Functionality in parent class needs to detect changes to child class properties

Question

I am trying to find a way for this parent \"Persistent\" class to add functionality so that the \"changed\" property becomes true whenever any property of the child object is ch

Answer 1

You can use the ChangeNotifier class like shown in the answers to this question

• Observe package from polymer dart
• How to use Dart ChangeNotifier class?
  see also
• https://api.dartlang.org/apidocs/channels/be/dartdoc-viewer/observe/observe.ChangeNotifier
• https://api.dartlang.org/apidocs/channels/be/dartdoc-viewer/observe/observe.Observable

Another attempt is to use reflection but this is discouraged especially in the browser. The above solution uses reflection too but as far as I know the Smoke transformer generates code that replaces the reflective code when you run pub build.

edit

Only after a call to Observable.dirtyCheck(); a change detection is initiated (for all observable instances).

import 'package:observe/observe.dart';

class Persistent extends Observable {
  bool changed = false;

  Persistent() : super() {
    changes.listen((e) => changed = true);
  }
}

class Child extends Persistent {
  @observable num number = 1;
}

main() {
  Child item = new Child();
  item.number = 2;
  Observable.dirtyCheck();
  assert(item.changed == true);
}