Non-Singleton Services in AngularJS

Question

AngularJS clearly states in its documentation that Services are Singletons:

AngularJS services are singletons

Counterintuitively, module.factory also returns a Singleton instance.

Given that there are plenty of use-cases for non-singleton services, what is the best way to implement the factory method to return instances of a Service, so that each time an ExampleService dependency is declared, it is satisfied by a different instance of ExampleService?

Answer 1

I'm not entirely sure what use case you are trying to satisfy. But it is possible to have a factory return instances of an object. You should be able to modify this to suit your needs.

var ExampleApplication = angular.module('ExampleApplication', []);


ExampleApplication.factory('InstancedService', function(){

    function Instance(name, type){
        this.name = name;
        this.type = type;
    }

    return {
        Instance: Instance
    }

});


ExampleApplication.controller('InstanceController', function($scope, InstancedService){
       var instanceA = new InstancedService.Instance('A','string'),
           instanceB = new InstancedService.Instance('B','object');

           console.log(angular.equals(instanceA, instanceB));

});

JsFiddle

Updated

Consider the following request for non-singleton services. In which Brian Ford notes:

The idea that all services are singletons does not stop you from writing singleton factories that can instantiate new objects.

and his example of returning instances from factories:

myApp.factory('myService', function () {
  var MyThing = function () {};
  MyThing.prototype.foo = function () {};
  return {
    getInstance: function () {
      return new MyThing();
    }
  };
});

I would also argue his example is superior due to the fact that you do not have to use the new keyword in your controller. It is encapsulated within the getInstance method of the service.