Warum AccessViolation?

[neolithos]

Delphi-Quellcode:

  TTest = class
  private
    TestString : string;
  public
    constructor create;
    procedure DoSomething;
    procedure ShowString;
  end;

var
  Form1 : TForm1;
  test  : TTest;

implementation

{$R *.dfm}

constructor TTest.create;
begin
  inherited; 
  TestString := 'Hallo';
end;

procedure TTest.DoSomething;
begin
  while true do
  begin
    Application.ProcessMessages;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  test := TTest.create; 
  test.DoSomething;
  test.free;
end;

procedure TTest.ShowString;
begin
  ShowMessage(TestString);  // Exception: EAccessViolation
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  test.ShowString;
end;

In deine alten wurde die Instance noch nihct freigegeben so schon.

Schon mal was von TThread's gehört?