如何在从 frokJoin 订阅接收数据后发出可观察的

Question

So basically I want to get data from 3 observables with forkJoin and once they emit values I want to emit another observable form subscription logic, so I can subscribe to it from another place. What I have now

 getOptionsArray = <T>(): Observable<any> => {
    forkJoin([
      get1(),
      get2(),
      get3()
    ]).subscribe(([data1, data2, data3]) => {
      // some necessary assignment logic which needs to be here...

      // here I want to emit observable so I can subscribe to getOptionsArray method from 
      // another place, but only after logic in subcription here is applied.
    })
}

I know I could just return forkJoin and just subscribe to it from another place, but I need to do some assignment logic first inside this function and then once this logic is applied I want to return observable from this method to which I could subscribe from another place.

Answer 1

You have 2 options:

getOptionsArray = <T>(): Observable<any> => {
    return forkJoin([
      get1(),
      get2(),
      get3()
    ]).pipe(map([data1, data2, data3]) => {
        ...
        return result;
    }))
}

or

getOptionsArray = <T>(): Observable<any> => {
    let subject = new Subject();
    forkJoin([
      get1(),
      get2(),
      get3()
    ]).subscribe(([data1, data2, data3]) => {
        ...
        subject.next(result);
        subject.completes();
    });
    return subject.asObservable();
}

I prefer the first one.