React too many re-renders because of data loading?

I have this chunk of code:

export default function CloseInquiryComponent(props) {

    const auth = getAuth();
    const db = getFirestore();

    const { id } = useParams();

    const [someVar, setSomeVar] = useState("");

    // get user 
    const [user, authLoading, authErr] = useAuthState(auth);
    // get user data of a collection
    const [userData, userDataLoading, dataErr] = useDocumentData(
      user ? doc(db, `users/${user.uid}`) : null,
    );

    // get the inquiry data
    const [inquiry, inquiryLoading, inquiryError] = useDocumentData(doc(db, "תקלות", id));

    // show loading until data is done loading
    if(inquiryLoading)
    {
        return <LoadingComponent/>
    }

    // this causes an error because there is a return before it.
    setSomeVar(inquiry.SomeData);

If I remove the if statement and try to set there, it might be null. If I try something like:

if(!inquiryLoading)
{
    setSomeVar(inquiry.SomeData);
    return <pagehtmlhere/>
}

I get an error “too many re-renders”.

each re-render calls the function and sets the variable, which causes more re-renders.

How can I set the data once it’s been loaded, while also keeping the react rules in mind?

Answer

Use useEffect hook.

useEffect(() => {
    if (inquiryLoading && inquiry) setSomeVar(inquiry.SomeData);
}, [inquiryLoading, inquiry])