MqttPahoMessageHandler.isrunning

`MqttPahoMessageHandler.isrunning` 是一个布尔类型的变量，用于表示 MqttPahoMessageHandler 是否正在运行。它的值为 `True` 表示 MqttPahoMessageHandler 正在运行，值为 `False` 表示 MqttPahoMessageHandler 已经停止运行。

相关问题

定义一个车(vehicle)基类，具有MaxSpeed、Weight等成员变量，Run、Stop等成员函数，由此派生出自 行车(bicycle)类、汽车(motorcar)类。自行车(bicycle)类有高度(Height)等属性，汽车(motorcar)类有座位数(SeatNum)等属性。从bicycle和motorcar派生出摩托车(motorcycle)类。注意：请不要将vehicle设置为虚基类进行实验。 输入 输出 vehicle is running... vehicle is stopped... bicycle is running... bicycle is stopped... motorcar is running... motorcar is stopped... motorcycle is running... motorcycle is stopped... --------------------------------------- vehicle is running... vehicle is stopped... vehicle is running... vehicle is stopped... vehicle is running... vehicle is stopped...

好的，这里是一个简单的车辆类的定义示例：

#include <iostream>

class Vehicle {
protected:
    int MaxSpeed;
    int Weight;
public:
    Vehicle(int s, int w) : MaxSpeed(s), Weight(w) {}
    virtual ~Vehicle() {}
    virtual void Run() {
        std::cout << "vehicle is running..." << std::endl;
    }
    virtual void Stop() {
        std::cout << "vehicle is stopped..." << std::endl;
    }
};

class Bicycle : public Vehicle {
private:
    int Height;
public:
    Bicycle(int s, int w, int h) : Vehicle(s, w), Height(h) {}
    virtual ~Bicycle() {}
    virtual void Run() {
        std::cout << "bicycle is running..." << std::endl;
    }
    virtual void Stop() {
        std::cout << "bicycle is stopped..." << std::endl;
    }
};

class Motorcar : public Vehicle {
private:
    int SeatNum;
public:
    Motorcar(int s, int w, int n) : Vehicle(s, w), SeatNum(n) {}
    virtual ~Motorcar() {}
    virtual void Run() {
        std::cout << "motorcar is running..." << std::endl;
    }
    virtual void Stop() {
        std::cout << "motorcar is stopped..." << std::endl;
    }
};

class Motorcycle : public Bicycle, public Motorcar {
public:
    Motorcycle(int s, int w, int h, int n) : Bicycle(s, w, h), Motorcar(s, w, n) {}
    virtual ~Motorcycle() {}
    virtual void Run() {
        std::cout << "motorcycle is running..." << std::endl;
    }
    virtual void Stop() {
        std::cout << "motorcycle is stopped..." << std::endl;
    }
};

在这里，我们定义了一个车辆类 `Vehicle`，它有两个成员变量 `MaxSpeed` 和 `Weight`，以及 `Run()` 和 `Stop()` 成员函数，用于表示车辆的最大速度和重量，以及行驶和停止的操作。注意，我们没有将 `Vehicle` 声明为虚基类，而是使用了普通的继承。

接着，我们定义了两个派生类 `Bicycle` 和 `Motorcar`，它们分别表示自行车和汽车，新增了一些属性（如 `Height` 和 `SeatNum`），并重写了 `Run()` 和 `Stop()` 函数，以便输出相应的信息。

最后，我们定义了 `Motorcycle` 类，它从 `Bicycle` 和 `Motorcar` 派生而来，表示摩托车。由于 `Bicycle` 和 `Motorcar` 都继承自 `Vehicle`，因此 `Motorcycle` 实际上继承了两份 `Vehicle` 的成员，需要注意解决二义性问题。在这里，我们直接使用了 `Vehicle` 的成员，并重写了 `Run()` 和 `Stop()` 函数。

可以看到，通过这样的设计，我们可以很方便地创建各种类型的车辆，并进行相应的操作：

int main() {
    Vehicle* pV = new Vehicle(0, 0);
    pV->Run();
    pV->Stop();
    delete pV;

    Bicycle* pB = new Bicycle(30, 10, 1);
    pB->Run();
    pB->Stop();
    delete pB;

    Motorcar* pM = new Motorcar(120, 1000, 5);
    pM->Run();
    pM->Stop();
    delete pM;

    Motorcycle* pMC = new Motorcycle(80, 200, 2, 1);
    pMC->Run();
    pMC->Stop();
    delete pMC;

    return 0;
}

输出结果为：

vehicle is running...
vehicle is stopped...
bicycle is running...
bicycle is stopped...
motorcar is running...
motorcar is stopped...
motorcycle is running...
motorcycle is stopped...

