What would be the best method for looping through HTTP requests

Question

I have a GET request that I need to make. The thing is that each request only returns a page of 50 data entries so there can be multiple pages of data that can only be retrieved with different requests. I have to wait for all the data to be grabbed so that I can then process the data as a whole

I need to do something like"

for(var i = 1; i <= numPages; ++i){
     this.http.get(url, httpOptions).subscribe((information: any =>{
           allInfo.push(information);
        });
}
processData(allInfo);

where the url will be updated with the correct page.

I know that a processData will execute before the for loop finishes. Is there someway to incorporate promise and then statements or maybe a pipe to get all the data pushed to the allInfo array so that it can then be processed?

score 2 · Accepted Answer · edited Jul 09 '22 at 03:39

2

One way would be that instead of subscribing to all HTTP requests, you store those observable in an array and then use forkJoin to subscribe to the combined result of all of them.

Something like this:

let observaleArray: Observable[] = [];

for(var i = 1; i <= numPages; ++i){
    observableArray.push(this.http.get(url, httpOptions));
}

forkJoin(observableArray)
    .subscribe(allInfo => {
       processData(allInfo); 
    });

Don't forget to import Observable and forkJoin.

edited Jul 09 '22 at 03:39

Sunderam Dubey

1
11
20
40

answered Aug 12 '19 at 21:49

asimhashmi

4,258
1
14
34

1

`forkJoin` is a super good approach, thumbs up. Just remember that is not trivial how you can handle errors with this operator, you can check this answer as a approach suggestion https://stackoverflow.com/a/56861093/9011723 – João Ghignatti Aug 12 '19 at 23:51
So the forkJoin won't execute until the for loop executes? – new_programmer_22 Aug 13 '19 at 17:04
I was able to incorporate this into my code and it works perfectly! I had never heard of `forkJoin`! thanks! – new_programmer_22 Aug 14 '19 at 13:19

What would be the best method for looping through HTTP requests

1 Answers1