Angular4 中常用的指令入门总结

<div *ngIf="false"></div> <!-- never displayed -->
<div *ngIf="a > b"></div> <!-- displayed if a is more than b -->
<div *ngIf="str == 'yes'"></div> <!-- displayed if str holds the string "yes" -->
<div *ngIf="myFunc()"></div> <!-- displayed if myFunc returns a true value -->

<div class="container">
 <div *ngIf="myVar == 'A'">Var is A</div>
 <div *ngIf="myVar == 'B'">Var is B</div>
 <div *ngIf="myVar != 'A' && myVar != 'B'">Var is something else</div>
</div>

<div class="container">
 <div *ngIf="myVar == 'A'">Var is A</div>
 <div *ngIf="myVar == 'B'">Var is B</div>
 <div *ngIf="myVar == 'C'">Var is C</div>
 <div *ngIf="myVar != 'A' && myVar != 'B' && myVar != 'C'">
 Var is something else
 </div>
</div>

<div class="container" [ngSwitch]="myVar">
 <div *ngSwitchCase="'A'">Var is A</div>
 <div *ngSwitchCase="'B'">Var is B</div>
 <div *ngSwitchCase="'C'">Var is C</div>
 <div *ngSwitchDefault>Var is something else</div>
</div>

<div [style.background-color="'yellow'"]>
 Use fixed yellow background
</div>

<!-- 支持单位: px | em | %-->
<div>
 <span [ngStyle]="{color: 'red'}" [style.font-size.px]="fontSize">
 red text
 </span>
</div>

<div [ngStyle]="{color: 'white', 'background-color': 'blue'}">
 Uses fixed white text on blue background
</div>

.bordered {
 border: 1px dashed black; background-color: #eee;
}

<!-- Use boolean value -->
<div [ngClass]="{bordered: false}">This is never bordered</div>
<div [ngClass]="{bordered: true}">This is always bordered</div>

<!-- Use component instance property -->
<div [ngClass]="{bordered: isBordered}">
 Using object literal. Border {{ isBordered ? "ON" : "OFF" }}
</div>

<!-- Class names contains dashes -->
<div[ngClass]="{'bordered-box': false}">
 Class names contains dashes must use single quote
</div>

<!-- Use a list of class names -->
<div class="base" [ngClass]="['blue', 'round']"> 
 This will always have a blue background and round corners
</div>

<div class="ui list" *ngFor="let c of cities; let num = index"> 
 <div class="item">{{ num+1 }} - {{ c }}</div>
</div>

@Component({
 selector: 'my-app',
 template: `
 <ul>
 <li *ngFor="let item of collection;trackBy: trackByFn">{{item.id}}</li>
 </ul>
 <button (click)="getItems()">Refresh items</button>
 `,
})
export class App {

 constructor() {
 this.collection = [{id: 1}, {id: 2}, {id: 3}];
 }

 getItems() {
 this.collection = this.getItemsFromServer();
 }

 getItemsFromServer() {
 return [{id: 1}, {id: 2}, {id: 3}, {id: 4}];
 }

 trackByFn(index, item) {
 return index; // or item.id
 }
}

<div class='ngNonBindableDemo'>
 <span class="bordered">{{ content }}</span>
 <span class="pre" ngNonBindable>
 ← This is what {{ content }} rendered
 </span>
</div>

<element *ngIf="[condition expression]; else [else template]"></element>

<ng-template #hidden>
 <p>You are not allowed to see our secret</p>
</ng-template>
<p *ngIf="shown; else hidden">
 Our secret is being happy
</p>

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of';
import 'rxjs/add/operator/delay';

@Component({
 selector: 'exe-app',
 template: `
 <ng-template #fetching>
 <p>Fetching...</p>
 </ng-template>
 <p *ngIf="auth | async; else fetching; let user">
 {{user.username }}
 </p>
 `,
})
export class AppComponent implements OnInit {
 auth: Observable<{}>;

 ngOnInit() {
 this.auth = Observable
 .of({ username: 'semlinker', password: 'segmentfault' })
 .delay(new Date(Date.now() + 2000));
 }
}

<div [hidden]="!showGreeting">
 Hello, there!
</div>

@Component({
 selector: 'my-comp',
 template: `
 <input type="text" />
 <div> Some other content </div>
 `
})
export class MyComp {
 constructor(el: ElementRef) {
 el.nativeElement.querySelector('input').focus();
 }
}

@Component({
 selector: 'my-comp',
 template: `
 <input #myInput type="text" />
 <div> Some other content </div>
 `
})
export class MyComp implements AfterViewInit {
 @ViewChild('myInput') input: ElementRef;

 constructor(private renderer: Renderer) {}

 ngAfterViewInit() {
 this.renderer.invokeElementMethod(
 this.input.nativeElement, 'focus');
 }
}

@ViewChild('myInput') myInput1: ElementRef;
@ViewChild('myInput', {read: ViewContainerRef}) myInput2: ViewContainerRef;