将日期和时间组合成单个 NSDate 的问题 [英] Problem combining a date and a time into a single NSDate

问题描述

我正在尝试将一个 NSDate 的时间值(小时、分钟、秒)与第二个 NSDate 的日期值(日、月、年)结合起来用这个方法:

I am trying to combine the time value (hours, minutes, seconds) of one NSDate with the date value (day, month, year) of a second NSDate with this method:

+ (NSDate *)combineDate:(NSDate *)date withTime:(NSDate *)time {

    NSCalendar *gregorian = [[NSCalendar alloc]
        initWithCalendarIdentifier:NSGregorianCalendar];

    NSDateComponents *dateComponents = [gregorian components:(NSDayCalendarUnit | 
        NSWeekdayCalendarUnit) fromDate:date];
    NSDateComponents *timeComponents = [gregorian components:(NSDayCalendarUnit | 
        NSWeekdayCalendarUnit) fromDate:time];

    NSDateComponents *comp = [NSDateComponents alloc];
    [comp setSecond:[timeComponents second]];
    [comp setHour:[timeComponents hour]];
    [comp setMinute:[timeComponents minute]];
    [comp setYear:[dateComponents year]];
    [comp setMonth:[dateComponents month]];
    [comp setDay:[dateComponents day]];

    NSDate *combDate = [gregorian dateFromComponents:comp]; 

    [gregorian release];
    [comp release];

    return combDate;
}

...但是它返回的实际上是胡言乱语(例如，年份显示为1").有人知道这种方法有什么问题吗?

... but what it's returning is effectively gibberish (the year comes out as "1", for example). Anybody see what's wrong with this method?

推荐答案

我使用了错误的日历组件.这是更正后的函数(现在用于 ARC):

I was using the wrong calendar components. Here's the corrected function (now for ARC):

+ (NSDate *)combineDate:(NSDate *)date withTime:(NSDate *)time {

    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:
        NSGregorianCalendar];

    unsigned unitFlagsDate = NSYearCalendarUnit | NSMonthCalendarUnit 
        |  NSDayCalendarUnit;
    NSDateComponents *dateComponents = [gregorian components:unitFlagsDate 
        fromDate:date];
    unsigned unitFlagsTime = NSHourCalendarUnit | NSMinuteCalendarUnit 
        |  NSSecondCalendarUnit;
    NSDateComponents *timeComponents = [gregorian components:unitFlagsTime 
        fromDate:time];

    [dateComponents setSecond:[timeComponents second]];
    [dateComponents setHour:[timeComponents hour]];
    [dateComponents setMinute:[timeComponents minute]];

    NSDate *combDate = [gregorian dateFromComponents:dateComponents];   

    return combDate;
}

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