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

You can use the curiously recurring template pattern to achieve this.

template
class Parent
{
    void DoSomething()
    {
        // This is what I need
        T::childMember = 0;
    }

    virtual ~Parent() {}
};

class Child1 : Parent
{
  int childMember;

  friend class Parent;
};