Something I've been doing several times a day with Angular and ngOnInit() since September 2016

home.html

<ion-header>
  <ion-navbar>
    <ion-title>
      My App
    </ion-title>
  </ion-navbar>
</ion-header>

<ion-content padding>
  Ok: {{ userFirstName }} <!-- Pluto -->
  Ok: {{ user | json }} <!-- { firstname: "Pippo" } -->
  Error: {{ user.firstname }}! <!-- ERROR Error: Uncaught (in promise): TypeError: Cannot read property 'firstname' of undefined
TypeError: Cannot read property 'firstname' of undefined -->
</ion-content>

home.ts

import { Component } from '@angular/core';

@Component({
    selector: 'wn-page-home',
    templateUrl: 'home.html'
})
export class HomePageComponent {
    user: any;
    userFirstName: string;

    constructor() {
        //
    }

    ionViewWillEnter() {
        this.userFirstName = 'Pluto';
        this.user = { firstname: 'Pippo' };
    }
}