state 状态模式

来源：互联网发布：java中九九乘法表编辑：程序博客网时间：2024/06/03 21:33
#include <iostream>#include <string>using namespace std;/*1) 将 State声明为 Context的友元类（friend class） ，其作用是让 State模式访问 Context的 protected接口 ChangeSate（） 。2) State 及其子类中的操作都将 Context*传入作为参数，其主要目的是 State 类可以通过这个指针调用 Context中的方法 （在本示例代码中没有体现） 。 这也是 State模式和 Strategy模式的最大区别所在。*/class state;class context{public:    context():_st(NULL){}    context(state *st):_st(st){}    ~context(){ delete _st; }    void operation_interface();private:    friend class state;    void operation_change_state();    bool change_state(state *st)    {        if (_st != NULL)            delete _st;        _st = st;        return true;    }private:    state *_st;};class state{public:    state(){};    virtual ~state(){};    virtual void operation_interface(context *) =0;    virtual void operation_change_state(context *) =0;protected:    bool change_state(context *con, state *st)    {        con->change_state(st);    }};void context::operation_interface(){    _st->operation_interface(this);    operation_change_state();}void context::operation_change_state(){    _st->operation_change_state(this);}class concrete_stateA : public state{public:    concrete_stateA(){}    ~concrete_stateA(){}    virtual void operation_interface(context *con)    {        cout<< "concrete_stateA::operation_interface"<<endl;    }    void operation_change_state(context *con);};class concrete_stateB : public state{public:    concrete_stateB(){}    ~concrete_stateB(){}    virtual void operation_interface(context *con)    {        cout<< "concrete_stateB::operation_interface"<<endl;    }    virtual void operation_change_state(context *con)    {        cout<< "concrete_stateB::operation_change_state"<<endl;        this->change_state(con, new concrete_stateA);    }};void concrete_stateA::operation_change_state(context *con){    cout<< "concrete_stateA::operation_change_state"<<endl;    this->change_state(con, new concrete_stateB);}int main(){    state *st = new concrete_stateA;    context *con = new context(st);    con->operation_interface();    con->operation_interface();    con->operation_interface();    delete con;    return 0;}////////////////////////////#include <iostream>#include <string>using namespace std;class context;class state{public:    ~state(){}    virtual string name() =0;    virtual void handle(context *) =0;};class context{public:    context(state *st):m_pst(st){}    ~context(){ set_state(NULL); }    void set_state(state *st)    {        if (m_pst != NULL)            delete m_pst;        m_pst = st;    }    state *get_state()    {        return m_pst;    }    void request()    {        cout<< m_pst->name() <<endl;        m_pst->handle(this);        cout<< m_pst->name() <<endl;    }private:    state *m_pst;};class concrete_stateA : public state{public:    void handle(context *con);    string name()    {        return "concrete_stateA";    }};class concrete_stateB : public state{public:    void handle(context *con)    {        con->set_state(new concrete_stateA);    }    string name()    {        return "concrete_stateB";    }};void concrete_stateA::handle(context *con){    con->set_state(new concrete_stateB);}int main(){    context * c = new context(new concrete_stateA);    c->request();    c->request();    c->request();    c->request();    c->request();    delete c;    return 0;}
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