C++用虚基类来避免成员变量或成员方法调用的二义性问题

青旅半醒 2022-02-22 15:44 154阅读 0赞

**注意：**  
若在继承时不将Vehicle类声明为虚基类，则在对象mc调用Vehicle类中的成员变量或成员方法时就会产生二义性。因为编译器不知道该成员变量或成员方法是来自Bicycle类还是来自Motorcar类。

/*-----------------------------------------------------
    功能：用虚基类来避免成员函数或成员方法调用的二义性问题
    运行结果：
    60
    12
    2
    100
    Black
    Vehicle is running...
    Vehicle is stopping...
    ------------------------------------------------------
    Author: Zhang Kaizhou
    Date: 2019-4-9 16:40:13
    -----------------------------------------------------*/
    #include <iostream>
    #include <string>
    
    using namespace std;
    
    class Vehicle{ // 定义一个交通工具类
    public:
        int maxSpeed;
        int weight;
        void setMaxSpeed(int s){ maxSpeed = s; }
        void setWeight(int w){ weight = w; }
        int getMaxSpeed()const{ return maxSpeed; }
        int getWeight()const{ return weight; }
        void run(){ cout << "Vehicle is running..." << endl; }
        void stop(){ cout << "Vehicle is stopping..." << endl; }
    };
    
    class Bicycle : virtual public Vehicle{ // 将Vehicle声明为虚基类，以公有的方式派生一个Bicycle类
    public:
        int height;
        void setHeight(int h){ height = h; }
        int getHeight()const { return height; }
    };
    
    class Motorcar : virtual public Vehicle{ // 将Vehicle声明为虚基类，以公有的方式派生一个Motorcar类
    public:
        int seatNum;
        void setSeatNum(int sn){ seatNum = sn; }
        int getSeatNum()const{ return seatNum; }
    };
    
    class Motorcycle : public Bicycle, public Motorcar{ // Motorcycle类以公有方式多派生自Bicycle类和Motorcar类
    public:
        string color;
        void setColor(string str){ color = str; }
        void showColor(){ cout << color << endl; }
    };
    
    int main(){
        Motorcycle mc;
        mc.setMaxSpeed(60);
        mc.setHeight(12);
        mc.setSeatNum(2);
        mc.setWeight(100);
        mc.setColor("Black");
        cout << mc.getMaxSpeed() << endl;
        cout << mc.getHeight() << endl;
        cout << mc.getSeatNum() << endl;
        cout << mc.getWeight() << endl;
        mc.showColor();
        mc.run();
        mc.stop();
    
        return 0;
    }