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< @angular/coreAngular/docs/8/api/core/contentchildren



Parameter decorator that configures a content query.

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Use to get the QueryList of elements or directives from the content 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.

Content queries are set before the ngAfterContentInit callback is called.

Does not retrieve elements or directives that are in other components' templates, since a component's template is always a black box to its ancestors.

Metadata Properties:

  • selector - The directive type or the name used for querying.
  • descendants - True to include all descendants, otherwise include only direct children.
  • read - True to read a different token from the queried elements.


Usage notes

Here is a simple demonstration of how the ContentChildren decorator can be used.

import {AfterContentInit, ContentChildren, Directive, QueryList} from '@angular/core';

@Directive({selector: 'child-directive'})
class ChildDirective {

@Directive({selector: 'someDir'})
class SomeDir implements AfterContentInit {
  @ContentChildren(ChildDirective) contentChildren !: QueryList<ChildDirective>;

  ngAfterContentInit() {
    // contentChildren is set

Tab-pane example

Here is a slightly more realistic example that shows how ContentChildren decorators can be used to implement a tab pane component.

import {Component, ContentChildren, Directive, Input, QueryList} from '@angular/core';

@Directive({selector: 'pane'})
export class Pane {
  @Input() id !: string;

  selector: 'tab',
  template: `
    <div class="top-level">Top level panes: {{serializedPanes}}</div>
    <div class="nested">Arbitrary nested panes: {{serializedNestedPanes}}</div>
export class Tab {
  @ContentChildren(Pane) topLevelPanes !: QueryList<Pane>;
  @ContentChildren(Pane, {descendants: true}) arbitraryNestedPanes !: QueryList<Pane>;

  get serializedPanes(): string {
    return this.topLevelPanes ? =>', ') : '';
  get serializedNestedPanes(): string {
    return this.arbitraryNestedPanes ? =>', ') : '';

  selector: 'example-app',
  template: `
      <pane id="1"></pane>
      <pane id="2"></pane>
      <pane id="3" *ngIf="shouldShow">
          <pane id="3_1"></pane>
          <pane id="3_2"></pane>

    <button (click)="show()">Show 3</button>
export class ContentChildrenComp {
  shouldShow = false;

  show() { this.shouldShow = true; }

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