Wrapper for Angular Material dialog that emits closed event only with return value

dialog-wrapper.ts

private showDialog<T, R>(component: ComponentType<T>, config: MatDialogConfig): Observable<R> {
  return new Observable(observer => {
    this.dialog.open<T, any, R>(component, config).afterClosed().subscribe(value => {
      if (value) {
        observer.next(value);
      }
      observer.complete();
    });
  });
}