flea-market-contract-service.ts

private widgetObservable = (id: number): Observable<PurchaseWidgetModel> =>
    from(this.contractToken.getContractKeyAtIndex(id)).pipe(
    
      switchMap(key => from(this.contractToken.getContractByKey(key)).pipe(
        map(address => {

          const widget: PurchaseWidgetModel = {
            productKey: utils.parseBytes32String(key as ethers.utils.Arrayish),
            contractAddress: address as string
          };
          return widget;
        })
      ))
    )

public getPurchaseContractList(): Observable<PurchaseWidgetModel[]> {

    return from(this.contractToken.getContractCount()).pipe(
    
      map((bigNumber: ethers.utils.BigNumber) => bigNumber.toNumber()),
      tap((contractCount: number) => console.log('contractCount: ', contractCount)),
      switchMap((contractCount: number) => {

        if (contractCount === 0) {
          return of([]);
        }
        else {
          // we get array [0,1,....contractCount-1]
          const countArr: number[] = Array.from(Array(contractCount)).map((e, i) => i);
          const source = of(countArr);
          return source.pipe(
            mergeMap(ids => forkJoin(ids.map(this.widgetObservable)))

          )
        }
      })
    )
  }