invoke function

Implementation

dynamic invoke(String instance, String method,
    {dynamic params, String? result}) {
  final ds = _currentRegistry?.find(instance);
  if (ds == null) return null;
  dynamic ret;
  switch (method.toLowerCase()) {
    case 'first':
      ds.first();
      break;
    case 'next':
      ds.next();
      break;
    case 'prior':
      ds.prior();
      break;
    case 'last':
      ds.last();
      break;
    case 'edit':
      ds.edit();
      break;
    case 'post':
      ds.post();
      break;
    case 'insert':
      ds.insert();
      break;
    case 'append':
      ds.append();
      break;
    case 'cancel':
      ds.cancel();
      break;
    case 'delete':
      ds.delete();
      break;
    case 'disablecontrols':
      ds.disableControls();
      break;
    case 'enablecontrols':
      ds.enableControls();
      break;
    // ??? beginwalk/endwalk were separate methods in the original code
    // (data_db2.dart's TDataSet has beginWalk/endWalk; their exact
    // semantics are unclear — the upstream implementation wasn't
    // available this time). Guessing it means "start/end a traversal
    // pass", which in effect is close to disableControls/enableControls
    // (suspend event broadcasting). Mapped to those two for now; revisit
    // here if the semantics turn out to be more than that.
    case 'beginwalk':
      ds.disableControls();
      break;
    case 'endwalk':
      ds.enableControls();
      break;
    case 'getbookmark':
      ret = ds.getBookmark();
      break;
    case 'gotobookmark':
      // @@@ In the full version, TBookmark is a Uint8List (4-byte index);
      // @@@ kept compatible with old callers that pass an int
      // @@@ (converted to the equivalent bookmark)
      if (params is Uint8List) {
        ds.gotoBookmark(params);
      } else {
        final idx = (params is int) ? params : int.tryParse("$params") ?? 0;
        final bd = ByteData(4);
        bd.setInt32(0, idx, Endian.little);
        ds.gotoBookmark(bd.buffer.asUint8List());
      }
      break;
    case 'freebookmark':
      break; // no need to free (Dart GC)
    default:
      break;
  }
  if (result != null && result.isNotEmpty) {
    _currentEvaluator?.setVar(result, ret);
  }
  return ret;
}