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docs(guide/displaying-data): proofread (#1819) 

* docs(displaying-data/dart): proofread

- Dart prose simplified by removing discussion of "additions to
pubspec.yaml" which are no longer necessary given the current state of
QuickStart.
- E2e suites passed:
  public/docs/_examples/displaying-data/dart
  public/docs/_examples/displaying-data/ts

Contributes to #1598 and #1508.

* docs(displaying-data/ts): proofread

- TS prose updated to include @kwalrath's revisions from a while ago,
with some of my edits as well.
- E2e suites passed:
  public/docs/_examples/displaying-data/dart
  public/docs/_examples/displaying-data/ts

* docs(displaying-data/ts): post-review edits
This commit is contained in:
Patrice Chalin 2016-07-07 14:00:19 -07:00 committed by Kathy Walrath
parent ff718f4211
commit 801ac76da0
17 changed files with 224 additions and 460 deletions
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40
public/docs/_examples/displaying-data/dart/lib/app_component.dart
View File

@ -3,30 +3,28 @@ import 'package:angular2/core.dart';
import 'hero.dart';
final List<Hero> _heroes = [
new Hero(1, 'Windstorm'),
new Hero(13, 'Bombasto'),
new Hero(15, 'Magneta'),
new Hero(20, 'Tornado')
];
@Component(
selector: 'my-app',
template: '''
<h1>{{title}}</h1>
<h2>My favorite hero is: {{myHero.name}}</h2>
<p>Heroes:</p>
<ul>
<li *ngFor="let hero of heroes">
{{ hero.name }}
</li>
</ul>
// #docregion message
<p *ngIf="heroes.length > 3">There are many heroes!</p>
// #enddocregion message
''')
<h1>{{title}}</h1>
<h2>My favorite hero is: {{myHero.name}}</h2>
<p>Heroes:</p>
<ul>
<li *ngFor="let hero of heroes">
{{ hero.name }}
</li>
</ul>
// #docregion message
<p *ngIf="heroes.length > 3">There are many heroes!</p>
// #enddocregion message
''')
class AppComponent {
String title = 'Tour of Heroes';
List<Hero> heroes = _heroes;
Hero myHero = _heroes[0];
List<Hero> heroes = [
new Hero(1, 'Windstorm'),
new Hero(13, 'Bombasto'),
new Hero(15, 'Magneta'),
new Hero(20, 'Tornado')
];
Hero get myHero => heroes.first;
}

9
public/docs/_examples/displaying-data/dart/lib/app_component_1.dart
View File

@ -3,11 +3,12 @@ import 'package:angular2/core.dart';
@Component(
selector: 'my-app',
// #docregion template
// #docregion template
template: '''
<h1>{{title}}</h1>
<h2>My favorite hero is: {{myHero}}</h2>'''
// #enddocregion template
<h1>{{title}}</h1>
<h2>My favorite hero is: {{myHero}}</h2>
'''
// #enddocregion template
)
class AppComponent {
String title = 'Tour of Heroes';

42
public/docs/_examples/displaying-data/dart/lib/app_component_2.dart
View File

@ -1,36 +1,26 @@
// #docregion
import 'package:angular2/core.dart';
// #docregion mock-heroes
const List<String> _heroes = const [
'Windstorm',
'Bombasto',
'Magneta',
'Tornado'
];
// #enddocregion mock-heroes
@Component(
selector: 'my-app',
// #docregion template
// #docregion template
template: '''
<h1>{{title}}</h1>
<h2>My favorite hero is: {{myHero}}</h2>
<p>Heroes:</p>
<ul>
// #docregion li-repeater
<li *ngFor="let hero of heroes">
{{ hero }}
</li>
// #enddocregion li-repeater
</ul>'''
// #enddocregion template
<h1>{{title}}</h1>
<h2>My favorite hero is: {{myHero}}</h2>
<p>Heroes:</p>
<ul>
// #docregion li
<li *ngFor="let hero of heroes">
{{ hero }}
</li>
// #enddocregion li
</ul>
'''
// #enddocregion template
)
// #docregion mock-heroes
// #docregion class
class AppComponent {
String title = 'Tour of Heroes';
List<String> heroes = _heroes;
String myHero = _heroes[0];
List<String> heroes = ['Windstorm', 'Bombasto', 'Magneta', 'Tornado'];
String get myHero => heroes.first;
}
// #enddocregion mock-heroes
// #enddocregion

