state模式

http://www.cnblogs.com/graphicsme/archive/2011/12/09/2282657.html

http://www.cnblogs.com/k-eckel/articles/204006.aspx

#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <set>
#include <algorithm>
#include <map>
#include <stack>
using namespace std;
class State;
class Context {
public:
    Context() {
    }

    Context(State* state);

    ~Context();
    void Handle();

    void OperationForStateA();
    void OperationForStateB();
    void ChangeState(State* state);

private:
    State* _state;

};

class State {
public:
    State() {
    }

    virtual ~State() {
    }

    virtual void Handle(Context* con) = 0;

protected:
    void ChangeState(Context* con, State* st);

};

class ConcreteStateA: public State {
public:
    ConcreteStateA() {
    }

    virtual ~ConcreteStateA() {
    }

    void Handle(Context* con);

};

class ConcreteStateB: public State {
public:
    ConcreteStateB() {
    }

    virtual ~ConcreteStateB() {
    }

    void Handle(Context* con);

};

Context::Context(State* state) {
    this->_state = state;
}

Context::~Context() {
    delete _state;
}

void Context::Handle() {
    _state->Handle(this);
}

void Context::ChangeState(State* state) {
    this->_state = state;

}

void Context::OperationForStateA() {
    cout << "Do operation in State A ";
}

void Context::OperationForStateB() {
    cout << "Do operation in State B ";
}

void State::ChangeState(Context* con, State* st) {
    con->ChangeState(st);
}

void ConcreteStateA::Handle(Context* con) {
    con->OperationForStateA();

    cout << ":: State change from A to B" << endl;

    State::ChangeState(con, new ConcreteStateB());
}

void ConcreteStateB::Handle(Context* con) {
    con->OperationForStateB();

    cout << ":: State change from B to A" << endl;

    State::ChangeState(con, new ConcreteStateA());
}

int main(int argc, char* argv[]) {
    State* st = new ConcreteStateA();

    Context* con = new Context(st);

    con->Handle();
    con->Handle();
    con->Handle();

    if (con != NULL)
        delete con;

    if (st != NULL)
        st = NULL;

    return 0;
}