Tfield em tempo de execução

procedure TForm1.btnCriaFieldClick(Sender: TObject);
var T: TStringField;
begin
   if qryCliente.Active then
      qryCliente.Close;
   T := TStringField.Create(Self);
   T.fieldName := ´cli_Nome´;
   T.FieldKind := fkData;
   T.DisplayLabel := ´Nome do Cliente´;
   T.Visible := True;
   T.Name := qryCliente.Name + T.FieldName;
   T.Index := qryCliente.FieldCount;
   T.DataSet := qryCliente;
   qryCliente.FieldDefs.UpDate;
   qryCliente.Open;
end;

procedure TForm1.btnApagaFieldClick(Sender: TObject);
var TC: TComponent;
begin
   TC := FindComponent(´qryClientecli_Nome´);
   if not (TC = nil) then
      begin
      qryCliente.Close;
      TC.Free;
      qryCliente.Open;
      end;
end;

var
  fCampo  : TStringField;
  fNome   : TStringField;
  fCodigo : TFloatField;
  fFloat  : TFloatField;
  fData   : TDateField;  

implementation

procedure TForm1.Button1Click(Sender: TObject);
begin
  // Fecha a query
  Query.Close;

  // Limpa o sql
  Query.SQL.Clear;

  // Cria o sql
  Query.SQL.Add(´Select(codigo, nome from funcionarios´);

  // Campo nome
  if not Assigned(fNome) then
     begin
       fNome := TStringField.Create(Self);
       fNome.FieldName    := ´nome´;
       fNome.FieldKind    := fkData;
       fNome.Size         := 30;
       fNome.DisplayWidth := 30;
       fNome.DataSet      := Query;
     end;

  // Campo Código
  if not Assigned(fCodigo) then
     begin
       fCodigo := TFloatField.Create(Self);
       fCodigo.FieldName    := ´codigo´;
       fCodigo.FieldKind    := fkData;
       fCodigo.DisplayWidth := 10;
       fCodigo.DataSet      := Query;
     end;

  // Campo Calculado
  if Assigned(fCampo) then
     begin
       fCampo              := TStringField.Create(Self);
       fCampo.FieldName    := ´Inicial´;
       fCampo.FieldKind    := fkCalculated;
       fCampo.Alignment    := taCenter;
       fCampo.Size         := 1;
       fCampo.DisplayWidth := 1;
       fCampo.DataSet      := Query;
     end;

  // Campo Calculado
  if Assigned(fFloat) then
     begin
       fFloat              := TFloatField.Create(Self);
       fFloat.FieldName    := ´Mult´;
       fFloat.FieldKind    := fkCalculated;
       fFloat.Alignment    := taCenter;
       fFloat.DisplayWidth := 10;
       fFloat.DataSet      := Query;
     end;
 
  // Campo Calculado
  if Assigned(fData) then
     begin
       fData               := TDateField.Create(Self);
       fData.FieldName    := ´Data´;
       fData.FieldKind    := fkCalculated;
       fData.Alignment    := taCenter;
       fData.DisplayWidth := 10;
       fData.DataSet      := Query;
     end;

  // Abre a Query...
  Query.Open;

  // Cria as colunas (OPCIONAL) usado para criar os titles.
  with Grid.Columns do
    begin
      Items[0].Title.Caption := ´Cód.´;
      Items[1].Title.Caption := ´Nome´;
      Items[2].Title.Caption := ´Letra Inicial´;
      Items[3].Title.Caption := ´2x Cód.´;
      Items[4].Title.Caption := ´Data´;
    end;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  // Se o campo foi criado tira-o da memória
  if Assigned(fCampo)  then FreeAndNil(fCampo);
  if Assigned(fNome)   then FreeAndNil(fNome);
  if Assigned(fCodigo) then FreeAndNil(fCodigo);
  if Assigned(fFloat)  then FreeAndNil(fFloat);
  if Assigned(fData)  then FreeAndNil(fData);
end;

procedure TForm1.QueryCalcFields(DataSet: TDataSet); // <------ Preste atenção para criar este evento!!
begin
  Query.FieldByName(´Inicial´).asString := Copy(Query.Campo(´nome´),1,1);
  Query.FieldByName(´mult´).asFloat     := Query.GetInteger(´codigo´) * 2;
  Query.FieldByName(´data´).asDateTime  := Now;
end;

procedure TForm1.FormShow(Sender: TObject);
begin
  Query.Select(´codigo,nome from funcion´);
  with Grid.Columns do
  begin
    Items[0].Title.Caption := ´Cód.´;
    Items[1].Title.Caption := ´Nome´;
  end;
end;