47
public/docs/_examples/displaying-data/dart/lib/app_component_3.dart
View File

@ -1,35 +1,34 @@
// #docregion
import 'package:angular2/core.dart';
// #docregion heroes
// #docregion import
import 'hero.dart';
final List<Hero> _heroes = [
new Hero(1, 'Windstorm'),
new Hero(13, 'Bombasto'),
new Hero(15, 'Magneta'),
new Hero(20, 'Tornado')
];
// #enddocregion heroes
// #enddocregion import
@Component(
selector: 'my-app',
// #docregion template
// #docregion template
template: '''
<h1>{{title}}</h1>
<h2>My favorite hero is: {{myHero.name}}</h2>
<p>Heroes:</p>
<ul>
<li *ngFor="let hero of heroes">
{{ hero.name }}
</li>
</ul>'''
// #enddocregion template
<h1>{{title}}</h1>
<h2>My favorite hero is: {{myHero.name}}</h2>
<p>Heroes:</p>
<ul>
<li *ngFor="let hero of heroes">
{{ hero.name }}
</li>
</ul>
'''
// #enddocregion template
)
// #docregion heroes
// #docregion class
class AppComponent {
String title = 'Tour of Heroes';
List<Hero> heroes = _heroes;
Hero myHero = _heroes[0];
// #docregion heroes
List<Hero> heroes = [
new Hero(1, 'Windstorm'),
new Hero(13, 'Bombasto'),
new Hero(15, 'Magneta'),
new Hero(20, 'Tornado')
];
Hero get myHero => heroes.first;
// #enddocregion heroes
}
// #enddocregion heroes
// #enddocregion

4
public/docs/_examples/displaying-data/dart/lib/hero.dart
View File

@ -1,9 +1,9 @@
// #docregion
class Hero {
int id;
final int id;
String name;
Hero(this.id, this.name);
String toString() => '$id: $name';
}
// #enddocregion

2
public/docs/_examples/displaying-data/dart/pubspec.yaml
View File

@ -1,6 +1,6 @@
# #docregion
name: displaying_data
description: Displaying Data Example
description: Displaying Data
version: 0.0.1
environment:
sdk: '>=1.13.0 <2.0.0'

7
public/docs/_examples/displaying-data/dart/web/index.html
View File

@ -3,13 +3,14 @@
<html>
<head>
<title>Displaying Data</title>
<link rel="stylesheet" href="styles.css">
<link rel="stylesheet" href="styles.css">
<script defer src="main.dart" type="application/dart"></script>
<script defer src="packages/browser/dart.js"></script>
</head>
<!-- #docregion body -->
<body>
<!-- #docregion my-app -->
<my-app>Loading...</my-app>
<!-- #enddocregion my-app -->
</body>
<!-- #enddocregion body -->
</html>

2
public/docs/_examples/displaying-data/dart/web/main.dart
View File

@ -9,7 +9,7 @@ import 'package:angular2/platform/browser.dart';
// #docregion final
import 'package:displaying_data/app_component.dart';
main() {
void main() {
// #enddocregion final
// pick one
// bootstrap(v1.AppComponent);

3
public/docs/_examples/displaying-data/ts/app/app-ctor.component.ts
View File

@ -7,7 +7,7 @@ import { Component } from '@angular/core';
<h2>My favorite hero is: {{myHero}}</h2>
`
})
// #docregion app-ctor
// #docregion class
export class AppCtorComponent {
title: string;
myHero: string;
@ -17,4 +17,3 @@ export class AppCtorComponent {
this.myHero = 'Windstorm';
}
}
// #enddocregion app-ctor

8
public/docs/_examples/displaying-data/ts/app/app.component.2.ts
View File

@ -9,20 +9,18 @@ import { Component } from '@angular/core';
<h2>My favorite hero is: {{myHero}}</h2>
<p>Heroes:</p>
<ul>
// #docregion li-repeater
// #docregion li
<li *ngFor="let hero of heroes">
{{ hero }}
</li>
// #enddocregion li-repeater
// #enddocregion li
</ul>
`
// #enddocregion template
})
// #docregion mock-heroes
// #docregion class
export class AppComponent {
title = 'Tour of Heroes';
heroes = ['Windstorm', 'Bombasto', 'Magneta', 'Tornado'];
myHero = this.heroes[0];
}
// #enddocregion mock-heroes
// #enddocregion

6
public/docs/_examples/displaying-data/ts/app/app.component.3.ts
View File

@ -1,8 +1,8 @@
// #docregion
import { Component } from '@angular/core';
// #docregion import-hero
// #docregion import
import { Hero } from './hero';
// #enddocregion import-hero
// #enddocregion import
@Component({
selector: 'my-app',
@ -32,5 +32,3 @@ export class AppComponent {
myHero = this.heroes[0];
// #enddocregion heroes
}
// #enddocregion class
// #enddocregion

