Managing user state in Ionic2 mobile application using BehaviorSubject - Also using Ionic Cloud for User Authentication
https://www.youtube.com/edit?o=U&video_id=QicFdqDi6ns
blog post: http://www.clearlyinnovative.com/user-authentication-with-ionic-cloud-auth-using-rxjsbehaviorsubject
source codet: https://github.com/aaronksaunders/Ionic2-Ionic.io-Auth-Example
more information on behaviorSubject here: http://stackoverflow.com/questions/39494058/angular-2-behavior-subject-vs-observable