angular-docs-cn/public/docs/js/latest/guide/displaying-data.jade

.l-main-section
    p.
      <strong>Mission:</strong> By the end of this chapter, you should be able to display data from both properties and
      lists from a component’s controller to the view.
    p.
        Displaying data is job number one for any good application.  In Angular, you bind data to elements in HTML
        templates and Angular automatically updates the UI as data changes.
    p.
        Let's walk through how we'd display a property, a list of properties, and then conditionally show content
        based on state.
    p.
        We'll end up with a UI that looks like this:
    div(align='center')
        img(src='displaying-data-example1.png')

    .l-sub-section
        h3#section-examples Examples:
        ul
         li
            a(href='http://plnkr.co/edit/pQojSb3CTfTEejX0wGjO?p=preview') TypeScript
         li
            a(href='http://plnkr.co/edit/GOJiWOEem9jrOyEeY3uW?p=preview') ES5

.l-main-section
    h2#section-create-an-entry-point Create an entry point

    p Open your favorite editor and create a show-properties.html file with the content:
    pre.prettyprint.linenums.lang-html
        code.
           //ES5
           &lt;display&gt;&lt;/display&gt;

    pre.prettyprint.linenums.lang-html
        code.
          //TypeScript
          &lt;display&gt;&lt;/display&gt;

    p
     | The <code>&lt;display&gt;</code> component here acts as the site where you'll insert your application.
     | We'll assume a structure like this for the rest of the examples here and just focus on the parts that
     | are different.

.l-main-section
    h2#section-showing-properties-with-interpolation Showing properties with interpolation
    p.text-body
     | The simple method for binding text into templates is through interpolation where you put the name of a property
     | inside <strong>{{ }}</strong>.

    p To see this working, create another file, <code>show-properties.js</code>, and add the following:

    pre.prettyprint.linenums.lang-javascript
        code.
          // ES5
          function DisplayComponent() {
            this.myName = "Alice";
          }
          DisplayComponent.annotations = [
            new angular.Component({
              selector: "display"
            }),
            new angular.View({
              template:
                 '&lt;p&gt;My name: {{ myName }}&lt;/p&gt;',
              directives: [angular.For, angular.If]
            })
          ];

    pre.prettyprint.linenums.lang-typescript
        code.
            // TypeScript
            import {Component, View, bootstrap, For} from 'angular2/angular2';

            @Component({
             selector: 'display'
            })
            @View({
              template: `
               &lt;p&gt;My name: {{ myName }}&lt;/p&gt
             `,
             directives: [For]
            })
            class DisplayComponent {
             myName: string;
             todos: Array&lt;string&gt;;

             constructor() {
               this.myName = "Alice";
             }
            }
    p.
     You've just defined a component that encompases a view and controller for the app. The view
     defines a template:
    pre.prettyprint.lang-html
     code.
       &lt;p&gt;My name: {{ myName }}&lt;/p&gt;

    p.
     Angular will automatically pull the value of <code>myName</code> and insert it into the browser and
     update it whenever it changes without work on your part.

    p.
     One thing to notice here is that though you've written your <code>DisplayComponent</code> class, you haven't
     called new to create one anywhere.  By associating your class with elements named 'display' in
     the DOM, Angular knows to automatically call new on <code>DisplayComponent</code> and bind its properties to
     that part of the template.

    p.
     When you're building templates, data bindings like these have access to the same scope of
     properties as your controller class does.  Here, your class is the <code>DisplayComponent</code> that has
     just one property, myName.