6
public/docs/_examples/displaying-data/ts/app/app.component.ts
View File

@ -1,8 +1,6 @@
// #docplaster
// #docregion final
// #docregion imports
import { Component } from '@angular/core';
// #enddocregion imports
import { Hero } from './hero';
@Component({
@ -17,12 +15,10 @@ import { Hero } from './hero';
</li>
</ul>
// #docregion message
<p *ngIf="heroes.length
> 3">There are many heroes!</p>
<p *ngIf="heroes.length > 3">There are many heroes!</p>
// #enddocregion message
`
})
export class AppComponent {
title = 'Tour of Heroes';
heroes = [

4
public/docs/_examples/displaying-data/ts/app/hero.ts
View File

@ -1,9 +1,9 @@
// #docregion
export class Hero {
constructor(
// #docregion id-parameter
// #docregion id
public id: number,
// #enddocregion id-parameter
// #enddocregion id
public name: string) { }
}
// #enddocregion

4
public/docs/_examples/displaying-data/ts/index.html
View File

@ -19,10 +19,10 @@
</script>
</head>
<!-- #docregion my-app -->
<!-- #docregion body -->
<body>
<my-app>loading...</my-app>
</body>
<!-- #enddocregion my-app -->
<!-- #enddocregion body -->
</html>

4
public/docs/dart/latest/_quickstart_repo.jade Normal file
View File

@ -0,0 +1,4 @@
.l-sub-section
:marked
Alternatively, begin with a
[download of the QuickStart source](https://github.com/angular-examples/quickstart/archive/master.zip).

