Promise.all not waiting to complete the requests-CodePudding

await Promise.all(
  endpoints.map((endpoint) =>
    this.httpService.get(endpoint).pipe(
      map((response) => {
        return response.data['result'];
      }),
    ),
  ),
).then(
  axios.spread((...allData) => {
    allData.forEach((res) =>
      res.subscribe((res) => {
        apiFeedBack.push(res);
        console.log(apiFeedBack);
      }),
    );
  }),
);

While debugging it is skipping promise.all execution and directly returns undefined as response. What am i missing here

CodePudding user response：

You need to return the array of promises received from the map function as below:

await Promise.all(
  return endpoints.map((endpoint) =>
    this.httpService.get(endpoint).pipe(
      map((response) => {
        return response.data['result'];
      }),
    ),
  ),
).then(
  axios.spread((...allData) => {
    allData.forEach((res) =>
      res.subscribe((res) => {
        apiFeedBack.push(res);
        console.log(apiFeedBack);
      }),
    );
  }),
)

CodePudding user response：

First of all, when you are using await don't use then. This is how it be like:

const promiseAll = async () => {
try {
  const res = await Promise.all(promises);
  return res;
} catch (e) {
 console.error(e);
}
}

Now, we need to get the values from the promises using await, Also, it would be clean if you write it this way:

const endpoints_Promises = endPoints.map(endPoint => {
 return new Promise((resolve, reject) => {
  this.httpService.get(endpoint).pipe(
    map((response) => {
      resolve(response.data['result']);
    })
   ) 
 })
})
try {
const responses = await Promise.all(endpoints_Promises);
responses.forEach(data =>  console.log(data));
} catch (e) {
   console.error(`Error occured: ${e}`);
}

CodePudding user response：

folks as you may know that @nestjs/axios in NestJS returns observable rather then promise however this is not the case of axios.

So in case you need to make observable asynchronous you will need to convert it to promise, although it's not a recommended way and .toPromise() is deprecated in the latest version of @nestjs/axios.

Promise.all(
  return endpoints.map((endpoint) =>
    this.httpService.get(endpoint).toPromise(),
  ),
).then((responses)=> {
   // here you get the resolved promises responses array
})

Check this out to learn more about Promise.all fulfillment.

Check this out for more information if you should be using observable async/await Is it a good practice using Observable with async/await?