## 模式定义
状态模式允许对象在内部状态改变时改变它的行为，对象看起来好像修改了它的类。
## 模式结构：
Context:
环境定义客户感兴趣的接口
维护一个ConcreteState子类的实例，这个实例定义当前状态
State:
定义一个接口封装与Context的一个特定状态相关的行为
ConcreteState subclasses:
每一子类实现一个与Context的一个状态相关的行为
## 举例：
一个工人一天的时间分为上班，睡觉，干其他事情三个时间段。我们可以用状态模式来表示一天中在干什么事情。
## UML设计：
## 编程实现及执行结果：
~~~
#include <iostream>
using namespace std;
class Worker; //类的前置声明
//状态类
class State
{
public:
virtual void doing(Worker* w){}
};
//工作状态
class WorkingState: public State
{
public:
void doing(Worker* worker);
};
//休息状态
class SleepingState: public State
{
public:
void doing(Worker* worker);
};
//其他状态
class OtherState : public State
{
public:
void doing(Worker* worker);
};
//工人类
class Worker
{
public:
Worker()
{
state = new WorkingState();
}
void setState(State* stat)
{
state = stat;
}
double getHour()
{
return hour;
}
void setHour(double hou)
{
hour = hou;
}
void requestDoing()
{
state->doing(this);
}
private:
State* state;
double hour;
};
//各个状态doing方法的实现
void WorkingState::doing(Worker* worker)
{
if(worker->getHour() > 8 && worker->getHour() < 16)
cout << "WorkingState!" << endl;
else
{
worker->setState(new OtherState());
worker->requestDoing();
}
}
void SleepingState::doing(Worker* worker)
{
if(worker->getHour() >= 21 || worker->getHour() < 5)
cout << "SleepingState!" << endl;
else
{
worker->setState(new OtherState());
worker->requestDoing();
}
}
void OtherState::doing(Worker* worker)
{
if((worker->getHour() >= 5 && worker->getHour() < 8)
|| (worker->getHour() >= 16 && worker->getHour() < 21))
cout << "SleepingState!" << endl;
else if(worker->getHour() >= 21 || worker->getHour() < 5)
{
worker->setState(new SleepingState());
worker->requestDoing();
}
else
{
worker->setState(new WorkingState());
worker->requestDoing();
}
}
//客户代码
int main()
{
Worker* pWorker = new Worker();
pWorker->setHour(24);
cout << "time 24" << endl;
pWorker->requestDoing();
pWorker->setHour(11.5);
cout << "time 11.5" << endl;
pWorker->requestDoing();
pWorker->setHour(19);
cout << "time 19" << endl;
pWorker->requestDoing();
delete pWorker;
return 0;
}
~~~
执行结果：
**time24**
**SleepingState!**
**time11.5**
**WorkingState!**
**time19**
**SleepingState!**
**请按任意键继续. . .**
