@ngdoc overview @name Tutorial: Step 5 @description
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Enough of building an app with three phones in a hard-coded dataset! Let's fetch a larger dataset from our server using one of angular's built-in {@link angular.service services} called {@link angular.service.$xhr $xhr}. We will use angular's dependency injection to provide the service to the `PhoneListCtrl` controller. 1. Reset your workspace to Step 5 using: git checkout --force step-5 or ./goto_step.sh 5 2. Refresh your browser or check the app out on {@link http://angular.github.com/angular-phonecat/step-5/app our server}. You should now see a list of 20 phones. The most important changes are listed below. You can see the full diff on {@link https://github.com/angular/angular-phonecat/compare/step-4...step-5 GitHub}: ## Data The `app/phones/phone.json` file in your project is a dataset that contains a larger list of phones stored in the JSON format. Following is a sample of the file: 
[
 {
  "age": 13,
  "id": "motorola-defy-with-motoblur",
  "name": "Motorola DEFY\u2122 with MOTOBLUR\u2122",
  "snippet": "Are you ready for everything life throws your way?"
  ...
 },
...
]
## Controller In this step, the view template will remain the same but the model and controller will change. We'll use angular's {@link angular.service.$xhr} service to make an HTTP request to your web server to fetch the data in the `phones.json` file. __`app/js/controllers.js:`__ 
function PhoneListCtrl($xhr) {
  var self = this;

  $xhr('GET', 'phones/phones.json', function(code, response) {
    self.phones = response;
  });

  self.orderProp = 'age';
}

//PhoneListCtrl.$inject = ['$xhr'];
We removed the hard-coded dataset from the controller and instead are using the `$xhr` service to access the data stored in `app/phones/phones.json`. The `$xhr` service makes a HTTP GET request to our web server, asking for `phone/phones.json` (the url is relative to our `index.html` file). The server responds by providing the data in the json file. Keep in mind that the response might just as well have been dynamically generated by a backend server. To the browser and our app they both look the same. For the sake of simplicity we used a json file in this tutorial. Notice that the `$xhr` service takes a callback as the last parameter. This callback is used to process the response. In our case, we just assign the response to the current scope controlled by the controller, as a model called `phones`. Have you realized that we didn't even have to parse the response? Angular took care of that for us. We already mentioned that the `$xhr` function we just used is an angular service. {@link angular.service Angular services} are substitutable objects managed by angular's {@link guide.di DI subsystem}. Dependency injection helps to make your web apps well structured, loosely coupled, and much easier to test. What's important to understand is how the controllers get access to these services through dependency injection. The dependency injection pattern is based on declaring the dependencies we require and letting the system provide them to us. To do this in angular, you simply provide the names of the services you need as arguments to the controller's constructor function, as follows: function PhoneListCtrl($xhr) { The name of the argument is significant, because angular recognizes the identity of a service by the argument name. Once angular knows what services are being requested, it provides them to the controller when the controller is being constructed. The dependency injector also takes care of creating any transitive dependencies the service may have (services often depend upon other services). As we mentioned earlier, angular infers the controller's dependencies from the names of arguments of the controller's constructor function. If you were to minify the JavaScript code for this controller, all of these function arguments would be minified as well, and the dependency injector would not being able to identify services correctly. To overcome issues caused by minification, just assign an array with service identifier strings into the `$inject` property of the controller function, just like the last line in the snippet (commented out) suggests: PhoneListCtrl.$inject = ['$xhr']; ## Test __`test/unit/controllersSpec.js`:__ 
describe('PhoneCat controllers', function() {

  describe('PhoneListCtrl', function(){
    var scope, $browser, ctrl;

    beforeEach(function() {
      scope = angular.scope();
      $browser = scope.$service('$browser');

      $browser.xhr.expectGET('phones/phones.json').respond([{name: 'Nexus S'},
                                                            {name: 'Motorola DROID'}]);
      ctrl = scope.$new(PhoneListCtrl);
    });


    it('should create "phones" model with 2 phones fetched from xhr', function() {
      expect(ctrl.phones).toBeUndefined();
      $browser.xhr.flush();

      expect(ctrl.phones).toEqual([{name: 'Nexus S'},
                                   {name: 'Motorola DROID'}]);
    });


    it('should set the default value of orderProp model', function() {
      expect(ctrl.orderProp).toBe('age');
    });
  });
});
Because we started using dependency injection and our controller has dependencies, constructing the controller in our tests is a bit more complicated. We could use the `new` operator and provide the constructor with some kind of fake `$xhr` implementation. However, the recommended (and easier) way is to create a controller in the test environment in the same way that angular does it in the production code behind the scenes. To create the controller in the test environment, do the following: * Create a root scope object by calling `angular.scope()` * Call `scope.$new(PhoneListCtrl)` to get angular to create the child scope associated with the `PhoneListCtrl` controller. Because our code now uses the `$xhr` service to fetch the phone list data in our controller, before we create the `PhoneListCtrl` child scope, we need to tell the testing harness to expect an incoming request from the controller. To do this we: * Use the `{@link angular.scope.$service $service}` method to retrieve the `$browser` service, a service that angular uses to represent various browser APIs. In tests, angular automatically uses a mock version of this service that allows you to write tests without having to deal with these native APIs and the global state associated with them. * We use the `$browser.expectGET` method to train the `$browser` object to expect an incoming HTTP request and tell it what to respond with. Note that the responses are not returned before we call the `$browser.xhr.flush()` method. * We then make assertions to verify that the `phones` model doesn't exist on the scope, before the response is received. * We flush the xhr queue in the browser by calling `$browser.xhr.flush()`. This causes the callback we passed into the `$xhr` service to be executed with the trained response. * Finally, we make the assertions, verifying that the phone model now exists on the scope. To run the unit tests, execute the `./scripts/test.sh` script and you should see the following output. Chrome: Runner reset. .. Total 2 tests (Passed: 2; Fails: 0; Errors: 0) (3.00 ms) Chrome 11.0.696.57 Mac OS: Run 2 tests (Passed: 2; Fails: 0; Errors 0) (3.00 ms) Now that you have learned how easy it is to use angular services (thanks to angular's implementation of dependency injection), go to Step 6, where you will add some thumbnail images of phones and some links.
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