[gnachman]

Anything added after iOS 6 is the cheeky answer, but it’s not totally wrong either. Auto layout is incredibly hard to debug; it’s great when it works right, though, fwiw. The audio APIs are a garbage fire (equally on both platforms, at least!) Mapkit has a lot of sharp edges if you try to do anything more than Apple envisioned, which is true of a lot of iOS and macOS APIs. View controller transitions are a mess, but they may have fixed the bugs by now—I’ve stayed away since being traumatized by them five years back. The Metal shader compiler is an absolute shit show of bugs on the Mac, but is better on iOS. Core Bluetooth has caused me pain (just doesn’t work sometimes). Stringly types objective c-isms like KVO. In app purchases are a mess (I’m told, haven’t used it myself). CoreData might look like a good idea but you will live to regret it if it’s an important part of your app. UITableView is really powerful but also gets complex fast, with legacy baggage showing up when you try to get fancy (like auto layout and dynamic row height). The security API is hard to use correctly, also on both platforms.

Mostly though Xcode is the worst piece of software I’ve ever used, besides Wind River’s IDE and Windows ME.