How to upcast an object?

In Matlab OOP, say I have a class B that inherits from A, then how do I upcast B to A without explicitly copying properties? (The cast function is for numeric values only and I'm interested in custom class objects.)

Answer 1

[Adam]

You would have to implement your own converter function as far as I know, with the name of the base class to convert to.

It seems a bit over the top for conversion to the base class rather than some other class, but I don't know of another method.