    .callout.is-helpful
        header Note
        p.
              While you've used <code>template:</code> to specify an inline view, for larger templates you'd
              want to move them to a separate file and load them with <code>templateUrl:</code> instead.

    p So you can see Angular dynamically update content, add a line after

        pre.prettyprint.lang-html
            code.
                &lt;p&gt;My name: {{ myName }}&lt;/p&gt;
    p to this:
        pre.prettyprint.lang-html
            code.
                &lt;p&gt;Current time: {{ time }}&lt;/p&gt;
    p.
        Then give the <code>DisplayComponent</code> a starting value for time and a call to update time
        via <code>setInterval</code>.

    pre.prettyprint.lang-javascript
        code.
            setInterval(function () { this.time = (new Date()).toString(); }.bind(this), 1000);
    p Reload the page in your browser and you'll now see the seconds updating automatically.
.l-main-section
    h2#Create-an-array Create an array property and use For on the view
    p Moving up from a single property, create an array to display as a list.
    pre.prettyprint.lang-javascript
        code.
            //ES5
            function DisplayComponent() {
              this.myName = "Alice";
              this.names = ["Aarav", "Martín", "Shannon", "Ariana", "Kai"];
            }
    pre.prettyprint.lang-typescript
        code.
            //Typescript
            constructor() {
              this.myName = "Alice";
              this.names = ["Aarav", "Martín", "Shannon", "Ariana", "Kai"];
            }
    p.
        You can then use this array in your template with the <code>for</code> directive to create copies of DOM elements
        with one for each item in the array.
    pre.prettyprint.lang-javascript
        code.
            //ES5
            template:
               &#39;&lt;p&gt;My name: {{ myName }}&lt;/p&gt;&#39; +
               &#39;&lt;p&gt;Friends:&lt;/p&gt;&#39; +
               &#39;&lt;ul&gt;&#39; +
               &#39;&lt;li *for=&quot;#name of names&quot;&gt;&#39; +
               &#39;{{ name }}&#39; +
               &#39;&lt;/li&gt;&#39; +
               &#39;&lt;/ul&gt;&#39;,

    pre.prettyprint.lang-typescript
        code.
            //Typescript
            template: `
              &lt;p&gt;My name: {{ myName }}&lt;/p&gt;
              &lt;p&gt;Friends:&lt;/p&gt;
              &lt;ul&gt;
                 &lt;li *for=&quot;#name of names&quot;&gt;
                    {{ name }}
                 &lt;/li&gt;
              &lt;/ul&gt;
            `,
    p.
        To make this work, you'll also need to add the <code>angular.For</code> directive used by the template so
        that Angular knows to include it:

