computed .@each

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',

  someArray: [
    Ember.Object.create({ name: 'foo' }),
    Ember.Object.create({ name: 'bar' }),
  ],

  computedEachArray: Ember.computed('someArray.@each.name', function () {
		return this.get('someArray').filter(el => el.get('name').length < 4)
  }),

  actions: {
	  addNewElement() {
			let value = this.get('newElementValue');
      let object = Ember.Object.create({ name: value });
      this.get('someArray').pushObject(object);
    },
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>

Add a new element to the array, but only those with less than 4 characters will be added to the computed.@each property:<br>
<br>
{{input type=text value=newElementValue}}
<button {{action 'addNewElement'}}>Add Element</button>

<br>
<br>
<br>
List of elements whose name has less than 4 characters:
<ul>
{{#each computedEachArray as |element|}}
	<li>{{element.name}}</li>
{{/each}}
</ul>

All elements:
<ul>
{{#each someArray as |element|}}
	<li>{{element.name}}</li>
{{/each}}
</ul>

tests.helpers.destroy-app.js

import Ember from 'ember';

export default function destroyApp(application) {
  Ember.run(application, 'destroy');
}

tests.helpers.resolver.js

import Resolver from '../../resolver';
import config from '../../config/environment';

const resolver = Resolver.create();

resolver.namespace = {
  modulePrefix: config.modulePrefix,
  podModulePrefix: config.podModulePrefix
};

export default resolver;

tests.helpers.start-app.js

import Ember from 'ember';
import Application from '../../app';
import config from '../../config/environment';

const { run } = Ember;
const assign = Ember.assign || Ember.merge;

export default function startApp(attrs) {
  let application;

  let attributes = assign({rootElement: "#test-root"}, config.APP);
  attributes = assign(attributes, attrs); // use defaults, but you can override;

  run(() => {
    application = Application.create(attributes);
    application.setupForTesting();
    application.injectTestHelpers();
  });

  return application;
}

tests.test-helper.js

import resolver from './helpers/resolver';
import {
  setResolver
} from 'ember-qunit';

setResolver(resolver);

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}