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What are @ViewChild and @ContentChild?

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01

Understand the problem

Explain the query decorators.

viewchildqueries
02

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03

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@ViewChild queries an element/component/directive from the component's own template; @ContentChild queries content projected into it via <ng-content>. Both give a reference (after the relevant lifecycle hook) to call methods or read properties on the child.

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04

Read the code

Query a child in the view
import { Component, ViewChild, ElementRef, AfterViewInit } from '@angular/core';

@Component({
  selector: 'app-root',
  standalone: true,
  template: '<input #box /> <button (click)="focus()">Focus</button>',
})
export class AppComponent implements AfterViewInit {
  @ViewChild('box') box!: ElementRef<HTMLInputElement>;

  ngAfterViewInit() {
    // available now (the view has been initialized)
    console.log('input found:', !!this.box);
  }
  focus() { this.box.nativeElement.focus(); }
}
05

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