Hey

    I would like to create object at runtime. The problem is that I don't
know the type at design time. And also I don't know how many classes
(actually I do know, but I am pretending that I don't) are derived from base
class.

--------------------------------------------------------------------
Structure:
TDevices (collection of TDevice)

TDevice  --> TDev1
               --> TDev2
               ....
               --> TDevN
--------------------------------------------------------------------

I would like to load 'ClassName' of all classes derived form TDevice into
ComboBox. And than at RunTime select a 'ClassName' from ComboBox, Create the
object of selected type and Add it to the collection (TDevices).

Thanks

btw:
Any suggestions on how to Create an object if you have its ClassName
(string)

"Damjan" <damjan.veng...@kompozitemra.si> skrev i melding
news:j3Ef9.1584$EM5.58805@news.siol.net...

Look at the TReader code (classes.pas), and see how it's done there.

--
Bj?rge S?ther
bjorge@hahaha_itte.no

The list of registerd classes is declared and maintained in the
Implementation section of one of the VCL units (I can't remember which one
off-hand). Without implementing your own mechanism for tracking descendants
its going to be quite difficult. I'd suggest that you implement a
RegisterDescendant<classname> procedure that maintains a list of descendant
classes:

type

tSomeClassClass = class of tSomeClass;

procedure RegisterSomeClassDescendant (aClass : tSomeClassClass);
procedure GetSomeClassDescendantNames (results : tStrings);

Implementation

var SomeClassDescendants : tList = tSomeClassClass;

procedure RegisterSomeClassDescendant (aClass : tSomeClassClass);

begin
if not Assigned (SomeClassDescendants)
then SomeClassDescendants := tList.Create;
if SomeClassDescendants.IndexOf (aClass) < 0
then SomeClassDescendants.Add (aClass);
end;

procedure GetSomeClassDescendantNames (results : tStrings);

var i : integer;

begin
results.BeginUpdate;
try
    results.Clear;
    if Assigned (SomeClassDescendants)
    then begin
        for i := 0 to (SomeClassDescendants.Count - 1) do
            results.Add (tObject (SomeClassDescendants [i]).ClassName;
        end;
finally
    results.EndUpdate;
    end;
end;

Finalization

if Assigned (SomeClassDescendants)
then SomeClassDescendants.Free;