NET委托：一個關(guān)于C#的睡前故事（2）

于是，彼得意識到接口雖然在很多情況都很有用，但是當(dāng)用作事件時，“粒度”不夠好。他希望能夠僅在別人想要時才通知他們，于是他決定把接口的方法分離為單獨的委托，每個委托都像一個小的接口方法：
    delegate void WorkStarted();
    delegate void WorkProgressing();
    delegate int WorkCompleted();
    class Worker {
    public void DoWork() {
    Console.WriteLine(“工作: 工作開始”);
    if( started != null ) started();
    Console.WriteLine(“工作: 工作進(jìn)行中”);
    if( progressing != null ) progressing();
    Console.WriteLine("“工作: 工作完成”");
    if( completed != null ) {
    int grade = completed();
    Console.WriteLine(“工人的工作得分＝” + grade);
    }
    }
    public WorkStarted started;
    public WorkProgressing progressing;
    public WorkCompleted completed;
    }
    class Boss {
    public int WorkCompleted() {
    Console.WriteLine("Better...");
    return 4; /* 總分為10 */
    }
    }
    class Universe {
    static void Main() {
    Worker peter = new Worker();
    Boss boss = new Boss();
    peter.completed = new WorkCompleted(boss.WorkCompleted);
    peter.DoWork();
    Console.WriteLine(“Main: 工人工作完成”);
    Console.ReadLine();
    }
    }
    靜態(tài)監(jiān)聽者
    這樣，彼得不會再拿他老板不想要的事件來煩他老板了，但是他還沒有把宇宙放到他的監(jiān)聽者列表中。因為宇宙是個包涵一切的實體，看來不適合使用實例方法的委托（想像一下，實例化一個“宇宙”要花費多少資源…..），于是彼得就需要能夠?qū)o態(tài)委托進(jìn)行掛鉤，委托對這一點支持得很好：
    class Universe {
    static void WorkerStartedWork() {
    Console.WriteLine("Universe notices worker starting work");
    }
    static int WorkerCompletedWork() {
    Console.WriteLine("Universe pleased with worker's work");
    return 7;
    }
    static void Main() {
    Worker peter = new Worker();
    Boss boss = new Boss();
    peter.completed = new WorkCompleted(boss.WorkCompleted);
    peter.started = new WorkStarted(Universe.WorkerStartedWork);
    peter.completed = new WorkCompleted(Universe.WorkerCompletedWork);
    peter.DoWork();
    Console.WriteLine(“Main: 工人工作完成”);
    Console.ReadLine();
    }
    }