Why routing does not accept normal conditional checking code in angularjs - angularjs

Question

I wanted to check some conditioning before the page loads, So I used resolve property
as
when('/home', { templateUrl: 'views/home.html', controller: 'homeController',resolve: {
user: function () {
if (localStorage.getItem('FBUserData') === null) {
$location.url('/login');
}
}()
}}).
But this did not work, as it was showing the error like:
Error: [ng:areq] Argument 'fn' is not a function, got undefined
'
So I moved the function to controller and tried calling from there, but this gave different error:
Modified code
var angAuth = angular.module('angularAuthApp'[...]);
angAuth.config(function ($routeProvider, $locationProvider) {
$routeProvider.
when('/home', { templateUrl: 'views/home.html', controller: 'homeController',resolve:homeController.checkUserFBSession})
....
....
});
And in homeController:
angAuth.controller('homeController', function ($scope, $location) {
$scope.checkUserFBSession = function(){
if(localStorage.getItem('FBUserData') === null){
$location.url('/login');
}
};
...
});
Here after adding resolve:homeController.checkUserFBSession, I am getting the error like
Failed to instantiate module angularAuthApp due to: homeController is not defined

Answer 1

The reason is that resolve's value is "an optional map of dependencies which should be injected into the controller. If any of these dependencies are promises, the router will wait for them all to be resolved or one to be rejected before the controller is instantiated."
This means that user needs to be evaluated before the controller is instantiated. Therefore you can't use a function defined in the controller to evaluate user.
You first approach should work thought (if properly implemented).
resolve is a key-value map, where key is the name of the dependency injected into the controller and value is either a string (denoting the name of a service) or a function. The function is called by Angular, but in your case you are calling it yourself and return undefined, so Angular sees undefined where it expects a function or a string.
You should change this:
user: function () {...}()
to that:
user: function ($location) {...}
Note: In order to use $location you also need to inject it into the function.
See, also, this short demo.