1 // ADBHelper.cpp : This file contains the 'main' function. Program execution begins and ends there.
2 //
3
4 //#include "pch.h"
5 #include <stdafx.h>
6 #include <iostream>
7 #include <list>
8 using namespace std;
9
10 class Observer
11 {
12 public:
13 virtual void Update(int) = 0;
14 };
15
16 class Subject
17 {
18 public:
19 virtual void Attach(Observer *) = 0;
20 virtual void Detach(Observer *) = 0;
21 virtual void Notify() = 0;
22 };
23
24 class ConcreteObserver : public Observer
25 {
26 public:
27 ConcreteObserver(Subject *pSubject) : m_pSubject(pSubject) {}
28
29 void Update(int value)
30 {
31 cout << "ConcreteObserver get the update. New State:" << value << endl;
32 }
33
34 private:
35 Subject *m_pSubject;
36 };
37
38 class ConcreteObserver2 : public Observer
39 {
40 public:
41 ConcreteObserver2(Subject *pSubject) : m_pSubject(pSubject) {}
42
43 void Update(int value)
44 {
45 cout << "ConcreteObserver2 get the update. New State:" << value << endl;
46 }
47
48 private:
49 Subject *m_pSubject;
50 };
51
52 class ConcreteSubject : public Subject
53 {
54 public:
55 void Attach(Observer *pObserver);
56 void Detach(Observer *pObserver);
57 void Notify();
58
59 void SetState(int state)
60 {
61 m_iState = state;
62 }
63
64 private:
65 std::list<Observer *> m_ObserverList;
66 int m_iState;
67 };
68
69 void ConcreteSubject::Attach(Observer *pObserver)
70 {
71 m_ObserverList.push_back(pObserver);
72 }
73
74 void ConcreteSubject::Detach(Observer *pObserver)
75 {
76 m_ObserverList.remove(pObserver);
77 }
78
79 void ConcreteSubject::Notify()
80 {
81 std::list<Observer *>::iterator it = m_ObserverList.begin();
82 while (it != m_ObserverList.end())
83 {
84 (*it)->Update(m_iState);
85 ++it;
86 }
87 }
88
89 int main()
90 {
91 // Create Subject
92 ConcreteSubject *pSubject = new ConcreteSubject();
93
94 // Create Observer
95 Observer *pObserver = new ConcreteObserver(pSubject);
96 Observer *pObserver2 = new ConcreteObserver2(pSubject);
97
98 // Change the state
99 pSubject->SetState(2);
100
101 // Register the observer
102 pSubject->Attach(pObserver);
103 pSubject->Attach(pObserver2);
104
105 pSubject->Notify();
106
107 // Unregister the observer
108 pSubject->Detach(pObserver);
109
110 pSubject->SetState(3);
111 pSubject->Notify();
112
113 delete pObserver;
114 delete pObserver2;
115 delete pSubject;
116 }
117
118 // Run program: Ctrl + F5 or Debug > Start Without Debugging menu
119 // Debug program: F5 or Debug > Start Debugging menu
120
121 // Tips for Getting Started:
122 // 1. Use the Solution Explorer window to add/manage files
123 // 2. Use the Team Explorer window to connect to source control
124 // 3. Use the Output window to see build output and other messages
125 // 4. Use the Error List window to view errors
126 // 5. Go to Project > Add New Item to create new code files, or Project > Add Existing Item to add existing code files to the project
127 // 6. In the future, to open this project again, go to File > Open > Project and select the .sln file
转载：https://www.cnblogs.com/carsonzhu/p/5770253.html
未完，待描述……
