完成 concatMap 后如何进行另一个 api 调用

Question

I would like to make an API call after my concatMap is finished.

from(array)
        .pipe(
           concatMap(el => return APICall(el))
        )
        .subscribe(
           response => { 
            if(!(response instanceof HttpErrorResponse)) {
              responses.push(response);
            }
          }
        ) 

How can I wait untill concatMap finish working and then do other API calls?

Answer 1

You could pipe in a switchMap (or a concatMap ) inside the outer concatMap .

from(array).pipe(
  concatMap(el => return APICall(el).pipe(
    switchMap(el2 => return OtherApiCall(el2))
  ))
).subscribe(
  response => { 
    if(!(response instanceof HttpErrorResponse)) {
      responses.push(response);
    }
  }
); 

Update: wait for all concatMap to complete

forkJoin(
  array.map(el => APICall(el))
).pipe(
  switchMap(res =>        // <-- here `res` would be an array of all responses from the array
    OtherApiCall()
  )
).subscribe(...);

Update 2: wait for all sequential requests to complete

There isn't a direct way to execute something after all the sequential requests using from + concatMap . You could however use toArray operator to collect all the responses and emit it as an array similar to the forkJoin 's output. This would essentially halt the workflow until all the responses are collected.

from(array).pipe(
  concatMap(el => return APICall(el)),
  toArray(),
  switchMap(res =>         // <-- here `res` would be an array of all responses from the array
    return OtherApiCall()
  )
).subscribe(
  response => { 
    if(!(response instanceof HttpErrorResponse)) {
      responses.push(response);
    }
  }
);