Using Ember v1.8 beta 3+ with Ember Data 1.0 beta 10- you receive this error:

Error while processing route: index Cannot read property 'async' of undefined TypeError: Cannot read property 'async' of undefined
    at Relationship [as _super$constructor] (.js:9523:46)
    at new BelongsToRelationship (.js:9736:12)
    at createRelationshipFor (.js:9840:16)
    at .js:6366:41
    at .js:9307:20
    at cb (.js:15907:13)
    at OrderedSet.forEach (.js:15703:13)
    at Map.forEach (.js:15911:19)
    at Function.Model.reopenClass.eachRelationship (.js:9306:42)
    at Ember.Object.extend._setup (.js:6365:26) 

Despite your models being set up correctly:

App.Color = DS.Model.extend({
  color: DS.attr(),
  foo: DS.belongsTo('foo', {async:true})
});


App.Foo = DS.Model.extend({
  foo: DS.attr()
});

Example:

Using Ember v1.8 beta 3+ with Ember Data 1.0 beta 10- you receive this error:

Error while processing route: index Cannot read property 'async' of undefined TypeError: Cannot read property 'async' of undefined
    at Relationship [as _super$constructor] (http://builds.emberjs./canary/ember-data.js:9523:46)
    at new BelongsToRelationship (http://builds.emberjs./canary/ember-data.js:9736:12)
    at createRelationshipFor (http://builds.emberjs./canary/ember-data.js:9840:16)
    at http://builds.emberjs./canary/ember-data.js:6366:41
    at http://builds.emberjs./canary/ember-data.js:9307:20
    at cb (http://builds.emberjs./ember-latest.js:15907:13)
    at OrderedSet.forEach (http://builds.emberjs./ember-latest.js:15703:13)
    at Map.forEach (http://builds.emberjs./ember-latest.js:15911:19)
    at Function.Model.reopenClass.eachRelationship (http://builds.emberjs./canary/ember-data.js:9306:42)
    at Ember.Object.extend._setup (http://builds.emberjs./canary/ember-data.js:6365:26) 

Despite your models being set up correctly:

App.Color = DS.Model.extend({
  color: DS.attr(),
  foo: DS.belongsTo('foo', {async:true})
});


App.Foo = DS.Model.extend({
  foo: DS.attr()
});

Example: http://emberjs.jsbin./OxIDiVU/1111/edit

• javascript
• dictionary
• ember.js
• ember-data

• 1 Thanks man, just came up against this! – cjroebuck Commented Sep 28, 2014 at 17:25
• I'm using Canary for both Ember & Ember Data and have run into this.. what's up with that? – Chris Commented Sep 29, 2014 at 10:14
• 1 It's just a bug for now, you'll have to use an older Ember for a day until an Ember Data fix is pushed. – Kingpin2k Commented Sep 29, 2014 at 14:29

1 Answer 1

This is a bug with Ember/Ember-data versions. Ember changed its Map implementation in Ember 1.8 beta 3 breaking any version of Ember Data less than 1.0 beta 10.

Here's the github issue: https://github./emberjs/data/issues/2323

It's fixed in 1.0.0-beta.11+canary.2997e47034 or above.