多继承中重写函数的语法

Question

class A
{
   protected:
    void func1() //DO I need to call this virtual?
};

class B
{
   protected:
    void func1() //and this one as well?
};

class Derived: public A, public B
{
    public:

    //here define func1 where in the code there is
    //if(statement) {B::func1()} else {A::func1()}
};

how do you override the func1? or can you just define it

class Derived: public A, public B
{
    public:

    void func1()
};

without any virtual or override? I don't understand the accessibility. Thank you.

Answer 1

Leonard Lie,

to override you can simply declare the function with the same name, to achieve the functionality in the comments in the code you need a variable being passed to Derived func1()

For example:

#include <iostream>

using namespace std;

class A
{
   protected:
    void func1()    {   cout << "class A\n";    } //DO I need to call this virtual?
};

class B
{
   protected:
    void func1()    {   cout << "class B\n";    } //and this one as well?
};

class Derived: public A, public B
{
    public:

    //here define func1 where in the code there is
    //if(statement) {B::func1()} else {A::func1()}
    void func1(bool select = true)
    {
        if (select == true)
        {
            A::func1();
        }
        else
        {
            B::func1();
        }
    }
};
int main()
{
   Derived d;
   d.func1();          //returns default value based on select being true
   d.func1(true);      //returns value based on select being set to true
   d.func1(false);     // returns value base on select being set to false
   cout << "Hello World" << endl; 

   return 0;
}

This should do what you are looking for, I have used a boolean as there are only 2 possible versions, but you could use an enum or int to suit a case with more options.