271
public/docs/dart/latest/guide/displaying-data.jade
View File

@ -1,257 +1,24 @@
include ../_util-fns
extends ../../../ts/latest/guide/displaying-data.jade
:marked
We typically display data in Angular by binding controls in an HTML template
to properties of an Angular component.
block includes
include ../_util-fns
- var _iterableUrl = 'https://api.dartlang.org/stable/dart-core/Iterable-class.html';
- var _boolean = 'boolean';
In this chapter, we'll create a component with a list of heroes. Each hero has a name.
We'll display the list of hero names and
conditionally show a selected hero in a detail area below the list.
block quickstart-repo
//- Must have this block so that Jade picks up the Dart include.
include ../_quickstart_repo
The final UI looks like this:
figure.image-display
img(src="/resources/images/devguide/displaying-data/final.png" alt="Final UI")
<a id="interpolation"></a>
.l-main-section
:marked
## Showing component properties with interpolation
The easiest way to display a component property
is to bind the property name through interpolation.
With interpolation, we put the property name in the view template, enclosed in double curly braces: `{{myHero}}`.
Let's build a small illustrative example together.
<a id="platform_directives"></a>
Create a new project folder (`displaying`) and create 3 files:
`pubspec.yaml`, `web/index.html`, and `web/main.dart`.
Put these contents in the files:
- var stylePattern = [{ otl: /(platform_directives.*$)/gm }, null, null];
+makeTabs('displaying-data/dart/pubspec.yaml, displaying-data/dart/web/index.html, displaying-data/dart/web/main.dart', ',,final', 'pubspec.yaml, web/index.html, web/main.dart', stylePattern)
:marked
All of this code should look familiar from the
[QuickStart](../quickstart.html),
except for the `platform_directives` entry in `pubspec.yaml`
and the imports in `main.dart`.
In `pubspec.yaml`, the `platform_directives` entry lets us use
core directives, such as the `ngFor` directive that we'll soon add to our app.
In `main.dart`, importing `app_component.dart` lets us implement part
of the app in a different Dart file. The QuickStart version of `main.dart`
imported `core.dart`, but we don't need that import here because
this version of `main.dart` is so basic: it only bootstraps the app,
and doesn't implement any components or other injectable types.
So that the code can run,
let's create a stub for the `<my-app>` component.
Create a new directory called `lib`.
In it, put a file called `app_component.dart`
with the following code:
+makeExample('displaying-data/dart/lib/app_component_1.dart', null, 'lib/app_component.dart')
:marked
We defined a component with two properties: `title` and `myHero`.
The template displays the two component properties using double curly brace
interpolation:
+makeExample('displaying-data/dart/lib/app_component_1.dart', 'template')(format=".")
:marked
Angular automatically pulls the value of the `title` and `myHero` properties from the component and
inserts those values into the browser. Angular updates the display
when these properties change.
.l-sub-section
block hero-class
:marked
More precisely, the redisplay occurs after some kind of asynchronous event related to
the view such as a keystroke, a timer completion, or an async `XHR` response.
We don't have those in this sample.
But then the properties aren't changing on their own either. For the moment we must operate on faith.
:marked
Notice that we haven't called **new** to create an instance of the `AppComponent` class.
Angular is creating an instance for us. How?
We've defined a class with a constructor, two properties (`id` and `name`),
and a `toString()` method.
Notice the CSS `selector` in the `@Component` decorator that specifies an element named "my-app".
Remember back in QuickStart that we added the `<my-app>` element to the body of our `index.html` file:
+makeExample('displaying-data/dart/web/index.html', 'my-app')(format=".")
:marked
When we bootstrap with the `AppComponent` class (in `main.dart`), Angular looks for a `<my-app>`
in the `index.html`, finds it, instantiates an instance of `AppComponent`, and renders it
inside the `<my-app>` tag.
Try running the app. It should display the title and hero name:
figure.image-display
img(src="/resources/images/devguide/displaying-data/title-and-hero.png" alt="Title and Hero")
// TODO: Here the TS version says "Let's review some of the choices we made and consider alternatives." However, it's unclear where this review ends. Clarify the structure in the TS, and make sure this is the best place for the Dart version of this section.
#performance.l-sub-section
:marked
### Template inline or template file?
We can store our component's template in one of two places.
We can define it *inline* using the `template` property, as we do here.
Or we can define the template in a separate HTML file and link to it in
the component metadata using the `@Component` decorator's `templateUrl` property.
The choice between inline and separate HTML is a matter of taste,
circumstances, and organization policy.
Here we're using inline HTML because the template is small, and the demo
is simpler without the additional HTML file.
In either style, the template data bindings have the same access to the component's properties.
<a id="ngFor"></a>
.l-main-section
:marked
## Showing a list property with ***ngFor**
We want to display a list of heroes. We begin by adding a list of hero names to the component and redefine `myHero` to be the first name in the list.
+makeExample('displaying-data/dart/lib/app_component_2.dart', 'mock-heroes', 'lib/app_component.dart (excerpt)')(format=".")
:marked
Now we use the Angular `ngFor` "repeater" directive in the template to display
each item in the `heroes` list.
+makeExample('displaying-data/dart/lib/app_component_2.dart', 'template','lib/app_component.dart (excerpt)')(format=".")
:marked
