Argument of type 'Observable<xyz[]>' is not assignable to parameter of type 'OperatorFunction<unknown, unknown>'

Issue

The error Argument of type 'Observable<HistoryBranch[]>' is not assignable to parameter of type 'OperatorFunction<unknown, unknown>'. is being thrown by

// private historyBranches$: Observable<historyBranches[]>;

this.historyBranches$ =  this.timeline$.pipe(
            switchMap((tmln) => this.getHistoryBranches$(tmln)));

this.getHistoryBranches is implemented as:

    private getHistoryBranches$(timelineData: Timeline[]): Observable<HistoryBranch[]> {
        return this.service.getHistoryBranches({
                startTime: timelineData[0].time,
                endTime: timelineData[timelineData.length - 1].time,
            }).pipe(map(response=>response.HistoryBranches));
    }

What is this OperatorFunction? (documentation didn't really clarify much for me.. https://rxjs.dev/api/index/interface/OperatorFunction) Why is there a type mismatch?

Solution

Issue is probably related to the returned value of the getHistoryBranches method

Double check it's return type, and also that the value of response is what you expect. That looks a bit off, but you'd need to post code for the service function tod someone to be sure

Answered By - Drenai