Please correct me if this question is duplicated.
I just came across Unity3D and I just want to ask if it is possible to integrate Unity3D on top of other UIView?
I think it's not possible that way because the generated AppController.mm acts as
UIApplicationDelegate. And even if you manage to get it working, it sounds like you won't have fun on the long run. Major Unity3D updates might change some internals.
But the other way round i.e. calling Obj-C code from Unity3D and showing arbitrary UIViews is definitly working. See How to use an xcode game on unity3d especially Clever Martian's Blog - An Experiment with iPhone Native UI and Unity 3 Pro.