委托和事件

1.委托是一种引用类型，用于将方法作为参数传递给其他方法。

通过委托进行冒泡排序

 1 using System;
 2 class delegatesample {
 3     // 定义一个委托
 4     public delegate bool del (int fir, int sec);
 5     public static void BubbleSort (int[] item,
 6         del com) {
 7         int i, j, temp;
 8         for (i = item.Length - 1; i >= 0; i--)
 9             for (j = 1; j <= i; j++) {
10                 if (com (item[j - 1], item[j])) {
11                     temp = item[j - 1];
12                     item[j - 1] = item[j];
13                     item[j] = temp;
14                 }
15             }
16     }
17     // 委托实例化
18     public static bool method (int fir, int sec) {
19         return fir > sec;
20     }
21     static void Main () {
22         int[] item = { 2, 3, 6, 5, 4, 9, 5, 4, 33 };
23         // 将方法当做参数传入另一个方法
24         BubbleSort (item, method);
25         for (int i = 0; i < item.Length; i++)
26             System.Console.WriteLine (item[i]);
27     }
28 }

使用匿名方法

 1 using System;
 2 class delegatesample {
 3     // 定义一个委托
 4     public delegate bool del (int fir, int sec);
 5     public static void BubbleSort (int[] item,
 6         del com) {
 7         int i, j, temp;
 8         for (i = item.Length - 1; i >= 0; i--)
 9             for (j = 1; j <= i; j++) {
10                 if (com (item[j - 1], item[j])) {
11                     temp = item[j - 1];
12                     item[j - 1] = item[j];
13                     item[j] = temp;
14                 }
15             }
16     }
17     static void Main () {
18         int[] item = { 2, 3, 6, 5, 4, 9, 5, 4, 33 };
19         // 匿名方法
20         BubbleSort (item, delegate (int fir, int sec) {
21             return fir > sec;
22         });
23         for (int i = 0; i < item.Length; i++)
24             System.Console.WriteLine (item[i]);
25     }
26 }匿名
niming

 

使用Lambda语句

1  static void Main () {
2         int[] item = { 2, 3, 6, 5, 4, 9, 5, 4, 33 };
3         // Lambda
4         BubbleSort (item, (fir, sec) => {
5             return fir > sec;
6         });
7         for (int i = 0; i < item.Length; i++)
8             System.Console.WriteLine (item[i]);
9     }

 

使用Lambda表达式

1 static void Main () {
2         int[] item = { 2, 3, 6, 5, 4, 9, 5, 4, 33 };
3         // Lambda
4         BubbleSort (item, (fir, sec) => fir > sec);
5         for (int i = 0; i < item.Length; i++)
6             System.Console.WriteLine (item[i]);
7     }

 

通用委托：System.Func和System.Action

func有返回值action没有

他俩不需要委托实例化，直接封装方法，需要命名空间System

Func最后一个类型总是委托的返回类型

 1 using System;
 2 class delegatesample {
 3     public static void BubbleSort (int[] item,
 4         Func<int, int, bool> com) {
 5         int i, j, temp;
 6         for (i = item.Length - 1; i >= 0; i--)
 7             for (j = 1; j <= i; j++) {
 8                 if (com (item[j - 1], item[j])) {
 9                     temp = item[j - 1];
10                     item[j - 1] = item[j];
11                     item[j] = temp;
12                 }
13             }
14     }
15     static void Main () {
16         int[] item = { 2, 3, 6, 5, 4, 9, 5, 4, 33 };
17         BubbleSort (item, (fir, sec) => fir > sec);
18         for (int i = 0; i < item.Length; i++)
19             System.Console.WriteLine (item[i]);
20     }
21 }

 

注意：避免在匿名函数内捕捉循环变量，委托没有结构相等性。

2.事件

简单多播委托

 1 using System;
 2 // 注释为不用action的方法
 3 /* delegate void del (string s); */
 4 class test {
 5     static void Yahoo (string s) {
 6         Console.WriteLine ("Yahoo,{0}!", s);
 7     }
 8     static void Huohua (string s) {
 9         Console.WriteLine ("Huohua {0}!", s);
10     }
11     static void main () {
12         /* del fir, sec, one, two; */
13         Action<string> fir = Yahoo, sec = Huohua,
14             two = fir + sec, one = two - sec;
15         /* fir = Yahoo;
16         sec = Huohua;
17         two = fir + sec;
18         one = two - sec; */
19         Console.WriteLine ("输出:fir");
20         fir ("a");
21         Console.WriteLine ("输出:sec");
22         sec ("b");
23         Console.WriteLine ("输出:two");
24         two ("c");
25         Console.WriteLine ("输出:one");
26         one ("d");
27     }
28 }

