Emberjs: check if user is logged with facebook on init - facebook

Question

I'm trying to use Facebook to log in an Ember application. The login action is working, but I can't find how to check if the user has already logged in when the app is initialized.
I'm calling the auth.authResponseChange event but it blocks the app and it never starts.
App.ApplicationController = Ember.Controller.extend({
fbUser: false,
init: function() {
this.checkFBUser()
},
checkFBUser: function() {
FB.Event.subscribe('auth.authResponseChange', function(response) {
// this is never triggered and the app does not init
console.log(response)
if (response.status === 'connected') {
console.log('Logged in')
}
else {
FB.login()
}
})
},
// this works
actions: {
loginFacebook: function() {
var self = this
FB.login(function(response) {
if (response.authResponse) {
FB.api('/me', function(response) {
self.set('fbUser', response)
})
}
})
}
}
})
How am I supposed to do this?

Answer 1

I haven't worked with FB lately, but I'm pretty sure the AuthResponeChange event is for being notified of a change in the AuthResponse status; in this instance you'll probably want to take a look at FB.getLoginStatus instead.
https://developers.facebook.com/docs/reference/javascript/FB.getLoginStatus
checkFBUser: function()
{
FB.getLoginStatus(function(response) {
if (response.status === 'connected') {
// the user is logged in and has authenticated your
// app, and response.authResponse supplies
// the user's ID, a valid access token, a signed
// request, and the time the access token
// and signed request each expire
var uid = response.authResponse.userID;
var accessToken = response.authResponse.accessToken;
} else if (response.status === 'not_authorized') {
// the user is logged in to Facebook,
// but has not authenticated your app
} else {
// the user isn't logged in to Facebook.
}
});

Answer 2

I've found the source of the problem and a solution. I'm not sure this is the best solution so I'm open to other suggestions but if this can help other people, here is the thing:
The issue was that the Facebook library was not loaded yet, so the FB variable was undefined. For some reason if you try to do something with an undefined variable in Ember the app just won't work without even a warning. So the solution is to wait:
App.deferReadiness()
function checkFB() {
if (typeof FB !== 'undefined') {
APp.advanceReadiness()
}
else {
setTimeout(checkFB, 10);
}
}
setTimeout(checkFB, 10);
10 milliseconds is pretty short so the app is still initialized very quick, and in my tests the app starts after ~20 milliseconds. This still feels a bit hacky but in place of a better solution this will do for now.

Answer 3

As Aaron said you need to use fb.getLoginStatus to check if a user is already logged in. To make sure Facebook is loaded before you to make any calls you can use an initializer and defer the app until the SDK has loaded.
http://nerdyworm.com/blog/2013/04/03/ember-initializers/
Ember.Application.initializer({
name: 'init_fb',
initialize: function (container) {
window.App.deferReadiness();
Ember.$.getScript( '//connect.facebook.net/en_UK/all.js', function( ) {
FB.init( {
appId : 'xxxxxxxxxxxxx',
xfbml : true,
version : 'v2.0',
} );
window.App.advanceReadiness();
} );
}
});