objective-c - 日期计算中的语法错误

Question

我在 Xcode 中使用以下代码：

(void)updateLabel 
{
    NSDate* now = [NSDate date];
    int hour = 23 - [[now dateWithCalendarFormat:nil timeZone:nil] hourOfDay];
    int min = 59 - [[now dateWithCalendarFormat:nil timeZone:nil] minuteOfHour];
    int sec = 59 - [[now dateWithCalendarFormat:nil timeZone:nil] secondOfMinute];
    countdownLabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hour, min,sec];
}  

并收到以下错误。我怎样才能解决这个问题？

错误：二进制的无效操作数 - （有'int'和'id'）

Answer 1

您必须以这种方式使用：-

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *dateComponents = [gregorian components:(NSHourCalendarUnit  | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate:[NSDate date]];
NSInteger hour = [dateComponents hour];
NSInteger minute = [dateComponents minute];
NSInteger second = [dateComponents second];
[gregorian release];

希望对你有帮助

Answer 2

使用这种方式

NSDate* now = [NSDate date];

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *dateComponents = [gregorian components:(NSHourCalendarUnit  | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate:now];
long hour =23-[dateComponents hour];
long min =59-[dateComponents minute];
long sec =59-[dateComponents second];

NSString *str = [NSString stringWithFormat:@"%02ld:%02ld:%02ld", hour, min,sec];
NSLog(@"--> %@",str);