title: Copying listeners/observers in a copy constructor
body: <p>I'm programming a class that implements the observable pattern (not the interface) and I'm thinking about whether or not the copy constructor should also copy the listeners.</p>
  
  <p>On the one hand the copy constructor should create an instance that is as close as possible to the original instance so that it can be swapped out in the display context.</p>
  
  <p>On the other hand this would assume the listeners can cope with that kind of thing.</p>
  
  <p>Any thoughts? Are there any best practices?</p>