[gjm11]

The code's nice and short, but note that if you are choosing from a large collection it's really inefficient: in order to generate a single random element it needs to do some computation for every element in the collection. That is, its runtime is O(n).

(For choosing from a small number of things this code has the advantage that it's not doing a lot of complicated stuff in Ruby, and in any case the speed probably doesn't matter too much. In fact, even when choosing from a large enough number of things to make this much slower than it need be, the speed may well not matter at all. But it's worth being aware.)