@ngdoc overview
@name Developer Guide: Angular Services: Creating Angular Services
@description

While angular offers several useful services, for any nontrivial application you'll find it useful
to write your own custom services. To do this you begin by registering a service factory function
that angular's DI will use to create the service object when it is needed.

The `angular.module.ng` method accepts three parameters:

- `{string} name` - Name of the service.
- `{function()} factory` - Factory function(called just once by DI).
- `{Object} config` -  Configuration object with the following properties:
  - `$inject` - {Array.<string>} - Array of service ids this service depends on. These services
will be passed as arguments into the factory function in the same order specified in the `$inject`
array. Defaults to `[]`.

The `this` of the factory function is bound to the root scope of the angular application.

All angular services participate in {@link dev_guide.di dependency injection (DI)} by registering
themselves with angular's DI system (injector) under a `name` (id) as well as by declaring
dependencies which need to be provided for the factory function of the registered service. The
ability to swap dependencies for mocks/stubs/dummies in tests allows for services to be highly
testable.

Following is an example of a very simple service. This service depends on the `$window` service
(which is passed as a parameter to the factory function) and is just a function. The service simply
stores all notifications; after the third one, the service displays all of the notifications by
window alert.

<pre>
    angular.module.ng('notify', function(win) {
      var msgs = [];
      return function(msg) {
        msgs.push(msg);
        if (msgs.length == 3) {
          win.alert(msgs.join("\n"));
          msgs = [];
        }
      };
    }, {$inject: ['$window']});
</pre>


## Related Topics

* {@link dev_guide.services.understanding_services Understanding Angular Services}
* {@link dev_guide.services.registering_services Registering Angular Services}
* {@link dev_guide.services.managing_dependencies Managing Service Dependencies}
* {@link dev_guide.services.injecting_controllers Injecting Services Into Controllers }
* {@link dev_guide.services.testing_services Testing Angular Services}

## Related API

* {@link api/angular.module.ng Angular Service API}