Passing classes to the store has been removed with Ember 2.0.1 and Ember-data 2.0

Ember Data
2

The solution I found is adding a serializer providing the following configuration:

export default DS.RESTSerializer.extend(DS.EmbeddedRecordsMixin, {
  attrs: {
    exchange: {
      embedded: 'always',
      serialize: 'id'
    }
  },
...

My model attribute id exchange and I have a DS.belongsTo relationship. With hasMany I guess you could use something like this:

//serializers/user.js

export default DS.RESTSerializer.extend(DS.EmbeddedRecordsMixin, {
  attrs: {
    conversation: {
      embedded: 'always',
      serialize: 'ids'
    }
  },
...