Ember - Get Value From Ember Data Array

I am trying to loop over some objects in Ember in a controller, and return an array of their name attributes. I am however confused with what Ember is returning from the findAll function.

In a controller, I have the following function -

possibleGenres: function() {
    var genres = this.store.findAll('genre');
    var genreNames = genres.map(function(item, index, enumerable){
        return item.get('name');
    });
    return genreNames;
}.property(),

Logging genres.get('length') gives me 0.

I have proven that there are genres available in the findAll function, as when returning the returned genres from just the findAll function, they are displayed in the template.

Am I misunderstanding something crucial about Ember controllers here?

As ever, any help is much appreciated.