safeform.pas

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unit SafeForm;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, SList;

type
  TForm1 = class(TForm)
    ButtonAddDates: TButton;
    ButtonAddButton: TButton;
    ButtonAddPointer: TButton;
    ButtonNewDate: TButton;
    ListBox1: TListBox;
    ButtonNewButton: TButton;
    ButtonNewPointer: TButton;
    procedure ButtonAddDatesClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure ButtonAddButtonClick(Sender: TObject);
    procedure ButtonAddPointerClick(Sender: TObject);
    procedure ButtonNewDateClick(Sender: TObject);
    procedure ButtonNewButtonClick(Sender: TObject);
    procedure ButtonNewPointerClick(Sender: TObject);
  private
    List: TSafeList;
  public
    procedure UpdateList;
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

uses
  Dates;

procedure TForm1.ButtonAddDatesClick(Sender: TObject);
var
  I: Integer;
begin
  Randomize;
  try
    for I := 1 to 10 do
      List.Add (TDate.Init (
        1 + Random (12), 1 + Random (28),
        1900 + Random (200)));
  finally
    UpdateList;
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  List := TSafeList.Create (TDate);
end;

procedure TForm1.ButtonAddButtonClick(Sender: TObject);
begin
  List.Add (Sender);
  UpdateList;
end;

procedure TForm1.ButtonAddPointerClick(Sender: TObject);
var
  P: Pointer;
begin
  P := @Form1;
  List.Add (P);
  UpdateList;
end;

procedure TForm1.UpdateList;
var
  I: Integer;
begin
  ListBox1.Clear;
  for I := 0 to List.Count - 1 do
    Listbox1.Items.Add ((
      TDate(List [I]).GetText));
end;

procedure TForm1.ButtonNewDateClick(Sender: TObject);
begin
  List [1] := TDate.Create (self);
  UpdateList;
end;

procedure TForm1.ButtonNewButtonClick(Sender: TObject);
begin
  List [1] := Sender;
  UpdateList;
end;

procedure TForm1.ButtonNewPointerClick(Sender: TObject);
var
  S: String;
begin
  S := 'Hi';
  List [1] := Pointer(S);
  UpdateList;
end;

end.