Is it possible to change a C++ object's class after instantiation?

Question

I have a bunch of classes which all inherit the same attributes from a common base class. The base class implements some virtual functions that work in general cases, whilst eac

Answer 1

You can by introducing a variable to the base class, so the memory footprint stays the same. By setting the flag you force calling the derived or the base class implementation.

#include 

class Base {
public:
    Base() : m_useDerived(true)
    {
    }

    void setUseDerived(bool value)
    {
        m_useDerived = value;
    }

    void whoami() {
        m_useDerived ? whoamiImpl() : Base::whoamiImpl();
    }

protected:
    virtual void whoamiImpl() { std::cout << "I am Base\n"; }

private:
    bool m_useDerived;
};

class Derived : public Base {
protected:
    void whoamiImpl() {
        std::cout << "I am Derived\n";
    }
};

Base* object;

int main() {
    object = new Derived; //assign a new Derived class instance
    object->whoami(); //this prints "I am Derived"

    object->setUseDerived(false);
    object->whoami(); //should print "I am Base"

    return 0;
}