How to implement Change Notifier along with moor?

Question

I am trying to make an app having a database it has a table Students

class Students extends Table{

  IntColumn get RollNumber=>integer().autoIncrement()();
  TextColumn get Name => text().withLength(min: 3,max:32)();

  Students( String name){
    Name==name;
  }

@UseMoor(tables: [Students])
class myDatabase extends _$myDatabase {

  myDatabase() : super(_openConnection());
  @override
  int get schemaVersion => 1;

  // loads all student entries

  Future<List<Student>> getAllStudents() => select(students).get();

  //Watches all entries in Students and automatically
  //emits new data when data changes
  Stream<List<Student>>  watchAllStudents()=> select(students).watch();

  Future insertStudent(Student student )=>into(students).insert(student);
  //Future UpdateStudent(Student student )=>update(students).replace(student);
  //Future DeleteStudent(Student student )=>into(students).insert(student);
}

Now I tried to use change notifier with myDatabase but here I cannot extend it so I tried to do this

class myDatabase extends _$myDatabase with ChangeNotifier{
..
}

but the student class showed an error. Now I don't know how to proceed.

Answer 1

The better way will be to create a service for the database operations eg

class DatabaseService with ChangeNotifier {
      Future<List<Students>> getListOfStudents() async {
        // fetch list of students here and return it to the function that calls the DB service
      }
   }

Then you create a ViewModel that implements ChangeNotifier for the Screen/Widget or View you intend to use to students in. The ViewModel will call the DatabaseService and return the values from the database. Eg

class StudentViewModel with ChangeNotifier {

setState() {
  notifyListeners();
 }

Future<void> getStudents() async {
  // get students list from db service and call setState() to notifyListeners
 }
}

NB: Database instances are sort of expensive, so you should create a Singleton instance of the db and the dbservice as well. If you try to open multiple instances of the db, moor will throw an exception to alert you to that.