ViewChildren

Property decorator that configures a view query.

Use to get the QueryList of elements or directives from the view DOM. Any time a child element is added, removed, or moved, the query list will be updated, and the changes observable of the query list will emit a new value.

View queries are set before the ngAfterViewInit callback is called.

Metadata Properties:

• selector - The directive type or the name used for querying.
• read - Used to read a different token from the queried elements.
• emitDistinctChangesOnly - The QueryList#changes observable will emit new values only if the QueryList result has changed. When false the changes observable might emit even if the QueryList has not changed. ** Note: *** This config option is deprecated, it will be permanently set to true and removed in future versions of Angular.

The following selectors are supported.

• Any class with the @Component or @Directive decorator
• A template reference variable as a string (e.g. query <my-component #cmp></my-component> with @ViewChildren('cmp'))
• Any provider defined in the child component tree of the current component (e.g. @ViewChildren(SomeService) someService!: SomeService)
• Any provider defined through a string token (e.g. @ViewChildren('someToken') someTokenVal!: any)
• A TemplateRef (e.g. query <ng-template></ng-template> with @ViewChildren(TemplateRef) template;)

In addition, multiple string selectors can be separated with a comma (e.g. @ViewChildren('cmp1,cmp2'))

The following values are supported by read:

• Any class with the @Component or @Directive decorator
• Any provider defined on the injector of the component that is matched by the selector of this query
• Any provider defined through a string token (e.g. {provide: 'token', useValue: 'val'})
• TemplateRef, ElementRef, and ViewContainerRef

          
import {AfterViewInit, Component, Directive, QueryList, ViewChildren} from '@angular/core';@Directive({  selector: 'child-directive',  standalone: false,})class ChildDirective {}@Component({  selector: 'someCmp',  templateUrl: 'someCmp.html',  standalone: false,})class SomeCmp implements AfterViewInit {  @ViewChildren(ChildDirective) viewChildren!: QueryList<ChildDirective>;  ngAfterViewInit() {    // viewChildren is set  }}
        

Another example

          
import {AfterViewInit, Component, Directive, Input, QueryList, ViewChildren} from '@angular/core';@Directive({  selector: 'pane',  standalone: false,})export class Pane {  @Input() id!: string;}@Component({  selector: 'example-app',  template: `    <pane id="1"></pane>    <pane id="2"></pane>    <pane id="3" *ngIf="shouldShow"></pane>    <button (click)="show()">Show 3</button>    <div>panes: {{ serializedPanes }}</div>  `,  standalone: false,})export class ViewChildrenComp implements AfterViewInit {  @ViewChildren(Pane) panes!: QueryList<Pane>;  serializedPanes: string = '';  shouldShow = false;  show() {    this.shouldShow = true;  }  ngAfterViewInit() {    this.calculateSerializedPanes();    this.panes.changes.subscribe((r) => {      this.calculateSerializedPanes();    });  }  calculateSerializedPanes() {    setTimeout(() => {      this.serializedPanes = this.panes.map((p) => p.id).join(', ');    }, 0);  }}