AngularJS Factory: undefined is not a function - angularjs

Question

I wrote the following factory service in AngularJS, but when I try to call the factory service in my RootController, I got the "undefined is not a function" error in my console.
MyService.js:
(function() {
angular.module('serviceTestApp')
.factory('MyService', ['$resource', '$log', '$q', '$http', MyService]);
function MyService($log, $resource, $http, $q) {
var name = "Tom";
var getName = function() {
return name;
}; //getName
var changeName = function(newName) {
name = newName;
}; //changeName
var getIP = function() {
var deferredObj = $q.defer();
$resource('http://jsonip.com').query().$promise.then(function(result) {
deferredObj.resolve(result);
}, function(errorMsg) {
deferredObj.reject(errorMsg);
});
return deferredObj.promise;
}; //getIP
return {
getName: getName,
changeName: changeName,
getIP: getIP
};
}
}());
in my RootController, I try to call the services, and everything worked until I call the getIP() service - return a promise object. Does anyone see anything wrong?
RootController.js:
(function() {
angular.module('serviceTestApp')
.controller('RootCtrl', ['$http', '$log', '$scope', 'MyService', RootCtrl]);
function RootCtrl($log, $scope, $http, MyService) {
var vm = this;
vm.message = "hello world from RootController";
MyService.changeName("Henry Tudor");
vm.message = "my name is: " + MyService.getName();
MyService.getIP().query().then(function(data) {
$log.info('in the promise, ip is: ' + data.ip);
vm.message = vm.message + ', your IP is ' + data.ip;
}, function(error) {
vm.message = vm.message + ', error: ' + error;
});
}
}());

Answer 1

It may sound stupid, but I've located the cause for the error:
The API used in the $resource() returns a single JSON object:
{"ip":"2601:0:b840:8077:a97f:ee9c:f5b8:1643","about":"/about","Pro!":"http://getjsonip.com"}
however, the query() expects an array, not a JSON object.
After changing to another API that returns an array in JSON format, it works. Sigh, wasted my 2 hours.
thanks everyone

Answer 2

in order to use your service like that
MyService.getName()
that mean you have a service called MyService and returns a function called getName
but in your case it dosen't you have to change
your return to something like that
return {
getName: function() {return getName();},
changeName: function() {return changeName();},
getIP: function() {return getIP();}
};