main-resolver.service.ts

import { Resolve, ActivatedRouteSnapshot, RouterStateSnapshot } from '@angular/router'
import { Observable } from 'rxjs';
import { first } from 'rxjs/operators';
import { MainService } from './main.service';
import { Injectable } from '@angular/core';
import { AngularFireDatabase, AngularFireList } from 'angularfire2/database';


@Injectable()
export class MainResolver implements Resolve<any> {
    constructor(private service: MainService, private db: AngularFireDatabase) {}
    resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<any> | Promise<any> | any {
        let user = this.db.list('users/'+route.params['id']);
        return new Promise((resolve, reject) => {
            user.first().subscribe(() => { // Property 'first' does not exist on type 'AngularFireList<{}>'.
                resolve(user)
            }, reject)
        });
    }
}