Angular ui router - Redirection doesn't work at all

Question

I'm using ui.router for routing in my Angular app. There is a typical login scenario, where I'm redirecting a user to the login url if he's not logged in. Without the ui.router library, this worked fine using $routeChangeStart event combined with $location.path. Now, I'm using the $stateChangeStart event, combined with $state.go, and the nothing works! It also sends my browser into an infinite loop. I read from other sources that this is a known bug, and none of the suggested solutions work for me. Moreover, $location.path too doesn't redirect to the login page.

This is how I've configured my paths:

 .config(['$stateProvider', '$urlRouterProvider', function ($stateProvider, $urlRouterProvider) {
    $stateProvider
        .state('main', {
            url: '/',
            templateUrl: 'views/main.html',
            controller: 'MainCtrl'
        })
        .state('about', {
            url: '/about',
            templateUrl: 'views/about.html',
            controller: 'AboutCtrl'
        })
        .state('login', {
            url: '/login',
            templateUrl: 'views/loginform.html',
            controller: 'LoginCtrl'
        });
    $urlRouterProvider.otherwise("/");
}])

And my run method:

.run(['$state', '$rootScope', '$location', function($state, $rootScope, $location) {
    //Check when routing starts
    //event, next, current
    $rootScope.$on( '$stateChangeStart', function(e, toState, toParams, fromState, fromParams) {
        //Redirect to login if the user is not logged in
        if (!isUserLoggedIn) {

            //Some suggestion
            //e.preventDefault();
            console.log('Not logged in');

            //Infinite loop, kills my browser!
            $state.go('login');
            $state.transitionTo('login');

            //Some suggestion
            $state.go('login', { url: '/login'});

            //Doesn't work
            $location.path('/login');

            //$location.path( $state.href('login');
            console.log('Redirected');
        }
    });

Answer 1

What we would need here, is to do NOT redirect, if the state TO is already the 'login'.

Just a drafted adjustment would be

$rootScope.$on( '$stateChangeStart', function(e, toState  , toParams
                                               , fromState, fromParams) {

    var isLogin = toState.name === "login";

    if(isLogin){

       return; // no need to redirect anymore 
    }
    ...

And also, we should call $state.go('login'); with the event.preventDefault();

 ...
 // also prevent default on redirect
 $state.go('login');
 event.preventDefault(); 
 ...

Please check this Q & A How can I fix 'Maximum call stack size exceeded' AngularJS And a plunker with similiar solution

Answer 2

I used something similar to this:

MyApp.run(['$rootScope', '$state', function ($rootScope, $state) {
  // The event
  $rootScope.$on('$stateChangeStart', function (e, toState, toParams, fromState, fromParams) {
    // Is user already logged in?
    var isUserLoggedIn = $rootScope.isUserLoggedIn();

    if (isUserLoggedIn) {
      // don't let user visit login state, he's already logged in.
      $state.go('home');
      // preventDefault as described in @radim's answer
      e.preventDefault();
    } else if (toState.name === "login") {
      // user is not logged in and is not going to login state right now, send him there first.
      $state.go('login');
      // preventDefault as described in @radim's answer
      e.preventDefault();
    }
  });
}]);