Example of view model wrapping normal model

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Expandable list',
  buttonName: 'expand all',
  families: [{title:'parent a', 
            children: [ 
              { title:'a son' },{ title:'a daughter' }
            ]
           },
           {title:'parent b', 
            children: [ 
             { title:'b son' }
            ]
           },
         { title:'single c' }
        ],
  familyModels: Ember.computed('families', function(){
  	return this.get('families').map((p)=>{
      return Ember.Object.create({
        isExpanded: false,
        parent:p
      });
    });
  }),
  
  expandedModels: Ember.computed.filterBy('familyModels', 'isExpanded', true),
  
  allExpanded: Ember.computed('expandedModels.length', function(){ return this.get('expandedModels.length') === this.get('familyModels.length'); }),
  
  actions:{
    toggleAllExpanded:function(){
      var expand = !this.get('allExpanded');
      this.get('familyModels').forEach((parent)=> parent.set('isExpanded', expand));
    }
  }
});

application.template.hbs

<h1>{{appName}}</h1>
<p>Click on the parents to see their children</p>
<br>
<button {{action 'toggleAllExpanded'}}>{{if allExpanded 'collapse all' 'expand all'}}</button>
<br>
<br>
{{#each familyModels as |model|}}
  {{item-list model=model expandAll=expandList}}
{{/each}}
<br>
<br>

item-list.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  model: null,
  parent: Ember.computed.alias('model.parent'),
  isExpanded: Ember.computed.alias('model.isExpanded'),
  click: function(){
    this.toggleProperty('isExpanded');
  }
});

item-list.template.hbs

{{parent.title}}<br>
{{#if isExpanded}}
  <ul>
  {{#each parent.children as |child|}}
  <li>{{child.title}}</li>
  {{/each}}
  </ul>
{{/if}}

twiddle.json

{
  "version": "0.4.13",
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.10/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/1.13.13/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.10/ember-template-compiler.js"
  }
}