无法将 Firestore 文档数据加载到 React-Native 中的变量

Question

I'm trying to push a new screen to display the selected item's detail, when I get the data it fetches the document correctly, however if I try to set my object to use it in my screen it is undefined, but if I reload the app it does populate the object, here's the code:

const [event, setEvent] = useState();
    const getEvent = async (dbx) => {
        const eventDoc = doc(dbx, 'events', eventId);
        try {
            const eventSnapshot = await getDoc(eventDoc);
            if(eventSnapshot.exists()) {
                const fetchedEvent = eventSnapshot.data();
                setEvent(fetchedEvent);
                
            } else {
                console.log("Document does not exist")
            }
        
        } catch(error) {
            console.log(error)
        }
        return;
      } 

    useEffect(
        ()=>{
            getEvent(db)
            console.log("Event Here: ", event);
        }
    ,[])

Answer 1

Setting a variable in the state is an asynchronous operation. In fact, so is loading data from Firestore, so neither of those operations is done by the time your console.log("Event Here: ", event) runs.

If you want to log the event value, use another effect that depends on that state variable to do so:

useEffect(()=>{
  console.log("Event Here: ", event);
},[event])