New Twiddle

components.child-component.js

import Ember from 'ember';

export default Ember.Component.extend({
   heightToggled: false,
  
  click() {
    this.toggleProperty('heightToggled'); 
  },
  
  actions: {
    toggleChecked(item) {
      this.sendAction('toggleChecked', item);
		}
	}
});

components.parent-component-a.js

import Ember from 'ember';

export default Ember.Component.extend({
  actions: {
      toggleChecked(item) {
        this.sendAction('toggleChecked', item);
      }
    }
});

components.parent-component-b.js

import Ember from 'ember';

export default Ember.Component.extend({
  actions: {
      toggleChecked(item) {
        this.sendAction('toggleChecked', item);
      }
    }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  items: Ember.A(['red', 'blue', 'green']),
  init() {
   	this.decoratedItems = this.get('items').map(item => 		{
      return new Ember.Object({
				item,
        checked: false
      });
    });
    
    this.get('items').addEnumerableObserver(this, {
     	 willChange: (items, removing) => {
       	removing.forEach(removeItem => {
          let decoratedItem = this.get('decoratedItems').findBy('item', removeItem);
 this.get('decoratedItems').removeObject(decoratedItem);
        });
       },
      didChange: (items, removeCount, adding) => {
        adding.forEach(newItem => {
        this.get('decoratedItems').addObject(new Ember.Object({ item: newItem, checked: false}))
        })
      }
    })
  },
  actions: {
   addItem() {
      this.get('items').pushObject('yellow');
    },
    removeItem() {
			this.get('items').removeObject('yellow');    
  	},
  	toggleChecked(item) {
      this.get('decoratedItems').findBy('item', item).toggleProperty('checked');
    },
    changeItem() {
      this.set('items.firstObject', 'orange')
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<button {{action 'addItem'}}>Add item</button>
<button {{action 'removeItem'}}>Remove item</button>
<button {{action 'changeItem'}}>Change item</button>
{{items.firstObject}}
{{parent-component-a items=decoratedItems toggleChecked="toggleChecked"}}
<hr/>
{{parent-component-b items=decoratedItems toggleChecked="toggleChecked"}}
<br>
<br>

templates.components.child-component.hbs

<li style="height: {{if heightToggled '100px' '50px'}}">
<input type="checkbox" 
       checked={{item.checked}} 
       onclick={{action "toggleChecked" item.item}} />
{{item.item}}
</li>

templates.components.parent-component-a.hbs

{{#each items as |item|}}
	{{child-component item=item toggleChecked="toggleChecked"}}
{{/each}}

templates.components.parent-component-b.hbs

{{#each items as |item|}}
	{{child-component item=item toggleChecked="toggleChecked"}}
{{/each}}

twiddle.json

{
  "version": "0.7.2",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.4.4",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.4.3/ember-data.js",
    "ember-template-compiler": "2.4.4"
  }
}