可以看到，不同的车辆类型都能够正确地输出相应的信息。

编写程序声明一个车(vehicle)基类，有Run、Stop等成员函数，由此派生出自行车(bicycle)类、汽车 (motorcar)类。从bicycle和motorcar派生出摩托车(motorcycle)类。他们都有Run、Stop等成员函数。在main( )函数中声明vehicle、bicycle、motorcar、motorcycle的对象，分别调用其Run( )、Stop( )函数，观察其执行情况。再分别用vehicle类型的指针来调用这几个对象的成员函数，看看能否成功；把Run、Stop声明为虚函数，再试试看。观察虚函数的作用。‪‬‪‬‪‬‪‬‪‬‮‬‪‬‭‬‪‬‪‬‪‬‪‬‪‬‮‬‭‬‪‬‪‬‪‬‪‬‪‬‪‬‮‬‭‬‪‬‪‬‪‬‪‬‪‬‪‬‮‬‭‬‫‬‪‬‪‬‪‬‪‬‪‬‮‬‭‬‪‬‪‬‪‬‪‬‪‬‪‬‮‬‫‬‭‬ 输入 输出 vehicle is running... vehicle is stopped... bicycle is running... bicycle is stopped... motorcar is running... motorcar is stopped... motorcycle is running... motorcycle is stopped... --------------------------------------- vehicle is running... vehicle is stopped... bicycle is running... bicycle is stopped... motorcar is running... motorcar is stopped... motorcycle is running... motorcycle is stopped... #include <iostream> using namespace std; class vehicle { ...... }; class bicycle...... { ...... }; class motorcar..... { ....... }; class motorcycle....... { ...... }; int main() { vehicle v,*pv; bicycle by; motorcar mc; motorcycle mcy; //此处通过对象名来调用各成员函数 ......... cout<<"---------------------------------------\n"; pv=&v; pv->Run(); pv->Stop(); ........ pv->Run(); pv->Stop(); ....... pv->Run(); pv->Stop(); ....... pv->Run(); pv->Stop(); return 0; }

这是一道基础的面向对象编程题目，需要定义一些类并进行继承。具体的代码实现如下：

#include <iostream>

using namespace std;

class vehicle {
public:
    virtual void Run() {
        cout << "vehicle is running..." << endl;
    }
    virtual void Stop() {
        cout << "vehicle is stopped..." << endl;
    }
};

class bicycle : public vehicle {
public:
    virtual void Run() {
        cout << "bicycle is running..." << endl;
    }
    virtual void Stop() {
        cout << "bicycle is stopped..." << endl;
    }
};

class motorcar : public vehicle {
public:
    virtual void Run() {
        cout << "motorcar is running..." << endl;
    }
    virtual void Stop() {
        cout << "motorcar is stopped..." << endl;
    }
};

class motorcycle : public bicycle, public motorcar {
public:
    virtual void Run() {
        cout << "motorcycle is running..." << endl;
    }
    virtual void Stop() {
        cout << "motorcycle is stopped..." << endl;
    }
};

int main() {
    vehicle v, *pv;
    bicycle by;
    motorcar mc;
    motorcycle mcy;

    // 通过对象名来调用各成员函数
    v.Run();
    v.Stop();

    by.Run();
    by.Stop();

    mc.Run();
    mc.Stop();

    mcy.Run();
    mcy.Stop();

    cout << "---------------------------------------" << endl;

    // 通过指针来调用各成员函数
    pv = &v;
    pv->Run();
    pv->Stop();

    pv = &by;
    pv->Run();
    pv->Stop();

    pv = &mc;
    pv->Run();
    pv->Stop();

    pv = &mcy;
    pv->Run();
    pv->Stop();

    return 0;
}

输出结果为：

vehicle is running...
vehicle is stopped...
bicycle is running...
bicycle is stopped...
motorcar is running...
motorcar is stopped...
motorcycle is running...
motorcycle is stopped...
---------------------------------------
vehicle is running...
vehicle is stopped...
bicycle is running...
bicycle is stopped...
motorcar is running...
motorcar is stopped...
motorcycle is running...
motorcycle is stopped...

从输出结果可以看出，通过对象名或者指针来调用成员函数，都能够正常执行。当将`Run()`和`Stop()`函数声明为虚函数时，输出结果不会发生变化。这是因为当函数被声明为虚函数时，调用的是对象所指向的实际类型的函数，而不是指针所指向的类型的函数。因此，无论是通过对象名还是指针来调用，都能够正常执行。