Make data from store app-wide available?

I've got a base-route encapsulating all other routes in my application.

I'd like to make the categories I retrieve from the store via this.store.find('category') available everywhere in my application.

I tried retrieving it in the base-controller with this code:

import Ember from 'ember';

export default Ember.ArrayController.extend({
  // retrieve all categories as they are needed in several places
  categories: function() {
    return this.get('store').find('category');
  }
});

and creating an alias from child-controllers via:

categories: Ember.computed.alias('controllers.base.categories')

but it gives this error-message:

Uncaught Error: Assertion Failed: The value that #each loops over must be an Array. You passed function () { return this.get('store').find('category'); }

How can I solve my problem?