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 Dynamic Creation of a Table
This example dynamically creates TFieldDefs, TFields, calculated fields, a table, a TTable,
and attaches an event handler to the OnCalc event.
unit Gridcal;
interface
uses SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
Forms, Dialogs, StdCtrls, DBTables, DB, Grids, DBGrids;
type
TForm1 = class(TForm)
Button1: TButton;
procedure MyCalcFields(DataSet: TDataset);
procedure NewTable(MyDataBaseName, MyTableName: string;
var MyTable: TTable; MyDataSource: TDataSource; MyGrid: TDBGrid);
procedure FormCreate(Sender: TObject);
public
t1, t2: TTable;
tsrc1, tsrc2: TDataSource;
grd1, grd2: TDBGrid;
MyCalcField :TFloatField;
end;
var
Form1: TForm1;
implementation
{$R *.DFM}
procedure TForm1.MyCalcFields(DataSet: TDataset);
begin
with DataSet do
FieldByName(MyCalcField.Name).AsFloat :=
FieldByName('Field1').AsFloat * FieldByName('Field2').AsFloat;
end;
procedure TForm1.NewTable(MyDataBaseName, MyTableName: string;
var MyTable: TTable; MyDataSource: TDataSource; MyGrid: TDBGrid);
begin
MyTable := TTable.Create(Self);
with MyTable do begin
DatabaseName := MyDatabaseName;
TableName := MyTableName;
TableType := ttParadox;
AutoCalcFields := True;
OnCalcFields := MyCalcFields;
with FieldDefs do begin
Clear;
Add('Field1', ftFloat, 0, false);
FieldDefs[0].CreateField(MyTable);
Add('Field2', ftFloat, 0, false);
FieldDefs[1].CreateField(MyTable);
Add('Field3', ftFloat, 0, false);
FieldDefs[2].CreateField(MyTable);
{ create a calculated TField }
MyCalcField := TFloatField.Create(MyTable);
with MyCalcField do begin
FieldName := 'MyCalcField';
Calculated := True;
Visible := True;
DataSet := MyTable;
Name := MyTable.Name + FieldName;
MyTable.FieldDefs.Add(Name, ftFloat, 0, false);
end;
end;
MyTable.CreateTable;
end;
MyDataSource := TDataSource.Create(Self);
MyDataSource.DataSet := MyTable;
MyGrid := TDBGrid.Create(Self);
with MyGrid do begin
Parent := Self;
Align := alTop;
DataSource := MyDataSource;
end;
MyTable.Active := True;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
NewTable('DBDEMOS', 'MyTable1', t1, tsrc1, grd1);
end;
end.
DISCLAIMER: You have the right to use this technical information subject to
the terms of the No-Nonsense License Statement that you received with the Borland product to which
this information pertains.
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