Our presentation is the familiar HTML unordered list with `<ul>` and `<li>` tags. Let's focus on the `<li>` tag.
+makeExample('displaying-data/dart/lib/app_component_2.dart', 'li-repeater')(format=".")
:marked
We added a somewhat mysterious `*ngFor` to the `<li>` element.
That's the Angular "repeater" directive.
Its presence on the `<li>` tag marks that `<li>` element (and its children) as the "repeater template".
.alert.is-important
:marked
Don't forget the leading asterisk (\*) in `*ngFor`. It is an essential part of the syntax.
Learn more about this and `ngFor` in the [Template Syntax](./template-syntax.html#ngFor) chapter.
:marked
Notice the `hero` in the `ngFor` double-quoted instruction;
it is an example of a [template input variable](./template-syntax.html#ngForMicrosyntax).
Angular duplicates the `<li>` for each item in the list, setting the `hero` variable
to the item (the hero) in the current iteration. Angular uses that variable as the
context for the interpolation in the double curly braces.
.l-sub-section
:marked
We happened to give `ngFor` a list to display.
In fact, `ngFor` can repeat items for any [Iterable](https://api.dartlang.org/stable/dart-core/Iterable-class.html) object.
:marked
Now the heroes appear in an unordered list.
figure.image-display
img(src="/resources/images/devguide/displaying-data/hero-names-list.png" alt="After ngfor")
.callout.is-important
header Did the app break?
:marked
If the app stops working after adding `*ngFor`,
make sure `pubspec.yaml` has the [correct **platform_directives** entry](#platform_directives).
A missing or incorrect `platform_directives` entry results in template parse errors.
.l-main-section
:marked
## Creating a class for the data
We are defining our data directly inside our component.
That's fine for a demo but certainly isn't a best practice. It's not even a good practice.
Although we won't do anything about that in this chapter, we'll make a mental note to fix this down the road.
At the moment, we're binding to a list of strings. We do that occasionally in real applications, but
most of the time we're binding to more specialized objects.
Let's turn our list of hero names into a list of `Hero` objects. For that we'll need a `Hero` class.
Create a new file in the `lib/` folder called `hero.dart` with the following code.
+makeExample('displaying-data/dart/lib/hero.dart',null,'lib/hero.dart')
:marked
We've defined a class with a constructor, a string description, and two properties: `id` and `name`.
.l-main-section
:marked
## Using the Hero class
Let's make the `heroes` property in our component return a list of these Hero objects.
- var stylePattern = { otl: /(import.*$)|(final)|(new Hero.*$)/gm };
+makeExample('displaying-data/dart/lib/app_component_3.dart', 'heroes', 'app_component.dart (excerpt)', stylePattern)(format=".")
:marked
We'll have to update the template.
At the moment it displays the string value of the `Hero` object.
Let's fix that so we display only the hero's `name` property.
- var stylePattern = { otl: /(myHero\.name)|(hero\.name)/gm };
+makeExample('displaying-data/dart/lib/app_component_3.dart', 'template','app_component.dart (template)', stylePattern)(format=".")
:marked
Our display looks the same, but now we know much better what a hero really is.
<a id="ngIf"></a>
.l-main-section
:marked
## Conditional display with NgIf
Sometimes the app should display a view or a portion of a view only under specific circumstances.
In our example, we'd like to display a message if we have a large number of heroes &mdash; say, more than 3.
The Angular `ngIf` directive inserts or removes an element based on a boolean condition.
We can see it in action by adding the following paragraph at the bottom of the template:
+makeExample('displaying-data/dart/lib/app_component.dart', 'message')
.alert.is-important
:marked
Don't forget the leading asterisk (\*) in `*ngIf`. It is an essential part of the syntax.
Learn more about this and `ngIf` in the [Template Syntax](./template-syntax.html#ngIf) chapter.
:marked
The [template expression](./template-syntax.html#template-expressions) inside the double quotes
looks much like Dart, and it _is_ much like Dart.
When the component's list of heroes has more than 3 items, Angular adds the paragraph to the DOM and the message appears.
If there are 3 or fewer items, Angular omits the paragraph, so no message appears.
.alert.is-helpful
:marked
Angular isn't showing and hiding the message. It is adding and removing the paragraph element from the DOM.
That hardly matters here. But it would matter a great deal, from a performance perspective, if
we were conditionally including or excluding a big chunk of HTML with many data bindings.
:marked
Try it out. Because the list has four items, the message should appear.
Go back into `app_component.dart` and delete or comment out one of the elements from the hero list.
The browser should refresh automatically and the message should disappear.
.l-main-section
:marked
## Summary
Now we know how to use:
- **interpolation** with double curly braces to display a component property
- **`ngFor`** to display a list of items
- a Dart class to shape the **model data** for our component and display properties of that model
- **`ngIf`** to conditionally display a chunk of HTML based on a boolean expression
Here's our final code:
+makeTabs(`displaying-data/dart/lib/app_component.dart,
displaying-data/dart/lib/hero.dart,
displaying-data/dart/pubspec.yaml,
displaying-data/dart/web/index.html,
displaying-data/dart/web/main.dart`,
',,,,final',
'lib/app_component.dart, lib/hero.dart, pubspec.yaml, web/index.html, web/main.dart')
block final-code
+makeTabs(`displaying-data/dart/lib/app_component.dart,
displaying-data/dart/lib/hero.dart,
displaying-data/dart/pubspec.yaml,
displaying-data/dart/web/index.html,
displaying-data/dart/web/main.dart`,
',,,,final',
'lib/app_component.dart, lib/hero.dart, pubspec.yaml, web/index.html, web/main.dart')

