Angular：如何访问 ng-template 中的引用变量

Question

Is there a way to access #interface, which is declared inside ng-template element?

I must put the <interface-settings inside <ng-template.

Because I would need to use the *ngTemplateOutlet.

As I could not find a solution for this, I have to add another <interface-settings #interface and not declare it inside ng-template.

would appreciate if you know other workaround. Thanks

 //  parent.html
 <button type="button" (click)="interface.apply()"></button>

 <ng-template>
    <interface-settings #interface></interface-settings>
 <ng-template>

---

 //child.ts (interface-settings.ts)

apply() {
   console.log("apply");
 }

Answer 1

ng-template is used by Angular for templating - meaning it is not rendered in DOM unless certain conditions tell Angular to use it in the actual DOM.

So when you have your component "interface-setting" inside ng-template - it is not accessible/known by your application unless:

• the ng-template condition was applied and
• your host (parent) component has a reference to it:

For instance, similar to your example:

<button type="button" (click)="hello.sayHello()">Method Inside Hello</button>

<ng-template>
  <hello #hello></hello>
<ng-template>

The above on its own won't work as 2 conditions mentioned above are not met. To fix you need to use ViewChild to get reference to the hello component. Like so:

import { Component, ViewChild } from '@angular/core';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent  {

  @ViewChild('hello') hello;

}

Then you need to make sure the ng-template is used (whatever triggers the ng-template to be placed in DOM for your app):

<ng-template [ngIf]="true">
  <hello #hello></hello>
<ng-template>

Now the reference to the method inside child component will work:

https://stackblitz.com/edit/angular-ivy-hnmw17?file=src/app/app.component.html

You can read more how Angular's structural directives under the hood use ng-template: https://angular.io/guide/structural-directives