如何将 .hour() 和 .minute() 从 Swift 转换为 Objective-C？

Question

如何将 .minute() 和 .hour() 转换为 Objective-C？

func nearestHour () -> Int {
    let halfHour = NSDate.minuteInSeconds() * 30
    var interval = self.timeIntervalSinceReferenceDate
    if  self.seconds() < 30 {
        interval -= halfHour
    } else {
        interval += halfHour
    }
    let date = NSDate(timeIntervalSinceReferenceDate: interval)
    return date.hour()
}

我试过这个：

- (int) nearestHour {
NSInteger halfHour = [NSDate minuteInSeconds].intValue * 30;
NSTimeInterval interval = [self timeIntervalSinceReferenceDate];
if ([self seconds] < 30) {
    interval -= halfHour;
}
else {
    interval += halfHour;
}
NSDate *date = [NSDate dateWithTimeIntervalSinceReferenceDate: interval];
return [date hour];
}

我在这些行中收到以下错误：

if ([self seconds] < 30) {

NSDate 没有可见的@interface 声明选择器秒数。

return [date hour];

NSDate 没有可见的@interface 声明选择器小时。

Answer 1

如前所述，NSDate 没有您需要的界面。您需要将其分解为日历界面。然后您可以单独设置 hour/minute/seconds 等，或者获取它们或您需要做的任何事情。

NSDateComponents *components = [[NSCalendar currentCalendar] components:(NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate:self];

if ([components seconds] < 30) {

以你的例子为例：

- (int) nearestHour {
    NSDateComponents *components = [[NSCalendar currentCalendar] components:(NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate:self];
    NSInteger halfHour = [NSDate minuteInSeconds].intValue * 30;
    NSTimeInterval interval = [self timeIntervalSinceReferenceDate];
    if ([components minutes] < 30) {
        interval -= halfHour;
    }
    else {
        interval += halfHour;
    }
    NSDate *date = [NSDate dateWithTimeIntervalSinceReferenceDate:    interval];
    return [date hour];
}

很多关于 SO 和 google 的例子：How do I get the current hour using Cocoa?

https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/DatesAndTimes/DatesAndTimes.html#//apple%5Fref/doc/uid/10000039

Answer 2

Apple 建议始终使用 NSCalendar 进行日期计算，因为例如，当夏令时更改时，某些按 adding/subtracting 秒计算的日期可能不存在。

nextDateAfterDate 根据指定的日期组件计算下一个日期，在本例中为分钟为零的下一个日期。要获得最近的过去一小时，您还可以向后搜索。

Swift

let now = NSDate()
let calendar = NSCalendar.currentCalendar()
let roundDown = calendar.component(.Minute, fromDate: now) < 30
let components = NSDateComponents()
components.minute = 0
let options : NSCalendarOptions = roundDown ? [.MatchNextTime, .SearchBackwards] : .MatchNextTime
let nearestDate = calendar.nextDateAfterDate(now, matchingComponents: components, options:  options)!
let nearestHour = calendar.component(.Hour, fromDate: nearestDate)

Objective-C

NSDate *now = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];
BOOL roundDown = [calendar component:NSCalendarUnitMinute fromDate: now] < 30 ;
NSDateComponents *components = [[NSDateComponents alloc] init];
components.minute = 0;
NSCalendarOptions options = roundDown ? (NSCalendarMatchNextTime | NSCalendarSearchBackwards) : NSCalendarMatchNextTime;
NSDate *nearestDate = [calendar nextDateAfterDate:now matchingComponents: components options:  options];
NSInteger nearestHour = [calendar component:NSCalendarUnitHour fromDate: nearestDate];

如何将 .hour() 和 .minute() 从 Swift 转换为 Objective-C？

How to convert .hour() and .minute() from Swift to Objective-C?

objective-c

swift

nsdate

hour

seconds