怎样保证useRef的初始值只被创建一次

function Image(props) {
  const ref = useRef(null);

  // ✅ IntersectionObserver is created lazily once
  function getObserver() {
    if (ref.current === null) {
      ref.current = new IntersectionObserver(onIntersect);
    }
    return ref.current;
  }

  // When you need it, call getObserver()
  // ...
}