A demo of how to create a structure of chapter-wise lessons, from a Set of Lesson objects

test.dart

import 'package:meghshala_app_flutter/core/dynamodb.dart';
import 'package:meghshala_app_flutter/core/lesson_store.dart';

// fetch lessons from database
Set<Lesson> lessons = await DynamoDB.listLessons();

// or, fetch from local storage
Set<Lesson> lessons = await LessonStore.getLessons();


// initialize an empty Map
Map<String, Set<Lesson>> chapterWiseLessons = {};

lessons.forEach((lesson) {
  // initialize an empty Set for the lessons of this chapter
  if (!chapterWiseLessons.containsKey(lesson.chapterId)) {
    chapterWiseLessons[lesson.chapterId] = Set();
  }
  chapterWiseLessons[lesson.chapterId].add(lesson);
});

print(chapterWiseLessons);