Angular 2 Async Pipe with Ngfor Observable

What is async pipe?

The async pipe subscribes to an Observable and returns the latest changed value. When a new value is changed, the async pipe marks the component to be checked for changes. When the component gets destroyed the async pipe unsubscribes automatically to avoid potential memory leaks.

How to use async pipe in Angular 2?

observable_expression | async

Example,

@Component({
  selector: 'async-observable-pipe',
  template: '<div><code>observable|async</code>: Time: {{ time | async }}</div>'
})

export class AsyncObservablePipeComponent {
  time = new Observable<string>((observer: Subscriber<string>) => {
    setInterval(() => observer.next(new Date().toString()), 1000);
  });
}

The async pipe with ngFor in Angular 2,

*ngFor="#obj of (myAsyncObject | async)?.prop1?.prop2"

Reference,

https://angular.io/docs/ts/latest/api/common/index/AsyncPipe-pipe.html

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