NET委托:一个关于C#的睡前故事(2)
于是,彼得意识到接口虽然在很多情况都很有用,但是当用作事件时,“粒度”不够好。他希望能够仅在别人想要时才通知他们,于是他决定把接口的方法分离为单独的委托,每个委托都像一个小的接口方法:
delegate void WorkStarted();
delegate void WorkProgressing();
delegate int WorkCompleted();
class Worker {
public void DoWork() {
Console.WriteLine(“工作: 工作开始”);
if( started != null ) started();
Console.WriteLine(“工作: 工作进行中”);
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; /* 总分为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();
}
}
静态监听者
这样,彼得不会再拿他老板不想要的事件来烦他老板了,但是他还没有把宇宙放到他的监听者列表中。因为宇宙是个包涵一切的实体,看来不适合使用实例方法的委托(想像一下,实例化一个“宇宙”要花费多少资源…..),于是彼得就需要能够对静态委托进行挂钩,委托对这一点支持得很好:
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();
}
}
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