nowDate2 timeIntervalSinceReferenceDate];
double closestTime = 0.0;
double secondsDifference = -99.0;

for (NSNumber* busMinute in busMinutes) {
    double busInterval = [busMinutes doubleValue];
    if (busInterval > nowInterval) {
        closestTime = busInterval;
        secondsDifference = busInterval - nowInterval;
    }
}

（当然，在你能解释它的作用之前，你不能使用上面的方案。）

Answer 2

NSDate 存储在 GMT 中。

当您调用 NSLog 时，它会以 GMT 格式输出日期，如果您设备上的时区不是 GMT，则不会考虑这一点。

尝试记录这个

NSString *localDate = [NSDateFormatter localizedStringFromDate:bus500_monday_To_Friday_T1 dateStyle:NSDateFormatterMediumStyle timeStyle:NSDateFormatterMediumStyle];