iphone - 如何改进此“DateFromNextWeekDay:FromDate”方法代码？

Question

很高兴听到有关如何改进/缩短此方法的建议。简而言之，需要:

查找星期几(例如星期三)与传递给该方法的内容匹配的下一个日期。

例如，给定日期(包括该给定日期)的下一个WED

下面的代码:

- (NSDate*)DateFromNextWeekDay:(NSInteger)weekDay FromDate:(NSDate*)fromDate {
    // Returns the next week day, as specified by "weekDay", from the specified "fromDate" 
    NSDate *fromDateMidday = [[NSDate date] dateBySettingHour:12 andMinute:0];
    NSDate *dateCounter  = [[fromDateMidday copy] dateByAddingTimeInterval:-86400];     // Take 1 day away, which will get incremented in the loop
    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSInteger day;
    do{
        dateCounter  = [dateCounter dateByAddingTimeInterval:86400];
        unsigned units = NSWeekdayCalendarUnit;
        NSDateComponents *components = [gregorian components:units fromDate:dateCounter];
        day = [components weekday];
    } while(day != weekDay);
    [gregorian release];
    return dateCounter;
}

谢谢

Answer 1

您可以找到传入日期的星期几，从目标星期几中减去该日期，最后将该结果添加到传入日期中。无需遍历日期。因此它将是:

daysToAdd =(targetDayOfWeek-currentDayDayOfWeek)％7

修改减法的原因是要处理目标日期小于当前日期的情况(例如，星期六，您正在寻找星期二)。