How in can connect to unbound signal on new approach

Hello,

I have code like this

 connect(SurfaceInterface::get(surface), &Resource::unbound,
            q, [this, xdgExported, handle]() {
                if (xdgExported) {
                    xdgExported->deleteLater();
                }
                exportedSurfaces.remove(handle);
                emit q->surfaceUnexported(handle);
            });

But i not see any signal or slot in the generated class. I have to implement the signal ?