Confused about Service vs Factory

Question

As I understand it, when inside a factory I return an object that gets injected into a controller. When inside a service I am dealing with the object using this and not returning anything.

I was under the assumption that a service was always a singleton, and that a new factory object gets injected in every controller. However, as it turns out, a factory object is a singleton too?

Example code to demonstrate:

var factories = angular.module('app.factories', []); var app = angular.module('app',  ['ngResource', 'app.factories']);  factories.factory('User', function () {   return {     first: 'John',     last: 'Doe'   }; });  app.controller('ACtrl', function($scope, User) {   $scope.user = User; });  app.controller('BCtrl', function($scope, User) {   $scope.user = User; }); 

When changing user.first in ACtrl it turns out that user.first in BCtrl is also changed, e.g. User is a singleton?

My assumption was that a new instance was injected in a controller with a factory?

Answer 1

All angular services are singletons:

Docs (see Services as singletons): https://docs.angularjs.org/guide/services

Lastly, it is important to realize that all Angular services are application singletons. This means that there is only one instance of a given service per injector.

Basically the difference between the service and factory is as follows:

app.service('myService', function() {    // service is just a constructor function   // that will be called with 'new'    this.sayHello = function(name) {      return "Hi " + name + "!";   }; });  app.factory('myFactory', function() {    // factory returns an object   // you can run some code before    return {     sayHello : function(name) {       return "Hi " + name + "!";     }   } }); 

Check out this presentation about $provide: http://slides.wesalvaro.com/20121113/#/

Those slides were used in one of the AngularJs meetups: http://blog.angularjs.org/2012/11/more-angularjs-meetup-videos.html