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Update guide chapter 2: displaying data

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Kathy Walrath 2015-04-22 16:00:37 -07:00
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public/docs/dart/latest/guide/displaying-data.jade
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@ -1,75 +1,117 @@
.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.
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
Let's walk through how to display a property and a list of properties,
and then to conditionally show content
based on state.
p.
We'll end up with a UI that looks like this:
The final UI looks like this:
figure.image-display
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 entry points and pubspec
p Open your favorite editor and create a <code>show-properties.html</code> file with the content:
pre.prettyprint.lang-html
p.
Open your favorite editor and create a directory with
a <code>web/main.dart</code> file,
a <code>web/index.html</code> file, and
a <code>pubspec.yaml</code> file:
.code-box
pre.prettyprint.lang-dart(data-name="dart")
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.
// web/main.dart
library displaying_data;
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';
main() {
reflector.reflectionCapabilities = new ReflectionCapabilities();
bootstrap(DisplayComponent);
}
pre.prettyprint.lang-html(data-name="html")
code.
&lt;!-- web/index.html --&gt;
&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;
&lt;link rel=&quot;stylesheet&quot; href=&quot;style.css&quot;&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;display&gt;&lt;/display&gt;
&lt;script type=&quot;application/dart&quot; src=&quot;main.dart&quot;&gt;&lt;/script&gt;
&lt;script src=&quot;packages/browser/dart.js&quot;&gt;&lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;
pre.prettyprint.lang-yaml(data-name="yaml")
code.
# pubspec.yaml
name: displaying_data
description: Dart version of Angular 2 example, Displaying Data
version: 0.0.1
dependencies:
angular2: 2.0.0-alpha.20
browser: any
p.
All of this code should look familiar from the previous page,
except for the <code>library</code> and <code>part</code> statements
in <code>main.dart</code>.
Those statements let you implement part of the app in a different Dart file.
All three of these files remain similar in the rest of the examples,
so we'll just focus on what's 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.dart</code>, and add the following:
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';
}
p.
The simple method for binding text into templates is through interpolation,
where you put the name of a property
inside <strong>{{ }}</strong>.
p.
You've just defined a component that encompases a view and controller for the app. The view
defines a template:
To see this working, create a Dart file under <code>web</code>
named <code>show_properties.dart</code>,
and add the following:
pre.prettyprint.lang-dart
code.
// web/show_properties.dart
part of displaying_data;
@Component(
selector: 'display'
)
@View(
template: '''
&lt;p>My name: {{ myName }}&lt/p>
'''
)
class DisplayComponent {
String myName = 'Alice';
}
p.
You've just defined a component that encompasses 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;
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.
Angular will automatically pull the value of <code>myName</code> and
insert it into the browser,
automatically updating it whenever it changes.
.callout.is-helpful
header Note
@ -77,18 +119,34 @@
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>.
One thing to notice is that although you've written
your <code>DisplayComponent</code> class, you haven't
used <code>new</code> to instantiate it.
Because your class is associated with <code>&lt;display&gt;</code> elements in
the DOM, Angular automatically calls <code>new</code> 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 <code>DisplayComponent</code>, which has
just one property, <code>myName</code>.
p.
Add a second line to the template,
so you can see Angular dynamically update content:
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.
@ -107,43 +165,50 @@
}
}
p Reload the page in your browser and you'll now see the seconds updating automatically.
p Reload the app, 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.
h2#Create-an-array Display an iterable using *for
p Moving up from a single value, create a property that's a list of values.
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.
You can then use this list in your template with the <code>for</code> directive to create copies of DOM elements
with one for each item in the list.
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;
@View(
template: '''
&lt;p>My name: {{ myName }}&lt;/p>
&lt;p>Friends:&lt;/p>
&lt;ul>
&lt;li *for="#name of friendNames">
{{ name }}
&lt;/li&gt;
&lt;/ul&gt;
''',
&lt;/li>
&lt;/ul>
'''
)
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:
To make this work, you'll also need to add the Angular <code>For</code> directive used by
the template to <code>show_properties.dart</code>, so that Angular knows to include it.
Add <code>For</code> using the optional <code>directives</code> parameter,
which contains a list of directives:
pre.prettyprint.lang-dart
code.
directives: const[For]
@View(
template: '''
// ...HTML...
''',
directives: const[For]
)
p Reload and you've got your list of friends!
p.
@ -162,47 +227,101 @@
p The way to read this is:
ul
li.
<code>*for</code> : create a DOM element for each item in an
<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
such as a list.
li <code>#name</code>: Refer to individual values of the iterable as <code>name</code>.
li <code>of friendNames</code>: The iterable to use is called <code>friendNames</code> 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
h2#Create-a-class Create a model and inject it
p.
Before we get too much further, we should mention that putting our model (array) directly in our controller isn't
Before we get too much further, we should mention that putting the model (list) directly into the 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:
Make a <code>FriendsService</code> class to implement a model containing a list of friends. We'll put this in a new
<code>friends_service.dart</code> under <code>web/</code>. Here's what the class looks like:
pre.prettyprint.lang-dart
code.
// web/friends_service.dart
part of displaying_data;
class FriendsService {
List&lt;String&gt; friendNames = ['Aarav', 'Martín', 'Shannon', 'Ariana', 'Kai'];
}
.callout.is-helpful
header Note
p.
Remember to tie <code>friends_service.dart</code> into the library's main file:
add <code>part friends_service.dart</code> to <code>main.dart</code>.
