设计模式---观察者模式（恐怖袭击、地震的例子，有类关系图）

 

1. using System;
2. using System.Collections.Generic;
3. using System.Text;
5. namespace ConsoleApplication1
6. {
7.     internal interface Warning
8.     {
9.         String Situation
10.         {
11.             get;
12.             set;
13.         }
15.         void Warn();
17.         void Add(PeopleInSchool p);
19.         void Sub(PeopleInSchool p);
20.     }
22.     class PoliceStation : Warning
23.     {
24.         private IList<PeopleInSchool> field = new List<PeopleInSchool>();
25.         string situation;
26.         public string Situation
27.         {
28.             get
29.             {
30.                 return situation;
31.             }
32.             set
33.             {
34.                 situation = value;
35.             }
36.         }
38.         public void Warn()
39.         {
40.             foreach (PeopleInSchool p in field)
41.             {
42.                 p.WarningReceived();
43.             }
44.         }
46.         public void Add(PeopleInSchool p)
47.         {
48.             field.Add(p);
49.         }
51.         public void Sub(PeopleInSchool p)
52.         {
53.             field.Remove(p);
54.         }
55.     }
57.     class EarthquakeDepartment : Warning
58.     {
60.         string situation;
62.         private IList<PeopleInSchool> field = new List<PeopleInSchool>();
64.         public string Situation
65.         {
66.             get
67.             {
68.                 return situation;
69.             }
70.             set
71.             {
72.                 situation = value;
73.             }
74.         }
76.         public void Warn()
77.         {
78.             foreach (PeopleInSchool p in field)
79.             {
80.                 p.WarningReceived();
81.             }
82.         }
84.         public void Add(PeopleInSchool p)
85.         {
86.             field.Add(p);
87.         }
89.         public void Sub(PeopleInSchool p)
90.         {
91.             field.Remove(p);
92.         }
93.     }
95.     abstract class PeopleInSchool
96.     {
98.         protected Warning field;
100.         public PeopleInSchool(Warning w)
101.         {
102.             field = w;
103.         }
105.         public abstract void WarningReceived();
108.     }
110.     class Teacher : PeopleInSchool
111.     {
112.         public Teacher(Warning w)
113.             : base(w)
114.         {
116.         }
118.         public override void WarningReceived()
119.         {
120.             Console.WriteLine("我是老师" + field.Situation);
121.         }
122.     }
124.     class Student : PeopleInSchool
125.     {
126.         public Student(Warning w)
127.             : base(w)
128.         {
130.         }
132.         public override void WarningReceived()
133.         {
134.             Console.WriteLine("我是学生" + field.Situation);
135.         }
136.     }
138.     class Client
139.     {
140.         public static void Main()
141.         {
142.             PoliceStation p = new PoliceStation();
143.             Teacher t = new Teacher(p);
144.             Student s = new Student(p);
145.             p.Add(t);
146.             p.Add(s);
147.             p.Situation = "有恐怖袭击！！！";
148.             p.Warn();
149.             p.Situation = "注意防火防盗！！！";
150.             p.Warn();
152.             EarthquakeDepartment e = new EarthquakeDepartment();
153.             t = new Teacher(e);
154.             s = new Student(e);
155.             e.Add(t);
156.             e.Add(s);
157.             e.Situation = "要地震了！！！";
158.             e.Warn();
160.             Console.Read();
161.         }
163.     }
164. }