121 lines
2.9 KiB
TypeScript
121 lines
2.9 KiB
TypeScript
// #docplaster
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// #docregion
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import { AfterViewChecked, AfterViewInit, Component, ViewChild } from '@angular/core';
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import { LoggerService } from './logger.service';
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//////////////////
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// #docregion child-view
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@Component({
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selector: 'my-child',
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template: '<input [(ngModel)]="hero">'
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})
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export class ChildViewComponent {
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hero = 'Magneta';
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}
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// #enddocregion child-view
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//////////////////////
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@Component({
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selector: 'after-view',
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// #docregion template
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template: `
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<div>-- child view begins --</div>
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<my-child></my-child>
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<div>-- child view ends --</div>`
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// #enddocregion template
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+ `
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<p *ngIf="comment" class="comment">
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{{comment}}
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</p>
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`,
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directives: [ChildViewComponent]
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})
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// #docregion hooks
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export class AfterViewComponent implements AfterViewChecked, AfterViewInit {
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private prevHero = '';
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// Query for a VIEW child of type `ChildViewComponent`
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@ViewChild(ChildViewComponent) viewChild: ChildViewComponent;
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// #enddocregion hooks
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constructor(private logger: LoggerService) {
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this.logIt('AfterView constructor');
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}
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// #docregion hooks
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ngAfterViewInit() {
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// viewChild is set after the view has been initialized
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this.logIt('AfterViewInit');
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this.doSomething();
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}
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ngAfterViewChecked() {
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// viewChild is updated after the view has been checked
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if (this.prevHero === this.viewChild.hero) {
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this.logIt('AfterViewChecked (no change)');
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} else {
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this.prevHero = this.viewChild.hero;
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this.logIt('AfterViewChecked');
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this.doSomething();
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}
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}
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// #enddocregion hooks
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comment = '';
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// #docregion do-something
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// This surrogate for real business logic sets the `comment`
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private doSomething() {
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let c = this.viewChild.hero.length > 10 ? `That's a long name` : '';
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if (c !== this.comment) {
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// Wait a tick because the component's view has already been checked
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this.logger.tick_then(() => this.comment = c);
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}
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}
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// #enddocregion do-something
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private logIt(method: string) {
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let child = this.viewChild;
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let message = `${method}: ${child ? child.hero : 'no'} child view`;
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this.logger.log(message);
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}
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// #docregion hooks
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// ...
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}
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// #enddocregion hooks
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//////////////
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@Component({
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selector: 'after-view-parent',
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template: `
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<div class="parent">
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<h2>AfterView</h2>
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<after-view *ngIf="show"></after-view>
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<h4>-- AfterView Logs --</h4>
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<p><button (click)="reset()">Reset</button></p>
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<div *ngFor="let msg of logs">{{msg}}</div>
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</div>
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`,
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styles: ['.parent {background: burlywood}'],
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providers: [LoggerService],
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directives: [AfterViewComponent]
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})
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export class AfterViewParentComponent {
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logs: string[];
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show = true;
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constructor(private logger: LoggerService) {
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this.logs = logger.logs;
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}
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reset() {
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this.logs.length = 0;
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// quickly remove and reload AfterViewComponent which recreates it
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this.show = false;
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this.logger.tick_then(() => this.show = true);
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}
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}
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