直接访问struct-within-struct的属性？

Question

I have made tree structs, two of them defined as follows;

template < class T, int W, int H >
struct dataRect {
    const int w = W;
    const int h = H;
    const int l = W * H;
    T d[W * H];
};

template < class T >
struct Vec2{
    T x;
    T y;
    // more things
};

And the third one is basically just a struct containing one of each of the previous structs;

template < class T, int W, int H >
struct xDataRect {
    dataRect<T, W, H> r;
    Vec2<int> p;
};

Now lets say I have an xDataRect xdr, is there a way to make it possible to access the properties of the first two structs directly as

xdr.x = 3;

instead of

xdr.p.x = 3;

such that they are perfectly interchangeable? ((In other words, changing xdr.x changes xdr.p, changing xdr.p changes xdr.x))

This is not critical (I can just write xdr.px always), but it would be nice to know if there is a way to do it.

Answer 1

C++ has inheritance.

It is possible to define Vec2<int> as a base of xDataRect. This way .x and .y can be used on a xDataRect object.

By overloading xDataRect::operator=(Vec2<int>) it is possible to only set x and y without affecting the other fields.