Guards

CanActivate

Interface that a class can implement to be a guard deciding if a route can be activated. If all guards return true, navigation continues. If any guard returns false, navigation is cancelled. If any guard returns a UrlTree, the current navigation is cancelled and a new navigation begins to the UrlTree returned from the guard.

interface CanActivate {
  canActivate(
    route: ActivatedRouteSnapshot, 
    state: RouterStateSnapshot): 
    Observable<boolean | UrlTree> | Promise<boolean | UrlTree> | boolean | UrlTree
}

Description

The following example implements a CanActivate function that checks whether the current user has permission to activate the requested route

class UserToken {}
class Permissions {
  canActivate(user: UserToken, id: string): boolean {
    return true;
  }
}

@Injectable()
class CanActivateTeam implements CanActivate {
  constructor(private permissions: Permissions, private currentUser: UserToken) {}

  canActivate(
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ): Observable<boolean|UrlTree>|Promise<boolean|UrlTree>|boolean|UrlTree {
    return this.permissions.canActivate(this.currentUser, route.params.id);
  }
}

How to implement a Guard?

Here, the defined guard function is provided as part of the Route object in the router configuration:

content_copy@NgModule({
  imports: [
    RouterModule.forRoot([
      {
        path: 'team/:id',
        component: TeamComponent,
        canActivate: [CanActivateTeam]
      }
    ])
  ],
  providers: [CanActivateTeam, UserToken, Permissions]
})
class AppModule {}