Automatical class registration

As you know, in Delphi you can create the class instance by the class name (streaming system uses it internally for creating components by the name when loading from streams), so you can write something like this:

AClass:=GetClass('TLabel');

L:=TComponentClass(AClass).Create(Self) as TLabel;

This means, that you can store class names in your application or database and create any components using string representations of class names. It's convenient. But there is a problem. VCL requires preregistering all the classes to link class name and class instance using RegisterClass or RegisterClasses procedures. It's not convenient, because you have to add all the used classes manually. Fortunately, there is a trick. You can just enumerate all the existing components on your form (or even in your application with enumerating the Application.Forms) and register all the classes with the following simple code:

procedure TForm1.FormCreate(Sender: TObject);

var

  i: Integer;

  AClass: TPersistentClass;

  L: TLabel;

begin

  for i:=0 to Pred(ComponentCount) do

    if Components[i] is TPersistent then

    begin

      AClass:=TPersistentClass(Components[i].ClassType);

      if Assigned(AClass) then RegisterClass(AClass);

    end;

end;