 

温度控制多播委托

 1 using System;
 2 class Cooler {
 3     public Cooler (float temperature) { Temperature = temperature; }
 4     public float Temperature { get; set; }
 5     public void OnTemperatureChanged (float newTemperature) {
 6         if (newTemperature > Temperature) {
 7             Console.WriteLine ("Cooler:On");
 8         } else Console.WriteLine ("Cooler:Off");
 9     }
10 }
11 class Heater {
12     public Heater (float tempreature) {
13         Temperature = tempreature;
14     }
15     public float Temperature { get; set; }
16     public void OnTemperatureChanged (float newTemperature) {
17         if (newTemperature < Temperature) {
18             System.Console.WriteLine ("Heatera:On");
19         } else System.Console.WriteLine ("Heater:Off");
20     }
21 }
22 public class Thermostat {
23     public Action<float> OnTemperatureChange { get; set; }
24     public float CurrentTem {
25         get { return _current; }
26         set {
27             if (value != CurrentTem) {
28                 _current = value;
29                 OnTemperatureChange?.Invoke (value);
30             }
31         }
32     }
33     private float _current;
34 }
35 //委托定义需要初始化
36 class P1 {
37     public static void Main () {
38         Thermostat thermostat = new Thermostat ();
39         Heater heater = new Heater (60);
40         Cooler cooler = new Cooler (80);
41         thermostat.OnTemperatureChange +=
42             heater.OnTemperatureChanged;
43         thermostat.OnTemperatureChange +=
44             cooler.OnTemperatureChanged;
45         // 从包容的类外部触发事件
46         thermostat.OnTemperatureChange (90);
47     }
48 }

 

注意：使用-=操作符会返回一个新实例 P371(c#本质论）

事件通过关键字event（event是CIL可以显示识别的一种东西）进行封装以更改委托两处问题。

  • 防止使用=操作符出错
  • 事件保证只有包容的类可以触发

 1 using System;
 2 class Cool : Handler {
 3     public Cool (float tempreature, Handler tem) {
 4         Tem = tempreature;
 5         tem.OnTemChange += OnTemChanged;
 6     }
 7     private float Tem;
 8     public void OnTemChanged (object sender, TemArgs T) {
 9         if (T.NewTem > Tem) {
10             Console.WriteLine ("Cooler:On");
11         } else Console.WriteLine ("Cooler:Off");
12     }
13 }
14 // 订阅者
15 class Heat : Handler {
16     public Heat (float tempreature, Handler tem) {
17         Tem = tempreature;
18         tem.OnTemChange += OnTemChanged;
19     }
20     private float Tem;
21     public void OnTemChanged (object sender, TemArgs T) {
22         if (T.NewTem < Tem) {
23             System.Console.WriteLine ("Heater:On");
24         } else System.Console.WriteLine ("Heater:Off");
25     }
26 }
27 class Handler {
28     // 事件数据类型
29     public class TemArgs : System.EventArgs {
30         public TemArgs (float newTem) {
31             NewTem = newTem;
32         }
33         public float NewTem;
34     }
35 
36     // 定义事件发布者
37     public event EventHandler<TemArgs>
38         OnTemChange = delegate { };
39 
40     // 事件触发器
41     public void handler (int i) {
42         if (OnTemChange != null)
43             OnTemChange (this,
44                 new Handler.TemArgs (i));
45     }
46 }
47 class P2 {
48     public static void Main () {
49         Handler publish = new Handler ();
50         Heat heater = new Heat (60, publish);
51         Cool cooler = new Cool (80, publish);
52         publish.handler (20);
53         Console.WriteLine ();
54         publish.handler (90);
55     }
56 }

 

posted @ 2019-04-27 14:26  0以太0  阅读(113)  评论(0)    收藏  举报