IOS: NSDateComponent的问题

Question

我有这样的代码：

- (void) setDataLabel{

for (int k = 0; k<31; k++){

    [[lineSunday objectAtIndex:k] setAlpha:0.00];
    [[arrayDay objectAtIndex:k] setTextColor:[UIColor whiteColor]];
}

NSDateComponents *components = [[[NSDateComponents alloc] init] autorelease];
[components setYear:2011];
[components setDay:1];
[components setMonth:10];
//NSLog(@"mese:%d", month);
NSCalendar *gregorianCalendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDate *firstDate = [gregorianCalendar dateFromComponents:components];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"dd"];

for (int i = 0; i < 31; i++) {
    NSTimeInterval seconds = 24*60*60 * i;
    NSDate *date = [NSDate dateWithTimeInterval:seconds sinceDate:firstDate];
    NSDateComponents *weekdayComponents = [gregorianCalendar components:NSWeekdayCalendarUnit fromDate:date];
    int weekday = [weekdayComponents weekday];
    NSString *strDate = [dateFormatter stringFromDate: date];
    [[arrayDay objectAtIndex:i] setText:strDate];
    if (weekday == 1) {
        [[arrayDay objectAtIndex:i] setTextColor:[UIColor redColor]];
        [[lineSunday objectAtIndex:i] setAlpha:1.00];
    }
}

这段代码设置了31个带有月份日期的标签，一切正常，但我不明白为什么10月份会有两个连续的工作日；例如:在今年，这段代码在月底的某一天这样写：

....25 26 27 28 29 30 30

30和30是红色的，但它不应该是这样的，它应该是

....25 26 27 28 29 30 31

只有30个必须是红色的

为什么会发生这种情况？

Answer 1

这是因为夏令时的原因。我们在该循环中为每一天增加了86400秒，但一天将有25个小时。

编辑：

最好的方法可能就是把date对象也放在循环中，根本不做花哨的计算。

- (void) setDataLabel{

    for (int k = 0; k<31; k++){
        [[lineSunday objectAtIndex:k] setAlpha:0.00];
        [[arrayDay objectAtIndex:k] setTextColor:[UIColor whiteColor]];
    }

    NSDateComponents *components = [[[NSDateComponents alloc] init] autorelease];
    [components setYear:2011];
    [components setMonth:10];
    NSCalendar *gregorianCalendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"dd"];

    for (int i = 0; i < 31; i++) {
        [components setDay:i+1];
        NSDate *date = [gregorianCalendar dateFromComponents:components];
        NSDateComponents *weekdayComponents = [gregorianCalendar components:NSWeekdayCalendarUnit fromDate:date];
        int weekday = [weekdayComponents weekday];
        NSString *strDate = [dateFormatter stringFromDate: date];
        [[arrayDay objectAtIndex:i] setText:strDate];
        if (weekday == 1) {
            [[arrayDay objectAtIndex:i] setTextColor:[UIColor redColor]];
            [[lineSunday objectAtIndex:i] setAlpha:1.00];
        }
    }
    [dateFormatter release];
    [gregorianCalendar release];
    [components release];
}