设计模式——状态模式（C++实现）

/////////context.cpp
#include "context.h"

void STContext::ChangeState(STState* pstState)
{
        m_pstState = pstState;
}

void STContext::request()
{
        m_pstState->Handle(this);
}
/////////// context.h 
#ifndef _CONTEXT_H_
#define _CONTEXT_H_

#include <iostream>
#include <string>

#include "state.h"

using namespace std;


class STState;

class STContext
{
public:
        void ChangeState(STState* pstState);
        void request();

        STState* m_pstState;
};

#endif


///////////////////////////// state.cpp
#include "state.h"

void STConcreteStateA::Handle(STContext* pstContext)
{
        cout<< "doing something in State A.
done, change state to State B"<< endl;
        pstContext->ChangeState(new STConcreteStateB());
}

void STConcreteStateB::Handle(STContext* pstContext)
{
        cout<< "doing something in State B.
done, change state to State C"<< endl;
        pstContext->ChangeState(new STConcreteStateC());
}

void STConcreteStateC::Handle(STContext* pstContext)
{
        cout<< "doing something in State C.
done."<< endl;
}

/////////////////////////////// state.h
#ifndef _STATE_H_
#define _STATE_H_
#include <iostream>
#include <string>

#include "context.h"

using namespace std;

class STContext;

class STState
{
public:
        virtual void Handle(STContext*) = 0;
};

class STConcreteStateA: public STState
{
public:
        virtual void Handle(STContext* pstContext);
};

class STConcreteStateB: public STState
{
public:
        virtual void Handle(STContext* pstContext);
};

class STConcreteStateC: public STState
{
public:
        virtual void Handle(STContext* pstContext);
};

#endif


////////////////////// main.cpp
#include <iostream>
#include <string>

#include "state.h"
#include "context.h"

using namespace std;

int main(int argc, char* argv[])
{
        STContext* pstContext = new STContext();

        STState* pstStateA = new STConcreteStateA();

        pstContext->ChangeState(pstStateA);
        pstContext->request();
        pstContext->request();

        return 0;
}

/////////////////////
[wenchaozeng@devnet_10_10_tlinux_64 ~/learn_code/design_pattern/13_state]$ ./main
doing something in State A.
done, change state to State B
doing something in State B.
done, change state to State C