NSDate/NSDateComponent问题

Question

假设我们是15/07/2010,我想获得前一周的第一天,也就是7月5日.我有以下方法,但它不起作用.似乎我的工作日属性有问题......

+ (NSDate *)getFirstDayOfPreviousWeek
{
// Get current date
NSCalendar *cal = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *now = [NSDate date];

// Get today date at midnight
NSDateComponents *components = [cal components:( NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit | NSTimeZoneCalendarUnit) fromDate:now];
[components setHour:0];
[components setMinute:0];
[components setSecond:0];
NSInteger *dayNbr = [components weekday];
NSLog(@"week day:%@",dayNbr); // CRASH
NSDate *todayMidnight = [cal dateFromComponents:components];

// Get first day of previous week midnight
components = [[[NSDateComponents alloc] init] autorelease];
NSInteger *wd = [dayNbr intValue] * -1 + 1;
[components setWeekDay:wd];
[components setWeek:-1];
NSDate *newDate = [cal dateByAddingComponents:components toDate:todayMidnight options:0];
[cal release];

NSLog(@"new date:%@", newDate);

return newDate;
}

能否请你帮忙 ？

非常感谢,

吕克

Answer 1

我觉得应该容易多了

- (NSDate *)getFirstDayOfPreviousWeek
{
    NSCalendar *cal = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDate *now = [NSDate date];
    NSLog(@"Current date: %@", now);

    // required components for today
    NSDateComponents *components = [cal components:( NSYearCalendarUnit | NSMonthCalendarUnit | NSWeekCalendarUnit | NSWeekdayCalendarUnit ) fromDate:now];

    // adjust them for first day of previous week (Monday)
    [components setWeekday:2];
    [components setWeek:([components week] - 1)];

    // construct new date and return
    NSDate *newDate = [cal dateFromComponents:components];
    NSLog(@"New date: %@", newDate);

    return newDate;
}

请注意,此解决方案假设一周的第一天是星期一.