gistfile1.js

// Error — Uncaught TypeError: Cannot set property 'object' of undefined 

App.Adapter = DS.RESTAdapter.extend({
  url: "http://api.tripster.im",
  serializer: DS.Serializer.extend({
    primaryKey: function(type) {
      var typeString = type.toString.split(".")[1].underscore();
      console.log("test");
      return typeString + "_id";
    }
  })
});

DS.Adapter.registerTransform('object', {
  serialize: function(obj) { return obj; },
  deserialize: function(obj) { return obj; }
});