Example of Angular Route Resolver

magical.lessons.resolver.ts

import { Injectable, } from '@angular/core';
import { ActivatedRouteSnapshot, Resolve, Router, RouterStateSnapshot } from '@angular/router';
import { Observable } from 'rxjs';
import { catchError } from 'rxjs/operators';
import { RoomDetail } from 'src/app/_models/rooms.model';
import { RoomService } from 'src/app/_services/room.service';

@Injectable()
export class MagicalLessonsResolver implements Resolve<RoomDetail> {
  constructor(
    private roomService: RoomService,
    private router: Router
  ) {}

  resolve(
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ): Observable<any> {

    return this.roomService.getRoom(route.params['id'])
      .pipe(catchError((err) => this.router.navigateByUrl('/')));

  }
}