State 状态模式

  

    GOOD：当一个对象的行为取决于它的状态，并且它必须在运行时刻根据状态改变它的行为时，可考虑用到状态模式。

例

#include <iostream>

using namespace std;

 

class Work;

class ForenoonState;

class NoonState;

 

class State

{

public:

       virtual void WriteProgram(Work* w)=0;

};

 

class Work

{

private:

       State* current;

public:

       double hour;

public:

       Work();

       void SetState(State* temp)

       {

       current =temp;

       }

       void Writeprogram()

       {

              current->WriteProgram(this);

       }

 

};

 

class NoonState :public State

{

public:

       virtual void WriteProgram(Work* w)

       {

              cout<<"execute"<<endl;

              if((w->hour)<13)

                     cout<<"还不错啦"<<endl;

              else

                     cout<<"不行了，还是睡觉吧"<<endl;

       }

};

 

class ForenoonState : public State

{

public:

       virtual void WriteProgram(Work* w)

       {

              if((w->hour)<12)

                     cout<<"现在的精神无敌好"<<endl;

              else

              {

                     w->SetState(new NoonState());

                    w->Writeprogram(); //注意加上这句

              }

       }

};

 

 

Work::Work()

{

              current = new ForenoonState();

}

 

客户端：

int main()

{

       Work* mywork=new Work();

       mywork->hour=9;

       mywork->Writeprogram();

       mywork->hour = 14;

       mywork->Writeprogram();

       return 0;

}