Access child members within parent class, C++

Question

I am facing a situation where I need to access child member variables inside the parent class. I know this is against OO principles but I have to deal with a scenario where

Answer 1

The only clean way is to use the virtual function approach.

If the Parent class has at least one virtual function (not necessarily DoSomething), there's also a yucky way to do it:

void DoSomething() {
    if (Child1* child = dynamic_cast(this)) {
        child->childMember = 0;
    } else if (Child2* child = dynamic_cast(this)) {
        child->childMember = 0;
    } // and so on, and so forth
}

(If Parent has no virtual functions, then the dynamic_cast won't work. Though, any class designed to be inherited from should have at least one virtual function, even if it's just the destructor.)