C++设计模式——状态模式

状态模式（State），当一个对象的内在状态改变时允许改变其行为，这个对象看起来像是改变了其类

状态模式主要解决的是当控制一个对象状态转换的条件表达式过于复杂时的情况，把状态的判断逻辑转移到表达不同状态的一系列当中，可以把复杂的判断逻辑简化

将特定的状态相关的行为都放入一个对象中，由于所有与状态相关的代码都存在于某个ConcreteState中，所以通过定义新的子类可以很容易的增加新的状态和转换 ....消除庞大的条件分支

状态模式就是通过各种状态转移逻辑分布到State的子类之间，来减少相互间的依赖........

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，就可以考虑使用状态模式了

 

 

 

#include<iostream>
using namespace std;

class State;
class ForenoonState;
class NoonState;
class AfternonnState;
class EveningState;
class SleepingState;
class RestState;
class Work;

// 抽象状态角色，负责定义各个状态有哪些行为，该抽象状态包含所有具体状态的方法。并且封装环境角色，帮助切换状态。
class State
{
public:
    virtual void writeprogram(Work* w) = 0;
    virtual ~State() = default;
};
// Context 角色，在该类内部维护一个ConcreteState子类的一个实例，可以负责具体状态的切换
class Work
{
private:
    State* current;
    double m_hour;
    bool m_finish = false;
public:
    Work();
    ~Work();
    void setHour(double hour) { m_hour = hour; }
    double getHour() { return m_hour; }

    void setFinish(bool finish) { m_finish = finish; }
    bool getFinish() { return m_finish; }
    void SetState(State* s)
    {
        delete current;
        current = s;
    }
    void WorkProgram()
    {
        current->writeprogram(this);
    }
};

// 下面都是具体的状态类，每一个具体状态类必须完成两个职责：该类本状态下要做的事情，以及如何执行到其他具体状态类的状态。
class ForenoonState :public State
{
public:
    void writeprogram(Work* w)override;
};

class NoonState :public State
{
public:
    void writeprogram(Work* w)override;
};

class AfternoonState :public State
{
public:
    void writeprogram(Work* w)override;
};

class EveningState :public State
{
public:
    void writeprogram(Work* w)override;
};

class SleepingState :public State
{// 睡眠状态
public:
    void writeprogram(Work* w)override;

};

class RestState :public State
{// 下班休息状态
public:
    void writeprogram(Work* w)override;

};

Work::Work()
{
    current = new ForenoonState();
}
Work::~Work()
{
    delete current;
}

void ForenoonState::writeprogram(Work* w)
{
    if (w->getHour() < 12)
    {
        cout << "当前时间：" << w->getHour() << "点，上午工作，精神百倍" << endl;
    }
    else
    {
        w->SetState(new NoonState());
        w->WorkProgram();
    }
}

void NoonState::writeprogram(Work* w)
{
    if (w->getHour() < 13)
    {
        cout << "当前时间：" << w->getHour() << "点，吃午饭，睡午觉" << endl;
    }
    else
    {
        w->SetState(new AfternoonState());
        w->WorkProgram();
    }
}

void AfternoonState::writeprogram(Work* w)
{
    if (w->getHour() < 17)
    {
        cout << "当前时间：" << w->getHour() << "点，下午状态还不错" << endl;
    }
    else
    {
        w->SetState(new EveningState());
        w->WorkProgram();
    }
}

void EveningState::writeprogram(Work* w)
{
    if (w->getFinish())
    {
        w->SetState(new RestState());
        w->WorkProgram();
    }
    else
    {
        if (w->getHour() < 21)
        {
            cout << "当前时间：" << w->getHour() << "点,加班哦，疲惫至极 " << endl;
        }
        else
        {
            w->SetState(new SleepingState());
            w->WorkProgram();
        }
    }
}

void SleepingState::writeprogram(Work* w)
{
    cout << "当前时间：" << w->getHour() << "点,不行了，睡着了 " << endl;
}

void RestState::writeprogram(Work* w)
{
    cout << "当前时间：" << w->getHour() << "点,下班回家了 " << endl;
}

int main()
{
    Work emergencyProjects;

    emergencyProjects.setHour(9);
    emergencyProjects.WorkProgram();

    emergencyProjects.setHour(10);
    emergencyProjects.WorkProgram();

    emergencyProjects.setHour(12);
    emergencyProjects.WorkProgram();

    emergencyProjects.setHour(13);
    emergencyProjects.WorkProgram();

    emergencyProjects.setHour(14);
    emergencyProjects.WorkProgram();

    emergencyProjects.setHour(17);
    emergencyProjects.WorkProgram();

    emergencyProjects.setFinish(false);

    emergencyProjects.setHour(19);
    emergencyProjects.WorkProgram();

    emergencyProjects.setHour(22);
    emergencyProjects.WorkProgram();

    system("pause");
    return 0;
}