useMemo does not guarantee value will not be recreated

From the React Hooks docs:

You may rely on useMemo as a performance optimization, not as a semantic guarantee. In the future, React may choose to “forget” some previously memoized values and recalculate them on next render, e.g. to free memory for offscreen components. Write your code so that it still works without useMemo — and then add it to optimize performance.

I think a ref would be more suitable for holding the machine instance - useMemo could break this hook in future!

[cdomigan]

A ref is where you should store the service. You will want to follow the lazy instantiation example for useRef from https://reactjs.org/docs/hooks-faq.html#how-to-create-expensive-objects-lazily

eg

const serviceRef = useRef(null);

// ✅ Service is created lazily once
function getService() {
  let service = serviceRef.current;
  if (service !== null) {
    return service;
  }
  let newService = interpret(machine);
  serviceRef.current = newService;
  return newService;
}

// When you need it, call getService()

[carloslfu]

Released in https://github.com/carloslfu/use-machine/tree/v1.1.0.