Ionic 2: Navigating from the Root Component
<p>What does it mean?</p>

<p>What if you want to control navigation from your root app component (the one decorated with @App, not @Page)? You can’t inject NavController <strong>because any components that are navigation controllers are children of the root component so they aren’t available to be injected.</strong></p>

<p>By adding an id to ion-nav, you can use the IonicApp service to get a reference to the Nav component, which is a navigation controller (it extends NavController):</p>