Creación de campos en runtime TClientdataset

[[nlsgarcia]]

fjcg02,

Empezado por fjcg02

...TClientDataset al que le creo en runtime los campos que necesito...me funciona perfectamente...cuando lanzo el proceso por segunda vez, cambiando los campos, me da un error...

Revisa este código:

Código Delphi [-]
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, DBClient, DB, Grids, DBGrids;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    DBGrid1: TDBGrid;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1 : TForm1;
  Table : TClientDataset;
  DS : TDataSource;

implementation

{$R *.dfm}

// Crea campos del CDS
function CreateField(CDS : TClientDataset; FieldName : String) : Boolean;
var
   F : TStringField;

begin

   F := TStringField.Create(CDS);
   F.FieldName := FieldName;
   F.Name := FieldName;
   F.DataSet := CDS;
   F.Size := 100;
   F.DisplayLabel := 'N-' + FieldName;
   F.DisplayWidth := 10;

end;

// Crea el CDS
procedure TForm1.Button1Click(Sender: TObject);
begin
   if not Assigned(Table) then
      Table := TClientDataset.Create(nil);
end;

// Asigna campos al CDS
procedure TForm1.Button2Click(Sender: TObject);
begin
   if Assigned(Table) and (Table.State <> dsBrowse) then
   begin
      CreateField(Table,'C1');
      CreateField(Table,'C2');
      CreateField(Table,'C3');
      CreateField(Table,'C4');
      Table.CreateDataset;
   end;
end;

// Llena los campos del CDS
procedure TForm1.Button3Click(Sender: TObject);
var
   i : Integer;
begin
   if Assigned(Table) and (Table.FieldCount <> 0) then
   begin
     Randomize;
     Table.Open;
     Table.Append;
     for i := 0 to Table.FieldCount - 1 do
        Table.Fields[i].Value := 'Data-' + IntToStr(Random(1000));
     Table.Post;
   end;
end;

// Visualiza el CDS
procedure TForm1.Button4Click(Sender: TObject);
var
   i : Integer;
begin
   if Assigned(Table) then
   begin
      DS := TDataSource.Create(nil);
      DS.DataSet := Table;
      DBGrid1.DataSource := DS;
      for i := 0 to Table.FieldCount - 1 do
         DBGrid1.Columns[i].Width := 100;
   end;
end;

// Libera el CDS
procedure TForm1.Button5Click(Sender: TObject);
var
   i : Integer;

begin

   if Assigned(Table) and (Table.FieldCount <> 0) then
   begin
      DS.DataSet := nil;
      DBGrid1.DataSource := nil;
      for i := Table.Fields.Count - 1 to 0 do
         Table.Fields[i].Free;
      Table.Free;
      Table := nil;
   end;

   if Assigned(Table) then 
   begin
      Table.Free;
      Table := nil;
   end;

end;

// Libera recursos de Form1
procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
   Action := caFree;
end;

end.

El código anterior en Delphi 7 sobre Windows 7 Professional x32, Permite crear y eliminar un TClientDataset de forma dinámica como se muestra en la siguiente imagen:



Espero sea útil

Nelson.