I'd like to watch an object/array, which ca be edited by a service or by a controllers routine. I thought that an Observable could watch an object/array. 

My implementation doesn't react on changes of the items :

```
  private data : Observable<Array<any>>;
  private dataObserver: Observer<Array<any>>;
  private sub : Subscription;
  private items: <Array<any>>;

  ngOnInit() {
     this.items = itemService.getItems();
     this.data = new Observable<Array<any>>(observer =>{
        this.dataObserver = observer;
     });
     this.data.subscribe(
        x => console.log('onNext: %s', x),
        e => console.log('onError: %s', e),
        () => console.log('onCompleted')
     );
     this.dataObserver.next(this.items);
  }

private start(){

  //change values of the array in an interval
  let loop = Observable.interval(250)
  let i=0;
  self.sub = loop.subscribe(() => {
      if(self.items[0]){
        self.items[0].id= i;
        if(i<100) i++;
        else i=1;
      }
  })
}

```

The observalbes subsciption doesn't react on changes of the items array. It only triggers on its next mehtod. On the other hand .. this is too cumbersome for a simple watch method.

What does angular-2 offer us to watch for changes, as $scope.$watch did in angular-1?