Thanks Lukas, I understand the problem. The source of it was in the full project.
In there I had the following
@
class SurfaceMeshIO : public ModelIO{
Q_INTERFACES(ModelIO)
...
@
@ // Source of error
class io_surfacemesh_off : public QObject, public SurfaceMeshIO{
Q_OBJECT
Q_INTERFACES(SurfaceMeshIO)
....
@
I was assuming that since "io_surfacemesh_off" inherited from SurfaceMeshIO, the Q_INTERFACE(ModelIO) was already taken care of from its superclass. I have to admit, it's kind of weird that I have to do what follows:
@ // Correction
class io_surfacemesh_off : public QObject, public SurfaceMeshIO{
Q_OBJECT
Q_INTERFACES(SurfaceMeshIO)
Q_INTERFACES(ModelIO)
....
@