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docs(devguide): Dart displaying-data chapter

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.l-main-section
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')
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-main-section
h2#section-create-an-entry-point Create an entry point
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
<display></display>
pre.prettyprint.linenums.lang-html
code.
//TypeScript
<display></display>
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.
p Open your favorite editor and create a <code>show-properties.html</code> file with the content:
pre.prettyprint.lang-html
code.
//show-properties.html
&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>.
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:
p To see this working, create another file, <code>show-properties.dart</code>, and add the following:
pre.prettyprint.linenums.lang-javascript
code.
// ES5
function DisplayComponent() {
this.myName = "Alice";
pre.prettyprint.linenums.lang-javascript
code.
// Dart
part of displaying_data;
@Component(
selector: 'display'
)
@View(
template: '''
&lt;p&gt;My name: {{ myName }}&lt;/p&gt;
'''
)
class DisplayComponent {
String 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';
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;
@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;;
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.
constructor() {
this.myName = "Alice";
}
}
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.
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;
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.
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 So you can see Angular dynamically update content, add a line after
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: `
pre.prettyprint.lang-html
code.
&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:
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-dart
code.
class DisplayComponent {
String myName = 'Alice';
String time;
Timer _timer;
DisplayComponent() {
_updateTime(null);
_timer = new Timer.periodic(new Duration(seconds: 1), _updateTime);
}
_updateTime(Timer _) {
time = new DateTime.now().toString();
}
}
p Reload the page in your browser and you'll now see the seconds updating automatically.
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]
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-dart
code.
class DisplayComponent {
String myName = 'Alice';
List&lt;String&gt; friendNames = ['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-dart
code.
//Dart
template: &#39;&#39;&#39;
&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 friendNames&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 to <code>show_properties.dart</code> so that Angular knows to include it:
pre.prettyprint.lang-dart
code.
directives: const[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.
&lt;li *for=&quot;#name of friendNames&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 friendNames</code> : the iterable to use is called 'friendNames' in the current controller
p Using this syntax, you can build UI lists from any iterable object.
.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"];
}
}
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. We'll put this in a new
<code>friends_service.dart</code> under <code>web/</code>, and add <code>part friends_service.dart</code>
to <code>main.dart</code>. Here's what the class looks like:
pre.prettyprint.lang-dart
code.
part of displaying_data;
class FriendsService {
List&lt;String&gt; friendNames = ['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-dart
code.
DisplayComponent(FriendsService friendsService) {
friendNames = friendsService.names;
}
p And then make FriendsService available to dependency injection
pre.prettyprint.lang-dart
code.
part of displaying_data;
@Component(
selector: 'display',
injectables: const[FriendsService]
)
@View(
template: &#39;&#39;&#39;
&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 friendNames&quot;&gt;
{{ name }}
&lt;/li&gt;
&lt;/ul&gt;
''',
directives: const[For]
)
class DisplayComponent {
String myName = 'Alice';
List&lt;String&gt; friendNames;
DisplayComponent(FriendsService friendsService) {
friendNames = friendsService.names;
}
}
.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.
pre.prettyprint.lang-dart
code.
directives: const[For, If]
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.
p Here's our final <code>show_properties.dart</code>
pre.prettyprint.lang-dart
code.
part of displaying_data;
@Component(
selector: 'display',
injectables: const[FriendsService]
)
@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 friendNames&quot;&gt;
{{ name }}
&lt;/li&gt;
&lt;/ul&gt;
&lt;p *if=&quot;friendNames.length &gt; 3&quot;&gt;You have many friends!&lt;/p&gt;
''',
directives: const[For, If]
)
class DisplayComponent {
String myName = 'Alice';
List&lt;String&gt; friendNames;
DisplayComponent(FriendsService friendsService) {
friendNames = friendsService.names;
}
}
p And the accompanying <code>main.dart</code>:
pre.prettyprint.lang-dart
code.
library displaying_data;
import 'dart:async';
import 'package:angular2/angular2.dart';
import 'package:angular2/src/reflection/reflection.dart' show reflector;
import 'package:angular2/src/reflection/reflection_capabilities.dart' show ReflectionCapabilities;
part 'show_properties.dart';
part 'friends_service.dart';
main() {
reflector.reflectionCapabilities = new ReflectionCapabilities();
bootstrap(DisplayComponent);
}

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@ -30,7 +30,7 @@
.l-main-section
h2#section-create-an-entry-point Create an entry point
p.
In the <code>web/</code> directory for you app, create an <code>index.html</code> file and add the Angular library
In the <code>web/</code> directory for your app, create an <code>index.html</code> file and add the Angular library
tags and a <code>main.dart</code> file where you'll build your first component.
p.