Angular 2, how to know the state of a child ngIf without touching the child/component's code?

Question

Angular

<roo-component>
    <div *ngIf="canOrNot">Oooops</div>
</root-component>

In the root component, I want to know the state of the ngIf directive, that is, ideally, in the root component, do something like:

@NgIfChildDirective() private ngIfD;
....
this.ngIfD.subscribe();

I want to track the state (show / hidden, that is, in the case of ngIf in the DOM or not the element)

Answer 1

if it is planned to use the subscriber, then it is enough to simply emit all changes to the canOrNot variable in the roo-component

Answer 2

I am making an analogue from vue js, I went the way of my directives instead of ngIf. <transition></transition>