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  Db, ExtCtrls, DBCtrls, Grids, DBGrids, DBTables;

type
  TForm1 = class(TForm)
    Table1: TTable;
    DataSource1: TDataSource;
    Table2: TTable;
    DBGrid1: TDBGrid;
    DBNavigator1: TDBNavigator;
    Table2VendorNo: TFloatField;
    Table2VendorName: TStringField;
    Table2Address1: TStringField;
    Table2Address2: TStringField;
    Table2City: TStringField;
    Table2State: TStringField;
    Table2Zip: TStringField;
    Table2Country: TStringField;
    Table2Phone: TStringField;
    Table2FAX: TStringField;
    Table2Preferred: TBooleanField;
    Table1PartNo: TFloatField;
    Table1VendorNo: TFloatField;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
    Table1VendorName: TStringField;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.FormCreate(Sender: TObject);
begin
  Table1VendorName := TStringField.Create(Self);
  Table1VendorName.FieldName := ´VendorName´;
  Table1VendorName.DataSet := Table1;
  Table1VendorName.LookupDataSet := Table2;
  Table1VendorName.LookupKeyFields := ´VendorNo´;
  Table1VendorName.LookupResultField := ´VendorName´;
  Table1VendorName.KeyFields := ´VendorNo´;
  Table1VendorName.Size := 30;
  Table1VendorName.Lookup := True;
  Table2.Open;
  Table1.Open;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  Table1.Close;
  Table2.Close;
  FreeAndNil(Table1VendorName);
end;

end.

object Form1: TForm1
  Left = 200
  Top = 108
  Width = 544
  Height = 375
  Caption = ´Form1´
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = ´MS Sans Serif´
  Font.Style = []
  OnCreate = FormCreate
  OnDestroy = FormDestroy
  PixelsPerInch = 96
  TextHeight = 13
  object DBGrid1: TDBGrid
    Left = 8
    Top = 64
    Width = 521
    Height = 249
    DataSource = DataSource1
    TabOrder = 0
    TitleFont.Charset = DEFAULT_CHARSET
    TitleFont.Color = clWindowText
    TitleFont.Height = -11
    TitleFont.Name = ´MS Sans Serif´
    TitleFont.Style = []
  end
  object DBNavigator1: TDBNavigator
    Left = 184
    Top = 32
    Width = 240
    Height = 25
    DataSource = DataSource1
    TabOrder = 1
  end
  object Table1: TTable
    DatabaseName = ´DBDemos´
    SessionName = ´Default´
    TableName = ´parts.db´
    Left = 56
    Top = 24
    object Table1PartNo: TFloatField
      FieldName = ´PartNo´
    end
    object Table1VendorNo: TFloatField
      FieldName = ´VendorNo´
    end
  end
  object DataSource1: TDataSource
    DataSet = Table1
    Left = 88
    Top = 24
  end
  object Table2: TTable
    DatabaseName = ´DBDemos´
    SessionName = ´Default´
    TableName = ´vendors.db´
    Left = 128
    Top = 24
    object Table2VendorNo: TFloatField
      FieldName = ´VendorNo´
    end
    object Table2VendorName: TStringField
      FieldName = ´VendorName´
      Size = 30
    end
    object Table2Address1: TStringField
      FieldName = ´Address1´
      Size = 30
    end
    object Table2Address2: TStringField
      FieldName = ´Address2´
      Size = 30
    end
    object Table2City: TStringField
      FieldName = ´City´
    end
    object Table2State: TStringField
      FieldName = ´State´
    end
    object Table2Zip: TStringField
      FieldName = ´Zip´
      Size = 10
    end
    object Table2Country: TStringField
      FieldName = ´Country´
      Size = 15
    end
    object Table2Phone: TStringField
      FieldName = ´Phone´
      Size = 15
    end
    object Table2FAX: TStringField
      FieldName = ´FAX´
      Size = 15
    end
    object Table2Preferred: TBooleanField
      FieldName = ´Preferred´
    end
  end
end