angular-cn/public/docs/_examples/router/ts/app/can-deactivate-guard.service.1.ts

// #docregion
import { Injectable }           from '@angular/core';
import { CanDeactivate,
         ActivatedRouteSnapshot,
         RouterStateSnapshot }  from '@angular/router';

import { CrisisDetailComponent } from './crisis-center/crisis-detail.component';

@Injectable()
export class CanDeactivateGuard implements CanDeactivate<CrisisDetailComponent> {

  canDeactivate(
    component: CrisisDetailComponent,
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ): Promise<boolean> | boolean {
    // Get the Crisis Center ID
    console.log(route.params['id']);

    // Get the current URL
    console.log(state.url);

    // Allow synchronous navigation (`true`) if no crisis or the crisis is unchanged
    if (!component.crisis || component.crisis.name === component.editName) {
      return true;
    }
    // Otherwise ask the user with the dialog service and return its
    // promise which resolves to true or false when the user decides
    return component.dialogService.confirm('Discard changes?');
  }
}