where do I push messages in the constructor? (Angular, Observables, Subject)

Question

I have a MessagesService, where i can sendMessage and getMessage:

export class MessagesService {

  constructor() { }

  private subject = new Subject<any>();

  sendMessage(message: string): void {
    this.subject.next({ text: message });
  }

  clearMessages(): void {
    this.subject.next();
  }

  getMessage(): Observable<any> {
    return this.subject.asObservable();
  }

}

In the MessagesComponent i call the getMessage method:

export class MessagesComponent implements OnInit {
  message: any = {};
  subscription: Subscription;


  constructor(public messagesService: MessagesService) {
    this.subscription = this.messagesService.getMessage().subscribe(message => { this.message = message; });
  }

And also in its template:

  {{message?.text}}

Now in another component, where I use sendMessage (in the .ts file) and put a string in it, I call in its template

Now my question: is it correct to put this into the brackets of the constructer of this file:

constructor(private heroService: HeroService, private route: ActivatedRoute, private enemyService: EnemyService,
  public messagesService: MessagesService) {

  this.subscription = this.messagesService.getMessage().subscribe(message => {
    if (message) {
      this.messages.push(message);
    } else {
      // clear messages when empty message received
      this.messages = [];
    }
  });
}

Answer 1

There is what we call life cycle hooks in Angular. It's ok to add your subscription in your constructor or in 'ngOnInit' to ensure that the component is already initialized.