如何设置 NSDate 上的时间？

Question

我想用我想要的小时：分钟：秒设置 NSDate 时间 目前我正在使用 NSDate 组件，但它没有给出期望的结果

[comps setHour: -hours];
[comps setMinute:0];
[comps setSecond:0];
NSDate *minDate = [calendar_c dateFromComponents:comps];

Answer 1

这非常适合作为 NSDate 类别。

/** Returns a new NSDate object with the time set to the indicated hour, 
  * minute, and second.
  * @param hour The hour to use in the new date.
  * @param minute The number of minutes to use in the new date.
  * @param second The number of seconds to use in the new date.
  */
-(NSDate *) dateWithHour:(NSInteger)hour 
                  minute:(NSInteger)minute 
                  second:(NSInteger)second 
{
   NSCalendar *calendar = [NSCalendar currentCalendar];
   NSDateComponents *components = [calendar components: NSYearCalendarUnit|
                                                         NSMonthCalendarUnit|
                                                         NSDayCalendarUnit
                                               fromDate:self];
    [components setHour:hour];
    [components setMinute:minute];
    [components setSecond:second];
    NSDate *newDate = [calendar dateFromComponents:components];
    return newDate;
}

对于上述类别，如果您想要更改现有日期的时间，则可以这样做：

NSDate *newDate = [someDate dateWithHour:10 分钟:30 秒:00];

如果但是，您尝试在现有日期中添加或减去小时数，执行此操作的类别方法也很简单：

/** Returns a new date with the given number of hours added or subtracted.
  * @param hours The number of hours to add or subtract from the date.
  */
-(NSDate*)dateByAddingHours:(NSInteger)hours
{
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setHour:hours];

    return [[NSCalendar currentCalendar] 
               dateByAddingComponents:components toDate:self options:0];
}

Answer 2

你的方法应该可以正常工作。我需要解决此类问题（设置单独的日期组件），并且以下代码按我的预期工作。我的情况：我想创建一个使用当前日期的日期对象，但将时间设置为作为字符串传入的值。

NSString *string = @"7:00";
NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"];
NSDateFormatter *timeOnlyFormatter = [[NSDateFormatter alloc] init];
[timeOnlyFormatter setLocale:locale];
[timeOnlyFormatter setDateFormat:@"h:mm"];

NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *today = [NSDate date];
NSDateComponents *todayComps = [calendar components:(NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) fromDate:today];

NSDateComponents *comps = [calendar components:(NSHourCalendarUnit | NSMinuteCalendarUnit) fromDate:[timeOnlyFormatter dateFromString:string]];
comps.day = todayComps.day;
comps.month = todayComps.month;
comps.year = todayComps.year;
NSDate *date = [calendar dateFromComponents:comps];
[calendar release];
[timeOnlyFormatter release];
[locale release];

需要注意的一件事是，当您判断时间是否准确时，您确实必须注意时区。例如，在我的应用程序中，当您在断点处停止时，您将看到 GMT 时间（因此它看起来与输入时间不同，输入时间是我的当地时间），但是当时间实际显示在屏幕上时应用程序，它正在被格式化以在本地时区中显示。您可能需要考虑这一点，以确定结果是否实际上与您的预期不同。

如果这没有帮助，你能详细说明“没有给出预期的结果”吗？它给出了什么结果？与您的预期相比如何？

Answer 3

是 Swift2

extension NSDate {
    func dateWithHour (hour: Int, minute:Int, second:Int) ->NSDate?{

        let calendar = NSCalendar.currentCalendar(),
            components = calendar.components([.Day,.Month,.Year], fromDate: self)
        components.hour = hour;
        components.minute = minute;
        components.second = second;

        return calendar.dateFromComponents(components)
    }
}

Answer 4

您可以将 0 设置为小时、分钟和秒。

NSDateFormatter *tFmt = [[NSDateFormatter alloc] init];

tFmt.dateFormat = @"yyyy-MM-dd";

NSString *strNowDate = [NSString stringWithFormat:@"%@ 00:00:00",[tFmt stringFromDate:[NSDate date]]];

NSDate *nowDate = [NSDate dateWithString:strNowDate formatString:@"yyyy-MM-dd HH:mm:ss"];

Answer 5

Swift 5 解决方案（基于 @dattk 答案）适合那些担心弃用警告的人:)

func date(withHour hour: Int, withMinute minute: Int, withSeconds second: Int) -> Date? { 
   let now = Date() 
   let calendar = NSCalendar.current 
   var components = calendar.dateComponents([.day,.month,.year], from: now)   
   components.hour = hour 
   components.minute = minute 
   components.second = second 
   return calendar.date(from: components) 
}

Answer 6

NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
NSDateComponents *comps = [calendar components:(NSCalendarUnitHour | NSCalendarUnitMinute) fromDate:[NSDate date]];
comps.hour = 0;
comps.minute = 15;
NSDate *date = [calendar dateFromComponents:comps];

iOS 8