先以一个例子来引入多重继承出现的问题：
#include <iostream>
class Person
{
public :
void sleep(){cout<<"this is a sleep function"<<endl;}
void eat(){cout<<"this is a eat function"<<endl;}
};
class Author:public Person
{
public:
void writeBook(){cout<<"this is a writeBook function"<<endl;}
};
class Coder:public Person
{
public:
void writecode(){cout<<"this is a writecode function"<<endl;}
};
class Teacher:public Author,public Coder
{
};
int main()
{
Teacher t;
t.writeBook();
t.writecode();
t.sleep();
t.eat();
return 0;
}
这是编译结果：
这里就充分体现了多重继承的缺点，如果派生类所继承的多个基类有相同的基类，而派生类对象需要调用这个祖先类的接口方法，就会容易出现二义性。通常有两种解决方案
1.加上全局符确定调用哪一份拷贝，上述的程序可改为：
t.Author::sleep();
t.Author::eat();
2.采用虚拟继承
class Author:virtual public Person
class Coder:virtual public Person
3.虚基类的构造函数和初始化
#include <iostream>
using namespace std;
class base
{
protected:
int x;
public :
base(int x1){
x=x1;
cout<<"base constructor x="<<x<<endl;
}
};
class base1:virtual public base
{
int y;
public :
base1(int x1,int y1):base(x1){
y=y1;
cout<<"base constructor y="<<y<<endl;
}
};
class base2:virtual public base
{
int z;
public :
base2(int x1,int y1):base(x1){
z=y1;
cout<<"base constructor z="<<z<<endl;
}
};
class user:public base1,public base2
{
int m;
public:
user(int x1,int y1,int z1,int m1):base(x1),base1(x1,y1),base2(x1,z1){
m=m1;
cout<<"base constructor m="<<m<<endl;
}
};
int main()
{
user t(1,2,3,4);
return 0;
}