title: ionic 2 check if user already logged in with angularfire2
body: <p>I did facebook login to my app and I'm trying to check if the user logged in then go to HomePage,if not go to loginPage.
  I did it with firebase but I'm trying to do that with angularfire2
  that's my code with firebase (I want it in angularfire2)</p>
  
  <pre><code> firebase.auth().onAuthStateChanged((user) =&gt; {
     var that=this;
    if (user) {
      if(this.reg_boolean=="true"){
        console.log("regCompleted");  
         this.nav.setRoot(TabsPage,{
         dep:this.department,year:this.year,semester:this.semester
  
      })
        this.rootPage=TabsPage;
      }
      else{
      this.rootPage = SignupPage;
      }
      console.log("I'm here! HomePage");
    } else {
      this.rootPage = LoginPage;
      console.log("I'm here! LoginPage");
    }
  });
  </code></pre>