如何从现在到特定工作日找到最近的未来日期？

Question

我有一个约会管理方案，其中我有一个 availableWeekDays 人员的字段列表，他们可以在工作日进行预订。例如，如果它们在星期一可用，我在 availableWeekDays 列表中的值为 1.

我使用 DateTime.now().

将 currentDate 存储在 DateTime 变量中

我要做的是首先查看今天的工作日是否与 person 的 availableWeekDay 匹配。如果是，那么 bookingDate 是有效的，否则我必须在工作日寻找最近的未来日期。我尝试了以下解决方案，但它可以工作一个星期，因为我使用的是第一个索引。

void main() {
  
  DateTime bookingDate = DateTime.now();
  int availableWeekDays = [1,4,7];
  
  getDate(){
    if(bookingDate.weekday == availableWeekDays[0]){
      print("Available on $bookingDate ");
    } else {
      bookingDate = bookingDate.add(Duration(days: 1));
      getDate();
    }
  }
  
  getDate();
  
}

我想在列表中的所有工作日中找到最近的未来日期。

Answer 1

我忘了将结果重新分配给变量。这现在有效。

void main() {
  
  DateTime bookingDate = DateTime.now();
  int availableWeekDay = 1;
  
  getDate(){
    if(bookingDate.weekday == availableWeekDay){
      print("Available on $bookingDate ");
    } else {

      bookingDate = bookingDate.add(Duration(days: 1));

      getDate();
    }
  }
  
  getDate();
  
}

Answer 2

更有效的解决方案是：

DateTime getDate() {
  var currentDay = bookingDate.weekday;
  var offset = (availableWeekDay - currentDay).remainder(7);
  return offset == 0 ? bookingDate : bookingDate.add(Duration(days: offset));
}

请注意，如果 bookingDate 的时间接近午夜，则向日期添加“天”（24 小时的倍数）可能运行会导致夏令时问题。

Answer 3

DateTime findNearestWeekday(List<int> availableWeekdays) {
  assert(availableWeekdays.isNotEmpty);

  var date = DateTime.now();
  final weekday = date.weekday;

  for (var num in availableWeekdays) {
    if (num == date.weekday) {
      return date;
    } else if (date.weekday < num) {
      return date.add(Duration(days: num - weekday));
    }
  }

  /// I have assumed that you will always have a sorted list of available
  /// weekdays, in case you do not have a sorted list, either you can sort
  /// the list first or just use this line (instead of the last one),
  ///
  /// ```dart
  /// import 'dart:math'; /// Add on Top of file.
  ///
  /// return date.add(Duration(days: 7 - weekday + availableWeekdays.reduce(min)))
  /// ```
  ///
  /// I will prefer to pre sort the array before storing it somewhere,
  /// because it will add an additional dependency dart:math


  return date.add(Duration(days: 7 - weekday + availableWeekdays[0]));
}

如何从现在到特定工作日找到最近的未来日期？

How to find nearest future date from now with specific weekday?

algorithm

logic

datetime

date

dart