Cómo esperar para varias solicitudes

Estoy tratando de averiguar cuál es la mejor manera de esperar a las múltiples solicitudes y hacer algo cuando se hace, tenga en cuenta que tanto la solicitud de almuerzo en el mismo tiempo y que no debe esperar el uno para el otro.

  // table filling
  public SUB_getActSearch: Subscription;


  // table filling 2
  public SUB_getDeclarationSearch: Subscription;

  public fillTable(): void {
    const searchOBJ = {
      CreateDateFrom: this.currentDate,
      CreateDateTo: this.currentDate,
      ActNumber: this.ActNumber == undefined ? '' : this.ActNumber,
      vinCode: this.vinCode == undefined ? '' : this.vinCode,
      GovNumber: this.GovNumber == undefined ? '' : this.GovNumber,
      IsFromDashboard: true
    };
    const searchOBJ2 = {
      ActNumber: this.ActNumber == undefined ? '' : this.ActNumber,
      vinCode: this.vinCode == undefined ? '' : this.vinCode,
      GovNumber: this.GovNumber == undefined ? '' : this.GovNumber,
    };
    if ((this.ActNumber && this.ActNumber != undefined && this.ActNumber != null) || (this.vinCode && this.vinCode != undefined && this.vinCode != null) || (this.GovNumber && this.GovNumber != undefined && this.GovNumber != null)) {
      this.SUB_getActSearch = this.searchService.getActSearch({ ...searchOBJ2, PageSize: this.pageSize, PageNumber: this.currentPage }).subscribe((res) => {
        this.Act_Data = [];
        let headerPagin = JSON.parse(res.headers.get('X-Pagination'));
        this.elementsLength = headerPagin.totalCount;
        this.currentPage = headerPagin.currentPage;
        this.pageSize = headerPagin.pageSize;
        res.body.map((param) => {
          this.Act_Data.push(param);
        });
        this.ActDataSource = new MatTableDataSource<Element>(this.Act_Data);
        // console.log('Your form data : ', this.ActDataSource);
      });
    } else {
      this.SUB_getActSearch = this.searchService.getActSearch({ ...searchOBJ, PageSize: this.pageSize, PageNumber: this.currentPage }).subscribe((res) => {
        this.Act_Data = [];
        let headerPagin = JSON.parse(res.headers.get('X-Pagination'));
        this.elementsLength = headerPagin.totalCount;
        this.currentPage = headerPagin.currentPage;
        this.pageSize = headerPagin.pageSize;
        res.body.map((param) => {
          this.Act_Data.push(param);
        });
        this.ActDataSource = new MatTableDataSource<Element>(this.Act_Data);
        // console.log('Your form data : ', this.ActDataSource);
      });
    }
  }


  public fillTable2(): void {
    const searchOBJ = {
      DeclarationCreateDateFrom: this.currentDate.substring(0, 10),
      DeclarationCreateDateTo: this.currentDate,
      DeclarationNumber: this.ActNumber == undefined ? '' : this.ActNumber,
      VinCode: this.vinCode == undefined ? '' : this.vinCode,
      TransitNumber: this.GovNumber == undefined ? '' : this.GovNumber,
    };
    const searchOBJ2 = {
      DeclarationNumber: this.ActNumber == undefined ? '' : this.ActNumber,
      VinCode: this.vinCode == undefined ? '' : this.vinCode,
      TransitNumber: this.GovNumber == undefined ? '' : this.GovNumber,
    };
    if ((this.ActNumber && this.ActNumber != undefined && this.ActNumber != null) || (this.vinCode && this.vinCode != undefined && this.vinCode != null) || (this.GovNumber && this.GovNumber != undefined && this.GovNumber != null)) {
      this.SUB_getDeclarationSearch = this.declarationsService.getDeclarations({ ...searchOBJ, IsFromDashboard: true, PageSize: this.pageSizeDecl, PageNumber: this.currentPageDecl }).subscribe((res) => {
        this.Declaration_Data = [];
        let headerPaginDecl = JSON.parse(res.headers.get('X-Pagination'));
        this.elementsLengthDecl = headerPaginDecl.totalCount;
        this.currentPageDecl = headerPaginDecl.currentPage;
        this.pageSizeDecl = headerPaginDecl.pageSize;
        res.body.map((param) => {
          this.Declaration_Data.push(param);
        });
        this.DeclarationDataSource = new MatTableDataSource<Element>(this.Declaration_Data);
        // console.log('Your form data : ', this.DeclarationDataSource);
      });
    } else {
      this.SUB_getDeclarationSearch = this.declarationsService.getDeclarations({ ...searchOBJ, IsFromDashboard: true, PageSize: this.pageSizeDecl, PageNumber: this.currentPageDecl }).subscribe((res) => {
        this.Declaration_Data = [];
        let headerPaginDecl = JSON.parse(res.headers.get('X-Pagination'));
        this.elementsLengthDecl = headerPaginDecl.totalCount;
        this.currentPageDecl = headerPaginDecl.currentPage;
        this.pageSizeDecl = headerPaginDecl.pageSize;
        res.body.map((param) => {
          this.Declaration_Data.push(param);
        });
        this.DeclarationDataSource = new MatTableDataSource<Element>(this.Declaration_Data);
        // console.log('Your form data : ', this.DeclarationDataSource);
      });
    }
  }

Hay dos métodos que se llama dentro de ngoninit: fillTable() y fillTable2().

He intentado usar el siguiente método para escuchar las suscripciones y esperar

  public testingforkJoin(): void {
    forkJoin([this.SUB_getActSearch, this.SUB_getDeclarationSearch]
    ).subscribe(val => 
console.log("xxxxx", val));
// call some method here as soon as both are done
  }

Pero como resulta que forkJoin no puede escuchar a las suscripciones, ¿hay alguna otra manera similar a forkjoin para las suscripciones?

Hay remolque métodos que incluyen las solicitudes HTTP y quiero esperar tanto para los requerimientos de la red para completar y hacer algo que tan pronto como hayan terminado.