从数周/数周计算某些 NSDates答案

【问题标题】：Calculating certain NSDates from days of weeks/weeks of years从数周/数周计算某些 NSDates
【发布时间】：2015-07-09 11:44:01
【问题描述】：

有没有一种简单的方法可以根据NSCalendar 和/或NSCalendarComponents 的条件计算日期？我已经看了一段时间的文档，但似乎有点复杂。例如，我需要接下来 15 个偶数周的“星期三下午 6:00”（如果是偶数周且尚未超过该日期/时间，则包括这一周。）

【问题讨论】：

标签： ios objective-c time nsdate nscalendar

【解决方案1】：

这是一种确定从哪个星期三开始然后获取下一个 14 偶数周星期三的方法。这没有考虑您问题的时间部分，但您可以使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];
}

【讨论】：

在看到这个之前我想出了别的东西。显然dateBySettingUnit 将自动提前到下一个日期以满足更改，因此不需要 if 子句或数学运算。

【解决方案2】：

我最终回答了我自己的问题。当您知道-[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);
}

【讨论】：