concatenatedProperties

application.controller.js

import Ember from 'ember';

//the foods array will concatinate, the colours are replaced

let Animal = Ember.Object.extend({
  concatenatedProperties: ['foods'],
  colours: ['white'],
  foods: ['milk']
});

let Cat = Animal.extend({
  colours: ['black'],
  foods: ['tuna']
});

let cat = Cat.create();

export default Ember.Controller.extend({
  appName:`[${cat.get('colours')}] [${cat.get('foods')}]`
});

application.template.hbs

<h1>{{appName}}</h1>

twiddle.json

{
  "version": "0.5.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.2.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}