使用异步获取 API 数据不渲染

Question

I'm pulling data from Firebase in getSubscriptions() which returns an array:

[
    {
        "price": 2000.01,
        "product_name": "Awesome product"
    },
    {
        "active": true,
        "product_name": "Other product",
        "Price": 599.99
    }
]

I'm iterating through the array and I'm able to get a result but I'm having trouble getting that result to render.

I know the issue has something to do with async and waiting for the result to return but I'm stuck on how to apply those concepts to my issue here.

When I uncomment the line useEffect(() => setActiveNotifications(active), [active]) , introducing the useState, the calls are put in an infinite loop calling the Firebase API ad infinitum.

export default function UserAccount(props) {

  const [activeNotifications, setActiveNotifications] = useState()

  function buildSubscriptions(userId) {
    getSubscriptions(userId).then(active => {
      console.log(JSON.stringify(active, null, 4))  // This returns output above 
      
      // useEffect(() => setActiveNotifications(active), [active])  // This will cause infinite loop 

      return (
        active.map(product =>
          <p key={product.product_name}>{product.product_name}</p>)  // key defined some value to not throw warning 
      )
    })
  }

  async function getSubscriptions(userId) {
    const subPtrCollection = await getUserSubs(userId)
    let a = []
    await Promise.all(subPtrCollection.map(async docId => {  // Promise.all used to execute commands in series
      const docData = await getDocData(docId.product)
      a.push(docData)
    }))
    return a

  }

  return (
    ...
    <Box>{buildSubscriptions(user.uid)}</Box>  // Not important where `user.uid` comes from 
    ...
  )
}

Answer 1

Infinite loop is because the method invoked in render method setting the state and that causes render. Try some thing like below 1) On change of uid, request for build 2) in when you receive the results from api save to state, this cause render 3) in render method used the state data.

export default function UserAccount(props) {
  const [activeNotifications, setActiveNotifications] = useState();

  // when ever uid changes, do the build subscriptions
  useEffect(() => buildSubscriptions(user.uid), [user.uid]);

  // get subscriptions and save to state
  function buildSubscriptions(userId) {
    getSubscriptions(userId).then((active) => setActiveNotifications(active));
  }

  async function getSubscriptions(userId) {
    const subPtrCollection = await getUserSubs(userId);
    let a = [];
    await Promise.all(
      subPtrCollection.map(async (docId) => {
        // Promise.all used to execute commands in series
        const docData = await getDocData(docId.product);
        a.push(docData);
      })
    );
    return a;
  }

  return (
    <Box>
      {activeNotifications.map((product) => (
        <p key={product.product_name}>{product.product_name}</p>
      ))}
    </Box>
  );
}