Issues accessing react state in firestore onSnapshot listener

Question

I want to wait to apply state updates from the back-end if a certain animation is currently running. This animation could run multiple times depending on the game scenario. I'm using react-native with hooks and firestore.

My plan was to make an array that would store objects of the incoming snapshot and the function which would use that data to update the state. When the animation ended it would set that the animation was running to false and remove the first item of the array. I'd also write a useEffect, which would remove the first item from the array if the length of the array had changed.

I was going to implement this function by checking whether this animation is running or whether there's an item in the array of future updates when the latest snapshot arrives. If that condition was true I'd add the snapshot and the update function to my array, otherwise I'd apply the state update immediately. I need to access that piece of state in all 3 of my firestore listeners.

However, in onSnapshot if I try to access my state it'll give me the initial state from when the function rendered. The one exception is I can access the state if I use the function to set the state, in this case setPlayerIsBetting and access the previous state through the function passed in as a callback to setPlayerIsBetting.

I can think of a few possible solutions, but all of them feel hacky besides the first one, which I'm having trouble implementing.

1. Would I get the future state updates if I modify the useEffect for the snapshots to not just run when the component is mounted? I briefly tried this, but it seems to be breaking the snapshots. Would anyone know how to implement this?

2. access the state through calling setPlayerIsBetting in all 3 listeners and just set setPlayerIsBetting to the previous state 99% of the time when its not supposed to be updated. Would it even re-render if nothing is actually changed? Could this cause any other problems?

3. Throughout the component lifecycle add snapshots and the update functions to the queue instead of just when the animation is running. This might not be optimal for performance right? I wouldn't have needed to worry about it for my initial plan to make a few state updates after an animation runs since i needed to take time to wait for the animation anyway.

4. I could add the state I need everywhere on the back-end so it would come in with the snapshot.

5. Some sort of method that removes and then adds the listeners. This feels like a bad idea.

6. Could redux or some sort of state management tool solve this problem? It would be a lot of work to implement it for this one issue, but maybe my apps at the point where it'd be useful anyway?

Here's my relevant code:

const Game = ({ route }) => {
  const [playerIsBetting, setPlayerIsBetting] = useState({
    isBetting: false,
    display: false,
    step: Infinity,
    minimumValue: -1000000,
    maximumValue: -5000,
  });
  const [updatesAfterAnimations, setUpdatesAfterAnimations] = useState([]); 
  // updatesAfterAnimations is currently always empty because I can't access the updated playerIsBetting state easily

  const chipsAnimationRunningOrItemsInQueue = (snapshot, updateFunction) => {
    console.log(
      "in chipsAnimationRunningOrItemsInQueue playerIsBetting is: ",
      playerIsBetting
    ); // always logs the initial state since its called from the snapshots. 
// So it doesn't know when runChipsAnimation is added to the state and becomes true. 
// So playerIsBetting.runChipsAnimation is undefined
    const addToQueue =
      playerIsBetting.runChipsAnimation || updatesAfterAnimations.length;
    if (addToQueue) {
      setUpdatesAfterAnimations((prevState) => {
        const nextState = cloneDeep(prevState);
        nextState.push({ snapshot, updateFunction });
        return nextState;
      });
      console.log("chipsAnimationRunningOrItemsInQueue returns true!");
      return true;
    }
    console.log("chipsAnimationRunningOrItemsInQueue returns false!");
    return false;
  };

  // listener 1
  useEffect(() => {
    const db = firebase.firestore();
    const tableId = route.params.tableId;
    const unsubscribeFromPlayerCards = db
      .collection("tables")
      .doc(tableId)
      .collection("players")
      .doc(player.uniqueId)
      .collection("playerCards")
      .doc(player.uniqueId)
      .onSnapshot(
        function (cardsSnapshot) {
          if (!chipsAnimationRunningOrItemsInQueue(cardsSnapshot, updatePlayerCards)) {
            updatePlayerCards(cardsSnapshot);
          }
        },
        function (err) {
          // console.log('error is: ', err);
        }
      );
    return unsubscribeFromPlayerCards;
  }, []);
};

// listener 2
useEffect(() => {
  const tableId = route.params.tableId;
  const db = firebase.firestore();
  const unsubscribeFromPlayers = db
    .collection("tables")
    .doc(tableId)
    .collection("players")
    .onSnapshot(
      function (playersSnapshot) {
        console.log("in playerSnapshot playerIsBetting is: ", playerIsBetting); // also logs the initial state 
        console.log("in playerSnapshot playerIsBetting.runChipsAnimation is: "playerIsBetting.runChipsAnimation); // logs undefined
        if (!chipsAnimationRunningOrItemsInQueue(playersSnapshot, updatePlayers)) {
          updatePlayers(playersSnapshot);
        }
      },
      (err) => {
        console.log("error is: ", err);
      }
    );
  return unsubscribeFromPlayers;
}, []);

// listener 3
useEffect(() => {
  const db = firebase.firestore();
  const tableId = route.params.tableId;
  // console.log('tableId is: ', tableId);
  const unsubscribeFromTable = db
    .collection("tables")
    .doc(tableId)
    .onSnapshot(
      (tableSnapshot) => {
        if (!chipsAnimationRunningOrItemsInQueue(tableSnapshot, updateTable)) {
          updateTable(tableSnapshot);
        }
      },
      (err) => {
        throw new err();
      }
    );
  return unsubscribeFromTable;
}, []);

Answer 1

I ended up not going with any of the solutions I proposed.

I realized that I could access the up to date state by using a ref. How to do it is explained here: (https://medium.com/geographit/accessing-react-state-in-event-listeners-with-usestate-and-useref-hooks-8cceee73c559) And this is the relevant code sample from that post: (https://codesandbox.io/s/event-handler-use-ref-4hvxt?from-embed)

Solution #1 could've worked, but it would be difficult because I'd have to work around the cleanup function running when the animation state changes. (Why is the cleanup function from `useEffect` called on every render?)

I could work around this by having the cleanup function not call the function to unsubscribe from the listener and store the unsubscribe functions in state and put them all in a useEffect after the component mounts with a 2nd parameter that confirmed all 3 unsubscribe functions had been added to state.

But if a user went offline before those functions were in state I think there could be memory leaks.

Answer 2

I would go with solution #1: In the UseEffect() hooks you could put a boolean flag in so the snapshot listener is only set once per hook. Then put the animation state property in the useEffect dependency array so that each useEffect hook is triggered when the animation state changes and you can then run whatever logic you want from that condition.