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];
}  

我收到以下错误。我该如何解决这个问题？

error: invalid operands to binary - (have 'int' and 'id')

Answer 1

你一定是这样使用的:-

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