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198 lines
6.3 KiB
Text
198 lines
6.3 KiB
Text
@ngdoc overview
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@name Tutorial: 4 - Two-way Data Binding
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@description
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<ul doc:tutorial-nav="4"></ul>
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In this step, you will add a feature to let your users control the order of the items in the phone
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list. The dynamic ordering is implemented by creating a new model property, wiring it together with
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the repeater, and letting the data binding magic do the rest of the work.
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<doc:tutorial-instructions step="4"></doc:tutorial-instructions>
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You should see that in addition to the search box, the app displays a drop down menu that allows
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users to control the order in which the phones are listed.
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The most important differences between Steps 3 and 4 are listed below. You can see the full diff on
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{@link https://github.com/angular/angular-phonecat/compare/step-3...step-4 GitHub}:
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## Template
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__`app/index.html`:__
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<pre>
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...
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<ul class="controls">
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<li>
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Search: <input type="text" name="query"/>
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</li>
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<li>
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Sort by:
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<select name="orderProp">
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<option value="name">Alphabetical</option>
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<option value="age">Newest</option>
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</select>
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</li>
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</ul>
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<ul class="phones">
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<li ng:repeat="phone in phones.$filter(query).$orderBy(orderProp)">
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{{phone.name}}
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<p>{{phone.snippet}}</p>
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</li>
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</ul>
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...
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</pre>
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We made the following changes to the `index.html` template:
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* First, we added a `<select>` html element named `orderProp`, so that our users can pick from the
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two provided sorting options.
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<img src="img/tutorial/tutorial_04-06_final.png">
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* We then chained the `$filter` method with {@link api/angular.Array.orderBy `$orderBy`} method to
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further process the input into the repeater. `$orderBy` is a utility method similar to {@link
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api/angular.Array.filter `$filter`}, but instead of filtering an array, it reorders it.
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Angular creates a two way data-binding between the select element and the `orderProp` model.
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`orderProp` is then used as the input for the `$orderBy` method.
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As we discussed in the section about data-binding and the repeater in step 3, whenever the model
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changes (for example because a user changes the order with the select drop down menu), Angular's
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data-binding will cause the view to automatically update. No bloated DOM manipulation code is
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necessary!
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## Controller
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__`app/js/controller.js`:__
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<pre>
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/* App Controllers */
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function PhoneListCtrl() {
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this.phones = [{"name": "Nexus S",
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"snippet": "Fast just got faster with Nexus S.",
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"age": 0},
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{"name": "Motorola XOOM™ with Wi-Fi",
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"snippet": "The Next, Next Generation tablet.",
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"age": 1},
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{"name": "MOTOROLA XOOM™",
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"snippet": "The Next, Next Generation tablet.",
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"age": 2}];
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this.orderProp = 'age';
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}
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</pre>
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* We modified the `phones` model - the array of phones - and added an `age` property to each phone
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record. This property is used to order phones by age.
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* We added a line to the controller that sets the default value of `orderProp` to `age`. If we had
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not set the default value here, angular would have used the value of the first `<option>` element
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(`'name'`) when it initialized the data model.
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This is a good time to talk about two-way data-binding. Notice that when the app is loaded in the
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browser, "Newest" is selected in the drop down menu. This is because we set `orderProp` to `'age'`
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in the controller. So the binding works in the direction from our model to the UI. Now if you
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select "Alphabetically" in the drop down menu, the model will be updated as well and the phones
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will be reordered. That is the data-binding doing its job in the opposite direction — from the UI
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to the model.
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## Test
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The changes we made should be verified with both a unit test and an end-to-end test. Let's look at
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the unit test first.
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__`test/unit/controllerSpec.js`:__
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<pre>
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describe('PhoneCat controllers', function() {
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describe('PhoneListCtrl', function(){
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var scope, $browser, ctrl;
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beforeEach(function() {
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ctrl = new PhoneListCtrl();
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});
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it('should create "phones" model with 3 phones', function() {
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expect(ctrl.phones.length).toBe(3);
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});
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it('should set the default value of orderProp model', function() {
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expect(ctrl.orderProp).toBe('age');
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});
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});
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});
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</pre>
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The unit test now verifies that the default ordering property is set.
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We used Jasmine's API to extract the controller construction into a `beforeEach` block, which is
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shared by all tests in the parent `describe` block.
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To run the unit tests, once again execute the `./scripts/test.sh` script and you should see the
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following output.
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Chrome: Runner reset.
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..
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Total 2 tests (Passed: 2; Fails: 0; Errors: 0) (3.00 ms)
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Chrome 11.0.696.57 Mac OS: Run 2 tests (Passed: 2; Fails: 0; Errors 0) (3.00 ms)
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Let's turn our attention to the end-to-end test.
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__`test/e2e/scenarios.js`:__
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<pre>
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...
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it('should be possible to control phone order via the drop down select box',
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function() {
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// narrow the dataset to make the test assertions shorter
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input('query').enter('tablet');
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expect(repeater('.phones li', 'Phone List').column('a')).
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toEqual(["Motorola XOOM\u2122 with Wi-Fi",
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"MOTOROLA XOOM\u2122"]);
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select('orderProp').option('alphabetical');
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expect(repeater('.phones li', 'Phone List').column('a')).
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toEqual(["MOTOROLA XOOM\u2122",
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"Motorola XOOM\u2122 with Wi-Fi"]);
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});
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...
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</pre>
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The end-to-end test verifies that the ordering mechanism of the select box is working correctly.
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You can now refresh the browser tab with the end-to-end test runner to see the tests run, or you
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can see them running on {@link
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http://angular.github.com/angular-phonecat/step-4/test/e2e/runner.html
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Angular's server}.
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# Experiments
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* In the `PhoneListCtrl` controller, remove the statement that sets the `orderProp` value and
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you'll see that the ordering as well as the current selection in the dropdown menu will default to
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"Alphabetical".
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* Add an `{{orderProp}}` binding into the `index.html` template to display its current value as
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text.
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# Summary
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Now that you have added list sorting and tested the app, go to {@link step_05 step 5} to learn
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about Angular services and how Angular uses dependency injection.
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<ul doc:tutorial-nav="4"></ul>
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