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

// #docregion
import { Injectable }    from '@angular/core';
import { CanDeactivate } from '@angular/router';
import { Observable }    from 'rxjs/Observable';

export interface CanComponentDeactivate {
 canDeactivate: () => boolean | Observable<boolean>;
}

@Injectable()
export class CanDeactivateGuard implements CanDeactivate<CanComponentDeactivate> {
  canDeactivate(component: CanComponentDeactivate): Observable<boolean> | boolean {
    return component.canDeactivate ? component.canDeactivate() : true;
  }
}