ObjectAt(0) doesn't work with Ember.Controller - ember.js

Question

I'm trying to upgrade my Ember application to the latest Ember 1.13.2 and therefore am trying to replace all Ember.ArrayController with Ember.Controller.
I've got a problem with the category-controller of my blog. The data retrieved from my server looks like this:
"posts": [
{
"category": {
"id": "1",
"name": "tech"}
"title": "my title",
"body": "post-content",
"isPublished": true,
},
...
]
In my category-controller I need both, the category-id and the category-name.
With the Ember.ArrayController I used objectAt(0) to get both from the first post loaded in the model for that purpose but this doesn't work with Ember.Controller anymore.
How can I get these two attributes in my controller?
This code doesn't work anymore:
breadCrumb: function(){
return this.objectAt(0).get('category').get('name');
}.property('model.[]'),
categoryId: function(){
return this.objectAt(0).get('category').get('id');
}.property('model.[]'),

Answer 1

You just get it from the model directly instead of using the proxy behavior:
return this.get('model').objectAt(0).get('category').get('name');
Or, if you like shorthand:
return this.get('model.firstObject.category.name');
EDIT: While I'm at it, you could also declare these as aliases:
breadCrumb: Ember.computed.alias('model.firstObject.category.name'),
If you don't do that, you should probably change your dependent key. Your property won't update if the nested properties change. You need to use something like model.firstObject.category.name or model.#each.category.name.