The dispatcher consists of two main parts -- the callback wrapper, and the callback container. The callback wrapper is a class which wraps the actual callback function being registered to the callback container. The callback container is precisely a container which exposes methods for accessing the callback wrappers and a method for accessing callbacks through indexes.

Recently added is the concept of invokers (thanks to Joel de Guzman for the pointers) to allow invoking more than one registered handler in succession, and aggregating the result using an accumulator functor.