    pre.prettyprint.lang-javascript
        code.
            //ES5
            directives: [angular.For]
    pre.prettyprint.lang-typescript
        code.
            //Typescript
            import {Component, View, bootstrap, For} from
            ...
              directives: [For]
    p Reload and you've got your list of friends!
    p.
        Again, Angular will mirror changes you make to this list over in the DOM. Add a new item and it appears in your
        list. Delete one and Angular deletes the &lt;li&gt;. Reorder items and Angular makes the corresponding reorder of
        the DOM list.
    p Let's look at the few lines that do the work again:
    pre.prettyprint.lang-html
        code.
            //HTML
            &lt;li *for=&quot;#name of names&quot;&gt;
               {{ name }}
            &lt;/li&gt;
    p The way to read this is:
    ul
        li.
            <code>*for</code> : create a DOM element for each item in an
            <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">iterable</a>
             like an array
        li <code>#name</code> : refer to individual values of the iterable as 'name'
        li <code>of names</code> : the iterable to use is called 'names' in the current controller
    p Using this syntax, you can build UI lists from any iterable object.
.l-main-section
    h2#Create-a-class Create a class for the array property and inject into component
    p.
        Before we get too much further, we should mention that putting our model (array) directly in our controller isn't
        proper form.  We should separate the concerns by having another class serve the role of model and inject it into
        the controller.
    p Make a <code>FriendsService</code> class to provide the model with the list of friends.
    pre.prettyprint.lang-javascript
        code.
            function FriendsService() {
              this.names = ["Alice", "Aarav", "Martín", "Shannon", "Ariana", "Kai"];
            }
    p.
        Replace the current list of friends in DisplayComponent by passing in the FriendsService and setting the list of
        names in DisplayComponent to the names provided by the service you passed in.
    pre.prettyprint.lang-javascript
        code.
            function DisplayComponent(friends) {
              this.myName = "Alice";
              this.names = friends.names;
            }
    p And then make FriendsService available to dependency injection
    pre.prettyprint.lang-javascript
        code.
            DisplayComponent.annotations = [
              new angular.Component({
                selector: "display",
                injectables: [FriendsService]
              }),
            ...
            DisplayComponent.parameters = [[FriendsService]];
    .callout.is-helpful
        header ES5 Note
        p.
            The dependency injection syntax here is using the low-level API and is...well...not very nice.  We're
            working on sugaring the syntax to match the way it works in Angular 1.  Expect this to change soon.
    pre.prettyprint.lang-javascript
        code.
            //ES5
            function FriendsService() {
              this.names = ["Alice", "Aarav", "Martín", "Shannon", "Ariana", "Kai"];
            }
            function DisplayComponent(friends) {
              this.myName = "Alice";
              this.names = friends.names;
            }
            DisplayComponent.annotations = [
              new angular.Component({
                selector: "display",
                injectables: [FriendsService]
                        }),
              new angular.View({
                template: '{{ myName }} &lt;ul&gt; &lt;li *for="#name of names"&lt;{{ name }}&gt;/li&lt; &gt;/ul&lt;',
                directives: [angular.For, angular.If]
              })
            ];
            DisplayComponent.parameters = [[FriendsService]];
            document.addEventListener("DOMContentLoaded", function() {
              angular.bootstrap(DisplayComponent);
            });
    pre.prettyprint.lang-typescript
        code.
            //TypeScript
            import {Component, View, bootstrap, For} from
            ...
              directives: [For]
.l-main-section
    h2#Conditionally-displaying-data-with-If Conditionally displaying data with If
    p.
        Lastly, before we move on, let's handle showing parts of our UI conditionally with <code>If</code>.  The
        <code>If</code> directive adds or removes elements from the DOM based on the expression you provide.
    p See it in action by adding a paragraph at the end of your template
    pre.prettyprint.lang-html
        code.
            &lt;p *if=&quot;names.length &gt; 3&quot;&gt;You have many friends!&lt;/p&gt;
    p You'll also need to add the If directive so Angular knows to include it.
    p [TODO: CODE]
    p.
        As there are currently 5 items it the list, you'll see the message congratulating you on your many friends.
        Remove two items from the list, reload your browser, and see that the message no longer displays.
    pre.prettyprint.lang-javascript
        code.
            //ES5
            function DisplayComponent() {
              this.myName = "Alice";
              this.names = ["Aarav", "Martín", "Shannon", "Ariana", "Kai"];
            }
            DisplayComponent.annotations = [
              new angular.Component({
                selector: "display"
              }),
            new angular.View({
              template:
                &#39;&lt;p&gt;My name: {{ myName }}&lt;/p&gt;&#39; +
                &#39;&lt;p&gt;Friends:&lt;/p&gt;&#39; +
                &#39;&lt;ul&gt;&#39; +
                &#39;&lt;li *for=&quot;#name of names&quot;&gt;&#39; +
                &#39;{{ name }}&#39; +
                &#39;&lt;/li&gt;&#39; +
                &#39;&lt;/ul&gt;&#39; +
                &#39;&lt;p *if=&quot;names.length &gt; 3&quot;&gt;You have many friends!&lt;/p&gt;&#39;,
              directives: [angular.For, angular.If]
            })
            ];
    pre.prettyprint.lang-typescript
        code.
            //TypeScript
            import {Component, View, bootstrap, For, If} from 'angular2/angular2';
                      @Component({
              selector: 'display'
            })
            @View({
              template: `
                &lt;p&gt;My name: {{ myName }}&lt;/p&gt;
                &lt;p&gt;Friends:&lt;/p&gt;
                &lt;ul&gt;
                  &lt;li *for=&quot;#name of names&quot;&gt;
                    {{ name }}
                  &lt;/li&gt;
                &lt;/ul&gt;
                &lt;p *if=&quot;names.length &gt; 3&quot;&gt;You have many friends!&lt;/p&gt;
              `,
              directives: [For, If]
            })
            class DisplayComponent {
              myName: string;
              todos: Array<string>;
                        constructor() {
                this.myName = "Alice";
                this.names = ["Aarav", "Martín", "Shannon", "Ariana", "Kai"];
              }
            }