Example of Angular2/TypeScript function returning an Observable after executing two nested forkJoin

returnObservableWithNestedForkJoin.ts

public fetchABunchOfData (rootObj: RootObj): Observable<Project> {
    // Returned original RootObj as an Observer when nested resource is fetched
    let returnedData = new ReplaySubject(1);

    let firstObservable = Observable.forkJoin(
      this._cloud.getSomeRestData(rootObj.id),
      this._cloud.getOtherRestData(rootObj.id)
    );

    // Execute first two Rest calls (someData and OtherData)
    firstObservable.subscribe(
      data => {
        let someData: Array<SomeData> = data[0];
        let otherData: Array<OtherData> = data[1];

        let someDataObservers = [];
        let someDataDict: SomeDataDictionary = {};
        someData.forEach(obj => {
          // console.log(obj);
          someDataObservers.push(this._cloud.getSomeDataNestedResource(obj.id));
        });
        // Fetch all nested resources 
        Observable.forkJoin(someDataObservers).subscribe(
          (nestedData) => {
            returnedData.next(rootObj);
          }
        );
      },
      err => {
        console.error(err);
      }
    );
    return returnedData;
  }