CODEWITHSUNDEEP
angularangular-routingangular-router-guards
user9052661
user9052661

Reputation: 161

Angular 2/4 prevent user to leave component if changes not saved

I have this interface that i'm using to prevent the user to leave page

export interface ComponentCanDeactivate {
  canDeactivate: () => boolean;
}

@Injectable()
export class PendingChangesGuard implements CanDeactivate<ComponentCanDeactivate> {
  canDeactivate(component: ComponentCanDeactivate): boolean {
    return  component.canDeactivate() ?
     //code : //more code
  }
}

In one of my component i have the following code

export class DashboardComponent implements ComponentCanDeactivate{
  @HostListener('window:beforeunload')
  canDeactivate(): boolean {
    return !this.isDirty;
  }

My problem is that my component -> (component: ComponentCanDeactivate) from PendingChangesGuard is always null so i get an error saying

Cannot call canDeactivate() of null

I also have this setup in my routing

 path: 'dashboard',
        canDeactivate: [PendingChangesGuard],
        loadChildren: './views/dashboard/dashboard.module#DashboardModule'

Can someone tell me what am i doing wrong?

Upvotes: 7

Views: 6248

Answers (3)

user9052661
user9052661

Reputation: 161

The issue was caused by lazy loading

Instead of having this in your app routing:

path: 'dashboard',
        canDeactivate: [PendingChangesGuard], <-- causing issue
        loadChildren: './views/dashboard/dashboard.module#DashboardModule'

You need to remove the canDeactive from the app routing and move it to the module routing.

const routes: Routes = [
  {
    path: '',
    component: DashboardComponent,
    canDeactivate: [ PendingChangesGuard ]
  }

Upvotes: 9

Dakota
Dakota

Reputation: 525

I implement like this

Deactive-guard-service.ts

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

@Injectable()
export class DeactivateGuardService implements  CanDeactivate<CanComponentDeactivate>{

  canDeactivate(component: CanComponentDeactivate) {
    return component.canDeactivate ? component.canDeactivate() : true;
  }
}

Component.ts

checkSave(): Promise<boolean> {
    var prom = new Promise<boolean>((resolve, reject) => {
      //check saved change
        if(saved) resolve(true);
        else reject(false);
    });
    return prom;
  }

  canDeactivate(): Promise<boolean> {

    return this.checkSave().catch(function () {
      return false;
    });
  }

Upvotes: 0

Fjut
Fjut

Reputation: 1324

In your PendingChangesGuard, try to inject the component itself, not the interface:

export class PendingChangesGuard implements CanDeactivate<DashboardComponent> {
  constructor() {}
  canDeactivate(component: DashboardComponent): boolean {
  ...
  }

You cannot inject an interface using Angular DI as interfaces are just Typescript constructs and do not exist in Javascript code produced with the compilation process.

For more information, have a look at this SO question.

Upvotes: 0

Related Questions