var datasource = {
     let page=0;
     let lastRow = 1200;
            getRows: (params: IGetRowsParams) => {
              this.info = "Getting datasource rows, start: " + params.startRow + ", end: " + params.endRow;

              this.api.getRowData(page+1)
                        .subscribe(data => params.successCallback(data,lastRow));

            }
      };
      params.api.setDatasource(datasource);

    }