CODEWITHSUNDEEP
angulartypescript
Benedict Lewis
Benedict Lewis

Reputation: 2813

Use async pipe and observable for entire block

I have an Observable, which returns a large object from an API. I need to display these values in my template.

For other data returned as an array, I can use:

<div *ngFor="let value of values | async">
  <p>{{ value.prop }}</p>
</div>

I don't need to wait for the async to complete within the *ngFor, as it's already got an async pipe in the parent element.

With my object, I'm looking for something similar. At the moment, I'm doing something like:

<h2>{{ (obj | async)?.title }}</h2>
<p>{{ (obj | async)?.prop.prop2 }}</p>
<p>{{ (obj | async)?.another.prop }}</p>

This obviously leaves a lot of duplicate code. Does something like this exist?

<div *using="obj | async">
  <!-- obj has resolved, can access obj.prop -->
</div>

Upvotes: 3

Views: 8725

Answers (2)

Julia Passynkova
Julia Passynkova

Reputation: 17889

Use 'as' syntax.

Also be aware that each async pipe creates a new subscription and if you subscription uses http - it means multiple http calls. Use Rx share() if you want to use the same observable multiple times in template with async pipe.

     @Component({
      selector: 'my-app',
      template: `
        <div>
          <div *ngIf="obj$ | async as obj; else empty">
         {{obj.x}}
         {{obj.y}}
         </div>
         <ng-template #empty>Empty. Wait 5 s...</ng-template>
        </div>
      `,
    })
    export class App {
      s = new Subject();
      obj$;
      constructor() {
        this.obj$ = this.s.asObservable();
        setTimeout(() => {
          this.s.next({x:12, y:100});
        }, 5000)
      }
    }

Upvotes: 7

Rodrigo Medeiros
Rodrigo Medeiros

Reputation: 91

You could create a alias like this:

<div *ngIf="(obj$ | async) as obj">
  <h2>{{ obj?.title }}</h2>
  <p>{{ obj?.prop.prop2 }}</p>
  <p>{{ obj?.another.prop }}</p>
</div>

Upvotes: 4

Related Questions