225
public/docs/ts/latest/guide/displaying-data.jade
View File

@ -1,34 +1,34 @@
include ../_util-fns
<!-- http://plnkr.co/edit/x9JYbC -->
block includes
include ../_util-fns
- var _iterableUrl = 'https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols';
- var _boolean = 'truthy/falsey';
:marked
We typically display data in Angular by binding controls in an HTML template
to properties of an Angular component.
In this chapter, we'll create a component with a list of heroes. Each hero has a name.
We'll display the list of hero names and
conditionally show a selected hero in a detail area below the list.
conditionally show a message below the list.
The final UI looks like this:
figure.image-display
img(src="/resources/images/devguide/displaying-data/final.png" alt="Final UI")
:marked
# Table Of Contents
* [Showing component properties with interpolation](#interpolation)
* [Showing an array property with NgFor](#ngFor)
* [Showing !{_an} !{_array} property with NgFor](#ngFor)
* [Conditional display with NgIf](#ngIf)
.l-sub-section
:marked
The [live example](/resources/live-examples/displaying-data/ts/plnkr.html)
demonstrates all of the syntax and code snippets described in this chapter.
The <live-example></live-example> demonstrates all of the syntax and code
snippets described in this chapter.
<a id="interpolation"></a>
.l-main-section
.l-main-section#interpolation
:marked
## Showing component properties with interpolation
The easiest way to display a component property
@ -37,14 +37,17 @@ figure.image-display
Let's build a small illustrative example together.
Create a new project folder (`displaying-data`) and follow the steps in the [QuickStart](../quickstart.html).
Create a new project folder (<ngio-ex path="displaying-data"></ngio-ex>) and follow the steps in the [QuickStart](../quickstart.html).
block quickstart-repo
include ../_quickstart_repo
include ../_quickstart_repo
:marked
Then modify the `app.component.ts` file by changing the template and the body of the component.
Then modify the <ngio-ex path="app.component.ts"></ngio-ex> file by
changing the template and the body of the component.
When we're done, it should look like this:
+makeExample('displaying-data/ts/app/app.component.1.ts', null, 'app/app.component.ts')
+makeExample('app/app.component.1.ts')
:marked
We added two properties to the formerly empty component: `title` and `myHero`.
@ -52,94 +55,99 @@ include ../_quickstart_repo
Our revised template displays the two component properties using double curly brace
interpolation:
+makeExample('displaying-data/ts/app/app.component.1.ts', 'template')(format=".")
.l-sub-section
:marked
The template is a multi-line string within ECMAScript 2015 backticks (\`).
The backtick (\`) &mdash; which is *not* the same character as a single
quote (') &mdash; has many nice features. The feature we're exploiting here
is the ability to compose the string over several lines, which makes for
much more readable HTML.
+makeExcerpt('app/app.component.1.ts', 'template', '')
+ifDocsFor('ts')
.l-sub-section
:marked
The template is a multi-line string within ECMAScript 2015 backticks (<code>\`</code>).
The backtick (<code>\`</code>) &mdash; which is *not* the same character as a single
quote (`'`) &mdash; has many nice features. The feature we're exploiting here
is the ability to compose the string over several lines, which makes for
much more readable HTML.
:marked
Angular automatically pulls the value of the `title` and `myHero` properties from the component and
inserts those values into the browser. Angular updates the display
when these properties change.
.l-sub-section
:marked
More precisely, the redisplay occurs after some kind of asynchronous event related to
the view such as a keystroke, a timer completion, or an async `XHR` response.
We don't have those in this sample.
But then the properties aren't changing on their own either. For the moment we must operate on faith.
:marked
Notice that we haven't called **new** to create an instance of the `AppComponent` class.
Angular is creating an instance for us. How?
Notice the CSS `selector` in the `@Component` decorator that specifies an element named "my-app".
Remember back in QuickStart that we added the `<my-app>` element to the body of our `index.html`
+makeExample('displaying-data/ts/index.html', 'my-app')(format=".")
Notice the CSS `selector` in the `@Component` !{_decorator} that specifies an element named `my-app`.
Remember back in [QuickStart](../quickstart.html) that we added the `<my-app>` element to the body of our `index.html` file:
+makeExcerpt('index.html', 'body')
:marked
When we bootstrap with the `AppComponent` class (see `main.ts`), Angular looks for a `<my-app>`
When we bootstrap with the `AppComponent` class (in <ngio-ex path="main.ts"></ngio-ex>), Angular looks for a `<my-app>`
in the `index.html`, finds it, instantiates an instance of `AppComponent`, and renders it
inside the `<my-app>` tag.
We're ready to see changes in a running app by firing up the npm script that both compiles and serves our applications
while watching for changes.
code-example(format="").
npm start
:marked
We should see the title and hero name:
Try running the app. It should display the title and hero name:
figure.image-display
img(src="/resources/images/devguide/displaying-data/title-and-hero.png" alt="Title and Hero")
:marked
Let's review some of the choices we made and consider alternatives.
