Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

{ 
  Question: How can I get all classes that are currently registered in my Application? 

  Answer: There is no way to get at classes registered via RegisterClasses, since the 
  list holding these is private to the classes unit.You can get at the classes 
  registered on a Form, however, since those use a Table connected to the Form 
  classes class record.The following is based on some spelunking in the classes unit: 
}

 // defined in classes.pas 
type
   PFieldClassTable = ^TFieldClassTable;
   TFieldClassTable = packed record
     Count: Smallint;
     Classes: array[0..8191] of ^TPersistentClass;
   end;


 function GetFieldClassTable(AClass: TClass): PFieldClassTable; assembler;
 asm
     MOV EAX,[EAX].vmtFieldTable
     OR EAX,EAX
     JE @@1
     MOV EAX,[EAX+2].Integer
     @@1:
 end;
   // end of quote from classes.pas 

procedure TForm1.Button1Click(Sender: TObject);

   procedure Display(const S: string);
   begin
     memo1.Lines.Add(S);
   end;

    var
   pFCT: PFieldClassTable;
   aClass: TClass;
   i: SmallInt;
 begin
   memo1.Clear;
   aClass := Classtype;
   while aClass <> TPersistent do
   begin
     Display('Registered classes for class ' + aClass.ClassName);
     pFCT := GetFieldClasstable(aClass);
     if not Assigned(pFCT) then
       Display(' No classes registered')
     else
     begin
       Display(Format(' %d classes registered', [pFCT^.Count]));
       for i := 0 to pFCT^.Count - 1 do
         Display(' ' + pFCT^.Classes[i]^.ClassName);
     end;
     aClass := aClass.ClassParent;
   end
 end;