dart - 过滤器列表对象包含值

Question

class Lesson {
  int idLesson;
  String nameLesson;
  List<DayLesson> dayLesson;
  Lesson({this.idLesson, this.dayLesson, this.nameLesson});
}

class DayLesson {
  int idDay;
  String nameDay;
  DayLesson({this.idDay, this.nameDay});
}

List<DayLesson> listDay = [
  DayLesson(idDay: 1, nameDay: 'Monday'),
  DayLesson(idDay: 2, nameDay: 'Tuesday'),
  DayLesson(idDay: 3, nameDay: 'Wednesday'),
  DayLesson(idDay: 4, nameDay: 'Thursday'),
  DayLesson(idDay: 5, nameDay: 'Friday'),
  DayLesson(idDay: 6, nameDay: 'Saturday'),
  DayLesson(idDay: 7, nameDay: 'Sunday'),
];

List<Lesson> listLesson = [
  Lesson(
    idLesson: 1,
    nameLesson: 'Matematic',
    dayLesson: [
      DayLesson(idDay: 1, nameDay: 'Monday'),
      DayLesson(idDay: 5, nameDay: 'Friday'),
    ],
  ),
  Lesson(
    idLesson: 2,
    nameLesson: 'Indonesia Language',
    dayLesson: [
      DayLesson(idDay: 2, nameDay: 'Tuesday'),
      DayLesson(idDay: 4, nameDay: 'Thursday'),
    ],
  ),
  Lesson(
    idLesson: 3,
    nameLesson: 'Chemistry',
    dayLesson: [
      DayLesson(idDay: 3, nameDay: 'Wednesday'),
    ],
  ),
  Lesson(
    idLesson: 4,
    nameLesson: 'Physics',
    dayLesson: [
      DayLesson(idDay: 4, nameDay: 'Thursday'),
      DayLesson(idDay: 5, nameDay: 'Friday'),
    ],
  ),
  Lesson(
    idLesson: 5,
    nameLesson: 'Basic Invesment',
    dayLesson: [
      DayLesson(idDay: 1, nameDay: 'Monday'),
    ],
  ),
];

在上面的代码中，我有两个名为 Lesson和 DayLesson的类。我想搜索 List<Lesson>，其中该列表包含ID为X的日期。类似 listLesson.where((element)=>element.dayLesson.contain(1)).toList()。

我对以上示例的期望将返回2个数据，因为listDay中的ID的值为1:

[
Lesson(
    idLesson: 1,
    nameLesson: 'Matematic',
    dayLesson: [
      DayLesson(idDay: 1, nameDay: 'Monday'),
      DayLesson(idDay: 5, nameDay: 'Friday'),
    ],
  ),
  Lesson(
    idLesson: 5,
    nameLesson: 'Basic Invesment',
    dayLesson: [
      DayLesson(idDay: 1, nameDay: 'Monday'),
    ],
  ),
]

但是问题是，我总是得到空名单。我的结构 List是问题还是我错过了什么？

Answer 1

我不认为contains是正确的方法。由于列表中嵌套了一个列表，因此必须嵌套where和any操作。

List<Lesson> _findLessons(int dayLessonId) {
   return listLesson
          .where((element)=> element.dayLesson.any((dL) => dL.idDay == dayLessonId))
          .toList();
}