What sets apart the async operator from subscribing to an observable?

Question

What sets apart the async operator from subscribing to an observable?

I recently began exploring Angular, RxJs, and Ngrx.

While learning about observing changes through subscribing to an Observable, I encountered this code snippet from the Ngrx getting started guide:

<div>Current Count: {{ count$ | async }}</div>

My question revolves around understanding the AsyncPipe. How does it differ from directly subscribing to an Observable? And in what scenarios would you choose one over the other?

angular typescript rxjs observable ngrx

Answer 1

Answer №1

Using the async pipe results in a much cleaner code structure

data$ = this.service.data$;

and when implemented in the template

{{data$ | async}}

This approach eliminates the need to manually manage subscriptions.

ngOnInit() {
  this.sub = this.service.data$.subscribe(data => { this.data = data });
}

ngOnDestroy() {
  this.sub.unsubscribe();
}

and in the template

{{data}}

Answer 2

Using the async pipe results in a much cleaner code structure

data$ = this.service.data$;

and when implemented in the template

{{data$ | async}}

This approach eliminates the need to manually manage subscriptions.

ngOnInit() {
  this.sub = this.service.data$.subscribe(data => { this.data = data });
}

ngOnDestroy() {
  this.sub.unsubscribe();
}

and in the template

{{data}}

Answer 3

Answer №2

Just as @jonrsharpe pointed out, there isn't really much of a difference. With the async pipe, a subscription is created under the hood to store the latest value, which is essentially what you would have to do if you were subscribing and displaying the result manually.

Furthermore, the async pipe handles unsubscribing from the observable when the component (or directive) is destroyed.

There might be a slight improvement in terms of efficiency with change detection, but this is not completely confirmed.

Primarily, it's all about convenience. Using an async pipe requires less code than creating a component variable, subscribing to it in the component's onInit or constructor, and keeping track of the subscription for later unsubscribe.

Answer 4

Just as @jonrsharpe pointed out, there isn't really much of a difference. With the async pipe, a subscription is created under the hood to store the latest value, which is essentially what you would have to do if you were subscribing and displaying the result manually.

Furthermore, the async pipe handles unsubscribing from the observable when the component (or directive) is destroyed.

There might be a slight improvement in terms of efficiency with change detection, but this is not completely confirmed.

Primarily, it's all about convenience. Using an async pipe requires less code than creating a component variable, subscribing to it in the component's onInit or constructor, and keeping track of the subscription for later unsubscribe.

What sets apart the async operator from subscribing to an observable?

Answer №1

Answer №2

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