Angular 6 ng lint combineLatest is deprecated

Question

I recently updated from Angular 5 to Angular 6.

I'm getting this warning combineLatest is deprecated: resultSelector no longer supported, pipe to map instead. Rxjs is version 6.1.0, tslint is 5.10.0, Angular CLI is 6.0.0 and Typescript 2.7.2. I'm using it like this:

const a$ = combineLatest(
  this.aStore.select(b.getAuth),
  this.cStore.select(b.getUrl),
  (auth, url) => ({auth, url}),
);

I've tried it also like this:

empty().pipe(
combineLatest(...),
  ...
)

But this gives me: combineLatest is deprecated: Deprecated in favor of static combineLatest and empty is also deprecated in favor of its static version.

Clearly

you can also try a$.pipe(a$ => combineLatest(a$,b$, c$)); with import { combineLatest } from 'rxjs'; – Janijania

Answer 1

combineLatest is deprecated: resultSelector no longer supported, pipe to map instead

The above warning is recommending to remove the resultSelector the last function you provided in combineLatest observable and provide it as part of map operator as follows

const a$ = combineLatest(
  this.aStore.select(b.getAuth),
  this.cStore.select(b.getUrl)
);

const result$ = a$.pipe(
  map(results => ({auth: results[0], url: results[1]}))
)

UPDATE:

If you see combineLatest is deprecated: Pass arguments in a single array instead then just add []:

const a$ = combineLatest([
  this.aStore.select(b.getAuth),
  this.cStore.select(b.getUrl)
]);
    
const result$ = a$.pipe(
  map(results => ({auth: results[0], url: results[1]}))
)

Find

Thank you! This works but combineLatest will make an array so I have to do it like this: const result$ = a$.pipe(map((a) => ({auth: a['0'], url: a['1']}))); – Clearly

Personal preference, but I much prefer a destructuring assignment here to mapping to a new object. So like: const result$ = a$.pipe(tap(([auth, url]) => { /* ... */ })); – Hydrokinetics

What if I wanted to use a projector function like in the old combineLatest(), how would I go about this? – Deprivation

Update https://mcmap.net/q/173936/-how-to-39-wait-39-for-two-observables-in-rxjs – Zoosperm

Answer 2

Unfortunately you might also get that tslint error if you import combineLatest from operators:

import { combineLatest } from 'rxjs/operators';
    
combineLatest(...array);

instead of,

import { combineLatest } from 'rxjs';
    
combineLatest(...array);

Zara

Answer 3

Unlike the deprecated versions, combineLatest accepts an Array of Observable and returns an array containing the latest values from each. Every stream has to yield in order for combineLatest to yield.

fruitType$ = combineLatest([this.entity$, this.datasetStateService.get$('Fruits')])
  .pipe(map(data => {
    const entity = data[0];
    const dataset = data[1];
    return {
       isApple: (dataset.find(ds => ds.label === 'Apple') as DataItem).id === entity.fruitId,
       isOrange: (dataset.find(ds => ds.label === 'Orange') as DataItem).id === entity.fruitId
    }
}));

Fabozzi

Answer 4

In my case it's because I explicitly set generic argument, so an incorrect combineLatest overload was selected. To get rid of the warning I've changed

combineLatest<void>([
    firstObservable$,
    secondObservable$
]);

to

combineLatest([
    firstObservable$,
    secondObservable$
]).pipe(
    mapTo(undefined)
);

Metatarsus

Answer 5

For trailing comma error, remove the comma after (auth, url) => ({auth, url})

const a$ = combineLatest(
  this.aStore.select(b.getAuth),
  this.cStore.select(b.getUrl),
  (auth, url) => ({auth, url}),  // Remove this comma.
);

For missing import error, Make sure you have imports for all the external var's or classes you are using in the file.

Example, in this case, if you havent imported combineLatest, then import it

import { combineLatest } from 'rxjs'; // For RxJS 6.x

import { combineLatest } from 'rxjs/operators'; // For RxJS 5.x

Enfold

Thanks but I think I wasn't being clear. Those were not actual issues but I was just giving an example to the problem how the issues were being reported twice. I've edited my question. – Clearly

Answer 6

i used depricated combineLatest to combine those two observables this.route.paramMap + this.route.queryParamMap:

combineLatest(this.route.paramMap, this.route.queryParamMap)
  .subscribe(combined => {
    const idFollower = combined[0].get('id');
    const page = combined[1].get('page');
  })

Podvin

Answer 7

I would solve that this way:

auth$ = this.aStore.select(b.getAuth);
url$ = this.cStore.select(b.getUrl);

combinedResult$ = combineLatest([this.auth$, this.url$]).pipe(
    map(([auth, url]) => ({auth, url}))
)

Mclin

Answer 8

This error can also be caused by passing in an array of Subscription items, instead of actual observables, lol. (I got really sloppy on this one.)

WRONG!

const foo = Foo$.subscribe(f => {
  // do something with f here
})

const bar = Bar$.subscribe(b => {
  // do something with b here
})

combineLatest([foo, bar]).subscribe(([f, b]) => {
  // do something after both foo$ and bar$ have emitted something
})

CORRECT!

const foo$ = Foo$.pipe(
  tap(f => {
    // do something with f here
  })
)

const bar$ = Bar$.pipe(
  tap(b => {
    // do something with b here
  })
)

combineLatest([foo$, bar$]).subscribe(([f, b]) => {
  // do something after both Foo$ and Bar$ have emitted something
})

Byplay