状态模式

#ifndef STATE_H
#define STATE_H

#include <QDebug>

class TemperatureMeasure;

class State
{
public:
    State() {};
    virtual ~State() {};

    virtual void update(TemperatureMeasure* measure) {};
};

class TemperatureMeasure
{
public:
    TemperatureMeasure(State *state)
        : m_state(state)
        , m_oldState(nullptr)
        , m_temp(0)
    {};
    virtual ~TemperatureMeasure() 
    {
        if (nullptr != m_oldState)
        {
            delete m_oldState;
            m_oldState = nullptr;
        }
        if (nullptr != m_state)
        {
            delete m_state;
            m_state = nullptr;
        }
    };
    
    void setState(State *state)
    {
        if (nullptr != state)
        {
            saveOldState();
            m_state = state;
        }
    };
    State* getState() { return m_state; };

    int getTemperature() { return m_temp; };
    void setTemp(float temp) 
    { 
        m_temp = temp; 
        updateState();
    };

private:
    void updateState() 
    { 
        m_state->update(this); 
        if (nullptr != m_oldState)
        {
            delete m_oldState;
            m_oldState = nullptr;
        }
    };

    void saveOldState() { m_oldState = m_state; };
private:
    State        *m_state;
    State        *m_oldState;
    float        m_temp;
};

class BurnoutState : public State
{
public:
    BurnoutState() {};
    virtual ~BurnoutState() {};

    virtual void update(TemperatureMeasure* measure)
    {
        if (measure->getTemperature() > 120)
        {
            qDebug() << "Current state is Burnout";
        }
    }
};

class OverState : public State
{
public:
    OverState() {};
    virtual ~OverState() {};

    virtual void update(TemperatureMeasure* measure)
    {
        if (measure->getTemperature() < 110 && measure->getTemperature() > 100)
        {
            qDebug() << "Current state is Over!";
        }
        else
        {
            measure->setState(new BurnoutState());
        }
    }
};

class NormalState : public State
{
public:
    NormalState() {};
    virtual ~NormalState() {};

    virtual void update(TemperatureMeasure* measure)
    {
        if (measure->getTemperature() < 100 && measure->getTemperature() > 0)
        {
            qDebug() << "Current state is Normal!";
        }
        else
        {
            measure->setState(new OverState());
        }
    }
};

#if 1
void main()
{
    TemperatureMeasure *measure = new TemperatureMeasure(new NormalState);
    for (int i = 99; i < 123; ++i)
    {
        measure->setTemp(i);
    }
}
#endif // 1

#endif // !State_h