来自NSDateComponents的NSDate

Question

我正在尝试将一个NSDate的hh，mm，ss部分更改为另一个NSDate的hh，mm，ss部分--但是由于某些原因，时间被设置为午夜。我不知道为什么！

以下是代码；

+ (NSDate *) fixTime:(NSDate*)fromDate  toDate:(NSDate *) toDate {
    NSCalendar *cal = [NSCalendar currentCalendar];
    [cal setTimeZone:[NSTimeZone localTimeZone]];
    [cal setLocale:[NSLocale currentLocale]];
    NSLog(@"fromDate=<%@>", [fromDate descriptionWithLocale:[NSLocale currentLocale]]);
    NSLog(@"toDate=  <%@>", [toDate descriptionWithLocale:[NSLocale currentLocale]]);

    NSDateComponents *fromTimeComponents = [cal components:( NSHourCalendarUnit   | 
                                                             NSMinuteCalendarUnit | 
                                                             NSSecondCalendarUnit   ) fromDate:fromDate];                               
    NSDateComponents *toDateComponents = [cal components:( NSYearCalendarUnit   | 
                                                           NSMonthCalendarUnit  |  
                                                           NSDayCalendarUnit      ) fromDate:toDate];
    NSDateComponents *toTimeComponents = [cal components:( NSHourCalendarUnit   | 
                                                           NSMinuteCalendarUnit | 
                                                           NSSecondCalendarUnit   ) fromDate:toDate];
    [toTimeComponents setHour:[fromTimeComponents hour]];
    [toTimeComponents setMinute:[fromTimeComponents minute]];
    [toTimeComponents setSecond:[fromTimeComponents second]];
    NSLog(@"toDateComponents year = %d", [toDateComponents year]);                                                     
    NSLog(@"toDateComponents mon  = %d", [toDateComponents month]);                                                    
    NSLog(@"toDateComponents day  = %d", [toDateComponents day]);
    NSLog(@"toTimeComponents hour = %d", [toTimeComponents hour]);                                                     
    NSLog(@"toTimeComponents min  = %d", [toTimeComponents minute]);                                                       
    NSLog(@"toTimeComponents sec  = %d", [toTimeComponents second]);

    NSDate *newDate = [cal dateFromComponents:toDateComponents];
    NSLogDebug(@"newDate=<%@>", [newDate descriptionWithLocale:[NSLocale currentLocale]]);
    return [[newDate retain] autorelease];
}

下面是控制台上的调试输出。注意小时、分钟、秒组件的值和newDate的最终值：

    <Util.m:229> fromDate=<Monday, July 11, 2011 10:35:00 PM Pacific Daylight Time>
    <Util.m:230> toDate=  <Saturday, July 23, 2011 9:35:00 PM Pacific Daylight Time>

    <Util.m:255> toDateComponents year = 2011
    <Util.m:256> toDateComponents mon  = 7
    <Util.m:257> toDateComponents day  = 23
    <Util.m:258> toTimeComponents hour = 22
    <Util.m:259> toTimeComponents min  = 35
    <Util.m:260> toTimeComponents sec  = 0
    <Util.m:266> newDate=<Saturday, July 23, 2011 12:00:00 AM Pacific Daylight Time>

提前谢谢。

Answer 1

您将在此处生成toDateComponents关闭日期，

NSDate *newDate = [cal dateFromComponents:toDateComponents];

toDateComponents中的信息只有日期、月份和年份。它没有时间细节。所以你得到了12:00:00 AM。您已将时间信息存储在toTimeComponents中，但它未被使用。如果你想让它起作用，你必须将时间信息添加到toDateComponents中，并可能完全删除toTimeComponents变量。

[toDateComponents setHour:[fromTimeComponents hour]];
[toDateComponents setMinute:[fromTimeComponents minute]];
[toDateComponents setSecond:[fromTimeComponents second]];