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In this step, you will add a clickable phone image swapper to the phone details page.

- The phone details view displays one large image of the current phone and several smaller thumbnail images. It would be great if we could replace the large image with any of the thumbnails just by clicking on the desired thumbnail image. Let's have a look at how we can do this with AngularJS.

## Component Controller

`app/phone-detail/phone-detail.component.js`:

    ...
    controller: ['$http', '$routeParams',
      function PhoneDetailController($http, $routeParams) {
        var self = this;

        self.setImage = function setImage(imageUrl) {
          self.mainImageUrl = imageUrl;
        };

        $http.get('phones/' + $routeParams.phoneId + '.json').then(function(response) {
          self.phone = response.data;
          self.setImage(self.phone.images[0]);
        });
      }
    ]
    ...

In the `phoneDetail` component's controller, we created the `mainImageUrl` model property and set its default value to the first phone image URL.

We also created a `setImage()` method (to be used as event handler), that will change the value of `mainImageUrl`.

## Component Template

`app/phone-detail/phone-detail.template.html`:

    <img ng-src="{{$ctrl.mainImageUrl}}" class="phone" />
    ...
    <ul class="phone-thumbs">
      <li ng-repeat="img in $ctrl.phone.images">
        <img ng-src="{{img}}" ng-click="$ctrl.setImage(img)" />
      </li>
    </ul>
    ...

We bound the `ngSrc` directive of the large image to the `$ctrl.mainImageUrl` property.

We also registered an ngClick handler with thumbnail images. When a user clicks on one of the thumbnail images, the handler will use the `$ctrl.setImage()` method callback to change the value of the `$ctrl.mainImageUrl` property to the URL of the clicked thumbnail image.

# Testing

To verify this new feature, we added two E2E tests. One verifies that `mainImageUrl` is set to the first phone image URL by default. The second test clicks on several thumbnail images and verifies that the main image URL changes accordingly.

`e2e-tests/scenarios.js`:

    ...

    describe('View: Phone detail', function() {

      ...

      it('should display the first phone image as the main phone image', function() {
        var mainImage = element(by.css('img.phone'));

        expect(mainImage.getAttribute('src')).toMatch(/img\/phones\/nexus-s.0.jpg/);
      });

      it('should swap the main image when clicking on a thumbnail image', function() {
        var mainImage = element(by.css('img.phone'));
        var thumbnails = element.all(by.css('.phone-thumbs img'));

        thumbnails.get(2).click();
        expect(mainImage.getAttribute('src')).toMatch(/img\/phones\/nexus-s.2.jpg/);

        thumbnails.get(0).click();
        expect(mainImage.getAttribute('src')).toMatch(/img\/phones\/nexus-s.0.jpg/);
      });

    });

    ...

You can now rerun the tests with `npm run protractor`.

We also have to refactor one of our unit tests, because of the addition of the `mainImageUrl` model property to the controller. As previously, we will use a mocked response.

`app/phone-detail/phone-detail.component.spec.js`:

    ...

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

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

        ...
      }));

      it('should fetch phone details', function() {
        expect(ctrl.phone).toBeUndefined();

        $httpBackend.flush();
        expect(ctrl.phone).toEqual(xyzPhoneData);
      });

    });

    ...

Our unit tests should now be passing again.

# Experiments

- Similar to the `ngClick` directive, which binds an AngularJS expression to the `click` event, there are built-in directives for all native events, such as `dblclick`, `focus`/`blur`, mouse and key events, etc.

  Let's add a new controller method to the `phoneDetail` component's controller:

      self.onDblclick = function onDblclick(imageUrl) {
        alert('You double-clicked image: ' + imageUrl);
      };

  and add the following to the `<img>` element in `phone-detail.template.html`:

      <img ... ng-dblclick="$ctrl.onDblclick(img)" />

  Now, whenever you double-click on a thumbnail, an alert pops-up. Pretty annoying!

# Summary

With the phone image swapper in place, we are ready for step 13 to learn an even better way to fetch data.