一个多重继承的问题

[bird528]

请问如果一个派生类多重继承于不同的基类。 但是在不同的基类中有相同名字的成员函数。 那对于派生类来说， 如何使用和区别这来自两个不同基类的相同名字的函数呢。 多谢

[家有萌宝V]

采用纯虚函数将要继承的基类类声明成抽象类是一个不错的方法

[jinwei1984]

[Quote=引用 8 楼 tsst 的回复:]
典型的多重继承二义性问题,采用virtual继承或者加作用域进行标记说明
[/Quote]

[e_sharp]

virtual继承 或者 ::类域操作符

[Learn-anything]

[Quote=引用 4 楼 sunhuanwen 的回复:]
使用的话,如下
class BaseA;
class BaseB;
class c: public BaseA, public BaseB
{
BaseA::func();
BaseB::func();
}

即，函数名前面加上所属类的名字，以及“::”类的域名操作符。
[/Quote]

个人感觉这个方法不错

[budweiser]

#include <iostream> 
using namespace std; 
 
class Vehicle 
{ 
    public: 
        Vehicle(int weight = 0) 
        { 
            Vehicle::weight = weight; 
        } 
        void SetWeight(int weight) 
        { 
            cout<<"重新设置重量"<<endl; 
            Vehicle::weight = weight; 
        } 
        virtual void ShowMe() = 0; 
    protected: 
        int weight; 
}; 
class Car:public Vehicle//汽车 
{ 
    public: 
        Car(int weight=0,int aird=0):Vehicle(weight) 
        { 
            Car::aird = aird; 
        } 
        void ShowMe() 
        { 
            cout<<"我是汽车！"<<endl; 
        } 
    protected: 
        int aird; 
}; 
 
class Boat:public Vehicle//船 
{ 
    public: 
        Boat(int weight=0,float tonnage=0):Vehicle(weight) 
        { 
            Boat::tonnage = tonnage; 

        } 
        void ShowMe() 
        { 
            cout<<"我是船！"<<endl; 
        } 
    protected: 
        float tonnage; 
}; 
 
class AmphibianCar:public Car,public Boat//水陆两用汽车,多重继续的体现 
{ 
    public: 
        AmphibianCar(int weight,int aird,float tonnage) 
        :Vehicle(weight),Car(weight,aird),Boat(weight,tonnage) 
        //多重继续要注重调用基类构造函数 
        { 
         
        } 
        void ShowMe() 
        { 
            cout<<"我是水陆两用汽车！"<<endl; 
        } 
}; 
int main() 
{ 
    AmphibianCar a(4,200,1.35f);//错误 
    a.SetWeight(3);//错误 
    system("pause");  
}

以上是你提出的问题，
编译报错 ：
error C2614: 'AmphibianCar' : illegal member initialization: 'Vehicle' is not a base or member
error C2385: 'AmphibianCar::SetWeight' is ambiguous
warning C4385: could be the 'SetWeight' in base 'Vehicle' of base 'Car' of class 'AmphibianCar'
warning C4385: or the 'SetWeight' in base 'Vehicle' of base 'Boat' of class 'AmphibianCar'
warning C4508: 'main' : function should return a value; 'void' return type assumed

大概意思就是有重复的 SetWeight 函数定义

解决这个问题，可以通过虚拟继承， 带那如下：

#include <iostream> 
using namespace std; 
 
class Vehicle 
{ 
    public: 
        Vehicle(int weight = 0) 

        { 
            Vehicle::weight = weight; 
            cout<<"载入Vehicle类构造函数"<<endl; 
        } 
        void SetWeight(int weight) 
        { 
            cout<<"重新设置重量"<<endl; 
            Vehicle::weight = weight; 
        } 
        virtual void ShowMe() = 0; 
    protected: 
        int weight; 
}; 
class Car:virtual public Vehicle//汽车，这里是虚拟继续 
{ 
    public: 
        Car(int weight=0,int aird=0):Vehicle(weight) 
        { 
            Car::aird = aird; 
            cout<<"载入Car类构造函数"<<endl; 
        } 
        void ShowMe() 
        { 
            cout<<"我是汽车！"<<endl; 
        } 
    protected: 
        int aird; 
}; 
 
class Boat:virtual public Vehicle//船,这里是虚拟继续 
{ 
    public: 
        Boat(int weight=0,float tonnage=0):Vehicle(weight) 
        { 
            Boat::tonnage = tonnage; 
            cout<<"载入Boat类构造函数"<<endl; 
        } 
        void ShowMe() 
        { 
            cout<<"我是船！"<<endl; 
        } 
    protected: 

        float tonnage; 
}; 
 
class AmphibianCar:public Car,public Boat//水陆两用汽车,多重继续的体现 
{ 
    public: 
        AmphibianCar(int weight,int aird,float tonnage) 
        :Vehicle(weight),Car(weight,aird),Boat(weight,tonnage) 
        //多重继续要注重调用基类构造函数 
        { 
            cout<<"载入AmphibianCar类构造函数"<<endl; 
        } 
        void ShowMe() 
        { 
            cout<<"我是水陆两用汽车！"<<endl; 
        } 
        void ShowMembers() 
        { 
            cout<<"重量："<<weight<<"顿，"<<"空气排量："<<aird<< "CC，"<<"排水量："<<tonnage<<"顿"<<endl; 
        } 
}; 
int main() 
{ 
    AmphibianCar a(4,200,1.35f); 
    a.ShowMe(); 
    a.ShowMembers(); 
    a.SetWeight(3); 
    a.ShowMembers(); 
    system("pause");  
}

就是在继承列表的前面加上 virtual 关键字 。

[wangdeqie]

http://www.pconline.com.cn/pcedu/empolder/gj/c/0503/579115.html

[pluminsnow]

如一楼所说

[sunhuanwen]

使用的话,如下
class BaseA;
class BaseB;
class c: public BaseA, public BaseB
{
BaseA::func();
BaseB::func();
}

即，函数名前面加上所属类的名字，以及“::”类的域名操作符。

[veloting]

[Quote=引用 4 楼 sunhuanwen 的回复:]
使用的话,如下
class BaseA;
class BaseB;
class c: public BaseA, public BaseB
{
BaseA::func();
BaseB::func();
}

即，函数名前面加上所属类的名字，以及“::”类的域名操作符。
[/Quote]
或者如你l楼所说

[帅得不敢出门]

使用虚拟成员函数

[zclever]

那么，方法就很清楚了。使用虚拟继承，或者使用类域操作符

[elegant87]

多态！把基类的成员函数设为虚函数，派生类的对象就可以访问！
1L说的很好啊！

[tsst]

典型的多重继承二义性问题,采用virtual继承或者加作用域进行标记说明