+ifDocsFor('ts')
:marked
Let's review some of the choices we made and consider alternatives.
:marked
## Template inline or template file?
We can store our component's template in one of two places.
We can define it *inline* using the `template` property, as we do here.
Or we can define the template in a separate HTML file and link to it in
the component metadata using the `@Component` decorator's `templateUrl` property.
the component metadata using the `@Component` !{_decorator}'s `templateUrl` property.
The choice between inline and separate HTML is a matter of taste,
circumstances, and organization policy.
Here we're using inline HTML because the template is small, and the demo
is simpler without the HTML file.
is simpler without the additional HTML file.
In either style, the template data bindings have the same access to the component's properties.
## Constructor or variable initialization?
+ifDocsFor('ts')
:marked
## Constructor or variable initialization?
We initialized our component properties using variable assignment.
This is a wonderfully concise and compact technique.
We initialized our component properties using variable assignment.
This is a wonderfully concise and compact technique.
Some folks prefer to declare the properties and initialize them within a constructor like this:
+makeExample('displaying-data/ts/app/app-ctor.component.ts', 'app-ctor')(format=".")
Some folks prefer to declare the properties and initialize them within a constructor like this:
+makeExcerpt('app/app-ctor.component.ts', 'class')
:marked
That's fine too. The choice is a matter of taste and organization policy.
We'll adopt the more terse "variable assignment" style in this chapter simply because
there will be less code to read.
.l-main-section#ngFor
:marked
## Showing !{_an} !{_array} property with ***ngFor**
We want to display a list of heroes. We begin by adding !{_an} !{_array} of hero names to the component and redefine `myHero` to be the first name in the !{_array}.
+makeExcerpt('app/app.component.2.ts', 'class')
:marked
That's fine too. The choice is a matter of taste and organization policy.
We'll adopt the more terse "variable assignment" style in this chapter simply because
there will be less code to read.
<a id="ngFor"></a>
.l-main-section
:marked
## Showing an array property with ***ngFor**
We want to display a list of heroes. We begin by adding a mock heroes name array to the component,
just above `myHero`, and redefine `myHero` to be the first name in the array.
+makeExample('displaying-data/ts/app/app.component.2.ts', 'mock-heroes', 'app/app.component.ts (class)')(format=".")
:marked
Now we use the Angular `ngFor` "repeater" directive in the template to display
Now we use the Angular `ngFor` directive in the template to display
each item in the `heroes` list.
+makeExample('displaying-data/ts/app/app.component.2.ts', 'template','app/app.component.ts (template)')(format=".")
+makeExcerpt('app/app.component.2.ts', 'template')
:marked
Our presentation is the familiar HTML unordered list with `<ul>` and `<li>` tags. Let's focus on the `<li>` tag.
+makeExample('displaying-data/ts/app/app.component.2.ts', 'li-repeater')(format=".")
+makeExcerpt('app/app.component.2.ts ()', 'li', '')
:marked
We added a somewhat mysterious `*ngFor` to the `<li>` element.
@ -152,7 +160,7 @@ figure.image-display
Learn more about this and `ngFor` in the [Template Syntax](./template-syntax.html#ngFor) chapter.
:marked
Notice the `hero` in the `ngFor` double-quoted instruction;
Notice the `hero` in the `ngFor` double-quoted instruction;
it is an example of a [template input variable](./template-syntax.html#ngForMicrosyntax).
Angular duplicates the `<li>` for each item in the list, setting the `hero` variable
@ -161,12 +169,11 @@ figure.image-display
.l-sub-section
:marked
We happened to give `ngFor` an array to display.
In fact, `ngFor` can repeat items for any [iterable](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols)
We happened to give `ngFor` !{_an} !{_array} to display.
In fact, `ngFor` can repeat items for any [iterable](!{_iterableUrl})
object.
:marked
Assuming we're still running under the `npm start` command,
we should see heroes appearing in an unordered list.
Now the heroes appear in an unordered list.
figure.image-display
img(src="/resources/images/devguide/displaying-data/hero-names-list.png" alt="After ngfor")
@ -179,57 +186,62 @@ figure.image-display
That's fine for a demo but certainly isn't a best practice. It's not even a good practice.
Although we won't do anything about that in this chapter, we'll make a mental note to fix this down the road.
At the moment, we're binding to an array of strings. We do that occasionally in real applications, but
most of the time we're displaying objects &mdash; potentially instances of classes.
At the moment, we're binding to !{_an} !{_array} of strings. We do that occasionally in real applications, but
most of the time we're binding to more specialized objects.
Let's turn our array of hero names into an array of `Hero` objects. For that we'll need a `Hero` class.
Let's turn our !{_array} of hero names into !{_an} !{_array} of `Hero` objects. For that we'll need a `Hero` class.
Create a new file in the `app/` folder called `hero.ts` with the following short bit of code.
+makeExample('displaying-data/ts/app/hero.ts', null, 'app/hero.ts')(format = ".")
