1 //==========================================
2 //Context.h
3 //==========================================
4 #pragma once
5
6 class State;
7 class Context
8 {
9 public:
10 Context(State* pState);
11 ~Context();
12 void Request();
13 private:
14 void UpdateState(State* pState);
15 friend class ConcreteStateA;
16 friend class ConcreteStateB;
17 private:
18 State* m_pState;
19 };
20
21 //==========================================
22 //Context.cpp
23 //==========================================
24 #include "Context.h"
25 #include <stdio.h>
26 #include "State.h"
27
28 Context::Context(State* pState)
29 :m_pState(pState)
30 {
31 }
32
33 Context::~Context()
34 {
35 delete m_pState;
36 }
37
38 void Context::Request()
39 {
40 if (NULL != m_pState)
41 {
42 m_pState->Handle(this);
43 }
44 }
45
46 void Context::UpdateState(State* pState)
47 {
48 delete m_pState;
49 m_pState = pState;
50 }
51
52 //==========================================
53 //State.h
54 //==========================================
55 #pragma once
56
57 class Context;
58 class State
59 {
60 public:
61 virtual ~State(){}
62 virtual void Handle(Context* pContex) = 0;
63 };
64
65 class ConcreteStateA : public State
66 {
67 public:
68 void Handle(Context* pContex);
69 };
70
71 class ConcreteStateB : public State
72 {
73 public:
74 void Handle(Context* pContex);
75 };
76
77 //==========================================
78 //State.cpp
79 //==========================================
80 #include "State.h"
81 #include <iostream>
82 #include "Context.h"
83 using namespace std;
84
85 //处理、更新状态
86 void ConcreteStateA::Handle(Context* pContex)
87 {
88 cout<<"ConcreteStateA :: Handle"<<endl;
89 pContex->UpdateState(new ConcreteStateB);
90 }
91
92 void ConcreteStateB::Handle(Context* pContex)
93 {
94 cout<<"ConcreteStateB :: Handle"<<endl;
95 pContex->UpdateState(new ConcreteStateA);
96 }
97
98 //==========================================
99 //main.cpp
100 //==========================================
101 #include "Context.h"
102 #include "State.h"
103
104 int main()
105 {
106 State *pState = new ConcreteStateA();
107 Context *pContext = new Context(pState);
108 pContext->Request();
109 pContext->Request();
110 pContext->Request();
111
112 delete pContext;
113
114 return 0;
115 }
