tab-routing.ts

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

import { SessionService } from '../providers/session.service';


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

  constructor(
    public platform: Platform,
    public sessionSvc: SessionService
  ) {
    // Cordova is available
    platform.ready().then(() => {


      // observe login state and route accordingly
      this.sessionSvc.isLoggedIn.subscribe(isLoggedIn => {
        if ( isLoggedIn ) {
          this.rootPage = TabsPage;
        } else {
          this.rootPage = LoginPage;
        } // end if
      });

     
    });
  }

}