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.
Now you can replace the current list of friends in DisplayComponent.
First add a FriendsService parameter to the constructor.
Then set <code>friendNames</code> to the names provided by the service.
pre.prettyprint.lang-dart
code.
DisplayComponent(FriendsService friendsService) {
friendNames = friendsService.names;
// In web/show_properties.dart
class DisplayComponent {
String myName = 'Alice';
List<String> friendNames;
DisplayComponent(FriendsService friendsService) {
friendNames = friendsService.names;
}
}
p And then make FriendsService available to dependency injection
p.
Next, make FriendsService available to dependency injection
by adding an <code>injectables</code> parameter to DisplayComponent's
<code>@Component</code> annotation:
pre.prettyprint.lang-dart
code.
@Component(
selector: 'display',
injectables: const[FriendsService]
)
.l-main-section
h2#Conditionally-displaying-data-with-If Conditionally display data using *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.
Also add <code>If</code> to the list of directives,
so Angular knows to include it:
pre.prettyprint.lang-dart
code.
directives: const[For, If]
p.
The list current has 5 items, so if you run the app 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.
<!-- PENDING: mention somewhere that once you start a web server,
you can just refresh the browser to see your changes. -->
p Here's the final code.
.code-box
pre.prettyprint.lang-dart(data-name="show_properties.dart")
code.
// web/show_properties.dart
part of displaying_data;
@Component(
@ -210,95 +329,120 @@
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;
template: '''
&lt;p>My name: {{ myName }}&lt;/p>
&lt;p>Friends:&lt;/p>
&lt;ul>
&lt;li *for="#name of friendNames">
{{ name }}
&lt;/li>
&lt;/ul>
''',
directives: const[For]
)
class DisplayComponent {
String myName = 'Alice';
List&lt;String&gt; friendNames;
List&lt;String> 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
pre.prettyprint.lang-dart(data-name="friends_service.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.
// web/friends_service.dart
part of displaying_data;
p Here's our final <code>show_properties.dart</code>
class FriendsService {
List&lt;String> names = ['Aarav', 'Martín', 'Shannon', 'Ariana', 'Kai'];
}
pre.prettyprint.lang-dart(data-name="main.dart")
code.
// web/main.dart
library displaying_data;
pre.prettyprint.lang-dart
code.
part of displaying_data;
import 'dart:async';
@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;
}
}
import 'package:angular2/angular2.dart';
import 'package:angular2/src/reflection/reflection.dart' show reflector;
import 'package:angular2/src/reflection/reflection_capabilities.dart' show ReflectionCapabilities;
p And the accompanying <code>main.dart</code>:
part 'show_properties.dart';
part 'friends_service.dart';
pre.prettyprint.lang-dart
code.
library displaying_data;
main() {
reflector.reflectionCapabilities = new ReflectionCapabilities();
bootstrap(DisplayComponent);
}
pre.prettyprint.lang-html(data-name="html")
code.
&lt;!-- web/index.html --&gt;
&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;
&lt;link rel=&quot;stylesheet&quot; href=&quot;style.css&quot;&gt;
&lt;/head&gt;
&lt;body&gt;
import 'dart:async';
&lt;display&gt;&lt;/display&gt;
import 'package:angular2/angular2.dart';
import 'package:angular2/src/reflection/reflection.dart' show reflector;
import 'package:angular2/src/reflection/reflection_capabilities.dart' show ReflectionCapabilities;
&lt;script type=&quot;application/dart&quot; src=&quot;main.dart&quot;&gt;&lt;/script&gt;
&lt;script src=&quot;packages/browser/dart.js&quot;&gt;&lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;
pre.prettyprint.lang-yaml(data-name="yaml")
code.
# pubspec.yaml
name: displaying_data
description: Dart version of Angular 2 example, Displaying Data
version: 0.0.1
dependencies:
angular2: 2.0.0-alpha.20
browser: any
.l-main-section
h2#section-explanations Explanations
part 'show_properties.dart';
part 'friends_service.dart';
.l-sub-section
h3 Using multiple Dart files in an Angular app
main() {
reflector.reflectionCapabilities = new ReflectionCapabilities();
bootstrap(DisplayComponent);
}
p.
Dart offers a few ways to implement an app in multiple files.
In this guide, all the code for each example is in a single library;
each Dart file under <code>web</code> is part of that library.
p.
To let the code in <code>main.dart</code>
use the code in <code>show_properties.dart</code>,
declare a library in <code>main.dart</code>.
Then make <code>show_properties.dart</code> part of that library.
.code-box
pre.prettyprint.lang-dart(data-name="main library file")
code.
// web/main.dart
library displaying_data;
// imports...
part 'show_properties.dart';
// Code goes here...
pre.prettyprint.lang-dart(data-name="additional library file")
code.
// web/show_properties.dart
part of displaying_data;
// Code goes here...
p.
Another way to split Dart code is to
define multiple libraries in a single package.
The additional libraries go under a <code>lib</code> directory
parallel to <code>web</code>.
<!-- PENDING: show or point to an example -->
p.
Yet another approach, often used when some of the code is highly reusable,
is to split the code into libraries in two or more packages.
p.
For more information on implementing Dart libraries, see
<a href="https://www.dartlang.org/docs/dart-up-and-running/ch02.html#libraries-and-visibility">Libraries and visibility</a>
in the
<a href="https://www.dartlang.org/docs/dart-up-and-running/ch02.html">Dart language tour</a>.