Template reference variable returns undefined inside ng-template

问题

Already tried this and this solution but nothing worked.

I am using Angular 7 and trying to get a reference variable which I've placed inside the ng-template tag. But it always returns undefined

test-component.html

<ng-template #abc>
  <div #xyz>    
  </div>
</ng-template>

test-component.ts

@ViewChild('abc') abc: ElementRef; //---> works fine
@ViewChild('xyz') xyz: ElementRef; //---> undefined

test-component.ts

ngAfterViewInit(){
  console.log(this.xyz); //---> undefined  
}

I've tried printing it in all the life cycle hooks of angular but it always returns undefined. But when I try putting it in out side of ng-template it works perfectly.

Is there any way around?

回答1:

That is because, the content inside ng-template is not yet rendered.

You should first activate it using ngTemplateOutlet.

Add the following code in your html, it should work

<ng-template #abc>
  <div #xyz>    
  </div>
</ng-template>

<ng-container *ngTemplateOutlet="abc"></ng-container>

DEMO

回答2:

The reason it's happening is because of the ng-template is never rendering on the HTML all by itself.

As per Angular docs:

The ng-template is an Angular element for rendering HTML. It is never displayed directly. In fact, before rendering the view, Angular replaces the and its contents with a comment.

It can be referred to using ngTemplateOutlet or when with *ngIf else or something like that. It doesn't exist on its own:

Update:

<div *ngIf="someConditionCheck;else abc">
  content here ...
</div>

<ng-template #abc>
  <div #xyz></div>
</ng-template>

You can find the demo code here.

来源：https://stackoverflow.com/questions/54783046/template-reference-variable-returns-undefined-inside-ng-template

标签

angular

ng-bootstrap

ng-template