objective-c - 如何在 NSDate 上设置时间？

Question

我想将 NSDate 时间设置为我想要的小时:分钟:秒目前我正在使用 NSDate 组件，但它没有给出预期的结果

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

Answer 1

这作为 NSDate 类别非常有用。

/** 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，如果您有一个现有日期想要更改时间，您可以这样做:

NSDate *newDate = [someDate dateWithHour:10 minute:30 second:00];

但是，如果您要尝试在现有日期中增加或减少小时数，则类别方法也很简单:

/** 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];
}