What it does
Configures a content query.
How to use
.
import {AfterContentInit, ContentChild, Directive} from '@angular/core';
@Directive({selector: 'child-directive'})
class ChildDirective {
}
@Directive({selector: 'someDir'})
class SomeDir implements AfterContentInit {
@ContentChild(ChildDirective) contentChild: ChildDirective;
ngAfterContentInit() {
// contentChild is set
}
}
Description
You can use ContentChild to get the first element or the directive matching the selector from
the content DOM. If the content DOM changes, and a new child matches the selector,
the property will be updated.
Content queries are set before the ngAfterContentInit
callback is called.
Metadata Properties:
- selector - the directive type or the name used for querying.
- read - read a different token from the queried element.
Let's look at an example:
import {Component, ContentChild, Directive, Input} from '@angular/core';
@Directive({selector: 'pane'})
export class Pane {
@Input() id: string;
}
@Component({
selector: 'tab',
template: `
<div>pane: {{pane?.id}}</div>
`
})
export class Tab {
@ContentChild(Pane) pane: Pane;
}
@Component({
selector: 'example-app',
template: `
<tab>
<pane id="1" *ngIf="shouldShow"></pane>
<pane id="2" *ngIf="!shouldShow"></pane>
</tab>
<button (click)="toggle()">Toggle</button>
`,
})
export class ContentChildComp {
shouldShow = true;
toggle() { this.shouldShow = !this.shouldShow; }
}
npm package: @angular/core
exported from core/index defined in core/src/metadata/di.ts