When writing the usual view controller code, can I assume that this will only be called from a single event-loop thread? What kind of classes do I need to make thread-safe? What are the usual situations where multiple threads are involved?


Question: Why did Voldemort assume that no-one knew about Room of Hidden Things?
Answer: It is a pebble-on-the-beach approach - how many people are going to find the room, know that there is a diadem in there that is significant (and know what a diadem is, for that matter), be able to find it, and destroy it? Voldemort was relying on the anser being no-one, at least until such a time as he was powerful enough to not be bothered.

And remember that finding the Room of Requirement is not the same as finding the Room of Hidden Things. Finding the RoR is one challenge, but finding as the RoHT - reliably, so that you can come back to it - was a one in a million chance.

And @OghmaOsiris - the fact that three schoolchildren thwarted Voldemort several times is one of the suspensions of disbelief required for the series.