状态模式 C++实现

#include<iostream>
#include<string>
#include<cstdlib>

using namespace std;
/*
state 模式： 三个角色： context class / state class / concreate state class

*/
class work;       //前置声明
// abstract state class
class state
{
public:
virtual void writeprogram(work *w) = 0;
};

// context class

class work    //该类 实现对state class 的修改，选择具体的 state
{
private:
state * current;   //将state  class 嵌入到  context 中以便对其进行修改 。
int hour;
public:

work(state *s):current(s),hour(0)
{

}

void setstate(state *s)
{ delete current;
current = s;
}
int get_hour()
{
return hour;
}
void set_hour(int value)
{
hour = value;
}
void writeprogram()
{
current->writeprogram(this);
}

};
// concreate state class
class rest: public state
{
public:
void writeprogram(work *w)
{
cout <<"now is"<<w->get_hour()<<"and is surposed to rest!"<< endl;
}
};

class evening: public state
{
public:
void writeprogram(work *w)
{
if(w->get_hour() < 20)
{
cout <<"time is "<<w->get_hour()<<"evening now !"<< endl;
}
else
{
w->setstate(new rest());
w->writeprogram();
}
}
};

class afternoon: public state
{
public:
void writeprogram(work *w)
{
if(w->get_hour() < 17)
{
cout <<"time is "<<w->get_hour()<<"afternoon go on!"<< endl;
}
else
{
w->setstate(new evening());
w->writeprogram();
}
}
};

class midlenoon: public state
{
public:
void writeprogram(work *w)
{
if(w->get_hour() < 14)
{
cout <<"time is "<<w->get_hour()<<" midlenoon rest time"<< endl;
}
else
{
w->setstate(new afternoon());
w->writeprogram();
}

}
};

class forenoon: public state
{
public:
void writeprogram(work *w)
{
if(w->get_hour() < 12)
{
cout <<"now time is "<<w->get_hour()<<"forenoon "<<"state is very good!"<< endl;
}
else
{
w->setstate(new midlenoon());  // 修改状态
w->writeprogram();  // 调用下一个状态的writeprogram()函数，以下同理。
}
}
};

int main()
{
work my_work(new forenoon());

for(int i = 0; i < 30; i = i + 1)
{
my_work.set_hour(i);
my_work.writeprogram();
}

system("pause");
return 0;
}