Emit event from parent to child

You can create one service which is shared between your parent and child component in which you can define Observable so that you can subscribe to that Observable from child and perform some action when you receive some value from parent.

//common.service.tsimport { Injectable, Inject } from '@angular/core';import { Subject }    from 'rxjs/Subject';@Injectable()export class CommonService {  private notify = new Subject<any>();  /**   * Observable string streams   */  notifyObservable$ = this.notify.asObservable();  constructor(){}  public notifyOther(data: any) {    if (data) {      this.notify.next(data);    }  }}

//parent.component.ts

import { Component, OnInit, OnDestroy } from '@angular/core';import { Subscription } from 'rxjs/Subscription';import { CommonService } from './common.service';@Component({  selector   : 'parent',  templateUrl : './parent.html'})export class ParentComponent implements OnInit, OnDestroy {  constructor( private commonService: CommonService ){  }  ngOnInit() {    this.commonService.notifyOther({option: 'call_child', value: 'From child'});  }}

//child.component.ts

import { Component, OnInit, OnDestroy } from '@angular/core';import { Subscription } from 'rxjs/Subscription';import { CommonService } from './common.service';@Component({  selector   : 'child',  templateUrl : './child.html'})export class ChildComponent implements OnInit, OnDestroy {  private subscription: Subscription;  constructor( private commonService: CommonService ){  }  ngOnInit() {    this.subscription = this.commonService.notifyObservable$.subscribe((res) => {      if (res.hasOwnProperty('option') && res.option === 'call_child') {        console.log(res.value);        // perform your other action from here      }    });  }  ngOnDestroy() {    this.subscription.unsubscribe();  }}

Child Component

In childComponent.ts

@Input() private uploadSuccess: EventEmitter<boolean>;

Additionally in childComponent.ts subscribe to the event:

ngOnInit() {  if (this.uploadSuccess) {    this.uploadSuccess.subscribe(data => {      // Do something in the childComponent after parent emits the event.    });  }}

Parent Component

In ParentComponent.html

<app-gallery  [uploadSuccess] = "uploadSuccess" > </app-gallery>

In ParentComponent.ts

private uploadSuccess: EventEmitter<boolean> = new EventEmitter();onImageUploadSuccess(event) {   console.log('Image Upload succes');   if (event.code === 'OK' && this.maxUploadLimit > 0) {      this.galleryImagesCount = this.galleryImagesCount + 1;      this.maxUploadLimit = this.maxUploadLimit - 1;    }   // The parent emits the event which was given as `@Input` variable to the child-component   this.uploadSuccess.emit(true);}