New Twiddle

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  errorReporting: Ember.inject.service('error-reporting'),
  actions: {
    causeError() {
      this.get('errorReporting').set('currentError', 'I\'ll get you next time, Inspector Gadget!');
    }
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  init() {
    this.clearError();
  },
  errorReporting: Ember.inject.service('error-reporting'),
  currentError: Ember.computed.reads('errorReporting.currentError'),
  clearError() {
    this.get('errorReporting').set('currentError', null);
  }
});

services.error-reporting.js

import Ember from 'ember';

export default Ember.Service.extend({
  currentError: null
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{#if currentError}}
<div class="error-thing">
  <h1>Uh, oh! It's poop again!</h1>
  <p>{{currentError}}</p>
  <button {{action clearError}}>Clear</button>
</div>
{{/if}}
{{outlet}}
{{#my-component}}{{/my-component}}
<br>
<br>

templates.components.my-component.hbs

{{yield}}
<button {{action 'causeError'}}>Cause error</button>

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": {}
}