AngularJS is giving TypeError exception

So, I am an Ionic and Angular newbie to making mobile apps. However, I have a basic login form, and a login button which successfully calls a controller. The controller looks like:

angular.module('starter.controllers', [])
    .controller('LoginCtrl', function($scope, LoginService, $ionicPopup, $state) {
        $scope.data = {};

        $scope.login = function() {
            LoginService.loginUser($scope.data.username, $scope.data.password)
                .success(function(data) {
                    // $state.go('tab.dash');
                    var alertPopup = $ionicPopup.alert({
                        title: 'Login HERE!',
                        template: 'HERE: your credentials!'
                    });
                }).error(function(data) {
                    var alertPopup = $ionicPopup.alert({
                        title: 'Login failed!',
                        template: 'Please check your credentials!'
                    });
                });
        }
    });

This now calls a service which looks like:

angular.module('starter.services', [])
    .service('LoginService', function($http,$q) {
        return {
            loginUser : function(name, pw) {
                console.log('username=' + name + ', password=' + pw);
                var deferred = $q.defer();
                var promise = deferred.promise;

                var url = 'https://myURL/myapi/authenticate?username=' + name + '&password=' + pw;
                console.log('url=' + url);

                $http.get(url)
                    .success(function(data) {
                        console.log("success: data=" +data);
                        deferred.resolve(data);
                    })
                    .error(function() {
                        console.log("error");
                        deferred.reject("Failed to authenticate");
                    });

                // Return the promise to the controller
                promise.success = function(fn) {
                    promise.then(fn);
                    return promise;
                }
                promise.error = function(fn) {
                    promise.then(null, fn);
                    return promise;
                }

                return promise;
            }
        }
    })

The URL I have gets built correctly, it calls the RESTful api correctly. In the event of a successful login, I get a token id as a single string. In the event of an unsuccessful login, I get an single line as an error message.

I did read that a GET restful web call expects an array of data. I can see in the controller.js that: String data = {};

The real error message I am getting is that .success in the controller is not mapped to getting a String, but an array instead.

If anyone can help me out with whether I can make my data an array, or if I can add a new .success and .error with a single string, that would be great.

Thanks!