C#经典机试题(猫叫)

　　猫大叫一声，所有的老鼠都开始逃跑，主人被惊醒。(C#语言)

　　1.要有联动性，老鼠和主人的行为是被动的。

　　2.考虑可扩展性，猫的叫声可能引起其他联动效应。

1、运用接口：

public interface Observer { 
    void Response(); //观察者的响应，这是老鼠见到猫的反映
}

public interface Subject { 
    void AimAt(Observer obs); //针对哪些观察者，这里指猫的要扑捉的对象---老鼠 
}
/// <summary>
/// 老鼠的相应，继承被观察的对象
/// </summary>
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 + " attempt to escape!"); 
    } 

}
/// <summary>
/// 主人的相应，继承被观察的对象
/// </summary>
public class Master : Observer { 
    public Master(Subject subj) {
        subj.AimAt(this); 
    }
    public void Response() { 
        Console.WriteLine("Host waken!"); 
    } 
}
/// <summary>
/// 猫观充当观察者的角色
/// </summary>
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() { 
        Console.WriteLine("Cat cryed!"); 
        foreach (Observer obs in this.observers) { 
            obs.Response(); 
        }
    }
}

class MainClass { 
    static void Main(string[] args) { 
        Cat cat = new Cat(); 
        Mouse mouse1 = new Mouse("mouse1", cat); 
        Mouse mouse2 = new Mouse("mouse2", cat); 
        Master master = new Master(cat);
        cat.Cry();
    }
}

2、 使用event -- delegate设计..

public delegate void SubEventHandler(); 

public abstract class Subject { 
    public event SubEventHandler SubEvent; 
    protected void FireAway() { 
        if (this.SubEvent != null) 
            this.SubEvent(); 
    }  
} 
public class Cat : Subject {  
    public void Cry() { 
        Console.WriteLine("cat cryed."); 
        this.FireAway();
    }
} 
public abstract class Observer {
    public Observer(Subject sub) { 
        sub.SubEvent += new SubEventHandler(Response); 
    } 
    public abstract void Response();  
} 
public class Mouse : Observer { 
    private string name; 
    public Mouse(string name, Subject sub) : base(sub) {  
        this.name = name;
    } 
    public override void Response() {
        Console.WriteLine(name + " attempt to escape!"); 
    } 
}
public class Master : Observer { 
    public Master(Subject sub) : base(sub){
    } 
    public override void Response() { 
        Console.WriteLine("host waken"); 
    } 
} 
class Class1 { 
    static void Main(string[] args) { 
        Cat cat = new Cat();
        Mouse mouse1 = new Mouse("mouse1", cat); 
        Mouse mouse2 = new Mouse("mouse2", cat); 
        Master master = new Master(cat); cat.Cry(); 
    } 
}

 转自：http://kb.cnblogs.com/page/50471/