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docs(architecture/dart): proofread, updated Dart/TS app and jade 

closes #1807
- e2e tests now also cover the tax calculator.
- Dart app updated to match TS (it had no sales tax calculator).
- TS sample source cleanup (e.g. removed many unnecessary `docregions`).
- Prose updated to include @kwalrath's revisions from a while ago, Ward's comments, and
some of my edits as well.

Contributes to #1598 and #1508.
This commit is contained in:
Patrice Chalin 2016-07-01 08:44:28 -07:00 committed by Ward Bell
parent 81b011c6ba
commit 761f857f13
28 changed files with 711 additions and 971 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
public/docs/_examples/architecture/dart/lib/app_component.dart Normal file
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@ -0,0 +1,15 @@
// #docregion import
import 'package:angular2/core.dart';
// #enddocregion import
import 'hero_list_component.dart';
import 'sales_tax_component.dart';
@Component(
selector: 'my-app',
template: '''
<hero-list></hero-list>
<sales-tax></sales-tax>''',
directives: const [HeroListComponent, SalesTaxComponent])
// #docregion export
class AppComponent { }

30
public/docs/_examples/architecture/dart/lib/backend_service.dart
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@ -1,4 +1,5 @@
// #docregion
import 'dart:async';
import 'package:angular2/core.dart';
import 'hero.dart';
@ -6,19 +7,22 @@ import 'logger_service.dart';
@Injectable()
class BackendService {
static final _mockHeroes = [
new Hero('Windstorm', 'Weather mastery'),
new Hero('Mr. Nice', 'Killing them with kindness'),
new Hero('Magneta', 'Manipulates metalic objects')
];
final Logger _logger;
List getAll(type) {
// TODO get from the database and return as a promise
if (type == Hero) {
return [
new Hero('Windstorm', power: 'Weather mastery'),
new Hero('Mr. Nice', power: 'Killing them with kindness'),
new Hero('Magneta', power: 'Manipulates metalic objects')
];
}
_logger.error('Cannot get object of this type');
throw new ArgumentError("TODO: put log content here");
}
BackendService(Logger this._logger);
Future<List> getAll(type) {
// TODO get from the database
if (type == Hero) return new Future.value(_mockHeroes);
var msg = 'Cannot get object of this type';
_logger.error(msg);
throw new Exception(msg);
}
}

10
public/docs/_examples/architecture/dart/lib/hero.dart
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@ -1,11 +1,7 @@
// #docregion
class Hero {
static int _nextId = 1;
int id;
String name;
String power;
final int id;
String name, power;
Hero(this.name, {this.power}) {
id = _nextId++;
}
Hero(this.name, [this.power = '']) : id = _nextId++;
}

8
public/docs/_examples/architecture/dart/lib/hero_detail_component.dart
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@ -1,9 +1,11 @@
// #docregion
import 'package:angular2/core.dart';
import 'hero.dart';
@Component(selector: 'hero-detail', templateUrl: 'hero_detail_component.html')
@Component(
selector: 'hero-detail',
templateUrl: 'hero_detail_component.html')
class HeroDetailComponent {
@Input() Hero hero;
@Input()
Hero hero;
}

8
public/docs/_examples/architecture/dart/lib/hero_detail_component.html
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@ -2,8 +2,8 @@
<h4>{{hero.name}} Detail</h4>
<div>Id: {{hero.id}}</div>
<div>Name:
<!-- #docregion ng-model -->
<input [(ngModel)]="hero.name"></div>
<!-- #enddocregion ng-model -->
<div>Power:<input [(ngModel)]="hero.power">
<!-- #docregion ngModel -->
<input [(ngModel)]="hero.name">
<!-- #enddocregion ngModel -->
</div>
<div>Power:<input [(ngModel)]="hero.power"></div>

36
public/docs/_examples/architecture/dart/lib/hero_list_component.dart
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@ -1,4 +1,3 @@
// #docplaster
import 'package:angular2/core.dart';
import 'hero.dart';
@ -6,32 +5,31 @@ import 'hero_detail_component.dart';
import 'hero_service.dart';
// #docregion metadata
// #docregion providers
@Component(
// #enddocregion providers
selector: 'hero-list',
templateUrl: 'hero_list_component.html',
directives: const [HeroDetailComponent],
// #docregion providers
providers: const [HeroService])
// #enddocregion providers
// #enddocregion metadata
/*
// #docregion metadata, providers
class HeroListComponent { ... }
// #enddocregion metadata, providers
*/
// #docregion providers
providers: const [HeroService]
// #enddocregion providers
)
// #docregion class
class HeroListComponent {
class HeroListComponent implements OnInit {
// #enddocregion metadata
List<Hero> heroes;
Hero selectedHero;
// #docregion ctor
HeroListComponent(HeroService heroService) {
heroes = heroService.getHeroes();
// #docregion ctor
final HeroService _heroService;
HeroListComponent(this._heroService);
// #enddocregion ctor
void ngOnInit() {
heroes = _heroService.getHeroes();
}
// #enddocregion ctor
selectHero(Hero hero) {
void selectHero(Hero hero) {
selectedHero = hero;
}
// #docregion metadata
}
// #enddocregion class

9
public/docs/_examples/architecture/dart/lib/hero_list_component.html
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@ -1,8 +1,11 @@
<!-- #docregion -->
<h2>Hero List</h2>
<div *ngFor="let hero of heroes" (click)="selectHero(hero)">
{{hero.name}}
</div>
<p><i>Pick a hero from the list</i></p>
<ul>
<li *ngFor="let hero of heroes" (click)="selectHero(hero)">
{{hero.name}}
</li>
</ul>
<hero-detail *ngIf="selectedHero != null" [hero]="selectedHero"></hero-detail>

11
public/docs/_examples/architecture/dart/lib/hero_list_component_1.html
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@ -1,10 +1,9 @@
<!--#docregion binding -->
<div ... >{{hero.name}}</div>
<hero-detail ... [hero]="selectedHero"></hero-detail>
<div ... (click)="selectHero(hero)">...</div>
<li>{{hero.name}}</li>
<hero-detail [hero]="selectedHero"></hero-detail>
<li (click)="selectHero(hero)"></li>
<!--#enddocregion binding -->
<!--#docregion structural -->
<div *ngFor="let hero of heroes" ...>...</div>
<hero-detail *ngIf="selectedHero != null" ...></hero-detail>
<!--#enddocregion structural -->
<li *ngFor="let hero of heroes"></li>
<hero-detail *ngIf="selectedHero != null"></hero-detail>

14
public/docs/_examples/architecture/dart/lib/hero_service.dart
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@ -4,16 +4,20 @@ import 'backend_service.dart';
import 'hero.dart';
import 'logger_service.dart';
// #docregion class
@Injectable()
// #docregion class
class HeroService {
final BackendService _backendService;
final Logger _logger;
HeroService(Logger this._logger, BackendService this._backendService);
final List<Hero> heroes = [];
HeroService(this._logger, this._backendService);
List<Hero> getHeroes() {
List<Hero> heroes = _backendService.getAll(Hero);
_logger.log('Got ${heroes.length} heroes from the server.');
_backendService.getAll(Hero).then((heroes) {
_logger.log('Fetched ${heroes.length} heroes.');
this.heroes.addAll(heroes); // fill cache
});
return heroes;
}
}
// #enddocregion class

7
public/docs/_examples/architecture/dart/lib/logger_service.dart
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@ -1,16 +1,11 @@
// #docregion
import 'dart:html';
import 'package:angular2/core.dart';
/// A service for logging messages of various types.
///
/// We could switch this implementation to use package:logging.
@Injectable()
// #docregion class
class Logger {
void log(Object msg) => window.console.log(msg);
void error(Object msg) => window.console.error(msg);
void warn(Object msg) => window.console.warn(msg);
}

28
public/docs/_examples/architecture/dart/lib/sales_tax_component.dart Normal file
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@ -0,0 +1,28 @@
import 'package:angular2/core.dart';
import 'sales_tax_service.dart';
import 'tax_rate_service.dart';
@Component(
selector: 'sales-tax',
template: '''
<h2>Sales Tax Calculator</h2>
Amount: <input #amountBox (change)="0">
<div *ngIf="amountBox.value != ''">
The sales tax is
{{ getTax(amountBox.value) | currency:'USD':false:'1.2-2' }}
<!-- would like to write currency:'USD':true:'1.2-2' but
currency as symbol is not currently supported; see
https://github.com/dart-lang/intl/issues/59 -->
</div>
''',
providers: const [SalesTaxService, TaxRateService])
class SalesTaxComponent {
SalesTaxService _salesTaxService;
SalesTaxComponent(this._salesTaxService) {}
num getTax(dynamic /* String | num */ value) =>
this._salesTaxService.getVAT(value);
}

14
public/docs/_examples/architecture/dart/lib/sales_tax_service.dart Normal file
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@ -0,0 +1,14 @@
import 'package:angular2/core.dart';
import 'tax_rate_service.dart';
@Injectable()
class SalesTaxService {
TaxRateService rateService;
SalesTaxService(this.rateService);
num getVAT(dynamic /* String | num */ value) =>
rateService.getRate('VAT') *
(value is num ? value : num.parse(value, (_) => 0));
}

6
public/docs/_examples/architecture/dart/lib/tax_rate_service.dart Normal file
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@ -0,0 +1,6 @@
import 'package:angular2/core.dart';
@Injectable()
class TaxRateService {
getRate(String rateName) => 0.10;
}

