TCustomClientDataSet.FetchParams Method

Retrieves parameter values from the provider.

Pascal

procedure FetchParams;

C++

__fastcall FetchParams();

Description

Call FetchParams to initialize the Params property with the current parameter values on the provider's dataset. FetchParams does nothing unless the provider's dataset can supply parameter values.

Note: At design time, you can fetch parameter values by right-clicking the client dataset and choosing Fetch Params.

Warning: If the provider is on a stateless application server, the values returned by FetchParams can be changed at any time by other clients. To obtain output parameters from a stateless application server, use the Execute method instead.

C++ Examples:

Copy Code

/*
  This example saves params from a ClientDataSet, alters them
  and restores them.
*/
TParams *SavedParams;

void __fastcall TForm1::SaveParamsClick(TObject *Sender)
{
  // Save the parameters for the TDataSet
  SavedParams->Assign(CDS->Params);
}

void __fastcall TForm1::AlterParamsClick(TObject *Sender)
{
  CDS->Params->CreateParam(ftString, "stringParam", ptInput);  // you can also edit the params in the CDS dynamically
  CDS->Params->CreateParam(ftSmallint, "smallIntParam", ptInput);
  CDS->Params->CreateParam(ftInteger, "intParam", ptInput);
  CDS->Params->CreateParam(ftWord, "wordParam", ptInput);
  CDS->Params->CreateParam(ftBoolean, "boolParam", ptInput);
  CDS->Params->CreateParam(ftFloat, "floatParam", ptInput);
  CDS->Params->CreateParam(ftCurrency, "currencyParam", ptInput);
  CDS->Params->CreateParam(ftBCD, "bcdParam", ptInput);
  CDS->Params->CreateParam(ftDate, "dateParam", ptInput);
  CDS->Params->CreateParam(ftTime, "timeParam", ptInput);
  CDS->Params->CreateParam(ftDateTime, "dateTimeParam", ptInput);
  // Call FetchParams to ensure parameters reflect server metadata
  CDS->FetchParams();
//  with CDS->Params do
  for (int I = 0; I < CDS->Params->Count; I++)
  {
    AnsiString ListItem = ListBox1->Items->Strings[I];
    switch (CDS->Params->Items[I]->DataType)
    {
      case ftString:
        CDS->Params->Items[I]->AsString = ListItem; break;
      case ftSmallint:
        CDS->Params->Items[I]->AsSmallInt = StrToIntDef(ListItem, 0); break;
      case ftInteger:
        CDS->Params->Items[I]->AsInteger = StrToIntDef(ListItem, 0); break;
      case ftWord:
        CDS->Params->Items[I]->AsWord = StrToIntDef(ListItem, 0); break;
      case ftBoolean:
        CDS->Params->Items[I]->AsBoolean = (ListItem == "True"); break;
      case ftFloat:
        CDS->Params->Items[I]->AsFloat = StrToFloat(ListItem); break;
      case ftCurrency:
        CDS->Params->Items[I]->AsCurrency = double(StrToFloat(ListItem)); break;
      case ftBCD:
        CDS->Params->Items[I]->AsBCD = StrToCurr(ListItem); break;
      case ftDate:
        CDS->Params->Items[I]->AsDate = StrToDate(ListItem); break;
      case ftTime:
        CDS->Params->Items[I]->AsTime = StrToTime(ListItem); break;
      case ftDateTime:
        CDS->Params->Items[I]->AsDateTime = StrToDateTime(ListItem); break;
    }
  }
}

void __fastcall TForm1::RestoreParamsClick(TObject *Sender)
{
  // Restore the parameters to TDataSet
  CDS->Params->AssignValues(SavedParams);
}

void __fastcall TForm1::FormCreate(TObject *Sender)
{
  // Initialize SavedParams
  SavedParams = new TParams;
  ListBox1->Items->Add("Here is a string");
  ListBox1->Items->Add("4");
  ListBox1->Items->Add("3456789");
  ListBox1->Items->Add("34");
  ListBox1->Items->Add("0");
  ListBox1->Items->Add("12.56");
  ListBox1->Items->Add("4.23");
  ListBox1->Items->Add("99.5");
  ListBox1->Items->Add("4/12/53");
  ListBox1->Items->Add("7:45:00");
  ListBox1->Items->Add("4/12/53 7:45:00");
}

