NSDate获得一周中的特定日期？

Question

我希望这只是我正在经历的学习曲线。

我创建了一个任意日期。我想找到第三个星期五之后的星期六。

    NSLog(@"Date: %@", [date description]);
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSTimeZone *zone = [NSTimeZone timeZoneWithName:@"EST"];
    [calendar setTimeZone:zone];
    NSDateComponents *components = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:date];
    [components setWeekday:6];        // 1 = Sunday ... 7 = Saturday
    [components setWeekdayOrdinal:3]; // 3rd Friday
    resultDate = [calendar dateFromComponents:components];
    NSLog(@"Date: %@", [resultDate description]);

输出：

日期：2010-11-01 05:00:00 GMT

日期：2010-11-01 05:00:00 GMT

为什么呢？我该如何解决这个问题？

Answer 1

// Sunday = 1, Saturday = 7

int weekday = [[[NSCalendar currentCalendar] components:NSWeekdayCalendarUnit fromDate: date] weekday];

Answer 2

将组件更改为：

(NSWeekdayCalendarUnit | NSYearCalendarUnit)

<击>

这有效：

 NSDate *today = [[NSDate alloc] init];
 NSLog([today description]);

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

 NSDateComponents *weekdayComponents = [gregorian components:(NSWeekdayCalendarUnit | NSWeekdayOrdinalCalendarUnit) fromDate:today];

 NSDateComponents *componentsToSubtract = [[NSDateComponents alloc] init];
 [componentsToSubtract setDay: 0 - ([weekdayComponents weekday])];
 [componentsToSubtract setWeekdayOrdinal:([weekdayComponents weekday] <= 6) ? 3 : 4];
 //[componentsToSubtract setWeekdayOrdinal:3]; //old way - not perfect

 NSDate *saturday = [gregorian dateByAddingComponents:componentsToSubtract toDate:today options:0]; 
 NSDateComponents *components =
 [gregorian components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit)
     fromDate: saturday];
 saturday = [gregorian dateFromComponents:components];

 NSLog([saturday description]);

希望这有帮助。