Caching and walking an ArrayController - ember.js

Question

I have a Phone model. I want to cache all phones on my application:
cachePhones : function () {
this.set('phones', this.Phone.find());
},
And get the countries for which I have available phones:
getCountries : function () {
var phones = this.get('phones.content');
var countries = new this.dataSet(), country;
console.log('phones=%o', phones.length);
for (var index = 0, length = phones.length; index < length; index++) {
country = phones[index].record.get('country');
console.log('Adding %o', country);
countries.add(country, true);
}
console.log('countries=%o', countries.keys());
return countries.keys();
},
(dataSet is just a set implementation in javascript)
I am not sure this is the right way to walk the ArrayController:
do I really need to access the content?
do I really need to access record?
This feels like hacking around my way in the ember internals. I have tried before this:
var phones = this.get('phones');
var countries = new this.dataSet(), country;
for (var index = 0, length = phones.length; index < length; index++) {
country = phones[index].country;
countries.add(country, true);
}
But it was not working at all. What is the canonical way of walking an ArrayController?

Answer 1

Have you tried something like this? Normally you should always be fine with using the functional methods Ember offers for its collections.
var phones = this.get('phones');
var countries = new this.dataSet(), country;
phones.forEach(function(phone, index){
country = phone.get("country");
countries.add(country, true);
});

Answer 2

Besides #mavilein correct answer one thing worth mentioning is that if you have a model like App.Phone then after you do App.Phone.find() and the records are fetched, your Store has already a cache which you can consult with App.Phone.all() this will not make another request but gives you the records available in the Store.
Hope it helps.