public override void RemoveObserver(ObserverAb observer)
{
//判断是否有该观察者
if (observers.Contains(observer))
{
observers.Remove(observer);
}
}
public override void AddObserver(ObserverAb observer)
{
//判断是否有该观察者
if (!observers.Contains(observer))
{
observers.Add(observer);
}
}
public abstract void RemoveObserver(ObserverAb observer);
public abstract void AddObserver(ObserverAb observer);
