Text Method doesn't work with Findclass(...) but with plain "TEdit"

Question

I want to use findclass and findcomponent to be able to pass the sender component as parameter in a procedure.

Thank you for reading.

Edit: I use Delphi 2005

---

[Error]: E2003 Undeclared identifier: 'text'

TestMemo.Text := (FindComponent(VonKomponente.name) as
  (Findclass(vonkomponente.ClassType.ClassName))).text; -> does not work

TestMemo.Text := (FindComponent(VonKomponente.name) as TEdit).text; -> works

---

procedure TFormTest.Edit7DblClick(Sender: TObject);
begin
  MemoEdit((Sender as TComponent),'table','row');
end;


procedure TFormTest.MemoEdit(VonKomponente :TComponent;table,row : String);
begin
  FormTestMemo.Max_Textlaenge := get_length(table,row);
  FormTestMemo.Text := (FindComponent(VonKomponente.name) as
    (Findclass(vonkomponente.ClassType.ClassName))).text;
  If FormTestMemo.Showmodal = MrOk then
  begin
    ...
  end;
end;

Answer 1

What you are trying to do is not possible. You cannot pass a metaclass type determined at runtime to the as operator.

For what you are trying to do, you will have to resort to using old-style RTTI via the TypInfo unit, in this case the TypInfo.GetStrProp() function, eg:

uses
  ..., TypInfo;

FormTestMemo.Text := GetStrProp(VonKomponente, 'Text');

Note that not all text-based components have a Text property, some have a Caption property, eg:

uses
  ..., TypInfo;

var
  prop: PPropInfo;

prop := GetPropInfo(VonKomponente, 'Text');
if prop = nil then
  prop := GetPropInfo(VonKomponente, 'Caption');

if prop <> nil then
  FormTestMemo.Text := GetStrProp(VonKomponente, prop)
else
  FormTestMemo.Text := '';