设计模式——状态模式（C++实现）

最新推荐文章于 2024-11-25 18:10:25 发布

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最新推荐文章于 2024-11-25 18:10:25 发布

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原文链接：http://www.cnblogs.com/070412-zwc/p/6858766.html

本文通过C++代码示例详细介绍了状态模式的实现过程。利用STContext类作为环境类持有当前状态，并通过请求方法触发状态变化；STState为抽象状态类定义接口，而STConcreteStateA、B、C则是具体的状态实现，每种状态中定义了如何处理环境对象的请求及如何改变状态。

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  1 /////////context.cpp
  2 #include "context.h"
  3 
  4 void STContext::ChangeState(STState* pstState)
  5 {
  6         m_pstState = pstState;
  7 }
  8 
  9 void STContext::request()
 10 {
 11         m_pstState->Handle(this);
 12 }
 13 /////////// context.h 
 14 #ifndef _CONTEXT_H_
 15 #define _CONTEXT_H_
 16 
 17 #include <iostream>
 18 #include <string>
 19 
 20 #include "state.h"
 21 
 22 using namespace std;
 23 
 24 
 25 class STState;
 26 
 27 class STContext
 28 {
 29 public:
 30         void ChangeState(STState* pstState);
 31         void request();
 32 
 33         STState* m_pstState;
 34 };
 35 
 36 #endif
 37 
 38 
 39 ///////////////////////////// state.cpp
 40 #include "state.h"
 41 
 42 void STConcreteStateA::Handle(STContext* pstContext)
 43 {
 44         cout<< "doing something in State A.\ndone, change state to State B"<< endl;
 45         pstContext->ChangeState(new STConcreteStateB());
 46 }
 47 
 48 void STConcreteStateB::Handle(STContext* pstContext)
 49 {
 50         cout<< "doing something in State B.\ndone, change state to State C"<< endl;
 51         pstContext->ChangeState(new STConcreteStateC());
 52 }
 53 
 54 void STConcreteStateC::Handle(STContext* pstContext)
 55 {
 56         cout<< "doing something in State C.\ndone."<< endl;
 57 }
 58 
 59 /////////////////////////////// state.h
 60 #ifndef _STATE_H_
 61 #define _STATE_H_
 62 #include <iostream>
 63 #include <string>
 64 
 65 #include "context.h"
 66 
 67 using namespace std;
 68 
 69 class STContext;
 70 
 71 class STState
 72 {
 73 public:
 74         virtual void Handle(STContext*) = 0;
 75 };
 76 
 77 class STConcreteStateA: public STState
 78 {
 79 public:
 80         virtual void Handle(STContext* pstContext);
 81 };
 82 
 83 class STConcreteStateB: public STState
 84 {
 85 public:
 86         virtual void Handle(STContext* pstContext);
 87 };
 88 
 89 class STConcreteStateC: public STState
 90 {
 91 public:
 92         virtual void Handle(STContext* pstContext);
 93 };
 94 
 95 #endif
 96 
 97 
 98 ////////////////////// main.cpp
 99 #include <iostream>
100 #include <string>
101 
102 #include "state.h"
103 #include "context.h"
104 
105 using namespace std;
106 
107 int main(int argc, char* argv[])
108 {
109         STContext* pstContext = new STContext();
110 
111         STState* pstStateA = new STConcreteStateA();
112 
113         pstContext->ChangeState(pstStateA);
114         pstContext->request();
115         pstContext->request();
116 
117         return 0;
118 }
119 
120 /////////////////////
121 [wenchaozeng@devnet_10_10_tlinux_64 ~/learn_code/design_pattern/13_state]$ ./main
122 doing something in State A.
123 done, change state to State B
124 doing something in State B.
125 done, change state to State C