This is an example of how I combine interaction/service classes with Wisper event broadcasting in Rails.

In this example, I show a `UsersController#create` API, a corresponding service object, and all the test code/listeners to make it all happen.

The outcome is:

* Concepts in your system ("Signing up a user", "Creating an order") have a single entry point in your codebase, vs. making stupid raw ActiveRecord calls to `object.save` in dozens of places.
* Since your concept has one entry point (the service class), you can easily `grep` for usage of it.
* Stupid easy to attach listeners to the service class
* All event listeners are very small and easily unit tested
* Controllers have zero `if/else` logic and are very stupid
* Unit tests stay fast
* Acceptance tests still exercise the whole system, including event listeners
* Plain old Ruby objects rule