从周中的天/年中的周计算某些nsdate

Question

是否有一种简单的方法可以根据NSCalendar和/或NSCalendarComponents的标准计算日期?我一直在看文档，但它似乎有点复杂。例如，我需要"接下来的15个偶数周的周三下午6:00(包括这个偶数周，如果它还没有超过那个日期/时间。)"

Answer 1

这里是一个方法，用于确定从哪个星期三开始，然后获得接下来的14个偶数周的星期三。这并没有把你的问题的时间部分考虑在内，但是你可以用类似的方法来处理时间。

+ (NSArray *)nextFifteenEvenNumberedWeekWednesdays:(NSDate *)startingDate
{
    static const NSInteger Wednesday = 4;
    static const NSInteger OneDay = 60 * 60 * 24;
    NSCalendar *calender = [NSCalendar currentCalendar];
    NSDateComponents *startingDateComponents = [calender components:(NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitWeekday | NSCalendarUnitWeekOfYear)
                                                           fromDate:startingDate];
    // Go to the closest Wednesday
    NSInteger daysToWednesday = Wednesday - startingDateComponents.weekday;
    if (startingDateComponents.weekday > Wednesday) {
        // We already passed wednesday, so go to the next wednesday
        if (startingDateComponents.weekOfYear % 2 == 0) {
            // If this date is past Wednesday but is on an even week, then moving to the next wednesday
            // will be an odd week. So skip forward one week.
            startingDate = [startingDate dateByAddingTimeInterval:7 * OneDay];
        }
        daysToWednesday = 7 + daysToWednesday; // get the next Wednesday
    }
    startingDate = [startingDate dateByAddingTimeInterval:daysToWednesday * OneDay]; // Move to wednesday
    NSMutableArray *wednesdays = [NSMutableArray array];
    for (NSInteger i = 0; i < 15; i++) {
        // Add every other wednesday
        [wednesdays addObject:[startingDate dateByAddingTimeInterval:14 * i * OneDay]];
    }
    return [wednesdays copy];
}

Answer 2

最后我回答了自己的问题。当你知道-[NSCalendar dateBySettingUnit:value:ofDate:options:]自动递增到下一个匹配日期时，这真的很容易。

NSCalendar *calendar = [NSCalendar calendarWithIdentifier:NSCalendarIdentifierISO8601];
NSDate *date = [NSDate date];
// find the next Wednesday 6 o'clock
date = [calendar dateBySettingUnit:NSCalendarUnitSecond value:0 ofDate:date options:0];
date = [calendar dateBySettingUnit:NSCalendarUnitMinute value:0 ofDate:date options:0];
date = [calendar dateBySettingUnit:NSCalendarUnitHour value:18 ofDate:date options:0];
date = [calendar dateBySettingUnit:NSCalendarUnitWeekday value:4 ofDate:date options:0];
// skip one week if it's not an even week
NSDateComponents *components = [calendar components:NSCalendarUnitWeekOfYear fromDate:date];
date = [calendar dateByAddingUnit:NSCalendarUnitWeekOfYear value:components.weekOfYear % 2 toDate:date options:0];
// 15 weeks of this
for (int i = 0; i < 15; i++)
{
    NSDate *testDate = [calendar dateByAddingUnit:NSCalendarUnitWeekOfYear value:i * 2 toDate:date options:0];
    NSLog(@"Date: %@", testDate);
}