title: How to listen some var from another class without reference in Kotlin
body: <p>When I developed android app with Java I used <a href="https://github.com/greenrobot/EventBus" rel="nofollow noreferrer">EventBus</a> , then I used <code>java.util.observable</code> to listen some var without getting a reference of a class/service.
  For example, I could listen in ViewModel/Activity some var from a service without getting instance of that service.</p>
  
  <p>I did it before I started using Clean Architecture, SOLID, MVVM etc.
  Now I am using widely LiveData and ViewModel pattern, and Dependency Injection with Dagger2. So, every time I have a reference to listen a LiveData var.</p>
  
  <p>I am wandering if exist in Kotlin a way to listen a var in one class from another class without getting an another class's reference?</p>
  
  <p>This is not practical question, it's just curiosity</p>