17
public/docs/_examples/architecture/dart/web/index.html
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@ -1,12 +1,15 @@
<!DOCTYPE html>
<html>
<head>
<title>Intro to Angular 2</title>
<link rel="stylesheet" href="styles.css">
<script defer src="main.dart" type="application/dart"></script>
<script defer src="packages/browser/dart.js"></script>
</head>
<head>
<title>Architecture of Angular 2</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="styles.css">
<script defer src="main.dart" type="application/dart"></script>
<script defer src="packages/browser/dart.js"></script>
</head>
<body>
<hero-list>Loading...</hero-list>
<my-app>Loading...</my-app>
</body>
</html>

9
public/docs/_examples/architecture/dart/web/main.dart
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@ -1,13 +1,14 @@
// #docregion
import 'package:angular2/platform/browser.dart';
// #docregion import
import 'package:developer_guide_intro/app_component.dart';
// #enddocregion import
import 'package:developer_guide_intro/backend_service.dart';
import 'package:developer_guide_intro/hero_list_component.dart';
import 'package:developer_guide_intro/hero_service.dart';
import 'package:developer_guide_intro/logger_service.dart';
main() {
void main() {
// #docregion bootstrap
bootstrap(HeroListComponent, [BackendService, HeroService, Logger]);
bootstrap(AppComponent, [BackendService, HeroService, Logger]);
// #enddocregion bootstrap
}

144
public/docs/_examples/architecture/e2e-spec.ts
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@ -1,63 +1,99 @@
/// <reference path='../_protractor/e2e.d.ts' />
'use strict';
describe('Architecture', function () {
let title = 'Hero List';
const nameSuffix = 'X';
beforeAll(function () {
browser.get('');
class Hero {
id: number;
name: string;
}
describe('Architecture', () => {
const expectedTitle = 'Architecture of Angular 2';
const expectedH2 = ['Hero List', 'Sales Tax Calculator'];
beforeAll(() => browser.get(''));
it(`has title '${expectedTitle}'`, () => {
expect(browser.getTitle()).toEqual(expectedTitle);
});
function itReset(name: string, func: () => any) {
it(name, function() {
browser.get('').then(func);
});
}
it(`should display correct title: ${title}`, function () {
expect(element(by.css('h2')).getText()).toEqual(title);
});
it('should display correct detail after selection', function() {
let detailView = element(by.css('hero-detail'));
expect(detailView.isPresent()).toBe(false);
// select the 2nd element
let selectEle = element.all(by.css('hero-list > div')).get(1);
selectEle.click().then(function() {
return selectEle.getText();
}).then(function(selectedHeroName) {
// works but too specific if we change the app
// expect(selectedHeroName).toEqual('Mr. Nice');
expect(detailView.isDisplayed()).toBe(true);
let detailTitleEle = element(by.css('hero-detail > h4'));
expect(detailTitleEle.getText()).toContain(selectedHeroName);
});
});
itReset('should display correct detail after modification', function() {
let detailView = element(by.css('hero-detail'));
expect(detailView.isPresent()).toBe(false);
// select the 2nd element
let selectEle = element.all(by.css('hero-list > div')).get(1);
selectEle.click().then(function () {
return selectEle.getText();
}).then(function (selectedHeroName) {
let detailTitleEle = element(by.css('hero-detail > h4'));
expect(detailTitleEle.getText()).toContain(selectedHeroName);
let heroNameEle = element.all(by.css('hero-detail input')).get(0);
// check that both the initial selected item and the detail title reflect changes
// made to the input box.
// heroNameEle.sendKeys('foo');
sendKeys(heroNameEle, 'foo');
expect(detailTitleEle.getText()).toContain('foo');
expect(selectEle.getText()).toContain('foo');
// getText on an input element always returns null
// http://stackoverflow.com/questions/20310442/how-to-gettext-on-an-input-in-protractor
// expect(heroNameEle.getText()).toEqual(selectedHeroName);
expect(heroNameEle.getAttribute('value')).toEqual(selectedHeroName + 'foo');
});
it(`has h2 '${expectedH2}'`, () => {
let h2 = element.all(by.css('h2')).map((elt) => elt.getText());
expect(h2).toEqual(expectedH2);
});
describe('Hero', heroTests);
describe('Salex tax', salesTaxTests);
});
function heroTests() {
const targetHero: Hero = { id: 2, name: 'Mr. Nice' };
it('has the right number of heroes', () => {
let page = getPageElts();
expect(page.heroes.count()).toEqual(3);
});
it('has no hero details initially', function () {
let page = getPageElts();
expect(page.heroDetail.isPresent()).toBeFalsy('no hero detail');
});
it('shows selected hero details', async () => {
await element(by.cssContainingText('li', targetHero.name)).click();
let page = getPageElts();
let hero = await heroFromDetail(page.heroDetail);
expect(hero.id).toEqual(targetHero.id);
expect(hero.name).toEqual(targetHero.name);
});
it(`shows updated hero name in details`, async () => {
let input = element.all(by.css('input')).first();
await sendKeys(input, nameSuffix);
let page = getPageElts();
let hero = await heroFromDetail(page.heroDetail);
let newName = targetHero.name + nameSuffix;
expect(hero.id).toEqual(targetHero.id);
expect(hero.name).toEqual(newName);
});
}
function salesTaxTests() {
it('has no sales tax initially', function () {
let page = getPageElts();
expect(page.salesTaxDetail.isPresent()).toBeFalsy('no sales tax info');
});
it('shows sales tax', async function () {
let page = getPageElts();
await sendKeys(page.salesTaxAmountInput, '10');
// Note: due to Dart bug USD is shown instead of $
let re = /The sales tax is (\$|USD)1.00/;
expect(page.salesTaxDetail.getText()).toMatch(re);
});
}
// Helper functions
function getPageElts() {
return {
heroes: element.all(by.css('my-app li')),
heroDetail: element(by.css('my-app hero-detail')),
salesTaxAmountInput: element(by.css('my-app sales-tax input')),
salesTaxDetail: element(by.css('my-app sales-tax div'))
};
}
async function heroFromDetail(detail: protractor.ElementFinder): Promise<Hero> {
// Get hero id from the first <div>
let _id = await detail.all(by.css('div')).first().getText();
// Get name from the h2
let _name = await detail.element(by.css('h4')).getText();
return {
id: +_id.substr(_id.indexOf(' ') + 1),
name: _name.substr(0, _name.lastIndexOf(' '))
};
}

6
public/docs/_examples/architecture/ts/app/hero-detail.component.html
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@ -2,8 +2,8 @@
<h4>{{hero.name}} Detail</h4>
<div>Id: {{hero.id}}</div>
<div>Name:
<!-- #docregion ngModel -->
<input [(ngModel)]="hero.name">
<!-- #enddocregion ngModel -->
<!-- #docregion ngModel -->
<input [(ngModel)]="hero.name">
<!-- #enddocregion ngModel -->
</div>
<div>Power:<input [(ngModel)]="hero.power"></div>

9
public/docs/_examples/architecture/ts/app/hero-list.component.1.html
View File

@ -1,12 +1,9 @@
<!--#docregion binding -->
<div>{{hero.name}}</div>
<li>{{hero.name}}</li>
<hero-detail [hero]="selectedHero"></hero-detail>
<div (click)="selectHero(hero)"></div>
<li (click)="selectHero(hero)"></li>
<!--#enddocregion binding -->
<!--#docregion structural -->
<div *ngFor="let hero of heroes"></div>
<li *ngFor="let hero of heroes"></li>
<hero-detail *ngIf="selectedHero"></hero-detail>
<!--#enddocregion structural -->

8
public/docs/_examples/architecture/ts/app/hero-list.component.html
View File

@ -2,8 +2,10 @@
<h2>Hero List</h2>
<p><i>Pick a hero from the list</i></p>
<div *ngFor="let hero of heroes" (click)="selectHero(hero)">
{{hero.name}}
</div>
<ul>
<li *ngFor="let hero of heroes" (click)="selectHero(hero)">
{{hero.name}}
</li>
</ul>
<hero-detail *ngIf="selectedHero" [hero]="selectedHero"></hero-detail>

20
public/docs/_examples/architecture/ts/app/hero-list.component.ts
View File

@ -1,4 +1,3 @@
// #docplaster
import { Component, OnInit } from '@angular/core';
import { Hero } from './hero';
@ -6,35 +5,28 @@ import { HeroDetailComponent } from './hero-detail.component';
import { HeroService } from './hero.service';
// #docregion metadata
// #docregion providers
@Component({
// #enddocregion providers
selector: 'hero-list',
templateUrl: 'app/hero-list.component.html',
directives: [HeroDetailComponent],
// #docregion providers
// #docregion providers
providers: [HeroService]
// #enddocregion providers
})
// #enddocregion providers
// #enddocregion metadata
/*
// #docregion metadata, providers
export class HeroesComponent { ... }
// #enddocregion metadata, providers
*/
// #docregion class
export class HeroListComponent implements OnInit {
// #enddocregion metadata
heroes: Hero[];
selectedHero: Hero;
// #docregion ctor
// #docregion ctor
constructor(private service: HeroService) { }
// #enddocregion ctor
// #enddocregion ctor
ngOnInit() {
this.heroes = this.service.getHeroes();
}
selectHero(hero: Hero) { this.selectedHero = hero; }
// #docregion metadata
}
// #enddocregion class

3
public/docs/_examples/architecture/ts/app/hero.service.ts
View File

@ -9,11 +9,9 @@ import { Logger } from './logger.service';
export class HeroService {
private heroes: Hero[] = [];
// #docregion ctor
constructor(
private backend: BackendService,
private logger: Logger) { }
// #enddocregion ctor
getHeroes() {
this.backend.getAll(Hero).then( (heroes: Hero[]) => {
@ -23,4 +21,3 @@ export class HeroService {
return this.heroes;
}
}
// #enddocregion class

2
public/docs/_examples/architecture/ts/app/logger.service.ts
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@ -1,4 +1,3 @@
// #docregion
import { Injectable } from '@angular/core';
@Injectable()
@ -8,4 +7,3 @@ export class Logger {
error(msg: any) { console.error(msg); }
warn(msg: any) { console.warn(msg); }
}
// #enddocregion class

17
public/docs/_examples/architecture/ts/app/sales-tax.component.ts
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@ -1,14 +1,9 @@
// #docplaster
// #docregion
import { Component } from '@angular/core';
import { SalesTaxService } from './sales-tax.service';
import { TaxRateService } from './tax-rate.service';
// #docregion metadata
// #docregion providers
@Component({
// #enddocregion providers
selector: 'sales-tax',
template: `
<h2>Sales Tax Calculator</h2>
@ -19,24 +14,12 @@ import { TaxRateService } from './tax-rate.service';
{{ getTax(amountBox.value) | currency:'USD':true:'1.2-2' }}
</div>
`,
// #docregion providers
providers: [SalesTaxService, TaxRateService]
})
// #enddocregion providers
// #enddocregion metadata
/*
// #docregion metadata, providers
export class SalesTaxComponent { ... }
// #enddocregion metadata, providers
*/
// #docregion class
export class SalesTaxComponent {
// #docregion ctor
constructor(private salesTaxService: SalesTaxService) { }
// #enddocregion ctor
getTax(value: string | number) {
return this.salesTaxService.getVAT(value);
}
}
// #enddocregion class

12
public/docs/_examples/architecture/ts/app/sales-tax.service.ts
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@ -1,20 +1,14 @@
// #docregion
import { Injectable } from '@angular/core';
import { TaxRateService } from './tax-rate.service';
// #docregion class
@Injectable()
export class SalesTaxService {
constructor(private rateService: TaxRateService) { }
getVAT(value: string | number) {
let amount: number;
if (typeof value === 'string') {
amount = parseFloat(value);
} else {
amount = value;
}
let amount = (typeof value === 'string') ?
parseFloat(value) : value;
return (amount || 0) * this.rateService.getRate('VAT');
}
}
// #enddocregion class

5
public/docs/_examples/architecture/ts/app/tax-rate.service.ts
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@ -1,9 +1,6 @@
// #docregion
import { Injectable } from '@angular/core';
// #docregion class
@Injectable()
export class TaxRateService {
getRate(rateName: string) {return 0.10; } // always 10% everywhere
getRate(rateName: string) { return 0.10; } // 10% everywhere
}
// #enddocregion class

1
public/docs/dart/latest/guide/animations.jade Normal file
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@ -0,0 +1 @@
!= partial("../../../_includes/_ts-temp")

487
public/docs/dart/latest/guide/architecture.jade
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@ -1,451 +1,72 @@
include ../_util-fns
extends ../../../ts/latest/guide/architecture.jade
block includes
include ../_util-fns
- var _library_module = 'library'
- var _at_angular = 'angular2'
:marked
Angular 2 is a framework to help us build client applications in HTML and
either JavaScript or a language (like Dart or TypeScript) that compiles to JavaScript.
Angular 2 for Dart is published as the `angular2` package, which
(like many other Dart packages) is available via the Pub tool.
With Angular, we write applications by composing HTML *templates* with Angularized markup,
writing *component* classes to manage those templates, adding application logic in *services*,
and handing the top root component to Angular's *bootstrapper*.
Angular takes over, presenting our application content in a browser and responding to user interactions
according to the instructions we provided.
<!-- figure img(src="/resources/images/devguide/architecture/airplane.png" alt="Us" align="left" style="width:200px; margin-left:-40px;margin-right:10px" ) -->
:marked
Of course there is more to it than this.
We're cruising at high altitude in this overview.
We're looking for landmarks. We should expect the object below to be fuzzy and obscured by occasional clouds.
Details become more clear and precise when we land in the chapters themselves.
<br clear="all">
:marked
An Angular 2 for Dart application rests on seven main building blocks:
1. [Components](#component)
1. [Templates](#template)
1. [Metadata](#metadata)
1. [Data binding](#data-binding)
1. [Directives](#directive)
1. [Services](#service)
1. [Dependency injection](#dependency-injection)
figure
img(src="/resources/images/devguide/architecture/overview.png" alt="overview" style="margin-left:-40px;" width="700")
:marked
Learn these seven and we're on our way.
.l-main-section
<a id="component"></a>
:marked
## Components
figure
img(src="/resources/images/devguide/architecture/hero-component.png" alt="Component" align="left" style="width:200px; margin-left:-40px;margin-right:10px" )
:marked
A **component** controls a patch of screen real estate that we could call a *view*.
A set of navigation links, a list of heroes, a hero editor ...
they're all views controlled by components.
We define a component's application logic — what it does to support the view — inside a class.
The class interacts with the view through an API of properties and methods.
<a id="component-code"></a>
A `HeroListComponent`, for example, might have a `heroes` property that returns an array of heroes
that it acquired from a service.
It might have a `selectHero()` method that sets a `selectedHero` property when the user clicks to choose a hero from that list.
The component might be a class like this:
+makeExample('architecture/dart/lib/hero_list_component.dart', 'class', 'lib/hero_list_component.dart')
:marked
Angular creates, updates, and destroys components as the user moves through the application.
The developer can take action at each moment in this lifecycle through optional lifecycle hooks.
<!-- PENDING: What was that supposed to link to? -->
.l-sub-section
block angular-parts
:marked
We may wonder who is calling the component's constructor? Who provides the service parameter?
For the moment, have faith that Angular will call the constructor and deliver an
appropriate `HeroService` when we need it.
Angular 2 for Dart is published as the `angular2` package, which
(like many other Dart packages) is available via the Pub tool.
.l-main-section
<a id="template"></a>
:marked
## Templates
figure
img(src="/resources/images/devguide/architecture/template.png" alt="Template" align="left" style="width:200px; margin-left:-40px;margin-right:10px" )
:marked
We define a component's view with its companion **template**. A template is a form of HTML
that tells Angular how to render the component.
block modules-in-dart
.callout.is-helpful
header Dart difference: Modules are compilation units or packages
:marked
In this guide, the term _module_ refers to a Dart compilation unit, such
as a library, or a package. (If a Dart file has no `library` or `part`
directive, then that file itself is a library and thus a compilation
unit.) For more information about compilation units, see
the chapter on "Libraries and Scripts" in the
[Dart Language Specification](https://www.dartlang.org/docs/spec/).
A template looks like regular HTML much of the time ... and then it gets a bit strange. Here is a
template for our `HeroListComponent`:
+makeExample('architecture/dart/lib/hero_list_component.html', null, 'lib/hero_list_component.html')
:marked
This template features typical HTML elements like `<h2>` and `<div>`.
But what are `*ngFor`, <code>{&zwnj;{hero.name}}</code>, `(click)`, `[hero]`, and `<hero-detail>`?
They're examples of Angular's template syntax. <!-- TODO: link to template-syntax.html -->
We'll grow accustomed to that syntax and may even learn to love it.
block modules-are-optional
//- N/A
Take a look at the last line,
which has the `<hero-detail>` tag.
That tag adds a custom element representing a component we haven't seen yet,
a `HeroDetailComponent`.
block export-qualifier
.callout.is-helpful
header Dart difference: Public names are exported by default
:marked
Contrary to TypeScript, a Dart library always exports all names and
declarations in its **public** namespace, making explicit `export`
qualifiers unnecessary.
The `HeroDetailComponent` is a *different* component than the `HeroListComponent` we've seen.
The `HeroDetailComponent` (code not shown) presents facts about a particular hero, the
hero that the user selects from the list presented by the `HeroListComponent`.
The `HeroDetailComponent` is a **child** of the `HeroListComponent`.
When we say that a module _exports_ a declaration, we mean that the
declaration is _public_. For more details about name spaces and export
statements, see the section on "Exports" in the
[Dart Language Specification](https://www.dartlang.org/docs/spec/).
figure
img(src="/resources/images/devguide/architecture/component-tree.png" alt="Metadata" align="left" style="width:300px; margin-left:-40px;margin-right:10px" )
:marked
Notice how `<hero-detail>` rests comfortably among native HTML elements.
We can and _will_ mix our custom components with native HTML in the same layouts.
block ts-import
//- N/A
In this manner we'll compose complex component trees to build out our richly featured application.
<br clear="all">
.l-main-section
<a id="metadata"></a>
:marked
## Metadata
figure
img(src="/resources/images/devguide/architecture/metadata.png" alt="Metadata" align="left" style="width:150px; margin-left:-40px;margin-right:10px" )
:marked
<p style="padding-top:10px">Metadata tells Angular how to process a class.</p>
<br clear="all">
:marked
[Looking back at the code](#component-code) for `HeroListComponent`, we see that it's just a class.
There is no evidence of a framework, no "Angular" in it at all.
In fact, it really is *just a class*. It's not a component until we *tell Angular about it*.
We tell Angular that `HeroListComponent` is a component by attaching **metadata** to the class.
In Dart, we attach metadata by using an **annotation**.
Here's some metadata for `HeroListComponent`:
+makeExample('architecture/dart/lib/hero_list_component.dart', 'metadata', 'lib/hero_list_component.dart')
:marked
Here we see the `@Component` annotation, which (no surprise) identifies the class
immediately below it as a component class.
Annotations often have configuration parameters.
The `@Component` annotation takes parameters to provide the
information Angular needs to create and present the component and its view.
Here we see a few of the possible `@Component` parameters:
* `selector`: A CSS selector that tells Angular to create and insert an instance of this component
where it finds a `<hero-list>` tag in *parent* HTML.
For example, if an app's HTML contains `<hero-list></hero-list>`, then
Angular inserts an instance of the `HeroListComponent` view between those tags.
* `templateUrl`: The address of this component's template, which we showed [above](#the-template).
* `directives`: An array of the components or directives that *this* template requires.
We saw in the last line of our template that we expect Angular to insert a `HeroDetailComponent`
in the space indicated by `<hero-detail>` tags.
Angular will do so only if we mention the `HeroDetailComponent` in this `directives` array.
* `providers`: An array of **dependency injection providers** for services that the component requires.
This is one way to tell Angular that our component's constructor requires a `HeroService`
so it can get the list of heroes to display. We'll get to dependency injection later.
figure
img(src="/resources/images/devguide/architecture/template-metadata-component.png" alt="Metadata" align="left" style="height:200px; margin-left:-40px;margin-right:10px" )
:marked
At runtime, Angular discovers the metadata specified by the `@Component`
annotation. That's how Angular learns how to do "the right thing".
The template, metadata, and component together describe the view.
We apply other metadata annotations in a similar fashion to guide Angular behavior.
`@Injectable`, `@Input`, `@Output`, and `@RouterConfig` are a few of the more popular annotations
we'll master as our Angular knowledge grows.
<br clear="all">
:marked
The architectural takeaway is that we must add metadata to our code
so that Angular knows what to do.
.l-main-section
<a id="data-binding"></a>
:marked
## Data binding
Without a framework, we would be responsible for pushing data values into the HTML controls and turning user responses
into actions and value updates. Writing such push/pull logic by hand is tedious, error-prone, and a nightmare to
read as any experienced jQuery programmer can attest.
figure
img(src="/resources/images/devguide/architecture/databinding.png" alt="Data Binding" style="width:220px; float:left; margin-left:-40px;margin-right:20px" )
:marked
Angular supports **data binding**,
a mechanism for coordinating parts of a template with parts of a component.
We add binding markup to the template HTML to tell Angular how to connect both sides.
There are four forms of data binding syntax. Each form has a direction — to the DOM, from the DOM, or in both directions —
as indicated by the arrows in the diagram.
<br clear="all">
:marked
We saw three forms of data binding in our [example](#template) template:
+makeExample('architecture/dart/lib/hero_list_component_1.html', 'binding')(format=".")
:marked
* The <code>{&zwnj;{hero.name}}</code> [interpolation](displaying-data.html#interpolation)
displays the component's `hero.name` property value within the `<div>` tags.
* The `[hero]` property binding <!-- TODO: link to template-syntax.html#property-binding-->
passes the value of `selectedHero` from
the parent `HeroListComponent` to the `hero` property of the child `HeroDetailComponent`.
* The `(click)` [event binding](user-input.html#click) calls the component's `selectHero` method when the user clicks a hero's name.
**Two-way data binding** is an important fourth form
that combines property and event binding in a single notation, using the `ngModel` directive.
We didn't have a two-way binding in the `HeroListComponent` template;
here's an example from the `HeroDetailComponent` template:
+makeExample('architecture/dart/lib/hero_detail_component.html', 'ng-model', 'lib/hero_detail_component.html (excerpt)')(format=".")
:marked
In two-way binding, a data property value flows to the input box from the component as with property binding.
The user's changes also flow back to the component, resetting the property to the latest value,
as with event binding.
Angular processes *all* data bindings once per JavaScript event cycle,
depth-first from the root of the application component tree.
<!-- PENDING: clarify what "depth-first from the root" really means,
or reassure that they'll learn it soon. -->
figure
img(src="/resources/images/devguide/architecture/component-databinding.png" alt="Data Binding" style="float:left; width:300px; margin-left:-40px;margin-right:10px" )
:marked
We don't know all the details yet,
but it's clear from these examples that data binding plays an important role in communication
between a template and its component.
<br clear="all">
figure
img(src="/resources/images/devguide/architecture/parent-child-binding.png" alt="Parent/Child binding" style="float:left; width:300px; margin-left:-40px;margin-right:10px" )
:marked
Data binding is also important for communication between parent and child components.
<br clear="all">
.l-main-section
<a id="directive"></a>
:marked
## Directives
figure
img(src="/resources/images/devguide/architecture/directive.png" alt="Parent child" style="float:left; width:150px; margin-left:-40px;margin-right:10px" )
:marked
Angular templates are *dynamic*. When Angular renders them, it transforms the DOM
according to the instructions given by **directives**.
A directive is a class with directive metadata. In Dart we apply the `@Directive` annotation
to attach metadata to the class.
<br clear="all">
:marked
We already met one form of directive: the component. A component is a *directive-with-a-template*;
a `@Component` annotation is actually a `@Directive` annotation extended with template-oriented features.
.l-sub-section
block angular-library-modules
:marked
While **a component is technically a directive**,
components are so distinctive and central to Angular applications that we chose
to separate components from directives in this architectural overview.
:marked
Two *other* kinds of directives exist: _structural_ and _attribute_ directives.
Angular ships as a collection of libraries within the
[**angular2**](https://pub.dartlang.org/packages/angular2) package.
They tend to appear within an element tag like attributes,
sometimes by name but more often as the target of an assignment or a binding.
block angular-imports
+makeExcerpt('app/app.component.ts', 'import')
**Structural** directives alter layout by adding, removing, and replacing elements in DOM.
Our [example](#template) template uses two built-in structural directives:
+makeExample('architecture/dart/lib/hero_list_component_1.html', 'structural')(format=".")
:marked
* [`*ngFor`](displaying-data.html#ng-for) tells Angular to stamp out one `<div>` per hero in the `heroes` list.
* [`*ngIf`](displaying-data.html#ng-if) includes the `HeroDetail` component only if a selected hero exists.
.l-sub-section
block ts-decorator
:marked
In Dart, **the only value that is true is the boolean value `true`**; all
other values are false. JavaScript and TypeScript, in contrast, treat values
such as 1 and most non-null objects as true. For this reason, the JavaScript
and TypeScript versions of this app can use just `selectedHero` as the value
of the `*ngIf` expression. The Dart version must use a boolean operator such
as `!=` instead.
Annotations often have configuration parameters.
The `@Component` annotation takes parameters to provide the
information Angular needs to create and present the component and its view.
:marked
**Attribute** directives alter the appearance or behavior of an existing element.
In templates they look like regular HTML attributes, hence the name.
Here are a few of the possible `@Component` parameters:
The `ngModel` directive, which implements two-way data binding, is
an example of an attribute directive. `ngModel` modifies the behavior of
an existing element (typically an `<input>`)
by setting its display value property and responding to change events.
+makeExample('architecture/dart/lib/hero_detail_component.html', 'ng-model')(format=".")
:marked
Angular ships with a small number of other directives that either alter the layout structure
(for example, `ngSwitch`) <!-- TODO: link to template-syntax.html#ng-switch -->
or modify aspects of DOM elements and components
(for example, `ngStyle` and `ngClass`).
<!-- PENDING: link to template-syntax.html#ng-style template-syntax.html#ng-class-->
Of course, we can also write our own directives. Components such as
`HeroListComponent` are one kind of custom directive.
<!-- PENDING: link to where to learn more about other kinds! -->
.l-main-section
<a id="service"></a>
:marked
## Services
figure
img(src="/resources/images/devguide/architecture/service.png" alt="Service" style="float:left; margin-left:-40px;margin-right:10px" )
:marked
_Services_ is a broad category encompassing any value, function, or feature that our application needs.
Almost anything can be a service.
A service is typically a class with a narrow, well-defined purpose. It should do something specific and do it well.
<br clear="all">
:marked
Examples include:
* logging service
* data service
* message bus
* tax calculator
* application configuration
There is nothing specifically _Angular_ about services. Angular itself has no definition of a service.
There is no service base class, and no place to register a service.
Yet services are fundamental to any Angular application. Our components are big consumers of services.
We prefer our component classes lean. Our components don't fetch data from the server,
they don't validate user input, and they don't log directly to console. They delegate such tasks to services.
A component's job is to enable the user experience and nothing more. It mediates between the view (rendered by the template)
and the application logic (which often includes some notion of a _model_).
A good component presents properties and methods for data binding.
It delegates everything nontrivial to services.
Angular doesn't *enforce* these principles.
It won't complain if we write a "kitchen sink" component with 3000 lines.
Angular does help us *follow* these principles by making it easy to factor our
application logic into services and make those services available to components through *dependency injection*.
.l-main-section
<a id="dependency-injection"></a>
:marked
## Dependency injection
figure
img(src="/resources/images/devguide/architecture/dependency-injection.png" alt="Service" style="float:left; width:200px; margin-left:-40px;margin-right:10px" )
:marked
Dependency injection is a way to supply a new instance of a class
with the fully-formed dependencies it requires. Most dependencies are services.
Angular uses dependency injection to provide new components with the services they need.
<br clear="all">
:marked
Angular can tell which services a component needs by looking at the types of its constructor parameters.
For example, the constructor of our `HeroListComponent` needs a `HeroService`:
+makeExample('architecture/dart/lib/hero_list_component.dart', 'ctor', 'lib/hero_list_component.dart (excerpt)')(format='.')
:marked
When Angular creates a component, it first asks an **injector** for
the services that the component requires.
An injector maintains a container of service instances that it has previously created.
If a requested service instance is not in the container, the injector makes one and adds it to the container
before returning the service to Angular.
When all requested services have been resolved and returned,
Angular can call the component's constructor with those services as arguments.
This is what we mean by *dependency injection*.
The process of `HeroService` injection looks a bit like this:
figure
img(src="/resources/images/devguide/architecture/injector-injects.png" alt="Service" )
:marked
If the injector doesn't have a `HeroService`, how does it know how to make one?
In brief, we must have previously registered a **provider** of the `HeroService` with the injector.
A provider is something that can create or return a service, typically the service class itself.
We can register providers at any level of the application component tree.
We often do so at the root when we bootstrap the application so that
the same instance of a service is available everywhere.
+makeExample('architecture/dart/web/main.dart', 'bootstrap', 'web/main.dart (excerpt)')(format='.')
:marked
Alternatively, we might register at a component level:
+makeExample('architecture/dart/lib/hero_list_component.dart', 'providers', 'lib/hero_list_component.dart (excerpt)')(format='.')
:marked
Registering at a component level means we get a new instance of the
service with each new instance of that component.
<!-- We've vastly oversimplified dependency injection for this overview.
The full story is in the [Dependency Injection](dependency-injection.html) chapter. -->
Points to remember about dependency injection:
* Dependency injection is wired into the Angular framework and used everywhere.
* The *injector* is the main mechanism.
* An injector maintains a *container* of service instances that it created.
* An injector can create a new service instance from a *provider*.
* A *provider* is a recipe for creating a service.
* We register *providers* with injectors.
<a id="other-stuff"></a>
.l-main-section
:marked
## Other stuff
We've learned just a bit about the seven main building blocks of an Angular application:
1. [Components](#component)
1. [Templates](#template)
1. [Metadata](#metadata)
1. [Data binding](#data-binding)
1. [Directives](#directive)
1. [Services](#service)
1. [Dependency injection](#dependency-injection)
That's a foundation for everything else in an Angular application,
and it's more than enough to get going.
But it doesn't include everything we'll need or want to know.
Here is a brief, alphabetical list of other important Angular features and services.
Most of them are covered in this Developers Guide (or soon will be).
>**Animations:** A forthcoming animation library makes it easy for developers to animate component behavior
without deep knowledge of animation techniques or CSS.
>**Bootstrap:** A method to configure and launch the root application component.
>**Change detection:** Learn how Angular decides that a component property value has changed and
when to update the screen.
Learn how it uses **zones** to intercept asynchronous activity and run its change detection strategies.
>**Component router:** With the component Router service, users can navigate a multi-screen application
in a familiar web browsing style using URLs.
>**Events:** The DOM raises events. So can components and services. Angular offers mechanisms for
publishing and subscribing to events including an implementation of the [RxJS Observable](https://github.com/zenparsing/es-observable) proposal.
>**[Forms](forms.html):** Support complex data entry scenarios with HTML-based validation and dirty checking.
>**HTTP:** Communicate with a server to get data, save data, and invoke server-side actions with this Angular HTTP client.
>**Lifecycle hooks:** We can tap into key moments in the lifetime of a component, from its creation to its destruction,
by implementing the lifecycle hook interfaces.
>**Pipes:** Services that transform values for display.
We can put pipes in our templates to improve the user experience. Consider
this `currency` pipe expression:
<div style="margin-left:40px">
code-example(language="javascript" linenumbers=".").
price | currency:'USD':true'
</div>
:marked
>It displays a price of "42.33" as `$42.33`.
>**Testing:** Angular provides a
[testing library](https://pub.dartlang.org/packages/angular2_testing)
to run unit tests on our application parts as they interact with the Angular framework.
block dart-bool
.callout.is-helpful
header Dart difference: Only true is true
:marked
In Dart, **the only value that is true is the boolean value `true`**; all
other values are false. JavaScript and TypeScript, in contrast, treat values
such as 1 and most non-null objects as true. For this reason, the JavaScript
and TypeScript versions of this app can use just `selectedHero` as the value
of the `*ngIf` expression. The Dart version must use a boolean operator such
as `!=` instead.

546
public/docs/ts/latest/guide/architecture.jade
View File

@ -1,44 +1,51 @@
include ../_util-fns
block includes
include ../_util-fns
- var _library_module = 'library module'
- var _at_angular = '@angular'
:marked
Angular 2 is a framework to help us build client applications in HTML and JavaScript.
Angular 2 is a framework to help us build client applications in HTML and
either JavaScript or a language (like Dart or TypeScript) that compiles to JavaScript.
The framework consists of several cooperating libraries, some of them core and some optional.
block angular-parts
:marked
The framework consists of several cooperating libraries, some of them core and some optional.
We write applications by composing HTML *templates* with Angularized-markup,
:marked
With Angular, we write applications by composing HTML *templates* with Angularized-markup,
writing *component* classes to manage those templates, adding application logic in *services*,
and handing the top root component to Angular's *bootstrapper*.
Angular takes over, presenting our application content in a browser and responding to user interactions
according to the instructions we provided.
Angular takes over, presenting our application content in a browser and
responding to user interactions according to the instructions we provided.
<!-- figure img(src="/resources/images/devguide/architecture/airplane.png" alt="Us" align="left" style="width:200px; margin-left:-40px;margin-right:10px" ) -->
:marked
Of course there is more to it than this. We'll learn the details when we dive into the guide chapters.
Of course there is more to it than this.
We'll learn the details when we dive into the guide chapters.
Let's get the big picture first.
figure
img(src="/resources/images/devguide/architecture/overview2.png" alt="overview" style="margin-left:-40px;" width="700")
:marked
The architecture diagram identifies the eight main building blocks of an Angular 2 application:
1. [Module](#module)
1. [Component](#component)
1. [Template](#template)
1. [Metadata](#metadata)
1. [Data Binding](#data-binding)
1. [Directive](#directive)
1. [Service](#service)
1. [Dependency Injection](#dependency-injection)
Learn these eight and we're on our way.
1. [Modules](#modules)
1. [Components](#components)
1. [Templates](#templates)
1. [Metadata](#metadata)
1. [Data binding](#data-binding)
1. [Directives](#directives)
1. [Services](#services)
1. [Dependency injection](#dependency-injection)
Learn these, and we're on our way.
.l-sub-section
:marked
The code referenced in this chapter is available as a [live example](/resources/live-examples/architecture/ts/plnkr.html).
<a id="module"></a>
p The code referenced in this chapter is available as a #[+liveExampleLink2()].
.l-main-section
:marked
## The Module
## Modules
figure
img(src="/resources/images/devguide/architecture/module.png" alt="Component" align="left" style="width:240px; margin-left:-40px;margin-right:10px" )
:marked
@ -49,134 +56,158 @@ figure
A typical module is a cohesive block of code dedicated to a single purpose.
A module **exports** something of value in that code, typically one thing such as a class.
<br clear="all"><br>
.l-sub-section
:marked
### Modules are optional
We highly recommend modular design. TypeScript has great support for ES2015 module syntax and our chapters assume we're taking a modular
approach using that syntax. That's why we list *Module* among the basic building blocks.
Angular itself doesn't require a modular approach nor this particular syntax. Don't use it if you don't want it.
Each chapter has plenty to offer after you steer clear of the `import` and `export` statements.
block modules-in-dart
//- N/A
Find setup and organization clues in the JavaScript track (select it from the combo-box at the top of this page)
which demonstrates Angular 2 development with plain old JavaScript and no module system.
block modules-are-optional
.l-sub-section
:marked
### Modules are optional
We highly recommend modular design. TypeScript has great support for ES2015 module syntax and our chapters assume we're taking a modular
approach using that syntax. That's why we list *Module* among the basic building blocks.
Angular itself doesn't require a modular approach nor this particular syntax. Don't use it if you don't want it.
Each chapter has plenty to offer after you steer clear of the `import` and `export` statements.
Find setup and organization clues in the JavaScript track (select it from the combo-box at the top of this page)
which demonstrates Angular 2 development with plain old JavaScript and no module system.
- var _app_comp_filename = _docsFor == 'dart' ? 'app_component.dart' : 'app.component.ts';
:marked
Perhaps the first module we meet is a module that exports a *component* class.
The component is one of the basic Angular blocks, we write a lot of them,
and we'll talk about components in the next segment. For the moment it is enough to know that a
component class is the kind of thing we'd export from a module.
Most applications have an `AppComponent`. By convention, we'll find it in a file named `app.component.ts`.
Look inside such a file and we'll see an `export` statement like this one.
+makeExample('architecture/ts/app/app.component.ts', 'export', 'app/app.component.ts (excerpt)')(format=".")
:marked
The `export` statement tells TypeScript that this is a module whose
`AppComponent` class is public and accessible to other modules of the application.
Most applications have an `AppComponent`. By convention, we'll find it in a file named `!{_app_comp_filename}`.
Look inside such a file and we'll see a declaration such as this one.
+makeExcerpt('app/app.component.ts ()', 'export')
block export-qualifier
:marked
The `export` statement tells TypeScript that this is a module whose
`AppComponent` class is public and accessible to other modules of the application.
When we need a reference to the `AppComponent`, we **import** it like this:
+makeExample('architecture/ts/app/main.ts', 'import', 'app/main.ts (excerpt)')(format=".")
:marked
The `import` statement tells the system it can get an `AppComponent` from a module named `app.component`
located in a neighboring file.
The **module name** (AKA module id) is often the same as the filename without its extension.
### Library Modules
When we need a reference to the `AppComponent`, we **import** it like this:
+makeExcerpt('app/main.ts', 'import')
block ts-import
:marked
The `import` statement tells the system it can get an `AppComponent` from a module named `app.component`
located in a neighboring file.
The **module name** (AKA module id) is often the same as the filename without its extension.
:marked
### Libraries
figure
img(src="/resources/images/devguide/architecture/library-module.png" alt="Component" align="left" style="width:240px; margin-left:-40px;margin-right:10px" )
block angular-library-modules
:marked
Some modules are _libraries_ of other modules.
Angular itself ships as a collection of library modules within several npm packages.
Their names begin with the `!{_at_angular}` prefix.
Each Angular library contains a [barrel](../glossary.html#barrel) module
that is actually a public façade over several logically-related private modules.
:marked
Some modules are libraries of other modules.
Angular itself ships as a collection of library modules within several npm packages.
Their names begin with the `@angular` prefix.
Each Angular library contains a [barrel](../glossary.html#barrel) module
that is actually a public façade over several logically-related private modules.
The `@angular/core` library is the primary Angular library module from which we get most of what we need.
`!{_at_angular}/core` is the primary Angular library from which we get most of what we need.
<br clear="all">
There are other important Angular library modules too such as `@angular/common`, `@angular/router`, and `@angular/http`.
There are other important Angular libraries too, such as `!{_at_angular}/common`, `!{_at_angular}/router`, and `!{_at_angular}/animate`.
We import what we need from an Angular !{_library_module}.
We import what we need from an Angular library module in much the same way.
For example, we import the Angular **`Component` *function*** from the *@angular/core* module like this:
+makeExample('architecture/ts/app/app.component.ts', 'import')(format=".")
:marked
Compare that syntax to our previous import of `AppComponent`.
+makeExample('architecture/ts/app/main.ts', 'import')(format=".")
:marked
Notice the difference?
In the first case, when importing from an Angular library module,
the import statement refers to the bare module name, `@angular/core`, *without a path prefix*.
When we import from one of *our* own files, we prefix the module name with the file path.
In this example we specify a relative file path (./). That means the
source module is in the same folder (./) as the module importing it.
We could path up and around the application folder structure if the source module were somewhere else.
.l-sub-section
block angular-imports
:marked
We import and export in the ECMAScript 2015 (ES2015) module syntax.
Learn more about that syntax [here](http://www.2ality.com/2014/09/es6-modules-final.html)
and many other places on the web.
For example, we import the Angular **`Component` *function*** from `@angular/core` like this:
+makeExcerpt('app/app.component.ts', 'import')
:marked
Compare that syntax to our previous import of `AppComponent`.
+makeExcerpt('app/main.ts', 'import')
The infrastructure *behind* module loading and importing is an important subject.
But it's a subject outside the scope of this introduction to Angular.
While we're focused on our application, *import* and *export*
is about all we need to know.
:marked
Notice the difference?
In the first case, when importing from an Angular library module,
the import statement refers to the bare module name, `@angular/core`, *without a path prefix*.
When we import from one of *our* own files, we prefix the module name with the file path.
In this example we specify a relative file path (`./`). That means the
source module is in the same folder (`./`) as the module importing it.
We could path up and around the application folder structure if the source module were somewhere else.
.l-sub-section
:marked
We import and export in the ECMAScript 2015 (ES2015) module syntax.
Learn more about that syntax [here](http://www.2ality.com/2014/09/es6-modules-final.html)
and many other places on the web.
The infrastructure *behind* module loading and importing is an important subject.
But it's a subject outside the scope of this introduction to Angular.
While we're focused on our application, *import* and *export*
is about all we need to know.
- var _export = _docsFor == 'dart' ? 'publicly declare' : 'export';
- var _declare = _docsFor == 'dart' ? 'declare' : 'export';
:marked
The key take-aways are:
* Angular apps are composed of modules.
* Modules export things &mdash; classes, function, values &mdash; that other modules import.
* Modules !{_export} things &mdash; classes, function, values &mdash; that other modules import.
* We prefer to write our application as a collection of modules, each module exporting one thing.
The first module we write will most likely export a component.
The first module we write will most likely !{_declare} a component.
.l-main-section
<a id="component"></a>
:marked
## The Component
## Components
figure
img(src="/resources/images/devguide/architecture/hero-component.png" alt="Component" align="left" style="width:200px; margin-left:-40px;margin-right:10px" )
:marked
A **Component** controls a patch of screen real estate that we could call a *view*.
The shell at the application root with navigation links, that list of heroes, the hero editor ...
they're all views controlled by Components.
We define a Component's application logic - what it does to support the view - inside a class.
:marked
A **component** controls a patch of screen real estate that we could call a *view*.
The shell at the application root with navigation links, a list of heroes, a hero editor ...
they're all views controlled by components.
We define a component's application logic &mdash; what it does to support the view &mdash; inside a class.
The class interacts with the view through an API of properties and methods.
<a id="component-code"></a>
A `HeroListComponent`, for example, might have a `heroes` property that returns an array of heroes
A `HeroListComponent`, for example, might have a `heroes` property that returns !{_an} !{_array} of heroes
that it acquired from a service.
It might have a `selectHero()` method that sets a `selectedHero` property when the user clicks on a hero from that list.
It might be a class like this:
It might have a `selectHero()` method that sets a `selectedHero` property when the user clicks to choose a hero from that list.
The component might be a class like this:
+makeExample('architecture/ts/app/hero-list.component.ts', 'class', 'app/hero-list.component.ts')
+makeExcerpt('app/hero-list.component.ts', 'class')
:marked
Angular creates, updates, and destroys components as the user moves through the application.
The developer can take action at each moment in this lifecycle through optional [Lifecycle Hooks](lifecycle-hooks.html).
The developer can take action at each moment in this lifecycle through optional [lifecycle hooks](lifecycle-hooks.html), like `ngOnInit()` declared above.
.l-sub-section
:marked
We're not showing those hooks in this example
but we are making a mental note to find out about them later.
We may wonder who is calling that constructor? Who provides the service parameter?
We may wonder who is calling the component's constructor? Who provides the service parameter?
For the moment, have faith that Angular will call the constructor and deliver an
appropriate `HeroService` when we need it.
.l-main-section
<a id="template"></a>
:marked
## The Template
## Templates
figure
img(src="/resources/images/devguide/architecture/template.png" alt="Template" align="left" style="width:200px; margin-left:-40px;margin-right:10px" )
:marked
We define a Component's view with its companion **template**. A template is a form of HTML
that tells Angular how to render the Component.
We define a component's view with its companion **template**. A template is a form of HTML
that tells Angular how to render the component.
A template looks like regular HTML much of the time ... and then it gets a bit strange. Here is a
template for our `HeroList` component.
+makeExample('architecture/ts/app/hero-list.component.html',null,'app/hero-list.component.html')
template for our `HeroListComponent`:
+makeExample('app/hero-list.component.html')
:marked
We recognize `<h2>` and `<div>`.
But there's other markup that no one told us about in school.
What are `*ngFor`, `{{hero.name}}`, `(click)`, `[hero]`, and `<hero-detail>`?
This template features typical HTML elements like `<h2>` and `<p>`.
But what are `*ngFor`, `{{hero.name}}`, `(click)`, `[hero]`, and `<hero-detail>`?
These are examples of Angular's [template syntax](template-syntax.html).
We will grow accustomed to that syntax and may even learn to love it.
@ -193,85 +224,86 @@ figure
figure
img(src="/resources/images/devguide/architecture/component-tree.png" alt="Metadata" align="left" style="width:300px; margin-left:-40px;margin-right:10px" )
:marked
Notice how `<hero-detail>` rests comfortably among the HTML elements we already know.
We can mix ... and will mix ... our custom components with native HTML in the same layouts.
Notice how `<hero-detail>` rests comfortably among native HTML elements.
We can and _will_ mix our custom components with native HTML in the same layouts.
And in this manner we can and will compose complex component trees to build out our richly featured application.
In this manner we'll compose complex component trees to build out our richly featured application.
<br clear="all">
.l-main-section
<a id="metadata"></a>
:marked
## Angular Metadata
## Metadata
figure
img(src="/resources/images/devguide/architecture/metadata.png" alt="Metadata" align="left" style="width:150px; margin-left:-40px;margin-right:10px" )
:marked
<p style="padding-top:10px">Metadata tells Angular how to process a class.</p>
<br clear="all">
:marked
[Looking back](#component-code) at the `HeroListComponent`, we see that it's just a class.
[Looking back at the code](#component-code) for `HeroListComponent`, we see that it's just a class.
There is no evidence of a framework, no "Angular" in it at all.
In fact, it really is *just a class*. It's not a component until we *tell Angular about it*.
We tell Angular that `HeroListComponent` is a component by attaching **metadata** to the class.
The easy way to attach metadata in TypeScript is with a **decorator**.
In !{_Lang}, we attach metadata by using !{_a} **!{_decorator}**.
Here's some metadata for `HeroListComponent`:
+makeExample('architecture/ts/app/hero-list.component.ts', 'metadata', 'app/hero-list.component.ts (metadata)')
+makeExcerpt('app/hero-list.component.ts', 'metadata')
:marked
Here we see the `@Component` decorator which (no surprise) identifies the class
immediately below it as a Component class.
Here we see the `@Component` !{_decorator} which (no surprise) identifies the class
immediately below it as a component class.
A decorator is a function. Decorators often have a configuration parameter.
The `@Component` decorator takes a required configuration object with the
information Angular needs to create and present the component and its view.
block ts-decorator
:marked
A decorator is a function. Decorators often have a configuration parameter.
The `@Component` decorator takes a required configuration object with the
information Angular needs to create and present the component and its view.
Here we see a few of the possible `@Component` configuration options:
Here are a few of the possible `@Component` configuration options:
* `selector` - a css selector that tells Angular to create and insert an instance of this component
:marked
- `selector`: CSS selector that tells Angular to create and insert an instance of this component
where it finds a `<hero-list>` tag in *parent* HTML.
If the template of the application shell (a Component) contained
<div style="margin-left:30px">
code-example(language="html").
&lt;hero-list>&lt;/hero-list>
</div>
:marked
>Angular inserts an instance of the `HeroListComponent` view between those tags.
For example, if an app's HTML contains `<hero-list></hero-list>`, then
Angular inserts an instance of the `HeroListComponent` view between those tags.
* `templateUrl` - the address of this component's template which we showed [above](#template).
- `templateUrl`: address of this component's template, which we showed [above](#templates).
* `directives` - an array of the Components or Directives that *this* template requires.
- `directives`: !{_array} of the components or directives that *this* template requires.
We saw in the last line of our template that we expect Angular to insert a `HeroDetailComponent`
in the space indicated by `<hero-detail>` tags.
Angular will do so only if we mention the `HeroDetailComponent` in this `directives` array.
Angular will do so only if we mention the `HeroDetailComponent` in this `directives` !{_array}.
* `providers` - an array of **dependency injection providers** for services that the component requires.
- `providers`: !{_array} of **dependency injection providers** for services that the component requires.
This is one way to tell Angular that our component's constructor requires a `HeroService`
so it can get the list of heroes to display. We'll get to dependency injection in a moment.
so it can get the list of heroes to display. We'll get to dependency injection later.
figure
img(src="/resources/images/devguide/architecture/template-metadata-component.png" alt="Metadata" align="left" style="height:200px; margin-left:-40px;margin-right:10px" )
:marked
The `@Component` function takes the configuration object and turns it into metadata that it attaches
to the component class definition. Angular discovers this metadata at runtime and thus knows how to do "the right thing".
Angular reads the metadata specified by the `@Component`
annotation. That's how Angular learns to do "the right thing".
The template, metadata, and component together describe the view.
The template, metadata, and component together describe a view.
We apply other metadata decorators in a similar fashion to guide Angular behavior.
The `@Injectable`, `@Input`, `@Output`, `@RouterConfig` are a few of the more popular decorators
We apply other metadata !{_decorator}s in a similar fashion to guide Angular behavior.
`@Injectable`, `@Input`, and `@Output` are a few of the more popular !{_decorator}s
we'll master as our Angular knowledge grows.
<br clear="all">
:marked
The architectural take-away is that we must add metadata to our code
The architectural takeaway is that we must add metadata to our code
so that Angular knows what to do.
.l-main-section
<a id="data-binding"></a>
:marked
## Data Binding
## Data binding
Without a framework, we would be responsible for pushing data values into the HTML controls and turning user responses
into actions and value updates. Writing such push/pull logic by hand is tedious, error-prone and a nightmare to
read as the experienced jQuery programmer can attest.
into actions and value updates. Writing such push/pull logic by hand is tedious, error-prone, and a nightmare to
read as any experienced jQuery programmer can attest.
figure
img(src="/resources/images/devguide/architecture/databinding.png" alt="Data Binding" style="width:220px; float:left; margin-left:-40px;margin-right:20px" )
:marked
@ -279,108 +311,118 @@ figure
a mechanism for coordinating parts of a template with parts of a component.
We add binding markup to the template HTML to tell Angular how to connect both sides.
There are four forms of data binding syntax. Each form has a direction - to the DOM, from the DOM, or in both directions -
There are four forms of data binding syntax. Each form has a direction &mdash; to the DOM, from the DOM, or in both directions &mdash;
as indicated by the arrows in the diagram.
<br clear="all">
:marked
We saw three forms of data binding in our [example](#template) template:
+makeExample('architecture/ts/app/hero-list.component.1.html', 'binding', 'app/hero-list.component.html (excerpt)')(format=".")
We saw three forms of data binding in our [example](#templates) template:
+makeExcerpt('app/hero-list.component.1.html', 'binding')
:marked
* The `{{hero.name}}` [*interpolation*](displaying-data.html#interpolation)
displays the component's `hero.name` property value within the `<div>` tags.
displays the component's `hero.name` property value within the `<li>` tags.
* The `[hero]` [*property binding*](template-syntax.html#property-binding) passes the `selectedHero` from
* The `[hero]` [*property binding*](template-syntax.html#property-binding) passes the value of `selectedHero` from
the parent `HeroListComponent` to the `hero` property of the child `HeroDetailComponent`.
* The `(click)` [*event binding*](user-input.html#click) calls the Component's `selectHero` method when the user clicks
on a hero's name
* The `(click)` [*event binding*](user-input.html#click) calls the component's `selectHero` method when the user clicks a hero's name.
**Two-way data binding** is an important fourth form
that combines property and event binding in a single notation using the `ngModel` directive.
that combines property and event binding in a single notation, using the `ngModel` directive.
We didn't have a two-way binding in the `HeroListComponent` template;
here's an example from the `HeroDetailComponent` template (not shown):
here's an example from the `HeroDetailComponent` template:
+makeExcerpt('app/hero-detail.component.html', 'ngModel')
+makeExample('architecture/ts/app/hero-detail.component.html', 'ngModel')(format=".")
:marked
In two-way binding, a data property value flows to the input box from the component as with property binding.
The user's changes also flow back to the component, resetting the property to the latest value,
as with event binding.
Angular processes *all* data bindings once per JavaScript event cycle,
depth-first from the root of the application component tree.
from the root of the application component tree down to the leaves.
figure
img(src="/resources/images/devguide/architecture/component-databinding.png" alt="Data Binding" style="float:left; width:300px; margin-left:-40px;margin-right:10px" )
:marked
We don't know all the details yet
We don't know all the details yet,
but it's clear from these examples that data binding plays an important role in communication
between a template and its component ...
between a template and its component.
<br clear="all">
figure
img(src="/resources/images/devguide/architecture/parent-child-binding.png" alt="Parent/Child binding" style="float:left; width:300px; margin-left:-40px;margin-right:10px" )
:marked
... ***and*** between parent and child components
Data binding is also important for communication between parent and child components.
<br clear="all">
.l-main-section
<a id="directive"></a>
:marked
## The Directive
## Directives
figure
img(src="/resources/images/devguide/architecture/directive.png" alt="Parent child" style="float:left; width:150px; margin-left:-40px;margin-right:10px" )
:marked
Our Angular templates are *dynamic*. When Angular renders them, it transforms the DOM
according to the instructions given by a **directive**.
Angular templates are *dynamic*. When Angular renders them, it transforms the DOM
according to the instructions given by **directives**.
A directive is a class with directive metadata. In TypeScript we'd apply the `@Directive` decorator
A directive is a class with directive metadata. In !{_Lang} we apply the `@Directive` !{_decorator}
to attach metadata to the class.
<br clear="all">
:marked
We already met one form of directive: the component. A component is a *directive-with-a-template*
and the `@Component` decorator is actually a `@Directive` decorator extended with template-oriented features.
We already met one form of directive: the component. A component is a *directive-with-a-template*;
a `@Component` !{_decorator} is actually a `@Directive` !{_decorator} extended with template-oriented features.
.l-sub-section
:marked
While the **component is technically a directive**,
it is so distinctive and central to Angular applications that we chose
to separate the component from the directive in our architectural overview.
While **a component is technically a directive**,
components are so distinctive and central to Angular applications that we chose
to separate components from directives in this architectural overview.
:marked
There are two *other* kinds of directives as well that we call "structural" and "attribute" directives.
Two *other* kinds of directives exist: _structural_ and _attribute_ directives.
They tend to appear within an element tag like attributes,
They tend to appear within an element tag as attributes do,
sometimes by name but more often as the target of an assignment or a binding.
**Structural** directives alter layout by adding, removing, and replacing elements in DOM.
We see two built-in structural directives at play in our [example](#template) template:
+makeExample('architecture/ts/app/hero-list.component.1.html', 'structural')(format=".")
Our [example](#templates) template uses two built-in structural directives:
+makeExcerpt('app/hero-list.component.1.html', 'structural')
:marked
