Lektion3_8

class Observable
{
public:
  Observable() : obs_list() {}

  void add_observer(Observer* o) { obs_list.push_back(o); }
  void remove_observer(Observer* o) { ... }

protected:
  void notify_all()
  {
    for (Observer* o : obs_list)
      o->notify();
  }

private:
  vector<Observer*> obs_list;
};

class Data : public Observable
{
  ...
};


class Observer
{
  virtual Observer();
  virtual void notify() = 0;
  ...
};

class Bar_Chart : public Observer
{
  Bar_Chart(){...}

  void notify() override
  {
    ...
  }
};

int main()
{
  Data& observable{};
  Bar_chart* bar_chart{new Bar_Chart{}};
  observable.add_observer(bar_chart);
  ...
}