What it does

Interface that class can implement to be a data provider.

How to use

class Backend {
  fetchTeam(id: string) {
    return 'someTeam';
  }
}

@Injectable()
class TeamResolver implements Resolve<Team> {
  constructor(private backend: Backend) {}

  resolve(
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ): Observable<any>|Promise<any>|any {
    return this.backend.fetchTeam(route.params.id);
  }
}

@NgModule({
  imports: [
    RouterModule.forRoot([
      {
        path: 'team/:id',
        component: TeamCmp,
        resolve: {
          team: TeamResolver
        }
      }
    ])
  ],
  providers: [TeamResolver]
})
class AppModule {}

You can alternatively provide a function with the resolve signature:

@NgModule({
  imports: [
    RouterModule.forRoot([
      {
        path: 'team/:id',
        component: TeamCmp,
        resolve: {
          team: 'teamResolver'
        }
      }
    ])
  ],
  providers: [
    {
      provide: 'teamResolver',
      useValue: (route: ActivatedRouteSnapshot, state: RouterStateSnapshot) => 'team'
    }
  ]
})
class AppModule {}

Interface Description