State

#include <iostream>

using namespace std;

class Context;

class State{
public:
    virtual void doOperation(Context * context) = 0;
    virtual ~State(){}
};

class Context{
public:
    Context(State * state):m_state(state){}
    void Request(){
        if(nullptr != m_state)
        m_state->doOperation(this);
    }
    void changeState(State * state){ m_state = state; }
private:
    State * m_state;
};


class State1 : public State{
public:
    void doOperation(Context * context);
};

class State2 : public State{
public:
    void doOperation(Context * context);
};

class State3 : public State{
public:
    void doOperation(Context * context);
};

void State1::doOperation(Context *context)
{
    cout<<"State1 doOperation"<<endl;
    context->changeState(new State2);
}

void State2::doOperation(Context *context)
{
    cout<<"State2 doOperation"<<endl;
    context->changeState(new State3);
}

void State3::doOperation(Context *context)
{
    cout<<"State3 doOperation"<<endl;
    context->changeState(new State1);
}





int main()
{
    cout << "Hello World!" << endl;


    Context * context = new Context(new State1);
    context->Request();
    context->Request();
    context->Request();
    context->Request();
    context->Request();
    context->Request();
    context->Request();
    return 0;
}