Calling a protected function from instance inside a derived class

Question

Currently, I am trying to solve the following situation.

I have a classB which contains some objects from a classA. Each classA has a function foo which needs to be executed. In the context of the program it makes since that classBinherits from classA since will need all of its functionality.

I would like to call the protected function from an instance of a base class.

I have the following test code:

#include <iostream>

class baseA 
{
    protected:
    virtual bool foo()
    {
        std::cout <<"Base foo in action" << std::endl;
        return true;
    }
};

class classB
:public baseA
{
    public:
    baseA obj1_;

    virtual bool foo()
    {
        std::cout <<"I am going to call base foo" << std::endl;
        bool a = obj1_.foo(); // Can't be called
    }
};

int main(int argc, char** argv)
{
    classB obj; 
    obj.foo();

    return 0;
}

Currently is does not work because the function foois protected in the current context.

I get the following error: error: ‘virtual bool baseA::foo()’ is protected within this contex

Is there a way to make it work while maintaining the protected specifier?

Best regards

Answer 1

Yes, there is a way. You can put a protected "forwarding" function into the base.

struct Base {
protected:
  virtual void theFunc() = 0;
  
  static void callTheFuncOn(Base *b) {
    b->theFunc();
  }
};

struct Derived: Base {
  void test(Base *b) {
    callTheFuncOn(b);
  }
};