Actually quite well. The fact that it's drag & drop is pretty irrelevant, except in that it's not something the interviewee has likely done before because it's

Actually quite well. The fact that it's drag & drop is pretty irrelevant, except in that it's not something the interviewee has likely done before because it's not a very common thing to interrupt. What's more important is that it's fairly basic usage of UIGestureRecognizer (which is a common thing to need, at least if you're doing any kind of UI development) as well as some basic management of state involving 2 views (the view being dragged, and the destination view it's dropped into).