ios - NSDateComponents/NSDate : get the last sunday

Question

我知道有一些与此类似的问题，但我就是找不到我的代码有什么问题。

基本上我想要的是如果今天不是星期天，currentDate 设置为最后一个星期日。如果今天是星期日，我将 currentDate 设置为之前的星期日。

这是我正在尝试的方法。

  NSDateComponents *components = [[NSCalendar currentCalendar] components:  NSWeekCalendarUnit | NSYearCalendarUnit | NSWeekdayCalendarUnit fromDate:currentDate];

    if (components.weekday == 1) { //Its sunday. We just need to subtract a week
        [components setWeek: -1];
        currentDate = [[NSCalendar currentCalendar] dateByAddingComponents:components toDate:currentDate options:0];

    }else{ //If its not sunday we just go to sunday
        [components setWeekday: 1];
        currentDate = [[NSCalendar currentCalendar] dateFromComponents:components];

    }

第一次执行这部分代码时，我得到了正确的答案。在我第一次得到奇怪的日期之后，比如 4026 年 12 月 2 日，并且年份一直在上升。

这是使它工作的代码:

   NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDateComponents *components = [calendar components: ( NSWeekCalendarUnit | NSWeekdayCalendarUnit | NSYearCalendarUnit) fromDate:currentDate];
    int weekday = components.weekday;

    if (weekday == 1) {
        [components setWeek:components.week -1];
    }else{
        [components setWeekday:1];
    }
    currentDate = [calendar dateFromComponents:components];

Answer 1

如果您使用的是 iOS 8.0+，请将 nextDateAfterDate 与 .SearchBackwards 选项一起使用

let calendar = NSCalendar.currentCalendar()
let options: NSCalendarOptions = [.MatchPreviousTimePreservingSmallerUnits, .SearchBackwards]
calendar.nextDateAfterDate(NSDate(), matchingUnit: .Weekday, value: 1, options: options)