Today I Learned

TIL, 2022-05-05, Resolver with Params, Multiple Async pipes

  • Angular - resolver with parameter on resolve method
  path: 'project/:id',
  component: ProjectComponent,
  resolve: { data: AppResolver },
  data: { resolvedata: 'myValue' }
  • And in the resolver:
export class AppResolver implements Resolve<MyComplexObject []> {
  constructor(private myService: MyService, private router: Router) {}
  resolve(route: ActivatedRouteSnapshot): Observable<MyComplexObject[]>|boolean {
    let myParam =['resolvedata'];
  • Reference
    • Resolvers are resolved in parallel. If Foo and Bar are supposed to be resolved in series they should be a single FooBar resolver. If they are supposed to be used by themselves in other routes, FooBar can wrap Foo and Bar resolvers:
class FooBarResolver implements Resolve<{ foo: any, bar: any }> {
    protected fooResolver: FooResolver,
    protected barResolver: BarResolver
  ) {}

  async resolve(route): Promise<{ foo: any, bar: any }> {
    const foo = await this.fooResolver.resolve(route);
    const bar = await this.barResolver.resolve(route);

    return { foo, bar };

How to avoid multiple async pipes in Angular

Reference Reference Reference

  • Async pipes - unsubscribe on component destroy, thus making it unnecessary to clean up manually.
  • Problem with multiple subscriptions - well, we still have to have multiple observable.
<ng-container *ngIf="
    obs1: obs1$ | async,
    obs2: obs2$ | async,
    obs3: obs3$ | async
  } as observables">
    <!--    already expanded observable!-->
  • Good approach if have a lot of observables and you need to user their values in a lot of places in the template.

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