Assign child properties without effecting parent?

Assuming I have two classes a parent and a child class each with its own property(s)

class Parent
{
private:
    int m_nParentX;
public:
    Parent(int nX)
    {
        m_nParentX = nX;
    }
    int GetParentX()
    {
        return m_nParentX;
    }
};
class Child : public Parent
{
private:
    int m_nChildY;
public:
    Child(int nX, int nY) : Parent(nX)
    {
        m_nChildY = nY;
    }
    int GetChildY()
    {
        return m_nChildY;
    }
    
};

Then I have two instances of the Child class both with distinct values for each instance.

    Child a(10,20);
    Child b(30,40);

What I’d like to do is assign the properties of Child b to that of Child A; however I’d like to do this without effecting it’s parent properties

If I do this

void Overwrite(Child* a, Child* b)
{
    *b = *a;
}
int main(int argc, const char * argv[])
{
    Child a(10,20);
    Child b(30,40);
    
    std::cout << a.GetParentX()<< ":" << a.GetChildY() << "\t" << b.GetParentX() << ":" << b.GetChildY() << std::endl;
    
    Overwrite(&a,&b);
    
    std::cout << a.GetParentX() << ":" << a.GetChildY() << "\t" << b.GetParentX() << ":" << b.GetChildY() << std::endl;
    return 0;
}

The output is

10:20   30:40
10:20   10:20

Which is not exactly what I want since I don’t want the parent’s X of Child b which is 30 to be replaced with Child a parent value of 10.
Essentially I’d like to output to be

10:20   30:40
10:20   30:20

Is it possible to do a quick assignment of classes without effecting parent properties?

>Solution :

Make a copy of the parent object first, Parent pCopyOfB = *b; then after you perform the assignment of the dereferenced pointers, cast b to its parent pointer and do a second assignment using the copy you saved earlier.

void Overwrite(Child* a, Child* b)
{
    Parent pCopyOfB = *b;
    *b = *a;
    Parent* pOfB = b;
    *pOfB = pCopyOfB;
}

This will restore the parent properties after overwriting the children properties. The output should be what you desired 10:20 30:20