Is there a different option similar to forkJoin for handling incomplete observables?

Question

Is there a different option similar to forkJoin for handling incomplete observables?

constructor(
    private route: ActivatedRoute,
    private http: Http
){
    // Retrieve parameter changes observable
    let paramObs = route.paramMap;

    // Fetch data once only
    let dataObs = http.get('...');

    // Subscribe to both observables together
    // and utilize their resolved values in the same scope
}

Is there a method similar to forkJoin that is triggered each time a parameter change occurs? Note that forkJoin depends on all observables being completed.

I'm hoping for an alternative approach to handle this without getting into callback hell. Any suggestions complying with this requirement would be appreciated.

angular typescript rxjs

Answer 1

Answer №1

If you're looking for ways to combine multiple source Observables, here are a few options:

One approach is to use take(1) along with forkJoin() to ensure each source Observable completes:
```
forkJoin(o1$.take(1), o2$.take(1))
```
Another method involves using zip() in conjunction with take(1), which emits only when all Observables have emitted the same number of items:
```
zip(o1$, o2$).take(1)
```
Alternatively, you can utilize combineLatest() to trigger emission whenever any of the source Observables emit a value:
```
combineLatest(o1$, o2$)
```

Updated as of January 2019 to reflect changes in RxJS 6

Answer 2

If you're looking for ways to combine multiple source Observables, here are a few options:

One approach is to use take(1) along with forkJoin() to ensure each source Observable completes:
```
forkJoin(o1$.take(1), o2$.take(1))
```
Another method involves using zip() in conjunction with take(1), which emits only when all Observables have emitted the same number of items:
```
zip(o1$, o2$).take(1)
```
Alternatively, you can utilize combineLatest() to trigger emission whenever any of the source Observables emit a value:
```
combineLatest(o1$, o2$)
```

Updated as of January 2019 to reflect changes in RxJS 6

Answer 3

Answer №2

Here's a handy tip to prevent observable subscriptions from breaking if one of the observables fails.


import { throwError, of, forkJoin } from "rxjs";
import { catchError, take } from "rxjs/operators";

//emits an error with specified value on subscription
const observables$ = [];
const observableThatWillComplete$ = of(1, 2, 3, 4, 5).pipe(take(1));

const observableThatWillFail$ = throwError(
  "This is an error hence breaking the stream"
).pipe(catchError((error) => of(`Error Catched: ${error}`)));

observables$.push(observableThatWillComplete$, observableThatWillFail$);

forkJoin(observables$).subscribe(responses => {
  console.log("Subscribed");
  console.log(responses);
});

Answer 4

Here's a handy tip to prevent observable subscriptions from breaking if one of the observables fails.


import { throwError, of, forkJoin } from "rxjs";
import { catchError, take } from "rxjs/operators";

//emits an error with specified value on subscription
const observables$ = [];
const observableThatWillComplete$ = of(1, 2, 3, 4, 5).pipe(take(1));

const observableThatWillFail$ = throwError(
  "This is an error hence breaking the stream"
).pipe(catchError((error) => of(`Error Catched: ${error}`)));

observables$.push(observableThatWillComplete$, observableThatWillFail$);

forkJoin(observables$).subscribe(responses => {
  console.log("Subscribed");
  console.log(responses);
});

Answer 5

Answer №3

Another helpful approach is to utilize Observable.concat(), which will process each observable in a specific order. To illustrate, consider the following code snippet:

const getPostOne$ = Rx.Observable.timer(3000).mapTo({id: 1});
const getPostTwo$ = Rx.Observable.timer(1000).mapTo({id: 2});

Rx.Observable.concat(getPostOne$, getPostTwo$).subscribe(res => console.log(res));

I also recommend reading this informative article on essential operators in RxJS.

Answer 6

Another helpful approach is to utilize Observable.concat(), which will process each observable in a specific order. To illustrate, consider the following code snippet:

const getPostOne$ = Rx.Observable.timer(3000).mapTo({id: 1});
const getPostTwo$ = Rx.Observable.timer(1000).mapTo({id: 2});

Rx.Observable.concat(getPostOne$, getPostTwo$).subscribe(res => console.log(res));

I also recommend reading this informative article on essential operators in RxJS.

Is there a different option similar to forkJoin for handling incomplete observables?

Answer №1

Answer №2

Answer №3

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