NSdate的UIDatePicker問題

Question

我有一個從我的數據庫中獲取的舊日期的NSDate對象。現在我需要將我的UIDatePicker日期設置爲當前日期，但是使用從我的數據庫獲取的存儲NSDate對象中的小時和分鐘值。

那麼如何從舊日期提取小時和分鐘並將其設置爲當前UIDatePicker NSdate。

感謝

Answer 1

因爲它是初始化後的NSDate不能改變，你必須重新創建：

要獲取的NSDate使用NSCalendar的小時和分鐘組件：

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

然後您可以創建一個新的NSDate（也使用NSCalendar）：

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar]; 
NSDateComponents *dateComponents = [gregorian components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:[NSDate date]]; //[NSDate date] is the current date 
[dateComponents setHour:hour]; 
[dateComponents setMinute:minute]; 
[dateComponents setSecond:second]; 
NSDate *newDate = [gregorian dateFromComponents:dateComponents]; 

Answer 2

NSCalendar *cal = [NSCalendar autoupdatingCurrentCalendar]; 
NSDateComponents *dbDateComps = [cal components:(kCFCalendarUnitHour | kCFCalendarUnitMinute) fromDate:YOUR_DATE_FRM_DB]; 
NSDateComponents *currentComps = [cal components:(kCFCalendarUnitYear | kCFCalendarUnitMonth | kCFCalendarUnitDay) fromDate:[NSDate date]]; 
[currentComps setHour:[dbDateComps hour]]; 
[currentComps setMinute:[dbDateComps minute]]; 

NSDate *resultDate = [currentComps date];