NSDate 来自 NSDateComponents答案

【问题标题】：NSDate from NSDateComponentsNSDate 来自 NSDateComponents
【发布时间】：2011-10-02 04:50:39
【问题描述】：

我正在尝试将 NSDate 的 hh、mm、ss 组件更改为另一个 NSDate 的组件 - 但由于某种原因，时间被设置为午夜。我不知道为什么！

这里是代码；

+ (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];
}

这是控制台上的调试输出。注意小时、分钟、秒分量的值和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>

提前致谢。

【问题讨论】：

标签： iphone objective-c nsdate nsdatecomponents

【解决方案1】：

您在此处生成日期为toDateComponents，

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12:00:00 AM。您已将时间信息存储在 toTimeComponents 中，但未使用。如果你想让它工作，你必须将时间信息添加到 toDateComponents 并可能完全删除 toTimeComponents 变量。

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

【讨论】：