useEffect 中的无限循环，useEffect 中的 async/await

Question

I know this question has been asked a lot - but I need some help!

I would like getExistingCards() to execute and setCards before updateActivity() .

getExistingCards() should setCards if 1) cards exist, and 2) cards is an empty array (I don't want to setCards to existingCards if cards is already set to existingCards !)

The below works perfectly, so this shouldn't have to change.

  const [cards, setCards] = useState([]);

  useEffect(() => {
    updateActivity(path, cards);
  }, [cards]);

Adding getExistingCards() below causes an infinite loop (which makes sense because I know I'm setting state within the effect, and cards is also in the dependency array):

  // useLayoutEffect executes before useEffect
  useLayoutEffect(() => {
    const getExistingCards = () => {
      if (activity) {
        if (path.field === "activity_milestones" || path.field === "activity_indicators") {
          let existingItems = activity[path.field]
          if (existingItems) {
            setCards(existingItems);
          }
        }
      }
    };
    getExistingCards();
  }, []);

  useEffect(() => {
    updateActivity(path, cards);
  }, [cards]);

I also tried to add both updateActivity() and getExistingCards() to the useEffect implementing async/await, but realize getExistingCards() is not actually a promise.

Any insight would be really appreciated - thank you

Answer 1

Just check the length of cards before your execute your embedded function

  useEffect(() => {
   if (cards.length === 0) updateActivity(path, cards);
  }, [cards]);