player.service.ts

import { Injectable } from '@angular/core';
import { BehaviorSubject } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class PlayerService {

  private currentPlayerSource = new BehaviorSubject(0);   // 0 is the default value
  currentPlayer = this.currentPlayerSource.asObservable();

  constructor() { }

  changeCurrentPlayer(player: number): void {
    this.currentPlayerSource.next(player);
    console.log('current player id:', player);
  }

}