Data Adapter API - option 2

gistfile1.js

// Disadvantage: releasing model types will clear all observers 
// irrespective of how many times getModelTypes was requested
// or who made the request
 
getModelTypes: function(target, typesReceived, typeAdded, typeUpdated, typeRemoved) {
  // code to fetch types ...
  // ...
  
  // call typesReceived and pass fetched types
  typesReceived.call(target, types);

   // .. setup array observers to call typeAdded, typeUpdated, and typeRemoved on changes
},

releaseModelTypes: function() {
  //.. code to clear all observers
}