Create a new file in the `!{_appDir}` folder called <ngio-ex path="hero.ts"></ngio-ex> with the following code:
+makeExcerpt('app/hero.ts')
:marked
We've defined a class with a constructor and two properties: `id` and `name`.
block hero-class
:marked
We've defined a class with a constructor and two properties: `id` and `name`.
It might not look like we have properties, but we do. We're taking
advantage of a TypeScript shortcut in our declaration of the constructor parameters.
It might not look like we have properties, but we do. We're taking
advantage of a TypeScript shortcut in our declaration of the constructor parameters.
Consider the first parameter:
+makeExample('displaying-data/ts/app/hero.ts', 'id-parameter')
Consider the first parameter:
:marked
That brief syntax does a lot:
* declares a constructor parameter and its type
* declares a public property of the same name
* initializes that property with the corresponding argument when we "new" an instance of the class
+makeExcerpt('app/hero.ts ()', 'id')
:marked
That brief syntax does a lot:
* Declares a constructor parameter and its type
* Declares a public property of the same name
* Initializes that property with the corresponding argument when we "new" an instance of the class
.l-main-section
:marked
## Using the Hero class
Let's redefine the `heroes` property in our component to return an array of these Hero objects
and also set the `myHero` property with the first of these mock heroes.
+makeExample('displaying-data/ts/app/app.component.3.ts', 'heroes', 'app.component.ts (excerpt)')(format=".")
Let's make the `heroes` property in our component return !{_an} !{_array} of these `Hero` objects.
+makeExcerpt('app/app.component.3.ts', 'heroes')
:marked
We'll have to update the template.
At the moment it displays the entire `hero` object, which used to be a string value.
Let's fix that so we interpolate the `hero.name` property.
+makeExample('displaying-data/ts/app/app.component.3.ts', 'template','app.component.ts (template)')(format=".")
At the moment it displays the hero's `id` and `name`.
Let's fix that so we display only the hero's `name` property.
+makeExcerpt('app/app.component.3.ts', 'template')
:marked
Our display looks the same, but now we know much better what a hero really is.
<a id="ngIf"></a>
.l-main-section
.l-main-section#ngIf
:marked
## Conditional display with NgIf
Sometimes the app should display a view or a portion of a view only under specific circumstances.
Sometimes an app needs to display a view or a portion of a view only under specific circumstances.
In our example, we'd like to display a message if we have a large number of heroes &mdash; say, more than 3.
In our example, we'd like to display a message if we have a large number of heroes, say, more than 3.
The Angular `ngIf` directive inserts or removes an element based on a truthy/falsey condition.
The Angular `ngIf` directive inserts or removes an element based on a !{_boolean} condition.
We can see it in action by adding the following paragraph at the bottom of the template:
+makeExample('displaying-data/ts/app/app.component.ts', 'message')
+makeExcerpt('app/app.component.ts', 'message')
.alert.is-important
:marked
Don't forget the leading asterisk (\*) in `*ngIf`. It is an essential part of the syntax.
@ -237,7 +249,7 @@ figure.image-display
:marked
The [template expression](./template-syntax.html#template-expressions) inside the double quotes
looks much like JavaScript and it _is_ much like JavaScript.
looks much like !{_Lang}, and it _is_ much like !{_Lang}.
When the component's list of heroes has more than 3 items, Angular adds the paragraph to the DOM and the message appears.
If there are 3 or fewer items, Angular omits the paragraph, so no message appears.
@ -248,23 +260,24 @@ figure.image-display
we were conditionally including or excluding a big chunk of HTML with many data bindings.
:marked
Try it out. Because the array has four items, the message should appear.
Go back into `app.component.ts` and delete or comment out one of the elements from the hero array.
Try it out. Because the !{_array} has four items, the message should appear.
Go back into <ngio-ex path="app.component.ts"></ngio-ex> and delete or comment out one of the elements from the hero !{_array}.
The browser should refresh automatically and the message should disappear.
.l-main-section
:marked
## Summary
Now we know how to use:
- **interpolation** with double curly braces to display a component property
- **`ngFor`** to display a list of items
- a TypeScript class to shape the **model data** for our component and display properties of that model
- **`ngIf`** to conditionally display a chunk of HTML based on a boolean expression
- **Interpolation** with double curly braces to display a component property
- **ngFor** to display !{_an} !{_array} of items
- A !{_Lang} class to shape the **model data** for our component and display properties of that model
- **ngIf** to conditionally display a chunk of HTML based on a boolean expression
Here's our final code:
+makeTabs(`displaying-data/ts/app/app.component.ts,
displaying-data/ts/app/hero.ts,
displaying-data/ts/app/main.ts`,
'final,,',
'app/app.component.ts, app/hero.ts, main.ts')
block final-code
+makeTabs(`displaying-data/ts/app/app.component.ts,
displaying-data/ts/app/hero.ts,
displaying-data/ts/app/main.ts`,
'final,,',
'app/app.component.ts, app/hero.ts, main.ts')