mutable-yield-hash

components.x-foo.js

import Ember from 'ember';

export default Ember.Component.extend({
  isOpen: true
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

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

{{#x-foo as |panel|}}
  <p>isOpen from block: {{panel.isOpen}}</p>
  <button onclick={{action (mut panel.isOpen) false}}>Make false</button>
{{/x-foo}}

templates.components.x-foo.hbs

{{yield (hash isOpen=isOpen)}}
<p>isOpen from parent: {{isOpen}}</p>

twiddle.json

{
  "version": "0.10.6",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.9.0",
    "ember-data": "2.9.0",
    "ember-template-compiler": "2.9.0",
    "ember-testing": "2.9.0"
  },
  "addons": {}
}