CODEWITHSUNDEEP
javascriptangularrxjsobservable
Sairam
Sairam

Reputation: 63

subscriber.next() is not firing after subscriber.error statement

Based on the input data I want to decide whether it is valid data or not and send the observable to the to end.

I have tried to create a observable and sequential subscribe.next() is working correctly but any error is coming then after that no statement is working.

const observable = new Observable((subscriber) => {
  subscriber.next(1);
  subscriber.next(2);
  subscriber.error('failed this after second');
  subscriber.next(3);
  subscriber.next(4);
  subscriber.complete();
});

observable.subscribe({
  next(x) {
    console.log('got value ' + x);
  },
  error(err) {
    console.error('something wrong occurred: ' + err);
  },
  complete() {
    console.log('done');
  },
});

Current output:

Expected output

Here is the stackblitz link https://stackblitz.com/edit/zlksm5?devtoolsheight=50&file=index.ts

Upvotes: 1

Views: 550

Answers (2)

Mrk Sef
Mrk Sef

Reputation: 8062

The Observable Contract

OnError:

  • Indicates that the Observable has terminated with a specified error condition and that it will be emitting no further items

Emphasis mine.

If you want something that keeps going after it completes, you don't want an observable.

Toward a solution

Just emit your error as a value. You could (for example) wrap your emissions in RxJS Notification objects so that you can materialize or dematerialize observables and keep a consistent API of emissions.

For example:

const observable = new Observable(subscriber => {
  subscriber.next({ kind: "N", value: 1 });
  subscriber.next({ kind: "N", value: 2 });
  subscriber.next({ kind: "E", error: new Error("failed this after second") });
  subscriber.next({ kind: "N", value: 3 });
  subscriber.next({ kind: "N", value: 4 });
  subscriber.next({ kind: "C" });
  subscriber.complete();
});

/**** Alternative written more succinctly ****/

const observable = of(
  { kind: "N", value: 1 },
  { kind: "N", value: 2 },
  { kind: "E", error: new Error("failed this after second") },
  { kind: "N", value: 3 },
  { kind: "N", value: 4 },
  { kind: "C" }
);


observable.subscribe((notification) => {
  switch (notification.kind) {
    case "N":
      console.log("got value ", notification.value);
      break;
    case "E":
      console.error("something wrong occurred: ", notification.error.message);
      break;
    case "C":
      console.log("done");
  }
});

Upvotes: 1

Dibyanshu Banerjee
Dibyanshu Banerjee

Reputation: 161

I don't think it's possible with an Observable, cause the observable will be closed if any error occurred.

I have tried couple of ways, putting it for reference

//interval(1000)
observable
  //.pipe(switchMap(() => observable))
  .pipe(
    catchError((d) => {
      observable.subscribe((nd) => {
        console.log('--again--', nd);
      });
      return of(d);
    })
    //retry(1)
  )
  .subscribe({
    next(x) {
      console.log('got value ' + x);
    },
    error(err) {
      console.error('something wrong occurred: ' + err);
    },
    complete() {
      console.log('done');
    },
  });

// interval(1000)
//   .pipe(switchMap(_ => observable))
//   .pipe(
//     catchError((d) => {return of(d)}),
//     switchMap(_ => observable)
//   )
// .subscribe(d => {
//   console.log(d)
// })

For your use case it's better to use a behavior subject instead.

Upvotes: 0

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