step_11.ngdoc

@ngdoc overview
@name Tutorial: 11 - REST and Custom Services
@description

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In this step, you will improve the way our app fetches data.


<div doc-tutorial-reset="11"></div>


The next improvement we will make to our app is to define a custom service that represents a {@link
http://en.wikipedia.org/wiki/Representational_State_Transfer RESTful} client. Using this client we
can make XHR requests for data in an easier way, without having to deal with the lower-level {@link
api/ng.$http $http} API, HTTP methods and URLs.

The most important changes are listed below. You can see the full diff on {@link
https://github.com/angular/angular-phonecat/compare/step-10...step-11
GitHub}:


## Template

The custom service is defined in `app/js/services.js` so we need to include this file in our layout
template. Additionally, we also need to load the `angular-resource.js` file, which contains the
`ngResource` module and in it the `$resource` service, that we'll soon use:

__`app/index.html`.__
<pre>
...
  <script src="js/services.js"></script>
  <script src="lib/angular/angular-resource.js"></script>
...
</pre>

## Service

__`app/js/services.js`.__
<pre>
var phonecatServices = angular.module('phonecatServices', ['ngResource']);

phonecatServices.factory('Phone', ['$resource',
  function($resource){
    return $resource('phones/:phoneId.json', {}, {
      query: {method:'GET', params:{phoneId:'phones'}, isArray:true}
    });
  }]);
</pre>

We used the module API to register a custom service using a factory function. We passed in the name
of the service - 'Phone' - and the factory function. The factory function is similar to a
controller's constructor in that both can declare dependencies via function arguments. The Phone
service declared a dependency on the `$resource` service.

The {@link api/ngResource.$resource `$resource`} service makes it easy to create a
{@link http://en.wikipedia.org/wiki/Representational_State_Transfer RESTful} client with just a few
lines of code. This client can then be used in our application, instead of the lower-level {@link
api/ng.$http $http} service.

__`app/js/app.js`.__
<pre>
...
angular.module('phonecatApp', ['ngRoute', 'phonecatControllers','phonecatFilters', 'phonecatServices']).
...
</pre>

We need to add the 'phonecatServices' module dependency to 'phonecatApp' module's requires array.


## Controller

We simplified our sub-controllers (`PhoneListCtrl` and `PhoneDetailCtrl`) by factoring out the
lower-level {@link api/ng.$http $http} service, replacing it with a new service called
`Phone`. Angular's {@link api/ngResource.$resource `$resource`} service is easier to
use than `$http` for interacting with data sources exposed as RESTful resources. It is also easier
now to understand what the code in our controllers is doing.

__`app/js/controllers.js`.__
<pre>
...

phonecatApp.controller('PhoneListCtrl', ['$scope', 'Phone', function($scope, Phone) {
  $scope.phones = Phone.query();
  $scope.orderProp = 'age';
}]);

phonecatApp.controller('PhoneDetailCtrl', ['$scope', '$routeParams', 'Phone', function($scope, $routeParams, Phone) {
  $scope.phone = Phone.get({phoneId: $routeParams.phoneId}, function(phone) {
    $scope.mainImageUrl = phone.images[0];
  });

  $scope.setImage = function(imageUrl) {
    $scope.mainImageUrl = imageUrl;
  }
}]);
</pre>

Notice how in `PhoneListCtrl` we replaced:

    $http.get('phones/phones.json').success(function(data) {
      $scope.phones = data;
    });

with:

    $scope.phones = Phone.query();

This is a simple statement that we want to query for all phones.

An important thing to notice in the code above is that we don't pass any callback functions when
invoking methods of our Phone service. Although it looks as if the result were returned
synchronously, that is not the case at all. What is returned synchronously is a "future" — an
object, which will be filled with data when the XHR response returns. Because of the data-binding
in Angular, we can use this future and bind it to our template. Then, when the data arrives, the
view will automatically update.

Sometimes, relying on the future object and data-binding alone is not sufficient to do everything
we require, so in these cases, we can add a callback to process the server response. The
`PhoneDetailCtrl` controller illustrates this by setting the `mainImageUrl` in a callback.


## Test

We have modified our unit tests to verify that our new service is issuing HTTP requests and
processing them as expected. The tests also check that our controllers are interacting with the
service correctly.

The {@link api/ngResource.$resource $resource} service augments the response object
with methods for updating and deleting the resource. If we were to use the standard `toEqual`
matcher, our tests would fail because the test values would not match the responses exactly. To
solve the problem, we use a newly-defined `toEqualData` {@link
https://github.com/pivotal/jasmine/wiki/Matchers Jasmine matcher}. When the
`toEqualData` matcher compares two objects, it takes only object properties into account and
ignores methods.


__`test/unit/controllersSpec.js`:__
<pre>
describe('PhoneCat controllers', function() {

  beforeEach(function(){
    this.addMatchers({
      toEqualData: function(expected) {
        return angular.equals(this.actual, expected);
      }
    });
  });


  beforeEach(module('phonecatServices'));


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

    beforeEach(inject(function(_$httpBackend_, $rootScope, $controller) {
      $httpBackend = _$httpBackend_;
      $httpBackend.expectGET('phones/phones.json').
          respond([{name: 'Nexus S'}, {name: 'Motorola DROID'}]);

      scope = $rootScope.$new();
      ctrl = $controller(PhoneListCtrl, {$scope: scope});
    }));


    it('should create "phones" model with 2 phones fetched from xhr', function() {
      expect(scope.phones).toEqual([]);
      $httpBackend.flush();

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


    it('should set the default value of orderProp model', function() {
      expect(scope.orderProp).toBe('age');
    });
  });


  describe('PhoneDetailCtrl', function(){
    var scope, $httpBackend, ctrl,
        xyzPhoneData = function() {
          return {
            name: 'phone xyz',
                images: ['image/url1.png', 'image/url2.png']
          }
        };


    beforeEach(inject(function(_$httpBackend_, $rootScope, $routeParams, $controller) {
      $httpBackend = _$httpBackend_;
      $httpBackend.expectGET('phones/xyz.json').respond(xyzPhoneData());

      $routeParams.phoneId = 'xyz';
      scope = $rootScope.$new();
      ctrl = $controller(PhoneDetailCtrl, {$scope: scope});
    }));


    it('should fetch phone detail', function() {
      expect(scope.phone).toEqualData({});
      $httpBackend.flush();

      expect(scope.phone).toEqualData(xyzPhoneData());
    });
  });
});
</pre>

You should now see the following output in the Karma tab:

    Chrome 22.0: Executed 4 of 4 SUCCESS (0.038 secs / 0.01 secs)


# Summary

With the phone image swapper in place, we're ready for {@link step_12 step 12} (the last step!) to
learn how to improve this application with animations.


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