@ngdoc overview
@name Tutorial: Step 4
@description
<table id="tutorial_nav">
<tr>
<td id="previous_step">{@link tutorial.step_03 Previous}</td>
<td id="step_result">{@link  http://angular.github.com/angular-phonecat/step-4/app Live Demo}</td>
<td id="tut_home">{@link tutorial Tutorial Home}</td>
<td id="code_diff">{@link https://github.com/angular/angular-phonecat/compare/step-3...step-4 Code
Diff}</td>
<td id="next_step">{@link tutorial.step_05 Next}</td>
</tr>
</table>

In this step, you will add a feature to let your users select the order of the items in the phone
list. The dynamic ordering is implemented by creating a new model property, wiring it together
with the repeater, and letting the data binding magic do the rest of the work.


1. Reset your workspace to Step 4 using:

    git checkout --force step-4

or

    ./goto_step.sh 4

2. Refresh your browser or check the app out on {@link
http://angular.github.com/angular-phonecat/step-4/app our server}. You should see that in addition
to the search box, the app displays a drop down menu that allows users to control the order in
which the phones are listed.

The most important changes are listed below. You can see the full diff on {@link
https://github.com/angular/angular-phonecat/compare/step-3...step-4
GitHub}:


## Template

__`app/index.html`:__
<pre>
...
  <ul class="predicates">
    <li>
      Search: <input type="text" name="query"/>
    </li>
    <li>
      Sort by:
      <select name="orderProp">
        <option value="name">Alphabetical</option>
        <option value="age">Newest</option>
      </select>
    </li>
  </ul>

  <ul class="phones">
    <li ng:repeat="phone in phones.$filter(query).$orderBy(orderProp)">
      {{phone.name}}
      <p>{{phone.snippet}}</p>
    </li>
  </ul>
...
</pre>

In the `index.html` template we made the following changes:

* First, we added a `<select>` html element named `orderProp`, so that our users can pick from the
two provided sorting options.

* We then chained the `$filter` method with `{@link angular.Array.orderBy $orderBy}` method to
further process the input into the repeater.

Angular creates a two way data-binding between the select element and the `orderProp` model.
`orderProp` is then used as the input for the `$orderBy` method.

As we discussed in the section about data-binding and the repeater in Step 3, whenever the model
changes (for example because a user changes the order with the select drop down menu), angular's
data-binding will cause the view to automatically update. No bloated DOM manipulation code is
necessary! 



## Controller

__`app/js/controller.js`:__
<pre>
/* App Controllers */

function PhoneListCtrl() {
  this.phones = [{"name": "Nexus S",
                  "snippet": "Fast just got faster with Nexus S.",
                  "age": 0},
                 {"name": "Motorola XOOM™ with Wi-Fi",
                  "snippet": "The Next, Next Generation tablet.",
                  "age": 1},
                 {"name": "MOTOROLA XOOM™",
                  "snippet": "The Next, Next Generation tablet.",
                  "age": 2}];

  this.orderProp = 'age';
}
</pre>

* We modified the `phones` model - the array of phones - and added an `age` property to each phone
record. This property is used to order phones by age.

* We added a line to the controller that sets the default value of `orderProp` to `age`. If we had
not set the default value here, angular would have used the value of the first `<option>` element
(`'name'`) when it initialized the data model.




## Test

The changes we made should be verified with both a unit test and an end-to-end test. Let's look at
the unit test first.

__`test/unit/controllerSpec.js`:__
<pre>
/* jasmine specs for controllers go here */
describe('PhoneCat controllers', function() {

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

    beforeEach(function() {
      ctrl = new PhoneListCtrl();
    });


    it('should create "phones" model with 3 phones', function() {
      expect(ctrl.phones.length).toBe(3);
    });


    it('should set the default value of orderProp model', function() {
      expect(ctrl.orderProp).toBe('age');
    });
  });
});
</pre>


The unit test now verifies that the default ordering property is set.

We used Jasmine's API to extract the controller construction into a `beforeEach` block, which is
shared by all tests in the nearest `describe` block.

To run the unit tests, once again 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)


Let's turn our attention to the end-to-end test.

__`test/e2e/scenarios.js`:__
<pre>
...
    it('should be possible to control phone order via the drop down select box', function() {
      input('query').enter('tablet'); //let's narrow the dataset to make the test assertions
      shorter

      expect(repeater('.phones li', 'Phone List').column('a')).
          toEqual(["Motorola XOOM\u2122 with Wi-Fi",
                   "MOTOROLA XOOM\u2122"]);

      select('orderProp').option('alphabetical');

      expect(repeater('.phones li', 'Phone List').column('a')).
          toEqual(["MOTOROLA XOOM\u2122",
                   "Motorola XOOM\u2122 with Wi-Fi"]);
    });
...
</pre>

The end-to-end test verifies that the ordering mechanism of the select box is working correctly.

You can now refresh the browser tab with the end-to-end test runner to see the tests run, or you
can see them running on {@link
http://angular.github.com/angular-phonecat/step-4/test/e2e/runner.html
angular's server}.

Now that you have added list sorting and tested the app, go to Step 5 to learn about angular
services and how angular uses dependency injection.


<table id="tutorial_nav">
<tr>
<td id="previous_step">{@link tutorial.step_03 Previous}</td>
<td id="step_result">{@link  http://angular.github.com/angular-phonecat/step-4/app Live Demo}</td>
<td id="tut_home">{@link tutorial Tutorial Home}</td>
<td id="code_diff">{@link https://github.com/angular/angular-phonecat/compare/step-3...step-4 Code
Diff}</td>
<td id="next_step">{@link tutorial.step_05 Next}</td>
</tr>
</table>