> if I only add this:

Index: playlistexporter.h
===================================================================
--- playlistexporter.h  (revision 701838)
+++ playlistexporter.h  (working copy)
@@ -29,6 +29,8 @@ class KAction;
  */ class PlaylistExporter : public QObject
 {
+    Q_OBJECT
+
 public:
     PlaylistExporter(QObject *parent = 0) : QObject(parent) { }
     virtual ~PlaylistExporter() { }

> I get:

CMakeFiles/juk.dir/k3bexporter.o: In function `K3bExporter::qt_metacall(QMetaObject::Call, int, void**)':
/var/tmp/kdemultimedia/juk/k3bexporter.moc:59: undefined reference to `PlaylistExporter::qt_metacall(QMetaObject::Call, int, void**)'
CMakeFiles/juk.dir/k3bexporter.o: In function `K3bExporter::qt_metacast(char const*)':
/var/tmp/kdemultimedia/juk/k3bexporter.moc:54: undefined reference to `PlaylistExporter::qt_metacast(char const*)'CMakeFiles/juk.dir/k3bexporter.o: In function `~PlaylistExporter':
/var/tmp/kdemultimedia/juk/playlistexporter.h:36: undefined reference to `vtable for PlaylistExporter'
/var/tmp/kdemultimedia/juk/playlistexporter.h:36: undefined reference to `vtable for PlaylistExporter'
/var/tmp/kdemultimedia/juk/playlistexporter.h:36: undefined reference to `vtable for PlaylistExporter'
/var/tmp/kdemultimedia/juk/playlistexporter.h:36: undefined reference to `vtable for PlaylistExporter'
CMakeFiles/juk.dir/k3bexporter.o:(.rodata+0x0): undefined reference to `PlaylistExporter::staticMetaObject'
CMakeFiles/juk.dir/k3bexporter.o:(.gnu.linkonce.r._ZTI11K3bExporter+0x10): undefined reference to `typeinfo for PlaylistExporter'
collect2: ld returned 1 exit status
make[3]: *** [juk/juk] Error 1
make[2]: *** [juk/CMakeFiles/juk.dir/all] Error 2
make[1]: *** [juk/CMakeFiles/juk.dir/rule] Error 2
make: *** [juk] Error 2