Data do not pass to the calling function React-Native-CodePudding

Hello I'm trying to call data from another function. The caller function is this,

 useEffect(() => {
    setFetching(true);
    const fetchMarketData = async () => {
      const marketData = await getMarketData(page);
      if (page === 1) {
        setData(marketData);
        return setFilteredData(marketData);
      } else {
        setFilteredData(data.concat(marketData));
        return setData(data.concat(marketData));
      }
    };
    fetchMarketData();
    if (data != undefined) {
      if (data.length > 0) setFetching(true);
    } else {
    }
    setFetching(false);
  }, [page]);

When I log marketData it returns undefined. But in these functions until return it gives the correct result.

const formatMarketData = (data) =>{
    let formattedData = [];
    data.forEach(item=>{
    const formattedItem = {
        ...item
    }
    formattedData.push(formattedItem);
    });
    return formattedData;
    }

    export const getMarketData = async (page) =>{
            const sending = {"page" : page,};
            const response = await fetch("https://us-central1-cnhtest-38661.cloudfunctions.net/getMarketDatas",{
              headers: {"Content-Type":"application/json"},
              method:"POST",
              body:JSON.stringify({data:sending})
              }).then((res)=>{
                res.json().then((r)=>{
                    return formatMarketData(r.result.data)
                })
            })
}

How can I correctly return this value to my caller function's marketData variable?

CodePudding user response：

You forgot to return the first inner promise chain. You need to change

.then((res)=> {
    res.json().then((r)=> {
       return formatMarketData(r.result.data)
     })
})

to the following.

.then((res)=> {
    return res.json().then((r)=> {
       return formatMarketData(r.result.data)
     })
})

Here is an updated code snippet.

const formatMarketData = (data) => {
   let formattedData = [];
   data.forEach(item => {
    const formattedItem = {
      ...item
    }
    formattedData.push(formattedItem);
   });
   return formattedData;
}

const getMarketData = async (page) => {
   const sending = {"page" : page};
   const response = await fetch("https://us-central1-cnhtest-38661.cloudfunctions.net/getMarketDatas", {
        headers: {"Content-Type":"application/json"},
        method: "POST",
        body: JSON.stringify({data:sending})}).then((res)=> {
            return res.json().then((r)=>{
                return formatMarketData(r.result.data)
            })
        })
 return response
}

async function printResult() {
  const result = await getMarketData(1)
  console.log(result)
}

printResult()