REACT useEffect() 称为不需要的

Question

I'm using useEffect which should update my component whenever the value selected of my state updates:

const Thumbnail = ({ image }) => {

    const [state, dispatch] = useContext(Context);
    const [checked, setChecked] = useState(getChecked());

    useEffect(() => {
        setChecked(getChecked())
    }, [state.selected])

...

}
export default Thumbnail

But the Function is called everytime anything in my state is updated. For example when an other component updates state.all , the useEffect() method is being called.

How can I avoit this and only call the useEffect() method when state.selected is being changed?

Answer 1

I think what you need is useMemo .

useMemo will only recompute the memoized value when one of the dependencies has changed.

const checked = useMemo(() => getChecked(), [state.selected]);