Delphi Examples:

Copy Code

{
  This example uses the FetchParams method to sync the params
  with the server.
}
procedure TForm1.SaveParamsClick(Sender: TObject);
begin
  { Save the parameters for the TDataSet }
  SavedParams.Assign(CDS.Params);
end;

procedure TForm1.AlterParamsClick(Sender: TObject);
var
  I : Integer;
  ListItem: string;
begin
  CDS.Params.CreateParam(ftString, 'stringParam', ptInput);  // you can also edit the params in the CDS dynamically
  CDS.Params.CreateParam(ftSmallInt, 'smallIntParam', ptInput);
  CDS.Params.CreateParam(ftInteger, 'intParam', ptInput);
  CDS.Params.CreateParam(ftWord, 'wordParam', ptInput);
  CDS.Params.CreateParam(ftBoolean, 'boolParam', ptInput);
  CDS.Params.CreateParam(ftFloat, 'floatParam', ptInput);
  CDS.Params.CreateParam(ftCurrency, 'currencyParam', ptInput);
  CDS.Params.CreateParam(ftBCD, 'bcdParam', ptInput);
  CDS.Params.CreateParam(ftDate, 'dateParam', ptInput);
  CDS.Params.CreateParam(ftTime, 'timeParam', ptInput);
  CDS.Params.CreateParam(ftDateTime, 'dateTimeParam', ptInput);
  { Call FetchParams to ensure parameters reflect server metadata }
  CDS.FetchParams;
  with CDS.Params do
  begin
    for I := 0 to Count - 1 do
    begin
      ListItem := ListBox1.Items[I];
      case Items[I].DataType of
        ftString:
          Items[I].AsString := ListItem;
        ftSmallInt:
          Items[I].AsSmallInt := StrToIntDef(ListItem, 0);
        ftInteger:
          Items[I].AsInteger := StrToIntDef(ListItem, 0);
        ftWord:
          Items[I].AsWord := StrToIntDef(ListItem, 0);
        ftBoolean:
          begin
            if ListItem = 'True' then
              Items[I].AsBoolean := True
            else
              Items[I].AsBoolean := False;
          end;
        ftFloat:
          Items[I].AsFloat := StrToFloat(ListItem);
        ftCurrency:
          Items[I].AsCurrency := StrToFloat(ListItem);
        ftBCD:
          Items[I].AsBCD := StrToCurr(ListItem);
        ftDate:
          Items[I].AsDate := StrToDate(ListItem);
        ftTime:
          Items[I].AsTime := StrToTime(ListItem);
        ftDateTime:
          Items[I].AsDateTime := StrToDateTime(ListItem);
      end;
    end;
  end;
end;

procedure TForm1.RestoreParamsClick(Sender: TObject);
begin
  { Restore the parameters to TDataSet }
  CDS.Params.AssignValues(SavedParams);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  { Initialize SavedParams }
  SavedParams := TParams.Create;
  ListBox1.Items.Add('Here is a string');
  ListBox1.Items.Add('4');
  ListBox1.Items.Add('3456789');
  ListBox1.Items.Add('34');
  ListBox1.Items.Add('0');
  ListBox1.Items.Add('12.56');
  ListBox1.Items.Add('4.23');
  ListBox1.Items.Add('99.5');
  ListBox1.Items.Add('4/12/53');
  ListBox1.Items.Add('7:45:00');
  ListBox1.Items.Add('4/12/53 7:45:00');
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  SavedParams.Free;
end;