intersection-with-promises

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle'
});

application.route.js

import Ember from 'ember';

export default Ember.Route.extend({
  model: function() {
    var section = this.store.createRecord('section');
    
    var items = [];
    for (var i = 0; i < 10; i++) {
      items.push(this.store.createRecord('item'));
    }

    for (i = 4; i < 10; i+=2) {
      section.get("selected").pushObject(items[i]);
    }
    
    section.set("items", DS.PromiseArray.create({
      promise: new Ember.RSVP.Promise(function(resolve, reject) {
        setTimeout(function(){ resolve(items); }, 1500);
      })
    }));

    return section;
  }
});

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
Section:
{{model.items}}
<br><br>
Items:<br>
{{#each model.items as |item|}}
  {{item}}<br>
{{/each}}
<br><br>
Selected:<br>
{{#each model.selected as |item|}}
  {{item}}<br>
{{/each}}
<br><br>
Ember.computed.intersect(selected, items):<br>
{{#each model.selectedItems as |item|}}
  {{item}}<br>
{{/each}}
<br>
<br>
Manual intersection with toArray():<br>
{{#each model.selectedItemsForcedArrays as |item|}}
  {{item}}<br>
{{/each}}
<br>
<br>

models.item.js

import DS from 'ember-data';

export default DS.Model.extend({
});

models.section.js

import DS from 'ember-data';

export default DS.Model.extend({
  items: [],
  selected: [],
  selectedItems: Ember.computed.intersect('selected', 'items'),
  
  selectedItemsForcedArrays: Ember.computed("items.[]", "selected.[]", function () {
    return _.intersection(this.get("items").toArray(), this.get("selected").toArray());
  })
});

twiddle.json

{
  "version": "0.4.9",
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.0.1/ember.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.0.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.0.1/ember-template-compiler.js",
    "lodash": "https://cdnjs.cloudflare.com/ajax/libs/lodash.js/3.10.1/lodash.js"
  }
}