CODEWITHSUNDEEP
angularrxjsobservable
Stefan
Stefan

Reputation: 1511

Chain multiple calls with foreach loop and Observable

I want to chain multiple request to the urls which I get from the array. Before next chain i want to wait for the previous one to finish. It's does not matter if the previous fails or not. I was trying to this with forkJoin but I know that if one of the request fails it will return error.

this.dataServers.forEach(dataServer => {
    observableBatch.push(this.getFoodsByQuery(dataServer.url, query));
});

return Observable.forkJoin(observableBatch).subscribe(data => {
    this.searchingServer.next(null);
    observer.complete();
});

I do not know how to do this with flatMap.

Upvotes: 3

Views: 5682

Answers (2)

taras-d
taras-d

Reputation: 1827

In your case suitable operator is concat

Concatenates multiple Observables together by sequentially emitting their values, one Observable after the other.

Example:

// Batch of requests
let batch = [
  Observable.of(1),
  Observable.of(2).delay(1500),
  Observable.throw('Error'),
  Observable.of(3).delay(300),
  Observable.throw('Error again'),
  Observable.of(4).delay(600)
];

// Catch (ignore) error of every request
batch = batch.map(obs => {
  return obs.catch(err => Observable.of(err));
});

// Concat observables 
Observable.concat(...batch).subscribe({
  next: v => console.log(v),
  complete: () => console.log('Complete')
});

Output:

1
2
'Error'
3
'Error again'
4
'Complete'

Upvotes: 8

amburt05
amburt05

Reputation: 514

Have you tried using OnErrorResumeNext() with forkJoin?

return Observable.forkJoin(observableBatch)
.OnErrorResumeNext()
.subscribe(data => {
  this.searchingServer.next(null);
  observer.complete();
});

Upvotes: 0

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