什么是代表团？我什么时候想用它？ [英] What is delegation? When would I want to use it?

问题描述

在OOP中，提到了一个术语委托。这是如何在课堂上建模的？我在雅虎等搜索，但获得了代表的链接。

In OOP, a term delegation is mentioned. How is this modelled in a class? I searched on yahoo etc but got links to delegates.

推荐答案

想象你有课程 code>和引擎：

public class Car {
   private Engine engine = new Engine(); //or inject it externally

   public void start() {
       engine.start();
   }
}

在这个例子中， Car 委托给底层的引擎。汽车的用户不能直接启动发动机（除非他是机械师）。但是他可以告诉汽车启动，而汽车依次告诉发动机启动。

In this example the Car delegates to the underlying Engine. The user of the car cannot directly start the engine (unless he is a mechanic). But he can tell the car to start, and the car in turn tells the engine to start.

当你使用对象组合，你需要使用它，你需要使用组合对象之一的方法。在这种情况下，您创建一个委托给它的方法。

You'd want to use it whenever you use object composition and you need to use a method of one of the composing objects. In that case you create a method that delegates to it.

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