public ObserverPattern()
{
ConcreteSubject subject = new ConcreteSubject();
ConcreteObserver observer1 = new ConcreteObserver("Rome", subject);
ConcreteObserver observer2 = new ConcreteObserver("Paris", subject);
ConcreteObserver observer3 = new ConcreteObserver("London", subject);
subject.Attach(observer1);
subject.Attach(observer2);
subject.Attach(observer3);
for (int i = 0; i < 10; i++)
{
subject.ChangeState($"Status #{i}");
subject.Notify();
Thread.Sleep(500);
}
}