Question

B is a class derived from A. I need to create a new object A from existing object B.

I need this because in my application I use a lot of A instances which are much more light weigh than B (which holds a lot of reference data), otherwise I would run out of memory.

How do I convert B to A without manually copying all A‘s fields’ values in a custom method?

Answer 1

Consider using composition (i.e. your B contains a private A as member data) instead of inheritance. Add a method to B to return its A, so you can keep hold of it while the rest of the B is garbage collected.