Tree

components.my-tree.js

import Ember from 'ember';

export default Ember.Component.extend({
  tagName: 'ul'
});

controllers.application.js

import Ember from 'ember';

const Item = Ember.Object.extend({
  isSelected: Ember.computed('_isSelected', 'children.@each.isSelected', {
    get() {
      return this.get('_isSelected') ||
        this.get('children').findBy('isSelected') != null;
    },

    set(key, value) {
      value = Boolean(value);
      
      const update = (item) => {
        if (item.get('children.length') === 0) {
          item.set('_isSelected', value);
        } else {
          item.get('children').forEach(update);
        }
      }
      
      update(this);
      
      return value;
    } 
  }),

  _isSelected: false
});

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  tree: [
   	Item.create({ name: 'One', children: [
      Item.create({ name: 'One One', children: [] }),
      Item.create({ name: 'One Two', children: [] }),
      Item.create({ name: 'One Three', children: [] }),
      Item.create({ name: 'One Four', children: [] })
		]}),
   	Item.create({ name: 'Two', children: [
      Item.create({ name: 'Two One', children: [] }),
      Item.create({ name: 'Two Two', children: [] }),
      Item.create({ name: 'Two Three', children: [] }),
      Item.create({ name: 'Two Four', children: [] })
		]})
  ]
});

templates.application.hbs

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

{{my-tree items=tree}}

<br>
<br>

templates.components.my-tree.hbs

{{#each items as |item|}}
	<li>
  	{{input type="checkbox" checked=item.isSelected}}
    {{item.name}}
    
    ({{if item.isSelected 'Y' 'N'}})
    
    {{#if item.children}}
      {{my-tree items=item.children}}
    {{/if}}
  </li>
{{/each}}

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"
  }
}