The signature of a function used as a canDeactivate guard on a Route.

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.

The following example implements and uses a CanDeactivateFn that checks whether the user component has unsaved changes before navigating away from the route.

@Component({
  template: '',
})
export class UserComponent {
  hasUnsavedChanges = true;
}

bootstrapApplication(App, {
  providers: [
    provideRouter([
      {
        path: 'user/:id',
        component: UserComponent,
        canDeactivate: [(component: UserComponent) => !component.hasUnsavedChanges],
      },
    ]),
  ],
});