设计模式C++实现——状态模式

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!

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