promises.js

// Our model does some calls to a server or whatever
var model = new Ember.RSVP.Promise(function(resolve, reject){
  if(someCondition){
    resolve(someData);
  } else {
    reject(err); 
  }
});

// We access the data here, through the success/resolved and fail/rejected callbacks
model.then(function(someData) {
  // Do whatever
}, function(err) {
  // Send to magic error handler
});