@angular/router

ResolveFn

Type Alias

Function type definition for a data provider.

  
    type ResolveFn<T> = (  route: ActivatedRouteSnapshot,  state: RouterStateSnapshot,) => MaybeAsync<T | RedirectCommand>

Function type definition for a data provider.

A data provider can be used with the router to resolve data during navigation. The router waits for the data to be resolved before the route is finally activated.

A resolver can also redirect a RedirectCommand and the Angular router will use it to redirect the current navigation to the new destination.

The following example implements a function that retrieves the data needed to activate the requested route.

          interface Hero {  name: string;}@Injectable()export class HeroService {  getHero(id: string) {    return {name: `Superman-${id}`};  }}export const heroResolver: ResolveFn<Hero>= (  route: ActivatedRouteSnapshot,  state: RouterStateSnapshot,) => {  return inject(HeroService).getHero(route.paramMap.get('id')!);};bootstrapApplication(App, {  providers: [    provideRouter([      {        path: 'detail/:id',        component: HeroDetailComponent,        resolve: {hero: heroResolver},      },    ]),  ],});

And you can access to your resolved data from HeroComponent:

          @Component({template: ''})export class HeroDetailComponent {  private activatedRoute = inject(ActivatedRoute);  ngOnInit() {    this.activatedRoute.data.subscribe(({hero}) => {      // do something with your resolved data ...    });  }}

If resolved data cannot be retrieved, you may want to redirect the user to a new page instead:

          export const heroResolver: ResolveFn<Hero>= async (  route: ActivatedRouteSnapshot,  state: RouterStateSnapshot,) => {  const router = inject(Router);  const heroService = inject(HeroService);  try {    return await heroService.getHero(route.paramMap.get('id')!);  } catch {    return new RedirectCommand(router.parseUrl('/404'));  }};

When both guard and resolvers are specified, the resolvers are not executed until all guards have run and succeeded. For example, consider the following route configuration:

          { path: 'base' canActivate: [baseGuard], resolve: {data: baseDataResolver} children: [  {    path: 'child',    canActivate: [childGuard],    component: ChildComponent,    resolve: {childData: childDataResolver}   } ]}

The order of execution is: baseGuard, childGuard, baseDataResolver, childDataResolver.