委托学习笔记- C# - JXASP源码网

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委托的定义以及如何理解委托#

委托现实的定义：

本人不需要亲自去执行，全权委托第三方，替它来执行具体事物的概念。

也就是让别人间接完成本该由我来完成的事情。

委托程序的定义：

首先是一个类(Class),引用类型的数据类型

可以指向一个或多个方法的引用。(类型兼容)

个人理解:

调用别人的方法(本身是第三方),也就是间接的使用;并且该方法可以为一个或者多个。

补充：

C#有五类数据类型，整个数据类型分为2种：值类型(结构体,枚举)和引用数据类型(类,接口,委托)
事件和LAMBDA表达式的基础都是委托；而LAMBDA表达式又是LINQ的基础。

委托的声明及其由来#

委托虽然是一种类(Class)，引用类型的数据类型；但是它和我们一般方法的声明格式很接近。


<span style="color:#596172"><span style="background-color:#ffffff"><code class="language-C language-C#">  <span style="color:#5c6370"><em>//声明委托类型</em></span>
 
public delegate <span style="color:#d19a66">void</span> <span style="color:#5c6370"><em>/*返回值类*/</em></span> MyDelegate(<span style="color:#5c6370"><em>/*参数列表*/</em></span>);
 
    <span style="color:#5c6370"><em>//这个委托类型可以指向任何一个：返值为空，参数列表为空的其他方法。</em></span>
 
    <span style="color:#5c6370"><em>/*目标方法：委托所指向的方法*/</em></span>
 
    <span style="color:#5c6370"><em>//C#允许嵌套类型，可以在类中进行委托的声明。</em></span>
</code></span></span>

委托的声明格式是仿照C/C++[函数指针]的声明格式。


<span style="color:#596172"><span style="background-color:#ffffff"><code class="language-C"><span style="color:#61aeee">#<span style="color:#7171bf">include</span> <span style="color:#3388aa"><stdio.h></span></span>
 
 
 
<span style="color:#5c6370"><em>//声明一个函数指针</em></span>
 
<span style="color:#7171bf">typedef</span> <span style="color:#61aeee">int</span>(* Calculator)(<span style="color:#d19a66">int</span> _x,<span style="color:#d19a66">int</span> _y);
 
 
 
<span style="color:#d19a66">int</span> <span style="color:#61aeee">add</span>(<span style="color:#d19a66">int</span> _a,<span style="color:#d19a66">int</span> _b){
 
    <span style="color:#7171bf">return</span> _a + _b;
 
}
 
 
 
<span style="color:#d19a66">int</span> <span style="color:#61aeee">Multiply</span>(<span style="color:#d19a66">int</span> _a,<span style="color:#d19a66">int</span> _b){
 
    <span style="color:#7171bf">return</span> _a * _b;
 
}
 
 
 
<span style="color:#d19a66">int</span> <span style="color:#61aeee">main</span>(<span style="color:#d19a66">void</span>) { 
 
    <span style="color:#d19a66">int</span> x = <span style="color:#d19a66">9</span>;
 
    <span style="color:#d19a66">int</span> y = <span style="color:#d19a66">9</span>;
 
	Calculator pointer01 = &add;
 
	Calculator pointer02 = &Multiply;
 
	<span style="color:#7171bf">printf</span>(<span style="color:#98c379">"Add Result (pointer01) : %d\n"</span>,pointer01(x,y));
 
	<span style="color:#7171bf">printf</span>(<span style="color:#98c379">"Multiply Result (pointer02) : %d\n"</span>,pointer02(x,y));
 
	<span style="color:#7171bf">return</span> <span style="color:#d19a66">0</span>;
 
}
 
<span style="color:#5c6370"><em>//输出：</em></span>
 
<span style="color:#5c6370"><em>//Add Result (pointer01) : 18</em></span>
 
<span style="color:#5c6370"><em>//Multiply Result (pointer02) : 81</em></span>
</code></span></span>

delegate关键字也就对应了C语言种的*号(也就是指针定义符)，其余都是一一对应的。

委托类型的实例#

用委托实现按空格时，物体随机移动。


<span style="color:#596172"><span style="background-color:#ffffff"><code class="language-C language-C#">using UnityEngine;
 
 
 
public <span style="color:#7171bf">class</span> <span style="color:#e6c07b">DelegateTest</span> : MonoBehaviour
 
{
 
     private SpriteRenderer image;
 
     
 
     private delegate <span style="color:#d19a66">void</span> <span style="color:#61aeee">MyDelegate</span>();<span style="color:#5c6370"><em>//声明委托</em></span>
 
     private MyDelegate myDelegate;
 
     
 
     private <span style="color:#d19a66">void</span> <span style="color:#61aeee">Start</span>()
 
     {
 
          image = GetComponent<SpriteRenderer>();
 
     }
 
 
 
     <span style="color:#5c6370"><em>//Awake之后Start之前调用</em></span>
 
     private <span style="color:#d19a66">void</span> <span style="color:#61aeee">OnEnable</span>()
 
     {
 
          myDelegate = new MyDelegate(Teleport);
 
          <span style="color:#5c6370"><em>//myDelegate = Teleport;</em></span>
 
     }
 
 
 
     private <span style="color:#d19a66">void</span> <span style="color:#61aeee">Update</span>()
 
     {
 
          <span style="color:#7171bf">if</span> (Input.GetKeyDown(KeyCode.Space))
 
          {
 
               myDelegate.Invoke();
 
               <span style="color:#5c6370"><em>//myDelegate();</em></span>
 
          }
 
     }
 
 
 
     <span style="color:#5c6370"><em>//随机位置移动</em></span>
 
     private <span style="color:#d19a66">void</span> <span style="color:#61aeee">Teleport</span>()
 
     {
 
          Vector2 currentPos = transform.position;
 
          currentPos.x = UnityEngine.Random.Range(<span style="color:#d19a66">-5F</span>, <span style="color:#d19a66">5F</span>);
 
          transform.position = currentPos;
 
 
 
     }
 
     <span style="color:#5c6370"><em>//随机颜色</em></span>
 
     private <span style="color:#d19a66">void</span> <span style="color:#61aeee">ChangeColor</span>()
 
     {
 
          image.color = new Color(UnityEngine.Random.value,UnityEngine.Random.value,UnityEngine.Random.value);
 
     }
 
     <span style="color:#5c6370"><em>//输出时间</em></span>
 
     private <span style="color:#d19a66">void</span> <span style="color:#61aeee">Log</span>()
 
     {
 
          Debug.Log(<span style="color:#98c379">"Current Time is : "</span> + System.DateTime.UtcNow);
 
     }
 
}
</code></span></span>

多播委托#

我们都知道，计算机中的“=”是赋值，这个就是单播委托，如果想要多个方法一起调用，需要用到“+=”，也就是多播委托。

我们可以在上述的基础上，加上变色和输出，效果如下。


<span style="color:#596172"><span style="background-color:#ffffff"><code class="language-C language-C#">...
 
<span style="color:#5c6370"><em>//Awake之后Start之前调用</em></span>
 
     private <span style="color:#d19a66">void</span> <span style="color:#61aeee">OnEnable</span>()
 
     {
 
          myDelegate = new MyDelegate(Teleport);
 
          myDelegate += new MyDelegate(ChangeColor);
 
          myDelegate += new MyDelegate(Log);
 
     }
 
...
</code></span></span>