一道常见的面试题目

题目:程序设计:锚大叫一声,所有的老鼠开始逃跑,主人被惊醒

要求:一:要具有联动性,老鼠和主人的行为是被动的.二:要具有可扩展性,猫的叫声还可能引起其他联动效应

第一种方法:

    public interface Observer
    {
        void Response();
    }
    public interface Subject
    {
       void AimAt(Observer obs);
    }
    public class Mouse : Observer
    {
        private string name;
        public Mouse(string name, Subject subj)
        {
            this.name = name;
            subj.AimAt(this);
        }
        public void Response()
        {
            Console.WriteLine(name + "  try to escape");
        }
    }
    public class Masrer : Observer
    {
        public Masrer(Subject sub )
        {
            sub.AimAt(this);
        }
       public void Response()
        {
            Console.WriteLine("Master waken");
        }
    }
    public class Cat : Subject
    {
        private ArrayList observers;
        public Cat()
        {
            this.observers = new ArrayList();
        }
        public void AimAt(Observer obs)
        {
            this.observers.Add(obs);
        }
        public void Cry()
        {
            foreach (Observer obs in observers)
            {
                obs.Response();
            }
        }
    }

主程序内部:

       Cat cat = new Cat();
            Mouse mouse1 = new Mouse("mouse1", cat);
            Mouse mouse2 = new Mouse("mouse2", cat);
            Masrer master = new Masrer(cat);
            cat.Cry();

第二种方法:

 

public delegate void SubeventHandler();
    public abstract class Subject
    {
        public event SubeventHandler subevent;
       public void FireAway()
        {
            if (this.subevent != null)
            {
                this.subevent();
            }
        }
    }
    public class Cat : Subject
    {
        public void Cry()
       {
           Console.WriteLine("Cat begun to cry");
           FireAway();
        }
   
    }
    public class Mouse : Observer
    {
        private string name;
        public Mouse(string name, Subject sub)
            : base(sub)
        {
            this.name = name;

        }
        public override void Response()
        {
            Console.WriteLine(this.name + "  attempe to run");
        }
    }
    public abstract class Observer
    {
        public Observer(Subject sub)
        {
            sub.subevent+=new SubeventHandler(Response);
        }
        public abstract void Response();
        
    }
    public class Master : Observer
    {
        public Master(Subject sub):base(sub)
        {
            
        }
        public override void Response()
        {
            Console.WriteLine("Host waken");
        }
    }

event-delegate设计