because your getData method is not triggered on your custom component, of course you can't write this method on ion-content .

it seems that there is nothing wrong with the code. In fact, you should not get data on ion-content. If you want to use child components, you can import directly in the parent component ts

import child from ../childCom.ts

then directly in the parent component html

<child (event)="getData($event)"></child>

it is recommended to change getData (msg:string) to getData (msg:event) or getData (msg)