如何查找从现在开始到特定工作日的最近的将来日期？

问题描述

我有一个约会管理方案，其中有一个availableWeekDays字段列表，该字段在工作日的工作日可以预订。例如，如果星期一有空，我在availableWeekDays列表中的值为1。

我使用DateTime将currentDate存储在DateTime.now()变量中。

我要做的是首先看一下今天的工作日是否与某人的availableWeekDay相匹配。如果是，则bookingDate有效，否则我必须与人的工作日一起寻找最近的将来日期。我尝试了以下解决方案，但由于我正在使用第一个索引，因此它可以工作一周。

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();
  
}

我想找到列表中所有工作日中最接近的将来日期。

解决方法

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，则在日期上添加“天”（24小时的整数倍）可能会遇到夏令时问题。

,

---

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]));
}

,

我忘记了将结果重新分配给变量。现在可以使用。

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();
  
}