title: Cake pattern: how to get all objects of type UserService provided by components
body: <p>This question may help you understand my needs.
  <a href="https://stackoverflow.com/questions/14532368/cake-pattern-one-component-per-implementation-or-one-component-per-trait">Cake pattern: one component per implementation, or one component per trait?</a></p>
  
  <p>I have a Scala application using multiple UserService implementations which will be provided by component(s?).</p>
  
  <p>I wonder if there is a way in another component to "scan" the application so that I can retrieve a set of all components providing an object which implement the trait UserService? 
  So that I can iterate over all the UserService interfaces provided by my cake built application?</p>
  
  <p>I guess I can have a component which build a list of UserService according to its dependency, but is it possible to have this component building the list without having any hardcoded dependency?</p>