Programming Clojure, 2nd Edition

reify

The reify macro lets you create an anonymous instance of a datatype that implements either a protocol or an interface. Note that you get access by closure, not by declaration. This is because there are no declared members.

(reify & opts+specs)

reify, like deftype and defrecord, takes the name of one or more protocols, or interfaces, and a series of method bodies. Unlike deftype and defrecord, it doesn’t take a name or a vector of fields; datatype instances produced with reify don’t have explicit fields, relying instead on closures.

Let’s compose some John Cage--style^[52] aleatoric music^[53] or, better yet, create an aleatoric music generator. We’ll use reify to create an instance of a MidiNote that will play a different random note ...