Data adapter: option 3

gistfile1.js

getModelTypes: function(typeAdded, typeUpdated, typeRemoved) {
  // code to fetch types ...
  // ...
  
  // .. setup array observers to call typeAdded, typeUpdated, and typeRemoved on changes
  
  var releaseMethod = function() {
    //.. code to clear all observers
  };

  return {
    types: RSVP.resolve(initialTypes), // promise that resolves to the initial types
    release: releaseMethod // method to call to clear observers
  };
}