app.component.ts

import { Component } from '@angular/core';
import { Platform } from 'ionic-angular';
import { StatusBar } from 'ionic-native';

import { HomePage } from '../pages/home/home';
import { LoginPage } from '../pages/login/login';

import firebase from 'firebase';


@Component({
  template: `<ion-nav [root]="rootPage"></ion-nav>`
})
export class MyApp {
  rootPage: any;

  constructor(platform: Platform) {
    firebase.initializeApp({
      apiKey: "",
      authDomain: "",
      databaseURL: "",
      storageBucket: "",
      messagingSenderId: ""
    });

    let unsubscribe = firebase.auth().onAuthStateChanged((user) => {
      if (user) {
        this.rootPage = HomePage;
        console.log("HomePage", user);
        unsubscribe();
      } else {
        this.rootPage = LoginPage;
        console.log("LoginPage", user);
        unsubscribe();
      }
    });

    platform.ready().then(() => {
      // Okay, so the platform is ready and our plugins are available.
      // Here you can do any higher level native things you might need.
      StatusBar.styleDefault();
    });
  }
}

/**
 * The code works with Firebase, I get back the user and log it to the console, 
 * but it's not assigning the rootPage.
 * 
 * Or it is, because if I log it I get the correct value, but is not redirecting to it.
 */

// However, if I just do 

rootPage = LoginPage;

// It goes to the login page.

Hello,

Finaly i can fixed using something like this:

import { Component, ViewChild } from '@angular/core';
import { Nav } from 'ionic-angular';

@component({
template: <ion-nav [root]="rootPage"></ion-nav>
})
export class MyApp
{
@ViewChild(Nav) nav: Nav;
......
firebase.auth().onAuthStateChanged((user) =>
{
if (user)
this.nav.setRoot(SlideMenuPage);
else
this.nav.setRoot(LoginPage);
});
}

And it's working.
Please some coments that i need know using this method?

Kind regards