angular - How to emit an event from parent to child?

Question

I am currently using Angular 2. Usually we use @Output() addTab = new EventEmitter<any>(); and then addTab.emit() to emit an event to parent component.

Is there any way we can do it vice cersa, from parent to child?

Answer 1

Using RxJs, you can declare a Subject in your parent component and pass it as Observable to child component, child component just need to subscribe to this Observable.

Parent-Component

eventsSubject: Subject<void> = new Subject<void>();

emitEventToChild() {
  this.eventsSubject.next();
}

Parent-HTML

<child [events]="eventsSubject.asObservable()"> </child>    

Child-Component

private eventsSubscription: Subscription;

@Input() events: Observable<void>;

ngOnInit(){
  this.eventsSubscription = this.events.subscribe(() => doSomething());
}

ngOnDestroy() {
  this.eventsSubscription.unsubscribe();
}