State (C++实现）

// State.cpp : 定义控制台应用程序的入口点。//

#include "stdafx.h"#include <iostream>

using namespace std;

 

class State;

class Context{public: Context(State* pState); ~Context(); void Request(); void ChangeState(State *pState);

private: State *m_pState;};

 

class State{public: virtual ~State(){}

 virtual void Handle(Context* pContext) = 0;};

class ConcreateStateA: public State{public: void Handle(Context* pContext);};

class ConcreateStateB: public State{public: void Handle(Context* pContext);};

Context::Context(State* pState): m_pState(pState){

}

Context::~Context(){ delete m_pState; m_pState = NULL;}

void Context::Request(){ if (NULL != m_pState) {  m_pState->Handle(this); }}

void Context::ChangeState(State *pState){ if (NULL != m_pState) {  delete m_pState;  m_pState = NULL; } m_pState = pState;}

void ConcreateStateA::Handle(Context* pContext){ std::cout << "Handle by ConcreateStateA/n";}

void ConcreateStateB::Handle(Context* pContext){ std::cout << "Handle by ConcreateStateB/n";}

int _tmain(int argc, _TCHAR* argv[]){

 State *pStateA = new ConcreateStateA(); State *pStateB = new ConcreateStateB(); Context *pContext = new Context(pStateA); pContext->Request(); cout<<"-------------------------------"<<endl; pContext->ChangeState(pStateB); pContext->Request();

 delete pContext;

 return 0;}