title: Input property not being updated when using callback function
body: <p>I need to update a property in a child component when a push notification is received from firebase. Firebase is configured correctly and I have the property configured as an input properly. The value is updated in the child successfully when I manually trigger the change using a button. However, when the value is changed using a callback the value will be updated but the child is not notified of the change. </p>
  
  <pre class="lang-js prettyprint-override"><code>export class AppComponent implements OnInit {
      private orders_updated:boolean = false;
  
      ngOnInit(): void {
          //firebase.init() removed for space
          firebase.addOnMessageReceivedCallback((data) =&gt; {
              this.interpret_message(data);
          });
      }
  
      private clicked() {
          this.orders_updated = !this.orders_updated;
          console.log(this.orders_updated)
      }
  
      private interpret_message(message:any) {
          if (message.body == "A new order was submitted") {
              this.clicked();
          }
      }
  }
  </code></pre>
  
  <pre class="lang-js prettyprint-override"><code>export class TransactionComponent implements OnInit {
      private _update:boolean;
  
      @Input() set update(value: boolean){
          this._update = value;
          console.log("Value updated")
      }
  }
  </code></pre>
  
  <p>When the clicked function is called manually I receive an update that the value in TransactionComponent was updated. However, when clicked is called as the result of a callback I do not receive "Value updated" message. I believe that by using an arrow function I am not running into a scope issue.</p>