Dart: Inheritance issues

inheritance_issue_example.dart

// Reference: https://talks.golang.org/2014/go4java.slide#41
// DartPad: https://dartpad.dev/bda7024a78cf0b819028b1435a5ed735
// Gist: https://gist.github.com/kranfix/bda7024a78cf0b819028b1435a5ed735

void main() {
  const List<Task> tasks = [Task("one"), Task("two"), Task("three")];
  final runner = ExtendedRunCounter("My run counter");
  //final runner = ComposedRunCounter("My run counter");
  runner.runAll(tasks);
  print("${runner.name} ran ${runner.count} tasks");
}

//void printd(Object object) => print(object);
void printd(Object object) => null;

class Task {
  final String key;
  
  const Task(this.key);
  
  run() => print("Running task $key");
}

class Runner {
  final String name;
  
  Runner(this.name);
  
  void run(Task task){
    printd("[$runtimeType($name).run]");
    task.run();
  }
  
  void runAll(List<Task> tasks){
    printd("[$runtimeType($name).runAll]");
    for(final task in tasks){
      run(task);
    }
  }
}

class ExtendedRunCounter extends Runner {
  ExtendedRunCounter(String name) : _count = 0, super(name);
  
  int _count;
  int get count => _count;
  
  @override
  void run(Task task){
    printd("[$runtimeType($name).run]");
    _count++;
    super.run(task);
  }
  
  @override
  void runAll(List<Task> tasks){
    printd("[$runtimeType($name).runAll]");
    _count += tasks.length;
    super.runAll(tasks);
  }
}

class ComposedRunCounter {
  ComposedRunCounter(String name) : _count = 0, _runner = Runner(name);
  
  int _count;
  int get count => _count;
  
  Runner _runner;
  String get name => _runner.name;
  
  void run(Task task){
    printd("[$runtimeType($name).run]");
    _count++;
    _runner.run(task);
  }
  
  void runAll(List<Task> tasks){
    printd("[$runtimeType($name).runAll]");
    _count += tasks.length;
    _runner.runAll(tasks);
  }
}