TParam.DataType Property

Indicates the type of field whose value the parameter represents.

Pascal

property DataType: TFieldType;

C++

__property TFieldType DataType;

Description

DataType is set automatically when a value is assigned to the parameter. Do not set DataType for bound fields, as that may cause the assigned value to be misinterpreted.

Read DataType to discover the type of data that was assigned to the parameter. Each possible value of DataType corresponds to a type of database field.

C++ Examples:

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/*
  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");
}

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/*
This example requires a TClientDataSet and a button on a form.
*/
void __fastcall TForm1::Button1Click(TObject *Sender)
{
for (int I = 0; I < CDS->Params->Count; I++)
{
  if (CDS->Params->Items[I]->IsNull &&
      CDS->Params->Items[I]->DataType == ftInteger)
    CDS->Params->Items[I]->AsInteger = -1;
}}

void __fastcall TForm1::FormCreate(TObject *Sender)
{
  CDS->LoadFromFile(GetCurrentDir() + L"/../CDS.XML");
  CDS->Params->CreateParam(ftInteger, "StateParam", ptInput);
  CDS->Params->CreateParam(ftInteger, "MyParam", ptInput);
}

Delphi Examples:

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{
  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;

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{
This example fills in the parameters of a client dataset
from the entries of a list box.
} 
procedure TForm1.Button4Click(Sender: TObject);
var
  I: Integer;
  ListItem: string;
begin
  { Call FetchParams to ensure parameters reflect server metadata }
  ClientDataSet1.FetchParams;
  with ClientDataSet1.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.FormCreate(Sender: TObject);
begin
  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;

Copy Code

{
This example requires a TClientDataSet and a button on a form.
}
{$IFNDEF UNICODE}
uses SwSystem;
{$ENDIF}

procedure TForm1.Button1Click(Sender: TObject);
var
  I : Integer;
begin
{ Assign -1 to any integer parameter which does not have a value. }
for I := 0 to CDS.Params.Count - 1 do
  if (CDS.Params.Items[I].IsNull) and
     (CDS.Params.Items[I].DataType = ftInteger) then
    { Items is the default property, so you can omit its name }
    CDS.Params[I].AsInteger := -1;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
{$IFDEF UNICODE}
  CDS.LoadFromFile(GetCurrentDir + '\CDS.XML');
{$ELSE}
  CDS.LoadFromFile(gsAppPath + 'CDS.XML');
{$ENDIF}
  CDS.Params.CreateParam(ftInteger, 'StateParam', ptInput);
  CDS.Params.CreateParam(ftInteger, 'MyParam', ptInput);
end;