angular service

@Injectable({
  providedIn: 'root'
})
export class UsersService {
  constructor(private http: HttpClient, private postsService: PostsService) { }

  private userSelectedAction = new Subject<number>();
  private usersUrl = 'https://jsonplaceholder.typicode.com/users';
  user$ = this.http.get<Users>(this.usersUrl).pipe(shareReplay());
  userWithPost$ = combineLatest(
    this.user$,
    this.postsService.post$
  ).pipe( map( ([users, posts]) => {
    return users.map( user => ({
      ...user,
      posts: posts.filter( post => post.userId == user.id)
    }))
  }));

  selectedUser$ = combineLatest(
    this.userSelectedAction,
    this.userWithPost$
  ).pipe(
    map( ([selectedUserId, users]) => users.find( user => user.id == selectedUserId))
  )