I wanted to do the right thing and use a proper constant in my code; kUTTypeURL to be specific. Out of the box though, Xcode won’t recognise that constant in a new project. You need to #import the correct framework, but which one is that?
Irritatingly, trying to use Open Quickly won’t find it (I find it often works for Objective-C things I’m yet to #import), and my poor Google-fu was turning up nothing. So here we go, documenting it here for future searchers perhaps: