angular-cn/aio/content/guide/cheatsheet.md

Cheat Sheet

速查表

Bootstrapping 启动	import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
platformBrowserDynamic().bootstrapModule(AppModule);	Bootstraps the app, using the root component from the specified NgModule. 用 NgModule 中指定的根组件进行启动。

NgModules Angular 模块	import { NgModule } from '@angular/core';
@NgModule({ declarations: ..., imports: ..., exports: ..., providers: ..., bootstrap: ...}) class MyModule {}	Defines a module that contains components, directives, pipes, and providers. 定义一个模块，其中可以包含组件、指令、管道和服务提供商。
declarations: [MyRedComponent, MyBlueComponent, MyDatePipe]	List of components, directives, and pipes that belong to this module. 属于当前模块的组件、指令和管道的列表。
imports: [BrowserModule, SomeOtherModule]	List of modules to import into this module. Everything from the imported modules is available to declarations of this module. 本模块所导入的模块列表
exports: [MyRedComponent, MyDatePipe]	List of components, directives, and pipes visible to modules that import this module. 那些导入了本模块的模块所能看到的组件、指令和管道的列表
providers: [MyService, { provide: ... }]	List of dependency injection providers visible both to the contents of this module and to importers of this module. 依赖注入提供商的列表，本模块以及本模块导入的所有模块中的内容都可以看见它们。
bootstrap: [MyAppComponent]	List of components to bootstrap when this module is bootstrapped. 当本模块启动时，随之启动的组件列表。

Template syntax 模板语法
<input [value]="firstName">	Binds property value to the result of expression firstName. 把value属性绑定到表达式firstName
<div [attr.role]="myAriaRole">	Binds attribute role to the result of expression myAriaRole. 把属性（Attribute）role绑定到表达式myAriaRole的结果。
<div [class.extra-sparkle]="isDelightful">	Binds the presence of the CSS class extra-sparkle on the element to the truthiness of the expression isDelightful. 根据isDelightful表达式的结果是否为真，决定CSS类extra-sparkle是否出现在当前元素上。
<div [style.width.px]="mySize">	Binds style property width to the result of expression mySize in pixels. Units are optional. 把CSS样式属性width的px（像素）值绑定到表达式mySize的结果。单位是可选的。
<button (click)="readRainbow($event)">	Calls method readRainbow when a click event is triggered on this button element (or its children) and passes in the event object. 当这个按钮元素（及其子元素）上的click事件触发时，调用方法readRainbow，并把这个事件对象作为参数传进去。
<div title="Hello {{ponyName}}">	Binds a property to an interpolated string, for example, "Hello Seabiscuit". Equivalent to: <div [title]="'Hello ' + ponyName"> 把一个属性绑定到插值字符串（如"Hello Seabiscuit"）。这种写法等价于<div [title]="'Hello ' + ponyName">
<p>Hello {{ponyName}}</p>	Binds text content to an interpolated string, for example, "Hello Seabiscuit". 把文本内容绑定到插值字符串（如"Hello Seabiscuit"）
<my-cmp [(title)]="name">	Sets up two-way data binding. Equivalent to: <my-cmp [title]="name" (titleChange)="name=$event"> 设置双向绑定。等价于<my-cmp [title]="name" (titleChange)="name=$event">。
<video #movieplayer ...> <button (click)="movieplayer.play()"> </video>	Creates a local variable movieplayer that provides access to the video element instance in data-binding and event-binding expressions in the current template. 创建一个局部变量movieplayer，支持在当前模板的数据绑定和事件绑定表达式中访问video元素的实例。
<p *myUnless="myExpression">...</p>	The * symbol turns the current element into an embedded template. Equivalent to: <template [myUnless]="myExpression"><p>...</p></template> 星号*会把当前元素转换成内嵌式模板，等价于：<template [myUnless]="myExpression"><p>...</p></template>
<p>Card No.: {{cardNumber | myCardNumberFormatter}}</p>	Transforms the current value of expression cardNumber via the pipe called myCardNumberFormatter. 使用名叫myCardNumberFormatter的管道对表达式cardNumber的当前值进行变幻
<p>Employer: {{employer?.companyName}}</p>	The safe navigation operator (?) means that the employer field is optional and if undefined, the rest of the expression should be ignored. 安全导航操作符（?）表示employer字段是可选的，如果它是 undefined ，那么表达式其余的部分就会被忽略，并返回 undefined。
<svg:rect x="0" y="0" width="100" height="100"/>	An SVG snippet template needs an svg: prefix on its root element to disambiguate the SVG element from an HTML component. 模板中的 SVG 片段需要给它的根元素加上svg:前缀，以便把 SVG 元素和 HTML 元素区分开。
<svg> <rect x="0" y="0" width="100" height="100"/> </svg>	An <svg> root element is detected as an SVG element automatically, without the prefix. 以<svg>作为根元素时会自动识别为 SVG 元素，不需要前缀。

Built-in directives 内置指令	import { CommonModule } from '@angular/common';
<section *ngIf="showSection">	Removes or recreates a portion of the DOM tree based on the showSection expression. 根据showSection表达式的结果，移除或重新创建 DOM 树的一部分。
<li *ngFor="let item of list">	Turns the li element and its contents into a template, and uses that to instantiate a view for each item in list. 把li元素及其内容变成一个模板，并使用这个模板为列表中的每一个条目实例化一个视图。
<div [ngSwitch]="conditionExpression"> <template [ngSwitchCase]="case1Exp">...</template> <template ngSwitchCase="case2LiteralString">...</template> <template ngSwitchDefault>...</template> </div>	Conditionally swaps the contents of the div by selecting one of the embedded templates based on the current value of conditionExpression. 根据conditionExpression的当前值选择一个嵌入式模板，并用它替换这个 div 的内容。
<div [ngClass]="{'active': isActive, 'disabled': isDisabled}">	Binds the presence of CSS classes on the element to the truthiness of the associated map values. The right-hand expression should return {class-name: true/false} map. 根据 map 中的 value 是否为真，来决定该元素上是否出现与 name 对应的 CSS 类。右侧的表达式应该返回一个形如 {class-name: true/false} 的 map。
<div [ngStyle]="{'property': 'value'}"> <div [ngStyle]="dynamicStyles()">	Allows you to assign styles to an HTML element using CSS. You can use CSS directly, as in the first example, or you can call a method from the component.

Forms 表单	import { FormsModule } from '@angular/forms';
<input [(ngModel)]="userName">	Provides two-way data-binding, parsing, and validation for form controls. 为表单控件提供双向数据绑定、解析和验证功能。

Class decorators 类装饰器（decorator）	import { Directive, ... } from '@angular/core';
@Component({...}) class MyComponent() {}	Declares that a class is a component and provides metadata about the component. 声明一个类是组件，并提供该组件的元数据。
@Directive({...}) class MyDirective() {}	Declares that a class is a directive and provides metadata about the directive. 声明一个类是指令，并提供该指令的元数据。
@Pipe({...}) class MyPipe() {}	Declares that a class is a pipe and provides metadata about the pipe. 声明一个类是管道，并提供该管道的元数据。
@Injectable() class MyService() {}	Declares that a class has dependencies that should be injected into the constructor when the dependency injector is creating an instance of this class. 声明一个类具有一些依赖，当依赖注入器试图创建该类的实例时，应该把这些依赖注入到该类的构造函数中。

Directive configuration 指令配置	@Directive({ property1: value1, ... })
selector: '.cool-button:not(a)'	Specifies a CSS selector that identifies this directive within a template. Supported selectors include element, [attribute], .class, and :not(). 指定一个 CSS 选择器，用于在模板中标记出该指令。支持的选择器类型包括：元素名、[属性名], .类名 和 :not()。 Does not support parent-child relationship selectors. 但不支持指定父子关系的选择器。
providers: [MyService, { provide: ... }]	List of dependency injection providers for this directive and its children. 该指令及其子指令的依赖注入提供商列表。

Component configuration 组件配置	@Component extends @Directive, so the @Directive configuration applies to components as well @Component 继承自 @Directive，因此 @Directive 的配置也能用于 @Component。
moduleId: module.id	If set, the templateUrl and styleUrl are resolved relative to the component. 如果设置了，那么 templateUrl 和 styleUrl 的路径就会相对于当前组件进行解析。
viewProviders: [MyService, { provide: ... }]	List of dependency injection providers scoped to this component's view. 依赖注入提供商列表，但它们的范围被限定为当前组件的视图。
template: 'Hello {{name}}' templateUrl: 'my-component.html'	Inline template or external template URL of the component's view. 当前组件视图的内联模板或外部模板的 URL 。
styles: ['.primary {color: red}'] styleUrls: ['my-component.css']	List of inline CSS styles or external stylesheet URLs for styling the component’s view. 用于为当前组件的视图提供样式的内联 CSS 或外部样式表 URL 的列表。

Class field decorators for directives and components 给指令或组件类用的属性装饰器	import { Input, ... } from '@angular/core';
@Input() myProperty;	Declares an input property that you can update via property binding (example: <my-cmp [myProperty]="someExpression">). 声明一个输入属性，你可以通过属性绑定来更新它，如 <my-cmp [myProperty]="someExpression">。
@Output() myEvent = new EventEmitter();	Declares an output property that fires events that you can subscribe to with an event binding (example: <my-cmp (myEvent)="doSomething()">). 声明一个输出属性，它发出事件，你可以用事件绑定来订阅它们（如：<my-cmp (myEvent)="doSomething()">）。
@HostBinding('class.valid') isValid;	Binds a host element property (here, the CSS class valid) to a directive/component property (isValid). 把宿主元素的一个属性（这里是 CSS 类 valid）绑定到指令或组件上的 isValid 属性。
@HostListener('click', ['$event']) onClick(e) {...}	Subscribes to a host element event (click) with a directive/component method (onClick), optionally passing an argument ($event). 用指令或组件上的onClick方法订阅宿主元素上的click事件，并从中获取$event参数（可选）
@ContentChild(myPredicate) myChildComponent;	Binds the first result of the component content query (myPredicate) to a property (myChildComponent) of the class. 把组件内容查询（myPredicate）的第一个结果绑定到该类的 myChildComponent 属性上。
@ContentChildren(myPredicate) myChildComponents;	Binds the results of the component content query (myPredicate) to a property (myChildComponents) of the class. 把组件内容查询（myPredicate）的全部结果绑定到该类的 myChildComponents 属性上
@ViewChild(myPredicate) myChildComponent;	Binds the first result of the component view query (myPredicate) to a property (myChildComponent) of the class. Not available for directives. 把组件视图查询（myPredicate）的第一个结果绑定到该类的 myChildComponent 属性上。对指令无效。
@ViewChildren(myPredicate) myChildComponents;	Binds the results of the component view query (myPredicate) to a property (myChildComponents) of the class. Not available for directives. 把组件视图查询（myPredicate）的全部结果绑定到该类的 myChildComponents 属性上。对指令无效。

Directive and component change detection and lifecycle hooks 指令和组件的变更检测与生命周期钩子	(implemented as class methods) 由类的方法实现。
constructor(myService: MyService, ...) { ... }	Called before any other lifecycle hook. Use it to inject dependencies, but avoid any serious work here. 在任何其它生命周期钩子之前调用。可以用它来注入依赖项，但不要在这里做正事。
ngOnChanges(changeRecord) { ... }	Called after every change to input properties and before processing content or child views. 每当输入属性发生变化时就会调用，但位于处理内容（ng-content）或子视图之前。
ngOnInit() { ... }	Called after the constructor, initializing input properties, and the first call to ngOnChanges. 在调用完构造函数、初始化完所有输入属性并首次调用过ngOnChanges之后调用。
ngDoCheck() { ... }	Called every time that the input properties of a component or a directive are checked. Use it to extend change detection by performing a custom check. 每当对组件或指令的输入属性进行变更检测时就会调用。可以用它来扩展变更检测逻辑，执行自定义的检测逻辑。
ngAfterContentInit() { ... }	Called after ngOnInit when the component's or directive's content has been initialized. ngOnInit完成之后，当组件或指令的内容（ng-content）已经初始化完毕时调用。
ngAfterContentChecked() { ... }	Called after every check of the component's or directive's content. 每当组件或指令的内容（ng-content）做变更检测时调用。
ngAfterViewInit() { ... }	Called after ngAfterContentInit when the component's view has been initialized. Applies to components only. 当ngAfterContentInit完毕，并且组件的视图已经初始化完毕时调用。只适用于组件。
ngAfterViewChecked() { ... }	Called after every check of the component's view. Applies to components only. 当组件视图每次执行变更检测时调用。只适用于组件。
ngOnDestroy() { ... }	Called once, before the instance is destroyed. 只在实例被销毁前调用一次。

Dependency injection configuration 依赖注入的配置
{ provide: MyService, useClass: MyMockService }	Sets or overrides the provider for MyService to the MyMockService class. 把 MyService 的服务提供商设置或改写为 MyMockService 类。
{ provide: MyService, useFactory: myFactory }	Sets or overrides the provider for MyService to the myFactory factory function. 把 MyService 的服务提供商设置或改写为 myFactory 工厂函数。
{ provide: MyValue, useValue: 41 }	Sets or overrides the provider for MyValue to the value 41. 把 MyValue 的服务提供商改写为一个特定的值 41 。

Routing and navigation 路由与导航	import { Routes, RouterModule, ... } from '@angular/router';
const routes: Routes = [ { path: '', component: HomeComponent }, { path: 'path/:routeParam', component: MyComponent }, { path: 'staticPath', component: ... }, { path: '**', component: ... }, { path: 'oldPath', redirectTo: '/staticPath' }, { path: ..., component: ..., data: { message: 'Custom' } } ]); const routing = RouterModule.forRoot(routes);	Configures routes for the application. Supports static, parameterized, redirect, and wildcard routes. Also supports custom route data and resolve. 为该应用配置路由。支持静态、参数化、重定向和通配符路由。也支持自定义路由数据和解析（resolve）函数。
<router-outlet></router-outlet> <router-outlet name="aux"></router-outlet>	Marks the location to load the component of the active route. 标记出一个位置，用来加载活动路由的组件。
<a routerLink="/path"> <a [routerLink]="[ '/path', routeParam ]"> <a [routerLink]="[ '/path', { matrixParam: 'value' } ]"> <a [routerLink]="[ '/path' ]" [queryParams]="{ page: 1 }"> <a [routerLink]="[ '/path' ]" fragment="anchor">	Creates a link to a different view based on a route instruction consisting of a route path, required and optional parameters, query parameters, and a fragment. To navigate to a root route, use the / prefix; for a child route, use the ./prefix; for a sibling or parent, use the ../ prefix. 使用路由体系创建一个到其它视图的链接。路由体系由路由路径、必要参数、可选参数、查询参数和文档片段组成。要导航到根路由，请使用/前缀；要导航到子路由，使用./前缀；要导航到兄弟路由或父级路由，使用../前缀。
<a [routerLink]="[ '/path' ]" routerLinkActive="active">	The provided classes are added to the element when the routerLink becomes the current active route. 当 routerLink 指向的路由变成活动路由时，为当前元素添加一些类（比如这里的 active）。
class CanActivateGuard implements CanActivate { canActivate( route: ActivatedRouteSnapshot, state: RouterStateSnapshot ): Observable<boolean>|Promise<boolean>|boolean { ... } } { path: ..., canActivate: [CanActivateGuard] }	An interface for defining a class that the router should call first to determine if it should activate this component. Should return a boolean or an Observable/Promise that resolves to a boolean. 用来定义类的接口。路由器会首先调用本接口来决定是否激活该路由。应该返回一个 boolean 或能解析成 boolean 的 Observable/Promise。
class CanDeactivateGuard implements CanDeactivate<T> { canDeactivate( component: T, route: ActivatedRouteSnapshot, state: RouterStateSnapshot ): Observable<boolean>|Promise<boolean>|boolean { ... } } { path: ..., canDeactivate: [CanDeactivateGuard] }	An interface for defining a class that the router should call first to determine if it should deactivate this component after a navigation. Should return a boolean or an Observable/Promise that resolves to a boolean. 用来定义类的接口。路由器会在导航离开前首先调用本接口以决定是否取消激活本路由。应该返回一个 boolean 或能解析成 boolean 的 Observable/Promise。
class CanActivateChildGuard implements CanActivateChild { canActivateChild( route: ActivatedRouteSnapshot, state: RouterStateSnapshot ): Observable<boolean>|Promise<boolean>|boolean { ... } } { path: ..., canActivateChild: [CanActivateGuard], children: ... }	An interface for defining a class that the router should call first to determine if it should activate the child route. Should return a boolean or an Observable/Promise that resolves to a boolean. 用来定义类的接口。路由器会首先调用本接口来决定是否激活一个子路由。应该返回一个 boolean 或能解析成 boolean 的 Observable/Promise。
class ResolveGuard implements Resolve<T> { resolve( route: ActivatedRouteSnapshot, state: RouterStateSnapshot ): Observable<any>|Promise<any>|any { ... } } { path: ..., resolve: [ResolveGuard] }	An interface for defining a class that the router should call first to resolve route data before rendering the route. Should return a value or an Observable/Promise that resolves to a value. 用来定义类的接口。路由器会在渲染该路由之前，首先调用它来解析路由数据。应该返回一个值或能解析成值的 Observable/Promise。
class CanLoadGuard implements CanLoad { canLoad( route: Route ): Observable<boolean>|Promise<boolean>|boolean { ... } } { path: ..., canLoad: [CanLoadGuard], loadChildren: ... }	An interface for defining a class that the router should call first to check if the lazy loaded module should be loaded. Should return a boolean or an Observable/Promise that resolves to a boolean. 用来定义类的接口。路由器会首先调用它来决定是否应该加载一个惰性加载模块。应该返回一个 boolean 或能解析成 boolean 的 Observable/Promise。