Q:

Detect route change in an Angular service

I'm trying to create a service to check if a certain route needs a user to be logged in to access the page. I have a working code but I want to place the $scope.$on('routeChangeStart) function inside the service. I want to place it in a service because I want to use it in multiple controllers. How do I go about this?
Current code:
profileInfoCtrl.js
angular.module('lmsApp', ['ngRoute'])

.controller('profileInfoCtrl', ['$scope', '$location', ' 'pageAuth', function($scope, $location, pageAuth){

  //I want to include this in canAccess function
  $scope.$on('$routeChangeStart', function(event, next) {

    pageAuth.canAccess(event, next);
  });
}]);

pageAuth.js
 angular.module('lmsApp')

.service('pageAuth', ['$location', function ($location) {

  this.canAccess = function(event, next) {

    var user = firebase.auth().currentUser;

    //requireAuth is a custom route property
    if (next.$$route.requireAuth && user == null ) {

      event.preventDefault(); //prevents route change
      alert("You must be logged in to access page!");

    }
    else {
      console.log("allowed");
    }

  }

}]);

routes.js
 angular.module('lmsApp')
    .config(['$routeProvider', '$locationProvider', function($routeProvider, $locationProvider){
      $routeProvider

.when('/admin', {
          templateUrl: 'view/admin.html',
          css: 'style/admin.css',
          controller: 'adminCtrl',
          requireAuth: true //custom property to prevent unauthenticated users
        })

        .otherwise({
          redirectTo: '/'
        });

    }]);

A:

By using $routeChangeStart, you are listening to a broadcast sent by $routeProvider on every change of the route. I don't think you need to call it in multiple places ( controllers ), just to check this.
In your service:
angular.module('lmsApp')
.service('pageAuth', ['$location', function ($location) {
var canAccess = function(event,next,current){

var user = firebase.auth().currentUser;
//requireAuth is a custom route property
    if (next.$$route.requireAuth && user == null ) {

      event.preventDefault(); //prevents route change
      alert("You must be logged in to access page!");

    }
    else {
      console.log("allowed");
    }

}

$rootScope.$on('$routeChangeStart',canAccess); 
}]);  

And then inject your service in the .run() part of your application. This will ensure the check will be done automatically ( by the broadcast as mentioned earlier ).
In you config part : 
angular.module('lmsApp')
    .run(function runApp(pageAuth){
 //rest of your stuff
}); 