* [`*ngFor`](displaying-data.html#ngFor) tells Angular to stamp out one `<div>` per hero in the `heroes` list.
* [`*ngFor`](displaying-data.html#ngFor) tells Angular to stamp out one `<li>` per hero in the `heroes` list.
* [`*ngIf`](displaying-data.html#ngIf) includes the `HeroDetail` component only if a selected hero exists.
block dart-bool
//- N/A
:marked
**Attribute** directives alter the appearance or behavior of an existing element.
In templates they look like regular HTML attributes, hence the name.
The `ngModel` directive, which implements two-way data binding, is an example of an attribute directive.
+makeExample('architecture/ts/app/hero-detail.component.html', 'ngModel')(format=".")
:marked
It modifies the behavior of an existing element (typically an `<input>`)
The `ngModel` directive, which implements two-way data binding, is
an example of an attribute directive. `ngModel` modifies the behavior of
an existing element (typically an `<input>`)
by setting its display value property and responding to change events.
Angular ships with a few other directives that either alter the layout structure
(e.g. [ngSwitch](template-syntax.html#ngSwitch))
+makeExcerpt('app/hero-detail.component.html', 'ngModel')
:marked
Angular ships with a small number of other directives that either alter the layout structure
(for example, [ngSwitch](template-syntax.html#ngSwitch))
or modify aspects of DOM elements and components
(e.g. [ngStyle](template-syntax.html#ngStyle) and [ngClass](template-syntax.html#ngClass)).
(for example, [ngStyle](template-syntax.html#ngStyle) and [ngClass](template-syntax.html#ngClass)).
And of course we can write our own directives.
Of course, we can also write our own directives. Components such as
`HeroListComponent` are one kind of custom directive.
<!-- PENDING: link to where to learn more about other kinds! -->
.l-main-section
<a id="service"></a>
:marked
## The Service
## Services
figure
img(src="/resources/images/devguide/architecture/service.png" alt="Service" style="float:left; margin-left:-40px;margin-right:10px" )
:marked
"Service" is a broad category encompassing any value, function or feature that our application needs.
_Service_ is a broad category encompassing any value, function, or feature that our application needs.
Almost anything can be a service.
A service is typically a class with a narrow, well-defined purpose. It should do something specific and do it well.
@ -393,27 +435,32 @@ figure
* tax calculator
* application configuration
There is nothing specifically *Angular* about services. Angular itself has no definition of a *service*.
There is no *ServiceBase* class.
There is nothing specifically _Angular_ about services. Angular itself has no definition of a service.
There is no service base class, and no place to register a service.
Yet services are fundamental to any Angular application.
Yet services are fundamental to any Angular application. Our components are big consumers of services.
Here's an example of a service class that logs to the browser console
+makeExample('architecture/ts/app/logger.service.ts', 'class', 'app/logger.service.ts (class only)')(format=".")
+makeExcerpt('app/logger.service.ts', 'class')
:marked
Here's a `HeroService` that fetches heroes and returns them in a resolved [promise](http://exploringjs.com/es6/ch_promises.html).
Here's a `HeroService` that fetches heroes and returns them in a resolved !{_PromiseLinked}.
The `HeroService` depends on the `Logger` service and another `BackendService` that handles the server communication grunt work.
+makeExample('architecture/ts/app/hero.service.ts', 'class', 'app/hero.service.ts (class only)')(format=".")
+makeExcerpt('app/hero.service.ts', 'class')
:marked
Services are everywhere.
Our components are big consumers of services. They depend upon services to handle most chores.
They don't fetch data from the server, they don't validate user input, they don't log directly to the console.
We prefer our component classes lean. Our components don't fetch data from the server,
they don't validate user input, and they don't log directly to the console.
They delegate such tasks to services.
A component's job is to enable the user experience and nothing more. It mediates between the view (rendered by the template)
and the application logic (which often includes some notion of a "model"). A good component presents
properties and methods for data binding. It delegates everything non-trivial to services.
and the application logic (which often includes some notion of a _model_).
A good component presents properties and methods for data binding.
It delegates everything nontrivial to services.
Angular doesn't *enforce* these principles.
It won't complain if we write a "kitchen sink" component with 3000 lines.
@ -422,25 +469,26 @@ figure
application logic into services and make those services available to components through *dependency injection*.
.l-main-section
<a id="dependency-injection"></a>
:marked
## Dependency Injection
## Dependency injection
figure
img(src="/resources/images/devguide/architecture/dependency-injection.png" alt="Service" style="float:left; width:200px; margin-left:-40px;margin-right:10px" )
:marked
"Dependency Injection" is a way to supply a new instance of a class
_Dependency injection_ is a way to supply a new instance of a class
with the fully-formed dependencies it requires. Most dependencies are services.
Angular uses dependency injection to provide new components with the services they need.
<br clear="all">
:marked
In TypeScript, Angular can tell which services a component needs by looking at the types of its constructor parameters.
For example, the constructor of our `HeroListComponent` needs the `HeroService`:
+makeExample('architecture/ts/app/hero-list.component.ts', 'ctor', 'app/hero-list.component (constructor)')(format=".")
Angular can tell which services a component needs by looking at the types of its constructor parameters.
For example, the constructor of our `HeroListComponent` needs a `HeroService`:
+makeExcerpt('app/hero-list.component.ts (constructor)', 'ctor')
:marked
When Angular creates a component, it first asks an **Injector** for
When Angular creates a component, it first asks an **injector** for
the services that the component requires.
An `Injector` maintains a container of service instances that it has previously created.
An injector maintains a container of service instances that it has previously created.
If a requested service instance is not in the container, the injector makes one and adds it to the container
before returning the service to Angular.
When all requested services have been resolved and returned,
@ -451,92 +499,98 @@ figure
figure
img(src="/resources/images/devguide/architecture/injector-injects.png" alt="Service" )
:marked
If the `Injector` doesn't have a `HeroService`, how does it know how to make one?
If the injector doesn't have a `HeroService`, how does it know how to make one?
In brief, we must have previously registered a **provider** of the `HeroService` with the `Injector`.
In brief, we must have previously registered a **provider** of the `HeroService` with the injector.
A provider is something that can create or return a service, typically the service class itself.
We can register providers at any level of the application component tree.
We often do so at the root when we bootstrap the application so that
the same instance of a service is available everywhere.
+makeExample('architecture/ts/app/main.ts', 'bootstrap','app/main.ts (excerpt)')(format=".")
+makeExcerpt('app/main.ts', 'bootstrap')
:marked
Alternatively, we might register at a component level ...
+makeExample('architecture/ts/app/hero-list.component.ts', 'providers','app/hero-list.component.ts (excerpt)')(format=".")
Alternatively, we might register at a component level, in the providers property of the `@Component` metadata:
+makeExcerpt('app/hero-list.component.ts', 'providers')
:marked
... in which case we get a new instance of the
Registering at a component level means we get a new instance of the
service with each new instance of that component.
We've vastly over-simplified dependency injection for this overview.
We can learn the full story in the [Dependency Injection](dependency-injection.html) chapter.
<!-- We've vastly oversimplified dependency injection for this overview.
The full story is in the [Dependency Injection](dependency-injection.html) chapter. -->
The points to remember are:
* dependency injection is wired into the framework and used everywhere.<br><br>
* the `Injector` is the main mechanism.
* an injector maintains a *container* of service instances that it created.
* an injector can create a new service instance using a *provider*.
* a *provider* is a recipe for creating a service.
Points to remember about dependency injection:
* we register *providers* with injectors.
* Dependency injection is wired into the Angular framework and used everywhere.
* The *injector* is the main mechanism.
* An injector maintains a *container* of service instances that it created.
* An injector can create a new service instance from a *provider*.
* A *provider* is a recipe for creating a service.
* We register *providers* with injectors.
<a id="other-stuff"></a>
.l-main-section
:marked
## Wrap up
We've learned just a bit about the eight main building blocks of an Angular application
1. [Module](#module)
1. [Component](#component)
1. [Template](#template)
We've learned just a bit about the eight main building blocks of an Angular application:
1. [Modules](#modules)
1. [Components](#components)
1. [Templates](#templates)
1. [Metadata](#metadata)
1. [Data Binding](#data-binding)
1. [Directive](#directive)
1. [Service](#service)
1. [Dependency Injection](#dependency-injection)
1. [Data binding](#data-binding)
1. [Directives](#directives)
1. [Services](#services)
1. [Dependency injection](#dependency-injection)
That's a foundation for everything else in an Angular application
That's a foundation for everything else in an Angular application,
and it's more than enough to get going.
But it doesn't include everything we'll need or want to know.
<a id="other-stuff"></a>
.l-main-section
:marked
## The Other Stuff
Here is a brief, alphabetical list of other important Angular features and services.
Most of them are covered in this Developers Guide (or soon will be):
Most of them are covered in this Developers Guide (or soon will be).
>**Animations** - A forthcoming animation library makes it easy for developers to animate component behavior
without deep knowledge of animation techniques or css.
> [**Animations**](animations.html): The animation library makes it easy for developers to animate component behavior
without deep knowledge of animation techniques or CSS.
>**Bootstrap** - A method to configure and launch the root application component.
> **Bootstrap**: A method to configure and launch the root application component.
>**Change Detection** - Learn how Angular decides that a component property value has changed and
> **Change detection**: Learn how Angular decides that a component property value has changed and
when to update the screen.
Learn how it uses **zones** to intercept asynchronous activity and run its change detection strategies.
>**[Component Router](router.html)** - With the Component Router service, users can navigate a multi-screen application
> **Component router**: With the component Router service, users can navigate a multi-screen application
in a familiar web browsing style using URLs.
>**Events** - The DOM raises events. So can components and services. Angular offers mechanisms for
publishing and subscribing to events including an implementation of the [RxJS Observable](https://github.com/zenparsing/es-observable) proposal.
> **Events**: The DOM raises events. So can components and services. Angular offers mechanisms for
publishing and subscribing to events.
>**[Forms](forms.html)** - Support complex data entry scenarios with HTML-based validation and dirty checking.
> [**Forms**](forms.html): Support complex data entry scenarios with HTML-based validation and dirty checking.
>**[HTTP](server-communication.html)** - Communicate with a server to get data, save data, and invoke server-side actions with this Angular HTTP client.
> [**HTTP**](server-communication.html): Communicate with a server to get data, save data, and invoke server-side actions with an HTTP client.
>**[Lifecycle Hooks](lifecycle-hooks.html)** - We can tap into key moments in the lifetime of a component, from its creation to its destruction,
by implementing the "Lifecycle Hook" interfaces.
> [**Lifecycle hooks**](lifecycle-hooks.html): We can tap into key moments in the lifetime of a component, from its creation to its destruction,
by implementing the lifecycle hook interfaces.
>**[Pipes](pipes.html)** - Services that transform values for display.
We can put pipes in our templates to improve the user experience. For example,
this `currency` pipe expression,
> [**Pipes**](pipes.html): Services that transform values for display.
We can put pipes in our templates to improve the user experience. Consider
this `currency` pipe expression:
<div style="margin-left:40px">
code-example(language="javascript" linenumbers=".").
code-example().
price | currency:'USD':true
</div>
:marked
>displays a price of "42.33" as `$42.33`.
> It displays a price of "42.33" as `$42.33`.
>**[Testing](testing.html)** - Angular provides a testing library for "unit testing" our application parts as they
interact with the Angular framework.
> [**Router**](router.html): Navigate from page to page within the client
application and never leave the browser.
> [**Testing**](testing.html): Angular provides a
[testing library](https://pub.dartlang.org/packages/angular2_testing)
to run unit tests on our application parts as they interact with the Angular framework.