Demo of code

components.component-here.js

import Ember from 'ember';

export default Ember.Component.extend({
  inputValue: null,
  
  test: function() {
    this.send('changeName', 'Name We Never See');
  }.observes('totalUsers'),
  
  actions: {
   	changeName(name) {
     	this.set('appName', name); 
    }
  }
  
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  data: [1, 2],
  
  actions: {
   	addItem(item) {
      this.get('data').pushObject(item);
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
{{component-here appName=appName totalUsers=data.length}}
<br>
<br>

<a href="#" {{action 'addItem' 44}}>Add Item & Change Application Name (This does not work fully)</a><br><br>

Now, this add item link is meant to add an item to the array (which it does) but if you go to the component-here.js file and look at the observer I've set-up, the application name should also change

templates.components.component-here.hbs

<a href="#" {{action 'changeName' 'Alex'}}>Change Name (This Works)</a>

<br><br>

Size of array<br>
{{totalUsers}}

twiddle.json

{
  "version": "0.11.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.10.2",
    "ember-data": "2.11.0",
    "ember-template-compiler": "2.10.2",
    "ember-testing": "2.10.2"
  },
  "addons": {}
}