CODEWITHSUNDEEP
rxjs
Royi Namir
Royi Namir

Reputation: 148624

How to use Rxjs 5.5 `first` operator which has mismatch type in arguments?

I'm using an external package which emits an Observable : 

getValue(key: string | Array<string>, interpolateParams?: Object): Observable<string | any> {
    return null;
  }

I also use the first lettable operator : 

import { first } from "rxjs/operators/first";
this.getValue('f').let(first);

But I'm getting an error :

Type 'Observable' provides no match for the signature '(value: any, index: number, source: Observable): value is any'.

I can see where the problem comes from. The first operator is :

export function first(predicate?: (value: T, index: number, source: Observable) => boolean): MonoTypeOperatorFunction;

And my Observable is type <any>

Question:

How can I fix my lettable operator to work with the Observable ^ ?

Online-demo which shows the problem

Upvotes: 0

Views: 213

Answers (1)

Suren Srapyan
Suren Srapyan

Reputation: 68665

Try to call first in the let. It will return a function which will be applied by the stream. Also use pipe instead if let

this.getValue('f').pipe(first())

Upvotes: 1

Related Questions