[tgv]

I've only written one fairly simple iOS app for my own use, just to get a feeling for it, but IMO getting familiar with the platform is not easy, but doable; I did have extensive mac experience, though (since the early 90s). An experienced programmer with knowledge of other fields can get quite a lot done in ... let's say: two months?

But we don't know what OP wants. Is it a game? Is it a social network? Is it a temperature conversion app? Because those require very different skill sets, and the iOS app may not be the hard part.