If you want to pass a variable from app.component.ts, where you use the ion-nav element, you could try to use a provider for communication between MyApp and ChildPage or try root params like this:
<ion-nav [root]="ChildPage" [rootParams]="stringTest"></ion-nav>
and in your ChildPage I think this should work: this.stringTest = navParams.data[0];
@khokhardheeraj : navParams is a nice way to go, if you use navCtrl for navigation. @Input is good for passing data into a child component by including it in the parents template with its selector (e.g. <child-comp></child-comp>. I guess that navParams is better for large amount of data, but I am not sure.
@rebuhleiv : How do you navigate to your ChildPage? If you use it as root, use the following: <ion-nav [root]="ChildPage" [rootParams]="stringTest"></ion-nav> and also keep stringTest in the constructor of your app.component.ts like you wrote: public stringTest:string = 'default'; constructor(platform: Platform) { this.stringTest = 'changed'; });
rootParams should be accessible via navParams. In your ChildPage include the following to access the string: import { NavParams } from 'ionic-angular'; constructor(public params: NavParams) { this.stringTest = params.data; }