Optional Actions

components.bar-component.js

import Ember from 'ember';

export default Ember.Component.extend({
});

components.foo-component.js

import Ember from 'ember';

export default Ember.Component.extend({
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  actions: {
    updateAppName(name) {
       this.set('appName', name); 
    }
  }
});

templates.application.hbs

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

With Passing the action
{{foo-component onChange=(action 'updateAppName')}}

<hr>
Without passing the action
{{foo-component}}
<br>
<br>

templates.components.bar-component.hbs

This is the bar component

{{input type='text' key-up=onChange}}

templates.components.foo-component.hbs

This is the foo component

{{bar-component onChange=onChange}}

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"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}