Thank you @elcapix These may be good examples to check out:
I just re-read your question, and you mentioned an existing app. I had not noticed that detail and thought that it is indeed possible to combine both worlds, but I don’t know how one would go about adding OF to an existing app. We always started with OF and added native components or methods to it using the AppDelegate from the second example above.
For instance, the whole part of social network sharing happens in native code in ObjC, as do some confirmation dialogs and text inputs (in WTL). We also did another app in which we capture live video with OF, process it with a shader, and at the end forward the frames to native iOS code to do the video exporting, because it is easier using native functions on iOS.