Pass a variable from child to parent component

So I am trying to get a value from my child component to print in my parent component and I tried the following:

In my child component ts:

export class ChildComponent  {
 message: string = 'Hello!!!'; 
}

In my parent component ts:

import { Component, ViewChild, AfterViewInit} from '@angular/core';
import { ChildComponent } from '../child/child.component'

 export class ShoppingCartComponent implements ControlValueAccessor, AfterViewInit  {
  messageFromChild : string;
  @ViewChild(ChildComponent) myChild;
  ngAfterViewInit() {
    this.messageFromChild = this.myChild.message;
  }
  }

In my parent component html:

<h1> From Child - {{ messageFromChild }} </h1>

I don’t get any errors but {{ messageFromChild }} is blank.
The tutorial that I followed said to add the parent component to the bootstrap array in app.module.ts but when I did that I got a blank page.

In the console, I get the error: TypeError: Cannot read property ‘message’ of undefined

I got it to work using eventemitter but now the problem is that I need to use a number as an eventemitter and I get the error: Type ‘number’ is not assignable to type ‘EventEmitter’