same array for all components

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  someArray: [1, 2],
  actions: {
    addElement() {
      this.get('someArray').pushObject(1);
    }
  }
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

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

{{my-component}}

{{my-component}}
<br>
<br>

templates.components.my-component.hbs

{{#each someArray as |element|}}
  {{element}}
{{/each}}
<br />
<button onClick={{action "addElement"}}>add me</button>

twiddle.json

{
  "version": "0.10.5",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.8.0",
    "ember-data": "2.8.0",
    "ember-template-compiler": "2.8.0",
    "ember-testing": "2.8.0"
  },
  "addons": {}
}